( PDF ) Avaliação dos efeitos do tratamento crônico com neurolépticos e sua interação com substâncias potencialmente antioxidantes sobre parâmetros de estresse oxidativo no fígado e rim de ratos

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UNIVERSIDADE FEDERAL DE SANTA MARIA

CENTRO DE CIÊNCIAS NATURAIS E EXATAS

PROGRAMA DE PÓS-GRADUAÇÃO EM CIÊNCIAS BIOLÓGICAS

BIOQUÍMICA TOXICOLÓGICA

AVALIAÇÃO DOS EFEITOS DO TRATAMENTO CRÔNICO COM

NEUROLÉPTICOS E SUA INTERAÇÃO COM SUBSTÂNCIAS

POTENCIALMENTE ANTIOXIDANTES SOBRE PARÂMETROS DE

ESTRESSE OXIDATIVO NO FÍGADO E RIM DE RATOS

DISSERTAÇÃO DE MESTRADO

CRISTIANE LENZ DALLA CORTE

Santa Maria, RS, Brasil

2008

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AVALIAÇÃO DOS EFEITOS DO TRATAMENTO CRÔNICO COM

NEUROLÉPTICOS E SUA INTERAÇÃO COM SUBSTÂNCIAS

POTENCIALMENTE ANTIOXIDANTES SOBRE PARÂMETROS

DE ESTRESSE OXIDATIVO NO FÍGADO E RIM DE RATOS

por

Cristiane Lenz Dalla Corte

Dissertação apresentada ao Programa de Pós-Graduação em

Bioquímica Toxicológica da Universidade Federal de Santa Maria

(UFSM, RS), como requisito parcial para obtenção do grau de

Mestre em Bioquímica Toxicológica.

Orientador: Prof. Dr. Félix Alexandre Antunes Soares

Co-orientador: Prof. Dr. João Batista Teixeira da Rocha

Santa Maria, RS, Brasil

2008

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AGRADECIMENTOS

Agradeço aos meus pais José Erom e Lourença e ao meu irmão Jefferson pelo

incentivo, pela sua dedicação, pelos seus ensinamentos e princípios e, sobretudo, pelo

seu amor incondicional.

Ao meu orientador, Prof. Félix Alexandre Antunes Soares pela paciência,

confiança, incentivo e suporte para a realização deste trabalho.

Ao meu co-orientador, Prof. João Batista Teixeira da Rocha pela orientação,

pela paciência e principalmente pelos ensinamentos ao longo da minha formação

acadêmica.

Aos Professores Cristina e Gilson pelo exemplo que são e por estarem sempre

dispostos a ajudar.

Aos demais professores do Programa de Pós-Graduação em Bioquímica

Toxicológica, que contribuíram para a minha formação.

Aos amigos e colegas do Laboratório do Prof. João: Rose, Robson, Carol e

Tiago, Daniel, Rafael Ineu, Matheus, Alessandro, Jéssie, Danúbia, Romaiana, Sally,

Alessandra e Cássia. Obrigada pelo carinho, companheirismo e pelo conhecimento

compartilhado.

Aos amigos e colegas do Laboratório do Prof. Félix: Gustavo, Rafael Portella,

Fernando, Luiza, Nelson, Rômulo, Guilherme, Priscila, Daiana, Dirleise e Aline.

Obrigada pela amizade, companheirismo também e pelos momentos de descontração.

Em especial gostaria de agradecer aqueles que contribuíram para a realização

deste trabalho: Rose, Romaiana, Jardel, Robson, Carol, Daiana e Dirleise. Sem vocês a

realização deste trabalho não seria possível.

Aos funcionários Angélica, Rinaldo e Márcia pela competência e dedicação com

que realizam seus trabalhos.

Ao CNPq e a CAPES pela bolsa de estudos e pelo suporte financeiro.

Aos animais utilizados, todo o meu respeito, pois, sem eles a realização deste

trabalho não seria possível.

Aos muitos amigos que conquistei ao longo desses anos, àqueles que, devido as

circunstância, estão longe e também àqueles que continuam perto. Em especial ao

Felipe, ao Guilherme, ao Musa, ao Leopoldo, à Fran, à Liz e à Camila. Obrigada por

compartilharem comigo tantos momentos inesquecíveis.

Agradeço novamente e em especial, ao Félix pelo amor, carinho, amizade e

companhia em todos os momentos. Agradeço todos os dias por ter te conhecido.

Enfim agradeço à Universidade Federal de Santa Maria e ao Programa de Pós-

Graduação em Bioquímica Toxicológica pela possibilidade de realização deste curso.

SUMÁRIO

LISTA DE ABREVIATURAS................................................................................ vi

LISTA DE FIGURAS.............................................................................................. vii

APRESENTAÇÃO.................................................................................................. viii

RESUMO................................................................................................................. ix

ABSTRACT............................................................................................................. xi

1. INTRODUÇÃO.................................................................................................. 1

1.1. Neurolépticos.................................................................................................... 1

1.1.1. Histórico............................................................................................. 1

1.1.2. Discinesia Tardia............................................................................... 2

1.1.3. Hepatotoxicidade............................................................................... 4

1.2. Estresse Oxidativo............................................................................................ 6

1.3. Disseleneto de Difenila..................................................................................... 7

1.4. Valeriana officinalis.......................................................................................... 9

2. OBJETIVOS....................................................................................................... 11

3. ARTIGOS CIENTÍFICOS................................................................................ 12

3.1. Artigo 1............................................................................................................. 13

3.2. Artigo 2............................................................................................................. 48

4. DISCUSSÃO....................................................................................................... 84

5. CONCLUSÕES.................................................................................................. 90

6. REFERÊNCIAS BIBLIOGRÁFICAS............................................................. 91

vii

LISTA DE ABREVIATURAS

ALA – ácido 5’-aminolevulínico

δ-ALA-D – delta aminolevulinato desidratase

ALT – alanina aminotransferase

ATP – adenosina trifosfato

AST – aspartato aminotransferase

CAT – catalase

CYP – citocromo P450

DCFH – diclorofluoresceína

DO – discinesia orofacial

DT – discinesia tardia

DTT – DL-ditiotreitol

EROS – espécies reativas de oxigênio

GABA – ácido gama aminobutírico

GAD – ácido glutâmico descarboxilase

GPx – glutationa peroxidase

GSH – glutationa reduzida

GSSG – glutationa oxidada

MDA – ácido malondialdeído

NMDA – N-metil-D-aspartato

SOD – superóxido dismutase

TBARS – espécies reativas ao ácido tiobarbitúrico

viii

LISTA DE FIGURAS E TABELAS

Artigo 1

Figura 1. Effect of diphenyl diselenide and/or fluphenazine treatments on

TBARS production in liver (A) and kidney (B) homogenates……………………

Figura 2. Effect of diphenyl diselenide and/or fluphenazine treatments on δ-

ALA-D activity in liver homogenates (A) and on the enzyme reactivation index

(B)………………………………………………………………………………….

Figura 3. Effect of diphenyl diselenide and/or fluphenazine treatments on δ-

ALA-D activity in kidney homogenates (A) and on the enzyme reactivation

index (B)…………………………………………………………………………..

Figura 4. Effect of diphenyl diselenide and/or fluphenazine treatments on SOD

activity in liver (A) and kidney (B) homogenates…………………………………

Figura 5. Effect of diphenyl diselenide and/or fluphenazine treatments on CAT

activity in liver (A) and kidney (B) homogenates…………………………………

Artigo 2

Figura 1. Effects of valerian and/ or HP treatments on TBARS production in

liver (A) and kidney (B) homogenates…………………………………………….

Figura 2. Effects of valerian and/ or HP treatments on DCFH oxidation in liver

(A) and kidney (B) homogenates………………………………………………….

Figura 3. Effects of valerian and/ or HP treatments on δ-ALA-D activity in liver

homogenates (A) and on the enzyme reactivation index

(B)…………………………………………………………………………………

Figura 4. Effects of valerian and/ or HP treatments on δ-ALA-D activity in

kidney homogenates (A) and on the enzyme reactivation index

(B)…………………………………………………………………………………

Figura 5. Effects of valerian and/ or HP treatments on serum AST (A) and ALT

(B) activities……………………………………………………………………….

Figura 6. Effects of valerian and/ or HP treatments on GSH/GSSG ratio in liver

(A) and kidney (B) homogenates………………………………………………….

APRESENTAÇÃO

No item INTRODUÇÃO, está descrita uma sucinta revisão biblio gráfica sobr e

os temas trabalhados nesta dissertação.

Os resultados que fazem parte desta dissertação estão apresentados sob a forma

de artigos, os quais se encontram no item ARTIGOS CIENTÍFICOS. As seções

Materiais e Métodos, Resultados, Discussão dos Resultados e Referências

Bibliográficas, encontram-se nos próprios artigos e representam a íntegra deste estudo.

Os itens, DISCUSSÃO E CONCLUSÕES, encontram-se no final desta

dissertação, apresentam interpretações e comentários gerais sobre os artigos científicos

contidos neste trabalho.

As REFERÊNCIAS BIBLIOGRÁFICAS referem-se somente às citações que

aparecem nos itens INTRODUÇÃO, DISCUSSÃO e CONCLUSÕES desta

dissertação.

RESUMO

Dissertação de Mestrado

Programa de Pós-Graduação em Bioquímica Toxicológica

Universidade Federal de Santa Maria, RS, Brasil

AVALIAÇÃO DOS EFEITOS DO TRATAMENTO CRÔNICO COM

NEUROLÉPTICOS E SUA INTERAÇÃO COM SUBSTÂNCIAS

POTENCIALMENTE ANTIOXIDANTES SOBRE PARÂMETROS DE

ESTRESSE OXIDATIVO NO FÍGADO E RIM DE RATOS

AUTORA: Cristiane Lenz Dalla Corte

ORIENTADOR: Félix Alexandre Antunes Soares

CO-ORIENTADOR: João Batista Teixeira da Rocha

LOCAL E DATA DA DEFESA: Santa Maria, Março de 2008.

O tratamento com drogas neurolépticas tem sido associado a efeitos colaterais

como a discinesia tardia (DT) e o dano hepático. Apesar dos inúmeros casos de

hepatotoxicidade após a administração de neurolépticos, são escassos os dados na

literatura a respeito desses efeitos e o mecanismo exato pelo qual neurolépticos induzem

hepatotoxicidade permanece incerto. Da mesma forma, existem poucos estudos

relatando os efeitos dos neurolépticos sobre o rim. Dessa forma, o primeiro objetivo

deste trabalho foi avaliar os efeitos da exposição crônica à flufenazina em fígado e rim

de ratos bem como o efeito protetor do disseleneto de difenila sobre o dano induzido por

flufenazina (artigo 1). O tratamento prolongado com flufenazina causou um aumento na

peroxidação lipídica no fígado e no rim, uma diminuição na atividade da SOD hepática,

e um aumento na atividade da CAT hepática. O disseleneto de difenila foi capaz de

proteger o fígado e o rim da peroxidação lipídica, melhorou a atividade da SOD no

fígado, e preveniu o aumento na atividade da CAT no fígado. O tratamento com

disseleneto de difenila não afetou a atividade da δ-ALA-D, mas a flufenazina e/ou em

combinação com disseleneto de difenila demonstrou ter efeito inibitório sobre a

atividade da δ-ALA-D no fígado e no rim. O segundo objetivo deste estudo foi

determinar se o tratamento com haloperidol (HP), valeriana ou a associação de ambas as

drogas pode alterar as funções hepáticas e renais (artigo 2). A valeriana não afetou

nenhum parâmetro de estresse oxidativo no fígado e no rim dos ratos. O HP apenas

aumentou a depleção de glutationa (GSH) no fígado, mas não no rim. Entretanto,

quando o HP foi associado com a valeriana, um aumento na peroxidação lipídica e

produção de espécies reativas foram observados no tecido hepático. HP e valeriana

quando administrados independentemente não afetaram a atividade da δ-ALA-D

hepática e renal, contudo, quando estas drogas foram administradas concomitantemente

provocaram uma inibição da atividade da δ-ALA-D hepática. A atividade da aspartato

aminotransferase (AST) do soro não foi alterada por nenhum dos tratamentos. No

entanto, a atividade da alanina aminotransferase (ALT) do soro estava aumentada nos

grupos tratados com HP e HP mais flufenazina. Juntos estes resultados indicam uma

relação entre o tratamento com flufenazina e o estresse oxidativo, e também apontam

para o papel protetor do disseleneto de difenila no dano oxidativo induzido por

flufenazina no fígado. Nossos dados também sugerem interações adversas no tratamento

com haloperidol e valeriana, ocasionando dano hepático associado ao estresse oxidativo.

Palavras-chave: flufenazina; selênio; disseleneto de difenila; haloperidol; Valeriana

officinalis; interação planta medicinal-fárm aco; estresse oxidativo; TBARS; δ-ALA-D.

xii

ABSTRACT

Dissertation of Master’s Degree

Graduate Course in Toxicological Biochemistry

Federal University of Santa Maria, RS, Brazil

ASSESSMENT OF THE EFFECTS OF CHRONIC TREATMENT WITH

NEUROLEPTICS AND THEIR INTERACTION WITH POTENTIALLY

ANTIOXIDANTS SUBSTANCES ON OXIDATIVE STRESS

PARAMETERS IN LIVER AND KIDNEY OF RATS

AUTHOR: Cristiane Lenz Dalla Corte

ADVISOR: Félix Alexandre Antunes Soares

CO-ADVISOR: João Batista Teixeira da Rocha

PLACE AND DATE OF THE DEFENSE: Santa Maria, March, 2008.

Treatment with neuroleptic drugs has been associated to side effects like tardive

diskynesia and hepatic damage. In spite of the several reports of hepatotoxicity after

neuroleptic administration, few data are available in the literature about these effects

and the precise mechanisms by which neuroleptics induce hepatotoxicity remain

unclear. In the same way, there are few studies about the effects of neuroleptics on

kidney. In this way, the first aim of the present work was to assess the effects of chronic

exposure to fluphenazine in liver and kidney of rats, as well as the protective effect of

diphenyl diselenide on the fluphenazine-induced damage (article 1). Long-term

treatment with fluphenazine caused an increase in lipid peroxidation levels in liver and

kidney homogenates, a decrease in hepatic SOD activity, and an increase in hepatic

CAT activity. Diphenyl diselenide was able to protect liver and kidney from lipid

peroxidation, ameliorate SOD activity in liver, and prevent the increase in hepatic CAT

activity. Diphenyl diselenide treatment did not affect δ-ALA-D activity, but

fluphenazine and/or in combination with diphenyl diselenide showed an inhibitory

effect on δ-ALA-D activity in liver and kidney. The second objective of this study was

to determine whether the treatment with haloperidol (HP), valerian or both in

association impairs liver or kidney functions (article 2). Valerian did not affect

oxidative stress parameters in the liver or kidney of rats. HP only increased glutathione

(GSH) depletion in liver, but not in kidney. However, when HP was associated with

valerian, an increase in lipid peroxidation levels and reactive species production was

observed in the hepatic tissue. HP and valerian when administered independently did

not affect the activity of hepatic and renal δ-ALA-D, however, these drugs administered

concomitantly provoked an inhibition of hepatic δ-ALA-D activity. Serum aspartate

aminotransferase (AST) activity was not altered by any treatment. However, serum

alanine aminotransferase (ALT) activity was higher in the HP group and HP plus

valerian group. Taken together, these results indicate the relationship between the

treatment with flufenazine and the oxidative stress, and also point to the protective role

xiii

of diphenyl diselenide on the oxidative damage induced by fluphenazine in liver. Our

data also suggest adverse interactions between haloperidol and valerian treatments

causing hepatic damage related to oxidative stress.

Keywords: fluphenazine; selenium; diphenyl diselenide; haloperidol; Valeriana

officinalis; herb-drug interaction; oxidative str ess; TBARS; δ-ALA-D.

1. INTRODUÇÃO

1.1. Neurolépticos

1.1.1. Histórico

Neurolépticos ou antipsicóticos são drogas utilizadas no tratamento de doenças

psiquiátricas graves, assim como, das psicoses e da mania. A descoberta do primeiro

antipsicótico, a clorpromazina, deu-se, em parte, ao acaso em 1950 por Laborit. No

entanto as primeiras tentativas de tratar as doenças mentais com clorpromazina foram

feitas por Delay e Deniker em 1952. Apesar do surgimento dos neurolépticos ter

representado um dos mais importantes avanços na história da psicofarmacologia e

psiquiatria, estes fármacos possuem eficácia comprometida devido ao surgimento de

efeitos colaterais extrapiramidais como a Discinesia Tardia (DT) e o Parkisonismo.

Atualmente, os esforços concentram-se na busca por drogas com menos efeitos

extrapiramidais e mais eficientes nos tratamento dos sintomas negativos da

esquizofrenia. Estas drogas são denominadas neurolépticos atípicos dentre os quais o

principal é a clozapina (Goodman, 2004; Silva, 2006).

As drogas antipsicóticas são agrupadas em antipsicóticos convencionais (ex.:

clorpromazina, flufenazina, haloperidol) e antipsicóticos atípicos (ex.:clozapina,

olanzapina). As diferenças entre ambos os grupos são definidas em termos clínicos e

farmacológicos. Clinicamente, drogas antipsicóticas atípicas causam menos efeitos

extrapiramidais, e são mais efetivos que as drogas convencionais em tratar os sintomas

negativos da esquizofrenia (ex.: isolamento social, embotamento afetivo) (Konradi e

Heckers, 2003). Farmacologicamente, os antipsicóticos convencionais, tais como o

haloperidol, tem maior afinidade por receptores D

(Levinson, 1991), enquanto

antipsicóticos atípicos como a clozapina tem afinidade por múltiplos sistemas de

receptores, incluindo os receptores D

(Remington e Chong, 1999). As drogas

antipsicóticas atuam primariamente sobre os sistemas dopaminérgicos e

serotoninérgicos (5-HT), e embora elas tenham efeitos diretos sobre o sistema

glutamatérgico, em geral estes efeitos são pequenos. Entretanto, através da sua interação

com sistemas monoaminérgicos, as drogas antipsicóticas podem modular a função

glutamatérgica através de um potente mecanismo indireto (Leveque e cols., 2000).

Estudos relataram que a potência clínica das drogas antipsicóticas convencionais

está diretamente relacionada com a sua afinidade por receptores dopaminérgicos D

(Seeman e Lee, 1975; Creese e cols., 1976; Seeman e Van Tol, 1993). Drogas

antipsicóticas convencionais inibem os receptores D

provocando, incialmente, no

neurônio pré-sináptico, aumento na produção e liberação de dopamina, por aumento de

atividade da enzima tirosina hidroxilase, na tentativa de vencer o bloqueio (Silva, 2006).

Os neurolépticos fenotiazínicos que apresentam um grupamento piperazínico

constituem alguns dos antipsicóticos mais potentes, é o caso da flufenazina. Estes

compostos apresentam atividade anticolinégica relativamente fraca, têm menor

tendência para produzir sedação e causam menos efeitos autonômicos, no entanto

possuem um acentuado risco de induzir efeitos extrapiramidais. Outra classe de

neurolépticos, as butirofenonas incluem o haloperidol. São drogas antipsicóticas

potentes, e frequentemente produzem sintomas extrapiramidais, possívelmente em

decorrência de sua baixa atividade anticolinérgica (Goodman, 2004; Silva, 2006).

1.1.2. Discinesia Tardia

Os efeitos colaterais mais prevalentes e incômodos associados ao uso de

neurolépticos envolvem o sistema motor extrapiramidal. O surgimento destes efeitos é

mais pronunciado nas drogas com menor ação anticolinérgica como butirofenonas

(haloperidol) e fenotiazinas piperazínicas (flufenazina). A DT pode surgir após meses

ou até anos após o uso de neurolépticos (Crane, 1973; Jeste e cols., 1979; Casey, 1985;

Glazer e cols., 1990), e manifesta-se através de movimentos orofaciais involuntários e

estereotipados, que pioram com a suspensão do tratamento. A DT ocorre em 20-25%

dos pacientes que recebem tratamento com neurolépticos clássicos. Esta razão aumenta

consideravelmente com a idade, uma prevalência acima de 50% foi descrita pra

pacientes com mais de 50 anos (Kane e Smith, 1982; Woerner e cols., 1991; Yassa e

Jeste, 1992).

Várias hipóteses têm sido propostas para explicar a fisiopatologia da DT, e é

possível que mecanismos diferentes estejam envolvidos no seu desenvolvimento. Uma

das hipóteses que têm recebido grande atenção nas últimas duas décadas é a da

hipersensibilidade dopaminérgica. Segundo esta hipótese, a DT é resultante de uma

supersensibilidade dopaminérgica devido ao bloqueio crônico dos receptores

dopaminérgicos pelos neurolépticos, em locais relacionados ao controle dos

movimentos (Klawans e Rubovits, 1972; Burt e cols., 1977; Rubinstein e cols., 1990).

Em resposta a este bloqueio crônico, há um aumento compensatório do número e

sensibilidade dos receptores dopaminérgicos levando a um estado hiperdopaminérgico e

a manifestações clínicas como, por exemplo, a DT (Cavallaro e Smeraldi, 1995; Kane,

1995). Essa hipótese, no entanto, possui algumas limitações, pois, não consegue

explicar porque a DT se desenvolve apenas em alguns pacientes, porque demora anos

para se desenvolver, porque persiste mesmo após a interrupção do tratamento, e porque

alguns fatores como idade, gênero, diabetes mellitus, etc. aumentam seu risco (Smith,

1988; Sachdev e cols., 1999).

Uma das primeiras hipóteses propostas para a DT diz respeito a alterações na

transmissão gabaérgica provocada por neurolépticos nos glânglios da base (Fibiger e

Lloyd, 1984). Esta hipótese baseia-se em relatos de que macacos e ratos com

movimentos orofaciais induzidos por neurolépticos apresentavam diminuição na

atividade da enzima glutamato descarboxilase (GAD) na substantia nigra, no globus

palidus e no núcleo subtalâmico (Gunne e Haggstrom, 1983; Gunne e cols., 1984;

Johansson e cols., 1990). Estudos em ratos onde agonistas gabaérgicos inibiram o

desenvolvimento de movimentos de mascar no vazio induzidos por neurolépticos

também corroboram com esta hipótese (Kaneda e cols., 1992; Gao e cols., 1994).

Outra hipótese proposta é da excitotoxicidade. Esta hipótese propõe que a

utilização em longo prazo de neurolépticos aumenta a liberação de glutamato a partir

dos terminais córtico-estriatais levando a excitotoxicidade estriatal (De Keyser, 1991).

O envolvimento da excitotoxicidade no dano neuronal agudo já é bem descrito, no

entanto o exato mecanismo para a excitotoxicidade na neurodegeneração crônica e DT

permanece a ser esclarecido. Uma possibilidade é o prejuízo do metabolismo energético

o qual é um dos efeitos dos neurolépticos convencionais (Burkhardt e cols., 1993). A

interrupção da síntese de ATP leva a diminuição do potencial de membrana que facilita

a ativação de receptores NMDA devido ao menor bloqueio do Mg

dependente da

voltagem. Dessa forma, níveis fisiológicos de glutamato podem induzir um influxo de

excessivo o qual desencadeia uma cascata de reações tóxicas levando à morte

celular (Novelli e cols., 1988).

Um mecanismo que vem ganhando reconhecimento nos últimos anos é a

hipótese dos radicais livres. Os neurolépticos induzem um aumento no “turnover” de

dopamina (See, 1991) o que pode levar a superprodução de espécies reativas de

oxigênio (EROS)

(Andreassen e Jorgensen, 2000). Estes níveis aumentados de EROS

podem afetar negativamente a neurotransmissão e a viabilidade celular (Andreassen e

Jorgensen, 2000). Vários estudos dão suporte a esta hipótese: 1) relatos da redução nos

ácidos graxos essenciais em fosfolipídios no plasma de pacientes com DT (Horrobin e

cols., 1989); 2) aumento nos níveis de peroxidação lipídica no fluído cerebroespinhal de

pacientes com DT (Lohr e cols., 1990); 3) possíveis efeitos benéficos da vitamina E e

outros antioxidantes na DT (Egan e cols., 1997; Burger e cols., 2003; Burger e cols.,

2005; Burger e cols., 2006); e 4) o papel da idade, diabetes, fumo, e dano cerebral como

fatores de risco (Sachdev e cols., 1999; Burger e cols., 2004).

1.1.3. Hepatotoxicidade

A estratégia para a escolha de um agente antipsicótico deve tomar em conta a

tolerância hepática com base na significante incidência de desordens hepáticas entre a

população (presença de fatores de risco como alcoolismo, drogas de abuso,

polimedicação incluindo drogas potencialmente hepatotóxicas, etc). Nos Estados

Unidos, em 2003, a injúria hepática induzida por drogas foi responsável por mais de 50

% dos casos de falência hepática aguda (Lee, 2003). A lista de fármacos capazes de

provocar efeitos colaterais hepáticos inclui mais de mil medicamentos, dos quais 16%

são drogas neuropsiquiátricas incluindo os neurolépticos (Dumortier e cols., 2002).

Elevações da atividade de enzimas hepáticas ocorrem frequentemente com drogas

fenotiazínicas (freqüência avaliada em 20%), mas também com outras classes de

agentes neurolépticos. Por outro lado, a hepatite clínica é mais raramente descrita para

drogas neurolépticas como as fenotiazínas (0,1-1 %) ou como o haloperidol (0,002 %)

(Dumortier e cols., 2002).

O mecanismo exato pelo qual neurolépticos induzem hepatotoxicidade

permanece incerto (Selim e Kaplowitz, 1999; Dumortier e cols., 2002). Uma substância

pode ser intrinsecamente hepatotóxica, ou então pode dar origem a um metabólito

tóxico, que o tecido hepático pode ter ou não capacidade de depurar. O citocromo P450,

uma família de enzimas largamente envolvida em reações oxidativas no metabolismo

das drogas, é responsável pela produção de intermediários altamente reativos. Assim

xenobióticos podem sofrer bioativação em eletrófilos e radicais livres e provocar

toxicidade pela modificação de macromoléculas celulares (Kaplowitz, 1996; Park e

cols., 2005). Dessa forma, os metabólitos das drogas podem participar de uma série de

reações químicas, como depleção da glutationa (GSH), ligação covalente com proteínas,

lipídios, ou ácidos nucléicos, ou indução de peroxidação lipídica. Todos estes eventos

têm efeitos diretos sobre as organelas celulares e podem também influenciar

indiretamente as organelas através da ativação e inibição de quinases sinalizadoras,

fatores de transcrição e da expressão gênica (Park e cols., 2005). O estresse intracelular

resultante leva à morte celular causada tanto por apoptose quanto por necrose

(Kaplowitz, 2000; 2002). A morte do hepatócito é o principal evento que leva à injúria

hepática, embora as células endoteliais sinusoidais (DeLeve e cols., 1996) e o epitélio

do ducto biliar (Odin e cols., 2001) também possam ser alvos.

Alguns fatores podem aumentar o risco de hepatotoxicidade como o uso

concomitante de compostos que causam indução ou inibição do citocromo P450

hepático (Gopaul, 2003) o que pode interferir no metabolismo e eliminação dos

fármacos. A proliferação de terapias alternativas e produtos naturais, por exemplo,

podem ter conseqüências deletérias. Fitoterápicos são considerados equivocadamente

pela população em geral como medicamentos seguros (Eisenberg e cols., 1998; Haller e

cols., 2002), no entanto, interações indesejáveis podem ocorrer entre fitoterápicos e

drogas convencionais e, portanto, deve se ter cautela com esse tipo de associação (Fugh-

Berman e Ernst, 2001).

1.2. Estresse Oxidativo

O balanço entre substâncias pró-oxidantes e antioxidantes é crucial para a

sobrevivência e funcionamento dos organismos aeróbicos. Um desequilíbrio

favorecendo pró-oxidantes e/ou desfavorecendo antioxidantes é denominado estresse

oxidativo sendo potencialmente nocivo (Sies, 1986).

As substâncias pró-oxidantes são naturalmente formadas como produtos do

metabolismo aeróbico, mas durante condições patológicas estas são produzidas em

níveis elevados. Radicas livres podem ser definidos como moléculas ou fragmentos de

moléculas contendo um ou mais elétrons desemparelhados em orbitais atômicos ou

moleculares (Halliwell e Gutteridge, 1999). Os elétrons desemparelhados usualmente

conferem um considerável grau de reatividade aos radicais livres. Radicais derivados de

oxigênio representam a mais importante classe de espécies radicais geradas em sistemas

vivos (Miller e cols., 1990). Os passos intermediários da redução do oxigênio consistem

na formação do radical ânion superóxido, peróxido de hidrogênio e radical hidroxila

correspondendo aos passos de redução por um, dois e três elétrons, respectivamente

(Halliwell e Gutteridge, 1999). Os radicais de oxigênio também podem ocorrer como

radicais alquila e peroxila, (ex.: em lipídios). Outro radical, o óxido nítrico, pode reagir

com o radical ânion superóxido formando o ânion peroxinitrito, o qual é altamente

reativo (Sies, 1997).

As estratégias de defesa fisiológicas e farmacológicas contra as substâncias pró-

oxidantes consistem em três categorias: prevenção, interceptação e reparo. A primeira

linha de defesa contra as espécies reativas é a prevenção contra a sua formação por

meios físicos ou bioquímicos. Na segunda linha de defesa, e interceptação, encontram-

se antioxidantes enzimáticos e não-enzimáticos. As defesas antioxidantes enzimáticas

incluem as enzimas supéroxido dismutase (SOD), glutationa peroxidase (GPx), catalase

(CAT). Os antioxidantes não enzimáticos são representados por ácido ascórbico

(vitamina C), α-tocoferol (vitamina E), glutationa (GSH), carotenóides e flavonóides

(Sies, 1997; Valko e cols., 2007). A proteção contra os efeitos do estresse oxidativo

também pode se dar pelo reparo do dano uma vez que este tenha ocorrido (reparo do

DNA, modificações no “turnover” de lipídios, proteólise) (Sies, 1993).

As EROS são bem conhecidas por desempenharem um papel duplo como

espécies deletérias e benéficas. Os efeitos benéficos das EROS ocorrem em

concentrações baixas a moderadas e envolvem papeis fisiológicos na resposta celular à

noxia, como por exemplo, na defesa contra agentes infecciosos, no funcionamento de

diversas vias de sinalização celular, e na indução de resposta mitogênica (Valko e cols.,

2007). Em contraste, em altas concentrações as EROS podem danificar lipídios das

células, proteínas ou DNA, inibindo a sua função normal. Devido a isso, o estresse

oxidativo tem sido implicado em várias doenças bem como no processo de

envelhecimento (Kovacic e Jacintho, 2001; Valko e cols., 2006; 2007).

1.3. Disseleneto de Difenila

Desde a descoberta da presença do elemento selênio, um calcogênio, no centro

ativo das enzimas antioxidantes glutationa peroxidase (GPx) e glutationa peroxidase de

hidroperóxidos lipídicos (PHGPx), os compostos orgânicos de selênio vêm despertando

grande interesse (Rotruck e cols., 1973; Nogueira e cols., 2004). Devido as possíveis

aplicações no tratamento de doenças, novos compostos orgânicos de selênio com

atividade mimética da GPx passaram a ser sintetizados e estudados (Parnham e Graf,

1991; Mugesh e cols., 2001; Nogueira e cols., 2004).

O Ebselen (2-fenil-1,2-benzisoselenazol-3[2H]-ona) é um composto orgânico de

selênio não tóxico que tem sido extensivamente estudado na última década. O interesse

particular neste composto é sua atividade mimética da GPx, especialmente da PHGPx

(Wendel e cols., 1984; Müller e cols., 1985; Nogueira e cols., 2002; Klotz e cols.,

2003). Além da atividade antioxidante, o ebselen demonstrou possuir propriedades

antiinflamatória, antinociceptiva, neuroprotetora e anti-úlcera em vários modelos

animais (Maiorino e cols., 1992; Nogueira e cols., 2004). O fígado é outro alvo

terapêutico dos compostos orgânicos de selênio. O Ebselen protegeu contra o dano

hepático induzido por paracetamol, CCl

, lipopolissacarídio e Propionibacterium acnes,

etanol, e injúria por isquemia-reperfusão (Li e cols., 1994; Ozaki e cols., 1997; Kono e

cols., 2001; Koyanagi e cols., 2001; Wasser e cols., 2001).

O disseleneto de difenila, outro composto orgânico de selênio, demonstrou ter

maior atividade tiol-peroxidase que o Ebselen (Wilson e cols., 1989), além de ser menos

tóxicos a roedores (Meotti e cols., 2003; Nogueira e cols., 2003a). O disseleneto de

difenila também possui potenciais antinociceptivo e antiflamatório melhores que o

ebselen (Nogueira e cols., 2003b). O disseleneto de difenila foi testado em vários

modelos de neuroproteção apresentando bons resultados (Ghisleni e cols., 2003;

Nogueira e cols., 2004). Em um modelo agudo de discinesia orofacial (DO), o

disseleneto de difenila protegeu contra a DO e a peroxidação lipídica em cérebro

causada pela administração de reserpina em ratos (Burger e cols., 2004). Da mesma

forma outro estudo demonstrou a proteção do disseleneto de difenila contra a DO em

um tratamento agudo com haloperidol (Burger e cols., 2006). Além disso, pré- e pós-

tratamentos com disseleneto de difenila foram efetivos em proteger contra o dano

hepático induzido por 2-nitropropano (Borges e cols., 2005; 2006).

O mecanismo catalítico para a ação dos compostos orgânicos de selênio é a

interação direta com tióis de baixo peso molecular oxidando-os a dissulfetos ao mesmo

tempo em que decompõem H

(Maiorino e cols., 1988; Nogueira e cols., 2004).

Embora a atividade do tipo tiol-peroxidase dos compostos orgânicos de selênio seja

importante para suas propriedades antioxidantes, também pode contribuir para suas

propriedades toxicológicas devido à oxidação de proteínas e metabólitos tióis

importantes. No caso de enzimas isto pode resultar na perda da atividade catalítica

(Nogueira e cols., 2004). Um exemplo disso é a enzima δ-aminolevulinato desidratase

(δ-ALA-D) uma enzima sulfidrílica extremamente sensível a agentes oxidantes

(Barbosa e cols., 1998; Folmer e cols., 2002; 2003; Soares e cols., 2003; Santos e cols.,

2005) que catalisa a condensação de duas moléculas do ácido 5’-aminolevulínico

(ALA) para formar o porfibilinogênio. Trabalhos demonstram que o tratamento agudo

com o composto disseleneto de difenila inibe a atividade da enzima δ-ALA-D devido à

oxidação dos resíduos cisteinil presentes no sítio ativo da enzima (Farina e cols., 2002).

1.4. Valeriana officinalis

A valeriana (Valeriana officinalis L., Valerianaceae) é uma das plantas

medicinais mais utilisadas em todo o mundo (Blumenthal, 2003; Gutierrez e cols.,

2004). É conhecida e utilizada há séculos devido a suas propriedades calmante,

sedativa, ansiolítica, entre outras (Houghton, 1999; Stevinson e Ernst, 2000; Krystal e

Ressler, 2001). Os extratos de valeriana são vendidos como suplementos dietéticos e

estiveram entre os 10 suplementos fitoterápicos mais vendidos nos Estados Unidos em

2002 (Blumenthal, 2003).

Atualmente não existe concordância no meio científico quanto ao mecanismo

pelo qual a valeriana ou seus compostos, exerce sua atividade sedativa, ou os compostos

responsáveis por esta atividade. Diversos estudos apontam para um mecanismo de ação

gabaérgico para esta planta. Valeriana pode interagir com receptores GABA

ativando-

os (Mennini e cols., 1993; Cavadas e cols., 1995; Ortiz e cols., 2004). Também parece

diminuir a degradação do ácido gama aminobutírico (GABA) (Houghton, 1999). O

aumento da concentração de GABA na fenda sináptica é um fator responsável pelas

propriedades sedativas da valeriana. Extratos de valeriana e ácido valerênico parecem

também ter efeito agonista parcial sobre receptores serotoninérgicos (Dietz e cols.,

2005). Além dos seus efeitos sedativos, um trabalho recente demonstrou que o extrato

de V. officinalis possui atividade antioxidante em baixas concentrações em um modelo

in vitro (Rocha e cols., dados não publicados).

Dados recentes demonstraram o efeito indutor da valeriana sobre as enzimas

citocromo P450 3A4 e 2D6 em culturas de hepatócitos de humanos (Hellum e cols.,

2006). Este efeito da valeriana sobre a atividade das enzimas citocromo P450 é

particularmente importante, pois pode afetar a disponibilidade de drogas convencionais

quando valeriana e a droga forem usadas concomitantemente. Vários relatos de casos

clínicos indicaram que a valeriana pode causar alterações nas funções hepáticas (Chan,

1998). Em alguns desses relatos de possível toxicidade hepática da valeriana, o

consumo foi geralmente crônico e, em alguns casos, outras plantas também foram

consumidas. Acredita-se que problemas hepáticos associados ao uso agudo de valeriana

sejam improváveis, no entanto, é possível que a valeriana em longo prazo, sozinha ou

em associação com outras plantas ou outras drogas possa causar hepatotoxicidade (Chan

e cols., 1995; Willey e cols., 1995; Chan, 1998).

2. OBJETIVOS

Objetivo Geral

Avaliar os efeitos de tratamentos crônicos com neurolépticos e suas interações

com disseleneto de difenila e V. officinalis sobre parâmetros de estresse oxidativo em

fígado e rim de ratos.

Objetivos Específicos

1- Avaliar o efeito de tratamentos com neurolépticos e suas interações com

disseleneto de difenila e V. officinalis sobre a atividade da enzima δ-ALA-D em fígado

e rim de ratos;

2- Investigar o efeito de tratamentos com neurolépticos e suas interações com

disseleneto de difenila e V. officinalis sobre parâmetros de estresse oxidativo e o status

antioxidante em fígado e rim de ratos;

3- Verificar a atividade das enzimas aspartato aminotransferase (AST) e alanina

aminotransferase (ALT) no soro de ratos tratados com haloperidol, V. officinalis ou a

associação dos dois compostos.

3. ARTIGOS CIENTÍFICOS

Os resultados que fazem parte desta dissertação estão apresentados sob a forma

de artigos científicos, os quais se encontram aqui organizados. Os itens Materiais e

Métodos, Resultados, Discussão dos Resultados e Referências Bibliográficas,

encontram-se nos próprios artigos. O artigo 1 e o artigo 2 estão dispostos na forma em

que foram submetidos para publicação.

3.1. – O TRATAMENTO CRÔNICO COM FLUFENAZINA ALTERA

PARÂMETROS DE ESTRESSE OXIDATIVO EM FÍGADO E RIM DE RATOS

Artigo 1

CHRONIC TREATMENT WITH FLUPHENAZINE ALTERS PARAMETERS

OF OXIDATIVE STRESS IN LIVER AND KIDNEY OF RATS

DALLA CORTE, C.L., FACHINETTO, R., PUNTEL, R., WAGNER, C., NOGUEIRA,

C.W., SOARES, F.A.A., ROCHA, J.B.T.

(Submetido à Archives of Toxicology)

Chronic treatment with fluphenazine alters parameters of oxidative stress

in liver and kidney of rats

Cristiane L. Dalla Corte, Roselei Fachinetto, Robson Puntel, Caroline Wagner,

Cristina W. Nogueira, Félix A. Antunes Soares

and João B. T. Rocha.

Universidade Federal de Santa Maria, Centro de Ciências Naturais e Exatas,

Departamento de Química, Programa de Pós-graduação em Ciências

Biológicas: Bioquímica Toxicológica, Camobi, Cep 97105-900, Santa Maria,

RS, Brasil.

Corresponding author:

Félix Alexandre Antunes Soares

UFSM – CCNE- Dep de Química

Cep 97105-900, Camobi, Santa Maria, RS, Brasil

Tel: #55-55-3220-9522

Fax: #55-55-3220-8978

e-mail: [email protected]

Abstract

The aim of this study was to assess the toxic effects of chronic exposure

to fluphenazine in liver and kidney of rats, as well as the protective effect of

diphenyl diselenide on the fluphenazine-induced damage. Treatment with

fluphenazine caused an increase in lipid peroxidation levels in liver and kidney

homogenates, a decrease in hepatic SOD activity, and an increase in hepatic

CAT activity. Diphenyl diselenide was able to protect liver and kidney from lipid

peroxidation, ameliorate SOD activity in liver, and prevent the increase in

hepatic CAT activity. Diphenyl diselenide treatment did not affect δ-

aminolevulinate dehydratase (δ-ALA-D) activity, but fluphenazine alone or in

combination with diphenyl diselenide showed an inhibitory effect on δ-ALA-D

activity in liver and kidney. Diphenyl diselenide and fluphenazine treatment

increased the reactivation index of hepatic δ-ALA-D. Taken together, these

results indicate a relationship between the oxidative stress and fluphenazine

treatment in liver and kidney of rats.

Key words: Fluphenazine; selenium; oxidative stress; δ-ALA-D; TBARS.

Introduction

Fluphenazine is one of the three antipsychotic drugs enlisted in the

recent (14

) World Health Organization Model List of Essential Medicines

(Ozdemir et al. 2006). However, the use of this first-generation antipsychotic

medication can be associated with tardive dyskinesia (TD), a debilitating

involuntary hyperkinetic movement disorder, in 20 – 50% of individuals with a

psychotic illness during chronic treatment (Creese et al. 1976; Gunne et al.

1986; Ozdemir et al. 2006; See et al. 1992). Of particular importance, the use of

fluphenazine and the symptoms of TD in humans or orofacial dyskinesia (OD) in

rodents have been associated with oxidative stress (Abílio et al. 2004; Burger et

al. 2003; Cadet et al. 1986; Lohr et al. 1988, 1990).

The use of phenothiazines like fluphenazine has been associated with

hepatic injury (Ishak and Irey 1972; Jones et al. 1983; Regal et al. 1987).

Indeed, agranulocytosis and the release of transaminase enzymes from liver

cells are described as consequences of neuroleptic drug use (Munyon et al.

1987). Zimmerman (1968) reported elevations of serum aspartate

aminotransferase (AST) and serum alanine aminotransferase (ALT) on persons

taking chlorpromazine, a phenothiazine derivative. The available evidence

suggests that the release of AST and ALT can be due to the direct cytotoxic

effect of phenothiazines on liver cells (Dujovne and Zimmerman 1969). Isolated

elevations of hepatic enzymes occur frequently with phenothiazine drugs

(frequency evaluated to 20%) (Dumortier et al. 2002). In this vein, literature has

indicated that phenothiazine causes cytotoxicity in hepatocytes, which can be

prevented by the antioxidants (Eghbal et al. 2004).

Seleno-organic compounds have been studied based on their potential

antioxidant properties (Mugesh et al. 2001; Rayman 2000). In fact, this class of

compounds exhibits glutathione peroxidase-like activity and oxidizes sulfhydryl

groups (-SH) during the reduction of H

(Klotz et al. 2003; Muller et al. 1985;

Nogueira et al. 2002; Wendel et al. 1984). Of particular importance, ebselen has

antioxidant properties in a variety of in vitro and in vivo models of neurotoxicity

in rats (Imai et al. 2001; Moussaoui et al. 2000; Namura et al. 2001; Porciúncula

et al. 2001; Roet ej7Ea.500oj7Ea.50.004).3

term treatment with fluphenazine in rats (Fachinetto et al. 2007). Furthermore,

diphenyl diselenide has a protective role in a variety of experimental models

associated with the overproduction of free radicals in the brain, liver, and kidney

(Borges et al. 2005, 2006; Burger et al. 2004; Ghisleni et al. 2003; Rossato et

al. 2002; Santos et al. 2005a). In contrast, several researches have

demonstrated that liver is a target of selenorganic compound actions, as well as

the various clinical conditions in which hydroperoxides play a role (Nogueira et

al. 2004).

δ-Aminolevulinate dehydratase (δ-ALA-D) is a sulfhydryl-containing

enzyme highly susceptible to oxidizing agents and is inhibited in different pro-

oxidant situations (Barbosa et al. 1998; Farina et al. 2002; Folmer et al. 2002,

2003; Gonçalves et al. 2005; Santos et al. 2005b; Soares et al. 2003). The

inhibition of δ-ALA-D may impair the heme biosynthesis and may result in the

accumulation of aminolevulinic acid (ALA) that has been demonstrated to be a

pro-oxidant molecule under significant physiological conditions (Bechara et al.

1993; Bechara 1996; Emanuelli et al. 2001). Based on this, δ-ALA-D can be

suggested as a marker of oxidative stress.

The hepatotoxicity mechanism of phenothiazines is not completely

understood but may involve a combination of physiochemical, immuno-allergic,

and oxidative stress induced toxicity (Dumortier 2002; Eghbal et al. 2004; Regal

1987). In spite of the several reports of hepatic injury of phenothiazinic drugs,

few data are available about their effects on kidney or whether oxidative stress

could be involved on these effects. In this way, the rationale for this study was

to evaluate the oxidative stress in liver and kidney of rats chronically treated

with fluphenazine, a phenothiazine, as well as to assess the potential protective

effect of diphenyl diselenide on the fluphenazine-induced damage.

Materials and Methods

Chemicals

Fluphenazine enantate (Flufenan®) was kindly donated by Cristália

(Brazil). Diphenyl diselenide was synthesized by the method previously

described (Paulmier 1986). Thiobarbituric acid, aminolevulinic acid, and DL-

dithiothreitol (DTT) were obtained from Sigma (St. Louis, MO, USA). HgCl

NaCl, K

HPO

, KH

, trichloroacetic acid (TCA), para-

dimethylaminobenzaldehyde, and glacial acetic acid were purchased from

Reagen (Rio de Janeiro, RJ, Brazil). All other chemicals were purchased from

Merck (Darmstadt, Germany).

Animals

Male Wistar rats weighing 270–320 g and with age from 3 to 3.5 months

from our own breeding colony were kept in cages of three or four animals each.

They were placed in a room with controlled temperature (22±3°C) on a 12-h

light/dark cycle with lights on at 7:00 A.M, and had continuous access to food

and water. The animals were maintained and used in accordance to the

guidelines of the Brazilian Association for Laboratory Animal Science.

Treatment

For chronic treatment, rats were divided into control, diphenyl diselenide,

fluphenazine, and fluphenazine plus diphenyl diselenide groups. Fluphenazine

enantate was administered intramuscularly (i.m.) every 21 days (25 mg/kg,

i.m.). Diphenyl diselenide was dissolved in soy oil and administered

subcutaneously (s.c.) three times per week in nonconsecutive days (1 mg/kg,

s.c.). The control group received soy oil (1 mL/kg) in the same way as the

diphenyl diselenide group. The treatment was carried out over the course of 6

months and was based on previous studies (See et al. 1992; Van Kampen and

Stoessl 2000; Burger et al. 2006; Fachinetto et al. 2007).

Animals were divided into four groups of 9 animals each:

Control: received soy oil (1mL/kg) every 21 days (i.m.) and 3 times a

week in alternating days (s.c.);

Diphenyl diselenide: received diphenyl diselenide 3 times a week in

alternating days (1mg/kg, s.c.), and the vehicle (1mL/kg soy oil) was

administered at each 21 days (i.m.);

Fluphenazine: received fluphenazine enantate at each 21 days (25

mg/kg, i.m.), and the vehicle (1mL/kg soy oil) was administered 3 times a week

in alternating days (s.c.);

Combined treatment: received fluphenazine enantate at each 21 days

(25 mg/kg, i.m.), and diphenyl diselenide 3 times a week in alternating days

(1mg/kg, s.c.).

Tissue preparation

Animals were killed by decapitation. Liver and kidney were quickly

removed, placed on ice, and homogenized at 7 and 5 volumes of 0.9% NaCl,

respectively. The homogenates were centrifuged at 4,000 x g for 10 min to yield

a low-speed supernatant fraction (S1) that was used for the biochemical and

enzymatic assays. In order to perform SOD and CAT assays, S1 was diluted as

described in the respective sections.

Lipid peroxidation assay

Thiobarbituric acid reactive species (TBARS) were determined as

described by Ohkawa et al. (1979). In brief, samples were incubated at 100 ºC

for 1 h in a medium containing 8.1 % sodium dodecyl sulfate, 1.4 M acetic acid,

pH 3.4, and 0.6% thiobarbituric acid. The pink chromogen produced by the

reaction of thiobarbituric acid with malondialdehyde (MDA), a secondary

product of lipid peroxidation, was measured spectrophotometrically at 532 nm.

Results were expressed as nmol of MDA/ gram of tissue.

Enzyme assay

-ALA-D activity

δ-ALA-D activity was assayed according to the method of Sassa (1982)

by measuring the rate of product (porphobilinogen/PBG) formation. The reaction

product was determined using modified Ehrlich’s reagent at 555 nm with a

molar absorption coefficient of 6.1×10

-1

for the Ehrlich-PBG salt. The

incubation medium contained δ-ALA 2.4 mM and potassium phosphate buffer

(pH 6.8) 0.084 M. The reaction was initiated by the addition of enzymatic

material and the incubations were carried out for 90 and 150 minutes, for liver

and kidney respectively, at 39°C. Afterwards, the reaction was stopped by the

addition of TCA 10% containing HgCl

0.01 M. The activity of δ-ALA-D was

expressed as nmol of PBG/ mg of protein/ h. Simultaneously, a set of tubes was

assayed using the same protocol, except that 2 mM DTT was added in order to

obtain the reactivation index. This index indicates the extent of the reactivation

of δ-ALA-D activity. The reactivation index of δ-ALA-D activity was calculated as

follows:

(δ-ALA-D activity with DTT - δ-ALA-D activity without DTT) x 100%

δ-ALA-D activity with DTT

SOD activity

To verify SOD activity, S1 of kidney and liver were adequately diluted to

40 and 60 volumes with 0.9% NaCl, respectively, and the assay was performed

according to the method of Misra and Fridovich (1972). Briefly, epinephrine

rapidly autooxidizes at pH 10.5 producing adrenochrome, a pink-colored

product that can be detected at 480 nm. The addition of samples (10, 20, 30 μL)

containing SOD inhibits the autooxidation of epinephrine. The rate of inhibition

was monitored during 180 seconds at intervals of 30 seconds. The amount of

enzyme required to produce 50% inhibition at 25°C was defined as one unit of

enzyme activity (UI).

CAT activity

CAT activity was measured by the method of Aebi (1974). An aliquot of

liver and kidney supernatants (10 µL) diluted with 60 and 40 volumes of 0.9%

NaCl, respectively, was added to a quartz cuvette and the reaction was started

by the addition of freshly prepared H

(30 mM) in phosphate buffer (50 mM,

pH 7). The rate of H

decomposition was measured spectrophotometrically at

240 nm during 120 seconds at intervals of 15 seconds. CAT activity was

expressed as percentage of control.

Protein measurement

Protein was assayed by the method of Lowry et al. (1951) with serum

bovine albumin as standard.

Statistical analysis

Data were analyzed statistically by one-way ANOVA, followed by

Duncan’s post-hoc tests. The results were considered statistically significant

when p<0.05.

Results

Lipid Peroxidation

Chronic treatment with fluphenazine increased TBARS production in the

liver when compared to control and diphenyl diselenide groups (p<0.05).

Diphenyl diselenide administration did not modify hepatic TBARS levels.

However, in the combined treatment, diphenyl diselenide caused a decrease in

hepatic TBARS levels observed after fluphenazine treatment, returning TBARS

levels to control values (Fig. 1A).

Long-term treatment with fluphenazine caused an increase in TBARS

levels of about 50% in kidney homogenates when compared to the control

group (p<0.05). Treatment with diphenyl diselenide did not change renal

TBARS levels, whereas when the combined treatment was used, diphenyl

diselenide reduced renal TBARS enhanced by fluphenazine to control level

(Fig. 1B).

-ALA-D activity

SOD activity

Long-term treatment with fluphenazine caused a significant decrease

(about 50%) in hepatic SOD activity (p<0.05). Treatment with diphenyl

diselenide did not modify hepatic SOD activity. However, in the combined

treatment, organoselenium compound recovered hepatic SOD activity inhibited

by fluphenazine. In fact, the activity of the combined treatment was not

significantly different from control or diphenyl diselenide alone groups (Fig. 4A).

Isolated treatment with either diphenyl diselenide or fluphenazine did not

change renal SOD activity. However, the combined treatment caused a

reduction in renal SOD activity (Fig. 4B, p<0.05).

CAT activity

Treatment with fluphenazine caused a significant increase in CAT activity

of rat liver homogenates (p<0.05). Isolated treatment with diphenyl diselenide

did not change hepatic CAT activity. However, combined treatment partially

prevented the increase in CAT activity caused by fluphenazine (Fig. 5A). Renal

catalase activity was not modified by diphenyl diselenide, fluphenazine or the

combined treatment (Fig. 5B).

Discussion

The present investigation was carried out with the purpose to evaluate

oxidative stress in liver and kidney of rats chronically treated with fluphenazine.

We demonstrated here that the long-term treatment with fluphenazine caused

an increase in lipid peroxidation (TBARS), a reduction in SOD activity, and an

increase in CAT activity in liver, showing a relationship of fluphenazine

administration and oxidative stress. Fluphenazine also induced lipid

peroxidation in kidney, although CAT and SOD activities were not altered in this

organ.

Phenothiazines are extensively oxidized in the body to form cation

radicals (Yang and Kulkarni 1997), which are believed to be sulfur centered

cation radicals as sulfoxide was the end product (Cheng et al. 1978; Hammerich

and Parker 1983). It has been hypothesized that peroxidase-catalyzed drug

oxidation causes protein binding and oxidative stress, which can contribute with

cell death (Tafazoli and O'Brien 2005). Furthermore, hepatocyte cytotoxicity

induced by phenothiazines was markedly enhanced by nontoxic concentrations

of extracellular H

/peroxidase, and also caused ascorbate, GSH and NADH

cooxidation and reactive oxygen species formation (Eghbal et al. 2004). In this

way, we could suggest that the fluphenazine-induced lipid peroxidation could

result from the production of fluphenazine radical metabolites catalyzed by

peroxidases.

Fluphenazine chronic treatment induced alterations in hepatic SOD and

CAT enzymes activities. These findings are consistent with those of Cadet and

Perumal (1990), who reported alterations of SOD and CAT activity in the brain

of rats after chronic fluphenazine treatment. Other researchers have been

documented reduced SOD activity in rat brain treated with haloperidol which

probably was the result of alterations in genetic expression of these enzymes

(Parikh et al. 2003). The decrease in hepatic SOD activity caused by

fluphenazine treatment also could contribute to the increase in TBARS levels in

the liver.

Diphenyl diselenide was used in this study based on its hepatoprotective

and antioxidant properties (Borges et al. 2005, 2006). Indeed, diphenyl

diselenide was effective in protecting liver and kidney against lipid peroxidation

induced by fluphenazine. This protective effect on TBARS was accompanied by

a partial restoration of CAT activity in liver. Diphenyl diselenide was able to

ameliorate SOD activity in liver of rats treated with fluphenazine. In this way, the

protective effects of diphenyl diselenide could be attributed to the thiol

peroxidase-like activity that has been described for organoselenium compounds

and to other antioxidant properties of diphenyl diselenide (Arteel et al. 2001;

Nogueira et al. 2004; Rossato et al. 2002). On the other hand, the renal SOD

activity was diminished by the combined treatment. The decrease in SOD

activity in this group was unexpected and may indicate a complex interaction

between the antioxidant properties of the selenium compound and a decrease

in an important antioxidant enzyme in kidney. Nevertheless, the administration

of diphenyl diselenide was not accompanied by any sign of lipid peroxidation

(TBARS) in the kidney.

Fluphenazine treatment caused an inhibition of hepatic δ-ALA-D activity,

and the combination of fluphenazine and diphenyl diselenide was unable to

restore the enzyme activity. In fact, this combination increased the partial

inhibition caused by fluphenazine alone. Diphenyl diselenide can oxidize the

cysteinyl residues in the active site of δ-ALA-D maybe due to a thiol nucleophilic

attack in the selenium atom of diphenyl diselenide to give an unstable

intermediate of the type E-Cys-S-SePh and selenophenol. Subsequently, the

other cysteinyl residue attacks the sulfur-selenium bound of the intermediate

producing the oxidized enzyme and regenerates a second molecule of

selenophenol (Barbosa et al. 1998; Farina et al. 2002). However, in this case

diphenyl diselenide alone did not affect δ-ALA-D activity, only when associated

to fluphenazine. In this way, the interaction of fluphenazine and diphenyl

diselenide could provoke the oxidation of δ-ALA-D sulfhydryl groups in a more

pronounced way than fluphenazine alone. This is supported by the fact that

DTT, a reducing agent that restores oxidized thiol containing enzymes

(Perottoni et al. 2005) could restore the inhibition of δ-ALA-D activity, and by

the reactivation index, which was higher in rats treated with the combined

treatment than other treated groups.

Quite the opposite of liver, fluphenazine alone did not cause any effect

on renal δ-ALA-D activity, although the combination of fluphenazine and

diphenyl diselenide resulted in inhibition of δ-ALA-D activity. DTT was able to

restore δ-ALA-D activity in kidney. However, we did not observed differences in

the reactivation index for δ-ALA-D among the groups. In this way, we could

suggest that the mechanism underlying the inhibitory effect of these compounds

on renal δ-ALA-D was not related to the oxidation of -SH groups. The

decreased activity of the renal δ-ALA-D in the combined treatment could be

attributed to an additive effect of fluphenazine and diphenyl diselenide on the

enzyme activity.

The treatment carried out in this work was based on previous studies and

is a rat model of TD (Fachinetto et al. 2007; See et al. 1992; Van Kampen and

Stoessl 2000). Several authors presented evidence of the involvement of

reactive oxygen species in the development of TD (Abílio et al. 2004; Burger et

al. 2003; Cadet et al. 1986; Lohr et al. 1988). In this way, the results presented

here could corroborate this hypothesis. The same cause of hepatic oxidative

stress may also trigger brain oxidative stress. In fact, one can suppose that

even a limited hepatotoxicity of neuroleptics might facilitate their neurotoxicity,

particularly, by increasing the susceptibility of the entire organism to the

damaging effect of free radicals.

Drug-induced liver toxicity is common and accounts for approximately

one-half of the cases of acute liver failure (Kaplowitz 2001). Neuroleptic drugs

have been implicated in biological or/and clinical hepatotoxicity although the

precise mechanisms remain unclear (Dumortier 2002). Since antipsychotics are

going to be the drugs of choice for the treatment of psychotic disorders, the

understanding of the effects of their action on oxidative stress and oxidative

cellular injury may be very important (Parikh et al. 2003). This study

demonstrated for the first time an association between oxidative stress and

fluphenazine chronic treatment in liver and kidney of rats. Moreover, these data

may provide useful indications about the benefits of diphenyl diselenide

administration to protect liver from a variety of hepatotoxicants since diphenyl

diselenide protected from oxidative damage caused by fluphenazine in liver of

rats. However, we believe that further studies are necessary to test the

hypothesis of whether oxidative stress could contribute to the fluphenazine-

induced hepatotoxicity.

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Acknowledgments

Supported by the Financiadora de Estudos e Projetos (FINEP)

research grant “Rede Instituto Brasileiro de Neurociência (IBN-Net)” #

01.06.0842-00. Additional support given by Conselho Nacional de

Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo

a Pesquisa do Estado do Rio Grande do Sul (FAPERGS), Coordenação

de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), and

Cristália-SP. C.L.D.C., R.F., R.P. and C.W. receive fellowship from

CAPES. C.W.N. and J.B.T.R. are the recipients of CNPq fellowships.

Legends

Figure 1. Effect of diphenyl diselenide and/or fluphenazine treatments on

TBARS production in liver (A) and kidney (B) homogenates. Data are expressed

as mean ± S.E.M. for nine rats per group. Experiments were performed in

duplicates. (*) represents p<0.05 as compared to control group by Duncan’s

multiple range test.

Figure 2. Effect of diphenyl diselenide and/or fluphenazine treatments on

δ-ALA-D activity in liver homogenates (A) and on the enzyme reactivation index

(B). Data are expressed as mean ± S.E.M. for nine rats per group. Experiments

were performed in duplicates. (*) represents p<0.05 as compared to control

group by Duncan’s multiple range test.

Figure 3. Effect of diphenyl diselenide and/or fluphenazine treatments on

δ-ALA-D activity in kidney homogenates (A) and on the enzyme reactivation

index (B). Data are expressed as mean ± S.E.M. for nine rats per group.

Experiments were performed in duplicates. (*) represents p<0.05 as compared

to control group by Duncan’s multiple range test.

Figure 4. Effect of diphenyl diselenide and/or fluphenazine treatments on

SOD activity in liver (A) and kidney (B) homogenates. Data are expressed as

mean ± S.E.M. for nine rats per group. Experiments were performed in

duplicates. (*) represents p<0.05 as compared to control group by Duncan’s

multiple range test.

Figure 5. Effect of diphenyl diselenide and/or fluphenazine treatments on

CAT activity in liver (A) and kidney (B) homogenates. Data are expressed as

mean ± S.E.M. for nine rats per group. Experiments were performed in

duplicates. (*) represents p<0.05 as compared to control group by Duncan’s

multiple range test. The CAT activity in control groups was 291.41 and 173.25

µmol H

/mg protein/min for liver and kidney enzyme, respectively.

Figure 1.

Figure 2.

Figure 3.

Figure 4.

Figure 5.

3.2 – INTERAÇÕERS POTENCIALMENTE ADVERSAS ENTRE

HALOPERIDOL E VALERIANA

Artigo 2

POTENTIALLY ADVERSE INTERACTIONS BETWEEN HALOPERIDOL

AND VALERIAN

DALLA CORTE, C.L., FACHINETTO, R., COLLE, D., PEREIRA, R.P., ÁVILA,

D.S., VILLARINHO, J.G., WAGNER, C., PEREIRA, M.E., NOGUEIRA, C.W.,

SOARES, F.A.A., ROCHA, J.B.T.

(Aceito para publicação na Food and Chemical Toxicology)

Potentially adverse interactions between haloperidol and valerian

Dalla Corte, C.L., Fachinetto, R., Colle, D., Pereira, R.P., Ávila, D.S., Villarinho,

J.G., Wagner, C., Pereira, M.E., Nogueira, C.W., Soares, F.A.A.

and Rocha,

J.B.T.

Universidade Federal de Santa Maria, Centro de Ciências Naturais e Exatas,

Departamento de Química, Programa de Pós-graduação em Ciências

Biológicas: Bioquímica Toxicológica, Camobi, Cep 97105-900, Santa Maria,

RS, Brasil.

Corresponding author:

Félix Alexandre Antunes Soares - UFSM – CCNE – Dep. de Química

Cep 97105-900, Camobi, Santa Maria, RS, Brasil

Tel: #55-55-3220-9522, Fax: #55-55-3220-8978

e-mail: [email protected]

Running title: Haloperidol, valerian and hepatic damage

Keywords: Haloperidol; Valeriana officinalis; Herb-drug interaction; Oxidative

stress; δ-ALA-D.

Abstract

This study was designed to determine whether the treatment of

haloperidol (HP), valerian or both in association impairs the liver or kidney

functions. Valerian alone did not affect oxidative stress parameters in the liver

or kidney of rats. HP alone only increased glutathione (GSH) depletion in liver,

but not in kidney. However, when HP was associated with valerian, an increase

in lipid peroxidation levels and dichlorofluorescein (DCFH) reactive species

production was observed in the hepatic tissue. Superoxide dismutase (SOD)

and Catalase (CAT) activities were not affected by the HP plus valerian

treatment in the liver and kidney of rats. HP and valerian when administered

independently did not affect the activity of hepatic and renal δ-aminolevulinate

dehydratase (δ-ALA-D), however, these drugs administered concomitantly

provoked an inhibition of hepatic δ-ALA-D activity. The δ-ALA-D reactivation

index was higher in rats treated with HP plus valerian than other treated groups.

These results strengthen the view that δ-ALA-D can be considered a marker for

oxidative stress. Serum aspartate aminotransferase (AST) activity was not

altered by any treatment. However, serum alanine aminotransferase (ALT)

activity was higher in the HP group and HP plus valerian group. Our findings

suggest adverse interactions between haloperidol and valerian.

1. Introduction

Haloperidol (HP) is a drug with useful properties in the management of

psychosis (Creese et al., 1976). The long-term use of HP, however, is

associated with extrapyramidal side effects, including tardive dyskinesia (See

and Ellison, 1990). This syndrome is characterized by involuntary orofacial

movements and is often irreversible even after drug withdrawal (Gerlach and

Casey, 1988; Glazer et al., 1990; Andreasen and Jorgensen, 2000). The

persistence of tardive dyskinesia after the discontinuation of HP treatment

suggests that this condition may be related to a neuronal lesion induced by HP

or a reactive metabolite(s) derived from its metabolism (Wright et al., 1998).

In line with this, HP can be metabolized to the toxic intermediate 4-(4-

chlorophenyl)-1-[4-(4-fluorophenyl)-4-oxobutyl]pyridinium) (HPP

) in the liver

(Subramanyam et al., 1991; Bloonquist et al., 1994; Rollema et al., 1994; Fang

et al., 1995). This reactive metabolite is thought to share some toxic similarities

with the neurotoxic agent 1-methyl 4-phenyl 1,2,3,6-tetrahydropyridine (MPTP)

and can be involved in the genesis of some Parkinson-like effects associated

with the chronic use of HP (Ablordeppey and Borne, 1993).

Valerian root (Valeriana officinalis L.) is the most commonly used herbal

product to induce sleep in both the United States and Europe (Richman and

Witkowski, 1998; 1999; Houghton, 1999; Ang-Lee et al., 2001; Malva et al.,

2004). Virtually all sleep-aid herbal dietary supplements contain valerian (Ang-

Lee, 2003). The pharmacological activities of valerian are attributed to the

different constituents, including valepotriates (valtrate/ isovaltrate and

dihydrovaltrate) (Von der Hude et al., 1985) and valerenic acid. Valerian or its

constituents could induce these effects by interacting with central gamma-

aminobutyric acid (GABA) receptors (Mennini et al., 1993; Cavadas et al.,

1995). In vitro studies testing the binding of valerian extract to GABA receptors

showed that the agonist muscimol was displaced, suggesting valerian binding to

these receptors (Cavadas et al., 1995). Valerenic acid has been shown to inhibit

enzyme-induced breakdown of GABA in the brain resulting in sedation

(Houghton, 1999). Recently data showed the inductive effect of valerian on

cytochrome P450 (CYP) 3A4 and 2D6 enzymes in vitro (Hellum et al., 2006).

This should be seen with caution since alterations of CYP activity could affect

the disposition of conventional pharmaceuticals (Gonzalez, 2005). This is a

major problem in human therapy especially with CYP3A4 involved in

metabolism of over 60% of all therapeutically used drugs (Wrighton et al.,

2000).

Reports of drug interaction with many botanicals, including valerian have

been noted in literature (Assemi, 2001; Brazier and Levine, 2003). Natural

products can interact with drugs by affecting the biological processes that

regulate their metabolism and elimination (Bailey and Dresser, 2004). The

widespread use of valerian supplements suggests that use with conventional

medications is inevitable, and the potential for drug interactions is undefined

(Fugh-Berman and Ernst, 2001).

HP was used in this study for the reason that it is extensively use in

clinical practice to treat psychotic disorders and severe behavioral problems,

and because the side effects of HP on the CNS could be attributed to toxic

metabolites and/or oxidative stress (Wright et al., 1998; Burger et al., 2005).

Also, other side effects of HP like anxiety, restlessness, agitation and insomnia

are of interest for this work since valerian major effect is sedation (Malva et al.,

2004). Long-term safety studies with valerian are lack in the literature (Hadley

and Petry, 2003). In view of the fact that valerian has been reported to affect the

metabolism of other drugs, considering that haloperidol is extensively

metabolized in the liver and used in long-term treatments (Forsman et al.,

1977), the present study was undertaken to determine whether the treatment of

haloperidol, valerian or both in association can affect the liver or kidney of rats

in a long-term study.

2. Materials and Methods

2.1. Chemicals

Haloperidol Decanoate was donated by Cristália (São Paulo, Brazil). A

standard tincture of Valeriana officinalis (10 g of valerian roots per 100 mL of

ethanol) was obtained from Bio extracts (São Paulo, Brazil). O-phthalaldehyde,

thiobarbituric acid and DL-dithiothreitol (DTT) were obtained from Sigma (St.

Louis, MO, USA). HgCl

, NaCl, K

HPO

, KH

, trichloroacetic acid, para-

dimethylaminobenzaldehyde, and glacial acetic acid were purchased from

Reagen (Rio de Janeiro, RJ, Brazil). All other chemicals were purchased from

Merck (Darmstadt, Germany).

2.2. Animals

Male Wistar rats weighing 295 (± 35.36) g with approximately 3 months

of age, from our own breeding colony were kept in cages with continuous

access to food and V. officinalis or its vehicle (ethanol 1%), in a room with

controlled temperature (22±3°C) and in 12h light/ dark cycle with lights on at

7:00 am. The animals were maintained and used in accordance with the

guidelines of the Committee on Care and Use of Experimental Animal

Resources, School of Veterinary Medicine and Animal Science of Federal

University of Santa Maria, Brazil.

2.3. Treatments

Treatment consisted of 1% ethanol (vehicle of V. officinalis) or 1% (final

concentration of 100 mg/mL) of a standard tincture of V. officinalis (10 g of

valerian roots per 100 mL of ethanol) in the drinking water. The dosage was

calculated every week by the amount of water drunk assuming equal drinking

among the four animals in each cage. Thus, each animal received V. officinalis

extract in a dosage about 200-250 mg/Kg/day. The doses of valerian were

based on the daily recommended dose for an adult human which is 3060 mg

(as inscribed on the commercially bottle of valerian by Nature’s way product).

These solutions were placed daily before the beginning of the dark cycle. It was

not observed a reduction in liquid intake. Haloperidol Decanoate or its vehicle

(soy oil) were administered intramuscularly (i.m.) every 28 days (38 mg/kg) that

is equivalent to 1mg/kg/day of unconjugated HP (Fachinetto et al., 2005). V.

officinalis treatment started 15 days before the administration of HP. The

treatment with haloperidol was carried out during 12 weeks concomitantly with

V. officinalis. This treatment was performed according to a previous study of

Fachinetto et al. (2007).

Animals were divided into four groups of 12 animals each:

1 -Control: received soy oil (i.m.) and 1% of ethanol in the drink water;

2 -Valerian: received soy oil (i.m.) and 1% of V. officinalis in the drink

water;

3 -HP: received Haloperidol Decanoate (i.m.) and 1% of ethanol in the

drink water;

4 -Combined treatment: received Haloperidol Decanoate (i.m.) and 1%

of V. officinalis in the drink water.

2.4. Tissue preparation

Animals were euthanized by decapitation. Liver and kidney were quickly

removed, placed on ice and homogenized at 7 and 5 volumes of 0.9% NaCl,

respectively. The homogenates were centrifuged at 4,000 x g for 10 min to yield

a low-speed supernatant fraction (S1) that was used for the biochemical and

enzymatic assays, (except for the GSH/GSSG assay). In order to perform SOD

and CAT assay, S1 was diluted as described in the respective sections (2.7.2

and 2.7.3).

2.5. Lipid peroxidation assay

Thiobarbituric acid reactive species (TBARS) were determined as

described by Ohkawa et al. (1979). In brief, samples were incubated at 100 ºC

for 1 h in a medium containing 8.1 % sodium dodecyl sulfate, 1.4 M acetic acid,

pH 3.4 and 0.6% thiobarbituric acid. The pink chromogen produced by the

reaction of thiobarbituric acid with malondialdehyde (MDA), a secondary

product of lipid peroxidation, was measured spectrophotometrically at 532 nm.

Standard curve of MDA was used in order to calculate MDA concentrations.

Results were expresses as nmol of MDA/ mg of protein.

2.6. Estimation of reactive species production

Formation of reactive species was estimated according to a previous

report (Ali et al., 1992). Liver and kidney tissue samples were homogenized in

2.2 mL of saline solution (0.9% NaCl). Aliquots of 2.5 mL were incubated in the

presence of 5 μM 2’,7’-dichlorofluorescein diacetate at 37 ºC for 60 min.

Fluorescent signals were recorded at the end of the incubation at an excitation

wavelength of 488 nm and an emission wavelength of 525 nm. Results were

expressed as fluorescence units.

2.7. Enzyme assays

2.7.1.

-ALA-D activity

δ-ALA-D activity was assayed according to the method of Sassa (1982)

by measuring the rate of product (porphobilinogen-PBG) formation. The

reaction product was determined using modified Ehrlich’s reagent at 555 nm,

with a molar absorption coefficient of 6.1×10

-1

for the Ehrlich-PBG salt. The

incubation medium contained δ-ALA 2.4 mM and potassium phosphate buffer

(pH 6.8) 0.084 M. The reaction was initiated by the addition of enzymatic

material and the incubations were carried out for 90 and 150 minutes, for liver

and kidney respectively, at 39°C. Afterwards, the reaction was stopped by the

addition of trichloroacetic acid 10% containing HgCl

0.01 M. The activity of

ALA-D was expressed as nmol of PBG/ mg of protein/ h. Simultaneously, a set

of tubes was assayed using the same protocol, except that 2 mM DTT was

added in order to obtain the reactivation index. This index indicates the extent of

the reactivation of δ-ALA-D activity. The reactivation index of δ-ALA-D activity

was calculated as follows:

(δ-ALA-D activity with DTT - δ-ALA-D activity without DTT)

x 100%

δ-ALA-D activity with DTT

2.7.2. SOD activity

S1 of kidney and liver was adequately diluted with 40 and 60 volumes of

0.9% NaCl, respectively, in order to perform the SOD assay (Misra and

Fridovich, 1972). Briefly, epinephrine undergoes auto-oxidation at pH 10.2 to

produce adrenochrome, a colored product that was detected at 480 nm. The

addition of samples (10, 20, 30 µL) containing SOD inhibits the auto-oxidation of

epinephrine. The rate of inhibition was monitored during 180 seconds. The

amount of enzyme required to produce 50% inhibition was defined as one unit

of enzyme activity.

2.7.3. CAT activity

CAT activity was measured by the method of Aebi (1974). An aliquot of

liver and kidney supernatants (10 µL) diluted with 60 and 40 volumes of 0.9%

NaCl, respectively, was added to a quartz cuvette and the reaction was started

by the addition of freshly prepared H

(30 mM) in phosphate buffer (50 mM,

pH 7). The rate of H

decomposition was measured spectrophotometrically at

240 nm during 120 seconds. The activity of CAT was expressed as µmol

/mg protein/min.

2.7.4. Serum transaminases

Serum enzymes, AST and ALT were used as biochemical markers of

hepatic damage, using a commercial Kit (LABTEST, Diagnostica S.A., Minas

Gerais, Brazil) (Reitman and Frankel, 1957).

2.8. Fluorometric assay of reduced (GSH) and oxidized (GSSG) glutathione

For measurement of GSH and GSSG levels, we used a method

previously described by Hissin and Hilf (1976). Briefly, 250 mg of the tissue was

homogenized in 3.75 mL phosphate-EDTA

buffer (pH 8) plus 1 mL HPO

(25%).

Homogenates were centrifuged at 4°C at 100,000 g for 30 min and the

supernatant were separated in two different aliquots for measurement of GSH

and GSSG.

For GSH measurement, 500 μL of the supernatant was added to 4.5 mL

of phosphate buffer. The final assay mixture (2.0 mL) contained 100 μL of the

diluted tissue supernatant, 1.8 μL of phosphate buffer, and 100 μL of o-

phthalaldehyde (1 μg/μL). The mixtures were incubated at room temperature for

15 min and their fluorescent signals were recorded in the luminescence

spectrometer at 420 nm of emission and 350 nm of excitation wavelengths.

For measurement of GSSG levels, a 500 μL portion of the original

supernatant was incubated at room temperature with 200 μL of N-

ethylmaleimide (NEM) (0.04 M) for 30 min to react with free GSH to prevent its

oxidation to GSSG. To this mixture, 4.3 μL of NaOH (0.1 N) was added. A 100-

μL portion of this mixture was taken for measurement of GSSG, using the

procedure outlined above for GSH assay, except that NaOH was employed as

diluent rather than phosphate-EDTA buffer. Results were expressed as

GSH/GSSG ratio.

2.9. Protein measurement

Protein was assayed by the method of Lowry et al. (1951), with bovine

serum albumin as standard.

2.10. Statistical analysis

Data were analyzed statistically by one-way ANOVA, followed by

Duncan’s multiple range test when appropriate. The results were considered

statistically significant for p<0.05.

3. Results

Lipid Peroxidation

TBARS levels in liver homogenates were not affected by HP or valerian

when compared to the control (Fig. 1A). However, in the combined treatment

group a significant increase in TBARS production (about 15%) was detected

when compared to the other groups (p<0.05, Fig. 1A). Renal TBARS levels

were not modified by any of the treatments (Fig. 1B). <Insert figure 1 here>

Estimation of reactive species production

Reactive species production was measured by DCFH oxidation.

Combined treatment significantly enhanced the oxidation of DCFH (about 70%)

in liver homogenates when compared to the control group (Fig. 2A, p<0.05). HP

and valerian alone did not alter hepatic reactive species production (Fig. 2A);

however, it is worth mentioning that they may have had an additive effect on

DCFH oxidation in liver. In kidney homogenates, DCFH oxidation was not

modified by any treatment (Fig. 2B). <Insert figure 2 here>

Enzyme activity

Hepatic and renal SOD activities were not altered by HP, valerian or

combined treatment (data not shown). CAT activity was not modified by any of

treatments in both organs (data not shown). Isolated HP and valerian treatment

did not affect hepatic or renal δ-ALA-D activity (Fig. 3A and 4A). <Insert figure 3

here> However, HP in combination with valerian showed an inhibitory effect on

δ-ALA-D activity in the liver (Fig 3A, p<0.05) but not in the kidney (Fig 4A). In

vitro, DTT, a classic agent that restores oxidized thiol groups, was able to

restore liver δ-ALA-D activity (Fig 3B). In fact, the combined treatment of HP

and valerian had the highest δ-ALA-D reactivation index (Fig 3B, p<0.05). In the

kidney, there was no difference in the δ-ALA-D reactivation index among groups

(Fig 4B). <Insert figure 4 here>

Serum AST activities were not modified by any treatment (Figure 5A).

Rats treated with HP presented an increase in serum ALT activities when

compared to control rats (Figure 5B, p<0.05). The valerian treatment did not

significantly alter serum ALT activities, although its association with HP

statistically increased this parameter (Figure 5B, p<0.05). The magnitude of the

increase observed in serum ALT activities deserves attention however it was

not high enough to be of clinical concern. <Insert figure 5 here>

GSH and GSSG

The HP treatment provoked a decrease in the GSH/GSSG ratio in liver

homogenates and the valerian concomitant treatment did not avoid the HP

effects (Fig. 6A, p<0.05). In fact valerian it self had no effect on the, GSH/GSSG

ratio. In the kidney, none of the treatments modified the GSH/GSSG ratio (Fig.

6B). <Insert figure 6 here>

4. Discussion

The long-term use of HP is associated to side effects such as

Parkinsonism and tardive dyskinesia, and these syndromes have been

attributed to a toxic metabolite of HP, the pyridinium metabolite HPP

(Wright et

al., 1998). Nevertheless, there are few reports demonstrating the toxic effects of

HP on the liver or kidney. Since haloperidol is widely used in clinical practice,

the knowledge of its toxicity is essential in the choice of this antipsychotic agent.

The results presented here showed that HP alone only altered one of the

oxidative stress parameters in the liver (GSH/GSSG) and none in the kidney.

On the other hand, when HP was associated to valerian, a significant increase

in TBARS levels and DCFH reactive species production was observed in the

hepatic tissue. Our results indicate an increase in oxidative damage evoked by

HP plus valerian.

Despite the oxidative damage, SOD and CAT activities were not affected

by combined treatment in the liver. Similarly, HP failed to alter plasma SOD and

CAT activities in patients taking this drug (Yao et al., 1998). Considering that

HP is extensively metabolized in the liver with only approximately 1% of the

administered dose excreted in the urine (Forsman et al., 1977), we were not

surprised that this treatment did not cause any deleterious effects on kidney

from rats of this study.

Valeriana officinalis is widely utilized for its sedative properties,

although there is a lack in the literature of long-term safety studies with

valerian (Hadley and Petry, 2003). In our study, valerian alone did not show

any effect on TBARS levels, DFCH production or SOD and CAT activities. Al-

Majed and colleagues (2006) reported an increase in the concentrations of

MDA and a decrease of non-protein sulfhydryl levels in hepatic cells of mice

after sub-acute treatment with valerian. However, in this study we only

observed side effects when valerian was associated to HP.

δ-ALA-D activity was tested here since it is a sulfhydryl-containing

enzyme that is susceptible to oxidizing agents and is inhibited after exposure to

pro-oxidant situations (Folmer et al., 2002, 2003; Soares et al., 2003;

Gonçalves et al., 2005; Santos et al., 2005). The inhibition of δ-ALA-D may

impair heme biosynthesis and can result in the accumulation of aminolevulinic

acid, which has been demonstrated to be a pro-oxidant molecule under

significant physiological conditions (Bechara et al., 1993; Bechara, 1996;

Emanuelli et al., 2001). HP and valerian when administered separately did not

affect the activity of δ-ALA-D, however, these drugs administered in association

provoked an inhibition of hepatic δ-ALA-D activity. This is supported by the δ-

ALA-D reactivation index which presented the highest level in the combined

treatment when compared to the other groups. HP and valerian could be

interacting in a manner that oxidizes δ-ALA-D sulfhydryl groups, probably by

producing some oxidative by-products. These data are in agreement with the

fact that DTT, a classic reducing agent that restores oxidized thiol containing

enzymes (Perottoni et al., 2005), could restore the inhibition caused by the

combined treatment. In fact, it has been reported that valtrate, a component of

valerian, may interact with free sulfhydryl groups (Keochanthala-Bounthanh et

al., 1990). Perhaps HP can enhance this capacity of valerian to interact with

sulfhydryl groups or affect the susceptibility of the liver. These results strengths

the view that δ-ALA-D can be considered a marker for oxidative stress.

The release of intracellular enzymes (AST and ALT), which is presumed

to be a result of injury to cellular membranes, was utilized here as an index of

hepatotoxicity. Serum AST activity was not altered by any treatment. However,

serum ALT activity was higher in the HP and combined treatment. Gaertner and

collaborators (2001) reported elevation in transaminases in patients treated with

HP, which support these results. Anyway the increase in ALT activity observed

here was small to be of clinical concern.

In our study, HP caused a decrease in the GSH/GSSG index in the liver,

which was also observed in the HP and valerian combined treatment. This

decrease, which lowers cellular defenses, can contribute to the increase in

TBARS and DCFH oxidation, and lead to the elevations observed in serum ALT

activity.

The results present here point to an interaction between HP and valerian

in the increase of oxidative stress in the liver. Gold and colleagues (2001)

identified a series of potential interactions between herbal natural health

products, including valerian, and conventional drug therapies. Herb–drug

interactions can appear when herbs and chemical drugs are co-administered

and the herbal preparation (one or more components) modulates the

metabolism of the chemical drug by induction or inhibition of CYP enzymes.

Hellum and collaborators (2006) showed the capacity of valerian extracts to

induce CYP enzymes in cultured primary human hepatocytes, including

CYP3A4, the most important P450 enzyme responsible for HP metabolic

pathways (Igarashi et al., 1995; Usuki et al., 1996; Fang et al., 2001; Kalgutkar

et al., 2003; Avent et al., 2006). Based on these reports, we suppose that the

mechanism by which valerian-HP association induced oxidative damage may

be related to CYP activity. The inducible effects of valerian on CYP enzymes

could increase the production of toxic HP metabolites, such as HPP

responsible for the deleterious effects seen in the valerian plus HP treatment in

the liver. The adverse effects of valerian plus HP treatment observed in the liver

and the absence of these effects in kidney also could be explaining by this

mechanism. CYP enzymes are found at highest levels in the liver, and

expressed at lower levels in kidney (Gonzalez, 2005). Thus, liver are the major

site of herb-drug interaction in which the production of toxic HP metabolites

could be elevated.

The route of administration of Haloperidol Decanoate (i.m.) as well as the

dose of HP used in this study was equivalent to that indicated for humans which

increase the relevance of this work since our model could be translated into the

human situation. The doses of valerian and HP used here was within the normal

range for humans, but a possible negative interaction between these drugs will

occur in a real human situation only after ingestion of supratherapeutic doses of

valerian and HP. Anyway a possible toxic additive effect of these two

compounds must be kept in mind. In this way, the administration of valerian in

people taking HP should be better studied to verify possible negative

interactions.

The use of herbs as alternative and/or complementary therapy in the

Western world is on the rise and gaining increasing popularity (Hellum et al.,

2006). Unfortunately, their use has often been accompanied by an unfounded

belief that “natural” is equal to “safe”. The widespread use of valerian

supplements suggests that its use with conventional medications is inevitable.

Moreover, the potential for drug interactions with natural products is undefined

(Fugh-Berman and Ernst, 2001). The findings from our study suggest an

adverse effect in the interactions between haloperidol and valerian causing

hepatic damage related to oxidative stress. However, further work is needed to

confirm the exact mechanism by which these compounds cause oxidative

stress. Moreover, caution is warranted if attempting to make such an

extrapolation to other herbals and drug therapies.

Acknowledgments: Supported by the FINEP research grant “Rede Instituto

Brasileiro de Neurociência (IBN-Net)” # 01.06.0842-00. Additional support

giving by CNPq, FAPERGS, CAPES, Cristália-SP and UFSM (FIPE). C.L.D.C.

and R.F. receive fellowship from CAPES and CNPq (Fomento Tecnológico),

R.P.P. received a scientific initiation fellowship from CNPq-Fomento

Tecnologico, D.E.C. received fellowship from UFSM (FIPE), C.W.N. and

J.B.T.R. are the recipients of CNPq fellowships.

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Legends

Figure 1. Effects of valerian and/ or HP treatments on TBARS production

in liver (A) and kidney (B) homogenates. Data are expressed as mean ± S.E.M.

for twelve rats per group. Experiments were performed in duplicates. (*)

represents p<0.05 as compared to control group by Duncan’s multiple range

test.

Figure 2. Effects of valerian and/ or HP treatments on DCFH oxidation in

liver (A) and kidney (B) homogenates. Data are expressed as mean ± S.E.M.

for twelve rats per group. Experiments were performed in duplicates. (*)

represents p<0.05 as compared to control group by Duncan’s multiple range

test.

Figure 3. Effects of valerian and/ or HP treatments on δ-ALA-D activity in

liver homogenates (A) and on the enzyme reactivation index (B). Data are

expressed as mean ± S.E.M. for twelve rats per group. Experiments were

performed in duplicates. (*) represents p<0.05 as compared to control group by

Duncan’s multiple range test.

Figure 4. Effects of valerian and/ or HP treatments on δ-ALA-D activity in

kidney homogenates (A) and on the enzyme reactivation index (B). Data are

expressed as mean ± S.E.M. for twelve rats per group. Experiments were

performed in duplicates. (*) represents p<0.05 as compared to control group by

Duncan’s multiple range test.

Figure 5. Effects of valerian and/ or HP treatments on serum AST (A) and

ALT (B) activities. Data are expressed as mean ± S.E.M. for twelve rats per

group. Experiments were performed in duplicates. (*) represents p<0.05 as

compared to control group by Duncan’s multiple range test.

Figure 6. Effects of valerian and/ or HP treatments on GSH/GSSG ratio

in liver (A) and kidney (B) homogenates. Data are expressed as mean ± S.E.M.

for twelve rats per group. Experiments were performed in duplicates. (*)

represents p<0.05 as compared to control group by Duncan’s multiple range

test.

Figure 1.

Figure 2.

Figure 3.

Figure 4.

Figure 5.

Figure 6.

4. DISCUSSÃO

O uso de drogas neurolépticas tem sido associado a efeitos colaterais como a DT

e o dano hepático. Apesar dos inúmeros casos de hepatotoxicidade após a administração

de neurolépticos, são escassos os dados na literatura a respeito desses efeitos e o

mecanismo exato pelo qual neurolépticos induzem hepatotoxicidade permanece incerto

(Dumortier, 2002).

Um dos objetivos do presente estudo foi avaliar os efeitos do tratamento crônico

com flufenazina sobre parâmetros de estresse oxidativo em fígado e rim de ratos bem

como o possível efeito protetor do disseleneto de difenila sobre o dano induzido por

flufenazina (artigo 1). Demonstramos neste estudo que a exposição prolongada à

flufenazina provocou um aumento na peroxidação lipídica (TBARS), uma diminuição

na atividade da SOD e um aumento na atividade da CAT no fígado de ratos. Estes

resultados indicam que a administração crônica de flufenazina pode estar associada ao

estresse oxidativo. A flufenazina também induziu peroxidação lipídica no rim, no

entanto as atividades da SOD e da CAT não foram afetadas neste órgão.

As drogas fenotiazínicas são extensivamente oxidadas no organismo formando

radicais catiônicos (O’Brien, 1988; Yang e Kulkarni, 1997; Galati e cols., 2002;

Tafazoli e O'Brien, 2005). Eghbal e cols. (2004) demonstraram que em pH fisiológico

enzimas peroxidases catalisam a oxidação de fenotiazinas em radicais pró-oxidantes, os

quais oxidam ascorbato, GSH e NADH bem como induzem estresse oxidativo e

citotoxicidade quando incubados com hepatócitos. Dessa forma, podemos sugerir que a

peroxidação lipídica induzida por flufenazina poderia ocorrer devido à produção de

metabólitos da flufenazina catalisada por enzimas peroxidas es.

O disseleneto de difenila foi utilizado neste estudo devido às suas propriedades

antioxidante e hepatoprotetora já descritas (Nogueira e cols., 2004; Borges e cols.,

2005; 2006). Os resultados deste estudo demonstraram que o disseleneto de difenila foi

eficiente em proteger o fígado e o rim da peroxidação lipídica (TBARS) induzida por

flufenazina. Este efeito protetor do disseleneto de difenila sobre o TBARS foi

acompanhado pela restauração parcial da atividade da CAT no fígado. O disseleneto de

difenila também foi capaz de restaurar a atividade da SOD no fígado dos ratos tratados

com flufenazina. A diminuição na atividade da SOD causada pelo tratamento com

flufenazina poderia contribuir para o aumento nos níveis de TBARS observados no

fígado. Podemos, então, atribuir a proteção do disseleneto de difenila à sua atividade

tiol-peroxidase e a outras propriedades antioxidantes deste composto (Arteel e cols.,

2001; Rossato e cols., 2002; Nogueira e cols., 2004). Por outro lado, a atividade da SOD

no rim foi diminuída somente quando a flufenazina foi administrada concomitantemente

com o disseleneto de difenila. Este resultado foi inesperado, e pode indicar uma

interação complexa entre as propriedades antioxidantes do composto de selênio e a

diminuição em uma enzima antioxidante importante no rim. Apesar disso, a

administração de disseleneto de difenila não foi acompanhada por nenhum sinal de

peroxidação lipídica (TBARS) no rim.

O tratamento com flufenazina provocou uma inibição na atividade da δ-ALA-D

e a associação da flufenazina com o disseleneto de difenila não foi capaz de restaurar a

atividade da enzima. Esta associação aumentou a inibição parcial causada pela

flufenazina sozinha. A flufenazina e o disseleneto de difenila poderiam estar interagindo

de tal forma que a oxidação dos grupos sulfidrila (-SH) da δ-ALA-D foi mais

pronunciada do que no grupo tratado apenas com a flufenazina. Estes dados são

reforçados pelo fato do DTT, um agente redutor clássico, ter restaurado a inibição da δ-

ALA-D (Perottoni e cols., 2005) e pelo índice de reativação, que foi o mais elevado no

grupo tratado com flufenazina e disseleneto de difenila.

Ao contrário do fígado, a atividade da δ-ALA-D renal não foi alterada pelo

tratamento com flufenazina, no entanto a associação de flufenazina com disseleneto de

difenila resultou em inibição da atividade da enzima. O DTT foi capaz de restaurar a

atividade da δ-ALA-D renal. Contudo, não houve diferença no índice de reativação para

a δ-ALA-D renal entre os grupos. Com base neste resultado podemos sugerir que a ação

inibitória dessas drogas sobre a atividade da δ-ALA-D no rim não está relacionada com

a oxidação de grupos –SH. A redução da atividade da δ-ALA-D renal poderia ser

atribuída a um efeito aditivo do disseleneto de difenila e da flufenazina sobre a atividade

da enzima.

O tratamento realizado neste trabalho foi baseado em estudos prévios, sendo um

modelo de DO em roedores (See e cols., 1992; Van Kampen e Stoessl, 2000; Fachinetto

e cols., 2007). Diversos autores já apresentaram evidências do envolvimento de EROS

no desenvolvimento da DT (Cadet e cols., 1986; Lohr e cols., 1988; Burger e cols.,

2003; Abílio e cols., 2004). Os resultados apresentados neste estudo podem contribuir

para uma melhor compreensão dos efeitos colaterais relacionados ao uso de

neurolépticos, pois, se um metabólito reativo é capaz de induzir estresse oxidativo no

fígado o mesmo também poderia ser produzido no cérebro e, portanto, exercer efeitos

deletérios neste tecido. Além disso, podemos supor que mesmo uma hepatotoxicidade

limitada dos neurolépticos poderia facilitar a sua neurotoxicidade particularmente por

aumentar a susceptibilidade do organismo como um todo aos efeitos danosos dos

radicais livres.

Juntos os resultados deste primeiro artigo, contribuem para um maior

entendimento dos danos hepáticos induzidos pela flufenazina. Os dados apresentados

aqui indicam claramente o importante papel das EROS no tratamento crônico com

flufenazina. Além disso, a proteção do disseleneto de difenila sobre o estresse oxidativo

causado pela flufenazina nos dá uma indicação dos benefícios do disseleneto de difenila

para proteger o fígado de uma variedade de agentes hepatotóxicos.

O segundo objetivo deste estudo foi o de avaliar os efeitos do tratamento

crônico com haloperidol e Valeriana officinalis bem como a sua combinação sobre o

fígado e o rim de ratos (artigo 2). Os resultados apresentados aqui demonstram que o

haloperidol apenas alterou um parâmetro de estresse oxidativo no fígado aumentando a

depleção de GSH, enquanto nenhum parâmetro foi alterado no rim. Por outro lado

quando o haloperidol foi associado a valeriana houve um aumento significativo nos

níveis de TBARS e na produção de espécies reativas (DCFH) no fígado. Nossos

resultados indicam um aumento do dano oxidativo provocado pela associação de

haloperidol e valeriana.

Apesar do dano oxidativo observado, as atividades das enzimas SOD e CAT não

foram afetadas por nenhum dos tratamentos no fígado. Da mesma forma, o haloperidol

não alterou as atividades da SOD e CAT plasmáticas em pacientes sob esta medicação

(Yao e cols., 1998). O haloperidol é extensivamente metabolizado no fígado, e apenas

40 % da dose administrada é excretado na urina, sendo aproximadamente 1% excretado

na forma inalterada (Forsman e cols., 1977). Dessa forma, não é surpresa que este

tratamento não tenha causado nenhum efeito deletério sobre o rim de ratos neste estudo.

A Valeriana officinalis é largamente utilizada devido às suas propriedades

sedativas, no entanto existe a necessidade de estudos sobre a segurança do uso

prolongado de valeriana quando associada a outras drogas (Hadley e Petry, 2003). Neste

estudo o tratamento com valeriana não alterou os níveis de TBARS, a oxidação da

DCFH, e as atividades da SOD e da CAT. Al-Majed e colaboradores (2006)

demonstraram o aumento nos níveis de MDA e uma diminuição nos níveis de –SH não

protéico em células hepáticas de camundongos após tratamento sub-agudo com

valeriana. Entretanto, no presente estudo apenas observou-se efeitos colaterais quando a

valeriana foi associada ao haloperidol.

A atividade da δ-ALA-D foi avaliada por esta ser uma enzima que contém

grupos SH os quais são suscetíveis a agentes oxidantes e, portanto, a enzima pode ser

inibida após a sua exposição a situações pró-oxidantes (Folmer e cols., 2002, 2003;

Soares e cols., 2003; Gonçalves e cols., 2005; Santos e cols., 2005). Haloperidol e

valeriana quando administrados separadamente não afetaram a atividade da enzima, no

entanto a sua associação resultou na perda de atividade da δ-ALA-D hepática.

Haloperidol e valeriana poderiam estar interagindo de forma a oxidar os grupos –SH da

δ-ALA-D provavelmente por produzirem algum metabólito mais tóxico para enzima.

Este resultado é reforçado pela restauração da atividade da δ-ALA-D pelo DTT

(Perottoni e cols., 2005), e pelo índice de reativação para a δ-ALA-D o qual foi mais

alto no tratamento combinado que nos outros grupos tratados. Este resultado corrobora a

hipótese de que a enzima foi inibida pela oxidação dos seus grupos -SH. Foi relatado

que o valtrato, um componente da valeriana, pode interagir com grupos –SH

(Keochanthala-Bounthanh e cols., 1990). Talvez o haloperidol possa aumentar esta

capacidade da valeriana de interagir com grupos –SH ou afetar a suscetibilidade do

fígado. Estes resultados fortalecem a visão de que a δ-ALA-D pode ser considerada um

marcador de estresse oxidativo.

A liberação de enzimas intracelulares (AST e ALT) é um indicativo de dano às

membranas celulares e é utilizado como um índice de hepatotoxicidade (Cohen e

Kaplan, 1979). A ALT é uma enzima citoplasmática e encontra-se principalmente no

fígado, enquanto a AST é predominantemente mitocondrial e pode aparecer elevada em

doenças de outros órgãos, como o coração ou o músculo. Dessa for ma, elevações na

ALT representam um marcador mais sensível de função hepática (Motta, 2003). A

atividade da AST no soro não foi alterada por nenhum dos tratamentos. No entanto, a

atividade da ALT no soro foi maior nos ratos tratados com haloperidol e com o

tratamento combinado. Gaertner e colaboradores (2001) reportaram uma elevação na

atividade das transaminases em pacientes tratados com haloperidol, o que corrobora

estes resultados. Contudo, o aumento na atividade da ALT observado neste estudo não

foi alto o suficiente para representar uma preocupação clínica. Aumentos de 3 a 50

vezes na atividade das transaminases no soro são encontrados frequentemente em

doenças hepáticas (Motta, 2003).

Neste estudo o haloperidol causou uma diminuição na razão GSH/GSSG no

fígado, o que também foi observado no tratamento combinado com haloperidol e

valeriana. A razão GSH/GSSG indica o balanço entre antioxidantes e oxidantes. Sendo

assim, um aumento nos níveis de GSSG e uma redução na razão GSH/GSSG é um

indicativo de estresse oxidativo (Jones e cols., 2000). O aumento na depleção de GSH

prejudica as defesas celulares e poderia estar contribuindo para o aumento no TBARS e

para a oxidação da DCFH.

Os resultados apresentados aqui apontam para uma interação entre o haloperidol

e a valeriana no aumento do estresse oxidativo no fígado. Gold e colaboradores (2001)

identificaram uma série de interações em potencial entre produtos naturais, incluindo

valeriana, e terapias com drogas convencionais. Interações plantas medicinais-fármacos

podem aparecer quando plantas medicinais e fármacos são administrados

concomitantemente e o preparado da planta (um ou mais componentes) modula o

metabolismo da droga pela indução ou inibição das enzimas citocromo P450. Hellum e

colaboradores (2006) mostraram a capacidade dos extratos de valeriana em induzir as

enzimas CYP em culturas primárias de hepatócitos humanos, incluindo CYP3A4, a

mais importante das enzimas P450 responsáveis pela via do metabolismo do haloperidol

(Igarashi e cols., 1995; Usuki e cols., 1996; Fang e cols., 2001; Kalgutkar e cols., 2003;

Avent e cols., 2006). Com base nesses trabalhos, nós supomos que o mecanismo pelo

qual a associação de valeriana e haloperidol induz dano oxidativo pode estar

relacionado com a atividade da CYP. Os efeitos indutores da valeriana sobre as enzimas

CYP poderiam aumentar a produção de metabólitos tóxicos do haloperidol como o

HPP

, ocasionando os efeitos deletérios observados no tratamento com haloperidol e

valeriana no fígado. Estes efeitos adversos do tratamento com valeriana e haloperidol no

fígado e a ausência destes efeitos no rim também poderiam ser explicados por deste

mecanismo. As enzimas CYP são encontradas nos níveis mais altos no fígado, e

expressa em baixos níveis no rim (Gonzalez, 2005). O fígado, dessa forma, seria o

principal sítio de interação erva-droga onde a produção de metabólitos tóxicos poderia

estar elevada.

As doses de valeriana e haloperidol utilizadas neste estudo estão dentro de uma

faixa normal para humanos, mas uma possível interação negativa entre estas duas

drogas irá ocorrer em uma situação real em humanos apenas após a ingestão de doses

supraterapêuticas de valeriana e haloperidol. De qualquer modo, um possível efeito

aditivo tóxico destes dois compostos deve ser considerado. Dessa forma, a

administração de valeriana em pessoas que estejam sob medicação com antipsicóticos

deve ser melhor estudada para evitar possíveis interações negativas.

O uso de plantas medicinais como terapia alternativa e/ ou complementar nos

países ocidentais vem ganhando grande popularidade (Hellum e cols., 2006).

Infelizmente, o seu uso tem sido acompanhado pela crença de que se é natural é

igualmente seguro. O uso difundido de suplementos de valeriana indica que o seu uso

com medicamentos convencionais é perfeitamente possível. Além disso, o potencial

para interações de drogas com produtos naturais ainda permanece bastante indefinido

(Fugh-Berman e Ernst, 2001). As descobertas deste estudo sugerem efeitos adversos nas

interações entre valeriana e haloperidol causando dano hepático relacionado ao estresse

oxidativo. Estudos posteriores são necessários para elucidar o exato mecanismo pelo

qual os compostos testados aqui causam estresse oxidativo. Além disso, é necessário

cautela ao tentar extrapolar estes resultados para outras plantas medicinais e fármacos.

5. CONCLUSÕES

Neste trabalho salientamos a importância da vigilância cuidadosa dos efeitos

colaterais de drogas neurolépticas especialmente sobre a função hepática. Os resultados

apresentados nesta dissertação indicam a possibilidade de um dano oxidativo induzido

pela flufenazina no fígado e no rim de ratos. Além disso, o disseleneto de difenila

demonstrou-se eficaz em proteger contra o dano oxidativo causado pela flufenazina no

tecido hepático. De acordo com estes dados podemos concluir que a administração de

flufenazina esta associada à produção de EROS. Além disso, podemos sugerir que o

estresse oxidativo poderia ser um mecanismo para explicar a hepatotoxicidade

provocada pelo tratamento com flufenazina.

A partir deste estudo também podemos concluir que a administração de

haloperidol e V. officinalis separadamente não parece apresentar nenhum risco às

funções hepáticas e renais em ratos. No entanto, a combinação de haloperidol e

valeriana provocou um dano oxidativo no fígado de ratos, talvez pela indução de

enzimas CYP e aumento na produção de metabólitos tóxicos do haloperidol. Dessa

forma, o uso de valeriana não seria recomendado a pacientes que estejam sob tratamento

com haloperidol.

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