O papel da L-carnitina na proteção de danos oxidativos induzidos pelo bisfenol A em fígado de rato
Ficheiros
Data
2015
Autores
Título da revista
ISSN da revista
Título do Volume
Editora
Resumo
O bisfenol A é um dos produtos químicos mais produzidos a nível global. É o monómero utilizado na síntese de plásticos de policarbonato e resinas epóxi aplicadas na produção de embalagens alimentares, garrafas de água, produtos eletrónicos, médicos e dentários. Além da sua atividade estrogénica, o bisfenol A é também um reconhecido indutor de stresse oxidativo. O composto tem sido associado a uma diversidade de complicações na saúde de animais e na população humana, assim, o estudo dos seus efeitos toxicológicos constitui uma área de interesse científico. Em ratos pode contribuir para a formação de espécies reativas, afetar a atividade do sistema antioxidante e induzir hepatotoxicidade.
A L-carnitina é uma pequena molécula hidrossolúvel, endógena da membrana mitocondrial e amplamente distribuída na natureza. Esta no organismo participa no metabolismo lipídico onde a sua principal função é o transporte de ácidos gordos de cadeia longa para a matriz mitocondrial, local da β-oxidação. É já conhecido que a L-carnitina melhora a capacidade antioxidante das células e tecidos, através da sua atividade contra radicais livres.
Este estudo pretendeu investigar os danos oxidativos promovidos pela exposição crónica ao bisfenol A, em fígado de rato, e avaliar a ação protetora da L-carnitina no combate ao stresse oxidativo.
O modelo animal usado foi o rato Wistar albino em idade adulta e do sexo masculino com 450-500 g de massa corporal. Os ratos foram divididos em quatro grupos: primeiro grupo, controlo, foi administrada apenas água potável aos animais; segundo grupo, bisfenol A, solução aquosa de bisfenol 0,05 mg/L administrada aos animais; terceiro grupo, L-carnitina, solução aquosa de L-carnitina 0,006 mg/L; quarto grupo, bisfenol A e L-carnitina, solução aquosa bisfenol 0,05 mg/L e L-carnitina 0,006 mg/L administrada aos animais. O período de exposição decorreu ao longo de oito meses, após o qual se procedeu à eutanásia dos animais e recolha dos fígados para estudos posteriores. Foram avaliados alguns marcadores da função hepática como a albumina sérica, a bilirrubina total e as atividades da alanina transaminase e aspartato transaminase, assim como a bioenergética mitocondrial do fígado e marcadores de stresse oxidativo e enzimas com papel relevante na proteção contra os radicais livres.
No grupo do Bisfenol A, os níveis séricos das transaminases foram significativamente aumentados para a alanina transaminase e para a aspartato transaminase, a bilirrubina surgiu também superior mas com um aumento não significativo, enquanto os níveis de albumina permaneceram semelhantes ao controlo.
Entre as enzimas antioxidantes analisadas apenas a glutatião redutase surgiu significativamente aumentada pela exposição ao BPA. As atividades da catalase e da superóxido dismutase apresentaram-se ligeiramente aumentadas, assim como a peroxidação lipídica. A produção de peróxido de hidrogénio na mitocôndria aumentou significativamente no grupo exposto ao bisfenol A exceto no caso do substrato ascorbato- N,N,N’,N’ - tetrametil-p-fenilenodiamina em que as diferenças não foram significativas. O conteúdo em glutatião nas formas oxidada e reduzida não sofreu alterações relevantes assim como a atividade da glutatião S-transferase. A velocidade de respiração diminuiu nos complexos I, II e IV em todos os estados respiratórios estudados, porém, não apresentou diferenças significativas quando utilizado o ascorbato- N,N,N’,N’ - tetrametil-p-fenilenodiamina como substrato respiratório.
Estes resultados mostram que o bisfenol A induz danos na função hepática e altera a bioenergética do fígado podendo resultar em stresse oxidativo provocado pela exposição a este xenoestrogénio. A suplementação com L-carnitina permitiu reverter, parcialmente, as alterações promovidas pela exposição ao bisfenol A em alguns dos parâmetros analisados. Podemos assim concluir que a L-carnitina poderá em determinadas condições promover uma ação protetora contra os danos oxidativos induzidos pelo bisfenol A no fígado dos animais.
Bisphenol A is one of the most widely chemicals produced in the world. Is the monomer used to manufacture polycarbonate plastics and epoxy resins applied in the production of food packages, water bottles and electronic, medical and dental products. Besides its estrogenic activity, bisphenol A is a recognized oxidative stress inducer. The compound has been associated with a diversity of health problems both in animal and human population, thereby, the study of their toxicological effects is an interesting field to the scientific community. In rat it can contribute to reactive species generation, affect antioxidant defense system and induce hepatotoxicity. L-carnitine is a water soluble small molecule, endogenous from mitochondrial membrane and broadly distributed in nature. In the organism participates in lipid metabolism where its main function is the transport of long chain fatty acids to the mitochondrial matrix, where β-oxidation takes place. Is already known that L-carnitine improves cell and tissue antioxidant capacity by its activity against free radicals. In this work we have studied the oxidative damage in rat liver promoted by chronic exposure to bisphenol A and evaluated the protective role to oxidative stress of L-carnitine. Adult male Wistar albine rat with 450-500 g of weight were used during eight months. The animals were divided in four groups: first group, control, only drinking water; second group, bisphenol A, an aqueous solution of bisphenol A 0.05 mg/L was given to animals as a drinking water; third group, L-carnitine, an aqueous solution of 0.06 mg/L was given to drink and a fourth group, Bisphenol A and L-carnitine, where a solution of bisphenol 0.05 mg/L and L-carnitine 0.06 mg/L was given as drinking water. Animals were euthanized eight months later the beginning of treatment and their livers were collected. Serum albumin, total bilirubin, alanine transaminase and aspartate aminotransferase activity were all measured, liver mitochondrial bioenergetics and several enzymes envolved in cell antioxidate activity as well several biomarkers for oxidative stress were evaluated. Among the enzymes studied only the activity of glutathione reductase was significantly increased in the bisphenol A group and catalase, superoxide dismutase were slightly increased as well as lipid peroxidation. The production of mitochondrial hydrogen peroxide was significantly increased in animals exposed to bisphenol A except with the ascorbate - N,N,N’,N’-tetramethyl-p-phenylenediamine substrate where the differences were not significant when compared to control group. The thiol content, in both forms (reduced and oxidized) and the glutathione S-transferase activity did not show differences, when compared to control group. The respiration rate was inhibited for complexes I, II and IV in all respiratory states studied, however, with ascorbate - N,N,N′,N′-tetramethyl-p-phenylenediamine substrate this inhibition was not significant. These results show that bisphenol A promote damage in hepatic function and induces changes in liver bioenergetics which can exacerbate the oxidative stress imposed by this xenostrogen. The co-administration of L-carnitine have partially reverted the alterations promoted by bisphenol A in some of the parameters studied. Therefore, L-carnitine has, in some conditions, the ability to counteract the oxidative damage in liver tissues of rats exposed to bisphenol A.
Bisphenol A is one of the most widely chemicals produced in the world. Is the monomer used to manufacture polycarbonate plastics and epoxy resins applied in the production of food packages, water bottles and electronic, medical and dental products. Besides its estrogenic activity, bisphenol A is a recognized oxidative stress inducer. The compound has been associated with a diversity of health problems both in animal and human population, thereby, the study of their toxicological effects is an interesting field to the scientific community. In rat it can contribute to reactive species generation, affect antioxidant defense system and induce hepatotoxicity. L-carnitine is a water soluble small molecule, endogenous from mitochondrial membrane and broadly distributed in nature. In the organism participates in lipid metabolism where its main function is the transport of long chain fatty acids to the mitochondrial matrix, where β-oxidation takes place. Is already known that L-carnitine improves cell and tissue antioxidant capacity by its activity against free radicals. In this work we have studied the oxidative damage in rat liver promoted by chronic exposure to bisphenol A and evaluated the protective role to oxidative stress of L-carnitine. Adult male Wistar albine rat with 450-500 g of weight were used during eight months. The animals were divided in four groups: first group, control, only drinking water; second group, bisphenol A, an aqueous solution of bisphenol A 0.05 mg/L was given to animals as a drinking water; third group, L-carnitine, an aqueous solution of 0.06 mg/L was given to drink and a fourth group, Bisphenol A and L-carnitine, where a solution of bisphenol 0.05 mg/L and L-carnitine 0.06 mg/L was given as drinking water. Animals were euthanized eight months later the beginning of treatment and their livers were collected. Serum albumin, total bilirubin, alanine transaminase and aspartate aminotransferase activity were all measured, liver mitochondrial bioenergetics and several enzymes envolved in cell antioxidate activity as well several biomarkers for oxidative stress were evaluated. Among the enzymes studied only the activity of glutathione reductase was significantly increased in the bisphenol A group and catalase, superoxide dismutase were slightly increased as well as lipid peroxidation. The production of mitochondrial hydrogen peroxide was significantly increased in animals exposed to bisphenol A except with the ascorbate - N,N,N’,N’-tetramethyl-p-phenylenediamine substrate where the differences were not significant when compared to control group. The thiol content, in both forms (reduced and oxidized) and the glutathione S-transferase activity did not show differences, when compared to control group. The respiration rate was inhibited for complexes I, II and IV in all respiratory states studied, however, with ascorbate - N,N,N′,N′-tetramethyl-p-phenylenediamine substrate this inhibition was not significant. These results show that bisphenol A promote damage in hepatic function and induces changes in liver bioenergetics which can exacerbate the oxidative stress imposed by this xenostrogen. The co-administration of L-carnitine have partially reverted the alterations promoted by bisphenol A in some of the parameters studied. Therefore, L-carnitine has, in some conditions, the ability to counteract the oxidative damage in liver tissues of rats exposed to bisphenol A.
Descrição
Dissertação de Mestrado em Bioquímica
Palavras-chave
Stresse oxidativo , Antioxidantes , Bisfenol , L-carnitina