RESUMO
Regulation of catalase (CAT) expression, a major antioxidant enzyme that detoxifies H2O2, is very complex. Garlic is effective to prevent or ameliorate oxidative stress probably through its intrinsic antioxidant properties and/or to its ability to modify antioxidant enzyme expression. In this paper we studied the effect of a 2% garlic diet on the renal and hepatic CAT expression (mRNA levels, and enzyme activity, content, synthesis, and degradation). The study was made 2 weeks after feeding rats with a 2% garlic diet. CAT activity and content were measured by a spectrophotometric method and Western blot, respectively. CAT mRNA levels and CAT synthesis (k(s)) and degradation (kD) in vivo were measured by Northern blot and kinetic of reappearance of CAT activity after aminotriazole injection, respectively. Garlic-treatment decreased CAT activity and content, and CAT mRNA levels were unchanged in both tissues. k(s) decreased and kD remained unchanged in kidney and liver. The decrease in k(s) without changes in kD and CAT mRNA levels could explain the low CAT expression in garlic-fed rats. In vivo H2O2 generation in kidney and liver was markedly decreased in garlic-fed rats which could be due to a direct antioxidant effect of garlic. This may be the initial event in the garlic-fed rats that leads to the decreased CAT expression. Our data strongly suggest that the diminished renal and hepatic CAT expression in garlic-fed rats is mediated by post-transcriptional changes (mainly low translational efficiency) which could be an adaptation to the low H2O2.
Assuntos
Catalase/biossíntese , Alho/uso terapêutico , Regulação Enzimológica da Expressão Gênica , Fitoterapia , Plantas Medicinais , Processamento Pós-Transcricional do RNA , Amitrol (Herbicida)/farmacologia , Animais , Antioxidantes/metabolismo , Northern Blotting , Western Blotting , Peso Corporal/efeitos dos fármacos , Creatinina/urina , Comportamento Alimentar/efeitos dos fármacos , Glutationa Peroxidase/biossíntese , Glutationa Peroxidase/sangue , Peróxido de Hidrogênio/metabolismo , Rim/metabolismo , Cinética , Peróxidos Lipídicos/metabolismo , Fígado/metabolismo , Masculino , Biossíntese de Proteínas , RNA/metabolismo , RNA Mensageiro/metabolismo , RNA Ribossômico 18S/metabolismo , Ratos , Ratos Wistar , Espectrofotometria , Superóxido Dismutase/biossíntese , Superóxido Dismutase/sangue , Fatores de TempoRESUMO
Reactive oxygen species have been involved in the pathophysiology of puromycin aminonucleoside (PAN)-nephrosis. The role of H2O2 in these rats may be studied modulating the amount or activity of catalase, which breakdowns H2O2 to water and oxygen. To explore the role of H2O2 in this experimental model, we studied the effect of the in vivo catalase inhibiton with 3-amino-1,2,4-triazole (ATZ) on the course of PAN-nephrosis. Four groups of rats were studied: control rats (CT group), PAN-injected rats (PAN group), ATZ-injected rats (ATZ group), and ATZ- and PAN-injected rats (ATZPAN group). Rats were placed in metabolic cages to collect 24 h urine along the study, ATZ (1 g/kg) was given 24 h before PAN injection (75 mg/kg), and the proteinuria was measured on days 0, 2, 4, 6, 8, and 10. Proteinuria started before (day 4) and was significantly higher on days 6, 8, and 10 in the ATZPAN group than in the PAN group. On day 10, hypercholesterolemia was significantly higher in the ATZPAN group than in the PAN group. These data indicate that the in vivo catalase inhibition magnifies PAN-nephrosis, suggesting that H2O2 is produced in vivo and involved in the renal damage in this experimental disease.
