Assuntos
Alternativas aos Testes com Animais , Absorção Intestinal/fisiologia , Mucosa Intestinal/fisiologia , Animais , Células CACO-2 , Diretrizes para o Planejamento em Saúde , Humanos , Mucosa Intestinal/enzimologia , Modelos Biológicos , Técnicas de Cultura de Órgãos , Xenobióticos/farmacologiaRESUMO
Oltipraz (OPZ) is a potent chemopreventive agent against chemically-induced carcinogenesis in several animal models. It affects the expression and/or activity of xenobiotic-metabolizing enzymes and its effects are altered in the course of inflammation in liver. The present study was undertaken to analyse the effect of OPZ alone or in combination with Escherichia coli lipopolysaccharide (LPS) on the expression and activities of glutathione S-transferases (GSTs) and cytochrome P450 (CYPs) in rat lung and kidney. Male Wistar rats were fed a diet containing OPZ for 1-5 days. LPS was injected 24 h before the end of OPZ treatment (from 48 to 72 h). Total GST activity, measured using 1-chloro-2,4-dinitrobenzene as a substrate, increased slightly in both lung and kidney during OPZ treatment. As previously demonstrated in the liver, OPZ induced rat GSTP1 in both kidney and lung and this effect was totally (kidney) or partially (lung) inhibited by co-treatment with LPS. CYP1A expression and activity were strongly increased in both tissues 24 h after starting OPZ treatment and maintained for 5 days. This increase was suppressed during the acute-phase response to endotoxin. OPZ has no effect on CYP2B1 mRNA expression in the lung, but it dramatically decreased the amount and activity of the corresponding apoprotein. The OPZ-dependent decrease in the CYP2B1 apoprotein was abolished and its corresponding activity partially reversed during LPS treatment. In reconstitution experiments using cytosol from OPZ-treated or control rat lungs and microsomal fractions, CYP2B1 apoprotein was rapidly degraded in the presence of cytosol from treated rats. This effect was partially reversed in the presence of MG132, a proteasome inhibitor. These observations support the conclusion that the decrease of CYP2B1 by OPZ involves proteasome-dependent degradation and represents a new mechanism of regulation by this compound.
Assuntos
Anticarcinógenos/farmacologia , Hidrocarboneto de Aril Hidroxilases , Citocromo P-450 CYP1A1/metabolismo , Sistema Enzimático do Citocromo P-450/metabolismo , Pulmão/efeitos dos fármacos , Oxirredutases N-Desmetilantes/metabolismo , Complexo de Endopeptidases do Proteassoma , Pirazinas/farmacologia , Animais , Citocromo P-450 CYP1A1/biossíntese , Citocromo P-450 CYP1A1/genética , Citocromo P-450 CYP2B1/biossíntese , Citocromo P-450 CYP2B1/genética , Citocromo P-450 CYP2B1/metabolismo , Citocromo P-450 CYP2B6 , Sistema Enzimático do Citocromo P-450/biossíntese , Sistema Enzimático do Citocromo P-450/genética , Citosol/enzimologia , Glutationa Transferase/biossíntese , Glutationa Transferase/genética , Glutationa Transferase/metabolismo , Isoenzimas/biossíntese , Isoenzimas/genética , Isoenzimas/metabolismo , Rim/efeitos dos fármacos , Rim/enzimologia , Lipopolissacarídeos/farmacologia , Pulmão/enzimologia , Masculino , Oxirredutases N-Desmetilantes/biossíntese , Oxirredutases N-Desmetilantes/genética , Peptídeo Hidrolases/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Ratos Wistar , Tionas , TiofenosRESUMO
The isothiocyanate sulforaphane (SF) is thought to be a potential chemoprotective agent. Its effects on Phase I and Phase II enzymes of carcinogen metabolism in primary cultures of rat and human hepatocytes have been investigated. Northern blot analyses of rat hepatocytes showed a dose-dependent induction of mRNAs for rat glutathione S-transferases (rGSTs) A1/A2 and P1 but not M1. This was associated with enhanced levels of not only rGSTA1, A2, A4, A5, and P1 but also of rGSTs M1 and M2. On the other hand, the enzyme activities in rat hepatocytes associated with cytochromes P-450 (CYPs) 1A1 and 2B1/2, namely ethoxyresorufin-O-deethylase and pentoxyresorufin-O-dealkylase, respectively, were decreased in a dose-dependent manner. In SF-treated human hepatocytes, hGSTA1/2 but not hGSTM1 mRNAs were induced, and the expression of CYP1A2 was unaffected, whereas the expression of CYP3A4, the major CYP in human liver, was markedly decreased at both mRNA and activity levels. These observations demonstrate that in intact human and rat hepatocytes, SF may both induce a number of GSTs and cause enzyme inhibition of some but not all CYPs and, in the case of CYP3A4, inhibit both its enzyme activity and its expression.
