RESUMO
Cigarette smoking is a worldwide health problem and is the greatest risk factor for lung cancer. By activating procarcinogens, hepatic and extrahepatic cytochromes P450 can participate in lung carcinogenesis. Tobacco smoke contains numerous cytochrome P450 inducers, substrates, and inhibitors. In the present study we investigated, in male NMRI mice, the effects of cigarette smoke on hepatic and pulmonary cytochrome P450 expression and their possible role in the induction of DNA lesions such as DNA single strand breaks (SSB). Hepatic and pulmonary mouse cytochrome P450 isozymes involved in carcinogenesis (Cyp1a, 2b, 2e, 3a) were differently induced by cigarette smoke. Cyp2e1 mRNA was dramatically enhanced (12.7-fold increase) while Cyp2b10 mRNA remained unchanged and Cyp1a1 was decreased or not detected. Cyp3a protein and mRNA were not detected in lung, suggesting that this isozyme is not expressed in mouse pulmonary tissue. The SSB of DNA increased in lung and liver treated mice. In contrast no modification was observed in lymphocytes that barely expressed cytochromes P450. Cimetidine and propylene glycol reduced SSB of DNA induced by smoking in liver and lung cells. The inhibition (-70%) observed in lung following treatment by propylene glycol, a CYP2E1 inhibitor, suggested that this isozyme is at least in part involved in pulmonary DNA damage induced by tobacco smoke. The high concentration of CYP2E1 function and regulation in mammals suggests that this protein could be involved in pulmonary carcinogenesis in human smokers.
Assuntos
Hidrocarboneto de Aril Hidroxilases , Sistema Enzimático do Citocromo P-450/genética , Dano ao DNA , DNA de Cadeia Simples , Isoenzimas/genética , Fígado/enzimologia , Pulmão/enzimologia , Poluição por Fumaça de Tabaco/efeitos adversos , Animais , Carboxihemoglobina/análise , Citocromo P-450 CYP1A1/genética , Citocromo P-450 CYP2B1/genética , Citocromo P-450 CYP2E1/genética , Citocromo P-450 CYP3A , Sistema Enzimático do Citocromo P-450/biossíntese , Citocromos b5/biossíntese , Citocromos b5/genética , Indução Enzimática , Regulação Enzimológica da Expressão Gênica , Isoenzimas/biossíntese , Neoplasias Pulmonares/etiologia , Masculino , Camundongos , Oxirredutases N-Desmetilantes/genética , RNA Mensageiro/análiseRESUMO
The effect of cigarette smoke on the expression of several cytochromes P450 (CYP) and UDP-glucuronosyl-transferases (UGT) was studied in mice. The animals were exposed to cigarette smoke for 4 to 30 days. Enzymatic activities supported by CYP1A1, 1A2, 2B, 2E1 and the glucuronidation activity toward phenols were measured in lung, liver and kidney microsomes. Cigarette smoke induced several CYPs, especially in lung. CYP2E1 was more induced than CYP1A1 in this organ. The expression of CYP2E1 was also increased in kidney (5.6 times after 30 days). The glucuronidation in kidney was non-sensitive to the treatment whatever substrate used. In contrast, this activity was enhanced in liver and particularly in lung, in which the glucuronidation of 1-naphthol and 2-hydroxybiphenyl was increased by 122 and 180%, respectively. Interestingly, the times of induction differed according to the substrate used, thus suggesting the presence of different UGTs active toward phenols that were differentially affected by cigarette smoke. The UGT activities toward phenols were low in lung, when compared with those measured in liver or kidney. In conclusion, cigarette smoke greatly affected both glucuronidation activity and the hydroxylation reactions supported by CYPs in mouse liver and lung.
Assuntos
Sistema Enzimático do Citocromo P-450/análise , Glucuronosiltransferase/análise , Rim/efeitos dos fármacos , Fígado/efeitos dos fármacos , Pulmão/efeitos dos fármacos , Microssomos/efeitos dos fármacos , Poluição por Fumaça de Tabaco/efeitos adversos , Animais , Citocromos b5/análise , Rim/enzimologia , Fígado/enzimologia , Pulmão/enzimologia , Masculino , Camundongos , Microssomos/enzimologiaRESUMO
Several studies have shown in humans an association between renal carcinoma and cigarette smoking. Cigarette smoke contains numerous cytochrome P450 inducers and substrates. In the present study we investigated the effect of cigarette smoke on the regulation of murine cytochrome P450 expression in kidney and its possible role in the induction of single strand breaks in DNA. Results demonstrated that CYP2E1 (activity, protein, and MRNA) was induced by tobacco smoke (2.1, 5.6 and 20.8, respectively). We did not detect any CYP1A, CYP2B, and CYP3A using Western blot and RT-PCR experiments. We have analyzed the renal single strand breaks of DNA in control and treated mice. The results indicated an increase of single strand breaks of DNA in kidney from treated mice which paralleled the high inducibility of the CYP2E1. No significant difference was observed between lymphocytes (which expressed very low or undetectable cytochrome P450 levels) of control and treated mice.
Assuntos
Sistema Enzimático do Citocromo P-450/biossíntese , Dano ao DNA , Regulação Enzimológica da Expressão Gênica , Rim/enzimologia , Oxirredutases N-Desmetilantes/biossíntese , Poluição por Fumaça de Tabaco , Animais , Sequência de Bases , Citocromo P-450 CYP2E1 , Sistema Enzimático do Citocromo P-450/genética , Sistema Enzimático do Citocromo P-450/metabolismo , Primers do DNA , DNA de Cadeia Simples , Indução Enzimática , Humanos , Masculino , Camundongos , Camundongos Endogâmicos , Microssomos/enzimologia , Dados de Sequência Molecular , Oxirredutases N-Desmetilantes/genética , Oxirredutases N-Desmetilantes/metabolismo , Reação em Cadeia da Polimerase , Valores de ReferênciaRESUMO
We have isolated a cDNA (named P450 A) which is a variant of CYP2E1 presenting some differences in the 3' non coding region. Two substitutions and only one polyadenylation signal were detected on P450 A compared to CYP2E1 where there are two. With the aim of studying the frequency of utilization of these polyadenylation signals, probe A and probe J specific for P450 A and CYP2E1, respectively, were hybridized on human hepatic and extra-hepatic cDNA samples. Results indicated that in all tissues tested only P450 A using the first polyadenylation signal was detected. The CYP2E1 cDNA isolated by Song et al could be representative of a transcript either rarely represented among the Caucasian population, or expressed in a particular individual or ethnic population, or rapidly degraded.
