Benzoapyrene Cytotoxicity Tolerance in Testicular Sertoli CellsInvolves Aryl-hydrocarbon Receptor and Cytochrome P450 1A1 ExpressionDeficiencies

摘要

Benzo[a]pyrene (B[a]P) is a potent carcinogen and is classified as anendocrine-disrupting chemical. In mammalian testes, Sertoli cells supportspermatogenesis. Therefore, if these cells are negatively affected by exposureto xenotoxic chemicals, spermatogenesis can be seriously disrupted. In thiscontext, we evaluated whether mouse testicular TM4 Sertoli cells are susceptibleto the induction of cytotoxicity-mediated cell death after exposure to B[a]P in vitro. In the present study, while B[a]P andB[a]P-7,8-diol were not able to induce cell death, exposure to BPDE resulted incell death. BPDE-induced cell death is accompanied by the activation ofcaspase-3 and caspase-7. Depolarization of the mitochondrial membrane andcytochrome c release from mitochondria were observed inbenzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE)-treated cells. These resultsindicate that TM4 cells are susceptible to apoptosis in a caspase-dependentmanner. Western blot and reverse transcription-polymerase chain reaction(RT-PCR) analyses showed that aryl hydrocarbon receptor (AhR) expression wasalmost undetectable in TM4 cells and that its expression was not altered afterB[a]P treatment. This indicates that TM4 cells are nearly AhR-deficient. In TM4cells, the CYP1A1 protein and its activity were not present. From these results,it is clear that AhR may be a prerequisite for CYP1A1 expression in TM4 cells.Therefore, TM4 cells can be referred to as CYP1A1-deficient cells. Thus, TM4Sertoli cells are believed to have a rigid and protective cellular machineryagainst genotoxic agents. In conclusion, it is suggested that tolerance to B[a]Pcytotoxicity is associated with insufficient AhR and CYP1A1 expression intesticular Sertoli cells.