CYP2E1 peptide

Benzene is a human carcinogen that requires metabolic activation. We previously observed that benzene and its hydroxylated metabolites induce micronuclei in mammalian cells expressing human CYP2E1. This study was initially aimed to study another endpoint, the induction of gene mutations by those compounds in the same cell models. A V79-derived cell line expressing human CYP2E1 and sulfotransferase (SULT) 1A1 (V79-hCYP2E1-hSULT1A1) pretreated with ethanol (a CYP2E1 stabilizer) was used in the hprt gene mutagenicity assay. Phenol, hydroquinone, catechol, and 1,2,4-trihydroxybenzene all induced gene mutations, while they were inactive, or only weakly positive (hydroquinone), in parental V79-Mz cells. Unexpectedly, benzene was non-mutagenic in both cell lines, but it became positive in V79-hCYP2E1-hSULT1A1 cells using regimes of short exposure/long recovery without ethanol pretreatment, for both gene mutations and micronuclei formation. In silico molecular simulation showed binding energies and positions favorable for each compound to be oxidized by human CYP2E1, benzene demonstrating the highest affinity. By tunnel analysis, ethanol binding did not limit benzene to pass tunnel S, which was specifically active for benzene. However, its end product, acetic acid, decreased the occurrence of tunnel S from 5.4 to 2.2% and extended the length of its bottleneck from 5.5 to 9.0 angstrom. With residual ethanol molecules still being present in CYP2E1 for a period of time after benzene exposure, the acetic acid formed could limit the entrance of benzene, thus inhibit its metabolic activation. In summary, ethanol may interfere with the activation of benzene to mutagenic metabolites, at least in cultured cells.

Alcohol consumption and smoking habits are risk-enhancing factors for head and neck squamous cell carcinoma (HNSCC). The CYP450 2E1 (CYP2E1) and acetaldehyde dehydrogenase 2 (ALDH2) enzymes play an important role in the metabolism of these carcinogens. Various polymorphisms have been identified on genes that expresses these enzymes The aim of this study was to investigate the associations between the ALDH2 and CYP2E1 polymorphisms and HNSCC susceptblity in the Turkish population. The genomic DNA was isolated from the peripheral blood leukocytes of 79 HNSCC patients and 98 healthy controls. ALDH2 genotyping was performed with the multiplex polymerase chain reaction (PCR) technique. CYP2E1-Dral, CYP2E1-Rsal and CYP2E1-Pstl genetic polymorphisms were determined via the PCR restriction fragment length polymorphism (PCR-RFLP) technique. The results of our study demonstrated that CYP2E1-Rsal heterozygous (c1/c2) genotyped individuals have an increased risk for HNSCC susceptibility (OR= 7.79; 95% CI, 0.92-179.64; p= 0.04). No other relationship was found between the other studied polymorphisms and HNSCC. The results are consistent with previous studies, which examined the ALDH2 and CYP2E1 polymorphisms in Caucasian subjects. However, there are still conflicting results in Caucasian races for CYP2E1 Rsal/Pstl polymorphisms. Consequently, the c1/c2 genotypes for Rsal polymorphisms may be a risk factor for HNSCC. Larger study populations and multi-centre studies are needed to more precisely demonstrate the susceptibility in the Turkish population.