Assessment of an Association between an Aryl Hydrocarbon Receptor Gene (AHR) Polymorphism and Risk of Male Infertility

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that mediates the toxicity of a variety of environmental chemicals, such as polycyclic aromatic hydrocarbons (PAHs) and dioxins. We hypothesized that polymorphisms of AHR may result in significant differences in sensitivity to toxic effects of PAHs or dioxins and contribute to susceptibility to male infertility. To address this possibility, we conducted a study including 580 idiopathic infertile subjects and 580 fertile controls to assess associations between the male infertility risk and six tagging single nucleotide polymorphisms of AHR gene. Additionally, correlations between AHR polymorphisms and sperm concentration, levels of DNA fragmentation, and benzo(a)pyrene diolepoxide (BPDE)-DNA adducts in sperm were determined in 420 patients. Genotypes were determined using the ABI OpenArray platform. Sperm DNA fragmentation was evaluated by terminal deoxyribonucleotidyl transferase (TdT)-mediated dUDP nick-end labelling (TUNEL) assay, and sperm BPDE-DNA adducts were measured by immunofluorescent assay using flow cytometry. We found that the G variant of rs2158041 was associated with significantly increased risk of male infertility (adjusted odds ratio 1.53, 95% confidence interval 1.21-1.93; p = 6.0 x 10(-6); GA/AA vs. GG genotypes). Furthermore, patients with rs2158041 AA genotype showed a reduced sperm concentration. In addition, a gradual increase of sperm DNA fragmentation and sperm BPDE-DNA adducts was found among the three rs2158041 subgroups (GG -> GA -> AA), though the differences were not statistically significant. These results suggested that the AHR polymorphism might be associated with individual risk of male infertility in the Chinese population study.