Smoking attenuated the association between IB rs696 polymorphism and defective spermatogenesis in humans

Defective spermatogenesis is prevalent in infertile men, but the molecular mechanisms underlying its aetiology are largely unknown. In this study, a proposed association between IB SNPs, smoking-related ROS and sperm quality was investigated. Two polymorphisms in the IB gene, rs2233406 and rs696 were genotyped in 342 controls and 338 patients with defective spermatogenesis from a southern Chinese population. The results showed the rs696 AA genotype to be significantly more common (21.60% versus 14.33%, P=0.013) and the rs696 GG genotype to be significantly rarer (28.99% versus 37.13%, P=0.024) in the cases than in the controls. After subjects were stratified into smokers and nonsmokers, these differences were only observed in nonsmokers. Further analysis showed the rs696 AA genotype to be significantly closely associated with defective spermatogenesis in all subjects (P=0.014, OR=1.647) and in nonsmokers (P=0.036, OR=1.889). In a TM3 cell model, exposure to cigarette smoke condensate was found to activate NF-B luciferase activity and altered transcriptional level of NF-B pathway genes. In conclusion, this study demonstrates an association between functional polymorphisms of the IB rs696 and cigarette smoking with the risk of defective spermatogenesis, suggesting some interaction between the NF-B signalling pathway and smoking-related ROS in human spermatogenesis.