Interaction of Interleukin 7 Receptor (IL7R) and IL6 Gene Polymorphisms with Smoking Associated with Susceptibility to Asthma in Chinese Han Adults

Abstract

ABSTRACT Background the aim of this study was to investigate the relationship between the risk of asthma and multiple single nucleotide polymorphisms (SNPs) in interleukin 7 receptor (IL7R) and IL6 genes, as well as the gene- environment interactions. Methods This is a hospital- based case- control study. A total of 430 patients with asthma were continuously recruited. Four SNPs within IL7R and IL6 gene were genotyped by PCR based restriction fragment length polymorphism. The Hardy- Weinberg balance of all participants was tested by SNPstats. The best interaction combination of four SNPs in IL7R and IL6 genes and smoking was screened by generalized multifactor dimensionality reduction (GMDR). Logistic regression was used to test the association between four SNPs and asthma, and stratified analysis for rs1800795 gene-smoking interaction, synergy index (SI) was calculated. Results The rs1494558-G and rs1800795-C were associated with an increased risk of asthma, adjusted ORs (95% CI) was 1.81 (1.29–2.42) and 1.75 (1.20–2.28), respectively. GMDR indicated that the test accuracy for two-locus model involving rs1800795 and smoking was 0.5721, and the p = .011, the results providing evidence for rs1800795 gene-smoking interaction. The asthma risk was higher in smokers with GC or CC genotype than the sum of risks in subjects with smoking or GC or CC genotype alone, compared to the never smokers with GG genotype, the OR (95%CI) was 4.97 (3.01–7.24), and the synergy index (SI) was 1.68 (1.08–2.60). Conclusions The rs1494558-G and rs1800795-C alleles, gene- environment interaction between rs1800795 and smoking were all associated with increased asthma risk.