Genetic variation in CYP1A1 and AHRR genes increase the risk of systemic lupus erythematosus and exacerbate disease severity in smoker patients.

BACKGROUND: Genetic variations of aryl hydrocarbon receptor (AHR) pathway genes could influence the imbalanced immune response to xenobiotics. Therefore, we aimed to investigate the polymorphism of AHR pathway genes in systemic lupus erythematosus (SLE) patients in association with smoking. METHODS: Genomic DNA from patients (N = 107) and controls (N = 105) of a population from northeast of Iran was used for genotyping of CYP1A1 T>C (rs4646903) and AHRR C>G (rs2292596) variants. The SLEDAI score and smoking status of the patients were registered. The AHR activity was estimated by CYP1A1 and CYP1B1 gene expression in peripheral blood mononuclear cells (PBMC). RESULTS: The C allele in rs4646903 (odds ratio [OR] = 2.67) and G allele in rs2292596 (OR = 1.79) SNPs were significantly associated with the increased risk of SLE. The AHR pathway was more active in high-risk CYP1A1/AHRR: C/G haplotype. The most severe disease was observed in smoker patients with high-risk haplotype and both smoking (Exp (s) = 9.5) and high-risk CYP1A1/AHRR (C/G) haplotype (Exp (s) = 3.7) can significantly increase the likelihood of having severe (SLEDAI ≥ 20) SLE disease activity. CONCLUSION: Our findings indicated the association of xenobiotic-metabolizing genes (CYP1A1, AHRR) polymorphisms with the susceptibility to SLE and disease severity regarding the smoking background, suggesting the interaction of gene and environmental risk factors in SLE pathogenesis.