Association between the -174 C/G polymorphism in the interleukin-6 (IL-6) gene and gastrointestinal involvement in patients with systemic sclerosis

Abstract

Genetic predisposition to systemic sclerosis (SSc) has still not been fully revealed. Interleukin-6 (IL-6) is a mediator of T cell proliferation and fibrotic events in SSc. Polymorphisms in the IL-6 are found to be important in susceptibility to development of SSc. We aimed to assess the frequency of -174 C/G of IL-6 gene polymorphism in SSc patients and healthy controls, as well as correlation with disease manifestations. In the case-control study, 102 patients with SSc and 93 controls were included. PCR-RFLP method was performed for genotyping promotor variants -174 C/G of IL-6 gene. The expression level of IL-6 was determined by qRT-PCR on subset of 50 patients and 13 healthy controls with different IL-6 genotypes. We used UCLA GIT 2.0 questionnaire to assess gastrointestinal involvement in SSc patients. The expression level of IL-6 gene was significantly higher in patients with SSc in comparison with healthy controls (p < 0.05). Carriers of C-allele of IL-6 gene compared to those with G allele, showed higher expression of IL-6 gene (95.8 vs. 41.2, p < 0.05), higher GIT total score (0.85 vs. 0.5, p < 0.05) and higher distension scale score (1.4 ± 0.9 vs. 0.78 ± 0.8, p = 0.05). No significant differences in genotype distribution and allele frequency were observed between patients and controls. The expression of IL6 gene varies significantly during the course of SSc. The IL-6 gene variant -174 C/G (presence of C-allele) is associated with higher IL-6 gene expression and greater GIT impairment in patients with SSc.