A link between promoter polymorphisms of the transforming growth factor β1 (TGFB1) and TGF-β1 receptor II (TGFBR2) genes and relapsing-remitting multiple sclerosis

Introduction
Multiple sclerosis (MS) is a chronic progressive autoimmune disease characterised by nerve demyelination, mediated by myelin-specific Th1 autoreactive cells. Transforming growth factor 1 (TGF-1) is a regulatory cytokine involved in MS aetiology by maintaining CD4+ cell differentiation and preventing autoimmune responses. Because of the important role of the TGF-1 signalling pathway in MS aetiopathogenesis, we aimed to investigate the association of two DNA polymorphisms: TGFB1C[-509]T and TGFBR2G[-875]A and their combined genotypes with the risk of MS development in a cohort of Bulgarian patients. The effect of the two promoter polymorphisms on the disease onset was also assessed.

Material and methods
In the study, a cohort of 183 patients with relapsing-remitting multiple sclerosis (RRMS) and 307 sex- and age-matched healthy subjects were recruited. Genotyping of the TGFB1C[-509]T (rs1800469) and TGFBR2G[-875]A (rs3087465) polymorphisms was performed by PCR-RFLP and PIRA-PCR approaches.

Results
Frequencies of the TGFB1T[-509]T genotype and TGFB1[-509]*T-allele were lower in RRMS men than in control healthy men (15.7% vs. 26.9%, 37.3% vs. 50.7%, respectively). Among males, the TGFB1T[-509]T genotype was related to a significantly reduced risk of RRMS (OR = 0.360, 95% CI: 0.126-1.028, p = 0.05) in comparison to the TGFB1C[-509]C genotype. Also, TGFB1[-509]*T-allele was more common in men with RRMS than in healthy men relative to the TGFB1[-509]*C-allele and was associated with a statistically significant protective effect (OR = 0.576, 95% CI: 0.341-0.974, p = 0.039). The combination of TGFB1T[-509]T/TGFB1T[-509]C and TGFBR2G[-875]A genotypes among men was associated with a significant protective effect compared to the wild-type homozygous TGFB1C[-509]C and TGFBR2G[-875]G genotypes (OR = 0.268, 95% CI: 0.088-0.818, p = 0.018). No significant association between rs1800469 and rs3087465 was observed among females with and without (controls) RRMS.

Conclusions
In summary, we suggest that in males, a higher TGF-1 level determined by TGFB1T[-509]T genotype in combination with the TGFBR2G[-875]A genotype might be a protective factor against RRMS development.