The Correlation Between Plasma Levels of Vitamin D and Epigenetic Alterations of Treg-Specific Demethylated Region (TSDR) in Rheumatoid Arthritis Patients

Rheumatoid arthritis (RA) is the most common autoimmune inflammatory disease of joints among adults. Regulatory T cells (Treg) control immune responses in this illness. Through the expression of FoxP3, a Treg transcription factor, Vitamin D keeps autoimmune diseases in check. Yet, the molecular mechanism of FoxP3 expression by vitamin D is not well-inspected. It may influence FoxP3 expression via epigenetic changes. This study aimed to investigate the correlation between plasma levels of vitamin D and the demethylation of the TSDR region in Foxp3 promoter in patients with RA. Twenty untreated RA patients and 41 healthy controls participated in this study. Plasma levels of 25-OH vitamin D were measured by competitive ELISA method. The demethylation of TSDR regions in Foxp3 gene was also assessed using the quantitative Methylation Specific PCR (qMSP) method. The demethylation of TSDR region was significantly lower in RA patients compared with healthy controls (P=0.006). Vitamin D plasma levels were significantly higher in RA patients rather than healthy people (P=0.034). There was no statistically significant correlation between vitamin D plasma levels and demethylation of TSDR region. As expected, epigenetic alternation showed considerable difference between RA patients and healthy controls, but about vitamin D correlation with methylation modification, more studies are needed.