Relationship between aberrant expression of interleukin-6 and gene methylation in ulcerative colitis

Objective To investigate the relationship between aberrant expression of interleukin 6 (IL-6) and gene methylation in patients with ulcerative colitis (UC), and to clarify the mechanism of epigenetics in UC. Methods From March 2017 to March 2018, a total of 59 UC patients admitted to the Department of Gastroenterology, General Hospital Affiliated to Tianjin Medical University were enrolled, and at the same time 58 normal individuals who received health checkups were selected as healthy controls. Blood samples and colonic mucosa specimens of UC group and healthy control group were collected. DNA methyltransferase (DNMT) activity, methylation level of CpG locus in IL-6 promoter region and expression level of IL-6 were detected. Chi-square test and student′s t test were performed for statistical analysis. Results The methylation level and IL-6 expression level examination were completed in 24 and 30 cases of UC group, respectively; which were detected in 21 and 20 cases of healthy control group, respectively. The activity of DNMT of UC group was significantly lower than that of healthy control group ((16.48±6.17) OD·h-1·mg-1 vs. (62.48±33.88) OD·h-1·mg-1), and the difference was statistically significant (t=3.707, P<0.05). The ratios of methylation, partial methylation and non-methylation of UC group were 31.2% (15/48), 50.0% (24/48) and 18.8% (9/48), respectively, and those of healthy control group were 58.3%(35/60), 21.7%(13/60) and 20.0%(12/60), and the difference between the two groups was statistically significant (χ2=10.495, P<0.05). The positive expression rate of IL-6 in intestinal mucosa of UC group was higher than that of healthy control group (100.0%, 21/21 vs. 25.0%, 5/20), and the difference was statistically significant (χ2=24.837, P<0.05). The serum IL-6 level of UC group was higher than that of healthy control group ((1 075.02±661.95) ng/L vs. (583.43±425.10) ng/L), and the difference was statistically significant (t=3.245, P<0.05). Conclusion The decrease of DNMT activity in the intestinal mucosa of UC patients may reduce the methylation level of IL-6 gene promoter region, which is correlated with the increased level of IL-6 expression in the intestinal mucosa and serum, and involve in the inflammatory process of UC. Key words: Colitis, ulcerative; DNA methylation; Methyltransferases; Interleukin-6