Interleukin-37 mRNA expression in Microscopic and Ulcerative Colitis

Interleukin-37 (IL-37) is a newly described mediator down-regulating pro-inflammatory cytokines following TLR stimulation. Furthermore, IL-37 mediates protective anti-inflammatory effects in a murine DSS-induced colitis model and in a myocardial ischaemia model. Since no previous study has reported mucosal IL-37 expression in microscopic colitis (MC) or ulcerative colitis (UC) patients, we analysed IL-37 mRNA expression in collagenous colitis (CC), lymphocytic colitis (LC), UC patients and controls. IL-37 mRNA was significantly decreased (2-fold), in MC patients versus controls. However, there was no difference between patients with active MC compared to those in histopathological remission. Opposite to the active disease/remission results for MC, we found a five-fold significantly increased IL-37 mRNA expression in UC patients in remission as compared to those with active disease. TLR stimulation of the colon epithelial cell line T84 resulted in significantly increased IL-37 mRNA expression, suggesting the importance of further IL-37 functional studies.

Having in mind the anti-inflammatory properties of IL-37, a constantly decreased mucosal expression of IL-37 in MC patients might be one of the reasons for development of inflammation in those patients. The increased IL-37 mRNA in UC remission patients indicates either a direct role for IL-37 in inducing remission, or simply being an indirect marker of remission.