IL-9 promotes the pathogenesis of ulcerative colitis through STAT3/SOCS3 signaling.

Ulcerative colitis (UC) is a chronic condition in which the overreacting immune system may play an important role. It has been confirmed that the interleukin (IL) 9 (IL-9) participates in the pathogenesis of UC but the molecular mechanism is not fully illustrated. Here, we show that levels of peripheral blood cytokines IL-9, IL-8, IL-10, IL-6, IL-1 beta, IL-12, and tumor necrosis factor (TNF) were higher in patients with UC than normal control, and serum and local IL-9 levels were positively correlated with the disease activity grade. Moreover, IL-9 stimulation inhibited suppressor of cytokine signaling 3 (SOCS3) expression and wound healing ability in colonic epithelial cells and promoted the phosphorylation level of signal transducers and activators of transcription 3 (STAT3). And IL-9 stimulation promoted claudin-2 expression while inhibited claudin-3 and occludin expression. Furthermore, SOCS3 overexpression rescued the IL-9-induced effects. Altogether, IL-9 participates in the pathogenesis of UC through STAT3/SOCS3 signaling pathway and has the potential to serve as a possible therapeutic candidate in patients with UC.