circSMAD4 Promotes Experimental Colitis and Impairs Intestinal Barrier Functions by Targeting Janus Kinase 2 Through Sponging miR-135a-5p
Jie Zhao, Zhiliang Lin, Pu Ying, Zhibin Zhao, Haojun Yang, Jun Qian, Yu Gong, Yan Zhou, Yi Dai, Yuwen Jiao, Weiming Zhu, Honggang Wang, Liming Tang
Abstract
BACKGROUND: Numerous studies have explored the association between circular RNAs [circRNAs] and Crohn's disease [CD]. However, the pathological role, biological functions, and molecular mechanisms of circRNAs in CD have not been fully elucidated. METHODS: The circRNA microarray analysis was performed to identify deregulated circRNAs in colon tissues. The identified circRNAs were verified through quantitative real-time polymerase chain reaction [qRT-PCR]. In vivo and in vitro functional studies were performed to verify the role of circSMAD4 in CD and investigate the mechanisms involved. RESULTS: We found that circSMAD4 was the most significantly upregulated circRNA. The expression level of circSMAD4 was positively correlated with levels of inflammatory factors. Overexpression of circSMAD4 impaired tight junction [TJ] proteins and enhanced apoptosis of epithelial cells. These effects were reversed by treatment with miR-135a-5p mimic. Mechanistic studies showed that circSMAD4 exerts its effects on CD by 'sponging' miR-135a-5p to regulate Janus kinase 2 [JAK2]. Si-circSMAD4 delivery through microspheres ameliorated experimental colitis and protected the intestinal barrier function in IL-10 knockout mice. CONCLUSION: This study shows that circSMAD4 regulates the progression of experimental colitis via the miR-135a-5p/JAK2 signalling axis and it may be a potential therapeutic target.