Project description:Inflammatory bowel disease (IBD) is a complex and relapsing inflammatory disease, and patients with IBD exhibit a higher risk of developing colorectal cancer (CRC). Epithelial barrier disruption is one of the major causes of inflammatory bowel disease (IBD) in which epigenetic modulations are pivotal elements. However, the epigenetic mechanisms underlying the epithelial barrier integrity regulation remain largely unexplored. Here, we investigated how SETD2, a histone H3K36 trimethyltransferase, maintains intestinal epithelial homeostasis under inflammatory conditions. GEO public database and IBD tissues were used to investigate the clinical relevance of SetD2 in IBD. To define the role of SetD2 in the colitis, we generated mice with epithelial-specific deletion of Setd2 (Setd2Vil-KO mice). Acute colitis was induced by 2% dextran sodium sulfate (DSS), and colitis-associated CRC was induced by injecting azoxymethane (AOM), followed by three cycles of 2% DSS treatments. Colon tissues were collected from mice and analyzed by histology, immunohistochemistry and immunoblots. Organoids were generated from Setd2Vil-KO and control mice, and were stained with 7-AAD to detect apoptosis. We isolated intestinal epithelial cells (IECs), performed RNA-seq and H3K36me3 ChIP-seq analysis to uncover the mechanism. Results were validated in functional rescue experiments by N-acetyl-l-cysteine (NAC) treatment and transgenes expression in IECs. SETD2 expression was decreased in IBD patients and DSS-treated colitis mice. Setd2Vil-KO mice had abnormal loss of mucosa-producing goblet cells and antimicrobial peptide (AMP)-producing Paneth cells, and promoted early intestinal inflammation development. Consistent with the reduced SETD2 expression in IBD patients, Setd2Vil-KO mice exhibited increased susceptibility to DSS-induced colitis, accompanied by more severe epithelial barrier disruption. Intestinal permeability was markedly increased in Setd2Vil-KO mice. Setd2 ablation drived inﬂammation-associated CRC. Deletion of Setd2 resulted in excess reactive oxygen species (ROS), which led to cellular apoptosis and the defects in barrier integrity. N-acetyl-l-cysteine (NAC) treatment in Setd2Vil-KO mice rescued epithelial barrier injury and apoptosis. Moreover, overexpression of antioxidase PRDX6 in Setd2Vil-KO IECs largely alleviated the overproductions of ROS and improved the cellular survival. Deficiency of Setd2 specifically in the intestine aggravates epithelial barrier disruption and inflammatory response in colitis via a mechanism dependent on oxidative stress. More importantly, we show that Setd2 depletion results in excess ROS by directly down-regulating PRDX6, an antioxidant protein that inhibit excess ROS. Thus, our results highlight an epigenetic mechanism by which Setd2 mediates oxidative stress to modulate intestinal epithelial homeostasis.

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