Role of Nox4 in Mitigating Inflammation and Fibrosis in Dextran Sulfate Sodium-Induced Colitis

BACKGROUND & AIMS: Fibrosis development in ulcerative colitis is associated directly with the severity of mucosal inflammation, which increases the risk of colorectal cancer. The transforming growth factor -5 (TGF-5) signaling pathway is an important source of tissue fibrogenesis, which is stim-ulated directly by reactive oxygen species produced from nicotinamide adenine dinucleotide phosphate oxidases (NOX). Among members of the NOX family, NOX4 expression is up -regulated in patients with fibrostenotic Crohn's disease (CD) and in dextran sulfate sodium (DSS)-induced murine colitis. The aim of this study was to determine whether NOX4 plays a role in fibrogenesis during inflammation in the colon using a mouse model.METHODS: Acute and recovery models of colonic inflamma-tion were performed by DSS administration to newly gener-ated Nox4-/-mice. Pathologic analysis of colon tissues was performed, including detection of immune cells, proliferation, and fibrotic and inflammatory markers. RNA sequencing was performed to detect differentially expressed genes between Nox4-/-and wild-type mice in both the untreated and DSS-treated conditions, followed by functional enrichment anal-ysis to explore the molecular mechanisms contributing to pathologic differences during DSS-induced colitis and after recovery.RESULTS: Nox4-/-mice showed increased endogenous TGF-5 signaling in the colon, increased reactive oxygen species levels, intensive inflammation, and an increased fibrotic region after DSS treatment compared with wild-type mice. Bulk RNA sequencing confirmed involvement of canonical TGF-5 signaling in fibrogenesis of the DSS-induced colitis model. Up -regulation of TGF-5 signaling affects collagen activation and T-cell lineage commitment, increasing the susceptibility for inflammation.CONCLUSIONS: Nox4 protects against injury and plays a crucial role in fibrogenesis in DSS-induced colitis through canonical TGF-5 signaling regulation, highlighting a new treatment target. (Cell Mol Gastroenterol Hepatol 2023