E3 ubiquitin ligase RNF180 mediates the ALKBH5/SMARCA5 axis to promote colon inflammation and Th17/Treg imbalance in ulcerative colitis mice

Abstract

SMARCA5, a protein in the SWI/SNF family, has been previously implicated in the development of ulcerative colitis (UC) through methylation. However, the specific molecular mechanisms by which SMARCA5 contributes to colonic inflammation and the imbalance between Th17 and Treg cells remain unclear. This study was designed to explore these molecular mechanisms. A UC mouse model was established using dextran sulfate sodium induction, followed by measurements of mouse weight, disease activity index (DAI) score, colon length, pathological changes in the colon, and FITC-dextran concentration. The levels of IL-17a, IFN-γ, IL-6, TNF-α, TGF-β, and IL-10 were measured, along with the protein expression of ZO-1 and Occludin. Flow cytometry was used to assess the presence of IL-17 + CD4 + (Th17 +) cells and FOXP3 + CD25 + CD4 + (Treg +) cells in the spleen and mesenteric lymph nodes of UC mice. We observed that SMARCA5 and RNF180 were increased, while ALKBH5 was downregulated in UC mouse colon tissue. SMARCA5 or RNF180 knockdown or ALKBH5 overexpression ameliorated the colon inflammation and Th17/Treg cell imbalance in UC mice, shown by increased body weight, colon length, FOXP3 + CD25 + CD4 + T cells, and the levels of ZO-1, Occludin, TGF-β, IL-10, and FOXP3. It decreased DAI scores, IL-17 + CD4 + T cells, and levels of IL-17a, IFN-γ, IL-6, TNF-α, and ROR-γt. ALKBH5 inhibited SMARCA5 expression via m6A modification, while RNF180 reduced ALKBH5 expression via ubiquitination. Our findings indicate that RNF180 aggravated the colon inflammation and Th17/Treg cell imbalance in UC mice by regulating the ALKBH5/SMARCA5 axis.