Indirubin regulates T cell differentiation by promoting αVβ8 expression in bone marrow-derived dendritic cells to alleviate inflammatory bowel disease

Inflammatory bowel disease is a disease that can invade the whole digestive tract and is accompanied by immune abnormalities. Immune dysfunction involving dendritic cells (DCs) and T cells is recognized as a key factor in diseases. Indirubin (IDRB) exerts antiinflammatory effects and can help in treating immune diseases. This study aimed to isolate bone marrow-derived dendritic cells (BMDCs) using lipopolysaccharide (LPS) to obtain mature DCs (mDCs). The expression of CD80, CD86, CD40, and MHC-II was detected using flow cytometry after treatment with IDRB. alpha V beta 8 siRNA was used to knock down alpha V beta 8 in mDCs, and the expression of CD80, CD86, CD40, and MHC-II was detected. Meanwhile, DCs were co-cultured with T cells. Then, T cell differentiation was detected using flow cytometry, and the cytokine levels were detected using enzyme-linked immunosorbent assay. The animal model of dextran sulfate sodium (DSS)-induced inflammatory bowel disease was established in mice. After intervention with IDRB and alpha V beta 8 shRNA, the intestinal tissues were evaluated using H&E staining, disease activity index (DAI) score, and histological damage index, and the corresponding factors and cytokines to regulatory T cells (Treg) and Th17 were measured. The results showed that alpha V beta 8 was expressed in immature DCs and mDCs. CD80, CD86, CD40, and MHC-II expression decreased after IDRB treatment in mDCs. Meanwhile, the expression of TNF-alpha and TGF-beta also decreased after IDRB treatment. The effect of IDRB on the expression of CD80, CD86, CD40, MHC-II, TNF-alpha, and TGF-beta in mDCs was reversed by alpha V beta 8 siRNA. The Treg differentiation increased after IDRB treatment, while the differentiation of Th17 cells was inhibited. This effect of IDRB was reversed by mDCs after treatment with alpha V beta 8 siRNA. In vivo experiments showed that IDRB alleviated the symptoms of inflammatory bowel disease in animals. Enteritis significantly reduced, and the effect of IDRB was reversed by alpha V beta 8 shRNA. The results suggested that IDRB regulated the differentiation of T cells by mediating the maturation of BMDCs through alpha V beta 8. This study confirmed the therapeutic effect of IDRB in inflammatory bowel disease and suggested that IDRB might serve as a potential drug.