Abstract

Objective24-Nor-ursodeoxycholic acid (NorUDCA) is a novel therapeutic bile acid for treating primary sclerosing cholangitis (PSC), an immune-mediated cholestatic liver disease. Since PSC strongly associates with inflammatory bowel diseases (IBD) driven by TH17/Treg imbalance, we aimed to explore NorUDCAs immunomodulatory potential on intestinal TH17/Treg balance. DesignNorUDCAs impact on TH17/Treg tissue distribution was first assessed in Mdr2-/- mouse model of PSC. We specifically investigated NorUDCAs effect on modulating TH17/Treg balance in a CD4+ T cell driven colitis model induced by adoptive transfer of CD25-CD44lowCD45RBhighCD4+ TNaive cells into Rag2-/- mice, mimicking human IBD. Mechanistic studies were performed using molecular approaches, flow cytometry and metabolic assays in murine TH17 cells in vitro. NorUDCAs signaling effects observed in murine system were further validated in circulating CD4+ T cells from PSC patients with co-existing IBD. ResultsNorUDCA promoted Treg generation in both liver and intestine in the Mdr2-/- model. In the experimental IBD model, NorUDCA attenuated intestinal immunopathology. Mechanistically, NorUDCA demonstrated strong immunomodulatory efficacy in counteracting TH17/Treg imbalance by restricting glutaminolysis in differentiating TH17 cells, thus suppressed -Ketoglutarate-dependent mTORC1 activation, glycolysis and enhanced FOXP3 expression. NorUDCAs impact on mTORC1 signaling was further confirmed in circulating CD4+ T-cells from PSC patients with IBD. ConclusionNorUDCA possesses direct immunometabolic modulatory potency to counteract TH17/Treg imbalance and ameliorate excessive TH17 cell driven intestinal immunopathology. These findings extend future clinical applications of NorUDCA for treatment of TH17 cell-mediated disorders along the gut-liver axis and beyond. Significance of this studyO_ST_ABSWhat is already known on this subject?C_ST_ABSO_LIPSC is an immune-mediated cholestatic liver disease highly associated with IBD where TH17/Treg imbalance drives immunopathogenesis; seeking effective therapeutics covering both liver and intestinal disease in PSC is of high clinical relevance. C_LIO_LIIndependent of anti-cholestatic effects, NorUDCA has recently been shown to possess direct immunomodulatory properties on CD8+ T cell metabolism, lymphoblastogenesis and clonal expansion through targeting mTORC1 signaling. C_LIO_LISince mTORC1 serves as critical metabolic checkpoint orchestrating TH17/Treg axis, inhibiting mTORC1 activity represents a potential treatment avenue counteracting TH17/Treg imbalance under intestinal inflammatory conditions. C_LI What are the new findings?O_LINorUDCA enriches FOXP3+ Treg population in both liver and intestinal tissue in the cholestatic Mdr2-/- mouse model of PSC. C_LIO_LINorUDCA exhibits direct immunomodulatory efficacies in suppressing excess TH17 cell-mediated intestinal immunopathology and promotes FOXP3+ Treg generation in an experimental IBD model. C_LIO_LIMechanistically, NorUDCA counteracts TH17/Treg imbalance by restricting glutaminolysis in differentiating TH17 cells, thus suppresses -Ketoglutarate-dependent mTORC1 activation, glycolysis and enhances FOXP3 expression. C_LIO_LINorUDCAs impact on mTORC1 signaling was further confirmed in circulating CD4+ T cells from patients with PSC and IBD. C_LI How might it impact on clinical practice in the foreseeable future?These findings advance our current understanding of therapeutic potentials of NorUDCA, which might represent a novel therapeutic strategy in the treatment of PSC and concomitant IBD and other TH17-mediated intestinal diseases.