24-Norursodeoxycholic acid reshapes immunometabolism in CD8+ T cells and alleviates hepatic inflammation.

BACKGROUND & AIMS: 24-Norursodeoxycholic acid (NorUDCA) is a novel therapeutic bile acid used to treat immune-mediated cholestatic liver diseases, such as primary sclerosing cholangitis (PSC), where dysregulated T cells including CD8+ T cells contribute to hepatobiliary immunopathology. We hypothesized that NorUDCA may directly modulate CD8+ T cell function thus contributing to its therapeutic efficacy. METHODS: NorUDCA's immunomodulatory effects were first studied in Mdr2-/- mice, as a cholestatic model of PSC. To differentiate NorUDCA's immunomodulatory effects on CD8+ T cell function from its anticholestatic actions, we also used a non-cholestatic model of hepatic injury induced by an excessive CD8+ T cell immune response upon acute non-cytolytic lymphocytic choriomeningitis virus (LCMV) infection. Studies included molecular and biochemical approaches, flow cytometry and metabolic assays in murine CD8+ T cells in vitro. Mass spectrometry was used to identify potential CD8+ T cell targets modulated by NorUDCA. The signaling effects of NorUDCA observed in murine cells were validated in circulating T cells from patients with PSC. RESULTS: NorUDCA demonstrated immunomodulatory effects by reducing hepatic innate and adaptive immune cells, including CD8+ T cells in the Mdr2-/- model. In the non-cholestatic model of CD8+ T cell-driven immunopathology induced by acute LCMV infection, NorUDCA ameliorated hepatic injury and systemic inflammation. Mechanistically, NorUDCA demonstrated strong immunomodulatory efficacy in CD8+ T cells affecting lymphoblastogenesis, expansion, glycolysis and mTORC1 signaling. Mass spectrometry identified that NorUDCA regulates CD8+ T cells by targeting mTORC1. NorUDCA's impact on mTORC1 signaling was further confirmed in circulating PSC CD8+ T cells. CONCLUSIONS: NorUDCA has a direct modulatory impact on CD8+ T cells and attenuates excessive CD8+ T cell-driven hepatic immunopathology. These findings are relevant for treatment of immune-mediated liver diseases such as PSC. LAY SUMMARY: Elucidating the mechanisms by which 24-norursodeoxycholic acid (NorUDCA) works for the treatment of immune-mediated liver diseases, such as primary sclerosing cholangitis, is of considerable clinical interest. Herein, we uncovered an unrecognized property of NorUDCA in the immunometabolic regulation of CD8+ T cells, which has therapeutic relevance for immune-mediated liver diseases, including PSC.

The guanine nucleotide exchange factor Rin-like controls Tfh cell differentiation via CD28 signaling.

T follicular helper (Tfh) cells are essential for the development of germinal center B cells and high-affinity antibody-producing B cells in humans and mice. Here, we identify the guanine nucleotide exchange factor (GEF) Rin-like (Rinl) as a negative regulator of Tfh generation. Loss of Rinl leads to an increase of Tfh in aging, upon in vivo immunization and acute LCMV Armstrong infection in mice, and in human CD4+ T cell in vitro cultures. Mechanistically, adoptive transfer experiments using WT and Rinl-KO naïve CD4+ T cells unraveled T cell-intrinsic GEF-dependent functions of Rinl. Further, Rinl regulates CD28 internalization and signaling, thereby shaping CD4+ T cell activation and differentiation. Thus, our results identify the GEF Rinl as a negative regulator of global Tfh differentiation in an immunological context and species-independent manner, and furthermore, connect Rinl with CD28 internalization and signaling pathways in CD4+ T cells, demonstrating for the first time the importance of endocytic processes for Tfh differentiation.

Blocking pannexin1 reduces airway inflammation in a murine model of asthma.

Stressed or injured cells release ATP into the extracellular milieu via the pannexin1 (Panx1) channels, which is the basis of inflammation in a variety of conditions, including allergic lung inflammation. Although the role of Panx1 in mediating inflammation has been well established, the role of its mimetic peptide, 10Panx1, which inhibits ATP release from Panx1 channels, in allergic asthma remains understudied. The aim of this study was to evaluate the effects of using 10Panx1 to inhibit Panx1 channel in a murine model of ovalbumin (OVA)-induced asthma. We demonstrate that blockade of Panx1 significantly attenuated goblet cell hyperplasia and inflammatory cell infiltration into the lungs of OVA-sensitized mice. Inhibition of Panx1 also reduced the total and eosinophil cell numbers in the bronchoalveolar lavage fluid (BALF) and reduced expression of CCL11 and CCL2 in lung tissues from mice. Moreover, we detected lower levels of IL-5 and IL-13 in the culture supernatant of OVA-restimulated splenocytes from 10Panx1-treated mice. Collectively, our findings suggest that Panx1 inhibition of allergen-mediated lung inflammation has the potential to suppress allergic responses in asthma.