Itaconate inhibits CD103⁺ T_RM cells and alleviates hepatobiliary injury in mouse models of primary sclerosing cholangitis

Background and aims: Primary sclerosing cholangitis (PSC) is a chronic progressive liver disease characterized by the infiltration of intrahepatic tissue-resident memory CD8(+) T cells (T-RM). Itaconate has demonstrated therapeutic potential in modulating inflammation. An unmet need for PSC is the reduction of biliary inflammation, and we hypothesized that itaconate may directly modulate pathogenic T-RM.Approach and results: The numbers of intrahepatic CD103(+) T-RM were evaluated by immunofluorescence in PSC (n = 32), and the serum levels of itaconate in PSC (n = 64), primary biliary cholangitis (PBC) (n = 60), autoimmune hepatitis (AIH) (n = 49), and healthy controls (n = 109) were determined by LC-MS/MS. In addition, the frequencies and immunophenotypes of intrahepatic T-RM using explants from PSC (n = 5) and healthy donors (n = 6) were quantitated by flow cytometry. The immunomodulatory properties of 4-octyl itaconate (4-OI, a cell-permeable itaconate derivative) on CD103(+) T-RM were studied in vitro. Finally, the therapeutic potential of itaconate was studied by the administration of 4-OI and deficiency of immune-responsive gene 1 (encodes the aconitate decarboxylase producing itaconate) in murine models of PSC. Intrahepatic CD103(+) T-RM was significantly expanded in PSC and was positively correlated with disease severity. Serum itaconate levels decreased in PSC. Importantly, 4-OI inhibited the induction and effector functions of CD103(+) T-RM in vitro. Mechanistically, 4-OI blocked DNA demethylation of RUNX3 in CD8(+)T cells. Moreover, 4-OI reduced intrahepatic CD103(+) T-RM and ameliorated liver injury in murine models of PSC.Conclusions: Itaconate exerted immunomodulatory activity on CD103(+) T-RM in both in vitro and murine PSC models. Our study suggests that targeting pathogenic CD103(+) T-RM with itaconate has therapeutic potential in PSC.