Ubiquitin-Conjugating Enzyme E2O Primes Hepatocytes to Restore Immune Tolerance in Autoimmune Hepatitis via Inhibiting Y-Box Binding Protein 1/Interleukin-6 Axis.

BACKGROUND & AIMS: Autoimmune hepatitis (AIH) is a chronic progressive inflammatory liver disease, with its incidence increasing continuously worldwide. The mechanisms underlying the regulation of immune tolerance in AIH remain largely unknown. This study investigated a novel regulatory pathway of regulatory T cell/T helper 17 (Treg/Th17) balance involving the ubiquitin-conjugating enzyme E2O (UBE2O) and underlying mechanisms.

METHODS

UBE2O expression was analyzed in patients and mice with AIH. In vivo UBE2O overexpression in a chronic AIH model and naïve CD4+ T differentiation induction assays were used to investigate the exact role of UBE2O in AIH. Liver samples were assessed by histology, immunochemistry, immunoblot, flow cytometry, and enzyme-linked immunosorbant assays. Mass spectrometry, co-immunoprecipitation, cytokine microarray, and site-specific mutation experiments were utilized to elucidate underlying molecular mechanisms.

RESULTS

We detected a reduction of UBE2O expression in livers of patients and mice with AIH. Low expression of UBE2O indicated severe liver inflammatory injury. Hepatic UBE2O overexpression experiments demonstrated that UBE2O alleviated hepatic injury, inflammation, and fibrosis, and restored Treg/Th17 balance in experimental AIH. Mechanistically, UBE2O was found to interact with and promote ubiquitination degradation of YBX1 at lysine 135 (K135), leading to the reduction of interleukin-6 transcription and secretion in hepatocytes, thus rewiring naïve CD4+ T cells differentiation into Tregs. Furthermore, YBX1 partially reversed the protective effects of UBE2O overexpression in AIH.

CONCLUSIONS

Our study revealed a previously unrecognized hepatocellular UBE2O/YBX1/interleukin-6 axis in AIH that primes hepatocytes to restore immune tolerance. Targeting UBE2O might provide a promising therapeutic target for AIH by linking posttranslational modification and hepatic immune tolerance.