Bile Acid-Activated IRE1α Pathway Promotes NK Cell-Mediated Cholangiocyte Injury in Primary Sclerosing Cholangitis

Abstract Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease characterized by progressive bile duct inflammation and fibrosis. Despite its significant clinical burden, the molecular mechanisms underlying PSC pathogenesis remain poorly understood, limiting therapeutic options. Here, we integrated bioinformatic analyses of transcriptomic datasets with experimental validation in a bile duct ligation mouse model and in vitro cell systems. Differential gene expression, weighted gene co-expression network analysis, and Mendelian randomization were performed to identify key molecular signatures. Single-cell RNA sequencing characterized cellular heterogeneity. The IRE1α-NK cell axis was validated using pharmacological inhibition, siRNA knockdown, and NK cell depletion approaches in bile acid-treated NK cells, co-culture systems, and a mouse model of cholestatic bile duct injury. We identified Endoplasmic Reticulum To Nucleus Signaling 1 (ERN1, also as a key mediator in PSC pathogenesis, with causal relationships to disease risk. Single-cell transcriptomic analysis revealed significant NK cell enrichment in PSC samples. In both the bile duct ligation mouse model and in vitro systems, bile acids induced IRE1α pathway activation in NK cells, leading to enhanced cytotoxicity against cholangiocytes. Pharmacological inhibition or genetic knockdown of IRE1α prevented bile acid-induced NK cell activation and cytotoxicity. In vivo, both IRE1α inhibition and NK cell depletion attenuated liver injury, inflammation, and fibrosis in the mouse model. Our data suggest a novel pathogenic mechanism in PSC involving bile acid-induced IRE1α activation in NK cells, promoting cholangiocyte injury. The IRE1α-NK cell axis represents a promising therapeutic target for PSC treatment.