Inhibition of intestinal bile acid absorption by ASBT inhibitor A4250 protects against cholestatic liver and bile duct injury in MDR2-/- mouse model of sclerosing Cholangitis

Background and Aims: Approximately 95% of bile acids (BAs) excreted into bile are reabsorbed in the gut and circulate back to the liver for further biliary secretion. Therefore, pharmacological inhibition of the ileal apical sodium-dependent BA transporter (ASBT/SLC10A2) may protect against BA-mediated cholestatic liver and bile duct injury. Methods: 8-week-old Mdr2-/- (Abcb4-/-) mice (model of cholestatic liver injury and sclerosing cholangitis) received either a diet supplemented with A4250 (0.01% w/w) – a highly potent and selective ASBT inhibitor – or a chow diet. Liver injury was assessed biochemically and histologically after 4 weeks of A4250 treatment. Expression profiles of genes involved in BA homeostasis, inflammation and fibrosis were assessed via RT-PCR from liver and ileum homogenates. Intestinal inflammation was assessed by RNA expression profiling and immunohistochemistry. Bile flow and composition as well as biliary BA profiles were analyzed after 1 week of ASBT inhibitor feeding. Results: Mdr2-/- mice treated with A4250 showed significantly decreased serum ALT, AP and BAs levels, reduced hepatic expression of pro-inflammatory (Tnf-α, Vcam1, Mcp-1) and pro-fibrogenic (Col1a1, Col1a2) genes and bile duct injury (mRNA and immunohistochemistry for CK19). Furthermore, A4250 significantly reduced bile flow and biliary BA output, which correlated with reduced Bsep transcription, while Ntcp and Cyp7a1 were induced. Importantly, biliary BA output was reduced while other components including protective bicarbonate did not change in A-4250 treated mice. Conclusions: Pharmacological ASBT inhibition attenuates cholestatic liver and bile duct injury by reducing biliary BA output.