Inhibition of bile acid conjugation improves cholestatic liver injury in mice with a humanized bile acid pool

Intrahepatic accumulation of bile acids (BAs) during cholestasis leads to liver and bile duct injury. We hypothesized that inhibiting BA conjugation would increase non-amidated BAs, alter BA composition, stimulate bile flow, and thereby improve liver and bile duct injury. Male FVB/N mice received 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) for 4 weeks to induce sclerosing cholangitis-like liver injury with/without siRNA against Cyp2c70 (siCyp2c70) for humanizing the BA pool. DDC-fed mice with/without siCyp2c70 were treated with siRNA inhibiting bile acid-CoA ligase BACL (siBacl) and subsequently BA conjugation. Liver injury was assessed biochemically and via (immune)histology. Bile flow, biliary BA and glutathione levels, hepatic hydroxyproline, transcriptomic and protein analyses were also evaluated. In DDC siCyp2c70 animals, siBacl reduced biliary conjugated BAs, associated with a 2-fold and 3-fold increase in bile flow and biliary glutathione output, respectively. Furthermore, biochemical and histological features of liver and bile duct injury improved. While hepatic inflammation was only partially reduced, fibrosis improved, reflected by decreased fibrogenic gene expression and lower hydroxyproline levels. CK19 and Vcam protein expression was significantly reduced. RNA sequencing indicated enhanced hepatic ROS-detoxifying gene expression accompanied by reduced malondialdehyde levels. Thus, inhibiting BA conjugation improved liver and bile duct injury, likely via increased bile flow, enhanced biliary glutathione secretion, and reduced oxidative stress.