Loss of cellular FLICE-inhibitory protein promotes acute cholestatic liver injury and inflammation from bile duct ligation

Background: Cholestatic liver injury results from impaired bile flow or metabolism and promotes hepatic inflammation and fibrogenesis. Toxic bile acids that accumulate in cholestasis induce apoptosis and contribute to early cholestatic liver injury, which is amplified by accompanying inflammation. Aim of the current study was to evaluate the role of the anti-apoptotic caspase 8-homologue cellular FLICE-inhibitory (cFLIP) protein during acute cholestatic liver injury. Methods: Transgenic mice exhibiting hepatocyte-specific deletion of cFLIP (cFLIP -/- ) were utilized for in vivo and in vitro analysis of cholestatic liver injury using bile duct ligation (BDL) and the addition of bile acids ex vivo. Results: Loss of cFLIP in hepatocytes promoted acute cholestatic liver injury early after BDL which was characterized by a rapid release of pro-inflammatory and chemotactic cytokines (TNF, IL-6, IL-1β, CCL2, CXCL1 and CXCL2), increased presence of CD68+ macrophages and influx of neutrophils in the liver and resulting apoptotic and necrotic hepatocyte cell death. Mechanistically, liver injury in cFLIP -/- mice was aggravated by reactive oxygen species (ROS) and sustained activation of the c-Jun-N-terminal kinases (JNK) signaling pathway. In parallel cytoprotective nuclear factor-kappaB (NF-κB) p65, A20 and the mitogen-activated protein kinase (MAPK) p38 were inhibited. Increased injury in cFLIP -/- mice was accompanied by activation of hepatic stellate cells (HSC) and profibrogenic regulators. Conclusion: The antagonistic caspase 8-homologue cFLIP is a critical regulator of acute, cholestatic liver injury.