Hepatocyte-specific NEMO deletion promotes NK/NKT cell– and TRAIL-dependent liver damage

Nuclear factor κB (NF-κB) is one of the main transcription factors involved in regulating apoptosis, inflammation, chronic liver disease, and cancer progression. The IKK complex mediates NF-κB activation and deletion of its regulatory subunit NEMO in hepatocytes (NEMO(Δhepa)) triggers chronic inflammation and spontaneous hepatocellular carcinoma development. We show that NEMO(Δhepa) mice were resistant to Fas-mediated apoptosis but hypersensitive to tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) as the result of a strong up-regulation of its receptor DR5 on hepatocytes. Additionally, natural killer (NK) cells, the main source of TRAIL, were activated in NEMO(Δhepa) livers. Interestingly, depletion of the NK1.1(+) cells promoted a significant reduction of liver inflammation and an improvement of liver histology in NEMO(Δhepa) mice. Furthermore, hepatocyte-specific NEMO deletion strongly sensitized the liver to concanavalin A (ConA)–mediated injury. The critical role of the NK cell/TRAIL axis in NEMO(Δhepa) livers during ConA hepatitis was further confirmed by selective NK cell depletion and adoptive transfer of TRAIL-deficient(−/−) mononuclear cells. Our results uncover an essential mechanism of NEMO-mediated protection of the liver by preventing NK cell tissue damage via TRAIL/DR5 signaling. As this mechanism is important in human liver diseases, NEMO(Δhepa) mice are an interesting tool to give insight into liver pathophysiology and to develop future therapeutic strategies.