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

Abstract

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 NEMOΔhepa 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 NEMOΔhepa 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 NEMOΔhepa 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, NEMOΔhepa mice are an interesting tool to give insight into liver pathophysiology and to develop future therapeutic strategies. © 2009 Beraza et al.