Dominant negative MORT1/FADD rescues mice from CD95 and TNF-induced liver failure.

Derangement of the apoptotic program is considered an important cause of liver disease. It became clear that receptor-mediated apoptosis is of specific interest in this context, and CD95 and CD120a, both members of the tumor necrosis factor (TNF) receptor superfamily, are the most prominent cell death receptors involved. The death signal is induced upon ligand binding by recruitment of caspases via the adapter molecule MORT1/FADD to the receptor and their subsequent activation. To investigate the role of MORT1/FADD in hepatocyte apoptosis, we generated transgenic mice expressing liver-specific dominant negative mutant. Mice looked grossly normal; breeding and liver development were not different compared with wild-type littermates. Expression of the transgene completely protected animals from liver failure induced by the anti-Fas antibody Jo2, whereas control animals died as expected 3 to 6 hours after i.p. injection of 15 microg antibody from acute hemorrhagic liver failure. Histology demonstrated only moderate inflammatory changes in the transgenic animals, whereas severe hemorrhagic hepatitis was observed in controls. Similar results were obtained in a model of TNF-mediated liver failure, in which transgenic animals survived significantly better than wild-type animals. In conclusion, our experiments provide evidence that MORT1/FADD is indispensable for Fas and TNF-mediated hepatic injury. This is not only of great importance for targeting future therapies for liver disease but might also serve as an intriguing model to study other causes of liver injury.