Integrated Omics Reveals Tollip as an Regulator and Therapeutic Target for Hepatic Ischemia-Reperfusion Injury in Mice.

Hepatic ischemia-reperfusion (IR) injury is the leading cause of liver dysfunction and failure after liver resection or transplantation and lacks effective therapeutic strategies. Here, we applied a systematic proteomic analysis to identify the prominent contributors to IR-induced liver damage and promising therapeutic targets for this condition. Based on an unbiased proteomic analysis, we found that toll-interacting protein (Tollip) expression was closely correlated with the hepatic IR process. RNA sequencing analysis and phenotypic examination showed a dramatically alleviated hepatic IR injury by Tollip deficiency both in vivo and in hepatocytes. Mechanistically, Tollip interacts with apoptosis signal-regulating kinase 1 (ASK1) and facilitates the recruitment of tumor necrosis factor receptor-associated factor 6 (TRAF6) to ASK1, leading to enhanced ASK1 N-terminal dimerization and the subsequent activation of downstream mitogen-activated protein kinase (MAPK) signaling. Furthermore, the Tollip methionine and phenylalanine motif and TRAF6 ubiquitinating activity are required for Tollip-regulated ASK1-MAPK axis activation. Conclusion: Tollip is a regulator of hepatic IR injury by facilitating ASK1 N-terminal dimerization and the resultant c-Jun N-terminal kinase/p38 signaling activation. Inhibiting Tollip or its interaction with ASK1 might be promising therapeutic strategies for hepatic IR injury.

Targeting CASP8 and FADD-like apoptosis regulator ameliorates nonalcoholic steatohepatitis in mice and nonhuman primates.

Nonalcoholic steatohepatitis (NASH) is a progressive disease that is often accompanied by metabolic syndrome and poses a high risk of severe liver damage. However, no effective pharmacological treatment is currently available for NASH. Here we report that CASP8 and FADD-like apoptosis regulator (CFLAR) is a key suppressor of steatohepatitis and its metabolic disorders. We provide mechanistic evidence that CFLAR directly targets the kinase MAP3K5 (also known as ASK1) and interrupts its N-terminus-mediated dimerization, thereby blocking signaling involving ASK1 and the kinase MAPK8 (also known as JNK1). Furthermore, we identified a small peptide segment in CFLAR that effectively attenuates the progression of steatohepatitis and metabolic disorders in both mice and monkeys by disrupting the N-terminus-mediated dimerization of ASK1 when the peptide is expressed from an injected adenovirus-associated virus 8-based vector. Taken together, these findings establish CFLAR as a key suppressor of steatohepatitis and indicate that the development of CFLAR-peptide-mimicking drugs and the screening of small-molecular inhibitors that specifically block ASK1 dimerization are new and feasible approaches for NASH treatment.