Hepatic ischemia and reperfusion (I/R) injury is an important cause of liver injury that occurs in many clinical conditions including liver transplantation and liver resection surgeries. In the past decades, with increased high fat/carbohydrate diet and alcohol consumption, nonalcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD) have become the major causes of chronic liver disease in developed countries. One of the early common pathogenesis of NAFLD and ALD is hepatic steatosis. Hepatic steatosis impairs liver function after transplantation and causes implantation failure, reduces tolerance to I/R injury, and increases mortality. As a result, steatotic livers make the shortage of donor livers worse. However, the mechanisms by which fatty liver exacerbates hepatic I/R injury are not fully understood. Necroptosis is a novel cell death form known as ?programmed necrosis?. Necroptosis is mediated by the receptor-interacting protein kinase 1 (RIP1), RIP3 and its downstream molecule mix lineage kinase domain-like protein (MLKL).Our preliminary data demonstrated that both western diet and alcohol consumption increased hepatic necroptotic proteins. Moreover, mice fed with western diet that have developed steatosis were more susceptible to I/R injury. The long-term goal of this proposal is to elucidate the molecular mechanisms by which RIP kinases and their downstream molecule MLKL regulate hepatic I/R injury in alcoholic and nonalcoholic fatty livers. The central hypothesis is that alcoholic liver steatosis increases expression of RIP3 and MLKL that exacerbates liver I/R injury via inducing hepatic necroptosis. We have proposed two specific aims to test the hypothesis.
In Specific Aim 1, we will determine the mechanism by which hepatic steatosis increases expression of RIP3 and MLKL. We will determine how ethanol impairs hepatic proteasomal functions resulting in the accumulation of RIP3 and MLKL proteins.
In specific Aim 2, we will determine the role of necroptosis in I/R injury of alcoholic fatty liver. We will combine both pharmacological and genetic approaches to manipulate necroptosis in mouse livers and determine their roles in I/R injury of alcoholic fatty liver. The successful completion of this project will advance our understanding of alcoholic liver steatosis in hepatic I/R injury, which will have a significant positive impact on developing novel therapeutic strategies to improve the patient care with fatty liver-associated I/R injury by modulating RIP kinases and MLKL.
Hepatic ischemia and reperfusion (I/R) injury is a major complication in liver transplantation and liver resection surgeries. Alcoholic and non-alcoholic fatty liver diseases are major causes of liver diseases that exacerbate I/R-induced liver injury resulting the rejection of the use of fatty livers for liver transplantation. Elucidating the molecular mechanisms of how hepatic steatosis exacerbates I/R-induced liver injury by promoting necrotic cells in the liver will help to develop novel therapeutic strategies for improving I/R injury in steatotic livers.