Hepatic NcoR1 deletion exacerbates ischemia and reperfusion (IR) induced liver injury regulated by NF-kB p65 [sham-IR]

Background & Aims: Liver ischemia-reperfusion (IR) injury is a common and serious complication in liver transplantation surgery. Disturbances of mitochondrial function, altered lipid metabolism, and insulin resistance are pathways shown to participate in acute and chronic liver diseases. NcoR1 was previously shown to integrate in all these damage pathways in liver, adipose tissue, and muscle, whereby its mechanistic role is not fully understood. Here, we delineated hepatocytic NcoR1 in liver ischemia-reperfusion injury. Methods: We established an IR model in mice, measured liver function related enzymes in serum, SOD, and combined these data with HE staining and PCR assays from liver sections and lysates, respectively to determine the extent of liver injury. We used mice with albumin-Cre/LoxP system mediated hepatocyte-specific NcoR1 depletion (NcoR1△Hep) to investigate the role of NcoR1 in the etiopathogenesis of liver IR and to delineate potential related mechanisms. We also analysed the impact of NcoR1 on oxidative stress mediated cell damage, including activation of NFB signaling activation in hepatocytes in gain and loss of function studies, using immunoblotting and immunofluorescence. Results: Upon ischemia and reperfusion injury (IR), as evidenced by increased levels of liver enzymes (ALT, AST), and inflammatory cytokines (Tnf, Mcp1 et al), NcoR1 expression levels decreased at both, mRNA and protein levels in total liver lysates. To discriminate cell type specific effects, we successfully established NcoR1△Hep mice, and found that depletion of Ncor1 in hepacotytes exhibited more severe liver injury from IR, as compared to NcoR1fl/fl control mice, as evidenced by the aforementioned parameters. Silencing NcoR1 or Ncor1 deficiency promoted both, parameters of inflammatory and oxidative stress such as Gclc, Gclm, Hmox1, and Ccl2, et, al. in AML12 cells and primary mouse hepatocytes, while NcoR1 over-expression shows the opposite results. Further, IR treated NcoR1△Hep mice displayed increased phosphorylation of p65, an essential parameter of the NFB signaling pathway, a critical mediator of stress signals in hepatocytes. Gene silencing of p65 in primary hepatocytes increased NcoR1 expression, suggesting that NFkB/p65 signaling is a negative regulator of NcoR1 expression. Conclusion: Our results indicate that damage mediated activation of NFB/p65 signaling decreases NcoR1 expression in hepatocytes, which is required for IR aggravation.