Aggravation of post-ischemic liver injury by overexpression of A20, an NF-κB suppressor

Abstract

Backgroud & Aims: A20 is an intracellular ubiquitin-editing enzyme that plays an important role in the negative feedback regulation of NF-kappa B activation in response to a diverse range of stimuli. Liver ischemia/reperfusion injury is associated with rapid activation of NF-kappa B signaling, but the role of NF-kappa B in hepatic ischemia/reperfusion injury remains controversial. The NF-kappa B signaling pathway mediates both protective and deleterious effects in the liver. Here, we examined whether A20 inhibited or aggravated hepatic ischemia/reperfusion injury. Methods: We used I kappa B alpha super-repressor as a positive control and overexpressed A20 and I kappa B alpha super-repressor in the liver of C57BL/6 mice. Mice underwent 45 min of partial hepatic ischemia and were then reperfused. Results: Protein level of A20 was increased after reperfusion. Mice subjected to ischemia/reperfusion injury showed increased NF-kappa B activation, as evidenced by phosphorylation of I kappa B alpha and nuclear translocation of NF-kappa B. Prior transfection with Ad-A20 or Ad-I kappa B alpha super-repressor attenuated NF-kappa B activation and aggravated liver injury. Serum aminotransferases and proinflammatory cytokines, hepatocellular necrosis, and hepatic neutrophil infiltration were markedly increased compared to those of uninfected or control virus infected mice. In addition, A20 abolished the beneficial effect of ischemic preconditioning. Conclusions: Our results suggest that inhibition of NF-kappa B activation by A20 aggravated partial hepatic ischemia/reperfusion injury. Understanding how the NF-kappa B pathway plays a role in directing a clinical outcome may lead to better prospects of more rational approaches to reduce post-ischemic liver injury. (C) 2010 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.