Abstract
BackgroundProgrammed cell death or apoptosis is an essential process for tissue homeostasis. Hepatocyte apoptosis is a common mechanism to many forms of liver disease. This study was undertaken to test the role of ILK in hepatocyte survival and response to injury using a Jo-2-induced apoptosis model.MethodsFor survival experiments, ILK KO and WT mice received a single intraperitoneal injection of the agonistic anti-Fas monoclonal antibody Jo-2 at the lethal dose (0.4 μg/g body weight) or sublethal dose (0.16 μg/g body weight). For further mechanistic studies sublethal dose of Fas monoclonal antibody was chosen.ResultsThere was 100% mortality in the WT mice as compared to 50% in the KO mice. We also found that hepatocyte specific ILK KO mice (integrin linked kinase) died much later than WT mice after challenge with a lethal dose of Fas agonist Jo-2. At sublethal dose of Jo-2, there was 20% mortality in KO mice with minimal apoptosis whereas WT mice developed extensive apoptosis and liver injury leading to 70% mortality due to liver failure at 12 h. Proteins known to be associated with cell survival/death were differentially expressed in the 2 groups. In ILK KO mice there was downregulation of proapoptotic genes and upregulation of antiapoptotic genes.ConclusionsMechanistic insights revealed that pro-survival pathways such as Akt, ERK1/2, and NFkB signaling were upregulated in the ILK KO mice. Inhibition of only NFkB and ERK1/2 signaling led to an increase in the susceptibility of ILK KO hepatocytes to Jo-2-induced apoptosis. These studies suggest that ILK elimination from hepatocytes protects against Jo-2 induced apoptosis by upregulating survival pathways. FAK decrease may also play a role in this process. The results presented show that the signaling effects of ILK related to these functions are mediated in part mediated through NFkB and ERK1/2 signaling.
Highlights
Programmed cell death or apoptosis is an essential process for tissue homeostasis
We report that genetic ablation of Integrin-linked kinase (ILK) from hepatocytes protects from Jo-2 induced apoptosis due to upregulation of survival signaling mainly ERK and NFB signaling
Effect of genetic ablation of ILK from hepatocytes on Fasinduced animal death and fulminant hepatitis To determine whether ILK may play a role in the regulation of hepatocyte survival from apoptosis inducing stimuli, we determined the sensitivity of mice lacking ILK to Fas-induced apoptosis
Summary
Programmed cell death or apoptosis is an essential process for tissue homeostasis. Hepatocyte apoptosis is a common mechanism to many forms of liver disease. Apoptosis can be triggered by Fas receptor mediated signaling as well as different stimuli that provoke cell stress. All these stimuli converge at the activation of caspase 3 that leads to internucleosomal DNA degradation, chromatin condensation, cell shrinkage, and formation of small apoptotic bodies that are phagocytosed by neighboring macrophages [4]. Administration anti-Fas agonistic antibody Jo-2 to mice leads to rapid death of the animals due to fulminant hepatitis, mimicking certain forms of acute liver failure (ALF) in humans [5]. Fas (CD95/APO-1), a 43-kDa cell surface glycoprotein, belongs to the tumor necrosis factor receptor superfamily, and mediates apoptosis upon binding with its cognate ligand, or artificially with specific agonistic antibodies
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