Role of TLR4-Mediated PI3K/AKT/GSK-3β Signaling Pathway in Apoptosis of Rat Hepatocytes.

Wei Jiang,Xian Zhang,Daorong Jiang,Min Zhao,Jianhe Gan

doi:10.1155/2015/631326

Abstract

We investigated the mechanism of the Toll-like receptor 4- (TLR4-) mediated PI3K/AKT/GSK-3β signaling pathway in rat hepatocytes apoptosis induced by LPS. The cultured rat hepatocytes were treated with LPS alone or first pretreated with TLR4 inhibitor, AKT inhibitor, and GSK-3β inhibitor, respectively, and then stimulated with the same dose of LPS. Cell viability, cell apoptotic rate, and apoptosis morphology were assessed; the level of P-AKTSer473, P-GSK-3βSer9, and active Caspase-3 and the ratio of Bax/Bcl-2 were evaluated. The results indicated that cell viability decreased, while cell apoptotic rate increased with time after LPS stimulation. The expression of P-AKTSer473 and P-GSK-3βSer9 in the LPS group decreased compared with the control, while the level of active Caspase-3 and the ratio of Bax/Bcl-2 were significantly increased. These effects were attenuated by pretreatment with CLI-095. In addition, the apoptotic ratio decreased after pretreatment with LiCl but increased following pretreatment with LY294002. The expression of P-AKTSer473 further decreased following pretreatment with LY294002 and the expression of P-GSK-3βSer9 increased following pretreatment with LiCl. Moreover, pretreatment with CLI-095 weakened LPS-induced nuclear translocation of GSK-3β. Our findings suggest that the TLR4-mediated PI3K/AKT/GSK-3β signaling pathway is present in rat hepatocytes and participates in apoptosis of BRL-3A cells.

Highlights

Acute liver failure (ALF) has a rapid onset, low cure rate, and high mortality rate
We investigated whether the TLR4/Phosphatidylinositol 3-kinase (PI3K)/AKT/glycogen synthase kinase-3β (GSK-3β) signaling pathway participates in apoptosis of BRL-3A cells
When P-GSK-3β activity was inhibited and stimulated with same dose of LPS, the expression level of P-GSK-3βSer9 was higher than that in LPS group. These results showed that the TLR4/PI3K/AKT/P-GSK-3β signaling pathway is involved in BRL-3A cell apoptosis

Summary

Introduction

Acute liver failure (ALF) has a rapid onset, low cure rate, and high mortality rate. The main pathological change is significant liver cell death which causes severe impairment of liver function [1]. Studies [2,3,4] have shown that apoptosis is one of the main forms of liver cell death in ALF. To date, the mechanism of cell apoptosis in ALF is unclear. The recently discovered toll-like receptors (TLRs), which are members of the pattern recognition receptor family, are attracting increasing attention due to their role in many infectious diseases and inflammatory lesions caused by nonpathogenic microorganisms. Takayashiki et al [7, 8] showed that the liver cell membrane expressed TLR4, and the level increased significantly in mice with hepatic failure [9]. To date, there are no reports on whether TLR4mediated signaling participates in liver cell apoptosis in ALF

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Conclusion