Basic Study
Copyright ©The Author(s) 2017. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Oct 28, 2017; 23(40): 7253-7264
Published online Oct 28, 2017. doi: 10.3748/wjg.v23.i40.7253
Prostaglandin E1 protects hepatocytes against endoplasmic reticulum stress-induced apoptosis via protein kinase A-dependent induction of glucose-regulated protein 78 expression
Fang-Wan Yang, Yu Fu, Ying Li, Yi-Huai He, Mao-Yuan Mu, Qi-Chuan Liu, Jun Long, Shi-De Lin
Fang-Wan Yang, Yu Fu, Ying Li, Yi-Huai He, Mao-Yuan Mu, Qi-Chuan Liu, Jun Long, Shi-De Lin, Department of Infectious Diseases, Affiliated Hospital of Zunyi Medical College, Zunyi 563003, Guizhou Province, China
Yu Fu, Department of Infectious Diseases, Heze Municipal Hospital, Heze 274000, Shandong Province, China
Author contributions: Yang FW and Fu Y contributed equally to this work; Yang FW, Fu Y, Li Y and He YH performed the experiments; Mu MY and Liu QC participated equally in the molecular investigations; Long J supervised the study; Lin SD designed and coordinated the research and wrote the manuscript.
Supported by the National Natural Science Foundation of China, No. 81160067 and No. 814600124.
Institutional review board statement: This study was approved by the Institutional Review Board of Affiliated Hospital of Zunyi Medical College, Guizhou Province, China.
Conflict-of-interest statement: The authors declare that they have no conflicts interest related to this study.
Data sharing statement: Technical appendix, statistical code, and dataset available from the corresponding author at linshide6@hotmail.com.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Shi-De Lin, MD, Professor of Medicine, Chief, Department of Infectious Diseases, Affiliated Hospital of Zunyi Medical College, 201 Dalian Street, Zunyi 563003, Guizhou Province, China. linshide6@hotmail.com
Telephone: +86-851-28609183 Fax: +86-851-28609183
Received: May 11, 2017
Peer-review started: May 13, 2017
First decision: June 22, 2017
Revised: July 24, 2017
Accepted: August 25, 2017
Article in press: August 25, 2017
Published online: October 28, 2017
Processing time: 170 Days and 13.3 Hours
Abstract
AIM

To investigate the protective effect of prostaglandin E1 (PGE1) against endoplasmic reticulum (ER) stress-induced hepatocyte apoptosis, and to explore its underlying mechanisms.

METHODS

Thapsigargin (TG) was used to induce ER stress in the human hepatic cell line L02 and hepatocarcinoma-derived cell line HepG2. To evaluate the effects of PGE1 on TG-induced apoptosis, PGE1 was used an hour prior to TG treatment. Activation of unfolded protein response signaling pathways were detected by western blotting and quantitative real-time RT-PCR. Apoptotic index and cell viability of L02 cells and HepG2 cells were determined with flow cytometry and MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] assay.

RESULTS

Pretreatment with 1 μmol/L PGE1 protected against TG-induced apoptosis in both L02 cells and HepG2 cells. PGE1 enhanced the TG-induced expression of C/EBP homologous protein (CHOP), glucose-regulated protein (GRP) 78 and spliced X box-binding protein 1 at 6 h. However, it attenuated their expressions after 24 h. PGE1 alone induced protein and mRNA expressions of GRP78; PGE1 also induced protein expression of DNA damage-inducible gene 34 and inhibited the expressions of phospho-PKR-like ER kinase, phospho-eukaryotic initiation factor 2α and CHOP. Treatment with protein kinase A (PKA)-inhibitor H89 or KT5720 blocked PGE1-induced up-regulation of GRP78. Further, the cytoprotective effect of PGE1 on hepatocytes was not observed after blockade of GRP78 expression by H89 or small interfering RNA specifically targeted against human GRP78.

CONCLUSION

Our study demonstrates that PGE1 protects against ER stress-induced hepatocyte apoptosis via PKA pathway-dependent induction of GRP78 expression.

Keywords: Hepatocytes; Endoplasmic reticulum stress; Thapsigargin; Glucose-regulated protein 78; Protein kinase A; Apoptosis

Core tip: The mechanism underlying the hepatoprotective effect of prostaglandin E1 (PGE1) remains unclear. In this study, we found that pretreatment with PGE1 protected hepatocytes against thapsigargin-induced apoptosis. PGE1 alone induced protein and mRNA expressions of glucose-regulated protein (GRP)78. Treatment with protein kinase A (PKA)-inhibitor H89, KT5720 or small interfering (si)RNA specifically targeted against human GRP78 blocked PGE1-induced up-regulation of GRP78. The hepatoprotective effect of PGE1 was lost by blocking GRP78 expression with either H89 or siRNA. Our study demonstrates for the first time that PGE1 protects against endoplasmic reticulum stress-induced hepatocyte apoptosis via PKA pathway-dependent induction of GRP78 expression.