Basic Study
Copyright ©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Apr 7, 2020; 26(13): 1450-1462
Published online Apr 7, 2020. doi: 10.3748/wjg.v26.i13.1450
Calpain-2 activity promotes aberrant endoplasmic reticulum stress-related apoptosis in hepatocytes
Ru-Jia Xie, Xiao-Xia Hu, Lu Zheng, Shuang Cai, Yu-Si Chen, Yi Yang, Ting Yang, Bing Han, Qin Yang
Ru-Jia Xie, Lu Zheng, Shuang Cai, Yu-Si Chen, Yi Yang, Ting Yang, Bing Han, Qin Yang, Guizhou Provincial Key Laboratory of Pathogenesis and Drug Research on Common Chronic Diseases, College of Basic Medical Sciences, Guizhou Medical University, Guiyang 550025, Guizhou Province, China
Ru-Jia Xie, Lu Zheng, Shuang Cai, Yu-Si Chen, Yi Yang, Ting Yang, Bing Han, Qin Yang, Department of Pathophysiology, College of Basic Medical Sciences, Guizhou Medical University, Guiyang 550025, Guizhou Province, China
Xiao-Xia Hu, Department of Physiology, College of Basic Medical Sciences, Guizhou Medical University, Guiyang 550025, Guizhou Province, China
Author contributions: Xie RJ, Han B and Zheng L performed the experiments; Hu XX, Cai S, Chen YS, Yang Y and Yang T analyzed the data; Xie RJ and Yang Q designed the study; Xie RJ wrote the manuscript; all authors approved the final manuscript. Xie RJ and Hu XX contributed equally to this work.
Supported by the National Natural Science Foundation of China, No. 81560105; the Department of Science and Technology of Guizhou Province, No. LH (2014) 7074.
Institutional animal care and use committee statement: All animal experiments conformed to the internationally accepted principles for the care and use of laboratory animals.
Conflict-of-interest statement: The authors declare no competing interests.
Data sharing statement: The datasets in the present study are available upon reasonable request.
ARRIVE guidelines statement: The authors have read the ARRIVE guidelines, and the manuscript was prepared and revised according to the ARRIVE guidelines.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (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/
Corresponding author: Bing Han, MD, Academic Research, Department of Pathophysiology, College of Basic Medical Sciences, Guizhou Medical University, Dongqing Road, Guiyang 550025, Guizhou Province, China. 47569390@qq.com
Received: December 2, 2019
Peer-review started: December 2, 2019
First decision: December 12, 2019
Revised: February 20, 2020
Accepted: March 9, 2020
Article in press: March 9, 2020
Published online: April 7, 2020
Processing time: 127 Days and 11.6 Hours
ARTICLE HIGHLIGHTS
Research background

Endoplasmic reticulum (ER) stress-mediated hepatocyte apoptosis is associated with many liver diseases, however, the underlying mechanisms remain unknown. Calpain-2 is a Ca2+-dependent cysteine protease, which can cleave several apoptosis-related proteins and mediate the process of apoptosis. Our data indicate that calpain-2 is crucial for the aberrant ER stress-induced apoptosis of hepatocytes and may be a novel therapeutic target for liver diseases.

Research motivation

Calpain-2 protease is involved in multiple signaling pathways mediating apoptotic processes, including the mitochondrial pathway. However, the regulatory mechanisms by which calpain-2 regulates ER stress-mediated hepatocyte apoptosis remain unclear. Our study further assessed its potential as a therapeutic target for inhibiting hepatocyte apoptosis.

Research objectives

In this study, the effect of calpain-2 on ER stress-mediated hepatocyte apoptosis and the underlying regulatory mechanisms were investigated. Our data indicates that ER stress may be a novel therapeutic target, and our findings provide new evidence to demonstrate the importance of Ca2+-dependent calpain-2 in caspase-12 activation and ER stress-related apoptosis in hepatocytes.

Research methods

Our study employed Western blotting, flow cytometry, confocal microscopy, and calpain-2 small interfering RNA to elucidate the mechanism of calpain-2-mediated activation of caspase-12, a key molecule in ER stress-related apoptosis. These research methods are relatively mature technically, thus ensuring the reliability of the results from this study.

Research results

The ER stress inducer dithiothreitol can significantly increase intracellular Ca2+content, calpain-2 expression and activity in hepatocytes and promote caspase-12 cleavage and apoptosis in hepatocytes. Moreover, calpain-2 silencing can mitigate dithiothreitol-enhanced calpain-2 expression, caspase-12 cleavage, and apoptosis in hepatocytes. These results indicated that enhanced calpain-2 activity promoted aberrant ER stress-mediated apoptosis of hepatocytes. In future studies, we will further investigate whether calpain-2 can mediate hepatocyte death through other mechanisms, such as regulating autophagy.

Research conclusions

Ca2+-dependent calpain-2 activity promoted the aberrant ER stress-related apoptosis of rat hepatocytes by activating caspase-12 in the ER. ER stress may be a novel therapeutic target and our findings may provide new evidence to demonstrate the importance of Ca2+-dependent calpain-2 in caspase-12 activation and ER stress-related apoptosis in hepatocytes. ER stress may induce Ca2+ release from the ER and lead to the recruitment and activation of calpain-2 in the ER, where, calpain-2 activates caspase-12 and caspase-3, and triggers apoptosis in hepatocytes. Calpain-2 activity plays an important role in aberrant ER stress-related apoptosis in hepatocytes. Inhibition of calpain-2 expression and activity is expected to be an effective way to alleviate hepatocyte apoptosis and liver injury.

Research perspectives

Because calpain-2 is a protease, in addition to focusing on its expression, studies should also focus on its activity. In our recent preliminary studies, we found that treatment with Z-LLY-fmk, a specific inhibitor of calpain activity, significantly mitigated DTT-induced hepatocyte apoptosis by more than 90%.