Original Article
Copyright ©2014 Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Dec 28, 2014; 20(48): 18189-18198
Published online Dec 28, 2014. doi: 10.3748/wjg.v20.i48.18189
Caspase-12 mediates carbon tetrachloride-induced hepatocyte apoptosis in mice
Hua Liu, Zhe Wang, Michael J Nowicki
Hua Liu, Michael J Nowicki, Division of Pediatric Gastroenterology, University of Mississippi Medical Center, Jackson, MS 39216, United States
Zhe Wang, Cancer Institute, University of Mississippi Medical Center, Jackson, MS 39216, United States
Author contributions: Liu H and Wang Z performed the research, analyzed the data, and drafted the article; Liu H and Nowicki MJ designed the study, and edited, revised, and gave final approval to the article.
Supported by Institutional research grant by the University of Mississippi Medical Center (to Dr. Hua Liu), No. 68512250711
Correspondence to: Hua Liu, MD, Division of Gastroenterology, Department of Pediatrics, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39216, United States. hliu@umc.edu
Telephone: +1-601-9845978 Fax: +1-601-9845981
Received: May 6, 2014
Revised: July 3, 2014
Accepted: September 5, 2014
Published online: December 28, 2014
Processing time: 245 Days and 6.8 Hours
Abstract

AIM: To investigate the role of caspase-12 and its downstream targets in carbon tetrachloride (CCl4)-induced hepatocyte apoptosis.

METHODS: The role of caspase-12 was determined by using caspase-12 knock-out (-/-) mice. CCl4 (300 μL/kg body weight) or vehicle (corn oil) was administered to caspase-12+/+ or caspase-12-/- mice as a single intraperitoneal injection. The animals were sacrificed 24 h after the CCl4 treatment. Blood was collected to evaluate liver function by the measurement of the activity of alanine aminotransferase. Liver samples were used for the measurements of reactive oxygen species using plasma malondialdehyde as biomarker, hepatocyte apoptosis was evaluated via terminal transferase-mediated dUTP nick-end labeling and controlled by morphologic study, and cytochrome C release and caspase activations were measured by Western blotting.

RESULTS: Administration of a low dose of CCl4 resulted in hepatocyte apoptosis and acute liver injury in wild-type mice. CCl4 also induced the generation of reactive oxygen species and induction of endoplasmic reticulum stress in the liver followed by activations of caspase-12, -9 and -3 as well as release of small amounts of cytochrome C. However, in the CCl4-treated caspase-12-/- mice, activation of caspase-9 and -3 were significantly attenuated (P < 0.05); no effect was seen in cytochrome C release. CCl4-induced apoptosis and liver damage was markedly reduced in caspase-12-/- mice compared to caspase-12+/+ mice (P < 0.05). The active form of caspase-8 was not detected in either caspase-12+/+ or caspase-12-/- mice. There was no significant different in the formation of reactive oxygen species in the livers of caspase-12+/+ and caspase-12-/- mice treated with CCl4.

CONCLUSION: Caspase-12 plays a pivotal role in CCl4-induced hepatic apoptosis through the activation of the downstream effector caspase-3 directly and/or indirectly via capase-9 activation.

Keywords: Apoptosis; Carbon tetrachloride; Caspases; Endoplasmic reticulum; Hepatocyte; Reactive oxygen species

Core tip: Sublethal doses of carbon tetrachloride (CCl4) induced significant hepatocyte apoptosis and acute liver injury in the wild-type mice. CCl4 also induced the generation of reactive oxygen species in the liver followed by activation of caspase-12, -9 and -3. Loss of caspase-12 in knock-out mice attenuated CCl4-induced activation of caspase-9 and -3, significantly reduced apoptosis, and preserved liver function. Caspase-8 was not detected, indicating that it does not play a significant role in this model of hepatocyte apoptosis. The data indicate that caspase-12 plays a pivotal role in CCl4-induced hepatocyte apoptosis through the downstream activation of the effector caspase-3 directly and/or indirectly via caspase-9 activation.