Basic Study
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Mar 14, 2015; 21(10): 2937-2948
Published online Mar 14, 2015. doi: 10.3748/wjg.v21.i10.2937
Heme oxygenase-1 protects rat liver against warm ischemia/reperfusion injury via TLR2/TLR4-triggered signaling pathways
Han-Fei Huang, Zhong Zeng, Kun-Hua Wang, Hai-Yan Zhang, Shuai Wang, Wen-Xiang Zhou, Zhan-Bo Wang, Wang-Gang Xu, Jian Duan
Han-Fei Huang, Zhong Zeng, Kun-Hua Wang, Hai-Yan Zhang, Shuai Wang, Wen-Xiang Zhou, Zhan-Bo Wang, Wang-Gang Xu, Jian Duan, Organ Transplantation Center, the First Affiliated Hospital of Kunming Medical University, Kunming 650032, Yunnan Province, China
Author contributions: Huang HF and Zeng Z contributed equally to this work; Huang HF, Zhang HY and Wang S performed the majority of experiments; Zhou WX and Wang ZB performed data analysis; Xu WG and Duan J were involved in editing the manuscript; Wang KH designed the study.
Supported by National Natural Science Foundation of China, No. 81360079; and Yunnan Provincial Science and Technology Department and Kunming Medical University Collaborative Fund, No. 2013FB142.
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:
Correspondence to: Zhong Zeng, MD, Organ Transplantation Center, the First Affiliated Hospital of Kunming Medical University, 295 Xichang Road, Kunming 650032, Yunnan Province, China.
Telephone: +86-871-65324888 Fax: +86-871-65359202
Received: July 3, 2014
Peer-review started: July 4, 2014
First decision: July 21, 2014
Revised: August 9, 2014
Accepted: November 7, 2014
Article in press: November 11, 2014
Published online: March 14, 2015

AIM: To investigate the efficacy and molecular mechanisms of induced heme oxygenase (HO)-1 in protecting liver from warm ischemia/reperfusion (I/R) injury.

METHODS: Partial warm ischemia was produced in the left and middle hepatic lobes of SD rats for 75 min, followed by 6 h of reperfusion. Rats were treated with saline, cobalt protoporphyrin (CoPP) or zinc protoporphyrin (ZnPP) at 24 h prior to the ischemia insult. Blood and samples of ischemic lobes subjected to ischemia were collected at 6 h after reperfusion. Serum transaminases level, plasma lactate dehydrogenase and myeloperoxidase activity in liver were measured. Liver histological injury and inflammatory cell infiltration were evaluated by tissue section and liver immunohistochemical analysis. We used quantitative reverse transcription polymerase chain reaction to analyze liver expression of inflammatory cytokines and chemokines. The cell lysates were subjected to immunoprecipitation with anti-Toll-IL-1R-containing adaptor inducing interferon-β (TRIF) and anti-myeloid differentiation factor 88 (MyD88), and then the immunoprecipitates were analyzed by SDS-PAGE and immunoblotted with the indicated antibodies.

RESULTS: HO-1 protected livers from I/R injury, as evidenced by diminished liver enzymes and well-preserved tissue architecture. In comparison with ZnPP livers 6 h after surgery, CoPP treatment livers showed a significant increase inflammatory cell infiltration of lymphocytes, plasma cells, neutrophils and macrophages. The Toll-like receptor (TLR)-4 and TANK binding kinase 1 protein levels of rats treated with CoPP significantly reduced in TRIF-immunoprecipitated complex, as compared with ZnPP treatment. In addition, pretreatment with CoPP reduced the expression levels of TLR2, TLR4, IL-1R-associated kinase (IRAK)-1 and tumor necrosis factor receptor-associated factor 6 in MyD88-immunoprecipitated complex. The inflammatory cytokines and chemokines mRNA expression rapidly decreased in CoPP-pretreated liver, compared with the ZnPP-treated group. However, the expression of negative regulators Toll-interacting protein, suppressor of cytokine signaling-1, IRAK-M and Src homology 2 domain-containing inositol-5-phosphatase-1 in CoPP treatment rats were markedly up-regulated as compared with ZnPP-treated rats.

CONCLUSION: HO-1 protects liver against I/R injury by inhibiting TLR2/TLR4-triggered MyD88- and TRIF-dependent signaling pathways and increasing expression of negative regulators of TLR signaling in rats.

Keywords: Heme oxygenase-1, Ischemia reperfusion injury, Toll-like receptor, Myeloid differentiation factor 88, Liver

Core tip: Heme oxygenase (HO)-1, a rate-limiting enzyme in heme degradation, has been shown to provide cytoprotection in various tissue and organ injury models. There is evidence suggesting that augmented Toll-like receptor (TLR) reactivity contributes to the development of heightened systemic inflammation following severe liver injury. In this study, by inducing the expression of HO-1 in a rat liver ischemia/reperfusion injury model, we demonstrated that HO-1 suppresses activation of the TLR2/TLR4-triggered myeloid differentiation factor 88 dependent pathway and promotes expression of negative regulators of TLR signaling.