Basic Study
Copyright ©The Author(s) 2016. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Dec 14, 2016; 22(46): 10148-10157
Published online Dec 14, 2016. doi: 10.3748/wjg.v22.i46.10148
C5a/C5aR pathway is essential for up-regulating SphK1 expression through p38-MAPK activation in acute liver failure
Yan-Chang Lei, Chun-Lei Lu, Ling Chen, Ke Ge, Ling-Ling Yang, Wen Li, Yuan-Hua Wu
Yan-Chang Lei, Ling Chen, Ke Ge, Department of Infectious Diseases, Zhejiang Hospital, Hangzhou 310013, Zhejiang Province, China
Yan-Chang Lei, Wen Li, Lingling Yang, Infectious Diseases Hospital of Nanchang University, Nanchang 330006, Jiangxi Province, China
Chun-Lei Lu, Yuan-Hua Wu, The First People’s Hospital of Pinghu, Pinghu 314200, Zhejiang Province, China
Author contributions: Lei YC designed this research; Lei YC, Yang LL, Li W, Lu CL, Chen L and Ge K performed the research and analyzed the data; Lei YC wrote the paper.
Supported by the National Natural Science Foundation of China, No. 81260455 and No. 81160065.
Institutional review board statement: The study was reviewed and approved by the Zhejiang Hospital Institutional Review Board.
Institutional animal care and use committee statement: All procedures involving animals were reviewed and approved by the Institutional Animal Care and Use Committee of the Zhejiang Hospital.
Conflict-of-interest statement: We declare that there are no conflicts of interest to disclose.
Data sharing statement: No additional data are available.
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: Dr. Yan-Chang Lei, Chief Physician, Department of Infectious Diseases, Zhejiang Hospital, 12 Lingyin Road, Hangzhou 310013, Zhejiang Province, China. ycleihust@sina.com
Telephone: +86-571-81595081 Fax: +86-571-87980175
Received: August 2, 2016
Peer-review started: August 3, 2016
First decision: August 19, 2016
Revised: September 8, 2016
Accepted: October 10, 2016
Article in press: October 10, 2016
Published online: December 14, 2016
Abstract
AIM

To investigate the role of the complement 5a (C5a)/C5a receptor (C5aR) pathway in the pathogenesis of acute liver failure (ALF) in a mouse model.

METHODS

BALB/c mice were randomly assigned to different groups, and intraperitoneal injections of lipopolysaccharide (LPS)/D-galactosamine (D-GalN) (600 mg/kg and 10 μg/kg) were used to induce ALF. The Kaplan-Meier method was used for survival analysis. Serum alanine aminotransferase (ALT) levels, at different time points within a 1-wk period, were detected with a biochemistry analyzer. Pathological examination of liver tissue was performed 36 h after ALF induction. Serum complement 5 (C5), C5a, tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6, high-mobility group protein B1 (HMGB1) and sphingosine-1-phosphate levels were detected by enzyme-linked immunosorbant assay. Hepatic morphological changes at 36 h after ALF induction were assessed by hematoxylin and eosin staining. Expression of C5aR, sphingosine kinase 1 (SphK1), p38-MAPK and p-p38-MAPK in liver tissue, peripheral blood mononuclear cells (PBMCs) and peritoneal exudative macrophages (PEMs) of mice or RAW 264.7 cells was analyzed by western blotting. C5aR mRNA levels were detected by quantitative real-time PCR.

RESULTS

Activation of C5 and up-regulation of C5aR were observed in liver tissue and PBMCs of mice with ALF. Blockade of C5aR with a C5aR antagonist (C5aRa C5aRa) significantly reduced the levels of serum ALT, inflammatory cytokines (TNF-α, IL-1β and IL-6) and HMGB1, as well as the liver tissue damage, but increased the survival rates (P < 0.01 for all). Blockade of C5aR decreased SphK1 expression in both liver tissue and PBMCs significantly at 0.5 h after ALF induction. C5aRa pretreatment significantly down-regulated the phosphorylation of p38-MAPK in liver tissues of ALF mice and C5a stimulated PEMs or RAW 264.7 cells. Moreover, inhibition of p38-MAPK activity with SB203580 reduced SphK1 protein production significantly in PEMs after C5a stimulation.

CONCLUSION

The C5a/C5aR pathway is essential for up-regulating SphK1 expression through p38 MAPK activation in ALF in mice, which provides a potential immunotherapeutic strategy for ALF in patients.

Keywords: Acute liver failure, C5a/C5aR, p38-MAPK, Sphingosine kinase 1

Core tip: Recent studies and our work show that SphK1 and complement activation play an important role in systemic inflammation in acute liver failure (ALF). It has been shown that C5a activates sphingosine kinase 1 (SphK1) in macrophages. However, the mechanism of C5a-induced SphK1 activation is unknown. In this study we found that excessive activation of C5 and up-regulation of C5aR in liver tissue, and the C5a/C5aR pathway is essential for potentiating SphK1 expression through p38 MAPK activation in ALF. To our knowledge, this is the first report of the mechanism of C5a-induced SphK1 activation, which provides a potential immunotherapeutic strategy for ALF in patients.