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©The Author(s) 2018. Published by Baishideng Publishing Group Inc. All rights reserved.
Sodium chloride exacerbates dextran sulfate sodium-induced colitis by tuning proinflammatory and antiinflammatory lamina propria mononuclear cells through p38/MAPK pathway in mice
Hong-Xia Guo, Nan Ye, Ping Yan, Min-Yue Qiu, Ji Zhang, Zi-Gang Shen, Hai-Yang He, Zhi-Qiang Tian, Hong-Li Li, Jin-Tao Li
Hong-Xia Guo, Jin-Tao Li, Department of Microbiology, Third Military Medical University (Army Medical University), District Shapingba, Chongqing 400038, China
Hong-Xia Guo, Nan Ye, Min-Yue Qiu, Jin-Tao Li, Institute of Tropical Medicine, Third Military Medical University (Army Medical University), District Shapingba, Chongqing 400038, China
Ping Yan, Department of Obstetrics and Gynecology, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing 400038, China
Ji Zhang, Zi-Gang Shen, Hai-Yang He, Zhi-Qiang Tian, Institute of Immunology, Third Military Medical University (Army Medical University), District Shapingba, Chongqing 400038, China
Hong-Li Li, Department of Histology and Embryology, College of Basic Medicine, Third Military Medical University (Army Medical University), Chongqing 400038, China
Author contributions: Li JT designed the research; Guo HX, Ye N, Li HL and Qiu MY performed the research; Yan P, Zhang J, Shen ZG, He HY and Tian ZQ contributed reagents and analytic tools; Ye N contributed to the statistical analysis; Guo HX and Li JT wrote the manuscript and carried out the critical revision of the manuscript; all authors provided final approval of the article.
Supported by National Natural Science Foundation of China, No. 81271813 and No. 81570497.
Institutional review board statement: This study was reviewed and approved by the Third Military Medical University (Army Medical University) Institutional Review Board.
Institutional animal care and use committee statement: All procedures involving the care and use of animals were approved by The Institutional Animal Care and Use Committee of the Third Military Medical University (Army Medical University).
Conflict-of-interest statement: All authors declared there were no conflicts of interests.
Data sharing statement: No additional data are available.
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 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: Jin-Tao Li, PhD, Professor, Institute of Tropical Medicine, Third Military Medical University (Army Medical University), Gaotanyan Street 30, Chongqing 400038, China. ljtqms@tmmu.edu.cn
Telephone: +86-23-68752329 Fax: +86-23-68752329
Received: January 25, 2018
Peer-review started: January 26, 2018
First decision: February 24, 2018
Revised: March 11, 2018
Accepted: March 18, 2018
Article in press: March 18, 2018
Published online: April 28, 2018
ARTICLE HIGHLIGHTS
Research background
At present, most diets are characterized by high salt content. Extant studies have shown that high salt intake contributes to inflammatory bowel disease (IBD) incidence and pathogenesis. However, the mechanism underlying these effects remains unclear.
Research motivation
NaCl mediates the inflammatory effects of immune cells. Both innate and adaptive immune proinflammatory cells play important roles in IBD. Studies have shown the high salt intake promotes the activation of Th17 cells in lamina propria (LP) and exacerbates experimental colitis in mice. However, the influence of high salt content in diet on other immune cells is still unclear. The present study explored the influence of high NaCl concentration on immune cell subsets and the underlying mechanisms.
Research objectives
The aim of the present study was to determine the impact of high NaCl concentration on dextran sulfate sodium (DSS)-induced colitis in mice and explore its influence on other immune cells, such as T helper 1 cells, regulatory T cells and macrophages, while attempting to elucidate the mechanism underlying this effect.
Research methods
DSS and NaCl were used to establish a proinflammatory animal model. The immune cell subsets were detected by flow cytometry in order to determine the target cells of NaCl. Cytokines secreted by intestinal tissue were detected. In the present study, clodronate liposomes treatment was used to deplete macrophages to further delineate their vital role in the promotion of DSS-induced colitis in mice by NaCl. In cell experiments, NaCl at different concentrations acted directly on lamina propria mononuclear cells (LPMCs) and macrophages. mRNA levels of inflammation genes and p38/MAPK proteins were determined by RT-PCR and western blot, respectively.
Research results
High NaCl concentration exacerbated the DSS-induced colitis. Intestinal CD4+IFN-γ+IL-17+ T cells and macrophages both play crucial roles in the promotion of inflammation by NaCl in mice with colitis. NaCl promotes M1 proinflammatory gene expression in lipopolysaccharide (LPS)-activated peritoneal macrophages. High NaCl concentrations promote the up-regulation of the p38/MAPK axis in the LPS and IFN-γ-activated LPMCs.
Research conclusions
NaCl evokes both innate and adaptive immune proinflammatory cell activation in mice affected by colitis. Colitis may be promoted by high NaCl levels, by NaCl initially by acting on macrophages, pushing them towards M1 polarization. Then, M1 polarization shifts the T cell response toward proinflammatory CD4+IFN-γ+IL-17+ T cells. Inflammation promotion by NaCl in LPS- and IFN-γ-activated LPMCs relies on the up-regulation of the p38/MAPK axis.
Research perspectives
Although results in this study indicate that high NaCl intake can promote the inflammation in mice with DSS-induced colitis, the causality of high-salt diet and IBD still needs to be confirmed by further investigations. More clinical and experimental studies are inspired to fully clarify the role of salt in IBD.
