Basic Study
Copyright ©The Author(s) 2018. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Jul 14, 2018; 24(26): 2867-2877
Published online Jul 14, 2018. doi: 10.3748/wjg.v24.i26.2867
Total polysaccharides of the Sijunzi decoction attenuate tumor necrosis factor-α-induced damage to the barrier function of a Caco-2 cell monolayer via the nuclear factor-κB-myosin light chain kinase-myosin light chain pathway
Yue Lu, Leng Li, Jin-Wei Zhang, Xiao-Qin Zhong, Jian-An Wei, Ling Han
Yue Lu, Leng Li, Jin-Wei Zhang, Xiao-Qin Zhong, Jian-An Wei, Ling Han, The Second Clinical College (Guangdong Provincial Hospital of Chinese Medicine), Guangzhou University of Chinese Medicine, Guangzhou 510006, Guangdong Province, China
Author contributions: Han L conceived and designed research; Lu Y, Li L and Zhang JW performed research; Lu Y and Zhong XQ analyzed data; Lu Y wrote the manuscript; Wei JA and Han L approved and reviewed the final manuscript; all authors have read and agreed with the final manuscript.
Supported by the National Natural Science Foundation of China, No. 81202635; and the Guangdong Provincial Bureau of Chinese Medicine, No. 20151244.
Institutional review board statement: This study was reviewed and approved by the review board of the Second Clinical College affiliated with Guangzhou University of Chinese Medicine.
Conflict-of-interest statement: All authors declare that there are no competing interests.
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: Ling Han, PhD, Research Scientist, The Second Clinical College, Guangzhou University of Chinese Medicine, Inner Ring Western Road, University Town, Guangzhou 510006, Guangdong Province, China. linghan99@gzucm.edu.cn
Telephone: +86-20-39318678 Fax: +86-20-39318678
Received: March 29, 2018
Peer-review started: March 30, 2018
First decision: May 17, 2018
Revised: May 25, 2018
Accepted: June 9, 2018
Article in press: June 9, 2018
Published online: July 14, 2018
Processing time: 105 Days and 20.6 Hours
Abstract
AIM

To explore the protective effects and underlying mechanisms of total polysaccharides of the Sijunzi decoction (TPSJ) on the epithelial barriers in vitro.

METHODS

Caco-2 cell monolayers were treated with or without TPSJ in the presence or absence of TNF-α, and paracellular permeability and transepithelial electrical resistance (TEER) were measured to evaluate the epithelial barrier function. Immunofluorescence and western blotting were respectively used to evaluate the distribution and expression of the tight junction proteins claudin 1, claudin 2, zo3, and occludin in Caco-2 cells. Western blotting was also used to evaluate the cellular expression of myosin light chain (MLC), phosphorylated MLC (pMLC), MLC kinase (MLCK), and nuclear factor (NF)-κB p65.

RESULTS

TPSJ promoted the proliferation of Caco-2 cells and inhibited TNF-α-induced secretion of pro-inflammatory cytokines. Furthermore, TPSJ significantly ameliorated both the reduction of TEER and the increased paracellular permeability observed in tumor necrosis factor (TNF)-α-damaged Caco-2 monolayers. Furthermore, TPSJ remarkably attenuated TNF-α-induced morphological changes, downregulated the expression of claudin 1, claudin 2, zo3, and occludin, and markedly suppressed TNF-α-mediated upregulation of p-MLC and MLCK expression. Finally, TPSJ inhibited the activation and expression of NF-κB p65.

CONCLUSION

Our results demonstrate that TPSJ alleviates the TNF-α-induced impairment of the intestinal epithelial cell barrier function by suppressing NF-κB p65-mediated phosphorylation of MLCK and MLC.

Keywords: Inflammatory bowel disease; Tight junction; Total polysaccharides of the Sijunzi decoction; Nuclear factor-κB pathway

Core tip: Total polysaccharides of the Sijunzi decoction (TPSJ) comprise the active ingredient of Sijunzi decoction, which has long been used to treat gastrointestinal tract disorders. However, the mechanisms by which TPSJ affects the intestinal epithelial barrier remain unclear. Our study results demonstrated that TPSJ attenuated tumor necrosis factor (TNF)-α-induced intestinal barrier dysfunction in a Caco-2 cell monolayer. Furthermore, TPSJ inhibited TNF-α-induced upregulation of myosin light chain (MLC) phosphorylation, which is mediated by MLC kinase and NF-κB, suggesting that this mechanism might underlie the protective effects of TPSJ against intestinal epithelial barrier dysfunction triggered by proinflammatory cytokines.