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:
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.
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
Research background

Sijunzi decoction (SJZD) is a traditional Chinese medicinal prescription that has been used to treat gastrointestinal tract diseases since ancient times. Our previous studies suggested that total polysaccharides of the Sijunzi decoction (TPSJ) could inhibit the proliferation of IEC-6 rat intestinal epithelial cells in vitro. However, no report has discussed the regulatory effects of TPSJ on the intestinal epithelial barrier.

Research motivation

Although TPSJ may inhibit intestinal epithelial cell proliferation, the mechanism by which it mediates barrier protection remains unclear.

Research objectives

To explore the protective effects of TPSJ on the epithelial barrier and the mechanism by which it mitigates tumor necrosis factor α (TNF-α)-induced damage in a Caco-2 cell monolayer.

Research methods

We first used a MTT assay to assess the effect of TPSJ on TNF-α-damaged Caco-2 cells. Secondly, we treated a Caco-2 cell monolayer with TNF-α for 24 h and subsequently analyzed the TEER, permeability, and cytokines of the cells after TPSJ treatment. Third, we examined the effects of TPSJ on the expression of the tight junction proteins claudin 1, claudin 2, zo3, and occludin by immunofluorescence and western blotting. Finally, we investigated the NF-κB-MLCK-MLC pathway in TNF-α treated intestinal epithelial cells.

Research results

TPSJ promoted the growth of TNF-α-treated Caco-2 cells in a dose-dependent manner and decreased the secretion of pro-inflammatory cytokines in response to TNF-α. Secondly, TPSJ treatment significantly increased the TEER and decreased the increased phenolsulfonphthalein flux induced by TNF-α. Third, TPSJ markedly upregulated the expression of claudin 1, claudin 2, and zo3 proteins and attenuated the reorganization of claudin 1, claudin 2, zo3, and occludin. Finally, TPSJ suppressed the TNF-a-induced upregulation of myosin light chain (MLC) phosphorylation, MLC kinase (MLCK), and NF-κB p65.

Research conclusions

TPSJ promoted proliferation of TNF-α-treated Caco2 cells. In Caco2 cell monolayers, TPSJ alleviated the TNF-α-induced decrease in TEER and increase in paracellular permeability, enhanced the expression of claudin 1, claudin 2, and zo3, and preserved the morphological distributions of these three tight junction proteins and occludin. Further, we found that the barrier protective effect of TPSJ was mediated through suppressing the NF-κB p65-mediated phosphorylation of MLCK and MLC.

Research perspectives

Our findings provide evidence that TPSJ is a potential protective agent of intestinal barrier function. Further investigation into the mechanism of TPSJ on intestinal barrier as well as in vivo research is required.