Basic Study
Copyright ©The Author(s) 2017. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Jul 14, 2017; 23(26): 4744-4751
Published online Jul 14, 2017. doi: 10.3748/wjg.v23.i26.4744
Effect of EPEC endotoxin and bifidobacteria on intestinal barrier function through modulation of toll-like receptor 2 and toll-like receptor 4 expression in intestinal epithelial cell-18
Xia Yang, Xian-Chun Gao, Jun Liu, Hong-Yu Ren
Xia Yang, Xian-Chun Gao, Jun Liu, Hong-Yu Ren, Division of Gastroenterology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, Hubei Province, China
Author contributions: Yang X and Gao XC contributed equally as co-first authors; Ren HY conceived and designed the experiments; Yang X and Gao XC performed the majority of experiments, analyzed the data and wrote the paper; Ren HY and Liu J provided reagents, materials and analytical tools; all authors read and approved the final manuscript.
Supported by Medjaden Academy and Research Foundation for Young Scientists, No. MJA20170410.
Institutional review board statement: This study was approved by the Institutional Review Board of Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, Hubei Province, China.
Conflict-of-interest statement: None of the authors have any potential conflicts of interest.
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: Hong-Yu Ren, MD, PhD, Division of Gastroenterology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 1277 Jiefang Road, Wuhan 430022, Hubei Province, China. hongyur@hotmail.com
Telephone: +86-27-85726381
Received: February 10, 2017
Peer-review started: February 11, 2017
First decision: March 16, 2017
Revised: April 23, 2017
Accepted: May 19, 2017
Article in press: May 19, 2017
Published online: July 14, 2017
Processing time: 154 Days and 7.3 Hours
Abstract
AIM

To investigate toll-like receptor 2 (TLR2) and TLR4 expression, following bifidobacteria and low-dose EPEC endotoxin treatment, and intestinal barrier function in rat intestinal epithelial cell18 (IEC18).

METHODS

Six experimental groups were established - normal control, EPEC, Bifidobacteria infantis (B. infantis), B. longum, B. bifidum, and B. youth groups. Optimal EPEC endotoxin concentration, bifidobacteria fold dilution, and treatment duration were determined. Quantitative real-time polymerase chain reaction and western blot, respectively, were conducted to detect TLR2 and TLR4 mRNA and protein expression in IEC-18 cells. Transepithelial electrical resistance (TEER) was measured by the EVOM chopstick voltohmmeter in each group. All experiments were conducted in triplicate and data were analyzed on SPSS 16.

RESULTS

TLR2 and TLR4 mRNA and protein expression in the EPEC group were significantly higher than in the control group (P < 0.05). TLR2 mRNA and protein expression in the B. infantis, B. longum and B. youth groups were significantly lower than in the normal control group (P < 0.05). TLR4 mRNA and protein expression in the B. bifidum and B. youth groups were significantly lower than in normal controls (P < 0.05). In addition, the TEER in B. infantis, B. longum, B. bifidum, and B. youth groups were decreased by 19%, 18%, 23% and 23%, respectively, after 120 min of intervention, as compared to the control group. However, the TEER in the EPEC group was significantly decreased by 67% in comparison to the normal control group (P < 0.05).

CONCLUSION

Bifidobacteria protect IEC-18 cells against injury by down-regulating TLR2 and TLR4 expression and enhance intestinal barrier function to protect the intestinal epithelial cells from pathogenic invasion.

Keywords: Bifidobacteria; Intestinal barrier function; Intestinal epithelial cells

Core tip: Toll-like receptor (TLRs) are key components of the innate immune system that trigger antimicrobial host defense responses. EPEC promoted the expression of toll-like receptor 2 (TLR2) and TLR4 and increased cell membrane permeability, where as bifidobacteria inhibited the expression of TLR2 and TLR4 and prevented TLR-mediated inflammation. Therefore, bifidobacteria can potentially play a protective role by inhibiting inflammation and preventing penetration of pathogenic bacteria in patients with inflammatory bowel disease.