Published online Jul 14, 2017. doi: 10.3748/wjg.v23.i26.4744
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
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).
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.
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).
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.
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.