Inhibitory Mechanism of Escherichia coli Adhesion to Caco-2 Monolayers by Polysaccharides from Bangia fusco-purpurea

In this study, the effect of Bangia fusco-purpurea polysaccharide (BFP) on Escherichia coli adhesion to Caco-2 monolayers and its potential mechanism was studied using an in vitro human colon adenocarcinoma cell (Caco-2) monolayer model. The effect of BFP on the adhesion of E. coli to Caco-2 monolayers was analyzed by fluorescence labeling with carboxyfluorescein diacetate and succinimidyl ester (CFDA-SE), and its effect on the gene expression of integrin β1 in Caco-2 cells, the adhesin FimH in E. coli, and inflammatory factors (IL-1β, IL-8 and TNF-α) induced by E. coli adhesion to Caco-2 cells and the tight junction proteins zonula occludens 1 (ZO-1) and occludin were analyzed using real-time polymerase chain reaction (real-time PCR). Also, the protein expression of ZO-1 and occludin in Caco-2 monolayers was detected using Western Blot analysis. Our results showed that BFP at concentrations of 400–800 μg/mL significantly inhibited the adhesion of E. coli to Caco-2 monolayers mainly by down-regulating the gene expression of integrin β1 in Caco-2 cells and FimH in E. coli. In addition, BFP significantly inhibited the up-regulation of inflammatory cytokine gene expression and the down-regulation of ZO-1 and occludin protein and gene expression induced by in Caco-2 cells induced by E. coli and its culture supernatant. In conclusion, BFP inhibited the adhesion of E. coli to Caco-2 cell monolayers, which will lay a scientific basis for the development of novel antimicrobial products and the high-value utilization and deep processing of BFP.