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.

In this study, the total sugar, protein, 3,6-anhydro galactose and sulfate contents, apparent molecular mass and monosaccharide composition of porphyran isolated from Porphyra yezoensis were analyzed. The pro-angiogenic activity and underlying mechanism of porphyran were further investigated using human umbilical vein endothelial cells (HUVECs) as an in vitro angiogenesis model. The effect of porphyran on the cell viability of HUVECs was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cell adhesion and migration capacity were evaluated using cell adhesion and wound healing assays. The number of lumens formed by HUVECs was analyzed using in vitro tube formation assay. The expression levels of E-cadherin and N-cadherin in HUVECs were analyzed by Western Blotting, and the pro-angiogenic mechanism of porphyran in HUVECs was explored using specific inhibitors of mitogen-activated protein kinases (MAPKs) and vascular endothelial growth factor (VEGF) receptor tyrosine kinase inhibitors. The results showed that porphyran contained (77.48 ± 2.62)% total sugar, (3.24 ± 0.58)% protein, and (20.30 ± 1.06)% 3,6-anhydrogalactose as well as (20.78 ± 3.31)% sulfate groups. The apparent molecular mass of porphyran was 39.81 kDa. Porphyran was mainly composed of galactose, 3,6-anhydrogalactose and sulfate groups, suggesting it to be a sulfated galactan. Furthermore, porphyran treatment in the concentration range of 0-200 µg/mL had no significant toxicity no HUVECs, but instead promote cell proliferation, adhesion, migration, and vascular network formation. Further studies demonstrated that porphyran exerted its pro-angiogenic effect primarily by mediating the down-regulation of E-cadherin expression and the up-regulation of N-cadherin expression through the c-Jun N-terminal kinase (JNK) MAPK and VEGF receptor signaling pathways. In conclusion, porphyran has pro-angiogenic potential, which will provide a scientific basis for the development of porphyran as a novel pro-angiogenic factor and the precision nutrition-guided deep processing and high-value utilization of the red seaweed P. yezoensis.