Fig. 2

Effects of surface molecular of probiotics on intestinal epithelial barrier. Flagellin, pili, and CPS can be bind to TIR domain in TLRs, thus interacting with adaptor molecules such as MyD88 to activate AP-1 and NF-κB signaling pathways in IEC. Flagellin of EcN can finally induce the expression of HBD-2 in the gut, which is beneficial for the prevention of pathogens. F1C pili of EcN can finally up-regulate the expression of tight junction to enhance gut barrier function. CPS of EcN can finally induce the secretion of cytokines such as IL-10 and IL-12 for the alleviation of intestinal inflammation. SlpA of Lactobacillus acidophilus can bind to DC-SIGN and increase ERK phosphorylation, which mediates interaction with NF-κB and then reduce the expression level of cell apoptosis. SLPs surface layer proteins, CPS capsular polysaccharide, TLRs toll-like receptors, DC-SIGN dendritic cell specific intercellular adhesion molecule grabbing nonintegrin, NF-κB nuclear factor kappa B, AP-1 activating protein-1, IECs intestinal epithelial cells, ERK extracellular signal-regulated kinase, MAPK mitogen-activated protein kinase, HBD-2 beta-defensin 2