Surface components and metabolites of probiotics for regulation of intestinal epithelial barrier

Abstract

The gut microbiota can significantly affect the function of the intestinal barrier. Some intestinal probiotics (such as Lactobacillus, Bifidobacteria, a few Escherichia coli strains, and a new generation of probiotics including Bacteroides thetaiotaomicron and Akkermansia muciniphila) can maintain intestinal epithelial homeostasis and promote health. This review first summarizes probiotics' regulation of the intestinal epithelium via their surface compounds. Surface layer proteins, flagella, pili and capsular polysaccharides constitute microbial-associated molecular patterns and specifically bind to pattern recognition receptors, which can regulate signaling pathways to produce cytokines or inhibit apoptosis, thereby attenuating inflammation and enhancing the function of the gut epithelium. The review also explains the effects of metabolites (such as secreted proteins, organic acids, indole, extracellular vesicles and bacteriocins) of probiotics on host receptors and the mechanisms by which these metabolites regulate gut epithelial barrier function. Previous reviews summarized the role of the surface macromolecules or metabolites of gut microbes (including both probiotics and pathogens) in human health. However, these reviews were mostly focused on the interactions between these substances and the intestinal mucosal immune system. In the current review, we only focused on probiotics and discussed the molecular interaction between these bacteria and the gut epithelial barrier.

Paraprobiotics and Postbiotics of Probiotic Lactobacilli, Their Positive Effects on the Host and Action Mechanisms: A Review

“…Cell surface proteins are classified as the proteins which are covalently or noncovalently attached to the cell surface. Recent study indicated that many types of surface proteins including LPXTG proteins, S-layer proteins, pili proteins, moonlight proteins are produced by Lactobacillus species including L. plantarum, L. rhamnosus, Lactobacillus helvetics (L. helveticus), and L. acidophilus (118). These proteins play significant positive roles on the host biological processes.…”

Probiotics and COVID-19

“…In other infections, such as HIV, in which intestinal inflammation and related microbiota impairment can affect gut epithelial barrier function, bacteriotherapy (through microbiota surface compounds and metabolites) has been shown to inhibit apoptosis, regulate signalling pathways to produce cytokines, maintain intestinal epithelial homoeostasis, and allow recovery of gut mucosal health, thereby attenuating inflammation. 8 , 9 We believe that studies of bacteriotherapy in SARS-CoV-2 are needed to evaluate the potential effects on intestinal mucosal inflammation and microbiome homoeostasis.…”

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“…Therefore, when clinicians prescribe drugs with little anti-COVID-19 data that can be further antagonistic towards the health conditions, probiotic strains documented for gut-microbiome homeostasis could be a part of the regimen to reduce the likely dysbiosis and consequent clinical fragility. Dietary foods, prebiotics, or probiotics can dramatically influence the gut micro-flora, which can rejuvenate the inherent immunity, restore the intestinal mucosa damage during infection, recover the intestinal eubiotic state and attenuate relevant inflammation, thus driving the patients' health in a favorable direction 53 . More research involving the wellreported probiotics and a gut-favoring diet are needed to shed light on the management of the patients to lessen the risk of COVID-19.…”