Molecular and Cellular Mechanisms Underlying Probiotic Activity

Dear Colleagues,

Basic and clinical studies have been providing increasing evidence that probiotic microorganisms can improve host health, e.g. by supporting the natural physiology of some organs and by preventing certain diseases. Indeed, many scientific papers document that probiotics—as live cells and, more recently, in the form of inactivated cells, cell components, and metabolites (i.e., paraprobiotics and postbiotics, respectively)—can balance the gut microbiota, reinforce the barrier function of gut mucosa, modulate the immune response, exert antitumor and anti-oxidant activity, and participate in gut–brain signaling. However, information on the mechanisms of action of probiotics and postbiotics remains limited and current research must now focus on the specific molecular players involved in the host–microbe crosstalk and underlying the health-promoting effects. Thus, it is necessary to characterize both the probiotic-derived molecules that trigger host response, as well as the host cell receptors and related molecular pathways that they stimulate.

Most of the key probiotic effectors identified so far are secreted metabolites and/or molecules located on the microbial cell surface including pili and fimbriae-like structures, surface structural proteins, lipoteichoic acids, exopolysaccharides, short-chain fatty acids, bacteriocins, and other antimicrobial agents. These microbial molecules have been found to interact with host cell receptors such as members of the Toll-like receptor (TLR) family, NODs, and DC-SIGN, leading to the modulation of signaling related to MAPK and NF-κB pathways. Yet, the molecular and cellular mechanisms underlying the beneficial effects of probiotics deserve deeper investigation, and this will be fundamental to implement the application of probiotics in clinical settings, to increase reproducibility of the studies, and to select targeted strains with specific attributes.

This Special Issue will present the recent progress on this topic, collecting both original research and review articles.

Dr. Daniela Fiocco
Guest Editor

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