Anti-Inflammatory and Immunomodulatory Effects of Probiotics in Gut Inflammation: A Door to the Body

Abstract

Hosting millions of microorganisms, the digestive tract is the primary and most important part of bacterial colonization. On one side, in cases of opportunistic invasion, the abundant bacterial population inside intestinal tissues may face potential health problems such as inflammation and infections. Therefore, the immune system has evolved to sustain the host–microbiota symbiotic relationship. On the other hand, to maintain host immune homeostasis, the intestinal microflora often exerts an immunoregulatory function that cannot be ignored. A field of great interest is the association of either microbiota or probiotics with the immune system concerning clinical uses. This microbial community regulates some of the host’s metabolic and physiological functions and drives early-life immune system maturation, contributing to their homeostasis throughout life. Changes in gut microbiota can occur through modification in function, composition (dysbiosis), or microbiota–host interplays. Studies on animals and humans show that probiotics can have a pivotal effect on the modulation of immune and inflammatory mechanisms; however, the precise mechanisms have not yet been well defined. Diet, age, BMI (body mass index), medications, and stress may confound the benefits of probiotic intake. In addition to host gut functions (permeability and physiology), all these agents have profound implications for the gut microbiome composition. The use of probiotics could improve the gut microbial population, increase mucus-secretion, and prevent the destruction of tight junction proteins by decreasing the number of lipopolysaccharides (LPSs). When LPS binds endothelial cells to toll-like receptors (TLR 2, 4), dendritic cells and macrophage cells are activated, and inflammatory markers are increased. Furthermore, a decrease in gut dysbiosis and intestinal leakage after probiotic therapy may minimize the development of inflammatory biomarkers and blunt unnecessary activation of the immune system. In turn, probiotics improve the differentiation of T-cells against Th2 and development of Th2 cytokines such as IL-4 and IL-10. The present narrative review explores the interactions between gut microflora/probiotics and the immune system starting from the general perspective of a biological plausibility to get to the in vitro and in vivo demonstrations of a probiotic-based approach up to the possible uses for novel therapeutic strategies.

A role for gut microbiota in early-life stress-induced widespread muscle pain in the adult rat

“…One mechanism may depend on modifying stress-induced gut dysbiosis. For example, early-life stress-induced gut dysbiosis and gut permeability, is ameliorated by probiotics, 18 , 26 , 30 , 44 as well as by the antibiotic, rifaximin. 22 , 45 Stress-induced increase in gut permeability results in increased levels of lipopolysaccharide (LPS) and inflammatory cytokines, an effect that is reversed by probiotics.…”

Probiotic Supplementation for Rheumatoid Arthritis: A Promising Adjuvant Therapy in the Gut Microbiome Era

“…Specific probiotic bacteria modulate the immune response by affecting different cells involved in innate and acquired immunity, such as epithelial cells and dendritic cells (DCs), natural killer cells (NK), macrophages, and lymphocytes (Bermudez-Brito et al, 2012;La Fata et al, 2018;Cristofori et al, 2021). The innate immune system develops the primary response to pathogens after activation of the pattern recognition receptors (PRRs), which are expressed on immune and non-immune cells, such as NK cells, DCs, macrophages, fibroblasts, and epithelial cells (Bermudez-Brito et al, 2012;Plaza-Diaz et al, 2019;Cristofori et al, 2021). Toll-like receptors (TLRs) are the most widely studied PRRs, which can activate signaling pathways that affect cell proliferation and cytokine production to modulate the immune system (Ferlazzo et al, 2011;Cristofori et al, 2021).…”

“…The innate immune system develops the primary response to pathogens after activation of the pattern recognition receptors (PRRs), which are expressed on immune and non-immune cells, such as NK cells, DCs, macrophages, fibroblasts, and epithelial cells (Bermudez-Brito et al, 2012;Plaza-Diaz et al, 2019;Cristofori et al, 2021). Toll-like receptors (TLRs) are the most widely studied PRRs, which can activate signaling pathways that affect cell proliferation and cytokine production to modulate the immune system (Ferlazzo et al, 2011;Cristofori et al, 2021). It is well established that probiotics can downregulate TLR expression, reducing inflammation (Gómez-Llorente et al, 2010).…”

“…Probiotics can also interact with the host immune system through indirect mechanisms, which involve the modulation of GM. The mechanisms by which probiotic strains have been proposed to modulate GM include regulating the gut epithelial barrier and the mucus layer characteristics, secretion of antimicrobial compounds and competition with pathogenic bacteria (Vieira et al, 2016;Jethwa and Abraham, 2017;Cristofori et al, 2021).…”

Strategies for Using Muramyl Peptides - Modulators of Innate Immunity of Bacterial Origin - in Medicine

“…Peptidoglycan undergoes structural rearrangements in the process of bacterial growth and division. These autolytic functions are performed by intracellular peptidoglycan hydrolases and amidases, which destroy peptidoglycan and form muramyl peptides (11)(12)(13).…”