Modulation of immunity and inflammatory gene expression in the gut, in inflammatory diseases of the gut and in the liver by probiotics

Abstract

The potential for the positive manipulation of the gut microbiome through the introduction of beneficial microbes, as also known as probiotics, is currently an active area of investigation. The FAO/WHO define probiotics as live microorganisms that confer a health benefit to the host when administered in adequate amounts. However, dead bacteria and bacterial molecular components may also exhibit probiotic properties. The results of clinical studies have demonstrated the clinical potential of probiotics in many pathologies, such as allergic diseases, diarrhea, inflammatory bowel disease and viral infection. Several mechanisms have been proposed to explain the beneficial effects of probiotics, most of which involve gene expression regulation in specific tissues, particularly the intestine and liver. Therefore, the modulation of gene expression mediated by probiotics is an important issue that warrants further investigation. In the present paper, we performed a systematic review of the probiotic-mediated modulation of gene expression that is associated with the immune system and inflammation. Between January 1990 to February 2014, PubMed was searched for articles that were published in English using the MeSH terms "probiotics" and "gene expression" combined with "intestines", "liver", "enterocytes", "antigen-presenting cells", "dendritic cells", "immune system", and "inflammation". Two hundred and five original articles matching these criteria were initially selected, although only those articles that included specific gene expression results (77) were later considered for this review and separated into three major topics: the regulation of immunity and inflammatory gene expression in the gut, in inflammatory diseases of the gut and in the liver. Particular strains of Bifidobacteria, Lactobacilli, Escherichia coli, Propionibacterium, Bacillus and Saccharomyces influence the gene expression of mucins, Toll-like receptors, caspases, nuclear factor-κB, and interleukins and lead mainly to an anti-inflammatory response in cultured enterocytes. In addition, the interaction of commensal bacteria and probiotics with the surface of antigen-presenting cells in vitro results in the downregulation of pro-inflammatory genes that are linked to inflammatory signaling pathways, whereas other anti-inflammatory genes are upregulated. The effects of probiotics have been extensively investigated in animal models ranging from fish to mice, rats and piglets. These bacteria induce a tolerogenic and hyporesponsive immune response in which many genes that are related to the immune system, in particular those genes expressing anti-inflammatory cytokines, are upregulated. By contrast, information related to gene expression in human intestinal cells mediated by the action of probiotics is scarce. There is a need for further clinical studies that evaluate the mechanism of action of probiotics both in healthy humans and in patients with chronic diseases. These types of clinical studies are necessary for addressing the influence of these microorga...

Identification and characterization of Bacillus subtilis from grass carp (Ctenopharynodon idellus) for use as probiotic additives in aquatic feed

“…Proinflammatory cytokines such as TNF-a and IL-1b mediate powerful inflammatory responses of fish after infection [14], while antiinflammatory cytokines such as TGF-b and IL-10 exert potent immunosuppressive effects predominantly through their multiple effects on T cells and B cells [62]. A number of probiotics can effectively modulate the expression of pro-and anti-inflammatory cytokines in many animals [14,18]. In this study, mRNA changes of the above cytokine genes in intestine were detected after oral administration of the spores of B. subtilis strains.…”

“…One is the competition between species: probiotics adhered to the intestinal mucosal surface can prevent the colonization of pathogenic bacteria, and alter the composition of the intestinal microbiota in animals [13]. Another is the stimulating of the intestinal immune system via the modulation of cytokine levels [14]. In addition, probiotics promote growth rate through producing enzymes, vitamins, and mineral supplements, which help to improve digestion and nutrients absorption [5].…”

Irritable bowel syndrome, the microbiota and the gut-brain axis

“…The interaction between beneficial commensal bacteria and the immune cells results in a downregulation of proinflammatory genes, whereas anti-inflammatory genes are upregulated. 29,30 Although identification of the microbiota is ongoing in the Human Microbiome Project, the majority of GI microbiota is still uncharacterized. It is now certain that it consists of a great variety of microbes with a majority of anaerobic bacteria.…”

Ex vivo anti-inflammatory effects of probiotics for periodontal health

“…The mechanism by which these strains inhibited the LPS-stimulated release of inflammatory mediators from the host cells has not been elucidated and warrants investigation in future studies. However, previous research has shown that probiotic strains used in the gut can interact with toll-like receptors on host cells to downregulate the expression of nuclear factor-kappa-B and proinflammatory cytokines [25]. …”