Induction of cytokine formation by human intestinal bacteria in gut epithelial cell lines

A single amino acid in the Salmonella effector SarA/SteE triggers supraphysiological activation of STAT3 for anti-inflammatory gene expression

Salmonella causes ∼1 million cases of gastroenteritis annually in the United States. Critical to virulence are secreted effectors that reprogram host functions. We previously discovered the effector SarA facilitates phosphorylation of STAT3, inducing expression of the anti-inflammatory cytokine interleukin-10 (IL-10). This STAT3 activation requires a region of homology with the host cytokine receptor gp130. Here, we demonstrate that a single amino acid difference is critical for the anti-inflammatory bias of SarA-STAT3 signaling. An isoleucine at pY+1 of the YxxQ motif in SarA (which binds the STAT3 SH2 domain) causes increased STAT3 recruitment and phosphorylation, biasing toward anti-inflammatory targets. This isoleucine renders SarA a better substrate for tyrosine phosphorylation by GSK-3. GSK-3 is canonically a serine/threonine kinase that nonetheless undergoes tyrosine autophosphorylation at a motif with isoleucine at the pY+1 position. Our results provide a molecular basis for how a Salmonella effector achieves supraphysiological levels of STAT3 activation to control host genes.

Antioxidant and Inflammation-Attenuating Ability of Human Milk, Infant Formulas and Their Oligosaccharides

Human milk (HM) provides maximum health benefits for infants. This is due in part to the activity of its minor components, including HM proteins and oligosaccharides (HMOs). Where HM is unavailable, infant formulas (IFs) are normally used, the two most common types being cow milk- and goat milk-based formulas (CIF and GIF). The aim of this study was to compare the antioxidant properties of HM, CIF and GIF, together with those of their respective oligosaccharides (HMOs, CMOs and GMOs), using in vitro model systems. The ability of these oligosaccharides to attenuate inflammation (expression of IL-1α, TNFα, IL-6 and IL-8) was also assessed using a U937 cell culture model. Results showed that GIF and GMOs exhibited the highest antioxidant potential. The iron-reducing and iron-chelating properties of both IFs were comparable to those for HM, while the iron-chelating ability of the CMOs was lowest. None of the oligosaccharides significantly reduced U937 cytokine expression following induction of inflammation; however, GMOs consistently reduced expression of IL-1α, TNFα and IL-6 to a greater extent than the other oligosaccharides, presumably by competitive binding to immune receptors. In conclusion, GMOs have a greater antioxidant potential than CMOs and may have some inflammation-attenuating ability as well.

Unveiling the influence of a probiotic combination of Heyndrickxia coagulans and Lacticaseibacillus casei on healthy human gut microbiota using the TripleSHIME® system

Probiotics are host-friendly microorganisms that can have important health benefits in the human gut microbiota as dietary supplements. Maintaining a healthy gut microbial balance relies on the intricate interplay among the intestinal microbiota, metabolic activities, and the host's immune response. This study aims to explore if a mixture of Heyndrickxia coagulans [ATB-BCS-042] and Lacticaseibacillus casei [THT-030-401] promotes in vitro this balance in representative gut microbiota from healthy individuals using the Triple-SHIME® (Simulation of the Human Intestinal Microbial Ecosystem). Metataxonomic analysis of the intestinal microbes revealed that the probiotic mix was not causing important disruptions in the biodiversity or microbial composition of the three simulated microbiota. However, some targeted populations analyzed by qPCR were found to be disrupted at the end of the probiotic treatment or after one week of washout. Populations such as Cluster IV, Cluster XVIa, and Roseburia spp., were increased indicating a potential gut health-promoting butyrogenic effect of the probiotic supplementation. In two of the systems, bifidogenic effects were observed, while in the third, the treatment caused a decrease in bifidobacteria. For the health-detrimental biomarker Escherichia-Shigella, a mild decrease in all systems was observed in the proximal colon sections, but these genera were highly increased in the distal colon sections. By the end of the washout, Bacteroides-Prevotella was found consistently boosted, which could have inflammatory consequences in the intestinal context. Although the probiotics had minimal influence on most quantified metabolites, ammonia consistently decreased after one week of daily probiotic supplementation. In reporter gene assays, aryl hydrocarbon receptor (AhR) activation was favored by the metabolic output obtained from post-treatment periods. Exposure of a human intestinal cell model to fermentation supernatant obtained after probiotic supplementation induced a trend to decrease the mRNA expression of immunomodulatory cytokines (IL-6, IL-8). Overall, with some exceptions, a positive impact of H. coagulans and L. casei probiotic mix was observed in the three parallel experiments, despite inter-individual differences. This study might serve as an in vitro pipeline for the impact assessment of probiotic combinations on the human gut microbiota.

Taxonomic and phenotypic analysis of bifidobacteria isolated from IBD patients as potential probiotic strains

BACKGROUND

Inflammatory Bowel Diseases (IBD) are a major public health issue with unclear aetiology. Changes in the composition and functionality of the intestinal microbiota are associated with these pathologies, including the depletion of strict anaerobes such as Feacalibacterium prausnitzii. Less evidence is observed for depletion in other anaerobes, among which bifidobacteria. This study characterized the taxonomic and functional diversity of bifidobacteria isolated from the human intestinal microbiota in active and non-active IBD patients by a culturomics approach and evaluated if these bifidobacteria might be used as probiotics for gut health.

RESULTS

A total of 341 bifidobacteria were isolated from the intestinal microbiota of IBD patients (52 Crohn's disease and 26 ulcerative colitis patients), with a high proportion of Bifidobacterium dentium strains (28% of isolated bifidobacteria). In ulcerative colitis, the major species identified was B. dentium (39% of isolated bifidobacteria), in active and non-active ulcerative colitis. In Crohn's disease, B. adolescentis was the major species isolated from non-active patients (40%), while similar amounts of B. dentium and B. adolescentis were found in active Crohn's disease patients. The relative abundance of B. dentium was increased with age, both in Crohn's disease and ulcerative colitis and active and non-active IBD patients. Antibacterial capacities of bifidobacteria isolated from non-active ulcerative colitis against Escherichia coli LF82 and Salmonella enterica ATCC 14028 were observed more often compared to strains isolated from active ulcerative colitis. Finally, B. longum were retained as strains with the highest probiotic potential as they were the major strains presenting exopolysaccharide synthesis, antibacterial activity, and anti-inflammatory capacities. Antimicrobial activity and EPS synthesis were further correlated to the presence of antimicrobial and EPS gene clusters by in silico analysis.

CONCLUSIONS

Different bifidobacterial taxonomic profiles were identified in the microbiota of IBD patients. The most abundant species were B. dentium, mainly associated to the microbiota of ulcerative colitis patients and B. adolescentis, in the intestinal microbiota of Crohn's disease patients. Additionally, the relative abundance of B. dentium significantly increased with age. Furthermore, this study evidenced that bifidobacteria with probiotic potential (antipathogenic activity, exopolysaccharide production and anti-inflammatory activity), especially B. longum strains, can be isolated from the intestinal microbiota of both active and non-active Crohn's disease and ulcerative colitis patients.

The inhibition mechanism of co-cultured probiotics on biofilm formation of Klebsiella pneumoniae

AIMS

Klebsiella pneumoniae, an important opportunistic pathogen of nosocomial inflection, is known for its ability to form biofilm. The purpose of the current study is to assess how co- or mono-cultured probiotics affect K. pneumoniae's ability to produce biofilms and investigate the potential mechanisms by using a polyester nonwoven chemostat and a Caco-2 cell line.

METHODS AND RESULTS

Compared with pure cultures of Lactobacillus rhamnosus and Lactobacillus sake, the formation of K. pneumoniae biofilm was remarkably inhibited by the mixture of L. rhamnosus, L. sake, and Bacillus subtilis at a ratio of 5:5:1 by means of qPCR and FISH assays. In addition, Lactobacillus in combination with B. subtilis could considerably reduce the adherence of K. pneumoniae to Caco-2 cells by using inhibition, competition, and displacement assays. According to the RT-PCR assay, the adsorption of K. pneumoniae to Caco-2 cells was effectively inhibited by the co-cultured probiotics, leading to significant reduction in the expression of proinflammatory cytokines induced by K. pneumoniae. Furthermore, the HPLC and RT-PCR analyses showed that the co-cultured probiotics were able to successfully prevent the expression of the biofilm-related genes of K. pneumoniae by secreting plenty of organic acids as well as the second signal molecule (c-di-GMP), resulting in inhibition on biofilm formation.

CONCLUSION

Co-culture of L. sake, L. rhamnosus, and B. subtilis at a ratio of 5:5:1 could exert an antagonistic effect on the colonization of pathogenic K. pneumoniae by down-regulating the expression of biofilm-related genes. At the same time, the co-cultured probiotics could effectively inhibit the adhesion of K. pneumoniae to Caco-2 cells and block the expression of proinflammatory cytokines induced by K. pneumoniae.

A single amino acid in the Salmonella effector SarA/SteE triggers supraphysiological activation of STAT3 for anti-inflammatory target gene expression

Non-typhoidal Salmonella enterica cause an estimated 1 million cases of gastroenteritis annually in the United States. These serovars use secreted protein effectors to mimic and reprogram host cellular functions. We previously discovered that the secreted effector SarA (Salmonella anti-inflammatory response activator; also known as SteE) was required for increased intracellular replication of S. Typhimurium and production of the anti-inflammatory cytokine interleukin-10 (IL-10). SarA facilitates phosphorylation of STAT3 through a region of homology with the host cytokine receptor gp130. Here, we demonstrate that a single amino acid difference between SarA and gp130 is critical for the anti-inflammatory bias of SarA-STAT3 signaling. An isoleucine at the pY+1 position of the YxxQ motif in SarA (which binds the SH2 domain in STAT3) causes increased STAT3 phosphorylation and expression of anti-inflammatory target genes. This isoleucine, completely conserved in ~4000 Salmonella isolates, renders SarA a better substrate for tyrosine phosphorylation by GSK-3. GSK-3 is canonically a serine/threonine kinase that nonetheless undergoes tyrosine autophosphorylation at a motif that has an invariant isoleucine at the pY+1 position. Our results provide a molecular basis for how a Salmonella secreted effector achieves supraphysiological levels of STAT3 activation to control host genes during infection.

Prevalence and virulence potential of Aeromonas spp. isolated from human diarrheal samples in North East Italy

IMPORTANCE

In this work, we demonstrate the epidemiologic relevance of the Aeromonas genus as the cause of infective diarrhea in North East Italy, both in children and adult subjects, with the significative presence of highly pathogenic strains. Aeromonas strains possess a heterogeneous armamentarium of pathogenicity factors that allows the microbe to affect a wide range of human intestinal epithelial cell processes that justify the ability to induce diarrhea through different mechanisms and cause diseases of variable severity, as observed for other gastrointestinal pathogens. However, it remains to be determined whether specific genotype(s) are associated with clinical pictures of different severity to implement the diagnostic and therapeutic approaches for this relevant enteric pathogen.

Effects of Lactobacillus rhamnosus DSM7133 on Intestinal Porcine Epithelial Cells

Antimicrobial resistance is one of the biggest health challenges nowadays. Probiotics are promising candidates as feed additives contributing to the health of the gastrointestinal tract. The beneficial effect of probiotics is species/strain specific; the potential benefits need to be individually assessed for each probiotic strain or species. We established a co-culture model, in which gastrointestinal infection was modeled using Escherichia coli (E. coli) and Salmonella enterica serovar Typhimurium (S. enterica serovar Typhimurium). Using intestinal porcine epithelial cells (IPEC-J2), the effects of pre-, co-, and post-treatment with Lactobacillus (L.) rhamnosus on the barrier function, intracellular (IC) reactive oxygen species (ROS) production, proinflammatory cytokine (IL-6 and IL-8) response, and adhesion inhibition were tested. E. coli- and S. Typhimurium-induced barrier impairment and increased ROS production could be counteracted using L. rhamnosus (p < 0.01). S. Typhimurium-induced IL-6 production was reduced via pre-treatment (p < 0.05) and post-treatment (p < 0.01); increased IL-8 secretion was decreased via pre-, co-, and post-treatment (p < 0.01) with L. rhamnosus. L. rhamnosus demonstrated significant inhibition of adhesion for both S. Typhimurium (p < 0.001) and E. coli (p < 0.001 in both pre-treatment and post-treatment; p < 0.05 in co-treatment). This study makes a substantial contribution to the understanding of the specific benefits of L. rhamnosus. Our findings can serve as a basis for further in vivo studies carried out in pigs and humans.

Integrative analysis revealed the role of glucagon-like peptide-2 in improving experimental colitis in mice by inhibiting inflammatory pathways, regulating glucose metabolism, and modulating gut microbiota

Introduction

Ulcerative colitis (UC) is an inflammatory bowel disease characterized by recurrent and remitting inflammation of the mucosa of the colon and rectum, the incidence of which is on the rise. Glucagon-like peptide-2 (GLP-2) is a newly discovered neurotrophic factor, but its efficacy and mechanism of action in UC remain unclear. In this study, we investigated the protective effects and potential targets of GLP-2 on dextran sodium sulfate (DSS)-induced UC in mice through integrative analysis.

Methods

The effects of GLP-2 on UC were assessed by calculating the disease activity index, colonic mucosal damage index, and pathological histological scores. Enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry were used to detect the expression of GLP-2, nuclear factor kappa-B (NF-κB), interleukin-6 (IL-6), and signal transducer and activator of transcription-3 (STAT3). The 16SrRNA gene was used to detect changes in gut microbiota in mouse colonic tissues, and oral glucose tolerance test (OGTT) blood glucose levels were used to analyze the differences in flora.

Results

The results showed that GLP-2 could reduce the inflammation of UC mice, which may be achieved by inhibiting the potential targets of NF-κB, and Janus kinase (JAK)/STAT3 inflammatory pathways, regulating sugar metabolism, increasing dominant species, and improving microbial diversity.

Discussion

This study provides new insight into the potential of GLP-2 for achieving more ideal UC treatment goals in future.

Prevention and potential repair of colitis: Beneficial effects and regulatory mechanisms of food-derived anti-inflammatory peptides

Intestinal inflammatory diseases are increasingly prevalent worldwide, and their pathogenesis is still not fully understood. As of late, studies have discovered that food-derived peptides have specific anti-inflammatory activity and can play a positive role in intestinal health. At the same time, it has broad application prospects in the prevention and treatment of colitis because of its wide source, fast absorption, and high safety. This article reviews the structure-activity and quantity-effect relationships of food-derived peptides for their anti-inflammatory effects. It then discusses their mechanism of action in inhibiting colitis from four aspects. Food-derived anti-inflammatory peptides can delay the progression of the disease by stimulating innate immunity, inhibiting inflammation, and promoting wound healing. Further experiments showed that food-derived anti-inflammatory peptides could prevent and treat colitis through four mechanisms: (a) regulation of inflammatory cytokines; (b) regulation of inflammatory pathways; (c) regulation of intestinal epithelial barrier; (d) regulation of intestinal flora balance. However, due to the treatment of colitis having limitations, there is an urgent to develop food-derived anti-inflammatory peptides as a treatment or adjunctive treatment for colitis. This review highlights the positive effects of food-derived peptides on colitis and anticipates the appearance of mitigating peptides for the therapy of colitis.

The Combined Effect of Potential Probiotic Bacillus licheniformis MCC 2514 and Bifidobacterium breve NCIM 5671 Towards Anti-inflammatory Activity on HT-29 Cell Lines

Probiotics are considered a natural source for treating many intestinal disorders, which deliver health benefits in different ways. The study aims to evaluate the immunomodulatory gene expression on HT-29 cell line using Bacillus licheniformis MCC 2514 and Bifidobacterium breve NCIM 5671 as a single culture and in combination. Upon inflammation induced by LPS, the combination of bacteria downregulated the pro-inflammatory cytokines IL-1α (13.4), IL-12 (14.6), IL-8 (2.6), and IL-6 (1.9), and in contrast, TNF-α (21.2) folds has upregulated. However, anti-inflammatory genes such as IL-4 (0.6), IL-10 (2.9), TGF-2 (92.2), and TGF-3 (85.8) folds were upregulated. The combination of bacteria against oxidative stress downregulated the pro-inflammatory cytokines such as IL-1α & β, IL-6, IL-8, IL-12, and IL-18, and upregulated the anti-inflammatory cytokines IL-10, IL-4, TGF-2, and TGF-3. On the introduction of Kocuria rhizophila, the pro-inflammatory cytokines were upregulated. On supplementation of B. licheniformis and B. breve, the upregulated pro-inflammatory cytokines were decreased, and anti-inflammatory cytokines such as IL-4 (6.2), IL-10 (23.5), TGF-2 (166), and TGF-3(28.4) folds were increased. However, gene expression of toll-like receptor-2 was found high (26 folds) upon introducing probiotic bacteria. ELISA results of Interferon-γ found that the expression was higher (7.19 ng/mL) on the introduction of both the bacteria in combination. The higher anti-inflammatory activity was observed when potential probiotic bacteria were used in combination compared to a single culture. Overall study indicates that the combination of aerobic B. licheniformis and anaerobic B. breve has an anti-inflammatory activity that can sustain an excellent gastrointestinal environment during pathogen invasion and inflammation.

Botanicals as a zinc oxide alternative to protect intestinal cells from an Escherichia coli F4 infection in vitro by modulation of enterocyte inflammatory response and bacterial virulence

Pharmacological doses of zinc oxide (ZnO) have been widely used in pig industry to control post-weaning diarrhea (PWD) symptoms exacerbated by enterotoxigenic Escherichia coli F4 infections. Because of environmental issues and regulatory restrictions, ZnO is no longer sustainable, and novel nutritional alternatives to manage PWD are urgently required. Botanicals represent a wide class of compounds employed in animal nutrition because of their diverse beneficial functions. The aim of this study was to investigate the in vitro protective action of a panel of essential oils and natural extracts on intestinal Caco-2 cells against an E. coli F4 infection. Moreover, we explored the potential mechanisms of action of all the botanicals compared to ZnO. Amongst the others, thyme essential oil, grape seed extract, and Capsicum oleoresin were the most effective in maintaining epithelial integrity and reducing bacterial translocation. Their mechanism of action was related to the modulation of cellular inflammatory response, the protection of tight junctions' expression and function, and the control of bacterial virulence, thus resembling the positive functions of ZnO. Moreover, despite their mild effects on the host side, ginger and tea tree essential oils provided promising results in the control of pathogen adhesion when employed during the challenge. These outcomes support the advantages of employing selected botanicals to manage E. coli F4 infections in vitro, therefore offering novel environmentally-friendly alternatives to pharmacological doses of ZnO capable to modulate host-pathogen interaction at different levels during PWD in pigs.

Functions of Small Non-Coding RNAs in Salmonella–Host Interactions

Simple Summary

In the process of infecting the host, Salmonella senses and adapts to the environment within the host, breaks through the host’s defense system, and survives and multiplies in the host cell. As a class of universal regulators encoded in intergenic space, an increasing number of small non-coding RNAs (sRNAs) have been found to be involved in a series of processes during Salmonella infection, and they play an important role in interactions with the host cell. In this review, we discuss how sRNAs help Salmonella resist acidic environmental stress by regulating acid resistance genes and modulate adhesion and invasion to non-phagocytic cells by regulating virulent genes such as fimbrial subunits and outer membrane proteins. In addition, sRNAs help Salmonella adapt to oxidative stress within host cells and promote survival within macrophages. Although the function of a variety of sRNAs has been studied during host–Salmonella interactions, many of sRNAs’ functions remain to be discovered.

Abstract

Salmonella species infect hosts by entering phagocytic and non-phagocytic cells, causing diverse disease symptoms, such as fever, gastroenteritis, and even death. Therefore, Salmonella has attracted much attention. Many factors are involved in pathogenesis, for example, the capsule, enterotoxins, Salmonella pathogenicity islands (SPIs), and corresponding regulators. These factors are all traditional proteins associated with virulence and regulation. Recently, small non-coding RNAs (sRNAs) have also been reported to function as critical regulators. Salmonella has become a model organism for studying sRNAs. sRNAs regulate gene expression by imperfect base-pairing with targets at the post-transcriptional level. sRNAs are involved in diverse biological processes, such as virulence, substance metabolism, and adaptation to stress environments. Although some studies have reported the crucial roles of sRNAs in regulating host–pathogen interactions, the function of sRNAs in host–Salmonella interactions has rarely been reviewed. Here, we review the functions of sRNAs during the infection of host cells by Salmonella, aiming to deepen our understanding of sRNA functions and the pathogenic mechanism of Salmonella.

RNA-seq reveals a novel porcine lncRNA MPHOSPH9-OT1 induces CXCL8/IL-8 expression in ETEC infected IPEC-J2 cells

Enterotoxigenic Escherichia coli (ETEC) is a major cause of bacterial diarrhea in piglets, leading to economic losses in the pig industry. In past decades, long non-coding RNAs (lncRNAs) have shown to be widely involved in the regulation of host immunity in porcine infection diseases. In this study, we explored the lncRNAs associated with ETEC F41 infection in IPEC-J2 cells by high-throughput sequencing and bioinformatic analysis. A total of 10150 novel porcine lncRNAs were identified. There were 161 differentially expressed (DE) lncRNAs associated with ETEC F41 infection, of which 65 DE lncRNAs were up-regulated and 96 DE lncRNAs were down-regulated. Functional and KEGG enrichment analysis of predicted target genes of DE lncRNAs indicated they are enriched in cell growth and inflammation-related pathways, such as endocytosis, focal adhesion, TGF-β signaling pathway, and adherens junctions. We revealed a novel candidate lncRNA MPHOSPH9-OT1 that was up-regulated after ETEC infection. The qRT-PCR validation and ELISA assessment showed the knockdown and overexpression of MPHOSPH9-OT1 resulted in significantly down- and up-regulation of cellular mRNA levels and secreted cytokine levels of CXCL8/IL-8, respectively. Meanwhile, MPHOSPH9-OT1 equilibrium is important to maintain the transepithelial electric resistance value and tight junction protein expression of IPEC-J2 cells. This study provides insights into the functionality of novel porcine lncRNAs in host immune responses to ETEC infection.

Effects of Bacillus licheniformis and Bacillus subtilis on Gut Barrier Function, Proinflammatory Response, ROS Production and Pathogen Inhibition Properties in IPEC-J2—Escherichia coli/Salmonella Typhimurium Co-Culture

The emergence of antimicrobial resistance raises serious concerns worldwide. Probiotics offer a promising alternative to enhance growth promotion in farm animals; however, their mode of action still needs to be elucidated. The IPEC-J2 cell line (porcine intestinal epithelial cells) is an appropriate tool to study the effect of probiotics on intestinal epithelial cells. In our experiments, IPEC-J2 cells were challenged by two gastrointestinal (GI) infection causing agents, Escherichia coli (E. coli) or Salmonella enterica ser. Typhimurium (S. Typhimurium). We focused on determining the effect of pre-, co-, and post-treatment with two probiotic candidates, Bacillus licheniformis or Bacillus subtilis, on the barrier function, proinflammatory cytokine (IL-6 and IL-8) response, and intracellular reactive oxygen species (ROS) production of IPEC-J2 cells, in addition to the adhesion inhibition effect. Bacillus licheniformis (B. licheniformis) and Bacillus subtilis (B. subtilis) proved to be anti-inflammatory and had an antioxidant effect under certain treatment combinations, and further effectively inhibited the adhesion of pathogenic bacteria. Interestingly, they had little effect on paracellular permeability. Based on our results, Bacillus licheniformis and Bacillus subtilis are both promising candidates to contribute to the beneficial effects of probiotic multispecies mixtures.

Coordinated interaction between Lon protease and catalase-peroxidase regulates virulence and oxidative stress management during Salmonellosis

This study investigates the interplay between Lon protease and catalase-peroxidase (KatG) in relation to virulence modulation and the response to oxidative stress in Salmonella Typhimurium (ST). Proteomic comparison of ST wild-type and lon deletion mutant led to the recognition of a highly expressed KatG protein product among five other protein candidates that were significantly affected by lon deletion. By employing a bacterium two-hybrid assay (B2H), we demonstrated that the catalytic domain of Lon protease potentially interacts with the KatG protein that leads to proteolytic cleavage. Assessment of virulence gene expression in single and double lon and katG mutants revealed katG to be a potential positive modulator of both Salmonella pathogenicity Island-1 (SPI-1) and -2, while lon significantly affected SPI-1 genes. ST double deletion mutant, ∆lon∆katG was more susceptible to survival defects within macrophage-like cells and exhibited meager colonization of the mouse spleen compared to the single deletion mutants. The findings reveal a previously unknown function of Lon and KatG interaction in Salmonella virulence. Taken together, our experiments demonstrate the importance of Lon and KatG to cope with oxidative stress, for intracellular survival and in vivo virulence of Salmonella.

Effect of Enterococcus faecium NCIMB 10415 on Gut Barrier Function, Internal Redox State, Proinflammatory Response and Pathogen Inhibition Properties in Porcine Intestinal Epithelial Cells

In farm animals, intestinal diseases caused by Salmonella spp. and Escherichia coli may lead to significant economic loss. In the past few decades, the swine industry has largely relied on the prophylactic use of antibiotics to control gastrointestinal diseases. The development of antibiotic resistance has become an important issue both in animal and human health. The use of antibiotics for prophylactic purposes has been banned, moreover the new EU regulations further restrict the application of antibiotics in veterinary use. The swine industry seeks alternatives that are capable of maintaining the health of the gastrointestinal tract. Probiotics offer a promising alternative; however, their mode of action is not fully understood. In our experiments, porcine intestinal epithelial cells (IPEC-J2 cells) were challenged by Salmonella Typhimurium or Escherichia coli and we aimed at determining the effect of pre-, co-, and post-treatment with Enterococcus faecium NCIMB 10415 on the internal redox state, paracellular permeability, IL-6 and IL-8 secretion of IPEC-J2 cells. Moreover, the adhesion inhibition effect was also investigated. Enterococcus faecium was able to reduce oxidative stress and paracellular permeability of IPEC-J2 cells and could inhibit the adhesion of Salmonella Typhimurium and Escherichia coli. Based on our results, Enterococcus faecium is a promising candidate to maintain the health of the gastrointestinal tract.

Effects of Multispecies Probiotic on Intestinal Microbiota and Mucosal Barrier Function of Neonatal Calves Infected With E. coli K99

Altered gut microbiota are implicated in inflammatory neonatal calf diarrhea caused by E. coli K99. Beneficial probiotics are used to modulate gut microbiota. However, factors that mediate host-microbe interactions remain unclear. We evaluated the effects of a combination of multispecies probiotics (MSP) on growth, intestinal epithelial development, intestinal immune function and microbiota of neonatal calves infected with E. coli K99. Twelve newborn calves were randomly assigned as follows: C (control, without MSP); D (E. coli O78:K99 + gentamycin); and P (E. coli O78:K99 + supplemental MSP). All groups were studied for 21 d. MSP supplementation significantly (i) changed fungal Chao1 and Shannon indices of the intestine compared with group D; (ii) reduced the relative abundance of Bacteroides and Actinobacteria, while increasing Bifidobacteria, Ascomycetes, and Saccharomyces, compared with groups C and D; (iii) improved duodenal and jejunal mucosal SIgA and total Short Chain Fatty Acids (SCFA) concentrations compared with group D; (iv) increased relative ZO-1 and occludin mRNA expression in jejunal mucosa compared with group D; and (v) enhanced intestinal energy metabolism and defense mechanisms of calves by reducing HSP90 expression in E. coli K99, thereby alleviating the inflammatory response and promoting recovery of mucosal function. Our research may provide direct theoretical support for future applications of MSP in ruminant production.

An in vitro intestinal model captures immunomodulatory properties of the microbiota in inflammation

Considerable effort has been put forth to understand mechanisms by which the microbiota modulates and responds to inflammation. Here, we explored whether oxidation metabolites produced by the host during inflammation, sodium nitrate and trimethylamine oxide, impact the composition of a human stool bacterial population in a gut simulator. We then assessed whether an immune-competent in vitro intestinal model responded differently to spent medium from bacteria exposed to these cues compared to spent medium from a control bacterial population. The host-derived oxidation products were found to decrease levels of Bacteroidaceae and overall microbiota metabolic potential, while increasing levels of proinflammatory Enterobacteriaceae and lipopolysaccharide in bacterial cultures, reflecting shifts that occur in vivo in inflammation. Spent microbiota media induced elevated intracellular mucin levels and reduced intestinal monolayer integrity as reflected in transepithelial electrical resistance relative to fresh medium controls. However, multiplexed cytokine analysis revealed markedly different cytokine signatures from intestinal cultures exposed to spent medium with added oxidation products relative to spent control medium, while cytokine signatures of cultures exposed to fresh media were similar regardless of addition of host-derived cues. Further, the presence of immune cells in the intestinal model was required for this differentiation of cytokine signatures. This study indicates that simple in vitro immune-competent intestinal models can capture bacterial-mammalian cross-talk in response to host-derived oxidation products and supports utility of these systems for mechanistic studies of interactions between the gut microbiome and host in inflammation.

Intestinal Organoids: New Tools to Comprehend the Virulence of Bacterial Foodborne Pathogens

Foodborne diseases cause high morbidity and mortality worldwide. Understanding the relationships between bacteria and epithelial cells throughout the infection process is essential to setting up preventive and therapeutic solutions. The extensive study of their pathophysiology has mostly been performed on transformed cell cultures that do not fully mirror the complex cell populations, the in vivo architectures, and the genetic profiles of native tissues. Following advances in primary cell culture techniques, organoids have been developed. Such technological breakthroughs have opened a new path in the study of microbial infectious diseases, and thus opened onto new strategies to control foodborne hazards. This review sheds new light on cellular messages from the host–foodborne pathogen crosstalk during in vitro organoid infection by the foodborne pathogenic bacteria with the highest health burden. Finally, future perspectives and current challenges are discussed to provide a better understanding of the potential applications of organoids in the investigation of foodborne infectious diseases.

Identification and Functional Analysis of Cytokine-Like Protein CLEC-47 in Caenorhabditis elegans

A variety of effector proteins contribute to host defense in Caenorhabditis elegans. However, beyond lytic enzymes and antimicrobial peptides and proteins, little is known about the exact function of these infection-related effectors. This study set out to identify pathogen-dependent cytokine-like molecules, focusing on C-type lectin domain-containing proteins (CLECs). In total, 38 CLECs that are differentially regulated in response to bacterial infections have been previously identified by microarray and transcriptome sequencing (RNA-seq) analyses in C. elegans. We successfully cloned 18 of these 38 CLECs and chose to focus on CLEC-47 because, among these 18 cloned CLECs, it was the smallest protein and was recombinantly expressed at the highest levels in prokaryotic cells examined by SDS-PAGE. Quantitative real-time PCR (qRT-PCR/qPCR) showed that the expression of clec-47 was induced by a variety of Gram-positive bacterial pathogens, including Enterococcus faecium, Staphylococcus aureus, and Cutibacterium acnes, but was suppressed by the Gram-negative bacteria Klebsiella pneumoniae and Pseudomonas aeruginosa. By expressing CLEC-47 in HEK 293 cells, we showed that CLEC-47 is released into the culture media, which the Golgi apparatus inhibitors (brefeldin A [BFA] and GolgiStop) could block. Purified recombinant CLEC-47 (maltose binding protein [MBP]–CLEC-47–His) did not display antimicrobial activity against ESKAPE pathogen isolates but bound directly to murine macrophage J774A.1 cells. Recombinant CLEC-47 attracted and recruited J774A.1 cells in a chemotaxis assay. In addition, qPCR studies and enzyme-linked immunosorbent assays (ELISAs) showed that CLEC-47 activates J774A.1 cells in a dose- and time-dependent manner to express the proinflammatory cytokines tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), IL-6, and Macrophage Inflammatory Protein 2 (MIP-2). Moreover, C. elegans, fed with CLEC-47-expressing Escherichia coli, demonstrated enhanced expression of several antimicrobial proteins (CNC-1, CNC-2, CPR-1, and CPR-2) as well as the detoxification protein MTL-1. These data suggest that CLEC-47 functions as a novel cytokine-like signaling molecule and exemplify how the study of infection-related effectors in C. elegans can help elucidate the evolution of immune responses.

Potential probiotic Lacticaseibacillus rhamnosus MTCC-5897 attenuates Escherichia coli induced inflammatory response in intestinal cells

Probiotics are microbes having tremendous potential to prevent gastrointestinal disorders. In current investigation, immunomodulatory action of probiotic Lacticaseibacillus rhamnosus MTCC-5897 was studied during exclusion, competition and displacement of Escherichia coli on intestinal epithelial (Caco-2) cells. The incubation of intestinal cells with Escherichia coli, enhanced downstream signalling and activated nuclear factor kappa B (NF-κB). This significantly increased (p < 0.01) the pro-inflammatory cytokines (IL-8, TNF-α, IFN-ϒ) expression. While, incubation of epithelial cells with Lacticaseibacillus rhamnosus during exclusion and competition with Escherichia coli, counteracted these enhanced expressions. The immunomodulatory feature of Lacticaseibacillus rhamnosus was also highlighted with increased (p < 0.05) transcription of toll-like receptor-2 (TLR-2) and single Ig IL-1-related receptor (SIGIRR) along with diminished expression of TLR-4. Likewise, attenuation (p < 0.05) of E. coli-mediated enhanced nuclear translocation of NF-κB p-65 subunit by Lacticaseibacillus rhamnosus during exclusion was confirmed with western blotting. Thus, present finding establishes the prophylactic potential of Lacticaseibacillus rhamnosus against exclusion of Escherichia coli in intestinal cells.

Contribution of the Microbiota and their Secretory Products to Inflammation and Colorectal Cancer Pathogenesis: The Role of Toll-like Receptors

Alterations in diversity and function of the gut microbiome are associated with concomitant changes in immune response, including chronic inflammation. Chronic inflammation is a major risk factor for colorectal cancer (CRC). An important component of the inflammatory response system are the toll-like receptors (TLRs). TLRs are capable of sensing microbial components, including nucleic acids, lipopolysaccharides, and peptidoglycans, as well as bacterial outer membrane vesicles (OMV). OMVs can be decorated with or carry as cargo these TLR activating factors. These microbial factors can either promote tolerance or activate signaling pathways leading to chronic inflammation. Herein we discuss the role of the microbiome and the OMVs that originate from intestinal bacteria in promoting chronic inflammation and the development of colitis-associated CRC. We also discuss the contribution of TLRs in mediating the microbiome-inflammation axis and subsequent cancer development. Understanding the role of the microbiome and its secretory factors in TLR response may lead to the development of better cancer therapeutics.

Vibrio cholerae toxin coregulated pilus provokes inflammatory responses in Coculture model of Caco-2 and peripheral blood mononuclear cells (PBMC) leading to increased colonization

The aim of this study was to assess the modulatory effect of TcpA in the expression of CEACAM1 adhesin molecule and IL-1, IL-8, and TNF-α pro-inflammatory cytokines in the Coculture model of Caco-2/PBMC (peripheral blood mononuclear cell) that can mimic the intestinal milieu. The TcpA gene from Vibrio cholerae ATCC14035 was cloned in pET-28a and transformed into Escherichia coli Bl-21. The recombinant TcpA-His6 protein was expressed and purified using Ni-column chromatography. The sequencing of transformed plasmid and Western blot analysis of purified protein confirmed the identity of rTcp. The cytotoxicity of different concentrations of recombinant protein for human colon carcinoma cell line (human colorectal adenocarcinoma cell [Caco-2 cell]) was assessed by MTT assay and showed viability of 92%, 82%, and 70%, for 10 µg/mL of TcpA after 24, 48, and 72 h, respectively. Co-cultures of Caco-2 and PBMCs were used to mimic the intestinal milieu and treated with different concentrations of rTcpA (1, 5, 10, and 50 µg/mL). Our data showed about 2.04-, 3.37-, 3.68-, and 42.7-fold increase in CEACAM1 gene expression, respectively, compared with the nontreated Caco-2/PBMC Coculture. Moreover, the expression of IL-1, IL-8, and TNF-α genes was significantly increased up to 15.75-, 7.04-, and 80.95-folds, respectively. In conclusion, V. cholerae TcpA induces statistically significant dose-dependent stimulatory effect on TNF-α, IL-,1, and IL-8 pro-inflammatory cytokines expression. Of these, TNF-α was much more affected which, consequently, elevated the CEACAM1 expression level in IECs. This suggests that TcpA protein is a critical effector as an inducer of increased adhesion potential of V. cholera as well as inflammatory responses of host intestinal tissue.

Lactobacillus fermentum (MTCC-5898) alleviates Escherichia coli-induced inflammatory responses in intestinal epithelial cells by modulating immune genes and NF-κB signalling

AIM

Dietary intervention using probiotic bacteria has emerged as a promising preventive strategy in addressing foodborne infections or gastrointestinal disorders. This study investigated the immunomodulatory effects of Lactobacillus fermentum (MTCC-5898) on Escherichia coli-induced inflammatory responses in intestinal epithelial cells.

METHODS AND RESULTS

The immune response of intestinal cells (Caco-2) in the presence of probiotic Lact. fermentum was determined during exclusion, competition and displacement of E. coli as the inflammatory agent. To achieve this objective, transcriptional modulation of key immune-related genes (cytokines, pattern recognition receptors and NF-κB), release of cytokines and nuclear translocation of the NF-κB subunit p-65 were studied. Expression of pro-inflammatory cytokines IL-8, TNF-α, IFN-ϒ and IL-23 was high in E. coli-exposed intestinal cells. However, overexpression of these E. coli-induced pro-inflammatory cytokines was prevented by Lact. fermentum during exclusion and competition assays. It also modulated the transcriptional expression of regulatory cytokines (IL-10 and TGF-β), pattern recognition receptors (TLR-2 and TLR-4) and genes associated with master inflammatory regulators (NF-κB and SIGIRR) to reduce E. coli-induced inflammation. The protective effect of Lact. fermentum was further confirmed by suppression of nuclear translocation of cytoplasmic NF-κB subunit (p-65).

CONCLUSION

Lactobacillus fermentum alleviated E. coli-induced inflammatory responses by modulating the NF-κB signalling besides pro-inflammatory and regulatory cytokines expression.

SIGNIFICANCE AND IMPACT OF THE STUDY

Lactobacillus fermentum holds significant promise as a potent nutraceutical that prevents and manages inflammatory gut-associated dysfunctions.

Escherichia coli K12 Upregulates Programmed Cell Death Ligand 1 (PD-L1) Expression in Gamma Interferon-Sensitized Intestinal Epithelial Cells via the NF-κB Pathway

Programmed cell death ligand-1 (PD-L1) is an immune checkpoint protein which is used by tumor cells for immune evasion. PD-L1 is upregulated in inflamed intestinal tissues. The intestinal tract is colonized by millions of bacteria, most of which are commensal bacterial species. We hypothesized that under inflammatory conditions, some commensal bacterial species contribute to increased PD-L1 expression in intestinal epithelium and examined this hypothesis. Human intestinal epithelial HT-29 cells with and without interferon (IFN)-γ sensitization were incubated with six strains of four enteric bacterial species. The mRNA and protein levels of PD-L1 in HT-29 cells were examined using quantitative real-time PCR and flow cytometry, respectively. The levels of interleukin (IL)-1β, IL-18, IL-6, IL-8, and tumor necrosis factor (TNF)-α secreted by HT-29 cells were measured using enzyme-linked immunosorbent assay. Apoptosis of HT-29 cells was measured using a caspase 3/7 assay. We found that Escherichia coli K12 significantly upregulated both PD-L1 mRNA and protein in IFN-γ-sensitized HT-29 cells. E. coli K12 induced the production of IL-8 in HT-29 cells, however, IL-8 did not affect HT-29 PD-L1 expression. Inhibition of the nuclear factor-kappa B pathway significantly reduced E. coli K12-induced PD-L1 expression in HT-29 cells. The other two E. coli strains and two enteric bacterial species did not significantly affect PD-L1 expression in HT-29 cells. Enterococcus faecalis significantly inhibited PD-L1 expression due to induction of cell death. Data from this study suggest that some gut bacterial species have the potential to affect immune function under inflammatory conditions via upregulating epithelial PD-L1 expression.

Comparison of cell invasion, macrophage survival and inflammatory cytokines profiles between Salmonella enterica serovars Enteritidis and Dublin from Brazil

AIMS

This study compared the capacity of strains of Salmonella enterica serovars Enteritidis and Dublin isolated in Brazil to invade epithelial cells, to be internalized by and survive within macrophages, and to stimulate cytokine release in vitro.

METHODS AND RESULTS

Both serovars infected 75 and 73% Caco-2 (human) and MDBK (bovine) epithelial cells respectively. Salmonella Dublin and S. Enteritidis (i) were internalized at the respective rates of 79·6 and 65·0% (P ≤ 0·05) by U937 (human) macrophages, and 70·4 and 66·9% by HD11 (chicken) macrophages; and (ii) multiplied at the respective rates of 3·2- and 2·7-fold within U937 cells, and 1·9- and 1·1-fold (P ≤ 0·05) within HD11 cells respectively. Seventy per cent of 10 S. Dublin strains stimulated IL-8 production, while 70% of S. Enteritidis strains enhanced production of IL-1β, IL-6, IL-8, IL-10, IL-12p70 and TNF in Caco-2 cells.

CONCLUSIONS

Compared with S. Enteritidis, S. Dublin had stronger ability to survive within macrophages and induced weak cytokine production, which may explain the higher incidence of invasive diseases caused by S. Dublin in humans.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study compared S. enterica serovars Enteritidis and Dublin to provide comparative data about the profile of the two serovars in cells from humans, the common host and their respective natural animal hosts and vice versa in order to check the differences between these two phylogenetically closely related serovars that share antigenic properties but present different phenotypic behaviours.

Application of a gut-immune co-culture system for the study of N-glycan-dependent host-pathogen interactions of Campylobacter jejuni

An in vitro gut-immune co-culture model with apical and basal accessibility, designed to more closely resemble a human intestinal microenvironment, was employed to study the role of the N-linked protein glycosylation pathway in Campylobacter jejuni pathogenicity. The gut-immune co-culture (GIC) was developed to model important aspects of the human small intestine by the inclusion of mucin-producing goblet cells, human enterocytes and dendritic cells, bringing together a mucus-containing epithelial monolayer with elements of the innate immune system. The utility of the system was demonstrated by characterizing host-pathogen interactions facilitated by N-linked glycosylation, such as host epithelial barrier functions, bacterial invasion and immunogenicity. Changes in human intestinal barrier functions in the presence of 11168 C. jejuni (wildtype) strains were quantified using GICs. The glycosylation-impaired strain 11168 ΔpglE was 100-fold less capable of adhering to and invading this intestinal model in cell infectivity assays. Quantification of inflammatory signaling revealed that 11168ΔpglE differentially modulated inflammatory responses in different intestinal microenvironments, suppressive in some but activating in others. Virulence-associated outer membrane vesicles produced by wildtype and 11168ΔpglE C. jejuni were shown to have differential composition and function, with both leading to immune system activation when provided to the gut-immune co-culture model. This analysis of aspects of C. jejuni infectivity in the presence and absence of its N-linked glycome is enabled by application of the gut-immune model, and we anticipate that this system will be applicable to further studies of C. jejuni and other enteropathogens of interest.

Campylobacter jejuni genes Cj1492c and Cj1507c are involved in host cell adhesion and invasion

Background

Campylobacter jejuni (C. jejuni) has been assigned as an important food-borne pathogen for human health but many pathogenicity factors of C. jejuni and human host cell responses related to the infection have not yet been adequately clarified. This study aimed to determine further C. jejuni pathogenicity factors and virulence genes based on a random mutagenesis approach. A transposon mutant library of C. jejuni NCTC 11168 was constructed and the ability of individual mutants to adhere to and invade human intestinal epithelial cells was evaluated compared to the wild type. We identified two mutants of C. jejuni possessing altered phenotypes with transposon insertions in the genes Cj1492c and Cj1507c. Cj1492c is annotated as a two-component sensor and Cj1507c is described as a regulatory protein. However, functions of both mutated genes are not clarified so far.

Results

In comparison to the wild type, Cj::1492c and Cj::1507c showed around 70-80% relative motility and Cj::1492c had around 3-times enhanced adhesion and invasion rates whereas Cj::1507c had significantly impaired adhesive and invasive capability. Moreover, Cj::1492c had a longer lag phase and slower growth rate while Cj::1507c showed similar growth compared to the wild type. Between 5 and 24 h post infection, more than 60% of the intracellular wild type C. jejuni were eliminated in HT-29/B6 cells, however, significantly fewer mutants were able to survive intracellularly. Nevertheless, no difference in host cell viability and induction of the pro-inflammatory chemokine IL-8 were determined between both mutants and the wild type.

Conclusion

We conclude that genes regulated by Cj1507c have an impact on efficient adhesion, invasion and intracellular survival of C. jejuni in HT-29/B6 cells. Furthermore, potential signal sensing by Cj1492c seems to lead to limiting attachment and hence internalisation of C. jejuni. However, as the intracellular survival capacities are reduced, we suggest that signal sensing by Cj1492c impacts several processes related to pathogenicity of C. jejuni.

In vitro spleen cell cytokine responses of adult mice immunized with a recombinant PorA (major outer membrane protein [MOMP]) from Campylobacter jejuni

There is no information on cytokine profiles for use as markers of protection in Campylobacter jejuni infection. To study this, we used outer membrane protein (MOMP [PorA]) as the vaccine for protection and spleen cell cytokines as markers of protection. We cloned and expressed porA from C. jejuni111 and immunized mice by the intraperitoneal route. Subsequently, mice were orally challenged with live C. jejuni 111. The vaccine induced protection as evidenced by reduced fecal excretion of C. jejuni111. Cytokines were measured in vitro after stimulation of spleen cells with MOMP. The levels of pro-inflammatory cytokines, IL-12, TNF-α, IL-17A and IL-17F were similar in control and test mice. The levels of pro-inflammatory cytokines, IL-2 and IFN-γ were higher in control mice than in test mice, and the levels of pro-inflammatory cytokines, IL-8 and IL-1β were higher in test mice than in control mice. Among the two anti-inflammatory cytokines, the levels were similar for IL-10 but higher for IL-4 in test mice than in control mice. Ratios of pro-inflammatory to anti-inflammatory cytokines showed a bias towards an anti-inflammatory response in favor of antibody production reflecting the role of antibodies in immunity. Cytokine production patterns by spleen cells may be used as markers of protection in the mouse model.

Downregulation of Salmonella Virulence Gene Expression During Invasion of Epithelial Cells Treated with Lactococcus lactis subsp. cremoris JFR1 Requires OppA

Invasion of Salmonella into host intestinal epithelial cells requires the expression of virulence genes. In this study, cell culture models of human intestinal cells (mucus-producing HT29-MTX cells, absorptive Caco-2 cells, and combined cocultures of the two) were used to determine the effects of Lactococcus lactis subsp. cremoris treatments (exopolysaccharide producing and nonproducing strains) on the virulence gene expression of Salmonella Typhimurium and its mutant lacking the oligopeptide permease subunit A (ΔoppA). During the course of epithelial cell (HT29-MTX, Caco-2, and combined) infection by Salmonella Typhimurium DT104, improved barrier function was reflected by increased transepithelial electrical resistance in cells treated with both strains of L. lactis subsp. cremoris. In addition, virulence gene expression was downregulated, accompanied with lower numbers of invasive bacteria into epithelial cells in the presence of L. lactis subsp. cremoris treatments. Similarly, virulence gene expression of Salmonella was also suppressed when coincubated with overnight cultures of both L. lactis subsp. cremoris strains in the absence of epithelial cells. However, in medium or in the presence of cell cultures, Salmonella lacking the OppA permease function remained virulent. HT29-MTX cells and combined cultures stimulated by Salmonella Typhimurium DT104 showed significantly lower secretion levels of pro-inflammatory cytokine IL-8 after treatment with L. lactis subsp. cremoris cell suspensions. Contrarily, these responses were not observed during infection with S. Typhimurium ΔoppA. Both the exopolysaccharide producing and nonproducing strains of L. lactis subsp. cremoris JFR1 exhibited an antivirulence effect against S. Typhimurium DT104 although no significant difference between the two strains was observed. Our results show that an intact peptide transporter is essential for the suppression of Salmonella virulence genes which leads to the protection of the barrier function in the cell culture models studied.

Saponins regulate intestinal inflammation in colon cancer and IBD

The saponins are natural surface-active glycosides which are the principal components of many popular herbal medicinal plants such as ginseng, astragalus, and bupleurum. Recent studies have suggested that saponins can exert strong anti-inflammatory effects and induce immune homeostasis in many diseases. Intestinal-inflammation-related digestive diseases include inflammatory bowel disease (IBD), irritable bowel syndrome, intestinal ischemia-reperfusion injury, necrotizing enterocolitis and radiation proctitis, as well as intestinal inflammation caused by nonsteroidal anti-inflammatory drugs. The pathogenesis of these diseases is poorly understood, and the patients with these diseases suffer from mental stress and physical pain, while their families (and society) experience heavy economic losses. Results from animal experiments suggest that saponins can suppress intestinal inflammation, promote intestinal barrier repair, maintain the diversity of the intestinal flora, and decrease the incidence rate of colon-inflammation-related colon cancer. In this review, we discuss new findings regarding the effects of saponins on intestinal inflammation and digestive diseases with intestinal inflammation. In addition, we provide a summary of the underlying mechanism for saponins-induced treatment on intestinal-inflammation-related disease.

Cytotoxic and inflammatory effects of individual and combined exposure of HepG2 cells to zearalenone and its metabolites

Zearalenone (ZEA), a mycotoxin produced by several Fusarium spp., is most commonly found as a contaminant in stored grain. ZEA derivatives (α-zearalenol (α-ZOL), β-zearalenol (β-ZOL)) can also be produced by Fusarium spp. in corn stems infected by fungi in the field. Also, following oral exposure, zearalenone is metabolized in various tissues, particularly in the liver, the major metabolites being α-ZOL and β-ZOL. The co-exposure of cells to mixture of a combination of mycotoxins may cause an increase of toxicity produced by these mycotoxins. In this in vitro study, we investigated the combined effects of ZEA, α-ZOL, β-ZOL in binary mixtures on the viability and inflammatory response of human liver cancer cell line (HepG2). Cell viability was assessed after 72 h using a neutral red assay. Effect of the toxins and their binary combinations on the expression of genes involved in inflammation (IL-1β, TNF-α, and IL-8) were assessed through qPCR. Our viability data showed that irrespective of the toxin combinations, the toxins have synergistic effect. ZEA + α-ZOL and ZEA + β-ZOL mixtures have induced a slight to high antagonistic response on inflammatory cytokines at low concentrations that have turned into strong synergism for high concentrations. α-ZOL + β-ZOL showed antagonistic effects on inflammation for IL-1β and TNF-α, but act synergic for IL-8 at high toxin concentrations. This study clearly shows that co-contamination of food and feed with ZEA metabolites should be taken into consideration, as the co-exposure to mycotoxins might result in stronger adverse effect than resulted from the exposure to individual toxin.

Campylobacter coli Clade 3 Isolates Induce Rapid Cell Death In Vitro

Campylobacter bacteria are major human enteropathogens. Campylobacter coli shows less genetic diversity than C. jejuni and clusters into three clades, of which clade 1 includes most human and farm animal isolates, while environmental C. coli isolates mainly belong to clades 2 and 3. Recently, we sequenced the whole genomes of eight C. coli clade 2 and 3 isolates cultivated from water, and here we studied their interaction with human HT-29 colon cancer cells compared to that of clinical clade 1 isolates. All C. coli clade 3 isolates already caused cell necrosis 1 to 2 h after inoculation, whereas none of the clade 1 and 2 isolates analyzed induced cell death. Isolates from clades 2 and 3 adhered to epithelial cells better than clade 1 isolates, but all isolates induced similar levels of interleukin-8 (IL-8). Alignment and phylogenetic analysis of the translated putative virulence genes cadF, flpA, iamA, ciaB, and ceuE revealed clade-specific protein sequence variations, with clade 1 and 2 sequences being more closely related and clade 3 sequences being further apart, in general. Moreover, when RNA levels were measured, clade 3 isolates showed significantly lower levels of expression of cadF, iamA, and ceuE than clade 2 isolates, while flpA expression levels were higher in clade 3 isolates. The cytolethal distending toxin genes were also expressed in clades 2 and 3, although there was no difference between clades. Our findings demonstrate differences between the effects of C. coli clade 1, 2, and 3 isolates on human cells and suggest that C. coli clade 3 might be more virulent than clade 2 due to the observed cytotoxicity.IMPORTANCECampylobacter coli is a common zoonotic cause of gastroenteritis in humans worldwide. The majority of infections are caused by C. coli clade 1 isolates, whereas infections due to clade 2 and 3 isolates are rare. Whether this depends on a low prevalence of clade 2 and 3 isolates in reservoirs important for human infections or their lower ability to cause human disease is unknown. Here, we studied the effects of C. coli clade 2 and 3 isolates on a human cell line. These isolates adhered to human cells to a higher degree than clinical clade 1 isolates. Furthermore, we could show that C. coli clade 3 isolates rapidly induced cell death, suggesting differences in the virulence of C. coli The exact mechanism of cell death remains to be revealed, but selected genes showed interesting clade-specific expression patterns.

Effectiveness of probiotics in the management of inflammatory arthritis: a systematic review protocol

REVIEW QUESTIONS

The questions of this systematic review are: i) What is the effectiveness of probiotics as a therapeutic intervention for individuals living with inflammatory arthritis? ii) What are the reported adverse effects of probiotics when used as a therapeutic intervention for individuals living with inflammatory arthritis?

Modulation of Enterohaemorrhagic Escherichia coli Survival and Virulence in the Human Gastrointestinal Tract

Enterohaemorrhagic Escherichia coli (EHEC) is a major foodborne pathogen responsible for human diseases ranging from diarrhoea to life-threatening complications. Survival of the pathogen and modulation of virulence gene expression along the human gastrointestinal tract (GIT) are key features in bacterial pathogenesis, but remain poorly described, due to a paucity of relevant model systems. This review will provide an overview of the in vitro and in vivo studies investigating the effect of abiotic (e.g., gastric acid, bile, low oxygen concentration or fluid shear) and biotic (e.g., gut microbiota, short chain fatty acids or host hormones) parameters of the human gut on EHEC survival and/or virulence (especially in relation with motility, adhesion and toxin production). Despite their relevance, these studies display important limitations considering the complexity of the human digestive environment. These include the evaluation of only one single digestive parameter at a time, lack of dynamic flux and compartmentalization, and the absence of a complex human gut microbiota. In a last part of the review, we will discuss how dynamic multi-compartmental in vitro models of the human gut represent a novel platform for elucidating spatial and temporal modulation of EHEC survival and virulence along the GIT, and provide new insights into EHEC pathogenesis.

Induction Effects of Bacteroides fragilis Derived Outer Membrane Vesicles on Toll Like Receptor 2, Toll Like Receptor 4 Genes Expression and Cytokines Concentration in Human Intestinal Epithelial Cells

Objective

Gastrointestinal (GI) tract, like other mucosal surface, is colonized with a microbial population known as gut microbiota. Outer membrane vesicles (OMVs) which are produced by gram negative bacteria could be sensed by Toll like receptors (TLRs). The interaction between gut microbiota and TLRs affects homeostasis and immune responses. In this study, we evaluated TLR2, TLR4 genes expression and cytokines concentration in Caco-2 cell line treated with Bacteroides fragilis (B. fragilis) and its OMVs.

Materials and Methods

In this experimental study, OMVs were extracted using sequential centrifugation and their physicochemical properties were evaluated as part of quality control assessment. Caco-2 cells were treated with B. fragilis and its OMVs (180 and 350 µg/ml). Quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) was performed to assess TLR2 and TLR4 mRNA expression levels. Pro-inflammatory (IFNᵧ) and anti-inflammatory (IL- 4 and IL-10) cytokines were evaluated by ELISA.

Results

B. fragilis significantly decreased TLR2 and slightly increased TLR4 mRNA levels in Caco-2 cell line. The TLR2 mRNA level was slightly increased at 180 and 350 µg/ml of OMVs. Conversely, the TLR4 mRNA level was decreased at 180 µg/ml of OMVs, while it was significantly increased at 350 µg/ml of OMVs. Furthermore, B. fragilis and its OMVs significantly increased and decreased IFNᵧ concentration, respectively. Anti-inflammatory cytokines were increased by B. fragilis and its OMVs.

Conclusion

B. fragilis and its OMVs have pivotal role in the cross talk between gut microbiota and the host especially in the modulation of the immune system. Based on the last studies on immunomodulatory effect of B. fragilis derived OMVs on immune cells and our results, we postulate that B. fragilis derived OMVs could be possible candidates for the reduction of immune responses.

Reduced intestinal epithelial mitochondrial function enhances in vitro interleukin-8 production in response to commensal Escherichia coli

Uncoupling of oxidative phosphorylation in epithelial mitochondria results in decreased epithelial barrier function as characterized by increased internalization of non-invasive Escherichia coli and their translocation across the epithelium. We hypothesized that the increased burden of intracellular commensal bacteria would activate the enterocyte, with the potential to promote inflammation. Treatment of human colon-derived epithelial cell lines in vitro with dinitrophenol (DNP) and commensal E. coli (strains F18, HB101) provoked increased production of interleukin (IL-8), which was not observed with conditioned medium from the bacteria, lipopolysaccharide or inert beads. The IL-8 response was inhibited by co-treatment with cytochalasin-D (blocks F-actin rearrangement), chloroquine (blocks phagosome acidification) and a MyD88 inhibitor (blocks TLR signaling), consistent with TLR-signaling mediating IL-8 synthesis subsequent to bacterial internalization. Use of the mitochondria-targeted antioxidant, mitoTEMPO, or U0126 to block ERK1/2 MAPK signalling inhibited DNP+E. coli-evoked IL-8 production. Mutations in the NOD2 (the intracellular sensor of bacteria) or ATG16L1 (autophagy protein) genes are susceptibility traits for Crohn's, and epithelia lacking either protein displayed enhanced IL-8 production in comparison to wild-type cells when exposed to DNP + E coli. Thus, metabolic stress perturbs the normal epithelial-bacterial interaction resulting in increased IL-8 production due to uptake of bacteria into the enterocyte: this potentially pro-inflammatory event is enhanced in cells lacking NOD2 or ATG16L1 that favor increased survival of bacteria within the enterocyte. We speculate that by increasing epithelial permeability and IL-8 production, reduced mitochondria function in the enteric epithelium would contribute to the initiation, pathophysiology, and reactivation of inflammatory disease in the gut.

In Vitro Transcriptome Response to a Mixture of Lactobacilli Strains in Intestinal Porcine Epithelial Cell Line

Background: Food and feed supplements containing microorganisms with probiotic potential are of increasing interest due to their healthy promoting effect on human and animals. Their mechanism of action is still unknown. Using a microarray approach, the aim of this study was to investigate the differences in genome-wide gene expression induced by a mixture of three Lactobacillus strains (L. rhamnosus, L. plantarum, and L. paracasei) in intestinal porcine epithelial cells (IPEC-1) and to identify the genes and pathways involved in intestinal barrier functions. Methods: Undifferentiated IPEC-1 cells seeded at a density of 2.0 × 10⁵/mL in 24-wells culture plates were cultivated at 37 °C and 5% CO₂ until they reached confluence (2–3 days). Confluent cells monolayer were then cultivated with 1 mL of fresh lactobacilli (LB) mixture suspension prepared for a concentration of approximately 3.3 × 10⁷ CFU/mL for each strain (1 × 10⁸ CFU/mL in total) for 3 h and analyzed by microarray using Gene Spring GX v.11.5. Results: The functional analysis showed that 1811 of the genes modulated by LB treatment are involved in signaling (95% up-regulation, 121 genes with a fold change higher than 10). The most enhanced expression was registered for AXIN2 (axis inhibition protein 2-AXIN2) gene (13.93 Fc, p = 0.043), a negative regulator of β-catenin with a key role in human cancer. LB affected the cellular proliferation by increasing 10 times (Fc) the NF1 gene encoding for the neurofibromin protein, a tumor suppressor that prevent cells from uncontrolled proliferation. The induction of genes like serpin peptidase inhibitor, clade A member 3 (SERPINA 3), interleukin-20 (IL-20), oncostatin M(OSM), granulocyte-macrophage colony-stimulating factor (GM-CSF), and the suppression of chemokine (C-X-C motif) ligand 2/macrophage inflammatory protein 2-alpha (CXCL-2/MIP-2), regulator of G-protein signaling 2 (RGS2), and of pro-inflammatory interleukin-18 (IL-18) genes highlights the protective role of lactobacilli in epithelial barrier function against inflammation and in the activation of immune response. Conclusion: Gene overexpression was the predominant effect produced by lactobacilli treatment in IPEC-1 cells, genes related to signaling pathways being the most affected. The protective role of lactobacilli in epithelial barrier function against inflammation and in the activation of immune response was also noticed.

HIV induces production of IL-18 from intestinal epithelial cells that increases intestinal permeability and microbial translocation

Interleukin-18 (IL-18) is a pleiotropic cytokine of the IL-1 family with multiple context dependent functions. We and others have shown that HIV infection is accompanied by increased circulating levels of IL-18 along with decreased levels of its antagonist, Interleukin-18 Binding Protein (IL-18BP). The infection is also accompanied by intestinal inflammation and decreased intestinal integrity as measured by intestinal permeability, regeneration and repair. However, little is known concerning the relation between high level of IL-18 associated with the viral infection and intestinal permeability. Here we demonstrate that HIV treatment increases production of IL-18 and decreases that of IL-18BP production in human intestinal epithelial cell (IEC) lines. IL-18 causes apoptosis of the IEC by activating caspase-1 and caspase-3. It induces epithelial barrier hyperpermeability by decreasing and disrupting both tight and adherens junction proteins, occludin, claudin 2 and beta-catenin. Disorganization of F-actin was also observed in the IEC that were exposed to the cytokine. Moreover IL-18 decreases transepithelial electrical resistance (TEER) in Caco-2 and increases permeability in HT29 monolayers. The cells' treatment with IL-18 causes an increase in the expression of phosphorylated myosin II regulatory light-chain (p-MLC) and myosin light-chain kinase (MLCK), and a decrease in phosphorylated Signal Transducer and Activator of Transcription (p-STAT)-5. This increase in p-MLC is suppressed by a Rho-kinase (ROCK)-specific inhibitor. Interestingly, the levels of the cytokine correlate with those of LPS in the circulation in three different categories of HIV infected patients (HAART-naïve and HAART-treated HIV-infected individuals, and Elite controls) as well as in healthy controls. Collectively, these results suggest that the HIV-induced IL-18 plays a role in increased intestinal permeability and microbial translocation observed in HIV-infected individuals.

Cytokine responses in campylobacteriosis: Linking pathogenesis to immunity

Campylobacter jejuni is an important enteric pathogen that causes diarrheas of different degrees of severity and several extra-intestinal manifestations, including Guillain-Barre syndrome. The variability of disease outcomes is thought to be linked to the immune response induced by C. jejuni. The virulence factors of C. jejuni induce a pro-inflammatory response, that is initiated by the intestinal epithelial cells, propagated by innate immune cells and modulated by the cells of the adaptive immune response. This review focuses on cytokines, that are reported to orchestrate the induction and propagation of pro-inflammatory immune response, and also those that are involved in control and resolution of inflammation. We describe the functional roles of a number of cytokines in modulating anti-Campylobacter immune responses: 1. cytokines of innate immunity (TNF-α, IL-6, and IL-8) as initiators of inflammatory response, 2. cytokines of antigen-presenting cells (IL-1β, IL-12, and IL-23) as promoters of pro-inflammatory response, 3. cytokines produced by T cells (IFN-γ, IL-17, IL-22) as activators of T cells, and 4. anti-inflammatory cytokines (IL-4 and IL-10) as inhibitors of pro-inflammatory responses. We highlight the roles of cytokines as potential therapeutic agents that are under investigation. In the end, we pose several questions that remain unanswered in our quest to understand Campylobacter immunity.

A human origin strain Lactobacillus acidophilus DDS-1 exhibits superior in vitro probiotic efficacy in comparison to plant or dairy origin probiotics

Background: The health benefits of probiotics are well established and known to be strain-specific. However, the role of probiotics obtained from different origins and their efficacy largely remains unexplored. The aim of this study is to investigate the in vitro efficacy of probiotics from different origins. Methods: Probiotic strains utilized in this study include Lactobacillus acidophilus DDS-1 (human origin), Bifidobacterium animalis ssp. lactis UABla-12 (human origin), L. plantarum UALp-05 (plant origin) and Streptococcus thermophilus UASt-09 (dairy origin). Screening assays such as in vitro digestion simulation, adhesion, cell viability and cytokine release were used to evaluate the probiotic potential. Results: All strains showed good resistance in the digestion simulation process, especially DDS-1 and UALp-05, which survived up to a range of 10⁷ to 10⁸ CFU/mL from an initial concentration of 10⁹ CFU/mL. Two human colonic mucus-secreting cells, HT-29 and LS174T, were used to assess the adhesion capacity, cytotoxicity/viability, and cytokine quantification. All strains exhibited good adhesion capacity. No significant cellular cytotoxicity or loss in cell viability was observed. DDS-1 and UALp-05 significantly upregulated anti-inflammatory IL-10 and downregulated pro-inflammatory TNF-α cytokine production. All the strains were able to downregulate IL-8 cytokine levels. Conclusion: Of the 4 strains tested, DDS-1 demonstrated superior survival rates, good adhesion capacity and strong immunomodulatory effect under different experimental conditions.

Salmonella small RNA fragment Sal-1 facilitates bacterial survival in infected cells via suppressing iNOS induction in a microRNA manner

Salmonella can hijack host atypical miRNA processing machinery to cleave its small non-coding RNA into a ~22-nt RNA fragment, Sal-1, which facilitates Salmonella survival in the infected host. The mechanism through which Sal-1 promotes Salmonella survival, however, remains unknown. In the present study, we reported that Sal-1 targets cellular inducible nitric oxide synthase (iNOS) in a miRNA manner, leading to attenuation of host cell iNOS/NO-mediated anti-microbial capacity. First, depletion of Sal-1 in Salmonella-infected epithelial cells significantly increased the iNOS level but not the levels of various inflammatory cytokines. Bioinformatics analysis and mutagenesis strategies were consistent with the identification of mRNA of iNOS as a target of Sal-1 in both human and mice. Second, western blot and immunohistochemical analysis confirmed that Sal-1 suppressed iNOS expression in vitro and in vivo, thus reducing the production of NO. Finally, Sal-1 facilitating Salmonella survival through suppressing iNOS induction was confirmed in mouse model by expressing mutated iNOS that is not targeted by Sal-1 in mice colon. In conclusion, our study provides new insight into the pathogenic mechanism of intracellular bacteria to modulate host innate immune response.

Bifidobacteria and Their Molecular Communication with the Immune System

Bifidobacterium represents a genus within the phylum Actinobacteria which is one of the major phyla in the healthy intestinal tract of humans. Bifidobacterium is one of the most abundant genera in adults, but its predominance is even more pronounced in infants, especially during lactation, when they can constitute the majority of the total bacterial population. They are one of the pioneering colonizers of the early gut microbiota, and they are known to play important roles in the metabolism of dietary components, otherwise indigestible in the upper parts of the intestine, and in the maturation of the immune system. Bifidobacteria have been shown to interact with human immune cells and to modulate specific pathways, involving innate and adaptive immune processes. In this mini-review, we provide an overview of the current knowledge on the immunomodulatory properties of bifidobacteria and the mechanisms and molecular players underlying these processes, focusing on the corresponding implications for human health. We deal with in vitro models suitable for studying strain-specific immunomodulatory activities. These include peripheral blood mononuclear cells and T cell-mediated immune responses, both effector and regulatory cell responses, as well as the modulation of the phenotype of dendritic cells, among others. Furthermore, preclinical studies, mainly germ-free, gnotobiotic, and conventional murine models, and human clinical trials, are also discussed. Finally, we highlight evidence supporting the immunomodulatory effects of bifidobacterial molecules (proteins and peptides, exopolysaccharides, metabolites, and DNA), as well as the role of bifidobacterial metabolism in maintaining immune homeostasis through cross-feeding mechanisms.

The Bacterial Species Campylobacter jejuni Induce Diverse Innate Immune Responses in Human and Avian Intestinal Epithelial Cells

Campylobacter remain the major cause of human gastroenteritis in the Developed World causing a significant burden to health services. Campylobacter are pathogens in humans and chickens, although differences in mechanistic understanding are incomplete, in part because phenotypic strain diversity creates inconsistent findings. Here, we took Campylobacter jejuni isolates (n = 100) from multi-locus sequence typed collections to assess their pathogenic diversity, through their inflammatory, cytotoxicity, adhesion, invasion and signaling responses in a high-throughput model using avian and human intestinal epithelial cells. C. jejuni induced IL-8 and CXCLi1/2 in human and avian epithelial cells, respectively, in a MAP kinase-dependent manner. In contrast, IL-10 responses in both cell types were PI 3-kinase/Akt-dependent. C. jejuni strains showed diverse levels of invasion with high invasion dependent on MAP kinase signaling in both cell lines. C. jejuni induced diverse cytotoxic responses in both cell lines with cdt-positive isolates showing significantly higher toxicity. Blockade of endocytic pathways suggested that invasion by C. jejuni was clathrin- and dynamin-dependent but caveolae- independent in both cells. In contrast, IL-8 (and CXCLi1/2) production was dependent on clathrin, dynamin, and caveolae. This study is important because of its scale, and the data produced, suggesting that avian and human epithelial cells use similar innate immune pathways where the magnitude of the response is determined by the phenotypic diversity of the Campylobacter species.

Toll-like receptors 2 and 4 modulate intestinal IL-10 differently in ileum and colon

Background

Inflammatory bowel diseases are consequence of an intestinal homeostasis breakdown in which innate immune dysregulation is implicated. Toll-like receptor (TLR)2 and TLR4 are immune recognition receptors expressed in the intestinal epithelium, the first physical-physiological barrier for microorganisms, to inform the host of the presence of Gram-positive and Gram-negative organisms. Interleukin (IL)-10 is an essential anti-inflammatory cytokine that contributes to maintenance of intestinal homeostasis.

Aim

Our main aim was to investigate intestinal IL-10 synthesis and release, and whether TLR2 and TLR4 are determinants of IL-10 expression in the intestinal tract.

Methods

We used Caco-2 cell line as an enterocyte-like cell model, and also ileum and colon from mice deficient in TLR2, TLR4 or TLR2/4 to test the involvement of TLR signaling.

Results

Intestinal epithelial cells are able to synthesize and release IL-10 and their expression is increased after TLR2 or TLR4 activation. IL-10 regulation seems to be tissue specific, with IL-10 expression in the ileum regulated by a compensation between TLR2 and TLR4 expression, whereas in the colon, TLR2 and TLR4 affect IL-10 expression independently.

Conclusions

Intestinal epithelial cells could release IL-10 in response to TLR activation, playing an intestinal tissue-dependent and critical intestinal immune role.

Initial Gut Microbial Composition as a Key Factor Driving Host Response to Antibiotic Treatment, as Exemplified by the Presence or Absence of Commensal Escherichia coli

Antibiotics are important for treating bacterial infection; however, efficacies and side effects of antibiotics vary in medicine and experimental models. A few studies have correlated microbiota composition variations with health outcomes in response to antibiotics; however, no study has demonstrated causality. We had noted variation in colonic expression of C-type lectins, regenerating islet-derived protein 3β (Reg3β) and Reg3γ, after metronidazole treatment in a mouse model. To investigate the effects of specific variations in the preexisting microbiome on host response to antibiotics, mice harboring a normal microbiota were allocated to 4 treatments in a 2-by-2 factorial arrangement with or without commensal Escherichia coli and with or without metronidazole in drinking water. E. coli colonized readily without causing a notable shift in the microbiota or host response. Metronidazole administration reduced microbiota biodiversity, indicated by decreased Chao1 and Shannon index values, and altered microbiota composition. However, the presence of E. coli strongly affected metronidazole-induced microbiota shifts. Remarkably, this single commensal bacterium in the context of a complex population led to variations in host responses to metronidazole treatment, including increased expression of antimicrobial peptides Reg3β and Reg3γ and intestinal inflammation indicated by tumor necrosis factor alpha levels. Similar results were obtained from 2-week antibiotic exposure and with additional E. coli isolates. The results of this proof-of-concept study indicate that even minor variations in initial commensal microbiota can drive shifts in microbial composition and host response after antibiotic administration. As well as providing an explanation for variability in animal models using antibiotics, the findings encourage the development of personalized medication in antibiotic therapies.IMPORTANCE This work provides an understanding of variability in studies where antibiotics are used to alter the gut microbiota to generate a host response. Furthermore, although providing evidence only for the one antibiotic, the study demonstrated that initial gut microbial composition is a key factor driving host response to antibiotic administration, creating a compelling argument for considering personalized medication based on individual variations in gut microbiota.

Systematic review: exercise-induced gastrointestinal syndrome-implications for health and intestinal disease

BACKGROUND

"Exercise-induced gastrointestinal syndrome" refers to disturbances of gastrointestinal integrity and function that are common features of strenuous exercise.

AIM

To systematically review the literature to establish the impact of acute exercise on markers of gastrointestinal integrity and function in healthy populations and those with chronic gastrointestinal conditions.

METHODS

Search literature using five databases (PubMed, EBSCO, Web of Science, SPORTSdiscus, and Ovid Medline) to review publications that focused on the impact of acute exercise on markers of gastrointestinal injury, permeability, endotoxaemia, motility and malabsorption in healthy populations and populations with gastrointestinal diseases/disorders.

RESULTS

As exercise intensity and duration increases, there is considerable evidence for increases in indices of intestinal injury, permeability and endotoxaemia, together with impairment of gastric emptying, slowing of small intestinal transit and malabsorption. The addition of heat stress and running mode appears to exacerbate these markers of gastrointestinal disturbance. Exercise stress of ≥2 hours at 60% VO_2max appears to be the threshold whereby significant gastrointestinal perturbations manifest, irrespective of fitness status. Gastrointestinal symptoms, referable to upper- and lower-gastrointestinal tract, are common and a limiting factor in prolonged strenuous exercise. While there is evidence for health benefits of moderate exercise in patients with inflammatory bowel disease or functional gastrointestinal disorders, the safety of more strenuous exercise has not been established.

CONCLUSIONS

Strenuous exercise has a major reversible impact on gastrointestinal integrity and function of healthy populations. The safety and health implications of prolonged strenuous exercise in patients with chronic gastrointestinal diseases/disorders, while hypothetically worrying, has not been elucidated and requires further investigation.