Colonic bacterial superantigens evoke an inflammatory response and exaggerate disease in mice recovering from colitis

Duodenal microbiota dysbiosis in functional dyspepsia and its potential role of the duodenal microbiota in gut-brain axis interaction: a systematic review

Background and aims

Functional dyspepsia (FD) is a common gastrointestinal disorder associated with brain-gut interaction disturbances. In recent years, accumulating evidence points to the duodenum as a key integrator in dyspepsia symptom generation. Investigations into the pathological changes in the duodenum of FD patients have begun to focus on the role of duodenal microbiota dysbiosis. This review summarizes duodenal microbiota changes in FD patients and explores their relationship with gut-brain interaction dysregulation.

Methods

Ten databases, including PubMed, MEDLINE, and the Cochrane Library, were searched from inception to 10th October 2023 for clinical interventional and observational studies comparing the duodenal microbiota of FD patients with controls. We extracted and qualitatively summarized the alpha diversity, beta diversity, microbiota composition, and dysbiosis-related factors.

Results

A total of nine studies, consisting of 391 FD patients and 132 non-FD controls, were included. The findings reveal that the alpha diversity of the duodenal microbiota in FD patients does not exhibit a significant difference compared to non-FD controls, although an upward trend is observed. Furthermore, alterations in the duodenal microbiota of FD patients are associated with the symptom burden, which, in turn, impacts their quality of life. In FD patients, a considerable number of duodenal microbiota demonstrate a marked ascending trend in relative abundance, including taxa such as the phylum Fusobacteria, the genera Alloprevotella, Corynebacterium, Peptostreptococcus, Staphylococcus, Clostridium, and Streptococcus. A more pronounced declining trend is observed in the populations of the genera Actinomyces, Gemella, Haemophilus, Megasphaera, Mogibacterium, and Selenomonas within FD patients. A negative correlation in the relative abundance changes between Streptococcus and Prevotella is identified, which correlates with the severity of symptom burden in FD patients. Moreover, the alterations in specific microbial communities in FD patients and their potential interactions with the gut-brain axis merit significant attention.

Conclusion

Microbial dysbiosis in FD patients is linked to the onset and exacerbation of symptoms and is related to the disorder of gut-brain interaction. Larger-scale, higher-quality studies, along with comprehensive meta-omics research, are essential to further elucidate the characteristics of the duodenal microbiota in FD patients and its role in FD pathogenesis.Systematic review registration: CRD42023470279, URL: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023470279.

Targeting staphylococcal enterotoxin B binding to CD28 as a new strategy for dampening superantigen-mediated intestinal epithelial barrier dysfunctions

Staphylococcus aureus is a gram-positive bacterium that may cause intestinal inflammation by secreting enterotoxins, which commonly cause food-poisoning and gastrointestinal injuries. Staphylococcal enterotoxin B (SEB) acts as a superantigen (SAg) by binding in a bivalent manner the T-cell receptor (TCR) and the costimulatory receptor CD28, thus stimulating T cells to produce large amounts of inflammatory cytokines, which may affect intestinal epithelial barrier integrity and functions. However, the role of T cell-mediated SEB inflammatory activity remains unknown. Here we show that inflammatory cytokines produced by T cells following SEB stimulation induce dysfunctions in Caco-2 intestinal epithelial cells by promoting actin cytoskeleton remodelling and epithelial cell-cell junction down-regulation. We also found that SEB-activated inflammatory T cells promote the up-regulation of epithelial-mesenchymal transition transcription factors (EMT-TFs) in a nuclear factor-κB (NF-κB)- and STAT3-dependent manner. Finally, by using a structure-based design approach, we identified a SEB mimetic peptide (pSEB116-132) that, by blocking the binding of SEB to CD28, dampens inflammatory-mediated dysregulation of intestinal epithelial barrier.

Characteristics of Lactococcus petauri GB97 lysate isolated from porcine feces and its in vitro and in vivo effects on inflammation, intestinal barrier function, and gut microbiota composition in mice

IMPORTANCE

Weaning is a crucial step in piglet management to improve pork production. During the weaning phase, disruption of epithelial barrier function and intestinal inflammation can lead to decreased absorption of nutrients and diarrhea. Therefore, maintaining a healthy intestine, epithelial barrier function, and gut microbiota composition in this crucial phase is strategic for optimal weaning in pigs. We isolated a lysate of Lactococcus petauri GB97 (LPL97) from healthy porcine feces and evaluated its anti-inflammatory activities, barrier integrity, and gut microbial changes in LPS-induced murine macrophages and DSS-induced colitis mice. We found that LPL97 regulated the immune response by downregulating the TLR4/NF-κB/MAPK signaling pathway both in vitro and in vivo. Furthermore, LPL97 alleviated the disruption of intestinal epithelial integrity and gut microbiota dysbiosis in colitis mice. This study indicates that LPL97 has the potential to be developed as an alternative feed additive to antibiotics for the swine industry.

In Vitro Evaluation of Probiotic Properties of Two Novel Probiotic Mixtures, Consti-Biome and Sensi-Biome

Changes in the gut microbiome cause recolonization by pathogens and inflammatory responses, leading to the development of intestinal disorders. Probiotics administration has been proposed for many years to reverse the intestinal dysbiosis and to enhance intestinal health. This study aimed to evaluate the inhibitory effects of two newly designed probiotic mixtures, Consti-Biome and Sensi-Biome, on two enteric pathogens Staphylococcus aureus and Escherichia coli that may cause intestinal disorders. Additionally, the study was designed to evaluate whether Consti-Biome and Sensi-Biome could modulate the immune response, produce short-chain fatty acids (SCFAs), and reduce gas production. Consti-Biome and Sensi-Biome showed superior adhesion ratios to HT-29 cells and competitively suppressed pathogen adhesion. Moreover, the probiotic mixtures decreased the levels of pro-inflammatory cytokines, such as tumor necrosis factor-α, interleukin (IL)-6 and IL-1β. Cell-free supernatants (CFSs) were used to investigate the inhibitory effects of metabolites on growth and biofilms of pathogens. Consti-Biome and Sensi-Biome CFSs exhibited antimicrobial and anti-biofilm activity, where microscopic analysis confirmed an increase in the number of dead cells and the structural disruption of pathogens. Gas chromatographic analysis of the CFSs revealed their ability to produce SCFAs, including acetic, propionic, and butyric acid. SCFA secretion by probiotics may demonstrate their potential activities against pathogens and gut inflammation. In terms of intestinal symptoms regarding abdominal bloating and discomfort, Consti-Biome and Sensi-Biome also inhibited gas production. Thus, these two probiotic mixtures have great potential to be developed as dietary supplements to alleviate the intestinal disorders.

Effect of the combination of Lactobacillus acidophilus (probiotic) with vitamin K3 and vitamin E on Escherichia coli and Staphylococcus aureus: An in vitro pathogen model

The gut microbiota plays a key role in maintaining health and regulating the host's immune response. The use of probiotics and concomitant vitamins can increase mucus secretion by improving the intestinal microbial population and prevent the breakdown of tight junction proteins by reducing lipopolysaccharide concentration. Changes in the intestinal microbiome mass affect multiple metabolic and physiological functions. Studies on how this microbiome mass and the regulation in the gastrointestinal tract are affected by probiotic supplements and vitamin combinations have attracted attention. The current study evaluated vitamins K and E and probiotic combinations effects on Escherichia coli and Staphylococcus aureus. Minimal inhibition concentrations of vitamins and probiotics were determined. In addition, inhibition zone diameters, antioxidant activities and immunohistochemical evaluation of the cell for DNA damage were performed to evaluate the effects of vitamins and probiotics. At the specified dose intervals, L. acidophilus and vitamin combinations inhibit the growth of Escherichia coli and Staphylococcus aureus. It could thus contribute positively to biological functions by exerting immune system‑strengthening activities.

Fucosylated Chondroitin Sulfate against Parkinson's Disease through Inhibiting Inflammation Induced by Gut Dysbiosis

Growing evidence for the importance of the gut-brain axis in Parkinson's disease (PD) has attracted researchers' interest in the possible application of microbiota-based treatment approaches. Using a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse model, we looked into the prospect of treating PD with fucosylated chondroitin sulfate obtained from sea cucumbers Isostichopus badionotus (fCS-Ib). We showed that giving fCS-Ib polysaccharide orally greatly reduced the motor deficits, dopamine depletion, and alpha-synuclein increase caused by MPTP in the substantia nigra (SN). It appears that the anti-PD action of fCS-Ib polysaccharide could be attained by squelching inflammation. Glial cell hyperactivation in SN and overproduction of proinflammatory substances in serum could both be suppressed by fCS-Ib polysaccharide injection. The bacterial DNA in fresh colonic feces was submitted to 16S rRNA and untargeted metabolic analyses to confirm the participation of the microbiota-gut-brain axis in the aforementioned interpretation. The findings showed that the MPTP treatment-induced decrease in norank_f_Muribaculaceae and the increase in Staphylococcus were reversed by the administration of fCS-Ib polysaccharide. The NF-κB signaling pathway was shown to be involved in the fCS-Ib polysaccharide-induced anti-inflammation. In conclusion, our research demonstrated for the first time how fCS-Ib polysaccharide combats PD by reducing inflammation caused by gut microbial dysbiosis.

Dietary Ethanolamine Plasmalogen Alleviates DSS-Induced Colitis by Enhancing Colon Mucosa Integrity, Antioxidative Stress, and Anti-inflammatory Responses via Increased Ethanolamine Plasmalogen Molecular Species: Protective Role of Vinyl Ether Linkages

Dietary ethanolamine plasmalogen (PlsEtn) has been reported to have several health benefits; however, its functional role during colon pathophysiology remains elusive. The present study investigated the anticolitis effect of dietary ethanolamine glycerophospholipids (EtnGpls) with high PlsEtn from ascidian muscle (86.2 mol %) and low PlsEtn from porcine liver (7.7 mol %) in dextran sulfate sodium (DSS)-induced colitis in mice. Dietary EtnGpls lowered myeloperoxidase activity, thiobarbituric acid-reactive substances, proinflammatory cytokines and proapoptosis-related protein levels in colon mucosa after 16 days of DSS treatment, with ascidian muscle (0.1% EtnGpl in diet) showing higher suppression than porcine liver (0.1% EtnGpl in diet). Moreover, dietary EtnGpls suppressed DSS symptoms after 38 days of DSS treatment as evidenced by increased body weight, colon length, and ameliorated colon mucosa integrity. Additionally, dietary EtnGpls elevated short-chain fatty acid production in DSS-treated mice. Altogether, these results indicate the potential of utilizing diets with abundant PlsEtn for the prevention of colon inflammation-related disorders.

Staphylococcus aureus Infection Influences the Function of Intestinal Cells by Altering the Lipid Raft-Dependent Sorting of Sucrase-Isomaltase

Staphylococcus aureus is an important nosocomial and community-acquired facultative intracellular pathogen. Many studies have reported that S. aureus infections are associated with intestinal symptoms, but little is known about the molecular mechanisms implicated in S. aureus-induced alterations of intestinal functions. In this study, we investigated the implication of lipid rafts in the interaction of S. aureus with Caco-2 cells. To assess potential alterations in the lipid raft structure and effects on the hydrolytic function, we utilized sucrase–isomaltase (SI) as the major intestinal α-glucosidase that is associated with and sorted to the apical membrane via lipid rafts. Seven days post-confluent, Caco-2 cells were infected with S. aureus Newman and further incubated for an additional 2 days. After 48 h, the levels of SI expression as well as the enzymatic function of this protein were assessed in the infected versus non-infected cells. Analysis of the sorting behavior of SI to the apical membrane constituted another crucial aspect in studying the effects of S. aureus on Caco-2 cells. For this purpose, the apical membranes or brush border membranes (BBMs; referred to as P2 fraction) were separated in both infected and non-infected cells from the basolateral and intracellular membranes (referred to as P1 fraction) by employing a cationic-based procedure using CaCl₂. The data show that there is no significant change in the overall expression levels of SI in the infected versus non-infected cells as assessed by Western blotting analysis using monoclonal anti-SI antibodies. By contrast, a significant decrease in the localization as well as the specific hydrolytic activities of SI toward sucrose and isomaltose (Palatinose) was observed in the BBM (P2 fraction) in Caco-2 cells 48 h post-infection. Concomitantly, the specific SI activities increased in the basolateral membrane/intracellular fraction (P1). Noteworthy, the specific activity of SI in the BBM of infected cells was markedly reduced as compared with that of the non-infected counterparts. The data accumulated from this study strongly suggest that infections with S. aureus influence the final step in the lipid raft-associated trafficking of human SI and thereby may trigger secondary functional gastrointestinal disorders.

The Effectiveness of Multi-Session FMT Treatment in Active Ulcerative Colitis Patients: A Pilot Study

The modification of the microbiome through fecal microbiota transplantation (FMT) is becoming a very promising therapeutic option for inflammatory bowel disease (IBD) patients. Our pilot study aimed to assess the effectiveness of multi-session FMT treatment in active ulcerative colitis (UC) patients. Ten patients with UC were treated with multi-session FMT (200 mL) from healthy donors, via colonoscopy/gastroscopy. Patients were evaluated as follows: at baseline, at week 7, and after 6 months, routine blood tests (including C reactive protein (CRP) and calprotectin) were performed. 16S rRNA gene (V3V4) sequencing was used for metagenomic analysis. The severity of UC was classified based on the Truelove–Witts index. The assessment of microbial diversity showed significant differences between recipients and healthy donors. FMT contributed to long-term, significant clinical and biochemical improvement. Metagenomic analysis revealed an increase in the amount of Lactobacillaceaea, Micrococcaceae, Prevotellaceae, and TM7 phylumsp.oral clone EW055 during FMT, whereas Staphylococcaceae and Bacillaceae declined significantly. A positive increase in the proportion of the genera Bifidobacterium, Lactobacillus, Rothia, Streptococcus, and Veillonella and a decrease in Bacillus, Bacteroides, and Staphylococcus were observed based on the correlation between calprotectin and Bacillus and Staphylococcus; ferritin and Lactobacillus, Veillonella, and Bifidobacterium abundance was indicated. A positive change in the abundance of Firmicutes was observed during FMT and after 6 months. The application of multi-session FMT led to the restoration of recipients’ microbiota and resulted in the remission of patients with active UC.

A mouse model of Staphylococcus aureus small intestinal infection

Introduction

Staphylococcus aureus is a recognised cause of foodborne intoxication and antibiotic-associated diarrhoea (AAD), which are both mediated by staphylococcal enterotoxins. However, unlike foodborne intoxication, AAD appears to require infection of the host. While S. aureus intoxication is widely studied, little is known about S. aureus pathogenesis in the context of gastrointestinal infection.

Aim

To develop a mouse model of S. aureus gastrointestinal infection.

Methodology

An established AAD mouse model was adapted for S. aureus infection, and damage observed via histopathological analysis and immunostaining of intestinal tissues.

Results

Various strains colonised the mouse model, and analysis showed that although clinical signs of disease were not seen, S. aureus infection induced damage in the small intestine, disrupting host structures essential for epithelial integrity. Studies using a staphylococcal enterotoxin B mutant showed that this toxin may contribute to damage during gastrointestinal infection.

Conclusion

This work presents a new mouse model of S. aureus gastrointestinal infection, while also providing insight into the pathogenesis of S. aureus in the gut.

Staphylococcal Superantigens: Pyrogenic Toxins Induce Toxic Shock

Staphylococcal enterotoxin B (SEB) and related superantigenic toxins produced by Staphylococcus aureus are potent activators of the immune system. These protein toxins bind to major histocompatibility complex (MHC) class II molecules and specific Vβ regions of T-cell receptors (TCRs), resulting in the activation of both monocytes/macrophages and T lymphocytes. The bridging of TCRs with MHC class II molecules by superantigens triggers an early “cytokine storm” and massive polyclonal T-cell proliferation. Proinflammatory cytokines, tumor necrosis factor α, interleukin 1 (IL-1), IL-2, interferon γ (IFNγ), and macrophage chemoattractant protein 1 elicit fever, inflammation, multiple organ injury, hypotension, and lethal shock. Upon MHC/TCR ligation, superantigens induce signaling pathways, including mitogen-activated protein kinase cascades and cytokine receptor signaling, which results in NFκB activation and the phosphoinositide 3-kinase/mammalian target of rapamycin pathways. In addition, gene profiling studies have revealed the essential roles of innate antimicrobial defense genes in the pathogenesis of SEB. The genes expressed in a murine model of SEB-induced shock include intracellular DNA/RNA sensors, apoptosis/DNA damage-related molecules, endoplasmic reticulum/mitochondrial stress responses, immunoproteasome components, and IFN-stimulated genes. This review focuses on the signaling pathways induced by superantigens that lead to the activation of inflammation and damage response genes. The induction of these damage response genes provides evidence that SEB induces danger signals in host cells, resulting in multiorgan injury and toxic shock. Therapeutics targeting both host inflammatory and cell death pathways can potentially mitigate the toxic effects of staphylococcal superantigens.

FDA-approved immunosuppressants targeting staphylococcal superantigens: mechanisms and insights

Immunostimulating staphylococcal enterotoxin B (SEB) and related superantigenic toxins cause diseases in human beings and laboratory animals by hyperactivating cells of the immune system. These protein toxins bind to the major histocompatibility complex class II (MHC II) molecules and specific Vβ regions of T-cell receptors (TCRs), resulting in the stimulation of both monocytes/macrophages and T lymphocytes. The bridging of TCR with MHC II molecules by superantigens triggers intracellular signaling cascades, resulting in excessive release of proinflammatory mediators and massive polyclonal T-cell proliferation. The early induction of tumor necrosis factor α, interleukin 1 (IL-1), interleukin 2 (IL-2), interferon gamma (IFNγ), and macrophage chemoattractant protein 1 promotes fever, inflammation, and multiple organ injury. The signal transduction pathways for staphylococcal superantigen-induced toxicity downstream from TCR/major histocompatibility complex (MHC) ligation and interaction of cell surface co-stimulatory molecules include the mitogen-activated protein kinase cascades and cytokine receptor signaling, activating nuclear factor κB (NFκB) and the phosphoinositide 3-kinase/mammalian target of rapamycin pathways. Knowledge of host regulation within these activated pathways and molecules initiated by SEB and other superantigens enables the selection of US Food and Drug Administration (FDA)-approved drugs to interrupt and prevent superantigen-induced shock in animal models. This review focuses on the use of FDA-approved immunosuppressants in targeting the signaling pathways induced by staphylococcal superantigens.

Metagenomic Characterization of Microbial Communities In Situ Within the Deeper Layers of the Ileum in Crohn's Disease

BACKGROUND & AIMS

Microbial dysbiosis and aberrant host-microbe interactions in the gut are believed to contribute to the development and progression of Crohn's disease (CD). Microbiome studies in CD typically have focused on microbiota in feces or superficial mucosal layers of the colon because accessing DNA from deeper layers of the bowel is challenging. In this study, we analyzed the deep tissue microbiome in patients who underwent surgical resection of the small intestine.

METHODS

Paraffin blocks were obtained from 12 CD patients undergoing ileocecal resection, and healthy ileum samples (inflammatory bowel disease-free controls) were obtained from 12 patients undergoing surgery for right-sided colon cancer. Diseased and healthy-appearing ileum was identified using microscopy, and paraffin blocks were macrodissected using a core needle to specifically isolate DNA. Illumina Whole Genome Sequencing was used for microbial sequence identification and subsequent taxonomic classification using the PathSeq tool.

RESULTS

We observed significant differences between the microbiome of CD samples vs inflammatory bowel disease-free controls, including depletion of Bacteroidetes and Clostridia. Notably, microbial composition at the phyla level did not differ markedly between healthy and diseased areas of CD patients. However, we observed enrichment of potentially pathogenic organisms at the species level.

CONCLUSIONS

Our study showed dysbiosis within deeper layers of the ileum of CD patients, specifically enrichment of enterotoxigenic Staphylococcus aureus and an environmental Mycobacterium species not described previously. Future studies with larger cohort sizes are warranted to confirm these findings. Studies would benefit from effective microbial DNA extraction methods from paraffin sections and host nucleic acid depletion approaches to increase microbial read coverage.

Targeting mitochondria-derived reactive oxygen species to reduce epithelial barrier dysfunction and colitis

Epithelial permeability is often increased in inflammatory bowel diseases. We hypothesized that perturbed mitochondrial function would cause barrier dysfunction and hence epithelial mitochondria could be targeted to treat intestinal inflammation. Mitochondrial dysfunction was induced in human colon-derived epithelial cell lines or colonic biopsy specimens using dinitrophenol, and barrier function was assessed by transepithelial flux of Escherichia coli with or without mitochondria-targeted antioxidant (MTA) cotreatment. The impact of mitochondria-targeted antioxidants on gut permeability and dextran sodium sulfate (DSS)-induced colitis in mice was tested. Mitochondrial superoxide evoked by dinitrophenol elicited significant internalization and translocation of E. coli across epithelia and control colonic biopsy specimens, which was more striking in Crohn's disease biopsy specimens; the mitochondria-targeted antioxidant, MitoTEMPO, inhibited these barrier defects. Increased gut permeability and reduced epithelial mitochondrial voltage-dependent anion channel expression were observed 3 days after DSS. These changes and the severity of DSS-colitis were reduced by MitoTEMPO treatment. In vitro DSS-stimulated IL-8 production by epithelia was reduced by MitoTEMPO. Metabolic stress evokes significant penetration of commensal bacteria across the epithelium, which is mediated by mitochondria-derived superoxide acting as a signaling, not a cytotoxic, molecule. MitoTEMPO inhibited this barrier dysfunction and suppressed colitis in DSS-colitis, likely via enhancing barrier function and inhibiting proinflammatory cytokine production. These novel findings support consideration of MTAs in the maintenance of epithelial barrier function and the management of inflammatory bowel diseases.

Serum bacterial toxins are related to the progression of inflammatory bowel disease

OBJECTIVES

Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), is an autoimmune disease. Disorder of intestinal microbes is thought to play a critical role in the pathogenesis of IBD. Detection of bacterial toxins could become a new approach to judge the situation of this disease.

MATERIALS AND METHODS

Serum samples were collected from 142 IBD patients and 40 healthy donors as well as 15 CD patients with anti-tumor necrosis factor (TNF) monoclonal antibody (infliximab [IFX]). Enzyme-linked immunosorbent assay kits for Clostridium difficile, Escherichia coli O157, salmonella, and Staphylococcus aureus were used to analyze these bacterial toxins in sera.

RESULTS

The positive rates of bacterial toxins from C. difficile, E. coli O157, salmonella, and S. aureus in the IBD patients were found in low incidences and associated with disease duration, colonic involvement, and treatment with prednisone and immunomodulators. The active CD and UC patients had significant higher positive rates of these bacterial toxins than those in remission or healthy controls. Blockage of TNF with IFX in CD patients resulted in significant decreases of the levels of toxins of C. difficile, E. coli O157, salmonella, and S. aureus in sera.

CONCLUSIONS

Some bacterial toxins are present in the sera of active IBD patients, and patients with long disease duration, colonic involvement, or treatment with prednisone and immunomodulators are more susceptible to bacterial infection. Inhibition of inflammation with IFX would reduce the bacterial toxins via improvement of intestinal inflammation. Detecting bacteria-derived toxins in sera can be used to predict the progression of IBD.

Oral nanotherapeutics: effect of redox nanoparticle on microflora in mice with dextran sodium sulfate-induced colitis

BACKGROUND

Patients with ulcerative colitis (UC) exhibit overproduction of reactive oxygen species (ROS) and imbalance of colonic microflora. We previously developed a novel redox nanoparticle (RNP(O)), which effectively scavenged ROS in the inflamed mucosa of mice with dextran sodium sulfate (DSS)-induced colitis after oral administration. The objective of this study was to examine whether the orally administered RNP(O) changed the colonic microflora in healthy mice and those with colitis.

METHODS

RNP(O) was synthesized by self-assembly of an amphiphilic block copolymer that contains stable nitroxide radicals in hydrophobic side chain via ether linkage. Colitis was induced in mice by supplementing DSS in drinking water for 7 days, and RNP(O) was orally administered daily during DSS treatment. The alterations of fecal microflora during treatment of DSS and RNP(O) were investigated using microbiological assays.

RESULTS

We investigated that RNP(O) did not result in significant changes to the fecal microflora in healthy mice. Although total aerobic and anaerobic bacteria were not significantly different between experimental groups, a remarkable increase in commensal bacteria (Escherichia coli and Staphylococcus sp.) was observed in mice with DSS-induced colitis. Interestingly, orally administered RNP(O) remarkably reduced the rate of increase of these commensal bacteria in mice with colitis.

CONCLUSIONS

On the basis of the obtained results, it was confirmed that the oral administration of RNP(O) did not change any composition of bacteria in feces, which strongly suggests a protective effect of RNP(O) on healthy environments in intestinal microflora. RNP(O) may become an effective and safe medication for treatment of UC.

Staphylococcal enterotoxins in the etiopathogenesis of mucosal autoimmunity within the gastrointestinal tract

The staphylococcal enterotoxins (SEs) are the products of Staphylococcus aureus and are recognized as the causative agents of classical food poisoning in humans following the consumption of contaminated food. While illness evoked by ingestion of the SE or its producer organism in tainted food are often self-limited, our current understanding regarding the evolution of S. aureus provokes the utmost concern. The organism and its associated toxins, has been implicated in a wide variety of disease states including infections of the skin, heart, sinuses, inflammatory gastrointestinal disease, toxic shock, and Sudden Infant Death Syndrome. The intricate relationship between the various subsets of immunocompetent T cells and accessory cells and the ingested material found within the gastrointestinal tract present daunting challenges to the maintenance of immunologic homeostasis. Dysregulation of the intricate balances within this environment has the potential for extreme consequences within the host, some of which are long-lived. The focus of this review is to evaluate the relevance of staphylococcal enterotoxin in the context of mucosal immunity, and the underlying mechanisms that contribute to the pathogenesis of gastrointestinal autoimmune disease.

Loss of NHE3 alters gut microbiota composition and influences Bacteroides thetaiotaomicron growth

Changes in the intestinal microbiota have been linked to diabetes, obesity, inflammatory bowel disease, and Clostridium difficile (C. difficile)-associated disease. Despite this, it remains unclear how the intestinal environment, set by ion transport, affects luminal and mucosa-associated bacterial composition. Na(+)/H(+)-exchanger isoform 3 (NHE3), a target of C. difficile toxin B, plays an integral role in intestinal Na(+) absorption. Thus the NHE3-deficient mouse model was chosen to examine the effect of pH and ion composition on bacterial growth. We hypothesized that ion transport-induced change in the intestinal environment would lead to alteration of the microbiota. Region-specific changes in ion composition and pH correlated with region-specific alteration of luminal and mucosal-associated bacteria with general decreases in Firmicutes and increases in Bacteroidetes members. Bacteroides thetaiotaomicron (B. thetaiotaomicron) increased in NHE3(-/-) terminal ileum and was examined in vitro to determine whether altered Na(+) was sufficient to affect growth. Increased in vitro growth of B. thetaiotaomicron occurred in 43 mM Na(+) correlating with the NHE3(-/-) mouse terminal ileum [Na(+)]. NHE3(-/-) terminal ileum displayed increased fut2 mRNA and fucosylation correlating with B. thetaiotaomicron growth. Inoculation of B. thetaiotaomicron in wild-type and NHE3(-/-) terminal ileum organoids displayed increased fut2 and fucosylation, indicating that B. thetaiotaomicron alone is sufficient for the increased fucosylation seen in vivo. These data demonstrate that loss of NHE3 alters the intestinal environment, leading to region-specific changes in bacteria, and shed light on the growth requirements of some gut microbiota members, which is vital for creating better treatments of complex diseases with an altered gut microbiota.

Impaired removal of Vβ8(+) lymphocytes aggravates colitis in mice deficient for B cell lymphoma-2-interacting mediator of cell death (Bim)

We investigated the role of B cell lymphoma (BCL)-2-interacting mediator of cell death (Bim) for lymphocyte homeostasis in intestinal mucosa. Lymphocytes lacking Bim are refractory to apoptosis. Chronic colitis was induced in Bim-deficient mice (Bim(-/-) ) with dextran sulphate sodium (DSS). Weight loss and colonoscopic score were increased significantly in Bim(-/-) mice compared to wild-type mice. As Bim is induced for the killing of autoreactive cells we determined the role of Bim in the regulation of lymphocyte survival at mucosal sites. Upon chronic dextran sulphate sodium (DSS)-induced colitis, Bim(-/-) animals exhibited an increased infiltrate of lymphocytes into the mucosa compared to wild-type mice. The number of autoreactive T cell receptor (TCR) Vβ8(+) lymphocytes was significantly higher in Bim(-/-) mice compared to wild-type controls. Impaired removal of autoreactive lymphocytes in Bim(-/-) mice upon chronic DSS-induced colitis may therefore contribute to aggravated mucosal inflammation.

Crohn’s disease complicated by intestinal infection with methicillin-resistant Staphylococcus aureus

We report on a 24-year-old male patient with history of bloody diarrhea, abdominal pain and vomiting. Endoscopy revealed massive ulcerative discontinuous proctosigmoiditis with deep, sharply demarcated epithelial denudations and enterotoxigenic methicillin-resistant Staphylococcus aureus (MRSA) was detected in mucosal biopsies. After treatment with linezolide and steroids, a significant amelioration of colitis was detected and testing for MRSA became negative. In face of the case presented here, we suggest that in patients with refractory inflammatory bowel disease (IBD), microbiological assessment should be performed to detect a possible Staphylococcus aureus infection in order to initiate an antimicrobial treatment in addition to IBD-specific treatment.

The staphylococcal enterotoxin (SE) family: SEB and siblings

Staphylococcus aureus plays an important role in numerous human cases of food poisoning, soft tissue, and bone infections, as well as potentially lethal toxic shock. This common bacterium synthesizes various virulence factors that include staphylococcal enterotoxins (SEs). These protein toxins bind directly to major histocompatibility complex class II on antigen-presenting cells and specific Vβ regions of T-cell receptors, resulting in potentially life-threatening stimulation of the immune system. Picomolar concentrations of SEs ultimately elicit proinflammatory cytokines that can induce fever, hypotension, multi-organ failure, and lethal shock. Various in vitro and in vivo models have provided important tools for studying the biological effects of, as well as potential vaccines/therapeutics against, the SEs. This review succinctly presents known physical and biological properties of the SEs, including various intervention strategies. In particular, SEB will often be portrayed as per biodefense concerns dating back to the 1960s.

Neonatal exposure to fecal antigens reduces intestinal inflammation

BACKGROUND

A role for bacterial antigens in the pathogenesis of inflammatory bowel disease (IBD) has been established in enhanced humoral and cellular immune response to ubiquitous antigens of the enteric flora. However, we have recently shown that bacterial antigens in the absence of live bacteria cannot initiate an intestinal inflammation in IBD-prone interleukin (IL)-10 gene-deficient mice. The objective was to investigate whether neonatal exposure to antigens of their own endogenous flora can tolerize mice to bacterial antigens.

METHODS

IL-10 gene-deficient neonates were injected intraperitoneally within 72 hours of birth with a sterile solution of bacterial lysates prepared from fecal material of either conventionally raised mice (contains bacterial antigens) or axenic mice (lacks bacterial antigens). The onset of intestinal inflammation was monitored as the appearance of occult blood in the stool in weekly hemoccult analysis. Mice were sacrificed between age 15 and 19 weeks and tested for histopathologic injury, intestinal inflammation, and systemic response to bacterial antigens.

RESULTS

In mice neonatally exposed to bacterial antigens the onset of intestinal inflammation was delayed and the incidence of histopathologic injury at age 18 weeks was reduced. In addition, mice injected with lysates from conventionally raised mice exhibited decreased release of proinflammatory cytokines (interferon gamma [IFN-γ] and IL-17) in intestinal tissue and demonstrated reduced bacteria-stimulated systemic responses when compared to mice injected with lysates derived from bacteria-free, axenic mice.

CONCLUSIONS

Neonatal intraperitoneal injection of antigens from the commensal flora causes long-lasting changes in systemic and mucosal immune responses resulting in delayed onset of intestinal inflammation and injury in IBD-prone IL-10 gene-deficient mice.

Effect of mother's weight on infant's microbiota acquisition, composition, and activity during early infancy: a prospective follow-up study initiated in early pregnancy

BACKGROUND

It has been reported that deviations in gut microbiota composition may predispose toward obesity, and specific groups of commensal gut bacteria may harvest energy from food more efficiently than others. Alterations in microbiota compositions of mothers may be transferred to infants and lead to an increased risk of overweight.

OBJECTIVE

We analyzed the fecal microbiota composition of infants of overweight and normal-weight mothers and assessed the relations of weight and excessive weight gain of mothers during pregnancy on the microbiota of infants.

DESIGN

Mothers (n = 16) whose prepregnancy body mass index (BMI; in kg/m²) was ≥25 were selected with their infants from a prospective follow-up study of 256 women. Women with a BMI <25 (n = 26) and their infants served as control subjects. At the ages of 1 and 6 mo, infant stool samples were available for the analysis of microbiota composition by fluorescence in situ hybridization combined with flow cytometry and quantitative real-time polymerase chain reaction.

RESULTS

Infants' fecal microbial composition was related to the weight and weight gain of their mothers during pregnancy. Fecal Bacteroides and Staphylococcus concentrations were significantly higher in infants of overweight mothers during the first 6 mo. Higher weights and BMIs of mothers were related to higher concentrations of Bacteroides, Clostridium, and Staphylococcus and lower concentrations of the Bifidobacterium group. Prevalences of Akkermansia muciniphila, Staphylococcus, and Clostridium difficile groups were lower in infants of normal-weight mothers and of mothers with normal weight gains during pregnancy.

CONCLUSION

The composition and development of infant gut microbiota are influenced by BMI, weight, and weight gain of mothers during pregnancy.

The glucocorticoid receptor: a revisited target for toxins

The hypothalamic-pituitary-adrenal (HPA) axis activation and glucocorticoid responses are critical for survival from a number of bacterial, viral and toxic insults, demonstrated by the fact that removal of the HPA axis or GR blockade enhances mortality rates. Replacement with synthetic glucocorticoids reverses these effects by providing protection against lethal effects. Glucocorticoid resistance/insensitivity is a common problem in the treatment of many diseases. Much research has focused on the molecular mechanism behind this resistance, but an area that has been neglected is the role of infectious agents and toxins. We have recently shown that the anthrax lethal toxin is able to repress glucocorticoid receptor function. Data suggesting that the glucocorticoid receptor may be a target for a variety of toxins is reviewed here. These studies have important implications for glucocorticoid therapy.

Regulatory T cells modulate staphylococcal enterotoxin B-induced effector T-cell activation and acceleration of colitis

Oral administration of bacterial superantigen Staphylococcus aureus enterotoxin B (SEB) activates mucosal T cells but does not cause mucosal inflammation. We examined the effect of oral SEB on the development of mucosal inflammation in mice in the absence of regulatory T (Treg) cells. SCID mice were fed SEB 3 and 7 days after reconstitution with CD4(+) CD45RB(high) or CD4(+) CD45RB(high) plus CD4(+) CD45RB(low) T cells. Mice were sacrificed at different time points to examine changes in tissue damage and in T-cell phenotypes. Feeding SEB failed to produce any clinical effect on SCID mice reconstituted with CD4(+) CD45RB(high) and CD4(+) CD45RB(low) T cells, but feeding SEB accelerated the development of colitis in SCID mice reconstituted with CD4(+) CD45RB(high) T cells alone. The latter was associated with an increase in the number of CD4(+) Vbeta8(+) T cells expressing CD69 and a significantly lower number of CD4(+) CD25(+) Foxp3(+) T cells. These changes were not observed in SCID mice reconstituted with both CD45RB(high) and CD45RB(low) T cells. In addition, SEB impaired the development of Treg cells in the SCID mice reconstituted with CD4(+) CD45RB(high) T cells alone but had no direct effect on Treg cells. In the absence of Treg cells, feeding SEB induced activation of mucosal T cells and accelerated the development of colitis. This suggests that Treg cells prevent SEB-induced mucosal inflammation through modulation of SEB-induced T-cell activation.

Distinct composition of gut microbiota during pregnancy in overweight and normal-weight women

BACKGROUND

Results of experimental studies suggest that deviations in gut microbiota composition predispose to excessive energy storage and obesity. The mother influences the original inoculum and the development of infant microbiota, which in turn is associated with later weight gain.

OBJECTIVE

We characterized the gut microbiota in women according to their body mass index (BMI) and the effect of weight gain over pregnancy on the composition of microbiota before delivery.

DESIGN

Overweight women (n = 18) were selected according to their prepregnancy BMI from a prospective follow-up study. Normal-weight women (n = 36) were selected as controls in consecutive order of recruitment. Excessive weight gain during pregnancy was defined as >16.0 kg for normal-weight and >11.5 kg for overweight states according to Institute of Medicine recommendations. The composition of gut microbiota was analyzed by fluorescent in situ hybridization coupled with flow cytometry (FCM-FISH) and by quantitative real-time polymerase chain reaction (qPCR).

RESULTS

Bacteroides and Staphylococcus were significantly higher in the overweight state than in normal-weight women as assessed by FCM-FISH and qPCR. Mother's weight and BMI before pregnancy correlated with higher concentrations of Bacteroides, Clostridium, and Staphylococcus. Microbial counts increased from the first to third trimester of pregnancy. High Bacteroides concentrations were associated with excessive weight gain over pregnancy (P = 0.014).

CONCLUSIONS

Gut microbiota composition and weight are linked, and mother's weight gain is affected by microbiota. Microbiota modification before and during pregnancy may offer new directions for preventive and therapeutic applications in reducing the risk of overweight and obesity.

Inflammatory bowel disease in rats: Bacterial and chemical interaction

AIM: To develop a novel model of colitis in rats, using a combination of iodoacetamide and enteropathogenic E. coli (EPEC), and to elucidate the pathophysiologic processes implicated in the development of ulcerative colitis (UC).

METHODS: Male Sprague-Dawley rats (n = 158) were inoculated intrarectally on a weekly basis with 4 different combinations: (a) 1% methylcellulose (MC), (b) 100 &mgr;L of 6% iodoacetamide (IA) in 1% MC, (c) 200 &mgr;L containing 4 × 10⁸ colony factor units (CFU) of EPEC, and (d) combined treatment of (IA) followed by bacteria (B) after 2 d. Thirty days post treatment, each of the four groups was divided into two subgroups; the inoculation was stopped for one subgroup and the other subgroup continued with biweekly inoculation until the end of the experiment. Colitis was evaluated by the clinical course of the disease, the macroscopic and microscopic alterations, activity of myeloperoxidase (MPO), and by TNF-α gene expression.

RESULTS: Findings indicative of UC were seen in the combined treatment (IA + B) as well as the IA continued treatment groups: the animals showed slow rate of increase in body weight, diarrhea, bloody stools, high colonic ulcer score, as well as histological alterations characteristic of UC, with an extensive inflammatory reaction. During the course of the experiment, the MPO activity was consistently elevated and the TNF-α gene expression was upregulated compared to the control animals.

CONCLUSION: The experimental ulcerative colitis model used in the present study resembles, to a great extent, the human disease. It is reproducible with characteristics indicative of chronicity.

Early differences in fecal microbiota composition in children may predict overweight

BACKGROUND

Experimental studies suggest that gut microbiota deviations predispose toward energy storage and obesity.

OBJECTIVE

We wanted to establish whether early gut microbiota composition can guide weight development throughout early childhood.

DESIGN

Overweight and obese children (n = 25) were selected from a prospective follow-up study at the age of 7 y and identified according to the International Obesity Task Force criteria. Normal-weight children (n = 24) were selected from the same cohort and matched for gestational age and body mass index at birth, mode of delivery, probiotic supplementation, duration of breastfeeding, use of antibiotics during infancy, and frequencies of atopic diseases and atopic sensitization. Early fecal microbiota composition was analyzed by fluorescent in situ hybridization (FISH) with microscopic and flow cytometry detection and by quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

The bifidobacterial numbers in fecal samples during infancy, as assessed by the FISH with flow cytometry, were higher in children remaining normal weight, [median: 2.19 x 10(9) cells/g (interquartile range: 1.10-5.28 x 10(9) cells/g)] than in children becoming overweight [1.20 x 10(9) cells/g (0.48-1.59x 10(9) cells/g); P = 0.02]. A similar tendency was found by FISH with microscopic detection and qRT-PCR. The microbiota aberrancy during infancy in children becoming overweight was also associated with a greater number of Staphylococcus aureus [0.64 x 10(6) cells/g (0.33-1.00 x 10(6) cells/g)] than in children remaining normal weight [0.27 x 10(6) cells/g (0.17-0.50 x 10(6) cells/g); P = 0.013].

CONCLUSION

Aberrant compositional development of the gut microbiota precedes overweight, offering new possibilities for preventive and therapeutic applications in weight management.

Enterotoxigenic bacteroides fragilis: a potential instigator of colitis

BACKGROUND

Inflammatory bowel disease (IBD) is proposed to result from a dysregulated mucosal immune response to the colonic flora in genetically susceptible individuals. Enterotoxigenic Bacteroides fragilis (ETBF), a molecular subclass of the common human commensal, B. fragilis, has been associated with IBD. This study investigated whether ETBF colonization of mice initiated colitis or modified the clinical course of a colitis agonist, dextran sodium sulfate (DSS).

METHODS

Four- and 6-week-old C57BL/6 mice were inoculated with buffer, nontoxigenic B. fragilis (NTBF) strain 9343(pFD340), or ETBF strain 86-5443-2-2 via orogastric tube. A subset of mice received 2% DSS several days pre- or post-inoculation of bacteria. Clinical status was assessed throughout the experiment and severity of colonic inflammation was scored after sacrifice.

RESULTS

All mice, including those receiving DSS, were clinically well prior to bacterial inoculation. NTBF and ETBF colonization was similar. Regardless of mouse age or timing of DSS administration, mice who received ETBF+DSS experienced worse colitis reflected by less weight gain, enhanced gross disease, and greater inflammation in their colons (P < 0.05), especially in the cecum. In particular, younger mice had more extensive disease. Mice inoculated only with ETBF also exhibited colitis with more severe inflammation when compared to all other groups (P < 0.05) except the ETBF+DSS group.

CONCLUSIONS

ETBF, a colonic commensal, alone stimulates colitis and significantly enhances colonic inflammation in DSS-treated mice. This study suggests that acquisition of ETBF colonization may be a potential factor in initiation and/or exacerbation of colitis.

Insights from advances in research of chemically induced experimental models of human inflammatory bowel disease

Inflammatory bowel disease (IBD), the most important being Crohn's disease and ulcerative colitis, results from chronic dysregulation of the mucosal immune system in the gastrointestinal tract. Although the pathogenesis of IBD remains unclear, it is widely accepted that genetic, environmental, and immunological factors are involved. Recent studies suggest that intestinal epithelial defenses are important to prevent inflammation by protecting against microbial pathogens and oxidative stresses. To investigate the etiology of IBD, animal models of experimental colitis have been developed and are frequently used to evaluate new anti-inflammatory treatments for IBD. Several models of experimental colitis that demonstrate various pathophysiological aspects of the human disease have been described. In this manuscript, we review the characteristic features of IBD through a discussion of the various chemically induced experimental models of colitis (e.g., dextran sodium sulfate-, 2,4,6-trinitrobenzene sulfonic acid-, oxazolone-, acetic acid-, and indomethacin-induced models). We also summarize some regulatory and pathogenic factors demonstrated by these models that can, hopefully, be exploited to develop future therapeutic strategies against IBD.

Induction of experimental acute ulcerative colitis in rats by administration of dextran sulfate sodium at low concentration followed by intracolonic administration of 30% ethanol

Several models of experimental ulcerative colitis have been reported previously. However, none of these models showed the optimum characteristics. Although dextran sulfate sodium-induced colitis results in inflammation resembling ulcerative colitis, an obvious obstacle is that dextran sulfate sodium is very expensive. The aim of this study was to develop an inexpensive model of colitis in rats. Sprague-Dawley rats were treated with 2% dextran sulfate sodium in drinking water for 3 d followed by an intracolonic administration of 30% ethanol. The administration of 2% dextran sulfate sodium followed by 30% ethanol induced significant weight loss, diarrhea and hematochezia in rats. Severe ulceration and inflammation of the distal part of rat colon were developed rapidly. Histological examination showed increased infiltration of polymorphonuclear leukocytes, lymphocytes and existence of cryptic abscesses and dysplasia. The model induced by dextran sulfate sodium at lower concentration followed by 30% ethanol is characterized by a clinical course, localization of the lesions and histopathological features similar to human ulcerative colitis and fulfills the criteria set out at the beginning of this study.

Herpes simplex virus colitis complicating ulcerative colitis: A case report and brief review on superinfections

In patients with inflammatory bowel disease herpes simplex virus infection has been described as a major cause of morbidity and mortality, especially in immunocompromised individuals. Here we present the case of a 35-year old woman with an exacerbation of ulcerative colitis caused by herlpes simplex virus infection (HSV-2). The diagnosis was confirmed histologically following subtotal colectomy. After intravenous treatment with aciclovir for 2 weeks postoperative hematochezia stopped. Herpes simplex virus colitis is a rare but potentially fatal complication of immunosuppressive treatment in patients with inflammatory bowel disease. Prompt diagnosis and efficient antiviral therapy are mandatory to improve prognosis.

Immune dysfunction in inflammatory bowel disease

Ulcerative colitis (UC) and Crohn's disease (CD) are idiopathic inflammatory bowel diseases (IBDs) that are characterized by chronic periods of exacerbation and remission. Research into the immunopathogenesis of IBD adds support to the theory that the disease results from a dysfunctional regulation of the immune system that leads to the polarization of intestinal immune cells toward a Th1 (T helper) response. The immunologic factors that mediate alterations in intestinal homeostasis and the development of intestinal mucosal inflammation have been at the forefront of IBD research. Cytokines, which are important regulators of leukocyte trafficking and apoptotic cell death, have emerged as essential immune molecules in the pathogenesis of IBD. In this study, recent advances in the understanding of the dynamism of cytokines and the consequences for mucosal immunity and inflammation in IBD are discussed. Furthermore, this study highlights the potential use of cytokines, anti-cytokine antibodies, and cytokine-related biologic therapies as novel targets for the treatment of IBD.

Amelioration of dextran sulfate sodium-induced colitis in mice by oral administration of β-caryophyllene, a sesquiterpene

beta-Caryophyllene (BCP), a naturally occurring plant sesquiterpene, was examined for anti-inflammatory activity in a mouse model of experimental colitis induced by dextran sulfate sodium (DSS). Colitis was induced by exposing male BALB/c mice to 5% DSS in drinking water for 7 days. BCP in doses of 30 and 300 mg/kg was administered orally once a day, beginning concurrently with exposure to DSS. The body weight and colon length were measured, and histological damage and myeloperoxidase (MPO) activity as well as inflammatory cytokines were assessed in both serum and colonic tissue after 7 days of treatment with DSS. The DSS treatment damaged the colonic tissue, increased MPO activity and inflammatory cytokines, lowered the body weight, and shortened the length of the colon. Oral administration of BCP at 300 mg/kg significantly suppressed the shortening of colon length and slightly offset the loss of body weight. BCP treatment (300 mg/kg) also significantly reduced the inflammation of colon and reversed the increase in MPO activity that had been induced by exposure to DSS. Further, BCP significantly suppressed the serum level of IL-6 protein (a 55% reduction) as well as the level of IL-6 mRNA in the tissue. These results demonstrate that BCP ameliorates DSS-induced experimental colitis, and may be useful in the prevention and treatment of colitis.

Gram-negative bacteria aggravate murine small intestinal Th1-type immunopathology following oral infection with Toxoplasma gondii

Oral infection of susceptible mice with Toxoplasma gondii results in Th1-type immunopathology in the ileum. We investigated gut flora changes during ileitis and determined contributions of gut bacteria to intestinal inflammation. Analysis of the intestinal microflora revealed that ileitis was accompanied by increasing bacterial load, decreasing species diversity, and bacterial translocation. Gram-negative bacteria identified as Escherichia coli and Bacteroides/Prevotella spp. accumulated in inflamed ileum at high concentrations. Prophylactic or therapeutic administration of ciprofloxacin and/or metronidazole ameliorated ileal immunopathology and reduced intestinal NO and IFN-gamma levels. Most strikingly, gnotobiotic mice in which cultivable gut bacteria were removed by quintuple antibiotic treatment did not develop ileitis after Toxoplasma gondii infection. A reduction in total numbers of lymphocytes was observed in the lamina propria of specific pathogen-free (SPF), but not gnotobiotic, mice upon development of ileitis. Relative numbers of CD4(+) T cells did not differ in naive vs infected gnotobiotic or SPF mice, but infected SPF mice showed a significant increase in the frequencies of activated CD4(+) T cells compared with gnotobiotic mice. Furthermore, recolonization with total gut flora, E. coli, or Bacteroides/Prevotella spp., but not Lactobacillus johnsonii, induced immunopathology in gnotobiotic mice. Animals recolonized with E. coli and/or total gut flora, but not L. johnsonii, showed elevated ileal NO and/or IFN-gamma levels. In conclusion, Gram-negative bacteria, i.e., E. coli, aggravate pathogen-induced intestinal Th1-type immunopathology. Thus, pathogen-induced acute ileitis may prove useful to study bacteria-host interactions in small intestinal inflammation and to test novel therapies based on modulation of gut flora.

Staphylococcus aureus adheres to human intestinal mucus but can be displaced by certain lactic acid bacteria

There is increasing evidence that Staphylococcus aureus may colonize the intestinal tract, especially among hospitalized patients. As Staph. aureus has been found to be associated with certain gastrointestinal diseases, it has become important to study whether this bacterium can colonize the intestinal tract and if so, whether it is possible to prevent colonization. Adhesion is the first step in colonization; this study shows that Staph. aureus adheres to mucus from resected human intestinal tissue. Certain lactic acid bacteria (LAB), mainly commercial probiotics, were able to reduce adhesion and viability of adherent Staph. aureus. In displacement assays the amount of adherent Staph. aureus in human intestinal mucus was reduced 39-44% by Lactobacillus rhamnosus GG, Lactococcus lactis subsp. lactis and Propionibacterium freudenreichii subsp. shermanii. Moreover, adherent Lactobacillus reuteri, Lc. lactis and P. freudenreichii reduced viability of adherent Staph. aureus by 27-36%, depending on the strain, after 2 h incubation. This was probably due to the production of organic acids and hydrogen peroxide and possibly in the case of L. reuteri to the production of reuterin. This study shows for the first time that Staph. aureus can adhere to human intestinal mucus and adherent bacteria can be displaced and killed by certain LAB strains via in situ production of antimicrobial substances.

Bacterial antigens alone can influence intestinal barrier integrity, but live bacteria are required for initiation of intestinal inflammation and injury

Intestinal flora plays a critical role in the initiation and perpetuation of inflammatory bowel disease. This study examined whether live fecal bacteria were necessary for the initiation of this inflammatory response or whether sterile fecal material would provoke a similar response. Three preparations of fecal material were prepared: (1) a slurry of live fecal bacteria, (2) a sterile lysate of bacterial antigens, and (3) a sterile filtrate of fecal water. Each preparation was introduced via gastric gavage into the intestines of axenic interleukin-10 gene-deficient mice genetically predisposed to develop inflammatory bowel disease. Intestinal barrier integrity and degrees of mucosal and systemic inflammations were determined for each preparation group. Intestinal barrier integrity, as determined by mannitol transmural flux, was altered by both live fecal bacterial and sterile lysates of bacterial antigens, although it was not altered by sterile filtrates of fecal water. However, only live fecal bacteria initiated mucosal inflammation and injury and a systemic immune response. Fecal bacterial antigens in the presence of live bacteria and sterile fecal bacterial antigens have different effects on the initiation and perpetuation of intestinal inflammation.

A possible link between sinusitis and lower airway hypersensitivity: the role of Staphylococcal enterotoxin B

Background and aims

The prevalence of asthma has been keeping arising with unknown etiology. The cumulative evidence indicates that chronic rhinosinusitis (CRS) closely relates to asthma, but the detailed mechanisms remain unclear. The present study aimed to take insight into the role of Staphylococcus enterotoxin B (SEB) in a possible association between CRS and asthma.

Methods

38 patients with both CRS and asthma underwent functional endoscopic sinus surgery. Serum specific IgE and cytokines, clinical symptoms of CRS and asthma were evaluated before and after the surgery. Peripheral blood mononuclear cells (PBMCs) were separated from the patients and cultured. Th2 response of the cultured PBMCs in the presence or absence of specific antigens and SEB was evaluated.

Results

Besides the improvement of CRS symptoms, amelioration of asthma was also observed in the patients with both CRS and asthma after the sinus surgery. The preoperatively elevated Th2 cytokines, IL-4 and IL-5, normalized postoperatively. Th2 response was generated with separated PBMCs in the presence of specific antigens. SEB was required for maintaining Th2 response in these separated PBMCs.

Conclusion

The present results indicate that a possible link exists between CRS and lower airway hypersensitivity. Sinusitis derived SEB may play a role in sustaining Th2 responses in the low airway hypersensitivity related to sinusitis.

Probiotics and commensals reverse TNF-alpha- and IFN-gamma-induced dysfunction in human intestinal epithelial cells

BACKGROUND & AIMS

Commensal bacteria are crucial for the development of the mucosal immune system. Probiotics are commensals with special characteristics and may protect mucosal surfaces against pathogens. Pathogens cause significant phenotypic alterations in infected epithelial cells, and probiotics reverse these deleterious responses. We hypothesized that probiotics and/or commensals may also reverse epithelial damage produced by cytokines.

METHODS

Human intestinal epithelial cells were exposed basolaterally to interferon (IFN)-gamma (10(3) U/mL) or tumor necrosis factor (TNF)-alpha (10 ng/mL) for up to 48 hours and assessed for ion transport, transepithelial resistance (TER), and epithelial permeability in the presence or absence of probiotics (Streptococcus thermophilus [ST] and Lactobacillus acidophilus [LA]), or the commensal, Bacteroides thetaiotaomicron (BT).

RESULTS

Agonist-stimulated chloride secretion was inhibited by IFN-gamma, an effect prevented by ST/LA or BT. The ability of ST/LA or BT to restore Cl(-) secretion was blocked by inhibitors of p38 MAPK, ERK1, 2, and PI3K. The cystic fibrosis transmembrane conductance regulator (CFTR) and the NKCC1 cotransporter were down-regulated by IFN-gamma, and ST/LA pretreatment reversed this effect. Both TNF-alpha and IFN-gamma significantly reduced TER and increased epithelial permeability, effects prevented by ST/LA or BT. A Janus kinase (JAK) inhibitor synergistically potentiated effects of ST/LA or BT on TER and permeability, but p38, ERK1, 2, or PI3K inhibition did not. Finally, only probiotic-treated epithelial cells exposed to cytokines showed reduced activation of SOCS3 and STAT1,3.

CONCLUSIONS

Deleterious effects of TNF-alpha and IFN-gamma on epithelial function are prevented by probiotic, and to a lesser extent, commensal pretreatment. These data extend the spectrum of effects of such bacteria on intestinal epithelial function and may justify their use in inflammatory disorders.

The influence of microbial metabolites on human intestinal epithelial cells and macrophages in vitro

Microbial metabolites may influence the metabolic integrity of intestinal epithelial cells and induce mucosal immune responses. Therefore, we investigated the effects of the microbial metabolites butyrate, iso-valerate, and ammonium on Caco-2 cells and macrophages. Barrier functioning was determined by measuring transepithelial electrical resistance and basolateral recoveries of metabolites. The barrier function of Caco-2 cells remained intact after exposures. Basolateral recoveries ranged from 6.2% to 15.2%. Tumour necrosis factor-alpha and interleukin-10 were measured to determine immune reactions. The Caco-2 cells did not secrete both cytokines. Physiological concentrations of butyrate and iso-valerate stimulated the secretion of tumour necrosis factor-alpha and suppressed the secretion of interleukin-10 by macrophages that are not protected by an epithelial barrier. In contrast, ammonium concentrations as high as those produced by microbiotas of IBD patients suppressed the release of both cytokines when the barrier function is impaired.

Immune cell activation and subsequent epithelial dysfunction by Staphylococcus enterotoxin B is attenuated by the green tea polyphenol (-)-epigallocatechin gallate

Bacterial superantigens (SAg) are potent T cell activators and when delivered systemically elicit a self-limiting enteropathy in mice. Also, SAg-stimulated human peripheral blood mononuclear cells (PBMC) increase enteric epithelial cell monolayer permeability in vitro. Epigallocatechin gallate (EGCG), the major polyphenol component of green tea (Camilla sinesis) leaf, has been presented as an anti-inflammatory agent. We tested the hypothesis that EGCG (10-100 microM) would block PBMC activation by the SAg, Staphylococcus aureus enterotoxin B (SEB, 1 microg/ml), thus preventing disruption of the epithelial barrier. Pretreatment or co-treatment of human PBMC or murine lymphnode cells with EGCG significantly reduced SEB-induced proliferation and IL-2, IFNgamma, and TNFalpha production. ConA-induced proliferation was also inhibited by EGCG (50 microM) co-treatment. These effects of EGCG were not due to induction of immune cell apoptosis, and were independent of EGCGs anti-oxidant activity, and inhibition of NF-kappaB or AP-1 activation. Moreover, addition of exogenous IL-2 (20 ng/ml) to the cultures could not overcome the immunosuppressive effect of EGCG. Culture supernatant from PBMC stimulated in the presence of EGCG failed to increase the permeability of T84 epithelial cell monolayers: a finding consistent with the reduced IFNgamma and TNFalpha production by SAg+EGCG treated PBMC. These data promote EGCG as a suppressor of T cell activation, and given the prominent role that bacteria and T cells play in inflammatory disease we suggest that EGCG could be a useful addition to current treatments for enteric immune disorders and T cell driven immunopathologies.

Rhinosinusitis derived Staphylococcal enterotoxin B possibly associates with pathogenesis of ulcerative colitis

Background

During clinical practice, we noticed that some patients with both ulcerative colitis (UC) and chronic rhinosinusitis (CRS) showed amelioration of UC after treatment of CRS. This study was designed to identify a possible association between CRS and UC.

Methods

Thirty-two patients with both CRS and UC received treatment with functional endoscopic sinus surgery (FESS) for CRS. Clinical symptom scores for CRS and UC, as well as serum levels of anti-Staphylococcal enterotoxin B (SEB) were evaluated at week 0 and week 12. Sinus wash fluid SEB content was measured with enzyme-linked immunosorbent assay (ELISA). The surgically removed tissues were cultured to identify growth of Staphylococcus. aureus (S. aureus). Immunohistochemistry was employed to identify anti-SEB positive cells in the colonic mucosa. Colonic biopsies were obtained and incubated with SEB. Mast cell activation in the colonic mucosa in response to incubation with SEB was observed with electron microscopy and immunoassay.

Results

The clinical symptom scores of CRS and UC severe scores (UCSS) were significantly reduced in the UC-CRS patients after FESS. The number of cultured S. aureus colonies from the surgically removed sinus mucosa significantly correlated with the decrease in UCSS. High levels of SEB were detected in the sinus wash fluids of the patients with UC-CRS. Histamine and tryptase release was significantly higher in the culture supernate in the patients with UC-CRS than the patients with UC-only and normal controls. Anti-SEB positive cells were located in the colonic mucosa.

Conclusion

The pathogenesis of UC in some patients may be associated with their pre-existing CRS by a mechanism of swallowing sinusitis-derived SEB. We speculate that SEB initiates inappropriate immune reactions and inflammation in the colonic mucosa that further progresses to UC.

A murine model of ulcerative colitis: induced with sinusitis-derived superantigen and food allergen

BACKGROUND

The etiology of ulcerative colitis (UC) is to be understood. The basic pathological feature of UC is intestinal chronic inflammation. Superantigen, such as Staphylococcus enterotoxin B (SEB), is reported to compromise intestinal barrier function by increasing epithelial permeability and initiate inflammation in the intestinal mucosa. Inasmuch as anatomic position of the sinus, chronic sinusitis-derived SEB may follow the secretion and to be swallowed down to the gastrointestinal tract and induce lesions to the intestinal mucosa.

METHODS

Sinus wash fluid (SWF, containing SEB) was collected from a group of patients with both chronic sinusitis (CS) and UC. A group of mice were sensitized to ovalbumin (OVA) in the presence of SWF. The sensitized mice were challenged with the specific antigen OVA. The inflammatory status of the colonic tissue was determined with histology, serology and electron microscopy. Using horseradish peroxidase (HRP) as a tracer, another group of mice was stimulated with SWF for 2 hours. The HRP activity was detected in the colonic tissue with enzymatic approaches and electron microscopy.

RESULTS

Epithelial hyperpermeability in colonic epithelium was induced by stimulating with SWF. The HRP activity in the colonic mucosa was almost 11 times more in the SWF treated group (3.2 +/- 0.6 microg/g tissue) than the control group (0.3 +/- 0.1 microg/g tissue). Mice were sensitized using a mixture of SWF and OVA (serum OVA-specific IgE was detected with a highest titer as 1:64). Challenge with OVA induced extensive inflammation in the colonic mucosa by showing (1) marked degranulation in mast cells (MC, 46.3 +/- 4.5%) and eosinophils (Eo, 55.7 +/- 4.2%); (2) inflammatory cell infiltration (MC = 145.2 +/- 11.4; Eo = 215.8 +/- 12.5; mononuclear cell = 258.4 +/- 15.3/mm2 tissue); (3) increased MPO activity (12.9 +/- 3.2 U/g tissue) and inflammatory scores (1.8 +/- 0.3); (4) mucosal surface ulcers; (5) edema in the lamina propria; (6) bacterial translocation and abscess formation in the subepithelial region.

CONCLUSION

Introducing Sinusitis-derived SEB-containing SWF to the gastrointestinal tract compromised colonic mucosal barrier function increasing epithelial permeability to luminal macromolecular protein in mice. The SWF facilitated colonic mucosal sensitization to luminal antigen. Multiple challenging the sensitized colonic mucosa with specific antigen OVA induced inflammation, induced a condition similar to human ulcerative colitis.

Good bug, bad bug: in the case of enteric inflammatory disease does the epithelium decide?

Many studies demonstrate that intestinal inflammation is either initiated or exaggerated by a component of the normal microbiota, most likely commensal bacteria or products derived from these organisms. We review the nature of human inflammatory bowel disease, the evidence for the involvement of the normal bacterial flora in these disorders and the relevance of maintaining the integrity of the epithelial barrier. Moreover, we, and others, have shown abnormal mitochondria structure in tissue resections from patients with inflammatory bowel disease and tissues from rodents that demonstrated psychological stress-induced increases in epithelial permeability. Thus, we also consider the possibility that a defect in epithelial mitochondrial function would predispose an individual to respond to their commensal bacteria flora--no longer considering them as a beneficial passive inhabitant, but rather perceiving them as a threatening and pro-inflammatory stimulus. In support of this postulate, we discuss our recent findings from an in vitro model showing that the human colon-derived T84 cell line exposed to the metabolic stressor, dinitrophenol, and the non-pathogenic, non-invasive, Escherichia coli (strain HB101) display a loss of barrier function, increased signal transduction and increased production of the chemokine, interleukin 8.