Preclinical and clinical evidence of the association of colibactin-producing Escherichia coli with anxiety and depression in colon cancer.

BACKGROUND: The association between the intestinal microbiota and psychiatric disorders is becoming increasingly apparent. The gut microbiota contributes to colorectal carcinogenesis (CRC), as demonstrated with colibactin-producing Escherichia coli (CoPEC). AIM: To evaluate the association between CoPEC prevalence and anxiety- and depressive-like behaviors with both preclinical and clinical approaches. METHODS: Patients followed after a CRC surgery and for whom the prevalence of CoPEC has been investigated underwent a psychiatric interview. Results were compared according to the CoPEC colonization. In parallel C57BL6/J wild type mice and mice with a CRC susceptibility were chronically infected with a CoPEC strain. Their behavior was assessed using the Elevated Plus Maze test, the Forced Swimming Test and the Behavior recognition system PhenoTyper®. RESULTS: In a limited cohort, all patients with CoPEC colonization presented with psychiatric disorders several years before cancer diagnosis, whereas only one patient (17%) without CoPEC did. This result was confirmed in C57BL6/J wild-type mice and in a CRC susceptibility mouse model (adenomatous polyposis colimultiple intestinal neoplasia/+). Mice exhibited a significant increase in anxiety- and depressive-like behaviors after chronic infection with a CoPEC strain. CONCLUSION: This finding provides the first evidence that CoPEC infection can induce microbiota-gut-brain axis disturbances in addition to its procarcinogenic properties.

Pasteurized akkermansia muciniphila improves irritable bowel syndrome-like symptoms and related behavioral disorders in mice.

Gut - brain communications disorders in irritable bowel syndrome (IBS) are associated with intestinal microbiota composition, increased gut permeability, and psychosocial disturbances. Symptoms of IBS are difficult to medicate, and hence much research is being made into alternative approaches. This study assesses the potential of a treatment with pasteurized Akkermansia muciniphila for alleviating IBS-like symptoms in two mouse models of IBS with different etiologies. Two clinically relevant animal models were used to mimic IBS-like symptoms in C57BL6/J mice: the neonatal maternal separation (NMS) paradigm and the Citrobacter rodentium infection model. In both models, gut permeability, colonic sensitivity, fecal microbiota composition and colonic IL-22 expression were evaluated. The cognitive performance and emotional state of the animals were also assessed by several tests in the C. rodentium infection model. The neuromodulation ability of pasteurized A. muciniphila was assessed on primary neuronal cells from mice dorsal root ganglia using a ratiometric calcium imaging approach. The administration of pasteurized A. muciniphila significantly reduced colonic hypersensitivity in both IBS mouse models, accompanied by a reinforcement of the intestinal barrier function. Beneficial effects of pasteurized A. muciniphila treatment have also been observed on anxiety-like behavior and memory defects in the C. rodentium infection model. Finally, a neuroinhibitory effect exerted by pasteurized A. muciniphila was observed on neuronal cells stimulated with two algogenic substances such as capsaicin and inflammatory soup. Our findings demonstrate novel anti-hyperalgesic and neuroinhibitory properties of pasteurized A. muciniphila, which therefore may have beneficial effects in relieving pain and anxiety in subjects with IBS.

Antihyperalgesic properties of gut microbiota: Parabacteroides distasonis as a new probiotic strategy to alleviate chronic abdominal pain.

ABSTRACT: The potential role of gut microbiota in pain modulation is arousing an emerging interest since recent years. This study investigated neuromodulatory properties of gut microbiota to identify next-generation probiotics to propose alternative therapies for visceral pain management. Neuromodulation ability of 10 bacterial strains isolated from a healthy donor was assessed both on ND7/23 immortalized cell line and primary neuronal cells from rat dorsal root ganglia. This screening highlighted the neuroinhibitory property of Parabacteroides distasonis (F1-2) strain, supported both by its intracellular content and membrane fraction, which was further investigated in visceral pain mouse models. Oral administration of F1-2 resulted in a significant decrease of colonic hypersensitivity (CHS) in dextran sulfate sodium (0.5%) model associated with low-grade inflammation and a significant decrease of CHS in Citrobacter rodentium postinfectious models. No effect of F1-2 oral administration on CHS was observed in a neonatal maternal separation stress model. Antihyperalgesic effect unlikely involved modulation of inflammatory processes or restoration of intestinal barrier. Exploration of direct dialogue mechanisms between this strain and nervous system, assessed by calcium imaging experiments, revealed that F1-2 interacts directly with nociceptors by reducing activation level on capsaicin, inflammatory soup, and bradykinin stimulations. Our study provides new insights about bacteria-host interaction and places P distasonis as a potential therapeutic strategy in the treatment of visceral pain observed in leaky gut-associated pathologies.

From In Vitro to In Vivo: A Rational Flowchart for the Selection and Characterization of Candidate Probiotic Strains in Intestinal Disorders.

Experimental and clinical evidence has demonstrated the potential of probiotic strains in the prevention or treatment of inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS). However, there is little data on what the methodology leading to the identification of such strains should be. In this work, we propose a new flowchart to identify strains with probiotic potential for the management of IBS and IBD, which we tested on a collection of 39 lactic acid bacteria and Bifidobacteria strains. This flowchart included in vitro tests of immunomodulatory properties on intestinal and peripheral blood mononuclear cells (PBMCs), assessment of the barrier-strengthening effect by measuring transepithelial electric resistance (TEER) and quantification of short-chain fatty acids (SCFAs) and aryl hydrocarbon receptor (AhR) agonists produced by the strains. The in vitro results were then combined in a principal component analysis (PCA) to identify strains associated with an anti-inflammatory profile. To validate our flowchart, we tested the two most promising strains identified in the PCA in mouse models of post-infectious IBS or chemically induced colitis to mimic IBD. Our results show that this screening strategy allows the identification of strains with potential beneficial effects on colonic inflammation and colonic hypersensitivity.

Serpin-positive Bifidobacterium breve CNCM I-5644 improves intestinal permeability in two models of irritable bowel syndrome.

Probiotic supplementation can help to mitigate the pathogenesis of irritable bowel syndrome (IBS) by reinforcing the intestinal barrier, and reducing both inflammation and proteolytic activity. Here, a combination of in vitro tests was performed on 33 Bifidobacterium strains as probiotic candidates for IBS. In addition to the classical tests performed, the detection of the serine protease inhibitor (serpin) enzyme capable of decreasing the high proteolytic activity found in IBS patients was included. Three serpin-positive strains were selected: Bifidobacterium breve CNCM I-5644, Bifidobacterium longum subsp. infantis CNCM I-5645 and B. longum CNCM I-5646 for their immunomodulation properties and protection of intestinal epithelial integrity in vitro. Furthermore, we found that B. breve CNCM I-5644 strain prevented intestinal hyperpermeability by upregulating Cingulin and Tight Junction Protein 1 mRNA levels and reducing pro-inflammatory markers. The ability of CNCM I-5644 strain to restore intestinal hyperpermeability (FITC-dextran) was shown in the murine model of low-grade inflammation induced by dinitrobenzene sulfonic acid (DNBS). This effect of this strain was corroborated in a second model of IBS, the neonatal maternal separation model in mice. Altogether, these data suggest that serpin-positive B. breve CNCM I-5644 may partially prevent disorders associated with increased barrier permeability such as IBS.

AhR/IL-22 pathway as new target for the treatment of post-infectious irritable bowel syndrome symptoms.

Alterations in brain/gut/microbiota axis are linked to Irritable Bowel Syndrome (IBS) physiopathology. Upon gastrointestinal infection, chronic abdominal pain and anxio-depressive comorbidities may persist despite pathogen clearance leading to Post-Infectious IBS (PI-IBS). This study assesses the influence of tryptophan metabolism, and particularly the microbiota-induced AhR expression, on intestinal homeostasis disturbance following gastroenteritis resolution, and evaluates the efficacy of IL-22 cytokine vectorization on PI-IBS symptoms. The Citrobacter rodentium infection model in C57BL6/J mice was used to mimic Enterobacteria gastroenteritis. Intestinal homeostasis was evaluated as low-grade inflammation, permeability, mucosa-associated microbiota composition, and colonic sensitivity. Cognitive performances and emotional state of animals were assessed using several tests. Tryptophan metabolism was analyzed by targeted metabolomics. AhR activity was evaluated using a luciferase reporter assay method. One Lactococcus lactis strain carrying an eukaryotic expression plasmid for murine IL-22 (L. lactisIL-22) was used to induce IL-22 production in mouse colonic mucosa. C. rodentium-infected mice exhibited persistent colonic hypersensitivity and cognitive impairments and anxiety-like behaviors after pathogen clearance. These post-infectious disorders were associated with low-grade inflammation, increased intestinal permeability, decrease of Lactobacillaceae abundance associated with the colonic layer, and increase of short-chain fatty acids (SCFAs). During post-infection period, the indole pathway and AhR activity were decreased due to a reduction of tryptophol production. Treatment with L. lactisIL-22 restored gut permeability and normalized colonic sensitivity, restored cognitive performances and decreased anxiety-like behaviors. Data from the video-tracking system suggested an upgrade of welfare for mice receiving the L.lactisIL-22 strain. Our findings revealed that AhR/IL-22 signaling pathway is altered in a preclinical PI-IBS model. IL-22 delivering alleviate PI-IBS symptoms as colonic hypersensitivity, cognitive impairments, and anxiety-like behaviors by acting on intestinal mucosa integrity. Thus, therapeutic strategies targeting this pathway could be developed to treat IBS patients suffering from chronic abdominal pain and associated well-being disorders.

Fecal dysbiosis associated with colonic hypersensitivity and behavioral alterations in chronically Blastocystis-infected rats.

BACKGROUND: Infectious gastroenteritis is a risk factor for the development of post-infectious Irritable Bowel Syndrome (PI-IBS). Recent clinical studies reported a higher prevalence of the intestinal parasite Blastocystis in IBS patients. Using a rat model, we investigated the possible association between Blastocystis infection, colonic hypersensitivity (CHS), behavioral disturbances and gut microbiota changes. METHODS: Rats were orally infected with Blastocystis subtype 4 (ST4) cysts, isolated from human stool samples. Colonic sensitivity was assessed by colorectal distension and animal behavior with an automatic behavior recognition system (PhenoTyper), the Elevated Plus Maze test and the Forced Swimming tests. Feces were collected at different time points after infection to study microbiota composition by 16 S rRNA amplicon sequencing and for short-chain fatty acid (SFCA) analysis. RESULTS: Blastocystis-infected animals had non-inflammatory CHS with increased serine protease activity. Infection was also associated with anxiety- and depressive-like behaviors. Analysis of fecal microbiota composition showed an increase in bacterial richness associated with altered microbiota composition. These changes included an increase in the relative abundance of Oscillospira and a decrease in Clostridium, which seem to be associated with lower levels of SCFAs in the feces from infected rats. CONCLUSIONS: Our findings suggest that experimental infection of rats with Blastocystis mimics IBS symptoms with the establishment of CHS related to microbiota and metabolic shifts.