Peyer's Patches: The Immune Sensors of the Intestine

The gut-associated lymphoid tissue (GALT) consists of isolated or aggregated lymphoid follicles forming Peyer's patches (PPs). By their ability to transport luminal antigens and bacteria, PPs can be considered as the immune sensors of the intestine. PPs functions like induction of immune tolerance or defense against pathogens result from the complex interplay between immune cells located in the lymphoid follicles and the follicle-associated epithelium. This crosstalk seems to be regulated by pathogen recognition receptors, especially Nod2. Although TLR exerts a limited role in PP homeotasis, Nod2 regulates the number, size, and T-cell composition of PPs, in response to the gut flora. In turn, CD4+ T-cells present in the PP are able to modulate the paracellular and transcellular permeabilities. Two human disorders, Crohn's disease and graft-versus-host disease are thought to be driven by an abnormal response toward the commensal flora. They have been associated with NOD2 mutations and PP dysfunction

Impact of anatase and rutile titanium dioxide nanoparticles on uptake carriers and efflux pumps in Caco-2 gut epithelial cells

International audienceTiO2 microparticles are widely used in food products, where they are added as a white food colouring agent. This food additive contains a significant amount of nanoscale particles; still the impact of TiO2 nanoparticles (TiO2-NPs) on gut cells is poorly documented. Our study aimed at evaluating the impact of rutile and anatase TiO2-NPs on the main functions of enterocytes, i.e. nutrient absorption driven by solute-liquid carriers (SLC transporters) and protection against other xenobiotics driven by efflux pumps from the ATP-binding cassette (ABC) family. We show that acute exposure of Caco-2 cells to both anatase (12 nm) and rutile (20 nm) TiO2-NPs induce early upregulation of a battery of efflux pumps and nutrient transporters. In addition they cause overproduction of reactive oxygen species and misbalance redox repair systems, without inducing cell mortality or DNA damage. Taken together, these data suggest that TiO2-NPs may increase the functionality of gut epithelial cells, particularly their property to form a protective barrier against exogenous toxicants and to absorb nutrients

CARD15/NOD2 Is Required for Peyer's Patches Homeostasis in Mice

BACKGROUND: CARD15/NOD2 mutations are associated with susceptibility to Crohn's Disease (CD) and Graft Versus Host Disease (GVHD). CD and GVHD are suspected to be related with the dysfunction of Peyer's patches (PP) and isolated lymphoid follicles (LFs). Using a new mouse model invalidated for Card15/Nod2 (KO), we thus analysed the impact of the gene in these lymphoid formations together with the development of experimental colitis. METHODOLOGY/PRINCIPAL FINDINGS: At weeks 4, 12 and 52, the numbers of PPs and LFs were higher in KO mice while no difference was observed at birth. At weeks 4 and 12, the size and cellular composition of PPs were analysed by flow cytometry and immunohistochemistry. PPs of KO mice were larger with an increased proportion of M cells and CD4(+) T-cells. KO mice were also characterised by higher concentrations of TNFalpha, IFNgamma, IL12 and IL4 measured by ELISA. In contrast, little differences were found in the PP-free ileum and the spleen of KO mice. By using chamber experiments, we found that this PP phenotype is associated with an increased of both paracellular permeability and yeast/bacterial translocation. Finally, KO mice were more susceptible to the colitis induced by TNBS. CONCLUSIONS: Card15/Nod2 deficiency induces an abnormal development and function of the PPs characterised by an exaggerated immune response and an increased permeability. These observations provide a comprehensive link between the molecular defect and the Human CARD15/NOD2 associated disorders: CD and GVHD

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Stress néonatal et conséquences sur la barrière intestinale et la viscérosensibilité

L'accumulation de nombreuses données fondamentales, cliniques et épidémiologiques a permis de caractériser et de mettre en évidence l'implication des facteurs environnementaux de la période néonatale dans l'apparition d'états pathologiques chez le jeune et l'adulte. Chez l'homme, les évènements traumatiques précoces sont connus pour être impliqués dans l'étiologie de pathologies digestives comme le syndrome de l'intestin irritable, caractérisé par des douleurs abdominales fréquemment associées à une augmentation de la perméabilité intestinale et à des troubles du transit intestinal. L'utilisation de modèles animaux a conforté ces données et a permis de montrer l'implication d'événements traumatiques précoces dans le développement de pathologies digestives chez le sujet adulte (ulcères gastriques et dysfonctionnements de la barrière épithéliale colique en réponse à un stress). Ainsi, un modèle expérimental présentant les mêmes caractéristiques physiopathologiques que celles du syndrome de l'intestin irritable a été mis au point. Ce modèle consiste à séparer les rats nouveau-nés de leur mère 3 heures par jour du deuxième au quatorzième jour de vie. Les rats ainsi néo-stressés développent à l'age adulte une hyperalgésie viscérale ainsi que des altérations du transit intestinal comparables à celles retrouvées dans le syndrome de l'intestin irritable. Le but de notre étude a été dans un premier temps, de caractériser les répercussions du stress néonatal sur la physiologie et sur le système immunitaire de la muqueuse intestinale. Dans un deuxième temps, nous avons cherché à déterminer en période néonatale les mécanismes impliqués dans ces altérations. Puis, dans une dernière étude nous avons recherché les médiateurs impliqués dans l'augmentation de la perméabilité intestinale induite par la séparation maternelle...Adverse events during childhood are considered as potent stressors often associated in humans with gastrointestinal diseases such as Crohn's disease or irritable bowel syndrome (IBS). The use of animal models of maternal deprivation has pointed out the importance of neonatal stress in favoring the occurrence of gastrointestinal diseases in adults. For example, early maternal separation has been found to predispose to gastric erosions, and colonic barrier dysfunction in response to a mild stress. As demonstrated with Ussing chambers, neonatal stress increases colonic ion transport but does not modify colonic permeability, at least in basal conditions and for the marker horseradish peroxidase. It has also been shown in rats that neonatal maternal deprivation triggers long-term hypersensitivity to rectal distension, which corresponds to the main pathophysiological characteristic of IBS in humans. Consequently, the present study aimed to establish whether maternal deprivation affects the integrity of colonic epithelial barrier and the immune status in adult rats. Secondly, we have investigated whether NGF was involved in the genesis of visceral hyperalgesia and immune alterations induced by neonatal maternal deprivation. Finally, we have determined whether mast cells, CRF and corticosterone were involved in maintaining elevated gut paracellular permeability observed in adult deprived rats...TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Impact du gène NOD2 sur l'homéostasie du microbiote et de la muqueuse intestinale

La maladie de Crohn (MC) est une maladie inflammatoire chronique de l'intestin. Sa physiopathologie est caractérisée par une réaction immunitaire excessive en réponse à des anomalies du microbiote chez des individus génétiquement prédisposés. Bien que les mutations du gène NOD2 aient été associées à la MC, leur rôle dans la genèse de la maladie reste inconnu. Nod2 est un récepteur intracellulaire au muramyl dipeptide, un fragment du peptidoglycane des bactéries Gram positif et Gram négatif. Les objectifs de thèse étaient d'étudier l'impact de Nod2 sur le microbiote et la fonction de la muqueuse digestive. Nous avons montré que les souris déficientes pour Nod2 présentaient des altérations du microbiote intestinal et que ces altérations étaient indépendantes des facteurs environnementaux. La dysbiose bactérienne liée à l'absence de Nod2 n'était pas capable d'affecter la fonctionnalité de l'épithélium intestinal. Nous avons montré que l'expression de Nod2 dans les cellules épithéliales contrôlait la stabilité du microbiote en modulant l'expression des peptides antimicrobiens. A l'inverse, Nod2 dans le compartiment immunitaire régulait les fonctions de l'épithélium. Nous avons observé que l'absence de Nod2 dans les lymphocytes T-CD4+ était suffisante pour altérer la perméabilité intestinal. Cependant, l'activation de Nod2 par son ligand dans les cellules épithéliales était capable de normaliser la perméabilité. Enfin, nous avons montré que Nod2 protégeait l'intestin grêle en cas d'inflammation colique. L'ensemble de ces résultats apporte de nouveaux éléments dans la connaissance des mécanismes par lesquels les mutations du gène Nod2 participent au développement de la MC.Crohn disease (CD) is a chronic inflammatory bowel disease characterized by an excessive immune reaction in response to abnormal microbiota in genetically predisposed individuals. Although NOD2 mutations have been associated with susceptibility to CD, their role in the genesis of the human disease remains unclear. Nod2 is a sensor of muramyl dipeptide that is the minimal bioactive peptidoglycan fragment from both Gram positive and Gram negative bacteria. Numerous studies have shown that Nod2 deficiency alters microbiota composition and the homeostasis of the intestinal mucosa. The aims of this thesis were to study the role of Nod2 inside immune and epithelial compartment in the control of the gut microbiota and mucosal homeostasis using animal and cellular models. We have shown Nod2 Knockout mice exhibited a microbiota dysbiosis at both ileal and colonic location and that these alterations of intestinal microbiota were independent of environmental factors. Nod2 inside hematopoietic lineage regulated the barrier function. However, Nod2 deficiency inside epithelial compartment maintained the bacterial dysbiosis by regulating the secretion of both mucins and antimicrobial peptides. Among immune cells, we have also shown that Nod2 deficiency in C134+ T cells was sufficient to modify the intestinal barrier function. Nevertheless, activation of Nod2 by their ligands normalized the increase of permeability induced by CD4+ T cells by MLCK-dependent mechanisms. Finally, we demonstrated that Nod2 protected the small intestine against colitis. Taken together, these results provide new evidence in favor of the mechanism by which NOD2 mutations are involved in the pathogenesis of CD.PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Crohn’s disease: is the cold chain hypothesis still hot?

International audienceCrohn’s disease (CD) is an inflammatory bowel disease of unknown etiology. During the last decades, significant technological advances led to development of -omic datasets allowing a detailed description of the disease. Unfortunately, these have not, to date, resolved the question of the etiology of CD. Thus, it may be necessary to (re)consider hypothesis-driven approaches to resolve the etiology of CD. According to the cold chain hypothesis, the development of industrial and domestic refrigeration has led to frequent exposure of human populations to bacteria capable of growing in the cold. These bacteria, at low levels of exposure, particularly those of the genus Yersinia, are believed to be capable of inducing exacerbated inflammation of the intestine in genetically predisposed subjects. We discuss the consistency of this working hypothesis in light of recent data from epidemiological, clinical, pathological, microbiological and molecular studies

Titanium dioxide particles from the diet: involvement in the genesis of inflammatory bowel diseases and colorectal cancer

International audienceAbstract The gastrointestinal tract is a complex interface between the external environment and the immune system. Its ability to control uptake across the mucosa and to protect the body from damage of harmful substances from the lumen is defined as the intestinal barrier function (IBF). The IBF involves four elements: the intestinal microbiota, the mucus layer, the epithelium and the immune system. Its dysfunction is linked with human diseases including inflammatory, metabolic, infectious, autoimmune and neurologic disorders. Most of these diseases are complex and involve genetic, psychological and environmental factors. Over the past 10 years, many genetic polymorphisms predisposing to inflammatory bowel disease (IBD) have been identified. Yet, it is now clear that they are insufficient to explain the onset of these chronic diseases. Although it has been evidenced that some environmental factors such as cigarette smoking or carbohydrate intake are associated with IBD, other environmental factors also present potential health risks such as ingestion of food additives introduced in the human diet, including those composed of mineral particles, by altering the four elements of the intestinal barrier function. The aim of this review is to provide a critical opinion on the potential of TiO 2 particles, especially when used as a food additive, to alter the four elements of the intestinal barrier function, and consequently to evaluate if this additive would likely play a role in the development and/or exacerbation of IBD

Optimization of biologics to reduce treatment failure in inflammatory bowel diseases

International audienceModerate to severe inflammatory bowel disease patients can fail to respond to conventional therapy and/or to biologic treatment. In the era of TNFα antagonists and other non-anti-TNF biologic drugs, it is important to review the literature on biologic treatment failure, which could be defined as primary non-response, secondary loss of response and intolerance. Therapeutic drug monitoring (TDM), that is, drug trough level and antidrug antibodies, should enable to determine the mechanisms of treatment failure and to optimize drug efficacy. There is a consensus on reactive TDM at the time of loss of response. Proactive TDM could be of interest during induction and/or maintenance, but randomized controlled trials are required