Chamaillard Mathias OR Poulin LF

  • A protective role of NOD2 on oxazolone-induced intestinal inflammation through IL-1-mediated signaling pathway

    J Crohns Colitis. 2022 Aug 2:jjac106. doi: 10.1093/ecco-jcc/jjac106. Online ahead of print.


    BACKGROUND AND AIMS: NOD2 has emerged as a critical player in the induction of both Th1- and Th2-responses for potentiation and polarization of antigen-dependent immunity. Loss-of-function mutations in the NOD2-encoding gene and deregulation of its downstream signaling pathway have been linked to Crohn's disease. While it is well documented that NOD2 is capable of sensing bacterial muramyl dipeptide, it remains counterintuitive to link development of overt intestinal inflammation to a loss of bacterial-induced inflammatory response. We hypothesized that a T-helper bias could also contribute to an auto-immune like colitis different than inflammation that is fully fledged by Th1-type cells.

    METHODS: An edematous bowel wall with a mixed Th1/Th2 response was induced in mice by intrarectal instillation of the haptenating agent oxazolone. Survival and clinical scoring were evaluated. At several time-points after instillation, colonic damage was assessed by macroscopic and microscopic observations. To evaluate the involvement of NOD2 in immunochemical phenomena, quantitative PCR and flow cytometry analysis were performed. Bone-marrow chimera experiment allowed us to evaluate the role of hematopoietic/non-hematopoietic NOD2-expressing cells.

    RESULTS: Herein, we identified a key regulatory circuit whereby NOD2-mediated sensing of MDP by radio-resistant cells improves colitis with a mixed Th1/Th2 response that is induced by oxazolone. Genetic ablation of either Nod2 or Ripk2 precipitated oxazolone colitis that is predominantly linked to a lack of Interferon-gamma. Bone-marrow chimera experiments revealed that inactivation of Nod2 signaling in non-hematopoietic cells is causing a biased M1-M2 polarization of macrophages and a decreased frequency of splenic regulatory T cells that correlates with an impaired activation of CD4 + T cells within mesenteric lymph nodes. Mechanistically, mice were protected from oxazolone-induced colitis upon administration of MDP in an interleukin-1- and interleukin-23-dependent manner.

    CONCLUSIONS: these findings indicate that Nod2 signaling may prevent pathologic conversion of T helper cells for maintenance of tissue homeostasis.

    PMID:35917251 | DOI:10.1093/ecco-jcc/jjac106

  • Diurnal Interplay between Epithelium Physiology and Gut Microbiota as a Metronome for Orchestrating Immune and Metabolic Homeostasis

    Metabolites. 2022 Apr 26;12(5):390. doi: 10.3390/metabo12050390.


    The behavior and physiology of most organisms are temporally coordinated and aligned with geophysical time by a complex interplay between the master and peripheral clocks. Disruption of such rhythmic physiological activities that are hierarchically organized has been linked to a greater risk of developing diseases ranging from cancer to metabolic syndrome. Herein, we summarize the molecular clockwork that is employed by intestinal epithelial cells to anticipate environmental changes such as rhythmic food intake and potentially dangerous environmental stress. We also discuss recent discoveries contributing to our understanding of how a proper rhythm of intestinal stem cells may achieve coherence for the maintenance of tissue integrity. Emerging evidence indicates that the circadian oscillations in the composition of the microbiota may operate as an important metronome for the proper preservation of intestinal physiology and more. Furthermore, in this review, we outline how epigenetic clocks that are based on DNA methylation levels may extensively rewire the clock-controlled functions of the intestinal epithelium that are believed to become arrhythmic during aging.

    PMID:35629894 | PMC:PMC9142987 | DOI:10.3390/metabo12050390

  • Virulent Bacteria as Inflammatory and Immune Co-Factor in Colon Carcinogenesis: Evidence From Two Monozygotic Patients and Validation in CRC Patient and Healthy Cohorts

    Front Cell Infect Microbiol. 2021 Nov 4;11:749750. doi: 10.3389/fcimb.2021.749750. eCollection 2021.


    Colorectal carcinoma (CRC) is a common disease, the incidence of which is increasing according to Western lifestyle; it remains to have a poor prognosis. Western nutriments are presumed to induce mild inflammation within the colonic mucosa, resulting in the accumulation of DNA alterations in colonocytes through a multistage carcinogenesis process. This suggests that most CRCs are related to the environment. Of interest, fecal microbiota composition has been shown yielding a novel approach regarding how environment changes may impact health and disease. Here, we compare whole shotgun metagenomic gut microbiota of two monozygotic twin sisters, one of whom is suffering from an advance colorectal tumor with a profound disequilibrium of the composition of the gut microbiota due to the overexpression of virulent bacteria such as E. coli, Shigella, and Clostridium species in the colon cancer patient's feces contrasting with low levels of bacterial species such as Faecalibacterium and Akkermansia usually enriched in the healthy adults' microbial flora. The disequilibrium in microbiota of the CRC patient's feces as compared to her monozygotic twin sister is linked to inflammatory and immune cell infiltrates in the patient's colonic tissue. We speculate on the role of microbiota disequilibrium on the immune-tolerant cell infiltrate within CRCs.

    PMID:34804993 | PMC:PMC8600479 | DOI:10.3389/fcimb.2021.749750

  • Role of NLRs in the Regulation of Type I Interferon Signaling, Host Defense and Tolerance to Inflammation

    Int J Mol Sci. 2021 Jan 28;22(3):1301. doi: 10.3390/ijms22031301.


    Type I interferon signaling contributes to the development of innate and adaptive immune responses to either viruses, fungi, or bacteria. However, amplitude and timing of the interferon response is of utmost importance for preventing an underwhelming outcome, or tissue damage. While several pathogens evolved strategies for disturbing the quality of interferon signaling, there is growing evidence that this pathway can be regulated by several members of the Nod-like receptor (NLR) family, although the precise mechanism for most of these remains elusive. NLRs consist of a family of about 20 proteins in mammals, which are capable of sensing microbial products as well as endogenous signals related to tissue injury. Here we provide an overview of our current understanding of the function of those NLRs in type I interferon responses with a focus on viral infections. We discuss how NLR-mediated type I interferon regulation can influence the development of auto-immunity and the immune response to infection.

    PMID:33525590 | PMC:PMC7865845 | DOI:10.3390/ijms22031301

  • NOD1 sensing of house dust mite-derived microbiota promotes allergic experimental asthma

    J Allergy Clin Immunol. 2021 Aug;148(2):394-406. doi: 10.1016/j.jaci.2020.12.649. Epub 2021 Jan 25.


    BACKGROUND: Asthma severity has been linked to exposure to gram-negative bacteria from the environment that are recognized by NOD1 receptor and are present in house dust mite (HDM) extracts. NOD1 polymorphism has been associated with asthma.

    OBJECTIVE: We sought to evaluate whether either host or HDM-derived microbiota may contribute to NOD1-dependent disease severity.

    METHODS: A model of HDM-induced experimental asthma was used and the effect of NOD1 deficiency was evaluated. Contribution of host microbiota was evaluated by fecal transplantation. Contribution of HDM-derived microbiota was assessed by 16S ribosomal RNA sequencing, mass spectrometry analysis, and peptidoglycan depletion of the extracts.

    RESULTS: In this model, loss of the bacterial sensor NOD1 and its adaptor RIPK2 improved asthma features. Such inhibitory effect was not related to dysbiosis caused by NOD1 deficiency, as shown by fecal transplantation of Nod1-deficient microbiota to wild-type germ-free mice. The 16S ribosomal RNA gene sequencing and mass spectrometry analysis of HDM allergen, revealed the presence of some muropeptides from gram-negative bacteria that belong to the Bartonellaceae family. While such HDM-associated muropeptides were found to activate NOD1 signaling in epithelial cells, peptidoglycan-depleted HDM had a decreased ability to instigate asthma in vivo.

    CONCLUSIONS: These data show that NOD1-dependent sensing of HDM-associated gram-negative bacteria aggravates the severity of experimental asthma, suggesting that inhibiting the NOD1 signaling pathway may be a therapeutic approach to treating asthma.

    PMID:33508265 | DOI:10.1016/j.jaci.2020.12.649

  • The role of the gut microbiome on radiation therapy efficacy and gastrointestinal complications: A systematic review

    Radiother Oncol. 2021 Mar;156:1-9. doi: 10.1016/j.radonc.2020.10.033. Epub 2020 Nov 1.


    Radiation therapy (RT) is an essential component of therapy either curative or palliative armamentarium in oncology, but its efficacy varies considerably among patients through many extrinsic and intrinsic mechanisms of the tumour, which are beginning to be better understood. Recent studies have shown that the gut microbiome represents a key factor in the modulation of the systemic immune response and consequently on patients' outcome. Moreover, the emergence of biomarkers that are derived from the gut microbiota has fuelled the development of adjuvant strategies for patients treated with immunotherapy in combination or not with RT. Despite progress in development of more precise radiotherapy techniques, almost all patients undergoing RT to the abdomen, pelvis, or rectum develop acute adverse events as a consequence of several dose-limiting parameters such as the location of irradiation that may subsequently damage normal tissue including the intestinal epithelium. Several lines of evidence in preclinical models identified that vancomycin improves RT-induced gastrointestinal toxicities such as diarrhea and oral mucositis. In order to gain further insight into this rapidly evolving field, we have systematically reviewed the studies that have described how the gut microbiome may directly or indirectly modulate RT efficacy and its gastro-intestinal toxicities. Lastly, we outline current knowledge gaps and discuss potentially more satisfactory therapeutic options to restore the functionality of the gut microbiome of patients treated with RT.

    PMID:33137398 | DOI:10.1016/j.radonc.2020.10.033

  • Paradoxical Roles of the MAL/Tirap Adaptor in Pathologies

    Front Immunol. 2020 Sep 25;11:569127. doi: 10.3389/fimmu.2020.569127. eCollection 2020.


    Toll-like receptors (TLRs) are at the forefront of pathogen recognition ensuring host fitness and eliciting protective cellular and humoral responses. Signaling pathways downstream of TLRs are tightly regulated for preventing collateral damage and loss of tolerance toward commensals. To trigger effective intracellular signaling, these receptors require the involvement of adaptor proteins. Among these, Toll/Interleukin-1 receptor domain containing adaptor protein (Tirap or MAL) plays an important role in establishing immune responses. Loss of function of MAL was associated with either disease susceptibility or resistance. These opposite effects reveal paradoxical functions of MAL and their importance in containing infectious or non-infectious diseases. In this review, we summarize the current knowledge on the signaling pathways involving MAL in different pathologies and their impact on inducing protective or non-protective responses.

    PMID:33072109 | PMC:PMC7544743 | DOI:10.3389/fimmu.2020.569127

  • Chemotherapy-induced ileal crypt apoptosis and the ileal microbiome shape immunosurveillance and prognosis of proximal colon cancer

    Nat Med. 2020 Jun;26(6):919-931. doi: 10.1038/s41591-020-0882-8. Epub 2020 May 25.


    The prognosis of colon cancer (CC) is dictated by tumor-infiltrating lymphocytes, including follicular helper T (TFH) cells and the efficacy of chemotherapy-induced immune responses. It remains unclear whether gut microbes contribute to the elicitation of TFH cell-driven responses. Here, we show that the ileal microbiota dictates tolerogenic versus immunogenic cell death of ileal intestinal epithelial cells (IECs) and the accumulation of TFH cells in patients with CC and mice. Suppression of IEC apoptosis led to compromised chemotherapy-induced immunosurveillance against CC in mice. Protective immune responses against CC were associated with residence of Bacteroides fragilis and Erysipelotrichaceae in the ileum. In the presence of these commensals, apoptotic ileal IECs elicited PD-1+ TFH cells in an interleukin-1R1- and interleukin-12-dependent manner. The ileal microbiome governed the efficacy of chemotherapy and PD-1 blockade in CC independently of microsatellite instability. These findings demonstrate that immunogenic ileal apoptosis contributes to the prognosis of chemotherapy-treated CC.

    PMID:32451498 | DOI:10.1038/s41591-020-0882-8

  • NOD2 Influences Trajectories of Intestinal Microbiota Recovery After Antibiotic Perturbation

    Cell Mol Gastroenterol Hepatol. 2020;10(2):365-389. doi: 10.1016/j.jcmgh.2020.03.008. Epub 2020 Apr 11.


    BACKGROUND & AIMS: Loss-of-function variants in nucleotide-binding oligomerization domain-containing protein 2 (NOD2) impair the recognition of the bacterial cell wall component muramyl-dipeptide and are associated with an increased risk for developing Crohn's disease. Likewise, exposure to antibiotics increases the individual risk for developing inflammatory bowel disease. Here, we studied the long-term impact of NOD2 on the ability of the gut bacterial and fungal microbiota to recover after antibiotic treatment.

    METHODS: Two cohorts of 20-week-old and 52-week-old wild-type (WT) C57BL/6J and NOD2 knockout (Nod2-KO) mice were treated with broad-spectrum antibiotics and fecal samples were collected to investigate temporal dynamics of the intestinal microbiota (bacteria and fungi) using 16S ribosomal RNA and internal transcribed spacer 1 sequencing. In addition, 2 sets of germ-free WT mice were colonized with either WT or Nod2-KO after antibiotic donor microbiota and the severity of intestinal inflammation was monitored in the colonized mice.

    RESULTS: Antibiotic exposure caused long-term shifts in the bacterial and fungal community composition. Genetic ablation of NOD2 was associated with delayed body weight gain after antibiotic treatment and an impaired recovery of the bacterial gut microbiota. Transfer of the postantibiotic fecal microbiota of Nod2-KO mice induced an intestinal inflammatory response in the colons of germ-free recipient mice compared with respective microbiota from WT controls based on histopathology and gene expression analyses.

    CONCLUSIONS: Our data show that the bacterial sensor NOD2 contributes to intestinal microbial community composition after antibiotic treatment and may add to the explanation of how defects in the NOD2 signaling pathway are involved in the etiology of Crohn's disease.

    PMID:32289499 | PMC:PMC7327897 | DOI:10.1016/j.jcmgh.2020.03.008

  • Lactobacillus reuteri 5454 and Bifidobacterium animalis ssp. lactis 5764 improve colitis while differentially impacting dendritic cells maturation and antimicrobial responses

    Sci Rep. 2020 Mar 24;10(1):5345. doi: 10.1038/s41598-020-62161-1.


    Crohn's disease is linked to a decreased diversity in gut microbiota composition as a potential consequence of an impaired anti-microbial response and an altered polarization of T helper cells. Here, we evaluated the immunomodulatory properties of two potential probiotic strains, namely a Bifidobacterium animalis spp. lactis Bl 5764 and a Lactobacillus reuteri Lr 5454 strains. Both strains improved colitis triggered by either 2,4,6-trinitrobenzenesulfonic acid (TNBS) or Citrobacter rodentium infection in mice. Training of dendritic cells (DC) with Lr 5454 efficiently triggered IL-22 secretion and regulatory T cells induction in vitro, while IL-17A production by CD4+ T lymphocytes was stronger when cultured with DCs that were primed with Bl 5764. This strain was sufficient for significantly inducing expression of antimicrobial peptides in vivo through the Crohn's disease predisposing gene encoding for the nucleotide-binding oligomerization domain, containing protein 2 (NOD2). In contrast, NOD2 was dispensable for the impact on antimicrobial peptide expression in mice that were monocolonized with Lr 5454. In conclusion, our work highlights a differential mode of action of two potential probiotic strains that protect mice against colitis, providing the rational for a personalized supportive preventive therapy by probiotics for individuals that are genetically predisposed to Crohn's disease.

    PMID:32210304 | PMC:PMC7093418 | DOI:10.1038/s41598-020-62161-1

  • The Ubiquitin Code of NODs Signaling Pathways in Health and Disease

    Front Immunol. 2019 Nov 19;10:2648. doi: 10.3389/fimmu.2019.02648. eCollection 2019.


    NOD1 and NOD2 belong to the family of intracellular Nod-like receptors (NLRs) that are involved in the maintenance of tissue homeostasis and host defense against bacteria and some viruses. When sensing such microbes, those NLRs act as hitherto scaffolding proteins for activating multiple downstream inflammatory signaling pathways to promote the production of cytokines and chemokines that are ultimately important for pathogen clearance. In recent years, substantial advances have been made on our understanding of a contextual series of intracellular processes that regulate such group of innate immune molecules, including phosphorylation and ubiquitination. Specifically, we will herein discuss those recently described posttranslational modifications of either NOD1 or NOD2 that fundamentally contribute to the robustness of protective responses within specific tissues through either internal domain association or external interactions with various proteins. From a public health perspective, it is then anticipated that a better understanding how genetic mutations and deregulation of these activating and repressing mechanisms might break down in diseases would open up new therapeutic avenues for humanity.

    PMID:31803185 | PMC:PMC6877504 | DOI:10.3389/fimmu.2019.02648

  • Comparative performances of machine learning methods for classifying Crohn Disease patients using genome-wide genotyping data

    Sci Rep. 2019 Jul 17;9(1):10351. doi: 10.1038/s41598-019-46649-z.


    Crohn Disease (CD) is a complex genetic disorder for which more than 140 genes have been identified using genome wide association studies (GWAS). However, the genetic architecture of the trait remains largely unknown. The recent development of machine learning (ML) approaches incited us to apply them to classify healthy and diseased people according to their genomic information. The Immunochip dataset containing 18,227 CD patients and 34,050 healthy controls enrolled and genotyped by the international Inflammatory Bowel Disease genetic consortium (IIBDGC) has been re-analyzed using a set of ML methods: penalized logistic regression (LR), gradient boosted trees (GBT) and artificial neural networks (NN). The main score used to compare the methods was the Area Under the ROC Curve (AUC) statistics. The impact of quality control (QC), imputing and coding methods on LR results showed that QC methods and imputation of missing genotypes may artificially increase the scores. At the opposite, neither the patient/control ratio nor marker preselection or coding strategies significantly affected the results. LR methods, including Lasso, Ridge and ElasticNet provided similar results with a maximum AUC of 0.80. GBT methods like XGBoost, LightGBM and CatBoost, together with dense NN with one or more hidden layers, provided similar AUC values, suggesting limited epistatic effects in the genetic architecture of the trait. ML methods detected near all the genetic variants previously identified by GWAS among the best predictors plus additional predictors with lower effects. The robustness and complementarity of the different methods are also studied. Compared to LR, non-linear models such as GBT or NN may provide robust complementary approaches to identify and classify genetic markers.

    PMID:31316157 | PMC:PMC6637191 | DOI:10.1038/s41598-019-46649-z

  • Proteasomal degradation of NOD2 by NLRP12 in monocytes promotes bacterial tolerance and colonization by enteropathogens

    Nat Commun. 2018 Dec 17;9(1):5338. doi: 10.1038/s41467-018-07750-5.


    Mutations in the nucleotide-binding oligomerization domain protein 12 (NLRP12) cause recurrent episodes of serosal inflammation. Here we show that NLRP12 efficiently sequesters HSP90 and promotes K48-linked ubiquitination and degradation of NOD2 in response to bacterial muramyl dipeptide (MDP). This interaction is mediated by the linker-region proximal to the nucleotide-binding domain of NLRP12. Consequently, the disease-causing NLRP12 R284X mutation fails to repress MDP-induced NF-κB and subsequent activity of the JAK/STAT signaling pathway. While NLRP12 deficiency renders septic mice highly susceptible towards MDP, a sustained sensing of MDP through NOD2 is observed among monocytes lacking NLRP12. This loss of tolerance in monocytes results in greater colonization resistance towards Citrobacter rodentium. Our data show that this is a consequence of NOD2-dependent accumulation of inflammatory mononuclear cells that correlates with induction of interferon-stimulated genes. Our study unveils a relevant process of tolerance towards the gut microbiota that is exploited by an attaching/effacing enteric pathogen.

    PMID:30559449 | PMC:PMC6297353 | DOI:10.1038/s41467-018-07750-5

  • The NLRP6 Inflammasome Recognizes Lipoteichoic Acid and Regulates Gram-Positive Pathogen Infection

    Cell. 2018 Nov 29;175(6):1651-1664.e14. doi: 10.1016/j.cell.2018.09.047. Epub 2018 Nov 1.


    The activator and composition of the NLRP6 inflammasome remain poorly understood. We find that lipoteichoic acid (LTA), a molecule produced by Gram-positive bacteria, binds and activates NLRP6. In response to cytosolic LTA or infection with Listeria monocytogenes, NLRP6 recruited caspase-11 and caspase-1 via the adaptor ASC. NLRP6 activation by LTA induced processing of caspase-11, which promoted caspase-1 activation and interleukin-1β (IL-1β)/IL-18 maturation in macrophages. Nlrp6-/- and Casp11-/- mice were less susceptible to L. monocytogenes infection, which was associated with reduced pathogen loads and impaired IL-18 production. Administration of IL-18 to Nlrp6-/- or Casp11-/- mice restored the susceptibility of mutant mice to L. monocytogenes infection. These results reveal a previously unrecognized innate immunity pathway triggered by cytosolic LTA that is sensed by NLRP6 and exacerbates systemic Gram-positive pathogen infection via the production of IL-18.

    PMID:30392956 | PMC:PMC6294477 | DOI:10.1016/j.cell.2018.09.047

  • The regenerating family member 3 β instigates IL-17A-mediated neutrophil recruitment downstream of NOD1/2 signalling for controlling colonisation resistance independently of microbiota community structure

    Gut. 2019 Jul;68(7):1190-1199. doi: 10.1136/gutjnl-2018-316757. Epub 2018 Oct 2.


    OBJECTIVE: Loss of the Crohn's disease predisposing NOD2 gene results in an intestinal microenvironment conducive for colonisation by attaching-and-effacing enteropathogens. However, it remains elusive whether it relies on the intracellular recruitment of the serine-threonine kinase RIPK2 by NOD2, a step that is required for its activation of the transcription factor NF-κB.

    DESIGN: Colonisation resistance was evaluated in wild type and mutant mice, as well as in ex-germ-free (ex-GF) mice which were colonised either with faeces from Ripk2-deficient mice or with bacteria with similar preferences for carbohydrates to those acquired by the pathogen. The severity of the mucosal pathology was quantified at several time points postinfection by using a previously established scoring. The community resilience in response to infection was evaluated by 16S ribosomal RNA gene sequence analysis. The control of pathogen virulence was evaluated by monitoring the secretion of Citrobacter-specific antibody response in the faeces.

    RESULTS: Primary infection was similarly outcompeted in ex-GF Ripk2-deficient and control mice, demonstrating that the susceptibility to infection resulting from RIPK2 deficiency cannot be solely attributed to specific microbiota community structures. In contrast, delayed clearance of Citrobacter rodentium and exacerbated histopathology were preceded by a weakened propensity of intestinal macrophages to afford innate lymphoid cell activation. This tissue protection unexpectedly required the regenerating family member 3β by instigating interleukin (IL) 17A-mediated neutrophil recruitment to the intestine and subsequent phosphorylation of signal transducer and activator of transcription 3.

    CONCLUSIONS: These results unveil a previously unrecognised mechanism that efficiently protects from colonisation by diarrhoeagenic bacteria early in infection.

    PMID:30279238 | DOI:10.1136/gutjnl-2018-316757