Role Of NOD2 Research Articles

Innate immunity gene Nod2 protects mice from orthotopic breast cancer

BackgroundNod2 is involved in innate immune responses to bacteria, regulation of metabolism, and sensitivity to cancer. A Nod2 polymorphism is associated with breast cancer, but the role of Nod2 in the development and progression of breast cancer is unknown.MethodsHere, we tested the hypothesis that Nod2 protects mice from breast cancer using the 4T1 orthotopic model of mammary tumorigenesis. WT and Nod2−/− mice were injected with 4T1 mammary carcinoma cells and the development of tumors was monitored. A detailed analysis of the tumor transcriptome was performed and genes that were differentially expressed and pathways that were predicted to be altered between WT and Nod2−/− mice were identified. The activation of key signaling molecules involved in metabolism and development of cancer was studied.ResultsOur data demonstrate that Nod2−/− mice had a higher incidence and larger tumors than WT mice. Nod2−/− mice had increased expression of genes that promote DNA replication and cell division, and decreased expression of genes required for lipolysis, lipogenesis, and steroid biosynthesis compared with WT mice. Nod2−/− mice also had lower expression of genes required for adipogenesis and reduced levels of lipids compared with WT mice. The tumors in Nod2−/− mice had decreased expression of genes associated with PPARα/γ signaling, increased activation of STAT3, decreased activation of STAT5, and no change in the activation of ERK compared with WT mice.ConclusionsWe conclude that Nod2 protects mice from the 4T1 orthotopic breast tumor, and that tumors in Nod2−/− mice are predicted to have increased DNA replication and cell proliferation and decreased lipid metabolism compared with WT mice.

NOD2 and Crohn's Disease Clinical Practice: From Epidemiology to Diagnosis and Therapy, Rewired.

Crohn's disease (CD) is a chronic inflammatory bowel disease with a multifactorial pathogenesis involving environmental and genetic factors. Since the late 20th century, the discovery of the first susceptibility gene (NOD2, previously referred to as CARD15) for CD has paved the way for further investigations into the correlations between clinical features and genetics, and its potential impact on clinical practice has fueled the research in the last 2 decades. Recent therapeutic advancements involving novel biologic drugs and small molecules have shifted inflammatory bowel disease management from a disease-centered to a patient-centric approach. To date, the role of NOD2 has not been fully understood yet. Recent data suggest that its clinical impact may be greater than currently recognized. This review overviews the most common NOD2 variants' role in real-life clinical practice. These genetic variants increase the risk of developing the disease and can aid in tailoring diagnosis and treatment. They are associated with the stricturing phenotype and ileal involvement and increase the risk of steroid refractoriness. In the meantime, limited and inconclusive evidence exists regarding their predictive role in response to azathioprine, biologic drugs, and small molecules. Eventually, their role in increasing the risk for surgery is evident, especially in those with the L1007fs variant. If further trials will support the initial evidence reported so far, NOD2 genetic variants will emerge as possible candidates for developing precision medicine in CD.

Loss of NOD2 in macrophages improves colitis and tumorigenesis in a lysozyme-dependent manner.

Crohn's disease (CD) is a complex and poorly understood myeloid-mediated disorder. Genetic variants with loss of function in the NOD2 gene confer an increased susceptibility to ileal CD. While Nod2 in myeloid cells may confer protection against T-cell mediated ileopathy, it remains unclear whether it may promote resolution of the inflamed colon. In this study, we evaluated the function of Nod2 in myeloid cells in a model of acute colitis and colitis-associated colon cancer (CAC). To ablate Nod2 specifically within the myeloid compartment, we generated LysMCre/+;Nod2fl/fl mice. The role of NOD2 was studied in a setting of Dextran Sodium Sulfate (DSS)-induced colitis and in azoxymethane (AOM)/DSS model. Clinical parameters were quantified by colonoscopy, histological, flow cytometry, and qRT-PCR analysis. Upon DSS colitis model, LysMCre/+;Nod2fl/fl mice lost less weight than control littermates and had less severe damage to the colonic epithelium. In the AOM/DSS model, endoscopic monitoring of tumor progression revealed a lowered number of adenomas within the colon of LysMCre/+;Nod2fl/fl mice, associated with less expression of Tgfb. Mechanistically, lysozyme M was required for the improved disease severity in mice with a defect of NOD2 in myeloid cells. Our results indicate that loss of Nod2 signaling in myeloid cells aids in the tissue repair of the inflamed large intestine through lysozyme secretion by myeloid cells. These results may pave the way to design new therapeutics to limit the inflammatory and tumorigenic functions of NOD2.

To be or NOD 2 be: The role of NOD2 in predisposing patients with cirrhosis towards infections.

To be or NOD 2 be: The role of NOD2 in predisposing patients with cirrhosis towards infections.

Giardia lamblia regulates the production of proinflammatory cytokines through activating the NOD2–Rip2–ROS signaling pathway in mouse macrophages

Giardia lamblia is a zoonotic protozoan that causes the diarrheal illness giardiasis, with the highest prevalence reported in the tropics and subtropics. Giardia is currently the most frequently identified pathogen in waterborne outbreaks in the United States. Nucleotide oligomerization domain (NOD) 1 and NOD2, intracellular NOD-like receptors, recognize pathogens to induce proinflammatory and antimicrobial responses. However, the roles of NOD1 and NOD2 signaling in Giardia infection have not yet been investigated. In the present study, the activation of NOD1 and NOD2 signaling pathways and the production of proinflammatory cytokines, reactive oxygen species (ROS) and nitric oxide in mouse macrophages stimulated with G. lamblia or parasite excretory-secretory products (ESPs) were examined. The results showed that G. lamblia and ESPs activated NOD2 and its downstream adaptor protein kinase, Receptor-interacting protein 2 (Rip2), in mouse macrophages. Blocking NOD2-Rip2 signaling significantly reduced the production of ROS and subsequently decreased the phosphorylation of nuclear factor-κB p65 and extracellular signal-regulated kinase, which in turn inhibited the production of four proinflammatory cytokines, namely, interleukin (IL)-1β, IL-6, IL-12p40 and tumor necrosis factor-α. In summary, our results indicate that the NOD2-Rip2 signal, which is activated by G. lamblia, contributes to the production of proinflammatory cytokines and ROS in mouse macrophages.

A Role of NOD2 in CARTp‐mediated Mechano‐hypersensitivity

Neuropathic pain is a debilitating chronic condition that remains difficult to treat. There is a high priority to identify novel non‐opioid‐based therapeutic targets as long‐term use of opioids is problematic due to its severe side effects and strong abuse potential. Our lab recently discovered G‐protein coupled receptor 160 (GPR160) has a role in neuropathic pain. Gpr160 was upregulated in the dorsal horn of the spinal cord (DH‐SC) on the side of nerve injury relative to the uninjured side in mice. Blocking GPR160 using siRNA or a neutralizing antibody (Ab) reversed and prevented pain hypersensitivity. In addition, our lab deorphanized GPR160 as the receptor for cocaine‐ and amphetamine‐regulated transcript peptide (CARTp). We showed that an intrathecal (i.th.) injection of CARTp in naive mice caused mechano‐hypersensitivity that was dependent on GPR160. CARTp‐induced gene expression is relatively unexplored and the mechanism by which CARTp/GPR160 signaling promotes chronic pain is not well known. Therefore, our objective was to perform an unbiased RNA transcriptomics analysis to identify which genes were altered at the time of CARTp‐mediated peak pain in the DH‐SC. We found that Nucleotide‐binding oligomerization domain‐containing protein 2 (Nod2) expression was increased upon i.th. injection of CARTp and its expression decreased after CARTp was co‐administered with GPR160 Ab, pointing to a potential interaction between CARTp/GPR160 and NOD2. NOD2 is a cytosolic pattern recognition receptor that is involved in activating the immune system in response to pathogens. Moreover, a recent study linked NOD2 to the development of neuropathic pain. This led to our hypothesis that CARTp/GPR160 causes mechano‐hypersensitivity through NOD2 and NOD2 has a functional role in neuropathic pain. C57BL/6 (WT) and NOD2‐/‐ mice received an i.th. injection of CARTp and mechano‐allodynia was assessed. The WT mice developed mechano‐allodynia by 30min and persisted for 5hrs. In contrast, mechano‐allodynia was attenuated for 4hrs in NOD2‐/‐ mice, suggesting CARTp/GPR160 induces mechano‐hypersensitivity through NOD2. Furthermore, we found that NOD2 has a functional role in a chronic constriction injury (CCI) model of neuropathic pain. WT mice started developing mechano‐allodynia on day 3 (D3) after CCI, reached a maximum by D7, and persisted until D14. However, NOD2‐/‐ mice did not develop mechano‐allodynia until D10, indicating that NOD2 is involved in the development of CCI neuropathic pain. Overall, our results provide a potential mechanistic insight on how CARTp causes mechano‐sensitivity and NOD2 has a functional role in CCI‐mediated neuropathic pain.

NOD2 PROMOTES HOST DEFENSE AND RECOVERY INDUCING MACROPHAGE-MEDIATED INNATE LYMPHOID CELLS TYPE 3 ACTIVATION FOLLOWING FUNGAL INFECTION IN EXPERIMENTAL COLITIS

Abstract Recent studies have documented the complexity of the intestinal fungal community (‘mycobiome’) in mice, and clinical and experimental observations have shown that the mycobiome influences both gut health and disease, e.g., inflammatory bowel disease (IBD). In fact, prior studies have shown that Crohn’s disease (CD) patients, compared to healthy controls, harbor higher levels of intestinal Candida tropicalis (Ct), which is the major fungal species detected in the colons of colitic mice after DSS challenge. More recently, Debaryomyces hansenii (also known as Candida famata) has been found in intestinal wounds of mice and inflamed mucosal tissues of CD patients. Moreover, proteins encoded by genes within IBD susceptibility loci, such as the pattern recognition receptor (PRR), NOD2, are known not only to recognize bacterial components, but also a fungal cell wall element, chitin. In fact, the role of PRRs in regulating immunity against intestinal fungi, and how fungi influence IBD remains poorly defined. We challenged DSS colitic WT and Nod2-/- mice with Ct 2 days before DSS administration and subsequently on day (d)0, 3 and 6. Our data confirms previous studies that Ct challenge does not exacerbate colitis in DSS-treated C57BL/6 wildtype (WT) mice, however, Ct-infected Nod2-/- mice possess a higher fungal burden and exhibit worse colitis symptoms, such as weight loss, decreased stool consistency, and presence of blood in stools, vs. Ct-infected WT mice, indicating an essential and protective role for NOD2 during colitis recovery after Ct challenge. Our results also show that Ct-infected Nod2-/- mice display a marked reduction in colonic Il22 and Il17, which are cytokines previously reported to be important in maintaining epithelial barrier integrity during DSS colitis, These data were confirmed in colons of Ct infected DSS challenged, ileitis-prone SAMP1/YitFc (SAMP) mice that were deficient in NOD2. Moreover, Our in vitro data show, a decrease in Il1b and Il23 in bone marrow-derived macrophages from SAMP Nod2-/- mice compared to WT after 2h of exposure to chitin. IL-17+ innate lymphoid cells (ILCs) are also known to control fungal burden during opportunistic fungal infections, and interestingly, our findings indicate that Ct infection of Nod2-/- vs. WT mice results in a decreased frequency of mesenteric lymph node–derived type 3 ILCs (ILC3s), suggesting that delay in fungal clearance and recovery in Nod2-/- mice may be due to the inability to mount protective type 3 immune responses. Taken together, the data so far collected suggests that NOD2 is essential to maintain gut mycobiome homeostasis and drives protective innate immune responses, via a macrophage-mediated ILC3 recruitment and IL-17 mechanism, by preventing the overgrowth of opportunistic fungi that may contribute to chronic intestinal inflammation, such as that observed in CD.

Nod2 protects mice from inflammation and obesity-dependent liver cancer

Nod2 is a pattern recognition receptor that modulates host innate immune responses and protects from inflammation, steatosis, and obesity. Obesity and inflammation are risk factors for hepatocellular carcinoma, however, the role of Nod2 in obesity-dependent hepatic tumorigenesis is not known. Here we tested the hypothesis that Nod2 protects from high fat diet (HFD)-dependent hepatic cancer. We used an obesity-dependent hepatic tumor model. WT and Nod2−/− mice were treated with the carcinogen dimethylbenz[a]anthracene (DMBA) and maintained on HFD. Nod2−/− mice treated with DMBA and maintained on HFD gain significantly more weight and develop more liver tumors than similarly treated WT mice. Livers of Nod2−/− tumorigenic mice had increased expression of genes involved in cell proliferation, immune responses, and cholesterol biosynthesis, increased infiltration of neutrophils, inflammatory monocytes, and T cells, and increased activation of STAT3 and ERK during the later stages of tumorigenesis. Bioinformatic analyses of genes with differential expression predicted an increase in cancer, immune, and cholesterol biosynthesis pathways. In summary, we have identified a novel role for Nod2 and demonstrate that Nod2 protects from HFD-dependent liver malignancy and this protection is accompanied by decreased cell proliferation, inflammation, steroid biosynthesis, neutrophils and macrophages infiltration, and STAT3 and MAPK signaling in the liver.

T cell-intrinsic role for Nod2 in protection against Th17-mediated uveitis

Mutations in nucleotide-binding oligomerization domain-containing protein 2 (NOD2) cause Blau syndrome, an inflammatory disorder characterized by uveitis. The antimicrobial functions of Nod2 are well-established, yet the cellular mechanisms by which dysregulated Nod2 causes uveitis remain unknown. Here, we report a non-conventional, T cell-intrinsic function for Nod2 in suppression of Th17 immunity and experimental uveitis. Reconstitution of lymphopenic hosts with Nod2−/− CD4+ T cells or retina-specific autoreactive CD4+ T cells lacking Nod2 reveals a T cell-autonomous, Rip2-independent mechanism for Nod2 in uveitis. In naive animals, Nod2 operates downstream of TCR ligation to suppress activation of memory CD4+ T cells that associate with an autoreactive-like profile involving IL-17 and Ccr7. Interestingly, CD4+ T cells from two Blau syndrome patients show elevated IL-17 and increased CCR7. Our data define Nod2 as a T cell-intrinsic rheostat of Th17 immunity, and open new avenues for T cell-based therapies for Nod2-associated disorders such as Blau syndrome.

Роль рецепторов NOD1 и NOD2 в распознавании патогенов в женском репродуктивном тракте

Роль рецепторов NOD1 и NOD2 в распознавании патогенов в женском репродуктивном тракте

Nod1 Imprints Inflammatory and Carcinogenic Responses toward the Gastric Pathogen Helicobacter pylori.

Helicobacter pylori (H. pylori) is the strongest known risk for gastric cancer. The H. pylori cag type IV secretion system is an oncogenic locus that translocates peptidoglycan into host cells, where it is recognized by NOD1, an innate immune receptor. Beyond this, the role of NOD1 in H. pylori-induced cancer remains undefined. To address this knowledge gap, we infected two genetic models of Nod1 deficiency with the H. pylori cag + strain PMSS1: C57BL/6 mice, which rarely develop cancer, and INS-GAS FVB/N mice, which commonly develop cancer. Infected C57BL/6 Nod1-/- and INS-GAS Nod1-/- mice acutely developed more severe gastritis, and INS-GAS Nod1-/- mice developed gastric dysplasia more frequently compared with Nod1+/+ mice. Because Nod1 genotype status did not alter microbial phenotypes of in vivo-adapted H. pylori, we investigated host immunologic responses. H. pylori infection of Nod1-/- mice led to significantly increased gastric mucosal levels of Th1, Th17, and Th2 cytokines compared with Nod1 wild-type (WT) mice. To define the role of specific innate immune cells, we quantified cytokine secretion from H. pylori-infected primary gastric organoids generated from WT or Nod1-/- mice that were cocultured with or without WT or Nod1-/- macrophages. Infection increased cytokine production from gastric epithelial cells and macrophages and elevations were significantly increased with Nod1 deficiency. Furthermore, H. pylori infection altered the polarization status of Nod1-/- macrophages compared with Nod1+/+ macrophages. Collectively, these studies demonstrate that loss of Nod1 augments inflammatory and injury responses to H. pylori. Nod1 may exert its restrictive role by altering macrophage polarization, leading to immune evasion and microbial persistence. SIGNIFICANCE: These findings suggest that manipulation of NOD1 may represent a novel strategy to prevent or treat pathologic outcomes induced by H. pylori infection.

Role of NOD2 in antiphospholipid antibody-induced and bacterial MDP amplification of trophoblast inflammation

Women with antiphospholipid antibodies (aPL) are at high risk for pregnancy complications, such as preeclampsia. We previously demonstrated that aPL recognizing β2GPI promote an extravillous trophoblast pro-inflammatory, anti-migratory and anti-angiogenic profile similar to that seen in preeclampsia. Since preeclampsia in the absence of aPL may have an underlying infectious element, women with aPL may be at increased risk for preeclampsia or other adverse outcomes if an infection is present. Our objective was to determine the impact the common bacterial component, muramyl dipeptide (MDP), has on trophoblast responses to aPL. Herein, we report that bacterial MDP amplifies trophoblast IL-1β expression, processing, and secretion in the presence of aPL through activation of NOD2. In the absence of MDP, NOD2 also mediates anti- β2GPI antibody-induced trophoblast IL-1β and VEGF secretion. Additionally, we report a role for extravillous trophoblast vimentin as a novel danger signal that contributes to the aPL-induced trophoblast IL-1β production. Together our data indicate that NOD2 mediates trophoblast inflammatory and angiogenic responses to aPL alone, and mediates trophoblast inflammation in the presence of bacterial MDP. These findings suggest that a bacterial infection at the maternal-fetal interface may exacerbate the impact aPL have on trophoblast inflammation and, thus, on pregnancy outcome.

NOD2 promotes dopaminergic degeneration regulated by NADPH oxidase 2 in 6-hydroxydopamine model of Parkinson\u2019s disease

BackgroundIn Parkinson’s disease (PD), loss of striatal dopaminergic (DA) terminals and degeneration of DA neurons in the substantia nigra (SN) are associated with inflammation. Nucleotide-binding oligomerization domain-containing protein (NOD)2, one of the first discovered NOD-like receptors, plays an important role in inflammation. However, the role of NOD2 has not been elucidated in PD.MethodsNOD2 mRNA and protein expression in the SN and the striatum of C57BL/6 mice treated with 6-hydroxydopamine (6-OHDA) was measured. We next investigated the potential contribution of the NOD2-dependent pathway to 6-OHDA-induced DA degeneration using NOD2-deficient (NOD2−/−) mice. Assays examining DA degeneration and inflammation include HPLC, Western blot, immunohistochemistry, TUNEL staining, and cytometric bead array. To further explore a possible link between NADPH oxidase 2 (NOX2) and NOD2 signaling in PD, microglia were transfected with shRNA specific to NOX2 in vitro and apocynin were given to mice subjected to 6-OHDA and muramyl dipeptide (MDP) striatal injection.ResultsThe expression of NOD2 was upregulated in an experimental PD model induced by the neurotoxin 6-OHDA. NOD2 deficiency resulted in a protective effect against 6-OHDA-induced DA degeneration and neuronal death, which was associated with the attenuated inflammatory response. Moreover, silencing of NOX2 in microglia suppressed the expression of NOD2 and the inflammatory response induced by 6-OHDA and attenuated the toxicity of conditioned medium from 6-OHDA or MDP-stimulated microglia to neuronal cells. Furthermore, apocynin treatment inhibited NOD2 upregulation and DA degeneration in the SN of WT mice induced by 6-OHDA and MDP.ConclusionThis study provides the direct evidence that NOD2 is related to 6-OHDA-induced DA degeneration through NOX2-mediated oxidative stress, indicating NOD2 is a novel innate immune signaling molecule participating in PD inflammatory response.

The NOD1 and NOD2 in mandarinfish (Siniperca chuatsi): molecular characterization, tissue distribution, and expression analysis

BackgroundNOD-like receptors (NLRs) are a family of cytoplasmic pattern recognition receptors (PRRs), of which NOD1 and NOD2, are the main representative members. Many investigations have focused on the role of NOD1 and NOD2 in the innate immune response in Cypriniformes and Siluriformes. As an important economic fish in Perciformes, little is known about the function of NOD1 and NOD2 in mandarinfish (Siniperca chuatsi).ResultsThe full-length NOD1 and NOD2 cDNA sequence was obtained using reverse transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE). The mandarinfish NOD1 and NOD2 cDNA sequences contain 3247 bp and 3257 bp, and encode 918 amino acids and 988 amino acids, respectively. Multiple sequence alignments showed that mNOD1 and mNOD2 share high similarity with that from other vertebrates. RT-PCR analysis revealed that relatively high levels of mNOD1 and mNOD2 mRNA were detected in gill and head kidney tissues, compared with the heart, spleen, liver, muscle, and intestine. In addition, the relative levels of mNOD1 and mNOD2 transcripts were significantly upregulated in three tissues when the fishes were challenged with LPS and Poly I:C, interestingly, the NOD1 mRNA got peaked earlier than NOD2 after LPS induction in the spleen, gill, and head kidney, and during Poly I:C treatment, the NOD2 mRNA got peaked at 8 h in spleen and gill, while NOD1 showed significant higher expression at 24 h post infection, besides, in head kidney, the NOD2 mRNA showed a great increasing trend and NOD1 got peaked at 16 h. Therefore the mNOD1 and mNOD2 may act differently within different tissues in different time during antiviral and antibacterial defense.ConclusionsThese results revealed the dynamic mNOD1 and mNOD2 expression during viral and bacterial infections, which suggested the NOD1 and NOD2 play important roles in innate immune of mandarinfish.

LSECs express functional NOD1 receptors: A role for NOD1 in LSEC maturation-induced T cell immunity in vitro

Liver sinusoidal endothelial cells (LSECs) are organ resident APCs capable of antigen presentation and subsequent tolerization of T cells under physiological conditions. In this study, we investigated whether LSEC pretreatment with NOD-like receptor (NLR) agonists can switch the cells from a tolerogenic to an immunogenic state and promote the development of T cell immunity. LSECs constitutively express NOD1, NOD2 and RIPK2. Stimulation of LSECs with DAP induced the activation of NF-κB and MAP kinases and upregulated the expression of chemokines (CXCL2/9, CCL2/7/8) and cytokines (IFN-γ, TNF-α and IL-2). Pretreatment of LSECs with DAP induced significantly increased IFN-γ and IL-2-production by HBV-stimulated CD8+ T cells primed by DAP-treated LSECs. Consistently, a significant reduction in the HBV DNA and HBsAg level occurred in mice receiving T cells primed by DAP-treated LSECs. MDP stimulation had no impact on LSECs or HBV-stimulated CD8+ T cells primed with MDP-treated LSECs except for the upregulation of PD-L1. DAP stimulation in vitro could promote LSEC maturation and activate HBV-specific T cell responses. These results are of particular relevance for the regulation of the local innate immune response against HBV infections.

NOD2: Activation During Bacterial and Viral Infections, Polymorphisms and Potential as Therapeutic Target.

Nucleotide-binding domain (NBD) leucine-rich repeat (LRR)-containing receptors or NLRs are a family of receptors that detect both, molecules associated to pathogens and alarmins, and are located mainly in the cytoplasm. NOD2 belongs to the NLR family and is a dynamic receptor capable of interacting with multiple proteins and modulate immune responses in a stimuli-dependent manner. The experimental evidence shows that interaction between NOD2 structural domains and the effector proteins shape the overall response against bacterial or viral infections. Other reports have focused on the importance of NOD2 not only in infection but also in maintaining tissue homeostasis. However, not only protein interactions relate to function but also certain polymorphisms in the gene that encodes NOD2 have been associated with inflammatory diseases, such as Crohn's disease. Here, we review the importance and general characteristics of NOD2, discussing its participation in infections caused by bacteria and viruses as well as its interaction with other pathogen recognition receptors or effectors to induce antibacterial and antiviral responses. Finally, the role of NOD2 in chronic inflammatory conditions and its potential to be targeted therapeutically are examined.

The host control of a clinical isolate strain of P. aeruginosa infection is independent of Nod-1 but depends on MyD88.

The objective of this study was to investigate the role of Nod1 in the recruitment of neutrophils into the infection site and in the establishment of the inflammatory response elicited by a clinical isolate strain of P. aeruginosa in vivo, while comparing it to the well-established role of MyD88 in this process. Wild-type, Nod1-/- and MyD88-/- mice, all with a C57Bl/6 background. Mice were intranasally infected with Pseudomonas aeruginosa DZ605. Bronchoalveolar lavage and blood were harvested 6 or 20h post-infection for evaluating bacterial load, chemokine levels and neutrophil migration. Survival post-infection was also observed. We show here that wild-type and Nod1-/- mice induce similar lung chemokine levels, neutrophil recruitment, and bacterial load, thus leading to equal survival rates upon P. aeruginosa pulmonary infection. Furthermore, we confirmed the essential role of MyD88-dependent signalling in recruiting neutrophils and controlling P. aeruginosa-induced pulmonary infection. The results suggest that in contrast to MyD88, under our experimental conditions, the absence of Nod1 does not impair the recruitment of neutrophils in response to P. aeruginosa DZ605.

Nucleotide-binding oligomerization domain 1 is dispensable for host immune responses against pulmonary infection of Acinetobacter baumannii in mice

Nucleotide-binding domain 1 (Nod1) is a cytosolic receptor that is responsible for the recognition of a bacterial peptidoglycan motif containing meso-diaminophimelic acid. In this study, we sought to identify the role of Nod1 in host defense in vivo against pulmonary infection by multidrug resistant Acinetobacter baumannii. Wildtype (WT) and Nod1-deficient mice were intranasally infected with 3x107 CFU of A. baumannii and sacrificed at 1 and 3 days post-infection (dpi). Bacterial CFUs, cytokines production, histopathology, and mouse β-defensins (mBD) in the lungs of infected mice were evaluated. The production of cytokines in response to A. baumannii was also measured in WT and Nod1-deficient macrophages. The bacterial clearance in the lungs was not affected by Nod1 deficiency. Levels of IL-6, TNF-α, and IL-1β in the lung homogenates were comparable at days 1 and 3 between WT and Nod1-deficient mice, except the TNF-α level at day 3, which was higher in Nod1-deficient mice. There was no significant difference in lung pathology and expression of mBDs (mBD1, 2, 3, and 4) between WT and Nod1-deficient mice infected with A. baumannii. The production of IL-6, TNF-α, and NO by macrophages in response to A baumannii was also comparable in WT and Nod1-deficient mice. Our results indicated that Nod1 does not play an important role in host immune responses against A. baumannii infection.

An inflammatory role for NOD1 in decidua and placenta of normal and preeclamptic pregnancies

An inflammatory role for NOD1 in decidua and placenta of normal and preeclamptic pregnancies

NOD1 deficiency impairs CD44a/Lck as well as PI3K/Akt pathway

Pattern recognition receptors (PRRs) are crucial for host defense and tissue homeostasis against infecting pathogens. PRRs are highly conserved cross species, suggesting their key roles in fundamental biological processes. Though much have been learned for NOD1 receptor in the innate and adaptive immune responses, the roles of NOD1 during embryonic and larval stages remain poorly understood. Here, we report that NOD1 is necessary for the modulation of PI3K-Akt pathway and larval survival in zebrafish. Transcriptome analysis revealed that the significantly enriched pathways in NOD1−/− zebrafish larvae were mainly involved in metabolism and immune system processes. Biochemical analysis demonstrated that NOD1 was required for the expression of CD44a that, in turn, activated the PI3K-Akt pathway during larval development. Conversely, over-expression of CD44a in NOD1-deficient zebrafish restored the modulation of the PI3K-Akt pathway and improved larval survival. Collectively, our work indicates that NOD1 plays a previously undetected protective role in larval survival through CD44a-mediated activation of the PI3K-Akt signaling.