Knockout NOD Mice Research Articles

AIEC colonization and pathogenicity: Influence of previous antibiotic treatment and preexisting inflammation

Inflammatory bowel diseases (IBD) patients are abnormally colonized by adherent-invasive Escherichia coli (AIEC). NOD2 gene mutations impair intracellular bacterial clearance. We evaluated the impact of antibiotic treatment on AIEC colonization in wildtype (WT) and NOD2 knockout mice (NOD2KO) and the consequences on intestinal inflammation. After 3 days of antibiotic treatment, mice were infected for 2 days with 10⁹ CFU AIEC and sacrificed 1, 5, and 60 days later. In parallel, mice were challenged with AIEC subsequent to a dextran sodium sulfate (DSS) treatment and sacrificed 9 days later. Ileum, colon, and mesenteric tissues were sampled for AIEC quantification and evaluation of inflammation. Without antibiotic treatment, AIEC was not able to colonize WT and NOD2KO mice. Compared with nontreated animals, antibiotic treatment led to a significant increase in ileal and colonic colonization of AIEC in WT and/or NOD2KO mice. Persistent AIEC colonization was observed until day 5 only in NOD2KO mice, disappearing at day 60. Mesenteric translocation of AIEC was observed only in NOD2KO mice. No inflammation was observed in WT and NOD2KO mice treated with antibiotics and infected with AIEC. During DSS-induced colitis, colonization and persistence of AIEC was observed in the colon. Moreover, a dramatic increase in clinical, histological, and molecular parameters of colitis was observed in mice infected with AIEC but not with a commensal E. coli strain. Antibiotic treatment was necessary for AIEC colonization of the gut and mesenteric tissues and persistence of AIEC was dependent on NOD2. AIEC exacerbated a preexisting DSS-induced colitis in WT mice.

NOD2 Deficiency Results in Increased Susceptibility to Peptidoglycan-Induced Uveitis in Mice

The innate immune receptor NOD2 is a genetic cause of uveitis (Blau syndrome). Intriguingly, in the intestine where polymorphisms of NOD2 predispose to Crohn's disease, NOD2 reportedly suppresses inflammation triggered by the bacterial cell wall component, peptidoglycan (PGN). Whether NOD2 exerts a similar capacity in the regulation of ocular inflammation to PGN has not been explored. NOD2, NOD1, or MyD88 knockout (KO) mice and their wild-type (WT) controls were administered an intravitreal injection of PGN (a metabolite of which is the NOD2 agonist, muramyl dipeptide), or synthetic TLR2/1 and TLR2/6 agonists, Pam₃CSK4 and FSL-1. Ocular inflammation was assessed by intravital microscopy and histopathology. Cytokine production in eye tissue homogenates was measured by ELISA. PGN triggered uveitis in mice. This inflammation was abolished in the absence of the TLR signaling mediator MyD88. NOD2 exerted a negative regulatory role because PGN-triggered eye inflammation was exacerbated in NOD2 KO mice. Increased intravascular response coincided with enhanced leukocytes within the aqueous and vitreous humors. The enhanced susceptibility of NOD2 KO mice to PGN uveitis coincided with increased cytokine production of IL-12p40, IL-17, and IL-23 but not IL-12p70, TNFα, or IFNγ. NOD1 deficiency did not result in the same sensitivity to PGN. Ocular inflammation induced by synthetic TLR2 agonists required MyD88 but not NOD2 or NOD1. NOD2 may serve differential roles in the eye to promote inflammation while also tempering cell responses to PGN akin to what has been reported in colitis.

Antibiotics Induced Commensal Flora Disruption Favours Escherichia coli AIEC (LF82) Colonization in Wild Type and NOD2 Knock-out Mice

Antibiotics Induced Commensal Flora Disruption Favours Escherichia coli AIEC (LF82) Colonization in Wild Type and NOD2 Knock-out Mice

Testing the Role of P2X7 Receptors in the Development of Type 1 Diabetes in Nonobese Diabetic Mice

Abstract Although P2rx7 has been proposed as a type 1 diabetes (T1D) susceptibility gene in NOD mice, its potential pathogenic role has not been directly determined. To test this possibility, we generated a new NOD stock deficient in P2X7 receptors. T1D development was not altered by P2X7 ablation. Previous studies found CD38 knockout (KO) NOD mice developed accelerated T1D partly because of a loss of CD4+ invariant NKT (iNKT) cells and Foxp3+ regulatory T cells (Tregs). These immunoregulatory T cell populations are highly sensitive to NAD-induced cell death activated by ADP ribosyltransferase-2 (ART2)-mediated ADP ribosylation of P2X7 receptors. Therefore, we asked whether T1D acceleration was suppressed in a double-KO NOD stock lacking both P2X7 and CD38 by rescuing CD4+ iNKT cells and Tregs from NAD-induced cell death. We demonstrated that P2X7 was required for T1D acceleration induced by CD38 deficiency. The CD38 KO-induced defects in homeostasis of CD4+ iNKT cells and Tregs were corrected by coablation of P2X7. T1D acceleration in CD38-deficient NOD mice also requires ART2 expression. If increased ADP ribosylation of P2X7 in CD38-deficient NOD mice underlies disease acceleration, then a comparable T1D incidence should be induced by coablation of both CD38 and ART2, or CD38 and P2X7. However, a previously established NOD stock deficient in both CD38 and ART2 expression is T1D resistant. This study demonstrated the presence of a T1D resistance gene closely linked to the ablated Cd38 allele in the previously reported NOD stock also lacking ART2, but not in the newly generated CD38/P2X7 double-KO line.

Mechanisms of TNF induction by heat-killed Staphylococcus aureus differ upon the origin of mononuclear phagocytes

Mononuclear phagocytes are among the first immune cells activated after pathogens invasion. Although they all derive from the same progenitor in the bone marrow, their characteristics differ on the compartment from which they are derived. In this work, we investigated the contribution of phagocytosis for tumor necrosis factor (TNF) production by murine mononuclear phagocytes (monocytes, peritoneal and alveolar macrophages) in response to heat-killed Staphylococcus aureus (HKSA). Mononuclear phagocytes behaved differently, depending on their compartment of residence. Indeed, when bacterial uptake or phagosome maturation was blocked, activation through membrane receptors was sufficient for a maximal production of TNF and interleukin-10 by peritoneal macrophages. In contrast, monocytes, and to a lesser extent alveolar macrophages, required phagocytosis for optimal cytokine production. While investigating the different actors of signalization, we found that p38 kinase and phosphatidylinositol 3-kinase were playing an important role in HKSA phagocytosis and TNF production. Furthermore, blocking the α(5)β(1)-integrin significantly decreased TNF production in response to HKSA in all three cell types. Finally, using mononuclear phagocytes from NOD2 knockout mice, we observed that TNF production in response to HKSA was dependent on NOD2 for monocytes and peritoneal macrophages. In conclusion, we demonstrate that the mechanisms of activation leading to TNF production in response to HKSA are specific for each mononuclear phagocyte population and involve different recognition processes and signaling pathways. The influence of the compartments on cell properties and behavior should be taken into account, to better understand cell physiology and host-pathogen interaction, and to define efficient strategies to fight infection.

NOD2 Negatively Regulates Organic Dust-Induced Inflammation in Monocytes/Macrophages

RATIONALE: Chronic organic dust exposure in the agricultural industry results in significant airway disease. Since we have recently demonstrated high concentration of peptidoglycan in large animal farming environments, we examined in vitro, the role of the intracellular peptidoglycan breakdown product sensor, nucleotide oligomerization domain (NOD)2, in regulating organic dust-induced inflammation.METHODS: Organic dust extract (ODE) from swine operations was utilized. Adherent THP-1 monocytes were transfected with NOD2 or non-targeting siRNA by HiPerfect system. Transfected cells were subsequently stimulated with and without 1% ODE and as a control, the NOD2 agonist, muramyl dipetide (MDP), for 24 hours. Transfection efficiency was evaluated by real-time RT-PCR. Next, lung macrophages isolated from wild type and NOD2 knockout mice were ex vivo stimulated with 1% ODE for 24 hours. Cell-free supernatants for mediators were evaluated by ELISA.RESULTS: Relative mRNA expression of NOD2 in MDP- and ODE-stimulated NOD2 knockdown cells was significantly reduced to 32.8% ± 9.6% and 34.85% ± 8.6%, respectively. As anticipated, TNFα and CXCL8 secretion was diminished in NOD2 knockdown cells stimulated with MDP (p < 0.05; N = 3). However, stimulation of NOD2 knockdown cells with ODE resulted in significantly enhanced CXCL8 and IL-6 secretion as compared to control, but no change in TNFα (N = 3). Confirming these findings, murine NOD2-/- lung macrophages demonstrated significantly enhanced KC and MIP-2 (human CXCL8 homologs), IL-6, but not TNFα secretion, with ODE stimulation as compared to wild type lung macrophages (p < 0.05; N = 4 mice/group).CONCLUSIONS: The peptidoglycan breakdown product intracellular sensor, NOD2, appears to negatively regulate organic dust-induced macrophage inflammation in a selective manner. RATIONALE: Chronic organic dust exposure in the agricultural industry results in significant airway disease. Since we have recently demonstrated high concentration of peptidoglycan in large animal farming environments, we examined in vitro, the role of the intracellular peptidoglycan breakdown product sensor, nucleotide oligomerization domain (NOD)2, in regulating organic dust-induced inflammation. METHODS: Organic dust extract (ODE) from swine operations was utilized. Adherent THP-1 monocytes were transfected with NOD2 or non-targeting siRNA by HiPerfect system. Transfected cells were subsequently stimulated with and without 1% ODE and as a control, the NOD2 agonist, muramyl dipetide (MDP), for 24 hours. Transfection efficiency was evaluated by real-time RT-PCR. Next, lung macrophages isolated from wild type and NOD2 knockout mice were ex vivo stimulated with 1% ODE for 24 hours. Cell-free supernatants for mediators were evaluated by ELISA. RESULTS: Relative mRNA expression of NOD2 in MDP- and ODE-stimulated NOD2 knockdown cells was significantly reduced to 32.8% ± 9.6% and 34.85% ± 8.6%, respectively. As anticipated, TNFα and CXCL8 secretion was diminished in NOD2 knockdown cells stimulated with MDP (p < 0.05; N = 3). However, stimulation of NOD2 knockdown cells with ODE resulted in significantly enhanced CXCL8 and IL-6 secretion as compared to control, but no change in TNFα (N = 3). Confirming these findings, murine NOD2-/- lung macrophages demonstrated significantly enhanced KC and MIP-2 (human CXCL8 homologs), IL-6, but not TNFα secretion, with ODE stimulation as compared to wild type lung macrophages (p < 0.05; N = 4 mice/group). CONCLUSIONS: The peptidoglycan breakdown product intracellular sensor, NOD2, appears to negatively regulate organic dust-induced macrophage inflammation in a selective manner.

Transplanted islets from MHC class I knockout NOD mice maintain function in diabetic NOD recipients

Transplanted islets from MHC class I knockout NOD mice maintain function in diabetic NOD recipients

Induction of anti-whole GAD65 reactivity in vivo results in disease suppression in type 1 diabetes

Most type 1 diabetes mellitus is caused by autoimmune pancreatic beta-cell destruction. Several antigens such as insulin, glutamic acid decarboxylase (GAD) and islet-specific glucose-6-phosphatase catalytic subunit related protein (IGRP) are considered to take part in the autoimmune destructive process. Because the role of GAD in the disease process of type 1 diabetes is still controversial, we investigated the disease phenotype upon in vivo induction of whole GAD65 reactivity using a GAD65 homo knockout NOD splenocytes to NOD-scid transfer system. Splenocytes from 8 to 10-week-old female GAD65 homo knockout (=KOT splenocytes) or age-matched wild type (=WTT splenocytes) NOD mice were transferred into female NOD-scid recipients. As compared to recipients of WTT splenocytes, the onset of diabetes in recipients of KOT splenocytes was significantly delayed ( p < 0.001). Moreover, TGF-β expression was enhanced in the pancreas from recipients of KOT splenocytes. Splenocytes from recipients of KOT splenocytes produced IL-10 (/IFN-γ) upon GAD65 stimulation, whereas those from recipients of WTT splenocytes did not. Based upon these results, we propose that anti-whole GAD65-reactive T cells have the ability to regulate the development of type 1 diabetes.

NOD2, the Gene Responsible for Familial Granulomatous Uveitis, in a Mouse Model of Uveitis

NOD2 plays an important role in the recognition of intracellular bacteria through its ability to sense the components of bacterial peptidoglycan (PGN), namely muramyl dipeptide (MDP) and muramyl tripeptide (MTP). Specific mutations in the human NOD2 gene cause Blau syndrome, an autosomal dominant form of uveitis, arthritis, and dermatitis. As a first step toward understanding the role of NOD2 in the pathogenesis of uveitis, the authors developed a mouse model of MDP-dependent uveitis. BALB/c mice and mice deficient in L-selectin or NOD2 received intravitreal injection of MDP, MTP, or PGN. The intravascular response within the iris and cellular infiltration was quantified by intravital microscopy and histologic assessment. MDP induced an acute, ocular inflammatory response, wherein rolling and adhering leukocytes within the vasculature were significantly increased within 6 hours after MDP treatment. A minor increase in cellular infiltration occurred at 12 hours after MDP treatment. The adhesion molecule L-selectin participated in MDP-induced vascular inflammation because L-selectin knockout mice showed a significant decrease in the number of rolling cells. Importantly, NOD2 plays an essential role in ocular inflammation induced by MDP, as indicated by the fact that uveitis did not develop in Nod2 knockout mice in response to MDP. Nod2 knockout mice also showed abolished ocular inflammation in response to MTP but not to PGN treatment. These findings demonstrate a novel mouse model of uveitis, wherein NOD2 plays an essential role in inflammation induced by the minimal components of PGN. Thus, innate immune responses mediated by NOD2 may participate in the development of uveitis in response to bacterial products.

Long‐Term Prevention of Diabetes and Marked Suppression of Insulin Autoantibodies and Insulitis in Mice Lacking Native Insulin B9–23 Sequence

We analyzed double native insulin gene knockout NOD mice with a mutated (B16:alanine) proinsulin transgene at multiple ages for the development of insulin autoantibodies, insulitis, and diabetes. In contrast to mice with at least one copy of a native insulin gene that expressed insulin antibodies, only 2 out of 21 (10%) double native insulin gene knockout mice with a mutated insulin transgene developed insulin autoantibodies. Of 21 double insulin knockout mice sacrificed between 10 to 48 weeks of age, only 5 showed minimal insulitis versus 100% of wild-type NOD and more than 90% of insulin 1 knockout mice. Consistent with robust suppression of insulin autoantibodies and insulitis, no double insulin knockout mice developed diabetes. In that the B9-23 peptide with B16A is an altered peptide ligand inducing Th2 responses, we analyzed transfer of splenocytes into NOD.SCID mice. There was no evidence for regulatory T cells able to inhibit transfer of diabetes by diabetogenic NOD splenocytes. Insulin peptide B9-23 is likely a crucial target for initiation of islet autoimmunity and further mutation of the sequence will be tested to attempt to eliminate all anti-islet autoimmunity.

CD4 T Cells Play Major Effector Role and CD8 T Cells Initiating Role in Spontaneous Autoimmune Myocarditis of HLA-DQ8 Transgenic IAb Knockout Nonobese Diabetic Mice

In humans, spontaneous autoimmune attack against cardiomyocytes often leads to idiopathic dilated cardiomyopathy (IDCM) and life-threatening heart failure. HLA-DQ8 transgenic IAb knockout NOD mice (NOD.DQ8/Ab(0); DQA1*0301, DQB1*0302) develop spontaneous anticardiomyocyte autoimmunity with pathology very similar to human IDCM, but why the heart is targeted is unknown. In the present study, we first investigated whether NOD/Ab(0) mice transgenic for a different DQ allele, DQ6, (DQA1*0102, DQB1*0602) would also develop myocarditis. NOD.DQ6/Ab(0) animals showed no cardiac pathology, implying that DQ8 is specifically required for the myocarditis phenotype. To further characterize the cellular immune mechanisms, we established crosses of our NOD.DQ8/Ab(0) animals with Rag1 knockout (Rag1(0)), Ig H chain knockout (IgH(0)), and beta(2)-microglobulin knockout (beta(2)m(0)) lines. Adoptive transfer of purified CD4 T cells from NOD.DQ8/Ab(0) mice with complete heart block (an indication of advanced myocarditis) into younger NOD.DQ8/Ab(0) Rag1(0) animals induced cardiac pathology in all recipients, whereas adoptive transfer of purified CD8 T cells or B lymphocytes had no effect. Despite the absence of B lymphocytes, NOD.DQ8/Ab(0)IgH(0) animals still developed complete heart block, whereas NOD.DQ8/Ab(0)beta(2)m(0) mice (which lack CD8 T cells) failed to develop any cardiac pathology. CD8 T cells (and possibly NK cells) seem to be necessary to initiate disease, whereas once initiated, CD4 T cells alone can orchestrate the cardiac pathology, likely through their capacity to recruit and activate macrophages. Understanding the cellular immune mechanisms causing spontaneous myocarditis/IDCM in this relevant animal model will facilitate the development and testing of new therapies for this devastating disease.

B7-2 (CD86) controls the priming of autoreactive CD4 T cell response against pancreatic islets.

The B7-1/2-CD28 system provides the critical signal for the generation of an efficient T cell response. We investigated the role played by B7-2 in influencing pathogenic autoimmunity from islet-reactive CD4 T cells in B7-2 knockout (KO) NOD mice which are protected from type 1 diabetes. B7-2 deficiency caused a profound diminishment in the generation of spontaneously activated CD4 T cells and islet-specific CD4 T cell expansion. B7-2 does not impact the effector phase of the autoimmune response as adoptive transfer of islet Ag-specific BDC2.5 splenocytes stimulated in vitro could easily induce disease in B7-2KO mice. CD4 T cells showed some hallmarks of hyporesponsiveness because TCR/CD28-mediated stimulation led to defective activation and failure to induce disease in NODscid recipients. Furthermore, CD4 T cells exhibited enhanced death in the absence of B7-2. Interestingly, we found that B7-2 is required to achieve normal levels of CD4+CD25+CD62L+ T regulatory cells because a significant reduction of these T regulatory cells was observed in the thymus but not in the peripheral compartments of B7-2KO mice. In addition, our adoptive transfer experiments did not reveal either pathogenic or regulatory potential associated with the B7-2KO splenocytes. Finally, we found that the lack of B7-2 did not induce a compensatory increase in the B7-1 signal on APC in the PLN compartment. Taken together these results clearly indicate that B7-2 plays a critical role in priming islet-reactive CD4 T cells, suggesting a simplified, two-cell model for the impact of this costimulatory molecule in autoimmunity against islets.