NOD2/CARD15 disease associations other than Crohn's disease

Selective autophagy of RIPosomes maintains innate immune homeostasis during bacterial infection

The NOD1/2-RIPK2 is a key cytosolic signaling complex that activates NF-κB pro-inflammatory response against invading pathogens. However, uncontrolled NF-κB signaling can cause tissue damage leading to chronic diseases. The mechanisms by which the NODs-RIPK2-NF-κB innate immune axis is activated and resolved remain poorly understood. Here, we demonstrate that bacterial infection induces the formation of endogenous RIPK2 oligomers (RIPosomes) that are self-assembling entities that coat the bacteria to induce NF-κB response. Next, we show that autophagy proteins IRGM and p62/SQSTM1 physically interact with NOD1/2, RIPK2 and RIPosomes to promote their selective autophagy and limit NF-κB activation. IRGM suppresses RIPK2-dependent pro-inflammatory programs induced by Shigella and Salmonella. Consistently, the therapeutic inhibition of RIPK2 ameliorates Shigella infection- and DSS-induced gut inflammation in Irgm1 KO mice. This study identifies a unique mechanism where the innate immune proteins and autophagy machinery are recruited together to the bacteria for defense as well as for maintaining immune homeostasis.

NOD2 deficiency increases retrograde transport of secretory IgA complexes in Crohn's disease

Intestinal microfold cells are the primary pathway for translocation of secretory IgA (SIgA)-pathogen complexes to gut-associated lymphoid tissue. Uptake of SIgA/commensals complexes is important for priming adaptive immunity in the mucosa. This study aims to explore the effect of SIgA retrograde transport of immune complexes in Crohn's disease (CD). Here we report a significant increase of SIgA transport in CD patients with NOD2-mutation compared to CD patients without NOD2 mutation and/or healthy individuals. NOD2 has an effect in the IgA transport through human and mouse M cells by downregulating Dectin-1 and Siglec-5 expression, two receptors involved in retrograde transport. These findings define a mechanism of NOD2-mediated regulation of mucosal responses to intestinal microbiota, which is involved in CD intestinal inflammation and dysbiosis.

Pathogenesis of Inflammatory Bowel Disease: Basic Science in the Light of Real-World Epidemiology

Major advances in the last few decades have favored the view of inflammatory bowel disease (IBD) as a disease of hyper- or, more often, paradoxical hyporesponsiveness of the gut-associated immune system. The relevant pivot seems to be the loss of the balance between gut-associated pro-inflammatory lymphocytes and the indwelling microbiome species, with inner regulatory circuits (regulatory T-lymphocytes, T-reg) and outer factors (such as drugs, tobacco, diet components) contributing to complicate the matter. Light might be shed by the observation of the real-world IBD epidemiology, which may help unveil the factors that tend to cluster IBD cases to certain geographical areas. A transitional mind frame between bench and real-world gastroenterology could hopefully contribute to restrain the mounting epidemic of IBD in the Western world and to halt the more recent increases seen in many Eastern countries.

RIP2 filament formation is required for NOD2 dependent NF-κB signalling

Activation of the innate immune pattern recognition receptor NOD2 by the bacterial muramyl-dipeptide peptidoglycan fragment triggers recruitment of the downstream adaptor kinase RIP2, eventually leading to NF-κB activation and proinflammatory cytokine production. Here we show that full-length RIP2 can form long filaments mediated by its caspase recruitment domain (CARD), in common with other innate immune adaptor proteins. We further show that the NOD2 tandem CARDs bind to one end of the RIP2 CARD filament, suggesting a mechanism for polar filament nucleation by activated NOD2. We combine X-ray crystallography, solid-state NMR and high-resolution cryo-electron microscopy to determine the atomic structure of the helical RIP2 CARD filament, which reveals the intermolecular interactions that stabilize the assembly. Using structure-guided mutagenesis, we demonstrate the importance of RIP2 polymerization for the activation of NF-κB signalling by NOD2. Our results could be of use to develop new pharmacological strategies to treat inflammatory diseases characterised by aberrant NOD2 signalling.

A Chinese case series of Yao syndrome and literature review

Yao syndrome (YAOS), formerly named NOD2-associated autoinflammatory disease, is a periodic disease characterized by fever, dermatitis, polyarthritis, distal extremity swelling, and gastrointestinal and sicca-like symptoms associated with specific NOD2 sequence variants. All patients in the literature were Caucasians. Herein, we report the first case series of YAOS in China to further expand the clinical and genetic characteristics of this disorder. A retrospective review of patients who were diagnosed with YAOS at our tertiary medical center was conducted. Three Han Chinese women with YAOS were included. Recurrent fever occurred in all patients and each febrile episode lasted several days to several weeks, and asymptomatic intervals ranged from several weeks to several months. Two patients experienced intermittent arthritis/arthralgia and abdominal pain, and one had sicca-like symptoms. None had dermatitis. Three variants in NOD2 were identified, including Q902K, R541P, and Y514H. The patients' symptoms significantly improved after treatment with glucocorticoids and/or sulfasalazine. YAOS exists in the Chinese population, and it may be a global disorder. Our patients appear to exhibit somewhat distinct clinical phenotypes from those in the Caucasian population, and three novel NOD2 variants have been identified in the disease.

Association of LACC1, CEBPB-PTPN1, RIPK2 and ADO-EGR2 with ocular Behcet's disease in a Chinese Han population

Background

An Immunochip study recently identified the association of a number of new genetic loci with Behcet’s disease (BD).

Objective

To confirm the association between new genetic loci reported in an Immunochip study and BD in a Han Chinese population.

Methods

A two-stage association study was carried out in 1238 patients with BD and 1458 healthy controls. Twenty-two candidate single nucleotide polymorphisms (SNPs) were selected for genotyping by iPLEXGold genotyping or TaqMan SNP assays and a meta-analysis was performed for significantly associated markers.

Results

The results showed that four SNPs (LACC1/rs9316059, CEBPB-PTPN1/rs913678, ADO-EGR2/rs224127 and RIPK2/rs10094579) were associated with BD in an allelic association test (rs9316059 T allele: p_c=4.95×10⁻⁸, OR=0.687; rs913678 C allele: p_c=3.01×10⁻⁴, OR=1.297; rs224127 A allele: p_c=3.77×10⁻⁴, OR=1.274; rs10094579 A allele: p_c=6.93×10⁻⁴, OR=1.302). For four SNPs tested by meta-analysis, the association with BD was strengthened and all exceeded genome-wide significance (rs9316059: p=2.96×10⁻¹⁶; rs913678: p=2.09×10⁻¹⁶; rs224127: p=5.28×10⁻¹³; rs10094579: p=9.21×10⁻¹¹).

Conclusions

Our findings confirmed the association of four loci (LACC1, CEBPB-PTPN1, ADO-EGR2 and RIPK2) in Chinese Han patients with BD.

Immunopathogenesis of inflammatory bowel disease and mechanisms of biological therapies

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract with a multifactorial pathophysiology. Full comprehension of IBD pathology is still out of reach and, therefore, treatment is far from ideal. Nevertheless, components involved in IBD pathogenesis including environmental, genetic, microbial, and immunological factors are continuously being investigated and the improved knowledge contributes to the development of new therapies. In this article we review the aspects of the immunopathogenesis of IBD, with focus on mucosal immunity, and discuss mechanisms of action for current and emerging biological therapies.

Crohn's disease - genetic factors and progress of the disease

BACKGROUND AND OBJECTIVES

Crohn's disease is a multifactorial inflammatory disease affecting mainly the gastrointestinal tract. The genetic factors that are involved in the disease include mainly three mutations of the gene NOD2/CARD15 (R702W, G908R, 3020insC). The aim of this study was to determine the relationship between the presence of these variants and disease phenotype.

MATERIAL AND METHODS

70 patients with Crohn's disease were examined for the presence of the above-mentioned mutations. The researchers used the medical records to retrospectively obtain clinical data and together with the information obtained prospectively according to the protocol they analysed the connection between gene mutations and disease phenotype.

RESULTS

At least one mutation was found in 22 patients with Crohn's disease (32%), four patients were found to have two different mutations (composed heterozygotes - 6%) and six patients (9%) were homozygotes for the 3020insC gene. No significant differences were found between the groups with wild-type form and the mutated form of the NOD2 / CARD15 gene with respect to age at the time of diagnosis, form of the disease or localization according to the Montreal classification.

CONCLUSION

Mutations of the NOD2 / CARD15 gene did not significantly affect the frequency of reoperations, homozygotes with 3020insC gene mutations, however, represented a high risk group. The phenotype was not related significantly to the presence of the examined mutations.

Identification of Potent and Selective RIPK2 Inhibitors for the Treatment of Inflammatory Diseases

NOD2 (nucleotide-binding oligomerization domain-containing protein 2) is an internal pattern recognition receptor that recognizes bacterial peptidoglycan and stimulates host immune responses. Dysfunction of NOD2 pathway has been associated with a number of autoinflammatory disorders. To date, direct inhibitors of NOD2 have not been described due to technical challenges of targeting the oligomeric protein complex. Receptor interacting protein kinase 2 (RIPK2) is an intracellular serine/threonine/tyrosine kinase, a key signaling partner, and an obligate kinase for NOD2. As such, RIPK2 represents an attractive target to probe the pathological roles of NOD2 pathway. To search for selective RIPK2 inhibitors, we employed virtual library screening (VLS) and structure based design that eventually led to a potent and selective RIPK2 inhibitor 8 with excellent oral bioavailability, which was used to evaluate the effects of inhibition of RIPK2 in various in vitro assays and ex vivo and in vivo pharmacodynamic models.

NLRs: Nucleotide-Binding Domain and Leucine-Rich-Repeat-Containing Proteins

Eukaryotes have evolved strategies to detect microbial intrusion and instruct immune responses to limit damage from infection. Recognition of microbes and cellular damage relies on the detection of microbe-associated molecular patterns (MAMPs, also called PAMPS, or pathogen-associated molecular patterns) and so-called "danger signals" by various families of host pattern recognition receptors (PRRs). Members of the recently identified protein family of nucleotide-binding domain andleucine-rich-repeat-containing proteins (NLR), including Nod1, Nod2, NLRP3, and NLRC4, have been shown to detect specific microbial motifs and danger signals for regulating host inflammatory responses. Moreover, with the discovery that polymorphisms in NOD1, NOD2, NLRP1, and NLRP3 are associated with susceptibility to chronic inflammatory disorders, the view has emerged that NLRs act not only as sensors butalso can serve as signaling platforms for instructing and balancing host immune responses. In this chapter, we explore the functions of these intracellular innate immune receptors and examine their implication in inflammatory diseases.

NOD2 Arg702Trp Polymorphism in Romanian Patients with Gastric Cancer

Purpose. Our study aimed to assess a possible correlation between NOD2 Arg702Trp (rs2066844) polymorphism and gastric cancer risk in a Romanian population. Material/Methods. A total of 322 subjects (72 patients with gastric adenocarcinoma and 250 healthy controls) were included. Genomic DNA was extracted from blood leukocytes and NOD2 Arg702Trp polymorphism was genotyped by Real-Time PCR using specific TaqMan probes. Results. No statistically significant difference was observed between gastric cancer patients and controls when we compared one genotype with other genotype (the CC genotype serves as reference) (OR 0.45, 95% CI: 0.10 - 2.05) or when we compared allele frequencies (the C allele serves as reference) (OR 0.46, 95% CI: 0.11 - 2.04). We examined separately the association of this polymorphism with tumor site and histologic type and no correlation was found. Conclusion. NOD2 Arg702Trp polymorphism is not associated with gastric cancer risk and further investigations are needed to elucidate the contribution of NOD2 gene in gastric carcinogenesis.

Structural models of zebrafish (Danio rerio) NOD1 and NOD2 NACHT domains suggest differential ATP binding orientations: insights from computational modeling, docking and molecular dynamics simulations

Nucleotide-binding oligomerization domain-containing protein 1 (NOD1) and NOD2 are cytosolic pattern recognition receptors playing pivotal roles in innate immune signaling. NOD1 and NOD2 recognize bacterial peptidoglycan derivatives iE-DAP and MDP, respectively and undergoes conformational alternation and ATP-dependent self-oligomerization of NACHT domain followed by downstream signaling. Lack of structural adequacy of NACHT domain confines our understanding about the NOD-mediated signaling mechanism. Here, we predicted the structure of NACHT domain of both NOD1 and NOD2 from model organism zebrafish (Danio rerio) using computational methods. Our study highlighted the differential ATP binding modes in NOD1 and NOD2. In NOD1, γ-phosphate of ATP faced toward the central nucleotide binding cavity like NLRC4, whereas in NOD2 the cavity was occupied by adenine moiety. The conserved ‘Lysine’ at Walker A formed hydrogen bonds (H-bonds) and Aspartic acid (Walker B) formed electrostatic interaction with ATP. At Sensor 1, Arg328 of NOD1 exhibited an H-bond with ATP, whereas corresponding Arg404 of NOD2 did not. ‘Proline’ of GxP motif (Pro386 of NOD1 and Pro464 of NOD2) interacted with adenine moiety and His511 at Sensor 2 of NOD1 interacted with γ-phosphate group of ATP. In contrast, His579 of NOD2 interacted with the adenine moiety having a relatively inverted orientation. Our findings are well supplemented with the molecular interaction of ATP with NLRC4, and consistent with mutagenesis data reported for human, which indicates evolutionary shared NOD signaling mechanism. Together, this study provides novel insights into ATP binding mechanism, and highlights the differential ATP binding modes in zebrafish NOD1 and NOD2.

A RIPK2 inhibitor delays NOD signalling events yet prevents inflammatory cytokine production

Intracellular nucleotide binding and oligomerization domain (NOD) receptors recognize antigens including bacterial peptidoglycans and initiate immune responses by triggering the production of pro-inflammatory cytokines through activating NF-κB and MAP kinases. Receptor interacting protein kinase 2 (RIPK2) is critical for NOD-mediated NF-κB activation and cytokine production. Here we develop and characterize a selective RIPK2 kinase inhibitor, WEHI-345, which delays RIPK2 ubiquitylation and NF-κB activation downstream of NOD engagement. Despite only delaying NF-κB activation on NOD stimulation, WEHI-345 prevents cytokine production in vitro and in vivo and ameliorates experimental autoimmune encephalomyelitis in mice. Our study highlights the importance of the kinase activity of RIPK2 for proper immune responses and demonstrates the therapeutic potential of inhibiting RIPK2 in NOD-driven inflammatory diseases.

IBD candidate genes and intestinal barrier regulation

Technological advances in the large scale analysis of human genetics have generated profound insights into possible genetic contributions to chronic diseases including the inflammatory bowel diseases (IBDs), Crohn's disease and ulcerative colitis. To date, 163 distinct genetic risk loci have been associated with either Crohn's disease or ulcerative colitis, with a substantial degree of genetic overlap between these 2 conditions. Although many risk variants show a reproducible correlation with disease, individual gene associations only affect a subset of patients, and the functional contribution(s) of these risk variants to the onset of IBD is largely undetermined. Although studies in twins have demonstrated that the development of IBD is not mediated solely by genetic risk, it is nevertheless important to elucidate the functional consequences of risk variants for gene function in relevant cell types known to regulate key physiological processes that are compromised in IBD. This article will discuss IBD candidate genes that are known to be, or are suspected of being, involved in regulating the intestinal epithelial barrier and several of the physiological processes presided over by this dynamic and versatile layer of cells. This will include assembly and regulation of tight junctions, cell adhesion and polarity, mucus and glycoprotein regulation, bacterial sensing, membrane transport, epithelial differentiation, and restitution.

In vivo inhibition of RIPK2 kinase alleviates inflammatory disease

The RIPK2 kinase transduces signaling downstream of the intracellular peptidoglycan sensors NOD1 and NOD2 to promote a productive inflammatory response. However, excessive NOD2 signaling has been associated with numerous diseases, including inflammatory bowel disease (IBD), sarcoidosis and inflammatory arthritis, making pharmacologic inhibition of RIPK2 an appealing strategy. In this work, we report the generation, identification, and evaluation of novel RIPK2 specific inhibitors. These compounds potently inhibit the RIPK2 tyrosine kinase activity in in vitro biochemical assays and cellular assays, as well as effectively reduce RIPK2-mediated effects in an in vivo peritonitis model. In conjunction with the development of these inhibitors, we have also defined a panel of genes whose expression is regulated by RIPK2 kinase activity. Such RIPK2 activation markers may serve as a useful tool for predicting settings likely to benefit from RIPK2 inhibition. Using these markers and the FDA-approved RIPK2 inhibitor Gefitinib, we show that pharmacologic RIPK2 inhibition drastically improves disease in a spontaneous model of Crohn Disease-like ileitis. Furthermore, using novel RIPK2-specific inhibitors, we show that cellular recruitment is inhibited in an in vivo peritonitis model. Altogether, the data presented in this work provides a strong rationale for further development and optimization of RIPK2-targeted pharmaceuticals and diagnostics.

Advances in IBD genetics

IBD is a spectrum of chronic disorders that constitute an important health problem worldwide. The hunt for genetic determinants of disease onset and course has culminated in the Immunochip project, which has identified >160 loci containing IBD susceptibility genes. In this Review, we highlight how genetic association studies have informed our understanding of the pathogenesis of IBD by focusing research efforts on key pathways involved in innate immunity, autophagy, lymphocyte differentiation and chemotaxis. Several of these novel genetic markers and cellular pathways are promising candidates for patient stratification and therapeutic targeting.

Possible implication of bacterial infection in acute graft-versus-host disease after allogeneic hematopoietic stem cell transplantation

Graft-versus-host disease (GVHD) is still one of the major causes of morbidity and mortality in allogeneic hematopoietic stem cell transplantation (HSCT). In the pathogenesis of acute GVHD, it has been established that donor-derived T-cells activated in the recipient play a major role in GVHD in initiation and maintenance within an inflammatory cascade. To reduce the risk of GVHD, intensification of GVHD prophylaxis like T-cell depletion is effective, but it inevitably increases the risk of infectious diseases and abrogates beneficial graft-versus-leukemia effects. Although various cytokines are considered to play an important role in the pathogenesis of GVHD, GVHD initiation is such a complex process that cannot be prevented by means of single inflammatory cytokine inhibition. Thus, efficient methods to control the whole inflammatory milieu both on cellular and humoral view are needed. In this context, infectious diseases can theoretically contribute to an elevation of inflammatory cytokines after allogeneic HSCT and activation of various subtypes of immune effector cells, which might in summary lead to an aggravation of acute GVHD. The appropriate treatments or prophylaxis of bacterial infection during the early phase after allogeneic HSCT might be beneficial to reduce not only infectious-related but also GVHD-related mortality. Here, we aim to review the literature addressing the interactions of bacterial infections and GVHD after allogeneic HSCT.

Nucleotide-binding oligomerization domain (NOD) inhibitors: a rational approach toward inhibition of NOD signaling pathway

Dysregulation of nucleotide-binding oligomerization domains 1 and 2 (NOD1 and NOD2) has been implicated in the pathology of various inflammatory disorders, rendering them and their downstream signaling proteins potential therapeutic targets. Selective inhibition of NOD1 and NOD2 signaling could be advantageous in treating many acute and chronic diseases; therefore, harnessing the full potential of NOD inhibitors is a key topic in medicinal chemistry. Although they are among the best studied NOD-like receptors (NLRs), the therapeutic potential of pharmacological modulation of NOD1 and NOD2 is largely unexplored. This review is focused on the scientific progress in the field of NOD inhibitors over the past decade, including the recently reported selective inhibitors of NOD1 and NOD2. In addition, the potential approaches to inhibition of NOD signaling as well as the advantages and disadvantages linked with inhibition of NOD signaling are discussed. Finally, the potential directions for drug discovery are also discussed.

Inflammatory bowel disease: An archetype disorder of outer environment sensor systems

The pathogenesis of the two inflammatory bowel diseases (IBDs) phenotypes ulcerative colitis (UC) and Crohn's disease (CD) has remained elusive, thus frustrating attempts at defining a cure. IBD often presents as a complex inflammatory process wherein colon lesions (UC) or widespread ulceration and fissure (CD) might be accompanied by ancillary extra-intestinal manifestations involving the eye, skin, joints or liver, but also by full-blown "autoimmune" disorders from psoriasis and multiple sclerosis to rheumatoid arthritis; attempts at unraveling a link or a hierarchical order in these entities have proven almost fruitless. More recently, the input of genetics has suggested that the IBDs might be multi-organ inflammatory processes, elicited by a large number of low-penetrance susceptibility genes, with environmental factors needed to induce full-blown disease. At a noteworthy exception to this rule, the description of the nucleotide-oligomerization domain (NOD) gene mutations in CD came at the beginning of the 2000s: the NOD-LRR are part of a highly conserved microbial sensor system which respond to bacterial peptidoglycans by mounting an inflammatory response. At least in Caucasian patients, the prevalently loss-of-function mutation of NOD permitted to unexpectedly define CD as an immune deficiency state, and upon its recent description in apparently unrelated disorders such as the Blau syndrome (a granulomatous pediatric syndrome), and perhaps in psoriasis and chronic obstructive pulmonary disorders, has contributed to revolutionize our view of IBD and CD in particular. The latter affection, together with psoriasis and chronic pulmonary disease can now be included into a newly identified category named "barrier organ disease", wherein a barrier organ is defined as a large mucosal or epithelial surface with an abundant metagenomic microbial population and an underneath reactive tissue, the whole structure being in contact with the outer environment and capable to react to it. Personalized treatments and empowerment of research across different disease phenotypes should be the advantages of this novel mindset.

Inflammatory bowel disease: An archetype disorder of outer environment sensor systems

The pathogenesis of the two inflammatory bowel diseases (IBDs) phenotypes ulcerative colitis (UC) and Crohn's disease (CD) has remained elusive, thus frustrating attempts at defining a cure. IBD often presents as a complex inflammatory process wherein colon lesions (UC) or widespread ulceration and fissure (CD) might be accompanied by ancillary extra-intestinal manifestations involving the eye, skin, joints or liver, but also by full-blown "autoimmune" disorders from psoriasis and multiple sclerosis to rheumatoid arthritis; attempts at unraveling a link or a hierarchical order in these entities have proven almost fruitless. More recently, the input of genetics has suggested that the IBDs might be multi-organ inflammatory processes, elicited by a large number of low-penetrance susceptibility genes, with environmental factors needed to induce full-blown disease. At a noteworthy exception to this rule, the description of the nucleotide-oligomerization domain (NOD) gene mutations in CD came at the beginning of the 2000s: the NOD-LRR are part of a highly conserved microbial sensor system which respond to bacterial peptidoglycans by mounting an inflammatory response. At least in Caucasian patients, the prevalently loss-of-function mutation of NOD permitted to unexpectedly define CD as an immune deficiency state, and upon its recent description in apparently unrelated disorders such as the Blau syndrome (a granulomatous pediatric syndrome), and perhaps in psoriasis and chronic obstructive pulmonary disorders, has contributed to revolutionize our view of IBD and CD in particular. The latter affection, together with psoriasis and chronic pulmonary disease can now be included into a newly identified category named "barrier organ disease", wherein a barrier organ is defined as a large mucosal or epithelial surface with an abundant metagenomic microbial population and an underneath reactive tissue, the whole structure being in contact with the outer environment and capable to react to it. Personalized treatments and empowerment of research across different disease phenotypes should be the advantages of this novel mindset.

The immunology of fibrosis

Fibrosis is the production of excessive amounts of connective tissue, i.e., scar formation, in the course of reactive and reparative processes. Fibrosis develops as a consequence of various underlying diseases and presents a major diagnostically and therapeutically unsolved problem. In this review, we postulate that fibrosis is always a sequela of inflammatory processes and that the many different causes of fibrosis all channel into the same final stereotypical pathways. During the inflammatory phase, both innate and adaptive immune mechanisms are operative. This concept is exemplified by fibrotic diseases that develop as a consequence of tissue damage, primary inflammatory diseases, fibrotic alterations induced by foreign body implants, "spontaneous" fibrosis, and tumor-associated fibrotic changes.

RIP2 activity in inflammatory disease and implications for novel therapeutics

The role of NOD2 and RIP2 in inflammatory disease has been paradoxical. Whereas loss-of-function NOD2 polymorphisms cause CD, a granulomatous disease of the gastrointestinal tract, gain-of-function mutations cause EOS-a granulomatous disease primarily affecting the skin, joints, and eyes. Thus, gain-of-function mutations and loss-of-function polymorphisms cause granulomatous inflammatory disease, only in different anatomic locations. The situation is complicated further by the fact that WT NOD2 and WT RIP2 activity has been implicated in diseases such as asthma, inflammatory arthritis and MS. This article reviews the role that the NOD2:RIP2 complex plays in inflammatory disease, with an emphasis on the inhibition of this signaling pathway as a novel pharmaceutical target in inflammatory disease.

Innate and adaptive immunity in inflammatory bowel disease

Inflammatory bowel disease (IBD) includes Crohn's disease (CD) and ulcerative colitis (UC). The exact cause of IBD remains unknown. Available evidence suggests that an abnormal immune response against the microorganisms of the intestinal flora is responsible for the disease in genetically susceptible individuals. The adaptive immune response has classically been considered to play a major role in the pathogenesis of IBD. However, recent advances in immunology and genetics have clarified that the innate immune response is equally as important in inducing gut inflammation in these patients. In particular, an altered epithelial barrier function contributes to intestinal inflammation in patients with UC, while aberrant innate immune responses, such as antimicrobial peptide production, innate microbial sensing and autophagy are particularly associated to CD pathogenesis. On the other hand, besides T helper cell type (Th)1 and Th2 immune responses, other subsets of T cells, namely Th17 and regulatory T (Treg) cells, are likely to play a role in IBD. However, given the complexity and probably the redundancy of pathways leading to IBD lesions, and the fact that Th17 cells may also have protective functions, neutralization of IL-17A failed to induce any improvement in CD. Studying the interactions between various constituents of the innate and adaptive immune systems will certainly open new horizons in the knowledge about the immunologic mechanisms implicated in gut inflammation.

Nucleotide oligomerization domain 2 polymorphisms in patients with intestinal failure

BACKGROUND

Nucleotide oligomerization domain 2 (NOD2) has been associated with intestinal immunity after the discovery that its polymorphisms are linked to Crohn's disease (CD). Intestinal failure (IF) represents a wider spectrum of diseases where intestinal homeostasis has been disrupted.

AIM

To evaluate the prevalence of NOD2 mutations in a population with IF as well as its association with the different conditions causing this problem.

METHODS

One hundred ninety-two consecutive patients with IF and 103 healthy controls were genotyped for the three most common NOD2 polymorphisms. Genotypes were compared between the groups and were related to the entities causing IF.

RESULTS

A high percentage (26%) of patients had at least one of the three most common NOD2 polymorphisms, while only a 4.8% of healthy controls had a mutant genotype. In patients with IF, specific mutations for the 702W, 908R and 1007fs alleles were 11, 5 and 12.5%, respectively, compared with 0.9% (P = 0.0003), 1.9% (P = 0.1) and 1.9% (P = 0.001) in the control group. If we consider patients with any cause of IF other than CD, the percentage is still as high as 18.8%, with specific mutation frequencies of 7.6% (702W; P = 0.01), 5.8% (908R; P = 0.1) and 8.2% (1007fs; P = 0.002). We could not establish an association between a NOD2 mutant genotype with any other specific clinical condition other than CD.

CONCLUSION

Our finding supports the importance of NOD2 in the maintenance of intestinal immune homeostasis and may be important to a variety of intestinal stressors.

Nucleotide-binding oligomerization domain containing 2: structure, function, and diseases

OBJECTIVES

To systematically review literature about the structure and function of nucleotide-binding oligomerization domain containing 2 (NOD2) and its disease association.

METHODS

The English literature was searched using keywords "NOD2" and "disease". Relevant original and review articles were reviewed.

RESULTS

NOD2 is an intracellular protein and shares similar molecular structure with NOD1, pyrin, and cryopyrin. There are more than 100 NOD2 gene mutations, some of which have been linked to diseases such as Crohn disease, Blau syndrome, and NOD2-associated autoinflammatory disease (NAID). The NOD2 variants located in the leucine-rich repeat (LRR) region are susceptible to Crohn disease, and the variants in the nucleotide-binding domain (NBD) and in between the NBD and LRR are associated with Blau syndrome and NAID, respectively. No disease association with the gene variants has been found in rheumatoid arthritis, systemic lupus erythematosus, ankylosing spondylitis, psoriasis/psoriatic arthritis, adult sarcoidosis, granulomatous polyangiitis, or multiple sclerosis. The potential association of the NOD2 variants with graft-versus-host-disease remains controversial. NOD2 functions mainly through RICK or RIP2 to activate p38 mitogen-activated protein kinases and NF-κB, resulting in inflammatory response, and enhanced autophagic activity. Biologic therapy may be beneficial for NOD2-associated diseases, and new drug development may be realized based upon the signaling pathways.

CONCLUSIONS

NOD2 gene mutations are associated with several diseases, and some of the mutations are of diagnostic value in Blau disease and NAID. To understand the NOD2 function, disease association, and its pathogenesis is important given the ever increasing clinical significance of NOD2.

NOD2 Polymorphisms and Their Impact on Haematopoietic Stem Cell Transplant Outcome

Haematopoietic stem cell transplantation (HSCT) is a valuable tool in the treatment of many haematological disorders. Advances in understanding HLA matching have improved prognoses. However, many recipients of well-matched HSCT develop posttransplant complications, and survival is far from absolute. The pursuit of novel genetic factors that may impact on HSCT outcome has resulted in the publication of many articles on a multitude of genes. Three NOD2 polymorphisms, identified as disease-associated variants in Crohn's disease, have recently been suggested as important candidate gene markers in the outcome of HSCT. It was originally postulated that as the clinical manifestation of inflammatory responses characteristic of several post-transplant complications was of notable similarity to those seen in Crohn's disease, it was possible that they shared a common cause. Since the publication of this first paper, numerous studies have attempted to replicate the results in different transplant settings. The data has varied considerably between studies, and as yet no consensus on the impact of NOD2 SNPs on HSCT outcome has been achieved. Here, we will review the existing literature, summarise current theories as to why the data differs, and suggest possible mechanisms by which the SNPs affect HSCT outcome.

Oral Crohn's disease: is it a separable disease from orofacial granulomatosis? A review

Symptomatic oral Crohn's disease is comparatively rare. The relationship between orofacial granulomatosis, (where there is granulomatous inflammation and ulceration of the mouth in the absence of gastrointestinal disease) and true oral Crohn's disease is discussed along with the plethora of clinical oral disease presentations associated with both disorders and the differential diagnosis of oral ulceration in patients presenting to a gastroenterological clinic. Specific oral syndromes are outlined including the association between oral manifestations in Crohn's disease and the pattern of intestinal disease and their relationship to other recorded extraintestinal manifestations. The histological and immunological features of oral biopsies are considered as well as the principles of management of symptomatic oral disease. At present, it is suggested that both orofacial granulomatosis and oral Crohn's disease appear to be distinct clinical disorders.

NOD2, an intracellular innate immune sensor involved in host defense and Crohn's disease

Nucleotide-binding oligomerization domain 2 (NOD2) is an intracellular sensor for small peptides derived from the bacterial cell wall component, peptidoglycan. Recent studies have uncovered unexpected functions of NOD2 in innate immune responses such as induction of type I interferon and facilitation of autophagy; moreover, they have disclosed extensive cross-talk between NOD2 and Toll-like receptors, which has an indispensable role both in host defense against microbial infection and in the development of autoimmunity. Of particular interest, polymorphisms of CARD15 encoding NOD2 are associated with Crohn's disease and other autoimmune states such as graft vs. host disease. In this review, we summarize recent findings regarding normal functions of NOD2 and discuss the mechanisms by which NOD2 polymorphisms associated with Crohn's disease lead to intestinal inflammation.

New insights into gastrointestinal and hepatic granulomatous disorders

Numerous diseases that involve the gastrointestinal tract reveal the presence of granulomas on histological analysis. Granulomatous diseases can be either primary or secondary to environmental factors. Granulomas are dynamic structures composed of organized collections of activated macrophages, including epithelioid and multinucleated giant cells, surrounded by lymphocytes. The formation of granulomas is usually in response to antigenic stimulation and is orchestrated through cytokines, immune cells and host genetics. In this Review, the pathogenesis and etiologies of granulomas of the gastrointestinal tract and liver are discussed, as are the available diagnostic tools to help differentiate their various underlying etiologies. In addition, the role of granulomas in harboring latent tuberculosis is reviewed. The effects of tumor necrosis factor antagonists and interferon-α on the development of granulomas are also discussed.

Cooperative regulation of NOTCH1 protein-phosphatidylinositol 3-kinase (PI3K) signaling by NOD1, NOD2, and TLR2 receptors renders enhanced refractoriness to transforming growth factor-beta (TGF-beta)- or cytotoxic T-lymphocyte antigen 4 (CTLA-4)-mediated impairment of human dendritic cell maturation

Dendritic cells (DCs) as sentinels of the immune system are important for eliciting both primary and secondary immune responses to a plethora of microbial pathogens. Cooperative stimulation of a complex set of pattern-recognition receptors, including TLR2 and nucleotide-binding oligomerization domain (NOD)-like receptors on DCs, acts as a rate-limiting factor in determining the initiation and mounting of the robust immune response. It underscores the need for "decoding" these multiple receptor interactions. In this study, we demonstrate that TLR2 and NOD receptors cooperatively regulate functional maturation of human DCs. Intriguingly, synergistic stimulation of TLR2 and NOD receptors renders enhanced refractoriness to TGF-β- or CTLA-4-mediated impairment of human DC maturation. Signaling perturbation data suggest that NOTCH1-PI3K signaling dynamics assume critical importance in TLR2- and NOD receptor-mediated surmounting of CTLA-4- and TGF-β-suppressed maturation of human DCs. Interestingly, the NOTCH1-PI3K signaling axis holds the capacity to regulate DC functions by virtue of PKCδ-MAPK-dependent activation of NF-κB. This study provides mechanistic and functional insights into TLR2- and NOD receptor-mediated regulation of DC functions and unravels NOTCH1-PI3K as a signaling cohort for TLR2 and NOD receptors. These findings serve in building a conceptual foundation for the design of improved strategies for adjuvants and immunotherapies against infectious diseases.

Inflammatory bowel disease: beyond the boundaries of the bowel

Dysregulated inflammation in the gut, designated clinically as inflammatory bowel disease (IBD), is manifested by the prototypic phenotypes of an Arthus-like reaction restricted to the mucosa of the colon, as in ulcerative colitis, or a transmural granulomatous reaction, as in Crohn's disease, or an indeterminate form of the two polar types. That the inflammation of IBD can trespass the boundaries of the bowel has long been known, with articular, ophthalmologic, cutaneous, hepatobiliary or other complications/associations - some autoimmune and others not - affecting significant numbers of patients with IBD. Also notable is the frequency of diagnosis of IBD-type diseases on a background of systemic, (mostly myelo-hematological) disorders, associated with alterations of either (or both) innate or adaptive arms of the immune response. Finally, cases of IBD are reported to occur as an adverse effect of TNF inhibitors. Bone marrow transplant has been proven to be the only curative measure for some of the above cases. Thus, in effect, the IBDs should now be regarded as a systemic, rather than bowel-localized, disease. Genome-wide association studies have been informative in consolidating the view of three phenotypes of IBD (ulcerative colitis, Crohn's disease and mixed) and, notably, are revealing that the onset of IBD can be linked to polymorphisms in regulatory miRNAs, or to nucleotide sequences coding for regulatory lymphokines and/or their receptors. At the effector level, we emphasize the major role of the Th17/IL-23 axis in dictating the perpetuation of intestinal inflammation, augmented by a failure of physiological control by regulatory T-cells. In conclusion, there is a central genesis of the defects underlying IBD, which therefore, in our opinion, is best accommodated by the concept of IBD as more of a syndrome than an autonomous disease. This altered mindset should upgrade our knowledge of IBD, influence its medical care and provide a platform for further advances.

Intracellular pathogen sensor NOD2 programs macrophages to trigger Notch1 activation

Intracellular pathogen sensor, NOD2, has been implicated in regulation of wide range of anti-inflammatory responses critical during development of a diverse array of inflammatory diseases; however, underlying molecular details are still imprecisely understood. In this study, we demonstrate that NOD2 programs macrophages to trigger Notch1 signaling. Signaling perturbations or genetic approaches suggest signaling integration through cross-talk between Notch1-PI3K during the NOD2-triggered expression of a multitude of immunological parameters including COX-2/PGE(2) and IL-10. NOD2 stimulation enhanced active recruitment of CSL/RBP-Jk on the COX-2 promoter in vivo. Intriguingly, nitric oxide assumes critical importance in NOD2-mediated activation of Notch1 signaling as iNOS(-/-) macrophages exhibited compromised ability to execute NOD2-triggered Notch1 signaling responses. Correlative evidence demonstrates that this mechanism operates in vivo in brain and splenocytes derived from wild type, but not from iNOS(-/-) mice. Importantly, NOD2-driven activation of the Notch1-PI3K signaling axis contributes to its capacity to impart survival of macrophages against TNF-α or IFN-γ-mediated apoptosis and resolution of inflammation. Current investigation identifies Notch1-PI3K as signaling cohorts involved in the NOD2-triggered expression of a battery of genes associated with anti-inflammatory functions. These findings serve as a paradigm to understand the pathogenesis of NOD2-associated inflammatory diseases and clearly pave a way toward development of novel therapeutics.

NOD2/CARD15 genotype, cardiovascular disease and cancer in 43,600 individuals from the general population

OBJECTIVES

The NOD2/CARD15 gene is involved in the innate immune response, and thus in inflammation. Three polymorphisms in this gene (Arg702Trp rs2066844, Gly908Arg rs2066845 and Leu1007fsinsC rs5743293) have been associated with increased risk of the inflammatory bowel disease, the Crohn's disease. We tested whether these polymorphisms are also associated with increased risk of cardiovascular disease and cancer, in which the innate immune system and inflammation may influence pathogenesis.

DESIGN, SETTING AND SUBJECTS

We genotyped 43,596 white individuals from two large Danish general population cohorts followed for 31 years: the Copenhagen City Heart Study (n = 10,597) and the Copenhagen General Population Study (n = 32,999). We examined the risk of cardiovascular disease (2743 and 3890, respectively, in the two studies) and cancer (2144 and 3241, respectively) by NOD2/CARD15 genotype using Cox and logistic regressions in both studies. To maximize statistical power, the three NOD2/CARD15 genetic variants were analysed together as follows: noncarriers for all three variants, heterozygotes for one of the three variants and homozygotes for one of the three variants pooled with compound heterozygotes for two variants.

RESULTS

Multifactorially adjusted hazard ratios for cardiovascular disease and cancer in NOD2/CARD15 heterozygotes or homozygotes/compound heterozygotes versus noncarries did not differ from 1.0 in the Copenhagen City Heart Study or in the Copenhagen General Population Study. The corresponding multifactorially adjusted odds ratios likewise did not differ from 1.0 in either study.

CONCLUSIONS

The NOD2/CARD15 Arg702Trp, Gly908Arg and Leu1007fsinsC polymorphisms were not associated with increased risk of cardiovascular disease or cancer in the Danish general population.

Exposure to animals and risk of oligoarticular juvenile idiopathic arthritis: a multicenter case-control study

Background

An inverse association between early contact with microbial compounds and respiratory allergies is well established. The protective effect of infant contact with animals was also shown for inflammatory bowel disease (IBD) and systemic lupus erythematosus (SLE). We aimed to test the association between animal contact in infancy and oligoarticular juvenile idiopathic arthritis (OA JIA).

Methods

Parents of children with OA JIA registered at the Hospital for Pediatric Rheumatology in Garmisch-Partenkirchen were asked to complete a questionnaire. Children who underwent strabismus surgery at six referral centers for ophthalmology served as controls. Children age 6 to 18 years born in Germany without malformations were included (238 cases; response 89% and 832 controls; response 86%). Data were analyzed using logistic regression models after adjusting for potential confounders.

Results

Neither place of living (urban vs. rural area), living on a farm, nor regular farm animal (adjusted odds ratio 0.79; 95% confidence interval 0.42-1.47) or pet contact (0.79; 0.55-1.14) during infancy were clearly related to case status. Allergic rhinitis was inversely related to OA JIA (0.57; 0.34-0.95).

Neither place of living (urban vs. rural area), living on a farm, nor regular farm animal (adjusted odds ratio 0.79; 95% confidence interval 0.42-1.47) or pet contact (0.79; 0.55-1.14) during infancy were related to case status. Allergic rhinitis was inversely related to OA JIA (0.57; 0.34-0.95).

Conclusions

Contact with farm environments in infancy might not be associated with OA JIA. This finding is consistent with previous findings for diabetes mellitus type 1 but contradicts results for IBD and SLE.

ITCH K63-ubiquitinates the NOD2 binding protein, RIP2, to influence inflammatory signaling pathways

BACKGROUND

The inability to coordinate the signaling pathways that lead to proper cytokine responses characterizes the pathogenesis of inflammatory diseases such as Crohn's disease. The Crohn's disease susceptibility protein, NOD2, helps coordinate cytokine responses upon intracellular exposure to bacteria, and this signal coordination by NOD2 is accomplished, in part, through K63-linked polyubiquitin chains that create binding surfaces for the scaffolding of signaling complexes.

RESULTS

In this work, we show that the NOD2 signaling partner, RIP2, is directly K63-polyubiquitinated by ITCH, an E3 ubiquitin ligase that when lost genetically causes widespread inflammatory disease at mucosal surfaces. We show that ITCH is responsible for RIP2 polyubiquitination in response to infection with listeria monocytogenes. We also show that NOD2 can bind polyubiquitinated RIP2 and that whereas ITCH E3 ligase activity is required for optimal NOD2:RIP2-induced p38 and JNK activation, ITCH inhibits NOD2:RIP2-induced nuclear factor kappa B (NFkappaB) activation. This effect can be seen independently at the whole-genome level by microarray analysis of muramyl dipeptide (MDP)-treated Itch(-/-) primary macrophages.

CONCLUSIONS

These findings suggest that ITCH helps regulate NOD2-dependent signal transduction pathways and, as such, may be involved in the pathogenesis of NOD2-mediated inflammatory disease.

Polymorphisms in innate immunity genes predispose to bacteremia and death in the medical intensive care unit

OBJECTIVE

Critically ill patients are at risk of sepsis, organ failure, and death. Studying the impact of genetic determinants may improve our understanding of the pathophysiology and allow identification of patients who would benefit from specific treatments. Our aim was to study the influence of single nucleotide polymorphisms in selected genes involved in innate immunity on the development of bacteremia or risk of death in patients admitted to a medical intensive care unit.

DESIGN, SETTING, AND PATIENTS

DNA was available from 774 medical intensive care unit patients. We selected 31 single nucleotide polymorphisms in 14 genes involved in host innate immune defense. Serum levels of MASP2 and chemotactic capacity, phagocytosis, and killing capacity of monocytes at admission were quantified. Univariate Kaplan-Meier estimates with log-rank analysis and multivariate logistic regression were performed. Bootstrap resampling technique and ten-fold cross-validation were used to assess replication stability, prognostic importance of the variables, and repeatability of the final regression model.

MAIN RESULTS

Patients with at least one NOD2 variant were shown to have a reduced phagocytosis by monocytes (p = 0.03) and a higher risk of bacteremia than wild-type patients (p = 0.02). The NOD2/TLR4 combination was associated with bacteremia using survival analyses (time to bacteremia development, log-rank p < 0.0001), univariate regression (p = 0.0003), and multivariate regression analysis (odds ratio [OR] 4.26, 95% confidence interval [CI] 1.85-9.81; p = 0.0006). Similarly, the same combination was associated with hospital mortality using survival analysis (log-rank p = 0.03), univariate regression (p = 0.02), and multivariate regression analysis (OR 2.27, 95% CI 1.09-4.74; p = 0.03). Also variants in the MASP2 gene were significantly associated with hospital mortality (survival analysis log-rank-p = 0.003; univariate regression p = 0.02; multivariate regression analysis OR 2.35, 95% CI 1.38-3.99; p = 0.002).

CONCLUSIONS

Functional polymorphisms in genes involved in innate immunity predispose to severe infections and death, and may become part of a risk model, allowing identification of patients at risk, who could benefit from early introduction of specific preventive or therapeutic interventions.

Granulomatous rosacea and Crohn's disease in a patient homozygous for the Crohn-associated NOD2/CARD15 polymorphism R702W

NOD2/CARD15 belongs to the N-terminal caspase recruitment domain family of proteins involved in regulating NF-kB activation in response to inflammatory stimuli transduced through Toll-like receptors. Mutations and polymorphisms in the NOD2/CARD15 gene reduce antibacterial responses and are associated with granulomatous inflammatory conditions such as Blau syndrome and early-onset sarcoidosis. The polymorphism R702W (arginine to tryptophan) is strongly associated with susceptibility to Crohn's disease in Caucasian populations. Skin abnormalities (other than cutaneous manifestations of Crohn's disease) have not been previously associated with R702W. We report on a female patient homozygous for R702W who developed granulomatous rosacea at the age of 12 years old. From the occurrence in the context of Crohn associated with R702W, we speculate that granulomatous rosacea may be an entity distinct from other forms of rosacea, which are associated with increased production of antibacterial proteins such as cathelicidin.

Evidence of allelic heterogeneity for associations between the NOD2/CARD15 gene and ulcerative colitis among North Indians

BACKGROUND

Three common disease susceptibility variants in the NOD2 gene are associated with inflammatory bowel disease in Caucasians, but not in Asians. Aim To screen for NOD2 variants and examine susceptibility for inflammatory bowel disease in North Indians.

METHODS

A case-control study was carried out in Punjab, India. Confirmed cases of ulcerative colitis and Crohn's disease and healthy controls matched for age (+/-10 years) and ethnicity were studied. Besides genotyping the three disease susceptibility variants (SNP8, SNP12 and SNP13), all 12 exons were resequenced to determine other potential single nucleotide polymorphisms.

RESULTS

Two hundred and ninety-eight ulcerative colitis, 25 Crohn's disease and 262 controls were investigated. Median age (range) at diagnosis was 39 (7-78) years for ulcerative colitis and 40 (32-58) years for Crohn's disease. All three disease susceptibility variants were either monomorphic or rare in the population. Sequencing (n = 30) revealed two single nucleotide polymorphisms: SNP5 (268 Pro/Ser) and rs2067085 (178 Ser/Ser). The frequency of SNP5 was higher among ulcerative colitis (17% vs. 12% in controls, P = 0.016) and Crohn's disease cases (20% vs. 12%, P = 0.28). SNP5 carriers had elevated risks for ulcerative colitis (OR = 1.72, 95% CI = 1.17-2.52, P = 0.005).

CONCLUSIONS

The absence of known inflammatory bowel disease susceptibility variants and potential associations between SNP5 and ulcerative colitis in North Indians suggests the presence of allelic heterogeneity for ulcerative colitis susceptibility.