Complex insertion/deletion polymorphism in NOD1 (CARD4) is not associated with inflammatory bowel disease susceptibility in East Anglia panel

Play the plug: How bacteria modify recognition by host receptors?

The diverse microbial community that colonizes the gastrointestinal tract has remarkable effects on the host immune system and physiology resulting in homeostasis or disease. In both scenarios, the gut microbiota interacts with their host through ligand-receptor binding whereby the downstream signaling processes determine the outcome of the interaction as disease or the counteractive immune responses of the host. Despite several studies on microbe-host interactions and the mechanisms by which this intricate process happens, a comprehensive and updated inventory of known ligand-receptor interactions and their roles in disease is paramount. The ligands which originate as a result of microbial responses to the host environment contribute to either symbiotic or parasitic relationships. On the other hand, the host receptors counteract the ligand actions by mounting a neutral or an innate response. The varying degrees of polymorphic changes in the host receptors contribute to specificity of interaction with the microbial ligands. Additionally, pathogenic microbes manipulate host receptors with endogenous enzymes belonging to the effector protein family. This review focuses on the diversity and similarity in the gut microbiome-host interactions both in health and disease conditions. It thus establishes an overview that can help identify potential therapeutic targets in response to critically soaring antimicrobial resistance as juxtaposed to tardy antibiotic development research.

NOD1 and NOD2: Molecular targets in prevention and treatment of infectious diseases

Nucleotide-binding oligomerization domain (NOD) 1 and NOD2 are pattern-recognition receptors responsible for sensing fragments of bacterial peptidoglycan known as muropeptides. Stimulation of innate immunity by systemic or local administration of NOD1 and NOD2 agonists is an attractive means to prevent and treat infectious diseases. In this review, we discuss novel data concerning structural features of selective and non-selective (dual) NOD1 and NOD2 agonists, main signaling pathways and biological effects induced by NOD1 and NOD2 stimulation, including induction of pro-inflammatory cytokines, type I interferons and antimicrobial peptides, induction of autophagy, alterations of metabolism. We also discuss interactions between NOD1/NOD2 and Toll-like receptor agonists in terms of synergy and cross-tolerance. Finally, we review available animal data on the role of NOD1 and NOD2 in protection against infections, and discuss how these data could be applied in human infectious diseases.

Homology modeling and in silico prediction of Ulcerative colitis associated polymorphisms of NOD1

Cytosolic pattern recognition receptors play key roles in innate immune response. Nucleotide binding and oligomerisation domain containing protein 1 (NOD1) belonging to the Nod-like receptor C (NLRC) sub-family of Nod-like receptors (NLRs) is important for detection and clearance of intra-cellular Gram negative bacteria. NOD1 is involved in activation of pro-inflammatory pathways. Limited structural data is available for NOD1. Using different templates for each domain of NOD1, we determined the full-length homology model of NOD1. ADP binding amino acids within the nucleotide binding domain (NBD) of NOD1 were also predicted. Key residues in inter-domain interaction were identified by sequence comparison with Oryctolagus cuniculus NOD2, a related protein. Interactions between NBD and winged helix domain (WHD) were found to be conserved in NOD1. Functional and structural effect of single nucleotide polymorphisms within the NOD1 NBD domain associated with susceptibility risk to Ulcerative colitis (UC), an inflammatory disorder of the colon was evaluated by in silico studies. Mutations W219R and L349P were predicted to be damaging and disease associated by prediction programs SIFT, PolyPhen2, PANTHER, SNP&GO, PhD SNP and SNAP2. We further validated the effect of W219R and L349P mutation on NOD1 function in vitro. Elevated mRNA expression of pro-inflammatory cytokines IL8 and IL-1β was seen as compared to the wild type NOD1 in intestinal epithelial cell line HT29 when stimulated with NOD1 ligand. Thus, these mutations may indeed have a bearing on pathogenesis of inflammation during UC.

Emerging significance of NLRs in inflammatory bowel disease

Pattern recognition receptors are essential mediators of host defense and inflammation in the gastrointestinal system. Recent data have revealed that toll-like receptors and nucleotide-binding domain and leucine-rich repeat-containing proteins (NLRs) function to maintain homeostasis between the host microbiome and mucosal immunity. The NLR proteins are a diverse class of cytoplasmic pattern recognition receptors. In humans, only about half of the identified NLRs have been adequately characterized. The majority of well-characterized NLRs participate in the formation of a multiprotein complex, termed the inflammasome, which is responsible for the maturation of interleukin-1β and interleukin-18. However, recent observations have also uncovered the presence of a novel subgroup of NLRs that function as positive or negative regulators of inflammation through modulating critical signaling pathways, including NF-κB. Dysregulation of specific NLRs from both proinflammatory and inhibitory subgroups have been associated with the development of inflammatory bowel disease (IBD) in genetically susceptible human populations. Our own preliminary retrospective data mining efforts have identified a diverse range of NLRs that are significantly altered at the messenger RNA level in colons from patients with IBD. Likewise, studies using genetically modified mouse strains have revealed that multiple NLR family members have the potential to dramatically modulate the immune response during IBD. Targeting NLR signaling represents a promising and novel therapeutic strategy. However, significant effort is necessary to translate the current understanding of NLR biology into effective therapies.

Genetic update on inflammatory factors in ulcerative colitis: Review of the current literature

Ulcerative colitis (UC) is one of the main types of inflammatory bowel disease, which is caused by dysregulated immune responses in genetically predisposed individuals. Several genetic factors, including interleukin and interleukin receptor gene polymorphisms and other inflammation-related genes play central role in mediating and modulating the inflammation in the human body, thereby these can be the main cause of development of the disease. It is clear these data are very important for understanding the base of the disease, especially in terms of clinical utility and validity, but summarized literature is exiguous for challenge health specialist that can used in the clinical practice nowadays. This review summarizes the current literature on inflammation-related genetic polymorphisms which are associated with UC. We performed an electronic search of Pubmed Database among publications of the last 10 years, using the following medical subject heading terms: UC, ulcerative colitis, inflammation, genes, polymorphisms, and susceptibility.

NOD-like receptors in intestinal homeostasis and epithelial tissue repair

The intestinal epithelium constitutes a dynamic physical barrier segregating the luminal content from the underlying mucosal tissue. Following injury, the epithelial integrity is restored by rapid migration of intestinal epithelial cells (IECs) across the denuded area in a process known as wound healing. Hence, through a sequence of events involving restitution, proliferation and differentiation of IECs the gap is resealed and homeostasis reestablished. Relapsing damage followed by healing of the inflamed mucosa is a hallmark of several intestinal disorders including inflammatory bowel diseases (IBD). While several regulatory peptides, growth factors and cytokines stimulate restitution of the epithelial layer after injury, recent evidence in the field underscores the contribution of innate immunity in controlling this process. In particular, nucleotide-binding and oligomerization domain-like receptors (NLRs) play critical roles in sensing the commensal microbiota, maintaining homeostasis, and regulating intestinal inflammation. Here, we review the process of intestinal epithelial tissue repair and we specifically focus on the impact of NLR-mediated signaling mechanisms involved in governing epithelial wound healing during disease.

The role of bacteria and pattern-recognition receptors in Crohn's disease

Crohn's disease is widely regarded as a multifactorial disease, and evidence from human and animal studies suggests that bacteria have an instrumental role in its pathogenesis. Comparison of the intestinal microbiota of patients with Crohn's disease to that of healthy controls has revealed compositional changes. In most studies these changes are characterized by an increase in the abundance of Bacteroidetes and Proteobacteria and a decrease in that of Firmicutes. In addition, a number of specific mucosa-associated bacteria have been postulated to have a role in Crohn's disease, including Mycobacterium avium subspecies paratuberculosis, adherent and invasive Escherichia coli, Campylobacter and Helicobacter species. The association between mutations in pattern-recognition receptors (Toll-like receptors and Nod-like receptors) and autophagy proteins and Crohn's disease provides further evidence to suggest that defective sensing and killing of bacteria may drive the onset of disease. In this Review, we present recent advances in understanding the role of bacteria and the contribution of pattern-recognition receptors and autophagy in the pathogenesis of Crohn's disease.

Association of NOD1 (CARD4) insertion/deletion polymorphism with susceptibility to IBD: A meta-analysis

AIM: To find evidences about whether NOD1/CARD4 insertion/deletion polymorphism is associated with inflammatory bowel disease by meta-analysis.

METHODS: We surveyed the studies on the association of NOD1/CARD4 insertion/deletion polymorphism with inflammatory bowel disease in PubMed. Meta-analysis was performed for genotypes GG/T vs T/T, GG/GG vs T/T, GG/T + GG/GG vs T/T, GG/GG vs T/T + GG/T, and GG allele vs T allele in a fixed/random effect model.

RESULTS: We identified 8 studies (6439 cases and 4798 controls) in Caucasian populations using PubMed search. We found no association between NOD1/CARD4 insertion/deletion polymorphism and inflammatory bowel disease, Crohn’s disease, and ulcerative colitis. Stratification of cases by age showed that NOD1/CARD4 insertion/deletion polymorphism was associated with inflammatory bowel disease in younger age group at onset (< 40 years) (GG vs T: OR = 0.68, 95% CI: 0.50-0.93, P = 0.02; GG/T + GG/GG vs T/T: OR = 0.71, 95% CI: 0.59-0.85, P = 0.0003).

CONCLUSION: This meta-analysis demonstrates an association between NOD1/CARD4 insertion/deletion polymorphism and inflammatory bowel disease in the younger age group at onset (< 40 years) in Caucasian populations.

The role of macrophages in inflammatory bowel diseases

The small and large intestine contain the largest number of macrophages in the body and these cells are strategically located directly underneath the epithelial layer, enabling them to sample the lumen. Such intestinal macrophages have a different phenotype from other tissue macrophages in that they ingest and may kill microbes but they do not mediate strong pro-inflammatory responses upon microbial recognition. These properties are essential for maintaining a healthy intestine. It is generally accepted that tolerance to the intestinal flora is lost in inflammatory bowel diseases, and genes involved in microbial recognition, killing and macrophage activation have already been associated with these diseases. In this review, we shed light on the intestinal macrophage and how it influences intestinal immunity.

Nucleotide-binding oligomerization domain containing 1 (NOD1) haplotypes and single nucleotide polymorphisms modify susceptibility to inflammatory bowel diseases in a New Zealand caucasian population: a case-control study

BACKGROUND

The nucleotide-binding oligomerization domain containing 1 (NOD1) gene encodes a pattern recognition receptor that senses pathogens, leading to downstream responses characteristic of innate immunity. We investigated the role of NOD1 single nucleotide polymorphisms (SNPs) on IBD risk in a New Zealand Caucasian population, and studied Nod1 expression in response to bacterial invasion in the Caco2 cell line.

FINDINGS

DNA samples from 388 Crohn's disease (CD), 405 ulcerative colitis (UC), 27 indeterminate colitis patients and 201 randomly selected controls, from Canterbury, New Zealand were screened for 3 common SNPs in NOD1, using the MassARRAY iPLEX Gold assay. Transcriptional activation of the protein produced by NOD1 (Nod1) was studied after infection of Caco2 cells with Escherichia coli LF82. Carrying the rs2075818 G allele decreased the risk of CD (OR = 0.66, 95% CI = 0.50-0.88, p < 0.002) but not UC. There was an increased frequency of the three SNP (rs2075818, rs2075822, rs2907748) haplotype, CTG (p = 0.004) and a decreased frequency of the GTG haplotype (p = 0.02).in CD. The rs2075822 CT or TT genotypes were at an increased frequency (genotype p value = 0.02), while the rs2907748 AA or AG genotypes showed decreased frequencies in UC (p = 0.04), but not in CD. Functional assays showed that Nod1 is produced 6 hours after bacterial invasion of the Caco2 cell line.

CONCLUSION

The NOD1 gene is important in signalling invasion of colonic cells by pathogenic bacteria, indicative of its' key role in innate immunity. Carrying specific SNPs in this gene significantly modifies the risk of CD and/or UC in a New Zealand Caucasian population.

Clinical and molecular characteristics of isolated colonic Crohn's disease

BACKGROUND

Clinical, serological, and molecular data support the existence of discrete subsets of Crohn's disease (CD) defined by location of disease. Little is known about the epidemiology and natural history of isolated CD of the colon (Montreal Classification L2) because most studies have not accurately distinguished it from ileocolonic disease. Our objectives were to describe the clinical features and natural history of isolated colonic CD in a rigorously characterized patient cohort and to investigate the association of polymorphisms in a number of genes with colonic location of disease and disease behavior.

METHODS

Patients with L2 disease were identified from a database of 675 CD patients. Only patients with a normal small bowel enema (70%), ileoscopy alone (30%), or both (20%) were included. Genotyping was performed using PCR-SSP or the iPLEX platform.

RESULTS

In all, 135 patients were classified with L2 disease. L2 disease was more common in women (74.0% versus 58.0%; P = 0.0004; odds ratio [OR] = 2.11, 95% confidence interval [CI] 1.36-3.26) and in never smokers (48.9% versus 36.9%; P = 0.008; OR = 1.64, 95% CI 1.09-2.45); 20.7% underwent colonic resection for severe disease. We confirmed that carriage of the HLA-DRB1*0103 allele is strongly associated with isolated colonic CD (14.9% versus 4.0%; P = 0.000016; OR 4.6, 95% CI 2.25-9.47) and report the novel association of this allele with time to first surgical event (log rank P = 0.001). There was no association with any of the known CD susceptibility loci (NOD2, IBD5, NOD1, IL23R, ATG16L1) and isolated colonic CD. A nonsynonymous polymorphism in MEKK1 (rs832582) was associated with CD susceptibility overall (15% versus 19%; P = 0.0083; OR = 1.28, 95% CI 1.07-1.54). The association was strongest in those patients not carrying a NOD2 mutation and had no effect on disease location.

CONCLUSIONS

This study describes the clinical features of isolated colonic CD and demonstrates the importance of the HLA region in determining the molecular basis of colonic inflammation.

NOD-like receptors and inflammation

The nucleotide-binding and oligomerization domain, leucine-rich repeat (also known as NOD-like receptors, both abbreviated to NLR) family of intracellular pathogen recognition receptors are increasingly being recognized to play a pivotal role in the pathogenesis of a number of rare monogenic diseases, as well as some more common polygenic conditions. Bacterial wall constituents and other cellular stressor molecules are recognized by a range of NLRs, which leads to activation of the innate immune response and upregulation of key proinflammatory pathways, such as IL-1beta production and translocation of nuclear factor-kappaB to the nucleus. These signalling pathways are increasingly being targeted as potential sites for new therapies. This review discusses the role played by NLRs in a variety of inflammatory diseases and describes the remarkable success to date of these therapeutic agents in treating some of the disorders associated with aberrant NLR function.

New global map of Crohn's disease: Genetic, environmental, and socioeconomic correlations

Seventy-five years after the initial characterization of Crohn's disease (CD), much remains obscure about its etiology. The authors sought to evaluate the incidence trends of the last 25 years worldwide, and the existence of potential correlations with genetic, environmental, and socioeconomic factors that could be etiologically implicated in the pathogenesis of CD. Relevant medical literature for individual countries on the incidence of CD, on the incidence of associated genetic mutations, and on the incidence of suggested etiologic infectious agents such as Mycobacterium avium paratuberculosis were retrieved from published medical literature, reports from relevant international congresses, and through official reports from national health authorities. Increasing trends have been observed almost worldwide, with a broad north-south gradient still prevailing in Europe. Distinct regions of New Zealand, Canada, Scotland, France, the Netherlands, and Scandinavia represent the highest incidence areas. Industrialized status and affluence are the common denominators between endemic areas, but are too broad as terms to strongly indicate any particular etiological role. The increasing trends observed in Asia still account for a low prevalence of the disease and may represent increased detection and diagnostic ability of local health systems. Genetic associations are variably reproduced worldwide, in a manner inconsistent with a strong etiologic relationship. Data on paratuberculosis incidence are scarce, and the existing ones are ambivalent regarding an even indirect correlation between CD and an infectious trigger.

Inflammatory bowel disease: Genetic and epidemiologic considerations

Genome-wide association studies have firmly established that many genomic loci contribute to inflammatory bowel disease, especially in Crohn’s disease. These studies have newly-established the importance of the interleukin 23 and autophagy pathways in disease pathogenesis. Future challenges include: (1) the establishment of precisely causal alleles, (2) definition of altered functional outcomes of associated and causal alleles and (3) integration of genetic findings with environmental factors.

NOD1 gene E266K polymorphism is associated with disease susceptibility but not with disease phenotype or NOD2/CARD15 in Hungarian patients with Crohn's disease

BACKGROUND

NOD1/CARD4, a member of the pattern-recognition receptor family, is a perfect candidate as a susceptibility gene for Crohn's disease. Since only limited and conflicting data are available on G796A polymorphisms in inflammatory bowel disease patients, we set out to study the effect of this polymorphism on the susceptibility and course of Crohn's disease in the Hungarian population.

METHODS

Four hundred thirty-four unrelated Crohn's disease patients (age at presentation: 28.6+/-9.6 years, female/male: 210/224, duration of Crohn's disease: 8.2+/-6.9 years) and 200 healthy subjects (blood donors) and 136 non-inflammatory bowel disease gastrointestinal controls with chronic gastritis were investigated. NOD1 G796A was detected by using polymerase chain reaction/restriction fragment length polymorphism. Detailed clinical phenotypes were determined by reviewing the medical charts.

RESULTS

The frequencies of the variant alleles of NOD1 G796A differed significantly between the Crohn's disease patients and both healthy (GG 49.5% vs. 67%; AG 41.5% vs. 28%; and AA 9.0% vs. 5.2%; p<0.0001) and non-inflammatory bowel disease controls with chronic gastritis. Carriage of the single nucleotide polymorphism of NOD1 G796A proved to be a highly significant risk factor for Crohn's disease compared to both healthy (p<0.0001, OR: 2.1, 95% CI: 1.5-2.9) and non-inflammatory bowel disease controls with chronic gastritis (p=0.008). Significant associations were not found between the different genotypes and the demographic data on the patients or the clinical characteristics of Crohn's disease. The different polymorphisms of pattern-recognition receptors (e.g. NOD2/CARD15 SNP8, SNP12 and SNP13 mutations, the TLR4 D299G polymorphism and NOD1 G796A) did not reveal a mutual basis.

CONCLUSIONS

Our results suggest that carriage of the NOD1 G796A mutation increases susceptibility for Crohn's disease in the Hungarian population.

The genetics of inflammatory bowel disease

Great progress in the understanding of the molecular genetics of inflammatory bowel disease (IBD) has been made over the last 10 years. Strong epidemiological evidence, based initially on concordance data in twin/family studies, led to the application of genome-wide linkage analysis involving multiply affected families and the identification of a number of susceptibility loci. Further characterization of the IBD1 locus on chromosome 16 led to the discovery of the NOD2/CARD15 gene as the first susceptibility gene in Crohn's disease for 2001. This landmark finding has led to a redirection of basic research in IBD with interest focused principally on regulation of the innate immune response and mucosal barrier function. Within the last year, the use of genome-wide association studies has provided new insights into primary pathogenetic mechanisms; several new genes such as the Interleukin-23 receptor (IL23R) and ATG16L1 (autophagy-related 16-like 1) genes are strongly implicated. Overall, these studies promise to change our fundamental understanding of IBD pathophysiology and to have implications for clinical practice.

Influence of a nucleotide oligomerization domain 1 (NOD1) polymorphism and NOD2 mutant alleles on Crohn's disease phenotype

AIM: To examine genetic variation of nucleotide oligomerization domain 1 (NOD1) and NOD2, their respective influences on Crohn's disease phenotype and gene-gene interactions.

METHODS: (ND₁+32656*1) NOD1 polymorphism and SNP8, SNP12 and SNP13 of NOD2 were analyzed in 97 patients and 50 controls. NOD2 variants were determined by reaction restriction fragment length polymorphism analysis. NOD1 genotyping and NOD2 variant confirmation were performed by specific amplification and sequencing.

RESULTS: The distribution of NOD1 polymorphism in patients was different from controls (P = 0.045) and not altered by existence of NOD2 mutations. In this cohort, 30.92% patients and 6% controls carried at least one NOD2 variant (P < 0.001) with R702W being the most frequent variant. Presence of at least one NOD2 mutation was inversely associated with colon involvement (9.09% with colon vs 36.4% with ileal or ileocolonic involvement, P = 0.04) and indicative of risk of penetrating disease (52.63% with penetrating vs 25.64% with non-penetrating or stricturing behavior, P = 0.02). L1007finsC and double NOD2 mutation conferred the highest risk for severity of disease (26.3% with penetrating disease vs 3.8% with non-penetrating or stricturing behavior presented L1007finsC, P = 0.01 and 21.0% with penetrating disease vs 2.5% with non-penentrating or stricturing behavior carried double NOD2 mutation, P = 0.007). Exclusion of patients with NOD2 mutations from phenotype/NOD1-genotype analysis revealed higher prevalence of *1*1 genotype in groups of younger age at onset and colonic location.

CONCLUSION: This study suggests population differences in the inheritance of risk NOD1 polymorphism and NOD2 mutations. Although no interaction between NOD1-NOD2 was noticed, a relationship between disease location and Nod-like receptor molecules was established.

Autoinflammatory syndromes with a dermatological perspective

The term autoinflammatory syndromes describes a distinct group of systemic inflammatory diseases apparently different from infectious, autoimmune, allergic and immunodeficient ones. Originally, it was almost synonymous with clinically defined hereditary periodic fever syndromes, including familial Mediterranean fever, hyper immunoglobulin D syndrome with periodic fever and tumor necrosis factor receptor-associated periodic syndrome. Similar but distinct periodic fever syndromes accompanied by urticarial rash, familial cold autoinflammatory syndrome, Muckle-Wells syndrome and chronic infantile neurological cutaneous articular syndrome, have all been reportedly associated with CIAS1 mutations and are collectively called cryopyrin-associated periodic syndromes. Consequently, the concept of autoinflammatory syndromes has been spread to contain other systemic inflammatory diseases: rare hereditary diseases with or without periodic fevers, such as pyogenic sterile arthritis, pyoderma gangrenosum and acne syndrome, Blau syndrome and chronic recurrent multifocal osteomyelitis, and the more common collagen disease-like diseases, such as Behcet's disease, Crohn's disease, sarcoidosis and psoriatic arthritis. These diseases are all caused by or associated with mutations of genes regulating innate immunity and have common clinical features accompanied with activation of neutrophils and/or monocytes/macrophages. In this review, major autoinflammatory syndromes are summarized and the pathophysiology of related skin disorders is discussed in association with dysregulated innate immune signaling.

Nod1 and Nod2 induce CCL5/RANTES through the NF-kappaB pathway

The Nod-like receptor proteins Nod1 and Nod2 participate in innate immune responses against bacteria through intracellular detection of peptidoglycan, a component of bacterial cell wall. Recent evidence has demonstrated that Nod1 stimulates the release of chemokines that attract neutrophils at the site of infection, such as CXCL8/IL-8 in humans, and CXCL1/keratinocyte-derived chemokine and CXCL2/MIP-2 in mice. We aimed to determine whether Nod proteins could trigger the release of CCL5/RANTES, a chemokine known to attract a number of immune cells, but not neutrophils. Our results demonstrate that activation of both Nod1 and Nod2 results in substantial secretion of CCL5 by murine macrophages. Moreover, in vivo, the intraperitoneal injection of murine Nod1 or Nod2 agonists resulted in a rapid secretion of CCL5 into the bloodstream. We also observed that Nod-dependent secretion of CCL5 did not correlate with the induction of the interferon-beta pathway, a major signaling cascade for the activation of CCL5 by viruses. In contrast, we identified a key role of the NF-kappaB pathway in Nod-dependent stimulation of the CCL5 promoter. Together, these results identify a novel target downstream of Nod1 and Nod2, which is likely to play a key role in orchestrating the global Nod-dependent immune defense during bacterial infections.

The Nodosome: Nod1 and Nod2 control bacterial infections and inflammation

Toll-like receptors (TLRs) and the nucleotide-binding domain, leucine rich repeat containing family (or Nod-like receptors, NLRs) are two important families of microbial sensors that are membrane-associated and cytosolic molecules, respectively. The Nod proteins Nod1 and Nod2 are two NLR family members that trigger immune defense in response to bacterial peptidoglycan. Nod proteins fight off bacterial infections by stimulating proinflammatory signaling and cytokine networks and by inducing antimicrobial effectors, such as nitric oxide and antimicrobial peptides. Nod1 is also critically implicated in shaping adaptive immune responses towards bacterial-derived constituents. In addition, recent evidence has demonstrated that mutations in Nod1 and Nod2 are associated with a number of human inflammatory disorders, including Crohn's disease, Blau syndrome, early-onset sarcoidosis, and atopic diseases. Together, Nod1 and Nod2 represent central players in the control of immune responses to bacterial infections and inflammation.

Contribution of the NOD1/CARD4 insertion/deletion polymorphism +32656 to inflammatory bowel disease in Northern Europe

BACKGROUND

NOD1/CARD4 and NOD2/CARD15 are both intracellular pattern-recognition receptors. The NOD1/CARD4 gene lies within a previously described inflammatory bowel disease (IBD) locus (7p14). An association has been suggested between the NOD1/CARD4+32656 deletion*1 variant of a complex deletion*1/insertion*2 polymorphism and IBD in 1 recent study in Europe. Our aim was to assess the influence of NOD1/CARD4+32656 on disease susceptibility and phenotype in the Scottish and Swedish IBD populations.

METHODS

A total of 3,962 individuals (1,791 IBD patients, 522 parents, 1,649 healthy controls) from 2 independent populations (Scotland and Sweden) were genotyped for NOD1/CARD4+32656 A/C by TaqMan and direct sequencing. Case-control, Transmission Disequilibrium Testing (TDT) and detailed genotype-phenotype (Montreal) analyses were performed. The case-control analysis had 80% power to detect an effect size of odds ratio (OR) 1.21 for IBD.

RESULTS

In case-control analyses in Scottish and Swedish patients, none of the genotypes studied in IBD, Crohn's disease (CD) or ulcerative colitis (UC), differed significantly from controls (deletion*1 allelic frequency 73.9%, 73.6%, 73.9%, and 73.6%, respectively: all P > 0.8). No epistatic interaction with NOD2/CARD15 was seen for CD susceptibility. TDT analysis in our Scottish early onset cohort was negative.

CONCLUSIONS

This variant allele of NOD1/CARD4+32656 is not associated with a strong effect on susceptibility to IBD in children and adults in Northern Europe. A gene-wide haplotype-based approach may be preferable to analysis of individual variants to assess the contribution of the NOD1/CARD4 gene to IBD.

Genetics of the innate immune response in inflammatory bowel disease

The discovery of nucleotide-binding oligomerization domain 2/caspase recruitment domain-containing protein 15 (NOD2/CARD15) as the first susceptibility gene in Crohn's disease (CD) has shifted the focus of research into the pathogenesis of inflammatory bowel disease (IBD) firmly to the innate immune response and the integrity of the epithelial barrier. The subsequent implication in IBD of variant alleles of OCTN, DLG5, MDR1, and TLRs has provided further support for a new, more complex model of innate immunity function in the gastrointestinal tract. In this review, we examine the recent advances in our understanding of the influence of genetics of the innate immune response on IBD. We will focus on germline variation of genes encoding pathogen-recognition receptors, proteins involved in epithelial homeostasis and secreted antimicrobial proteins.