Themistocles Dassopoulos

A genome-wide association study identifies IL23R as an inflammatory bowel disease gene.

The inflammatory bowel diseases Crohns disease and ulcerative colitis are common, chronic disorders that cause abdominal pain, diarrhea, and gastrointestinal bleeding. To identify genetic factors that might contribute to these disorders, we performed a genome-wide association study. We found a highly significant association between Crohns disease and the IL23R gene on chromosome 1p31, which encodes a subunit of the receptor for the proinflammatory cytokine interleukin-23. An uncommon coding variant (rs11209026, c.1142G>A, p.Arg381Gln) confers strong protection against Crohns disease, and additional noncoding IL23R variants are independently associated. Replication studies confirmed IL23R associations in independent cohorts of patients with Crohns disease or ulcerative colitis. These results and previous studies on the proinflammatory role of IL-23 prioritize this signaling pathway as a therapeutic target in inflammatory bowel disease.

Genome-wide association defines more than 30 distinct susceptibility loci for Crohn's disease

Several risk factors for Crohns disease have been identified in recent genome-wide association studies. To advance gene discovery further, we combined data from three studies on Crohns disease (a total of 3,230 cases and 4,829 controls) and carried out replication in 3,664 independent cases with a mixture of population-based and family-based controls. The results strongly confirm 11 previously reported loci and provide genome-wide significant evidence for 21 additional loci, including the regions containing STAT3, JAK2, ICOSLG, CDKAL1 and ITLN1. The expanded molecular understanding of the basis of this disease offers promise for informed therapeutic development.

IL-15 Receptor Maintains Lymphoid Homeostasis by Supporting Lymphocyte Homing and Proliferation

The IL-15 receptor alpha subunit (IL-15Ralpha) mediates high-affinity binding of IL-15, a pleiotropic cytokine implicated in the development of innate immune cells. We have generated IL-15Ralpha null (IL-15Ralpha-/-) mice to understand the role of IL-15Ralpha in immune development and function. IL-15Ralpha-/- mice are markedly lymphopenic despite grossly normal T and B lymphocyte development. This lymphopenia is due to decreased proliferation and decreased homing of IL-15Ralpha-/- lymphocytes to peripheral lymph nodes. These mice are also deficient in natural killer cells, natural killer T cells, CD8+ T lymphocytes, and TCRgammadelta intraepithelial lymphocytes. In addition, memory phenotype CD8+ T cells are selectively reduced in number. Thus, IL-15Ralpha has pleiotropic roles in immune development and function, including the positive maintenance of lymphocyte homeostasis.

MicroRNAs Are Differentially Expressed in Ulcerative Colitis and Alter Expression of Macrophage Inflammatory Peptide-2α

BACKGROUND & AIMS Chronic inflammatory bowel diseases such as ulcerative colitis (UC) are associated with differential expression of genes involved in inflammation and tissue remodeling. MicroRNAs (miRNAs), which direct mRNA degradation and translational inhibition, influence a number of disease processes. We examined whether miRNAs are differentially expressed in UC tissues and are associated with expression of genes that regulate inflammation. METHODS miRNA expression was assessed in patients with active UC, inactive UC, Crohns disease, irritable bowel syndrome, infectious colitis, and microscopic colitis, as well as in healthy subjects by microarray, quantitative reverse transcription-polymerase chain reaction and in situ hybridization analyses. Colonic epithelial cell (HT29) expression of miRNAs was assessed. Regulation of gene expression by miRNAs was assessed by luciferase reporter construct assays and transfection of specific miRNA mimics. RESULTS Active UC was associated with the differential expression of 11 miRNAs; 3 were significantly decreased and 8 were significantly increased in UC tissues. In situ hybridization analysis indicated that miR-192, an miRNA with decreased expression in active UC, was predominantly localized to colonic epithelial cells. Macrophage inflammatory peptide (MIP)-2 alpha, a chemokine expressed by epithelial cells, was identified as a target of miR-192. In colon epithelial cells, induction of MIP-2 alpha expression by tumor necrosis factor-alpha was accompanied by a concomitant reduction in miR-192 expression and miR-192 was observed to regulate the expression of MIP-2 alpha. CONCLUSIONS These findings expand the known roles of miRNAs, indicating that tissues from patients with UC, and possibly other chronic inflammatory diseases, have altered miRNA expression patterns. These findings also demonstrate that miRNAs regulate colonic epithelial cell-derived chemokine expression.

Identification of microRNAs associated with ileal and colonic Crohn's disease.

Background: Crohns disease (CD) and ulcerative colitis (UC) are associated with expression differences in genes involved in immune function, wound healing, and tissue remodeling. MicroRNAs (miRNAs) are small, noncoding RNAs that act as potent negative regulators of gene expression and are differentially expressed in chronic inflammatory diseases, including UC. We examined the expression of miRNAs in tissues from different intestinal regions and in patients with active ileal and colonic CD. Methods: Colonoscopic pinch biopsies were obtained from the terminal ileum, cecum, transverse colon, sigmoid colon, and rectum of normal, healthy adults and from the ileum and sigmoid colon of patients with active ileal and colonic CD. miRNA expression was assessed using miRNA microarray and validated by mature miRNA quantitative reverse‐transcription polymerase chain reaction (RT‐PCR). Results: Ten intestine region‐specific miRNAs were identified. Three miRNAs were increased and one miRNA was decreased in the terminal ileum as compared to the colon. Six other miRNAs expressed varying levels of expression among the colon regions. Five miRNAs were found to be differentially expressed in tissues of patients with active colonic CD, with three increased and two decreased as compared to normal, healthy controls. Similarly, four miRNAs were found to be significantly increased in tissues of patients with active ileal CD. Conclusions: The expression differences between ileal CD, colonic CD, and previously identified UC‐associated miRNAs support the likelihood that miRNAs influence differing inflammation‐related gene expression in each inflammatory bowel disease (IBD) subtype and may form the basis for future diagnostic tests and therapeutic targets for IBD. Inflamm Bowel Dis 2010

Inflammatory bowel disease characteristics among African Americans, Hispanics, and non-Hispanic Whites: characterization of a large North American cohort.

OBJECTIVES:Inflammatory bowel disease (IBD), comprising primarily of Crohns disease (CD) and ulcerative colitis (UC), is increasingly prevalent in racial and ethnic minorities. This study was undertaken to characterize racial differences in disease phenotype in a predominantly adult population.METHODS:Phenotype data on 830 non-Hispanic white, 127 non-Hispanic African American, and 169 Hispanic IBD patients, recruited from six academic centers, were abstracted from medical records and compiled in the NIDDK-IBD Genetics Consortium repository. We characterized racial differences in family history, disease location and behavior, surgical history, and extraintestinal manifestations (EIMs) using standardized definitions.RESULTS:African American CD patients were more likely than whites to develop esophagogastroduodenal CD (OR = 2.8; 95% CI: 1.4–5.5), colorectal disease (OR = 1.9; 95% CI: 1.1–3.4), perianal disease (OR = 1.7; 95% CI: 1.03–2.8), but less likely to have ileal involvement (OR = 0.55; 95% CI: 0.32–0.96). They were also at higher risk for uveitis (OR = 5.5; 95% CI: 2.3–13.0) and sacroiliitis (OR = 4.0; 95% CI: 1.55–10.1). Hispanics had higher prevalence of perianal CD (OR = 2.9; 95% CI: 1.8–4.6) and erythema nodosum (3.3; 95% CI: 1.7–6.4). Among UC patients, Hispanics had more proximal disease extent. Both African American and Hispanic CD patients, but not UC patients, had lower prevalences of family history of IBD than their white counterparts.CONCLUSIONS:There are racial differences in IBD family history, disease location, and EIMs that may reflect underlying genetic variations and have important implications for diagnosis and management of disease. These findings underscore the need for further studies in minority populations.

Defining complex contributions of NOD2/CARD15 gene mutations, age at onset, and tobacco use on Crohn's disease phenotypes

BackgroundMultiple factors, particularly IBD family history, tobacco use, age at diagnosis and recently, NOD2 mutant genotypes may influence Crohns disease (CD) heterogeneity. MethodsWe performed a multicenter retrospective record analysis of 275 unrelated patients with CD. Age at diagnosis, IBD family history, Jewish ethnicity, tobacco use at diagnosis, surgical history, disease site and clinical behavior were correlated with genotypes for NOD2 mutations, and all risk factors were assessed for independent influence on outcomes of disease site, behavior and surgery free survival. ResultsRisk of ileal disease was increased for CD patients with two NOD2 mutations (Odds Ratio, O.R. 10.1), a smoking history (O.R. 2.25 per pack per day at diagnosis) or a younger age at diagnosis (O.R. 0.97 per each increased year). Presence of ileal disease (O.R. 4.8) and carrying one or two NOD2 mutations (O.R. 1.9 and 3.5, respectively) were independent risk factors for stricturing or non-perianal fistulizing behavior. Ileal disease, youthful onset and smoking at diagnosis (but not NOD2 mutations) were risk factors for early surgery. ConclusionsCarrying two NOD2 mutations predicts youthful onset, ileal disease involvement, and development of stricturing or non-perianal fistulizing complications. Smoking and early onset independently influence ileal site and time to surgery.

Genome‐wide gene expression differences in Crohn's disease and ulcerative colitis from endoscopic pinch biopsies: Insights into distinctive pathogenesis

Background: Ulcerative colitis (UC) and Crohns disease (CD) are inflammatory bowel diseases (IBD) with variable, overlapping clinical features and complex pathophysiologies. Methods: To identify pathogenic processes underlying these disease subtypes, we used single endoscopic pinch biopsies to elucidate patterns of gene expression in active and inactive areas of UC and CD and compared these to infectious colitis and healthy control samples. Results: Unsupervised classification of a total of 36 samples yielded promising separation between the affected IBD, unaffected IBD, non‐IBD colitis, and normal control samples, suggesting each sample type had a distinctive gene expression pattern. Genes differentially expressed in the CD samples compared to in the controls were related to IFN&ggr;‐inducible TH1 processes (IFITM1, IFITM3, STAT1, and STAT3) and antigen presentation (TAP1, PSME2, PSMB8). The most noticeable change in the UC samples was reduced expression of genes regulating biosynthesis, metabolism, and electrolyte transport (HNF4G, KLF5, AQP8, ATP2B1, and SLC16A). Twenty‐five percent of genes down‐regulated in the UC samples were also down‐regulated in the infectious colitis samples. Unaffected biopsy samples of IBD patients also registered differences expression of genes compared to in the normal controls. Of these differentially expressed genes, only 2 were up‐regulated, PSKH1, a regulator of mRNA processing, and PPID, a suppressor of apoptosis. Conclusions: The study shows that the gene expression patterns of IBD, CD in particular, are quite different from those of infectious colitis, highlighting distinctive expression of genes and pathways in UC and CD. (Inflamm Bowel Dis 2007)

The role of the Toll receptor pathway in susceptibility to inflammatory bowel diseases.

The intestinal flora has long been thought to play a role either in initiating or in exacerbating the inflammatory bowel diseases (IBD). Host defenses, such as those mediated by the Toll-like receptors (TLR), are critical to the host/pathogen interaction and have been implicated in IBD pathophysiology. To explore the association of genetic variation in TLR pathways with susceptibility to IBD, we performed a replication study and pooled analyses of the putative IBD risk alleles in NFKB1 and TLR4, and we performed a haplotype-based screen for association to IBD in the TLR genes and a selection of their adaptor and signaling molecules. Our genotyping of 1539 cases of IBD and pooled analysis of 4805 cases of IBD validates the published association of a TLR4 allele with risk of IBD (odds ratio (OR): 1.30, 95% confidence interval (CI): 1.15–1.48; P=0.00017) and Crohns disease (OR: 1.33, 95% CI: 1.16–1.54; P=0.000035) but not ulcerative colitis. We also describe novel suggestive evidence that TIRAP (OR: 1.16, 95% CI: 1.04–1.30; P=0.007) has a modest effect on risk of IBD. Our analysis, therefore, offers additional evidence that the TLR4 pathway – in this case, TLR4 and its signaling molecule TIRAP – plays a role in susceptibility to IBD.

Thiopurine methyltransferase activity influences clinical response to azathioprine in inflammatory bowel disease.

BACKGROUND & AIMS Genetic polymorphism in thiopurine methyltransferase (TPMT) activity may influence clinical responsiveness to azathioprine (AZA) therapy. Our aim was to determine if the measurement of erythrocyte TPMT enzyme activity could be used to optimize clinical responsiveness to AZA therapy in patients with inflammatory bowel disease (IBD). METHODS A total of 142 consecutive patients were studied. Forty-one patients (32 with Crohns disease [CD] and 9 with ulcerative colitis [UC]) were enrolled in a 4-month prospective nonrandomized study with AZA, and 101 (65 with CD and 36 with UC) were on either maintenance AZA or 6-mercaptopurine (6-MP). Erythrocyte TPMT activity and AZA metabolite levels were measured blinded to the clinical response. RESULTS The response rate after 4 months of continuous AZA therapy was 69% (9/13) in those patients with below-average (</=12 U/mL blood) TPMT activity, and 29% (8/27) in patients with enzyme activity levels >12 U/mL blood (P < 0.001). Patients with TPMT activity </=12 achieved a mean (SEM) erythrocyte 6-thioguanine ribonucleotide (6-TGn) level of 394 +/- 29 pmol/8 x 10(8) red blood cells (RBCs); higher than in patients with TPMT activity >12 (218 +/- 28), despite similar mean (1.6 mg/kg/day) dosages of AZA (P < 0.001). By multivariate logistic regression analysis, patients with a TPMT level <15.3 U/mL blood were 6.2 times more likely to respond to AZA therapy. A 6-TGn level of >292 pmol/8 x 10(8) RBCs was associated with a positive predictive value of clinical response of 85.7%. CONCLUSIONS Patients with higher than average TPMT activity (>12) may remain refractory to conventional dosages of AZA, and may require high (>292) 6-TGn levels. Prospective, randomized, controlled trials are needed to determine whether prior TPMT phenotype testing can be used to adjust the dose of AZA effectively to improve clinical response time and rate.