Carbamylation of Integrin IIb 3: The Mechanistic Link to Platelet Dysfunction in ESKD

BACKGROUND

Bleeding diatheses, common among patients with ESKD, can lead to serious complications, particularly during invasive procedures. Chronic urea overload significantly increases cyanate concentrations in patients with ESKD, leading to carbamylation, an irreversible modification of proteins and peptides.

METHODS

To investigate carbamylation as a potential mechanistic link between uremia and platelet dysfunction in ESKD, we used liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) to quantify total homocitrulline, and biotin-conjugated phenylglyoxal labeling and Western blot to detect carbamylated integrin α IIb β 3 (a receptor required for platelet aggregation). Flow cytometry was used to study activation of isolated platelets and platelet-rich plasma. In a transient transfection system, we tested activity and fibrinogen binding of different mutated forms of the receptor. We assessed platelet adhesion and aggregation in microplate assays.

RESULTS

Carbamylation inhibited platelet activation, adhesion, and aggregation. Patients on hemodialysis exhibited significantly reduced activation of α IIb β 3 compared with healthy controls. We found significant carbamylation of both subunits of α IIb β 3 on platelets from patients receiving hemodialysis versus only minor modification in controls. In the transient transfection system, modification of lysine 185 in the β 3 subunit was associated with loss of receptor activity and fibrinogen binding. Supplementation of free amino acids, which was shown to protect plasma proteins from carbamylation-induced damage in patients on hemodialysis, prevented loss of α IIb β 3 activity in vitro.

CONCLUSIONS

Carbamylation of α IIb β 3-specifically modification of the K185 residue-might represent a mechanistic link between uremia and dysfunctional primary hemostasis in patients on hemodialysis. The observation that free amino acids prevented the carbamylation-induced loss of α IIb β 3 activity suggests amino acid administration during dialysis may help to normalize platelet function.

Effects of statins on multispecies oral biofilm identify simvastatin as a drug candidate targeting Porphyromonas gingivalis

BACKGROUND

Statins effectively reduce risk of cardiovascular-related morbidity and mortality in patients with hyperlipidemia, hypertension, or type 2 diabetes. In addition to lowering cholesterol levels, several studies have attributed statins with immunomodulatory and bactericidal properties. Therefore, the aim of this study was to investigate statins' antimicrobial activity against periodontal homeostasis bacteria.

METHODS

Statin effect on bacterial growth was tested using planktonic monocultures and multibacterial biofilms. The latter consisted of five microbial species (Porphyromonas gingivalis, Fusobacterium nucleatum, Actinomyces naeslundii, Tannerella forsythia, and Streptococcus gordonii) associated with dysbiosis of the oral microbiota underlying establishment and perpetuation of periodontitis.

RESULTS

All four tested statins efficiently inhibited P. gingivalis growth and significantly decreased the cumulative bacterial load in developing and established biofilms. Simvastatin was most efficient and decreased P. gingivalis counts more than 1,300-fold relative to the control.

CONCLUSIONS

These findings suggest that similar effects on bacterial composition of the dental plaque may occur in vivo in patients on statins, thus, leading to a shift of the oral microbiome from a dysbiotic to a more homeostatic one. Simvastatin, being highly effective against P. gingivalis while not affecting commensal microbiota, possesses many properties qualifying it as a potential adjunctive treatment for chronic periodontitis. Further studies are needed to evaluate whether similar effects on bacterial composition of the dental plaque may occur in vivo in patients on statins, thus, leading to a shift of the oral microflora from dysbiotic to a more homeostatic one.

Impact of fibrinogen carbamylation on fibrin clot formation and stability

Carbamylation is a non-enzymatic post-translational modification induced upon exposure of free amino groups to urea-derived cyanate leading to irreversible changes of protein charge, structure and function. Levels of carbamylated proteins increase significantly in chronic kidney disease and carbamylated albumin is considered as an important biomarker indicating mortality risk. High plasma concentrations and long half-life make fibrinogen a prime target for carbamylation. As aggregation and cross-linking of fibrin monomers rely on lysine residues, it is likely that carbamylation impacts fibrinogen processing. In this study we investigated carbamylation levels of fibrinogen from kidney disease patients as well as the impact of carbamylation on fibrinogen cleavage by thrombin, fibrin polymerisation and cross-linking in vitro. In conjunction, all these factors determine clot structure and stability and thus control biochemical and mechanical properties. LC-MS/MS analyses revealed significantly higher homocitrulline levels in patient fibrinogen than in fibrinogen isolated from control plasma. In our in vitro studies we found that although carbamylation does not affect thrombin cleavage per se, it alters fibrin polymerisation kinetics and impairs cross-linking and clot degradation. In addition, carbamylated fibrin clots had reduced fiber size and porosity associated with decreased mechanical stability. Using mass spectroscopy, we discovered that N-terminally carbamylated fibrinopeptide A was generated in this process and acted as a strong neutrophil chemoattractant potentially mediating recruitment of inflammatory cells to sites of fibrin(ogen) turnover. Taken together, carbamylation of fibrinogen seems to play a role in aberrant fibrin clot formation and might be involved in haemostatic disorders associated with chronic inflammatory diseases.

Carbamylated LL-37 as a modulator of the immune response

Carbamylation of lysine residues and protein N-termini is an ubiquitous, non-enzymatic post-translational modification. Carbamylation at sites of inflammation is due to cyanate formation during the neutrophil oxidative burst and may target lysine residues within the antimicrobial peptide LL-37. The bactericidal and immunomodulatory properties of LL-37 depend on its secondary structure and cationic nature, which are conferred by arginine and lysine residues. Therefore, carbamylation may affect the biological functions of LL-37. The present study examined the kinetics and pattern of LL-37 carbamylation to investigate how this modification affects the bactericidal, cytotoxic and immunomodulatory function of the peptide. The results indicated that LL-37 undergoes rapid modification in the presence of physiological concentrations of cyanate, yielding a spectrum of diverse carbamylated peptides. Mass spectrometry analyses revealed that theN-terminal amino group of Leu-1 was highly reactive and was modified almost instantly by cyanate to generate the predominant form of the modified peptide, named LL-37(C1) This was followed by the sequential carbamylation of Lys-8, Lys-12, and Lys-15 to yield LL-37(C8), and Lys-15 to yield LL-37(C12,15) Carbamylation had profound and diverse effects on the structure and biological properties of LL-37. In some cases, anti-inflammatory LL-37 was rapidly converted to pro-inflammatory LL-37.

Antibodies against carbamylated proteins are present in primary Sjögren's syndrome and are associated with disease severity

Objectives

Herein, we investigate the presence and prognostic value of autoantibodies against carbamylated proteins (anti-CarP) in the serum of patients with primary Sjögren's syndrome (pSS).

Patients and methods

Serum levels of anti-CarP antibodies were measured in Norwegian patients with pSS (n=78) and corresponding controls (n=74) using ELISA and analysed in relation with exocrine gland function, degree of salivary gland inflammation, signs of ectopic germinal centre (GC) formation and immunological markers. For univariate comparisons, the Mann–Whitney U test and χ² or Fisher's exact tests were used. Correlations were assessed with Spearman's rank testing. Multivariate regression analyses were used to assess the effect of anti-CarP positivity on clinical manifestations.

Results

Of the patients with pSS, 27% were positive for anti-CarP IgG antibodies. Levels of anti-CarP correlated positively with total IgG, IgM, rheumatoid factor and β2-microglobulin. Importantly, after adjusting for confounding factors, patients positive for anti-CarP had significantly higher focus score. Furthermore, positive anti-CarP status coincided with 9.2-fold higher odds of having developed GC-like structures in the minor salivary glands. As a patient group considered having worse disease outcome, individuals with ectopic GC-like structures also presented with significantly higher levels of anti-CarP antibodies.

Conclusions

Presence of anti-CarP in patients with pSS is strongly associated with increased focal lymphocytic infiltration, formation of ectopic GC-like structures in minor salivary glands, and diminished salivary gland function. Even taking into consideration our relatively small cohort we believe that anti-CarP antibodies offer new possibilities for identifying patients with more active disease and at risk of developing additional comorbidity.

Carbamylation of immunoglobulin abrogates activation of the classical complement pathway

Post-translational modifications of proteins significantly affect their structure and function. The carbamylation of positively charged lysine residues to form neutral homoitrulline occurs primarily under inflammatory conditions through myeloperoxidase-dependent cyanate (CNO-) formation. We analyzed the pattern of human IgG1 carbamylation under inflammatory conditions and the effects that this modification has on the ability of antibodies to trigger complement activation via the classical pathway. We found that the lysine residues of IgG1 are rapidly modified after brief exposure to CNO- . Interestingly, modifications were not random, but instead limited to only few lysines within the hinge area and the N-terminal fragment of the CH2 domain. A complement activation assay combined with mass spectrometry analysis revealed a highly significant inverse correlation between carbamylation of several key lysine residues within the hinge region and N-terminus of the CH2 domain and the proper binding of C1q to human IgG1 followed by subsequent complement activation. This severely hindered complement-dependent cytotoxicity of therapeutic IgG1 . The reaction can apparently occur in vivo, as we found carbamylated antibodies in synovial fluid from rheumatoid arthritis patients. Taken together, our data suggest that carbamylation has a profound impact on the complement-activating ability of IgG1 and reveals a pivotal role for previously uncharacterized lysine residues in this process.

The myeloperoxidase product hypochlorous acid generates irreversible high-density lipoprotein receptor inhibitors

OBJECTIVE

Elevated levels of advanced oxidation protein products have been described in several chronic inflammatory diseases, like chronic renal insufficiency, rheumatoid arthritis, and atherosclerosis. Recent findings revealed that advanced oxidation protein products are inhibitors of the major high-density lipoprotein receptor, scavenger receptor class B, type 1 (SR-BI). Here, we investigated which oxidation-induced structural alterations convert plasma albumin into a high-density lipoprotein-receptor inhibitor.

APPROACH AND RESULTS

Exposure of albumin to the physiological oxidant, hypochlorous acid, generated high-affinity SR-BI ligands. Protection of albumin-lysine residues before exposure to hypochlorous acid as well as regeneration of N-chloramines after oxidation of albumin completely prevented binding of oxidized albumin to SR-BI, indicating that modification of albumin-lysine residues is required to generate SR-BI ligands. Of particular interest, N-chloramines within oxidized albumin promoted irreversible binding to SR-BI, resulting in permanent receptor blockade. We observed that the SR-BI inhibitory activity of albumin isolated from chronic kidney disease patients correlated with the content of the myeloperoxidase-specific oxidation product 3-chlorotyrosine and was associated with alterations in the composition of high-density lipoprotein.

CONCLUSIONS

Given that several potential atheroprotective activities of high-density lipoprotein are mediated by SR-BI, the present results raise the possibility that oxidized plasma albumin, through permanent SR-BI blockade, contributes to the pathophysiology of cardiovascular disease.

Myeloperoxidase-derived chlorinating species induce protein carbamylation through decomposition of thiocyanate and urea: novel pathways generating dysfunctional high-density lipoprotein

AIMS

Protein carbamylation through cyanate is considered as playing a causal role in promoting cardiovascular disease. We recently observed that the phagocyte protein myeloperoxidase (MPO) specifically induces high-density lipoprotein (HDL) carbamylation, rather than chlorination, in human atherosclerotic lesions, raising the possibility that MPO-derived chlorinating species are involved in cyanate formation.

RESULTS

Here, we show that MPO-derived chlorinating species rapidly decompose the plasma components thiocyanate (SCN) and urea, thereby promoting (lipo)protein carbamylation. Strikingly, the presence of physiologic concentrations of SCN completely prevented MPO-induced 3-chlorotyrosine formation in HDL. SCN scavenged a 2.5-fold molar excess of hypochlorous acid, promoting HDL carbamylation, but not chlorination. Cyanate significantly impaired (i) HDL's ability to activate lecithin-cholesterol acyltransferase; (ii) the activity of paraoxonase, a major HDL-associated anti-inflammatory enzyme; and (iii) the antioxidative activity of HDL.

INNOVATION

Here, we report that MPO-derived chlorinating species preferentially induce protein carbamylation-rather than chlorination-in the presence of physiologically relevant SCN concentrations. The carbamylation of HDL results in the loss of its anti-inflammatory and antioxidative activities.

CONCLUSION

MPO-mediated decomposition of SCN and/or urea might be a relevant mechanism for generating dysfunctional HDL in human disease.

Array-based sequence capture and next-generation sequencing for the identification of primary immunodeficiencies

Primary immunodeficiencies are genetic disorders in which components of immunological pathways are either missing or dysregulated. With the advent of next-generation sequencing, testing for genes in conditions with a heterogeneous genetic background seems more promising. We designed a custom microarray with 385K probe capacity to capture exons of 395 human genes, known or predicted to be associated with primary immunodeficiency and immune regulation. Enriched target DNA was sequenced using a GS FLX Titanium 454 platform. The patients selected were likely to have an underlying immunodeficiency. In one patient with hepatosplenomegaly, recurrent infections and an elevated IgM level, sequence analysis of the patient and his two unaffected parents identified ATM (ataxia telangiectasia mutated) as the underlying defect. In a second child with a clinical SCID phenotype, we detected a mutation in the ARTEMIS gene after focusing on SCID-associated genes. 454 sequencing yielded 152,000-397,000 high-quality reads per patient. 78-99% of the targeted nucleotides were covered at least one time, 76-82% at least five times. Array-based sequence capture expands our capacities to sequence large targeted DNA regions in a less laborious and time-consuming approach. Our array was capable to find the underlying genetic defect in two patients with suspected primary immunodeficiency. Upcoming whole-exome sequencing definitely will add more valuable data, but bioinformatical analysis and validation of variants already pose major challenges.

Cyanate is a novel inducer of endothelial icam-1 expression

AIM

Recent work has shown that humans are significantly exposed to isocyanic acid/cyanate, which is generated when coal, biomass, or tobacco is burned. In vivo, cyanate is formed by the phagocyte protein myeloperoxidase and by breakdown of urea. Carbamylation of proteins through cyanate has been demonstrated to predict cardiovascular risk and is thought to promote vascular dysfunction; however, the underlying mechanisms remain unclear.

RESULTS

Here, we show that cyanate induces intercellular cell adhesion molecule-1 (ICAM-1) expression with subsequently enhanced neutrophil adhesion in human coronary artery endothelial cells. Cyanate triggers ICAM-1 expression through a mechanism depending on activation of the mitogen-activated protein kinase p38 and nuclear factor-kappaB. Endothelial ICAM-1 expression was not induced when low-molecular-weight substances were removed from cell culture medium, thus ruling out a role of carbamylated (lipo)proteins in ICAM-1 induction. In mice, oral administration of cyanate induced marked endothelial ICAM-1 expression in the aorta. Moreover, in patients with end-stage renal disease, the extent of plasma protein carbamylation (a marker for cyanate exposure) significantly correlated with plasma levels of soluble ICAM-1.

INNOVATION

Here, we demonstrate for the first time that cyanate, rather than carbamylated lipoproteins, induces vascular ICAM-1 expression in vivo.

CONCLUSION

Collectively, our data raise the possibility that cyanate amplifies vascular inflammation, linking inflammation, smoking, and uremia.

Uremia alters HDL composition and function

Functional impairment of HDL may contribute to the excess cardiovascular mortality experienced by patients with renal disease, but the effect of advanced renal disease on the composition and function of HDL is not well understood. Here, we used mass spectrometry and biochemical analyses to study alterations in the proteome and lipid composition of HDL isolated from patients on maintenance hemodialysis. We identified a significant increase in the amount of acute phase protein serum amyloid A1, albumin, lipoprotein-associated phospholipase A2, and apoC-III composing uremic HDL. Furthermore, uremic HDL contained reduced phospholipid and increased triglyceride and lysophospholipid. With regard to function, these changes impaired the ability of uremic HDL to promote cholesterol efflux from macrophages. In summary, the altered composition of HDL in renal disease seems to inhibit its cardioprotective properties. Assessing HDL composition and function in renal disease may help identify patients at increased risk for cardiovascular disease.

TNFSF15 polymorphisms are associated with susceptibility to inflammatory bowel disease in a new European cohort

OBJECTIVES

Inflammatory bowel disease (IBD), e.g., Crohn's disease (CD) and ulcerative colitis (UC), is a complex genetic disorder. Tumor necrosis factor (ligand) superfamily, member 15 (TNFSF15) has been previously identified as a susceptibility gene for CD in Japanese and UK cohorts. This replication study was designed in order to confirm and further validate the role of TNFSF15 in IBD.

METHODS

A total of 666 IBD families (corresponding to 2,982 relatives) with European ancestry were genotyped for the rs6478108 and rs7869487 polymorphisms, which define the main TNFSF15 haplotypes previously associated with CD. An association between the main haplotypes and CD, UC and IBD was tested using the Genehunter TDT and Unphased statistics. Caspase recruitment domain 15 (CARD15)/TNFSF15 interaction and genotype/phenotype correlations were also studied.

RESULTS

The previously reported "high-risk" haplotype (A) was associated with IBD (P=0.001) (OR=1.25 (1.05-1.50)) and CD (P=0.02) (OR=1.31 (1.03-1.67)) whereas the "protective" (B) haplotype was significantly less transmitted to IBD and CD patients. No interaction between CARD15 and TNFSF15 was detected. We also failed to define a clinical subgroup of CD patients specifically associated with TNFSF15 haplotype A.

CONCLUSIONS

This study confirms that TNFSF15 or a closely linked gene is involved in the genetic predisposition to CD.

Oral graft vs. host disease in children--treatment with topical tacrolimus ointment

Oral chronic graft vs. host disease (GVHD) frequently presents in patients with sclerotic features of skin GVHD and is often associated with considerable limitations of oral food intake and decreased quality of life. Systemic tacrolimus is efficacious for prophylaxis and treatment of acute and chronic GVHD and topical tacrolimus has shown activity in chronic GVHD skin lesions. We therefore initiated a pilot study to investigate the safety and efficacy of topical tacrolimus ointment in children with oral GVHD. Six patients suffering from oral GVHD (five chronic and one acute) were included in the study. Tacrolimus ointment 0.1% was applied twice daily using sterile gauze. The only side-effects observed were a slight burning discomfort after the first application in one patient and after food intake in another patient. Tacrolimus was absorbed systemically in four of six patients. Of six patients, we observed a complete response in two, a very good partial response (VGPR) in two, and a PR in two patients, respectively. We conclude that topical application of tacrolimus ointment holds promise as a safe and efficacious treatment for oral GVHD in children. The Food and Drug Administration has recently issued a health advisory about a potential cancer risk associated with topical tacrolimus treatment of the skin; therefore, its benefits should be weighed against its potential risks and diligent long-term follow-up should be carried out especially in children.

Screening for dysplasia and TP53 mutations in closed rectal stumps of patients with ulcerative colitis or Crohn disease

BACKGROUND

Patients who undergo colectomy due to intractable chronic inflammatory bowel disease (IBD) may keep a closed rectal stump for several years, which may be at increased risk of malignant transformation owing to residual inflammatory activity. We examined a hospital series of patients with ulcerative colitis or Crohn colitis to describe the clinical, endoscopical and histological features of the closed rectal stump and to screen for dysplasia and mutations in the TP53 tumour suppressor gene.

METHODS

During rigid proctoscopy, rectal mucosal biopsy specimens and rectal lavage fluid were collected from 42 patients. Biopsy specimens were examined histologically, and genomic DNA extracted from frozen biopsies and lavage fluid was analysed for mutations in TP53 exons 4-9.

RESULTS

The median disease duration was 8.5 years (range 1.3-34 years). No endoscopic or histological signs of dysplasia or carcinoma were seen and no mutations in the TP53 gene were detected in any biopsy or lavage fluid specimens. Histological moderate to severe mucosal inflammation was present in 78% (33/42) of the patients, however, and rectal stump involution was noted in 43% (18/42).

CONCLUSION

No signs of malignancy or premalignant degeneration were detected in this prospective series of IBD patients with a closed rectal stump. Although this is reassuring for patients, the presence of moderate to severe inflammation in the majority of rectal stumps indicates a role for adjuvant molecular markers to improve colorectal cancer surveillance on this subgroup of IBD patients.

Intestinal and extra-intestinal cancer in Crohn's disease: follow-up of a population-based cohort in Copenhagen County, Denmark

AIM

To determine the long-term risk of intestinal and extra-intestinal malignancies in Crohn's disease patients in Copenhagen County, Denmark.

METHODS

In Copenhagen County, a strictly population-based cohort of 374 patients with Crohn's disease diagnosed between 1962 and 1987 was followed until 1997 in order to determine the long-term risk of intestinal and extra-intestinal malignancies. Information on cancer occurrence was provided by the Danish National Cancer Registry and confirmed by the examination of hospital files. The observed number of cases was compared with the expected number, calculated from individually computed person-years at risk and 1995 cancer incidence rates for the background population.

RESULTS

The risk of small bowel adenocarcinoma was significantly increased, independent of age and gender (standardized morbidity ratio, 66.7; 95% confidence interval, 18.1-170.7). The risk of colorectal cancer was not increased, either in the total group of patients or in patients with colonic Crohn's disease exclusively (standardized morbidity ratio, 1.64; 95% confidence interval, 0.20-5.92). Extra-intestinal cancer did not occur more frequently than expected.

CONCLUSIONS

This population-based study of patients with Crohn's disease revealed no increase in colorectal cancer risk, possibly due to maintenance treatment with 5-aminosalicylic acid preparations and surgery in treatment failure. In contrast, the risk of small bowel cancer was increased more than 60-fold, but the numbers were small. The risk of extra-intestinal cancer was not increased and no lymphomas were observed.

Association of NOD2 leucine-rich repeat variants with susceptibility to Crohn's disease

Crohn's disease and ulcerative colitis, the two main types of chronic inflammatory bowel disease, are multifactorial conditions of unknown aetiology. A susceptibility locus for Crohn's disease has been mapped to chromosome 16. Here we have used a positional-cloning strategy, based on linkage analysis followed by linkage disequilibrium mapping, to identify three independent associations for Crohn's disease: a frameshift variant and two missense variants of NOD2, encoding a member of the Apaf-1/Ced-4 superfamily of apoptosis regulators that is expressed in monocytes. These NOD2 variants alter the structure of either the leucine-rich repeat domain of the protein or the adjacent region. NOD2 activates nuclear factor NF-kB; this activating function is regulated by the carboxy-terminal leucine-rich repeat domain, which has an inhibitory role and also acts as an intracellular receptor for components of microbial pathogens. These observations suggest that the NOD2 gene product confers susceptibility to Crohn's disease by altering the recognition of these components and/or by over-activating NF-kB in monocytes, thus documenting a molecular model for the pathogenic mechanism of Crohn's disease that can now be further investigated.

[Therapeutic principles for chronic inflammatory bowel disease]

Whereas the incidence of ulcerative colitis has remained stable at around 8-9/10(5), the incidence of Crohn's disease has increased from below 1 to more than 5/10(5) per year during the last three decades. The new disease entities, collagenous colitis and lymphocytic colitis, are now covered by the term, chronic inflammatory bowel disease. The general principles of treatment of these diseases are to induce remission of outbreaks and to prevent outbreaks during remission. Available pharmaceutical products are 5-aminosalicylic acid preparations, with different delivery profiles in the gastrointestinal tract, glucocorticoids, and other immunosuppressants, especially azathioprine. New immunomodulating agents, with a specific effect on intracellular processes in the inflammatory cascade are now being developed, and infliximab, a TNF-alpha antibody, is now an accepted agent for use in severe, treatment-resistant cases of fistulising Crohn's disease. When medical treatment fails, surgical treatment is an option. In ulcerative colitis, colectomy is, in principle, curative, but it leaves the patient with either a permanent ileostomy or an ileal pouch, which serves as an artificial rectum after ileoanal anastomosis. This latter procedure has the obvious advantage of giving the patient a normal bowel continuity, but complications in the form of intractable "pouchitis" have been experienced in a small number of patients, thus necessitating removal of the pouch. Patients with Crohn's disease, who do not respond to medical treatment or present signs of stenosis in either the small or the large bowel, must be given surgical treatment, although an operation is less curative than in ulcerative colitis. Surgical resections for Crohn's disease must therefore be more conservative, so as to preserve the bowel and only remove macroscopically affected tissue.

Genetic analyses of chromosome 12 loci in Crohn's disease

BACKGROUND AND AIMS

Inflammatory bowel disease (IBD) includes ulcerative colitis and Crohn's disease, both of which are multifactorial diseases involving the interaction of genetic and environmental factors. A region on chromosome 12 centred around the marker locus D12S83 has previously been associated with IBD predisposition. The aim of the study was to investigate this genetic region in an independent panel of European families affected by Crohn's disease.

METHODS

A sample of 95 families with two or more affected relatives and 75 simplex nuclear families were genotyped for 19 microsatellite loci located on chromosome 12. A search for linkage and linkage disequilibrium was performed using non-parametric two point and multipoint analyses with the Analyze and Genehunter packages.

RESULTS

No evidence of linkage or linkage disequilibrium was observed for any of the marker loci, including D12S83 (p=0.35 for the two point linkage test). Multipoint linkage analysis also failed to reveal positive linkage on chromosome 12. Power calculations allowed us to reject the hypothesis that the genetic region of chromosome 12 centred on D12S83 contains a susceptibility locus with a relative risk (lambda(s)) equal to or greater than 2.0 in these families.

CONCLUSION

Failure to detect linkage or linkage disequilibrium in these families suggests that the chromosome 12 locus previously reported to be associated with genetic predisposition to IBD does not play a role in all European family samples. This observation is compatible with heterogeneity in the genetic basis of susceptibility to the disease and/or exposure to various environmental factors among Caucasian families.

Results of multiple diagnostic tests for Mycobacterium avium subsp. paratuberculosis in patients with inflammatory bowel disease and in controls

Mycobacterium avium subsp. paratuberculosis has been incriminated as a cause of Crohn's disease (CD); however, studies to date have been relatively small and generally only used a single diagnostic assay. The objective of the study was to reexamine the association of M. avium subsp. paratuberculosis and CD using multiple diagnostic tests. Five methods were used to detect M. avium subsp. paratuberculosis infections in 439 inflammatory bowel disease (IBD) patients and 324 control subjects in the United States and Denmark. Most assays were adaptations of diagnostic tests for this infection performed routinely on animals. PCR for IS900, a genetic element unique to M. avium subsp. paratuberculosis, was positive significantly more often on resected bowel and lymph node tissues from CD patients (19.0%) and ulcerative colitis (UC) patients (26.2%) than from controls (6. 3%) (P < 0.05). Positive IS900 PCR results occurred more often in U. S. than in Danish IBD patients, 32.0 versus 13.3% (P = 0.025). The majority of Danish patients were bacillus Calmette-Guérin (Mycobacterium bovis BCG) vaccinated (CD, 77.5%; UC, 86.6%; controls, 83.0%) whereas none of the U.S. patients with IBD and only 2% of U. S. controls were vaccinated. Among Danish IBD patients, positive PCR findings were four times more common among subjects who were not BCG vaccinated (33.3%) than among BCG vaccinates (8.8%, P = 0.02). Culture of the same tissues tested by PCR using modified BACTEC 12B medium failed to grow M. avium subsp. paratuberculosis from patients or controls. U.S. CD patients had the highest serological evidence (enzyme-linked immunosorbent assay [ELISA] for serum antibodies) of M. avium subsp. paratuberculosis infection (20.7% of patients positive) which was higher than for all UC patients studied (6.1%) or healthy controls (3.8%, P < 0.005). Among Danish patients alone, however, no significant differences in rates of ELISA-positive results among CD, UC, or control patients were found. For 181 study subjects, both IS900 PCR and ELISA were performed. Although 11 were ELISA positive and 36 were PCR positive, in no instance was a patient positive by both tests, suggesting that these states are mutually exclusive. Evaluation of cytokine-mediated immune responses of IBD patients was complicated by the influence of immunosuppressive therapy given most IBD patients. Gamma interferon (IFN-gamma) release by peripheral blood leukocytes after M. avium purified protein derivative PPD antigen stimulation showed significantly lower responses in CD patients than in UC patients or controls in both U.S. (by ex vivo assay) and Danish (by in vitro assay) populations (P < 0.05). Interleukin-5 responses were not different among CD, UC, or control groups. Collectively, the PCR, ELISA, and IFN-gamma tests for M. avium subsp. paratuberculosis together with the unexpected observation that BCG vaccination influenced M. avium subsp. paratuberculosis detection, lead us to conclude that M. avium subsp. paratuberculosis, or some similarly fastidious mycobacterial species, infects at least a subset of IBD patients. Whether the infection is primary (causal) or secondary, it may contribute to the etiopathogenesis of IBD.

Concordance of inflammatory bowel disease among Danish twins. Results of a nationwide study

BACKGROUND

Previous studies have shown an increased risk of inflammatory bowel disease (IBD) among relatives of patients with Crohn disease and ulcerative colitis. In the present study the probandwise concordance rates for ulcerative colitis and Crohn disease among mono- and dizygotic twins were estimated. Further we aimed to evaluate whether smoking habits might influence the concordance, and to look for clinical characteristics of concordant versus discordant twin pairs.

METHODS

Among the 38,507 identified twins born in Denmark from 1953 to 1982, a questionnaire was sent to the 34,076 who previously had accepted to participate in studies. For twins reporting IBD, the diagnosis was verified by applying standard criteria to records requested from hospitals or practitioners.

RESULTS

Among the 29,421 (86.3%) twins answering the questionnaire, 103 pairs had at least one twin who suffered from IBD. In the Crohn disease group five of 10 monozygotic pairs, but none of 27 dizygotic pairs were concordant. In the ulcerative colitis group three of 21 monozygotic, and two of 44 dizygotic pairs were concordant. The probandwise concordance rate among monozygotic pairs was 58.3% for Crohn disease and 18.2% for ulcerative colitis; among the dizygotic pairs the rates were 0 and 4.5%, respectively. The frequency of smokers was higher among twins with Crohn disease and lower among twins with ulcerative colitis compared to the frequency in the twin register. Furthermore, smoking habits were found to be of significance for discordance for disease. Regarding the clinical characteristics no homogenous pattern was observed within the concordant pairs and the differences between concordant and discordant pairs were not significant.

CONCLUSION

The observation of a significantly higher concordance rate among monozygotic than among dizygotic twin pairs strongly points to a genetic influence on occurrence of IBD, which seems to be more pronounced with regard to Crohn disease than to ulcerative colitis. Differences in smoking habits among the members of the discordant twin pairs may influence the discordance.

Quality of life study in a regional group of patients with Crohn disease. A structured interview study

BACKGROUND

The course and prognosis of Crohn disease has previously been described in a regional group of patients in Copenhagen County. The aim of the present study was to reveal the quality of life. as judged by the patients, and compared to age- and sex-matched healthy controls.

METHODS

Out of 100 consecutive out-patients with Crohn disease, 94 patients accepted to participate together with 94 age- and sex-matched healthy controls. A modified McMaster Inflammatory Bowel Disease Questionnaire (IBDQ23) was used, excluding bowel-related questions. Medical students conducted interviews without knowing who were Crohn disease patients and who were controls. The bowel-related questions and Crohn's Disease Activity Index (CDAI) were assessed by gastroenterologists at inclusion in the study. Responses were indicated on a seven-point scale (7 best/1 worst). Mean numeric score was calculated as well as a delta score, i.e. the difference in score between a patient and the matched control.

RESULTS

In 21 of 23 questions the median delta score was zero, indicating no difference between patient and control. The median total delta score was 0.4 in favour of healthy controls (P < 0.001), and significantly higher in patients in relapse, 0.9, than in patients in remission, 0.3 (P < 0.01). The median total numeric score was 5.7 for patients and 6.1 for controls.

CONCLUSIONS

Although patients with Crohn disease scored significantly lower on the quality of life scale than matched healthy controls, the differences were smaller than could be expected, taking the chronic disease into consideration. Disease activity correlated with the quality of life score.

Arthritis and the gut

Mild arthritis/arthralgia is the most frequent extraintestinal manifestation in inflammatory bowel disease (IBD) and has been reported to occur in 10-35% of patients in different studies. A classification of peripheral arthropathy in relation to inflammatory bowel disease has recently been proposed. Type 1: pauciarticular, asymmetrical, preferably large joints, and related to IBD activity. Type 2: polyarticular, symmetrical, preferably small joints, and occurring independently of IBD activity. While this classification requires the presence of synovitis, arthralgia without swelling or other objective signs are of equal frequency but are not covered by this system. In this issue of the journal, Thomas et al. report a prospective study, incorporating strict endoscopic and histological criteria for pouchitis, which elucidates the correlation to arthropathy. Both pouchitis and symptoms of the joints occurred more frequently in ulcerative colitis patients than in patients with familial polyposis. Surprisingly, arthropathy was not more frequent among patients with pouchitis than among patients without pouchitis in this study. Extraintestinal manifestations of the joints are thus not likely to be a reactive arthritis secondary to pouchitis, which would have been an obvious explanation. Preoperative occurrence of extraintestinal manifestations from the joints does not seem to be predictive for the outcome of an ileo-anal pouch anastomosis and especially development of pouchitis. The arthritic symptoms were generally mild and not disabling.

Lauroyldextran and crosslinked galactomannan as coating materials for site-specific drug delivery to the colon

Lauroyldextran (LD) and crosslinked galactomannan (XGM) were investigated as microbiologically degradable film coating materials for site-specific drug delivery to the colon. LD was used with degrees of substitution between 0.12 and 0.40, and swelling in aqueous media between 195 and 50%, XGM-batches showed swelling between 309 and 520%. Theophylline tablets were coated in a Hüttlin Kugelcoater with coating quantities of 4-17 mg/cm2. Sprayable coating formulations were obtained with 4% aqueous dispersions of XGM or 4% dispersions of LD in a 1:1 mixture of 1-propanol and water with 10% glycerol (based on the polymer) as a plasticizer. Theophylline dissolution was monitored in a USP XXIII paddle dissolution apparatus with buffer pH 5.5. After 4 h, which is an average small intestine transit time, colon conditions were simulated by adding galactomannanase or dextranase, respectively. Results showed similar dissolution rates for all XGMs and high-swelling LDs during the first 4 h and a relatively quick disintegration after enzyme addition. Both parameters decreased with increasing coating quantities. Dissolution from low-swelling lauroyldextrans was very low but no disintegration was observed after enzyme addition. The disintegration rate was found to be proportional to the square root of the enzyme activity. All swollen materials exhibited low mechanical stability. XGM coatings, especially at higher coating quantities, showed small transient ruptures at the edges not caused by enzyme addition. This behaviour was explained by internal stress due to the high degree of swelling. In principle, materials of both types proved to be suitable as degradable coating materials. The ideal zero-dissolution before and quick disintegration after enzyme addition, however, was not realized with the present materials.

Genetic epidemiology in inflammatory bowel disease

Family studies of different designs have been carried out in the last few years. Five to ten percent of patients have another case of inflammatory bowel disease (IBD) among their first-degree relatives, with about 75-80% concordance for the same disease within the family. About 20% of multi-affected families present both cases with ulcerative colitis and Crohn's disease. The population relative risk in first-degree relatives of patients show a 14-15 times higher prevalence of IBD. Prevalence values of 1.5-3.5% in first-degree relatives have been found, with an even higher calculated lifetime risk especially in offspring and siblings of patients with IBD. Earlier disease onset in offspring of patients with IBD have consistently been found, and genetic anticipation has been hypothesized. The phenomenon, however, may be a result of a combination of a time trend - increasing the incidence of Crohn's disease - and the fact that patients with early onset of IBD may have lower fertility and therefore may be underrepresented in the parent-child pairs studied. Twin studies have shown significantly higher concordance rates in monozygotic than in dizygotic twins. Further, the concordance rate in monozygotic twins is higher in Crohn's disease than in ulcerative colitis, indicating a stronger genetic influence in this condition. Disease course and prognosis within families have been studied without convincing concordance found in this respect among family members.

[Inflammatory bowel diseases in children]

From an incidence cohort diagnosed during 1962-1987 we identified all patients with onset of IBD before the age of 15 in order to describe the course and to compare course and prognosis with adult onset IBD. The mean incidence of IBD among children below 15 years was 2.2/10(5), 2.0 for ulcerative colitis (UC), and 0.2 for Crohns disease (CD). At diagnosis, UC children had more extensive disease compared to adults (p < 0.05). Abdominal pains were also more frequent. The cumulative colectomy probability was 6% after one year and 29% after 20 years, not different from adults. Regarding disease activity, it was found that 60-70% of UC patients were in remission in the first 10 years of disease, for CD about 50% were in remission. One UC patient developed carcinoma of the sigmoid colon. Time between onset and development of carcinoma was 12 years. For CD no differences in clinical appearance at diagnosis and course between children and adults were found. No deaths occurred among CD patients. Three CD patients were found to have severe growth retardation already at diagnosis. In conclusion, the incidence of IBD is low in childhood. At diagnosis children with UC have more widespread disease than adults. Children with CD do not differ in clinical presentation, course or prognosis compared to adult onset CD. However, growth retardation is a problem among CD patients.

Preliminary applicability tests of different methacrylic acid copolymers, type C NF, particularly relevant to spreading and film formation

The intention of this study was to show under which conditions a film forming methacrylic acid copolymer coating excipient, corresponding to the requirements of pharmacopoeia, but obtained from different sources, can be substituted without severe problems. The mechanical properties of the film coats were investigated by dynamic-mechanical thermo-analysis (DMTA) experiments to determine with respect to the glass transition the storage modulus E', the loss modulus E'', and the loss factor tan delta. Further determinations concerned the surface tensions of the different coating dispersions. This attribute plays an important role in spreading, distribution and coalescence of the film forming preparations. Finally by a series of small experimental fluidized bed batches cores containing a model drug were coated with the different methacrylic acid copolymers. The resistance of these coated tablets in 0.1 N HC1 as well as their dissolution rates in artificial intestinal juice were tested. The coatings proved themselves so similar that in this case substitutions of products of different provenance are possible. The determinations of surface tension and the DMTA measurements seem to be useful and reliable preliminary applicability tests.

Inflammatory bowel diseases with onset in childhood. Clinical features, morbidity, and mortality in a regional cohort

BACKGROUND AND METHODS

In a geographically derived incidence cohort diagnosed from 1962 to 1987 we identified all patients with onset of inflammatory bowel diseases (IBD) before the age of 15 years, to describe the clinical course and to compare the course and prognosis with those of adult-onset IBD.

RESULTS

The mean incidence of IBD among children below 15 years was 2.2/10(5), 2.0 for ulcerative colitis (UC) and 0.2 for Crohn's disease (CD). At diagnosis children with UC had more extensive disease than adults (P < 0.05). Abdominal pain was also more frequent. The cumulative colectomy probability was 6% after 1 year and 29% after 20 years, not different from that of adults. More females underwent colectomy. With regard to disease activity, apart from the year of diagnosis 60-70% of UC patients were in remission in each of the first 10 years of disease; for CD about 50% were in remission. One patient with UC developed carcinoma of the sigmoid colon. Time between onset of UC and development of carcinoma was 12 years. For CD no differences in clinical appearance at diagnosis and course between children and adults were found in relationship to surgery. No deaths occurred among CD patients. Three CD patients were severely growth-retarded already at diagnosis.

CONCLUSION

The incidence of IBD is low in childhood. At diagnosis children with UC have more widespread disease than adults. Childhood-onset CD does not differ in clinical presentation, disease course, or prognosis from adult-onset CD. However, growth retardation is a problem among male CD patients.

Changes in extent of ulcerative colitis: a study on the course and prognostic factors

BACKGROUND

The prognosis of patients with ulcerative colitis (UC) has previously been described with regard to mortality, cancer occurrence, and need for colectomy on the basis of an annual follow-up of a regional cohort of UC patients in Copenhagen County diagnosed in 1962-87. The objective of this study was to examine the prognosis with regard to spread of disease and to evaluate possible prognostic factors with regard to spread of disease and colectomy by multivariate regression analysis.

METHODS

An inception cohort of 1161 patients with UC was examined by actuarial analysis and by multivariate regression analysis of a subgroup of 467 patients diagnosed in 1979-87.

RESULTS

The probability for further progression of proctosigmoiditis, evaluated by sigmoidoscopy and radiology, was 53% after 25 years. The probability for regression was 76.8% for substantial colitis and 75.7% for pancolitis after 25 years. Multivariate regression analysis showed that the occurrence of the symptoms abdominal pain and diarrhoea was prognostically unfavourable with regard to the progression from proctosigmoiditis. Age influenced the regression probability in extensive disease. With regard to colectomy the following variables influenced the prognosis: fever, general condition, serum albumin, mucopus in stools, and diarrhoea at onset.

CONCLUSIONS

Disease extent in UC is not static but changes with time in approximately half of the patients. This finding should have implications for the follow-up. Ulcerative proctitis should be considered the same disease as UC and needs the same long-term follow-up.

Familial occurrence and inheritance studies in inflammatory bowel disease

A number of studies have demonstrated aggregation of cases of ulcerative colitis or Crohn's disease in families, and of cases of both diseases within the same families, suggesting that patients share a genetic background. Perhaps because of differences in the selection of patients, study design and diagnostic criteria, different patterns of occurrence of inflammatory bowel disease (IBD) have been found among relatives of patients with these disorders. In recent years, however, several studies have been carried out, aiming by epidemiological methods to reveal (1) the frequency of familial occurrence of IBD among patients with ulcerative colitis and Crohn's disease, and (2) the prevalence of IBD among 1(0) relatives to patients with these diseases. Results from these studies show a relatively uniform pattern of family occurrence in about 10% of patients with ulcerative colitis and Crohn's disease, and a prevalence among 1(0) relatives of about 10 times that of the background population. A twin study reported a significantly higher concordance rate for Crohn's disease than for ulcerative colitis in monozygotic twins. By use of complex segregation analyses in 3 different studies, a very similar model of inheritance was found to fit for ulcerative colitis, namely a major dominant or additive gene with a low penetrance. For Crohn's disease the best-fitting model was a major recessive gene, with a high penetrance. This difference strongly supports the concept of ulcerative colitis and Crohn's disease as two separate disease entities. The occurrence of both diseases within the same families in certain members of the affected families is difficult to explain. The search for distinct associations of HLA genes with inflammatory bowel disease has shown a positive correlation between DR2 and ulcerative colitis and a negative association with DR4 and DRw6, compared with ethnically matched controls. In contrast, in Crohn's disease a positive association with the combination of DR1 and DQw5 alleles was revealed, thus indicating genetically different disease susceptibility for the two disorders. In general, however, no consistent pattern has been revealed from studies of association of HLA-A or -B antigens or blood group and serum protein markers. In two French families with several members affected with Crohn's disease no evidence for an HLA haplotype association could be revealed. Possible inherited markers of ulcerative colitis or Crohn's disease have been sought but without convincing success. Increased intestinal permeability, presence of anticolon antibodies and presence of antineutrophil leukocyte antibodies have been proposed, but not proved. Thorough studies are now needed of multimember families with disease for linkage studies to identify loci which contribute to increased liability. Such studies are in progress in different centres.

Epidemiology in gastroenterology

A review of the literature on gastrointestinal epidemiology during the last 25 years shows a comprehensive contribution from Danish studies. This is partly explained by very favourable conditions in Denmark for epidemiological research, due to various valid registers and a long tradition for longitudinal population and patient cohorts. Data are presented on prevalence, incidence, demography, clinical risk factors, clinical course, and prognosis of various gastrointestinal disorders. Main emphasis is put on Danish studies, which are compared with international results. Present possibilities for prophylaxis against gastrointestinal diseases and delimitation of treatment of benign diseases are discussed. It is expected that research within gastrointestinal epidemiology in Denmark will increase in the coming years.

Disease activity courses in a regional cohort of Crohn's disease patients

BACKGROUND

The study was a follow-up of an inception cohort of 373 patients with Crohn's disease.

METHODS

Annual assessments, life table analyses, and Markov chain analyses, estimating the probability for remission and relapse with time, and working capacity were carried out.

RESULTS

The clinical course of Crohn's disease differs markedly over time, from ever-relapsing cases to a quiescent course with remission for several years, interrupted by years with relapse. No predictive factors have been found for the subsequent course with regard to age, sex, extent of disease at diagnosis, and treatment in the year of diagnosis. The relapse rate within the year of diagnosis and the following 2 years, however, does correlate positively (p = 0.00001) with the relapse rate in the following 5 years. Furthermore, the relapse rate for 1 year during the disease course influences the relapse rate the following year, indicating a disease pattern over time with waves of at least 2 years' duration. A slight tendency towards burning out was found. The disease course reflected in working capacity for the patients showed that a minor part--up to 15% after 15 years--will become incapable and obtain disablement pension, while 75% of the patients each year are fully capable of work. Within 10 years 50% of the patients will not have experienced any year with impaired capacity for work.