Immunopathogenesis of inflammatory bowel disease

Helicobacter pylori may be an initiating factor in newly diagnosed ulcerative colitis patients: A pilot study

AIM

To directly visualize Helicobacter pylori (H. pylori) by the highly sensitive and specific technique of immunohistochemical staining in colonic tissue from patients newly diagnosed with ulcerative colitis (UC).

METHODS

Colonoscopic biopsies from thirty patients with newly diagnosed UC and thirty controls were stained with Giemsa stain and immunohistochemical stain for detection of H. pylori in the colonic tissue. Results were confirmed by testing H. pylori Ag in the stool then infected patients were randomized to receive either anti H. pylori treatment or placebo.

RESULTS

Twelve/30 (40%) of the UC patients were positive for H. pylori by Giemsa, and 17/30 (56.6%) by immunohistochemistry stain. Among the control group 4/30 (13.3%) and 6/30 (20 %) were positive for H. pylori by Giemsa and immunohistochemistry staining respectively. H. pylori was significantly higher in UC than in controls (P = 0.04 and 0.007). All Giemsa positive patients and controls were positive by immunohistochemical stain. Four cases of the control group positive for H. pylori also showed microscopic features consistent with early UC.

CONCLUSION

H. pylori can be detected in colonic mucosa of patients with UC and patients with histological superficial ulcerations and mild infiltration consistent with early UC. There seems to be an association between UC and presence of H. pylori in the colonic tissue. Whether this is a causal relationship or not remains to be discovered.

Staphylococcus aureus induces IL-8 expression through its lipoproteins in the human intestinal epithelial cell, Caco-2

Staphylococcus aureus can cause the intestinal inflammatory diseases. However, little is known about the molecular mechanism of S. aureus infection in the intestine. In the present study, we investigated whether S. aureus could stimulate human intestinal epithelial cells triggering inflammation. When the human intestinal epithelial cell-line, Caco-2, and the primary colon cells were stimulated with ethanol-inactivated S. aureus, IL-8 expression was induced in a dose-dependent manner. The inactivated S. aureus preferentially stimulated Toll-like receptor (TLR) 2 rather than TLR4. Lipoproteins, lipoteichoic acid (LTA), and peptidoglycan (PGN) are considered as potential TLR2 ligands of S. aureus. Interestingly, S aureus lipoproteins and Pam2CSK4 mimicking Gram-positive bacterial lipoproteins, but not LTA and PGN of S. aureus, significantly induced IL-8 expression in Caco-2 cells. Furthermore, lipoprotein-deficient S. aureus mutant strain failed to induce IL-8 production. Collectively, these results suggest that S. aureus stimulates the human intestinal epithelial cells to induce the chemokine IL-8 production through its lipoproteins, potentially contributing the development of intestinal inflammation.

Novel effects of ectoine, a bacteria-derived natural tetrahydropyrimidine, in experimental colitis

Evidence suggests an important role of intestinal barrier dysfunction in the etiology of inflammatory bowel disease (IBD). Therefore stabilizing mucosal barrier function constitutes a new therapeutic approach in its management. Ectoine is a compatible solute produced by aerobic chemoheterotrophic and halophilic/halotolerant bacteria, where it acts as osmoprotectant and effective biomembrane stabilizer, protecting the producing cells from extreme environmental stress. Since this natural compound was also shown to prevent inflammatory responses associated with IBD, its potential usefulness was studied in a model of colitis. Groups of rats were treated orally with different doses of ectoine (30-300 mg/kg) or sulfasalazine (reference drug) daily for 11 days. On day 8 colitis was induced by intracolonic instillation of 2,4,6-trinitrobenzenesulfonic acid, when overt signs of lesions develop within the next 3 days. On day 12, blood was withdrawn from the retro-orbital plexus of the rats and the animals were sacrificed. The colon was excised and examined macroscopically and microscopically. Relevant parameters of oxidative stress and inflammation were measured in serum and colon homogenates. Induction of colitis led to marked weight loss, significant histopathological changes of the colon, and variable changes in levels of myeloperoxidase, reduced glutathione, malondialdehyde, and all inflammatory markers tested. Treatment with ectoine ameliorated the inflammatory changes in TNBS-induced colitis. This effect was associated with reduction in the levels of TNF-α, IL-1β, ICAM-1, PGE2 and LTB4. The findings suggest that intestinal barrier stabilizers from natural sources could offer new therapeutic measures for the management of IBD.

The role of N-acetyltransferase 2 polymorphism in the etiopathogenesis of inflammatory bowel disease

BACKGROUND AND PURPOSE

Inflammatory bowel disease (IBD) consists of ulcerative colitis (UC) and Crohn's disease (CD), which are complex genetic disorders resulting from the interplay between several genetic and environmental risk factors. The arylamine N-acetyltransferase 2 (NAT2) enzyme detoxifies a wide spectrum of naturally occurring xenobiotics including carcinogens and drugs. Acetylation catalyzed by NAT2 is an important process in metabolic activation of arylamines to electrophilic intermediates that initiate carcinogenesis. The aim of our study was to determine whether there is any association between the susceptibility to inflammatory bowel disease among the variations of NAT2 genotypes.

METHODS

This study was carried out in 80 patients with IBD. The control group consisted of 100 healthy volunteers. The most common mutations found in the Caucasian population are at the positions 481T, 803G, 590A and 857A on the NAT2 gene. This was determined using the polymerase chain reaction-restriction fragment length polymorphism method with DNA extracted from peripheral blood.

RESULTS

Risk of IBD development was 3.86 for the carriers of the NAT2*5/NAT2*7 genotype and 2.53 for the carriers with NAT2*6/NAT2*7, but it was not statistically significant. A statistically significant correlation between the NAT2*7 allele prevalence and the risk for developing IBD was found (OR = 5.8; P = 0.005).

CONCLUSIONS

Higher prevalence of the NAT2*7 allele in patients with IBD and the obtained OR values could suggest that this mutation has the effect of increasing IBD development. Future studies are needed to confirm our assumptions on larger group of patients.

Inflammatory bowel disease in rats: Bacterial and chemical interaction

AIM: To develop a novel model of colitis in rats, using a combination of iodoacetamide and enteropathogenic E. coli (EPEC), and to elucidate the pathophysiologic processes implicated in the development of ulcerative colitis (UC).

METHODS: Male Sprague-Dawley rats (n = 158) were inoculated intrarectally on a weekly basis with 4 different combinations: (a) 1% methylcellulose (MC), (b) 100 &mgr;L of 6% iodoacetamide (IA) in 1% MC, (c) 200 &mgr;L containing 4 × 10⁸ colony factor units (CFU) of EPEC, and (d) combined treatment of (IA) followed by bacteria (B) after 2 d. Thirty days post treatment, each of the four groups was divided into two subgroups; the inoculation was stopped for one subgroup and the other subgroup continued with biweekly inoculation until the end of the experiment. Colitis was evaluated by the clinical course of the disease, the macroscopic and microscopic alterations, activity of myeloperoxidase (MPO), and by TNF-α gene expression.

RESULTS: Findings indicative of UC were seen in the combined treatment (IA + B) as well as the IA continued treatment groups: the animals showed slow rate of increase in body weight, diarrhea, bloody stools, high colonic ulcer score, as well as histological alterations characteristic of UC, with an extensive inflammatory reaction. During the course of the experiment, the MPO activity was consistently elevated and the TNF-α gene expression was upregulated compared to the control animals.

CONCLUSION: The experimental ulcerative colitis model used in the present study resembles, to a great extent, the human disease. It is reproducible with characteristics indicative of chronicity.

Butyrate regulates the expression of pathogen-triggered IL-8 in intestinal epithelia

Inflammatory bowel disease (IBD) is characterized by an exaggerated immune response that involves pro-inflammatory cytokines including IL-8. Production of these pro-inflammatory cytokines is triggered by pathogen-associated molecular patterns (PAMP). Butyrate, a product of bacterial fermentation of carbohydrates, has been reported to modulate inflammation in IBD, possibly by regulating production of pro-inflammatory cytokines. However, this effect of butyrate is controversial. In this study, we used Pam3CSK4 (Pam3CysSerLys4), the acylated NH2-terminus of the bacterial lipoprotein (a PAMP), to mimic in vivo infection of pathogens. Butyrate transiently down-regulated expression of IL-8 stimulated by Pam3CSK4. Treatment of cells with butyrate before Pam3CSK4, however, enhanced production of IL-8. Furthermore, butyrate induced expression of A20, a negative regulator of the nuclear factor-kappaB pathway. Over-expression of A20 inhibited Pam3CSK4-triggered IL-8 expression. Our data suggest that the inflammatory modulation of butyrate in IBD is mediated by A20 and a short pulse rather than continuous administration of butyrate may provide a protective effect on IBD.

Stimulatory and costimulatory effects of IL-18 directed to different small intestinal CD43 T cell subsets

This study has examined the stimulatory and costimulatory effects of IL-18 on two subsets of murine small intestinal intraepithelial lymphocytes (IELs) defined by the expression of the CD43 S7 glycoform. Data from gene array studies and real-time PCR indicated that S7(+) IELs had significantly higher levels of gene expression for the IL-18 receptor and the IL-18R accessory protein than S7(-) IELs. IL-18 costimulation of IELs in conjunction with CD3-induced activation resulted in significantly greater proliferation than CD3 stimulation alone. In CFSE dilution experiments, IL-18 costimulation favored the S7(+) IEL population. IL-18 costimulation did not affect apoptosis of either S7(-) or S7(+) IELs compared with CD3 stimulation alone. Although IL-18 costimulation did not alter the total number of IFN-gamma-producing cells relative to CD3 stimulation alone, twice as many S7(+) IELs were IFN-gamma -secreting cells than S7(-) IELs in both CD3-stimulated and IL-18-costimulated cultures. Notably, direct IL-18 stimulation in the absence of CD3 activation induced an IFN-gamma response that was predominantly directed to the S7(+) population, indicating that IL-18 is itself an IFN-gamma activational signal for intestinal T cells. In contrast, direct IL-18 stimulation of IELs did not generate TNF-alpha-producing cells, indicating a differential response in the activation of proinflammatory cytokines following IL-18 exposure. These findings point to distinctly different activational effects of IL-18 on IELs, both with regard to the type of functional responses elicited and with respect to the IEL subsets affected.

Evaluation of Helicobacter species in inflammatory bowel disease

BACKGROUND

Bacteria have been implicated in the pathogenesis of inflammatory bowel disease. Helicobacter species have been shown to cause colitis in animal models and have been identified in human diarrhoeal illness and Crohn's disease.

AIM

To determine whether Helicobacter species are present in human inflammatory bowel disease tissue.

METHODS

Thirty patients undergoing colonoscopy for clinical reasons were studied. Nine had Crohn's disease, 11 had ulcerative colitis and 10 had histologically normal colons. Tissue was snap-frozen at -70 degrees C. DNA was extracted and examined by five different polymerase chain reaction (PCR) assays that were either genus or species specific for Helicobacter.

RESULTS

Analyses of colonic biopsies by two Helicobacter genus-specific PCR assays, two H. pylori-specific assays and a PCR assay designed to amplify fragments of 'H. heilmannii'-like organisms demonstrated that product was not generated by any test. Internal control PCR demonstrated that PCR results for the five assays were not negative due to the presence of residual substances inhibitory to PCR.

CONCLUSIONS

Helicobacter species were not identified in this study, using multiple PCRs to eliminate the problems of non-specific cross-reaction. This suggests that Helicobacter species do not play a role in the pathogenesis of inflammatory bowel disease.

Natural history and clinical behavior of Crohn's disease extending beyond two decades

Crohn's disease is a heterogeneous inflammatory disorder characterized by strictures or perforating complications. Information on natural history is limited. In the present study, 150 patients with long-standing Crohn's disease, including 81 females and 69 males, were seen continuously by a single clinician for at least 20 years. Additional retrospective data were available extending for >40 years and 13 have now died, usually with an advanced malignancy. To evaluate disease expression, phenotypic clinical characteristics defined by the 1998 Vienna classification for Crohn's disease were used and included age at diagnosis, location of disease, and disease behavior at the time of diagnosis or 10 years or 20 years after diagnosis. Most patients were initially diagnosed before the age of 40 years (94%) and had ileocolonic disease (65.3%). At diagnosis, both females and males were most often classified with inflammatory disease (nonstenosing, nonpenetrating); however, over the course of the disease, particularly in the first decade, decreased numbers of patients with inflammatory disease and increased numbers with penetrating disease were seen. In addition, some with stenosing disease eventually developed penetrating disease. Disease localized to ileum alone was most often complicated by stricture formation, whereas ileocolonic disease was usually complicated by a penetrating complication. This shift in disease behavior indicates that Crohn's disease is a dynamic process that phenotypically evolves and progresses with time.