Inflammatory bowel disease and smoking: a review of epidemiology, pathophysiology, and therapeutic implications

Therapeutic effectiveness of orally administered transgenic low-alkaloid tobacco expressing human interleukin-10 in a mouse model of colitis

Inflammatory bowel disease (IBD) represents a spectrum of diseases in which inflammation leads to acute and chronic gut injury. It is a growing health issue for which no cure exists. The pathogenesis is multifactorial with links to infectious and environmental events that trigger disease in genetically predisposed individuals. Treatment of the two major forms of IBD, Crohn's disease and ulcerative colitis, involves the reduction of inflammation with toxic immunosuppressive drugs or blocking of the pro-inflammatory effects of tumour necrosis factor-alpha (TNF-alpha) with antibodies. Here, we show that the oral administration of transgenic low-alkaloid tobacco expressing the contra-inflammatory cytokine human interleukin-10 (hIL-10) reduces the severity of colitis by down-regulating TNF-alpha expression directly at the sites of inflammation in IBD-susceptible IL-10(-/-) mice. hIL-10 expressed in plants is biologically active and displays resistance to gastrointestinal degradation. Dietary supplementation with plant tissue delivering up to 9 microg of hIL-10 daily for 4 weeks was well tolerated by treated mice. Gut histology was significantly improved relative to controls (P = 0.002), and was correlated with a decrease in small bowel TNF-alpha mRNA levels and an increase in IL-2 and IL-1beta mRNA levels. Transgenic plants expressing IL-10 to directly attenuate TNF-alpha expression at sites of inflammation in the gut may become a useful new approach in the luminal therapy of IBD.

Exploitation of the nicotinic anti-inflammatory pathway for the treatment of epithelial inflammatory diseases

Discoveries in the first few years of the 21st century have led to an understanding of important interactions between the nervous system and the inflammatory response at the molecular level, most notably the acetylcholine (ACh)-triggered, α7-nicotinic acetylcholine receptor (α7nAChR)-dependent nicotinic anti-inflammatory pathway. Studies using the α7nAChR agonist, nicotine, for the treatment of mucosal inflammation have been undertaken but the efficacy of nicotine as a treatment for inflammatory bowel diseases remains debatable. Further understanding of the nicotinic anti-inflammatory pathway and other endogenous anti-inflammatory mechanisms is required in order to develop refined and specific therapeutic strategies for the treatment of a number of inflammatory diseases and conditions, including periodontitis, psoriasis, sarcoidosis, and ulcerative colitis.

Mechanisms of disease: pathogenesis of Crohn's disease and ulcerative colitis

Crohn's disease and ulcerative colitis are idiopathic, chronic, relapsing, inflammatory conditions that are immunologically mediated. Although their exact etiologies remain uncertain, results from research in animal models, human genetics, basic science and clinical trials have provided important new insights into the pathogenesis of chronic, immune-mediated, intestinal inflammation. These studies indicate that Crohn's disease and ulcerative colitis are heterogeneous diseases characterized by various genetic abnormalities that lead to overly aggressive T-cell responses to a subset of commensal enteric bacteria. The onset and reactivation of disease are triggered by environmental factors that transiently break the mucosal barrier, stimulate immune responses or alter the balance between beneficial and pathogenic enteric bacteria. Different genetic abnormalities can lead to similar disease phenotypes; these genetic changes can be broadly characterized as causing defects in mucosal barrier function, immunoregulation or bacterial clearance. These new insights will help develop better diagnostic approaches that identify clinically important subsets of patients for whom the natural history of disease and response to treatment are predictable.

Nicotine modulates expression of amyloid precursor protein and amyloid precursor-like protein 2 in mouse brain and in SH-SY5Y neuroblastoma cells

Epidemiological studies indicate that tobacco smoking can be protective against neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD). The objective of the present study was to examine the changes in gene expression induced by chronic oral nicotine administration (100 mug/ml in 2% saccharin for 14 days), with special emphasis on amyloid precursor protein (APP) and its homologue, amyloid precursor-like protein 2 (APLP2), in different brain regions of C57BL/6 mice using a pathway-focused microarray. Our results revealed that nicotine stimulated mRNA expression of APP in the amygdala (64%; P = 0.003) and hippocampus (32%; P = 0.034) and of APLP2 in the amygdala (39%; P = 0.002). These results were verified by quantitative real-time RT-PCR except that expression of APLP2 was also significantly upregulated by nicotine in the hippocampus. In addition, in vitro nicotine treatment of SH-SY5Y neuroblastoma cells resulted in a significant increase in expression of APP protein, soluble APP, and APLP2, whereas co-treatment with mecamylamine (an antagonist of nicotinic acetylcholine receptors) attenuated the stimulating effect of nicotine on APP and APLP2 expression. These findings suggest that nicotine treatment facilitates the increase in the expression of mRNA and protein of the APP and APLP2 genes in rat brain and SH-SY5Y neuroblastoma cells.

Acute gastroenteritis is followed by an increased risk of inflammatory bowel disease

BACKGROUND & AIMS

Bacterial intestinal infections have been implicated as a possible cause of exacerbation of inflammatory bowel disease (IBD). We explored the relationship between infectious gastroenteritis and the occurrence of IBD using data from the General Practice Research Database.

METHODS

A cohort of patients aged 20-74 years with an episode of acute infectious gastroenteritis (n = 43,013) was identified. From the same source population, an age-, sex-, and calendar time-matched control group free of gastroenteritis was sampled (n = 50,000). Both cohorts were followed up for a mean duration of 3.5 years.

RESULTS

The estimated incidence rate of IBD was 68.4 per 100,000 person-years after an episode of gastroenteritis and 29.7 per 100,000 person-years in the control cohort. The hazard ratio of IBD was 2.4 (95% confidence interval [CI], 1.7-3.3) in the gastroenteritis cohort compared with the control cohort, and the excess risk was greater during the first year after the infective episode (hazard ratio, 4.1; 95% CI, 2.2-7.4). The relative risk of developing Crohn's disease in the gastroenteritis cohort was greater than that of ulcerative colitis, especially during the first year after the infective episode (hazard ratio, 6.6; 95% CI, 1.9-22.4).

CONCLUSIONS

Our results are compatible with the hypothesis that infectious agents causing an episode of infectious gastroenteritis could play a role in the initiation and/or exacerbation of IBD.

Heat stress increases protein antigen transport across the intestinal epithelium via a mechanism of impairing proteolytic enzymatic activity

It has not been fully understood how intact protein antigens escape digestion in the course of absorption. The present study was designed to investigate the mechanism that heat stress induced an increase in intact protein antigen absorption. Human colonic cell line Caco-2 cells were treated with high temperature (37 to 43 degrees C) for 60 min. Epithelial permeability was evaluated by horseradish peroxidase (HRP) flux and dextran flux. Activity of the major intracellular proteolytic enzyme, acid phosphatase, in Caco-2 cells was determined. HRP products in Caco-2 cells were observed by electron microscopy (EM) and analyzed with a computerized image processing system. Heat stress significantly increased intact protein HRP transport across Caco-2 monolayers, decreased acid phosphatase activity of the cells, and significantly reduced transepithelial electric resistance of Caco-2 cells. EM results showed that HRP transport across Caco-2 monolayers occurred mainly via the intracellular pathway.

Investigating the hygiene hypothesis as a risk factor in pediatric onset Crohn's disease: a case-control study

BACKGROUND AND OBJECTIVES

Evidence for the hygiene hypothesis in the etiology of Crohn's disease (CD) is unclear. We investigated the relationship between infection-related exposures and risk for CD in children.

METHODS

A hospital-based case-control was carried out. Newly-diagnosed cases of CD (n = 194), less than 20 yr of age were recruited from the gastroenterology clinic of a large-pediatric inflammatory bowel disease (IBD) center in Montreal, Canada. Orthopedic patients pair-matched (n = 194) for timing of diagnosis and area of residence were recruited as controls. Information on infection-related exposures between birth and disease diagnosis was ascertained by administering a structured questionnaire to the mother and the index subject. The relationship between the frequency and timing of infection-related exposures with CD was studied.

RESULTS

The mean age (SD) at diagnosis was 12.3 (5.1). CD was more common after 10 yr of age. Gender distribution was similar between comparison groups. In multivariate conditional logistic regression, family history of IBD (odds ratio (OR) = 4.6; 95% confidence interval (CI) = 1.6-13.3), age (OR = 1.2; 95% CI = 1.1-1.3), and owning a pet (OR = 2.0; 95% CI = 0.9-4.5) were associated with risk for CD, whereas regular use of a personal towel (OR = 0.5; 95% CI = 0.2-0.9) and lesser crowding in homes (OR = 0.3; 95% CI = 0.1-0.8) were protective. Day-care attendance during the first 6 months of life and "physician-diagnosed infections" between 5 and 10 yr of age were associated with increased risks for CD.

CONCLUSIONS

Infection-related exposures seem to enhance risk for CD in children. The timing of these exposures during early childhood may be relevant to the etiology of pediatric CD.

Association of intestinal granulomas with smoking, phenotype, and serology in Chinese patients with Crohn's disease

INTRODUCTION

Crohn's disease (CD) is a heterogenous disease characterized by variable manifestations and outcomes, and increasing in incidence in China. Phenotypic classification has been proposed to assist in subtyping of disease. Non-caseating intestinal granulomas are a hallmark of CD, but whether intestinal granulomas help predict Chinese CD phenotypes or determine severity, is not known.

AIMS

To determine the association between intestinal granulomas with CD phenotype, severity, risk factors, and serological markers.

METHODS

This was a single-centre study of consecutive definite Chinese CD cases. Granulomas were diagnosed by an experienced GI pathologist. Correlation with the Vienna Classification and other parameters was performed.

RESULTS

Eighty Chinese CD patients were recruited, 40 (50%) of whom had intestinal granulomas. Intestinal granulomas were independently associated with the stricturing behavior (OR: 4.71; 95% CI: 1.41-15.72), colonic location of disease (OR: 26.96; 95% CI: 2.68-271.14), but not with age of CD diagnosis. Current or previous smoking protected against the development of granulomas (OR: 0.16; 95% CI: 0.04-0.59). Granulomas were not associated with peri-anal involvement, extra-intestinal manifestations, anti-neutrophil cytoplasmic antibody or anti-Saccharomyces cerevisiae antibody serology, or severity of CD gauged by the requirement of major intestinal surgery or immunomodulating therapy.

CONCLUSIONS

Intestinal granulomas in the setting of CD may be helpful in determining phenotypic subtypes of CD, but is unhelpful in predicting disease severity. Smoking impairs the formation of granulomas in CD.

Comparison of the efficacy and safety of Eudragit-L-coated mesalazine tablets with ethylcellulose-coated mesalazine tablets in patients with mild to moderately active ulcerative colitis

BACKGROUND

There are no comparative studies of coated mesalazine.

AIM

To compare the efficacy and tolerability of Eudragit-L- and ethylcellulose-coated mesalazine tablets in patients with mild to moderately active ulcerative colitis.

METHODS

A double-blind, double-dummy, randomized parallel group trial was performed across 18 centres in Australia, and 20 in Eastern Europe. Patients were treated with 3 g mesalazine for 8 weeks with the primary efficacy end point being clinical remission.

RESULTS

Of 215 patients, 69% achieved clinical remission in both treatment groups (P < 0.001; chi-square test) with no differences in frequency of adverse events. In the Australian cohort (n = 63), the Eudragit-L group had a higher remission rate (73% vs. 36%) and responded 13 days faster, compared with those in the European group (67% vs. 84%, and 2 days respectively). No clear reasons for differences in treatment responses were identified.

CONCLUSIONS

Eudragit-L and ethylcellulose-coated mesalazine tablets are well tolerated and equally effective in achieving remission in mild-moderately active ulcerative colitis over 8 weeks.

Environment as a Critical Factor for the Pathogenesis and Outcome of Gastrointestinal Disease: Experimental and Human Inflammatory Bowel Disease and Helicobacter-Induced Gastritis

Environmental factors play an important role in the manifestation, course, and prognosis of diseases of the gastrointestinal tract such as inflammatory bowel disease (IBD) and Helicobacter pylori-induced gastritis. These two disease complexes were chosen for a discussion of the contribution of environmental factors to the disease outcome in humans and animal models. Dissecting complex diseases like IBD and Helicobacter-induced gastritis has shown that the outcome of disease depends on the allelic constellation of a host and the microbial and physical environments. Host alleles predisposing to a disease in one genomic and/or environmental milieu may not be deleterious in other constellations; on the other hand, microbes can have different effects in different hosts and under different environmental conditions. The impact of the complex interaction between host genetics and environmental factors, particularly microflora, also underlines the importance of a defined genetic background and defined environments in animal studies and is indicative of the difficulties in analyzing complex diseases in humans.

Enteric nervous system

PURPOSE OF REVIEW

Our aim was to provide a synopsis of how the field of enteric neurobiology has advanced during the past year.

RECENT FINDINGS

With such a large number of studies to choose from and given our emphasis in last year's issue on developmental aspects of the enteric nervous system, we have focused on several key themes reflecting the current interest in the way the enteric nervous system is altered in disease.

SUMMARY

The new basic science information gathered during the past year provides insight into pathophysiological processes and will pave the way for improved understanding of both organic and 'functional' gastrointestinal disorders.

Evidence that stress contributes to inflammatory bowel disease: evaluation, synthesis, and future directions

BACKGROUND

There is a long but inconsistent history of observations suggesting that psychologic stress contributes to the course of ulcerative colitis (UC) and Crohn's disease (CD). This study evaluated the strength of evidence for a causal link between stress, depression, and inflammatory bowel disease course.

METHODS

Literature review and unstructured qualitative analysis of all reported prospective studies of stress or depression and disease outcomes and randomized controlled studies (RCTs) of stress reduction interventions.

RESULTS

Although results remain inconsistent, prospective studies support a role for psychologic stress in the course of UC and for depressive symptoms in the course of CD. RCTs do not support the benefit of stress reduction for unselected patients with CD. UC has not been studied with adequately designed RCTs. Animal models suggest mechanisms whereby stress can exacerbate preexisting inflammatory disease, especially through increased epithelial permeability.

CONCLUSIONS

A synthesis of the literature is presented suggesting approaches to reconcile apparently contradictory findings. Recommendations for further research emphasize refinements to avoid type II error and to identify subgroups of patients who are most likely to experience stress-related effects on illness or to benefit from stress reduction intervention.