Tobacco and IBD: relevance in the understanding of disease mechanisms and clinical practice

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.

The vagus nerve: a tonic inhibitory influence associated with inflammatory bowel disease in a murine model

BACKGROUND & AIMS

The recently proposed Inflammatory Reflex describes an interaction between the vagus nerve and peripheral macrophages, resulting in attenuation of proinflammatory cytokine release in response to systemic exposure to bacterial endotoxin. The purpose of this study was to determine whether a similar vagus/macrophage axis modulates the inflammatory responses in the colon in mice.

METHODS

We assessed the Disease Activity Index (DAI), macroscopic and histologic damage, serum amyloid-P level, and myeloperoxidase activity in colitis induced by administration of dextran sodium sulfate (DSS) in healthy and vagotomized C57BL/6 and in mice deficient in macrophage-colony stimulating factor (M-CSF)-induced and in hapten-induced colitis. A pyloroplasty was performed in vagotomized mice.

RESULTS

DAI, macroscopic and histologic scores, myeloperoxidase activity, levels of serum amyloid-P, and colonic tissue levels of interleukin (IL)-1beta, IL-6, and tumor necrosis factor-alpha were increased significantly in vagotomized mice 5 days post-DSS and 3 days after hapten-induced colitis compared with sham-operated mice that received DSS or the hapten. Pretreatment with nicotine significantly decreased each of these markers in vagotomized mice with DSS colitis, and all markers except DAI and IL-6 in sham-operated DSS-treated mice. Conversely, hexamethonium treatment significantly increased each of these markers in the sham-operated DSS-treated mice. Vagotomy had no effect on the colitis in M-CSF-deficient mice.

CONCLUSIONS

The vagus nerve plays a counterinflammatory role in acute colitis via a macrophage-dependent mechanism, involving hexamethonium-sensitive nicotinic receptors. The identification of a counterinflammatory neural pathway would open new therapeutic avenues for treating acute exacerbations of inflammatory bowel disease.

Sinonasal involvement as a rare extraintestinal manifestation of Crohn's disease

Crohn's disease is a chronic idiopathic slowly developing transmural inflammation of the digestive system. It usually involves the small intestine and/or the area around the anus but can also affect the entire gastrointestinal tract anywhere from the mouth to the anus. Extra intestinal manifestations occur frequently and multiple organ systems may be affected: the skin, joints, spine, eyes, liver and bile ducts. In contrast, nasal manifestations are extremely rare and only a few cases have been reported up to date in the worldwide literature. The authors report two cases with nasal manifestations concomitant to intestinal Crohn's disease and go over the relevant literature on such an association.

Geographical variations of inflammatory bowel disease in France: a study based on national health insurance data

BACKGROUND AND AIM

A north-south gradient in inflammatory bowel disease (IBD) incidence has been found in Europe and the United States. Its existence is inferred from comparisons of registries that cover only small portions of territories. Several studies suggest that IBD incidence in the north has reached a plateau, whereas in the south it has risen sharply. This evolution tends to reduce the north-south gradient, and it is uncertain whether it still exists. In France, patients with IBD are fully reimbursed for their health expenses by the national health insurance system, which is a potential source of data concerning the incidence of IBD at the national level. The aim of this study was to assess the geographical distribution of Crohn's disease (CD) and ulcerative colitis (UC) in France and to test the north-south gradient hypothesis.

METHODS

This study was conducted in metropolitan France and included patients to whom IBD reimbursement was newly attributed between January 1, 2000 and December 31, 2002. Data provided relate to age, sex, postcode area of residence, and IBD type. The mapping of geographical distribution of smoothed relative risks (RR) of CD and UC was carried out using a Bayesian approach, taking into account autocorrelation and population size in each département.

RESULTS

In the overall population, incidence rates were 8.2 for CD and 7.2 for UC per 100,000 inhabitants. A clear north-south gradient was shown for CD. Départements with the highest smoothed RR were located in the northern third of France. By contrast, the geographical distribution of smoothed RR of UC was homogeneous.

CONCLUSIONS

This study shows a north-south gradient in France for CD but not for UC.

Higher platelet P-selectin in male patients with inflammatory bowel disease compared to healthy males

AIM: To observe if the total amount of platelet P-selectin (tP-selectin) in patients with inflammatory bowel disease (IBD) was related to disease entity or activity, 5-aminosalicylic acid (5-ASA) medication or gender.

METHODS: tP-selectin was measured by immunoassay in seventeen IBD patients and twelve healthy controls.

RESULTS: Compared to controls, there was no difference of tP-selectin in patients related to disease entity or activity and 5-ASA medication. When the groups were split according to gender the male patient group showed higher levels of tP-selectin compared to male controls (153 ng/mL vs 94 ng/mL, P< 0.05).

CONCLUSION: Increased tP-selectin levels may alter the inflammatory response and susceptibility to thromboembolic disease. As previously shown with soluble P-selectin, tP-selectin shows gender dependent differences important to consider in future studies.

Prior appendectomy and the phenotype and course of Crohn's disease

AIM

To determine whether prior appendectomy modifies the phenotype and severity of Crohn's disease.

METHODS

Appendectomy status and smoking habits were specified by direct interview in 2838 patients consecutively seen between 1995 and 2004. Occurrence of complications and therapeutic needs were reviewed retrospectively. Additionally, annual disease activity was assessed prospectively between 1995 and 2004 in patients who had not had ileocecal resection and of a matched control group.

RESULTS

Compared to 1770 non-appendectomized patients, appendectomized patients more than 5 years before Crohn's disease diagnosis (n=716) were more often females, smokers, with ileal disease. Cox regression showed that prior appendectomy was positively related to the risk of intestinal stricture (adjusted hazard ratio, 1.24; 95% confidence interval, 1.13 to 1.36; P=0.02) and inversely related to the risk of perianal fistulization (adjusted hazard ratio, 0.75; 95% confidence interval, 0.68 to 0.83; P=0.002). No difference was observed between the two groups regarding the therapeutic needs, except for an increased risk of surgery in appendectomized patients, attributable to the increased prevalence of ileal disease. Between 1995 and 2004, Crohn's disease was active during 50% of years in appendectomized patients (1318 out of 2637 patient-years) and 51% in non-appendectomized patients (1454 out of 2841 patient-years; NS).

CONCLUSION

Prior appendectomy is associated with a more proximal disease and has an increased risk of stricture and a lesser risk of anal fistulization. However, the severity of the disease is unaffected.

Determinants of vitamin D status in adult Crohn's disease patients, with particular emphasis on supplemental vitamin D use

OBJECTIVE

To investigate determinants (pathophysiologic and physiologic, behavioural and lifestyle) of vitamin D status in Irish Crohn's disease (CD) patients.

DESIGN

A cross-sectional observational study.

SETTING

Cork City, Ireland (52 degrees N).

SUBJECTS

Crohn's Disease patients (n=58; mean age 38.1 years) were recruited from Cork University Hospital.

RESULTS

Fifty and nineteen percent of Irish CD patients were vitamin D deficient (defined by serum 25 hydroxyvitamin (OH) D levels <50 nmol/l) during winter and summer, respectively. Multiple regression analysis showed that summer-time serum 25 (OH) D levels were positively associated with use of vitamin D supplements (P=0.033) and negatively associated with smoking (P=0.006) and being male (P=0.063). During winter-time, use of vitamin D supplements (P=0.041) and sun habits (P=0.066) were positively associated, whereas small intestinal involvement (P=0.005) and body mass index (BMI) (P=0.083) were negatively associated with serum 25 (OH) D levels. There was no significant association between other non-pathophysiologic (age, dietary calcium or vitamin D) or pathophysiologic factors (steroid use, resection), and serum 25 (OH) D levels, at either season. Approximately 41 and 60% of the total variation in summer- and winter-time serum 25 (OH) D, respectively, was explained by this model.

CONCLUSION

A high proportion of Irish CD patents had some level of vitamin D deficiency (<50 nmol/l) during late-wintertime. Use of regular low-dose supplemental vitamin D, particularly by patients with small intestinal involvement, cessation of smoking and adequate, but responsible, exposure to summer sunlight as well as maintaining BMI in the normal range could help maintain adequate vitamin D levels during wintertime.

Factors affecting recurrence after surgery for Crohn’s disease

Although in Crohn’s disease post-operative recurrence is common, the determinants of disease recurrence remain speculative. The aim of this study was to examine factors affecting post-operative recurrence of Crohn’s disease. A Medline-based literature review was carried out. The following factors were investigated: age at onset of disease, sex, family history of Crohn’s disease, smoking, duration of Crohn’s disease before surgery, prophylactic medical treatment (corticosteroids, 5-amino salicylic acid [5-ASA] and immunosuppressants), anatomical site of involvement, indication for surgery (perforating or non-perforating disease), length of resected bowel, anast-omotic technique, presence of granuloma in the specimen, involvement of disease at the resection margin, blood transfusions and post-operative complications. Smoking significantly increases the risk of recurrence (risk is approximately twice as high), especially in women and heavy smokers. Quitting smoking reduces the post-operative recurrence rate. A number of studies have shown a higher risk when the duration of the disease before surgery was short. There were, however, different definitions of ‘short’ among the studies. Prophylactic cortic-osteroids therapy is not effective in reducing the post-operative recurrence. A number of randomized controlled trials offered evidence of the efficacy of 5-ASA (mesalazine) in reducing post-operative recurrence. Recently, the thera-peutic efficacy of immunosuppressive drugs (azathioprine and 6-mercaptopurine) in the prevention of post-operative recurrence has been investigated and several studies have reported that these drugs might help prevent the recurrence. Further clinical trials would be necessary to evaluate the prophylactic efficacy of immunosuppressants. Several studies showed a higher recurrence rate in patients with perforating disease than in those with non-perforating disease. However, evidence for differing recurrence rates in perforating and non-perforating diseases is inconclusive. A number of retrospective studies reported that a stapled functional end-to-end anastomosis was associated with a lower recurrence rate compared with other types of anastomosis. However, prospective randomized studies would be necessary to draw a definite conclusion. Many studies found no difference in the recurrence rates between patients with radical resection and non-radical resection. Therefore, minimal surgery including strictureplasty has been justified in the management of Crohn’s disease. In this review, the following factors do not seem to be predictive of post-operative recurrence: age at onset of disease, sex, family history of Crohn’s disease, anatomical site of disease, length of resected bowel, presence of granuloma in the specimen, blood transfusions and post-operative complications. The most significant factor affecting post-operative recurrence of Crohn’s disease is smoking. Smoking significantly increases the risk of recurrence. A short disease duration before surgery seems, albeit to a very minor degree, to be associated with a higher recurrence rate. 5-ASA has been shown with some degree of confidence to lead to a lower recurrence rate. The prophylactic efficacy of immunosuppressive drugs should be assessed in future. A wider anastomotic technique after resection may reduce the post-operative recurrence rate, though this should be investigated with prospective randomized controlled trials.

Increased severity of experimental colitis in alpha5 nicotinic acetylcholine receptor subunit-deficient mice

Substantial evidence suggests a negative association between cigarette smoking and the incidence and severity of ulcerative colitis, a common human inflammatory bowel disease. Nicotine has been implicated in this association. The detection of nicotinic acetylcholine receptors in colonic epithelium, the primary tissue affected in ulcerative colitis, suggests a role for these receptors in the beneficial effect of nicotine on colonic inflammation. Using an animal model, we demonstrate for the first time that alpha5 nicotinic acetylcholine receptor knockout mice have significantly more severe experimental colitis than wild-type controls and that nicotine significantly ameliorates its course when compared with wild-type controls. These findings suggest that alpha5-containing nicotinic acetylcholine receptors participate in the modulation of colitis in mice, but other nicotinic acetylcholine receptor subunits also mediate the antiinflammatory effects of nicotine.