The role of cigarettes and nicotine in the onset and treatment of ulcerative colitis

Development of Mucosal PNAd+ and MAdCAM-1+ Venules during Disease Course in Ulcerative Colitis

PNAd and MAdCAM-1 addressins on venules are of importance in T-cell homing and potential therapeutic targets in ulcerative colitis (UC). Normally, PNAd⁺ high endothelial venules (HEVs) are only present in lymphoid organs, whereas small numbers of MAdCAM-1⁺ venules can be seen in non-lymphoid tissue. We aimed to study their presence in the intestinal mucosa of UC patients at diagnosis and during follow-up, and their correlation with disease activity. Colonic biopsy specimens of 378 UC patients were analyzed by immunohistochemistry for CD3, CD20, ERG, MECA-79 (PNAd) and MECA-376 (MAdCAM-1) and compared to healthy controls (HC). The proportion of PNAd⁺HEVs in UC at diagnosis was 4.9% (IQR 2.0%-8.3%), while none were detected in HC. During follow-up, PNAd⁺HEVs completely disappeared in remission (n = 93), whereas the proportion in active disease was similar to baseline (n = 285, p = 0.39). The proportion of MAdCAM-1⁺venules in UC at baseline was 5.8% (IQR 2.6-10.0). During follow-up, the proportion in remission was comparable to diagnosis, but upregulated (7.5% (IQR 4.4-10.9), p = 0.001) in active disease. In conclusion, PNAd⁺HEVs appear in UC during active inflammation which could thus serve as a marker for disease activity, whereas MAdCAM-1⁺venules remain present after inflammation is resolved and increase after subsequent flares, reflecting chronicity and potentially serving as a therapeutic target.

Nicotine treatment ameliorates DSS-induced colitis by suppressing MAdCAM-1 expression and leukocyte recruitment

The enhanced recruitment of leukocytes to the inflamed colon is a key feature of ulcerative colitis (UC). The gut-specific adhesion molecules involved in leukocyte recruitment have emerged as recent therapeutic targets. Nicotine absorbed from smoking has been reported to work protectively in UC patients. Our hypothesis is that nicotine may suppress the aberrant leukocyte recruitment and colonic inflammation via the suppression of the overexpressed gut-specific adhesion molecules in the inflamed colon. To test this hypothesis, the severity of colitis and the degree of leukocyte recruitment induced by gut-specific adhesion molecules were assessed in dextran sulfate sodium (DSS) colitis mice (C57BL/6J mice treated with 3% DSS) with or without nicotine treatment. We also studied the in vitro changes in the expression of adhesion molecules by using a vascular endothelial cell line. DSS-induced colitis was accompanied by increases in disease activity index (DAI), histological score, recruitment of leukocytes, and the expression of adhesion molecules, mucosal vascular addressin cell adhesion molecule-1 (MAdCAM-1) and VCAM-1. Nicotine treatment significantly attenuated MAdCAM-1 expression, leukocyte recruitment, DAI, and histological score. The expression of β7-integrin, the ligand for MAdCAM-1, on leukocytes was not affected by nicotine treatment. In vitro study, the TNF-α-enhanced mRNA expression of MAdCAM-1 was reduced by the coadministration of nicotine in a dose-dependent manner, possibly via nicotinic receptor activation. These results supported our hypothesis that nicotine treatment ameliorated colitis through the suppression of MAdCAM-1 expression on the microvessels in the inflamed colon. Further investigation is warranted on the role of nicotine in the treatment of UC.

Anti-inflammatory effects of nicotine in obesity and ulcerative colitis

Cigarette smoke is a major risk factor for a number of diseases including lung cancer and respiratory infections. Paradoxically, it also contains nicotine, an anti-inflammatory alkaloid. There is increasing evidence that smokers have a lower incidence of some inflammatory diseases, including ulcerative colitis, and the protective effect involves the activation of a cholinergic anti-inflammatory pathway that requires the α7 nicotinic acetylcholine receptor (α7nAChR) on immune cells. Obesity is characterized by chronic low-grade inflammation, which contributes to insulin resistance. Nicotine significantly improves glucose homeostasis and insulin sensitivity in genetically obese and diet-induced obese mice, which is associated with suppressed adipose tissue inflammation. Inflammation that results in disruption of the epithelial barrier is a hallmark of inflammatory bowel disease, and nicotine is protective in ulcerative colitis. This article summarizes current evidence for the anti-inflammatory effects of nicotine in obesity and ulcerative colitis. Selective agonists for the α7nAChR could represent a promising pharmacological strategy for the treatment of inflammation in obesity and ulcerative colitis. Nevertheless, we should keep in mind that the anti-inflammatory effects of nicotine could be mediated via the expression of several nAChRs on a particular target cell.

Nicotine and inflammatory neurological disorders

Cigarette smoke is a major health risk factor which significantly increases the incidence of diseases including lung cancer and respiratory infections. However, there is increasing evidence that smokers have a lower incidence of some inflammatory and neurodegenerative diseases. Nicotine is the main immunosuppressive constituent of cigarette smoke, which inhibits both the innate and adaptive immune responses. Unlike cigarette smoke, nicotine is not yet considered to be a carcinogen and may, in fact, have therapeutic potential as a neuroprotective and anti-inflammatory agent. This review provides a synopsis summarizing the effects of nicotine on the immune system and its (nicotine) influences on various neurological diseases.

Risk factors for ulcerative colitis in a Chinese population: an age-matched and sex-matched case-control study

BACKGROUND AND AIMS

Cigarette smoking, alcohol use, appendectomy, and family history of inflammatory bowel disease (IBD) have all been shown to be associated with IBD, but there were no reports of risk factors for IBD in a Chinese population in which the incidence of IBD is increasing during the past decade. We conducted a case-control study to examine associations between previously reported environmental risk factors and development of ulcerative colitis (UC) in Wuhan city, central China.

METHODS

A total of 177 patients with UC and 177 age-matched and sex-matched controls were prospectively studied in Wuhan city from January 2004 to December 2004. An age-matched and sex-matched case-control study was conducted to assess the role of smoking, alcohol use, appendectomy, and other potential risk factors in the development of UC by a detailed questionnaire.

RESULTS

Smoking was a protective factor and exsmoking is a risk factor for UC [compared with nonsmokers, smokers: odds ratios (OR)=0.28, 95% confidence intervals (CI): 0.16-0.48, P=0.0001; exsmokers: OR=4.36, 95%CI: 1.46-13.04, P=0.008]. Positive family history of IBD was a risk factor (OR=4.35, 95%CI: 1.21-15.71, P=0.025) whereas appendectomy was a protective factor (OR=0.24, 95%CI: 0.07-0.86, P=0.028) for UC. There were no significant associations between UC and other factors examined.

CONCLUSIONS

Although the incidence of UC in Chinese is relatively lower than that in white, the same risk factors for UC that were reported in white populations were associated with Chinese UC patients. Specifically, smoking was a protective factor for UC and exsmoking was associated with an increase risk of UC in a Chinese population. Family history of IBD was shown to be a risk for UC, whereas appendectomy was associated with a low risk for UC.

Case-control genetic association studies in gastrointestinal disease: review and recommendations

As our knowledge of genetic variation grows, our ability to use this information to unravel the mysteries of human disease expands. Identification of genes and inexpensive methods to sequence them has resulted in a rising interest in evaluating specific variants and whether they may result in clinical manifestations or symptoms. Genetic variants include restriction fragment length polymorphisms, variable number tandem repeats, DNA microsatellites, and single nucleotide polymorphisms. Using these variants, genetic association studies, also referred to as candidate gene association or genotype-disease association studies are being performed by clinical and basic researchers alike. They are relatively easy to perform, but as a result of their deceivingly simple design, can be conducted or interpreted poorly. A positive association between a genotype and a GI disease of interest may be because the genotype causes (or increases susceptibility to) the disease, but may also be the result of the genotype being in linkage disequilibrium with the actual disease susceptibility gene, or be a false positive due to chance or bias in study design. An excellent understanding of the genetic and methodological issues surrounding these studies is therefore essential. We provide an overview of terminology and provide insight into the complexities underlying these studies. Recommendations for reporting the results of a genetic association study are provided to assist with study planning and manuscript preparation.

Is smoking an indirect risk factor for the development of ulcerative colitis? An age- and sex-matched case-control study

BACKGROUND

It has been suggested that smoking protects against the development of ulcerative colitis (UC). Evidence is mainly driven from the way data from a multitude of case-control studies have been interpreted.

METHODS

An age- and sex-matched case-control study was conducted to further assess the association between history of smoking, past surgery, childhood, and other potential causative factors with the development of UC using the answers to a detailed questionnaire. The data were analyzed using univariate analysis and logistic regression. The results are presented as odds ratios (OR) and 95% confidence intervals.

RESULTS

One hundred and two cases and an equal number of matched controls were included in the study. Using a three-level comparison, at the age of diagnosis, the risks of developing UC were 0.41 (0.19-0.87), 3.45 (1.62-7.35) and 0.78 (0.44-1.37) for smokers, ex-smokers and non-smokers, respectively. When compared to individuals who have never smoked, ex-smokers were at a higher risk of developing the disease (OR = 3.00 (1.38-6.51)). The specific history of quitting smoking prior to the age of onset of symptoms was associated with an increased risk for developing the disease (OR = 3.45 (1.62-7.35)).

CONCLUSIONS

Active smoking was associated with a low risk for the development of UC, but the lack of history of smoking was not associated with an increase in the risk. History of quitting smoking prior to the onset of symptoms, in contrast, was associated with a significant increase in the risk of developing the disease. These findings make the theory of a simple protective effect of smoking on the development of UC difficult to justify. It may be plausible to suggest that the withdrawal of the immunosuppressive effect of smoking triggers the disease onset in a genetically susceptible individual or simply unmasks its symptoms.

Nicotinic acetylcholine receptors in health and disease

Nicotinic acetylcholine receptors (AChRs) are a family of acetylcholine-gated cation channels that form the predominant excitatory neurotransmitter receptors on muscles and nerves in the peripheral nervous system. AChRs are also expressed on neurons in lower amounts throughout the central nervous system. AChRs are even being reported on unexpected cell types such as keratinocytes. Structures of these AChRs are being determined with increasing precision, but functions of some orphan subunits are just beginning to be established. Functional roles for postsynaptic AChRs in muscle are well known, but in neurons the post-, peri-, extra-, and presynaptic roles of AChRs are just being revealed. Pathogenic roles of AChRs are being discovered in many diseases involving mechanisms ranging from mutations, to autoimmune responses, to the unknown; involving cell types ranging from muscles, to neurons, to keratinocytes; and involving signs and symptoms ranging from muscle weakness to epilepsy, to neurodegenerative disease, to psychiatric disease, to nicotine addiction. Awareness of AChR involvement in some of these diseases has provoked new interests in development of therapeutic agonists for specific AChR subtypes and the use of expressed cloned AChR subunits as possible immunotherapeutic agents. Highlights of recent developments in these areas will be briefly reviewed.