Mechanisms of Disease: Nicotine -- A Review of its Actions in the Context of Gastrointestinal Disease

Gareth AO Thomas; John Rhodes; John R Ingram

Disclosures

Nat Clin Pract Gastroenterol Hepatol. 2005;2(11):536-544. 

In This Article

Summary and Introduction

Smoking tobacco is associated with a number of gastrointestinal disorders. In some, such as Crohn's disease and peptic ulcer disease, it increases the risk of disease and has a detrimental effect on their course. In others, such as ulcerative colitis, it decreases the risk of disease and can have a favorable effect on disease course and severity. In the eighteenth and nineteenth centuries, nicotine was used as a 'panacea' for various ailments, including abdominal symptoms -- it is now under investigation to elucidate its role in gastrointestinal diseases that are associated with smoking. The actions of nicotine are complex; it is likely that its effects on the central nervous system, gastrointestinal tract and immune system interact with other risk factors, such as genetic susceptibility, to influence disease outcomes. This review focuses on the mechanisms of action of nicotine that might be relevant in gastrointestinal disease.

Whilst the detrimental effects of smoking on health are both well known and overwhelming, there is increasing evidence that smoking actually protects against some conditions. Smokers have a lower incidence of some neurodegenerative conditions such as Parkinson's and perhaps Alzheimer's diseases,[1] and gastrointestinal disorders such as ulcerative colitis.[2] The tobacco smoker is exposed to a cocktail of over 4,000 chemicals, which makes it difficult to identify the agents responsible for the wide-ranging effects of smoking, both detrimental and otherwise. Nicotine, the best known and most 'psychoactive' pharmacologic ingredient, is often considered synonymous with smoking in the context of disease, but whilst some of the harmful or 'negative' effects might involve nicotine, it is likely that most do not. Conversely, nicotine might be responsible for some protective or 'positive' effects. By teasing out the role of nicotine in this conundrum it is to be hoped that we will gain a better understanding of disease mechanisms, and possibly open the door to therapeutic alternatives.

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