Nicotine in Ulcerative Colitis: How Does It Work and How Can We Use It?

Purinergic component of mechanosensory transduction is increased in a rat model of colitis

ATP contributes to mechanosensory transduction in the rat colorectum. P2X3 receptors are present on dorsal root ganglia (DRG) neurons that supply this area of the gut. Previous studies have shown an increased role for ATP in inflamed tissues. We aimed to investigate whether an increased purinergic component exists during mechanosensory transduction in a rat model of colitis. An in vitro rat colorectal preparation was used to investigate whether distension increased ATP release and to evaluate the role of purinergic antagonists in distension-evoked sensory discharges in the pelvic nerve in normal and colitis preparations. DRG neuron purinoceptors were also studied. Distension-evoked responses in the colitis model were attenuated to a significantly greater extent by 2',3'-O-trinitrophenyl-ATP and pyridoxyl 5-phosphate 6-azophenyl-2',4'-disulfonic acid. Inflammation caused augmented distension-evoked sensory nerve excitation after application of ATP and alpha,beta-methylene ATP. Single-fiber analysis confirmed that mean firing per unit was increased. Distension-evoked increases in ATP release from epithelial cells were substantially higher. The number of DRG neurons responding to ATP and the number of those staining for the P2X3 receptor, particularly those containing calcitonin gene-related peptide, were increased. Adenosine, after ectoenzymatic breakdown of ATP, is involved to a lesser degree in the longer-lasting distension-evoked sensory discharge, suggesting reduced ATPase activity. It was therefore concluded that ATP has an enhanced role in mechanosensory transduction in the inflamed rat colorectum. The underlying mechanisms appear to involve increased distension-evoked release of ATP as well as an increase in the number of DRG neurons supplying the colorectum expressing P2X3 receptors, especially those containing calcitonin gene-related peptide.

Evolving medical therapies for ulcerative colitis

Therapies for patients with ulcerative colitis have, until recently, been limited in scope and efficacy. New formulations of mesalamine and corticosteroids have challenged the older therapies with respect to both efficacy and safety. The application of 6-mercaptopurine and azathioprine for steroid-refractory disease and maintenance of remission has resulted in studies of other candidate immunomodulatory agents. Biologic therapies targeting tumor necrosis factor, adhesion molecules, or other cytokines are under intense scrutiny as potential disease-altering agents that may even replace currently available products. Other approaches, including such wide-ranging products as heparin, nicotine, and probiotics, suggest that control of ulcerative colitis may require an individualized approach for each patient.

Inflammatory bowel disease: new insights into pathogenesis and treatment

Despite all the advances in our understanding of the pathophysiology of inflammatory bowel disease (IBD), we do not know the cause. Some of the most recently available data have been discussed here and yet it is now becoming increasingly accepted that immunogenetics play an important role in the predisposition, modulation, and perpetuation of IBD. The mucosal immune system is the central effector of intestinal inflammation and injury, with cytokines playing a central role in modulating inflammation. The role of intestinal milium, and enteric flora in particular, appears to be of greater significance than previously held. A review is made of the main areas of research exploring the mechanisms more intimately associated with the development of IBD, providing advances in the agents currently used, and identifying a host of new therapeutic agents potentially interacting with or interrupting specific targets in the genesis of IBD.

Chronic nicotine administration differentially alters jejunal and colonic inflammation in interleukin-10 deficient mice

BACKGROUND

Cigarette smoking alters the course of inflammatory bowel disease, is associated with protection against ulcerative colitis, but aggravates or has no effect on Crohn's disease. While the aetiology of this discrepancy remains unclear, differences between location of involvement in ulcerative colitis and Crohn's disease have not been examined in these studies.

AIM

To examine the effects of nicotine administration on the course of jejunitis and colitis in interleukin-10 deficient mice.

METHODS

Male C57/BL10 IL-10 -/- and wild type mice were given nicotine (12.5 microg/ml) in their drinking water at age 12-14 weeks when they had developed clinical signs of inflammatory bowel disease. Gender and age matched control mice received tap water alone. All mice were killed after 2 weeks of treatment. Whole tissue sections of jejunum, proximal and distal colon were separated and examined by macroscopic and histological score. Northern blots were examined for somatostatin, intestinal trefoil factor and mucin-2.

RESULTS

At 14-16 weeks, when the mice were killed, IL-10 -/- untreated control mice developed jejunitis (macroscopic score 1.4 +/- 0.5, microscopic score 2.0 +/- 0.2) and colitis (2.0 +/- 0.2 and 5.9 +/- 0.9, respectively). IL-10 -/- mice treated for 2 weeks with nicotine had significantly reduced colonic scores (1.4 +/- 0.6 and 2.2 +/- 0.15, respectively). In contrast, the jejunum was more severely damaged (2.6 +/- 0.4 and 4.0 +/- 0.3; P = 0.01, respectively). Nicotine significantly increased both somatostatin and intestinal trefoil factor mRNA expression in the colon but not in the jejunum; no effect was noted on mucin-2 or beta-actin mRNA expression.

CONCLUSIONS

(1) Two weeks of nicotine administration leads to contrasting effects on jejunal and colonic inflammation in IL-10 -/- mice. (2) Nicotine ameliorated inflammation in the colon, which was associated with enhanced expression of two protective peptides.

Nitric oxide mediates a therapeutic effect of nicotine in ulcerative colitis

BACKGROUND

Ulcerative colitis is a condition of nonsmokers in which nicotine is of therapeutic benefit.

AIMS

To examine the in vitro effect of nicotine on colonic smooth muscle activity and the role of nitric oxide (NO) as a mediator.

METHODS

Nicotine, 1-10 microM, was administered to strips of circular muscle from the distal sigmoid colon of 9 patients with active ulcerative colitis and 18 with colorectal cancer. The effect of electrical field stimulation (EFS) was examined before nicotine was added. Finally L-NAME, a NO synthetase inhibitor, was added before nicotine was administered again.

RESULTS

Muscle strips developed similar spontaneous resting tone. In response to EFS, ulcerative colitis tissue developed lower tensions than the controls. Nicotine significantly reduced the resting tone and peak tension after EFS, with a greater effect in controls. With L-NAME, peak tensions were increased more in ulcerative colitis than controls, and nicotine produced a much smaller reduction.

CONCLUSIONS

Nicotine reduces circular muscle activity, predominantly through the release of nitric oxide-this appears to be 'up-regulated' in active ulcerative colitis. These findings may explain some of the therapeutic benefit from nicotine (and smoking) in ulcerative colitis and may account for the colonic motor dysfunction in active disease.

Lack of association between smoking and Crohn's disease but the usual association with ulcerative colitis in Jewish patients in Israel: a multicenter study

OBJECTIVE

The association between smoking and inflammatory bowel disease (IBD) is well established, but data in Jewish patients in Israel were discrepant. The aim of this study was to examine the smoking habits of Jewish IBD patients in Israel in a large scale, multicenter study.

METHODS

Patients with established IBD aged 18-70 yr were interviewed in relation to smoking and other habits. Two controls (one clinic and one neighborhood control matched by age, sex, community group, and education) were sought for each subject.

RESULTS

A total of 534 patients (273 ulcerative colitis [UC], and 261 Crohn's disease [CD]), along with 478 clinic controls and 430 neighborhood controls, were interviewed. There was no significant difference in the smoking habits between CD patients and their controls. Of patients with CD, 24.5% were current smokers, as compared to 19.9% of clinic controls and 25.2% of neighborhood controls (NS). The odds ratio for CD in current smokers was 1.30 (95% confidence interval 0.85-1.99) versus clinic controls, and 0.96 (0.63-1.46) versus neighborhood controls. There were also no significant differences in the proportion of ex-smokers between the groups. Only 12.9% of UC patients were current smokers versus 21.9. % Clinic controls, and 26.4% community controls (p<0.005). The proportions of ex-smokers were higher in UC patients 29.7% versus 25.9%, and 19.5% in their respective controls (p<0.001 vs. community controls). No significant differences were found in the proportions of never-smokers between IBD patients and controls. All the above trends were similar in four different parts of the country. The proportion of current smokers in UC decreased with the extent of disease (19.7% in proctitis, 13.6% in left-sided, and 4.5% in total colitis) (p<0.05). Patients with UC were more likely to be light smokers(1-10 cigarettes/day), whereas patients with CD were more likely to be moderate smokers (11-20 cigarettes/day) in comparison to their controls.

CONCLUSIONS

The lack of association between smoking and CD has now been established in Jewish patients in Israel. The association was found in UC. The stronger genetic tendency in CD may contribute to this discrepancy.

Transdermal nicotine decreases mucosal IL-8 expression but has no effect on mucin gene expression in ulcerative colitis

Our goal was to determine the effect of transdermal nicotine on cytokine and mucin gene transcription in ulcerative colitis (UC). Sixty-four nonsmoking patients with active UC were randomly assigned to transdermal nicotine (maximum dose 22 mg/day) or placebo for 4 weeks. Clinical assessment and colonic mucosal biopsies were obtained at entry and after 4 weeks. Inflammatory and immunoregulatory cytokines were assessed by qualitative reverse transcriptase-polymerase chain reaction (RT-PCR). Based on this initial screen. IL-8 mRNA levels were measured by RT-competitive PCR. MUC1, MUC2, MUC3, MUC4, MUC5AC, MUC5B, and MUC6 mRNA concentrations were measured by quantitative dot blot analysis. Cytokine mRNA expression, except for IL-8, was similar in all patients. IL-8 mRNA levels were significantly decreased in the colonic mucosa of nicotine-treated patients who improved (p = 0.04). IL-8 mRNA values were similar before and after treatment in nonresponding nicotine-treated patients and in all placebo-treated patients. Mucin gene expression was similar in all patient groups. Beneficial effects of transdermal nicotine in active UC may result from decrease of IL-8 expression at the transcriptional level. Transdermal nicotine has no effect on mucin gene transcription.

Nicotine therapy for ulcerative colitis: a review of rationale, mechanisms, pharmacology, and clinical results

Smoking is protective against developing ulcerative colitis. Nicotine may be the cause of this protective effect. Controlled trials have demonstrated efficacy of transdermal nicotine for active ulcerative colitis. Side effects observed with transdermal nicotine include contact dermatitis, nausea, and lightheadedness. Topical administration of nicotine to the colon reduces nicotine blood concentrations and side effects, and may be of clinical benefit.

Lack of effect of nicotine or ethanol on the activity of 11beta-hydroxysteroid dehydrogenase type 2

Low birth weight in combination with a large placenta predicts human hypertension. The pathophysiological link remains unclear, but glucocorticoid excess impairs fetal growth and leads to offspring hypertension. A key controller of fetal glucocorticoid exposure and local tissue availability is 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2). The activity of placental 11beta-HSD2 correlates with fetal growth in animals and humans. Ethanol abuse and smoking are known to retard fetal growth which may relate to altered glucocorticoid action or dynamics. This study has examined whether nicotine or ethanol modulate glucocorticoid action in the placenta or fetus by inhibiting 11beta-HSD2, using clonal cell cultures, freshly isolated dually perfused intact human placentas and placentas from in vivo treated rats. No significant effect on the activity of 11beta-HSD2 by pathophysiologically relevant nicotine or ethanol concentrations was observed. The mechanism of action of nicotine and ethanol relevant to reduced fetal growth requires further study.