Damage to DNA in cervical epithelium related to smoking tobacco.

OBJECTIVE--To determine whether tobacco smoking causes increased DNA modification (adducts) in human cervical epithelium. DESIGN--Comparison of DNA adducts measured by the technique of postlabelling with phosphorus-32 in normal ectocervical epithelium of smokers and non-smokers. A questionnaire on smoking habit and a urinary cotinine assay were used to identify smokers and non-smokers. SETTING--Cytology unit in large teaching hospital. SUBJECTS--39 women (11 current smokers, seven former smokers, and 21 who had never smoked) undergoing gynaecological treatment (colposcopy or hysterectomy). Nineteen members of staff who did not smoke as controls. INTERVENTIONS--Biopsy of normal ectocervical epithelium. Urine sample. MAIN OUTCOME MEASURES--Measurement of DNA adducts in cervical epithelial tissue of smokers and non-smokers. Smoking habit derived from results of questionnaire and urinary cotinine:creatinine ratio. Proportion of adducts in women with abnormal and normal results of cervical smear test. RESULTS--DNA samples from smokers (identified from questionnaire) had significantly higher median proportions of DNA adducts that non-smokers (4.62 (95% confidence interval 4.04 to 7.74) v 3.47 (2.84 to 4.78) adducts/10(8) nucleotides; p = 0.048). Exclusion of women whose urinary cotinine:creatinine ratio did not confirm their self reported smoking habit (smoker or non-smoker) increased this difference (4.7 (3.85 to 8.08) v 3.52 (2.32 to 4.95) adducts/10(8) nucleotides; p = 0.03). Women who had abnormal results of cervical smear tests had significantly higher proportions of adducts than those with normal results (4.7 (3.90 to 8.13) v 3.47 (3.06 to 5.36) adducts/10(8) nucleotides; p = 0.03). CONCLUSIONS--Tobacco smoking by women leads to increased modification of DNA in cervical epithelium, suggesting biochemical evidence consistent with smoking as a cause of cervical cancer.     

Ultrastructural study of bronchial epithelium in chronic respiratory diseases.

The fine structure of bronchial epithelium in thirty-six patients, thirty-one men and five women, suffering from chronic obstructive pneumonopathy or bronchial carcinoma was studied. No remarkable alterations were found with electron microscopy, in most non-smokers in contrast to the smokers who presented destruction of the epithelial cells and loss of the cilia or many pathological cilia with an abnormal microtubular configuration and irregular orientation. The severity, however, of the alterations was not related to the severity of smoking and to the presence of bronchial cancer.     

Smoking cessation and bronchial epithelial remodelling in COPD: a cross-sectional study

Background

Chronic Obstructive Pulmonary Disease (COPD) is associated with bronchial epithelial changes, including squamous cell metaplasia and goblet cell hyperplasia. These features are partially attributed to activation of the epidermal growth factor receptor (EGFR). Whereas smoking cessation reduces respiratory symptoms and lung function decline in COPD, inflammation persists. We determined epithelial proliferation and composition in bronchial biopsies from current and ex-smokers with COPD, and its relation to duration of smoking cessation.

Methods

114 COPD patients were studied cross-sectionally: 99 males/15 females, age 62 ± 8 years, median 42 pack-years, no corticosteroids, current (n = 72) or ex-smokers (n = 42, median cessation duration 3.5 years), postbronchodilator FEV₁ 63 ± 9% predicted. Squamous cell metaplasia (%), goblet cell (PAS/Alcian Blue⁺) area (%), proliferating (Ki-67⁺) cell numbers (/mm basement membrane), and EGFR expression (%) were measured in intact epithelium of bronchial biopsies.

Results

Ex-smokers with COPD had significantly less epithelial squamous cell metaplasia, proliferating cell numbers, and a trend towards reduced goblet cell area than current smokers with COPD (p = 0.025, p = 0.001, p = 0.081, respectively), but no significant difference in EGFR expression. Epithelial features were not different between short-term quitters (<3.5 years) and current smokers. Long-term quitters (≥3.5 years) had less goblet cell area than both current smokers and short-term quitters (medians: 7.9% vs. 14.4%, p = 0.005; 7.9% vs. 13.5%, p = 0.008; respectively), and less proliferating cell numbers than current smokers (2.8% vs. 18.6%, p < 0.001).

Conclusion

Ex-smokers with COPD had less bronchial epithelial remodelling than current smokers, which was only observed after long-term smoking cessation (>3.5 years).

Trial registration

NCT00158847     

Factors Associated with Tobacco Smoking and Cessation among HIV-Infected Individuals under Care in Rio de Janeiro,Brazil

Worldwide the prevalence of smoking among people living with HIV/AIDS is elevated compared to the general population. This probably reflects the cluster of individual characteristics that have shared risk factors for HIV infection and smoking. A cross-sectional study, enrolling a convenience sample from a Brazilian HIV clinical cohort was conducted to evaluate the prevalence of tobacco smoking and the factors associated with current smoking and abstinence. A total of 2,775 HIV-infected individuals were interviewed: 46.2% have never smoked, 29.9% were current smokers and 23.9% were former smokers. Current smokers had a higher prevalence of alcohol and illicit drug use when compared to the other two groups. A higher proportion of heterosexual individuals were former smokers or never smokers while among men who have sex with men (MSM) a higher proportion were current smokers. Former smokers had been more frequently diagnosed with high blood pressure, diabetes mellitus, cardiovascular diseases and depression, while for current smokers lung diseases were more frequent. Former smokers and current smokers were more likely to have had any hospital admission (42.0% and 41.2%, respectively) than participants who never smoked (33.5%) (p<0.001). Multivariate model results showed that current smokers (versus never smokers) were more likely to be less educated, to report the use of alcohol, crack and cocaine and to present clinical comorbidities. Former smokers (versus current smokers) were more likely to be older, to have smoked for a shorter amount of time and to have smoked >31 cigarettes/day. MSM (compared to heterosexuals) and cocaine users (versus non-users) had lower odds of being former smokers. Considering our results, smoking cessation interventions should be tailored to younger individuals, MSM and substance users.     

Smoking among Yale medical school faculty

A 1985 survey of a random sample of faculty at the Yale University School of Medicine investigated smoking prevalence and attitudes. The overall prevalence of cigarette smoking was estimated to be 9.8 percent, much lower than the prevalence in the general population. A higher proportion of women than men were current cigarette smokers. With regard to department affiliation, surgeons were most frequently current cigarette smokers, with psychiatrists having the lowest prevalence of current cigarette smoking and the highest percentage of people who had never smoked. In general, attitudes toward smoking were negative.     

Cigarette tar yields in relation to mortality from lung cancer in the cancer prevention study II prospective cohort, 1982-8

Objective To assess the risk of lung cancer in smokers of medium tar filter cigarettes compared with smokers of low tar and very low tar filter cigarettes.Design Analysis of the association between the tar rating of the brand of cigarette smoked in 1982 and mortality from lung cancer over the next six years. Multivariate proportional hazards analyses used to assess hazard ratios, with adjustment for age at enrolment, race, educational level, marital status, blue collar employment, occupational exposure to asbestos, intake of vegetables, citrus fruits, and vitamins, and, in analyses of current and former smokers, for age when they started to smoke and number of cigarettes smoked per day.Setting Cancer prevention study II (CPS-II).Participants 364 239 men and 576 535 women, aged ≥ 30 years, who had either never smoked, were former smokers, or were currently smoking a specific brand of cigarette when they were enrolled in the cancer prevention study.Main outcome measure Death from primary cancer of the lung among participants who had never smoked, former smokers, smokers of very low tar (≤ 7 mg tar/cigarette) filter, low tar (8-14 mg) filter, high tar (≥ 22 mg) non-filter brands and medium tar conventional filter brands (15-21 mg).Results Irrespective of the tar level of their current brand, all current smokers had a far greater risk of lung cancer than people who had stopped smoking or had never smoked. Compared with smokers of medium tar (15-21 mg) filter cigarettes, risk was higher among men and women who smoked high tar (≥ 22 mg) non-filter brands (hazard ratio 1.44, 95% confidence interval 1.20 to 1.73, and 1.64, 1.26 to 2.15, respectively). There was no difference in risk among men who smoked brands rated as very low tar (1.17, 0.95 to 1.45) or low tar (1.02, 0.90 to 1.16) compared with those who smoked medium tar brands. The same was seen for women (0.98, 0.80 to 1.21, and 0.95, 0.82 to 1.11, respectively).Conclusion The increase in lung cancer risk is similar in people who smoke medium tar cigarettes (15-21 mg), low tar cigarettes (8-14 mg), or very low tar cigarettes (≤ 7 mg). Men and women who smoke non-filtered cigarettes with tar ratings ≥ 22 mg have an even higher risk of lung cancer.     

Decreased expression of intelectin 1 in the human airway epithelium of smokers compared to nonsmokers

Lectins are innate immune defense proteins that recognize bacterial cell wall components. Based on the knowledge that cigarette smoking is associated with an increased risk of infections, we hypothesized that cigarette smoking may modulate the expression of lectin genes in airway epithelium. Affymetrix microarrays were used to survey the expression of lectin genes in large airway epithelium from nine nonsmokers and 20 healthy smokers and in small airway epithelium from 13 nonsmokers and 20 healthy smokers. There were no changes (>2-fold change; p < 0.05) in lectin gene expression among healthy smokers compared with nonsmokers except for down-regulation of intelectin 1, a lectin that binds to galactofuranosyl residues in bacterial cell walls (large airway epithelium, p < 0.01; small airway epithelium, p < 0.01). This was confirmed by TaqMan RT-PCR in both large (p < 0.05) and small airway epithelium (p < 0.02). Immunohistochemistry assessment of airway biopsies demonstrated that intelectin 1 was expressed in secretory cells, while Western analysis confirmed the decreased expression of intelectin 1 in airway epithelium of healthy smokers compared with healthy nonsmokers (p < 0.02). Finally, compared with healthy nonsmokers, intelectin 1 expression was also decreased in small airway epithelium of smokers with lone emphysema and normal spirometry (n = 13, p < 0.01) and smokers with established chronic obstructive pulmonary disease (n = 14, p < 0.01). In the context that intelectin 1 plays a role in defense against bacteria, its down-regulation in response to cigarette smoking is another example of the immunomodulatory effects of smoking on the immune system and may contribute to the increase in susceptibility to infections observed in smokers.     

Job strain and tobacco smoking: an individual-participant data meta-analysis of 166,130 adults in 15 European studies

Background

Tobacco smoking is a major contributor to the public health burden and healthcare costs worldwide, but the determinants of smoking behaviours are poorly understood. We conducted a large individual-participant meta-analysis to examine the extent to which work-related stress, operationalised as job strain, is associated with tobacco smoking in working adults.

Methodology and Principal Findings

We analysed cross-sectional data from 15 European studies comprising 166 130 participants. Longitudinal data from six studies were used. Job strain and smoking were self-reported. Smoking was harmonised into three categories never, ex- and current. We modelled the cross-sectional associations using logistic regression and the results pooled in random effects meta-analyses. Mixed effects logistic regression was used to examine longitudinal associations. Of the 166 130 participants, 17% reported job strain, 42% were never smokers, 33% ex-smokers and 25% current smokers. In the analyses of the cross-sectional data, current smokers had higher odds of job strain than never-smokers (age, sex and socioeconomic position-adjusted odds ratio: 1.11, 95% confidence interval: 1.03, 1.18). Current smokers with job strain smoked, on average, three cigarettes per week more than current smokers without job strain. In the analyses of longitudinal data (1 to 9 years of follow-up), there was no clear evidence for longitudinal associations between job strain and taking up or quitting smoking.

Conclusions

Our findings show that smokers are slightly more likely than non-smokers to report work-related stress. In addition, smokers who reported work stress smoked, on average, slightly more cigarettes than stress-free smokers.     

Gastrin-releasing peptide receptor expression in non-cancerous bronchial epithelia is associated with lung cancer: a case-control study

Background

Normal bronchial tissue expression of GRPR, which encodes the gastrin-releasing peptide receptor, has been previously reported by us to be associated with lung cancer risk in 78 subjects, especially in females. We sought to define the contribution of GRPR expression in bronchial epithelia to lung cancer risk in a larger case-control study where adjustments could be made for tobacco exposure and sex.

Methods

We evaluated GRPR mRNA levels in histologically normal bronchial epithelial cells from 224 lung cancer patients and 107 surgical cancer-free controls. Associations with lung cancer were tested using logistic regression models.

Results

Bronchial GRPR expression was significantly associated with lung cancer (OR = 4.76; 95% CI = 2.32-9.77) in a multivariable logistic regression (MLR) model adjusted for age, sex, smoking status and pulmonary function. MLR analysis stratified by smoking status indicated that ORs were higher in never and former smokers (OR = 7.74; 95% CI = 2.96-20.25) compared to active smokers (OR = 1.69; 95% CI = 0.46-6.33). GRPR expression did not differ by subject sex, and lung cancer risk associated with GRPR expression was not modified by sex.

Conclusions

GRPR expression in non-cancerous bronchial epithelium was significantly associated with the presence of lung cancer in never and former smokers. The association in never and former smokers was found in males and females. Association with lung cancer did not differ by sex in any smoking group.     

Excess smoking in malignant-phase hypertension

The smoking habits of 82 patients with malignant-phase hypertension were compared with those of subjects in three control groups matched for age and sex. Sixty-seven (82%) of the patients with malignant-phase hypertension were smokers compared with 41 (50%) and 71 (43%) of the patients in two control groups with non-malignant hypertension, and 43 people (52%) in a general population survey. The excess of smokers in the malignant-phase group was significant for men and women, together and separately, for cigarette smoking alone, and for all forms of smoking. There were no significant differences between the control groups. The chance of a hypertensive patient who smoked having the malignant phase was five times that of a hypertensive patient who did not. Twelve patients in the malignant-phase group had never smoked. All were alive three and a half years on average after presentation (range 11 months to seven years). Twenty-four (36%) of the smokers with malignant-phase hypertension died during the same period. The mortality rate was significantly higher among patients with renal failure, as was the prevalence of smoking. Eighteen patients with malignant-phase hypertension had a serum creatinine concentration higher than 250 μmol/l (2·8 mg/100 ml); 17 were smokers and one an ex-smoker. Eleven of these 18 patients died.It is concluded that hypertensive patients who smoke are much more likely to develop the malignant phase than those who do not, and that once the condition has developed it follows a particularly lethal course in smokers.     

Glucocorticoid receptor expression in human bronchial epithelial cells: effects of smoking and COPD.

Previously, we found that inflammatory mediators modulated the number and binding affinity of glucocorticoid receptors (GR) in human bronchial epithelial cell lines. In this study we investigated whether smoking and chronic obstructive pulmonary disease (COPD), both characterized by airway inflammation with increased levels of inflammatory mediators, affect GR characteristics in cultured human bronchial epithelial cells (HBEC). A statistically significant difference was found between the dissociation constant (Kd) values in HBEC from smoking (Kd = 0.98+/-0.08 nM; n = 6) and nonsmoking controls (Kd = 0.76+/-0.10 nM, P = 0.03; n = 5), but no significant difference was found between the mean number of binding sites. Our results are the first indication that cultured HBEC from smokers possess GR with a lower binding affinity. This may result from the inflammation found in the airways from smokers. Furthermore, these results provide further evidence that the bronchial epithelium may be an actual target for inhaled glucocorticoid therapy.     

Prevalence and patterns of smoking in Delhi: cross sectional study.

OBJECTIVE--To determine the prevalence and predictors of smoking in urban India. DESIGN--Cross sectional. SETTING--Delhi, urban India, 1985-6. SUBJECTS--Random sample of 13,558 men and women aged 25-64 years. MAIN OUTCOME MEASURES--Smoking prevalence; subjects who were currently smoking and who had smoked > or = 100 cigarettes or beedis or chuttas in their lifetime were defined as smokers. RESULTS--45% (95% confidence interval 43.8 to 46.2) of men and 7% (6.4 to 7.6) of women were smokers. Education was the strongest predictor of smoking, and men with no education were 1.8 (1.5 to 2.0) times more likely to be smokers than those with college education, and women with no education were 3.7 (2.9 to 4.8) times more likely. Among smokers, 52.6% of men and 4.9% of women smoked only cigarettes while the others also smoked beedi or chutta. Compared with cigarette smokers, people smoking beedi or chutta were more likely to be older and married; have lower education, manual occupations, incomes, and body mass index; and not drink alcohol or take part in leisure exercise. CONCLUSION--There are two subpopulations of smokers in urban India, and the prevention strategy required for each may be different. The educated, white collar cigarette smoker in India might respond to measures that make non-smoking fashionable, while the less educated, low income people who smoke beedi or chutta may need strategies aimed at socioeconomic improvement.     

Cigarette Smoking and Fat Distribution in 21, 828 British Men and Women: A Population‐based Study

Objective: To examine the relationship between cigarette smoking habits and fat distribution in a population‐based cohort of men and women. Research Methods and Procedures: We analyzed cross‐sectional data from 21, 828 men and women who were 45 to 79 years of age, residents in Norfolk, United Kingdom, and were recruited between 1993 and 1997. Cigarette smoking habits and other lifestyle factors were assessed using self‐reported questionnaires. Anthropometric measures were obtained during a health examination. Results: Waist‐hip ratio was highest among current smokers and least among never smokers after adjusting for age, BMI, alcohol intake, total energy intake, physical activity, and education. Higher waist‐hip ratio was directly associated with higher smoking pack‐years in current and former smokers and inversely with duration since quitting smoking in former smokers. Adjusting for age, BMI, and other covariates, current smokers had higher waist circumference but lower hip circumference compared with former or never smokers. Discussion: Cigarette smoking habits seem to influence fat distribution patterns. Although smokers have lower mean BMI compared with nonsmokers, they have a more metabolically adverse fat distribution profile, with higher central adiposity. The explanation for this association may help elucidate the mechanisms underlying the adverse health consequences of cigarette smoking and abdominal obesity.     

Delay and probability discounting as related to different stages of adolescent smoking and non-smoking

This study examined relations between different patterns of adolescent cigarette smoking and discounting of monetary rewards due to delay (delay discounting) and probabilistic uncertainty (probability discounting). The study also examined the relation between smoking and the number of peer friends who smoke and level of parent education. Participants were 55 adolescents (28 females) between 14 and 16 years of age who were categorized according to the following patterns of smoking behavior: "never smokers" (n=19; 10 females) who had not tried even one cigarette; "triers" (n=17; 9 females) who had recently tried cigarettes for the first time; and "current smokers" (n=19; 9 females) who smoked a minimum of one cigarette every week for at least 6 months prior to data collection. It was hypothesized that current smokers would discount more than those who had never smoked. No specific hypotheses were made for participants only trying cigarettes. Unexpectedly, results indicated no differences in discounting between the current smokers and never smokers. However, the trier group discounted probabilistic rewards significantly more than the never- and current-smoker groups. Also, triers and current smokers both reported having more friends who smoked than never smokers, and fathers of never smokers had significantly more education than fathers of either triers or current smokers. These results suggest that impulsive discounting may be more related to adolescents trying cigarettes than to their becoming regular smokers, whereas number of peer friends who smoke and parent level of education seem to differentiate between those who have smoked to some extent (triers and current smokers) and those who have not even tried cigarettes (never smokers).     

Association of current smoking with airway inflammation in chronic obstructive pulmonary disease and asymptomatic smokers

Background

Inflammation in the airways and lung parenchyma underlies fixed airway obstruction in chronic obstructive pulmonary disease. The exact role of smoking as promoting factor of inflammation in chronic obstructive pulmonary disease is not clear, partly because studies often do not distinguish between current and ex-smokers.

Methods

We investigated airway inflammation in sputum and bronchial biopsies of 34 smokers with chronic obstructive pulmonary disease (9 Global initiative for Chronic Obstructive Lung Disease stage 0, 9 stage I, 10 stage II and 6 stage III) and 26 asymptomatic smokers, and its relationship with past and present smoking habits and airway obstruction.

Results

Neutrophil percentage, interleukin-8 and eosinophilic-cationic-protein levels in sputum were higher in chronic obstructive pulmonary disease (stage I-III) than asymptomatic smokers. Inflammatory cell numbers in bronchial biopsies were similar in both groups. Current smoking correlated positively with macrophages: in bronchial biopsies in both groups, and in sputum in chronic obstructive pulmonary disease. Pack-years smoking correlated positively with biopsy macrophages only in chronic obstructive pulmonary disease.

Conclusion

Inflammatory effects of current smoking may mask the underlying ongoing inflammatory process pertinent to chronic obstructive pulmonary disease. This may have implications for future studies, which should avoid including mixed populations of smokers and ex-smokers.     

Modifying risk of developing lung cancer by changing habits of cigarette smoking.

Data from a hospital based case-control study of lung cancer in Western Europe were used to examine changes in the risk of developing lung cancer after changes in habits of cigarette smoking. Only data for subjects who had smoked regularly at some time in their lives were included. The large size of the study population (7181 patients and 11 006 controls) permitted precise estimates of the effect of giving up smoking. Risks of developing lung cancer for people who had given up smoking 10 or more years before interview were less than half of those for people who continued to smoke. The reduction in risk was seen in men and women and in former smokers of both filter and non-filter cigarettes but varied by duration of smoking habit before giving up. The protective effect of giving up became progressively greater with shorter duration of smoking habit. The risks after not smoking for 10 years for both men and women who had previously smoked for less than 20 years were roughly the same as those for lifelong non-smokers. Reducing the number of cigarettes smoked a day or switching from non-filter to filter cigarettes also lowered the risk of developing lung cancer but not to the extent associated with giving up smoking.     

Whole Exome Re-Sequencing Implicates CCDC38 and Cilia Structure and Function in Resistance to Smoking Related Airflow Obstruction

Chronic obstructive pulmonary disease (COPD) is a leading cause of global morbidity and mortality and, whilst smoking remains the single most important risk factor, COPD risk is heritable. Of 26 independent genomic regions showing association with lung function in genome-wide association studies, eleven have been reported to show association with airflow obstruction. Although the main risk factor for COPD is smoking, some individuals are observed to have a high forced expired volume in 1 second (FEV₁) despite many years of heavy smoking. We hypothesised that these “resistant smokers” may harbour variants which protect against lung function decline caused by smoking and provide insight into the genetic determinants of lung health. We undertook whole exome re-sequencing of 100 heavy smokers who had healthy lung function given their age, sex, height and smoking history and applied three complementary approaches to explore the genetic architecture of smoking resistance. Firstly, we identified novel functional variants in the “resistant smokers” and looked for enrichment of these novel variants within biological pathways. Secondly, we undertook association testing of all exonic variants individually with two independent control sets. Thirdly, we undertook gene-based association testing of all exonic variants. Our strongest signal of association with smoking resistance for a non-synonymous SNP was for rs10859974 (P = 2.34×10⁻⁴) in CCDC38, a gene which has previously been reported to show association with FEV₁/FVC, and we demonstrate moderate expression of CCDC38 in bronchial epithelial cells. We identified an enrichment of novel putatively functional variants in genes related to cilia structure and function in resistant smokers. Ciliary function abnormalities are known to be associated with both smoking and reduced mucociliary clearance in patients with COPD. We suggest that genetic influences on the development or function of cilia in the bronchial epithelium may affect growth of cilia or the extent of damage caused by tobacco smoke.     

Nitric oxide formation in the oropharyngeal tract: possible influence of cigarette smoking.

Cigarette smoking reduces the level of nitric oxide (NO) in exhaled air by an unknown mechanism. The view that part of the effect of cigarette smoking on NO production should occur in the oropharyngeal tract is supported by several studies. We have therefore compared smokers and non-smokers regarding non-enzymatic formation of NO from nitrite in the oral cavity since this is a primary candidate target for cigarette smoke. We have also looked at NO synthase-dependent NO formation in the mucosa of the oropharyngeal tract as an alternative target for the inhibitory effect induced by cigarette smoke. Smokers exhaled 67% lower levels of NO than controls (p<0.01, n=15 each group). We could not detect any significant difference in salivary nitrite, nitrate or ascorbate between smokers and non-smokers. Mouthwash with the antibacterial agent chlorhexidine reduced salivary nitrite (-65%) and exhaled NO levels (-10%) similarly in the two groups. Immunohistochemical techniques revealed dense expression of inducible (but not endothelial or neuronal) NO synthase in the squamous epithelium of non-inflamed tonsillar and gingival tissue biopsies. In the same biopsies, significant Ca2+ -independent citrulline-forming activity was detected. We found no difference between smoking and non-smoking subjects regarding NO-synthase expression and in vitro activity. In another group of non-smoking subjects (n=10), spraying the oropharyngeal tract with the NO-synthase inhibitor NG-monomethyl-L-arginine (250 mg) significantly reduced exhaled NO levels for at least 30 min (-18%, p<0.01). Our data suggest that cigarette smoking does not affect non-enzymatic NO formation from nitrite in saliva. However, NO is also formed by inducible NO synthase in the squamous epithelium of the normal oropharyngeal tract. We suggest that cigarette smoking may down-regulate enzymatic NO formation in the oropharyngeal compartment as well as in the bronchial compartment.