Pharmacogenetics of smoking cessation: role of nicotine target and metabolism genes

Many smokers attempt to quit smoking but few are successful in the long term. The heritability of nicotine addiction and smoking relapse have been documented, and research is focused on identifying specific genetic influences on the ability to quit smoking and response to specific medications. Research in genetically modified cell lines and mice has identified nicotine acetylcholine receptor subtypes that mediate the pharmacological and behavioral effects of nicotine sensitivity and withdrawal. Human genetic association studies have identified single nucleotide polymorphisms (SNPs) in genes encoding nicotine acetylcholine receptor subunits and nicotine metabolizing enzymes that influence smoking cessation phenotypes. There is initial promising evidence for a role in smoking cessation for SNPs in the β2 and α5/α3/β4 nAChR subunit genes; however, effects are small and not consistently replicated. There are reproducible and clinically significant associations of genotypic and phenotypic measures of CYP2A6 enzyme activity and nicotine metabolic rate with smoking cessation as well as response to nicotine replacement therapies and bupropion. Prospective clinical trials to identify associations of genetic variants and gene–gene interactions on smoking cessation are needed to generate the evidence base for both medication development and targeted therapy approaches based on genotype.     

Cigarette smoking,nicotine dependence,and treatment.

Since the 1988 Surgeon General''s report on nicotine addiction, more attention is being given to nicotine dependence as a substantial contributing factor in cigarette smokers'' inability to quit. Many new medications are being investigated for treating nicotine withdrawal and for assisting in long-term smoking abstinence. Medications alone probably will not be helpful; they should be used as adjuncts in comprehensive smoking abstinence programs that address not only the physical dependence on nicotine but also the psychological dependence on cigarette smoking.     

Pathophysiological effects of nicotine on the pancreas: an update

Epidemiological evidence strongly suggests an association between cigarette smoking and pancreatic diseases. It is well recognized that nicotine, a major component in cigarette smoke, is an addictive agent and, therefore, reinforces smoking behavior. The current review update focuses on the genetics of nicotine dependence and its role on the development of pancreatic diseases. The role of smoking and nicotine in pancreatitis and pancreatic cancer development is also discussed. Exposure of laboratory animals to nicotine clearly supports the notion that nicotine can induce pancreatic injury. The mechanism by which nicotine induces such effects is perhaps mediated via signal transduction pathways in the pancreatic acinar cell, leading to enhanced levels of intracellular calcium release, resulting in cytotoxicity and eventual cell death. The induction of pancreatic injury by nicotine may also involve activation and expression of protooncogene, H-ras, which can increase cytosolic calcium via second messenger pathways. Development of pancreatic carcinoma in cigarette smokers as observed in human populations may be the result of activation and mutation of the H-ras gene. A possible pathogenetic mechanism of nicotine in the pancreas activating multiple signal transduction pathways is schematically summarized in Figure 1.     

High reinforcing efficacy of nicotine in non-human primates

Although tobacco appears highly addictive in humans, there has been persistent controversy about the ability of its psychoactive ingredient nicotine to induce self-administration behavior in laboratory animals, bringing into question nicotine's role in reinforcing tobacco smoking. Because of ethical difficulties in inducing nicotine dependence in na?ve human subjects, we explored reinforcing effects of nicotine in experimentally-naive non-human primates given access to nicotine for periods of time up to two years. Five squirrel monkeys with no experimental history were allowed to intravenously self-administer nicotine by pressing one of two levers. The number of presses on the active lever needed to obtain each injection was fixed (fixed-ratio schedule) or increased progressively with successive injections during the session (progressive-ratio schedule), allowing evaluation of both reinforcing and motivational effects of nicotine under conditions of increasing response cost. Over time, a progressive shift toward high rates of responding on the active lever, but not the inactive lever, developed. The monkeys' behavior was clearly directed toward nicotine self-administration, rather than presentation of environmental stimuli associated with nicotine injection. Both schedules of reinforcement revealed a high motivation to self-administer nicotine, with monkeys continuing to press the lever when up to 600 lever-presses were needed for each injection of nicotine. Thus, nicotine, by itself, in the absence of behavioral or drug-exposure history, is a robust and highly effective reinforcer of drug-taking behavior in a non-human primate model predictive of human behavior. This supports the use of nicotinic ligands for the treatment of smokers, and this novel preclinical model offers opportunities to test future medications for the treatment of nicotine dependence.     

Targeting heavy smokers in general practice: randomised controlled trial of transdermal nicotine patches.

OBJECTIVES--(a) To evaluate the efficacy of transdermal nicotine patches as an aid to stopping smoking when used as an adjunct to brief advice and support in a general practice setting; (b) to see whether an increase in nicotine patch dosage enhances the rate of initial cessation. DESIGN--Randomised double blind placebo controlled parallel group study with one year of follow up. SETTING--30 general practices in 15 English counties. SUBJECTS--600 dependent heavy smokers (> or = 15 cigarettes daily) who were well motivated to give up. INTERVENTIONS--Brief general practitioner advice, booklet, and 16 hours per day patch treatment for 18 weeks with brief support and follow up at one, three, six, 12, 26, and 52 weeks. MAIN OUTCOME MEASURES--Self reported complete abstinence for up to one year with biochemical validation at all follow up points. RESULTS--Nicotine patches reduced the severity of craving and adverse mood changes in the first weeks of withdrawal and doubled the rate of initial cessation at week 3 (nicotine group 36% of patients (144/400), placebo group 16.5% of patients (33/200)) and of continuous abstinence throughout one year (nicotine group 9.3% (37), placebo group 5.0% (10)). A dose increase at week 1 among patients experiencing difficulty in quitting increased the proportion who achieved abstinence at week 3. There were no adverse systemic effects attributable to nicotine, but the incidence of moderate or severe local irritation or itching at the patch site was 16.4% (63 patients), compared with 3.8% (seven) with placebo. CONCLUSION--Transdermal nicotine patches used as an adjunct to brief advice and support in a general practice setting are an effective aid to long term cessation of smoking in highly dependent smokers.     

Metabolic effects of cigarette smoking.

The inverse relationship between cigarette smoking and body weight, a potent obstacle to stopping smoking, may be due in part to effects of smoking on increasing whole body metabolism. Studies examining chronic and acute metabolic effects of smoking, as well as its constituent nicotine, are reviewed. Evidence suggests the absence of a chronic effect; most studies indicate that smokers and nonsmokers have similar resting metabolic rates (RMR) and that RMR declines very little after smoking cessation. Although an acute effect due to smoking is apparent, its magnitude is inconsistent across studies, possibly because of variability in smoke exposure or nicotine intake. In smokers at rest, the acute effect of smoking (and nicotine intake) appears to be significant but small (less than 10% of RMR) and transient (less than or equal to 30 min). However, the specific situations in which smokers tend to smoke may mediate the magnitude of this effect, inasmuch as smoking during casual physical activity may enhance it while smoking after eating may reduce it. Sympathoadrenal activation by nicotine appears to be primarily responsible for the metabolic effect of smoking, but possible contributions from nonnicotine constituents of tobacco smoke and behavioral effects of inhaling may also be important. Improved understanding of these metabolic effects may lead to better prediction and control of weight gain after smoking cessation, thus increasing the likelihood of maintaining abstinence.     

Circadian and Ultradian Rhythms in Heart Rate and Motor Activity of Smokers,Abstinent Smokers,and Nonsmokers

In a field study, heart rate and motor activity were assessed continuously in 12 male smokers during 2 smoking and 2 abstinence days and in 12 male nonsmokers during 4 days. A circadian analysis revealed earlier activity acrophases in smokers than nonsmokers and earlier heart rate acrophases in abstinent than smoking smokers. Furthermore, heart rate acrophases of smoking smokers significantly anticipated activity acrophases;, whereas in abstinent smokers and nonsmokers the two parameters oscillated in phase. With the use, in smoking smokers, of the individual average smoking interval as a hypothetical ultradian period length, significant periodicities were found for heart rates in 16 and for activity in 15 of 24 observation days. These rhythms were nicotine independent and based on heart rate and activity increases prior to lighting up the cigarettes. Individual frequency spectra for the 16 h after getting up and the 7 h after going to bed did not reveal single dominant frequencies but rather complex frequency distributions. Power spectra of the daytime data revealed no group differences for activity and no heart rate differences between smoking smokers and nonsmokers. In abstinent smokers, however, a significant reduction of heart rate frequencies slower than 1 cycle/135 min and a significant increase of heart rate frequencies faster than 1 cycle/20 min were observed as compared with all other groups. This effect persisted over the 2 abstinence days, suggesting an activity-independent change in the frequency distribution of heart rates after quitting smoking.     

Circadian and Ultradian Rhythms in Heart Rate and Motor Activity of Smokers, Abstinent Smokers, and Nonsmokers

In a field study, heart rate and motor activity were assessed continuously in 12 male smokers during 2 smoking and 2 abstinence days and in 12 male nonsmokers during 4 days. A circadian analysis revealed earlier activity acrophases in smokers than nonsmokers and earlier heart rate acrophases in abstinent than smoking smokers. Furthermore, heart rate acrophases of smoking smokers significantly anticipated activity acrophases;, whereas in abstinent smokers and nonsmokers the two parameters oscillated in phase. With the use, in smoking smokers, of the individual average smoking interval as a hypothetical ultradian period length, significant periodicities were found for heart rates in 16 and for activity in 15 of 24 observation days. These rhythms were nicotine independent and based on heart rate and activity increases prior to lighting up the cigarettes. Individual frequency spectra for the 16 h after getting up and the 7 h after going to bed did not reveal single dominant frequencies but rather complex frequency distributions. Power spectra of the daytime data revealed no group differences for activity and no heart rate differences between smoking smokers and nonsmokers. In abstinent smokers, however, a significant reduction of heart rate frequencies slower than 1 cycle/135 min and a significant increase of heart rate frequencies faster than 1 cycle/20 min were observed as compared with all other groups. This effect persisted over the 2 abstinence days, suggesting an activity-independent change in the frequency distribution of heart rates after quitting smoking.     

Nicotine increases sucrose self-administration and seeking in rats

Associations between nicotine in cigarettes and food consumption may alter the incentive value of food such that food cue-reactivity is exaggerated during abstinence from smoking. This effect may contribute to the weight gain associated with cessation of smoking. We examined the effects of nicotine (0.4 mg/kg base subcutaneous) paired (NPD) or unpaired (NUP) with 10% sucrose self-administration (SA; 0.2 ml/delivery, 1 h/day for 10 days) on SA response rate and intake as well as sucrose cue-reactivity following either 1 or 30 days of forced abstinence. Rats were administered the training dose of nicotine prior to a second, consecutive cue-reactivity session. NPD rats responded at over three times the rate for sucrose and earned nearly twice the number of sucrose deliveries as NUP rats or saline controls. Sucrose cue-reactivity was greater after 30 days versus 1 day of forced abstinence for all groups. History of nicotine exposure had no effect on sucrose cue-reactivity. However, the subsequent injection of nicotine increased sucrose cue-reactivity only in the NPD groups. There were no abstinent-dependent effects of nicotine challenge on sucrose cue-reactivity. A study conducted in parallel with water as the reinforcer revealed a less dramatic effect of nicotine on intake. There was no history or abstinence-dependent effects of nicotine on water cue-reactivity. Nicotine increases the reinforcing effects of sucrose and sucrose-paired cues when nicotine is present. An implication of these findings is that relapse to nicotine (cigarettes) could substantially elevate food cue-reactivity.     

Influence of escalating alternative reinforcer values on cigarette choice

The availability of alternative reinforcers reduces drug taking. Escalating alternative reinforcer values have been used to initiate and maintain abstinence from drug use. A reset in reinforcer value has been added to the schedule of alternative reinforcer presentation to discourage relapse. The purpose of this preliminary study was to test the influence of escalating and escalating and resetting alternative reinforcer value on cigarette choice in the human laboratory. Fourteen daily cigarette smokers completed this experiment, which required one practice and three experimental sessions. During each experimental session, subjects made six choices between smoking a cigarette and receiving money, available under Constant, Escalating or Escalating and Resetting conditions. The total number of cigarettes chosen and puffs taken, but not the maximum consecutive number of cigarettes choices, was decreased in the Escalating condition relative to the Constant condition. The maximum number of consecutive cigarettes chosen was decreased in the Escalating and Resetting condition relative to the Constant condition. The proportion of money earned was increased in the Escalating condition relative to the Constant and Escalating and Resetting conditions. These initial findings indicate that whereas an escalating alternative reinforcer schedule reduces cigarette smoking overall, an escalating and resetting alternative reinforcer schedule may reduce repeated cigarette smoking (i.e., relapse).     

“A Cigarette a Day Keeps the Goodies Away”: Smokers Show Automatic Approach Tendencies for Smoking—But Not for Food-Related Stimuli

Smoking leads to the development of automatic tendencies that promote approach behavior toward smoking-related stimuli which in turn may maintain addictive behavior. The present study examined whether automatic approach tendencies toward smoking-related stimuli can be measured by using an adapted version of the Approach-Avoidance Task (AAT). Given that progression of addictive behavior has been associated with a decreased reactivity of the brain reward system for stimuli signaling natural rewards, we also used the AAT to measure approach behavior toward natural rewarding stimuli in smokers. During the AAT, 92 smokers and 51 non-smokers viewed smoking-related vs. non-smoking-related pictures and pictures of natural rewards (i.e. highly palatable food) vs. neutral pictures. They were instructed to ignore image content and to respond to picture orientation by either pulling or pushing a joystick. Within-group comparisons revealed that smokers showed an automatic approach bias exclusively for smoking-related pictures. Contrary to our expectations, there was no difference in smokers’ and non-smokers’ approach bias for nicotine-related stimuli, indicating that non-smokers also showed approach tendencies for this picture category. Yet, in contrast to non-smokers, smokers did not show an approach bias for food-related pictures. Moreover, self-reported smoking attitude could not predict approach-avoidance behavior toward nicotine-related pictures in smokers or non-smokers. Our findings indicate that the AAT is suited for measuring smoking-related approach tendencies in smokers. Furthermore, we provide evidence for a diminished approach tendency toward food-related stimuli in smokers, suggesting a decreased sensitivity to natural rewards in the course of nicotine addiction. Our results indicate that in contrast to similar studies conducted in alcohol, cannabis and heroin users, the AAT might only be partially suited for measuring smoking-related approach tendencies in smokers. Nevertheless, our findings are of special importance for current etiological models and smoking cessation programs aimed at modifying nicotine-related approach tendencies in the context of a nicotine addiction.     

Prevalence of Cigarette Smoking and Associated Factors in a Large Sample of HIV-Positive Patients Receiving Antiretroviral Therapy in Vietnam

BackgroundCigarette smoking presents a salient risk for HIV-positive populations. This study is among the first to examine smoking prevalence, nicotine dependence, and associated factors in a large sample of HIV-positive patients receiving antiretroviral therapy (ART) in Vietnam.MethodsA cross-sectional study of 1133 HIV-positive people was conducted from January to September 2013 at 8 ART clinics in Hanoi (the capital) and Nam Dinh (a rural area). Smoking history and nicotine dependence (Fagerstrom Test of Nicotine Dependence–FTND) were assessed by participant self-report. Logistic regression and Tobit linear regression were performed to identify factors significantly associated with smoking outcomes.ResultsPrevalence of current, former, and never smokers in the sample was 36.1%, 9.5%, and 54.4%, respectively. The current smoking proportion was higher in males (59.7%) than females (2.6%). The mean FTND score was 3.6 (SD = 2.1). Males were more likely to currently smoke than females (OR = 23.4, 95% CI = 11.6–47.3). Individuals with problem drinking (OR = 1.8, 95% CI = 1.1–2.9) and ever drug use (OR = 3.7, 95%CI = 2.5–5.7) were more likely to be current smokers. Older age and currently feeling pain were associated with lower nicotine dependence. Conversely, receiving care in Nam Dinh, greater alcohol consumption, ever drug use, and a longer smoking duration were associated with greater nicotine dependence.ConclusionsGiven the high prevalence of smoking among HIV-positive patients, smoking screening and cessation support should be offered at ART clinics in Vietnam. Risk factors (i.e., substance use) linked with smoking behavior should be considered in prevention programs.     

Financial incentives for smoking cessation in lowincome smokers: study protocol for a randomized controlled trial

ABSTRACT: BACKGROUND: Tobacco smoking is the leading avoidable cause of death in high-income countries. The smoking-related disease burden is borne primarily by the least educated and least affluent groups. Thus, there is a need for effective smoking cessation interventions that reach to, and are effective in this group. Research suggests that modest financial incentives are not very effective in helping smokers quit. What is not known is whether large financial incentives can enhance longer-term (1 year) smoking cessation rates, outside clinical and workplace settings. Trial design A randomized, parallel groups, controlled trial. METHODS: Participants: Eight hundred low-income smokers in Switzerland (the less affluent third of the population, based on fiscal taxation). Intervention: A smoking cessation program including: (a) financial incentives given during 6 months; and (b) Internet-based counseling. Financial rewards will be offered for biochemically verified smoking abstinence after 1, 2, and 3 weeks and 1, 3, and 6 months, for a maximum of 1,500 CHF (1,250 EUR, 1,600 USD) for those abstinent at all time-points. All participants, including controls, will receive Internet-based, individually-tailored, smoking cessation counseling and self-help booklets, but there will be no in-person or telephone counseling, and participants will not receive medications. The control group will not receive financial incentives. OBJECTIVE: To increase smoking cessation rates. Outcome: Smoking abstinence after 6 and 18 months, not contradicted by biochemical tests. We will assess relapse after the end of the intervention, to test whether 6-month effects translate into sustained abstinence 12 months after the incentives are withdrawn.Randomization: Will be done using sealed envelopes drawn by participants. Blinding: Is not possible in this context. DISCUSSION: Smoking prevention policies and interventions have been least effective in the least educated, low-income groups. Combining financial incentives and Internet-based counseling is an innovative approach that, if proven acceptable and effective, could be later implemented on a large scale at a reasonable cost, decrease health disparities, and save many lives. Trial registration Current Controlled Trials ISRCTN04019434.     

Nicotine dependence in rats

Health hazards associated with nicotine and tobacco use are well known. A contributing factor, the dependence producing potential of this drug, has become widely accepted. However, there are only a few human and animal studies that provide objective measures of the behavioral consequences of nicotine abstinence. The purpose of the present experiment was to use sensitive measures to examine behavioral disruptions that resulted when nicotine administration was terminated. Six rats were administered 96 daily intravenous infusions of nicotine (0.125 mg/kg/infusion) for at least 10 days. They were trained to respond on a tongue-operated solenoid-driven drinking device that delivered 0.005 ml of a glucose and saccharin solution (G + S) per lick. When nicotine access was terminated for six days, there was a marked suppression in behavior reinforced by the sweetened solution, and this disruption was immediately reversed when nicotine was reinstated. In contrast, nicotine removal also resulted in a decrease in food intake on the first day, but on subsequent days food intake was significantly higher than when nicotine was administered. When cotinine (0.25 mg/kg/infusion), a metabolite of nicotine was substituted for nicotine for six days, similar disruptions resulted in responding maintained by G + S, but food intake was not significantly decreased on the first day of nicotine abstinence. These findings illustrate the utility of sensitive behavioral tests to reveal effects of nicotine abstinence.     

Prospective study of factors predicting outcome of transdermal nicotine treatment in smoking cessation.

OBJECTIVE--To assess the factors associated with cessation of smoking with transdermal nicotine and brief behavioural counselling. DESIGN--Interviews, treatment, and follow up for 26 weeks. SUBJECTS--1481 subjects recruited by mass media publicity who smoked > or = 15 cigarettes a day and were motivated to stop smoking. INTERVENTIONS--Twelve weeks'' treatment with transdermal nicotine and brief behavioural counselling at monthly visits. MAIN OUTCOME MEASURE--Sustained smoking cessation for the 28 days before the visit at week 26 verified by expired carbon monoxide concentrations. The logistic regression analysis included all subjects. RESULTS--Most subjects were dependent on nicotine, and the mean (SD) number of cigarettes smoked a day was 32 (12). Overall, 316/1481 subjects (21.3%) stopped smoking. Factors associated with stopping were being male (adjusted odds ratio 2.0; 95% confidence interval 1.5 to 2.7), age > or = 40 years (1.5; 1.1 to 2.0), living with a spouse or partner (1.5; 1.1 to 2.1), motivation ("want to quit" 1.7; 1.2 to 2.3), and concern about weight gain (1.7; 1.3 to 2.2). Negative associations were smoking marijuana (0.4; 0.2 to 0.8) and the presence of other smokers in the household (0.8; 0.6 to 0.9). Almost all subjects who smoked three or more cigarettes in the first four weeks of treatment resumed smoking in the long term (525/547, 96%). CONCLUSIONS--Age, sex, marital status (living with a spouse or partner), motivation, concern about weight gain, recent marijuana smoking, and other smokers in the household were baseline factors associated with differences in outcome of smoking cessation attempts. Smoking three or more cigarettes in the first few weeks after stopping strongly predicted long term relapse.     

Clinical considerations in study designs that use cotinine as a biomarker.

Subjects enrolled in studies are not always screened for routine habits such as smoking. Personal history is not always reliable and therefore an objective biomarker is necessary to screen for smokers. The objectives of this article were to review the metabolism of nicotine and other metabolic considerations associated with smoking; to review some of the routine methods used to assess exposure to nicotine-containing products; to revisit cotinine breakpoints utilized to distinguish smokers from non-smokers during screening for clinical trials; to assess the utility of screening questions regarding smoking practices; and to recommend standards for clinical pharmacology studies. The results indicated that cotinine levels serve as a useful biomarker of tobacco exposure; racial issues may be clinically relevant in determining smoking status; cessation of smoking should occur at least 14 days prior to the start of the study; adverse effects from nicotine withdrawal such as craving, hunger and weight gain may persist for more than 6 months; potential metabolic interactions via cytochrome P2A6 and P1A2 need to be considered when designing a study; and the use of a single calibrator as a breakpoint is acceptable if a categorical outcome such as 'smoker' versus 'non-smoker' is desired. Nicotine from food products is not expected to impact assay sensitivity or to be clinically relevant; a serum cotinine concentration of 10 ng ml(-1) be employed as a breakpoint for non-smokers versus smokers; other non-invasive alternatives are collection of urine, saliva, or hair (with suggested breakpoints of 200 ng ml(-1), 5 ng ml(-1) and 0.3 ng mg(-1), respectively; screening questions be accompanied by testing for cotinine; and the inclusion of smokers in studies should be considered once the impact of smoking on the targeted population is understood.     

The implication of cigarette smoking and cessation on macrophage cholesterol efflux in coronary artery disease patients

We investigated ATP-binding cassette transporters A1/G1 expression and function in mediating cholesterol efflux by examining the macrophages of cigarette-smoking patients with coronary artery disease (CAD) before and after smoking abstinence. Peripheral blood monocyte cells were collected from nonsmokers (n = 17), non-CAD (NCAD) smokers (n = 35), and CAD smokers (n = 32) before and after 3 months of smoking cessation. We found that the ABCA1 expression level was lower in macrophages from NCAD and CAD smokers than from nonsmokers at baseline. The ABCA1 function of mediating cholesterol efflux was reduced in NCAD and CAD smokers as compared with nonsmokers. After 3 months of smoking cessation, ABCA1 expression and function were improved in CAD smokers. However, ABCG1 expression and function did not change after smoking cessation. Furthermore, ABCA1 expression was inhibited by tar in human acute monocytic leukemia cell line THP-1-derived macrophages through the inhibition of liver X receptors. Nicotine and carbon monoxide did not inhibit ABCA1 expression. Our results indicate that chronic cigarette smoking impaired ABCA1-mediated cholesterol efflux in macrophages and that tobacco abstinence reversed the function and expression of ABCA1, especially in CAD patients. It was tobacco tar, rather than nicotine or carbon monoxide, that played a major role in the tobacco-induced disturbance of cellular cholesterol homeostasis.     

Clinical considerations in study designs that use cotinine as a biomarker

Subjects enrolled in studies are not always screened for routine habits such as smoking. Personal history is not always reliable and therefore an objective biomarker is necessary to screen for smokers. The objectives of this article were to review the metabolism of nicotine and other metabolic considerations associated with smoking; to review some of the routine methods used to assess exposure to nicotine-containing products; to revisit cotinine breakpoints utilized to distinguish smokers from non-smokers during screening for clinical trials; to assess the utility of screening questions regarding smoking practices; and to recommend standards for clinical pharmacology studies. The results indicated that cotinine levels serve as a useful biomarker of tobacco exposure; racial issues may be clinically relevant in determining smoking status; cessation of smoking should occur at least 14 days prior to the start of the study; adverse effects from nicotine withdrawal such as craving, hunger and weight gain may persist for more than 6 months; potential metabolic interactions via cytochrome P2A6 and P1A2 need to be considered when designing a study; and the use of a single calibrator as a breakpoint is acceptable if a categorical outcome such as 'smoker' versus 'non-smoker' is desired. Nicotine from food products is not expected to impact assay sensitivity or to be clinically relevant; a serum cotinine concentration of 10 ng ml^-1 be employed as a breakpoint for non-smokers versus smokers; other non-invasive alternatives are collection of urine, saliva, or hair (with suggested breakpoints of 200 ng ml^-1, 5 ng ml^-1 and 0.3 ng mg^-1, respectively; screening questions be accompanied by testing for cotinine; and the inclusion of smokers in studies should be considered once the impact of smoking on the targeted population is understood.     

Products of 5-lipoxygenase and myeloperoxidase activities are increased in young male cigarette smokers

Abstract The significance of 5-lipoxygenase and myeloperoxidase activities has not been extensively studied among young male smokers. Leukotriene B(4), 20-hydroxy-leukotriene B(4), 20-carboxy-leukotriene B(4) and 3-chlorotyrosine were measured in plasma and urinary samples of young male smokers at 8 hours following cigarette abstinence and an hour after cigarette smoking. Leukotriene B(4) and 3-chlorotyrosine were determined in neutrophils isolated from these individuals. The levels of these markers were compared with those of age-matched controls. In vitro studies were performed to evaluate the production of leukotriene B(4) and 3-chlorotyrosine from human neutrophils following exposure to nicotine and cotinine. Thirty male smokers (mean age, 27.4 years) and 28 male non-smokers (mean age, 28.7 years) were studied. Plasma levels of leukotriene B(4), 20-carboxy-leukotriene B(4) and 3-chlorotyrosine were higher in smokers than in non-smokers; leukotriene B(4) and 20-carboxy-leukotriene B(4) levels increased further an hour after cigarette smoking. Peripheral neutrophils isolated from smokers showed greater expressions of myeloperoxidase and 5-lipoxygenase activities compared with non-smokers, while plasma leukotriene B(4) and 3-chlorotyrosine were correlated significantly with high-sensitivity C-reactive protein and plasma nicotine concentrations. Exposure of human neutrophils to nicotine and cotinine resulted in a higher production of leukotriene B(4) and 3-chlorotyrosine. To conclude, leukotriene B(4) and 3-chlorotyrosine levels are increased in young male cigarette smokers. These results suggest that cigarette smoking aggravates neutrophil-mediated inflammation by modulating the activities of myeloperoxidase and 5-lipoxygenase pathways.