Effect of nicotine or cotinine on metabolism of 4-methylnitrosamino-1-(3-pyridyl)-1-butanone (NNK) in isolated rat lung and liver

The scope of the present study was to investigate whether nicotine or cotinine will affect the metabolism of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in isolated perfused rat lungs and livers and to study the effect of starvation on pulmonary metabolism of NNK. NNK metabolism was investigated in isolated perfused liver and lung of male F344 rats perfused with 35 nM [5-³H]NNK in presence of a 1400-fold excess of the main tobacco alkaloid nicotine and its metabolite cotinine. In perfused rat livers, nicotine and cotinine inhibited NNK elimination and metabolism and led to a substantial increase of elimination half-life from 14.6 min in controls to 25.5 min after nicotine and 36.6 min after cotinine co-administration, respectively. In parallel, the pattern of NNK metabolites was changed by nicotine and cotinine. The pathway of α-hydroxylation representing the metabolic activation of NNK was decreased to 77% and 85% of control values, whereas N-oxidation of NNK and glucuronidation of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) was increased 2.6- and 1.2-fold in presence of nicotine and cotinine, respectively. When isolated rat lungs were perfused with 35 nM NNK for 3 h neither the elimination nor the pattern of metabolites were substantially affected due to co-administration of 50 μM nicotine or cotinine. Cytochrome P450 2E1 is known to participate in the activation of NNK and can be induced by starvation. However, isolated rat lungs from male Sprague Dawley rats perfused with [1-¹⁴C]NNK at about 2 μM for 3 h, revealed only small differences in pulmonary elimination and pattern of NNK metabolites between fed and starved animals. These results suggest that nicotine and its main metabolite cotinine inhibit the metabolic activation of NNK predominantly in the liver whereas activation in lung, a main target organ of NNK induced carcinogenesis, remained almost unaffected. Received: 13 March 1997 / Accepted: 21 November 1997     

An automated colorimetric assay for urine nicotine metabolites: a suitable alternative to cotinine assays for the assessment of smoking status

We have modified the direct barbituric acid (DBA) test for urine nicotine metabolites so that it can be used on a continuous flow auto-analyser. The performance of the method was compared with a cotinine radio-immunoassay (RIA). The auto-analyser DBA method and cotinine RIA performed equally well in terms of assessing smoking status, yielding a false positive rate of 1.5% at a detection rate of 98% when compared to self-reported smoking information. The results obtained with the two methods were well correlated, r = 0.91, although the DBA method results were consistently higher than the corresponding cotinine RIA results; the method detects cotinine and other nicotine metabolites. The coefficient of variation for the DBA method was 3.4% compared with 10% for the RIA. The DBA method has a throughput of about 250 samples per day compared to about 70 per day by RIA and the reagents are readily obtained and inexpensive.     

Nicotine metabolism in isolated perfused lung and liver of phenobarbital- and benzoflavone-treated rats

The kinetics of nicotine elimination was investigated in isolated perfused lung and liver of phenobarbital (PB)- and 5,6-benzoflavone (BF)-pretreated rats. The estimated kinetic parameters demonstrated a high nicotine elimination rate in rat lung approaching the capacity of liver when both organs were in an uninduced state. The concentration-time profiles of cotinine as the main metabolite were almost identical for isolated lung and liver. In both organs the cotinine plasma concentrations reached a plateau level after 60 min of perfusion. Pretreatment of rats with 5,6-benzoflavone did not affect the rate of nicotine elimination and cotinine formation either in the lung or in the liver. Phenobarbital treatment, however, induced nicotine clearance in lung approximately 2-fold. This effect is quantitatively lower than the PB-related 8-fold induction of hepatic nicotine elimination observed in a previous study. The present results also indicate that the turnover of cotinine is markedly enhanced after PB induction. The elimination half-lives and clearance values for cotinine as the substrate were approximately 10-fold increased in rat liver after PB pretreatment. Thus, an important contribution of extrahepatic tissues to nicotine metabolism in rats has to be assumed. Moreover, since cotinine elimination is significantly increased after PB induction it is questionable whether cotinine plasma concentrations can further be used as suitable parameter for nicotine consumption.This study was supported by a grant from the German Council on Smoking and Health (Forschungsrat Rauchen und Gesundheit), Hamburg, FRG     

The influence of smoking on success of tympanoplasty measured by serum cotinine analysis

The aim of this study was to evaluate the effects of smoking on surgical outcome and hearing results in tympanoplasty by serum cotinine analysis as an objective method. Furthermore, type of grafting for the smoking patients has been investigated in a prospective cohort in a tertiary medical center. The overall success rate of long-term surgical outcome was 70.1% out of 77 tympanoplasty operations. On the basis of cotinine enzyme immunoassay, 56 patients had a serum cotinine measurement below 17.5 ng/ml and 21 patients above that. While the graft take rate in the non-smoking group was 76.8%, it was 52.4% in the smoking group and this difference was statistically significant (p = 0.037). While mean graft take rate in the temporalis fascia group was 25% for smokers, mean graft take rate in cartilage shield tympanoplasty group it was 88.9%, and for smokers it was 52.4%. Cotinine is a major metabolite of nicotine and is a reliable marker to differentiate smoking patients from non-smokers. Smoking status was found as a significant prognostic factor influencing the success rate of tympanoplasty negatively and the influence of a more stable grafting technique was demonstrated on smoking patients undergoing tympanoplasty procedure.     

Degree of dependence influences the effect of smoking on cognitive flexibility

Pre-frontal cortical (PFC) dysfunction has been put forward as the basis for development and maintenance of addiction. To explore this relationship, the present study investigated the effects of smoking on PFC-mediated cognitive flexibility and subjective states in low- (LD) and high-dependent (HD) smokers.Twenty-four LD and 24 HD smokers (Fagerström dependence scores ≤ 4 and ≥ 5, respectively) were randomly allocated to non-smoking or smoking condition (12 LD and 12 HD participants per condition). After abstaining from smoking for a minimum of two hours volunteers completed a battery of questionnaires [nicotine-specific Visual Analogue Scales (Nic-VAS), Questionnaire of Smoking Urges (QSU) and Profile of Mood States (POMS)] at baseline [T1] and again after smoking one cigarette or remaining abstinent [T2]. Cognitive flexibility was evaluated at T2 using the Intra-Extra Dimensional Set-Shift test. The Rapid Visual Information Processing test was performed as a control nicotine-sensitive task at several time points during the experiment.Compared to LD smokers, HD smokers had higher salivary cotinine and breath CO levels at baseline and reported more craving (QSU) and felt less stimulated (Nic-VAS), vigorous, friendly and elated (POMS) throughout the experiment. Smoking increased Nic-VAS ratings of ‘Buzzed’ and ‘Dizzy’ and decreased craving in all participants. Smoking selectively impaired cognitive flexibility in HD smokers since HD smokers allocated to the smoking condition made significantly more errors with the intra-dimensional set-shift than their counterparts in the abstinent condition. No effect of smoking on RVIP test was observed, most likely due to the practice effect which was significant in both groups of smokers. The practice effect, however, was more pronounced in LD smokers.This study demonstrates that PFC-mediated cognitive effects of smoking as well as subjective reports vary according to the degree of nicotine dependence.     

华北地区城乡居民烟草暴露与动脉弹性关系的研究

目的运用烟草暴露特异性指标可替宁调查中国华北地区城乡居民烟草暴露状况,并探讨其对动脉弹性的不良影响。方法2008年2月至8月于北京军区总医院和河北省巨鹿县人民医院体检中心共招募受检志愿者897例,血清可替宁浓度大于1ng／ml者被确认为烟草暴露人群。采用全自动检测仪测定所有受检者踝臂脉搏波传导速度（baPWV）。结果289例（32．2％）受检者被认定存在显著的烟草暴露。巨鹿农村地区暴露率比北京市东城区高（34．8％比25．0％,P=0．006）。校正混杂因素后,烟草暴露的受检者baPWV比没有暴露的人群高（1429cm／s比1393cm／s,P=0．017）。没有烟草暴露的受检者中北京东城区居民比巨鹿农村地区居民baPWV高（1447cm／s比1380cm／s,P=0．001）;但在严重和轻度暴露人群中,两地之间动脉弹性差异无统计学意义。结论可替宁确定的烟草暴露人群动脉弹性较差;无论是轻度还是重度的烟草暴露对北方经济落后地区居民动脉弹性造成的影响要大于城市居民。     

GC–MS determined cotinine in an epidemiological study on smoking status at delivery

The objective of this study was to measure the plasma cotinine levels in pregnant women and their newborns using a gas chromatography–mass spectrometry (GC–MS) method in an epidemiological-delivered population with a wide range of tobacco intakes. Nearly 1000 pregnant women from regional maternity wards (n=1007) were selected for the study. Each patient kept a tobacco diary and underwent a blood test to assess cotinine levels and at the same time that the newborns’ cordonal plasma was taken. These values were then cross-checked.Cotinine was estimated using a selected-ion monitoring mode with a 1.5 ng/ml quantification limit. The cotinine levels in mothers and newborns were highly correlated, whatever the mother's smoking status, with a calculated cut-off for cotinine levels in active smokers of 21.5 ng/ml. Finally, the cotinine determined through this GC–MS method offered a sensitive and accurate measure of tobacco exposition of the pregnant women and their babies.     

Nicotine,cotinine, and β-nicotyrine inhibit NNK-induced DNA-strand break in the hepatic cell line HepaRG

Recent in vitro work using purified enzymes demonstrated that nicotine and/or a nicotine metabolite could inhibit CYPs (CYP2A6, 2A13, 2E1) involved in the metabolism of the genotoxic tobacco nitrosamine NNK. This observation raises the possibility of nicotine interaction with the mechanism of NNK bioactivation. Therefore, we hypothesized that nicotine or a nicotine metabolite such as cotinine might contribute to the inhibition of NNK-induced DNA strand breaks by interfering with CYP enzymes. The effect of nicotine and cotinine on DNA strand breaks was evaluated using the COMET assay in CYP competent HepaRG cells incubated with bioactive CYP-dependent NNK and CYP-independent NNKOAc (4-(acetoxymethylnitrosoamino)-1-(3-pyridyl)-1-butanone). We report a dose-dependent reduction in DNA damage in hepatic-derived cell lines in the presence of nicotine and cotinine. Those results are discussed in the context of the in vitro model selected.     

Exposure to secondhand tobacco smoke and the frailty syndrome in US older adults

Exposure to secondhand tobacco smoke (SHS) is a well-established risk factor for cardiovascular disease and lung cancer in nonsmoking adults. However, few studies have focused on the health consequences of exposure to SHS in older adults. This is the first study to assess the association between SHS and the frailty syndrome in the nonsmoking older adult population. Cross-sectional study was conducted among 2059 nonsmoking adults aged ≥60 years who participated in the third US National Health and Nutrition Examination Survey and had completed a physical examination. Exposure to SHS was assessed by serum cotinine concentrations and by self-reported data from the home questionnaire. Frailty was ascertained with a slight modification of the Fried criteria. Analyses were performed with logistic regression and adjusted for the main confounders. The median (interquartile range) concentration of serum cotinine was 0.095 (IQR 0.035–0.211) ng/mL. The prevalence of frailty was 6.0 %. The odds ratios (95 % confidence interval [CI]) of frailty comparing the second, third, and fourth to the lowest quartile of serum cotinine were, respectively, 1.44 (0.67–3.06), 1.46 (0.75–2.85), and 2.51 (1.06–5.95), p value for trend 0.04. An increased frequency of frailty was also observed in participants reporting to live with ≥2 smokers at home (odds ratio 5.37; 95 % CI 1.13–25.5). In the US nonsmoking older adult population, exposure to SHS was associated with an increased frequency of frailty. More efforts are needed to protect older adults from SHS, especially at home and in other areas not covered by smoke-free regulations.     

Elevated urinary thioether excretion among bidi rollers exposed occupationally to processed tobacco

Summary Manufacture of bidis — the Indian version of cigarettes — is one of the largest cottage industries in India. Bidi rollers handle 225–450 g of bidi tobacco per day and inhale tobacco dust and volatile components present in the work environment. Since tobacco is known to be mutagenic and carcinogenic, urinary cotinine was estimated in bidi rollers and control subjects as an index of tobacco-specific exposure while the concentration of urinary thioethers was determined to ascertain exposure to electrophilic moieties. Detection of cotinine in urine samples from bidi rollers with no tobacco habits indicated that occupational exposure leads to cutaneous absorption of tobacco constituents and the resultant increase in exposure to alkylating agents was evident from elevated urinary thioether levels.