Pharmacokinetics of nicotine in rats after single-cigarette smoke inhalation

Influence of current and previous smoking on current phenotype in Parkinson's disease

INTRODUCTION

Although an inverse correlation between smoking and Parkinson's disease (PD) has been reported, research into the effect of smoking on current clinical progression remains limited for PD patients. Elucidation of a specific PD population who would benefit from smoking is challenging.

METHODS

We evaluated 110 consecutive PD patients (mean age; 71.0 ± 8.0 years) at a single neurology clinic between 2010 and 2018. The association with smoking status was evaluated in sex- and age-matched controls (non-PD). This study assessed the impact of previous smoking exposure on the outcome of current PD-related parameters, along with any confounders, in addition to assessing fluctuation of parkinsonism induced by smoking exposure.

RESULTS

The current smoking rate was significantly lower in PD versus non-PD (5.5% vs. 15.5%, P = 0.026), while there were similar rates between former and never smokers. Among the former smokers, most PD patients (97.3%) quit smoking prior to the onset of PD. There were no differences between PD patients with and without a history of smoking for current clinical parameters. Three PD patients with the mean onset age of 51.0 ± 5.3 y reported transient deterioration of their parkinsonism when smoking. Negative mood during cigarette smoke exposure was significantly increased over the entire life in PD patients with a history of smoking than those without (p < 0.001).

CONCLUSIONS

Although previous smoking history reportedly had a neuroprotective effect prior to onset, the association between the previous history and current phenotype in PD was not visible in the present study. However, the possibility that current nicotine intake might modify the parkinsonism deterioration will need to be further evaluated, especially in non-elderly patients. Cigarette smoke-related negative mood could be a confounder for quitting smoking in PD patients.

In vitro-in vivo correlations for nicotine transdermal delivery systems evaluated by both in vitro skin permeation (IVPT) and in vivo serum pharmacokinetics under the influence of transient heat application

The in vitro permeation test (IVPT) has been widely used to characterize the bioavailability (BA) of compounds applied on the skin. In this study, we performed IVPT studies using excised human skin (in vitro) and harmonized in vivo human serum pharmacokinetic (PK) studies to evaluate the potential in vitro-in vivo correlation (IVIVC) of nicotine BA from two, matrix-type, nicotine transdermal delivery systems (TDS). The study designs used for both in vitro and in vivo studies included 1h of transient heat (42±2°C) application during early or late time periods post-dosing. The goal was to evaluate whether any IVIVC observed would be evident even under conditions of heat exposure, in order to investigate further whether IVPT may have the potential to serve as a possible surrogate method to evaluate the in vivo effects of heat on the bioavailability of a drug delivered from a TDS. The study results have demonstrated that the BA of nicotine characterized by the IVPT studies correlated with and was predictive of the in vivo BA of nicotine from the respective TDS, evaluated under the matched study designs and conditions. The comparisons of single parameters such as steady-state concentration, heat-induced increase in partial AUCs and post-treatment residual content of nicotine in TDS from the in vitro and in vivo data sets showed no significant differences (p≥0.05). In addition, a good point-to-point IVIVC (Level A correlation) for the entire study duration was achieved by predicting in vivo concentrations of nicotine using two approaches: Approach I requiring only an in vitro data set and Approach II involving deconvolution and convolution steps. The results of our work suggest that a well designed IVPT study with adequate controls can be a useful tool to evaluate the relative effects of heat on the BA of nicotine from TDS with different formulations.

Whole tobacco smoke extracts to model tobacco dependence in animals

Smoking tobacco is highly addictive and a leading preventable cause of death. The main addictive constituent is nicotine; consequently it has been administered to laboratory animals to model tobacco dependence. Despite extensive use, this model might not best reflect the powerful nature of tobacco dependence because nicotine is a weak reinforcer, the pharmacology of smoke is complex and non-pharmacological factors have a critical role. These limitations have led researchers to expose animals to smoke via the inhalative route, or to administer aqueous smoke extracts to produce more representative models. The aim was to review the findings from molecular/behavioural studies comparing the effects of nicotine to tobacco/smoke extracts to determine whether the extracts produce a distinct model. Indeed, nicotine and tobacco extracts yielded differential effects, supporting the initiative to use extracts as a complement to nicotine. Of the behavioural tests, intravenous self-administration experiments most clearly revealed behavioural differences between nicotine and extracts. Thus, future applications for use of this behavioural model were proposed that could offer new insights into tobacco dependence.

Effect of menthol on nicotine pharmacokinetics in rats after cigarette smoke inhalation

INTRODUCTION

The effect of menthol on nicotine disposition is important in understanding smoking behaviors among different racial groups. The present study was to evaluate whether menthol affects the pharmacokinetics of nicotine after cigarette smoke inhalation.

METHODS

Rats were exposed to mainstream smoke from either a nonmentholated or mentholated cigarette (1 puff/min for 10 min) using a smoke inhalation apparatus. For the multiple-cigarette smoke inhalation, rats received the smoke from either nonmentholated or mentholated cigarette (10 puffs) every 12 hr for a total of 17 cigarettes. Serial blood samples were collected during the 10-min inhalation phase for the single-cigarette smoke or the 17th cigarette inhalation and for 30 hr thereafter. Nicotine and its major metabolite cotinine were assayed by radioimmunoassay methods.

RESULTS

Following single-cigarette smoke inhalation, mentholated cigarettes significantly decreased the mean peak concentrations of nicotine in plasma (C(max)) from 27.1 to 9.61 ng/ml and the total area under the plasma concentration-time curves (AUC) from 977 to 391 ng min/ml as compared with those after nonmentholated cigarette smoke inhalation. C(max) and AUC values for cotinine were also significantly reduced by menthol. Similarly after multiple smoke inhalation, C(max), AUC, and the mean average steady-state plasma concentration of nicotine as well as cotinine were significantly lower in mentholated cigarette inhalation. Interestingly, there was a significant increase in the cotinine to nicotine AUC ratio from 13.8 for the nonmentholated to 21.1 for the mentholated cigarette.

CONCLUSIONS

These results suggest that menthol in mentholated cigarettes can substantially decrease the absorption and/or increase the clearance of nicotine.

Vaccination against nicotine alters the distribution of nicotine delivered via cigarette smoke inhalation to rats

Preclinical models of nicotine vaccine pharmacology have relied on i.v. or s.c. administration of nicotine. Models using cigarette smoke inhalation might more accurately simulate nicotine exposure in smokers. Nicotine vaccine effects were examined in rats using two cigarette smoke exposure models: a 10 min nose-only exposure (NSE) producing serum nicotine levels equivalent to the nicotine boost from 1 cigarette in a smoker, and a 2h whole-body exposure (WBE) producing serum nicotine levels similar to those associated with regular mid-day smoking. Vaccination prior to 10min smoke NSE reduced nicotine distribution to brain by 90%, comparable to its effect on nicotine administered i.v. Vaccination prior to 2 h smoke WBE reduced nicotine distribution to brain by 35%. The nicotine concentration in broncheoalveolar lavage (BAL) fluid obtained after 2 h WBE was increased by 230% in vaccinated rats but was also increased in rats passively immunized with a nicotine-specific monoclonal antibody, and so was likely due to transfer of antibody from serum rather than local production at the pulmonary mucosa. Nicotine-specific IgA was not detectable in BAL fluid, but titers in serum were appreciable at 21-25% of the IgG titer and could contribute to vaccine efficacy. Both vaccination and passive immunization are effective in reducing nicotine distribution to brain in rats when nicotine is delivered via inhaled cigarette smoke. These data validate results previously obtained in rodents for nicotine vaccines using i.v. or s.c. nicotine dosing and provide a quantitative method for studying aspects of nicotine exposure which are unique to cigarette smoke inhalation.

Effects of pentoxyfilline and heparin on reperfusion injury island skin flaps in rats exposed to tobacco

BACKGROUND

Ischemia-reperfusion injury is believed to be a major cause of transferred skin flap failure. Cigarette smoking is known to be associated with endogenous antioxidant depletion, hypercoagulability, and cutaneous vasoconstriction. This investigation was carried out to study possible effects of pentoxyfilline or heparin on rat skin reperfusion injury under tobacco exposure.

MATERIALS AND METHODS

Thirty-six rats were randomized into two major groups: 18 were exposed to cigarette smoke during a 4 wk period prior to surgery; the remaining 18 underwent a sham smoking procedure. Each group was further divided into three equal subgroups: heparin, pentoxyfilline, and saline solution. One identical skin flap was raised in each animal. The vasculature of the flap was clamped for 3 h and reperfused for 5 min. A venous blood sample was obtained from the flap after reperfusion for serum malondialdehyde (MDA) and myeloperoxidase (MPO) analysis. Flap survival was assessed 7 d after the procedure.

RESULTS

The lipid peroxidation levels and flap necrosis were significantly higher in the cigarette-smoking group skin flaps. There was also a decrease of MPO activity in this group compared with the non-smoking group. Heparin-treated rats had significantly lower MDA levels and showed the most viable percent area among smoking rats.

CONCLUSIONS

These data suggest that heparin had a significant beneficial effect both on flap survival and on the lipid peroxidation reduction after smoke exposure in the rat axial-pattern skin flap subjected to ischemia and reperfusion injury. Pharmacologic therapy may represent an alternative way to counteract tobacco effects in flap surgery in emergency situations.

Comparison of the behavioral effects of cigarette smoke and pure nicotine in rats

Animal models of tobacco dependence typically rely on parenteral administration of pure nicotine. Models using cigarette smoke inhalation might more accurately simulate nicotine exposure in smokers. The primary goal of this study was to validate methods for administering cigarette smoke to rats using exposure conditions that were clinically relevant and also produced brain nicotine levels similar to those produced by behaviorally active doses of pure nicotine. A secondary goal was to begin examining the behavioral effects of smoke. Nose-only exposure (NOE) to smoke for 10-45min or whole-body exposure (WBE) to smoke for 1-4h produced serum nicotine concentrations similar to those in smokers (14-55ng/ml), without excessive carbon monoxide exposure. Daily nicotine (0.1mg/kg, s.c.) induced locomotor sensitization whereas 45-min NOE producing brain nicotine levels within the same range did not. Nicotine 0.125mg/kg s.c. reversed withdrawal from a chronic nicotine infusion as measured by elevations in intracranial self-stimulation thresholds whereas 4-h WBE producing similar brain nicotine levels did not. These data demonstrate the feasibility of delivering cigarette smoke to rats at clinically relevant doses, and provide preliminary evidence that the behavioral effects of nicotine delivered in smoke may differ from those of pure nicotine.

Crucial aspects of smoking in wound healing after breast reduction surgery

BACKGROUND

The aim of this study was to investigate the influence of cigarette smoking on wound-healing in patients undergoing breast reduction.

METHODS

In our prospective study, 50 patients (25 smokers, 25 nonsmokers) scheduled for breast reduction have been evaluated. Urine cotinine levels were measured to analyse perioperative smoking habits. Urine samples were taken preoperatively and on the fourth postoperative day. Cotinine as a metabolite of nicotine allows precise evaluation of nicotine exposure. To assess the progress of woundhealing we classified secreting, instable, inflamed or necrotic wound conditions, which required a dressing after the tenth postoperative day as impaired wound healing. For statistical analysis non-parametrical tests for independent and dependent data were used.

RESULTS

Ten of 25 smokers presented impaired wound healing compared to 4 of 25 nonsmokers. The median cotinine level of smokers was 1964 (783/3963)ng/cc preoperatively and 432 (148/1695)ng/cc postoperatively. Nonsmokers had a preoperative cotinine level of 18 (7/37)ng/cc and 15 (4/34)ng/cc postoperatively. Smokers who developed impaired wound-healing showed higher levels of cotinine pre- (2117 ng/cc) and especially postoperatively (485 ng/cc) compared to smokers with regular woundhealing (1614 ng/cc and 389 ng/cc). Both differences in cotinine levels were statistically significant (p=0.03 and p=0.02).

CONCLUSIONS

The data of the present study confirm the negative effect of smoking on wound healing in patients undergoing breast reduction.

Chronic nicotine and smoke treatment modulate dopaminergic activities in ventral tegmental area and nucleus accumbens and the ?-aminobutyric acid type B receptor expression of the rat prefrontal cortex

Dopaminergic afferents from the mesencephalic areas, such as ventral tegmental area (VTA), synapse with the gamma-aminobutyric acid (GABA)-ergic interneurons in the prefrontal cortex (PFC). Pharmacological and electrophysiological data show that the reinforcement, the dependence-producing properties, as well as the psychopharmacologic effects of nicotine depend to a great extent on activation of nicotinic receptors within the mesolimbocortical dopaminergic projection. To explore further the relationship between the mesencephalic dopaminergic neurons and PFC GABAergic neurons, we investigated the effects of nicotine and passive exposure to cigarette smoke on the regulation of tyrosine hydroxylase (TH) in VTA and substantia nigra (SNC) and dopamine (DA) D1 receptor levels in nucleus accumbens (NAc) and caudate-putamen (CPu). Also, the simultaneous changes in GABAB receptors mRNAs in the PFC were studied. The results showed that chronic nicotine and smoking treatment differentially changed the levels of TH protein in VTA and SNC and DA D1 receptor levels in Nac and CPu. GABAB1 and GABAB2 receptor mRNA levels also showed different change patterns. Ten and thirty minutes of smoke exposure increased GABAB1 receptor mRNA to a greater extent than that of GABAB2, whereas GABAB2 was greatly enhanced after 1 hr of smoke exposure. The TH levels in VTA were closely related to DA D1 receptor levels in NAc and with GABAB receptor mRNA changes in PFC. These results suggest that the mesolimbic pathway and GABAB receptor mRNA in PFC are modulated by nicotine and cigarette smoke, implying an important role in nicotine's psychopharmacological effects.

Investigations using immunization to attenuate the psychoactive effects of nicotine

Despite the enormous health risks, people continue to smoke and use tobacco primarily as a result of nicotine addiction. As part of our immunopharmacotherapy research, the effects of active and passive immunizations on acute nicotine-induced locomotor activity in rats were investigated. To this end, rats were immunized with either a NIC-KLH immunoconjugate vaccine designed to elicit an antinicotine immune response, or were administered an antinicotine monoclonal antibody, NIC9D9, prior to a series of nicotine challenges and testing sessions. Vaccinated rats showed a 45% decrease in locomotor activity compared to a 16% decrease in controls. Passive immunization with NIC9D9 resulted in a 66.9% decrease in locomotor activity versus a 3.4% decrease in controls. Consistent with the behavioral data, much less nicotine was found in the brains of immunized rats. The results support the potential clinical value of immunopharmacotherapy for nicotine addiction in the context of tobacco cessation programs.

Simultaneous GC-MS determination of nicotine and cotinine in plasma for the pharmacokinetic characterization of nicotine in rats

A gas liquid chromatography/mass spectrometry assay method was developed for the simultaneous determination of nicotine and its major metabolite, cotinine, in rat plasma. Of particular interest was improving the low and variable extraction recovery for the parent drug and the metabolite. In addition, the feasibility of this assay method for pharmacokinetic studies of nicotine and cotinine after intravenous (i.v.), oral, and intraperitoneal (i.p.) administration of 1 mg kg(-1) of nicotine was tested. The low (30 and 48% for nicotine and cotinine, respectively) and variable (25 and 22% coefficient of variation for nicotine and cotinine, respectively) extraction recovery for nicotine and cotinine into dichloromethane was significantly improved by the addition of NaCl to the plasma. As a result, the recoveries for nicotine and cotinine were improved to 68 and 65%, respectively. The coefficient of variation was less than 10% in the 50-500 ng ml(-1) range and less than 16.58% at 10 ng ml(-1) for both nicotine and cotinine, indicating that the reproducibility of the assay was also improved by the extraction procedure. When injected intravenously at a dose of 1 mg kg(-1), the temporal profile of plasma concentration for nicotine followed a bi-exponential decline. Moment analysis revealed that pharmacokinetic parameters for nicotine (i.e. Cl, 46.30 ml min(-1) kg(-1); Vss, 2.77 1 kg(-1)) was similar to those reported in studies using 14C-nicotine. Absolute bioavailabilities of nicotine for i.p. and oral administration were 87.0 and 80.4%, respectively. The concentration of the metabolite increased up to 4 h to reach Cmax after i.p. and oral administrations and then declined slowly with time. These results indicate that this convenient analytical procedure is readily applicable to pharmacokinetic studies of nicotine and cotinine involving small laboratory animals with a sensitivity comparable with that reported for studies using 14C-nicotine.

Effects of smoking in patients with early-onset Parkinson's disease

Smoking a cigarette relieved symptoms in 6 patients with early-onset Parkinson's disease. In these patients smoking reduced tremor, rigidity, bradykinesia, and gait disturbance including frozen gait. These effects lasted for about 10-30 min, and relieved parkinsonian symptoms in the off-period. Nicotine chewing gum had a lesser effect. Nicotine is thought to activate the nigrostriatal dopaminergic pathway and increase the release of dopamine in the striatum, and this can explain the effects of smoking in these patients.

A physiologically based pharmacokinetic model for nicotine disposition in the Sprague-Dawley rat

A physiologically based pharmacokinetic (PBPK) model was developed to describe the disposition of nicotine in the Sprague-Dawley (SD) rat. Parameters for the model were either obtained from the literature (blood flows, organ volumes) or determined experimentally (partition coefficients). Nicotine metabolism was defined in the liver compartment by the first-order rate constants KNC and KNP which control the rate of nicotine metabolism to cotinine and "polar metabolites" (PM), respectively. These rate constants were estimated by optimizing the model fit to pharmacokinetic data obtained by administering an intraarterial (S)-[5-3H]nicotine bolus of 0.1 mg/kg to 6 rats. Model simulations that optimized for the appearance of cotinine in plasma estimated KNC and KNP to be 75.8 and 24.3 hr-1, respectively. Use of these constants in the model allowed us to accurately predict nicotine plasma kinetics and the fraction of the dose eliminated by renal (8.5%) and metabolic (91.5%) clearance. To validate the model's ability to predict tissue kinetics of nicotine, 21 male SD rats were administered 0.1 mg/kg (S)-[5-3H]nicotine intraarterially. At seven time points following treatment, 3 rats were euthanized and tissues were removed and analyzed for nicotine. Model-predicted nicotine tissue kinetics were in agreement with those determined experimentally in muscle, liver, skin, fat, and kidney. The brain, heart, and lung exhibited nonlinear nicotine elimination, suggesting that saturable nicotinic binding sites may be important in nicotine disposition in these organs. Inclusion of saturable receptor binding expressions in the mathematical description of these compartments resulted in better agreement with the experimental data. The Bmax and KD estimated by model simulations for these tissues were brain, 0.009 and 0.12; lung, 0.039 and 2.0; and heart, 0.039 nmol/tissue and 0.12 nM, respectively. This PBPK model can successfully describe the tissue and plasma kinetics of nicotine in the SD rat and will be a useful tool for pharmacologic studies in humans and experimental animals that require insight into the plasma or tissue concentration-effect relationship.

The effect of cigarette smoking on gingival blood flow in humans

This paper presents the acute effects of cigarette smoking on blood flow to the gingiva in 12 young smokers. Relative gingival blood flow (GBF) was measured by a laser Doppler fiberoptic probe placed 1 mm into the buccal sulcus of tooth no. 26. The probe continuously measured the flux of blood cells (velocity X number of cells) in the gingival crest. Relative skin blood flow (SBF) to the forearm and heart rate were also monitored continously; blood pressure (BP) was assessed at 5-min intervals. After resting for 5 min, subjects sham smoked an unlighted cigarette for 5 min, then smoked the cigarette, and finally rested for 25 min afterwards. Mean changes from resting for all variables were compared to sham smoking for each 5 min block. Mean GBF rose significantly above sham smoking values during smoking, and remained elevated during the first 5 min after smoking (p less than 0.05). Mean SBF decreased slightly during and after smoking, but the changes were not significantly depressed compared to sham smoking (p greater than 0.05). During smoking, BP and heart rate increased significantly over sham smoking (p less than 0.05). GBF increased almost linearily when the probe was placed into the gingival sulcus; this phenomenon did not occur when the probe was placed externally to the gingival crest. The theory that smoking impairs gingival blood flow may not be true in humans.

Acute effects of tobacco smoking on blood flow in the cutaneous micro-circulation

p6 experimental model has been designed to help study the acute effects of tobacco smoking on the cutaneous micro-circulation. Arterioles in the nude mouse ear are directly visualised by intravital microscopy and the blood flow is quantified. Arteriolar vasoconstriction and decreased blood flow are seen in response to smoking. The implications of post-operative smoking for the patient undergoing flap surgery are discussed.

Elevated nicotine levels in patients undergoing hemodialysis. A role in cardiovascular mortality and morbidity?

The incidence of cardiovascular disease in patients with end-stage renal disease undergoing long-term maintenance hemodialysis is excessively high. The reason for this excess morbidity and mortality has remained unclear. Cigarette smoking is one factor that has been associated with increased cardiovascular risk. To learn more about the effects of tobacco smoking in these patients, nicotine levels were assayed in the serum of 10 patients with end-stage renal disease undergoing maintenance hemodialysis. Specimens were obtained before and after smoking one cigarette and following dialysis or an equivalent period in control subjects. Serum nicotine levels (+/-SEM) in control subjects measured 19.0 +/- 7.2 ng/ml initially, 36.1 +/- 8.2 ng/ml after smoking, and 9.3 +/- 3.5 ng/ml after a period of 4.35 hours. These compare with respective values of 76.6 +/- 16.8 ng/ml (p less than 0.004), 132.9 +/- 19.7 ng/ml (p less than 0.001), and 51.9 +/- 10.5 ng/ml (p less than 0.001) in patients undergoing hemodialysis. These data demonstrate markedly higher nicotine levels in hemodialysis patients compared with control subjects, which may have serious implications regarding morbidity and mortality.

Pharmacokinetics of nicotine in rats after multiple-cigarette smoke exposure

The pharmacokinetics of nicotine and its major metabolites was evaluated in male rats after multiple-cigarette smoke exposure. A smoke-exposure apparatus was used to deliver cigarette smoke to the exposure chamber. The rats were exposed to smoke from a single cigarette every 8 hr for 14 days and to the smoke of a cigarette spiked with radiolabeled nicotine on the 15th day. Blood and urine samples were collected at timed intervals during the 10-min smoke-exposure period of the last cigarette and up to 48 hr thereafter. Nicotine, cotinine, and other polar metabolites were separated by thin-layer chromatography and quantified by liquid scintillation counting. The data were analyzed by computer fitting, and the derived pharmacokinetic parameters were compared to those observed after a single iv injection of nicotine and after a single-cigarette smoke exposure. The results indicated that the amount of nicotine absorbed from multiple-cigarette smoke was approximately 10-fold greater than that absorbed from a single cigarette. Also, unlike the single-cigarette smoke exposure experiment, nicotine plasma levels did not decay monotonically but increased after the 5th hr, and high plasma concentrations persisted for 30 hr. The rate and extent of the formation of cotinine, the major metabolite of nicotine, were decreased as compared with their values following a single-cigarette smoke exposure. It was concluded that nicotine or a constituent of tobacco smoke inhibits the formation of cotinine and may affect the biotransformation of other metabolites. Urinary excretion tended to support the conclusions that the pharmacokinetic parameters of nicotine and its metabolites were altered upon multiple as compared to single dose exposure.