Populations of Black-African descent have slower rates of nicotine and cotinine metabolism, smoke fewer cigarettes (~10 cigarettes/day), and have higher incidences of tobacco-related illnesses compared to Caucasians. Cytochrome P450 2A6 (CYP2A6) is the main enzyme involved in the metabolism of nicotine and its proximal metabolite cotinine, as well as tobacco-specific nitrosamines. Genetic polymorphisms in CYP2A6 contribute to the large variability observed in rates of nicotine metabolism. Reduced CYP2A6 activity has been associated with fewer cigarettes smoked, higher quit rates, and lower lung cancer risk in predominantly moderate to heavy-smoking (~20–30 cigarettes/day) Caucasians. CYP2A6 genetic variants and their impact on smoking behaviours have not been well studied among individuals of Black-African descent. The main objectives herein were to identify and characterize new CYP2A6 variants that may explain the slower rates of metabolism, and determine whether CYP2A6 variation is a predictor of smoking phenotypes in this population. Furthermore, we examined whether previously validated biomarkers of tobacco exposure have limitations among individuals of Black-African descent given their low and sporadic smoking patterns. A new CYP2A6 variant (CYP2A6*23) was found in individuals of Black-African descent recruited for a nicotine pharmacogenetic-pharmacokinetic study. CYP2A6*23 reduced activity towards nicotine and coumarin in vitro and was associated with slower rates of CYP2A6 kinetics in vivo. In a clinical trial of African-American light smokers, CYP2A6 slow metabolizers were more successful at smoking cessation compared to normal metabolizers, although no differences in cigarette consumption were found. Two common biochemical markers of tobacco smoke exposure, cotinine and exhaled carbon monoxide, were weakly correlated with self-reported cigarette consumption. These biomarkers were not substantially affected by variables previously shown to alter amount smoked and/or rates of cotinine metabolism such as gender, age, body mass index or smoking menthol cigarettes. However, CYP2A6 slow metabolizers had significantly higher cotinine without smoking more cigarettes. Identification and characterization of novel variants adds to our understanding of nicotine pharmacokinetic differences between racial/ethnic minority groups and improves accuracy of CYP2A6 genotype groupings for genetic association studies. Furthermore, better insight into the biological factors associated with smoking behaviours will aid in the development of more efficacious targeted treatments for this understudied population.

Populations of Black-African descent have slower rates of nicotine and cotinine metabolism, smoke fewer cigarettes (~10 cigarettes/day), and have higher incidences of tobacco-related illnesses compared to Caucasians. Cytochrome P450 2A6 (CYP2A6) is the main enzyme involved in the metabolism of nicotine and its proximal metabolite cotinine, as well as tobacco-specific nitrosamines. Genetic polymorphisms in CYP2A6 contribute to the large variability observed in rates of nicotine metabolism. Reduced CYP2A6 activity has been associated with fewer cigarettes smoked, higher quit rates, and lower lung cancer risk in predominantly moderate to heavy-smoking (~20–30 cigarettes/day) Caucasians. CYP2A6 genetic variants and their impact on smoking behaviours have not been well studied among individuals of Black-African descent. The main objectives herein were to identify and characterize new CYP2A6 variants that may explain the slower rates of metabolism, and determine whether CYP2A6 variation is a predictor of smoking phenotypes in this population. Furthermore, we examined whether previously validated biomarkers of tobacco exposure have limitations among individuals of Black-African descent given their low and sporadic smoking patterns. A new CYP2A6 variant (CYP2A6*23) was found in individuals of Black-African descent recruited for a nicotine pharmacogenetic-pharmacokinetic study. CYP2A6*23 reduced activity towards nicotine and coumarin in vitro and was associated with slower rates of CYP2A6 kinetics in vivo. In a clinical trial of African-American light smokers, CYP2A6 slow metabolizers were more successful at smoking cessation compared to normal metabolizers, although no differences in cigarette consumption were found. Two common biochemical markers of tobacco smoke exposure, cotinine and exhaled carbon monoxide, were weakly correlated with self-reported cigarette consumption. These biomarkers were not substantially affected by variables previously shown to alter amount smoked and/or rates of cotinine metabolism such as gender, age, body mass index or smoking menthol cigarettes. However, CYP2A6 slow metabolizers had significantly higher cotinine without smoking more cigarettes. Identification and characterization of novel variants adds to our understanding of nicotine pharmacokinetic differences between racial/ethnic minority groups and improves accuracy of CYP2A6 genotype groupings for genetic association studies. Furthermore, better insight into the biological factors associated with smoking behaviours will aid in the development of more efficacious targeted treatments for this understudied population.

The nucleus tractus solitarii (NTS) is the primary integrative center for baroreflex. NTS not only integrates convergent information from peripheral baroreceptors and higher blood pressure (BP) control centers in CNS but itself is the site of substantial modulation. Our previous studies demonstrated that microinjection of nicotine into the NTS decrease BP and heart rate (HR), which indicates nicotine plays cardiovascular modulatory role in the NTS. However, the mechanisms how nicotine modulate cardiovascular functions in the NTS remained unclear. The aim of this study was to investigate the molecular mechanisms of nicotine-induced depressor and bradycardic effects in the NTS. Male anesthetized Wistar-Kyoto rats, with or without intra-NTS nitric oxide synthase (NOS) inhibitors or ionotropic glutamate receptor inhibitors pretreatment, received intra-NTS nicotine microinjection. BP and HR were monitored. Besides, NTS with/without nicotine microinjection were dissected and subjected to immunoblotting and nitric oxide (NO) analysis. Our results demonstrated that NO analysis study revealed intra-NTS NO production elevated after nicotine microinjection. The depressor and bradycardic effects of intra-NTS nicotine microinjection were diminished by pretreatment of calmodulin inhibitor (W7, 0.33 nmol), non-specific NOS inhibitor (L-NAME, 33 nmol) and eNOS specific inhibitor (L-NIO, 6 nmol). The cardiovascular effects of nicotine were also attenuated by NMDA receptor inhibitor (MK801, 1 nmol), not by non-NMDA receptor inhibitor (NBQX, 10 pmol). Immunoblotting and immunohistochemical studies did not revealed nicotine induced eNOSS1177 phosphorylation in NTS. Using MEK inhibitor, PD98059, and nNOS specific inhibitor,Vinyl-L-NIO and 7-NI, there were no effect on the depressor and bradycardic effects of intra-NTS nicotine microinjection, and the phosphorylation of AktT473 was not induced by nicotine. Therefore, our results indicate that nicotine-induced depressor and bradycardic responses maybe mediated through activating eNOS by calmodulin and stimulating glutamate release in the NTS.

Thesis (M.S.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains xi, 110 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 87-93).

Developmental nicotine exposure (DNE) exerts negative consequences on the CNS via the activation of nAChRs that are available early and widely throughout development (refs). In this work, we examined how DNE changed excitatory and inhibitory neurotransmission in brainstem regions involved in central breathing control. Previous work using the brainstem-spinal cord preparation had shown that DNE augmented the respiratory-related response to AMPA, muscimol (a GABAA agonist), and glycine (Luo et al., 2004; Luo et al., 2007; Pilarski and Fregosi, 2009a). These studies used a split-bath preparation in which a drug (AMPA, muscimol, or glycine) was applied to medulla, and the frequency of the respiratory response (in the form of spontaneous, rhythmic bursting activity) was recorded from cervical nerve 4 (C4), which provides output to the diaphragm. Although these studies showed that DNE AMPA, GABA(A), and glycine neurotransmission in the medulla, the regions mediating the effect and the mechanism of DNE's action remained unclear. In this study we tested the hypothesis that the observed changes in respiratory burst frequency were mediated through the preBötzinger complex (preBötC), and the mechanism of enhanced activity involved an upregulation of neurotransmitter receptors. Additionally, we were interested in studying the effect of DNE on breathing-related motor pools, and therefore studied DNE's effect on excitatory and inhibitory neurotransmission in the XIIMN. We approached these questions and aims using a combination of techniques, including extracellular recordings from whole nerve output in rhythmic brainstem slices, immunohistochemistry, and Western blotting. We found enhanced AMPA, GABA(A), and glycine neurotransmission in the XIIMN and preBötC, and varying changes in neurotransmitter receptor expression in both groups. Additionally, we found a decrease in motoneuron soma size in XII motoneurons that stained positively for the glycine receptor. Overall, this study shows that DNE alters inhibitory and excitatory neurotransmission in both the preBötC and XIIMN, and that these changes may be mediated through a combination of change in cell size and receptor expression.

This study examined the number of conditioning trials necessary to produce associative nicotine tolerance and the changes in corticosterone levels during the procedures. Six independent groups of rats (N = 355) were run through tolerance acquisition procedures for 1, 5, or 10 conditioning sessions. Treatment groups were comprised of animals that received nicotine-environment pairings, animals that received nicotine explicitly unpaired with the drug administration environment, and control groups that received either saline throughout or no treatment. Three of the groups were tested for nicotine-induced analgesia using the tail-flick and hot-plate assays, and three groups were blood sampled after either nicotine or saline injection. Pairing of environment with nicotine produced greater tolerance for rats after 5 conditioning sessions in the tail flick and after 10 conditioning sessions in the hot-plate. Corticosterone levels were elevated in all rats given nicotine. Rats that received the nicotine-environment pairing showed a conditioned release of corticosterone in response the environment after both 5 and 10 conditioning sessions.

No description available.

Cytochromes P450 (CYPs) metabolize a vast array of xenobiotics, including many drugs and toxins. Induction or downregulation of the CYPs can have important consequences such as changes in drug efficacy and altered susceptibility to toxicity. Our study investigated the independent and combined effects of ethanol and nicotine on hepatic and/or brain levels of CYP2E1, CYP2B6 and CYP2A6 in African green monkeys. Monkeys were randomized into four groups (N = 10/group): an ethanol-only group, a nicotine-only group, an ethanol + nicotine group and a control (no drug) group. Ethanol (10% ethanol in sucrose solution) was voluntarily self-administered by the monkeys and nicotine was given as subcutaneous injections (0.5 mg/kg bid). Protein levels and/or in vitro activity were assessed in liver and brain tissue. Also, in vivo pharmacokinetics for chlorzoxazone (metabolized selectively by CYP2E1) and nicotine (metabolized primarily by CYP2A6 and to a lesser extent CYP2B6) were assessed. Hepatic CYP2E1 protein levels, in vitro hepatic CYP2E1 activity and in vivo chlorzoxazone metabolism were increased by ethanol and nicotine, alone and in combination. Hepatic CYP2B6 protein levels and in vitro hepatic CYP2B6 activity were increased by ethanol alone or combined ethanol and nicotine exposure, but were unaffected by nicotine alone. Hepatic CYP2A6 protein levels and in vitro hepatic CYP2A6 activity were decreased by nicotine alone or combined ethanol and nicotine exposure, but unaffected by ethanol alone. Chronic nicotine resulted in higher nicotine plasma levels achieved after nicotine administration, consistent with decreased CYP2A6 activity. Ethanol, alone or combined with nicotine, resulted in lower nicotine plasma levels, an effect that was not mediated by changes in CYP activity. Protein levels of CYP2E1 and CYP2B6 were induced in specific regions and cells in the brain as a result of ethanol self-administration, nicotine treatment and the combined exposure to both drugs. In summary, ethanol and nicotine can alter the expression and/or activity of several important CYP2 family enzymes in primate liver and/or brain.

Thesis (Ph.D.)--Tufts University, 2001. / Adviser: Robin B. Kanarek. Submitted to the Dept. of Psychology. Includes bibliographical references (leaves 99-122). Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Diss. (sammanfattning) Uppsala : Univ., 2001. / Härtill 5 uppsatser.