Regioselective C-2 and C-6 substitution of (S)-nicotine and nicotine derivatives

[reaction: see text] Regioselective deprotonations of (S)-nicotine and derivatives at the C-2 and C-6 positions of the pyridine ring were performed in good to excellent yields. These methodologies allow the direct introduction of a plethora of functional groups onto the pyridine ring of nicotine.

Role in the Selectivity of Neonicotinoids of Insect-Specific Basic Residues in Loop D of the Nicotinic Acetylcholine Receptor Agonist Binding Site

The insecticide imidacloprid and structurally related neonicotinoids act selectively on insect nicotinic acetylcholine receptors (nAChRs). To investigate the mechanism of neonicotinoid selectivity, we have examined the effects of mutations to basic amino acid residues in loop D of the nAChR acetylcholine (ACh) binding site on the interactions with imidacloprid. The receptors investigated are the recombinant chicken alpha4beta2 nAChR and Drosophila melanogaster Dalpha2/chicken beta2 hybrid nAChR expressed in Xenopus laevis oocytes. Although mutations of Thr77 in loop D of the beta2 subunit resulted in a barely detectable effect on the imidacloprid concentration-response curve for the alpha4beta2 nAChR, T77R;E79V double mutations shifted the curve dramatically to higher affinity binding of imidacloprid. Likewise, T77K;E79R and T77N;E79R double mutations in the Dalpha2beta2 nAChR also resulted in a shift to a higher affinity for imidacloprid, which exceeded that observed for a single mutation of Thr77 to basic residues. By contrast, these double mutations scarcely influenced the ACh concentration-response curve, suggesting selective interactions with imidacloprid of the newly introduced basic residues. Computational, homology models of the agonist binding domain of the wild-type and mutant alpha4beta2 and Dalpha2beta2 nAChRs with imidacloprid bound were generated based on the crystal structures of acetylcholine binding proteins of Lymnaea stagnalis and Aplysia californica. The models indicate that the nitro group of imidacloprid interacts directly with the introduced basic residues at position 77, whereas those at position 79 either prevent or permit such interactions depending on their electrostatic properties, thereby explaining the observed functional changes resulting from site-directed mutagenesis.

Six-Step Synthesis of (S)-Brevicolline from (S)-Nicotine

[reaction: see text] A six-step synthesis of (S)-brevicolline from (S)-nicotine is reported. Regioselective trisubstitution of the pyridine ring of nicotine, followed by successive Suzuki cross-coupling and Buchwald amination reactions, afforded the enantiopure beta-carboline alkaloid, brevicolline.

Final steps in the catabolism of nicotine

New enzymes of nicotine catabolism instrumental in the detoxification of the tobacco alkaloid by Arthrobacter nicotinovorans pAO1 have been identified and characterized. Nicotine breakdown leads to the formation of nicotine blue from the hydroxylated pyridine ring and of gamma-N-methylaminobutyrate (CH(3)-4-aminobutyrate) from the pyrrolidine ring of the molecule. Surprisingly, two alternative pathways for the final steps in the catabolism of CH(3)-4-aminobutyrate could be identified. CH(3)-4-aminobutyrate may be demethylated to gamma-N-aminobutyrate by the recently identified gamma-N-methylaminobutyrate oxidase. In an alternative pathway, an amine oxidase with noncovalently bound FAD and of novel substrate specificity removed methylamine from CH(3)-4-aminobutyrate with the formation of succinic semialdehyde. Succinic semialdehyde was converted to succinate by a NADP(+)-dependent succinic semialdehyde dehydrogenase. Succinate may enter the citric acid cycle completing the catabolism of the pyrrolidine moiety of nicotine. Expression of the genes of these enzymes was dependent on the presence of nicotine in the growth medium. Thus, two enzymes of the nicotine regulon, gamma-N-methylaminobutyrate oxidase and amine oxidase share the same substrate. The K(m) of 2.5 mM and k(cat) of 1230 s(-1) for amine oxidase vs. K(m) of 140 microM and k(cat) of 800 s(-1) for gamma-N-methylaminobutyrate oxidase, determined in vitro with the purified recombinant enzymes, may suggest that demethylation predominates over deamination of CH(3)-4-aminobutyrate. However, bacteria grown on [(14)C]nicotine secreted [(14)C]methylamine into the medium, indicating that the pathway to succinate is active in vivo.

Synthesis and pharmacological evaluation of novel 9- and 10-substituted cytisine derivatives. Nicotinic ligands of enhanced subtype selectivity

We report the synthesis and pharmacological properties of several cytisine derivatives. Among them, two 10-substituted derivatives showed much higher selectivities for the alpha4beta2 nAChR subtype in binding assays than cytisine. The 9-vinyl derivative was found to have a very similar agonist activity profile to that of cytisine.

Application of a novel electrosynthesized polydopamine-imprinted film to the capacitive sensing of nicotine

The application of novel electrosynthesized polydopamine (PDA)-imprinted film as a recognition element for the capacitive sensing of nicotine is reported. The PDA-imprinted film was electropolymerized directly on the gold electrode surface in the presence of nicotine without an additional self-assembled thiol sublayer. The compact PDA film has various functional groups that aid the imprinting procedure. Furthermore, the film shows good capacitive response since it is insulating in nature and ultrathin. The sensor's linear response range for nicotine was between 1-25 micromol L(-1), with a detection limit of 0.5 micromol L(-1). The proposed molecularly imprinted polymer capacitive (MIPC) sensor exhibited good selectivity for nicotine. The reproducibility and repeatability of the MIPC sensor were all found to be satisfactory. The results from sample analysis confirmed the applicability of the MIPC sensor to quantitative analysis.

Effect of ozone on nicotine desorption from model surfaces: evidence for heterogeneous chemistry

Assessment of secondhand tobacco smoke exposure using nicotine as a tracer or biomarker is affected by sorption of the alkaloid to indoor surfaces and by its long-term re-emission into the gas phase. However, surface chemical interactions of nicotine have not been sufficiently characterized. Here, the reaction of ozone with nicotine sorbed to Teflon and cotton surfaces was investigated in an environmental chamber by monitoring nicotine desorption over a week following equilibration in dry or humid air (approximately 0% or 65-70% RH, respectively). The Teflon and cotton surfaces had N2-BET surface areas of 0.19 and 1.17 m2 g(-1), and water mass uptakes (at 70% RH) of 0 and 7.1% respectively. Compared with dry air baseline levels in the absence of O3, gas-phase nicotine concentrations decreased by 2 orders of magnitude for Teflon after 50 h at 20-45 ppb O3, and by a factor of 10 for cotton after 100 h with 13-15 ppb O3. The ratios of pseudo first-order rate constants for surface reaction (r) to long-term desorption (k) were r/k = 3.5 and 2.0 for Teflon and cotton surfaces, respectively. These results show that surface oxidation was competitive with desorption. Hence, oxidative losses could significantly reduce long-term re-emissions of nicotine from indoor surfaces. Formaldehyde, N-methylformamide, nicotinaldehyde, and cotinine were identified as oxidation products, indicating that the pyrrolidinic N was the site of electrophilic attack by O3. The presence of water vapor had no effect on the nicotine-O3 reaction on Teflon surfaces. By contrast, nicotine desorption from cotton in humid air was unaffected by the presence of ozone. These observations are consistent with complete inhibition of ozone-nicotine surface reactions in an aqueous surface film present in cotton but not in Teflon surfaces.

Identification of adducts formed in the reaction of 5'-acetoxy-N'-nitrosonornicotine with deoxyguanosine and DNA

N'-Nitrosonornicotine (NNN) is believed to play an important role as a cause of cancer in people who use tobacco products and is considered to be a human carcinogen. NNN requires metabolism to form DNA adducts, which are absolutely critical to its carcinogenic properties. Previous studies have identified cytochrome P450-catalyzed 2'- and 5'-hydroxylation of NNN as potential DNA adduct forming metabolic pathways. 5'-Hydroxylation is the more prevalent of these in monkeys and humans and is known to generate mutagenic intermediates, but the DNA adducts formed by this pathway have never been characterized. In this study, we used 5'-acetoxyNNN as a stable precursor to 5'-hydroxyNNN and investigated its esterase-catalyzed reactions with deoxyguanosine (dGuo) and DNA. Adducts resulting from carbocation and oxonium ion intermediates, produced by the spontaneous decomposition of 5'-hydroxyNNN, were identified. The carbocation pathway resulted in the formation of 2-[2-hydroxy-5-(3-pyridyl)pyrrolidin-1-yl]deoxyinosine (12) which was characterized by comparison to an independently synthesized standard. Treatment of 12 with NaBH(3)CN produced two diastereomers of 2-[2-(3-pyridyl)pyrrolidin-1-yl]deoxyinosine (14), and their absolute configurations at the 2-position were determined by comparison to synthetic standards. The oxonium ion pathway produced diastereomers of N(2)[5-(3-pyridyl)tetrahydrofuran-2-yl]dGuo (16), identified by comparison to synthetic standards. The absolute configuration at the 5-position was determined by establishing the stereochemistry of the enantiomers of 5-(3-pyridyl)-2-hydroxytetrahydrofuran at the 5-position and allowing these to react individually with dGuo. Treatment of 16 with NaBH(3)CN produced N(2)[4-hydroxy-4-(3-pyridyl)but-1-yl]dGuo (18) which was also synthesized independently. Using liquid chromatography-electrospray ionization-tandem mass spectrometry with selected reaction monitoring, we identified adducts 12 and 16 as products of the reactions of 5'-acetoxyNNN with dGuo. Similarly, adducts 14 and 18 were identified as products of the reaction of 5'-acetoxyNNN with DNA followed by NaBH(3)CN treatment and enzymatic hydrolysis. These results provide the first structural characterization of DNA adducts that can be formed by 5'-hydroxylation of NNN.

In vivo human buccal permeability of nicotine

The aim was to examine the in vivo buccal pH-dependent permeability of nicotine in humans and furthermore compare the in vivo permeability of nicotine to previous in vitro permeability data. The buccal permeability of nicotine was examined in a three-way cross-over study in eight healthy non-smokers using a buccal perfusion cell. The disappearance of nicotine from perfusion solutions with pH 6.0, 7.4, and 8.1 was studied for 3h. The apparent permeability of nicotine (P(app)) was determined at each pH value. Parotid saliva was collected in an attempt to assess systemic levels of nicotine. The disappearance rate of nicotine increased significantly as the pH increased, which resulted in P(app) values of 0.57+/-0.55 x 10(-4), 2.10+/-0.23 x 10(-4), and 3.96+/-0.54 x 10(-4)cms(-1) (mean+/-S.D.) at pH 6.0, 7.4, and 8.1, respectively. A linear relationship (R(2)=0.993) was obtained between the P(app) values and non-ionised nicotine, which indicates that the nicotine transfer occurred by means of passive diffusion. P(app) values of 0.60 x 10(-4) and 6.18 x 10(-4)cms(-1) were obtained for the mono-protonated and non-ionised species of nicotine, respectively. The analysis of the parotid saliva samples indicated that these samples might be useful in the assessment of systemic absorption of nicotine. Previous buccal in vitro models underestimated the in vivo human permeability of nicotine. However, the in vitro models were capable of predicting the effect of pH on the nicotine permeability.

Nicotine carboxylate insecticide emulsions: effect of the fatty acid chain length

The effect of fatty acid chain length on nicotine carboxylate insecticide emulsions has been studied in terms of particle size, interfacial tension, nicotine encapsulation on emulsion droplets, and bioactivity. The particle size of the nicotine emulsion and the interfacial tension at the nicotine carboxylate oil phase (0.03 M)--Tween 80 aqueous phase (0.001 M) were affected in a similar way by the change in the fatty acid chain length, which was correlated by the packing conformation of Tween 80 and nicotine carboxylate molecules as obtained by AM1 theoretical calculations. The amount of encapsulated nicotine inside the nicotine carboxylate emulsion droplets influenced the insecticide bioactivity of nicotine; this relationship was explained in terms of the acid value of the different fatty acids used to prepare the nicotine formulation.

Synthesis of Nicotine Derivatives via Reductive Disilylation of (S)-Nicotine

[reaction: see text] A variety of novel nicotine derivatives were prepared via reductive disilylation of (S)-nicotine. Treatment of nicotine with lithium powder and chlorotrimethylsilane afforded 1,4-bis(trimethylsilyl)-1,4-dihydronicotine in high yield. Addition of various carbonyl electrophiles and a catalytic amount of TBAF provided either C-5 substituted nicotines or 1,4-dihydronicotine derivatives.

Myeloperoxidase generates 5-chlorouracil in human atherosclerotic tissue: a potential pathway for somatic mutagenesis by macrophages

Somatic mutations induced by oxidative damage of DNA might play important roles in atherogenesis. However, the underlying mechanisms remain poorly understood. Myeloperoxidase, a heme protein expressed by select populations of artery wall macrophages, initiates one potentially mutagenic pathway by generating hypochlorous acid. This potent chlorinating agent reacts rapidly with primary amines to yield long-lived, selectively reactive N-chloramines. In the current studies, we demonstrate that myeloperoxidase produced by human macrophages differentiated in the presence of granulocyte macrophage colony-stimulating factor generates 5-chlorouracil, a mutagenic thymine analog. The primary amine taurine fails to block the reaction, suggesting that N-haloamines produced by macrophages might oxidize uracil. Model system studies demonstrated that N-chloramines convert uracil to 5-chlorouracil. Interestingly, the tertiary amine nicotine dramatically enhances uracil chlorination, suggesting that cigarette smoke might promote nucleobase oxidation by N-chloramines. To look for evidence that myeloperoxidase promotes uracil oxidation in vivo, we measured 5-chlorouracil levels in human aortic tissue, using isotope dilution gas chromatography-mass spectrometry. The level of 5-chlorouracil was 10-fold higher in atherosclerotic aortic tissue obtained during vascular surgery than in normal aortic tissue, suggesting that halogenated nucleobases produced by macrophages might contribute to atherogenesis. Because 5-chlorouracil can be incorporated into nuclear DNA, our observations raise the possibility that halogenation reactions initiated by phagocytes provide one pathway for mutagenesis, phenotypic modulation, and cytotoxicity during atherogenesis.

Extracellular Domain Nicotinic Acetylcholine Receptors Formed by α4 and β2 Subunits

Models of the extracellular ligand-binding domain of nicotinic acetylcholine receptors (nAChRs), which are pentameric integral membrane proteins, are attractive for structural studies because they potentially are water-soluble and better candidates for x-ray crystallography and because their smaller size is more amenable for NMR spectroscopy. The complete N-terminal extracellular domain is a promising foundation for such models, based on previous studies of alpha7 and muscle-type subunits. Specific design requirements leading to high structural fidelity between extracellular domain nAChRs and full-length nAChRs, however, are not well understood. To study these requirements in heteromeric nAChRs, the extracellular domains of alpha4 and beta2 subunits with or without the first transmembrane domain (M1) were expressed in Xenopus oocytes and compared with alpha4beta2 nAChRs based on ligand binding and subunit assembly properties. Ligand affinities of detergent-solubilized, extracellular domain alpha4beta2 nAChRs formed from subunits with M1 were nearly identical to affinities of alpha4beta2 nAChRs when measured with [3H]epibatidine, cytisine, nicotine, and acetylcholine. Velocity sedimentation suggested that these extracellular domain nAChRs predominantly formed pentamers. The yield of these extracellular domain nAChRs was about half the yield of alpha4beta2 nAChRs. In contrast, [3H]epibatidine binding was not detected from the extracellular domain alpha4 and beta2 subunits without M1, implying no detectable expression of extracellular domain nAChRs from these subunits. These results suggest that M1 domains on both alpha4 and beta2 play an important role for efficient expression of extracellular domain alpha4beta2 nAChRs that are high fidelity structural models of full-length alpha4beta2 nAChRs.

Modeling multiple species of nicotine and deschloroepibatidine interacting with alpha4beta2 nicotinic acetylcholine receptor: from microscopic binding to phenomenological binding affinity

A variety of molecular modeling, molecular docking, and first-principles electronic structure calculations were performed to study how the alpha4beta2 nicotinic acetylcholine receptor (nAChR) binds with different species of two typical agonists, (S)-(-)-nicotine and (R)-(-)-deschloroepibatidine, each of which is distinguished by different free bases and protonation states. On the basis of these results, predictions were made regarding the corresponding microscopic binding free energies. Hydrogen-bonding and cation-pi interactions between the receptor and the respective ligands were found to be the dominant factors differentiating the binding strengths of different microscopic binding species. The calculated results and analyses demonstrate that, for each agonist, all the species are interchangeable and can quickly achieve a thermodynamic equilibrium in solution and at the nAChR binding site. This allows quantitation of the equilibrium concentration distributions of the free ligand species and the corresponding microscopic ligand-receptor binding species, their pH dependence, and their contributions to the phenomenological binding affinity. The predicted equilibrium concentration distributions, pK(a) values, absolute phenomenological binding affinities, and their pH dependence are all in good agreement with available experimental data, suggesting that the computational strategy from the microscopic binding species and affinities to the phenomenological binding affinity is reliable for studying alpha4beta2 nAChR-ligand binding. This should provide valuable information for future rational design of drugs targeting nAChRs. The general strategy of the "from-microscopic-to-phenomenological" approach for studying interactions of alpha4beta2 nAChRs with (S)-(-)-nicotine and (R)-(-)-deschloroepibatidine may also be useful in studying other types of ligand-protein interactions involving multiple molecular species of a ligand and in associated rational drug design.

Conversion of nicotine to nornicotine in Nicotiana tabacum is mediated by CYP82E4, a cytochrome P450 monooxygenase

Nornicotine is a secondary tobacco alkaloid that is produced by the N-demethylation of nicotine. Nornicotine production and accumulation in tobacco are undesirable because nornicotine serves as the precursor in the synthesis of the well characterized carcinogen N'-nitrosonornicotine during the curing and processing of tobacco. Although nornicotine is typically a minor alkaloid in tobacco plants, in many tobacco populations a high percentage of individuals can be found that convert a substantial proportion of the nicotine to nornicotine during leaf senescence and curing. We used a microarray-based strategy to identify genes that are differentially regulated between closely related tobacco lines that accumulate either nicotine (nonconverters) or nornicotine (converters) as the predominant alkaloid in the cured leaf. These experiments led to the identification of a small number of closely related cytochrome P450 genes, designated the CYP82E2 family, whose collective transcript levels were consistently higher in converter versus nonconverter tobacco lines. RNA interference-induced silencing of the CYP82E2 gene family suppressed the synthesis of nornicotine in strong converter plants to levels similar to that observed in nonconverter individuals. Although each of the six identified members of the P450 family share >90% nucleotide sequence identity, sense expression of three selected isoforms revealed that only one (CYP82E4v1) was involved in the conversion of nicotine to nornicotine. Yeast expression analysis revealed that CYP82E4v1 functions as a nicotine demethylase. Identification of the gene(s) responsible for nicotine demethylation provides a potentially powerful tool toward efforts to minimize nornicotine levels, and thereby N'-nitrosonornicotine formation, in tobacco products.

[Spectroscopic studies on the interaction of nicotine and BSA]

The interaction of nicotine and bovine serum albumin(BSA) was investigated by fluorescence spectra and UV-vis spectra. The fluorescence spectrum showed that BSA fluorescence quench regularly with the addition of nicotine.The fluorescence quenching mechanisms were also studied in pH 5.0, pH 7.4 and pH 11.0 by Stern-Volmer equation, indicating dynamic quenching(pH 5.0) and static quenching(pH 7.4 and pH 11.0) respectively. Association constants (k) of nicotine and BSA at pH 7.4 and pH 11.0 at the temperatures of 20 and 37 degrees C were given by the Lineweaver-Buck equation, which are: k(20 degrees C) = 140.15 L x mol(-1) and k(37 degrees C) = 131.83 mol x L(-1) (pH 7.4), and k(20 degrees C) = 141.76 mol x L(-1), k(37 degrees C) = 27.79 mol x L(-1) (pH 11.0), suggesting that the association constant is effected by the temperature much more remarkably at pH 7.4 than that at pH 11.0 because of the different states of nicotine at different pHs. The UV-Vis spectra exhibit that the absorbance of BSA(210 nm) shifts to red and decreases gradually with the addition of nicotine, reflecting the transition of secondary structure of BSA, namely, the helix of BSA becomes looser. The UV-Vis second derivative spectra and synchronous spectra (delta wavelength = wavelength(em) - wavelength(ex) = 15 nm and delta wavelength = wavelength(em) - wavelength(ex) = 60 nm) imply the change of the microcircumstance of aromatic amino residues of BSA(Trp, Tyr and Phe) from hydrophobicity to hydrophilicity at high concentration of nicotine.

Synthesis of C-4 Substituted Nicotine Derivatives via an N-Acylpyridinium Salt of (S)-Nicotine

[reaction: see text] A variety of novel nicotine derivatives were prepared from (S)-nicotine via a two-step sequence. Addition of a cuprate reagent to an N-acylpyridinium salt of nicotine, followed by aromatization with elemental sulfur, afforded C-4 substituted nicotines in moderate to high yield. Using this method, 4-(dimethylphenylsilyl)nicotine was prepared and oxidized to afford (S)-4-hydroxynicotine.

In vivo evaluation of nicotine lyophilised nasal insert in sheep

The nasal route offers an attractive means of delivering a drug directly to the systemic circulation and avoiding hepatic first-pass metabolism, although rapid mucociliary clearance can be detrimental to nasal absorption. The in vitro and in vivo characteristics of a nasal insert formulation prepared by lyophilisation of a viscous HPMC gel solution designed to overcome this problem were studied. In vitro release of nicotine from the lyophilised insert was compared with powder and spray formulations. Stability and characterisation studies were carried out using dynamic vapour sorption, scanning electron microscopy and HPLC analysis. Nicotine formulations were administered to eight wether sheep in a randomised four-way cross-over study, and plasma nicotine assessed comparing the nasal insert formulation with conventional nasal powder, nasal spray and IV doses. In vitro release studies demonstrated prolonged nicotine release from the nasal insert formulation compared to a powder and liquid. In vivo plasma profiles appeared to show prolonged plasma nicotine levels compared to the conventional formulations, although T(max), C(max) and AUC parameters for the insert were not significantly different due to high variability in the pharmacokinetic data. In conclusion, the nasal insert displayed a promising prolonged plasma profile, which must be investigated further to provide statistical significance to prove the effect.

"Green" route to 6-hydroxy-3-succinoyl-pyridine from (S)-nicotine of tobacco waste by whole cells of a Pseudomonas sp

A new technology for 6-hydroxy-3-succinoyl-pyridine (HSP) production from (S)-nicotine in tobacco waste by whole cells of a Pseudomonas sp. has been developed. When deionized water was used in the transformation reaction as a medium and the initial pH value of reaction mixture was adjusted to 7.0, 1.45 g/L HSP was produced from 3 g/L of nicotine in 5 h with 3.4 g/L of cells in a 5-L flask at 30 degrees C. HSP could be easily purified from the reaction without perplexing separation steps. A quantity of 1.3 g of HSP was recovered without impurity, and the overall yield of HSP was 43.8% (w/w), based on an initial concentration of 3.0 g/L of nicotine in reaction. This biotransformation made it possible to convert nicotine in tobacco wastes with high nicotine content into valuable compounds.

Regions of interest in FTIR imaging applications: Diffusion of nicotine into ethylene-co-vinyl acetate films

Effective image analysis of dynamic processes, such as diffusion and dissolution, requires precise reporting of component locations in space and time. An improved method for analyzing FTIR images is described which employs hypothesis testing in the spatial and temporal domains. Changes in the observed absorbance (over space and time) are revealed by comparison to a reference statistic, which can be tailored by choosing the size of a region of interest. This improved analysis method was used to compare the rates of diffusion of nicotine into poly(ethylene-co-vinyl acetate) film from aqueous solutions containing anionic and nonionic surfactants. Compared to a solution without surfactant, sodium dodecyl sulfate inhibited the uptake of nicotine from aqueous solution whereas Tween 40 enhanced the uptake. The nicotine diffusion rate also showed a dependence on the length of the hydrophobic segment of nonionic surfactants. These results demonstrate the roles of solubilization, wetting, and viscosity on diffusion-controlled drug release.

Effects of pH on nicotine-induced DNA damage and oxidative stress

Epidemiological evidence suggests that chewing betel quid and smoking have synergistic potential in the development of oral squamous-cell carcinoma in Taiwan. Chewing betel quid produces alkalization of saliva. This study investigated the response of human oral cancer OEC-M1 cells to nicotine in different pH environments (6.5 and 8) by examining its effects on DNA damage as evidenced by single-cell gel electrophoresis. Nicotine (1 and 10 muM) significantly induced DNA strand breakage when cultured at pH 8 for 6 h but did not induce DNA damage at pH 6.5. Nicotine-induced DNA damage was also time dependent. When cells were pretreated with catalase or N-acetylcysteine, a significant reduction in nicotine-induced DNA damage was observed. Flow cytometric analyses showed that the production of 8-oxoguanine was significantly increased following nicotine (10 muM) treatment. Posttreatment of nicotine-damaged DNA by endonuclease III and formamidopyrimidine-DNA glycosylase, recognizing oxidized DNA bases, increased the extent of DNA damage. These results suggest that nicotine-induced DNA strand breakage is pH dependent, and oxidative stress might be involved in nicotine-induced DNA damage. Finally, cigarette smoke condensate (equivalent to 8 muM nicotine) induced significant DNA strand breaks in OEC-M1 cells at pH 8 and correlated with the generation of oxidative DNA damage. Thus, alkaline saliva generated by chewing betel quid plays an important role in cigarette-related nicotine-induced DNA damage, and reactive oxygen species may be involved in generating this DNA damage.

Nitric oxide control of lower vertebrate blood vessels by vasomotor nerves

In mammals, much is understood about the endothelial and neural NO control mechanisms in the vasculature. In contrast, NO control of blood vessels in lower vertebrates is poorly understood, with the majority of research focusing on the presence of an endothelial NO system; however, its presence remains controversial. This study examined the mechanisms by which NO regulates the large blood vessels of non-mammalian vertebrates. In all species examined, the arteries and veins contained a plexus of NOS-positive perivascular nerves that included nerve bundles and fine, varicose nerve terminals. However, in the large arteries and veins of various species of fishes and amphibians, no anatomical evidence was found for endothelial NOS using both NADPH-diaphorase and eNOS immunohistochemistry. In contrast, perinuclear NOS staining was readily apparent in blue-tongue lizard, pigeon and rat, which suggested that eNOS first appeared in reptiles. Physiological analysis of NO signalling in the vascular smooth muscle of short-finned eel and cane toad could not find any evidence for endothelial NO signalling. In contrast, it appears that activation of the nitrergic vasomotor nerves is responsible for NO control of the blood vessels.

Introduction of unsaturation into the N-n-alkyl chain of the nicotinic receptor antagonists, NONI and NDNI: effect on affinity and selectivity

N-n-octylnicotinium iodide (NONI) and N-n-decylnicotinium iodide (NDNI) are selective nicotinic receptor (nAChR) antagonists mediating nicotine-evoked striatal dopamine (DA) release, and inhibiting [3H]nicotine binding, respectively. This study evaluated effects of introducing unsaturation into the N-n-alkyl chains of NONI and NDNI on inhibition of [3H]nicotine and [3H]methyllycaconitine binding (alpha4beta2* and alpha7* nAChRs, respectively), (86)Rb+ efflux and [3H]DA release (agonist or antagonist effects at alpha4beta2* and alpha6beta2*-containing nAChRs, respectively). In the NONI series, introduction of a C3-cis- (NONB3c), C3-trans- (NONB3t), C7-double-bond (NONB7e), or C3-triple-bond (NONB3y) afforded a 4-fold to 250-fold increased affinity for [3H]nicotine binding sites compared with NONI. NONB7e and NONB3y inhibited nicotine-evoked 86Rb+ efflux, indicating alpha4beta2* antagonism. NONI analogs exhibited a 3-fold to 8-fold greater potency inhibiting nicotine-evoked [3H]DA overflow compared with NONI (IC50 = 0.62 microM; Imax = 89%), with no change in Imax, except for NONB3y (Imax = 50%). In the NDNI series, introduction of a C4-cis- (NDNB4c), C4-trans-double-bond (NDNB4t), or C3-triple-bond (NDNB3y) afforded a 4-fold to 80-fold decreased affinity for [3H]nicotine binding sites compared with NDNI, whereas introduction of a C9 double-bond (NDNB9e) did not alter affinity. NDNB3y and NDNB4t inhibited nicotine-evoked 86Rb+ efflux, indicating antagonism at alpha4beta2* nAChRs. Although NDNI had no effect, NDNB4t and NDNB9e potently inhibited nicotine-evoked [3H]DA overflow (IC50 = 0.02-0.14 microM, Imax = 90%), as did NDNB4c (IC50 = 0.08 microM; Imax = 50%), whereas NDNB3y showed no inhibition. None of the analogs had significant affinity for alpha7* nAChRs. Thus, unsaturated NONI analogs had enhanced affinity at alpha4beta2*- and alpha6beta2*-containing nAChRs, however a general reduction of affinity at alpha4beta2* and an uncovering of antagonist effects at alpha6beta2*-containing nAChRs were observed with unsaturated NDNI analogs.

Stimulation of the vagus nerve attenuates macrophage activation by activating the Jak2-STAT3 signaling pathway

Acetylcholine released by efferent vagus nerves inhibits macrophage activation. Here we show that the anti-inflammatory action of nicotinic receptor activation in peritoneal macrophages was associated with activation of the transcription factor STAT3. STAT3 was phosphorylated by the tyrosine kinase Jak2 that was recruited to the alpha7 subunit of the nicotinic acetylcholine receptor. The anti-inflammatory effect of nicotine required the ability of phosphorylated STAT3 to bind and transactivate its DNA response elements. In a mouse model of intestinal manipulation, stimulation of the vagus nerve ameliorated surgery-induced inflammation and postoperative ileus by activating STAT3 in intestinal macrophages. We conclude that the vagal anti-inflammatory pathway acts by alpha7 subunit-mediated Jak2-STAT3 activation.

Altered retinoid homeostasis catalyzed by a nicotine metabolite: implications in macular degeneration and normal development

Retinoids (vitamin A) serve two distinct functions in higher animals: light absorption for vision and gene regulation for growth and development. Cigarette smoking is a contributing factor for diseases that affect vision such as age-related macular degeneration and increases the risk of birth defects; however, altered retinoid homeostasis has received little attention as a potential mechanism for smoking-associated toxicities. Herein, we demonstrate that nornicotine, a nicotine metabolite and component of cigarette smoke, catalyzes the Z-to-E alkene isomerization of unsaturated aldehydes and ketones, including retinals. Despite the recent explosion in the use of organic compounds as chemical catalysts, minimal effort has been devoted to biologically relevant organocatalysis. Our study demonstrates a system in which a lowest unoccupied molecular orbital-lowering intermediate similar to the endogenous protein rhodopsin effectively catalyzes isomerization under biologically relevant conditions. The product of retinal isomerization is all-E-retinal, which in the eye is a biosynthetic precursor to N-retinylidene-N-retinylethanolamine, a hallmark of age-related macular degeneration. Furthermore, 9-Z- and all-E-retinal isomers are biosynthetic precursors to 9-Z- and all-E-retinoic acids, ligands that mediate specific cellular responses by binding to transcriptional regulatory proteins critical in growth and development. Strict maintenance of retinal isomer composition is essential for proper transcriptional regulation. Nornicotine-catalyzed retinal isomerization implies an underlying molecular mechanism for age-related macular degeneration, the birth defects associated with smoking, and other smoking-associated abnormalities that stem from disruption of retinoid metabolism.

Recolorization of museum specimens: a modification of Romhanyi’s technique based on pyridine/nicotine hemochromogen reactions

Romhanyi's technique for preservation and restoration of color in museum specimens is almost unknown outside Hungary. The technique was based on the use of pyridine, nicotine and sodium dithionite (sodium hydrosulphite) for restoring the natural red color of formalin-fixed gross specimens. We developed a modification of the original technique using a mounting medium containing citrate-phosphate-dextrose (CPD) buffer and glycerin to control pH and osmolality. Specimens re-colorized with the modified and improved Romhanyi technique remained stable with a natural red color, and no histological deterioration, for more than 18 years. The technique demonstrates the formation of red colored complexes between nicotine and pyridine and ferro-hemochromes such as hemoglobin, myoglobin and other cytochromes in tissues, giving specimens a natural color. The modified technique enables further improvement for the old process of re-colorization of museum specimens. In addition, it opens up new methods for demonstration of nicotine, pyridine and their analogues in biological tissues.

Impact of nicotine replacement therapy on smoking behavior

This review summarizes evidence pertaining to the role of nicotine medications in smoking cessation and focuses particularly on evaluating evidence of the impact that nicotine replacement therapies (NRT) have had on altering population trends in smoking behavior. Accumulated evidence from controlled clinical trials has demonstrated that available forms of NRT (e.g., gum, transdermal patch, nasal spray, inhaler, and lozenge) increase quit rates compared with placebos by 50%-100%. However, despite the positive results from these studies, fewer than one in five smokers making a quit attempt do so with the benefit of NRT. Because not enough smokers are using NRT, the availability of NRT has not had a measurable impact on influencing population trends in smoking behavior. Among the factors contributing to the low utilization of nicotine medications are the inadequacies of the current dosage strengths and formulations of existing medications, smokers' perceptions of the high cost of the drugs, and concerns that many smokers have about safety and efficacy of nicotine medications.

The effect of a novel smoking system--Accord--on ongoing smoking and toxin exposure

Multiple potentially reduced exposure products (PREPs) are being introduced to the market, yet little is known about how they will be used and what their public health impact might be. To determine the impact of one such PREP--Accord--on ongoing smoking and toxin exposure, 11 smokers of light cigarettes were required to use increasing amounts of Accord (5, 10, and 15 per day) with the option of using their traditional cigarettes. Accord suppressed ongoing cigarettes per day and carbon monoxide (CO), but not cotinine, in a dose-dependent manner. Smoking 15 Accord per day decreased the number of traditional cigarettes smoked by 32% (-8.6 cigarettes per day) and CO levels by 27% (-5.9 ppm). However, Accord did not function as a perfect (i.e., one to one) substitute for cigarettes because the total number of nicotine products (Accord plus usual brand) per day increased by 24%. Participants believed that Accord was safer than traditional cigarettes but rated Accord as ineffective at suppressing cravings for cigarettes. These findings suggest that use of Accord results in significant decreases in cigarettes smoked and CO exposure. Whether these reductions will translate into health benefits or endure beyond 2 weeks is unknown. Because most PREPs will probably be used along with traditional cigarettes, their net health impact is a function of not only their toxicological profile but also their effect on ongoing smoking.

Modified nicotine metabolism in transgenic tobacco plants expressing the human cytochrome P450 2A6 cDNA

In this study, the human cytochrome P450 (CYP) 2A6 was used in order to modify the alkaloid production of tobacco plants. The cDNA for human CYP2A6 was placed under the control of the constitutive 35S promoter and transferred into Nicotiana tabacum via Agrobacterium-mediated transformation. Transgenic plants showed formation of the recombinant CYP2A6 enzyme but no obvious phenotypic changes. Unlike wild-type tobacco, the transgenic plants accumulated cotinine, a metabolite which is usually formed from nicotine in humans. This result substantiates that metabolic engineering of the plant secondary metabolism via mammalian P450 enzymes is possible in vivo.

Hydrogen-Bond Accepting Strength of Protonated Nicotine

Recent crystal structures of nicotine bound to the acetylcholine binding protein (AChBP) ended a long debate confirming that the pyridine nitrogen of nicotine is indeed hydrogen-bonded to receptor residues through a bridging water molecule. Here, we describe the first direct experimental evaluation of the hydrogen-bond affinity of the nicotinium pyridine nitrogen. The equilibrium constant of its association with a phenol is 1 order of magnitude greater than the association of the acetylcholine carbonyl oxygen.

Hammett Correlation of Nornicotine Analogues in the Aqueous Aldol Reaction: Implications for Green Organocatalysis

[reaction: see text] A series of meta- and para-substituted 2-arylpyrrolidines were synthesized and examined for their ability to catalyze an aqueous aldol reaction under buffered conditions. Kinetic analysis of arylpyrrolidine-catalyzed reactions displayed a linear Hammett correlation with rho = 1.14 (R(2) = 0.996), indicating that the reaction is accelerated by electron-withdrawing aryl rings. These results show promise for the development of a synthetically viable aqueous organo-catalyst.

Nicotine Inactivation of the Proapoptotic Function of Bax through Phosphorylation

Nicotine-induced cell survival is associated with chemoresistance of human lung cancer cells, but our understanding of the intracellular mechanism(s) is fragmentary. Bax is a major proapoptotic member of the Bcl2 family and a molecule required for apoptotic cell death. Growth factor (i.e. granulocyte-macrophage colony-stimulating factor)-induced phosphorylation of Bax has been reported to negatively regulate its proapoptotic function. Because Bax is ubiquitously expressed in both small cell lung cancer and non-small cell lung cancer cells, nicotine may mimic growth factor(s) to regulate the activity of Bax. We found that nicotine potently induces Bax phosphorylation at Ser-184, which results in abrogation of the proapoptotic activity of Bax and increased cell survival. AKT, a known physiological Bax kinase, is activated by nicotine, co-localizes with Bax in the cytoplasm, and can directly phosphorylate Bax in vitro. Treatment of cells with the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 or specific depletion of AKT expression by RNA interference can block both nicotine-induced Bax phosphorylation and cell survival. Importantly, nicotine-induced Bax phosphorylation potently blocks stress-induced translocation of Bax from cytosol to mitochondria, impairs Bax insertion into mitochondrial membranes, and reduces the half-life of Bax protein (i.e. from 9-12 h to <6 h). Because knockdown of Bax expression by gene silencing results in prolonged cell survival following treatment with cisplatin in the absence or presence of nicotine, Bax may be an essential component in the nicotine survival signaling pathway. Thus, nicotine-induced survival and chemoresistance of human lung cancer cells may occur in a novel mechanism involving activation of PI3K/AKT that directly phosphorylates and inactivates the proapoptotic function of Bax.

In vitro microsomal [correction of mircosomal] metabolism of N-benzyl and N-benzoylnornicotine derivates by rat

The in vitro hepatic microsomal metabolism of N-1'-benzylnornicotine, N-l'-(p-chlorobenzyl)nornicotine, N-1'-benzoylnornicotine and N-1'-(p-chlorobenzoyl) nornicotine was studied using hepatic washed rat microsomal preparations fortified with NADPH. Substrates and their potential metabolites were synthesized, characterised by spectral methods, and separated using a reverse phase HPLC system consisted of a C18 column and a mobile phase composition of acetonitrile: phosphate buffer. Substrates and their potential metabolites were extracted from biological systems with dichloromethane. Metabolites detected were compared with retention times and uv spectra of authentic standards. Metabolic experiments indicated that oxidative dealkylation leading to the formation of nornicotine and the corresponding aldehydes was a major route of metabolism for N-alkylnornicotine substrates. In addition, N-1'-(p-chlorobenzyl)nornicotine produced the corresponding lactam and amide metabolites. N-Acylnornicotines were hydrolysed to nornicotine.

Effect of nicotine on lung S-adenosylmethionine and development of Pneumocystis pneumonia

Because S-adenosylmethionine (AdoMet) is required by Pneumocystis carinii in vitro, Pneumocystis infection depletes plasma AdoMet of rats and humans, nicotine reduces AdoMet of guinea pig lungs, and smoking correlates with reduced episodes of Pneumocystis pneumonia (PCP) in AIDS patients, we tested the effect of nicotine treatment on PCP using a rat model. Intraperitoneal infusion of 400 microg of R-(+) nicotine kg(-1) h(-1) intraperitoneal for 21 days caused a 15-fold reduction in lung AdoMet although neither plasma nor liver were changed. Infusion of 4 and 400 microg kg(-1) h(-1) into immunosuppressed rats, beginning when rats were inoculated with P. carinii, caused 85 and 99.88% reductions, respectively, in P. carinii cysts at sacrifice 21 days later; P. carinii nuclei were reduced by 91.2 and >99.99%, respectively. This effect was reversed by concomitant administration of AdoMet with nicotine. Treatment with AdoMet alone increased infection intensity. We conclude that AdoMet is a critical and limiting nutrient for Pneumocystis thus can serve as a therapeutic target for PCP. Regarding the mechanism, nicotine treatment caused no change in rat lung activity of AdoMet synthesizing methionine ATP transferase activity nor was there any evidence of increased AdoMet utilization for methylation reactions. Except of a doubling of putrescine, nicotine treatment also did not change lung polyamine content. However, key polyamine anabolic and catabolic enzymes were upregulated, and there were corresponding changes in polyamine metabolic intermediates. We conclude that chronic nicotine treatment increases lung polyamine catabolic/anabolic cycling and/or excretion leading to increased AdoMet-consuming polyamine biosynthesis and depletion of lung AdoMet.

Determination of the natural abundance delta15N of nicotine and related alkaloids by gas chromatography/isotope ratio mass spectrometry

A method is described by which the natural abundance delta15N values of nicotine, analogues, and metabolites can be determined. The alkaloids are extracted from their biological matrix by solid-phase extraction and analysis is conducted using isotope ratio mass spectrometry interfaced to gas chromatography. Repeatability and precision are sufficient to allow differences in the delta15N values of less than 1.0 per thousand to be satisfactorily measured, with a standard deviation routinely less than 0.5 per thousand. The methodology has been tested by determining the changes in the delta15N values of nicotine, N-methyl-2-phenylpyrrolidine and their respective demethylation products, nornicotine and 2-phenylpyrrolidine, during biotransformation by cell suspension cultures of Nicotiana species. Sufficient precision and reproducibility were obtained to allow the kinetic isotope effects associated with the demethylation reaction to be calculated.

Using Physical Chemistry To Differentiate Nicotinic from Cholinergic Agonists at the Nicotinic Acetylcholine Receptor

The binding of three distinct agonists-acetylcholine (ACh), nicotine, and epibatidine-to the nicotinic acetylcholine receptor has been probed using unnatural amino acid mutagenesis. ACh makes a cation-pi interaction with Trp alpha149, while nicotine employs a hydrogen bond to a backbone carbonyl in the same region of the agonist binding site. The nicotine analogue epibatidine achieves its high potency by taking advantage of both the cation-pi interaction and the backbone hydrogen bond. A simple structural model that considers only possible interactions with Trp alpha149 suggests that a novel aromatic C-H...O=C hydrogen bond further augments the binding of epibatidine. These studies illustrate the subtleties and complexities of the interactions between drugs and membrane receptors and establish a paradigm for obtaining detailed structural information.

Protonation-induced stereoisomerism in nicotine: Conformational studies using classical (AMBER) and ab initio (Car–Parrinello) molecular dynamics

A variety of biologically active small molecules contain prochiral tertiary amines, which become chiral centers upon protonation. S-nicotine, the prototypical nicotinic acetylcholine receptor agonist, produces two diastereomers on protonation. Results, using both classical (AMBER) and ab initio (Car-Parrinello) molecular dynamical studies, illustrate the significant differences in conformational space explored by each diastereomer. As is expected, this phenomenon has an appreciable effect on nicotine's energy hypersurface and leads to differentiation in molecular shape and divergent sampling. Thus, protonation induced isomerism can produce dynamic effects that may influence the behavior of a molecule in its interaction with a target protein. We also examine differences in the conformational dynamics for each diastereomer as quantified by both molecular dynamics methods.

Conformational Mobility of Immobilized α3β2, α3β4, α4β2, and α4β4 Nicotinic Acetylcholine Receptors

Four affinity chromatography stationary phases have been developed based upon immobilized nicotinic acetylcholine receptor (nAChR) subtypes, the alpha3beta2, alpha3beta4, alpha4beta2, and alpha4beta4 nAChRs. The stationary phases were created using membranes from cell lines expressing the subtypes and an immobilized artificial membrane stationary phase. The immobilized nAChRs were characterized using frontal chromatography with the agonist epibatidine as the marker. The observed binding affinities for the agonists epibatidine, nicotine, and cytisine were consistent with reported values, indicating that the nAChRs retained their ability to bind agonists. The noncompetitive inhibitors (NCIs) of the nAChR (R)- and (S)-mecamylamine, phencylcidine, dextromethoprphan, and levomethorphan were also chromatographed on the columns using nonlinear chromatography techniques. The studies were carried out before and after exposure of the columns to epibatidine. The NCI retention times increased after exposure to epibtatidine as did the enantioselective separation of mecamylamine and methorphan. The results indicate that the immobilized nAChRs retained their ability to undergo agonist-induced conformational change from the resting to the desensitized states. The columns provide a unique ability to study the interactions of NCIs with both of these conformational states.

On-line screening of conformationally constrained nicotines and anabasines for agonist activity at the α3β4- and α4β2-nicotinic acetylcholine receptors using immobilized receptor-based liquid chromatographic stationary phases

Liquid chromatography columns containing stationary phases based upon immobilized nicotinic acetylcholine receptors (nAChRs) were used to screen a series of conformationally constrained nicotine and anabasine derivatives for agonist activity. The alpha3beta4 nAChR and alpha4beta2 nAChR subtypes were used to prepare the chromatographic columns and [(3)H] epibatidine dihydrochloride ([(3)H] EB) was used as the marker ligand. Single displacement experiments were conducted with the test ligands and with nicotine and carbachol. Nicotine was used as an internal control for compounds with agonist activity and carbachol was used as an internal control for compounds with very weak agonistic activity (K(d) > 4700 nM for alpha3beta4). The displacement of [(3)H] EB by each of the test compounds and internal controls was calculated and expressed as Deltaml. Functional studies were then conducted using a stably transfected cell line that expresses the alpha3beta4 nAChR and EC(50) values were determined for the test compounds and the internal controls. A comparison of the Deltaml and EC(50) values indicated that 9/11 compounds had been correctly identified as agonists or non-agonists of the alpha3beta4 nAChR. A similar comparison could not be made for the alpha4beta2 nAChR, since the intact cell line was not available for testing. The results of the study suggest that the immobilized nAChR columns can be used for the rapid on-line screening of compounds for their relative affinities for the immobilized receptor and as an initial determination of qualitative functional activities.

Electrochemical investigation into the redox activity of Fe(II)/Fe(III) in the presence of nicotine and possible relations to neurodegenerative diseases

The biological relevance of Fe(II)/Fe(III) is becoming evermore apparent, especially in relation to its potential role in the progression of neurodegenerative diseases such as Parkinson's and Alzheimer's disease. The reported relationship between smoking and a reduced incidence of neurodegenerative disorders prompted this work. In order to investigate whether nicotine can interact with iron, we have studied the electrochemical behaviour of a Fe(II)/Fe(III) redox couple in the presence of nicotine. Solubility issues and lack of available nonreacting salts of nicotine necessitated studies being conducted at low pH values. Cyclic voltammetry experiments revealed a definite alteration in the electrochemical behaviour of the Fe(II)/Fe(III) redox couple suggesting the capability of nicotine to complex with free iron and, hence, reduce its reactivity. This is evident from a slower rate of heterogeneous electron transfer, ks, and a shift from reversible to quasi-reversible behaviour, as characterised from the diffusion coefficient (D), the full width half maximum (FWHM), DeltaEp and Ef. Additional complexation titrations, pH ranging from 1 to 7, confirm a weak complexation reaction occurring between Fe(III) and nicotine.

Anatalline and other methyl jasmonate-inducible nicotine alkaloids from Nicotiana tabacum cv. By-2 cell cultures

Anatalline [2,4-di(3-pyridyl)piperidine] accumulation was shown to be induced by methyl jasmonate in Nicotiana tabacum cv. BY-2 cell cultures. Beside anatabine, anatalline represented the most abundant alkaloid, moreover, it was always present in two isomeric forms occurring always in similar concentrations. Both isomers could be completely separated by GC-MS. For structural analysis, the isolation of both isomers was performed using a semi-preparative HPLC system. The structures of anatalline [cis-2,4-di(3-pyridyl)piperidine] and its stereoisomer trans-2,4-di(3-pyridyl)piperidine were confirmed by MS and 1D and 2D NMR spectral data. The biosynthetic origin of anatalline was studied by feeding alkaloid precursors to BY-2 cell cultures.

Nornicotine Aqueous Aldol Reactions: Synthetic and Theoretical Investigations into the Origins of Catalysis

The recent discovery that nornicotine 1, a minor nicotine metabolite, can catalyze the aldol reaction under physiologically relevant conditions has initiated research efforts into the potential chemical roles of nicotine metabolites. Herein, we disclose studies aimed at determining the origin and thus mechanism of the nornicotine-catalyzed aqueous aldol reaction. Conformationally constrained compounds designed to mimic the low-energy conformations of nornicotine were synthesized and tested for aldol catalysis; however, none showed rate enhancements on par with nornicotine. To further explore the mechanism of this process, a density functional theory (DFT) study was performed by using a variety of compounds previously tested for catalysis. These in silico studies have uncovered an unprecedented mechanistic subtlety of aqueous aldol reactions. Unlike the single transition state model observed for aldol reactions in organic solvent, the nornicotine-catalyzed reaction in water proceeds via a two-step mechanism in which a water molecule is utilized in both steps and a stable intermediate is generated. In total, these studies validate the proposed enamine-based mechanism of nornicotine-catalyzed aqueous aldol reactions and also provide the basis for future studies into the stereoelectronic nature of individual catalyst structures.

On the deposition of volatiles and semivolatiles from cigarette smoke aerosols: relative rates of transfer of nicotine and ammonia from particles to the gas phase

The hypothesis that elevated levels of ammonia-releasing compounds in tobacco and ammonia in mainstream (MS) smoke increase the rate and amount of nicotine evaporation from the particles of MS smoke aerosol was examined by kinetic modeling and experiments with MS cigarette smoke. Computational simulation of a kinetic mechanism describing volatile loss of nicotine, ammonia, and acetic acid from an aqueous solution was used to compute the time-dependent concentration of all species in the model. Because of the high volatility of ammonia relative to that of nicotine, variation over a wide range of initial ammonia concentration had no significant effect upon the rate of loss of nicotine from the model system. The effects of a variation in the volatile loss rate constant for ammonia and for the acid were examined. The simulations show that ammonia is lost from the model solution at a greater rate than nicotine and acid, and the loss of volatile acid has a significant role in the rate and amount of nicotine loss. Simulations with a model system undergoing a continuous steady addition of ammonia showed that high rates of ammonia addition could significantly increase the rate of nicotine volatile loss from the model solution. A series of smoking experiments was performed using blended cigarettes connected to a denuder tube. Deposition of smoke constituents can occur directly from the gas phase and by the deposition of smoke aerosol particles themselves. As nicotine exists >99% in the particle phase of MS smoke, in the absence of particle deposition, denuder tube deposition of nicotine occurs via the evaporation-deposition pathway. Solanesol, a nonvolatile tobacco and smoke terpene, was used to quantify the amount of particle deposition onto the denuder tube. The amount of ammonia deposited on the denuder tube was an order of magnitude greater than that of nicotine, showing that ammonia evaporates from the MS smoke particles much faster than does nicotine. The experimental results were supported and explained by the aqueous model simulations. Included in these experiments are cigarettes that differ in their MS smoke ammonia content by a factor of ca. five. However, an increased amount of MS smoke ammonia does not increase the rate of nicotine loss from the particles. The combined results support the conclusion that ammonia in mainstream smoke has little effect, if any, upon the rate and amount of nicotine evaporation from MS smoke particles.

The "low-tar" strategy and the changing construction of Australian cigarettes

This article documents design changes in Australian cigarettes since the adoption of a "low-tar" harm reduction strategy in 1966. It also determines the relative contributions of specific technologies to machine-tested tar and nicotine yields in 1980 and 1994, using data from tobacco industry documents. Our findings are consistent with a first generation of low-tar cigarettes, which relied primarily on filtration efficiency, being displaced by a second generation, which relied heavily on filter ventilation and were more attractive to consumers. In 1980, both tar and nicotine yields correlated most strongly with filter density (r=-.66, p<.01, and r=-.70, p<.01), whereas in 1994 both tar and nicotine yields correlated most strongly with percentage filter ventilation (r=-.97, p<.01, and r=-.95, p<.01). We also found that median percentage alkaloid content of tobacco rods rose from 2.16% in 1980 to 2.4% in 1994, despite median nicotine yield declining from 1.0 mg to.58 mg. These changes can be expected to reduce the utility of the FTC/ISO yield testing system.

Sorption of nicotine to cellulose powders

The purpose of this study was to investigate the influence of the crystallinity, surface area, and pore volume of cellulose powders on the loading, release, and stability of nicotine. Four different types of cellulose powders with varying crystallinity index, surface area, and pore volume were produced and characterized. The powders were loaded with nicotine by rotary evaporation from an ethanol solution and by adsorption from nicotine-saturated air. The release of nicotine from loaded cellulose powders into both a passing airstream and water was investigated by UV spectroscopy. A 3-month stability study was conducted and the total sum of nicotine oxidation products was measured. Nicotine loading and release were independent of cellulose powder crystallinity, whereas it was possible to load more nicotine on the cellulose powder with a large surface area and pore volume. Release into water was very rapid and almost complete for all samples. Nicotine was most stable when loaded on the powder with a large surface area and pore volume. Highly porous cellulose matrices could be useful for stabilization and handling of both nicotine and other liquid active pharmaceutical ingredients.

Evaluation of Selected Polysaccharide Excipients in Buccoadhesive Tablets for Sustained Release of Nicotine

Some naturally occurring biocompatible materials were evaluated as mucoadhesive controlled release excipients for buccal drug delivery. A range of tablets were prepared containing 0-50% w/w xanthan gum, karaya gum, guar gum, and glycol chitosan and were tested for swelling, drug release, and mucoadhesion. Guar gum was a poor mucoadhesive and lacked sufficient physical integrity for buccal delivery. Karaya gum demonstrated superior adhesion to guar gum and was able to provide zero-order drug release, but concentrations greater than 50% w/w may be required to provide suitable sustained release. Xanthan gum showed strong adhesion to the mucosal membrane and the 50% w/w formulation produced zero-order drug release over 4 hours, about the normal time interval between daily meals. Glycol chitosan produced the strongest adhesion, but concentrations greater than 50% w/w are required to produce a nonerodible matrix that can control drug release for over 4 hours. Swelling properties of the tablets were found to be a valuable indicator of the ability of the material to produce sustained release. Swelling studies also gave an indication of the adhesion values of the gum material where adhesion was solely dependent upon penetration of the polymer chains into the mucus layer.

A touching picture of nicotinic binding

The snail acetylcholine binding protein (AChBP) is homologous to the extracellular domains of the nicotinic ACh receptors. In this issue of Neuron, Celie et al. show how the crystal structures of AChBP in complexes with carbamylcholine and nicotine reveal the basis for agonist recognition by ACh receptors.

In utero and lactation exposure of rats to 1R4F reference cigarette mainstream smoke: effect on prenatal and postnatal development

Childhood cognitive and behavioral deficits have been reported in children born to mothers who smoked during pregnancy (Institute of Medicine, 2001). To investigate these potential responses in an animal model, reproductive and neurotoxicity evaluations based on the U.S. FDA guidelines were used to examine the offspring of male and female Sprague-Dawley rats exposed 2 h/day, 7 days/week by nose-only inhalation to whole mainstream smoke total particulate matter (TPM). Concentrations of 150, 300, or 600 mg/m(3) were used (males: 4 weeks prior to and during mating; and females: 2 weeks prior to mating, during mating, and through weaning at postnatal day 21). Sham air controls receiving filtered air and cage controls were also maintained. F(1) rats were weighed, identified by gender, examined for clinical signs of toxicity, and evaluated for neurobehavioral effects through postnatal day 65. Parental exposure was evidenced by smoke concentration-related increases in blood carboxyhemoglobin, nicotine, and cotinine and by characteristic cigarette smoke-related rodent respiratory tract histopathology. Also, nicotine and cotinine were found in F(1) blood through the lactation period. Maternal toxicity occurred at concentrations of 300 and 600 mg TPM/m(3), where total body weight gain during gestation was significantly (p < or = 0.05) decreased compared to sham controls. While smoke concentration-related decreases in F(1) birth weight and growth were evident (600 mg TPM/m(3), significantly different from sham at all time points), no adverse effects on developmental landmarks, including age at vaginal patency or preputial separation, motor activity, acoustic startle response or learning, and memory, were observed in the F(1) generation. This study confirmed that maternal exposure to high levels of mainstream cigarette smoke during gestation and lactation reduces birth weight and retards growth in the rat neonate; however, the developmental and neurobehavioral testing methodologies employed did not appear to be sensitive for an evaluation of neonatal behavioral effects following parental smoke exposure.

Surveillance of smokeless tobacco nicotine, pH, moisture, and unprotonated nicotine content

Smokeless tobacco is a complex chemical mixture, including not only the components of the tobacco leaf but also chemicals added during the manufacturing process. Smokeless tobacco contains the addictive chemical nicotine and more than 20 cancer-causing chemicals, including the potent tobacco-specific nitrosamines. The National Toxicology Program of the National Institutes of Health has concluded that oral use of smokeless tobacco is a human carcinogen. Therefore, smokeless tobacco is not a safe alternative to cigarettes. In fact, smokeless tobacco use begins primarily during early adolescence and can lead to nicotine dependence and increased risk of becoming a cigarette smoker. Under the Comprehensive Smokeless Tobacco Health Education Act of 1986 (15 U.S.C. 4401 et seq., Pub. L. 99-252), tobacco manufacturers report annually to the Centers for Disease Control and Prevention (CDC) on the total nicotine, unprotonated nicotine, pH, and moisture content of their smokeless tobacco products. This information is considered "trade secret," or confidential, in accordance with 5 U.S.C. 552(b)(4) and 18 U.S.C. 1905 and cannot be released to the public. In an effort to provide consumers and researchers with information on the nicotine content of smokeless tobacco, CDC arranged for the analysis of popular brands of smokeless tobacco. The results of this CDC study show that pH is a primary factor in the amount of nicotine that is in the most readily absorbable, unprotonated form. Furthermore, this study found that the brands of moist snuff smokeless tobacco with the largest amount of unprotonated nicotine also are the most frequently sold brands.