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Analytical Chemistry Dec 2013The determination of tobacco derived nicotine alkaloids in biofluid samples is of great importance to testing for tobacco use, tobacco cessation treatment, and studies...
The determination of tobacco derived nicotine alkaloids in biofluid samples is of great importance to testing for tobacco use, tobacco cessation treatment, and studies on exposure to secondhand smoke. Paper spray mass spectrometry (MS) has been adapted for direct, quantitative analysis of tobacco alkaloids from biofluid samples, such as blood, urine, and saliva in liquid and dried form. Limits of quantitation as low as several nanograms per milliliter were obtained for nicotine, cotinine, trans-3'-hydroxycotinine, and anabasine. Direct analysis of fresh blood samples has also been achieved with improved sensitivity using print paper substrates of high density. Quantitation of the cotinine in the blood of a rat was performed with both direct analysis using paper spray and a traditional analysis protocol using liquid chromatography MS. Comparable results were obtained and the precision of the two methods was similar. The paper spray MS method is rapid and shows potential for significantly improved analytical efficiency in clinical laboratories as well as for point-of-care tobacco use assessment.
Topics: Alkaloids; Animals; Cattle; Mass Spectrometry; Nicotine; Paper; Rats
PubMed: 24195719
DOI: 10.1021/ac402798m -
Proceedings of the National Academy of... Nov 2013Large-scale losses of honey bee colonies represent a poorly understood problem of global importance. Both biotic and abiotic factors are involved in this phenomenon that...
Large-scale losses of honey bee colonies represent a poorly understood problem of global importance. Both biotic and abiotic factors are involved in this phenomenon that is often associated with high loads of parasites and pathogens. A stronger impact of pathogens in honey bees exposed to neonicotinoid insecticides has been reported, but the causal link between insecticide exposure and the possible immune alteration of honey bees remains elusive. Here, we demonstrate that the neonicotinoid insecticide clothianidin negatively modulates NF-κB immune signaling in insects and adversely affects honey bee antiviral defenses controlled by this transcription factor. We have identified in insects a negative modulator of NF-κB activation, which is a leucine-rich repeat protein. Exposure to clothianidin, by enhancing the transcription of the gene encoding this inhibitor, reduces immune defenses and promotes the replication of the deformed wing virus in honey bees bearing covert infections. This honey bee immunosuppression is similarly induced by a different neonicotinoid, imidacloprid, but not by the organophosphate chlorpyriphos, which does not affect NF-κB signaling. The occurrence at sublethal doses of this insecticide-induced viral proliferation suggests that the studied neonicotinoids might have a negative effect at the field level. Our experiments uncover a further level of regulation of the immune response in insects and set the stage for studies on neural modulation of immunity in animals. Furthermore, this study has implications for the conservation of bees, as it will contribute to the definition of more appropriate guidelines for testing chronic or sublethal effects of pesticides used in agriculture.
Topics: Anabasine; Animals; Antimicrobial Cationic Peptides; Bees; Gene Knockdown Techniques; Guanidines; Immunity, Innate; Insecticides; Italy; Neonicotinoids; Real-Time Polymerase Chain Reaction; Statistics, Nonparametric; Thiazoles
PubMed: 24145453
DOI: 10.1073/pnas.1314923110 -
Analytical Chemistry Mar 2013This publication reports the first known use of gas chromatography-tandem mass spectrometry for the quantitation of five minor tobacco alkaloids (nornicotine, myosmine,...
This publication reports the first known use of gas chromatography-tandem mass spectrometry for the quantitation of five minor tobacco alkaloids (nornicotine, myosmine, anabasine, anatabine, and isonicoteine) in various tobacco samples. A summary of the concentrations of these minor alkaloid levels in the filler from 50 popular cigarette brands were found to be 659-986 μg/g nornicotine, 8.64-17.3 μg/g myosmine, 127-185 μg/g anabasine, 927-1390 μg/g anatabine, and 23.4-45.5 μg/g isonicoteine. Levels of minor alkaloids found in reference cigarettes (1R5F, 2R4F, 3R4F, CM4, and CM6) as well as burley, flue-cured, oriental, reconstituted, and Nicotiana rustica and Nicotiana glauca tobacco types are also reported. Quantitation of the minor tobacco alkaloids is important because the alkaloids have been shown to be precursors of carcinogenic tobacco specific N'-nitrosamines.
Topics: Alkaloids; Gas Chromatography-Mass Spectrometry; Tandem Mass Spectrometry; Nicotiana; Tobacco Products
PubMed: 23394466
DOI: 10.1021/ac400077e -
Biochemical Pharmacology Mar 2013The homomeric α7 nicotinic acetylcholine receptor is a well-studied therapeutic target, though its characteristically rapid desensitization complicates the development...
Point-to-point ligand-receptor interactions across the subunit interface modulate the induction and stabilization of conformational states of alpha7 nAChR by benzylidene anabaseines.
The homomeric α7 nicotinic acetylcholine receptor is a well-studied therapeutic target, though its characteristically rapid desensitization complicates the development of drugs with specific agonist effects. Moreover, some experimental compounds such as GTS-21 (2,4diMeOBA), a derivative of the α7-selective partial agonist benzylidene anabaseine (BA), produce a prolonged residual desensitization (RD) in which the receptor remains non-activatable long after the drug has been removed from extracellular solution. In contrast, the desensitization caused by GTS-21's dihydroxy metabolite (2,4diOHBA) is relatively short-lived. RD is hypothetically due to stable binding of the ligand to the receptor in its desensitized state. We can attribute the reduction in RD to a single BA hydroxyl group on the 4' benzylidene position. Computational prediction derived from homology modeling showed the serine36 (S36) residue of α7 as a reasonable candidate for point-to-point interaction between BA compounds and the receptor. Through evaluating the activity of BA and simple derivatives on wild-type and mutant α7 receptors, it was observed that the drug-receptor pairs which were capable of hydrogen bonding at residue 36 exhibited significantly less stable desensitization. Further experiments involving the type II positive allosteric modulator (PAM) PNU-120596 showed that the various BA compounds' preference to induce either a PAM-sensitive (D(s)) or PAM-insensitive (D(i)) desensitized state is concentration dependent and suggested that both states are destabilized by S36 H-bonding. These results indicate that the fine-tuning of agonists for specific interaction with S36 can facilitate the development of therapeutics with targeted effects on ion channel desensitization properties and conformational state stability.
Topics: Anabasine; Animals; Benzylidene Compounds; DNA, Complementary; Humans; Ligands; Models, Molecular; Protein Binding; Protein Conformation; Receptors, Nicotinic; Xenopus laevis; alpha7 Nicotinic Acetylcholine Receptor
PubMed: 23352650
DOI: 10.1016/j.bcp.2013.01.010 -
The Journal of General Physiology Jan 2013A primary target for nicotine is the acetylcholine receptor channel (AChR). Some of the ability of nicotine to activate differentially AChR subtypes has been traced to a...
A primary target for nicotine is the acetylcholine receptor channel (AChR). Some of the ability of nicotine to activate differentially AChR subtypes has been traced to a transmitter-binding site amino acid that is glycine in lower affinity and lysine in higher affinity AChRs. We studied the effects of mutations of this residue (αG153) in neuromuscular AChRs activated by nicotine and eight other agonists including nornicotine and anabasine. All of the mutations increased the unliganded gating equilibrium constant. The affinity of the resting receptor (K(d)) and the net binding energy from the agonist for gating (ΔG(B)) were estimated by cross-concentration fitting of single-channel currents. In all but one of the agonist/mutant combinations there was a moderate decrease in K(d) and essentially no change in ΔG(B). The exceptional case was nicotine plus lysine, which showed a large, >8,000-fold decrease in K(d) but no change in ΔG(B). The extraordinary specificity of this combination leads us to speculate that AChRs with a lysine at position αG153 may be exposed to a nicotine-like compound in vivo.
Topics: Anabasine; Dose-Response Relationship, Drug; Glycine; HEK293 Cells; Humans; Ion Channel Gating; Kidney; Lysine; Mutation; Nicotine; Patch-Clamp Techniques; Receptors, Cholinergic; Serine
PubMed: 23277476
DOI: 10.1085/jgp.201210896 -
Molecules (Basel, Switzerland) Aug 2012The structure-based design and synthesis of a series of novel neonicotinoid analogues are described. The novel neonicotinoid analogues were designed based upon the...
The structure-based design and synthesis of a series of novel neonicotinoid analogues are described. The novel neonicotinoid analogues were designed based upon the reaction of enamine derivatives with electron-withdrawing β-substituents with electrophilic thiocyanogen reagents. These compounds were characterized by spectroscopic methods. Bioassays indicated that some of the synthesized compounds exhibited excellent bioactivity against cowpea aphids (Aphis craccivora). The LC₅₀ values of compounds 7, 9,12, 13, 15, 17, 19, 20 and commercial imidacloprid were 0.01567, 0.00974, 0.02494, 0.01893, 0.02677, 0.01778, 0.0220, 0.02447 and 0.03502 mmol L⁻¹, respectively, which suggested that they could be used as leads for future development of new insecticides.
Topics: Anabasine; Animals; Aphids; Imidazoles; Insecticides; Methane; Molecular Structure; Neonicotinoids; Nitro Compounds; Nitroparaffins; Thiocyanates
PubMed: 22922273
DOI: 10.3390/molecules170910014 -
The Journal of Biological Chemistry Jun 2012A series of arylidene anabaseines were synthesized to probe the functional impact of hydrogen bonding on human α7 nicotinic acetylcholine receptor (nAChR) activation...
A series of arylidene anabaseines were synthesized to probe the functional impact of hydrogen bonding on human α7 nicotinic acetylcholine receptor (nAChR) activation and desensitization. The aryl groups were either hydrogen bond acceptors (furans), donors (pyrroles), or neither (thiophenes). These compounds were tested against a series of point mutants of the ligand-binding domain residue Gln-57, a residue hypothesized to be proximate to the aryl group of the bound agonist and a putative hydrogen bonding partner. Q57K, Q57D, Q57E, and Q57L were chosen to remove the dual hydrogen bonding donor/acceptor ability of Gln-57 and replace it with hydrogen bond donating, hydrogen bond accepting, or nonhydrogen bonding ability. Activation of the receptor was compromised with hydrogen bonding mismatches, for example, pairing a pyrrole with Q57K or Q57L, or a furan anabaseine with Q57D or Q57E. Ligand co-applications with the positive allosteric modulator PNU-120596 produced significantly enhanced currents whose degree of enhancement was greater for 2-furans or -pyrroles than for their 3-substituted isomers, whereas the nonhydrogen bonding thiophenes failed to show this correlation. Interestingly, the PNU-120596 agonist co-application data revealed that for wild-type α7 nAChR, the 3-furan desensitized state was relatively stabilized compared with that of 2-furan, a reversal of the relationship observed with respect to the barrier for entry into the desensitized state. These data highlight the importance of hydrogen bonding on the receptor-ligand state, and suggest that it may be possible to fine-tune features of agonists that mediate state selection in the nAChR.
Topics: Allosteric Site; Anabasine; Cloning, Molecular; Cysteine; Dose-Response Relationship, Drug; Electrophysiology; Humans; Hydrogen Bonding; Isoxazoles; Ligands; Models, Molecular; Molecular Conformation; Mutagenesis, Site-Directed; Mutation; Phenylurea Compounds; Protein Conformation; Receptors, Nicotinic; alpha7 Nicotinic Acetylcholine Receptor
PubMed: 22556416
DOI: 10.1074/jbc.M112.339796 -
Chimia 2011cis-Neonicotinoids are a type of neonicotinoid, in which the nitro or the cyano group are in cis-configuration relative to heteroaromatic moiety, which show excellent... (Review)
Review
cis-Neonicotinoids are a type of neonicotinoid, in which the nitro or the cyano group are in cis-configuration relative to heteroaromatic moiety, which show excellent activities against a range of insect species. This review covers cis-neonicotinoids with commercialization perspectives, structural optimization (phenylazoneonicotinoids and chlorothiazolyl analogues of Paichongding), modes of action studies, radiao-synthesis of Paichongding and Cycloxaprid, and photostability of neonicotinoids.
Topics: Anabasine; Insecticides; Molecular Structure; Photochemistry
PubMed: 22273379
DOI: 10.2533/chimia.2011.957 -
European Journal of Medicinal Chemistry Nov 2011AChBPs isolated from Lymnaea stagnalis (Ls), Aplysia californica (Ac) and Bulinus truncatus (Bt) have been extensively used as structural prototypes to understand the...
Docking studies of benzylidene anabaseine interactions with α7 nicotinic acetylcholine receptor (nAChR) and acetylcholine binding proteins (AChBPs): application to the design of related α7 selective ligands.
AChBPs isolated from Lymnaea stagnalis (Ls), Aplysia californica (Ac) and Bulinus truncatus (Bt) have been extensively used as structural prototypes to understand the molecular mechanisms that underlie ligand-interactions with nAChRs [1]. Here, we describe docking studies on interactions of benzylidene anabaseine analogs with AChBPs and α7 nAChR. Results reveal that docking of these compounds using Glide software accurately reproduces experimentally-observed binding modes of DMXBA and of its active metabolite, in the binding pocket of Ac. In addition to the well-known nicotinic pharmacophore (positive charge, hydrogen-bond acceptor, and hydrophobic aromatic groups), a hydrogen-bond donor feature contributes to binding of these compounds to Ac, Bt, and the α7 nAChR. This is consistent with benzylidene anabaseine analogs with OH and NH(2) functional groups showing the highest binding affinity of these congeners, and the position of the ligand shown in previous X-ray crystallographic studies of ligand-Ac complexes. In the predicted ligand-Ls complex, by contrast, the ligand OH group acts as hydrogen-bond acceptor. We have applied our structural findings to optimizing the design of novel spirodiazepine and spiroimidazoline quinuclidine series. Binding and functional studies revealed that these hydrogen-bond donor containing compounds exhibit improved affinity and selectivity for the α7 nAChR subtype and demonstrate partial agonism. The gain in affinity is also due to conformational restriction, tighter hydrophobic enclosures, and stronger cation-π interactions. The use of AChBPs structure as a surrogate to predict binding affinity to α7 nAChR has also been investigated. On the whole, we found that molecular docking into Ls binding site generally scores better than when a α7 homology model, Bt or Ac crystal structure is used.
Topics: Anabasine; Animals; Benzylidene Compounds; Carrier Proteins; Drug Design; Hydrogen Bonding; Ligands; Models, Molecular; Protein Conformation; Rats; Receptors, Nicotinic; Substrate Specificity; alpha7 Nicotinic Acetylcholine Receptor
PubMed: 21986237
DOI: 10.1016/j.ejmech.2011.09.033 -
Journal of Chromatography. B,... Nov 2011A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for simultaneous quantification of nicotine (NIC), cotinine (COT), nornicotine (NNIC), norcotinine...
A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for simultaneous quantification of nicotine (NIC), cotinine (COT), nornicotine (NNIC), norcotinine (NCOT), nicotine-N-β-D-glucuronide (NIC GLUC), cotinine-N-β-D-glucuronide (COT GLUC), nicotine-1'-oxide (NNO), cotinine-N-oxide (CNO), trans-3'-hydroxycotinine (3-HC), anabasine (AB) and anatabine (AT) was modified and validated for quantification of these selected analytes in rat brain tissue. This analytical method provides support for preclinical NIC pharmacokinetic and toxicological studies after controlled dosing protocols. After brain homogenization and solid-phase extraction, target analytes and corresponding deuterated internal standards were chromatographically separated on a Discovery(®) HS F5 HPLC column with gradient elution and analyzed by LC-MS/MS in positive electrospray ionization (ESI) mode with multiple reaction monitoring (MRM) data acquisition. Method linearity was assessed and calibration curves were determined over the following ranges: 0.1-7.5 ng/mg for NIC, COT GLUC and AB; and 0.025-7.5 ng/mg for COT, NNIC, NCOT, NIC GLUC, NNO, CNO, 3-HC and AT (R(2)≥0.99 for all analytes). Extraction recoveries ranged from 64% to 115%, LC-MS/MS matrix effects were ≤21%, and overall process efficiency ranged from 57% to 93% at low and high quality control concentrations. Intra- and inter-assay imprecisions and accuracy for all analytes were ≤12.9% and ≥86%, respectively. The method was successfully applied to quantification of NIC and metabolites in the brain of post-natal day 90 rats that were sacrificed 2-h after a single 0.8 mg/kg s.c. administration of (-)NIC. In these tissues, striatal concentrations were 204.8±49.4, 138.2±14.2 and 36.1±6.1 pg/mg of NIC, COT and NNIC, respectively. Concentrations of NIC, COT and NNIC in the remaining whole brain (RWhB) were 183.3±68.0, 130.0±14.1 and 46.7±10.3 pg/mg, respectively. Quantification of these same analytes in plasma was also performed by a previously validated method. NIC, COT, NNIC, NCOT, NNO and CNO were detected in plasma with concentrations comparable to those reported in previous studies. However, and in contrast to brain tissues, COT concentrations in plasma were significantly higher than were those of NIC (194.6±18.6 ng/mL versus 52.7±12.9 ng/mL). Taken together, these results demonstrate that a sensitive and selective method has been developed for the determination of NIC biomarkers in rat brain.
Topics: Alkaloids; Anabasine; Animals; Biomarkers; Brain Chemistry; Chromatography, Liquid; Cotinine; Linear Models; Male; Nicotine; Pyridines; Rats; Rats, Sprague-Dawley; Reproducibility of Results; Sensitivity and Specificity; Tandem Mass Spectrometry
PubMed: 21963483
DOI: 10.1016/j.jchromb.2011.09.026