title: Tobacco nitrosamine N-nitrosonornicotine as inhibitor of neuronal nicotinic acetylcholine receptors.
abstract: Nitrosamines are well known for their carcinogenic potential. Recently, it was found that some of them may also interact with human nicotinic acetylcholine receptor (nAChR) subtypes. This work studied the effects of N-nitrosonornicotine (NNN) on recombinant rat α3β4 nAChR in HEK cells as well as on nAChR endogenously expressed in PC12 pheochromocytoma cells and in BC3H1 muscle-type cells. Whole-cell recording in combination with the cell-flow technique for agonist and inhibitor application in the millisecond time region revealed that NNN inhibits the activity of neuronal nAChR expressed in HEK or PC12, whereas weak inhibitory effects on muscle-type nAChR were observed at NNN concentrations up to 3 mM. Pharmacological actions of NNN and the inhibition mechanism were studied in detail using recombinant α3β4 nAChR expressed in HEK cells as a model. NNN-induced inhibition of nicotine-evoked α3β4 nAChR activity was dose-dependent with an inhibitory constant (IC(50)) of 0.92 ± 0.05 mM. Analysis based on mathematical models indicated a noncompetitive inhibition mechanism of the rat α3β4 nAChR by NNN. NNN's mechanism of action involves acceleration of conversion of the receptor from active to desensitized forms. In summary, this work shows that NNN inhibits rat α3β4 nAChR in a noncompetitive way and interacts weakly with muscular nAChR.
authors: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, São Paulo, São Paulo 05508-900, Brazil.
authors: Ariane
authors: A
authors: Nunes-Alves
authors: Arthur A
authors: AA
authors: Nery
authors: Henning
authors: H
authors: Ulrich
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D004305:Dose-Response Relationship, Drug; D057809:HEK293 Cells; D006801:Humans; D018722:Nicotinic Agonists / Q000494:pharmacology; D018733:Nicotinic Antagonists / Q000494:pharmacology*; D009602:Nitrosamines / Q000494:pharmacology*; D016716:PC12 Cells; D051381:Rats; D011978:Receptors, Nicotinic / Q000378:metabolism*
chemical_list: D018722:Nicotinic Agonists; D018733:Nicotinic Antagonists; D009602:Nitrosamines; D011978:Receptors, Nicotinic; C403530:nicotinic receptor alpha3beta4; C008655:N'-nitrosonornicotine