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Long‐term exposure to the new nicotinic antagonist 1,2‐bis N ‐cytisinylethane upregulates nicotinic receptor subtypes of SH‐SY5Y human neuroblastoma cells
Author(s) -
Riganti Loredana,
Matteoni Cosetta,
Di Angelantonio Silvia,
Nistri Andrea,
Gaimarri Annalisa,
Sparatore Fabio,
CanuBoido Caterina,
Clementi Francesco,
Gotti Cecilia
Publication year - 2005
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0706434
Subject(s) - methyllycaconitine , cytisine , epibatidine , nicotinic antagonist , nicotinic agonist , agonist , chemistry , receptor , pharmacology , acetylcholine receptor , alpha 4 beta 2 nicotinic receptor , muscarinic acetylcholine receptor , nicotinic acetylcholine receptor , endocrinology , biology , biochemistry
Nicotinic drug treatment can affect the expression of neuronal nicotinic acetylcholine receptors (nAChR) both in vivo and in vitro through molecular mechanisms not fully understood. The present study investigated the effect of the novel cytisine dimer 1,2‐bis N ‐cytisinylethane (CC4) on nAChR natively expressed by SH‐SY5Y neuroblastoma cells in culture. CC4 lacked the agonist properties of cytisine and was a potent antagonist (IC 50 =220 n M ) on nAChRs. Chronic treatment of SH‐SY5Y cells with 1 m M CC4 for 48 h increased the expression of 3 H‐epibatidine ( 3 H‐Epi; 3–4‐fold) or 125 I‐ α ‐bungarotoxin ( 125 I‐ α Bgtx; 1.2‐fold) sensitive receptors present on the cell membrane and in the intracellular pool. Comparable data were obtained with nicotine or cytisine, but not with carbamylcholine, d ‐tubocurarine, di‐hydro‐ β ‐erythroidine or hexametonium. Immunoprecipitation and immunopurification studies showed that the increase in 3 H‐Epi‐binding receptors was due to the enhanced expression of α 3 β 2 and α 3 β 2 β 4 subtypes without changes in subunit mRNA transcription or receptor half‐life. The upregulation was not dependent on agonist/antagonist properties of the drugs, and did not concern muscarinic or serotonin receptors. Whole‐cell patch clamp analysis of CC4‐treated cells demonstrated larger nicotine‐evoked inward currents with augmented sensitivity to the blockers α ‐conotoxin MII or methyllycaconitine. In conclusion, chronic treatment with CC4 increased the number of nAChRs containing β 2 and α 7 subunits on the plasma membrane, where they were functionally active. In the case of β 2‐containing receptors, we propose that CC4, by binding to intracellular receptors, triggered a conformational reorganisation of intracellular subunits that stimulated preferential assembly and membrane‐directed trafficking of β 2‐containing receptor subtypes.British Journal of Pharmacology (2005) 146 , 1096–1109. doi: 10.1038/sj.bjp.0706434