Studi cellulari e molecolari degli effetti di un trattamento cronico con un nuovo farmaco nicotinico sull'espressione dei recettori nicotinici neuronali

Cellular and molecular studies of the effects of chronic treatment with a new nicotinic drug on the expression of neuronal nicotinic receptors Neuronal nicotinic receptors (nAChRs) are a heterogenous family of ionic channel widely express in the CNS; nicotinic drug treatment can affect the expression of neuronal nicotinic acetylcholine receptors both in vivo and in vitro through molecular mechanisms not fully understood. The aim of this study is the characterization of a novel nicotinic ligand, named 1,2-bisN-cytisilethane (CC4) on the expression of nAChRs in the neuroblastoma cell line SH-SY5Y. CC4 is a cytisine derivative, avoid of the agonist/partial agonist properties of the parental compound and with a strong antagonistic profile on nAChRs in SH-SY5Y. Chronic treatment of SH-SY5Y cells with 1 mM CC4 for 48 h increased the expression of 3H-epibatidine (3H-Epi; 3-4-fold) or 125I-(bungarotoxin (125I-(Bgtx; 1.2-fold) sensitive receptors present on the cell membrane and in the intracellular pool. Immunoprecipitation and immunopurification studies showed that the increase in 3H-Epi-binding receptors was due to the enhanced expression of alpha3beta2 and alpha3beta2beta4 subtypes without changes in subunit mRNA transcription or receptor half-life. Whole-cell patch clamp analysis of CC4-treated cells demonstrated larger nicotine-evoked inward currents with augmented sensitivity to the blockers alpha-conotoxin MII or methyllycaconitine. In conclusion, chronic treatment with CC4 increased the number of nAChRs containing beta2 and alpha7 subunits on the plasma membrane, where they were functionally active.