U18666A, a cholesterol-inhibition agent, modulates human neuronal nicotinic acetylcholine receptors heterologously expressed in SH-EP1 cell line.
In this study, we evaluate the effects of (3beta)-3-[2-(diethylamino)ethoxy]androst-5-en-17-one dihydrochloride (U18666A), a cholesterol synthesis/transporter inhibitor, on selected human neuronal nicotinic acetylcholine receptors (nAChRs) heterologously expressed in the SH-EP1 cell line using whole-cell patch-clamp recordings. The results indicate that with 2-min pretreatment, U18666A inhibited different nAChR subtypes with a rank-order of potency (IC(50) of whole-cell peak current): alpha4beta2 (8.0 +/- 3.0 nM) > alpha3beta2 (1.7 +/- 0.4 microM) > alpha4beta4 (26 +/- 7.2 microM) > alpha7 (> 100 microM), suggesting this compound is more selective to alpha4beta2-nAChRs. Thus, the pharmacological profiles and mechanisms of U18666A acting on alpha4beta2-nAChRs were investigated in detail. U18666A suppresses both peak and steady state components of whole-cell currents mediated by human alpha4beta2-nAChRs in response to nicotine. In nicotine-induced concentration-response curves, U18666A reduces nicotine-induced current at maximally effective agonist concentrations without influencing nicotine's EC(50) value, suggesting a non-competitive inhibition. U18666A-induced inhibition of nAChR function is concentration-, voltage-, and use-dependent, suggesting an open channel block. Taken into consideration of approximately 10 000-fold enhancement of the potency of U18666A after 2-min pre-treatment, this compound also likely inhibits alpha4beta2-nAChRs through a close channel block. In addition, the U18666A-induced inhibition in alpha4beta2-nAChRs is not mediated by either increased receptor endocytosis or altered cell cholesterol. These data indicate that U18666A is a potent antagonist of alpha4beta2-nAChRs and may be useful as a tool in the functional characterization and pharmacological profiling of nAChRs, as well as a potential candidate for smoking cessation.
Zheng
Chao
C
Division of Neurology, Barrow Neurological Institute, St Joseph's Hospital and Medical Center, Phoenix, Arizona, USA.
Wang
Meng-Ya
MY
Liu
Qiang
Q
Wakui
Makoto
M
Whiteaker
Paul
P
Lukas
Ronald J
RJ
Wu
Jie
J
D000736:Androstenes / Q000737:chemistry / Q000494:pharmacology*; D000924:Anticholesteremic Agents / Q000494:pharmacology*; D055592:Biophysical Phenomena / Q000502:physiology; D002461:Cell Line, Transformed; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation / Q000379:methods; D004847:Epithelial Cells / Q000187:drug effects / Q000502:physiology; D015870:Gene Expression / Q000187:drug effects*; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D009538:Nicotine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011978:Receptors, Nicotinic / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D013873:Thionucleotides / Q000494:pharmacology; D001371:trans-1,4-Bis(2-chlorobenzaminomethyl)cyclohexane Dihydrochloride / Q000737:chemistry / Q000494:pharmacology
D000736:Androstenes; D000924:Anticholesteremic Agents; D011978:Receptors, Nicotinic; D013873:Thionucleotides; D006153:Guanosine Diphosphate; C006261:3-beta-(2-(diethylamino)ethoxy)androst-5-en-17-one; D001371:trans-1,4-Bis(2-chlorobenzaminomethyl)cyclohexane Dihydrochloride; D009538:Nicotine; C023427:guanosine 5'-O-(2-thiodiphosphate)