Antagonism of L-type Ca2+ channels Cav1.3 and Cav1.2 by 1,4-dihydropyrimidines and 4H-pyrans as dihydropyridine mimics

The L-type calcium channel (LTCC) Ca(v)1.3 is regarded as a new potential therapeutic target for Parkinson's disease. Calcium influx through Ca(v)1.3 LTCC during autonomous pacemaking in adult dopaminergic neurons of the substantia nigra pars compacta is related to the generation of mitochondrial oxidative stress in animal models. Development of a Ca(v)1.3 antagonist selective over Ca(v)1.2 is essential because Ca(v)1.2 pore-forming subunits are the predominant form of LTCCs and are abundant in the central nervous and cardiovascular systems. We have explored 1,4-dihydropyrimidines and 4H-pyrans to identify potent and selective antagonists of Ca(v)1.3 relative to Ca(v)1.2 LTCCs. A library of 36 dihydropyridine (DHP)-mimic 1,4-dihydropyrimidines and 4H-pyrans was synthesized, and promising chiral compounds were resolved. The antagonism studies of Ca(v)1.3 and Ca(v)1.2 LTCCs using DHP mimic compounds showed that dihydropyrimidines and 4H-pyrans are effective antagonists of DHPs for Ca(v)1.3 LTCCs. Some 1,4-dihydropyrimidines are more selective than isradipine for Ca(v)1.3 over Ca(v)1.2, shown here by both calcium flux and patch-clamp electrophysiology experiments, where the ratio of antagonism is around 2-3. These results support the hypothesis that the modified hydrogen bonding donor/acceptors in DHP-mimic dihydropyrimidines and 4H-pyrans can interact differently with DHP binding sites, but, in addition, the data suggest that the binding sites of DHP in Ca(v)1.3 and Ca(v)1.2 LTCCs are very similar. (C) 2013 Elsevier Ltd. All rights reserved.