DY-9760E, A NOVEL CALMODULIN ANTAGONIST WITH CYTOPROTECTIVE ACTION

We report the pharmacological characterization and cytoprotective effe ct of DY-9760e, 3-chloro-2-methylphenyl)-1-piperazinyl]ethyl]-5,6- dim ethoxy-1-(4-imidazolylmethyl)-1H-indazole dihydrochloride 3.5 hydrate, a novel antagonist of calmodulin. DY-9760e inhibited calmodulin-depen dent enzymes, including calmodulin-dependent phosphodiesterase and myo sin light chain kinase with K-i values of 1.4, 12, 2.0, 3.8 and 133 mu M, respectively. These antagonistic effects of DY-9760e were more pot ent than those of W-7, -(6-aminohexyl)-5-chloro-1-naphthalenesulfonami de, another calmodulin antagonist. This compound showed little or no e ffect on calmodulin-independent enzymes, such as protein kinase A and C and calpain I and II. Analysis of the hydrophobic interaction of DY- 9760e with calmodulin by using 2-p-toluidinylnaphthalene-6-sulfonate a nd 9-anthroylcholine revealed that, like W-7, DY-9760e bound to the hy drophobic regions of calmodulin. The [C-14]DY-9760e binding assay indi cated that DY-9760e bound to calmodulin at one class of binding site. Finally, DY-9760e substantially protected N1E-115 neuroblastoma cells from cytotoxicity induced by the Ca2+ ionophore, A23187. These results indicate that DY-9760e, a novel calmodulin antagonist, possesses a cy toprotective action and suggest that calmodulin plays a critical role in mediating some of the biochemical events leading to cell death foll owing Ca2+ overload. (C) 1997 Elsevier Science B.V.