Cerivastatin Activates Endothelial Calcium-Activated Potassium Channels and Thereby Modulates Endothelial Nitric Oxide Production and Cell Proliferation

Abstract

Statins are known to counteract the process of arteriosclerosis by exerting direct pleiotropic effects on vascular endothelium. The aim of this study was to investigate a possible effect of cerivastatin on endothelial Ca2+-activated K+ channels (BKCa) and to assess their contribution to cerivastatin-mediated changes of endothelial nitric oxide (NO) production and proliferation. Membrane potential was measured using bis-1,3-dibutylbarbituric acid-trimethine oxonol-fluorescence imaging. Patch-clamp recordings of BKCa were performed on cultured human umbilical vein endothelial cells. NO production was measured using 4,5-diaminofluorescein-fluorescence imaging and a [3H]cGMP RIA. Proliferation was analyzed by means of cell counts and [3H]thymidine incorporation (TI). Cerivastatin (0.001 to 0.05 μmol/L) caused a significant membrane hyperpolarization (n = 30; P < 0.05). This effect was abolished using the BKCa inhibitor iberiotoxin (IBX; 100 nmol/L). The addition of mevalonate (500 μmol/L) blocked the BKCa activation induced by cerivastatin (n = 19; P < 0.05). Endothelial cGMP level was increased by acetylcholine (ACh; 1 μmol/L). The combination of ACh and cerivastatin additionally increased cGMP levels, with a maximum at 0.03 μmol/L cerivastatin (84%; n = 10, P < 0.01). ACh-induced increase of cGMP-level was significantly reduced by IBX (n = 10, P < 0.01) as it was with all combined administrations of ACh and cerivastatin. 4,5-Diaminofluorescein-fluorescence measurements revealed a significant increase of NO levels by cerivastatin, which was abolished by IBX (n = 30; P < 0.05). Cell counts and TI demonstrated significant inhibition of human umbilical vein endothelial cell proliferation with a maximum at 0.03 μmol/L (cell count, -32.2%; TI, -70%; n = 12; P < 0.01). These data show that cerivastatin activates endothelial BKCa, which plays an important role in the signaling of cerivastatin-mediated endothelial NO production and proliferation.