Clotrimazole inhibits smooth muscle cell proliferation and has a vasodilator effect on resistance arteries

Clotrimazole (CLT) is a drug known to interfere with cellular calcium homeo stasis, which in turn is reported to intervene in cell proliferation and in the reactivity of small blood vessels. Experiments were designed to test t he influence of CLT on the proliferative and vasorelaxant effect of bradyki nin (BK) and on calcium homeostasis in smooth muscle cells (SMC). To this p urpose two model systems were employed: (i) cultured human smooth muscle ce lls (HSMC), and (ii) isolated resistance arteries maintained in an organ ba th. The effect of various concentrations of CLT (2-15 muM) on BK-induced pr oliferation of HSMC was quantitated by spectrometry following [H-3]thymidin e incorporation, and intracellular calcium [Ca2+](i) was determined by spec trofluorimetry using Fura 2-AM assay. In other experiments the roles of BK receptor (AB2) and of thapsigargin were assessed. The reactivity of the res istance arteries was measured by the myograph technique, and the effects of BK, CLT, and NO synthase blocker, L-NAME were evaluated. The results showe d that 10 muM CLT: (i) inhibits the BK-induced proliferation of HSMC by 45- 50%; (ii) prevents the rise of [Ca2+](i) induced by BK (120.8 +/- 12.4 nM v s. 235.8 +/- 34.1 nM), an effect similar to that of "classic" L-type calciu m channels blockers; (iii) reduces the release of Ca2+ entry induced by tha psigargin suggesting a possible inhibition of the capacitative Ca2+ entry. Organ bath assays showed that CLT enhanced the BK-induced relaxation of the resistance arteries by an endothelium NO-independent pathway. Together, th ese data suggest that the mechanism of action of CLT on SMC implies mainly a modification of intracellular calcium homeostasis, with a minor contribut ion of BK B2 receptors. These new distinctive features of CLT effects sugge st the potential use of this drug in the therapy of cardiovascular diseases associated with SMC increased proliferation and impeded relaxation in smal l arteries, such as atherosclerosis and restenosis. (C) 2000 Editions scien tifiques et medicales Elsevier SAS.