Selective calmodulin antagonists fail to inhibit phorbol ester-induced superoxide anion release from human neutrophils: effects of antifungal azole derivatives.

Abstract

The ability of antifungal azole derivatives to inhibit superoxide anion release from human leucocytes and the relevance of their documented calmodulin (CaM) antagonism was investigated with respect to anti-inflammatory drug activity. Econazole, miconazole and clotrimazole were found to inhibit phorbol ester-induced release of superoxide anions from human polymorphonuclear leucocytes effectively with IC50 values in the range of 36-162 mumol/l. In contrast, bifonazole and ketoconazole produced minimal or no inhibition, thus suggesting that mechanisms other than inhibition of superoxide anion release may largely account for their clinical activity in inflammatory skin disorders. The selective CaM antagonist J-8, which was used as a reference, failed to inhibit the release process, whereas W-7 as a dual CaM/protein kinase C inhibitor induced dose-dependent inhibition. When tested on protein kinase C activity in vitro, econazole, miconazole and clotrimazole were inhibitory, but bifonazole and ketoconazole were without significant effect. It is thus concluded that inhibition of superoxide anion release reflects the ability of these drugs to inhibit protein kinase C, but not their potency to antagonize CaM. Given the role of reactive oxygen species in tissue damage by neutrophils, we propose protein kinase C, rather than CaM, as another potential target of anti-inflammatory therapy.