Mechanism of Action of Miconazole: Labilization of Rat Liver Lysosomes In Vitro by Miconazole

Abstract

Miconazole, a potent antifungal agent, labilizes rat liver lysosomes. Its labilizing effect is followed by measuring the release of lysosomal hydrolases, namely, acid phosphatase, (-glucuronidase, and arylsulfatase A. The effect of miconazole is concentration dependent in the range of 10-5 to 1.2 x 10-4 M. However, at higher concentrations, miconazole inhibits enzyme release but does not inhibit enzyme activities per se. The effect of miconazole depends on the drug/ lysosome ratio and is influenced by the pH of the incubation media, being minimal at alkaline pH. Membrane-active drugs such as nystatin, 2-phenethylalcohol, hexachlorophene, and digitonin have been compared with miconazole for their lysosome-labilizing action. The effect of miconazole on the lysosomal membrane is confirmed by a decrease in turbidity of the lysosomal suspension.Miconazole {1-[2,4-dichloro-,8-(2,4-dichlorobenzyloxy)-phenethyl]imidazole nitrate} has a broad spectrum of antimicrobial activity against pathogenic and nonpathogenic yeasts, dermatophytes, numerous saprophytic fungi, and gram-positive bacteria (13,25,31). Chemotherapeutic activity of miconazole as a topical applicant is well documented in the treatment of skin and nail infections and vaginal candidiasis (2,5,14,29,32). Studies on the mechanism of biological action of miconazole have been recently reported (9, 10, 28, 33; K. H. Sreedhara Swamy, M. Sirsi, and G. Ramananda Rao, Biochem. Pharmacol., in press). The drug induces leakage of intracellular materials from cells of Candida albicans (28), and at low concentrations it selectively inhibits the uptake of purines and glutamine into these cells (33). Electron microscopic examination of cells of C. albicans exposed to miconazole revealed that the earliest drug-induced alterations are seen at the plasma membrane (9, 10). Further, miconazole has been shown to induce hemolysis of mammalian erythrocytes and binds strongly to erythrocyte membrane lipoproteins (Sreedhara Swamy et al., in press). These investigations clearly indicate that the paramount feature of the biological action of miconazole is its interaction with cell membrane of sensitive organisms, resulting in the impairment of membrane function and eventually cell death.In an attempt to delineate the mode of action of miconazole on cellular and organellar membranes and to obtain a more comprehensive view of biological action, we have carried out studies on the interaction of miconazole with rat liver lysosomes. The present paper describes the effect of miconazole on the integrity of lysosomal membrane, providing further evidence that miconazole interacts with biological systems by impairing membrane function. MATERIALS AND METHODSChemicals. Miconazole nitrate was a gift sample from Ethnor Ltd., Bombay, India. Hexachlorophene, digitonin, 2-phenethylalcohol, p-nitrophenylphosphate, p-nitrocatechol sulfate, phenolphthalein-,-nglucuronide, Triton X-100, and tris(hydroxymethyl)-aminomethane (Trizma base) were purchased from Sigma Chemical Co., St. Louis, Mo. Nystatin was kin...

Primary site of action of ketoconazole on Candida albicans

“…The fact that these compounds interact with cell membranes seems to have been well established by the results of Iwata et al (4,5) and Yamaguchi and Iwata (21,22) with clotrimazole, of Swamy et al (12)(13)(14) with miconazole, and of with econazole. More recently, Van den Bossche et al reported the inhibition of ergosterol biosynthesis by miconazole (17) and ketoconazole (16); ergosterol is the characteristic constituent of yeast cell membranes.…”