Effect of antifungal agents on lipid biosynthesis and membrane integrity in Candida albicans

Abstract

Eight antifungal agents were examined for effects on lipid biosynthesis and membrane integrity in Candida albicans. Lipids were labeled in vivo or in vitro with [14C]acetate and analyzed by thin-layer and gas chromatography. Membrane integrity was measured by a recently developed ['4C]aminoisobutyric acid radiolabel release assay. The imidazole antifungal agents miconazole, econazole, clotrimazole, and ketoconazole, at concentrations inhibiting ergosterol biosynthesis (0.1 ,uM), decreased the ratio of unsaturated to saturated fatty acids in vivo but not in vitro. Similarly, naftifine, tolnaftate, and the azasterol A25822B, at concentrations inhibiting ergosterol biosynthesis (10, 100, and 1 ,uM, respectively), decreased the ratio of unsaturated to saturated fatty acids in vivo only. This suggests that the effect on fatty acids observed with ergosterol biosynthesis inhibitors may be secondary to the effect on ergosterol. With imidazoles, oleic acid antagonized inhibition of cell growth but not inhibition of ergosterol. This suggests that, with the C-14 demethylase inhibitors, decreased unsaturated fatty acids, rather than decreased ergosterol, are responsible for growth inhibition. Cerulenin, previously reported to be a potent inhibitor of both fatty acid and ergosterol biosynthesis, was found in the present study to inhibit the former (at 5 ,uM) but not the latter (up to 100 ,uM). Of the antifungal agents tested, econazole and miconazole (at 100 ,uM) produced complete release of[14C]aminoisobutyric acid, which is consistent with membrane damage.

Antifungal activity of ibuprofen alone and in combination with fluconazole against Candida species

“…Several lipophilic antimicrobial agents can exert their activity either through direct damage of the cell membrane or by interfering with metabolic pathways. This is the case, for example, with the lipophilic azoles [30,31], butena®ne [32] and phenothiazines [33,34]. In those studies, the concentrations needed to produce direct membrane damage were higher than those producing metabolic imbalance.…”

Effects of Fluconazole on the Secretome, the Wall Proteome, and Wall Integrity of the Clinical Fungus Candida albicans

“…Conceivably, at a higher concentration, fluconazole could inhibit another cytochrome P450 enzyme, Erg5, which is responsible for a later step in ergosterol synthesis that involves ⌬ 22 -desaturation in the side chain (34). It is further known that at higher azole concentrations, desaturation and elongation of fatty acids are inhibited (19,66), further perturbing cellular membranes and consequently growth. In both experimental setups, azole-treated cultures grew predominantly in the yeast form with some clusters of nondissociated yeast cells.…”

Zeamatin, an antifungal protein from maize with membrane-permeabilizing activity

“…Under these experimental conditions as little as 1 pg zeamatin ml-l produced detectable cell leakage. (Georgopapadakou et al, 1987), and following its release from cells after treatment with zeamatin or the membrane-permeabilizing antifungal drug amphotericin B (Fig. 6b).…”