Effect of miconazole on the structure and function of plasma membrane of Candida albicans

Abstract

The primary mode of action of azoles is the inhibition of cytochrome P‐450 dependent 14α‐demethylase, a key enzyme in ergosterol biosynthesis in fungi. Our results demonstrated that Candida albicans cells grown in the presence of 10 μg ml−1 of miconazole (miconazole‐grown), do not possess ergosterol in their plasma membranes and this ergosterol depletion leads to a drastic change in membrane fluidity as shown by fluorescence polarization measurements and unsaturation index. There was an increase in membrane order in miconazole‐grown cells and a reduced rate of uptake of amino acids. We also checked for membrane permeability changes in normal mid‐log phase cells (normal‐grown) in short incubations (10 min) with 10 μg ml−1 miconazole (miconazole‐incubated). Interestingly, the amino acid uptake rates except that Gly were not affected significantly in these cells. The results suggest that in the miconazole‐incubated cells, the drug is not able to alter the level of ergosterol of inhibit ergosterol biosynthesis during 10 min incubation and therefore the interaction of the drug neither leads to significant disorganization of membrane components, nor affects permease activity, whereas in the miconazole‐grown cells there is ergosterol depletion leading to accumulation of biosynthetic intermediates, resulting in membrane rearrangement thereby causing a major fluidity change. This fluidity change may explain the drastic reduction of amino acid transport in miconazole‐grown cells. To investigate whether the reduction in amino acid transport was only due to change in membrane fluidity, as a consequence of absence of ergosterol, the PM‐ATPase activity was checked in the miconazole‐grown cells and was found to be unaffected, which suggests that changes in amino acid uptake were due to change in membrane fluidity.

Lipidomics of Candida albicans biofilms reveals phase-dependent production of phospholipid molecular classes and role for lipid rafts in biofilm formation

“…Since adhesion to a substrate is an important early step in biofilm formation, lipids that were elevated in early-phase biofilms may be important regulators of fungal adherence in biofilms. In this regard, altered lipid composition is reported to affect Candida adherence (Ghannoum et al , 1986) and nutrient uptake (Ansari & Prasad, 1993; Dudani & Prasad, 1985; Singh et al , 1978). In an early study, Ghannoum et al (1986) showed that lipids from C. albicans and Candida tropicalis , but not from the weakly adherent Candida pseudotropicalis , significantly blocked in vitro adherence of the respective yeast cells to buccal epithelial cells.…”

“…Since adhesion to a substrate is an important early step in biofilm formation, lipids that were elevated in early-phase biofilms may be important regulators of fungal adherence in biofilms. In this regard, altered lipid composition is reported to affect Candida adherence (Ghannoum et al, 1986) and nutrient uptake (Ansari & Prasad, 1993;Dudani & Prasad, 1985;Singh et al, 1978).…”

Nonapoptotic Death of Saccharomyces cerevisiae Cells That Is Stimulated by Hsp90 and Inhibited by Calcineurin and Cmk2 in Response to Endoplasmic Reticulum Stresses

“…Azoles target essential enzymes of the pathogen's endoplasmic reticulum (ER) that are required for biosynthesis of ergosterol (2,51). A major limitation of these drugs is their inability to directly kill cells of most fungal pathogens (20).…”

The effect of antifungal agents and human monocytes on in vitro galactomannan release by Aspergillus spp. in liquid culture medium

“…The effects of fluconazole on the aspergillus cell membrane are unknown. However, in common with all azoles, fluconazole acts on lanosterol 14‐alpha‐demethylase in the plasma membrane of yeast cells, reducing ergosterol content in the plasma membrane (12, 13), and possibly altering the membrane permeability (14–17). Culture of A. terreus with fluconazole resulted in a modest decrease in GM levels.…”