title: Phytosphingosine kills Candida albicans by disrupting its cell membrane.
abstract: The mechanism of action of phytosphingosine (PHS), a member of the sphingosine family which has candidacidal activity when added externally, was investigated. Previously, it has been reported that the fungicidal activity of PHS is based on the induction of caspase-independent apoptosis. In contrast, we found that addition of PHS causes a direct permeabilization of the plasma membrane of yeast, highlighted by the influx of the membrane probe propidium iodide, and the efflux of small molecules (i.e., adenine nucleotides) as well as large cellular constituents such as proteins. Freeze-fracture electron microscopy revealed that PHS treatment causes severe damage of the plasma membrane of the cell, which seems to have lost its integrity completely. We also found that PHS reverts the azide-induced insensitivity to histatin 5 (Hst5) of Candida albicans. In a previous study, we had found that the decreased sensitivity to Hst5 of energy-depleted cells is due to rigidification of the plasma membrane, which could be reverted by the membrane fluidizer benzyl alcohol. In line with the increased membrane permeabilization and ultrastructural damage, this reversal of the azide-induced insensitivity by PHS also points to a direct interaction between PHS and the cytoplasmic membrane of C. albicans.
authors.affiliation: Department of Oral Biochemistry, Academic Center for Dentistry Amsterdam (ACTA), VU University Amsterdam and University of Amsterdam, NL-1081 BT Amsterdam, The Netherlands. eci.veerman@vumc.nl
authors.forename: Enno C I
authors.initials: EC
authors.lastname: Veerman
authors.forename: Marianne
authors.initials: M
authors.lastname: Valentijn-Benz
authors.forename: Wim
authors.initials: W
authors.lastname: van't Hof
authors.forename: Kamran
authors.initials: K
authors.lastname: Nazmi
authors.forename: Jan
authors.initials: J
authors.lastname: van Marle
authors.forename: Arie V Nieuw
authors.initials: AV
authors.lastname: Amerongen
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects* / Q000648:ultrastructure; D002462:Cell Membrane / Q000187:drug effects*; D002463:Cell Membrane Permeability / Q000187:drug effects; D054808:Histatins / Q000494:pharmacology; D019810:Sodium Azide / Q000494:pharmacology; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D000935:Antifungal Agents; D054808:Histatins; D019810:Sodium Azide; C012491:phytosphingosine; D013110:Sphingosine