Candidacidal effects of two antimicrobial peptides: histatin 5 causes small membrane defects, but LL-37 causes massive disruption of the cell membrane.
The effects of antimicrobial peptides on artificial membranes have been well-documented; however, reports on the ultrastructural effects on the membranes of micro-organisms are relatively scarce. We compared the effects of histatin 5 and LL-37, two antimicrobial peptides present in human saliva, on the functional and morphological properties of the Candida albicans cell membrane. Fluorescence microscopy and immunogold transmission electron microscopy revealed that LL-37 remained associated with the cell wall and cell membrane, whereas histatin 5 transmigrated over the membrane and accumulated intracellularly. Freeze-fracture electron microscopy revealed that LL-37 severely affected the membrane morphology, resulting in the disintegration of the membrane bilayer into discrete vesicles, and an instantaneous efflux of small molecules such as ATP as well as larger molecules such as proteins with molecular masses up to 40 kDa. The effects of histatin 5 on the membrane morphology were less pronounced, but still resulted in the efflux of nucleotides. As the morphological defects induced by histatin 5 are much smaller than those induced by LL-37, but the efflux of nucleotides is similar at comparable candidacidal concentrations, we suggest that the loss of nucleotides plays an important role in the killing process.
den Hertog
Alice L
AL
Department of Oral Biochemistry, Academic Centre for Dentistry Amsterdam (ACTA), Vrije Universiteit and Universiteit van Amsterdam, Van der Boechorststraat 7, 1081 BT, Amsterdam, The Netherlands. al.denhertog@vumc.nl
van Marle
Jan
J
van Veen
Henk A
HA
Van't Hof
Wim
W
Bolscher
Jan G M
JG
Veerman
Enno C I
EC
Nieuw Amerongen
Arie V
AV
D000935:Antifungal Agents / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects*; D002462:Cell Membrane / Q000187:drug effects*; D054808:Histatins; D009711:Nucleotides; D012471:Salivary Proteins and Peptides / Q000494:pharmacology*; D054804:Cathelicidins
D000935:Antifungal Agents; D023181:Antimicrobial Cationic Peptides; C068075:HTN3 protein, human; D054808:Histatins; D009711:Nucleotides; D012471:Salivary Proteins and Peptides; D054804:Cathelicidins