Salivary histatin 5 induces non-lytic release of ATP from Candida albicansleading to cell death

Salivary histatins are potent in vitro antifungal proteins and have promise as therapeutic agents against oral candidiasis. We performed pharmacologic al studies directed at understanding the biochemical basis of list 5 candid acidal activity. Three inhibitors of mitochondrial metabolism: carbonyl cya nide p-chlorophenylhydrazone, dinitrophenol, and azide inhibited Hst 5 kill ing of Candida albicans, while not inhibiting cellular ATP production. In c ontrast, Hst 5 caused a drastic reduction of C, albicans intracellular ATP content, which was a result of an efflux of ATP, Carbonyl cyanide p-chlorop henylhydrazone, dinitrophenol, and azide inhibited Hst 5-induced ATP efflux , thus establishing a correlation between ATP release and cell killing. Fur thermore, C, albicans cells were respiring and had polarized membranes at l east 80 min after ATP release, thus implying a non-lytic exit of cellular A TP in response to Hst 5. Based on evidence that transmembrane ATP efflux ca n occur in the absence of cytolysis through a channel-like pathway and that released ATP can act as a cytotoxic mediator by binding to membrane purine rgic receptors, we evaluated whether extracellular ATP released by Hst 5 ma y have further functional role in cell killing. Consistent with this hypoth esis, purinergic agonists BzATP and adenosine 5'O-(thiotriphosphate) induce d loss of C. albicans cell viability and purinergic antagonists prevented H st 5 killing.