Amphotericin B mediates killing in Cryptococcus neoformans through the induction of a strong oxidative burst

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Sangalli-Leite, Fernanda [UNESP]
Scorzoni, Liliana [UNESP]
Cecilia Mesa-Arango, Ana
Casas, Celia
Herrero, Enrique
Mendes-Giannini, Maria José Soares [UNESP]
Luis Rodriguez-Tudela, Juan
Cuenca-Estrella, Manuel
Zaragoza, Oscar
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Elsevier B.V.
We studied the effects of Amphotericin B (AmB) on Cryptococcus neoformans using different viability methods (CFUs enumeration, XTT assay and propidium iodide permeability). After 1 h of incubation, there were no viable colonies when the cells were exposed to AmB concentrations >= 1 mg/L. In the same conditions, the cells did not become permeable to propidium iodide, a phenomenon that was not observed until 3 h of incubation. When viability was measured in parallel using XTT assay, a result consistent with the CFUs was obtained, although we also observed a paradoxical effect in which at high AmB concentrations, a higher XTT reduction was measured than at intermediate AmB concentrations. This paradoxical effect was not observed after 3 h of incubation with AmB, and lack of XTT reduction was observed at AmB concentrations higher than 1 mg/L. When stained with dihydrofluorescein, AmB induced a strong intracellular oxidative burst. Consistent with oxidative damage, AmB induced protein carbonylation. Our results indicate that in C. neoformans, Amphotericin B causes intracellular damage mediated through the production of free radicals before damage on the cell membrane, measured by propidium iodide uptake. (C) 2011 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.
Cryptococcus neoformans, Amphotericin B, Oxidative burst, XTT, Propidium iodide
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Microbes and Infection. Amsterdam: Elsevier B.V., v. 13, n. 5, p. 457-467, 2011.