Differential Contribution of ROS Production to the Fungicidal Action of Amphotericin B and Micafungin in Candida albicans

J. Argüelles;

Author address: 

Univ. de Murcia, Murcia, Spain

Abstract: 

As well acting according to the well established mechanism, recent evidence suggests that the lethal effect of some clinical antifungals depends on previously unknown targets. In this study, we have examined the hypothetical role played by the intracellular formation of ROS in the fungicidal action carried out by Amphotericin B (AMB) and Micafungin (MF) on the opportunistic yeast Candida albicans, which remains the most prevalent fungal pathogen. The clinical MIC90 for MF and AMB were 0.016 and 0.12 mg/L, respectively. The ROS levels were measured by flow cytometry with dihydrofluorescein diacetate and the level of survival was assessed by counting viable cells. Whereas AMB (0.5-1.0 x MIC) induced a marked production of ROS in parallel with a severe degree of cell killing in the C. albicans SC5314 strain, the fungicidal effect of MF was still effective with only a slight degree of ROS generation. Preincubation with rotenone or thiourea suppressed the generation of ROS and caused a marked increase of cell viability regardless of the antifungal supplied. Simultaneous measurement of a set of well established antioxidant enzymes (catalase, glutathione reductase and superoxide dismutase) revealed a strong AMB-induced activation of the three activities, whereas MF only had a weak stimulating effect. Likewise, AMB but not MF promoted a conspicuous intracellular synthesis of trehalose, the non-reducing disaccharide which acts as a specific protector against oxidative stress in C. albicans. Taken together, our results strongly point to that the induction of an internal oxidative stress in C. albicans through the release of ROS is a contributory factor to the antifungal action of polyenes (AMB) but not echinocandins (MF). Acknowledgements. The experimental work reported here was supported by financial contracts provided by Vitalgaia España, S.L. and Cespa, Servicios Auxiliares de Murcia, S.A. The authors declare that they have no disclosures.
2016

abstract No: 

SUNDAY-433

Full conference title: 

ASM Microbe 2016
    • ASM microbe 1st (2016)