Mechanism of the Synergistic Effect of Amiodarone and Fluconazole inCandida albicans

Abstract

ABSTRACTThe antiarrhythmic drug amiodarone has been found to have fungicidal activity. InSaccharomyces cerevisiae, its antifungal activity is mediated by calcium overload stress, which leads to a rapid nuclear accumulation of the calcineurin-regulated transcription factorCRZ1. In addition, low doses of amiodarone have been reported to be synergistic with fluconazole in fluconazole-resistantCandida albicans. To establish its mechanism of toxicity inC. albicans, we used expression profiling of key pathway genes to examine cellular responses to amiodarone alone and in combination with fluconazole. Gene expression profiling of 59 genes was done in fiveC. albicansstrains (three fluconazole-susceptible strains and two fluconazole-resistant strains) after amiodarone and/or fluconazole exposure. Of the 59 genes, 27 analyzed showed a significant change (>2-fold) in expression levels after amiodarone exposure. The up- or downregulated genes included genes involved in Ca2+homeostasis, cell wall synthesis, vacuolar/lysosomal transport, diverse pathway regulation, stress response, and pseudohyphal morphogenesis. As expected, fluconazole induces an increase in ergosterol pathway genes expression levels. The combination treatment significantly dampened the transcriptional response to either drug, suggesting that synergism was due to an inhibition of compensatory response pathways. This dampening resulted in a decrease in total ergosterol levels and decreased pseudohyphal formation, a finding consistent with decreased virulence in a murine candidiasis model.