Calcium dependence of eugenol tolerance and toxicity in Saccharomyces cerevisiae.

Stephen K Roberts,Sean Sandison,Martin Mcainsh,Hanna Cantopher,Stephan Neil Witt

doi:10.1371/journal.pone.0102712

Stephen K Roberts, Sean Sandison + Show 3 more

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https://doi.org/10.1371/journal.pone.0102712

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Journal: PloS one	Publication Date: Jul 18, 2014
Citations: 34	License type: CC BY 4.0

Affiliation: Lancaster University

Abstract

Eugenol is a plant-derived phenolic compound which has recognised therapeutical potential as an antifungal agent. However little is known of either its fungicidal activity or the mechanisms employed by fungi to tolerate eugenol toxicity. A better exploitation of eugenol as a therapeutic agent will therefore depend on addressing this knowledge gap. Eugenol initiates increases in cytosolic Ca2+ in Saccharomyces cerevisiae which is partly dependent on the plasma membrane calcium channel, Cch1p. However, it is unclear whether a toxic cytosolic Ca2+elevation mediates the fungicidal activity of eugenol. In the present study, no significant difference in yeast survival was observed following transient eugenol treatment in the presence or absence of extracellular Ca2+. Furthermore, using yeast expressing apoaequorin to report cytosolic Ca2+ and a range of eugenol derivatives, antifungal activity did not appear to be coupled to Ca2+ influx or cytosolic Ca2+ elevation. Taken together, these results suggest that eugenol toxicity is not dependent on a toxic influx of Ca2+. In contrast, careful control of extracellular Ca2+ (using EGTA or BAPTA) revealed that tolerance of yeast to eugenol depended on Ca2+ influx via Cch1p. These findings expose significant differences between the antifungal activity of eugenol and that of azoles, amiodarone and carvacrol. This study highlights the potential to use eugenol in combination with other antifungal agents that exhibit differing modes of action as antifungal agents to combat drug resistant infections.

Highlights

There is increasing interest in the use of plant-derived antimicrobial compounds as both natural preservatives and in the treatment of fungal infections
To investigate the role of Ca2+ in eugenol toxicity, 10 minute transient exposure of wild type (Jk9-3da) yeast to varying concentrations of eugenol were performed in the presence (10 mM CaCl2; Figure 1B) and absence (10 mM BAPTA; Figure 1 C) of extracellular Ca2+ before immediately transferring to growth media to monitor cell viability
Removal of extracellular Ca2+ had no apparent effect on eugenol toxicity towards yeast suggesting that an influx of Ca2+ across the plasma membrane is unlikely to play a role in eugenol toxicity

Summary

Introduction

There is increasing interest in the use of plant-derived antimicrobial compounds as both natural preservatives and in the treatment of fungal infections. To investigate the role of Ca2+ in eugenol toxicity, 10 minute transient exposure of wild type (Jk9-3da) yeast to varying concentrations of eugenol were performed in the presence (10 mM CaCl2; Figure 1B) and absence (10 mM BAPTA; Figure 1 C) of extracellular Ca2+ before immediately transferring to growth media to monitor cell viability.

Results

Conclusion