Calcium dependence of eugenol tolerance and toxicity in Saccharomyces cerevisiae

PLoS One. 2014 Jul 18;9(7):e102712. doi: 10.1371/journal.pone.0102712. eCollection 2014.

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.

MeSH terms

  • Antifungal Agents / pharmacology*
  • Calcium / metabolism*
  • Calcium Channels / metabolism
  • Cell Membrane / drug effects
  • Cell Membrane / metabolism
  • Cytosol / drug effects
  • Cytosol / metabolism
  • Drug Tolerance / physiology
  • Eugenol / pharmacology*
  • Saccharomyces cerevisiae / drug effects*
  • Saccharomyces cerevisiae / metabolism*

Substances

  • Antifungal Agents
  • Calcium Channels
  • Eugenol
  • Calcium

Grants and funding

The authors have no funding or support to report.