Monitoring Oxidative Stress and DNA Damage Induced by Heavy Metals in Yeast Expressing a Redox-Sensitive Green Fluorescent Protein

Reactive oxygen species (ROS) has been proposed to play an important role in heavy metal-associated toxicity and pathology. Conventional methods for determining ambient redox state in cells are usually labor-intensive, precluding real-time or single-cell monitoring changes in intracellular redox poise resulting from either metabolic processes or environmental influences. Redox-sensitive green fluorescent protein (roGFP) was expressed in Saccharomyces cerevisiae and recombinant cells were evaluated in monitoring the changes in the redox state of living cells when challenged with toxicologically relevant metal ions. roGFP expressed in yeast responded not only to typical membrane-permeant oxidants and reductants, but also to toxicological metal ion-induced intracellular redox changes. Moreover, exposure of yeast cells to NaAsO₂ or Pb(NO₃)₂ at concentrations that induced redox changes reported by roGFP caused up to two- to three-fold increases in DNA mutation frequency. This mutagenic effect was largely caused by oxidative stress since blocking the production of hydryl radicals significantly reduced the mutation rate as well as delayed the cell death.