Imaging Intracellular and Intramitochondrial Zinc Concentrations Following Hypoxia/Hypoglycemia with an Expressible Fluorescence Biosensor

Zinc is a “trace” metal necessary for cellular function, but excess free zinc ion is toxic to most cells. We and others have observed that the intra‐ and extra‐cellular concentrations of labile zinc increase dramatically in models of cerebral ischemia. As well, substantial evidence indicates that mitochondrial dysfunction plays a significant role in neuronal death following ischemia. Zinc potently inhibits major mitochondrial enzymes involved in energy production and destruction of reactive oxygen species (ROS) potentially promoting mitochondrial dysfunction. Therefore, we have adapted our expressible fluorescent zinc biosensor to target the mitochondria of PC12 cells, enabling us to ratiometrically image the intramitochondrial zinc concentration at resting (picomolar) levels. We then imaged cytoplasmic and mitochondrial zinc levels in cells following oxygen glucose deprivation (OGD), a widely used model of ischemia. Our data indicates that both the intramitochondrial and cytoplasmic zinc concentrations increase substantially following OGD. Further experiments suggest that the observed increases in zinc are likely due to release from intracellular sources, rather than from an influx of extracellular zinc. Supported by NIH EB03924