Monitoring the Dynamics of Redox Events in Human Airway Epithelial Cells Exposed to an Environmental Peroxide in Real Time
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Reactive oxygen species (ROS) play an essential role in maintaining intracellular redox homeostasis by regulating critical signaling pathways. However, supra-physiological levels of ROS promote oxidative stress and inappropriate oxidation of regulatory thiols. Studies have shown that exposure to ambient air pollutants such as ozone, particulate matter, and secondary organic aerosols (SOA) creates an imbalance in intracellular redox homeostasis, although the mechanism(s) remain poorly understood. Here, we examined the effect of isoprene hydroxy hydroperoxide (ISOPOOH), an environmental peroxide and known constituent of SOA, on the interplay of redox endpoints in human airway epithelial cells (HAECs). Our approach relies on live cell imaging of HAECs expressing genetically encoded ratiometric redox biosensors roGFP, iNAP1, and HyPER. Non-cytotoxic exposure of HAECs to ISOPOOH induced transient increases in the glutathione redox potential (EGSH), which was markedly potentiated by glucose deprivation. ISOPOOH-induced changes in EGSH were not driven by intracellular H2O2. Following ISOPOOH exposure, glucose supplementation rapidly restored EGSH and reductions in NADPH levels, while the 2-deoxyglucose supplementation distinctly impacted restoration of EGSH and NADPH levels. Furthermore, a knockdown of glucose-6-phosphate dehydrogenase (G6PD) did not impact glucose-mediated recovery of EGSH nor NADPH levels. However, a complete knockout of G6PD differentially impaired glucose-mediated recovery of EGSH and NADPH levels. These findings highlight early mechanisms involved in the cellular response to environmental oxidants, such as the peroxide ISOPOOH, while providing a unique live view of the dynamic regulation of redox homeostasis in the human airway. This abstract of a proposed presentation does not necessarily reflect EPA policy.