Real Time Monitoring of Redox Events in Human Airway Epithelial Cells Exposed to an Environmental Peroxide
On this page:
ABSTRACT-Exposure to air pollutants such as ozone, particulate matter, and secondary organic aerosols (SOA) induces intracellular oxidative stress. Reactive oxygen species play an essential role in maintaining intracellular redox balance by regulating critical signaling pathways. Intracellular redox homeostasis is maintained by a high ratio of reduced to oxidized glutathione (GSH and GSSG, respectively), which is tightly regulated by reducing equivalents such as NADPH. In this study, we investigated the effects of isoprene hydroxy hydroperoxide (ISOPOOH), a known constituent of secondary organic aerosols, on the intracellular redox status of human airway epithelial cells (HAEC). Our approach uses the genetically encoded ratiometric biosensors roGFP, iNAP1, and HyPER to monitor changes in intracellular redox endpoints including the glutathione redox potential (EGSH), and fluxes in NADPH and H2O2, respectively. Exposure of HAEC to ISOPOOH induced oxidation of intracellular glutathione that was markedly potentiated by glucose deprivation. Spontaneous recovery of EGSH was observed initially but not upon exposure to higher ISOPOOH concentrations, suggesting irreversible changes with sustained oxidative stress. Strikingly, addition of 1 mM glucose following ISOPOOH challenge induced rapid and complete restoration of EGSH, which was accompanied by increased NADPH levels, as reported by iNAP1. Furthermore, ISOPOOH-induced changes in EGSH and NADPH did not lead to increased intracellular H2O2, as measured by HyPER, suggesting that induction of EGSH by ISOPOOH is independent of intracellular H2O2. These findings highlight the early mechanisms involved in the cellular response to environmental peroxides such as ISOPOOH and provide an unprecedented live view of the dynamic regulation of redox homeostasis in human lung cells. THIS ABSTRACT OF A PROPOSED PRESENTATION DOES NOT NECESSARILY REFLECT EPA POLICY.