Live Cell Imaging of Oxidative Stress in Human Airway Epithelial Cells Exposed to Environmental Peroxides

Exposure to air pollution is a leading cause of global morbidity and mortality. Specifically, exposure to fine particulate matter (PM2.5) is known to cause a range of pathological conditions and premature deaths. The largest atmospheric source of PM2.5 is the photooxidation of isoprene, the most abundant non-methane hydrocarbon in the atmosphere, to isoprene hydroxy hydroperoxide (ISOPOOH). ISOPOOH leads to the formation of isoprene-derived secondary organic aerosols (SOA). Previous research has shown that isoprene-derived SOA exposure in human airway epithelial cells (HAEC) induces increased expression of cyclooxygenase-2 and interleukin-8 linking potential inflammation and oxidative stress. Furthermore, it has been demonstrated that isoprene-derived SOA can generated reactive oxygen species and exposure to HAEC leads to activation of Nrf-2 (a genetic transcription factor) and the antioxidant response element. However, the molecular initiating events of ISOPOOH exposure remain unknown. The current study tests the hypothesis that ISOPOOH exposure of HAEC leads to intracellular glutathione oxidation, a marker of oxidative stress. Our experimental approach uses live-cell imaging of HAEC expressing roGFP, a genetically encoded fluorogenic sensor that specifically reports on the changes in the intracellular glutathione redox potential. Exposure of HAEC to micromolar concentrations of ISOPOOH induced a rapid and robust glutathione oxidation independent of the generation of hydrogen peroxide, suggesting ISOPOOH induces lipid peroxidation. Consistent with this, total lipid extracts of ISOPOOH-exposed HAEC showed oxidative potency towards unexposed cells. Furthermore, supplementation of HAEC with polyunsaturated fatty acids exacerbated ISOPOOH-induced glutathione oxidation. These findings demonstrate that ISOPOOH is a potent environmental peroxide that contributes to the oxidative burden posed by exposure of SOA by initiating lipid peroxidation of the plasma membrane in HAEC. THIS ABSTRACT OF A PROPOSED PRESENTATION DOES NOT NECESSARILY REFLECT EPA POLICY

Impact/Purpose

Exposure to air pollution is a leading cause of global morbidity and mortality. Specifically, exposure to fine particulate matter (PM2.5) is known to cause a range of pathological conditions and premature deaths. The largest atmospheric source of PM2.5 is the photooxidation of isoprene, the most abundant non-methane hydrocarbon in the atmosphere, to isoprene hydroxy hydroperoxide (ISOPOOH). ISOPOOH leads to the formation of isoprene-derived secondary organic aerosols (SOA). Previous research has shown that isoprene-derived SOA exposure in human airway epithelial cells (HAEC) induces increased expression of cyclooxygenase-2 and interleukin-8 linking potential inflammation and oxidative stress. These findings demonstrate that ISOPOOH is a potent environmental peroxide that contributes to the oxidative burden posed by exposure of SOA by initiating lipid peroxidation of the plasma membrane in HAEC. 

Citation

Masood, S., P. Bromberg, R. Pennington, A. Gold, Z. Gold, AND J. Samet. Live Cell Imaging of Oxidative Stress in Human Airway Epithelial Cells Exposed to Environmental Peroxides. Society of Toxicology (SOT) Annual Meeting 2022, San Diego, CA, March 23 - 31, 2022.