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Investigating Mitochondrial Dysfunction in Human Lung Cells Exposed to Redox-Active PM Components
Citation:
Lavrich, K., E. Corteselli, P. Wages, P. Bromberg, Steve Simmons, E. Gibbs-Flournoy, AND J. Samet. Investigating Mitochondrial Dysfunction in Human Lung Cells Exposed to Redox-Active PM Components. TOXICOLOGY AND APPLIED PHARMACOLOGY. Academic Press Incorporated, Orlando, FL, 342:99-107, (2018).
Impact/Purpose:
This article reports from an in vitro study into the effects of exposure to air pollution electrophiles on cellular bioenergetics. It shows that quinones, ubiquitous environmental contaminants found associated with particulate matter, can impose an oxidative stress on human airway epithelial cells through redox cycling and electrophilic attack of mitochondrial targets. This article also identifies pitfalls associated with the use of extracellular flux analyzer technology to study the effects of xenobiotics. Ultimately, this study provides biological plausibility for the effects of environmental agents on human lung cells and identifies strategies for the elucidation of the adverse outcome pathways for a broad class of air pollutants.
Description:
Exposure to ambient particulate matter (PM) causes cardiopulmonary morbidity and mortality through mechanisms that involve oxidative stress. 1,2-naphthoquinone (1,2-NQ) is a ubiquitous component of PM and a potent redox-active electrophile. We previously reported that 1,2-NQ increases mitochondrial H2O2 production through an unidentified mechanism. We sought to characterize the effects of 1,2-NQ exposure on mitochondrial respiration as a source of H2O2 in human airway epithelial cells. We measured the effects of acute exposure to 1,2-NQ on oxygen consumption rate (OCR) in the human bronchial epithelial cell line BEAS-2B and mitochondrial preparations using extracellular flux analysis. Complex-specific assays and NADPH depletion by glucose deprivation distinguished between mitochondrial and non-mitochondrial oxygen utilization. 1,2-NQ exposure of BEAS cells caused a rapid, marked dose-dependent increase in OCR that was independent of mitochondrial respiration, exceeded the OCR observed after mitochondrial uncoupling, and remained sensitive to NADPH depletion, implicating extra-mitochondrial redox cycling processes. Similar effects were observed with the environmentally relevant redox-cycling quinones 1,4- naphthoquinone and 9,10-phenanthrenequinone, but not with quinones that do not redox cycle, such as 1,4-benzoquinone. In mitochondrial preparations, 1,2-NQ caused a decrease in Complex I-linked substrate oxidation, suggesting impairment of pyruvate utilization or transport, a novel mechanism of mitochondrial inhibition by an environmental exposure. This study also highlights the methodological utility and challenges in the use of extracellular flux analysis to elucidate the mechanisms of action of redox-active electrophiles present in ambient air.
