Investigating mitochondrial dysfunction in human lung cells exposed to redox-active PM components

Abstract

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 HO production through an unidentified mechanism. We sought to characterize the effects of 1,2-NQ exposure on mitochondrial respiration as a source of HO 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.

Urban air particulate matter induces mitochondrial dysfunction in human olfactory mucosal cells

“…Oxidative stress and mitochondrial dysfunction has been reported to occur in diverse cell types exposed to PM [4,42,[44][45][46][47]. Our findings of increased oxidative stress in hOM cells upon PM exposure are in line with published findings in an immortalized nasal epithelial cell line showing increased levels of ROS upon exposure to PM 2.5-1 [48].…”

“…These studies have demonstrated that exposure to PM triggers oxidative stress and inflammation. Specifically, Lavrich et al reported PM induced functional perturbation in human lung cell mitochondria, which play a critical role in energy metabolism and oxidative stress [4]. However, the exact mechanisms through which the PM drive oxidative stress or inflammation remain largely unknown.…”

Oleic acid and derivatives affect human endothelial cell mitochondrial function and vasoactive mediator production

“…A whole cell mitochondrial stress test was performed (modified from Lavrich KS, Corteselli EM, Wages PA, Bromberg PA, Simmons SO, Gibbs-Flournoy EA and Samet JM [28]) using the Seahorse XF instrument (Agilent Technologies), which measures extracellular oxygen consumption rate (OCR). HUVEC were seeded at 40,000 cells per well in XF24 microplates 2 days prior to the assay and exposed for 24 h prior to assessment, with wells divided into blanks, vehicle control, 50, 100, and 250 μM OA, and 100 μM me-OA or 12-OH OA in EGM-2.…”

Particulate matter and the airway epithelium: the special case of the underground?

“…Furthermore, PM can induce mitochondrial toxicity with consequent overproduction of ROS by mitochondria, dysregulation of the electron transport chain, loss of mitochondrial membrane potential and impaired oxidative phosphorylation [38,39]. Further effects on the mitochondria and ATP generation may manifest directly or indirectly through different mechanisms for water-soluble metallic and water-insoluble organic PM components [40,41], with nuclear factor erythroid 2-related factor 2 (Nrf2) potentially playing an important role in the maintenance of mitochondrial function, as well as more canonically through induction of phase II enzymes [41]. ROS can trigger release of the Nrf2 transcription factor from its cytoplasmic anchor kelch-like ECH-associated protein 1 (KEAP1) through mechanisms which may include direct oxidative attack or non-oxidative mechanisms, followed by binding of Nrf2 to the antioxidant response element, under the control of which are multiple antioxidant and detoxification enzymes including those relating to antioxidant activity (haemoxygenase-1 (HO-1), glutathione peroxidase), glutathione synthesis and (re)cycling (e.g.…”