Air Pollutant 1,2-Naphthoquinone Inhibits Glycolysis Through Peroxide-Mediated Protein Ina ctivation in Human Bronchial Epithelial Cells

Ambient particulate matter (PM) exposure is one of the leading causes of morbidity and mortality in humans. PM-linked health outcomes are thought to be mediated by oxidative stress mechanisms, but the specific redox events involved have not been well-characterized. PM-associated quinones, such as 1,2-naphthoquinine (1,2-NQ), can contribute to cellular oxidative stress through reactive oxygen species (ROS) generation by redox cycling and direct adduction to proteins. We have previously shown that 1,2-NQ induces production of the H 2 O 2 , a potent signaling molecule that can oxidize proteins and inhibit their function. We specifically identified the glycolytic enzyme GAPDH as a target of H 2 O 2 oxidation induced by 1,2-NQ exposure in human epithelial cells and hypothesized that this modification could cause a functional inactivation of the enzyme. GAPDH inactivation by 1,2-NQ leading to inhibition of glycolysis could greatly impair cellular function and growth. Here, we examined the functional effect of 1,2-NQ on glycolysis in the human bronchial epithelial cell line, BEAS-2B. We found that environmentally-relevant doses of 1,2-NQ rapidly inhibited glycolytic function as measured using Seahorse extracellular flux technology. Overexpression of catalase, an enzyme that detoxifies H 2 O 2 , reversed the glycolytic inhibition caused by low doses of 1,2-NQ, suggesting an underlying H 2 O 2 -dependent mechanism to inactivate glycolytic proteins rather than adduction. To our knowledge, this is the first report that exposure to low doses of an environmental toxicant produced a functional inhibition in glycolysis through peroxide-mediated mechanisms. These results could also inspire novel cancer therapies, as cancer cells are highly reliant on glycolysis for energy production. Ultimately, this study will better inform the mechanistic understanding of PM-induced human health effects and help better predict toxicity of similar PM-associated quinones. THIS ABSTRACT DOES NOT NECESSARILY REFLECT EPA POLICY.