ABSTRACT
One host susceptibility factor for ozone identified in epidemiologic studies is NAD(P)H quinone oxidoreductase 1 (NQO1). We hypothesized that after ozone exposure, NQO1 is required to increase 8-isoprostane (also known as F(2)-isoprostane) production, a recognized marker of ozone-induced oxidative stress, and to enhance airway inflammation and hyperresponsiveness. In this report, we demonstrate that in contrast to wild-type mice, NQO1-null mice are resistant to ozone and have blunted responses, including decreased production of F(2)-isoprostane and keratinocyte chemokine, decreased airway inflammation, and diminished airway hyperresponsiveness. Importantly, these results in mice correlate with in vitro findings in humans. In primary human airway epithelial cells, inhibition of NQO1 by dicumarol blocks ozone-induced F(2)-isoprostane production and IL-8 gene expression. Together, these results demonstrate that NQO1 modulates cellular redox status and influences the biologic and physiologic effects of ozone.
Subject(s)
Bronchi/drug effects , Bronchial Hyperreactivity/enzymology , Epithelial Cells/drug effects , NADPH Dehydrogenase/metabolism , Oxidants/toxicity , Oxidative Stress/drug effects , Ozone/toxicity , Pneumonia/enzymology , Animals , Bronchi/enzymology , Bronchi/physiopathology , Bronchial Hyperreactivity/chemically induced , Bronchial Hyperreactivity/physiopathology , Bronchial Hyperreactivity/prevention & control , Bronchial Provocation Tests , Cells, Cultured , Chemokines/metabolism , Dicumarol/pharmacology , Dinoprost/analogs & derivatives , Dinoprost/metabolism , Enzyme Inhibitors/pharmacology , Epithelial Cells/enzymology , Humans , Interleukin-8/metabolism , Mice , Mice, Inbred C57BL , Mice, Knockout , NAD(P)H Dehydrogenase (Quinone) , NADPH Dehydrogenase/antagonists & inhibitors , NADPH Dehydrogenase/deficiency , NADPH Dehydrogenase/genetics , Oxidation-Reduction , Pneumonia/chemically induced , Pneumonia/physiopathology , Pneumonia/prevention & control , Time FactorsABSTRACT
Neutrophil elastase (NE), a potent neutrophil inflammatory mediator, increases MUC5AC mucin gene expression through undefined pathways involving reactive oxygen species. To determine the source of NE-generated reactive oxygen species, we used pharmacologic inhibitors of oxidoreductases to test whether they blocked NE-regulated MUC5AC mRNA expression. We found that dicumarol, an inhibitor of the NADP(H):quinone oxidoreductase 1 (NQO1), inhibited MUC5AC mRNA expression in A549 lung adenocarcinoma cells and primary normal human bronchial epithelial cells. We further tested the role of NQO1 in mediating NE-induced MUC5AC expression by inhibiting NQO1 expression using short interfering RNA (siRNA). Transfection with siRNA specific for NQO1 suppressed NQO1 expression and significantly abrogated MUC5AC mRNA expression. NE treatment caused lipid peroxidation in A549 cells; this effect was inhibited by pretreatment with dicumarol, suggesting that NQO1 also regulates oxidant stress in A549 cells after NE exposure. NE exposure increased NQO1 protein and activity levels; NQO1 expression and activity were limited to the cytosol and did not translocate to the plasma membrane. Our results indicate that NQO1 has an important role as a key mediator of NE-regulated oxidant stress and MUC5AC mucin gene expression.
