Individual responses to ozone vary widely with some individuals having a much lower threshold of ozone sensitivity for pulmonary toxicity. Therefore, a complex of individual genetic factors likely controls the transmission and propagation of oxidant signaling following ozone exposure. Epidemiologic studies support the role of the wild-type NADPH quinone oxidoreductase1 (NQO1) genotype as an asthma susceptibility factor in the presence of ozone. NQO1 catalyzes the obligate 2-electron reduction of quinones and is considered an intracellular antioxidant. Our preliminary data demonstrate that NQO1 is required for ozone-induced IL-8/ KC expression, increased neutrophilic airway inflammation, and airway hyperresponsiveness in mice. This poses a conundrum to explain how an oxidoreductase that recycles antioxidants propagates ROS signaling linking oxidant stress to an inflammatory response. We will use primary human airway epithelial cells and mouse (wild-type and NQO1-null) model systems to test the following unprecedented hypothetical mechanism to explain how NQO1 links oxidant stress to epithelial inflammation: NQO1 and ozone-generated ROS are central regulators of airway inflammation following ozone exposure. We propose that NQO1 regulates the intracellular redox environment resulting in a shift in the balance of isoprostanes (isoP). In the presence of NQO1, ROS and F2-isoP activate NF-(B, resulting in increased IL-8/ KC expression and increased neutrophilic inflammation. In the absence of NQO1, the cell favors A2-isoP production, which inhibits NF-(B activation, causing the paradoxical effect of blocking IL-8/ KC expression and neutrophilic inflammation.
The specific aims are:
Aim 1 a: To determine whether following ozone exposure, NQO1 mediates neutrophilic inflammation and airway hyperresponsiveness via upregulation of the neutrophil chemokines KC/ IL-8.
Aim 1 b: To determine whether NQO1 expression in structural airway epithelial cells and/or in hematopoetic cells is required for pulmonary responses to ozone.
Aim 2 a: To determine whether NQO1 alters the cellular redox state, inducing a relative reducing environment as determined by levels of reduced: oxidized (-tocopherol, reduced: oxidized ubiquinone and reduced: oxidized glutathione.
Aim 2 b: To determine whether following ozone exposure, NQO1 causes a shift in isoprostane production with a relative increase in F2- isoP formation and conversely, a loss of NQO1 in vivo, causes increased formation of A2-isoP.
Aim 3 a: To determine whether following ozone exposure, F2-isoP and/or ozone-generated ROS upregulate IL-8/KC expression by NF-(B activation.
Aim 3 b: To determine whether this regulation is abrogated in the absence of NQO1 by A2-isoP inhibition of NF-(B release from I(B.

Public Health Relevance

Ozone is an environmental health threat to vulnerable populations including patients with chronic cardiopulmonary disease. We propose that a candidate for a genetic susceptibility factor related to ozone-induced pulmonary toxicity is NADPH quinone oxidoreductase 1 (NQO1). We hypothesize that NQO1 functions as a gate-keeper in airway epithelial cells to transmit ozone-generated oxidant stress to an inflammatory response which causes ozone-triggered airway disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Environmental Health Sciences (NIEHS)
Type
Research Project (R01)
Project #
7R01ES016836-05
Application #
8707722
Study Section
Special Emphasis Panel (ZRG1-CVRS-H (02))
Program Officer
Nadadur, Srikanth
Project Start
2010-01-01
Project End
2014-11-30
Budget Start
2013-07-01
Budget End
2013-11-30
Support Year
5
Fiscal Year
2013
Total Cost
$64,625
Indirect Cost
$22,248
Name
Virginia Commonwealth University
Department
Pediatrics
Type
Schools of Medicine
DUNS #
105300446
City
Richmond
State
VA
Country
United States
Zip Code
23298
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Kummarapurugu, Apparao B; Fischer, Bernard M; Zheng, Shuo et al. (2013) NADPH:quinone oxidoreductase 1 regulates host susceptibility to ozone via isoprostane generation. J Biol Chem 288:4681-91
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