Oxidative injury, mediated by the toxic effects of reactive oxygen species (ROS), is implicated in the pathogenesis of many diseases including carcinogenesis, aging and inflammation. The lung is a major target for exogenous oxidants, such as smoke and air pollution, as well as for the endogenous ROS generated by inflammatory cells. In addition, patients succumbing to respiratory failure (e.g. adult respiratory distress syndrome) require supplemental oxygen therapy which further increases the oxidant burden of the lung. Aerobic organisms have developed antioxidant defenses to defend against oxidative stress. One such defense strategy is the up-regulation of various stress-response gene such as heme oxygenase-1 (HO-1), a ubiquitous mammalian enzyme. There has been recent evidence implicating HO-1 as a cytoprotective gene product given its marked induction with oxidant stress and its ability to decrease the pro-oxidant state of the cell, by degrading heme. The by-products of HO-1 activity, bilirubin and ferritin, also have anti-oxidant properties by scavenging radicals and sequestering highly-reactive free iron, respectively. We have observed HO-1 to be highly induced in vivo and in vitro after hyperoxia (95% 0/2). Furthermore, we found HO-1 induction in hyperoxic RAW 264.7 macrophage cells to be transcriptionally regulated and dependent on cooperation between the proximal promoter and a distal enhancer site. Functionally, studies with lung epithelial cells show HO-1 protects against hyperoxic death and preliminary survival studies with transgenic mice show HO-1 offers protection against hyperoxia in vivo as well. We hypothesize hyperoxia up-regulates HO-1 as a protective mechanism. We will examine the transcriptional regulation and functional significance of HO-1 in hyperoxia by addressing the following specific aims: 1) Determine the transcriptional regulation of HO-1 gene expression in response to hyperoxia. 2) Identify the upstream signal transduction pathway(s) involved in the activation of the HO-1 gene after hyperoxia. 3) Determine the functional role of HO-1 after hyperoxia in vitro following hyperoxia. 4) Determine the functional role of HO-1 after hyperoxia in vivo using HO- 1 transgenic and knock-out mice.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Clinical Investigator Award (CIA) (K08)
Project #
5K08HL004034-05
Application #
6526874
Study Section
Special Emphasis Panel (ZHL1-CSR-Y (F1))
Program Officer
Rothgeb, Ann E
Project Start
1998-09-30
Project End
2003-08-31
Budget Start
2002-09-01
Budget End
2003-08-31
Support Year
5
Fiscal Year
2002
Total Cost
$123,525
Indirect Cost
Name
Yale University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
082359691
City
New Haven
State
CT
Country
United States
Zip Code
06520
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Zhang, Xuchen; Shan, Peiying; Sasidhar, Madhu et al. (2003) Reactive oxygen species and extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase mediate hyperoxia-induced cell death in lung epithelium. Am J Respir Cell Mol Biol 28:305-15
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