Biological processes occurring in post-ischemic vasculature commonly initiate events that produce failure of endogenous inflammatory systems, precipitating vascular and parenchymal organ injury. Hypoxia Inducible Factor-1 (HIF-1), a heterodimeric protein consisting of alpha and beta subunits activated in vascular endothelium during hypoxia, modulates expression of genes essential for cell survival (i.e., inducible nitric oxide synthase and heme oxygenase-1) in ischemic environments. Little research to date has established a role for HIF-1 in modulating inflammatory events that occur in post ischemic vasculature. New research leading to submission of this revised application reveals that stabilization of the alpha subunit of HIF-1 dramatically reduces infarct size and polymorphonuclear neutrophil infiltration in post-ischemic rabbit and murine hearts, lnterleukin-8 (IL-8), a pro-inflammatory chemokine consistently associated with post-ischemic vascular injury and organ damage was strikingly repressed by HIF-1 activation in our studies. In vitro experiments using human microvascular endothelial cells suggest that HIF-1 modulates secretion of IL-8 acting directly at a transcriptional level or indirectly through generation of nitric oxide (NO) and carbon monoxide (CO) following induction of nitric oxide synthase and heme oxygenase-1 (HO-1) genes respectively. We hypothesize that: Hypoxia inducible factor-1 acting independently or in concert with key effector genes regulates chemokine expression in reoxygenating microvascular endothelium.
Four aims are proposed in this application: (1) To determine the role of HIF-1 activation in attenuation of cardiac chemokine generation following ischemia/reperfusion; (2) To examine molecular interdependency between NO and CO in regulation of IL-8 expression in reoxygenating microvascular endothelium; (3) To evaluate the role of HIF-1 in modulating HO-1-induced IL-8 generation; (4) To determine the functional significance of IL-8 promoter binding by HIF-1 in microvascular endothelium. The research proposed here will produce substantial new knowledge, establishing HIF-1 as a pivotal molecule in modulation of inflammatory events. Further, the results of this work will open a new era of understanding of the regulation of chemokine induced inflammation and permit the rational design of tools targeted specifically to attenuate post-ischemic vascular injury. ? ?

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL076423-04
Application #
7342378
Study Section
Vascular Cell and Molecular Biology Study Section (VCMB)
Program Officer
Schwartz, Lisa
Project Start
2005-02-09
Project End
2009-01-31
Budget Start
2008-02-01
Budget End
2009-01-31
Support Year
4
Fiscal Year
2008
Total Cost
$353,197
Indirect Cost
Name
Virginia Commonwealth University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
105300446
City
Richmond
State
VA
Country
United States
Zip Code
23298
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Natarajan, Ramesh; Salloum, Fadi N; Fisher, Bernard J et al. (2008) Hypoxia inducible factor-1 upregulates adiponectin in diabetic mouse hearts and attenuates post-ischemic injury. J Cardiovasc Pharmacol 51:178-87
Natarajan, Ramesh; Fisher, Bernard J; Fowler 3rd, Alpha A (2007) Hypoxia inducible factor-1 modulates hemin-induced IL-8 secretion in microvascular endothelium. Microvasc Res 73:163-72
Natarajan, Ramesh; Salloum, Fadi N; Fisher, Bernard J et al. (2007) Activation of hypoxia-inducible factor-1 via prolyl-4 hydoxylase-2 gene silencing attenuates acute inflammatory responses in postischemic myocardium. Am J Physiol Heart Circ Physiol 293:H1571-80
Natarajan, Ramesh; Salloum, Fadi N; Fisher, Bernard J et al. (2006) Hypoxia inducible factor-1 activation by prolyl 4-hydroxylase-2 gene silencing attenuates myocardial ischemia reperfusion injury. Circ Res 98:133-40
Ockaili, Ramzi; Natarajan, Ramesh; Salloum, Fadi et al. (2005) HIF-1 activation attenuates postischemic myocardial injury: role for heme oxygenase-1 in modulating microvascular chemokine generation. Am J Physiol Heart Circ Physiol 289:H542-8