Abstract 15905: Silencing Prolyl Hydroxylase-1(phd-1) Induces Neovascularization, Reduces Ventricular Remodeling by Stabilization and Activation of Hif-1 Alpha, Nf-Kappab/Hspa12b in the Infarcted Myocardium: A Study With Phd-1 Knockout Mice
Hypoxia-inducible factor (HIF)-prolylhydroxylases (PHDs) are oxygen sensors that regulate the stability of HIF in an oxygen-dependent manner thus mediating cellular adaptive responses to changes in oxygen supply. Three PHD isoforms (PHD1-3) have been identified in mammalian cells. Disease states such as myocardial ischemia-reperfusion and heart failure result in upregulation of PHD1 expression and subsequent HIF-1 stabilization. We examined whether removing PHD1 activity triggers pro-angiogenic and anti-apoptotic mechanisms and prevent ventricular remodeling after myocardial infarction (MI).
Methods: Homozygous PHD1 knockout (KO) and wild type (WT) mice were randomized into (1) WT sham control (sham), (2) KO sham (3) WT MI and (4) KOMI. MI was induced by permanent occlusion of the LAD coronary artery. Sham groups underwent identical time matched surgical procedures without LAD ligation.
Results: We observed increased capillary (3066 ± 364 vs. 2415 ± 92 counts/mm2, P<0.05) and arteriolar (29.41 ± 3.45 vs 19.51 ± 2.65 counts/mm2, P<0.05) density in PHD-1 KO MI mice compared to the WTMI. Echocardiographic analysis revealed increased ejection fraction (42 % vs. 37 %, P<0.01) and fractional shortening (20% vs 18%, P<0.01) in the PHD-1 KO mice as compared to WT 30 days after MI. Gel-shift analysis 8hrs after MI revealed increased HIF-1 alpha DNA binding activity in PHD-1 KO mice compared to WT. Western blot analysis 7 days after MI revealed increased (1.5 fold) expression of HSPA12B, a newly described endothelial angiogenesis regulator and a member of HSP70 family of proteins, and is expressed predominantly in vascular endothelium and essential for angiogenesis and cell migration, in the PHD1 KO mice compared to the WTMI. In vitro matrigel analysis of tuborogenesis with HUVECs pretreated with PHD-1 siRNA exposed to hypoxia demonstrated increased tube formation compared to non-treated cells.
Conclusion: These studies are the first to show that silencing PHD1 promotes angiogenesis, decreases loss of myocardial function after infarction and provides a newly described potential therapeutic target, HSPA12B, in the management of ischemic heart disease.
- © 2011 by American Heart Association, Inc.