Abstract 18496: Disruption of Prolyl Hydroxylase-1 Attenuates Ischemia/Reperfusion Injury by Stabilizing HIF-1 Alpha Transcription Factor Followed by Activation of Beta-Catenin/VEGF/Ang-1 and NF-kappaB Signaling in Mice
Hypoxia inducible factor 1alpha (HIF-1alpha) is a transcription factor that regulated by HIF-prolyl 4-hydroxylase(s) (PHDs) in response to changes in oxygen tension. Once activated, HIF-1alpha plays an important role in angiogenesis, proliferation, cell survival and apoptosis. We hypothesized that homozygous disruption of PHD1 (PHD1−/−), could facilitate HIF-1alpha-mediated angiogenesis signaling and protect the heart from ischemia/reperfusion (I/R) injury. Wild type (WT) and PHD1−/− knockout mice were divided into WT time matched control (WTMC), PHD1−/− TMC (PHDTMC), WT I/R (WIR) and PHD1−/− I/R (PHDIR). Isolated hearts from each group were subjected to 30 min of global ischemia followed by 2 h of reperfusion. TMC hearts were perfused for 2h 30 min without I/R. Significant increase in LVDP(59±1vs.55±0.9 mm Hg), dp/dtmax (1270±90vs.769±116 mm Hg/sec) and aortic flow (2.12±0.1vs.0.3±0.2 ml/min) was observed in PHDIR compared with WTIR after 120min of reperfusion. Decreased infarct size (36.6±4vs.45.5±3 %) and apoptotic cardiomyocytes (1.8 fold) were observed in PHDIR compared with WTIR. Real-time q PCR analysis showed significant upregulation in mRNA expression of HIF-1α (1.9 fold), b-catenin (1.4 fold), VEGF (2 fold), Ang-1 (5 fold) and Bcl-2 (2.7 fold) in PHDIR compared to WTIR. Further, gel-shift analysis showed increase in DNA binding activity of HIF-1 alpha and NF-kappaB in PHDIR compared to WTIR. Immunohistochemical analysis showed significant increase in nuclear translocation of b-catenin in PHDIR compared to WTIR. Furthermore, at the basal level, we observed increased cardiac functions, capillary and arteriolar density, VEGF and Ang-1 expression in PHD1−/− mice compared to WT. These findings indicated for the first time that silencing of PHD1 attenuates I/R injury by enhancing angiogenic and anti-apoptotic signaling, probably through upregulation of HIF-1alpha/b-catenin/VEGF/Ang-1/NFkappaB and Bcl-2 pathway.
- © 2010 by American Heart Association, Inc.