Objective: The tumor suppressor protein p53 regulates angiogenesis and is a key regulatory mediator of cellular apoptosis, proliferation, and growth. p53 expression is induced in response to ischemia; however, its role in regulating ischemia-induced angiogenesis and arteriogenesis remains undefined. The objective of this study was to define the role of p53 in regulating ischemia-induced angiogenesis and arteriogenesis and to identify mechanisms by which this regulation occurs in vivo. Methods: Surgically induced hindlimb ischemia or mesenteric artery ligation was performed in wild-type (p53 +/+ ) and p53 knockout (p53 −/− ) mice. Limb perfusion and revascularization were assessed by laser Doppler perfusion imaging, capillary density, and collateral artery development. Mesenteric collateral artery flow and development were determined by arterial flow measurement and by histologic analysis, respectively. An in vitro aortic ring assay was performed on p53 +/+ and p53 −/− aortic tissue to evaluate endothelial function. The p53 inhibitor and activator pifithrin-α and quinacrine, respectively, were used to modulate p53 activity in vivo after ischemia. Results: Absence of p53 in mice resulted in increased limb perfusion (P <.05), capillary density (P <.05), and collateral artery development (P <.05) after induction of hindlimb ischemia. In the nonischemic mesenteric artery ligation model of arteriogenesis, p53 expression was induced in collateral arteries and increased arterial blood flow in mice lacking p53 (P <.05). Lack of p53 decreased apoptosis in ischemic hindlimb tissue (P <.05) and increased proangiogenic factors hypoxia-inducible factor 1α and vascular endothelial growth factor (VEGF). Endothelial cell outgrowth in vitro increased in the absence of p53 (P <.05). Pharmacologic augmentation of p53 expression after ischemia impaired perfusion and collateral artery formation and decreased VEGF levels (P <.05). Conversely, inhibition of p53 with pifithrin-α augmented limb perfusion (P <.05) and collateral artery formation (P <.05) and increased protein levels of hypoxia-inducible factor 1α and VEGF. Pharmacologic augmentation and inhibition of p53 had no significant effect in mice lacking p53. Conclusions: p53 negatively regulates ischemia-induced angiogenesis and arteriogenesis. Inhibition of p53 increases ischemia-induced arteriogenesis and limb perfusion and thus represents a potential therapeutic strategy for arterial occlusive disease. Clinical Relevance: This study demonstrates that p53 inhibits the angiogenic and arteriogenic responses to arterial occlusion; p53 inhibits ischemia-induced hypoxia-inducible factor 1α and vascular endothelial growth factor expression; p53 inhibits hypoxia-induced endothelial cell growth and augments apoptosis; and positive and negative pharmacologic modulation of p53 reciprocally regulates limb blood flow and arteriogenesis in response to ischemia. These results identify p53 as an endogenous negative regulator of ischemia-induced angiogenesis and arteriogenesis and a novel pharmacologic target to improve tissue perfusion after ischemia.
- Hypoxia-inducible factor 1α
- Vascular endothelial growth factor