Effects of Neuropeptide Y on Collateral Development in a Swine Model of Chronic Myocardial Ischemia

Abstract

Objective We investigated the role of neuropeptide Y (NPY), abundant in the myocardial sympathetic nervous system and endothelial cells, in angiogenesis during chronic myocardial ischemia.

Methods Adult male Yorkshire swine underwent ameroid constrictor placement on the proximal left circumflex coronary artery. After three weeks, an osmotic pump was placed to deliver either placebo (control, n=8) or NPY3-36 (NPY, n=8) to the collateral dependent region. Five weeks after pump placement, after cardiac catheterization and hemodynamic assessment, the heart was harvested for analysis.

Results NPY treated animals demonstrated increased mean arterial pressures and improved left ventricular function (+dP/dt). Cardiac catheterization demonstrated a significant increase in the blush score in the NPY group (p<0.001). Blood flow to the ischemic myocardium was not different between groups at rest or during ventricular pacing. Immunohistochemical double staining for CD-31 and smooth muscle actin demonstrated an increase in capillary and arteriole formation in NPY treated animals (p=0.02 and p<0.001). Immunoblotting showed a significant upregulation of DPPIV (p=0.009) and NPY receptors 1 (p=0.008), 2 (p=0.02) and 5 (p=0.03) in the NPY treated group. Additionally, there was significant upregulation of VEGF (p=0.04), eNOS (p=0.014), phospho-eNOS(ser1177)(p=0.02), and PDGF (p<0.001) in NPY treated group. The anti-angiogenic factors endostatin and angiostatin were significantly decreased in NPY treated animals (endostatin, p=0.03, angiostatin p=0.04).

Conclusion Exogenous NPY3-36 resulted in improved myocardial function and increased angiogenesis and arteriogenesis by stimulating growth factor, pro-angiogenic receptor upregulation, and decreasing anti-angiogenic expression, but did not increase blood flow to the ischemic myocardium. NPY may act as a good adjunct to primary agents of therapeutic angiogenesis.