Abstract 131: P2Y 6 Receptor Inhibition Impairs Arteriogenesis

Abstract

Purinergic signaling plays a role in vessel remodeling among developing collateral arteries. We have previously shown that the P2Y 2 receptor, an ATP/UTP receptor, mediates arteriogenesis in a murine model of hindlimb ischemia. Intra-arterial administration of UTP increases perivascular inflammation and macrophage accumulation, necessary early events of arteriogenesis, an effect which was abolished among P2Y 2 -/- mice. Extracellular nucleotides can be dephosphorylated by ectonuclotidases which are expressed in various tissues, converting ATP/UTP into ADP/UDP. Our objective was to identify whether receptors for these derivative nucleotides would also have a role in arteriogenesis. Muscular branches of the caudal femoral artery were explanted from rat and assessed for purinergic receptor expression by immunofluorescence. Baseline expression of P2Y 2 is found among endothelial cells predominantly. Conversely, the P2Y 6 receptor is highly expressed in the media, with no appreciable staining in the endothelium. CD39, an ectonucleotidase, is expressed among VSMCs in developing collateral arteries (Figure). We then sought to identify whether inhibition of the P2Y 6 receptor, the ligand for which is UDP, would alter perfusion recovery after femoral artery ligation (FAL). Selective P2Y 6 receptor antagonist MRS2578 was intraperitoneally delivered via osmotic minipump at a rate of 20 ng/hr. FAL was performed and perfusion recovery monitored over 14 days using laser Doppler perfusion imaging (LDPI). Perfusion recovery was reduced in animals treated with MRS2578 when compared to vehicle (DMSO) at 7 and 14 days (figure). Two (out of 12) animals receiving MRS2578 were euthanized due to gangrene of the hindlimb. We have demonstrated in this work that the P2Y 6 receptor is another mediator of arteriogenesis. Our results also suggest an interesting spatial localization of purinergic receptors among resident vascular cells which may facilitate their function in arteriogenesis.