Endothelial Cell-Specific Deletion of P2Y ₂ Receptor Promotes Plaque Stability in Atherosclerosis-Susceptible ApoE-Null Mice

Abstract

Objective

Nucleotide P2Y ₂ receptor (P2Y ₂R) contributes to vascular inflammation by increasing vascular cell adhesion molecule (VCAM)-1 expression in endothelial cells (EC), and global P2Y ₂R deficiency prevents fatty streak formation in ApoE ^−/− mice. Since P2Y ₂R is ubiquitously expressed in vascular cells, we investigated the contribution of endothelial P2Y ₂R in the pathogenesis of atherosclerosis.

Approach and Results

EC-specific P2Y ₂R-deficient mice were generated by breeding VEcadherin5-Cre mice with the P2Y ₂R “floxed” mice. Endothelial P2Y ₂R deficiency reduced eNOS activity and significantly altered ATP-and UTP-induced vasorelaxation without affecting vasodilatory responses to acetylcholine. Telemetric blood pressure and echocardiography measurements indicated that EC-specific P2Y ₂R-deficient mice did not develop hypertension. We investigated the role of endothelial P2Y ₂R in the development of atherosclerotic lesions by crossing the EC-specific P2Y ₂R knockout mice onto an ApoE ^−/− background and evaluated lesion development after feeding a standard chow diet for 25 weeks. Histopathological examination demonstrated reduced atherosclerotic lesions in the aortic sinus and entire aorta, decreased macrophage infiltration and increased smooth muscle cell and collagen content leading to the formation of a subendothelial fibrous cap in EC-specific P2Y ₂R-deficient ApoE ^−/− mice. Expression and proteolytic activity of matrix metalloproteinase (MMP)-2 was significantly reduced in atherosclerotic lesions from EC-specific P2Y ₂R-deficient ApoE ^−/− mice. Furthermore, EC-specific P2Y ₂R deficiency inhibited NO production leading to significant increase in SMC migration out of aortic explants.

Conclusions

EC-specific P2Y ₂R-deficiency reduces atherosclerotic burden and promotes plaque stability in ApoE ^−/− mice through impaired macrophage infiltration acting together with reduced MMP-2 activity and increased SMC migration.

Graphical Abstract