Altogether, this work identifies EP as an enhancer of atherogenesis and defines the Neuraminidase 1/PI3Kγ signalling pathway as a key mediator of this function in vitro and in vivo.

Background/Aims: High-density lipoproteins (HDL) exert multiple cardioprotective functions on the arterial wall, including the promotion of endothelial cell survival and proliferation. Among mechanism contributing to endothelial protection, it has been reported that apolipoprotein A-I (apoA-I), the major protein in HDL, binds and activates the endothelial ecto-F₁-ATPase receptor. This generates extracellular ADP, which in turn promotes endothelial cell survival. In this study we aimed to further investigate the signaling pathway involved downstream of apoA-I-induced ecto-F₁-ATPase activation. Methods: In human umbilical vein endothelial cells (HUVECs), pharmacological and gene silencing approaches were used to study pathways involved downstream ecto-F₁-ATPase activation by apoA-I. Results: ApoA-I and HDL both induced Akt phosphorylation. F₁-ATPase inhibitors such as inhibitory factor 1 and oligomycin completely blocked apoA-I-induced Akt phosphorylaton and significantly blocked HDL-induced phosphorylation, indicating that this signaling pathway is dependent on ecto-F₁-ATPase activation by apoA-I. Further, we were able to specify roles for the P2Y₁-ADPreceptor and the PI3Kβ isoform in this pathway since pharmacological inhibition and silencing of these proteins dramatically inhibited apoA-I-induced Akt phosphorylation and cell proliferation. Conclusion: Altogether, these data highlight a key role of the P2Y₁/PI3Kβ axis in endothelial cell proliferation downstream of ecto-F₁-ATPase activation by apoA-I. Pharmacological targeting of this pathway could represent a promising approach to enhance vascular endothelial protection.