Abstract 1161: PKA-activated p85alpha Prevents Neointimal Hyperplasia after Balloon Endothelial Denudation without Impairing Endothelial Regeneration.
Impaired re-endothelialization of the stented arterial segment seems to be a potential dangerous drawback of drug eluting stents (DES). One way to circumvent this would be the identification of intracellular pathways/molecules that play differential roles on vascular smooth muscle cell (VSMC) and endothelial cell (EC) growth. cAMP/PKA-activated p85α, the regulatory subunit of phosphatidylinositol 3′-Kinase (PI3K), inhibits ras protein function and consequently the proliferation of cancer cells. Importantly, the PI3K pathway has been shown to promote EC survival. Aim of the study were to evaluate:
the differential role, if any, of p85α in the regulation of VSMC vs. EC growth in vitro and
the effects of p85α on vascular healing after balloon injury in vivo. VSMCs and HUVECs were transfected in vitro with plasmids carrying a mutated cAMP/PKA-activated p85α (p85active) or dominant negative p85α (p85DN).
VSMC and HUVEC proliferation and apoptosis were measured by BrdU and TdT staining, respectively. Balloon injury of the right carotid was produced in Wistar rats. Straight after the vascular injury, the balloon-dilated arteries were randomly transfected with p85active (n = 8), dominant negative p85 (p85DN) (n = 8) or green fluorescent protein (GFP, n = 6; controls). Transfection of p85active decreased VSMC proliferation in the absence of cAMP while cAMP inhibition of VSMC growth was prevented by p85DN. p85active formed a stable complex with ras proteins, resulting in a selective switch-off of ras effectors in VSMCs. On the other hand, p85active did not affect HUVEC growth in vitro. Interestingly, p85active significantly reduced VSMC and HUVEC apoptosis in vitro. In both vascular cell lineages, p85active increased while p85DN decreased Akt phosphorylation. Importantly, the in vivo transfection of activated p85-active significantly reduced VSMC proliferation and then neointimal formation after balloon injury. Finally, arterial healing with endothelial regeneration of the injured segment occurred normally despite p85-active efficient transfection. In conclusions, cAMP-PKA-activated p85α has protective vascular effects reducing neointimal formation without affecting endothelial regeneration following arterial injury.