Abstract 3638: Pitavastatin Augments Angiogenetic Activity in Human Endothelial Cells via Notch Signal Activation

We have reported that Notch1 plays an important role in embryonic vasculogenesis and the activation of endothelial Notch1, which is induced by crosstalk between VEGF-mediated activation of PI3K/Akt and gamma-secretase, is essential for postnatal vasculogenesis in response to tissue ischemia. Meanwhile pleiotropic effects of statins, inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, have been recently reported to modulate angiogenesis. However it has been under investigation whether Notch signal would be involved in the effects of statins on angiogenesis. We determined whether Notch1 was required for statin-induced promotion of angiogenesis using hindlimb ischemia model in wild type (WT) and Notch1 heterozygous deficient mice. The statin treatment (pitavastatin, 3mg / kg / day, p.o.) did not efficiently restore blood flow in ischemic limbs in Notch1mutant mice as measured by Laser Doppler image and capillary density analyses although the treatment augmented collateral flow in WT mice. Treatment of human umbilical vein endothelial cells (HUVECs), but not human aortic smooth muscle cells, with pitavastatin (100nM) increased the expression of cleaved Notch1 (active form) and Hes-1 (a downstream transcriptional factor of Notch signaling) within 30 min without an increase in total Notch1 and Notch ligand, Jagged-1. The rapid activation of Notch1 and gamma-secretase by pitavastatin was blocked by mevalonic acid (Mev, 500 uM), and inhibitors of PI3K (LY294002, 10 uM), Akt (SH-5, 10 uM), and gamma-secretase (DAPT, 20 uM). Knockdown of Akt using an siRNA approach also reduced Notch1 activation by pitavastatin. Pitavastatin also augmented endothelial proliferation and tube formation on Matrigel in a dose dependent manner, which were suppressed by an inhibition of gamma-secretase. Pitavastatin activated Notch1 via PI3K-Akt-dependent activation of gamma-secretase in endothelial cells, and stimulated angiogenic activity. Our findings indicate that Notch signaling pathway would be, at least in part, involved in statin-induced augmentation of angiogenesis.