12/15‐Lipoxygenase gene knockout severely impairs ischemia‐induced angiogenesis due to lack of Rac1 farnesylation

Abstract

Previously, we have reported that 15(S)‐hydroxyeicosatetraenoic acid (15(S)‐HETE)‐induced migration and tube formation of endothelial cells require Rac1 activation. To understand the mechanisms by which 15(S)‐HETE activates Rac1, here, we have studied the role of HMG‐CoA reductase and RhoGFP, α‐Pix. 15(S)‐HETE by inducing HMG‐CoA reductase expression caused increased farnesylation and membrane translocation of Rac1, where it became activated by Src‐dependent α‐Pix stimulation in human dermal microvascular endothelial cells (HDMVECs) and these events enhanced the migration and tube formation of these cells. Mevalonate rescued 15(S)‐HETE‐induced Rac1 farnesylation in HDMVECs and the migration and tube formation of these cells from inhibition by simvastatin. Hind limb ischemia induced Rac1 farnesylation and activation leading to increased angiogenesis and these effects were blocked by simvastatin and rescued by mevalonate in C57BL/6 mice. In contrast, hind limb ischemia failed to induce Rac1 farnesylation and activation as well as angiogenic response in 12/15‐Lox−/− mice. Activation of Src and α‐Pix were also compromised at least to some extent in 12/15‐Lox−/− mice. Together, these findings demonstrate that HMG‐CoA reductase‐dependent farnesylation and α‐Pix‐dependent GDP/GTP exchange of Rac1 is essential for 12/15‐Lox‐12/15 (S)‐HETE‐induced angiogenesis.