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

Abstract

To understand the mechanisms by which 15(S)-hydroxyeicosatetraenoic acid (15(S)- HETE) activates Rac1 in the induction of angiogenesis, we studied the role of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase and αPix. 15(S)-HETE stimulated Rac1 in a sustained manner in human dermal microvascular endothelial cells (HDMVECs). Simvastatin, a potent inhibitor of HMG-CoA reductase, suppressed 15(S)-HETE-induced Rac1 activation in HDMVECsaffecting their migration and tube formation. 15(S)-HETE by inducing HMG-CoAreductase expression caused increased farnesylation and membrane translocation of Rac1 where it became activated by Srcdependent αPix stimulation. Mevalonate rescued 15(S)-HETE-induced Rac1 farnesylation and membrane translocation in HDMVECsandthe migrationandtube formation of these cells from inhibition by simvastatin. Down-regulation of αPix inhibited 15(S)-HETE-induced HDMVEC migration and tube formation. Hind-limb ischemia induced Rac1 farnesylation and activation leading to increased angiogenesis and these effects were blocked by simvastatin and rescued by mevalonate in WT 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 αPix were also compromised at least to some extent in 12/15-Lox-/- mice compared with WT mice in response to hind-limb ischemia. Together, these findings demonstrate for the first time that HMG-CoA reductase plays a determinant role in 12/15-Lox-induced angiogenesis. © 2011 by The American Society of Hematology.