Phosphoinositide 3-kinase gamma gene knockout impairs postischemic neovascularization and endothelial progenitor cell functions.
OBJECTIVE
We evaluated whether phosphatidylinositol 3-kinase gamma (PI3Kgamma) plays a role in reparative neovascularization and endothelial progenitor cell (EPC) function.


RESULTS
Unilateral limb ischemia was induced in mice lacking the PI3Kgamma gene (PI3Kgamma-/-) or expressing a catalytically inactive mutant (PI3Kgamma(KD/KD)) and wild-type controls (WT). Capillarization and arteriogenesis were reduced in PI3Kgamma-/- ischemic muscles resulting in delayed reperfusion compared with WT, whereas reparative neovascularization was preserved in PI3Kgamma(KD/KD). In PI3Kgamma-/- muscles, endothelial cell proliferation was reduced, apoptosis was increased, and interstitial space was infiltrated with leukocytes but lacked cKit+ progenitor cells that in WT muscles typically surrounded arterioles. PI3Kgamma is constitutively expressed by WT EPCs, with expression levels being upregulated by hypoxia. PI3Kgamma-/- EPCs showed a defect in proliferation, survival, integration into endothelial networks, and migration toward SDF-1. The dysfunctional phenotype was associated with nuclear constraining of FOXO1, reduced Akt and eNOS phosphorylation, and decreased nitric oxide (NO) production. Pretreatment with an NO donor corrected the migratory defect of PI3Kgamma-/- EPCs. PI3Kgamma(KD/KD) EPCs showed reduced Akt phosphorylation, but constitutive activation of eNOS and preserved proliferation, survival, and migration.


CONCLUSIONS
We newly demonstrated that PI3Kgamma modulates angiogenesis, arteriogenesis, and vasculogenesis by mechanisms independent from its kinase activity.
Madeddu
Paolo
P
Bristol Heart Institute, University of Bristol, Upper Maudlin Street, Bristol, BS2 8HW, UK. madeddu@yahoo.com
Kraenkel
Nicolle
N
Barcelos
Luciola S
LS
Siragusa
Mauro
M
Campagnolo
Paola
P
Oikawa
Atsuhiko
A
Caporali
Andrea
A
Herman
Andrew
A
Azzolino
Ornella
O
Barberis
Laura
L
Perino
Alessia
A
Damilano
Federico
F
Emanueli
Costanza
C
Hirsch
Emilio
E
D000818:Animals; D058544:Class Ib Phosphatidylinositol 3-Kinase; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000502:physiology*; D005121:Extremities / Q000098:blood supply; D007511:Ischemia / Q000503:physiopathology*; D007527:Isoenzymes / Q000235:genetics / Q000502:physiology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009130:Muscle, Smooth / Q000502:physiology; D018919:Neovascularization, Physiologic / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000502:physiology*; D013234:Stem Cells / Q000502:physiology*; D019737:Transplants
D007527:Isoenzymes; D019869:Phosphatidylinositol 3-Kinases; D058544:Class Ib Phosphatidylinositol 3-Kinase; C546764:Pik3cg protein, mouse