Akt1/protein kinase Bα is critical for ischemic and VEGF-mediated angiogenesis
Eric Ackah, Jun Yu, Stefan Zoellner, Yasuko Iwakiri, Carsten Skurk, Rei Shibata, Noriyuki Ouchi, Rachael M. Easton, Gennaro Galasso, Morris J. Birnbaum, Kenneth Walsh, William C. Sessa
Eric Ackah, Jun Yu, Stefan Zoellner, Yasuko Iwakiri, Carsten Skurk, Rei Shibata, Noriyuki Ouchi, Rachael M. Easton, Gennaro Galasso, Morris J. Birnbaum, Kenneth Walsh, William C. Sessa
View: Text | PDF
Research Article Vascular biology

Akt1/protein kinase Bα is critical for ischemic and VEGF-mediated angiogenesis

Abstract

Akt, or protein kinase B, is a multifunctional serine-threonine protein kinase implicated in a diverse range of cellular functions including cell metabolism, survival, migration, and gene expression. However, the in vivo roles and effectors of individual Akt isoforms in signaling are not explicitly clear. Here we show that the genetic loss of Akt1, but not Akt2, in mice results in defective ischemia and VEGF-induced angiogenesis as well as severe peripheral vascular disease. Akt1 knockout (Akt1–/–) mice also have reduced endothelial progenitor cell (EPC) mobilization in response to ischemia, and reintroduction of WT EPCs, but not EPCs isolated from Akt1–/– mice, into WT mice improves limb blood flow after ischemia. Mechanistically, the loss of Akt1 reduces the basal phosphorylation of several Akt substrates, the migration of fibroblasts and ECs, and NO release. Reconstitution of Akt1–/– ECs with Akt1 rescues the defects in substrate phosphorylation, cell migration, and NO release. Thus, the Akt1 isoform exerts an essential role in blood flow control, cellular migration, and NO synthesis during postnatal angiogenesis.

Authors

Eric Ackah, Jun Yu, Stefan Zoellner, Yasuko Iwakiri, Carsten Skurk, Rei Shibata, Noriyuki Ouchi, Rachael M. Easton, Gennaro Galasso, Morris J. Birnbaum, Kenneth Walsh, William C. Sessa

×

Figure 6

Options: View larger image (or click on image) Download as PowerPoint
Impaired cell migration and NO release in Akt1–/– cells. (A) Migration o...
Impaired cell migration and NO release in Akt1–/– cells. (A) Migration of MLECs was examined in modified Boyden chambers using sphingosine-1-phosphate (S-1-P) as a chemoattractant. Migration of Akt1–/– cells was reduced at all doses examined. Data are mean ± SEM; n = 4 from 3 independent experiments. (B) Migration of lung fibroblasts was examined in the modified Boyden chamber using serum-free DMEM (Basal) or 10% FBS as agonist. (C) Basal production of NO in MLECs (assayed as NO2– in the media) over a 24-hour period was determined by chemiluminescence. Levels of NO2– in media alone were subtracted out. (D) Cells were stimulated with VEGF (50 ng/ml) for 30 minutes, and NO release was quantified by chemiluminescence. For stimulated NO2– release, values were calculated by subtracting out levels obtained with nonstimulated cells. Data are mean ± SEM; n = 9–12 from 3 independent experiments. *P < 0.05; **P < 0.01; ***P < 0.001.