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 2

Options: View larger image (or click on image) Download as PowerPoint
Akt1–/– mice have impaired ischemia-initiated blood flow recovery. (A) B...
Akt1–/– mice have impaired ischemia-initiated blood flow recovery. (A) Blood flow in the gastrocnemius muscle was measured before, immediately after, and at 2 and 4 weeks after left femoral artery resection. Data are expressed as a ratio of the left (ischemic) to right (control) limb perfusion. WT, n = 14; Akt1–/–, n = 12; Akt2–/–, n = 6. (B) Akt1–/– mice developed necrotic toes at 1 week to 2 weeks after left femoral artery resection while Akt2–/– and WT littermate mice did not. (C) Clinical score at 4 weeks after femoral arteriectomy as an index of severity of limb ischemia: 0, normal; 1, pale foot or gait abnormalities; 2, less than half of foot necrotic; 3, more than half of foot necrotic without lower limb necrosis; 4, more than half of foot necrotic with some lower limb necrosis; 5, necrosis or autoamputation of entire lower limb. WT, n = 14; Akt1–/–, n = 12; Akt2–/–, n = 6. (D) Representative lectin staining of capillaries from sections of the gastrocnemius/soleus muscles 4 weeks after femoral ligation in WT, Akt1–/–, and Akt2–/– mice. Magnification, ×200. (E) Quantification of capillary density, calculated as the number of capillaries per muscle fiber. For each animal, 6–8 randomly selected fields (×200) from 3–4 sections were counted; n = 5. **P < 0.01; ***P < 0.001.