Activation of phosphatidylinositol 3-kinase/Akt limits FGF-2-induced VEGF release in osteoblasts.
We previously reported that basic fibroblast growth factor (FGF-2) activates stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) and p44/p42 mitogen-activated protein (MAP) kinase, resulting in the release of vascular endothelial growth factor (VEGF) in osteoblast-like MC3T3-E1 cells. In the present study, we investigated the role of Akt/protein kinase B in the FGF-2-stimulated VEGF release in these cells. FGF-2 time-dependently induced the phosphorylation of Akt and GSK-3beta, a downstream element of Akt. The Akt inhibitor, 1L-6-hydroxymethyl-chiro-inositol 2-(R)-2-O-methyl-3-O-octadecylcarbonate, significantly amplified the FGF-2-induced VEGF release, in a dose-dependent manner between 1 and 70microM, while it suppressed the FGF-2-induced phosphorylation of GSK-3beta. The phosphorylation of Akt induced by FGF-2 was markedly attenuated by wortmannin and LY294002, inhibitors of phosphatidylinositol 3-kinase (PI3-kinase) in osteoblast-like MC3T3-E1 cells. Both wortmannin and LY294002 enhanced the FGF-2-induced VEGF release. In addition, Akt inhibitor had no significant effect on the FGF-2-induced phosphorylation of p44/p42 MAP kinase and SAPK/JNK. Furthermore, the FGF-2-induced Akt phosphorylation was not affected by PD98059, a MEK inhibitor, or SP600125, a SAPK/JNK inhibitor. Taken together, our findings strongly suggest that PI3-kinase/Akt plays an inhibitory role in FGF-2-induced VEGF release in osteoblasts.
Takai
Shinji
S
Department of Pharmacology, Gifu University Graduate School of Medicine, Gifu 501-1194, Japan.
Tokuda
Haruhiko
H
Hanai
Yoshiteru
Y
Kozawa
Osamu
O
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D005419:Flavonoids / Q000494:pharmacology; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D010006:Osteoblasts / Q000187:drug effects* / Q000201:enzymology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*; D000077191:Wortmannin
D000730:Androstadienes; D002867:Chromones; D005419:Flavonoids; D009025:Morpholines; D042461:Vascular Endothelial Growth Factor A; D016222:Fibroblast Growth Factor 2; D003609:Dactinomycin; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D019869:Phosphatidylinositol 3-Kinases; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D038362:Glycogen Synthase Kinase 3; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D000077191:Wortmannin