Platelet-derived growth factor-BB amplifies PGF2alpha-stimulated VEGF synthesis in osteoblasts: function of phosphatidylinositol 3-kinase.
We have reported that prostaglandin F2alpha (PGF2alpha) stimulates the synthesis of vascular endothelial growth factor (VEGF) via p44/p42 mitogen-activated protein (MAP) kinase in osteoblast-like MC3T3-E1 cells. In addition, we recently showed that phosphatidylinositol 3 (PI3)-kinase activated by platelet-derived growth factor-BB (PDGF-BB) negatively regulates the interleukin-6 synthesis in these cells. In the present study, we investigated the effect of PDGF-BB on the PGF2alpha-induced VEGF synthesis in MC3T3-E1 cells. PDGF-BB, which alone did not affect the levels of VEGF, significantly enhanced the PGF2alpha-stimulated VEGF synthesis. The amplifying effect of PDGF-BB was dose dependent in the range between 10 and 70 ng/ml. LY294002 or wortmannin, specific inhibitors of PI3-kinase, which by itself failed to affect the PGF2alpha-stimulated VEGF synthesis, significantly suppressed the amplification by PDGF-BB. PD98059, a specific inhibitor of MEK1/2, suppressed the amplification by PDGF-BB of the PGF2alpha-stimulated VEGF synthesis similar to the levels of PGF2alpha with PD98059. PDGF-BB itself induced the phosphorylation of p44/p42 MAP kinase in these cells, and the effects of PDGF-BB and PGF2alpha on the phosphorylation of p44/p42 MAP kinase were additive. Moreover, LY294002 had little effect on the phosphorylation of p44/p42 MAP kinase induced by PGF2alpha with PDGF-BB. These results strongly suggest that PGF2alpha-stimulated VEGF synthesis is amplified by PI3-kinase-mediating PDGF-BB signaling in osteoblasts, and that the effect is exerted at a point downstream from p44/p42 MAP kinase.
Tokuda
Haruhiko
H
Department of Clinical Laboratory, National Hospital for Geriatric Medicine, National Center for Geriatrics and Gerontology, Obu, Aichi 4748511, Japan.
Takai
Shinji
S
Hanai
Yoshiteru
Y
Harada
Atsushi
A
Matsushima-Nishiwaki
Rie
R
Akamatsu
Shigeru
S
Ohta
Toshiki
T
Kozawa
Osamu
O
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D000077214:Becaplermin; D002867:Chromones / Q000494:pharmacology; D015237:Dinoprost / Q000494:pharmacology*; D005419:Flavonoids / Q000494:pharmacology; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D020574:Proto-Oncogene Proteins c-sis; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis*; D000077191:Wortmannin
D000730:Androstadienes; D000077214:Becaplermin; D002867:Chromones; D015237:Dinoprost; D005419:Flavonoids; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D042461:Vascular Endothelial Growth Factor A; D000077191:Wortmannin; C467480:vascular endothelial growth factor A, mouse; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one