title: Rac limits TGF-β-induced VEGF synthesis in osteoblasts.
abstract: We previously showed that transforming growth factor-β (TGF-β) stimulates vascular endothelial growth factor (VEGF) synthesis via p44/p42 mitogen-activated protein (MAP) kinase, p38 MAP kinase and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) in osteoblast-like MC3T3-E1 cells. In the present study, we investigated the involvement of Rac, which is a member of the Rho family of small GTPases, in the TGF-β-stimulated VEGF synthesis in MC3T3-E1 cells. TGF-β markedly increased the levels of GTP-bound Rac. NSC23766, a selective inhibitor of Rac-guanine nucleotide exchange factor interaction, significantly increased both the release of VEGF and the mRNA expression levels induced by TGF-β. In addition, the release of VEGF stimulated by TGF-β was amplified in Rac-knock down cells. Meanwhile, SIS3, a specific inhibitor of TGF-β-dependent Smad3 phosphorylation, significantly reduced the TGF-β-stimulated VEGF release. However, the phosphorylation of Smad2 or Smad3 induced by TGF-β was hardly affected by NSC23766. On the other hand, NSC23766 enhanced the TGF-β-induced phosphorylation of p38 MAP kinase without affecting the phosphorylation of p44/p42 MAP kinase or SAPK/JNK. Furthermore, the phosphorylation of p38 MAP kinase induced by TGF-β was markedly upregulated in the Rac-knock down cells. These results strongly suggest that Rac negatively regulates the TGF-β-stimulated VEGF synthesis via the inhibition of p38 MAP kinase in osteoblasts.
authors: Department of Orthopedic Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan; Department of Pharmacology, Gifu University Graduate School of Medicine, Gifu 501-1194, Japan.
authors: Naohiro
authors: N
authors: Yamamoto
authors: Department of Orthopedic Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan.
authors: Takanobu
authors: T
authors: Otsuka
authors: Department of Orthopedic Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan.
authors: Akira
authors: A
authors: Kondo
authors: Department of Pharmacology, Gifu University Graduate School of Medicine, Gifu 501-1194, Japan.
authors: Rie
authors: R
authors: Matsushima-Nishiwaki
authors: Department of Orthopedic Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan; Department of Pharmacology, Gifu University Graduate School of Medicine, Gifu 501-1194, Japan.
authors: Gen
authors: G
authors: Kuroyanagi
authors: Department of Pharmacology, Gifu University Graduate School of Medicine, Gifu 501-1194, Japan.
authors: Osamu
authors: O
authors: Kozawa
authors: Department of Pharmacology, Gifu University Graduate School of Medicine, Gifu 501-1194, Japan; Department of Clinical Laboratory, National Center for Geriatrics and Gerontology, Obu 474-8511, Japan. Electronic address: tokuda@ncgg.go.jp.
authors: Haruhiko
authors: H
authors: Tokuda
mesh_terms: D000634:Aminoquinolines / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D051379:Mice; D009479:Neuropeptides / Q000037:antagonists & inhibitors / Q000502:physiology*; D010006:Osteoblasts / Q000378:metabolism*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D011743:Pyrimidines / Q000494:pharmacology; D015533:Transcriptional Activation; D016212:Transforming Growth Factor beta / Q000502:physiology*; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis* / Q000235:genetics; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000502:physiology*
chemical_list: D000634:Aminoquinolines; C487513:NSC 23766; D009479:Neuropeptides; D011743:Pyrimidines; C484602:Rac1 protein, mouse; D016212:Transforming Growth Factor beta; D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse; D048051:p38 Mitogen-Activated Protein Kinases; D020830:rac1 GTP-Binding Protein
keywords: Osteoblast; Rac; Transforming growth factor-β; Vascular endothelial growth factor