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Rho-kinase inhibitors decrease TGF-beta-stimulated VEGF synthesis through stress-activated protein kinase/c-Jun
Masashi Kuno1, Shinji Takai, Rie Matsushima-Nishiwaki
1Department of Pharmacology, Gifu University Graduate School of Medicine, Gifu, Japan.
Biochemical Pharmacology
|November 11, 2008
Summary
Transforming growth factor-beta (TGF-beta) stimulates vascular endothelial growth factor (VEGF) synthesis in osteoblasts. Rho-kinase regulates this process by activating stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK).
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Transforming growth factor-beta (TGF-beta) is known to stimulate vascular endothelial growth factor (VEGF) synthesis.
- Previous studies identified p44/p42 mitogen-activated protein (MAP) kinase, p38 MAP kinase, and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) as mediators of this process in osteoblasts.
- The role of Rho-kinase in TGF-beta-stimulated VEGF synthesis remained unclear.
Purpose of the Study:
- To investigate the involvement of Rho-kinase in TGF-beta-stimulated VEGF synthesis in osteoblast-like MC3T3-E1 cells.
- To elucidate the specific signaling pathways regulated by Rho-kinase in this context.
Main Methods:
- Treatment of MC3T3-E1 cells with TGF-beta.
- Application of Rho-kinase inhibitors (Y27632 and fasudil).
- Assessment of VEGF synthesis and phosphorylation of key signaling proteins (MYPT-1, p44/p42 MAP kinase, p38 MAP kinase, Smad2, SAPK/JNK) using Western blotting or similar techniques.
Main Results:
- TGF-beta time-dependently induced the phosphorylation of myosin phosphatase targeting subunit (MYPT-1), a Rho-kinase substrate.
- Inhibition of Rho-kinase significantly reduced TGF-beta-stimulated VEGF synthesis and MYPT-1 phosphorylation.
- Rho-kinase inhibitors did not affect TGF-beta-induced phosphorylation of p44/p42 MAP kinase, p38 MAP kinase, or Smad2.
- Rho-kinase inhibition markedly suppressed TGF-beta-induced phosphorylation of SAPK/JNK.
Conclusions:
- Rho-kinase plays a significant role in regulating TGF-beta-stimulated VEGF synthesis in osteoblasts.
- The mechanism involves the activation of SAPK/JNK signaling pathway by Rho-kinase.
- These findings provide new insights into the molecular regulation of VEGF production in bone cells.
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