Tokuda Haruhiko, Takai Shinji, Hanai Yoshiteru, Harada Atsushi, Matsushima-Nishiwaki Rie, Akamatsu Shigeru, Ohta Toshiki, Kozawa Osamu
Department of Clinical Laboratory, National Hospital for Geriatric Medicine, National Center for Geriatrics and Gerontology, Obu, Aichi 4748511, Japan.
Prostaglandins Leukot Essent Fatty Acids. 2007 Oct-Nov;77(3-4):187-93. doi: 10.1016/j.plefa.2007.10.001. Epub 2007 Nov 5.
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.
我们曾报道过，前列腺素F2α（PGF2α）通过p44/p42丝裂原活化蛋白（MAP）激酶刺激成骨样MC3T3-E1细胞中血管内皮生长因子（VEGF）的合成。此外，我们最近发现，血小板衍生生长因子-BB（PDGF-BB）激活的磷脂酰肌醇3（PI3）-激酶对这些细胞中白细胞介素-6的合成具有负调控作用。在本研究中，我们调查了PDGF-BB对MC3T3-E1细胞中PGF2α诱导的VEGF合成的影响。单独使用时不影响VEGF水平的PDGF-BB，显著增强了PGF2α刺激的VEGF合成。在10至70 ng/ml范围内，PDGF-BB的放大作用呈剂量依赖性。PI3-激酶的特异性抑制剂LY294002或渥曼青霉素本身虽未影响PGF2α刺激的VEGF合成，但显著抑制了PDGF-BB的放大作用。MEK1/2的特异性抑制剂PD98059抑制了PDGF-BB对PGF2α刺激的VEGF合成的放大作用，其程度与使用PD98059时PGF2α的水平相似。PDGF-BB本身可诱导这些细胞中p44/p42 MAP激酶的磷酸化，且PDGF-BB和PGF2α对p44/p42 MAP激酶磷酸化的作用具有加和性。此外，LY294002对PGF2α联合PDGF-BB诱导的p44/p42 MAP激酶磷酸化影响很小。这些结果强烈表明，在成骨细胞中，PGF2α刺激的VEGF合成通过PI3-激酶介导的PDGF-BB信号传导得以放大，且该作用在p44/p42 MAP激酶的下游位点发挥。
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