Kim Tack-Joong, Han Hyeong-Jun, Hong Seong-Su, Hwang Ji-Hye, Hwang Bang-Yeon, Yoo Hwan-Soo, Jin Yong-Ri, Lee Jung-Jin, Yu Ji-Yeon, Lee Kwang-Ho, Kang Byoung-Won, Yun Yeo-Pyo
Research Center for Bioresource and Health, College of Pharmacy, Chungbuk National University, Korea.
Biol Pharm Bull. 2007 Apr;30(4):805-9. doi: 10.1248/bpb.30.805.
Platelet derived growth factor (PDGF)-BB is one of the most potent vascular smooth muscle cell (VSMC) proliferative factors, and abnormal VSMC proliferation by PDGF-BB plays an important role in the development and progression of cardiovascular problems, including restenosis after coronary angioplasty and atherosclerosis. Previous phytochemical studies on the stems or root barks of Cudrania tricuspidata (Moraceae) resulted in the isolation of various isoprenylated xanthones and flavonoids, some of which have anti-cancer, hepatoprotective, anti-inflammatory and anti-oxidant activities. In the present study, we investigated the antiproliferative effect of cudratricusxanthone A isolated from the root bark of C. tricuspidata and its underlying mechanism in VSMCs. Antiproliferative effects of cudratricusxanthone A on VSMCs were examined by direct cell counting and [3H]-thymidine incorporation assays. Cudratricusxanthone A inhibited [3H]-thymidine incorporations into DNA in VSMCs that occurred in response to treatment with 50 ng/ml PDGF-BB. PDGF-BB-stimulated DNA synthesis was significantly reduced to 86.1, 80.2, 64.2 and 25.1% at concentrations of 0.1, 1, 2 and 3 microM, respectively. Moreover, pre-treatment with cudratricusxanthone A (0.1-3 microM) suppressed this PDGF-BB-stimulated cell number in a concentration-dependent manner. The inhibition percentages were 11.1, 22.7, 51.3 and 81.5% at the concentrations of 0.1, 1, 2 and 3 microM, respectively. We also investigated the mechanism of antiproliferative effects by cudratricusxanthone A in PDGF-BB-stimulated VSMCs. In Western blot analysis, 50 ng/ml PDGF-BB-stimulated phospholipase C (PLC)gamma1, Ras, and extracellular signal-regulated kinase1/2 (ERK1/2) phosphorylations were inhibited by cudratricusxanthone A (0.1-3 microM). Consisted with these findings, cudratricusxanthone A inhibited PDGF-receptor beta chain (PDGF-Rbeta) phosphorylation induced by PDGF-BB in a concentration-dependent manner. These findings suggest that the inhibitory effects of cudratricusxanthone A on DNA synthesis and proliferation by PDGF-BB-stimulated VSMCs are mediated by the suppressions of the PDGF-Rbeta and its downstream signaling pathways. Our observation may explain in part mechanistic basis for the prevention of cardiovascular diseases, such as atherosclerosis and restenosis after coronary angioplasty by cudratricusxanthone A.
血小板衍生生长因子（PDGF）-BB是最有效的血管平滑肌细胞（VSMC）增殖因子之一，PDGF-BB引起的VSMC异常增殖在心血管疾病的发生和发展中起重要作用，包括冠状动脉血管成形术后再狭窄和动脉粥样硬化。先前对柘树（桑科）茎或根皮的植物化学研究导致分离出各种异戊烯基化的呫吨酮和黄酮类化合物，其中一些具有抗癌、保肝、抗炎和抗氧化活性。在本研究中，我们研究了从柘树根皮中分离出的柘树黄酮A对VSMC的抗增殖作用及其潜在机制。通过直接细胞计数和[3H]-胸苷掺入试验检测柘树黄酮A对VSMC的抗增殖作用。柘树黄酮A抑制了50 ng/ml PDGF-BB处理后VSMC中[3H]-胸苷掺入DNA的过程。在0.1、1、2和3 microM浓度下，PDGF-BB刺激的DNA合成分别显著降低至86.1%、80.2%、64.2%和25.1%。此外，用柘树黄酮A（0.1-3 microM）预处理以浓度依赖的方式抑制了这种PDGF-BB刺激的细胞数量。在0.1、1、2和3 microM浓度下，抑制百分比分别为11.1%、22.7%、51.3%和81.5%。我们还研究了柘树黄酮A在PDGF-BB刺激的VSMC中抗增殖作用的机制。在蛋白质印迹分析中，0.1-3 microM的柘树黄酮A抑制了50 ng/ml PDGF-BB刺激的磷脂酶C（PLC）γ1、Ras和细胞外信号调节激酶1/2（ERK1/2）的磷酸化。与这些发现一致，柘树黄酮A以浓度依赖的方式抑制了PDGF-BB诱导的血小板衍生生长因子受体β链（PDGF-Rβ）的磷酸化。这些发现表明，柘树黄酮A对PDGF-BB刺激的VSMC的DNA合成和增殖的抑制作用是通过抑制PDGF-Rβ及其下游信号通路介导的。我们的观察结果可能部分解释了柘树黄酮A预防心血管疾病（如动脉粥样硬化和冠状动脉血管成形术后再狭窄）的机制基础。
