Takahashi A, Taniguchi T, Ishikawa Y, Yokoyama M
First Department of Internal Medicine, Kobe University School of Medicine, Chuo-ku, Kobe, Japan.
Circ Res. 1999 Mar 19;84(5):543-50. doi: 10.1161/01.res.84.5.543.
Tranilast, which is an antiallergic drug, has a potent effect on preventing postangioplasty restenosis. To elucidate this mechanism, we studied the effect of tranilast on the proliferation of vascular smooth muscle cells (SMCs) in vitro and in vivo. Tranilast decreased the growth rate of SMCs stimulated by either 10% FBS or platelet-derived growth factor. The IC50 value, evaluated as cell number, was 100 micromol/L. These inhibitory effects were associated with inhibition of the retinoblastoma gene product (pRb) phosphorylation. Because pRb phosphorylation is regulated by cyclin-dependent kinases (CDK), we investigated CDK2 and CDK4 activities and the expression of CDK inhibitor p21(waf1/cip1/sdi1) (p21). When SMCs were stimulated by 10% FBS or platelet-derived growth factor, CDK2 and CDK4 activities reached a maximum near the G1/S transition. Tranilast suppressed their activities by >80% without reduction of CDK2/cyclin E and CDK4/cyclin D1 protein levels. These inhibitory effects were associated with enhanced expression of p21 and elevated complexing of p21 with CDK2/CDK4. Next, rat balloon-injured carotid artery was analyzed for intimal thickening and p21 expression. Tranilast-treated rats had a 70% (P<0.001) smaller neointima/media area ratio at 14 days after balloon injury compared with the controls. Immunohistochemical staining demonstrated that, in tranilast-treated rats, p21 was already present in the neointima at day 7 and strongly expressed throughout the neointima at day 14. In control rats, p21 was not observed in the neointima at day 7 but was sparsely expressed at day 14. These data demonstrate that inhibition of CDK2/CDK4 activities by the increased expression of p21 may be one mechanism by which tranilast inhibits SMC proliferation and prevents postangioplasty restenosis.
曲尼司特是一种抗过敏药物，对预防血管成形术后再狭窄具有显著作用。为阐明其作用机制，我们研究了曲尼司特在体外和体内对血管平滑肌细胞（SMC）增殖的影响。曲尼司特降低了由10%胎牛血清（FBS）或血小板衍生生长因子刺激的SMC的生长速率。以细胞数量评估的IC50值为100微摩尔/升。这些抑制作用与视网膜母细胞瘤基因产物（pRb）磷酸化的抑制有关。由于pRb磷酸化受细胞周期蛋白依赖性激酶（CDK）调节，我们研究了CDK2和CDK4的活性以及CDK抑制剂p21（waf1/cip1/sdi1）（p21）的表达。当SMC受到10%FBS或血小板衍生生长因子刺激时，CDK2和CDK4的活性在G1/S转换附近达到最大值。曲尼司特抑制它们的活性超过80%，而不降低CDK2/细胞周期蛋白E和CDK4/细胞周期蛋白D1的蛋白水平。这些抑制作用与p21表达增强以及p21与CDK2/CDK4的结合增加有关。接下来，对大鼠球囊损伤的颈动脉进行内膜增厚和p21表达分析。与对照组相比，曲尼司特治疗的大鼠在球囊损伤后14天的新生内膜/中膜面积比小70%（P<0.001）。免疫组织化学染色显示，在曲尼司特治疗的大鼠中，p21在第7天已存在于新生内膜中，并在第14天在整个新生内膜中强烈表达。在对照大鼠中，第7天在新生内膜中未观察到p21，但在第14天稀疏表达。这些数据表明，p21表达增加对CDK2/CDK4活性的抑制可能是曲尼司特抑制SMC增殖并预防血管成形术后再狭窄的一种机制。
