Department of Biochemistry, Zhongshan Medical School, Sun Yat-sen University, Guangzhou 510080, Guangdong Province, China.
Apoptosis. 2011 Aug;16(8):846-55. doi: 10.1007/s10495-011-0618-9.
Plasminogen Kringle 5(K5) is a proteolytic fragment of plasminogen, which displays potent anti-angiogenic activities. K5 has been shown to induce apoptosis in proliferating endothelial cells; however the exact mechanism has not been well explored. The present study was designed to elucidate the possible molecular mechanism of K5-induced endothelial cell apoptosis. Our results showed that K5 inhibited basic fibroblast growth factors activated in human umbilical vein endothelial cells (HUVECs), indicating proliferation in a dose-dependent manner and induced endothelial cell death via apoptosis. K5 exposure activated caspase 7, 8 and 9. These results suggested that both the intrinsic mitochondrial apoptosis pathway and extrinsic pathway might be involved in K5-induced apoptosis. K5 reduced mitochondrial membrane potential (MMP) of HUVECs, demonstrating mitochondrial depolarization in HUVECs. K5 increased the ratio of Bak to Bcl-x(L) on mitochondria, decreased the ratio in cytosol, and had no effect on the total amounts of these proteins. K5 also did not effect on Bax/Bcl-2 distribution. K5 increased the ratio of Bak to Bcl-x(L) on mitochondrial that resulted in mitochondrial depolarization, cytochrome c release and consequently the cleavage of caspase 9. These results suggested that K5 induces endothelial cell apoptosis at least in part via activating mitochondrial apoptosis pathway. The regulation of K5 on Bak and Bcl-x(L) distribution may play an important role in endothelial cell apoptosis. These results provide further insight into the anti-angiogenesis roles of K5 in angiogenesis-related ocular diseases and solid tumors.
纤溶酶原kringle5（K5）是纤溶酶原的蛋白水解片段，具有很强的抗血管生成活性。研究表明，K5 可诱导增殖内皮细胞凋亡；然而，其确切机制尚未得到很好的探索。本研究旨在阐明 K5 诱导内皮细胞凋亡的可能分子机制。我们的结果表明，K5 抑制碱性成纤维细胞生长因子激活的人脐静脉内皮细胞（HUVECs），表明增殖呈剂量依赖性，并通过凋亡诱导内皮细胞死亡。K5 暴露激活了半胱天冬酶 7、8 和 9。这些结果表明，K5 诱导的凋亡可能涉及内在的线粒体凋亡途径和外在的途径。K5 降低了 HUVECs 的线粒体膜电位（MMP），表明 HUVECs 中的线粒体去极化。K5 增加了线粒体上 Bak 与 Bcl-x(L)的比值，降低了细胞质中的比值，对这些蛋白的总量没有影响。K5 也不影响 Bax/Bcl-2 的分布。K5 增加了线粒体上 Bak 与 Bcl-x(L)的比值，导致线粒体去极化、细胞色素 c 释放，从而导致 caspase 9 的裂解。这些结果表明，K5 通过激活线粒体凋亡途径至少部分诱导内皮细胞凋亡。K5 对 Bak 和 Bcl-x(L)分布的调节可能在内皮细胞凋亡中起重要作用。这些结果为 K5 在与血管生成相关的眼部疾病和实体肿瘤中的抗血管生成作用提供了进一步的认识。
