Blei F, Wilson E L, Mignatti P, Rifkin D B
Department of Pediatrics, New York University Medical Center, New York, New York.
J Cell Physiol. 1993 Jun;155(3):568-78. doi: 10.1002/jcp.1041550315.
Recently, a novel class of angiostatic steroids which block angiogenesis in several systems has been described. Since the elaboration of proteases is believed to be an important component of angiogenesis, we tested whether these steroids blocked the fibrinolytic response of endothelial cells to the angiogenic protein, basic fibroblast growth factor [bFGF]). Cultured bovine aortic endothelial (BAE) cells were incubated with bFGF and/or medroxyprogesterone acetate (MPA), an angiostatic steroid which has been shown to inhibit vascularization, collagenolysis, and tumor growth. When bFGF (3 ng/ml) was added to confluent monolayers of BAE cells, plasminogen activator (PA) activity in the medium was increased threefold. In contrast, MPA at 10(-6) M, 10(-7) M, 10(-8) M, and 10(-9) M decreased PA levels in the medium by 83%, 83%, 75%, and 39%, respectively. The stimulation of PA levels in BAE cells by bFGF (3 ng/ml) was abrogated by the presence of 10(-6) M MPA. This decrease in PA activity was found to be mediated by a significant increase in plasminogen activator inhibitor type-1 (PAI-1) production. MPA, therefore, negated one of the important enzymatic activities associated with the angiogenic process. In contrast to the decreased levels of secreted PA in cultures exposed simultaneously to MPA and bFGF, cell-associated PA levels remained high, consistent with earlier observations indicating that PAI-1 does not inhibit cell-associated PA. Thus, angiostatic steroids may exert their inhibitory effects on angiogenesis by increasing the synthesis of PAI-1. This, in turn, inhibits PA activity and, therefore, plasmin generation, which is essential for the invasive aspect of angiogenesis.
最近，已描述了一类新型的血管生成抑制类固醇，其可在多个系统中阻断血管生成。由于蛋白酶的释放被认为是血管生成的一个重要组成部分，我们测试了这些类固醇是否能阻断内皮细胞对血管生成蛋白碱性成纤维细胞生长因子[bFGF]的纤溶反应。将培养的牛主动脉内皮（BAE）细胞与bFGF和/或醋酸甲羟孕酮（MPA）一起孵育，MPA是一种血管生成抑制类固醇，已被证明可抑制血管形成、胶原溶解和肿瘤生长。当将bFGF（3 ng/ml）添加到BAE细胞的汇合单层中时，培养基中的纤溶酶原激活物（PA）活性增加了三倍。相比之下，10⁻⁶ M、10⁻⁷ M、10⁻⁸ M和10⁻⁹ M的MPA分别使培养基中的PA水平降低了83%、83%、75%和39%。10⁻⁶ M MPA的存在消除了bFGF（3 ng/ml）对BAE细胞中PA水平的刺激作用。发现这种PA活性的降低是由1型纤溶酶原激活物抑制剂（PAI-1）产生的显著增加介导的。因此，MPA消除了与血管生成过程相关的一项重要酶活性。与同时暴露于MPA和bFGF的培养物中分泌型PA水平降低相反，细胞相关PA水平仍然很高，这与早期观察结果一致，即PAI-1不抑制细胞相关PA。因此，血管生成抑制类固醇可能通过增加PAI-1的合成来发挥其对血管生成的抑制作用。这反过来又抑制了PA活性，因此抑制了纤溶酶的产生，而纤溶酶的产生对于血管生成的侵袭方面至关重要。
