Hayashi K, Berman M, Smith D, el-Ghatit A, Pease S, Kenyon K R
Cornea Unit, Eye Research Institute, Boston, MA.
Curr Eye Res. 1991 May;10(5):381-98. doi: 10.3109/02713689109001747.
Previous studies have suggested that the plasminogen activator (PA)/plasmin system has important roles in the pathogenesis of epithelial defects and stromal ulceration. The current studies were performed to localize PA species and identify them as tissue-type PA (tPA) or urokinase-like PA (uPA) as the two have distinct regulatory properties potentially related to the mechanisms of defect formation and ulceration. To determine the locations and types of PA species, antibodies to tPA or to uPA or the drug amiloride (a drug that inhibits uPA but not tPA) were incorporated into fibrin/fibronectin (Fn) clots overlying frozen sections to block regional fibrinolysis. Normal rabbit eyes showed tPA activity in association with corneal epithelium, corneal endothelium, and ciliary body/iris. After epithelial scrape or alkali burn, corneal tPA activity was detected initially in the defect zone colinear with fibrin/Fn and was symmetrical to resurfacing epithelium. The observation that initial fibrinolysis occurs in the defect zone, known to contain fibrin/Fn, suggests that tPA from blood (limbal vascular endothelium) and/or from corneal epithelium has become bound to (and activated on) the fibrin/Fn. PA activity was also associated with the leading edges of migrating epithelium post-scrape and post-burn and was not inhibited by antibodies to either tPA or uPA but was inhibited by amiloride. After complete closure of the primary defect post-scrape, only tPA appeared to be associated with the epithelium in that all PA activity was inhibited by antibodies to tPA. The observation that leading edge activity post-burn, in correlation with the formation of secondary defects, continues to be inhibitable by amiloride but not by antibodies to tPA suggests that uPA remains abnormally on the leading edge, and that sustained uPA activity in that location results in inappropriate degradation of subepithelial fibrin/Fn to result in a defect. Successful regulation of uPA activity at the leading edge of corneal epithelium post-burn would be expected to be useful therapeutically in the healing of epithelial defects and the prevention of stromal ulceration.
先前的研究表明，纤溶酶原激活剂（PA）/纤溶酶系统在上皮缺损和基质溃疡的发病机制中起重要作用。进行当前研究以定位PA种类，并将它们鉴定为组织型PA（tPA）或尿激酶样PA（uPA），因为这两者具有与缺损形成和溃疡机制潜在相关的不同调节特性。为了确定PA种类的位置和类型，将抗tPA或抗uPA的抗体或药物阿米洛利（一种抑制uPA但不抑制tPA的药物）掺入覆盖冰冻切片的纤维蛋白/纤连蛋白（Fn）凝块中，以阻断局部纤维蛋白溶解。正常兔眼在角膜上皮、角膜内皮和睫状体/虹膜中显示有tPA活性。上皮刮除或碱烧伤后，最初在与纤维蛋白/Fn共线的缺损区检测到角膜tPA活性，且与再生上皮对称。最初的纤维蛋白溶解发生在已知含有纤维蛋白/Fn的缺损区这一观察结果表明，来自血液（角膜缘血管内皮）和/或角膜上皮的tPA已与纤维蛋白/Fn结合（并在其上被激活）。PA活性也与刮除和烧伤后迁移上皮的前沿相关，并且不受抗tPA或抗uPA抗体的抑制，但受阿米洛利抑制。刮除后原发性缺损完全闭合后，似乎只有tPA与上皮相关，因为所有PA活性都受抗tPA抗体抑制。烧伤后前沿活性与继发性缺损形成相关，且仍可被阿米洛利抑制而不能被抗tPA抗体抑制这一观察结果表明，uPA异常地保留在上皮前沿，并且该位置持续的uPA活性导致上皮下纤维蛋白/Fn的不适当降解，从而导致缺损。预计成功调节烧伤后角膜上皮前沿的uPA活性在治疗上皮缺损愈合和预防基质溃疡方面将是有用的。
