Okada H, Shatos M A, Doherty J M, Sobel B E, Fujii S
Department of Medicine, University of Vermont College of Medicine, Burlington 05446, USA.
Coron Artery Dis. 1999 Oct;10(7):437-42. doi: 10.1097/00019501-199910000-00001.
Determinants of predisposition to intracranial bleeding in response to the administration of thrombolytic drugs have not yet been well characterized.
To delineate factors involved, by characterizing susceptibility of human cerebral microvascular endothelium (HCME) to injury associated with inflammatory cytokines, levels of which are typically elevated in blood in patients who have suffered a myocardial infarction or stroke and been treated with thrombolytic drugs.
Elaboration of fibrinolytic system proteins by HCME exposed either to interleukin-1 beta or to tumor necrosis factor-alpha (TNF) in serum-free medium for 24 h was characterized. Cell-conditioned medium was assayed for tissue-type plasminogen activator (t-PA), urokinase-type plasminogen activator (u-PA), and plasminogen activator inhibitor type 1--(PAI-1) by enzyme-linked immunosorbent assay. To determine whether the induction of u-PA was mediated by oxygen-centered radicals, the following were added to media: superoxide dismutase (a scavenger of O2-.), catalase (a scavenger of O2-. and H2O2) and dimethylthiourea (a scavenger of OH.).
Interleukin-1 beta had no effect upon elaboration of fibrinolytic system proteins by HCME. By contrast, TNF selectively increased elaboration of u-PA. Accumulation of t-PA and PAI-1 remained unchanged. Accumulation of u-PA was inhibited by cycloheximide, implying that there was a requirement for protein synthesis. Dimethylthiourea abolished the increase elaboration of u-PA induced by TNF completely, catalase did so partially, and SOD did not do so at all.
The propensity of HCME to elaborate u-PA rather than PAI-1 appears to render cerebral microvasculature particularly vulnerable to proteolytic attack in settings in which inflammatory cytokines are elaborated locally or in which their concentrations in blood are elevated.
溶栓药物给药后颅内出血易感性的决定因素尚未得到充分表征。
通过表征人脑海微血管内皮细胞（HCME）对与炎症细胞因子相关损伤的易感性来确定相关因素，在心肌梗死或中风并接受溶栓药物治疗的患者血液中，炎症细胞因子水平通常会升高。
表征HCME在无血清培养基中暴露于白细胞介素-1β或肿瘤坏死因子-α（TNF）24小时后纤溶系统蛋白的分泌情况。通过酶联免疫吸附测定法检测细胞条件培养基中的组织型纤溶酶原激活剂（t-PA）、尿激酶型纤溶酶原激活剂（u-PA）和纤溶酶原激活剂抑制剂1（PAI-1）。为了确定u-PA的诱导是否由以氧为中心的自由基介导，在培养基中添加了以下物质：超氧化物歧化酶（O2-的清除剂）、过氧化氢酶（O2-和H2O2的清除剂）和二甲基硫脲（OH-的清除剂）。
白细胞介素-1β对HCME分泌纤溶系统蛋白没有影响。相比之下，TNF选择性地增加了u-PA的分泌。t-PA和PAI-1的积累保持不变。u-PA的积累被放线菌酮抑制，这意味着需要蛋白质合成。二甲基硫脲完全消除了TNF诱导的u-PA分泌增加，过氧化氢酶部分消除了这种增加，而超氧化物歧化酶根本没有消除这种增加。
HCME分泌u-PA而非PAI-1的倾向似乎使脑微血管在局部产生炎症细胞因子或血液中炎症细胞因子浓度升高的情况下特别容易受到蛋白水解攻击。
