Biochemical properties potentially rendering human brain microvasculature vulnerable to proteolytic injury associated with the use of fibrinolytic drugs.
BACKGROUND
Determinants of predisposition to intracranial bleeding in response to the administration of thrombolytic drugs have not yet been well characterized.


OBJECTIVE
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.


METHODS
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.).


RESULTS
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.


CONCLUSIONS
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.
Okada
H
H
Department of Medicine, University of Vermont College of Medicine, Burlington 05446, USA.
Shatos
M A
MA
Doherty
J M
JM
Sobel
B E
BE
Fujii
S
S
D001921:Brain / Q000098:blood supply* / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D001930:Brain Injuries / Q000139:chemically induced / Q000378:metabolism / Q000503:physiopathology; D002374:Catalase / Q000494:pharmacology; D002478:Cells, Cultured; D017077:Culture Media, Conditioned; D003513:Cycloheximide / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology* / Q000503:physiopathology; D004797:Enzyme-Linked Immunosorbent Assay; D005342:Fibrinolysis; D005343:Fibrinolytic Agents / Q000009:adverse effects / Q000378:metabolism*; D016166:Free Radical Scavengers / Q000494:pharmacology; D005609:Free Radicals / Q000378:metabolism; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D008833:Microcirculation / Q000201:enzymology / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D017382:Reactive Oxygen Species / Q000378:metabolism; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D017077:Culture Media, Conditioned; D005343:Fibrinolytic Agents; D016166:Free Radical Scavengers; D005609:Free Radicals; D007375:Interleukin-1; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; D003513:Cycloheximide; D002374:Catalase