Injury-induced 92-kilodalton gelatinase and urokinase expression in rat brain.
BACKGROUND
Proteolytic disruption of the extracellular matrix is important in pathologic processes. We have shown that activated 72-kilodalton (kd) type IV collagenase injected intracerebrally attacks brain extracellular matrix and opens the blood-brain barrier. Therefore, we tested the hypothesis that endogenous production of matrix-degrading proteases may be a factor in secondary brain injury.


METHODS
Adult rats had a hemorrhagic injury produced by injection of 0.4 units of bacterial collagenase into the caudate/putamen. Endogenous production of matrix metalloproteinases and plasminogen activators (PA) was measured by substrate-gel sodium dodecyl sulfate-polyacrylamide gel electrophoresis (zymography) at 1, 4, 8, 16, 24, and 48 hours, and 7 and 14 days after the injury.


RESULTS
Gelatin-containing zymograms had bands of the expected molecular weights from the injected bacterial collagenase at 1 hour. By 8 hours a new 92-kd gelatinase was seen in zymograms. EDTA eliminated the 92-kd band, indicating that it was a metalloproteinase. The 92-kd type IV collagenase/gelatinase was maximally increased by 24 hours (p < 0.0001). Plasminogen-casein zymography showed 40- and 60-kd bands from PA. The 40-kd PA reached a maximum at 24 hours (p < 0.05) and remained elevated for 7 days. Amiloride completely eliminated the 40-kd band and reduced the 60-kd band, suggesting that they were a urokinase-type PA.


CONCLUSIONS
Hemorrhagic injury induces both 92-kd type IV collagenase/gelatinase and 40-kd urokinase-plasminogen activator expression in brain. We propose that metalloproteinases and serine proteases take part in a proteolytic cascade that breaks down extracellular matrix, opening the blood-brain barrier with secondary brain edema and cell death.
Rosenberg
G A
GA
Department of Neurology, University of New Mexico School of Medicine, Albuquerque.
Dencoff
J E
JE
McGuire
P G
PG
Liotta
L A
LA
Stetler-Stevenson
W G
WG
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000201:enzymology*; D001930:Brain Injuries / Q000201:enzymology*; D004591:Electrophoresis, Polyacrylamide Gel; D018093:Gelatinases / Q000737:chemistry / Q000378:metabolism*; D008297:Male; D008970:Molecular Weight; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014568:Urokinase-Type Plasminogen Activator / Q000737:chemistry / Q000378:metabolism*
D000584:Amiloride; D014568:Urokinase-Type Plasminogen Activator; D018093:Gelatinases