INJURY-INDUCED 92-KILODALTON GELATINASE AND UROKINASE EXPRESSION IN RAT-BRAIN

BACKGROUND: Proteolytic disruption of the extracellular matrix is impo rtant in pathologic processes. We have shown that activated 72-kilodal ton (kd) type IV collagenase injected intracerebrally attacks brain ex tracellular matrix and opens the blood-brain barrier. Therefore, we te sted the hypothesis that endogenous production of matrix-degrading pro teases may be a factor in secondary brain injury. EXPERIMENTAL DESIGN: Adult rats had a hemorrhagic injury produced by injection of 0.4 unit s of bacterial collagenase into the caudate/putamen. Endogenous produc tion of matrix metal-loproteinases and plasminogen activators (PA) was measured by substrate-gel sodium dodecyl sulfate-polyacrylamide gel e lectrophoresis (zymography) at 1, 4, 8, 16, 24, and 48 hours, and 7 an d 14 days after the injury. RESULTS: Gelatin-containing zymograms had bands of the expected molecular weights from the injected bacterial co llagenase at 1 hour. By 8 hours a new 92-kd gelatinase was seen in zym ograms. EDTA eliminated the 92-kd band, indicating that it was a metal loproteinase. The 92-kd type IV collagenase/gelatinase was maximally i ncreased by 24 hours (p < 0.0001). Plasminogen-casein zymography showe d 40- and 60-kd bands from PA. The 40-kd PA reached a maximum at 24 ho urs (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-plasmin ogen activator expression in brain. We propose that metalloproteinases and serine proteases take part in a proteolytic cascade that breaks d own extracellular matrix, opening the blood-brain barrier with seconda ry brain edema and cell death.