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Matrix metalloproteinases and TIMPs are associated with blood-brain barrier opening after reperfusion in rat brain
G A Rosenberg1, E Y Estrada, J E Dencoff
1Departments of Neurology, Cell Biology and Physiology, and Neuroscience, University of New Mexico, Albuquerque, NM 87131, USA grosen@unm.edu
Background And Purpose:
Reperfusion disrupts cerebral capillaries, causing cerebral edema and hemorrhage. Middle cerebral artery occlusion (MCAO) induces the matrix-degrading metalloproteinases, but their role in capillary injury after reperfusion is unknown. Matrix metalloproteinases (MMPs) and tissue inhibitors to metalloproteinases (TIMPs) modulate capillary permeability. Therefore, we measured blood-brain barrier (BBB) permeability, brain water and electrolytes, MMPs, and TIMPs at multiple times after reperfusion.
Methods:
Adult rats underwent MCAO for 2 hours by the suture method. Brain uptake of 14C-sucrose was measured from 3 hours to 14 days after reperfusion. Levels of MMPs and TIMPs were measured by zymography and reverse zymography, respectively, in contiguous tissues. Other rats had water and electrolytes measured at 3, 24, or 48 hours after reperfusion. Treatment with a synthetic MMP inhibitor, BB-1101, on BBB permeability and cerebral edema was studied.
Results:
Brain sucrose uptake increased after 3 and 48 hours of reperfusion, with maximal opening at 48 hours and return to normal by 14 days. There was a correlation between the levels of gelatinase A at 3 hours and the sucrose uptake (P<0.05). Gelatinase A (MMP-2) was maximally increased at 5 days, and TIMP-2 was highest at 5 days. Gelatinase B and TIMP-1 were maximally elevated at 48 hours. The inhibitor of gelatinase B, TIMP-1, was also increased at 48 hours. Treatment with BB-1101 reduced BBB opening at 3 hours and brain edema at 24 hours, but neither was affected at 48 hours.
Conclusions:
The initial opening at 3 hours correlated with gelatinase A levels and was blocked by a synthetic MMP inhibitor. The delayed opening, which was associated with elevated levels of gelatinase B, failed to respond to the MMP inhibitor, suggesting different mechanisms of injury for the biphasic BBB injury.
Insights
Reperfusion after stroke causes brain injury. Matrix metalloproteinases (MMPs) contribute to blood-brain barrier (BBB) damage, with early injury responsive to MMP inhibitors but later injury showing different mechanisms.
Area of Science:
- Neuroscience
- Biochemistry
- Pathology
Background:
- Reperfusion following ischemic stroke can disrupt cerebral capillaries, leading to brain edema and hemorrhage.
- Matrix-degrading metalloproteinases (MMPs) are induced by middle cerebral artery occlusion (MCAO), but their precise role in reperfusion-induced capillary injury remains unclear.
- Matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) are known to regulate capillary permeability.
Purpose of the Study:
- To investigate the role of MMPs and TIMPs in blood-brain barrier (BBB) disruption after reperfusion.
- To measure BBB permeability, brain water and electrolytes, and MMP/TIMP levels at various time points post-reperfusion.
- To evaluate the effect of a synthetic MMP inhibitor on BBB permeability and cerebral edema.
Main Methods:
- Adult rats underwent 2-hour MCAO followed by reperfusion.
- Blood-brain barrier permeability was assessed using 14C-sucrose uptake from 3 hours to 14 days post-reperfusion.
- MMP and TIMP levels were quantified using zymography and reverse zymography, respectively. Brain water and electrolytes were measured, and the effects of MMP inhibitor BB-1101 were assessed.
Main Results:
- Brain sucrose uptake increased at 3 and 48 hours post-reperfusion, peaking at 48 hours and normalizing by 14 days.
- Early BBB opening at 3 hours correlated with elevated gelatinase A (MMP-2) levels.
- Delayed BBB opening at 48 hours was associated with increased gelatinase B levels, and this phase was not affected by the MMP inhibitor.
Conclusions:
- Early BBB opening post-reperfusion is linked to gelatinase A and can be mitigated by MMP inhibitors.
- Delayed BBB injury involves different mechanisms, potentially related to gelatinase B, and is unresponsive to the tested MMP inhibitor.
- These findings suggest a biphasic pattern of BBB injury following MCAO with distinct underlying molecular pathways.