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Topographically graded postischemic presence of metalloproteinases is inhibited by hypothermia
Simone Wagner1, Simon Nagel, Britta Kluge
1Department of Neurology University of Heidelberg Medical School, INF 400, 69120, Heidelberg, Germany. simone_wagner@med.uni-heidelberg.de
Abstract:
To test the hypothesis that presence of metalloproteases (MMPs), their inhibitors (TIMPs) and their substrate laminin-5 differs between the ischemic core and the surrounding tissue, we examined the impact of middle cerebral artery occlusion/reperfusion (MCA:O/R) on these molecules in different regions of the infarct. We also investigated the influence of hypothermia on the progression of the ischemic lesion and MMP activity. Brain sections from 64 Wistar rats subjected to MCA:O/R were examined by means of cytohistochemistry and zymography. The artery was occluded for 2 h followed by 3, 5, 8 and 12 h of reperfusion. Well characterized antibodies against laminin-5, MMPs and TIMP-2 were used. A total of 32 rats were treated with hypothermia. The presence of each antigen was related to the following regions of interest: ischemic core with BBB breakdown (I(c)), surrounding ischemic tissue without BBB breakdown (I(r)), and the contralateral non-ischemic region (N). Regions of interest were defined by MRI. The I(c) increased over time at the cost of the I(r). BBB breakdown occurred early in the ischemic core and increased over time. Hypothermia reduced the BBB breakdown at all time points. A graded decreased presence of laminin-5 was observed with 16.5+/-3.7(N)>10+/-2.8(I(r))>4+/-1.4(I(c)) immunopositive microvessels/mm(2) at 3 h of reperfusion. MMP-9 showed a reverse pattern with 0 (N)<4+/-0.8(I(r))<10+/-1.5(I(c)) immunopositive microvessels/mm(2). Hypothermia decreased the MMP activity measured by zymography. Laminin-5 and MMP presence relate directly to the degree of postischemic injury. Hypothermia reduces the conversion from the I(r) to ischemic core and the degree of BBB as well as MMP abundance.
Insights
Metalloproteases (MMPs) and laminin-5 levels vary in ischemic brain tissue, impacting injury. Hypothermia reduces blood-brain barrier breakdown and MMP activity, mitigating stroke progression.
Area of Science:
- Neuroscience
- Biochemistry
- Pathology
Background:
- Matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) play roles in tissue remodeling and degradation.
- Laminin-5 is a key component of basement membranes, crucial for tissue integrity.
- Ischemic stroke involves complex molecular changes in the brain, including alterations in extracellular matrix components.
Purpose of the Study:
- To investigate the differential expression of MMPs, TIMPs, and laminin-5 in the ischemic core versus surrounding tissue after middle cerebral artery occlusion/reperfusion (MCA:O/R).
- To evaluate the impact of hypothermia on the progression of ischemic lesions and MMP activity.
Main Methods:
- Middle cerebral artery occlusion/reperfusion (MCA:O/R) model in Wistar rats (n=64).
- Cytohistochemistry and zymography to analyze laminin-5, MMPs, and TIMP-2.
- Immunohistochemistry to assess antigen presence in ischemic core (I(c)), surrounding ischemic tissue (I(r)), and contralateral non-ischemic region (N).
- Hypothermia treatment in 32 rats.
Main Results:
- A graded decrease in laminin-5 was observed from non-ischemic to ischemic core regions.
- MMP-9 expression showed a reverse pattern, being highest in the ischemic core.
- BBB breakdown increased over time in the ischemic core and was reduced by hypothermia.
- Hypothermia significantly decreased MMP activity and attenuated the expansion of the ischemic core.
Conclusions:
- Laminin-5 and MMP presence correlate directly with the severity of post-ischemic brain injury.
- Hypothermia effectively reduces blood-brain barrier disruption and MMP abundance, thereby limiting ischemic lesion expansion.
