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Dexamethasone regulation of matrix metalloproteinase expression in CNS vascular endothelium
K A Harkness1, P Adamson, J D Sussman
1Division of Biomedical Science, Sheffield Hallam University, Department of Neurology, Royal Hallamshire Hospital, Sheffield, UK.
Abstract:
Matrix metalloproteinases (MMPs) have been implicated in the early breakdown of the blood-brain barrier in neuroinflammatory disease. Although expression of these enzymes by resident glial cells and recruited immune cells has been described, altered expression of MMPs by the CNS vascular endothelial cells may also contribute to barrier disruption. In the present study, the in vitro expression of MMP-2 and -9 as well as tissue inhibitor of metalloproteinase (TIMP)-2 by rat CNS microvascular endothelial cells has been determined and compared with that by endothelial cell lines derived from rat aorta and high endothelial venules. Primary cultures of rat brain microvascular endothelial cells as well as the rat brain (GP8/3.9) and rat retinal endothelial (JG2/1) cell lines constitutively expressed MMP-2, -9 and TIMP-2. In vitro activation of CNS endothelium with the pro-inflammatory cytokines, tumour necrosis factor-alpha and interleukin-1beta, resulted in selective upregulation of MMP-9 activity, whereas no significant changes were seen in MMP-2 or TIMP-2 levels at 24 h. The addition of dexamethasone partially inhibited the cytokine-induced upregulation of MMP-9. Treatment of GP8/3.9 brain endothelial cells with active MMP-9 caused subtle but distinct alterations in the expression of the junctional protein, ZO-1. Quantitative differences found between CNS and non-CNS endothelial cells in the expression of both MMP-2 and -9, and in the expression of TIMP-2 demonstrate that CNS vascular endothelium is functionally distinct from non-CNS endothelium. These results suggest that cytokine-induced upregulation of MMP-9 expression by the CNS vascular endothelium may play a role in the pathogenesis of blood-brain and blood-retinal barrier breakdown in vivo.
Insights
Matrix metalloproteinases (MMPs) like MMP-9 are upregulated in central nervous system (CNS) endothelial cells by inflammation, potentially disrupting the blood-brain barrier. Dexamethasone partially inhibits this MMP-9 increase.
Area of Science:
- Neuroscience
- Cell Biology
- Immunology
Background:
- Matrix metalloproteinases (MMPs) are implicated in blood-brain barrier (BBB) breakdown during neuroinflammation.
- While glial and immune cells express MMPs, CNS vascular endothelial cells may also contribute to barrier disruption.
Purpose of the Study:
- To investigate the expression of MMP-2, MMP-9, and TIMP-2 by rat CNS microvascular endothelial cells.
- To compare CNS endothelial cell expression with non-CNS endothelial cells (aortic and high endothelial venule lines).
- To determine the effect of pro-inflammatory cytokines and dexamethasone on MMP expression in CNS endothelium.
Main Methods:
- Primary cultures of rat brain microvascular endothelial cells and rat brain/retinal endothelial cell lines were used.
- Cells were treated with tumor necrosis factor-alpha, interleukin-1beta, and dexamethasone.
- Expression and activity of MMP-2, MMP-9, and TIMP-2 were analyzed.
- Effects of MMP-9 on junctional protein ZO-1 expression were assessed.
Main Results:
- Rat CNS microvascular endothelial cells constitutively expressed MMP-2, MMP-9, and TIMP-2.
- Pro-inflammatory cytokines selectively upregulated MMP-9 activity in CNS endothelium.
- Dexamethasone partially inhibited the cytokine-induced MMP-9 upregulation.
- MMP-9 altered ZO-1 expression in brain endothelial cells.
- Quantitative differences in MMP and TIMP-2 expression distinguished CNS from non-CNS endothelium.
Conclusions:
- CNS vascular endothelium is functionally distinct from non-CNS endothelium.
- Cytokine-induced MMP-9 upregulation in CNS endothelium may contribute to BBB and blood-retinal barrier breakdown in vivo.
- Targeting MMP-9 could be a therapeutic strategy for neuroinflammatory diseases.