and Purpose-Stroke-induced blood-brain barrier (BBB)-disruption can contribute to further progression of cerebral damage. There is rising evidence for a strong involvement of chemokines in postischemic BBB-breakdown. In a previous study, we showed that monocyte chemoattractant protein-1 (MCP-1)-deficiency results in a markedly reduced inflammatory reaction with decreased levels of interleukin-6, interleukin-1β, and granulocyte colony-stimulating factor after experimental stroke. With MCP-1 as

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... e of the key players in stroke-induced inflammation, in this study, we investigated the influence of MCP-1 on poststroke BBB-disruption as well as transcription/translation of BBB-related genes/proteins after cerebral ischemia. Methods-Sixteen wild-type and 16 MCP-1 −/− mice were subjected to 30 minutes of middle cerebral artery occlusion. By injecting high molecular-tracer, we compared the degree of BBB-disruption after middle cerebral artery occlusion. Realtime polymerase chain reactions and Western blot technique were used to compare tight-junction gene expression, protein secretion, and BBB-leakage. Results-Here, we report that MCP-1-deficiency results in a reduced BBB-leakage and a diminished expression of BBBrelated genes occludin, zonula occludens-1, and zonula occludens-2. Real-time polymerase chain reactions and Western blot analysis revealed elevated claudin-5-levels in MCP-1 −/− animals. MCP-1-deficiency resulted in reduced infarct sizes and an increased vascular accumulation of fluorescein-isothiocyanate-albumin. Conclusions-The results of the study provide further insights into the molecular mechanisms of BBB-opening and may help to better understand the mechanisms of infarct development after cerebral ischemia. (Stroke. 2013;44:2536-2544.) Key Words: brain-blood barrier ◼ brain ischemia ◼ CCL2, claudin-5 ◼ inflammation ◼ occludin