Song Li, Pachter Joel S
Blood-Brain Barrier Laboratory, Department of Pharmacology, University of Connecticut Health Center, Farmington, CT 06030, USA.
Microvasc Res. 2004 Jan;67(1):78-89. doi: 10.1016/j.mvr.2003.07.001.
The chemokine monocyte chemoattractant protein (MCP-1) is recognized to mediate extravasation of mononuclear leukocytes into the brain during a variety of neuroinflammatory conditions. In large part produced by parenchymal neural cells during these disease states, it is unclear how this chemokine can stimulate the migration of circulating leukocytes that lie behind the highly impermeant blood-brain barrier (BBB). Based on the premise that disruption of tight junctions (TJs) could foster leukocyte extravasation, experiments were conducted to test the hypothesis that MCP-1 alters the expression and/or distribution of the TJ-associated proteins zonulae occludens-1 (ZO-1) and occludin in brain microvascular endothelial cells (BMEC) comprising the BBB. Exposure to MCP-1 caused a loss in immunostaining of ZO-1 at inter-endothelial junctional regions in both cultured BMEC and isolated brain microvessels, as well as a similar effect on occludin in cultured BMEC, but did not alter occludin staining in microvessels. In cellular fractionation experiments, ZO-1 associated predominantly with the detergent-resistant cytoskeletal framework (CSK) in both cultured BMEC and brain microvessels, while a slimmer majority of occludin partitioned with the CSK. Following MCP-1 exposure, ZO-1 was reduced in the CSK fraction of cultured BMEC and microvessels, with a shift of ZO-1 to the detergent-soluble fraction in both cases. Occludin exhibited a similar pattern of MCP-1-induced loss and shift from the CSK in cultured BMEC, but remained nearly constant in microvessels. Lastly, expression of caveolin-1, a major structural component of membrane microdomains thought to be functionally complexed with TJs, was additionally altered by MCP-1 treatment of both cultured BMEC and microvessels. These results indicate that, in addition to its chemotactic activity, MCP-1 might alter BBB integrity during CNS inflammation.
趋化因子单核细胞趋化蛋白（MCP-1）被认为在多种神经炎症状态下介导单核白细胞渗入脑内。在这些疾病状态下，该趋化因子大部分由实质神经细胞产生，目前尚不清楚它如何刺激位于高度致密的血脑屏障（BBB）后的循环白细胞迁移。基于紧密连接（TJ）破坏可促进白细胞渗出这一前提，进行了实验以检验MCP-1改变构成BBB的脑微血管内皮细胞（BMEC）中TJ相关蛋白闭合蛋白-1（ZO-1）和闭合蛋白的表达和/或分布这一假设。暴露于MCP-1会导致培养的BMEC和分离的脑微血管中内皮细胞间连接区域的ZO-1免疫染色丧失，对培养的BMEC中的闭合蛋白也有类似影响，但不会改变微血管中闭合蛋白的染色。在细胞分级分离实验中，ZO-1在培养的BMEC和脑微血管中主要与抗去污剂细胞骨架框架（CSK）相关，而闭合蛋白只有较少部分与CSK分配在一起。暴露于MCP-1后，培养的BMEC和微血管的CSK组分中的ZO-1减少，两种情况下ZO-1都向去污剂可溶组分转移。闭合蛋白在培养的BMEC中表现出类似的MCP-1诱导的从CSK丧失和转移模式，但在微血管中几乎保持不变。最后，小窝蛋白-1（一种被认为在功能上与TJ复合的膜微区主要结构成分）的表达在MCP-1处理培养的BMEC和微血管后也发生了改变。这些结果表明，除了其趋化活性外，MCP-1可能在中枢神经系统炎症期间改变BBB的完整性。
