Witt Ken A, Mark Karen S, Hom Sharon, Davis Thomas P
Department of Pharmacology, College of Medicine, University of Arizona, Tucson, AZ 85724, USA.
Am J Physiol Heart Circ Physiol. 2003 Dec;285(6):H2820-31. doi: 10.1152/ajpheart.00589.2003. Epub 2003 Aug 7.
Cerebral microvessel endothelial cells that form the blood-brain barrier (BBB) have tight junctions (TJs) that are critical for maintaining brain homeostasis. The effects of initial reoxygenation after a hypoxic insult (H/R) on functional and molecular properties of the BBB and TJs remain unclear. In situ brain perfusion and Western blot analyses were performed to assess in vivo BBB integrity on reoxygenation after a hypoxic insult of 6% O2 for 1 h. Model conditions [blood pressure, blood gas chemistries, cerebral blood flow (CBF), and brain ATP concentration] were also assessed to ensure consistent levels and criteria for insult. In situ brain perfusion revealed that initial reoxygenation (10 min) significantly increased the uptake of [14C]sucrose into brain parenchyma. Capillary depletion and CBF analyses indicated the perturbations were due to increased paracellular permeability rather than vascular volume changes. Hypoxia with reoxygenation (10 min) produced an increase in BBB permeability with associated alterations in tight junctional protein expression. These results suggest that H/R leads to reorganization of TJs and increased paracellular diffusion at the BBB, which is not a result of increased CBF, vascular volume change, or endothelial uptake of marker. Additionally, the tight junctional protein occludin had a shift in bands that correlated with functional changes (i.e., increased permeability) without significant change in expression of claudin-3, zonula occludens-1, or actin. H/R-induced changes in the BBB may result in edema and/or associated pathological outcomes.
构成血脑屏障（BBB）的脑微血管内皮细胞具有紧密连接（TJ），这对于维持脑内稳态至关重要。缺氧损伤（H/R）后的初始复氧对BBB和TJ的功能及分子特性的影响仍不清楚。进行了原位脑灌注和蛋白质印迹分析，以评估在6%氧气条件下缺氧1小时后复氧时体内BBB的完整性。还评估了模型条件[血压、血气化学、脑血流量（CBF）和脑ATP浓度]，以确保损伤的水平和标准一致。原位脑灌注显示，初始复氧（10分钟）显著增加了[14C]蔗糖向脑实质的摄取。毛细血管耗竭和CBF分析表明，这些扰动是由于细胞旁通透性增加而非血管容积变化所致。缺氧复氧（10分钟）导致BBB通透性增加，并伴有紧密连接蛋白表达的改变。这些结果表明，H/R导致TJ重组，BBB处细胞旁扩散增加，这不是CBF增加、血管容积变化或标记物内皮摄取的结果。此外，紧密连接蛋白闭合蛋白的条带发生了移位，这与功能变化（即通透性增加）相关，而闭合蛋白-3、闭锁小带蛋白-1或肌动蛋白的表达没有显著变化。H/R诱导的BBB变化可能导致水肿和/或相关的病理结果。
