Abdullah Zuraidah, Bayraktutan Ulvi
Stroke, Division of Clinical Neuroscience, University of Nottingham, UK.
Stroke, Division of Clinical Neuroscience, University of Nottingham, UK.
Mol Cell Neurosci. 2014 Jul;61:72-84. doi: 10.1016/j.mcn.2014.06.002. Epub 2014 Jun 4.
The pro-inflammatory cytokine TNF-α severely perturbs the integrity of the blood-brain barrier (BBB). This study explored the specific roles of NADPH oxidase and associated downstream effectors by using human brain microvascular endothelial cells (HBMECs) and human astrocytes (HAs), the key components of BBB, alone or in co-cultures to mimic human BBB. Exposure to TNF-α (6h) impaired BBB integrity as evidenced by marked decreases in transendothelial electrical resistance and concurrent increases in paracellular flux which appeared to subside with time (24h). Increased barrier dysfunction concurred with increases in endothelial NADPH oxidase activity, O2(-) production, actin stress fibre formation, MMP-2/9 activities and concomitant decreases in antioxidant (CuZn-SOD and catalase) and tight junction (claudin-5 and occludin) protein expressions. Conversely, TNF-α did not affect astrocytic MMP activities and antioxidant enzyme expressions. Unlike BBB damage, rates of HBMEC and HA apoptosis increased by time. Suppression of NADPH oxidase by apocynin or diphenyleneiodonium prevented TNF-α-evoked morphological changes and apoptosis, attenuated endothelial MMP activity and helped retain usual tight junction protein expression and barrier function. In conclusion, HBMECs constitute the main source of oxidative stress and basement-membrane degrading endopeptidases in inflammatory conditions associated with excessive release of TNF-α where targeting NADPH oxidase may prove extremely beneficial in maintaining proper barrier activity through prevention of cytoskeletal and tight junction reorganisations.
促炎细胞因子肿瘤坏死因子-α（TNF-α）严重扰乱血脑屏障（BBB）的完整性。本研究利用人脑血管内皮细胞（HBMECs）和人星形胶质细胞（HAs）这两种血脑屏障的关键组成部分，单独培养或共培养以模拟人类血脑屏障，探讨了NADPH氧化酶及相关下游效应器的具体作用。暴露于TNF-α（6小时）会损害血脑屏障的完整性，表现为跨内皮电阻显著降低，同时细胞旁通量增加，且这种情况似乎会随时间（24小时）而缓解。屏障功能障碍的增加与内皮NADPH氧化酶活性、超氧阴离子（O2(-)）生成、肌动蛋白应激纤维形成、基质金属蛋白酶-2/9（MMP-2/9）活性增加以及抗氧化剂（铜锌超氧化物歧化酶和过氧化氢酶）和紧密连接（claudin-5和occludin）蛋白表达的同时降低相一致。相反，TNF-α不影响星形胶质细胞的MMP活性和抗氧化酶表达。与血脑屏障损伤不同，HBMEC和HA的凋亡率随时间增加。鱼藤酮或二苯碘鎓对NADPH氧化酶的抑制可防止TNF-α诱发的形态变化和凋亡，减弱内皮MMP活性，并有助于维持正常的紧密连接蛋白表达和屏障功能。总之，在与TNF-α过度释放相关的炎症条件下，HBMECs是氧化应激和降解基底膜的内肽酶的主要来源，靶向NADPH氧化酶可能通过防止细胞骨架和紧密连接的重组来维持适当的屏障活性，从而极具益处。
