Dept, Neurology, University of California, San Francisco & San Francisco Veterans Affairs Medical Center, San Francisco 94121 USA.
J Inflamm (Lond). 2011 Mar 7;8:7. doi: 10.1186/1476-9255-8-7.
We previously showed that microglia damage blood brain barrier (BBB) components following ischemic brain insults, but the underlying mechanism(s) is/are not well known. Recent work has established the contribution of toll-like receptor 4 (TLR4) activation to several brain pathologies including ischemia, neurodegeneration and sepsis. The present study established the requirement of microglia for lipopolysaccharide (LPS) mediated endothelial cell death, and explored pathways involved in this toxicity. LPS is a classic TLR4 agonist, and is used here to model aspects of brain conditions where TLR4 stimulation occurs.
METHODS/RESULTS: In monocultures, LPS induced death in microglia, but not brain derived endothelial cells (EC). However, LPS increased EC death when cocultured with microglia. LPS led to nitric oxide (NO) and inducible NO synthase (iNOS) induction in microglia, but not in EC. Inhibiting microglial activation by blocking iNOS and other generators of NO or blocking reactive oxygen species (ROS) also prevented injury in these cocultures. To assess the signaling pathway(s) involved, inhibitors of several downstream TLR-4 activated pathways were studied. Inhibitors of NF-κB, JAK-STAT and JNK/SAPK decreased microglial activation and prevented cell death, although the effect of blocking JNK/SAPK was rather modest. Inhibitors of PI3K, ERK, and p38 MAPK had no effect.
We show that LPS-activated microglia promote BBB disruption through injury to endothelial cells, and the specific blockade of JAK-STAT, NF-κB may prove to be especially useful anti-inflammatory strategies to confer cerebrovascular protection.
我们之前表明，小胶质细胞在缺血性脑损伤后会破坏血脑屏障（BBB）的成分，但具体机制尚不清楚。最近的研究已经确定了 Toll 样受体 4（TLR4）的激活对包括缺血、神经退行性变和败血症在内的几种脑部疾病的贡献。本研究确定了小胶质细胞在脂多糖（LPS）介导的内皮细胞死亡中的作用，并探讨了参与这种毒性的途径。LPS 是一种经典的 TLR4 激动剂，在此用于模拟 TLR4 刺激发生的脑状况的某些方面。
方法/结果：在单核培养物中，LPS 诱导小胶质细胞死亡，但不诱导脑源性内皮细胞（EC）死亡。然而，当与小胶质细胞共培养时，LPS 会增加 EC 死亡。LPS 导致小胶质细胞中一氧化氮（NO）和诱导型一氧化氮合酶（iNOS）的诱导，但不诱导 EC 中 NO 和诱导型一氧化氮合酶（iNOS）的诱导。通过阻断 iNOS 和其他 NO 生成酶或阻断活性氧（ROS）来抑制小胶质细胞的激活，也可以防止这些共培养物中的损伤。为了评估涉及的信号通路，研究了几种下游 TLR-4 激活途径的抑制剂。NF-κB、JAK-STAT 和 JNK/SAPK 的抑制剂减少了小胶质细胞的激活并防止了细胞死亡，尽管阻断 JNK/SAPK 的效果相当温和。PI3K、ERK 和 p38 MAPK 的抑制剂没有影响。
我们表明，LPS 激活的小胶质细胞通过损伤内皮细胞促进 BBB 破坏，而对 JAK-STAT、NF-κB 的特异性阻断可能被证明是一种特别有用的抗炎策略，可提供脑血管保护。
