Isolated Amyloid-β(1-42) Protofibrils, But Not Isolated Fibrils, Are Robust Stimulators of Microglia
Isolated Amyloid-β(1-42) Protofibrils, But Not Isolated Fibrils, Are Robust Stimulators of Microglia
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DOI：
10.1021/cn2001238
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发表时间：
2012-04-01
影响因子：
5
通讯作者：
Nichols, Michael R.
中科院分区：
文献类型：
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作者：
Paranjape, Geeta S.;Gouwens, Lisa K.;Nichols, Michael R.
由淀粉样β蛋白（A β）组成的老年斑是阿尔茨海默病（AD）大脑的一个不可动摇的特征。尽管斑块在AD进展中的作用存在重大争议，但在疾病背景下，它们在刺激强烈炎症反应中的作用几乎没有分歧。显著的炎症标志物，如活化的小胶质细胞和细胞因子，几乎完全围绕斑块观察。然而，最近的证据表明，斑块外部可能含有可测量水平的可溶性A β聚集体。小胶质细胞在体内的激活被不同的A β沉积物选择性地刺激的观察结果使我们研究了A β的哪种特定形式是体外最有效的促炎介质。我们在此报道，在BV-2和原代小鼠小胶质细胞中，A β（1-42）的可溶性前原纤维种类在诱导小胶质细胞肿瘤坏死因子α（TNF α）产生方面优于原纤维。在NaOH中重构A β（1-42），然后稀释到F-12培养基中，并用尺寸排阻色谱法（SEC）分离，显示长度为100 nm的经典曲线β-折叠原纤维。原纤维，而不是单体，显着激活BV-2小胶质细胞。还对新鲜分离的原纤维和由SEC纯化的单体制备的A β（1-42）原纤维进行了比较。令人惊讶的是，虽然分离的原纤维每摩尔具有高得多的硫磺素T荧光水平，但与原纤维相比，它们在刺激原代或BV-2鼠小胶质细胞方面无效。此外，SEC-分离的A β（1-40）原纤维显示出比浓度匹配的A β（1-42）显著更低的活性。这份报告是第一次证明SEC纯化的原纤维激活小胶质细胞，总体结果表明，小，可溶性A β（1-42）原纤维诱导更大的小胶质细胞激活比成熟的不溶性原纤维。
Senile plaques composed of amyloid-beta protein (A beta) are an unshakable feature of the Alzheimer's disease (AD) brain. Although there is significant debate on the role of the plaques in AD progression, there is little disagreement on their role in stimulating a robust inflammatory response within the context of the disease. Significant inflammatory markers such as activated microglia and cytokines are observed almost exclusively surrounding the plaques. However, recent evidence suggests that the plaque exterior may contain a measurable level of soluble A beta aggregates. The observations that microglia activation in vivo is selectively stimulated by distinct A beta deposits led us to examine what specific form of A beta is the most effective proinflammatory mediator in vitro. We report here that soluble prefibrillar species of A beta(1-42) were better than fibrils at inducing microglial tumor necrosis factor alpha (TNF alpha) production in either BV-2 and primary murine microglia. Reconstitution of A beta(1-42) in NaOH followed by dilution into F-12 media and isolation with size exclusion chromatography (SEC) revealed classic curvilinear beta-sheet protofibrils 100 nm in length. The protofibrils, but not monomers, markedly activated BV-2 microglia. Comparisons were also made between freshly isolated protofibrils and A beta(1-42) fibrils prepared from SEC-purified monomer. Surprisingly, while isolated fibrils had a much higher level of thioflavin T fluorescence per mole, they were not effective at stimulating either primary or BV-2 murine microglia compared to protofibrils. Furthermore, SEC-isolated A beta(1-40) protofibrils exhibited significantly less activity than concentration-matched A beta(1-42). This report is the first to demonstrate microglial activation by SEC-purified protofibrils, and the overall findings indicate that small, soluble A beta(1-42) protofibrils induce much greater microglial activation than mature insoluble fibrils.