Cirrito John R, May Patrick C, O'Dell Mark A, Taylor Jennie W, Parsadanian Maia, Cramer Jeffrey W, Audia James E, Nissen Jeffrey S, Bales Kelly R, Paul Steven M, DeMattos Ronald B, Holtzman David M
Department of Neurology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
J Neurosci. 2003 Oct 1;23(26):8844-53. doi: 10.1523/JNEUROSCI.23-26-08844.2003.
Soluble amyloid-beta (Abeta) peptide converts to structures with high beta-sheet content in Alzheimer's disease (AD). Soluble Abeta is released by neurons into the brain interstitial fluid (ISF), in which it can convert into toxic aggregates. Because assessment of ISF Abeta levels may provide unique insights into Abeta metabolism and AD, an in vivo microdialysis technique was developed to measure it. Our Abeta microdialysis technique was validated ex vivo with human CSF and then in vivo in awake, freely moving mice. Using human amyloid precursor protein (APP) transgenic mice, we found that, before the onset of AD-like pathology, ISF Abeta in hippocampus and cortex correlated with levels of APP in those tissues. After the onset of Abeta deposition, significant changes in the ISF Abeta40/Abeta42 ratio developed without changes in Abeta1-x. These changes differed from changes seen in tissue lysates from the same animals. By rapidly inhibiting Abeta production, we found that ISF Abeta half-life was short ( approximately 2 hr) in young mice but was twofold longer in mice with Abeta deposits. This increase in half-life, without an increase in steady-state levels, suggests that inhibition of Abeta synthesis reveals a portion of the insoluble Abeta pool that is in dynamic equilibrium with ISF Abeta. This now measurable in vivo pool is a likely target for new diagnostic and therapeutic strategies.
在阿尔茨海默病（AD）中，可溶性β淀粉样蛋白（Aβ）肽会转变为具有高β折叠含量的结构。可溶性Aβ由神经元释放到脑间质液（ISF）中，在其中它可以转化为有毒聚集体。由于评估ISF中Aβ水平可能为Aβ代谢和AD提供独特见解，因此开发了一种体内微透析技术来测量它。我们的Aβ微透析技术先用人类脑脊液进行了离体验证，然后在清醒、自由活动的小鼠体内进行了验证。使用人类淀粉样前体蛋白（APP）转基因小鼠，我们发现，在类似AD病理开始之前，海马体和皮质中的ISF Aβ与这些组织中的APP水平相关。在Aβ沉积开始后，ISF中Aβ40/Aβ42比值发生了显著变化，而Aβ1-x没有变化。这些变化与同一动物组织裂解物中的变化不同。通过快速抑制Aβ产生，我们发现年轻小鼠中ISF Aβ的半衰期很短（约2小时），但在有Aβ沉积的小鼠中则长两倍。半衰期的这种增加，而稳态水平没有增加，表明抑制Aβ合成揭示了一部分与ISF Aβ处于动态平衡的不溶性Aβ池。这个现在可以在体内测量的池可能是新诊断和治疗策略的一个靶点。
