Department of Clinical Chemistry, The Alzheimer Center, VU University Medical Center Amsterdam, P.O. Box 7057, 1007 MB Amsterdam, The Netherlands.
Exp Neurol. 2012 Jan;233(1):373-9. doi: 10.1016/j.expneurol.2011.11.001. Epub 2011 Nov 10.
Astrocytes appear to be important mediators in the clearance of amyloid beta1-42 (Aβ), the key component of senile plaques characteristic of Alzheimer's disease (AD). Recently, we found the amyloid associated proteins (AAPs) α1-antichymotrypsin (ACT), apolipoprotein J and E (ApoJ and ApoE) and a mixture of serum amyloid P (SAP) and C1q (SAP-C1q) to modify Aβ-uptake by human astrocytes. Here we investigated the effect of oligomeric (Aβoligo) and fibrillar Aβ (Aβfib), alone and in combination with a panel of AAPs on the astrocytic expression of genes proposed to be involved in Aβ-uptake and degradation. Primary human astrocytes (isolated from non-demented control (n=4) and AD patient (n=4) brain specimens) were exposed to either Aβoligo or Aβfib preparations with or without the above mentioned AAPs. Quantitative gene expression analysis of Aβ-receptors Scavenger receptor B1 (SCARB1), macrophage receptor with collagenous structure (MARCO) and low density lipoprotein receptor related protein-2 (LRP2 or megalin) as well as of Aβ-degrading enzymes neprilysin (NEP), insulin-degrading enzyme (IDE) and metalloproteinase-9 (MMP-9) was performed by real-time PCR. Basal expression of NEP, IDE and SCARB1 was easily detected whereas expression of MARCO, LRP2 and MMP-9 could only be detected upon pre-amplification. Basal expression of NEP, IDE and SCARB1 did not change upon exposure to Aβoligo or Aβfib alone in any of the investigated astrocyte cultures. Interestingly NEP expression was increased upon exposure to ApoE in combination with both Aβ-preparations, and also SCARB1 expression was induced upon treatment with ApoE in combination with Aβfib in astrocytes from non-demented controls. Further, SAP-C1q increased SCARB1 expression in control astrocytes when combined with Aβoligo. These alterations were not found in astrocytes from AD patients. Thus, we conclude that Aβ alone apparently does not affect the astrocytic expression of IDE, NEP or SCARB1. However, NEP and SCARB1 expression is increased in astrocytes from non-demented subjects when exposed to Aβ combined with AAPs like ApoE. These astrocytic gene expression-regulatory mechanisms appear to be defective in AD and thus might contribute to the development and progression of AD pathology.
星形胶质细胞似乎是清除淀粉样β 1-42（Aβ）的重要介质，Aβ 是阿尔茨海默病（AD）特征性老年斑的关键成分。最近，我们发现淀粉样相关蛋白（AAP）α1-抗胰蛋白酶（ACT）、载脂蛋白 J 和 E（ApoJ 和 ApoE）以及血清淀粉样蛋白 P（SAP）和 C1q（SAP-C1q）的混合物可改变人星形胶质细胞对 Aβ 的摄取。在这里，我们研究了寡聚体（Aβoligo）和纤维状 Aβ（Aβfib）单独以及与一组 AAP 联合对星形胶质细胞中拟参与 Aβ摄取和降解的基因表达的影响。原代人星形胶质细胞（从非痴呆对照（n=4）和 AD 患者（n=4）脑标本中分离）分别暴露于 Aβoligo 或 Aβfib 制剂中，同时存在或不存在上述 AAP。通过实时 PCR 对 Aβ 受体清道夫受体 B1（SCARB1）、巨噬细胞胶原结构受体（MARCO）和低密度脂蛋白受体相关蛋白-2（LRP2 或 megalin）以及 Aβ 降解酶神经肽酶（NEP）、胰岛素降解酶（IDE）和金属蛋白酶-9（MMP-9）的基因表达进行定量分析。在任何一种研究的星形胶质细胞培养物中，NEP、IDE 和 SCARB1 的基础表达均容易检测到，而 MARCO、LRP2 和 MMP-9 的表达仅在预扩增后才能检测到。在任何一种研究的星形胶质细胞培养物中，Aβoligo 或 Aβfib 单独暴露均未改变 NEP、IDE 和 SCARB1 的基础表达。有趣的是，在与两种 Aβ 制剂联合使用时，ApoE 可增加 NEP 的表达，并且在与 Aβfib 联合使用时，在非痴呆对照的星形胶质细胞中也可诱导 SCARB1 的表达。此外，SAP-C1q 与 Aβoligo 联合使用时可增加控制星形胶质细胞中 SCARB1 的表达。在 AD 患者的星形胶质细胞中未发现这些改变。因此，我们得出结论，Aβ 单独显然不会影响 IDE、NEP 或 SCARB1 的星形胶质细胞表达。然而，当与 AAP 如 ApoE 联合暴露时，非痴呆受试者的星形胶质细胞中 NEP 和 SCARB1 的表达增加。这些星形胶质细胞基因表达调节机制在 AD 中似乎存在缺陷，因此可能有助于 AD 病理的发展和进展。
