School of Health Sciences, Purdue University, West Lafayette, IN 47907, USA.
Neurotoxicology. 2010 Sep;31(5):524-32. doi: 10.1016/j.neuro.2010.05.004. Epub 2010 May 19.
The choroid plexus (CP), constituting the blood-cerebrospinal fluid barrier, has the capacity to remove beta-amyloid (Abeta) from the cerebrospinal fluid. Our previous work indicates that exposure to lead (Pb) results in Abeta accumulation in the CP by decreasing the expression of low density lipoprotein receptor protein-1 (LRP1), a protein involved in the transport and clearance of Abeta. The current study was designed to explore the relationship between Abeta accumulation, protein kinase C (PKC) activity, and LRP1 status in the CP following Pb exposure. Confocal microscopy revealed that LRP1 was primarily localized in the cytosol of the CP in control rats and migrated distinctly towards the apical surface and the microvilli following acute Pb exposure (27 mg Pb/kg, i.p., 24h). Co-immunostaining revealed a co-localization of both PKC-delta and LRP1 in the cytosol of control rats, with a distinct relocalization of both towards the apical membrane following Pb exposure. Preincubation of the tissues with PKC-delta inhibitor rottlerin (2 microM) prior to Pb exposure in vitro, resulted in abolishing the Pb-induced relocalization of LRP1 to the apical surface. Importantly, a significant elevation in intracellular Abeta levels (p<0.01) was observed in the cytosol of the CP following Pb exposure, which was abolished following preincubation with rottlerin. In addition, rottlerin caused a relocalization of Abeta from the cytosol to the nucleus in both Pb-treated and control CP tissues. Finally, co-immunoprecipitation studies revealed a strong protein-protein interaction between LRP1 and PKC-delta in the CP. These studies suggest that Pb exposure disrupts Abeta homeostasis at the CP, owing partly to a Pb-induced relocalization of LRP1 via PKC-delta.
脉络丛（CP）构成了血脑屏障，具有从脑脊液中清除β-淀粉样蛋白（Abeta）的能力。我们之前的工作表明，暴露于铅（Pb）会通过降低低密度脂蛋白受体蛋白-1（LRP1）的表达来导致 CP 中 Abeta 积累，LRP1 是一种参与 Abeta 转运和清除的蛋白。本研究旨在探讨 Pb 暴露后 CP 中 Abeta 积累、蛋白激酶 C（PKC）活性和 LRP1 状态之间的关系。共聚焦显微镜显示，LRP1 在对照组大鼠的 CP 细胞质中主要定位于细胞质中，在急性 Pb 暴露后（27mg Pb/kg，腹腔内，24h）明显迁移到顶表面和微绒毛。共免疫染色显示，PKC-delta 和 LRP1 在对照组大鼠的细胞质中均有共定位，在 Pb 暴露后明显向顶膜重新定位。在体外 Pb 暴露之前，用 PKC-delta 抑制剂 rottlerin（2μM）预孵育组织，导致 LRP1 向顶表面的 Pb 诱导重新定位消失。重要的是，在 CP 细胞质中观察到 Abeta 水平的显著升高（p<0.01）在 Pb 暴露后，在用 rottlerin 预孵育后消失。此外，rottlerin 导致 Abeta 从 CP 中细胞质到细胞核的重新定位在 Pb 处理和对照 CP 组织中均发生。最后，免疫共沉淀研究表明 LRP1 和 PKC-delta 在 CP 之间存在很强的蛋白-蛋白相互作用。这些研究表明，Pb 暴露破坏了 CP 中的 Abeta 动态平衡，部分原因是 Pb 诱导的 LRP1 通过 PKC-delta 重新定位。
