Department of Alzheimer's Disease Research, National Institute for Longevity Sciences, National Center for Geriatrics and Gerontology, Obu, Aichi 474-8522, Japan.
J Biol Chem. 2011 May 20;286(20):17536-42. doi: 10.1074/jbc.M111.225532. Epub 2011 Apr 6.
Apolipoprotein E (apoE) is a major apolipoprotein in the brain. The ε4 allele of apoE is a major risk factor for Alzheimer disease, and apoE deficiency in mice leads to blood-brain barrier (BBB) leakage. However, the effect of apoE isoforms on BBB properties are as yet unknown. Here, using an in vitro BBB model consisting of brain endothelial cells and pericytes prepared from wild-type (WT) mice, and primary astrocytes prepared from human apoE3- and apoE4-knock-in mice, we show that the barrier function of tight junctions (TJs) was impaired when the BBB was reconstituted with primary astrocytes from apoE4-knock-in mice (apoE4-BBB model). The phosphorylation of occludin at Thr residues and the activation of protein kinase C (PKC)η in mBECs were attenuated in the apoE4-BBB model compared with those in the apoE3-BBB model. The differential effects of apoE isoforms on the activation of PKCη, the phosphorylation of occludin at Thr residues, and TJ integrity were abolished following the treatment with an anti-low density lipoprotein receptor-related protein 1 (LRP1) antibody or a LRP1 antagonist receptor-associated protein. Consistent with the results of in vitro studies, BBB permeability was higher in apoE4-knock-in mice than in apoE3-knock-in mice. Our studies provide evidence that TJ integrity in BBB is regulated by apoE in an isoform-dependent manner.
载脂蛋白 E (apoE) 是大脑中的主要载脂蛋白。apoE 的 ε4 等位基因是阿尔茨海默病的主要危险因素，而小鼠 apoE 缺乏会导致血脑屏障 (BBB) 渗漏。然而，apoE 异构体对 BBB 特性的影响尚不清楚。在这里，我们使用由野生型 (WT) 小鼠制备的脑内皮细胞和周细胞以及由人 apoE3 和 apoE4 基因敲入小鼠制备的原代星形胶质细胞组成的体外 BBB 模型，显示当用来自 apoE4 基因敲入小鼠的原代星形胶质细胞重建 BBB 时，紧密连接 (TJ) 的屏障功能受损 (apoE4-BBB 模型)。与 apoE3-BBB 模型相比，apoE4-BBB 模型中 mBECs 中 occludin 的 Thr 残基磷酸化和蛋白激酶 C (PKC)η 的激活减弱。apoE 异构体对 PKCη 的激活、occludin 在 Thr 残基上的磷酸化以及 TJ 完整性的差异影响在使用抗低密度脂蛋白受体相关蛋白 1 (LRP1) 抗体或 LRP1 拮抗剂受体相关蛋白处理后被消除。与体外研究结果一致，apoE4 基因敲入小鼠的 BBB 通透性高于 apoE3 基因敲入小鼠。我们的研究提供了证据，表明 apoE 以依赖于异构体的方式调节 BBB 中 TJ 的完整性。
