Department of Pharmaceutical Microbiology, Faculty of Life Sciences, Kumamoto University, 5-1 Oe-honmachi, Chuo-ku, Kumamoto, 862-0973, Japan.
Department of Pharmaceutical Microbiology, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Chuo-ku, Kumamoto, 862-0973, Japan.
Fluids Barriers CNS. 2023 Sep 14;20(1):66. doi: 10.1186/s12987-023-00466-9.
Blood-brain barrier (BBB) dysfunction is supposed to be an early event in the development of Alzheimer's disease (AD). This study aimed to investigate the relationship between BBB alterations and AD progression in terms of amyloid-β peptide (Aβ) accumulation in the brains of humanized amyloid precursor protein knock-in (APP-KI) mice.
Brain Aβ accumulation was examined using immunohistochemical analysis. Alterations in differentially expressed proteins were determined using sequential window acquisition of all theoretical fragment ion mass spectroscopy (SWATH-MS)-based quantitative proteomics, and Metascape, STRING, Gene Ontology, and KEGG were used for network analyses of altered biological pathways and processes. Statistical significance was determined using the unpaired two-tailed Student's t-test and Welch's t-test for two groups and one-way analysis of variance followed by Tukey's test for more than two groups. Correlations between two groups were determined using Pearson's correlation analysis.
Brain Aβ accumulation in APP-KI mice was detectable at 2 months, increased significantly at 5 months, and remained elevated at 12 months of age. The levels of differentially expressed proteins in isolated brain capillaries were higher in younger mice, whereas those in the brain were higher in older mice. Network analyses indicated changes in basement membrane-associated and ribosomal proteins in the brain capillaries. There were no significant changes in key proteins involved in drug or Aβ transport at the BBB. In contrast, solute carrier transporter levels in astrocytes, microglia, and neurons were altered in the brain of older mice. Moreover, the levels of the lipid transporters Apoe and Apoj were upregulated in both the brain and isolated brain capillaries after Aβ accumulation.
Our results suggest that changes in the brain occurred after advanced Aβ accumulation, whereas initial Aβ accumulation was sufficient to cause alterations in the BBB. These findings may help elucidate the role of BBB alterations in AD progression and predict the distribution of drugs across the BBB in the brain of patients with AD.
血脑屏障（BBB）功能障碍被认为是阿尔茨海默病（AD）发展的早期事件。本研究旨在探讨 BBB 改变与 AD 进展之间的关系，特别是在人源化淀粉样前体蛋白敲入（APP-KI）小鼠脑内淀粉样β肽（Aβ）积累方面。
采用免疫组织化学分析检测脑内 Aβ 积累情况。采用基于顺序窗口采集所有理论片段离子质荷比质谱（SWATH-MS）的定量蛋白质组学技术确定差异表达蛋白的改变，并采用 Metascape、STRING、GO 和 KEGG 对改变的生物学途径和过程进行网络分析。使用未配对的双尾学生 t 检验和两组之间的 Welch t 检验确定统计显著性，对于两组以上，使用单因素方差分析，随后进行 Tukey 检验。使用 Pearson 相关分析确定两组之间的相关性。
APP-KI 小鼠脑内 Aβ 积累可在 2 月龄时检测到，在 5 月龄时显著增加，并在 12 月龄时仍保持升高。分离的脑毛细血管中差异表达蛋白的水平在年幼的小鼠中较高，而在大脑中的水平在年长的小鼠中较高。网络分析表明，脑毛细血管中基底膜相关和核糖体蛋白发生改变。在 BBB 中，参与药物或 Aβ 转运的关键蛋白没有明显变化。相反，在年老小鼠的大脑中，溶质载体转运蛋白水平发生改变。此外，在 Aβ 积累后，载脂蛋白 E（Apoe）和载脂蛋白 J（Apoj）的脂质转运蛋白在大脑和分离的脑毛细血管中均上调。
我们的研究结果表明，在 Aβ 积累后大脑发生变化，而早期 Aβ 积累足以引起 BBB 改变。这些发现可能有助于阐明 BBB 改变在 AD 进展中的作用，并预测 AD 患者大脑中药物穿过 BBB 的分布。
