Effective clearance of neurotoxic amyloid-beta (Aβ) from the brain is a critical process to prevent Alzheimer’s disease (AD). One major clearance mechanism is Aβ transcytosis mediated by low-density lipoprotein receptor-related protein 1 (LRP1) in capillary endothelial cells. A marked loss of endothelial LRP1 is found in AD brains and is believed to significantly impair Aβ clearance. Recently, we demonstrated that pro-inflammatory cytokines IL-1β, IL-6 and TNF-α, significantly down-regulated LRP1 in human primary microvascular endothelial cells (MVECs). In this study, we sought to determine the underlying molecular mechanism by which IL-1β led to LRP1 loss in MVECs. Reduced LRP1 protein and transcript were detected up to 24 h post-exposure and returned to the baseline levels after 48 h post-exposure with 1 ng/ml IL-1β. This reduction was in part mediated by microRNA-205-5p, -200b-3p, and -200c-3p, as these microRNAs were concomitantly upregulated in MVECs exposed to IL-1β. Synthetic microRNA-205-5p, -200b-3p, and -200c-3p mimics recapitulated LRP1 loss in MVECs without IL-1β, and their synthetic antagomirs effectively reversed IL-1β-mediated LRP1 loss. Importantly, we found that the expression of these three microRNAs was controlled by NF-κB as pharmacological NF-κB inhibitor, BMS-345541, inhibited the IL-1β-mediated upregulation of these microRNAs and rescued LRP1 expression. siRNA-mediated silencing of IκB in MVECs elevated microRNA-200b-3p and decreased LRP1 transcript, partially confirming our overall findings. In conclusion, our study provides a mechanism by which pro-inflammatory IL-1β instigates the suppression of LRP1 expression in MVECs. Our findings could implicate spatiotemporal loss of LRP1 and impairment of the LRP1-mediated clearance mechanism by endothelial cells.

从大脑中有效清除具有神经毒性的β-淀粉样蛋白 (Aβ) 是预防阿尔茨海默病 (AD) 的关键过程。一种主要的清除机制是毛细血管内皮细胞中低密度脂蛋白受体相关蛋白 1 (LRP1) 介导的 Aβ 转胞吞作用。 AD 大脑中发现内皮 LRP1 显着缺失，并被认为会显着损害 Aβ 清除率。最近，我们证明促炎细胞因子 IL-1β、IL-6 和 TNF-α 显着下调人原代微血管内皮细胞 (MVEC) 中的 LRP1。在这项研究中，我们试图确定 IL-1β 导致 MVEC 中 LRP1 丢失的潜在分子机制。暴露后 24 小时内检测到 LRP1 蛋白和转录物减少，并在暴露于 1 ng/ml IL-1β 后 48 小时后恢复到基线水平。这种减少部分是由 microRNA-205-5p、-200b-3p 和 -200c-3p 介导的，因为这些 microRNA 在暴露于 IL-1β 的 MVEC 中同时上调。合成的 microRNA-205-5p、-200b-3p 和 -200c-3p 模拟物重现了没有 IL-1β 的 MVEC 中 LRP1 的丢失，并且它们的合成的 antagomir 有效逆转了 IL-1β 介导的 LRP1 丢失。重要的是，我们发现这三种 microRNA 的表达受 NF-κB 控制，作为药理学 NF-κB 抑制剂 BMS-345541，抑制 IL-1β 介导的这些 microRNA 的上调并挽救 LRP1 表达。 MVEC 中 siRNA 介导的 IκB 沉默提高了 microRNA-200b-3p 并减少了 LRP1 转录，部分证实了我们的总体发现。总之，我们的研究提供了促炎性 IL-1β 抑制 MVEC 中 LRP1 表达的机制。 我们的研究结果可能表明 LRP1 的时空缺失和内皮细胞 LRP1 介导的清除机制受损。