Department of Pharmacology, Kirksville College of Osteopathic Medicine, A.T. Still University of Health Sciences, Kirksville, MO 63501, USA.
College of Pharmacy, Seoul National University, Seoul 08826, Korea.
Int J Mol Sci. 2022 May 24;23(11):5885. doi: 10.3390/ijms23115885.
Deposition of fibrillar forms of amyloid β-protein (Aβ) is commonly found in patients with Alzheimer's disease (AD) associated with cognitive decline. Impaired clearance of Aβ species is thought to be a major cause of late-onset sporadic AD. Aβ secreted into the extracellular milieu can be cleared from the brain through multiple pathways, including cellular uptake in neuronal and non-neuronal cells. Recent studies have showed that the naturally-occurring polyphenol amentoflavone (AMF) exerts anti-amyloidogenic effects. However, its effects on metabolism and cellular clearance of Aβ remain to be tested. In the present study, we demonstrated that AMF significantly increased the cellular uptake of both Aβ and Aβ, but not inverted Aβ in mouse neuronal N2a cells. Though AMF promoted internalization of cytotoxic Aβ, it significantly reduced cell death in our assay condition. Our data further revealed that the internalized Aβ is translocated to lysosomes and undergoes enzymatic degradation. The saturable kinetic of Aβ uptake and our pharmacologic experiments showed the involvement of receptor-mediated endocytosis, in part, through the class A scavenger receptors as a possible mechanism of action of AMF. Taken together, our findings indicate that AMF can lower the levels of extracellular Aβ by increasing their cellular uptake and clearance, suggesting the therapeutic potential of AMF for the treatment of AD.
淀粉样β-蛋白(Aβ)纤维形式的沉积通常在与认知能力下降相关的阿尔茨海默病(AD)患者中发现。Aβ 物种清除受损被认为是迟发性散发性 AD 的主要原因。分泌到细胞外环境中的 Aβ 可以通过多种途径从大脑中清除,包括神经元和非神经元细胞的细胞摄取。最近的研究表明,天然存在的多酚杨梅素(AMF)具有抗淀粉样蛋白形成的作用。然而,其对 Aβ 的代谢和细胞清除的影响仍有待测试。在本研究中,我们证明 AMF 显著增加了 Aβ 和 Aβ 的细胞摄取,但对反向 Aβ 没有影响。尽管 AMF 促进了细胞毒性 Aβ 的内化,但在我们的检测条件下,它显著降低了细胞死亡。我们的数据进一步表明,内化的 Aβ 被转运到溶酶体并进行酶降解。Aβ 摄取的饱和动力学和我们的药理学实验表明,内吞作用涉及受体介导的内吞作用,部分通过 A 类清道夫受体作为 AMF 的作用机制之一。总之,我们的研究结果表明,AMF 通过增加细胞摄取和清除来降低细胞外 Aβ 的水平,提示 AMF 治疗 AD 的治疗潜力。