Martín-Aragón Sagrario, Jiménez-Aliaga Karim Lizeth, Benedí Juana, Bermejo-Bescós Paloma
Departamento de Farmacología, Facultad de Farmacia, Universidad Complutense de Madrid (UCM), Plaza Ramón y Cajal s/n, 28040 Madrid, Spain.
Departamento de Farmacología, Facultad de Farmacia, Universidad Complutense de Madrid (UCM), Plaza Ramón y Cajal s/n, 28040 Madrid, Spain.
Phytomedicine. 2016 Nov 15;23(12):1285-1294. doi: 10.1016/j.phymed.2016.07.007. Epub 2016 Jul 22.
Plant secondary metabolites may induce adaptive cellular stress-responses in a variety of cells including neurons at the sub-toxic doses ingested by humans. Such 'neurohormesis' phenomenon, activated by flavonoids such as quercetin or rutin, may involve cell responses driven by modulation of signaling pathways which are responsible for its neuroprotective effects.
We attempt to explore the molecular mechanisms involved in the neurohormetic responses to quercetin and rutin exposure, in a SH-SY5Y cell line which stably overexpresses the amyloid precursor protein (APP) Swedish mutation, based on a biphasic concentration-response relationship for cell viability.
We examined the impact of both natural compounds, at concentrations in its hormetic range on the following cell parameters: chymotrypsin-like activity of the proteasome system; PARP-1 protein levels and expression and caspase activation; APP processing; and the main endogenous antioxidant enzymes.
Proteasome activities following quercetin or rutin treatment were significantly augmented in comparison with non-treated cells. Activity of caspase-3 was significantly attenuated by treatment with quercetin or rutin. Modest increased levels of PARP-1 protein and mRNA transcripts were observed in relation to the mild increase of proteasome activity. Significant reductions of the full-length APP and sAPP protein and APP mRNA levels were related to significant enhancements of α-secretase ADAM-10 protein and mRNA transcripts and significant increases of BACE processing in cells exposed to rutin. Furthermore, quercetin or rutin treatment displayed an overall increase of the four antioxidant enzymes.
The upregulation of the proteasome activity observed upon quercetin or rutin treatment could be afforded by a mild increased of PARP-1. Consequently, targeting the proteasome by quercetin or rutin to enhance its activity in a mild manner could avoid caspase activation. Moreover, it is likely that APP processing of cells upon rutin treatment is mostly driven by the non-amyloidogenic pathway leading to a putative reduction of βA production. Overall induction of endogenous antioxidant enzymes under quercetin or rutin treatments of APPswe cells might modulate its proteasome activity. We might conclude that quercetin and rutin might exert a neurohormetic cell response affecting various signaling pathways and molecular networks associated with modulation of proteasome function.
植物次生代谢产物可能会在人类摄入的亚毒性剂量下，在包括神经元在内的多种细胞中诱导适应性细胞应激反应。由槲皮素或芦丁等黄酮类化合物激活的这种“神经激素效应”现象，可能涉及由负责其神经保护作用的信号通路调节所驱动的细胞反应。
基于细胞活力的双相浓度-反应关系，我们试图在稳定过表达淀粉样前体蛋白（APP）瑞典突变体的SH-SY5Y细胞系中，探索槲皮素和芦丁暴露后神经激素效应反应所涉及的分子机制。
我们研究了这两种天然化合物在其激素效应范围内的浓度对以下细胞参数的影响：蛋白酶体系统的胰凝乳蛋白酶样活性；PARP-1蛋白水平、表达及半胱天冬酶激活；APP加工；以及主要的内源性抗氧化酶。
与未处理的细胞相比，槲皮素或芦丁处理后的蛋白酶体活性显著增强。用槲皮素或芦丁处理可显著减弱半胱天冬酶-3的活性。观察到PARP-1蛋白和mRNA转录本水平适度增加，这与蛋白酶体活性的轻度增加有关。在暴露于芦丁的细胞中，全长APP和sAPP蛋白以及APP mRNA水平的显著降低与α-分泌酶ADAM-10蛋白和mRNA转录本的显著增强以及BACE加工的显著增加有关。此外，槲皮素或芦丁处理使四种抗氧化酶总体增加。
槲皮素或芦丁处理后观察到的蛋白酶体活性上调可能是由PARP-1的轻度增加所致。因此，通过槲皮素或芦丁靶向蛋白酶体以轻度增强其活性可避免半胱天冬酶激活。此外，芦丁处理后细胞的APP加工很可能主要由非淀粉样生成途径驱动，从而可能减少βA的产生。在APPswe细胞的槲皮素或芦丁处理下内源性抗氧化酶的总体诱导可能会调节其蛋白酶体活性。我们可以得出结论，槲皮素和芦丁可能会产生一种神经激素效应细胞反应，影响与蛋白酶体功能调节相关的各种信号通路和分子网络。
