Conte A, Pellegrini S, Tagliazucchi D
Department of Agricultural Science, University of Modena e Reggio Emilia, Reggio Emilia, Italy.
Drugs Exp Clin Res. 2003;29(5-6):243-55.
beta-Amyloid peptide (beta-AP) is the main component of amyloid deposits around the cerebral vessel and in the brain parenchyma in Alzheimer's disease and Down's syndrome. In vitro studies in neuronal cells or in PC12 and Hela cell lines have shown that the aggregate form of beta-AP is toxic. Many genetic and environmental factors including metal ions, proteoglycans, plasma proteins and antioxidants modify beta-AP toxicity. We investigated the effect of two plant polyphenols--resveratrol and catechin--on soluble and particulate tyrosine kinase activity from PC12 cells and the protective action of these compounds against beta-AP (1-41) toxicity. beta-AP (1-41) decreased PC12 viability with an IC50 value of 1.1 +/- 0.14 x 10(-8) M. Resveratrol and catechin protected PC12 cells from beta-AP (1-41) toxicity. With 25 microM resveratrol the IC50 value increased to 2.2 +/- 0.19 x 10(-7) M. In the presence of beta-AP (1-41) resveratrol showed a concentration-dependent biphasic effect, and at a concentration of up to 40 microM it protected PC12 cells from beta-AP (1-41) toxicity. At concentrations higher than 40 microM, an inhibitory activity on cell proliferation appeared. This antiproliferative effect was also seen in the absence of beta-AP (1-41). With 100 microM catechin the IC50 value increased from 1.1 +/- 0.14 x 10(-8) M to 3.2 +/- 0.25 x 10(-7) M beta-AP (1-41). The protective effect was concentration dependent. Resveratrol and catechin had a synergistic protective action. In the presence of 40 microM catechin and 10 microM resveratrol or 20 microM resveratrol and 10 microM catechin, the toxicity determined by 10(-7) M beta-AP (1-41) was almost completely removed. Resveratrol and catechin had different effects on PC12 tyrosine kinase activity. With peptide 1-17 of gastrin as substrate, resveratrol inhibited particulate tyrosine kinases while it had no effect on soluble activity. With the same substrate, catechin increased the activity of soluble fraction while it inhibited particulate activity. When peptide 6-20 of cell division kinase p34cdc2 was utilized, catechin showed an opposite effect, inhibiting soluble tyrosine kinase activity and increasing particulate activity. With peptide 6-20, resveratrol inhibited both soluble and particulate activities. These results demonstrate that resveratrol and catechin have different activities on the signal transduction pathway involving protein phosphorylation. These differences may contribute not only to the different effects of these compounds on PC12 growth but also to the synergistic effect against beta-AP (1-41) toxicity. The different activity of resveratrol and catechin on signal transduction pathways, as well as the differences in metal chelation, partition coefficient between water and lipids, hydrogen donation redox potential and enzyme inhibition may be at least in part based on synergistic protection against beta-AP (1-41) toxicity.
β-淀粉样肽（β-AP）是阿尔茨海默病和唐氏综合征中脑血管周围及脑实质内淀粉样沉积物的主要成分。在神经元细胞或PC12和Hela细胞系中的体外研究表明，β-AP的聚集形式具有毒性。许多遗传和环境因素，包括金属离子、蛋白聚糖、血浆蛋白和抗氧化剂，都会改变β-AP的毒性。我们研究了两种植物多酚——白藜芦醇和儿茶素——对PC12细胞中可溶性和颗粒性酪氨酸激酶活性的影响，以及这些化合物对β-AP（1-41）毒性的保护作用。β-AP（1-41）降低PC12细胞活力，IC50值为1.1±0.14×10^(-8) M。白藜芦醇和儿茶素可保护PC12细胞免受β-AP（1-41）的毒性。加入25μM白藜芦醇后，IC50值增至2.2±0.19×10^(-7) M。在存在β-AP（1-41）的情况下，白藜芦醇呈现浓度依赖性双相效应，在浓度高达40μM时可保护PC12细胞免受β-AP（1-41）的毒性。在浓度高于40μM时，出现对细胞增殖的抑制活性。在不存在β-AP（1-41）时也可见到这种抗增殖效应。加入100μM儿茶素后，β-AP（1-41）的IC50值从1.1±0.14×10^(-8) M增至3.2±0.25×10^(-7) M。保护作用呈浓度依赖性。白藜芦醇和儿茶素具有协同保护作用。在存在40μM儿茶素和10μM白藜芦醇或20μM白藜芦醇和10μM儿茶素的情况下，由10^(-7) Mβ-AP（1-41）所测定的毒性几乎完全消除。白藜芦醇和儿茶素对PC12酪氨酸激酶活性有不同影响。以胃泌素的1-17肽为底物时，白藜芦醇抑制颗粒性酪氨酸激酶，而对可溶性活性无影响。以相同底物时，儿茶素增加可溶性部分的活性，同时抑制颗粒性活性。当使用细胞分裂激酶p34cdc2的6-20肽时，儿茶素表现出相反的效应，抑制可溶性酪氨酸激酶活性并增加颗粒性活性。以6-20肽时，白藜芦醇抑制可溶性和颗粒性活性。这些结果表明，白藜芦醇和儿茶素在涉及蛋白质磷酸化的信号转导途径上具有不同活性。这些差异可能不仅导致这些化合物对PC12生长的不同影响，还导致对β-AP（1-41）毒性的协同效应。白藜芦醇和儿茶素在信号转导途径上的不同活性，以及在金属螯合、水与脂质之间的分配系数、氢供体氧化还原电位和酶抑制方面的差异，可能至少部分基于对β-AP（1-41）毒性的协同保护作用。
