Kennedy D O, Nishimura S, Hasuma T, Yano Y, Otani S, Matsui-Yuasa I
Department of Food and Nutrition, Faculty of Human Life Science, Osaka City University, Osaka, Japan.
Chem Biol Interact. 1998 Apr 3;110(3):159-72. doi: 10.1016/s0009-2797(98)00005-2.
Green tea extract and its polyphenolic components have been found to possess anticarcinogenic, antimutagenic, antihypertensive and antihepatotoxic effects, and several mechanisms have been proposed for these effects. In this study, the effects of five tea polyphenols, (-)-epigallocatechin-3-gallate (EGCG), (-)-epigallocatechin (EGC), (-) epicatechin-3-gallate (ECG), ( -) epicatechin (EC) and (+)-catechin (C), were examined on the viability of Ehrlich ascites tumor cells in vitro and a possible relationship with tyrosine phosphorylation was determined. Proteins extracted from the cells treated with the tea polyphenols were separated by SDS-PAGE, and tyrosine-phosphorylated proteins were detected by immunoblotting with anti-phosphotyrosine antibody and the extent of phosphorylation determined. EGC (100 microM) caused a significant decrease in cell viability to 4.1 +/- 0.2% of the control value, and this correlated with a stimulation of protein tyrosine kinase (PTK) activity. EGCG (100 microM) also caused a slight decrease in cell viability (approximately 70% of the control value) but this and the other polyphenols, which had no effect on cell viability likewise, had no effect on tyrosine phosphorylation. Tyrosine phosphorylations of 42 and 45 kDa proteins were also observed for EGC. Further evaluation of the effect of EGC showed that the activity of ornithine decarboxylase (ODC), a key enzyme in polyamine biosynthesis in cells, decreased significantly as well. A significant correlation has therefore been observed between a cellular event, namely, a reduction in the viability of Ehrlich ascites tumor cells and an association with a tyrosine phosphorylation of 42 and 45 kDa proteins by the polyphenol EGC.
绿茶提取物及其多酚成分已被发现具有抗癌、抗诱变、抗高血压和抗肝毒性作用，并且针对这些作用提出了多种机制。在本研究中，检测了五种茶多酚，即（-）-表没食子儿茶素-3-没食子酸酯（EGCG）、（-）-表没食子儿茶素（EGC）、（-）-表儿茶素-3-没食子酸酯（ECG）、（-）-表儿茶素（EC）和（+）-儿茶素（C）对艾氏腹水瘤细胞体外活力的影响，并确定了其与酪氨酸磷酸化的可能关系。用茶多酚处理的细胞中提取的蛋白质通过SDS-PAGE分离，并用抗磷酸酪氨酸抗体通过免疫印迹检测酪氨酸磷酸化蛋白，并确定磷酸化程度。EGC（100微摩尔）使细胞活力显著降低至对照值的4.1±0.2%，这与蛋白酪氨酸激酶（PTK）活性的刺激相关。EGCG（100微摩尔）也使细胞活力略有降低（约为对照值的70%），但这以及其他对细胞活力无影响的多酚对酪氨酸磷酸化均无作用。EGC还观察到42 kDa和45 kDa蛋白的酪氨酸磷酸化。对EGC作用的进一步评估表明，细胞中多胺生物合成的关键酶鸟氨酸脱羧酶（ODC）的活性也显著降低。因此，在一个细胞事件，即艾氏腹水瘤细胞活力降低与多酚EGC导致的42 kDa和45 kDa蛋白酪氨酸磷酸化之间观察到显著相关性。
