Nutritional and Biochemical Study on the Role of Nitric Oxide in the Physiological Effects of Tea Extract

我们已经表明，表没食子儿茶素具有最抗肿瘤作用的茶多酚和效果是由多胺代谢的抑制介导的。本文研究了茶多酚对肿瘤细胞癌基因和信号转导的影响，发现茶多酚影响癌基因c-fos的表达。我们还研究了多酚对酪氨酸磷酸化的影响，发现多酚以剂量和时间依赖的方式增强42和45 KDa蛋白质酪氨酸残基的磷酸化。这些蛋白质的功能正在研究中。这些研究结果对了解茶多酚的抗癌作用机制具有重要意义。此外，我们还研究了茶多酚对一氧化氮产生的影响。一氧化氮在调节免疫功能、血管扩张、大脑和周围神经系统以及各种其他细胞和组织的相互作用中起着重要作用。在心血管系统内，它介导血管平滑肌松弛，抑制白细胞粘附和血小板聚集，并且是内皮源性松弛因子的生化终产物。在这项研究中，我们检测了多酚类物质对埃利希腹水肿瘤细胞一氧化氮产生的影响，发现多酚类物质增强了一氧化氮的产生。这些结果表明，茶多酚形成的一氧化氮参与了茶叶的某些药理作用。我们还研究了茶提取物和茶多酚对原代培养的大鼠肝细胞中药物诱导的肝毒性的影响。加入舒尼芬和茶多酚，特别是表没食子儿茶素没食子酸酯和表儿茶素没食子酸酯，肝细胞的损伤得到改善，这是通过维持蛋白硫醇介导的。

We have shown that epigallocatechin has the most antitumor effect in tea polyphenols and the effect is mediated by the inhibition of polyamine metabolism. Here, we studied the effects of the tea polyphenol on oncogenes and signal transduction in tumor cells and found that the polyphenol affects the expression of the oncogene c-fos. We also studied the effect of the polyphenol on tyrosine phosphorylation and found that the polyphenol enhanced the phosphorylation of the tyrosine residues of 42 and 45KDa proteins in a dose- and time-dependent manner. The functions of these proteins are under investigation. These findings on the effect of tea polyphenol on the expression of oncogene and tyrosine phosphorylation is new and important to understand the mechanism of anticarcinogenic effect. Furthermore, we studied the effect of tea polyphenols upon nitric oxide production. Nitric oxide plays important roles in regulating immune function, blood vessel dilation, brain and peripheral nervous system and interactions of the various other cells and tissue. Within the cardiovasucular system, it mediates vascular smooth muscle relaxation, inhibits both leukocyte adhesion and platelet aggregation, and is the biochemical endproduct of endothelium-derived relaxing factor. In this study, we examined the effects of polyphenols on nitric oxide production in Ehrlich ascites tumor cells, and found that polyphenols enhanced the production of nitric oxide. These results suggested that nitric oxide formed by tea polyphenols is involved inome pharmacological functions of tea. We also examined the effect of tea extract and tea polyphenols against drug-induced hepatotoxicity in primary cultured rat hepatocytes. The injury of hepatocytes was improved by the addition of sunphenon and tea polyphenols, especially epigallocatechin gallate and epicatechin gallate, and this was mediated by the maintenance of protein thiols.