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

一氧化氮在茶提取物生理作用中的营养和生化研究

基本信息

批准号：
07680033
负责人：
YUASA Isao
金额：
$ 1.66万
依托单位：
OSAKA CITY UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

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.

研究表明，表没食子儿茶素的抗肿瘤作用在茶多酚中最为显著，其作用机制是通过抑制多胺代谢介导的。在此，我们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性的方式增强了42和45KDa蛋白酪氨酸残基的磷酸化。这些蛋白质的功能正在研究中。这些关于茶多酚对致癌基因表达和酪氨酸磷酸化的影响的新发现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生成的影响。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其他各种细胞和组织的相互作用中发挥重要作用。在心血管系统中，它介导血管平滑肌舒张，抑制白细胞粘附和血小板聚集，是内皮源性舒张因子的生化终产物。在本研究中，我们检测了多酚对埃利希腹水肿瘤细胞一氧化氮生成的影响，发现多酚增强了一氧化氮的生成。这些结果表明，茶多酚形成的一氧化氮参与了茶的药理作用。我们还研究了茶提取物和茶多酚对原代培养大鼠肝细胞药物性肝毒性的影响。添加茶多酚和茶多酚，尤其是没食子儿茶素没食子酸酯和表儿茶素没食子酸酯，可以改善肝细胞的损伤，这是通过维持蛋白质硫醇介导的。