MODULATION BY TEA OF EARLY EFFECTS OF UV ON SKIN

在先前的研究中，我们发现口服绿茶或红茶可以抑制紫外线诱导的小鼠癌变。在目前的提案中，我们计划研究口服绿茶和红茶及其成分(-)-表没食子儿茶素没食子酸酯（EGCG）和咖啡因对紫外线诱导的小鼠皮肤早期变化的影响。一个主要的焦点将是测试茶管理上调紫外线诱导的野生型p53和p53下游效应物的增加的假设。我们计划实现以下具体目标：1。测定单次或多次低剂量紫外线照射对SKH-1小鼠的影响(a)野生型p53表达，(b) p300、ARF和MDM-2 （p53稳定性和功能调节剂）表达，(c) p21（WAF1/CIP1）表达，(d)溴代嘧啶与DNA结合，(e)表皮增厚（增生），(f)凋亡晒伤细胞的形成和(g)凋亡相关蛋白(BAX、BCL-2、Fas、Fas配体和半胱天冬酶)是p53的下游效应物。胸腺嘧啶二聚体的形成，DNA中的氧化碱基和链断裂也将被确定。如果绿茶和红茶有效，我们将确定茶叶成分EGCG和咖啡因对茶叶调节参数的影响。2. 确定口服绿茶或红茶对紫外线诱导的p53阳性细胞持久斑块的形成和消除的影响。将对这些斑块进行测序，以确定茶对p53突变谱的影响。如果茶改变了紫外线诱导突变的特征，我们将评估EGCG和咖啡因的影响。3. 通过对p53（-/-）和Bax（-/-）敲除小鼠的研究，验证野生型p53和Bax在绿茶对紫外线诱导的晒伤细胞凋亡增加的刺激作用和茶对紫外线诱导的致癌作用中的重要性。

In previous studies, we found that oral administration of green or black tea inhibits ultraviolet light (UV)-induced carcinogenesis in mice. In the present proposal, we plan to investigate the effects of orally administered green and black tea, as well as their constituents (-)-epigallocatechin gallate (EGCG) and caffeine, on mechanistically important UV-induced early changes in mouse skin. A major focus will be to test the hypothesis that tea administration upregulates UV-induced increases in wild-type p53 and downstream effectors of p53. We plan to pursue the following specific aims: 1. Determine the effects of oral administration of green and black tea to SKH-1 mice on the time course for effects of single or multiple low- dose exposures to UV on (a) wild-type p53 expression, (b) expression of p300, ARF and MDM-2 (modulators of p53 stability and function), (c) p21(WAF1/CIP1) expression, (d) bromodemyuridine incorporation into DNA, (e) epidermal thickening (hyperplasia), (f) formation of apoptotic sunburn cells and (g) expression of apoptosis related proteins (BAX, BCL-2, Fas, Fas ligand and caspases) that are downstream effectors of p53. The formation of thymine dimers, oxidized bases and strand breaks in DNA will also be determined. If green and black tea are effective, we will determine the effects of the tea constituents EGCG and caffeine on the parameters that are modulated by tea. 2. Determine the effects of oral administration of green or black tea on the formation and elimination of UV-induced persistent patches of p53 positive cells. These patches will be sequenced to determine the effects of tea administration on the profile of p53 mutations. If tea alters the profile of UV-induced mutations, we will evaluate the effects of EGCG and caffeine. 3. Test the importance of wild-type p53 and Bax for the stimulatory effect of green tea on UV-induced increases in apoptotic sunburn cells and for the inhibitory effect of tea on UV-induced carcinogenesis by studies in p53(-/-) and Bax(-/-) knockout mice.