MODULATION BY TEA OF EARLY EFFECTS OF UV ON SKIN

在以前的研究中，我们发现口服绿茶或红茶可以抑制紫外线(UV)诱导的小鼠致癌作用。在目前的提案中，我们计划研究口服绿茶和红茶，以及它们的成分(-)-表没食子儿茶素没食子酸酯(EGCG)和咖啡因，对机械上重要的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这一假设，即茶叶管理上调紫外线诱导的野生型P53和P53下游效应因子的增加。我们计划追求以下特定目标：1.确定SKH-1小鼠口服绿茶和红茶对单次或多次低剂量紫外线照射对(A)野生型p53表达，(B)p300，ARF和mdm-2(P53稳定和功能调节因子)，(C)p21(WAF1/CIP1)表达，(D)溴去肌尿苷掺入DNA，(E)表皮增厚(增殖)，(F)凋亡性晒伤细胞形成和(G)凋亡相关蛋白(bax，bcl2，Fas、Fas配体和半胱氨酸天冬氨酸氨基转移酶)是P53的下游效应因子。DNA中胸腺嘧啶二聚体、氧化碱基和链断裂的形成也将被确定。如果绿茶和红茶有效，我们将确定茶成分EGCG和咖啡因对茶调节的参数的影响。2.测定口服绿茶和红茶对紫外线诱导的P53阳性细胞持续斑块的形成和消除的影响。这些补丁将被测序，以确定茶叶给药对p53突变情况的影响。如果茶叶改变了紫外线诱导突变的特征，我们将评估EGCG和咖啡因的效果。3.通过对P53(-/-)和Bax(-/-)基因敲除小鼠的研究，验证野生型P53和Bax在绿茶促进紫外线诱导的晒伤细胞凋亡增加和TEA抑制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.