Coleus forskohlii extract: melanization and UV protection by a natural product

描述(由申请人提供)： 皮肤的白皙与真皮中真黑色素的表达减少有关，真黑素是一种导致皮肤黝黑的棕色/黑色色素。取而代之的是Peomelanin的优先表达，Peomelanin是一种硫酸盐化的金发/红色黑色素物种，可溶，抗紫外线能力较差。皮肤中有高水平的褐黑素和低水平的真黑素的人对紫外线辐射的基本保护作用很小，因此遭受紫外线介导的皮肤损伤和皮肤癌的发生率最高。为了阐明紫外线暴露和色素沉着之间的关系，并开发新的基于色素的紫外线防护策略，我们开发了一种具有诱导色素沉着的人源化皮肤小鼠模型。像人类一样，在我们的动物模型中，皮肤白皙的表型是由黑素皮质素-1受体(MC1R)在黑素细胞中的信号缺陷引起的，MC1R是一种蛋白质，当与其天然配体黑素细胞刺激素(MSH)结合时，介导腺苷环化酶激活和cAMP的产生。与皮肤白皙的人类相似，在阳光照射下，皮肤白皙的人往往会被灼伤，而不是晒黑，我们的皮肤白皙的动物表现出对紫外线的高度敏感性，并且不能适应性地晒黑。利用这个新的小鼠模型，我们研究了Forskolin诱导黑色素的作用，Forskolin是一种拉布丹二萜类化合物，直接激活腺苷环化酶并促进cAMP在细胞内的积累。通过将Forskohlii植物的根提取物(Forsklin的天然来源)局部应用于皮肤，我们可以通过化学方法绕过与突变的MC1R相关的缺陷cAMP信号来诱导紫外线保护eumelanin的产生。利用我们的动物模型，我们将直接调节cAMP信号和黑色素水平，以阐明沙棘提取物对紫外线介导的皮肤损伤的保护作用。我们推测，药物上调皮肤中的cAMP将通过促进真黑素的合成和促进紫外线诱导的DNA光刻的修复来保护皮肤免受紫外线介导的损伤。为了解决我们的假设，我们提出了三个具体的目标：i)表征MC1R功能在紫外线介导的氧化损伤中的作用，并确定MC1R功能的药物替代是否具有保护紫外线氧化损伤的作用；ii)描述MC1R功能在紫外线诱导的DNA损伤修复中的影响；以及iii)确定通过cAMP上调而使MC1R功能的分子旁路是否促进紫外线暴露后的修复。我们的目标是开发一种新的方法，通过无日晒晒黑来保护紫外线，这种方法是基于局部使用这种根提取物或小分子衍生物。我们的研究战略将提供一个坚实的基础，我们可以在此基础上开发紫外线防护策略来预防而不是治疗皮肤癌。与公众健康相关：我们的目标是(1)了解紫外线辐射如何损害不同色素类型的皮肤；(2)设计基于天然色素的策略，防止紫外线介导的皮肤损害；以及(3)有效预防皮肤癌。利用独特的模仿人类皮肤的转基因小鼠，我们将测量紫外线照射下皮肤的DNA损伤和修复，并探索减轻这种损伤和促进修复的方法。我们提出的研究包括体内和体外分析紫外线对整个皮肤和来自我们的动物模型的黑素细胞的影响。

DESCRIPTION (provided by applicant): Fairness of skin correlates with diminished epidermal expression of eumelanin, the brown/black pigment responsible for dark complexion. Instead, there is preferential expression of pheomelanin, a sulfated blonde/red melanin species that is soluble and has poor UV-blocking abilities. Persons with high levels of pheomelanin and low levels of eumelanin in the skin have little basal protection from UV radiation, and therefore suffer the highest incidence of UV-mediated skin damage and skin cancer. To delineate the relationship between UV exposure and pigmentation and develop novel pigment-based UV protective strategies, we have developed a mouse model of "humanized skin" with inducible pigmentation. Like in humans, the fair-skinned phenotype in our animal model is caused by defective signaling in melanocytes by the melanocortin-1 receptor (MC1R), a protein that mediates adenylate cyclase activation and cAMP generation when bound by its natural ligand, melanocyte stimulating hormone (MSH). Similar to fair- skinned humans who tend to burn rather than tan after sunlight exposure, our fair-skinned animals demonstrate heightened UV sensitivity and failure to tan adaptively. Using this novel mouse model, we study melanin induction by forskolin, a labdane diterpenoid that directly activates adenylate cyclase and promotes intracellular accumulation of cAMP. By topically applying root extract from the C. forskohlii plant (the natural source of forskolin) to the skin, we can induce the production of UV-protective eumelanin by chemically circumventing the defective cAMP signaling associated with the mutant MC1R. Using our animal model, we will directly modulate cAMP signaling and melanin levels to clarify the protective effects of C. forskohlii extract against UV-mediated skin damage. We hypothesize that pharmacologic up- regulation of cAMP in the skin will protect against UV-mediated damage by promoting eumelanin synthesis and by enhancing the repair of UV-induced DNA photolesions. To address our hypothesis, we propose three specific aims: i) Characterize the role of MC1R function in UV-mediated oxidative damage, and determine whether pharmacologic replacement of MC1R function protects against oxidative UV injury; ii) Delineate the impact of MC1R function in the repair of UV-induced DNA lesions; and iii) Determine whether molecular bypass of MC1R function by cAMP up-regulation enhances repair following UV exposure. Our goal is to develop the novel approach of UV protection by sunless tanning based on topical administration of this root extract or small molecule derivatives. Our research strategy will provide a substantial foundation on which we can develop UV-protective strategies to prevent, rather than treat, skin cancer. PUBLIC HEALTH RELEVANCE: Our goals are to (1) understand how UV irradiation damages skin of different pigment types; (2) devise natural pigment-based strategies that protect against UV-mediated skin damage; and (3) effectively prevent skin cancer. Using unique transgenic mice that mimic human skin, we will measure DNA damage and repair in UV- exposed skin, and explore mitigation of this damage and enhancement of repair. Our proposed research includes both in vivo and in vitro analyses of UV effects in whole skin and in melanocytes derived from our animal model, respectively.