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

描述（由申请人提供）： 皮肤的白皙与真黑素的表皮表达减少相关，真黑素是导致深色肤色的棕色/黑色色素。相反，有优先表达的褐黑素，硫酸化的金色/红色黑色素的物种，是可溶的，具有差的紫外线阻断能力。在皮肤中具有高水平的褐黑素和低水平的真黑素的人几乎没有对紫外线辐射的基本保护，因此遭受紫外线介导的皮肤损伤和皮肤癌的最高发病率。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。与人类一样，我们的动物模型中的白皙皮肤表型是由黑素皮质素-1受体（MC 1 R）在黑素细胞中的信号传导缺陷引起的，MC 1 R是一种蛋白质，当与其天然配体黑素细胞刺激激素（MSH）结合时，介导腺苷酸环化酶激活和cAMP生成。与皮肤白皙的人类在阳光照射后倾向于燃烧而不是晒黑类似，我们的皮肤白皙的动物表现出对紫外线的高度敏感性和不能适应性地晒黑。使用这种新的小鼠模型，我们研究黑色素诱导毛喉素，一个唇形科二萜，直接激活腺苷酸环化酶，促进细胞内cAMP的积累。通过局部应用C.通过将毛喉植物（毛喉素的天然来源）施用到皮肤，我们可以通过化学规避与突变体MC 1 R相关的有缺陷的cAMP信号传导来诱导UV保护性真黑素的产生。使用我们的动物模型，我们将直接调节cAMP信号和黑色素水平，以阐明C。Forskohlii提取物对抗紫外线介导的皮肤损伤。我们推测，皮肤中cAMP的药理学上调将通过促进真黑素合成和通过增强UV诱导的DNA光损伤的修复来保护免受UV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）描述MC 1 R功能在UV介导的氧化损伤中的作用，并确定MC 1 R功能的药物替代是否保护免受氧化UV损伤; ii）描述MC 1 R功能在UV诱导的DNA损伤修复中的影响;和iii）确定通过cAMP上调的MC 1 R功能的分子旁路是否增强UV暴露后的修复。我们的目标是开发一种新的紫外线防护方法，通过基于局部施用这种根提取物或小分子衍生物的免晒晒黑。我们的研究策略将提供一个坚实的基础，在此基础上，我们可以开发紫外线防护策略，以预防，而不是治疗，皮肤癌。公共卫生相关性：我们的目标是（1）了解紫外线照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，以防止紫外线介导的皮肤损伤;（3）有效预防皮肤癌。我们将使用模仿人类皮肤的独特转基因小鼠，测量紫外线暴露皮肤中的DNA损伤和修复，并探索这种损伤的减轻和修复的增强。我们提出的研究包括在体内和体外分析紫外线对整个皮肤和黑素细胞的影响，分别来自我们的动物模型。

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.