Role of Vitamin D in cutaneous DNA repair

维生素D缺乏症和表皮角质形成细胞引起的皮肤癌在非洲和非洲都非常普遍。 老兵虽然暴露在阳光中通常发现的紫外线（UV）波长下会引发维生素D， 由于紫外线对生物合成的影响，目前不推荐这种做法，因为紫外线也是皮肤癌的主要原因。 然而，相对较低的剂量是否足以在体内产生维生素D， 皮肤与健康个体患皮肤癌的有意义的风险有关， 医学关于这个主题的报告确定解决这个问题是一个主要的研究需求。基于在两个方面的工作 我们的实验室和其他人的实验室，有证据表明，紫外线诱导机制，如DNA修复可能 与维生素D信号直接相连。例如，我们观察到缺乏维生素D的老鼠 受体容易发生UV诱导的表皮肿瘤，维生素D及其代谢产物诱导 DNA修复蛋白另一方面，小鼠不能合成最具生物活性的维生素 D不是肿瘤。然而，仍然有可能一种或多种其他维生素D 代谢物确实具有抗光致癌作用，包括诱导核苷酸切除修复活性， 去除紫外线引起的DNA损伤的主要机制。这项研究的总体假设 建议维生素D或其衍生物刺激代偿机制以修复侧枝DNA 它可以减少与其自身的紫外线介导的光合作用相关的损害，从而最大限度地减少光致癌作用。 在目的I中，将使用来自CYP27B1缺失小鼠的培养角质形成细胞和表皮外植体， 比较主要维生素D3代谢物对核苷酸切除修复的影响。两 调节内源性维生素D代谢物水平的外源性补充和化学抑制将 并将测定修复基因的表达以及修复活性和UV抗性。在 目的二，研究维生素D对DNA修复的基因组和非基因组机制。 培养的角质形成细胞和小鼠表皮外植体将用于评估维生素D 受体在DNA修复中的作用，以及核苷酸切除修复因子在损伤处的组装和稳定性。目标三 将使用最活跃的维生素D衍生物和广泛的细胞色素P450抑制剂治疗的小鼠， 酮康唑，以评估是否补充或消耗主要维生素D3代谢产物保护 TP 53和TP 54中肿瘤的突变谱， XPC基因也将被分析，以了解所涉及的途径。这些研究将使 对理解维生素D的生理和细胞机制作用的重要贡献， 调节皮肤中的DNA修复和抑制UV光致癌作用。由此产生的基础生物学 这些见解可以提供合理的依据，帮助指导有关营养中维生素D的卫生政策决定， 皮肤癌的预防退伍军人以及一般人群。

Both vitamin D deficiency and skin cancers arising from epidermal keratinocytes are highly prevalent in Veterans. Although exposure to the ultraviolet (UV) wavelengths normally found in sunlight initiates vitamin D biosynthesis, the practice is not currently recommended since UV is also the principal cause of skin cancers. However, there remains uncertainty as to whether the relatively low doses sufficient for vitamin D production in the skin are associated with a meaningful risk of skin cancer in healthy individuals, and the Institute of Medicine's report on this topic identified resolving this issue as a major research need. Based on work in both our laboratory and those of others, there is evidence that UV-inducible mechanisms such as DNA repair might be directly coupled to vitamin D signaling. For example, we have observed that mice lacking the vitamin D receptor are prone to develop UV-induced epidermal tumors, and vitamin D and some of its metabolites induce DNA repair proteins. On the other hand, mice unable to synthesize the most biologically active form of vitamin D are not tumor-prone. However, it remains possible that one or more of the multiple other vitamin D metabolites does have anti-photocarcinogenic effects, including induction of nucleotide excision repair activity, the principal mechanism for removing UV-induced DNA lesions. The overall hypothesis of this research proposal is that vitamin D or its derivatives stimulate compensatory mechanisms to repair the collateral DNA damage associated with its own UV-mediated photosynthesis and thus minimizes photocarcinogenic effects. In Aim I, cultured keratinocytes and epidermal explants derived from CYP27B1-null mice will be used to compare the activities of major vitamin D3 metabolites for their effects on nucleotide excision repair. Both exogenous supplementation and chemical inhibition to modulate endogenous vitamin D metabolite levels will be employed, and expression of repair genes as well as repair activity and UV resistance will be assayed. In Aim II, both genomic and non-genomic mechanisms for vitamin D's effects on DNA repair will be investigated. Cultured keratinocytes and mouse epidermal explants will be used to assess the relevance of the vitamin D receptor in DNA repair, and the assembly and stability of nucleotide excision repair factors at lesions. Aim III will use mice treated with the most active vitamin D derivative and the broad cytochrome P450 inhibitor, ketoconazole, to assess whether supplementation or depletion of the major vitamin D3 metabolites protects animals from photocarcinogenesis, or predisposes them to it. Mutational spectra of tumors in the TP53 and XPC genes will also be analyzed to understand the pathways involved. These studies should make an important contribution to understanding the physiological and cellular mechanistic role of vitamin D in regulating DNA repair in skin and in suppressing UV photocarcinogenesis. The resulting fundamental biological insights may allow a rational basis to help guide health policy decisions regarding vitamin D in nutrition and skin cancer prevention for Veterans as well as the general population.