Department of Dermatology, Dresden University of Technology, Germany.
Dermatol Ther. 2010 Jan-Feb;23(1):2-12. doi: 10.1111/j.1529-8019.2009.01286.x.
Irradiation of human skin with ultraviolet B (280-320 nm) initiates the photochemical conversion of 7-dehydrocholesterol via previtamin D3 to vitamin D3. Vitamin D3 needs for its activation two hydroxylation steps in the liver and kidney. The final product, hormonally active 1alpha,25-dihydroxyvitamin D3 (calcitriol), arrives via the circulation to its target tissues and acts in a genomic or nongenomic manner. It has been found that human skin irradiated with ultraviolet B also is able to produce calcitriol in substantial amounts. This cutaneous vitamin D3 pathway is unique and, most likely, of considerable relevance for healthy and diseased skin. It is well known that topical application of calcitriol and its analogs can improve hyperproliferative skin diseases. Some studies have convincingly demonstrated that calcitriol and other vitamin D analogs may also be used for the treatment of immunological, inflammatory, and infectious skin diseases. More recently, it has been found that calcitriol or vitamin D analogs have photoprotective effects and can reduce UV-induced deoxyribonucleic acid damage.
人体皮肤受到紫外线 B（280-320nm）的照射，会通过前维生素 D3 将 7-脱氢胆固醇转化为维生素 D3。维生素 D3 需要在肝脏和肾脏中进行两次羟化反应才能被激活。最终产物，具有生物活性的 1α，25-二羟维生素 D3（骨化三醇），通过血液循环到达靶组织，并以基因组或非基因组方式发挥作用。现已发现，人体皮肤经紫外线 B 照射后也能大量产生骨化三醇。这种皮肤维生素 D3 途径是独特的，很可能对健康和患病皮肤具有重要意义。众所周知，局部应用骨化三醇及其类似物可以改善过度增殖性皮肤病。一些研究令人信服地证明，骨化三醇和其他维生素 D 类似物也可用于治疗免疫、炎症和感染性皮肤病。最近发现，骨化三醇或维生素 D 类似物具有光保护作用，可减少 UV 诱导的脱氧核糖核酸损伤。
