Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA.
Photochem Photobiol Sci. 2017 Mar 16;16(3):411-415. doi: 10.1039/c6pp00308g.
Acheson et al. (1960) observed an inverse relationship between sunlight exposure and the incidence of Multiple Sclerosis (MS). This led to the suggestion that increased levels of vitamin D caused by sunlight in some way suppresses MS. Further, super physiological doses of the metabolically active metabolite of vitamin D, i.e. 1α,25 dihydroxy vitamin D suppresses the animal model of MS i.e. experimental autoimmune encephalomyelitis (EAE). However, this response was accompanied by hypercalcemia. Hypercalcemia itself can suppress EAE. The ability of 1,25(OH)D to suppress EAE in mice is largely eliminated by a low calcium diet until hypercalcemia is induced by high doses of 1,25(OH)D that causes mobilization of calcium from the skeleton. Of great importance is the finding that vitamin D deficiency prevents EAE, a finding dramatically opposite to the original hypothesis. Further, vitamin D receptor knock out animals do not develop EAE supporting the idea that vitamin D does not suppress EAE. Upon revisiting the inverse relationship between light exposure and incidence of MS, a narrow band of light (300-315 nm) was discovered that prevents EAE without a change in serum levels of 25 hydroxy vitamin D (indicator of vitamin D status). Clinical trials are underway to explore the possible use of this narrow band light as a treatment to stop the progression of MS, while biochemical studies are underway to evaluate the mechanism of action of the narrow band light.
Acheson 等人（1960 年）观察到阳光照射与多发性硬化症（MS）发病率之间存在反比关系。这导致了这样一种观点，即阳光照射以某种方式增加维生素 D 的水平会抑制 MS。此外，维生素 D 的代谢活跃代谢物 1α,25 二羟维生素 D 的超生理剂量会抑制 MS 的动物模型，即实验性自身免疫性脑脊髓炎（EAE）。然而，这种反应伴随着高钙血症。高钙血症本身可以抑制 EAE。低钙饮食可大大消除 1,25(OH)D 在小鼠中抑制 EAE 的能力，直到高剂量 1,25(OH)D 引起钙从骨骼动员导致高钙血症。非常重要的是发现维生素 D 缺乏会阻止 EAE 的发生，这一发现与最初的假设截然相反。此外，维生素 D 受体敲除动物不会发生 EAE，这支持了维生素 D 不会抑制 EAE 的观点。重新审视光照与 MS 发病率之间的反比关系时，发现了一种窄带光（300-315nm），它可以预防 EAE，而血清 25 羟维生素 D 水平（维生素 D 状态的指标）没有变化。正在进行临床试验以探索使用这种窄带光作为阻止 MS 进展的治疗方法的可能性，同时正在进行生化研究以评估窄带光的作用机制。
