Research Laboratories and Academic Division of Clinical Rheumatology, Department of Internal Medicine, University of Genova, Genova, Italy.
Ann N Y Acad Sci. 2014 May;1317:39-46. doi: 10.1111/nyas.12432. Epub 2014 Apr 16.
The endogenous serum metabolite of vitamin D (calcitriol, 1,25(OH)2 D3 ) is considered a true steroid hormone (D hormone), and like glucocorticoids (GCs) and gonadal hormones, may exert several immunomodulatory activities. Serum vitamin D deficiency (25(OH) D), and therefore reduced 1,25(OH)2 D3 availability, is considered a risk factor for several chronic/inflammatory or autoimmune conditions, including infectious diseases, type 1 diabetes, multiple sclerosis, and especially autoimmune rheumatic diseases (ARD). In ARD in particular, 1,25(OH)2 D3 regulates both innate and adaptive immunity, potentiating the innate response (antimicrobial activity) but reducing adaptive immunity (antigen presentation, T and B cell activities). Regarding a possible synergism between vitamin D and GCs, several studies show that 1,25(OH)2 D3 has significant additive effects on dexamethasone-mediated inhibition of human lymphocyte and monocyte proliferation. Conversely, vitamin D deficiency seems to play a role in increasing autoantibody production by B cells, and seasonal vitamin D declines may trigger flares in ARD, as recently shown. Finally, 1,25(OH)2 D3 seems to reduce aromatase activity and limit the negative effects related to increased peripheral estrogen metabolism (cell proliferation, B cell overactivity).
维生素 D（1,25-二羟维生素 D3，calcitriol）的内源性血清代谢物被认为是一种真正的甾体激素（D 激素），与糖皮质激素（GCs）和性腺激素类似，可能具有多种免疫调节作用。血清维生素 D 缺乏（25-羟维生素 D，25(OH) D），从而导致 1,25-二羟维生素 D3 的可用性降低，被认为是几种慢性/炎症或自身免疫性疾病的危险因素，包括传染病、1 型糖尿病、多发性硬化症，特别是自身免疫性风湿病（ARD）。在 ARD 中，1,25-二羟维生素 D3 调节固有免疫和适应性免疫，增强固有免疫反应（抗微生物活性），但降低适应性免疫（抗原呈递、T 和 B 细胞活性）。关于维生素 D 和 GCs 之间可能存在协同作用，有几项研究表明，1,25-二羟维生素 D3 对地塞米松介导的人淋巴细胞和单核细胞增殖具有显著的增效作用。相反，维生素 D 缺乏似乎在增加 B 细胞产生自身抗体中起作用，并且维生素 D 的季节性下降可能会引发 ARD 的发作，最近已经表明了这一点。最后，1,25-二羟维生素 D3 似乎可以降低芳香酶的活性，并限制与外周雌激素代谢增加相关的负面影响（细胞增殖、B 细胞过度活跃）。
