Canonical and non-canonical vitamin D activation pathways in systemic lupus

项目摘要 在系统性红斑狼疮（SLE）中，缺乏维生素D3（D3）是免疫系统的重要调节因子， 系统，是常见的，并与疾病的严重程度和疲劳。然而，对维生素D的反应 补充剂的范围从有些益处到没有益处，即使在正常血清中 获得25（OH）D3（肝脏维生素D3代谢物）。这种可变反应的潜在机制 是未知的，代表了我们知识中的一个关键空白。这项提议将检验一个非常新颖的假设， 免疫应答的有效调节需要免疫细胞固有的D3代谢。拟议 机制与当前的教条形成鲜明对比，例如，D3首先在肝脏中通过羟基化被激活， 25（OH）D3，然后在肾脏中通过CYP 27 B1在C1α处进行第二次羟基化，产生1，25（OH）2D 3， 与先天性和适应性免疫细胞中的维生素D受体（VDR）相互作用启动信号级联， 是免疫调节的。最近发现的一种非典型的代谢产物， 维生素D活化途径，始于D3被类固醇生成酶CYP 11 A1羟基化， C20并产生20（OH）D3作为第一代谢物，其可以下调T细胞应答，而不需要 关于VDR重要的是，CYP 11 A1在T细胞和其他免疫细胞中表达，提供了一种替代方案 免疫细胞内在产生非典型肝脏非依赖性活性形式D3的机制 在免疫调节中的重要作用。这种非经典途径的缺陷将产生以下表型效应： 维生素D缺乏症不能通过规范补充来纠正。CYP11A1- 依赖性内源性产生的20（OH）D3和20，23（OH）2D 3可通过以下方式发挥免疫调节活性： 通过经典途径（VDR依赖性）拮抗NF-κB和通过（ii）抑制IL 17表达 通过作为RORα和RORγ的反向激动剂发挥作用。这些途径并不被认为是 SLE中维生素D依赖性调节丧失的机制，这是本提案的目标。解决 这一挑战，提出了以下目标：（1）确定是否规范和/或非规范 维生素D信号传导的组分在SLE患者的免疫细胞中减少，以及（2）为了评估 假设维生素D3依赖的NFκB和/或RORγ/α信号通路衰减是 与正常受试者相比，SLE患者的免疫细胞有缺陷。后者将包括一个高度 机械的方法。这项提案的发现将极大地推动维生素D领域的发展 在SLE/自身免疫的背景下，T细胞、B细胞和单核细胞的调节活性。此外还 预计他们将为使用非钙维生素D衍生物治疗自身免疫性疾病铺平道路。 紊乱

Project Summary In systemic lupus erythematosus (SLE) the deficiency in vitamin D3 (D3), an essential regulator of immune system, is common and is associated with disease severity and fatigue. However, responses to vitamin D supplementation ranged from some benefit to no benefit even in situations where normal serum levels of 25(OH)D3 (liver vitamin D3 metabolite) was achieved. The underlying mechanism/s for this variable response is unknown and represents a critical gap in our knowledge. This proposal will test a very novel hypothesis that efficient regulation of immune response requires immune cell intrinsic metabolism of D3. The proposed mechanism strikingly contrasts the current dogma, e.g., D3 is first activated in the liver by hydroxylation into 25(OH)D3 followed by a second hydroxylation at C1α by CYP27B1 in kidneys to produce 1,25(OH)2D3 that by interacting with vitamin D receptor (VDR) in innate and adaptive immune cells initiates a signaling cascade that is immunoregulatory. What has not been appreciated is the recent discovery of a non-canonical metabolic pathway of vitamin D activation that starts with hydroxylation of D3 by the steroidogenic enzyme CYP11A1 at C20 and produces 20(OH)D3 as the first metabolite that can down regulate T cell responses without the need for VDR. Importantly, CYP11A1 is expressed in T cells and other immune cells, providing an alternative mechanism for immune cell intrinsic production of non-canonical liver-independent active forms of D3 with critical role in immune regulation. Defects in this non-canonical pathway will have the phenotypic effects of vitamin D deficiency that cannot be rectified by canonical supplementation. Mechanistically, CYP11A1- dependent endogenously produced (20(OH)D3 and 20,23(OH)2D3 can exert immunoregulatory activity by (i) antagonizing NF-κB through classical pathway (VDR-dependent) and by (ii) suppressing Il17 expression through action as inverse agonists on RORα and RORγ. These pathways have not been considered as the mechanism for loss of vitamin D dependent regulation in SLE, which is the goal of this proposal. To address this challenge, the following aims are proposed: (1) To determine if canonical and/or non-canonical components of vitamin D signaling are decreased in immune cells from patients with SLE, and (2) To evaluate the hypothesis that the vitamin D3-dependent attenuation of NFκB and/or RORγ/α signaling pathways is defective in immune cells from SLE patients in comparison to normal subjects. The latter will include a highly mechanistic approach. The findings from this proposal will greatly advance the field with respect to vitamin D regulatory activity in T cells, B cells and monocytes within the context of SLE/autoimmunity. In addition, it is expected that they will pave the way for use of non-calcemic vitamin D derivatives for therapy of autoimmune disorders.