Studying the effects of vitamin D on FOXP3 and IL-17 expression in human CD4+ T c

描述（由申请人提供）：维生素及其代谢物是许多生理过程所必需的，包括调节免疫系统。例如，维生素D3 （VD3）可以影响免疫细胞的功能，包括巨噬细胞、树突状细胞（DC）、B细胞和T细胞。25-羟基维生素D3 （25(OH)VD3）是VD3的主要循环形式，而1,25(OH)2VD3是VD3最具生理活性的形式。令人感兴趣的是，25(OH)VD3血清水平降低在自身免疫性疾病患者中有报道，包括类风湿关节炎（RA）、系统性红斑狼疮（SLE）、1型糖尿病（DM）和多发性硬化症（MS）。事实上，在MS患者和实验性变应性脑炎（EAE， MS动物模型）小鼠中补充VD3可以减轻他们的疾病。尽管这些发现支持VD3在自身免疫中的作用，但其机制在很大程度上是未知的。解决这一问题至关重要，因为它为补充VD3提供了科学依据，并可能导致开发新的自身免疫治疗方法。白细胞介素-17 （IL-17）产生T辅助17 （Th17）细胞和叉头盒P3 （FOXP3）阳性调节性T细胞（以下简称FOXP3+ Treg）在自身免疫和炎症中发挥重要作用。Treg群可能包含两个亚群，一个称为自然发生的Treg，由胸腺发育（FOXP3+ nTreg），另一个称为外周常规CD4+ T细胞诱导（FOXP3+ iTreg）。IL-17的过量产生以及FOXP3+ Treg的数量和功能的改变与各种自身免疫性疾病的动物模型及其人类对应体有关。有研究表明，Th17细胞和FOXP3+ iTreg从普通CD4+ T细胞中分化出来具有相互关系。目前的应用解决了1,25(OH)2VD3直接调节人CD4+ T细胞中FOXP3和IL-17基因表达的假设，导致FOXP3+iTreg的发育增强，并相互抑制Th17细胞分化和IL-17的产生。目的1)研究1,25(OH)2VD3对FOXP3+ iTreg和Th17细胞发育的影响，以及这种影响在人CD4+ T细胞中的机制；2)通过鉴定和表征人FOXP3和IL-17基因中维生素D受体的结合位点，探讨1,25(OH) 2vd3介导的FOXP3和IL-17基因调控的分子机制。这些研究的结果将通过FOXP3+ Treg和Th17细胞确定自身免疫和VD3之间的机制联系，并为自身免疫补充VD3和开发VD3及其类似物的新治疗方法提供科学依据。

DESCRIPTION (provided by applicant): Vitamins and their metabolites are essential for a number of physiological processes including regulating the immune systems. For instance, vitamin D3 (VD3) can affect the functions of immune cells including macrophages, dendritic cells (DC), B and T cells. 25-hydroxyvitamin D3 (25(OH)VD3) is the main circulating form of VD3 whereas 1,25(OH)2VD3 is the most physiologically active form of VD3. Of interest, decreased serum levels of 25(OH)VD3 have been reported in patients with autoimmune diseases including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), type I diabetes mellitus (DM) and multiple sclerosis (MS). In fact, VD3 supplementation in patients with MS and mice with experimental allergic encephalitis (EAE, animal model of MS) reduced their disease. Although these findings support a role for VD3 in autoimmunity, its mechanism(s) is largely unknown. Addressing this issue is critical since it provides a scientific rationale for supplementing VD3 as well as can lead to developing new treatments in autoimmunity. Interleukin-17 (IL-17)-producing T helper 17 (Th17) cells and forkhead box P3 (FOXP3)-positive regulatory T cells (hereafter called FOXP3+ Treg) play major roles in autoimmunity and inflammation. The Treg population likely contains two subsets, one called naturally occurring Treg developed from the thymus (FOXP3+ nTreg) and the other one induced from conventional CD4+ T cells in the periphery (FOXP3+ iTreg). Overproduction of IL-17 as well as alterations in the numbers and function of FOXP3+ Treg have been linked to animal models of various autoimmune diseases and their human counterparts. Studies suggest that the differentiation of Th17 cells and FOXP3+ iTreg from na¿ve CD4+ T cells have a reciprocal relationship. The current application address the hypothesis that 1,25(OH)2VD3 directly regulates the FOXP3 and IL-17 gene expression in human CD4+ T cells, leading to the enhanced development of FOXP3+iTreg with a reciprocal suppression of Th17 cell differentiation and IL-17 production. The goal of the application is addressing the hypothesis with the following specific aims: Aim 1) Investigate the effects of 1,25(OH)2VD3 on developing FOXP3+ iTreg and Th17 cells as well as the mechanisms underlying such effects in human CD4+ T cells; and Aim 2) Investigate the molecular mechanism underlying 1,25(OH)2VD3-mediated FOXP3 and IL-17 gene regulation through identifying and characterizing the binding site(s) of the vitamin D receptor in the human FOXP3 and IL-17 genes. The results of the proposed studies will identify a mechanistic link between autoimmunity and VD3 via FOXP3+ Treg and Th17 cells and provide a scientific rationale for supplementing VD3 in autoimmunity and developing new treatments with VD3 and its analogues. Public Health Relevance: Vitamins are known to modulate immune cells like CD4+ T cells, a type of white blood cells. The goal of the current application is to investigate the effects of vitamin D on two different CD4+ T cell subsets: T-helper 17 cells with inflammatory property and regulatory T cells with anti-inflammatory property. The results of the studies will advance our knowledge on how vitamin D can be used as a therapeutic agent to improve inflammation in humans.