柚皮素在炎性脱髓鞘疾病中的免疫调节作用

Multiple sclerosis (MS) is an autoimmue disease charaterized by proinflammatory cytokines and CD4+ T cell-mediated demyelination of the central nervous system (CNS). Experimental autoimmune encephalomyelitis (EAE) is a well-established animal model for human MS due to the similarities in clinical, immunological, and neuropathological features betweem MS and EAE. The key pathogenesis of MS involves a process in which myelin-reactive CD4+ T cells enter the CNS and orchestrate their effector function on the myelin sheath resulting in tissue destruction and consequent loss of function.CD4+ T helper (Th) subsets Th1, Th9, and Th17 cells are implicated in inducing autoimmunity whereas regulatory T cells (Treg) have a protective effect. Currently, the common therapies have limited efficacy and often follow by serious side effect. Etiology of autoimmune diseases is not clear. Genetic predisposition is a key risk factor and environmental factors are also involved. Nutritional intervention has been shown potentially to have a positive impact on autoimmune disorders via modulating CD4+ T cell subset balance. Our and other studies have showed that naringenin from the grapefruits has beneficial effects, i.e.,,anti-inflammation, delaying the onset of EAE, attenuating the clinical symptoms, reducing demylination and infiltration of CNS, inhibiting T cell, especially CD4+ T cell proliferation, and reducing the production of IFN-γ (Th1) and IL-17 (Th17) secreted by MOG-specific CD4+ T cells. Furthermore, naringenin could inhibit anti-inflammatory cytokine IL-6 and TNF-α production from splenocytes induced by LPS that contribute to naïve CD4+ T cell to differentiate different Th cell subset, and directly induce naïve CD4+ T cell to differentiate Treg cells. In this project, using the EAE mice as in vivo animal model, CD4+ T cell differentiation and chemokine experiments as in vitro models, we will explore the underlying mechanisms what narigenin reduce the inflammatory cell infiltration and demylination of CNS via impacting the production of chemokine and adhesion moleculars by flow cytometry, adoptive-transfer, and immunohistopathology methods. If done this study, it will contribute to elucidating the anti-inflammatory and immunomodulatory effects of bioactivte componds from food and further providing clues to develop the new anti-inflammatory and anti-autoimmune drugs from food.

炎症及CD4+T细胞亚群之间的免疫平衡介导多发性硬化症（MS）的发生、发展及转归。营养干预在临床中表现出抗炎和对CD4+T细胞亚群的双向免疫调节作用，因此研究源于食物的植物化合物在免疫中的调节作用已引起广泛的关注。前期研究证实，源于柚子类的多酚化合物柚皮素具有抗炎、推迟MS的动物模型EAE的发病时间和缓解临床症状、减少中枢神经系统（CNS）髓鞘脱失及炎症细胞浸润、抑制T细胞的增殖和促炎症细胞因子的产生。本项目在体内以EAE为动物模型，体外以细胞分化和趋化试验为模型，证明柚皮素在EAE中的作用机制，采用流式细胞术、过继转移试验、免疫荧光组织化学等，明确柚皮素通过影响趋化因子和粘附因子的产生而导致削弱炎症细胞的迁移能力及CD4+T细胞亚群的平衡，最终实现减少CNS髓鞘脱失和炎症细胞浸润的作用。研究结果为柚皮素用于MS的辅助治疗及开发膳食来源的植物化合物的抗炎和免疫调节作用药物提供新的理论基础。

炎症及自身T细胞介导的炎症反应是自身免疫病发生的关键。选择性抑制T细胞所介导的免疫反应可以用于预防和治疗炎症性疾病和自身免疫相关疾病。由于传统的治疗方法疗效有限，且常伴有明显的副作用，营养干预可能为改善自身免疫病提供一种替代和互补的方法。膳食来源的植物活性成分柚皮素具有抗炎和抗氧化的功效。本研究利用多发性硬化症小鼠模型（EAE）、T细胞活化和分化及趋化实验，探讨柚皮素是否及如何影响EAE的发生发展。体内研究发现柚皮素膳食干预降低EAE的发病率和延缓EAE的发生发展。其机理是柚皮素膳食干预减少中枢神经系统（CNS）炎症细胞的浸润和髓鞘的脱失及抑制CNS和外周免疫器官淋巴结中促炎症 Th1、Th9和Th17细胞的数量，但不影响抗炎症Th2和Treg细胞的数量，同时也抑制它们的特异性转录因子T-bet、PU.1和RORγt的表达；再者其可以通过调控趋化因子或其受体的表达、抗原递呈细胞（树突状细胞）的成熟及迁移能力而削弱抗原特异性T细胞的免疫应答及缓解过继转移病理性T细胞的迁移而维持血脑屏障的完整性进而延缓EAE。进一步机理研究发现柚皮素通过调控T细胞的细胞周期和IL-2/IL-2R信号通路而抑制T细胞的活性。在CD4+ naive T细胞分化为不同的Th细胞亚群的过程中，柚皮素通过调控Th细胞分化的网络相关蛋白的表达而影响Th细胞亚群的分化，如抑制Th1和Th17细胞及Treg细胞的产生，但不影响Th2细胞分化所产生的IL-4和IL-13，而抑制IL-10的产生。重要的是其体外可以通过影响IL-6的下游信号而调控Treg和Th17细胞的分化的免疫平衡。本研究明确了营养干预可以作为一种防治自身免疫病发生发展的替代方法，为柚皮素可能成为具有改善自身免疫性疾病和调节自身免疫平衡的膳食成分或药物提供了重要的实验数据。