The Role of Mercury Exposures in Disrupting Central Tolerance

描述（由申请人提供）：汞（Hg）是一种有效的免疫调节剂，在动物模型和人类中都被认为是导致自身免疫性疾病的因素。在动物模型中，对汞的易感性受到遗传限制，但由于人类种群的异质性，很难确定人类的遗传限制。然而，由于汞在环境中广泛分布，汞是暴露于环境因素与自身免疫性疾病发展相关，以及外源性因素与选择性遗传背景相互作用导致免疫性疾病的一个很好的例子。不幸的是，目前对汞如何破坏免疫功能的机制理解仍然难以捉摸。此外，虽然研究清楚地表明汞暴露与自身免疫性疾病风险增加之间存在关联，但目前还没有分子生物标志物可作为暴露标志，在影响人类的80多种具有个体特征的自身免疫性疾病的广谱范围内确定汞的参与。最近有越来越多的人认识到B细胞在自身免疫性疾病中的作用。已知B细胞受体（BCR）信号通路的缺陷会破坏中枢耐受性，因此与自身免疫性疾病有关。Lyn是Src家族蛋白酪氨酸激酶，已被证明与BCR信号通路的启动和调控密切相关。Lyn功能是通过几种不同酪氨酸残基的磷酸化来控制的。在初步实验中，研究人员采用先进的蛋白质组学和多色磷酸流式细胞术方法来研究汞与小鼠B细胞的相互作用。这些实验的结果使他们假设，汞暴露后Lyn磷酸化谱和功能的改变可能是汞中毒个体中介导暴露于汞的B细胞免疫毒性和自身免疫B细胞库出现的关键相关现象。在这种情况下，特定Lyn磷酸化谱在B细胞中的表达可能是汞暴露个体中汞诱导自身免疫的有用暴露标志。研究人员现在提议在初步实验的基础上进行扩展。他们将利用对汞中毒具有不同但明确的遗传易感性的小鼠品系，并采用互补的蛋白质组学和多色磷酸流式细胞术方法直接研究汞暴露改变Lyn磷酸化谱和功能的能力，从而干扰BCR信号转导，并最终破坏脾B细胞的中枢耐受。

DESCRIPTION (provided by applicant): Mercury (Hg) is a potent immunomodulator that has been implicated as a factor contributing to autoimmune disease in animal models as well as in humans. In animal models, susceptibility to Hg is genetically restricted, but genetic restriction i humans has been difficult to establish because of the heterogeneous nature of human populations. Nevertheless, because Hg is widely distributed in the environment, Hg is an excellent example of where exposure to an environmental agent has been associated with the development of autoimmune disease, and where an extrinsic agent interacts with selective genetic backgrounds to cause immunologic disease. Unfortunately at this time a mechanistic understanding of how Hg disrupts immune function remains elusive. Furthermore, while studies clearly demonstrate an association between Hg exposures and increased risk of autoimmune disease, there are currently no molecular biomarkers that can be utilized as an exposure signature to identify Hg involvement across the broad spectrum of the over 80 individually characterized autoimmune diseases which affect humans. Recently there has been increased appreciation of the involvement of B cells in autoimmune disease. Defects in the B Cell Receptor (BCR) signaling pathway are known to disrupt central tolerance and consequently to be associated with autoimmune disease. Lyn is a Src family protein tyrosine kinase which has been shown to be intimately involved in the initiation and regulation of the BCR signaling pathway. Lyn functionality is controlled through the phosphorylation of several different tyrosine residues. In preliminary experiments the investigators have employed advanced proteomic and multicolor phosphoflow cytometric approaches to investigate the interaction of Hg with mouse B cells. Results from these experiments have led them to hypothesize that an altered Lyn phosphorylation profile and functionality consequent to Hg exposure may be key interrelated phenomena mediating immuntoxicity of B cells which have been exposed to Hg, and the emergence of an autoimmune B cell repertoire in mercury intoxicated individuals. This being the case, the expression of specific Lyn phosphorylation profiles in B cells may be a useful exposure signature of Hg-induced autoimmunity in Hg exposed individuals. The investigators now propose to expand upon preliminary experiments. They will utilize mouse strains with different, but well defined genetic susceptibilities to Hg intoxication, and employ complementary proteomic and multicolor phosphoflow cytometric approaches to directly investigate the ability of Hg exposures to alter Lyn phosphophorylation profiles and functionality, so as to interfere with BCR signal transduction, and ultimately disrupt central tolerance in splenic B cells.