Analyzing genetic and environmental molecular mechanisms causing autoimmune thyroid diseases

自身免疫性甲状腺疾病(AITD)、Graves病(GD)和桥本甲状腺炎(HT)是最常见的自身免疫性疾病。由于AITD的发病机制尚不完全清楚，因此对其进行对症治疗(高血压患者采用激素替代治疗，GD患者采用激素抑制治疗)，因此患者往往难以处理。因此，需要针对导致AITD的自身免疫机制的新的治疗方法。AITD是由易感基因和环境因素相互作用引起的复杂疾病。我们和其他人已经定位并确认了几个AITD基因，包括甲状腺球蛋白(TG)。我们还表明，在病毒感染过程中产生的干扰素α(干扰素α)是触发AITD的关键细胞因子。目前的提案旨在剖析导致AITD的遗传和环境机制，以便为它们提供新的治疗方法。我们的重点是易患AITD的遗传机制(AIM 1)、AITD的环境诱因(AIM 2)和AITD的药物诱因(AIM 3)。在目标1中，我们将验证这样的假设，即与AITD相关的TG中的SNPs错义通过增加TG的错误折叠并促进其降解为免疫原肽而易患AITD。我们将使用我们开发的一种新的AITD小鼠模型，在该模型中，用人TG基因在非复制型腺病毒载体中免疫诱导自身免疫性甲状腺炎。这个模型使我们能够测试不同的TG SNPs对AITD的易感或保护作用，并评估这些TG变异引发AITD的体内机制。在目标2中，我们将验证这样的假设，即干扰素α通过将甘油三酯的自噬降解转化为免疫原肽来触发AITD。我们将使用细胞系和甲状腺干扰素α过度表达的小鼠模型来确定TG降解的自噬-溶酶体途径；我们还将在小鼠模型和AITD患者的PBMC中测试产生的TG多肽的免疫原性。这一目标将定义一种新的统一机制，通过干扰素α介导的自身抗原降解来触发自身免疫。在目标3中，我们将检验一种假设，即表达在甲状腺细胞上的程序性死亡配体1(PD-L1)具有内在活性，在炎症过程中保护甲状腺细胞免受细胞内应激的影响，免疫检查点抑制物(ICI)通过阻断PD-L1的这些内在保护作用而触发甲状腺炎。我们将使用我们开发的一种新的ICI-甲状腺炎小鼠模型来剖析PD-L1阻断在体内触发甲状腺炎的机制。这一目标将明确ICI诱导的甲状腺炎的机制以及甲状腺PD-L1在AITD中的作用。总的来说，这项提案中的研究将有助于推进我们的长期目标，即为自身免疫性甲状腺疾病设计有针对性的基于机制的疗法。

The autoimmune thyroid diseases (AITD), Graves’ disease (GD) and Hashimoto’s thyroiditis (HT), are the most common autoimmune diseases. Because their mechanisms are not fully understood, AITD are treated symptomatically (hormone replacement in HT or hormone suppression in GD) and as a result, patients are often difficult to manage. Therefore, new therapies are needed that target the autoimmune mechanisms causing AITD. AITD are complex diseases caused by interactions between susceptibility genes and environmental triggers. We and others have mapped & confirmed several AITD genes, including thyroglobulin (Tg). We have also shown that interferon alpha (IFNα), produced during viral infections, is the key cytokine triggering AITD. The current proposal aims to dissect the genetic and environmental mechanisms causing AITD in order to target them with novel therapies. Our focus is on genetic mechanisms predisposing to AITD (Aim 1), environmental triggers of AITD (Aim 2), and medication triggers of AITD (Aim 3). In Aim 1 we will test the hypothesis that missense SNPs in Tg that are associated with AITD predispose to AITD by increasing Tg misfolding and enhancing its degradation into immunogenic peptides. We will use a novel muse model of AITD developed by us, in which autoimmune thyroiditis is induced by immunization with human Tg cDNA in a non-replicating Adenovirus vector. This model enables us to test the effects of different Tg SNPs shown to be susceptible or protective for AITD, and to assess in vivo mechanisms by which these Tg variants trigger AITD. In Aim 2 we will test the hypothesis that IFNα triggers AITD by engaging the autophagic degradation of Tg into immunogenic peptides. We will use cell lines and a mouse model with thyroid over-expression of IFNα to define the autophagy-lysosomal pathways of Tg degradation; we will also test the immunogenicity of the generated Tg peptides in mouse models and PBMC’s from AITD patients. This aim will define a new unifying mechanism for triggering autoimmunity by IFNα-mediated autoantigen degradation. In Aim 3 we will test the hypothesis that Programmed death-ligand 1 (PD-L1) expressed on thyrocytes has intrinsic activity protecting them from intracellular stress during inflammation, and that Immune Checkpoint Inhibitors (ICI’s) trigger thyroiditis by blocking these intrinsic protective effects of PD-L1. We will use a new mouse model of ICI-thyroiditis we developed to dissect the mechanisms by which PD-L1 blockade triggers thyroiditis in vivo. This aim will define the mechanisms of ICI-induced thyroiditis as well as the role of thyroidal PD-L1 in AITD. Collectively, the studies in this proposal will help advance our long-term goal, to design targeted mechanism-based therapies for autoimmune thyroid diseases.