Interferon gamma in autoimmune thyroiditis & thyroid function

干扰素γ（IFN γ）已被牵连在自身免疫性（桥本氏）甲状腺炎的发病机制。我们已经产生了在甲状腺特异性表达IFNg的转基因小鼠，并表明IFN γ a）直接诱导原发性甲状腺功能减退伴NIS表达降低; B）诱导Hurthle细胞样并增加甲状腺脂肪; c）保护免受自身免疫性甲状腺炎。具体目的1是检验IFN-γ驱动的免疫蛋白酶体激活对Hurthle细胞个体发育至关重要的假设。我们将：i）测试免疫蛋白酶体的药理学或遗传阻断是否抑制Hurthle细胞的出现; ii）评估来自thyr-IFN γ转基因小鼠以及来自Hurthle细胞病变患者的甲状腺中的原位免疫蛋白酶体表达。具体目标2是阐明IFN γ保护自身免疫性甲状腺炎的机制。我们推测这种保护作用是通过caspase-8依赖性的细胞凋亡激活介导的，这导致了自身反应性甲状腺特异性淋巴细胞的死亡。我们将用半胱天冬酶-8的失活形式抑制自身反应性T细胞，并将T细胞过继转移到野生型或thyr-IFN γ转基因宿主中，然后评估甲状腺炎的发病率和严重程度。我们还将thyr-IFN γ转基因与缺乏IRF-1或IRF-4的敲除小鼠杂交，IRF-1或IRF-4是两种将IFN γ信号传导与caspase-8依赖性凋亡联系起来的关键转录因子。具体目的3是研究IFNg与白细胞介素-12（IL-12）对甲状腺自身免疫和功能的相互作用。我们已经产生了转基因小鼠，表达IL-12特异性在甲状腺。小鼠自发地发展淋巴细胞性甲状腺炎和原发性甲状腺功能减退症，NIS表达增加。我们将thyr-IL-12转基因与thyr-IFNg转基因杂交，以评估IFN γ的疾病抑制作用是否优于IL-12的疾病促进作用，以及IFNg和IL-12是否协同诱导更严重形式的甲状腺功能减退症。具体目标4是研究为什么来自thyr-IFNg转基因的甲状腺含有增加数量的脂肪细胞，并评估这种增加是否影响甲状腺功能。我们推测，甲状腺巨噬细胞在体内引发IFNg促进基质前脂肪细胞分化为成熟的脂肪细胞。我们将从转基因和控制与同基因前脂肪细胞甲状腺巨噬细胞共培养，监测收购典型的脂肪细胞的形态特征。我们还假设需要增强的TSH信号传导来诱导富含脂肪细胞的表型，并将thyr-IFNg转基因小鼠与TSH受体敲除小鼠杂交。

Interferon gamma (IFNgamma) has been implicated in the pathogenesis of autoimmune (Hashimoto's) thyroiditis. We have generated transgenic mice that express IFNg specifically in the thyroid gland, and shown that IFNgamma a) directly induces primary hypothyroidism with decreased NIS expression; b) induces Hurthle cells-like and increase thyroidal fat; c) protects from autoimmune thyroiditis. Specific aim 1 is to test the hypothesis that the IFNg-driven activation of the immunoproteasome is critical to the ontogeny of Hurthle cells. We will: i) test whether pharmacologic or genetic blocks of the immunoproteasome inhibit the appearance of Hurthle cells; ii) evaluate in situ immunoproteasome expression in thyroids from thyr-IFNgamma transgenic mice, as well as from patients with Hurthle cell lesions. Specific aim 2 is to unravel the mechanism through which IFNgamma protects from autoimmune thyroiditis. We hypothesize that this protective effect is mediated by a caspase-8 dependent activation of apoptosis, which results in death of autoreactive, thyroid-specific lymphocytes. We will transduce autoreactive T cells with an inactive form of caspase-8 and adoptively transfer T cells to wild type or thyr-IFNgamma transgenic hosts, assessing thereafter the incidence and severity of thyroiditis. We wil also cross thyr-IFNgamma transgenics to knockout mice that lack IRF-1 or IRF-4, two critical transcription factors linking IFNgamma signaling with caspase-8 dependent apoptosis. Specific aim 3 is to study the interaction between IFNg interleukin-12 (IL-12) on thyroid autoimmunity and function. We have generated transgenic mice that express IL-12 specifically in the thyroid gland. The mice develop spontaneously lymphocytic thyroiditis and primary hypothyroidism with increased NIS expression. We will cross thyr-IL-12 transgenics to thyr-IFNg transgenics to assess whether the disease suppressive effect of IFNgamma prevails on the disease-promoting effect of IL-12, and whether IFNg and IL-12 synergistically induce a more severe form of hypothyroidism. Specific aim 4 is to investigate why thyroids from thyr-IFNg transgenic contain an increased number of adipocytes, and to assess whether this increase influences thyroid function. We hypothesize that thyroid macrophages primed in vivo by IFNg promote differentiation of stromal preadipocytes into mature adipocytes. We will co-culture thyroid macrophages from transgenics and controls with syngeneic pre-adipocytes, monitoring acquisition of morphological features typical of adipocytes. We also hypothesize that augmented TSH signaling is required to induce the adipocyte-rich phenotype, and cross thyr-IFNg transgenics to TSH receptor knockout mice.