Regulation of T Cell TNF Production

描述（由申请人提供）：雌激素（E2）具有多种复杂的 对T细胞功能的调节作用，这可能与 绝经后骨质疏松症的发病机制。然而，因果关系 T细胞改变和绝经后骨质流失之间的关系仍然存在 有待确定。我们发现卵巢切除术（OVX）未能诱导骨丢失 在T细胞缺陷的裸鼠中。OVX诱导骨丢失的能力是 通过用野生型T细胞重建T细胞而不是通过用野生型T细胞重建T细胞而恢复。 用来自TNF-/-小鼠的T细胞构建。此外，OVX还增加了T细胞TNF 通过增强T细胞增殖和减少T细胞凋亡来产生。 这些事件导致了TNF产生T细胞的数量增加， 骨髓这些结果表明，T细胞和T细胞产生TNF 是体内E2缺乏引起骨消耗效应的重要介质。 然而，E2调节的产生TNF的T细胞的特异性表型， 仍有待鉴定。同样神秘的是E2 下调骨髓中产生TNF的T细胞的数量。 因此，我们的第一个具体目标将是确定特定的T细胞 细胞群（CD 4 + CD 8+和/或γ-δ T细胞）产生增加的 大量的TNF并导致OVX小鼠的骨丢失。的相关性 候选T细胞群将通过确定OVX是否诱导 缺乏CD 4+、CD 8+和/或γ-δ淋巴细胞的小鼠的骨丢失。 在具体目标2中，我们将确定E2是否阻断T细胞依赖性骨丢失 通过直接靶向T细胞或通过对骨髓辅助细胞的作用， 细胞这将通过分析ovx和E2的影响来实现。 骨密度、T细胞增殖、T细胞凋亡和T细胞 用从E2收获的T细胞重建的裸鼠中的TNF产生 受体α和β缺陷的供体。我们的实验证据表明 E2通过抑制IL-7来阻断T细胞TNF的产生，IL-7是一种细胞因子， 调节T细胞增殖并诱导骨丢失。所以我们会 通过测定IL-7的体内中和作用来评价IL-7的作用， IL- 7阻止T细胞TNF产生的增加和诱导的骨丢失 关于OVX我们的数据还表明，E2抑制T细胞TNF的产生， 减弱IFN-γ诱导的巨噬细胞抗原呈递细胞（APC）活性， 通过下调CIITA基因的表达。因此，我们将得出结论， 目的2通过使用IFN-γ中和和IFN-gR 1-/-小鼠来确定 CIITA沉默对T细胞TNF产生和骨丢失的影响。在 目的3：探讨E2抑制CIITA基因表达的机制 表情这将通过分析E2对 转录和翻译的CIIT A和通过确定顺式调节 赋予E2对CIITA启动子的反应性的因子。的 该项目的意义很高，因为它可能揭示发病机制 绝经后骨质疏松症和确定新的目标E2在骨。

DESCRIPTION (provided by applicant): Estrogen (E2) has multiple and complex regulatory effects on T cell function which may be relevant for the pathogenesis of postmenopausal osteoporosis. However, a cause-effect relationship between T cell alterations and postmenopausal bone loss remains to be established. We found that ovariectomy (ovx) failed to induce bone loss in T cell deficient nude mice. The capacity of ovx to induce bone loss was restored by T cell reconstitution with Wild type T cells but not by constitution with T cells from TNF-/- mice. Moreover, ovx increased T cell TNF production by enhancing T cell proliferation and decreasing T cell apoptosis. These events led to an increase in the number of TNF producing T cells in the bone marrow. These findings demonstrated that T cells and T cell produced TNF are essential mediators of the bone-wasting effects of E2 deficiency in vivo. However, the specific phenotype of the E2 regulated TNF producing T cell remains to be characterized. Equally enigmatic are the mechanisms by which E2 down regulates the number of TNF producing T cells in the bone marrow. Therefore, our first Specific Aim will be to identify the specific T cell population (CD4+ CD8+ and/or gamma-delta T cells) that produces increased amounts of TNF and cause bone loss in ovx mice. The relevance of the candidate T cell population will be demonstrate by determining if ovx induces bone loss in mice lacking either CD4+, CD8+ and/or gamma-delta lymphocytes. In Specific Aim 2 we will determine if E2 blocks T cell dependent bone loss via a direct targeting of T cells or via effects on bone marrow accessory cells. This will be accomplished by analyzing the effects of ovx and E2 replacement on bone density, T cell proliferation, T cell apoptosis and T cell TNF production in nude mice reconstituted with T cell harvested from E2 receptor alpha and beta deficient donors. Our experimental evidence suggests that E2 blocks T cell TNF production by repressing IL-7, a cytokine which regulates T cell proliferation and induces bone loss. Therefore, we will evaluate the contribution of IL-7 by determining if in vivo neutralization of IL- 7 prevents the increase in T cell TNF production and the bone loss induced by ovx. Our data also suggest that E2 represses T cell TNF production by blunting IFN-gamma induced macrophage antigen presenting cell (A PC) activity, through down regulation of CIITA gene expression. Therefore, we will conclude Aim 2 by using IFN-gamma neutralization and IFN-gR1 -/- mice to determine the effects of CIITA silencing on T cell TNF production and bone loss. In specific Aim 3 we will investigate the mechanism which E2 represses CIITA gene expression. This will be accomplished by analyzing the effects of E2 on the transcription and the translation of CIIT A and by determining the Cisregulating factors that confer E2 responsiveness to the CIITA promoter. The significance of this project is high, as it may shed light on the pathogenesis of postmenopausal osteoporosis and identify novel target of E2 in bone.