Mechanisms by which TLR9-deficiency and FasL Promote Cutaneous Lupus

摘要 共同的病理生理机制被认为是促进皮肤和全身表现 狼疮因此，更好地了解促进CLE的因素可能会提供重要的见解， SLE的发病机制。然而，也可能是组织特异性效应器机制解释了 SLE患者人群表现出的不同临床表现。因为75%的SLE患者 某种皮肤病变，皮肤的紫外线暴露通常与狼疮耀斑有关，令人惊讶的是， 关于CLE的发生、发展和复发的机制研究相对较少。 这种差距的一个原因是，可用于CLE研究的鼠模型有限--尽管已经发现了许多新的CLE模型。 许多SLE小鼠模型，准确反映CLE中心特征的模型， 有限公司我们现在已经建立了一个诱导型狼疮样皮肤炎症（LLSI）模型，由T细胞介导， 转移，这概括了CLE的许多特征。其中包括皮肤浸润的突出作用 产生IFNγ的Th 1细胞，过度角质形成细胞死亡，真皮/表皮的自身抗体沉积 边界，增加CxCL 9、CxCL 10、CxCL 11、CCL 8的表达，以及皮肤中pDC的积累。那里 我们的LLSI模型与其他诱导型和遗传型模型之间也存在机制相似性。 SLE的程序化鼠模型;它们都依赖于TLR 7的表达，并由TLR 7的表达加重。 没有TLR 9。因此，我们的LLSI小鼠提供了一种新的，快速的和可重复的系统，用于探索 负责诱导和调节皮肤狼疮的效应器机制。此应用程序将 关注TLR 9和FasL。如前所述，TLR 9负调节皮肤和淋巴细胞的发育。 系统性狼疮，但是否TLR 9的作品被动地简单地与TLR 7竞争进入 内体运输分子伴侣Unc 93 B1，或通过诱导依赖于TLR 9信号传导的分子而主动地 限制炎症的级联反应尚未得到解决。我们最近还表明， 皮损的发生完全依赖于T细胞FasL的表达，但FasL是否间接促进了疾病的发生， 通过诱导细胞死亡和产生细胞碎片和/或直接通过诱导促炎性因子的产生 细胞因子尚未解决。TLR 9和FasL之间的相互作用可能是LLSI中重要的放大环。 TLR配体诱导Fas的上调，并且FasL产生可以激活内体TLR的细胞碎片。我们 我建议通过使用基因靶向小鼠来解决这个问题，这些小鼠在体外具有两种突变， 和体内（LLSI）研究。在目标1中，我们将使用表达正常水平的TLR 9形式的小鼠， 在目标2中，我们将使用表达Caspase 8突变的小鼠，该突变去除了MyD 88， Caspase 8自切割位点，从而阻止FasL诱导的细胞凋亡，但不阻止趋化因子的产生。 总之，这些研究应该有助于确定靶向TLR 9的最有效的治疗策略， FasL途径预防或改善皮肤狼疮的发展。

ABSTRACT Common pathophysiological mechanisms are thought to promote the cutaneous and systemic manifestations of lupus. Thus a better understanding of the factors that promote CLE are likely to provide important insights as far as the pathogenesis of SLE. Nevertheless, it is also likely that tissue specific effector mechanisms account for the diverse clinical presentations exhibited by SLE patient populations. Since 75% of SLE patients exhibit skin lesions of some sort, and UV exposure of the skin is often associated with lupus flares, it is surprising that there have been relatively few mechanistic studies that address initiation, progression and recurrence of CLE. One reason for this gap is that murine models available for the study of CLE have been limited – despite the numerous murine models of SLE, models that accurately reflect the central features of CLE are much more limited. We have now develop an inducible model of lupus like skin inflammation (LLSI), initiated by T cell transfer, that recapitulates many of the features of CLE. These include a prominent role for skin-infiltrating IFNγ-producing Th1 cells, excessive keratinocyte death, autoantibody deposition at the dermal/epidermal border, increased expression of CxCL9, CxCL10, CxCL11, CCL8, and accumulation of pDCs in the skin. There are also mechanistic similarities between our LLSI model and other inducible as well as genetically programmed murine models of SLE; they all depend on the expression of TLR7 and are exacerbated by the absence of TLR9. Therefore our LLSI mice provide a novel, rapid and reproducible system for exploring the effector mechanisms responsible for the induction and regulation of cutaneous lupus. This application will focus on TLR9 and FasL. As mentioned, TLR9 negatively regulates the development of both cutaneous and systemic lupus, but whether TLR9 works passively by simply competing with TLR7 for access to the endosomal trafficking chaperone Unc93B1, or actively by inducing molecules dependent on a TLR9 signaling cascade that limit inflammation, has not been addressed. We have also recently shown that the development of skin lesions is completely dependent T cell FasL expression, but whether FasL promotes disease indirectly by inducing cell death and creating cell debris and/or directly by inducing the production of pro-inflammatory cytokines is unresolved. Interplay between TLR9 and FasL may be an important amplification loop in LLSI - TLR ligands induce upregulation of Fas and FasL generates cell debris that can activate endosomal TLRs. We propose to address the questions by using gene-targeted mice with discriminating mutations for both in vitro and in vivo (LLSI) studies. In Aim 1, we will use mice that express normal levels of a form of TLR9 that cannot engage MyD88, and in Aim 2, we will use mice that express a Caspase 8 mutation which removes the Caspase 8 autocleavage site and thereby prevents FasL-induced apoptosis but not chemokine production. Together, these studies should help identify the most effective therapeutic strategies for targeting TLR9 and FasL pathways to prevent or ameliorate the development of cutaneous lupus.