Mast cell Stat5-regulatory pathway in atopic dermatitis

描述（由申请人提供）：特应性皮炎（AD）是一种慢性瘙痒性炎症性皮肤病，发病率越来越高。虽然阿尔茨海默病的病因尚不完全清楚，但许多研究表明，皮肤屏障功能受损和免疫失调是该病的根本原因。我们已经开发了一种新的过敏原诱导和自发的小鼠模型来模拟人类AD：由皮肤上的过敏原治疗引起的AD样皮肤病变需要肥大细胞和胸腺基质淋巴生成素（TSLP）受体。我们发现，磷脂酶C (PLC)-¿3缺陷小鼠自发发生ad样皮肤病变，并以肥大细胞依赖的方式增加TSLP和骨膜蛋白的表达；与野生型小鼠相比，PLC-¿3-/-组变应原性皮炎更为严重。病变皮肤的基因表达谱在变应原性皮炎、PLC-¿3-/-小鼠自发性皮炎和人AD之间表现出高度的相似性。我们最近报道，PLC-¿3通过形成含有SHP-1（蛋白磷酸酶）、PLC-¿3和Stat5（转录因子）的多分子SPS复合物，抑制包括肥大细胞在内的造血细胞的增殖；PLC-¿3与SHP-1和Stat5相互作用，增强SHP-1对Stat5的去磷酸化活性，抑制Stat5活性。Stat5和Jak2（一种激活Stat5的激酶）对肥大细胞的发育和增殖至关重要。我们的初步数据表明，肥大细胞Stat5和SHP-1参与了AD的发病机制，在肥大细胞特异性缺失Stat5或SHP-1的小鼠中，过敏原诱导的皮炎的严重程度分别减轻或增强，以及Jak-Stat5抑制剂预防过敏原诱导的皮炎的强效。此外，人类AD皮肤中STAT5高激活水平的肥大细胞数量增加，编码SPS成分的基因与人类AD的风险和/或其严重程度有关。这些和其他的初步数据导致了以下假设：(1)肥大细胞中的Stat5-调控通路在AD的发病中起关键作用。(2) SPS成分调节由Th2细胞因子（肥大细胞）、骨膜蛋白（成纤维细胞）和TSLP（角质形成细胞）组成的皮炎放大/持续恶性循环的细胞成分的活性。(3) SPS成分不仅调控小鼠肥大细胞生物学，而且调控人类肥大细胞生物学。因此，（Aim 1）利用SPS组分基因的条件敲除小鼠以及药理学方法，我们将进一步评估肥大细胞stat5调控途径在PLC-¿3-/-小鼠皮炎发生和持续中的作用。（目的2）通过体外培养和体内模型，我们将研究SPS成分如何调节肥大细胞产生Th2细胞因子、成纤维细胞产生骨膜蛋白和角质形成细胞产生TSLP。（目的3）最后，我们将研究SPS成分在生长、存活和Fc？RI（高亲和力IgE受体）介导的人肥大细胞的激活，并比较人AD和健康个体之间的肥大细胞。总的来说，这个项目可能会建立一个新的AD发病机制范式，并提供一个新的治疗策略。

DESCRIPTION (provided by applicant): Atopic dermatitis (AD) is a chronic pruritic inflammatory skin disease with an increasing prevalence. Although the etiology of AD is not completely understood, numerous studies suggest that impaired skin barrier function and immune dysregulation underlie the disease. We have developed novel allergen-inducible and spontaneous mouse models that mimic human AD: AD-like skin lesions induced by epicutaneous treatment with allergen require mast cells and the receptor for thymic stromal lymphopoietin (TSLP). We found that phospholipase C (PLC)-¿3-deficient mice spontaneously develop AD-like skin lesions with increased expression of TSLP and periostin in a mast cell-dependent manner; allergen-induced dermatitis was more severe in PLC-¿3-/- than in wild-type mice. Gene expression profiles in lesional skin exhibited high similarity between allergen-induced dermatitis, spontaneous dermatitis in PLC-¿3-/- mice, and human AD. We recently reported that PLC-¿3 inhibits the proliferation of hematopoietic cells, including mast cells, through formation of the multi-molecular SPS complex containing SHP-1 (protein phosphatase), PLC-¿3, and Stat5 (transcription factor); PLC-¿3 interacts with SHP-1 and Stat5, augments the dephosphorylating activity of SHP-1 toward Stat5, and inhibits Stat5 activity. Stat5 and Jak2 (a Stat5-activating kinase) are essential for the development and proliferation of mast cells. Our preliminary data indicated the involvement of mast-cell Stat5 and SHP-1 in AD pathogenesis, as revealed by reduced or enhanced severity of allergen-induced dermatitis in mice with mast cell-specific deletion of Stat5 or SHP-1, respectively, as well as strong efficacy of a Jak-Stat5 inhibitor to prevent allergen-induced dermatitis. Moreover, human AD skin had increased numbers of mast cells with high activation levels of STAT5 and the genes encoding the SPS components were linked to the risk of human AD and/or its severity. These and other preliminary data have led to the following hypotheses: (1) The Stat5- regulatory pathway in mast cells plays a critical pathogenic role in AD. (2) SPS components regulate the activity of the cellular elements of the dermatitis-amplifying/perpetuating vicious cycle consisting of Th2 cytokines (mast cells), periostin (fibroblasts), and TSLP (keratinocytes). (3) The SPS components regulate not only mouse, but also human mast cell biology. Therefore, (Aim 1) using conditional knockout mice of SPS component genes as well as pharmacological approaches, we will further evaluate the role of the mast cell Stat5-regulatory pathway in development and persistence of dermatitis in PLC-¿3-/- mice. (Aim 2) Using in vitro cultures and in vivo models, we will study how SPS components regulate Th2 cytokine production from mast cells, periostin production from fibroblasts, and TSLP production from keratinocytes. (Aim 3) Finally, we will study the role of SPS components in the growth, survival, and Fc?RI (high-affinity IgE receptor)-mediated activation of human mast cells and compare mast cells between human AD and healthy individuals. Overall, this project will likely establish a novel paradigm of AD pathogenesis and provide a novel therapeutic strategy.