The role of leukotriene B4 and its receptor BLT1 in the pathogenesis of the prototypical organ-specific autoimmune disease epidermolysis bullosa acquisita

连续的脂质-细胞因子-趋化因子级联协调免疫细胞募集到炎症部位是免疫反应效应期的一个标志。在这里，白三烯B4 （LTB4）通常是启动这些级联反应的脂质介质。因此，在多种自身免疫性疾病模型中，抑制LTB4或其受体BLT1可防止炎症。LTB4/BLT1在自身抗体诱导的关节炎中的作用被详细阐述。在该小鼠模型中，LTB4需要作为化学引诱剂启动中性粒细胞募集。大疱性表皮松解症（EBA）是一种典型的皮肤大疱性自身免疫性疾病，由抗VII型胶原的自身抗体引起，这种抗体存在于真皮-表皮交界处的锚定原纤维中。2005年，英国<s:1>贝克大学皮肤学系的一个研究小组描述了一种EBA小鼠模型，在该模型中，真皮-表皮交界处形成的免疫复合物启动了中性粒细胞向皮肤的募集，这反过来又通过释放自由基氧（ROS）诱导真皮-表皮分离，这是EBA的标志性病变。然而，在该模型中诱导中性粒细胞释放ROS的机制尚不清楚。申请人最近的体外实验表明，LTB4可能是必需的。尽管在大疱性类天疱疮（另一种类似EBA的自身免疫性疾病）患者的水泡液中可以发现高水平的LTB4，但LTB4/BLT1在自身免疫性皮肤病中的作用尚未得到解决。该提案的首次申请人在阐明LTB4在关节炎中性粒细胞募集中的作用和调节以及在设计脂质细胞因子-趋化因子级联作为炎症驱动因素的范例方面发挥了重要作用，这些都是由波士顿马萨诸塞州总医院的Lusters教授实验室率先提出的，申请人在那里工作了3.5年。在过去的6个月里，申请人在DFG的资助下，在l<e:1>贝克的Zillikens教授实验室学习进行EBA小鼠模型。他已经生成了初步数据，表明白三烯在EBA发病机制中的主要作用。本提案的主要假设是，EBA需要LTB4，中性粒细胞既是其主要来源，也是其主要细胞靶点。此外，据推测，在EBA中，LTB4以双峰的方式起作用，并介导对中性粒细胞的两种关键作用：首先作为化学引诱剂，启动第一批中性粒细胞进入真皮层，然后激活真皮层中的中性粒细胞释放ROS并诱导真皮-表皮分离。本项目将确定EBA小鼠模型对LTB4/BLT1的总体需求，并确定LTB4的基本细胞来源和靶点。此外，LTB4参与驱动皮肤炎症的分子机制将被精确定义。这些数据将阐明LTB4在皮肤自身免疫性大疱性疾病中的作用。

Sequential lipid-cytokine-chemokine cascades orchestrating the recruitment of immune cells to inflammatory sites are a hallmark of the effector phase of the immune response. Herein, leukotriene B4 (LTB4) is often the lipid mediator initiating these cascades. Accordingly, inhibition of LTB4 or its receptor BLT1 protects from inflammation in diverse models of autoimmune disease. This role of LTB4/BLT1 was elaborated in most detail for autoantibody-induced arthritis. In this mouse model, LTB4 is required to act as chemoattractant initiating neutrophil recruitment.Epidermolysis bullosa acquisita (EBA) is a prototypical bullous autoimmune disease of the skin caused by autoantibodies against type VII collagen, present in the anchoring fibrils at the dermal-epidermal junction. In 2005 a research group at the Department of Dermatology in Lübeck described a mouse model of EBA, in which the formation of immune complexes at the dermal-epidermal junction initiates the recruitment of neutrophils to the skin, which in turn induce dermal-epidermal separation, the signature lesion of EBA, by radical oxygen species (ROS) release. The mechanisms inducing the release of ROS from neutrophils in this model, however, are still unknown. Recent in vitro experiments of the applicant suggest that LTB4 may be required. Although high levels of LTB4 can be found in blister fluid of bullous pemphigoid patients, another autoimmune disease similar to EBA, the role of LTB4/BLT1 in autoimmune skin diseases has not been addressed. The first-time applicant of this proposal was instrumental in elucidating the role and regulation of LTB4 in neutrophil recruitment in arthritis and in contriving the paradigm of lipid-cytokine-chemokine cascades as drivers of inflammation, which was spearheaded by Prof. Lusters lab at the Massachusetts General Hospital in Boston, where the applicant was working for 3.5 years. In the last 6 months, the applicant, funded by the DFG, learned to conduct the EBA mouse model in Prof. Zillikens lab in Lübeck. He has generated preliminary data indicating a major role of leukotrienes in the pathogenesis of EBA. The major hypothesis of the present proposal is that LTB4 is required for EBA, and that neutrophils are both its major source, and its major cellular target. Furthermore, it is hypothesized that in EBA, LTB4 acts in a bimodal way of action and mediates two pivotal effects on neutrophils by first acting as a chemoattractant initiating the recruitment of the first neutrophils into the dermis, and later by activating neutrophils in the dermis to release ROS and induce dermal-epidermal separation.In this project the overall requirement for LTB4/BLT1 in the EBA mouse model will be determined and the essential cellular sources and targets of LTB4 will be identified. Additionally, the molecular mechanisms LTB4 engages to drive skin inflammation will be precisely defined. These data will clarify the role of LTB4 in autoimmune bullous diseases of the skin.