组织蛋白酶C调控上皮细胞免疫防御的作用及分子途径

The Papillon-Lefevre syndrome (PLS) is an autosomal recessive disorder characterized by a diffuse palmoplanter hyperkeratosis and rapidly progressive and devastating periodontitis, affecting the primary as well as the permanent dentition, attributed to a point mutation of the cathepsin C gene (CTSC). However, the exact etiology and pathogenesis is unknown. Previous study showed that cathepsin C plays an essential role in the in vivo processing and activation of granzymes A and B, which are required for cytotoxic lymphocyte granule-mediated apoptosis, but can't explain why the lesion mainly locats in periodontal and skin, instead of other organs or tissue. The clarity of epithelial cell immune function might provide the best answer to this question. In the last few years, it has bocome clear that epithelial cells play an important role in the initiation and perpetuation of skin inflammatory, provide active signals related to barrier compromise and distinguish different types of challenges. Recently, studies showed that a variety of environmental stimuli can induce epithelial cells to release inflmmatroy cytokines and expression of Toll like receptors. In addition, epithelial cells can also induce expression of major histocompatibility complex (MHC) classⅡmolecules in a varitety of pathologic conditions that lead to infiltration of lymphocytic cells. Through these mechanisms, epithelial cells can significantly influence the resultant innate and adaptive immune repsones. Our previous studies revealed novel mutations, and found that PLS patient has high level of serum IgE. So it is proposed that CTSC mutation might disturb activation of key pathway during epithelial cells immune response and lead to impaired local defense and differentation. The purpose of this investigation is to ascertain the role of CTSC in epithelial cell immune function, illuminate the pathogenesis of PLS, provide information for developing new approaches for PLS therapy.

掌跖角化牙周破坏综合征（PLS）是组织蛋白酶C基因(CTSC)突变导致的，以早发性牙周炎和皮肤过角化为主要表现的遗传疾病，关于病变为何只集中于牙龈、皮肤等上皮部位至今无法解释。近年来上皮细胞免疫功能的发现为该疑问解答提供了新的思路。课题组在前期研究中，多次在患者体内发现了CTSC新的突变位点，随后在PLS患者体内发现免疫球蛋白高表达的异常免疫现象，推测CTSC突变可能对炎症刺激下上皮细胞的生物学行为造成干扰，进而引起免疫和分化异常。本课题拟采用CTSC敲除小鼠重现PLS发病过程，同时培养人上皮细胞，沉默CTSC基因，进行体外平行实验，全面检测CTSC缺失对上皮细胞免疫防御的影响，探明其干扰上皮细胞功能的分子途径，并寻找PLS中上皮细胞分化和免疫异常的内在联系。该项目的进行不仅对阐明PLS致病机理具有重要意义，而且将为研究上皮细胞免疫防御的调控和相关疾病治疗手段的更新奠定基础。

上皮细胞处于机体内外环境相互作用的界面，又是机体统抵御病原体的首道防线，注定使其承担着多种重要的生理功能。近年来研究发现，上皮细胞除了发挥天然生理屏障作用外，还可通过“免疫转分化”作用，在细胞因子应答、模式抗原识别和抗原呈递方面显示强大的潜力。然而，上皮细胞如何从严密受控的、逐级分化的程序中逃离，转变为具有免疫功能的免疫细胞，其调控机制目前尚无报道。课题组前期研究发现，组织蛋白酶C功能缺陷可以导致上皮细胞分化——免疫异常，从而为研究上皮细胞免疫转分化调控机理提供了一个契机。本课题在前期研究的基础上，利用组织蛋白酶C基因敲除小鼠，应用Elisa，流式细胞，PCR，Western blot 等对其上皮细胞免疫功能进行全面评价，研究相关分子调控机理，并通过主要信号通路，探索此基因缺陷型疾病新的治疗途径。研究结果发现，CTSC对处于不同分化程度的上皮细胞作用不同，其生物学功能主要体现于分化较为成熟的上皮细胞，CTSC基因缺陷导致上皮细胞在抗原加工、呈递以及天然免疫反应等方面出现异常。除此之外，对上皮细胞的胞外基质构建、炎症细胞趋化、蛋白酶活性等方面均有广泛的影响。其中对上皮细胞天然免疫的影响可能通过NFkB通路的调节而实现。除基础研究之外，我们还对CTSC缺陷患者的牙周及全身免疫状态的增龄性变化进行追踪，发现其发病规律。该课题研究对于深入探讨众多与上皮细胞免疫功能相关疾病的发病机制、临床预防和治疗均具有重要意义。