模式识别受体介导的足细胞免疫调控在肾小球疾病中的作用

Kidney is a vital organ which is associated with systemic immune and autoimmune diseases and the contribution of local immune activity of the kidney to the development of glomerular diseases because of the glomerular cells’ unique structure and functions. Among glomerular cells, podocytes are highly specialized, terminally differentiated epithelial cells that are integral components of the renal glomerular filtration barrier, which are vulnerable to a variety of injuries and as a result, they undergo a series of changes ranging from hypertrophy, detachment, autophagy to apoptosis. As podocytes have limited ability to repair and regenerate, the extent of podocyte injury is considered as a major prognostic determinant in end-stage renal disease (2). Focal segmental glomerulosclerosis (FSGS) and minimal change disease (MCD) are the two major forms of acquired glomerular disease that are widely accepted to be podocytopathies. In addition, there is mounting evidence of podocyte injury in a variety of other renal diseases such as diabetic nephropathy (DN), membranous glomerulonephritis (MGN) and IgA nephropathy. In these conditions, podocytes lose specific markers of differentiation, undergo foot process effacement and eventual detachment, and reduce the capacity to maintain the glomerular filtration barrier, thereby resulting in proteinuria. In addition, podocytes have immune potential and function as “part-time” immune cells that are involved in the glomerular disease development by the fact that the expression of immune-associated receptors, phagocytosis and antigen presentation activity of podocytes and stimulating T cells and neutrophils by podocytes. However, it still keep unclear the innate immune system and the regulatory mechanisms in podocytes. The innate immune system includes several classes of pattern recognition receptors (PRRs), such as membrane-bound Toll-like receptors (TLRs), nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) and C-type lectin receptors (CLR). These receptors detect pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs) in the extracellular and intracellular space. Intracellular NLRs constitute inflammasomes, which activate and release caspase-1, IL-1β, and IL-18 thereby initiating an inflammatory response. Systemic and local low-grade inflammation and release of proinflammatory cytokines are implicated in the development and progression of podocyte injuries. The present study is to determine how PRR-mediated innate immune system-driven inflammatory processes in podocytes can lead to glomerular disease by in vitro and in vivo animal studies by Cre-LOXP mice. Our study may provide novel insights into the immune mechanism underlying glomerular disease development. Pharmacological targeting of PRR-mediated immune signaling pathways at multiple levels may provide a novel approach for treatment of glomerular disease.

肾脏与免疫系统关系密切，其中肾小球足细胞不仅具有调节肾小球滤过率、参与肾小球基底膜重构等功能，而且还是肾脏发挥固有免疫功能，促进炎症并驱动和调节适应性免疫应答的关键细胞之一。足细胞抗原的确定为足细胞参与肾小球疾病中的免疫机制提供直接的证据。除足细胞表达MHC I类及II类分子、共刺激因子及粘附因子和其具有抗原递呈能力及T细胞激活功能外，对于足细胞如何参与固有免疫的调控尚不明确。模式识别受体（PRR）是细胞固有免疫的重要调控因子，但其又如何调控足细胞的固有免疫并不清楚。本课题拟利用生物芯片及Cre-LoxP足细胞特异性PRR基因敲除小鼠等手段主要探讨（一）明确足细胞中PRR参与肾脏区域免疫及肾小球疾病中的亚型及作用；（二）足细胞PRR的表观遗传学调控机制; （三）在肾小球疾病中足细胞PRR与补体系统的相互调控及作用。本课题将拓展对足细胞免疫功能的认识，为肾小球疾病的防治提供新靶点和思路。

肾脏病与免疫系统的关系十分密切。本项目从肾小球疾病的发病机制和治疗靶标发现的角度，深入了解肾脏区域免疫的基本属性、网络调控机制以及区域免疫特性在肾脏疾病发生发展中的作用机制，重点探讨足细胞作为肾脏“非专职的”的免疫细胞在肾脏区域免疫中的作用。在本项目资助下，研究团队聚焦模式识别受体及肾脏区域免疫调控在肾脏疾病中的作用并取得如下进展：①揭示了模式识别受体NLRC5对CD4+T细胞的调控在肾脏损伤中的作用。我们发现NLRC5的缺失可以通过上调CEACAM1的表达抑制CD4+T细胞的浸润和激活，提示肾脏区域免疫细胞，尤其是T淋巴细胞，在肾脏疾病进展过程中发挥重要作用；②阐明了JAML对模式识别受体介导的肾脏区域免疫和糖脂代谢异常的网络调控作用。模式识别受体介导的糖脂代谢紊乱是导致肾脏区域免疫细胞代谢重编程从而驱动免疫细胞的炎性反应，并加剧糖尿病肾病的进展的重要因素。我们首次发现连接粘附分子家族成员JAML参与诱导的糖尿病肾病损伤，并改善足细胞中异常的脂质沉积和模式识别受体激活导致的炎症反应；该调控与组蛋白去乙酰化酶SIRT家族介导的信号通路密切相关。③进一步发现组织定居型记忆T细胞(Resident Memory T cells, TRM)的激活参与了足细胞损伤过程。通过质谱流式以及普通流式分析我们鉴定了肾脏CD8+TRM的marker为CD69及 CD44，并发现阿霉素诱导的足细胞损伤模型及糖尿病肾病模型中CD8+TRM比例数量均明显升高。给予CD122封闭抗体抑制了小鼠阿霉素肾病模型中CD8+TRM的形成，同时改善肾损伤。此外，我们研究发现Sparsentan作为治疗FSGS的二期临床药物通过抑制足细胞IL-15的提呈能力从而抑制CD8+TRM的分化与功能。 .在本项目的资助下，团队在国际权威期刊中发表多篇论文，得到国际同行的广泛关注和高度评价。其中，作为独立通讯作者发表在Cell metabolism上的论文被选为封面文章。发表在Nature Communication上的论文被 2017 年 09 月 20 日的科技日报头版报道，相关研究也被国际知名学术网站 F1000 推荐。发表在Circulation Research中论文获得编辑特约述评并被评为封面文章。发表在肾脏领域TOP期刊JASN及KI上的论文也在国际肾脏病研究领域产生了重要的影响。