白念珠菌细胞壁磷脂甘露聚糖与识别受体TLR2在诱导固有免疫耐受中的作用及机制研究

How to balance the benefits and hazard of the innate immune responses against infection of Candida albicans was unknown. We have demonstrated that Candida albicans phospholipomannan (PLM) could induce the production of inflammatory cytokines, anti-microbial peptides and proteins (AMPs) through Toll- like receptor 2 (TLR2). Additionally, our preliminary findings have showed that the "tolerance" phenomenon could be induced in human monocytes by the pretreatment of PLM, which demonstrated the decreased secretion of TNFα, no change in AMPs. Further study will clarify whether PLM could induce immune tolerance effect in human monocyte-macrophages, dendritic cells, and keratinocytes. The molecular mechanism of this effect could be elucidated in the following aspects: the changes of TLR2 expression and key downstream signaling molecules (NF-κB, MAPK kinase), the activation of negative regulator of the signaling pathway factor (PI3K, the zinc finger protein A20), the impact of histone acetylation on the epigenetic expression of inflammatory cytokines and AMPs genes, the roles of microRNAs (mir155, mir146) in the immune tolerance, un-inhibition of AMPs whether is dependent on bypass pathway activation of NF-κB through IL-1β and VDR. The intervention role of interferon-γ in reversing this immune tolerance effect and underlying mechanism will also be explored. Better understanding of this regulatory mechanism could provide theoretical basis for the development of novel, specific therapy strategies and preventive measurements for infections of Candida albicans.

机体抗白念珠菌感染固有免疫的益处与危害的调控机制尚未充分揭示。我们证实TLR2识别白念珠菌细胞壁磷脂甘露聚糖（PLM），诱导产生炎性因子、抗微生物多肽、蛋白（AMPs）。初步发现PLM预处理可诱导人单核细胞出现"耐受"的现象（TNFα分泌降低、AMPs无变化）。进一步研究PLM诱导单核巨噬细胞、树突状细胞、角质形成细胞等固有免疫细胞的耐受效应。并从如下方面探明这一效应的分子机制：TLR2受体表达及其关键信号分子如NF-κB、MAPK激酶等的变化情况；信号通路的负性调节因子（PI3K、锌指蛋白A20等）的活化； 组蛋白乙酰化对炎性因子和AMPs基因表达的表观遗传学影响；MicroRNA（mir155、mir146）在耐受中的作用；AMPs未受抑制是否依赖IL-1β和VDR旁路激活NF-κB。探讨γ-干扰素逆转耐受效应的干预作用及机制。深入揭示上述调控机制，初步为寻找新的防治策略提供理论依据。

念珠菌是引起浅部、深部念珠菌病的最常见病原菌。据报道超过72%的院内真菌感染为念珠菌所致，而念珠菌在引起院内血行播散感染的病原体中排第4位。深入揭示抗念珠菌感染免疫机制，对疾病防治将大有裨益。.获得了白念珠菌及医学上重要的非白念的近平滑念珠菌、热带念珠菌体外影响人THP-1及人外周血单个核细胞（PBMC）的炎症反应及相关模式识别受体及信号通路分子的结果，国际上报道了近平滑念珠菌、热带念珠菌体外诱导的炎症反应，依赖NF-κB, MAPKs信号通路激活和模式识别受体的识别。研究结果已有1篇Mycopathologia发表，1篇Can J Microbiol 接受，1篇SCI在投。发表中文论著5篇，待发表1篇。.采用RNAseq检测获得白念珠菌细胞壁成分β-glucan作用THP-1 的miRNA 表达谱，国际上首次发现miR-146a能够负反馈调控激活Dectin-1（识别β-glucan的关键受体）所引起的炎症反应。结果表明β-glucan上调miR-146a效应依赖于Dectin-1-Syk-NF-κB，p38MAPK通路，miR-146a能够负反馈调控Dectin-1激活后的炎症反应，通过抑制NF-κB信号通路来下调炎症反应。研究结果已发表于Oncotarget。并初步证实miR-30a-5p能够通过靶向Atg5和Beclin1，抑制LC3-II 的总量的上升，从而抑制由白念珠菌胞壁多糖增加的基础自噬流。初步获得白念珠菌细胞壁成分作用THP-1细胞的和人CD14+单核细胞的lncRNA表达谱，将对lncRNA调控炎症反应机制进行深入研究。初步通过氯喹、E64d+pepstatin、巴弗洛霉素、氯化铵体系，发现人THP-1巨噬细胞及小鼠骨髓源巨噬细胞体外在吞噬白念珠菌后基础自噬流显著抑制。通过经典自噬诱导剂雷帕霉素处理发现，THP-1巨噬细胞吞噬白念珠菌后自噬响应机制显著抑制，LC3被LAP途径优势利用；这种机制为mTOR非依赖性。