miR-155对白念珠菌活化的Dectin-1信号通路的调节作用

Dendritic cell plays a critical role in the defence of the host to against infectious events, as well as a bridge between innate and adaptive immunity system. Dectin-1 is one of the most critical pattern recognition receptors on Dendritic cells responsible for sensing Candida albicans. In addtion to initiate the innate immunity response of infectione in the early phase, the Dectin-1 signal pathway activated by Candida albicans could also shape the adaptive immunity response subsequently. Our previous study, based on microRNA array, shown that miR-155 in human immature dendritic cell was up-regulated by heat-killed Candida albicans. More importantly, the production of IL-23 induced by heat-killed Candida albicans in human immature dendritic cell could be modulated by miR-155, as identified by gain- and loss of function approach. Given the above findings, the present project aims to: 1) clarify the mechanisms underlying the up-regulation of miR-155 caused by heat-killed Candida albicans stimulation; 2) identify the potential target mediated the regulatory role of miR-155 for IL-23 production, and its effect one the differentiation of Th17 response subsequently.

树突状细胞是机体对抗病原体入侵的重要防御力量，同时也是连接固有免疫与获得性免疫的枢纽。Dectin-1是树突状细胞上负责感知白念珠菌的最重要的模式识别受体之一。由白念珠菌活化的Dectin-1信号通路不仅拉开了固有免疫应答的序幕，同时还通过调节T细胞的分化而"导演"的获得性免疫应答的强度，类型和持续时间。在前期研究中，我们通过芯片筛选发现了白念珠菌可以上调人单核源性树突状细胞内miR-155的表达，且miR-155可以抑制树突状细胞释放IL-23。本课题拟在前期研究的基础上，进一步研究：①白念珠菌上调人单核源性树突状细胞内miR-155表达的机制；②miR-155调节树突状细胞释放IL-23的机制及其对后续Th17反应的影响及其机制。

白念珠菌引发的固有免疫应答必须处在精细的调节之中，由其引发的炎症反应不论是过强还是过弱都会对机体造成损伤。以往的研究表明miR-155调节了诸多病原体引发的免疫应答过程，但是其在变念珠菌免疫应答中的作用尚不明确。本研究的目的在于探讨miR-155在白念珠菌引发的固有免疫应答中的调节作用。我们通过siRNA、流式细胞术、报告基因技术等分子生物学手段，发现白念珠菌可以上调人单核源性树突状细胞内miR-155的表达，且miR-155表达上调与NF-κB的活化有关，因为抑制NF-κB可以削弱白念珠菌上调miR-155表达的能力。报告基因技术证实miR-155可以与Bcl-10 mRNA的3’非编码区发生相互作用。通过改变白念珠菌刺激的单核源性树突状细胞内miR-155表达，我们发现miR-155可以直接调节Bcl-10的表达，并由此影响NF-κB的活性、IL-23的产生以及Th17细胞的分化。通过siRNA下调Bcl-103的表达后，我们证实白念珠菌调节IL-23的表达和NF-κB的活性与其作用与Bcl-10有关。总之，本研究表明在白念珠菌引发的固有免疫应答中，依赖于NF-κB的miR-155表达上调并且通过作用于Bcl-10而调节IL-23的产生以及后续Th17细胞的分化。