NMDA受体激活在肺纤维化时骨髓变化中的调控作用及意义研究

Pulmonary fibrosis (PF) is an inexorably fatal disorder, caused by various acute or chronic lung diseases. Previous work suggested that in the lung, fibrocytes and/or bone derived MSCs (BM-MSCs), played important roles in fibrogenesis, which resulted in aggravation/alleviation of lung fibrosis. However, change of bone marrow itself on the course of pulmonary fibrosis has been scarcely noted. We for the first time put forward the hypothesis that bone marrow, an extra lung organ, should play a key role in the development of PF. On the basis of previous studies in our lab showing that MSCs can express glutamate NMDA receptor, this project will further explore expression and activation/over-activation of glutamate NMDA receptor in BM-MSCs and its relation to the bone marrow alteration during PF. We will establish a new bone marrow remodeling animal model in which NMDAR gene expression is knockdowned, and will also explore the regulatory importance of activation of NMDA receptor to bone marrow in vivo and its influences on activities of BM-MSCs, including protective effect of antifibrosis in vivo, and proliferation, apoptosis, chemotaxis, and paracrine in vitro. Finally, NMDAR activation-induced changes of signaling pathway in BM-MSCs will be included in the project.. In summary, this project will for the first time try to explore the crucial role of bone marrow, an extra lung organ, in the development of PF. Better understanding of the involvement of glutamate NMDA receptor activation including over-activation in BM-MSCs, should provide new thinking for prevention and treatment of PF, and also offer new therapeutic options for PF.

肺纤维化严重危害人们身体健康，是多种急性和慢性肺损伤的最后共同结局，但肺纤维化发病机制远未阐明。虽然大量研究显示，肺外来源的纤维细胞和间充质干细胞（MSCs）可分别促进和抑制肺纤维化的发生，人们对产生纤维细胞和MSCs的骨髓却很少关注。申请者基于前期初步结果，创新性提出探讨肺纤维化过程中自身骨髓的变化，在首次观察骨髓谷氨酸分泌及MSCs谷氨酸NMDA受体表达和功能变化的基础上，通过构建骨髓NMDA受体敲减动物模型揭示NMDA受体对肺纤维化时自身骨髓功能的不利影响，并进一步在整体和离体水平阐明NMDA受体激活对MSCs生物学活性（增殖、凋亡、趋化、旁分泌）和体内抗肺纤维化保护效应的直接影响及胞内信号途径。首次以NMDA受体过度激活为切入点探索肺纤维化时自身骨髓异常的调控机制，从而跨出肺脏本身，以肺外的视角探索肺纤维化发生发展的病理生理机制，为临床肺纤维化防治的研究提供新的启示。

肺纤维化严重危害人们身体健康，是多种急性和慢性肺损伤的最后共同结局，但肺纤维化发病机制远未阐明。虽然大量研究显示，肺外来源的纤维细胞和间充质干细胞（MSCs）可分别促进和抑制肺纤维化的发生，人们对产生纤维细胞和MSCs的骨髓却很少关注。申请者基于自己有关前期研究，以NMDA受体过度激活为切入点首次提出探索肺纤维化过程中自身骨髓的变化，从肺外的视角探索肺纤维化发生发展中机体自身内源性抗损伤机制变化的病理生理机制及意义，为临床肺纤维化防治的研究提供新的启示。为此，开展三方面的研究：.（1）在整体博来霉素肺纤维化模型首次发现，博来霉素可引起骨髓细胞选择性释放谷氨酸，骨髓内释放的谷氨酸在体内可通过NMDA受体促进BM-MSCs的凋亡，降低骨髓细胞的抗纤维化保护作用。在离体培养水平证实谷氨酸的释放与谷氨酸转运系统xc-的激活有关。.（2）在离体培养水平证实BM-MSCs有NMDA受体的功能表达；NMDA受体激活抑制BM-MSCs的增殖、迁移，并选择性地调节部分旁分泌因子；经NMDA预处理的BM-MSCs在博来霉素肺纤维化小鼠体内的抗炎、抗纤维化保护作用降低，表明NMDA受体激活可减弱BM-MSCs的抗博来霉素诱导的急性肺损伤和肺纤维化的作用。细胞内MAPK/ERK磷酸化信号通路参与介导了NMDA受体激活对BM-MSCs的抑制效应。.（3））本项目还在整体水平及离体水平证实，骨髓动员剂G-CSF可显著促进BM-MSCs归巢到博来霉素损伤的肺组织，明显改善BLM诱导的肺纤维化程度。.上述研究表明，BM-MSCs有NMDA受体的功能表达。内源性BM-MSCs是机体抗肺纤维化的重要保护机制。在博来霉素肺纤维的过程中，由于骨髓谷氨酸的大量释放，通过NMDA受体的介导是导致自身骨髓BM-MSCs保护功能异常的重要机制，减轻骨髓内源性BM-MSCs的损伤或激活BM-MSC是肺纤维化防治的潜在靶点。