Department of Neurology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, 710004, China.
Department of Laboratory Medicine, Xi'an Central Hospital, Xi'an Jiaotong University, Xi'an, Shaanxi, 710003, China.
Brain Res Bull. 2021 Dec;177:73-80. doi: 10.1016/j.brainresbull.2021.09.014. Epub 2021 Sep 20.
Our previous study showed that neuronal apoptosis was significantly increased upon treatment of conditioned medium (CM) from necroptotic astrocytes (NAS), leaving the underlying mechanism unclear. Considering the nutritive and supportive roles of astrocytes, we first examined the neurotrophic phenotype of necroptotic astrocytes with focus on glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF), two important neurotrophic factors, and it was unexpectedly found that the expression of GDNF and BDNF were up-regulated in necroptotic astrocytes in vitro. A question was raised as to whether the functional secreted forms of neurotrophic factors were increased. Considering that extracellular vesicles (EVs) were carriers of secreted substances and their roles in cellular interaction, we isolated EVs from astrocytes and found EVs from normal and necroptotic astrocytes (EVs-NAS) had characteristics of exosomes. We then examined GDNF and BDNF in EVs-NAS, and BDNF was interestingly found as an immature form of pro-BDNF. The expression of pro-BDNF was found to be increased in EVs-NAS, and EVs-NAS had a negative effect on neuronal survival. To verify that whether pro-BDNF was involved in the detrimental effect of EVs-NAS, anti-pro-BDNF antibody was applied, and we found that neuronal apoptosis-induced by EVs-NAS could be significantly attenuated by blocking pro-BDNF, which suggested that necroptotic astrocytes induced neuronal apoptosis partially through EVs-derived pro-BDNF. The data expand our understanding in neurotrophic phenotype of necroptotic astrocytes, and may provide us new strategies targeting on EVs-NAS in treatment of neurological diseases.
我们之前的研究表明，星形胶质细胞发生坏死性凋亡（Necroptosis）后，培养基（Conditioned Medium，CM）可显著诱导神经元凋亡，但具体的作用机制尚不清楚。考虑到星形胶质细胞具有营养和支持神经元的作用，我们首先研究了坏死性凋亡星形胶质细胞的神经营养表型，重点关注胶质细胞系衍生的神经营养因子（Glial Cell Line-Derived Neurotrophic Factor，GDNF）和脑源性神经营养因子（Brain-Derived Neurotrophic Factor，BDNF），这两种因子都是重要的神经营养因子。但出乎意料的是，我们发现体外培养的坏死性星形胶质细胞中 GDNF 和 BDNF 的表达上调。于是我们提出了一个问题，即神经营养因子的功能分泌形式是否增加。由于细胞外囊泡（Extracellular Vesicles，EVs）是分泌物质的载体，其在细胞间相互作用中发挥重要作用，我们从星形胶质细胞中分离出 EVs，并发现正常星形胶质细胞和坏死性星形胶质细胞（EVs-NAS）来源的 EVs 具有外泌体的特征。然后，我们检测了 EVs-NAS 中的 GDNF 和 BDNF，有趣的是发现 BDNF 是不成熟的 pro-BDNF 形式。我们发现 EVs-NAS 中 pro-BDNF 的表达增加，并且 EVs-NAS 对神经元的存活有负面影响。为了验证 pro-BDNF 是否参与了 EVs-NAS 的有害作用，我们应用了抗 pro-BDNF 抗体，发现阻断 pro-BDNF 可显著减轻 EVs-NAS 诱导的神经元凋亡，这表明坏死性星形胶质细胞通过 EVs 衍生的 pro-BDNF 诱导部分神经元凋亡。该研究结果扩展了我们对坏死性星形胶质细胞神经营养表型的认识，并为我们针对 EVs-NAS 在神经退行性疾病治疗中的策略提供了新的思路。
