Haga Akira, Takahashi Eri, Inomata Yasuya, Kawahara Koichi, Tanihara Hidenobu
Department of Ophthalmology Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Niigata University of Pharmacy and Applied Life Sciences, Niigata, Japan.
Invest Ophthalmol Vis Sci. 2016 May 1;57(6):2814-23. doi: 10.1167/iovs.15-18509.
The purpose of this study was to elucidate the differentiated expression patterns and phagocytic activities of two subtypes of microglia.
A rat optic nerve crush model was used to identify the expression patterns of two subtypes of microglia. Primary microglia were isolated from rat mixed glial cultures. Subsequently, in vitro experiments evaluating the phagocytosis of axonal debris were performed to analyze responsiveness to immunologic modulators (lipopolysaccharide [LPS], interleukin [IL]-4 and interferon [IFN]-γ), and we assessed the effects of LPS and IL-4 in the optic nerve crush model. The expression levels of IL-4-associated signaling molecules were analyzed in immunoblotting experiments.
In the optic nerve crush model, increased numbers of microglia were found, and a minor and transient population was identified as type 1 microglia. The type 2 microglia phagocytosed more axonal debris than the type 1 microglia. The activities of both subtypes of microglia were enhanced by treatment with LPS and IFN-γ. However, the phagocytic activity of the type 1 microglia, which showed activated STAT6 signal transduction, was significantly inhibited by stimulation with the anti-inflammatory cytokine IL-4. LPS reduced the fragmentation of axons in crushed nerve fibers, whereas the axonal debris remained in IL-4-treated rats subjected to optic nerve crush.
The present study revealed the time-dependent distribution of the two subpopulations of microglia in an optic nerve crush model and IL-4-dependent inhibition of the phagocytosis of axonal debris by type 1 but not type 2 microglia.
本研究旨在阐明两种小胶质细胞亚型的差异表达模式和吞噬活性。
采用大鼠视神经挤压模型来确定两种小胶质细胞亚型的表达模式。从小鼠混合胶质细胞培养物中分离出原代小胶质细胞。随后，进行体外实验评估轴突碎片的吞噬作用，以分析对免疫调节剂（脂多糖 [LPS]、白细胞介素 [IL]-4 和干扰素 [IFN]-γ）的反应性，并评估 LPS 和 IL-4 在视神经挤压模型中的作用。在免疫印迹实验中分析了 IL-4 相关信号分子的表达水平。
在视神经挤压模型中，发现小胶质细胞数量增加，并且一小部分短暂存在的细胞群被鉴定为 1 型小胶质细胞。2 型小胶质细胞比 1 型小胶质细胞吞噬更多的轴突碎片。LPS 和 IFN-γ 处理可增强两种小胶质细胞亚型的活性。然而，显示激活 STAT6 信号转导的 1 型小胶质细胞的吞噬活性被抗炎细胞因子 IL-4 刺激显著抑制。LPS 减少了挤压神经纤维中轴突的碎片化，而在接受视神经挤压的 IL-4 处理大鼠中轴突碎片仍然存在。
本研究揭示了视神经挤压模型中两种小胶质细胞亚群的时间依赖性分布，以及 IL-4 对 1 型而非 2 型小胶质细胞吞噬轴突碎片的依赖性抑制作用。
