AMPA受体在精神分裂症模型小鼠小胶质细胞和髓鞘发育中的作用

The role of AMPA receptors in the development of microglia and myelin in mice with schizophrenia

目的 探讨谷氨酸受体(AMPAR)在精神分裂症模型小鼠小胶质细胞和髓鞘发育中的作用。方法 15只AMPAR条件性敲除线(GluA1-3亚基的敲除,KO组)和15只野生型(WT组)小鼠喂食含0.2%CPZ食物4周以诱导脱髓鞘(4周时间点),然后喂食不含CPZ食物3周以使髓鞘再生(4+3周时间点)。通过Solochrome染色和电子显微镜观察髓鞘损失和髓鞘再生情况。通过Iba1、dMBP免疫组化分析小胶质细胞对脱髓鞘反应和髓鞘碎片的变化。结果 CPZ喂食4周后,观察到WT组与KO组小鼠的胼胝体都出现了强烈的脱髓鞘。恢复3周后,与WT组相比,KO组的髓鞘再生受损(P<0.01)。在CPZ喂食4周后,与WT组相比,KO组小鼠的小胶质细胞浸润减少(P<0.01)。4+3周时间点,在WT组和KO组小鼠的病变中观察到相似数量的小胶质细胞。与WT组小胶质细胞相比,KO组小胶质细胞在伤口闭合方面表现出缺陷(P<0.05)。在4周和4+3周时间点观察到KO组较WT组中央和外侧胼胝体中有过多的髓鞘碎片(P<0.01)。KO组小胶质细胞对凋亡细胞的清除较WT组小胶质细胞减少(P<0.01)。结论 AMPAR是精神分裂症模型小鼠中小胶质细胞对脱髓鞘和随后髓鞘再生的反应所必需的。

Objective Schizophrenia is a demyelinating and inflammatory disease that affects the central nervous system. Glutamate receptor(AMPAR) is related to the pathophysiology of schizophrenia and plays a central role in synaptic events, including plasticity, neuronal maturation, memory formation and synaptogenesis. However, the role of AMPAR in the development of microglia and myelin sheath in schizophrenia has not been explored. Therefore, this study aims to explore the role of AMPAR in the development of microglia and myelin in mice with schizophrenia. Methods 15 AMPAR conditional knockout line(knockout of GluA1-3 subunits, KO group) and 15 wild-type(WT group) mice were fed chow with 0.2% CPZ for 4 weeks to induce demyelination(4-week time point), and then fed without CPZ food for 3 weeks for remyelination(4+3 week time point). Myelin loss and remyelination were observed by Solochrome staining and electron microscopy. The changes of microglia response to demyelination and myelin debris were analyzed by Iba1 and dMBP immunohistochemistry. Fluorescence activated cell sorting(FACS) was used to separate Annexin V+ and Annexin V-cells from the corpus callosum of demyelinated KO group, and the percentage of Annexin V+ cells in KO group was observed. Microglia were isolated from the brains of WT group and KO group on the 1stday(P1)-P3 after birth, and their phagocytosis and migration ability were determined. Results After 4 weeks of CPZ feeding, strong demyelinations of the corpus callosum were observed in both WT group and KO group. After 3 weeks of recovery, remyelination was significantly impaired in KO group compared with WT group(P<0.01). At the 4-week time point, there were more myelinated axons in KO group than those in WT group(P<0.01). At the 4+3 week time point, there were fewer myelinated axons in KO group than those in WT group(P<0.05). After 4 weeks of CPZ feeding, microglial infiltration was significantly reduced in KO group compared with that in WT group(P<0.01). However, at the 4+3 week time point, similar numbers of microglia in lesions of both WT and KO groups were observed. Compared with WT group, KO group showed defects in wound closure of microglia(P<0.05). KO group showed more myelin debris in the central and lateral corpus callosum than WT group at the 4-week and 4+3-week time points(P<0.01). Annexin V+ and Annexin V-cells were isolated from the demyelinated corpus callosum of KO group. It was observed that the percentage of Annexin V+ cells in KO group was higher than that in WT group(average 4.38% vs. 1.14%). Compared with Annexin V-cells, Annexin V+ cells expressed higher levels of microglia marker genes, while other CNS cell types expressed lower levels of genes. The clearance of apoptotic cells by microglia in KO group was less than that in WT group(P<0.01). Conclusion In this study, the model of schizophrenia is induced in mice by feeding CPZ for 4 weeks, and it is found that myelinated axons and myelin sheath in the corpus callosum of mice are almost completely missing, but recovered after stopping feeding CPZ for 3 weeks, which confirms that myelinated axons and myelin sheath loss participate in the pathological process of schizophrenia. AMPAR is essential for the microglia response to demyelination and subsequent remyelination in a mouse model of schizophrenia. In particular, AMPAR plays an important role in the phagocytosis and migration of microglia.