Distinct Residential and Infiltrated Macrophage Populations and Their Phagocytic Function in Mild and Severe Neonatal Hypoxic-Ischemic Brain Damage
Distinct Residential and Infiltrated Macrophage Populations and Their Phagocytic Function in Mild and Severe Neonatal Hypoxic-Ischemic Brain Damage
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不同的驻留和浸润巨噬细胞群及其在轻度和重度新生儿缺氧缺血性脑损伤中的吞噬功能。
DOI：
10.3389/fncel.2020.00244
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发表时间：
2020-08-10
影响因子：
5.3
通讯作者：
Li, Fan
中科院分区：
文献类型：
--
作者：
Min, Yingjun;Yan, Lin;Li, Fan
新生儿脑损伤，尤其是严重的缺氧缺血性脑损伤，可导致死亡和长期的神经功能损害。我们先前的研究表明，在缺氧缺血性脑损伤（HIBD）的小鼠模型中，CD 11b+髓样细胞（包括居住性小胶质细胞（MG）和浸润性单核细胞衍生的巨噬细胞（MDM））活化，功能未知。在这里，我们研究MG和MDM的吞噬功能的差异，以阐明它们在HIBD后的潜在作用。在出生后9-10天的小鼠中诱导HI。伤后第1天和第3天进行病理学和神经行为学检查，以将脑损伤分为轻度和重度。流式细胞仪检测MG和MDM数量的动态变化，并根据CD 11b+细胞中CD 45的相对表达水平进行定量。CX 3CR 1GFPCCR 2 RFP双转化小鼠用于鉴定HIBD后脑实质中的MG和MDM。测定溶酶体相关膜蛋白1（LAMP 1）、toll样受体2（TLR 2）、CD 36和转化生长因子（TGF-β）表达水平，以评估这些细胞中吞噬细胞和神经保护因子的潜在功能。应用荧光素标记的葡聚糖40（FITC-dextran 40）吞噬实验检测体外氧糖剥夺（OGD）条件下细胞吞噬功能的变化。我们发现新生儿HI引起不同程度的脑损伤：轻度或重度损伤。与轻度损伤的动物相比，重度损伤的小鼠体重较低，神经行为评分较差，脑形态异常。在严重损伤的脑中，CD 11b+细胞显著增加，包括MDM群体的增加和MG群体的减少。此外，在CX 3CR 1GFPCCR 2 RFP双转化小鼠中，MDM浸润到脑实质中是明显的。轻度和重度脑损伤引起不同的吞噬相关反应和神经保护功能的MDM和MG在HI后1和3天。体外实验表明，OGD可激活BV 2细胞的吞噬功能，而下调Raw264.7细胞的吞噬功能。这些观察结果表明，新生儿HI引起不同程度的脑损伤。重型脑损伤时，巨噬细胞MDM浸润比例增加，并被募集到损伤的脑实质中。轻、重型脑损伤后，滞留巨噬细胞MGs的比例均降低，并维持活化的吞噬功能，而重型脑损伤后，滞留巨噬细胞MGs的比例则恢复了神经保护功能。
Neonatal brain injury, especially severe injury induced by hypoxia-ischemia (HI), causes mortality and long-term neurological impairments. Our previous study demonstrated activation of CD11b+ myeloid cells, including residential microglial cells (MGs) and infiltrating monocyte-derived macrophages (MDMs) in a murine model of hypoxic-ischemic brain damage (HIBD), with unknown functions. Here, we study the differences in the phagocytic function of MGs and MDMs to clarify their potential roles after HIBD. HI was induced in 9–10-day postnatal mice. On days 1 and 3 after injury, pathological and neurobehavioral tests were performed to categorize the brain damage as mild or severe. Flow cytometry was applied to quantify the dynamic change in the numbers of MGs and MDMs according to the relative expression level of CD45 in CD11b+ cells. CX3CR1GFPCCR2RFP double-transformed mice were used to identify MGs and MDMs in the brain parenchyma after HIBD. Lysosome-associated membrane protein 1 (LAMP1), toll-like receptor 2 (TLR2), CD36, and transforming growth factor (TGF-β) expression levels were measured to assess the underlying function of phagocytes and neuroprotective factors in these cells. The FITC-dextran 40 phagocytosis assay was applied to examine the change in phagocytic function under oxygen-glucose deprivation (OGD) in vitro. We found that neonatal HI induced a different degree of brain damage: mild or severe injury. Compared with mildly injured animals, mice with severe injury had lower weight, worse neurobehavioral scores, and abnormal brain morphology. In a severely injured brain, CD11b+ cells remarkably increased, including an increase in the MDM population and a decrease in the MG population. Furthermore, MDM infiltration into the brain parenchyma was evident in CX3CR1GFPCCR2RFP double-transformed mice. Mild and severe brain injury caused different phagocytosis-related responses and neuroprotective functions of MDMs and MGs at 1 and 3 days following HI. The phagocytic function was activated in BV2 cells but downregulated in Raw264.7 cells under OGD in vitro. These observations indicate that neonatal HI induced different degrees of brain injury. The proportion of infiltrated macrophage MDMs was increased and they were recruited into the injured brain parenchyma in severe brain injury. The resident macrophage MGs proportion decreased and maintained activated phagocytic function in both mild and severe brain injury, and restored neuroprotective function in severe brain injury.