Cranial irradiation induces transient microglia accumulation, followed by long-lasting inflammation and loss of microglia.

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Cranial irradiation induces transient microglia accumulation, followed by long-lasting inflammation and loss of microglia.

Oncotarget. 2016 Oct 26;:

Authors: Han W, Umekawa T, Zhou K, Zhang XM, Ohshima M, Dominguez CA, Harris RA, Zhu C, Blomgren K

Abstract
The relative contribution of resident microglia and peripheral monocyte-derived macrophages in neuroinflammation after cranial irradiation is not known. A single dose of 8 Gy was administered to postnatal day 10 (juvenile) or 90 (adult) CX3CR1GFP/+ CCR2RFP/+ mouse brains. Microglia accumulated in the subgranular zone of the hippocampal granule cell layer, where progenitor cell death was prominent. The peak was earlier (6 h vs. 24 h) but less pronounced in adult brains. The increase in juvenile, but not adult, brains was partly attributed to proliferation. Microglia numbers then decreased over time to 39% (juvenile) and 58% (adult) of controls 30 days after irradiation, largely as a result of cell death. CD68 was expressed in 90% of amoeboid microglia in juvenile hippocampi but only in 9% of adult ones. Isolated hippocampal microglia revealed reduced CD206 and increased IL1-beta expression after irradiation, more pronounced in juvenile brains. CCL2 and IL-1 beta increased after irradiation, more in juvenile hippocampi, and remained elevated at all time points. In summary, microglia activation after irradiation was more pronounced, protracted and pro-inflammatory by nature in juvenile than in adult hippocampi. Common to both ages was long-lasting inflammation and the absence of monocyte-derived macrophages.

PMID: 27793054 [PubMed - as supplied by publisher]

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