title: Accumulating microglia phagocytose injured neurons in hippocampal slice cultures: involvement of p38 MAP kinase.
abstract: In this study, microglial migration and phagocytosis were examined in mouse organotypic hippocampal slice cultures, which were treated with N-methyl-D-aspartate (NMDA) to selectively injure neuronal cells. Microglial cells were visualized by the expression of enhanced green fluorescent protein. Daily observation revealed microglial accumulation in the pyramidal cell layer, which peaked 5 to 6 days after NMDA treatment. Time-lapse imaging showed that microglia migrated to the pyramidal cell layer from adjacent and/or remote areas. There was no difference in the number of proliferating microglia between control and NMDA-treated slices in both the pyramidal cell layer and stratum radiatum, suggesting that microglial accumulation in the injured areas is mainly due to microglial migration, not to proliferation. Time-lapse imaging also showed that the injured neurons, which were visualized by propidium iodide (PI), disappeared just after being surrounded by microglia. Daily observation revealed that the intensity of PI fluorescence gradually attenuated, and this attenuation was suppressed by pretreatment with clodronate, a microglia toxin. These findings suggest that accumulating microglia phagocytosed injured neurons, and that PI fluorescence could be a useful indicator for microglial phagocytosis. Using this advantage to examine microglial phagocytosis in living slice cultures, we investigated the involvements of mitogen-activated protein (MAP) kinases in microglial accumulation and phagocytosis. p38 MAP kinase inhibitor SB203580, but not MAP kinase/extracellular signal-regulated kinase inhibitor PD98059 or c-Jun N-terminal kinase inhibitor SP600125, suppressed the attenuation of PI fluorescence. On the other hand, microglial accumulation in the injured areas was not inhibited by any of these inhibitors. These data suggest that p38 MAP kinase plays an important role in microglial phagocytosis of injured neurons.
authors: Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
authors: Takahiro
authors: T
authors: Katayama
authors: Hayato
authors: H
authors: Kobayashi
authors: Toshiyuki
authors: T
authors: Okamura
authors: Yuko
authors: Y
authors: Yamasaki-Katayama
authors: Tatsuya
authors: T
authors: Kibayashi
authors: Hiroshi
authors: H
authors: Kimura
authors: Keiko
authors: K
authors: Ohsawa
authors: Shinichi
authors: S
authors: Kohsaka
authors: Masabumi
authors: M
authors: Minami
mesh_terms: D000818:Animals; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D004268:DNA-Binding Proteins; D005260:Female; D005453:Fluorescence; D006624:Hippocampus / Q000473:pathology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D017628:Microglia / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D016202:N-Methylaspartate / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology*; D009687:Nuclear Proteins / Q000378:metabolism; D010587:Phagocytosis / Q000187:drug effects; D011419:Propidium / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017966:Pyramidal Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D013997:Time Factors; D059008:Time-Lapse Imaging; D046509:Tissue Culture Techniques; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D009419:Nerve Tissue Proteins; C492380:NeuN protein, mouse; D009687:Nuclear Proteins; D047428:Protein Kinase Inhibitors; D011419:Propidium; D016202:N-Methylaspartate; D048051:p38 Mitogen-Activated Protein Kinases