| Research Abstract |
I have guessed that active oxygen species produced in microglia cells were involved in death of neuron after cerebral ischemia. Thus I compared active oxygen-producing mechanisms of microglia with that of neutrophils which kill bacteria using active oxygen.
First, to use primary cultures of microglia as model system of microglia in brain, conditions for primary cultures were examined and the best condition was established.
Next, properties of production of superoxide anion (02-), first material of active oxygen species, in microglia was examined. The cultured microglia cells produced 02- by the stimulation of PMA, a protein kinase C (PKC) activator. 02- was produced more than one hour, and the production was one sixth to one eighth of that in neutrophils. PKC inhibitors suppressed the production. Furthermore, I confirmed the existence of p47-phox and gp9l-phox, the components of neutrophil NADPH oxidase, in microglia. These results strongly indicate that microglia possess neutrophil-like NADPH oxidase which is activated by PKC and produce 02-. It is well known that translocation of p4.7-phox to plasma membranes is necessary for the activation of NADPH oxidase in neutrophils. But, in microglia, translocation of p47-phox to membrane fraction was not observed. The activation mechanism of NADPH oxidase of microglia may differ from that of neutrophils.
Finally, I found that microglia produced nitric oxide (NO) under the hypoxia condition similar to brain ischemia, and continuously produced NO after reoxygenation. This may lighten the new role of microglia at brain ischemia.
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