Induction and prolonged expression of B-crystallin in microglia in the brain after transient global ischemia

초록

B-crystallin, which is a member of small heat shock protein (sHSP) family, has been shown to be up-regulated in the brain in various neuropathological states including Alzheimer’s disease. Here we report that B-crystallin immunoreactivity was markedly increased in hippocampus after transient global ischemia, whereas its expression in neurons and oligodendrocytes was similar to that in normal brain. The induction of B-crystallin, starting from several hours and reaching to the maximal level 4 days after reperfusion, was most prominent in the regions associated with severe neuronal damage in this model, which include CA1 region of hippocampus and layers 3 and 5 of neocortex. The induced expression of B-crystallin was identified mainly in activated microglia. The spatial and temporal patterns of B-crystallin induction in ischemic brain is sharply contrast to that of Hsp27, which was induced mainly in astrocytes and neurons in the brain after global or focal ischemia. These results suggest a distinct role of B-crystallin in microglia which are activated in post ischemic brain.