Changes in immunoreactivity of HSP60 and its neuroprotective effects in the gerbil hippocampal CA1 region induced by transient ischemia

Heat shock proteins act as molecular chaperones and are involved in protein folding, refolding, transport, and translocation. In the present study, we observed changes in heat shock protein 60 (HSP60) immunoreactivity and protein level in the gerbil hippocampal CA1 region after 5 min of transient forebrain ischemia and its neuroprotective effect against ischemic damage. HSP60 immunoreactivity in the CA1 region began to increase in the stratum pyramidale at 30 min after ischemia/reperfusion, and peaked 24 h after ischemia/reperfusion. Thereafter, HSP60 immunoreactivity was decreased in the CA1 region with time. Seven days after ischemia/reperfusion, HSP60 immunoreactivity was increased again in the CA1 region: at this time point after ischemia/reperfusion, HSP60 immunoreactivity was expressed in glial cells in the ischemic CA1 region. HSP60 immunoreactive glial cells were astrocytes containing glial fibrillar acidic protein. In contrast, change in HSP60 immunoreactivity in the ischemic CA2/3 region was not significant compared with that in the ischemic CA1 region. In Western blot study, HSP60 protein level in the CA1 region was increased after ischemia/reperfusion and highest 24 h after ischemia/reperfusion. Animals treated with recombinant adenoviruses expressing Hsp60 (Ad-Hsp60) showed the neuroprotection of CA1 pyramidal neurons from ischemic damage. These results suggest that HSP60 may be associated with delayed neuronal death of CA1 pyramidal neurons after transient ischemia, and the induction of HSP60 protects the neurons from ischemic damage.