Study on the activities' alteration of the proteasome in neurons of cortex and its relation with delayed neuron death after reperfusion following ischemia

Abstract

To investigate the activities' alteration of the proteasome in neurons of cortex and its relation with delayed neuron death after reperfusion following ischemia. 20 minutes transient global ischemia rat model was used. Following different reperfusion period, all the 50 rats were divided into 5 groups, sham-operation group, 0.5 hour recovery group, 4 hours recovery group, 24 hours recovery group and 72 hours recovery group, 10 rats each group. Suc-llvy-amc was used as substrate for measuring proteasome's activities. Delayed neuron death after reperfusion following ischemia was observed under light microscope by HE staining. Proteasome's distribution was observed under laser scanning confocal microscope after immuno-histo-chemical staining. The proteasome activity of sham group was 54 602 +/- 1602, and that of 0.5 h reperfusion following ischemia was 42,036 +/- 1465 (compared with sham group, P < 0.01). Although the proteasome activity temporarily recovered to 47,536 +/- 2532 (P < 0.05) after 4 h reperfusion, it still decreased to 45,450 +/- 649 (P < 0.01) after 24 h reperfusion, and to 43,108 +/- 995 (P < 0.01) after 72 h reperfusion. HE staining showed that parts of neurons in the cortex died after 72 hours reperfusion. Under laser scanning microscope, we could observe that after 24 hours reperfusion, proteasome in both nucleus and cytoplasma significantly decreased; after 72 hours reperfusion, proteasome almost disappeared totally in nucleus and only a small part of proteasome still existed in cytoplasm. Decreasing of the proteasome's activities is an important factor for delayed neuron death after reperfusion following ischemia.