Inhibition and machanisms of total saponins from Panax notoginseng on apoptosis of hippocampal CA1 subfield neurons of rats following global cerebral ischemia / 中草药

ABSTRACT

Objective: To explore whether total saponins of Panax notoginseng (TSPN) can protect hippocampal CA1 subfield neurons against apoptosis following global cerebral ischemia via up-regulating the Bcl-2/Bax ratio and preventing Caspase-3 activation. Methods: Using four-vessel occlusion method to build the global cerebral ischemia model and the ischemia time was 30 min. All rats were divided into Sham group, vehicle group, and different doses (25, 50, 75, and 100 mg/kg) of TSPN groups. The rats in TSPN groups were ip administered with TSPN. The dose of TSPN was suspended in 0.9% saline (10 g/L), while rats in vehicle group were treated with equal volume of 0.9% saline, one injection per day. Compared the survival rate and hippocampal CA1 subfield neuronal density by Nissl staining after reperfusion of 14 d to make sure the best dose of TSPN for neuroprotection. Then to evaluate the neurological score and investigate the expression level of the Caspase-3, Bcl-2, and Bax in the hippocampus CA1 region at days 1, 3, 7, and 14 post-ischemia by immunohistochemistry; In addition, the Western-blotting was adopted to test the protein level of these three proteins. Results: The survival rate of the rats in 75 mg/kg TSPN groups was 100%, and its neuronal density was significantly higher than that in vehicle group and other doses of TSPN groups (P < 0.05); The neurological score in TSPN group was significantly less than that in vehicle group (P < 0.01); The Caspase-3 neuronal density in the CA1 subfield of TSPN group on days 7 and 14 was significantly less than that in vehicle group (P < 0.001); The statistical meaning existed about the protein level of Caspase-3 with molecular weight of 20 000 on days 3, 7, and 14 and 17 000 on days 7 and 14 in two groups (P < 0.001). The neuronal density of Bcl-2 cells in the CA1 subfield and Bcl-2 protein level in the hippocampus of TSPN group at days 7 and 14 was significantly higher than that in vehicle group (P < 0.001); Besides, the Bax neuronal density at days 7 and 14 was significantly lower than that in vehicle group (P < 0.001); And its protein level of the hippocampus was less than that in vehicle group at days 3, 7 and 14 (P < 0.001). The results of ratio of Bcl-2/Bax from not only the neuronal density but also the protein expression demonstrated that the Bcl-2/Bax ratio in TSPN group was significantly higher than that in vehicle groups on days 7 and 14 (P < 0.001). Conclusion: TSPN can protect the hippocampal CA1 subfield neurons against apoptosis following global cerebral ischemia in adult rats via up-regulating the Bcl-2/Bax ratio and preventing Caspase-3 activation.