Expressions of Smac/Diablo and caspase-9 in the cytoplasm of cerebral cortex of neonatal rats with hypoxic-ischemic brain damage and interference effects of Shenfu injection on them

Objective To investigate the expressions of Smac/Diablo and caspase-9 and their corelations in the cytoplasm of cerebral cortex of neonatal rats with hypoxic-ischemic brain damage (HIBD), and the possible interference effects of Shenfu injection on them. Methods Postnatal 7-d SD rats were randomly divided into Shenfu treatment group (group SF), normal saline group (group C) and sham-operated group (group S). Rat models of HIBD were established according to Rice's method.Based on the observing times after the success of model making, each group (n=48) was equally divided into 6 subgroups (3, 6, 12 and 24 h, and 3 and 7 d observing groups). Rats in the group S were not performed ligation of the right common carotid artery and not underwent hypoxia but only performed the separation of right common carotid artery. Shenfu injection was administered by intraperitioneal injection right after H/I insult and then once daily at a dosage of 10 mL/kg for 3 d into the rats of group SF. Saline was also administered into the rats of group C by the same methods and at the same dosage. Cytoplasm proteins were extracted from the cerebral cortex tissue, and then, Western blotting was employed to detect the protein levels of Smac/Diablo and activated caspase-9 in cytoplasm. Results Western blotting showed that the expression levels of Smac/Diablo and activated caspase-9 in cytoplasm of group S were very low; the expression levels of Smac/Diablo and activated caspase-9 in cytoplasm of group SF and group C were increased markedly since the 3rd h of the success of model making as compared with those in group S (P＜0.05): these in the 2 groups reached their peak levels 24 h after H/I insult, gradually decreased 3 d after H/I insult, and almost returned to the original levels 7 d after H/I insult. The expressions of Smac/Diablo in cytoplasm of group SF 12, 24 h and 3 d after H/I insult was significantly lower than that of group C (P＜0.05); the expression of activated caspase-9 in cytoplasm of group SF 12,24 h and 3 d after H/I insult was significantly decreased as compared with that of group C (P＜0.05).Conclusion Smac/Diablo cytoplasm translocation and increased expression level of caspase-9 appear in the cytoplasm of cerebral cortex cells after H/I injury; Shenfu injection can inhibit the expressions of Smac/Diablo and caspase-9; Smac/Diablo and caspase-9 involve in the pathophysiological mechanisms of neuronal damage after H/I. Key words: Apoptosis;  Hypoxic-ischemic brain damage;  Smac/Diablo;  Caspase-9; Shenfu injection