Effect Of Insulin-like Growth Factor-1on Neonatal Mice With Hypoxic Ischemic Brain Damage About Brain Cells Mitochondria Membrane Potential

Objective：To investigate the effect of insulin-like growth factor-1(IGF-1) on brainmitochondria membrane potential in neonatal mice with hypoxic ischemic brain damage(HIBD) in acute phase.Methods：The7-day-old neonatal mice (C57/BL,91mice) were randomly divided into normalcontrol group (n=7), sham group (n=22), sham+IGF-1group (n=18), HI group (n=22),HI+IGF-1group (n=22). The7-day-old C57/BL neonatal mice were anesthetized withanhydrous ether, and the right common carotid artery was ligated. Then the mice wereplaced into anoxic tank (8%O2) about2h to establish HIBD animal model. The normalcontrol group was not done any treatment. The sham group just separated the rightcommon carotid artery. After the operation, the two groups (sham+IGF-1group,HI+IGF-1group) were injected IGF-150μg/kg immediately, sham group and HI groupwere injected the same amount of saline solution (0.1ml/10g). The behavioral changeswere observed. The mice were killed on postoperative0,3,6,12,24,48h respectively.The dry-wet method was used to detect the brain water content. The HE and Nisslstaining were used to observe pathological changes. The cerebral cortex, hippocampus,thalamencephalon were removed immediately, and digested into single cell suspension.The Rhodamine123was used to dye, and the flow cytometry was used to detect themitochondrial membrane potential. Results：(1) The right brain water content in HI group after operation48h was significantlyincreased comparing with the sham group(P＜0.01). Compared with HI group, the rightbrain water content was significantly decreased in HI+IGF-1group (P＜0.01).(2) Compared with HI group, neonatal mice neurobehavioral abnormalities after24hwere significantly decreased in HI+IGF-1group (P＜0.01).(3) HE and Nissl staining showed that the both side of the brain in normal controlgroup, sham group, sham+IGF-1group have no pathological changes in brain structureand the same with the left side of the brain in HI group. While the right side of the brainin HI group appeared edema, degeneration, apoptosis and necrosis compared with theright side of the brain in HI+IGF-1group, which the pathological changes werelightened. The cortex, hippocampus, thalamus on postoperative3,6,12h began toappear edema, apoptosis. The neurons were swelling, degeneration significantly and theapoptosis neurons were peaked at48h after HI. Compared with HI group, the brainedema, degeneration, apoptosis and necrosis were significantly alleviated in HI+IGF-1group.(4) The Rhodamine123staining results showed that the mean fluorescence intensity incerebral cortex, hippocampus, thalamus of normal control group, sham group,sham+IGF-1group at different time points has no obviously differences (P>0.05). InHI group, the decrease of mitochondrial membrane potential was appeared at3h incerebral cortex, at6h in hippocampus and at12h in thalamus. Compared with HI group,the mitochondrial membrane potential in cortex, hippocampus and thalamus wasincreased in HI+IGF-1group (P <0.01).Conclusion：The IGF-1intervention therapy can significantly reduce cerebral edema caused byhypoxia ischemia, reduce the incidence of early neurobehavioral abnormalities after HIBD, and decrease the neuronal apoptosis. The neuronal damage of HIBD of neonatalmice may be occurred from cortex, hippocampus to thalamus. The data suggest that theprotective effect of exogenous IGF-1may be related to reduce neonatal mice brainmitochondrial membrane potential in the acute phase of HIBD, improved mitochondrialfunction.