| ObjectiveHypoxic-ischemic brain damage (HIBD) caused by perinatal asphyxiaoften leads to the death of neonates or severe neurological sequelae. Ithas been the single most problem in neonatal period. There is increasingevidence that recombinant human erythropoietin plays an important rolein the pathogenesis of neonate hypoxic-ischemic brain damage. In theexperiment when HIBD model was established, different EPO dosages wereintraperitoneally injected. Then we study the effects of EPOon expressionof Bcl-2 and Bax protein, to explore the neuroprotective molecularmechanism of EPO. Our experiment may provide an efficacious treatment forclinical therapy of neonatal HIBD.Methods1. Mading of HIBD model: Neonatal 7-day-old Wistar rats were undera middle anterior neck incision. The left common carotid artery wasisolated and ligated, then the pups were exposed to hypoxic environment(8％O2 92％N2) for 2 hours. We observed the rat's behavior ability duringhypoxic, then observed microscopical changes.2. Observing of behavior ability of rats: Observed turnover abilityand levorotary ability when their tails are gripped of each rat beforethe experiment and after hypoxia 1 hour3. Expression of Bcl-2 and Bax protein. 42 seven-day-old Wistar ratswere randomly assigned to sham operation group, HIBD group, saline-treated control group, EPO-treated group. Different EPO dosages were intraperitoneally injected 15 minute after HI insult. We measured theexpression of Bcl-2 and Bax protein at 24 hour after injection byimmunohistochemistry.Results1. Observing of behavior ability of the rats:Before the experiment each rat is healthy. 1 hour after hypoxia, thesham operation group is still healthy, while in the 35 rats which barehypoxic-ischemic injury, 19 rats couldn't turn themselves over and 28 ratsbecome levorotary when their tails are gripped. There are 13 rats couldn'tturn themselves and become levorotary when their tails are gripped.2. HE staining and the histological studySham operation group: There was no obvious sign of neuronal damageand with cells of apparently normal appearance in the brain tissue. Therewas no edema and degenerated neurons.HIBD group: The edema in the brain tissue was apparent, themorphological alteration of the neuron were cellular shrinkage,cytoplasmic homogeneity changing, nuclear pyknosis, and theproliferation of glial cell appeared.3. Expression of Bcl-2 proteinThe level of Bcl-2 protein was low in Sham operation group. After HIBD,the expression of Bcl-2 protein increased significantly. Each EPO-treatedgroup was higher than HIBD group and saline-treated group. There was nosignificant difference between saline-treated group and HIBD group(P＞0.05), there was also no difference significantly between theEPO-treated(low dose)group and above the two groups (P＞0.05). There was significant difference in the left groups (P＜0.05).4. Expression of Bax proteinThe level of Bax protein was low in Sham operation group. After HIBD,the expression of Bax protein decreased significantly. Each EPO-treatedgroup was lower than HIBD group and saline-treated group. There was nosignificant difference between saline-treated group and HIBD group(P＞0.05), there was also no difference significantly between theEPO-treated(low dose)group and above the two groups(P＞0.05). There wassignificant difference in the left groups (P＜0.05).5. The change of Bcl-2/BaxAfter HIBD, the ratio of Bcl-2/Bax decreased significantly. Itincreased in EPO-treated groups. There was no significant differencebetween saline-treated group and HIBD group (P＞0.05), there was also nodifference significantly between the EPO-treated(low dose)group andabove the two groups (P＞0.05). There was significant difference in theleft groups (P＜0.05).Conclusions1. We confirmed the success of the model HIBD in neonatal rats throughobserving the rat's behavior ability and the histopathology of braintissue.2. The neuroprotective mechanism of EPO might be related to upregulating the expression of Bcl-2 protein, down regulating theexpression of Bax protein and alter the ratio of Bcl-2/Bax in brain tissue,consequently it could decrease the apoptosis of neuron after HIBD. Ourconclusion may be useful for the clinical treatment of HIBD. |
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