The expression changes and role of hypoxia-inducible factor-1a in the early stage of hypoxic-ischemic brain damage in neonatal rats / 中华实用儿科临床杂志

ABSTRACT

Objective To study the expression of hypoxia-inducible factor-1a(HIF-1α) at mRNA and protein levels in the early stage of hypoxic-ischemic brain damage (HIBD) in neonatal rats and its role.Methods (1) Experiment 1thirty-six postnatal 7-day SD rats were divided into Sham group (n =6) and model group (HIBD,n =30) according to the random table method,then the rats in the model group were divided into 5 subgroups according to the time of sacrifice after HIBD(6 h,12 h,24 h,48 h,72 h,n =6).The expression levels of HIF-1cα mRNA and protein were detected by quantitative Real-time PCR(qPCR) and Western blot,respectively.(2) Experiment 2forty-five postnatal 7-day SD rats were randomized into 3 groupsSham group (n =15),HIBD group (n =15) and 2-methoxyestradiol(2ME2) group(n =15).According to the experiment 1,at the time point of the highest expression levels of HIF-1 α mRNA and protein,rats were killed and the brains were collected.The location and expression of HIF-1 α protein were detected by immunofluorescence,histopathological changes of brain were observed by HE staining,brain water content was measured by dry-wet method,cell apoptosis was detected by nick end labeling(TUNEL) method.Results At the early stage of HIBD,the expression levels of HIF-1 α mRNA and protein increased at first and then decreased,and the mRNA expression level (3.38 ± 0.21) and protein expression level (2.81 ± 0.36) were the highest at 24 h after HIBD.In Sham group,HIF-1 α protein was mainly expressed in the cytoplasm,while in HIBD group it was mainly expressed in the nucleus.The number of HIF-1α staining positive cells,brain water content and apoptosis rate were significantly different among Sham group,HIBD group and 2ME2 group (all P ＜ 0.05),and which were significantly lower in 2ME2 group than those in HIBD group (all P ＜ 0.05),and the pathological changes were also less serious than those in HIBD group.Conclusions The mRNA and protein levels of HIF-1 α are the highest at 24 h after HIBD.Inhibiting the expression of HIF-1 α can ameliorate the brain damage of neonatal rats induced by hypoxia-ischemia.Therefore,it is hypothesized that HIF-1α may cause injury in the early stage of HIBD in neonatal rats.