Protective effects of hyperbaric oxygen on neurons in neonatal rats with hypoxic-ischemic brain damage and its impact on the extracellular signal-regulated protein kinase 1/2 signaling pathway
Objective To explore the protective effects of hyperbaric oxygen(HBO)on neurons in neonatal rats with hypoxic-ischemic brain damage(HIBD)and its impact on the extracellular signal-regulated protein kinase 1/2(ERK1/2)signaling pathway.Methods Sixty 7-day-old healthy SD rats were divided in accordance with a random number table into a sham operation group,a model group,an intervention group,and a blocker group,with 15 rats in each group.A neonatal rat HIBD model was constructed with reference to the Rice-Vannucci model.In the sham operation group,the carotid arteries of rats were exposed and then directly sutured;in the model group,no treatment was given to the rats after modeling;in the intervention group,HBO intervention was given to the rats one hour after modeling;in the blocker group,before each HBO intervention,0.05 mg/kg ERK1/2 blocker U0126 was injected into the cauda vein of rats.After the intervention,10 rats in each group were randomly selected and then euthanized for sampling.The infarct volume of brain tissue was measured through TTC staining;the pathological morphological changes of brain tissue were observed by HE staining;the apoptosis rate of neuronal cells in brain tissue was observed and counted by TUNEL staining;the expressions of ERK1/2,p-ERK1/2,Bcl-2,and Bax proteins in brain tissue were determined by Western Blot assay;the levels of ERK1/2 mRNA,Bcl-2 mRNA,and Bax mRNA in brain tissue were determined by reverse transcription polymerase chain reaction(RT-PCR).The remaining rats in the 4 groups were fed for another 14 days,and the learning and memory abilities of the rats were detected by Morris water maze experiment.Results Compared with the sham operation group,the cerebral infarct volume ratio and neuronal cell apoptosis rates of the other three groups of rats were significantly increased(P＜0.05);compared with the model group,the intervention group rats showed a significant decrease in the cerebral infarct volume ratio and neuronal cell apoptosis rates(P＜0.05);compared with the intervention group,the cerebral infarct volume ratio and neuronal cell apoptosis rates of the rats in blocker group were significantly increased(P＜0.05).The morphology of brain neurons of the rats in the sham operation group was normal,neat and dense,and the tissue structure was intact.The number of neurons of the rats in the model group decreased,their arrangement became disordered,and cavities were formed,with visible cytoplasmic vacuoles and the nuclei were pyknosed.The rats in the intervention group showed local damage to brain tissue neurons,but its degree was milder than that of the model group.The neuronal damage in the brain tissue of the rats in the blocker group was more severe than that of the intervention group,which was close to that of the model group.Compared with the sham operation group,the expression level of p-ERK1/2 protein in the brain tissue of the rats in the intervention group was significantly increased(P＜0.05),while the expression levels of Bcl-2 protein in the brain tissue of the rats in other three groups were significantly decreased,and the expression level of Bax protein was significantly increased(P＜0.05);compared with the model group,the expression levels of p-ERK 1/2 and Bcl-2 proteins in the brain tissue of the intervention group rats were significantly increased,while the expression level of Bax protein was significantly decreased(P＜0.05);compared with the intervention group,the expression levels of p-ERKl/2 and Bcl-2 proteins in the brain tissue of rats in the blocker group were significantly reduced,while the expression level of Bax protein was significantly increased(P＜0.05).Compared with the sham operation group,the intervention group showed a significant increase in ERK 1/2 mRNA levels in brain tissue,while the other three groups showed a significant decrease in Bcl-2 mRNA levels and a significant increase in Bax mRNA levels(P＜0.05);compared with the model group,the levels of ERK 1/2 mRNA and Bcl-2 mRNA in the brain tissue of the intervention group rats were significantly increased,while the level of Bax mRNA was significantly decreased(P＜0.05);compared with the intervention group,the levels of ERK1/2 mRNA and Bcl-2 mRNA in the brain tissue of rats in the blocker group were significantly reduced,while the level of Bax mRNA was significantly increased(P＜0.05).Compared with the sham operation group,the escape latencies of the other three groups of rats was significantly prolonged,and the number of platform crossings was significantly reduced(P＜0.05);compared with the model group,the intervention group rats showed a significant reduction in escape latency and a significant increase in the number of platform crossings(P＜0.05);compared with the intervention group,the escape latency of rats in the blocker group was significantly prolonged,and the number of platform crossings was significantly reduced(P＜0.05).Conclusion HBO may up-regulate the ratio of downstream apoptosis-related protein Bcl-2/Bax by activating the ERK1/2 signaling pathway,inhibit neuronal apoptosis in neonatal rats with HIBD,thus exerting a protective effect on brain tissue.
Hyperbaric oxygenHypoxic-ischemic brain damageExtracellular signal-regulated protein kinase 1/2Neuronal protectionApoptosis
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