褪黑素抑制新生大鼠脑缺血缺氧损伤后海马内Bcl-2/Bax的下调和caspase-3的活化

Melatonin inhibits the decrease of Bcl-2/Bax ratio and activation of caspase-3induced by hypoxia-ischemia brain damage in the hippocampal neurons of neonatal rats

目的探讨褪黑素对新生大鼠缺氧缺血性脑损伤(hypoxic-ischemic brain damage,HIBD)后脑内Bcl-2、Bax和caspase-3表达的影响。方法用电凝结扎第7天的新生SD大鼠右颈总动脉制备新生大鼠脑缺血缺氧损伤模型,用称重法测定脑水肿程度;hematoxylin-eosin(HE)和triphenyltetrazolium chloride(TTC)染色观察脑组织的梗死范围;Fluoro-Jade B(FJB)染色观察细胞的死亡情况;免疫荧光染色、Westernblot检测caspase-3、Bcl-2和Bax在各组的表达。结果 HIBD大鼠右侧大脑半球出现明显的梗死灶,且含水量较假手术组明显增加;褪黑素可使之减轻。HE和FJB染色显示,褪黑素可减轻大鼠缺血缺氧损伤引起的海马神经元的形态改变,降低FJB阳性细胞的数量。免疫荧光染色和Western Blot检测显示,HIBD大鼠右侧海马caspase-3、Bcl-2和Bax水平升高,Bcl-2/Bax降低;褪黑素干预后caspase-3和Bax水平达降低,Bcl-2水平升高,Bcl-2/Bax升高。结论褪黑素可通过抑制新生大鼠脑缺血缺氧损伤后海马内Bcl-2/Bax的下调和caspase-3的活化,抑制细胞凋亡,对新生鼠脑缺血缺氧损伤产生保护作用。

Objective To investigate the effects of melatonin on expression of Bcl-2,Bax and caspase-3 of hippocampus induced by hypoxia-ischemia brain damage in neonatal rats.Methods The effects of melatonin were studied in hypoxia-ischemia brain damage models,which were established by occlusion of the right common carotid artery.Brain edema was measured by the gravimetric method.The infarct volume was evaluated by HE and TTC staining.The dead cells were assayed by FJB staining.The expressions of Bcl-2 and Bax were evaluated by immunofluorescent staining and western blot.Results Obvious infarcts were found in the right hemispheres of the rats in HIBD groups,and the water contents were significantly higher than in sham groups;Melatonin relieved these effects.HE and FJB staining showed that melatonin alleviated the morphological change of hippocampal neurons caused by HIBD,and reduced the number of FJB positive cells.Immunofluorescent staining and WB detection results showed increased expression of cleaved caspase-3,Bcl-2 and Bax in HIBD groups,as well as decreased Bcl-2/Bax ratio.The melatonin-treated groups showed reduced caspase-3 and Bax expressions,and increased Bcl-2 expression and Bcl-2/Bax ratio.Conclusion Our work demonstrated that melatonin had protective effect on HIBD rat models by decreasing expression of cleaved caspase-3,increasing the ratio of Bcl-2/Bax,and inhibiting hippocampal neuron apoptosis.