| BackgroundIschemic cerebrovascular disease is a very common vascular disease of cerebral circulation,which also occur in the elderly lead to high morbidity and mortality.In an ischemic stroke,blood can’t reach the brain,and brain cells suffer from the lack of nutrients and oxygen that they would normally get.So it is particularly important to find a treatment or drug that can improve ischemic injury.Nerve growth factor(NGF)and brain-derived neurotrophic factor(BDNF)are members of the neurotrophic factor family that induce the development,survival and function of neurons.Pathophysiological changes in cerebral ischemia can activate a variety of neurotrophic factors,thus promote regeneration and repair of neuron.Anti-apoptotic protein Bcl-2 and pro-apoptotic protein Bax are two important apoptosis-regulating genes.During cerebral ischemia,apoptosis-related genes were activated;Bax/Bcl-2 ratio was increased,leading to neuronal apoptosis by activating downstream signaling molecules.Thyroid hormone(T3)is tyrosine-based hormones produced by the thyroid gland that is required for normal development of the nervous system as well as regulating metabolism in the adult,and maintain the excitability of the nervous system.Researchers found that thyroid hormone deficiency after cerebral ischemia may impair cognitive function.But whether it can promote ischemic cerebrovascular disease neurological recovery is unclear.In this study we investigated the effect of thyroid hormone on the expression of NGF,BDNF,Bcl-2 and Bax in middle cerebral artery occlusion rat model to explore the neuroprotective effect of thyroid hormone.ObjectiveTo observe the effect of thyroid hormone(T3)on the expression of NGF,BDNF,Bax and Bcl-2 after cerebral ischemia-reperfusion injury in rats with middle cerebral artery occlusion(MCAO),investigate the neuroprotective effect and mechanism of thyroid hormone.Methods1.SD rats were randomly divided into 4 groups(n = 8):sham group(Sham = 1),sham + T3 group(Sham),ischemia-reperfusion group(IR),IR + T3 group(T3).The middle cerebral artery occlusion(MCAO)rat model was prepared by intraluminal suture emboli method.Thyroid hormone(T3)(10ug/100g)was administrated to rats 1h after ischemia and 6h after reperfusion,physiological saline as placebo-controlled.The neurological function scores of rats in different groups were observed at 24 h after operation,and the changes of infarct volume were observed by TTC staining.2.Total RNA was extracted from rat cerebral cortex in different groups,and the mRNA levels of NGF and BDNF were detected by RT-PCR.3.Total protein was extracted from rat cerebral cortex in different groups,and the protein levels of NGF,BDNF,Bax and Bcl-2 were detected by Western Blot.Results 1.Effect of T3 on the neurological functional score of cerebral ischemia-reperfusion rats24 hours after MCAO operation,the Longa’s score of sham group and sham + T3 group also were 0,without neurological deficit;and Longa’s score(2.71 + 0.56)in ischemia reperfusion group rats significantly higher than in sham and sham + T3 group(n = 8,P < 0.05).And the rats showed partial paralysis.The Longa’s score(1.63 ± 0.58)in the rats treated with T3 was lower than that in the ischemia reperfusion group(n = 8,P < 0.05),and the hemiplegia were also alleviated.2.Effects of T3 on cerebral infarction volume in cerebral ischemia-reperfusion ratsThere was no infarction in sham group and sham + T3 group 24 hours after MCAO,while the ischemia-reperfusion group rats showed obvious infarction;the percentage of infarction volume(45.12 + 2.32)significantly higher than the sham and sham + T3 group(n = 8,P < 0.05),but lower than the rats treated with T3(26.36 + 1.04)(n = 8,P < 0.05).3.Effects of T3 on the expression of NGF and BDNF mRNA levels in cerebral ischemia-reperfusion ratsThe levels of NGF and BDNF mRNA in ischemic cerebral cortex were detected by Western Blot 24 hours after MCAO.It was found that the levels of NGF and BDNF mRNA in ischemia-reperfusion group were higher than those in sham group and sham + T3 group(n = 8,P < 0.05).And the levels of NGF and BDNF mRNA in rats treated with T3 were significantly higher than those in ischemia-reperfusion rats(n = 8,P < 0.05).4.Effects of T3 on the expression of NGF and BDNF in cerebral ischemia-reperfusion ratsThe levels of NGF and BDNF protein in ischemic cerebral cortex were detected by Western Blot 24 hours after MCAO.It was found that the levels of NGF and BDNF protein in ischemia-reperfusion group were higher than those in sham group and sham + T3 group(n = 8,P < 0.05).And the levels of NGF and BDNF protein in rats treated with T3 were higher than those in ischemia-reperfusion rats(n = 8,P < 0.05).5.Effects of T3 on the expression of Bcl-2 and Bax in cerebral ischemia-reperfusion ratsThe levels of anti-apoptotic protein Bcl-2 and pro-apoptotic protein Bax in ischemic cerebral cortex were detected by Western Blot 24 hours after MCAO.The level of Bcl-2 protein in ischemia-reperfusion group was significantly lower than that in sham group and sham + T3 group(n = 8,P < 0.05);The level of Bcl-2 in rats treated with T3 was higher than that in ischemia-reperfusion rats(n = 8,P < 0.05).At the same time,the level of Bax protein in ischemia-reperfusion group was significantly higher than that in sham group and sham + T3 group(n = 8,P < 0.05).The level of Bax in rats treated with T3 was lower than that in ischemia-reperfusion rats(n = 8,P < 0.05).Conclusions 1.Thyroid hormone T3 can significantly improve the neurological dysfunction in rats with ischemia-reperfusion injury,reduce the percentage of infarct volume,indicating that T3 had neuroprotective and repair effect on cerebral ischemia-reperfusion injury rats.2.Thyroid hormone T3 can increase the mRNA and protein levels of NGF and BDNF in rats with ischemia-reperfusion injury,and promote the regeneration and repair of neurons.3.Thyroid hormone T3 can inhibit the apoptosis of neurons and promote the recovery of nerve function by increase the expression of anti-apoptotic protein Bcl-2 and reduce the expression of pro-apoptotic protein Bax in rats with ischemia reperfusion injury. |
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