胸腺素β4对大鼠脑缺血再灌注后内质网应激的影响

Effect of thymosin β4 on endoplasmic reticulum stress after cerebral ischemia-reperfusion in rats

目的研究胸腺素β4(Tβ4)对SD大鼠脑缺血再灌注损伤后内质网应激的影响。方法选取健康成年雄性SD大鼠48只,采用随机数字表法分为假手术组(Sham组)、脑缺血再灌注组(I/R组)和Tβ4干预组(Tβ4组),每组16只。采用线栓法制作大鼠大脑中动脉栓塞模型;Tβ4组在造模前、后1 h各腹腔注射1次Tβ4(8μg·kg^-1),Sham组和I/R组腹腔注射等量生理盐水。采用Longa评分法进行神经功能评分;采用TTC染色法测定脑梗死体积;采用TUNEL法检测神经细胞凋亡指数;采用HE染色法观察脑组织病理学改变;采用Western-blot法检测缺血脑组织葡萄糖调节蛋白78(GRP78)、C/EBP同源蛋白(CHOP)和Caspase 12表达水平。结果大鼠缺血再灌注24 h后,与Sham组相比,I/R组和Tβ4组大鼠神经功能评分、脑梗死体积及神经细胞凋亡指数均明显增加(P<0.05),GRP78、CHOP、Caspase 12蛋白表达增多(P<0.05);与I/R组相比,Tβ4组大鼠神经功能评分、脑梗死体积及神经细胞凋亡指数均有减少(P<0.05),GRP78表达增高,而CHOP和Caspase12表达明显降低(P<0.05)。结论胸腺素β4对大鼠脑缺血再灌注损伤具有一定的保护作用,该机制可能与其上调GRP78表达、下调CHOP和Caspase 12表达,从而减轻内质网应激有关。

Objective To determine the effect of thymosinβ4(Tβ4)on endoplasmic reticulum stress in SpragueDawley(SD)rats after cerebral ischemia-reperfusion injury.Methods Forty-eight adult male SD rats were randomly divided into 3 groups:a sham operaion group(sham group),an ischemia/reperfusion group(I/R group)and a Tβ4 group,16 rats in each group.The cerebral ischemia/reperfusion model was established by blocking the right middle cerebral artery(MCAO)for 2 h before reperfusion for 24 h.The rats in Tβ4 group were intraperitoneally injected Tβ4(8μg·kg^-1)1 h before and 1 h after the modeling.The rats in the Sham group and the I/R group were intraperitoneally injected equal amount of saline.Longa method was used to assess the neurological deficits.Cerebral infarct volume was assessed with 2,3,5-Triphenyltetrazolium chloride(TTC)staining.TUNEL assay was used to detect the apoptosis in the brain tissue.HE staining was used to observe the pathological changes of the brain.Western blot was used to detect the expression levels of GRP78,C/EBP homologous protein(CHOP)and Caspase 12 in the ischemic brain tissue.Results After 24 h of ischemic reperfusion in the rats,compared with the Sham group,the neurological function score,cerebral infarct volume and neuronal apoptosis index in the I/R group and the Tβ4 group were significantly increased(P<0.05).The expression of GRP78,CHOP and Caspase 12 increased(P<0.05);Compared with the I/R group,the neurological function score,cerebral infarct volume and neuronal apoptosis index were all decreased in Tβ4 group(P<0.05);Compared with the I/R group,the expression of GRP78 increased in the Tβ4 group,while the expression of CHOP and Caspase12 decreased significantly(P<0.05).Conclusion Thymosinβ4 may protected against cerebral ischemia-reperfusion injury in rats,whose mechanism may be related to its up-regulation of GRP78 expression,and down-regulation of CHOP and Caspase 12 expression,thus reducing endoplasmic reticulum stress.