摘要
观察马赛替尼对大鼠脑缺血/再灌注损伤的保护作用并探讨其机制。雄性SD大鼠随机分成假手术组、模型组、马赛替尼低、中、高剂量治疗组,每组12只。线栓法制备大鼠大脑中动脉梗阻2 h后复灌模型,即刻给药,每天给药两次,连续7 d。再灌注7 d后行神经功能症状缺损评分,检测脑梗死体积及脑含水量,Western blot和PCR检测损伤周围脑组织自噬和凋亡相关蛋白和基因的表达。术后7 d,与模型组相比,各给药组大鼠神经功能缺损评分、脑梗死体积和脑积水均明显降低。模型组大鼠脑组织中明显上升,p62的表达明显下降。马赛替尼各组均能不同程度地下调LC3II/I、Beclin-1、Bax等凋亡蛋白和NF-κB的表达,上调p62的表达。马赛替尼发挥神经保护作用的机制之一可能与抑制自噬和细胞凋亡通路有关。
脑卒中是一种常见的神经系统疾病,因其具有高发病率、高致残率和高致死率的特点,对人类健康带来极大威胁。缺血性脑卒中是脑卒中的主要类型,占脑卒中患者总数的60%~70%。一项世界卫生组织调查报道,我国脑卒中的发病率居于世界首位,且随着人口老龄化,发病率还在逐年上
马赛替尼(法国AB Science公司);2,3,5-氯化三苯基四氮唑(TTC,中国医药上海化学试剂公司);TUNEL细胞凋亡检测试剂盒(上海碧云天生物科技有限公司);全蛋白抽提试剂盒、BCA蛋白含量检测试剂盒(江苏凯基生物技术股份有限公司);cDNA第一链合成试剂盒、One Step TB Green™ PrimeScript™ RT-PCR Kit II (SYBR Green,日本TaKaRa公司)。LC3抗体(美国Santa Cruz公司),Beclin-1、IkB-α、P62、p65、Bcl-2、Bcl-xl、Bax、Bad、caspase 8抗体(美国Abcam公司),Bid抗体(美国Proteintech公司),p-IkB-α、cleaved-caspase 3、GAPDH抗体(美国CST公司),羊抗兔IgG-HRP(江苏凯基生物技术股份有限公司),其他试剂均为市售分析纯。
Sartorius BT 125D电子天平(北京赛多利斯仪器系统有限公司);5804R型台式冷冻高速离心机(德国Eppendorf公司);Trans-Blot Turbo全能型蛋白转印系统(美国Bio-Rad公司);凝胶成像系统(英国Syngene公司);荧光定量PCR循环仪(美国应用生物系统公司);2838MCAO栓线(北京沙东生物技术有限公司)。
大鼠适应环境7 d后,随机分成伪手术(Sham)组、I/R模型组、马赛替尼低剂量组(18.9 mg/kg)、马赛替尼中剂量组(37.8 mg/kg)、马赛替尼高剂量组(75.6 mg/kg)、依达拉奉(3 mg/kg)组,每组12只。
马赛替尼的具体配制方法如下:称取马赛替尼7.56 g溶于生理盐水10 mL中,配制成756 mg/mL的母液。临用前取母液0.5 mL至生理盐水50 mL中,稀释得到7.56 mg/mL的高剂量组母液,则高剂量组的给药体积V(mL) = (75.6 mg/kg×大鼠体重(kg))/7.56 mg/mL,以此类推,配制好中剂量组和低剂量组的受试药。大鼠缺血2 h后再灌注时即刻给药,每天两次,连续给药7 d。Sham组和I/R组大鼠灌胃给予等容积生理盐水。实验流程如

Figure 1 Effects of masitinib on neurological score and infarction after ischemia/reperfusion (I/R)
A: Experimental outline; B: Neurologic deficits were assessed at 7 d after reperfusion (); C: Infarcted brain regions were visualized using TTC staining. Representative examples are shown from each treatment group;D: The ratio of corrected infarct area to whole brain area was calculated for the cerebral infarct size (). (E) Brain edema were detected in ischemic cerebral cortex after cerebral I/R in rats ()
参照Longa
再灌注7 d后,根据Zea Longa的神经功能缺损5分制标
再灌注7 d后,异氟烷过量深度麻醉处死大鼠,快速断头取脑,去除嗅球、小脑和低位脑干,迅速称取脑湿重。然后将脑组织置于110 ℃干燥箱中烘至恒重,称取脑组织干重。脑组织含水量 = (脑组织湿重-脑组织干重)/脑组织湿重 × 100%。
采用TTC染色法测定脑组织梗死体积。再灌注7 d后,10%水合氯醛过量深度麻醉处死大鼠,快速断头取脑,去除嗅球、小脑和低位脑干,即刻放入鼠脑专用切片模具中,按2 mm的规格冠状切为5片,迅速加入2% TTC染色液,避光置于37 ℃水浴中保温20 min,其间每隔7 ~ 8分钟上下面翻动一次。根据切片颜色结束染色过程,正常脑组织呈玫瑰红色,梗死组织呈白色。将切片按层面顺序排列整齐并用数码相机拍摄照片后输入电脑,使用Image-Pro Plus 6图像分析软件测定大脑健侧半脑面积及梗死侧正常组织面积。梗死面积百分比(%) = [(梗死面积 × 2 mm) /(2 × 健侧脑面积 × 2 mm)] × 100。
再灌注7 d后处死动物,取缺血侧脑组织皮质部分,放入预冷的组织裂解液(1∶9),冰浴中进行匀浆,得到的组织匀浆于4 ℃ 12 000 r/min离心20 min,取上清液获得总蛋白,BCA法测定蛋白浓度。加入适当量的蛋白上样缓冲液混匀、离心、变性、上样。每孔加入上样蛋白50 µg,SDS-PAGE凝胶电泳分离,然后进行转膜、封闭。加入一抗后4 ℃孵育过夜,二抗室温摇床孵育2 h。采用ECL发光试剂显色,并经 Image J凝胶成像系统进行显影检测。涉及到的一抗包括:LC3(1∶500),Beclin-1(1∶2 000),IkB-α(1∶2 000),p-IkB-α(1∶2 000),P62(1∶3 000),p65(1∶2 000),Bcl-2(1∶1 000),Bcl-xl(1∶1 000),Bax(1∶5 000),Bid(1∶5 000),Bad(1∶2 000),caspase 8(1∶2 000),cleaved-caspase 3(1∶1 000),GAPDH(1∶1 000);二抗:羊抗兔IgG-HRP(1∶5 000)。
称取各组大鼠脑组织100 mg,加Trizol 1 mL,提取总RNA,定量后取RNA 2 μg 逆转为cDNA,用SYBR Green进行扩增,采用的循环为:95 ℃ 15 s,60 ℃ 1 min,95 ℃ 1 min,65 ℃ 10 s,共40个循环。采用GAPDH作为每次扩增过程中的内参,引物的序列见
制备脑组织石蜡切片,将组织切片经过梯度乙醇常规脱蜡至水,经苏木精-伊红(HE)染色、二甲苯透明后中性树胶封片,光学显微镜下观察。此外,依据TUNEL试剂盒说明书操作,光学显微镜下观察各组大鼠脑组织凋亡神经元并拍照计数。
Sham组无明显神经功能损伤。I/R损伤后,各组动物表现出不同程度的神经功能障碍,出现强迫体态和对侧前肢偏瘫,爬行时向偏瘫侧转圈、追尾等相应症状。如
再灌注7 d后,对脑组织进行TTC染色,评估脑梗死的情况。正常脑组织因含有脱氢酶而被染成红色,梗死脑组织因细胞膜损伤,导致脱氢酶被完全释放丢失而不被染色。如
与健侧脑组织相比,缺血侧脑组织出现明显水肿(
HE染色结果如

Figure 2 Effects of masitinib on neuronal injury and apoptosis in ischemic cerebral cortex
A: Cerebral sections were stained with hematoxylin and eosin and examined under light microscope at 7 d after reperfusion;B:Representative microphotographs of TUNEL staining in the ischemic cortex at 7 d after perfusion(Scale bar, 20 µm)
TUNEL染色结果如
采用Western blot法检测自噬标记物LC3、Beclin-1和p62的蛋白水平。结果如

Figure 3 Effects of masitinib on autophagy in ischemic cerebral cortex after I/R
A: Representative Western blots of LC3, Beclin-1 and p62 protein expression in ischemic cerebral cortex after I/R; B-D: Quantitation of the Western blot analysis for LC3, Beclin-1 and p62 compared with GAPDH; E: p62 mRNA expression was normalized to GAPDH level ()
结果如

Figure 4 Effects of masitinib on autophagic cell apoptosis in ischemic cerebral cortex after I/R
A: Representative Western blots of Bcl-2, Bcl-xl, Bax, Bad, Bid, caspase 8 and cleaved caspase 3 protein expression in ischemic cerebral cortex after I/R;B: Quantitation of the Western blot analysis for Bcl-2, Bcl-xl, Bax, Bad, Bid, caspase 8 and cleaved caspase3 compared with GAPDH ()
如

Figure 5 Effects of Masitinib on NF-κB signaling pathway in ischemic cerebral cortex after I/R
A: Representative Western blots of NF-κB, IκB and p-IκB protein expression in ischemic cerebral cortex after I/R; B-C: Quantitation of the Western blot and PCR analysis for NF-κB; D-E: Quantitation of the Western blot and PCR analysis for IκB; F: Quantitation of the Western blot analysis for p-IκB ()
脑缺血损伤可阻断脑血流,导致缺血缺氧,进而过度激活氧化应激和炎症反应,导致神经元细胞死
本研究结果显示,I/R损伤可导致严重的神经功能障碍,并伴有自噬的激活。给予马赛替尼治疗后,不仅能明显降低模型组大鼠脑组织的梗死面积和脑含水量,而且能显著改善神经功能缺损。TUNEL染色结果表明,马赛替尼能显著抑制I/R损伤引起的神经元凋亡。
近年来脑缺血后自噬的研究已成为国内外关注的热
P62还可以通过锌指结构与调节细胞凋亡的分子开关RIP1结合形成信号复合物。近年来,研究表明p62/RIP1信号复合物可作为支架蛋白激活IKK,降解IκB,激活NF-κB信号通
自从Beclin-1在自噬过程中被发现以来, Beclin-1作为一种Bcl-2相互作用蛋白的新作用被注意到
综上所述,马赛替尼减轻了缺血再灌注的神经损伤作用,其作用机制可能是通过抑制过度自噬和凋亡发挥的。自噬参与了脑血管疾病的发生过程这一点毋庸置疑,但自噬在脑缺血损伤后的作用仍然是有争议的。有的研究报道自噬在缺血/低氧性脑病发病机制中加重脑损伤,但也有报道在脑缺血后,自噬的激活减轻脑损伤,起到脑保护作用。关于自噬在缺血性脑损伤中呈现的相反作用,一方面推测这可能与实验中采用了不同的缺血再灌注时间、使用了非特异性的药物或者方法有关;另一方面也进一步提示自噬在脑缺血的病理生理机制中是一把“双刃剑”。选择合适的药物,引导自噬在疾病中发挥积极作用,这将为脑血管疾病的治疗开启新纪元。
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