CPB期间静脉泵注Dex的大鼠海马CA1区神经细胞凋亡情况、脑皮质组织IL-6表达变化及其机制

Neuronal apoptosis in hippocampal CA1 area and IL-6 expression changes in cerebral cortex of rats after intravenous pumping of dexmedetomidine during cardiopulmonary bypass and its mechanism

目的观察体外循环(CPB)期间静脉泵注右美托咪定(Dex)的大鼠海马CA1区神经细胞凋亡情况、脑皮质组织IL-6表达变化,并探讨其机制。方法48只SPF级成年健康雄性SD大鼠随机分为3组各16只。Dex组(D组)在制模前10 min按照5μg/kg的负荷剂量静脉泵注Dex,后制备CPB模型,制模后转CPB机2 h,转流期间Dex以5μg/(kg·h)的泵注速度维持,转流2 h后停CPB机;体外循环组(C组)建立大鼠CPB模型,模型制备方法参照D组,制模后转CPB机2 h,转流期间给予与D组等量生理盐水;假手术组(S组)只作动静脉血管穿刺置管,不转CPB机,给予与D组等量生理盐水。CPB转流结束后立即处死各组8只大鼠,取脑组织,TUNEL法检测海马CA1区凋亡神经细胞,计算神经细胞凋亡率。CPB转流2 h结束后立即处死各组余下的8只大鼠,冰上分离皮质和海马组织,ELISA法检测皮质组织匀浆上清液白细胞介素6(IL-6),Western blot法检测海马组织磷酸化Janus激酶2(pJAK2)、磷酸化STAT3(pSTAT3)蛋白。结果与S组比较,C组大鼠海马CA1区神经细胞凋亡率、皮质组织匀浆上清液IL-6水平及海马组织pJAK2、pSTAT3蛋白相对表达量升高(P均<0.05);与C组比较,D组大鼠海马CA1区神经细胞凋亡率、皮质组织匀浆上清液IL-6水平及海马组织pJAK2、pSTAT3蛋白相对表达量降低(P均<0.05)。结论CPB期间静脉泵注Dex可减轻大鼠神经细胞凋亡和脑部炎症,机制可能与其可抑制JAK2/STAT3信号通路的激活有关。

Objective To observe the neuronal apoptosis in hippocampal CA1 area and the IL-6 expression changes in cerebral cortex of rats undergoing intravenous pumping of dexmedetomidine(Dex)during cardiopulmonary bypass(CPB),and to explore its mechanism.Methods Forty-eight SPF adult healthy male SD rats were randomly divided into three groups with 16 rats in each group.In the Dex group(group D),Dex was injected intravenously at a loading dose of 5μg/kg by a microinfusion pump for 10 minutes before molding,and then a CPB model was established.The CPB machine was transferred for 2 h and Dex was maintained at a pumping speed of 5μg/(kg·h)during the transfer period.In the cardiopulmonary bypass group(group C),a rat CPB model was established.The model preparation method was similar to that of group D.The CPB machine was performed for 2 h.During the bypass,rats in the group C were given the same amount of normal saline as that of group D.In the sham operation group(group S),only the arteriovenous vascular puncture and catheterization were performed,and the same amount of normal saline as that of group D was given.Immediately after CPB,8 rats in each group were killed,brain tissues were taken,and the apoptosis of nerve cells in hippocampal CA1 area was detected by TUNEL method,and the rate of nerve cell apoptosis was calculated.After 2 h of CPB,the remaining 8 rats in each group were killed immediately.The cortex and hippocampus tissues were separated on ice.The interleukin 6(IL-6)in the supernatant of the cortical tissue homogenates was detected by ELISA,and the phosphorylated Janus kinase 2(pJAK2)and phosphorylated STAT3(pSTAT3)protein in the hippocampal tissues were detected by Western blotting.Results Compared with group S,the apoptosis rate of nerve cells in hippocampal CA1 area,the level of IL-6 in the supernatant of cortical tissue homogenates and the relative expression of pJAK2 and pSTAT3 protein in hippocampus increased in the group C(all P<0.05).Compared with group C,the apoptosis rate of nerve cells in hippocampus CA1 area,the level of IL-6 in the supernatant of cortical tissue homogenates and the relative expression of pJAK2 and pSTAT3 protein in hippocampus of group D decreased(all P<0.05).Conclusion Intravenous pumping of Dex during CPB can reduce neuronal apoptosis and brain inflammation in rats,and the mechanism may be related to its inhibition of the activation of JAK2/STAT3 signaling pathway.