钙网蛋白介导缺氧预处理对心脏保护机制的研究

Mechanism of calreticulin-mediated hypoxic preconditioning in protection of heart

目的探讨缺氧预处理(HPC)对于心肌钙网蛋白表达与肌浆网钙稳态的影响及其信号转导机制。方法选择SD大鼠22只,随机分为假手术组6只,模型组8只,HPC组8只。复制SD大鼠HPC和心肌梗死模型,检测左心室压力最大上升速率和最大下降速率(±dp/dtmax)、TTC法测定心肌梗死面积,差速离心法制备心肌肌浆网并鉴定其纯度,以Millipore滤过法测定肌浆网Ca2+摄取活性和肌浆网Ca2+释放速率,Western blot检测钙网蛋白、p38丝裂原活化蛋白激酶和磷酸化p38丝裂原活化蛋白激酶水平。结果与假手术组比较,模型组+dp/dtmax和-dp/dtmax分别下降39%和46%(P<0.05);与模型组比较,HPC组分别升高43%和59%(P<0.05),肌浆网Ca2+摄取升高[(60.38±5.76)nmol Ca2+/(mg·min)vs(31.10±3.13)nmol Ca2+/(mg·min)],肌浆网Ca2+释放降低[(32.12±1.18)nmol Ca2+/(mg·15s)vs(39.61±1.16)nmol Ca2+/(mg·15s),P<0.05],钙网蛋白表达和p38丝裂原活化蛋白激酶水平明显升高(P<0.05)。结论 HPC通过p38丝裂原活化蛋白激酶途径上调钙网蛋白表达,改善心肌肌浆网Ca2+摄取和肌浆网Ca2+释放功能、减轻细胞内钙超载而保护缺血心肌。

Objective To study the effect of hypoxic preconditioning（HPC）on myocardial calreticulin（CRT）expression and calcium homeostasis in sarcoplasmic reticulum（SR）and its signal transduction mechanism.Methods Twenty-two SD rats were randomly divided into sham operation group（n=6）,model group（n=8）,and HPC group（n=8）.SD rat HPC model and myocardial infarction（MI）model were established.The LV ±dp/dtmaxwas assayed.The infarction size was measured by TTC.The SR vesicle was prepared and its purity was identified by differential centrifugation.The SR Ca^2＋uptake and release were detected by Millipore filtration.CRT expression and p38 MAPK phosphorylation were detected by Western blot.Results The LV ＋dp/dt max and-dp/dtmaxwere 39%and 46%lower in HPC group than in sham operation group（P〈0.05）,and 43%and 59%higher in HPC group than in model group（P〈0.05）.The SR Ca^2＋uptake was higher and the SR Ca^2＋release was lower in HPC group than in model group（P〈0.05）.The CRT expression and p38 MAPK phosphorylation levels were higher in HPC group than in model group（P〈0.05）.Conclusion HPC can upregulate the Ca^2＋expression,improve the SR Ca^2＋uptake and release,and reduce the calcium overload in myocardiocytes through the p38 MAPK pathway,thus protecting the heart against ischemia injury.