【摘要】 持久激动β肾上腺素受体(β adrenergic receptor,βAR)可导致病理性心肌肥厚,但其机制尚不明确。本研究观察抗氧化剂N-乙酰半胱氨酸(N-acetylcysteine,NAC)对异丙肾上腺素(isoproterenol,ISO)诱导的心肌肥厚大鼠的心肌氧化应激水平及钙/钙调蛋白依赖性蛋白激酶II(calcium/calmodulin-dependent protein kinase II,CaMKII)表达的影响,探讨βAR持久激动诱发心肌肥厚机制中CaMKII和氧化应激的作用。健康雄性Wistar大鼠,随机分成4组:正常对照组(CTRL),ISO处理组(ISO),正常NAC组(CTRL+NAC)和ISO处理+NAC组(ISO+NAC),每组6只。ISO及ISO+NAC组动物每天腹腔注射3mg/kgISO,CTRL及CTRL+NAC组腹腔注射相同体积的生理盐水;CTRL+NAC及ISO+NAC组动物每日自由饮用含15g/LNAC的饮用水。每周用无创动脉血压仪检测鼠尾动脉血压,连续2周;以心重指数(HW/BW)和左心室组织HE染色检测心肌肥厚情况;荧光测定法检测心肌线粒体活性氧(reactive oxygen species,ROS)水平;Western blot检测左室心肌NADPH氧化酶4(NADPH oxidase 4,NOX4)以及有活性的CaMKII(p-CaMKII/CaMKII)的表达变化。结果显示,与CTRL组相比,ISO组大鼠出现明显的心肌肥厚,心肌线粒体ROS水平升高(P<0.05),心肌组织NOX4和p-CaMKII的表达均显著增加(分别为CTRL组的1.4倍和1.6倍,P<0.05);NAC显著改善了ISO诱导的心肌肥厚,降低了ISO诱导的心肌线粒体ROS过度生成(P<0.05vsISO),有效抑制了ISO诱发的NOX4及p-CaMKII表达上调(P<0.05vsISO);CTRL+NAC组各项指标与CTRL组大鼠无差异;各组动物尾动脉血压亦无显著性差异。上述结果提示,氧化应激和CaMKII在βAR持久兴奋诱发心肌肥厚机制中起重要作用,NAC可以通过抑制心肌细胞线粒体及NADPH氧化酶应激途径降低氧化应激水平,抑制CaMKII激活,从而改善βAR持久激动引起的心肌肥厚。更多还原

【Abstract】 Sustained activation of β adrenergic receptor(βAR) leads to pathologic cardiac hypertrophy.However,the related mechanisms still remain unclear.In this study,we observe how N-acetylcysteine(NAC) affects the oxidative stress and calcium/calmodulindependent protein kinase II(CaMKII) expression in heart of isoproterenol(ISO)-stimulated rats,and investigate whether oxidative stress and CaMKII contribute to the development of sustained βAR-stimulated cardiac hypertrophy.Healthy male Wistar rats were randomly separated into 4 groups:control(CTRL),ISO-treated(ISO),control with NAC supplement(CTRL+NAC) and ISO-treated with NAC supplement(ISO+NAC) groups(6 rats in each group).Systolic blood pressure(SBP) was measured in awake rats with the tail-cuff method every week for two weeks.Heart weight/body weight ratio(HW/BW) and HE staining were used for the detection of myocardial hypertrophy.Myocardial mitochondrial reactive oxygen species(ROS) levels were measured by DCF fluorometry.The expressions of activated-CaMKII(p-CaMKII/CaMKII) and NADPH oxidase 4(NOX4) were determined by Western blot analysis.The results showed that ISO-treated(i.p.,daily 3 mg/kg,2 weeks) rats developed an obvious cardiac hypertrophy as expressed by increases of HW/BW and myocyte cross-section area.Cardiac mitochondrial ROS level was significantly enhanced in ISO group as compared to CTRL group(P<0.05).The expressions of NOX4 and p-CaMKII in ISO group were also up-regulated as compared to CTRL group(1.4 and 1.6 times of CTRL,respectively,P<0.05).NAC supplement significantly suppressed the hypertrophic development of heart in ISO-stimulated rats.The cardiac mitochondrial ROS level showed a significant decrease in rats of ISO+NAC group(P<0.05 vs ISO).In accordance with this,ISO+NAC group rats also showed marked reductions in the expressions of NOX4 and p-CaMKII/CaMKII compared to ISO group rats(P<0.05).There were no significant differences of the detected indices between the rats from CTRL+NAC and CTRL groups.SBP showed no differences among four groups.These results suggest that both oxidative stress and CaMKII play important roles in sustained βAR-stimulated cardiac hypertrophy.NAC may suppress ISO-induced cardiac hypertrophy by down-regulating the expression of activated-CaMKII,and by reducing the level of oxidative stress originated from mitochondria and NADPH oxidase pathways.更多还原