蛋白磷酸激酶2A调控心肌梗死后L型钙离子通道对β肾上腺素敏感性钝化的机制研究  

Protein phosphates 2Amodulates-adrenergic sensitivity of L-type Ca^(2+) channel in post-myocardial infarction heart

作　　者：郑明奇[1] 刘刚[1] 吉立双[1] 王乐[1] 董梅[1] 刘衍恭 

机构地区：[1]河北医科大学第一医院心内科,石家庄050031

出　　处：《临床心血管病杂志》2014年第5期443-446,共4页Journal of Clinical Cardiology

基　　金：国家自然科学基金项目(No:81100127);河北省自然科学基金(No:C2011206056);河北省科技计划项目(No:13277720D);河北省留学人员科技活动项目择优资助经费(No:2012);河北省医学科学研究重点课题计划(No:20130274)

摘　　要：目的:心肌梗死后心肌对β肾上腺素刺激的收缩反应显著降低,本研究的目的是探求使心肌梗死后大鼠心肌L型钙离子通道(LTCC)电流对肾上腺素能刺激钝化的细胞内信号机制。方法:心肌梗死大鼠模型建立6~8周后,用胶原蛋白酶消化技术分离获得单一的心室肌细胞,用全细胞膜片钳技术记录用丙酮酸治疗前后LTCC密度大小;分子生物学分析蛋白激酶A(PKA)的活性和蛋白磷酸激酶2A(PP2A)的活性。结果:①丙酮酸恢复了心肌梗死心肌LTCC电流对细胞内cAMP的钝化反应;②在假手术组和心肌梗死组的基础PKA活性和cAMP刺激的PKA活性是相似的;③PP2A活性和结合到a1C亚基的量在心肌梗死组显著降低;④PP2A抑制剂冈田酸明显增大了假手术组心肌LTCC电流,但在心肌梗死组没有反应,但丙酮酸使之正常化。结论:心肌梗死后心肌细胞LTCC高磷酸化状态是由于氧化应激引起的PP2A活性降低,从而钝化了肾上腺素的反应,而丙酮酸作为体内重要的还原物质,可以逆转这一过程。Objective：To explore the mechanisms in which the impairedβ-adrenergic modulation of L-type Ca2＋ channels（LTCC）in a rat infarction model of heart failure.Method：Chronic ventricular dysfunction was induced in Sprague-Dawley rats by myocardial infarction（MI）,and studies were done after 6-8weeks.The single ventricle myocytes obtained by enzyme isolation was patched to record the LTCC current（ICa,L）by using of patch-clamp technique.Proteins from tissue samples were extracted for LTCC following standard protocols,and protein expression was measured by Western blotting.Result：①ICa,L of mycytes from the MI hearts showed a blunted response to intracellular cAMP that was reversed by treatment with exogenous pyruvate.②Biochemical studies showed that basal and cAMP-stimulated protein kinase A（PKA）activities were not significant in MI and sham hearts（P〈0.05）,which in parallel that molecular analysis also found binding of PKA to theα1Csubunit of Cav1.2 was not different between two groups.③The protein phophatase 2A（PP2A）inhibitor okadaic acid markedly increased ICa,L in sham,but this response was significantly less in MI hearts.However,pyruvate normalized ICa,L stimulation by okadaic acid.Conclusion：These data suggest that bluntedβ-adrenergic stimulation of ICa,L in failing hearts results from hyperphosphorylation of Ca2＋channels secondary to oxidation-induced impairment of PP2Afunction.

关 键 词：心肌梗死 L型钙通道电流 蛋白磷酸激酶2A 丙酮酸 

分 类 号：R542.2[医药卫生—心血管疾病]