Ⅰ型磷酸酶抑制亚基1对大鼠心肌细胞缺氧／复氧损伤的保护作用

Protective effects of inhibitor - 1 of protein phosphatase 1 on cardiac myocyte of neonatal mice injured by hypoxia/reoxygenafion

目的探讨Ⅰ型磷酸酶抑制亚基1（PPIl）对大鼠乳鼠心肌细胞（H／R）损伤的保护作用及其机制。方法用PPll野生型和活化型突变体表达质粒分别转染乳鼠心肌细胞，并建立乳鼠心肌细胞H／R模型，测定各组心肌细胞的存活率、丙二醛（MDA）、乳酸脱氢酶（LDH）的含量、caspase-3活性及超氧化物歧化酶（SOD）活力，此外用流式细胞术测定各组心肌细胞凋亡率，Western blot分析PPIl对凋亡相关蛋白表达及P13K／Akt信号通路的影响。结果与正常组比较，模型组LDH、MDA含量、caspase-3活性及细胞凋亡率增高（P〈0．05），细胞存活率和SOD活性降低（P〈0．05）；PPll活化型突变体转染组细胞的LDH、MDA含量、caspase-3活性和细胞凋亡率则降低，细胞存活率和SOD活性升高，与缺氧／复氧组比较各实验指标差异均具有统计学意义（P〈0．05）。Western blot表明该组细胞P53、Bax表达下调，pAkt表达上调。结论PPIl活化型突变体对H／R造成的心肌细胞损伤具有保护作用，其机制与稳定心肌细胞膜、减轻氧自由基损伤及减少细胞凋亡有关。

Objective To observe the effects of expression of PPI1 on cardiac myocyte of neonatal mice injured by hypoxia/reoxygenation, and to explore its possible mechanism. Methods Plasmids containing wild type or activated mutant of PPI1 gene were transfected into cardiac myocyte of neonatal mice, and the myocardial hypoxia/reoxygenation model was established. The cell viability, activity of superoxide dismutase （SOD） and caspase - 3, the content of malondialdehyde （MDA） and lactate dehydrogenase （LDH） were measured. Moreover, Flow cytometry was used to analyze the cell apoptosis, and immunoblotting was used to determine apoptosis related proteins and the effects of PPI1 on PI3K/Akt signal transduction. Results Hypoxia/reoxygenation resulted in significantly increased MDA and LDH contents, caspase - 3 activity and apoptosis of the cardiac myocytes （ P 〈 0.05 ）, but lowered SOD activity and cell viability （P 〈 0.05 ）. The MDA and LDH contents, caspase -3 activity and apoptotic rate were significantly lower but cell viability, SOD content significantly higher in PPI1 activated mutant gene transfected cells（ P 〈 0.05 ）, moreover, the expression of p53, Bax were down - regulated, while the expression of pAkt were up -regulated. Conclusion PPI1 activated mutant gene can significantly reduce hypoxia/reoxygenation - induced oxidative stress in cardiac myocytes, which might involve stabilizing the membrane of myocardium, restricting oxygen free radical injury, and reducing the aooototic rate of the cardiac mvocytes.