MKP—1在血管紧张素Ⅱ导致心肌肥大反应中的调控作用

本研究主要从丝裂原活化蛋白激酶磷酸酶－１（ＭＫＰ－１）角度,研究丝裂原活化蛋白激酶（ＭＡＰＫ）信号途径在血管紧张素Ⅱ介导的新生大鼠心肌细胞肥大反应中的作用及调控机制。实验以心肌细胞蛋白合成速率、蛋白含量及细胞表面积作为心肌肥大反应的指标,以凝胶内ＭＢＰ原位磷酸化测定ＭＡＰＫ活性,以免疫印迹法（Ｗｅｓｔｅｒｎ ｂｏｌｔｔｉｎｇ）分别测定ＭＫＰ－１及磷酸化ｐ４４ＭＡＰＫ、ｐ４２ＭＡＰＫ蛋白表达。结果发

MKP-1 regulates the cardiomyocyte hypertrophic responses induced by angiotensin II

The aim of this study was to determine the regulation by MKP-1 of MAPK activity and protein expression in cardiomyocyte hypertrophic response induced by Ang II. Neonatal rat cardiomyocyte hypertrophic response was assayed by cell surface area, protein synthesis rate and protein content. MAPK activity was determined by an in-gel kinase assay. Protein expression of MAPK and MKP-1 were detected by Western blotting. The results are as follows. (1) Ang II induced promotion of (3)H-leucine incorporation and increase in cell protein content and cell surface area in a dose-dependent manner. Pretreatment with a selective AT(1) receptor antagonist CV11974 or a specific MEK inhibitor PD098059, cardiomyocyte hypertrophic response induced by Ang II was inhibited by 85% and 32.5%, respectively. (2) After pretreatment with PD098059 or CV11974, AngII-induced increases in p44MAPK and p42MAPK protein expression and enzyme activity (expressed by gamma-(32)P-ATP incorporation) were all inhibited obviously. (3) With treatment of myocytes by Ang II for 5 min, MAPK activity determined by p44MAPK and p42MAPK protein expression began to increase, while MKP-1 protein expression was detected within 30 min and lasted more than 2 h following treatment with Ang II. (4) Pretreatment of cardiomyocytes with actinomycin D (3 microgram/ml) for 30 min inhibited MKP-1 protein expression, while p44MAPK and p42MAPK protein expression was still detected 120 min after Ang II treatment. The above results demonstrate that activation of MAPK plays an important role in Ang II-induced cardiomyocyte hypertrophic response in neonatal rat cardiomyocytes through MKP-1 mediated inactivation of p44MAPK and p42MAPK.cardiomyocyte hypertrophic response in neonatal rat cardiomyocytes through MKP-1 mediated inactivation of p44MAPK and p42MAPK.