L-精氨酸-NO途径抑制血管紧张素Ⅱ诱导的心肌细胞肥大反应

L-Arginine-NO pathway inhibits the hypertrophic response of cultured cardiomyocytes induced by angiotensin Ⅱ

目的探讨L-精氨酸(L-arginine,L-Arg)对心肌细胞血管紧张素Ⅱ受体(angiotensin Ⅱ receptor,ATR)及丝裂原活化蛋白激酶(mitogen-activated protein kinase,MAPK)表达的影响,进而阐述L-Arg对病理性心肌肥大的影响作用及相关机制。方法用血管紧张素Ⅱ(angiotensinⅡ,ATⅡ)、ATR抑制剂、L-Arg和(或)L-NAME(L-硝基精氨酸甲酯)分别作用于心肌细胞,然后以[3H]-亮氨酸参入法检测细胞蛋白合成速率、比色法检测一氧化氮(NO)生成量、RT-PCR及Western blot检测ATR及p38MAPK的表达水平。结果①给予L-Arg可缓解ATⅡ引起的心肌细胞NO合成量下降,减弱血管紧张素Ⅱ-1型受体(angiotensin receptor type1,ATR1)表达及下调p38MAPK蛋白磷酸化水平,并降低心肌细胞蛋白合成速率给予ATⅡ或L-Arg均未影响血管紧张素Ⅱ-2受体(angiotensin receptor type 2,ATP2)的表达水平;②心肌ATR1表达水平及p38MAPK蛋白磷酸化水平均与NO合成量之间存在线性负相关。多元逐步回归分析显示在ATR1与ATR2中,仅ATR1的表达水平与p38MAPK蛋白磷酸化水平之间存在回归关系。结论①L-Arg可致心肌细胞NO合成量增加,后者可抑制ATR1介导的p38MAPK蛋白磷酸化水平上调,进而抑制心肌细胞肥大反应;②ATR2未参与上述过程。

Aim This study is designed to analyze the influence of L-arginine （L-Arg） on expression level of angiotensin Ⅱ receptors （ATR） and the mitogen-activated protein kinase （MAPK） in cultured cardiomyocytes, with the intention to clarify the mechanisms relative to L-Arg＇s inhibitory effects on formation of cardiac hypertrophy. Methods Five groups of cardiomyocytes were established： control group, Angiotensin Ⅱ （AT Ⅱ ） group, AT Ⅱ ＋ Saralasin group, AT Ⅱ＋ L-Arg group, AT Ⅱ＋ L-Arg ＋ L-NAME （N-nitro-L-arginine methyl ester） group. After 48 hours in supplemented culture, synthetic velocity of protein, NO production, expression level of ATR and p38 MAPK in cardiomyocytes were detected through the [ 3H l-leucine incorporation method, eolorimetry, RT-PCR and western blotting, respectively. Results L-Arg could decrease the expression level of ATR1 and phosphorylated p38 MAPK, enhance NO production and reduce the syn-thetic velocity of protein in cultured cardiomyocytes stimulated by AT 11. Both AT 11 and L-Arg had no influence on the expression level of angiotensin receptor type 2（ATR 2）. Correlation analysis revealed that the relationship of negative correlation was significant between NO production and each of following factors： ATR1 expression level and phosphorylated p38MAPK expression level; As indicated by multiple stepwise regression analysis, not ATR2 expression level, but ATR1 expression level acted as the regression predictor of expression level of phosphorylated p38MAPK. Conelusion By enhancing myocardial NO production, L- Arg-NO pathway inhibits the p38MAPK activation mediated by ATR1, leading to inhibition of the hypertrophic response of cardiomyocytes. ATR2 seems to be independent from the activation process of p38 MAPK.