Hiroi Y, Hiroi J, Kudoh S, Yazaki Y, Nagai R, Komuro I
Department of Cardiovascular Medicine, University of Tokyo Graduate School of Medicine, Tokyo, Japan.
Hypertens Res. 2001 Jul;24(4):385-94. doi: 10.1291/hypres.24.385.
Increasing evidence has suggested that mitogen-activated protein kinases (MAPKs) play important roles in the development of cardiac hypertrophy. We and others have reported that the activity of MAPKs is tightly regulated by angiotensin II (Ang II) in cardiac myocytes. In the present study, we determined the molecular mechanism of Ang II-induced inactivation of MAPKs in rat neonatal cardiac myocytes. Ang II increased MAPK phosphatase 1 (MKP-1) gene expressions within 10 min. Levels of MKP-1 transcripts peaked at 30 min and gradually decreased thereafter. The increase in MKP-1 mRNA levels was Ang II-concentration dependent. An Ang II type 1 receptor (AT1)-specific antagonist, CV-11974, completely suppressed the Ang II-induced increase in MKP-1 gene expression, while a type 2 receptor (AT2)-specific antagonist, PD-123319, had no significant effects. Induction of MKP-1 gene expressions by Ang II was inhibited by pretreatment with an intracellular Ca2+ chelator, BAPTA-AM, or with the protein kinase C inhibitors, H-7 and Calphostin C. Phorbol ester and Ca2+ ionophore both significantly increased MKP-1 mRNA levels and showed synergistic action. Overexpression of MKP-1 cDNA blocked the Ang II-induced increase in expressions of immediate early response genes. In addition, Ang II-induced MAPK activation was significantly inhibited by pretreatment with CV-11974, but significantly enhanced by pretreatment with PD-123319. Addition of the AT2 agonist, CGP42112A, reduced basal MAPK activities, and pretreatment with PD-123319 abolished MAPK inactivation by CGP42112A. In conclusion, these observations suggest that Ang II negatively regulates MAPKs through AT1 receptors by increasing MKP-1 mRNA levels and through AT2 receptors by unknown mechanisms.
越来越多的证据表明，丝裂原活化蛋白激酶（MAPKs）在心肌肥大的发展中起重要作用。我们和其他人已经报道，心肌细胞中MAPKs的活性受到血管紧张素II（Ang II）的严格调控。在本研究中，我们确定了Ang II诱导大鼠新生心肌细胞中MAPKs失活的分子机制。Ang II在10分钟内增加了丝裂原活化蛋白激酶磷酸酶1（MKP-1）基因的表达。MKP-1转录本水平在30分钟时达到峰值，此后逐渐下降。MKP-1 mRNA水平的增加是Ang II浓度依赖性的。Ang II 1型受体（AT1）特异性拮抗剂CV-11974完全抑制了Ang II诱导的MKP-1基因表达增加，而2型受体（AT2）特异性拮抗剂PD-123319则无显著影响。用细胞内Ca2+螯合剂BAPTA-AM或蛋白激酶C抑制剂H-7和Calphostin C预处理可抑制Ang II诱导的MKP-1基因表达。佛波酯和Ca2+离子载体均显著增加MKP-1 mRNA水平并显示协同作用。MKP-1 cDNA的过表达阻断了Ang II诱导的即刻早期反应基因表达增加。此外，CV-11974预处理可显著抑制Ang II诱导的MAPK激活，但PD-123319预处理则显著增强。添加AT2激动剂CGP42112A可降低基础MAPK活性，PD-123319预处理可消除CGP42112A对MAPK的失活作用。总之，这些观察结果表明，Ang II通过增加MKP-1 mRNA水平通过AT1受体对MAPKs进行负调控，并通过未知机制通过AT2受体进行负调控。
