Zheng J S, Boluyt M O, Long X, O'Neill L, Lakatta E G, Crow M T
Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, MD, 21224, USA.
Circ Res. 1996 Apr;78(4):525-35. doi: 10.1161/01.res.78.4.525.
We have previously shown that extracellular ATP, like norepinephrine (NE) and many other hypertrophy-inducing agents, increases expression of the immediate-early genes c-fos and junB in cultured neonatal cardiac myocytes but that the intracellular signaling pathways activated by ATP and responsible for these changes differ from those stimulated by NE. Furthermore, whereas NE increases incorporation of [14C]phenylalanine (14C-Phe) and cell size in neonatal cardiomyocytes, ATP does not. Since ATP is coreleased with NE from sympathetic nerve endings in the heart, we investigated whether ATP could modulate cardiac hypertrophy induced by adrenergic agonists, such as NE. We report in the present study that extracellular ATP inhibited the increase in incorporation of 14C-Phe into cellular protein and the increase in cell size in neonatal rat cardiac myocytes that was induced by NE, phenylephrine (PE), basic fibroblast growth factor, or endothelin-1. This inhibition was dose dependent, occurred predominantly through P2 purinergic receptors, and was observed even when cells were treated with ATP for as little as 1 hour before the addition of the hypertrophy-inducing agent. ATP also selectively affected changes in gene expression associated with hypertrophy. It prevented PE-stimulated increases in atrial natriuretic factor and myosin light chain-2 mRNA levels, while appearing to augment basal and PE-stimulated skeletal alpha-actin mRNA levels. ATP alone increased sarcoplasmic reticulum Ca2+-ATPase mRNA levels but had no effect when added with PE. ATP did not significantly affect the level of the constitutively expressed mRNA for GAPDH. Neither the PE-stimulated increase in immediate-early gene expression nor the initial induction of mitogen-activated protein kinase activity by PE was inhibited by ATP. These results demonstrate that extracellular ATP can inhibit hypertrophic growth of neonatal cardiac myocytes and differentially alter the changes in gene expression that accompany hypertrophy.
我们之前已经表明，细胞外ATP与去甲肾上腺素（NE）以及许多其他诱导肥大的因子一样，可增加培养的新生心肌细胞中即早基因c-fos和junB的表达，但ATP激活的并导致这些变化的细胞内信号通路不同于NE所刺激的信号通路。此外，虽然NE可增加新生心肌细胞中[14C]苯丙氨酸（14C-Phe）的掺入量和细胞大小，但ATP却没有这种作用。由于ATP与NE从心脏交感神经末梢共同释放，我们研究了ATP是否能够调节由肾上腺素能激动剂（如NE）诱导的心肌肥大。我们在本研究中报告，细胞外ATP可抑制NE、苯肾上腺素（PE）、碱性成纤维细胞生长因子或内皮素-1诱导的新生大鼠心肌细胞中14C-Phe掺入细胞蛋白的增加以及细胞大小的增加。这种抑制作用呈剂量依赖性，主要通过P2嘌呤能受体发生，并且即使在添加诱导肥大的试剂前仅用ATP处理细胞1小时也可观察到。ATP还选择性地影响与肥大相关的基因表达变化。它可阻止PE刺激引起的心房利钠因子和肌球蛋白轻链-2 mRNA水平的增加，同时似乎增强基础状态和PE刺激下的骨骼肌α-肌动蛋白mRNA水平。单独的ATP可增加肌浆网Ca2+-ATP酶mRNA水平，但与PE一起添加时则没有作用。ATP对组成性表达的甘油醛-3-磷酸脱氢酶mRNA水平没有显著影响。ATP既不抑制PE刺激引起的即早基因表达增加，也不抑制PE对丝裂原活化蛋白激酶活性的初始诱导。这些结果表明，细胞外ATP可抑制新生心肌细胞的肥大生长，并差异性地改变伴随肥大的基因表达变化。
