Laskowski Adrienne, Woodman Owen L, Cao Anh H, Drummond Grant R, Marshall Tanneale, Kaye David M, Ritchie Rebecca H
Wynn Department of Metabolic Cardiology, Baker Heart Research Institute, Melbourne 8008, Australia.
Cardiovasc Res. 2006 Oct 1;72(1):112-23. doi: 10.1016/j.cardiores.2006.07.006. Epub 2006 Jul 12.
Reactive oxygen species (ROS) such as superoxide have been linked to the hypertrophic response of the heart to stimuli including angiotensin II (AngII), mechanical stretch, and pressure overload. We have previously demonstrated that cGMP and protein kinase G mediate the antihypertrophic actions of the natriuretic peptides in rat cardiomyocytes and isolated whole hearts. The impact of natriuretic peptides on cardiac ROS generation, however, has not been investigated. We tested the hypothesis that reduced superoxide accumulation contributes to the antihypertrophic action of atrial natriuretic peptide (ANP).
Neonatal rat cardiomyocytes were cultured in serum-free medium with and without AngII (1 micromol/L) or endothelin-1 (ET(1), 60 nmol/L) in the presence and absence of ANP (1 micromol/L) or tempol (100 micromol/L). Hypertrophic responses, cardiomyocyte superoxide generation, and cardiomyocyte expression of NADPH oxidase were determined.
AngII induced increases in cardiomyocyte size (to 176 +/- 9% n = 8 p < 0.001, at 48 h), beta-myosin heavy chain expression (to 4.0 +/- 1.6-fold n = 6 p < 0.05, at 48 h), c-fos expression (to 1.9 +/- 0.5-fold n = 7 p < 0.01, at 6 h), superoxide generation (to 181+/-21% n = 8 p < 0.005, at 24 h), and expression of the gp91phox subunit of NADPH oxidase (to 2.4 +/- 0.5-fold n = 7 p < 0.05, at 48 h). These effects were all significantly inhibited by ANP: cardiomyocyte size, beta-myosin heavy chain expression, c-fos expression, superoxide generation and gp91phox expression were reduced to 107 +/- 5% (n = 5 p < 0.05), 1.2 +/- 0.2-fold (n = 6 p < 0.05), 0.9 +/- 0.2-fold (n = 7 p < 0.05), 141 +/- 21% (n = 8 p < 0.05), and to 1.0 +/- 0.5-fold (n = 7 p < 0.05), respectively. These effects were mimicked by tempol. ANP and tempol also significantly inhibited ET1-induced increases in cardiomyocyte size and superoxide generation, but had no effect on markers of hypertrophy when studied alone.
This data indicates that the antihypertrophic actions of ANP are accompanied by reduced levels of superoxide, suggesting an antioxidant action contributes to the antihypertrophic actions of ANP.
活性氧（ROS）如超氧化物已被证明与心脏对包括血管紧张素II（AngII）、机械牵张和压力超负荷等刺激的肥厚反应有关。我们之前已经证明，环磷酸鸟苷（cGMP）和蛋白激酶G介导了利钠肽在大鼠心肌细胞和离体全心中的抗肥厚作用。然而，利钠肽对心脏ROS生成的影响尚未得到研究。我们检验了以下假设：超氧化物积累的减少有助于心房利钠肽（ANP）的抗肥厚作用。
将新生大鼠心肌细胞在无血清培养基中培养，在有和没有ANP（1微摩尔/升）或tempol（100微摩尔/升）的情况下，分别加入或不加入AngII（1微摩尔/升）或内皮素-1（ET-1，60纳摩尔/升）。测定肥厚反应、心肌细胞超氧化物生成以及心肌细胞中NADPH氧化酶的表达。
AngII导致心肌细胞大小增加（48小时时增加到176±9%，n = 8，p < 0.001）、β-肌球蛋白重链表达增加（48小时时增加到4.0±1.6倍，n = 6，p < 0.05）、c-fos表达增加（6小时时增加到1.9±0.5倍，n = 7，p < 0.01）、超氧化物生成增加（24小时时增加到181±21%，n = 8，p < 0.005）以及NADPH氧化酶的gp91phox亚基表达增加（48小时时增加到2.4±0.5倍，n = 7，p < 0.05）。这些效应均被ANP显著抑制：心肌细胞大小、β-肌球蛋白重链表达、c-fos表达、超氧化物生成和gp91phox表达分别降至107±5%（n = 5，p < 0.05）、1.2±0.2倍（n = 6，p < 0.05）、0.9±0.2倍（n = 7，p < 0.05）、141±21%（n = 8，p < 0.05）和1.0±0.5倍（n = 7，p < 0.05）。tempol模拟了这些效应。ANP和tempol也显著抑制了ET-1诱导的心肌细胞大小增加和超氧化物生成，但单独研究时对肥厚标志物没有影响。
这些数据表明，ANP的抗肥厚作用伴随着超氧化物水平的降低，提示抗氧化作用有助于ANP的抗肥厚作用。
