Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester, Rochester, NY, USA.
J Mol Cell Cardiol. 2013 Nov;64:11-9. doi: 10.1016/j.yjmcc.2013.08.003. Epub 2013 Aug 27.
Phosphodiesterase 3A (PDE3A) is a major regulator of cAMP in cardiomyocytes. PDE3 inhibitors are used for acute treatment of congestive heart failure, but are associated with increased incidence of arrhythmias and sudden death with long-term use. We previously reported that chronic PDE3A downregulation or inhibition induced myocyte apoptosis in vitro. However, the cardiac protective effect of PDE3A has not been demonstrated in vivo in disease models. In this study, we examined the role of PDE3A in regulating myocardial function and survival in vivo using genetically engineered transgenic mice with myocardial overexpression of the PDE3A1 isozyme (TG). TG mice have reduced cardiac function characterized by reduced heart rate and ejection fraction (52.5±7.8% vs. 83.9±4.7%) as well as compensatory expansion of left ventricular diameter (4.19±0.19mm vs. 3.10±0.18mm). However, there was no maladaptive increase of fibrosis and apoptosis in TG hearts compared to wild type (WT) hearts, and the survival rates also remained the same. The diminution of cardiac contractile function is very likely attributed to a decrease in beta-adrenergic receptor (β-AR) response in TG mice. Importantly, the myocardial infarct size (4.0±1.8% vs. 24.6±3.8%) and apoptotic cell number (1.3±1.0% vs. 5.6±1.5%) induced by ischemia/reperfusion (I/R) injury were significantly attenuated in TG mice. This was associated with decreased expression of inducible cAMP early repressor (ICER) and increased expression of anti-apoptotic protein BCL-2. To further verify the anti-apoptotic effects of PDE3A1, we performed in vitro apoptosis study in isolated adult TG and WT cardiomyocytes. We found that the apoptotic rates stimulated by hypoxia/reoxygenation or H2O2 were indeed significantly reduced in TG myocytes, and the differences between TG and WT myocytes were completely reversed in the presence of the PDE3 inhibitor milrinone. These together indicate that PDE3A1 negatively regulates β-AR signaling and protects against I/R injury by inhibiting cardiomyocyte apoptosis.
磷酸二酯酶 3A（PDE3A）是心肌细胞中环磷酸腺苷（cAMP）的主要调节剂。PDE3 抑制剂用于充血性心力衰竭的急性治疗，但长期使用与心律失常和猝死发生率增加有关。我们之前报道过，慢性 PDE3A 下调或抑制会诱导体外心肌细胞凋亡。然而，在疾病模型中，PDE3A 在体内对心脏的保护作用尚未得到证实。在这项研究中，我们使用心肌过表达 PDE3A1 同工型的基因工程转基因小鼠（TG），研究 PDE3A 在体内调节心肌功能和存活中的作用。TG 小鼠的心脏功能降低，表现为心率和射血分数降低（52.5±7.8% vs. 83.9±4.7%），以及左心室直径代偿性扩张（4.19±0.19mm vs. 3.10±0.18mm）。然而，与野生型（WT）心脏相比，TG 心脏没有适应性增加纤维化和凋亡，存活率也保持不变。心脏收缩功能的降低很可能归因于 TG 小鼠β-肾上腺素能受体（β-AR）反应的下降。重要的是，缺血/再灌注（I/R）损伤引起的心肌梗死面积（4.0±1.8% vs. 24.6±3.8%）和凋亡细胞数（1.3±1.0% vs. 5.6±1.5%）在 TG 小鼠中明显减轻。这与诱导型 cAMP 早期阻遏物（ICER）的表达减少和抗凋亡蛋白 BCL-2 的表达增加有关。为了进一步验证 PDE3A1 的抗凋亡作用，我们在分离的成年 TG 和 WT 心肌细胞中进行了体外凋亡研究。我们发现，缺氧/复氧或 H2O2 刺激的凋亡率在 TG 心肌细胞中确实明显降低，而在 PDE3 抑制剂米力农存在的情况下，TG 和 WT 心肌细胞之间的差异完全逆转。这些结果表明，PDE3A1 通过负调控β-AR 信号转导和抑制心肌细胞凋亡来保护 I/R 损伤。
