INSERM UMR-S 769, Châtenay-Malabry, France.
Cardiovasc Res. 2013 Nov 1;100(2):336-46. doi: 10.1093/cvr/cvt193. Epub 2013 Aug 9.
Multiple phosphodiesterases (PDEs) hydrolyze cAMP in cardiomyocytes, but the functional significance of this diversity is not well understood. Our goal here was to characterize the involvement of three different PDEs (PDE2-4) in cardiac excitation-contraction coupling (ECC).
Sarcomere shortening and Ca(2+) transients were recorded simultaneously in adult rat ventricular myocytes and ECC protein phosphorylation by PKA was determined by western blot analysis. Under basal conditions, selective inhibition of PDE2 or PDE3 induced a small but significant increase in Ca(2+) transients, sarcomere shortening, and troponin I phosphorylation, whereas PDE4 inhibition had no effect. PDE3 inhibition, but not PDE2 or PDE4, increased phospholamban phosphorylation. Inhibition of either PDE2, 3, or 4 increased phosphorylation of the myosin-binding protein C, but neither had an effect on L-type Ca(2+) channel or ryanodine receptor phosphorylation. Dual inhibition of PDE2 and PDE3 or PDE2 and PDE4 further increased ECC compared with individual PDE inhibition, but the most potent combination was obtained when inhibiting simultaneously PDE3 and PDE4. This combination also induced a synergistic induction of ECC protein phosphorylation. Submaximal β-adrenergic receptor stimulation increased ECC, and this effect was potentiated by individual PDE inhibition with the rank order of potency PDE4 = PDE3 > PDE2. Identical results were obtained on ECC protein phosphorylation.
Our results demonstrate that PDE2, PDE3, and PDE4 differentially regulate ECC in adult cardiomyocytes. PDE2 and PDE3 play a more prominent role than PDE4 in regulating basal cardiac contraction and Ca(2+) transients. However, PDE4 becomes determinant when cAMP levels are elevated, for instance, upon β-adrenergic stimulation or PDE3 inhibition.
多种磷酸二酯酶（PDEs）在心肌细胞中水解 cAMP，但这种多样性的功能意义尚不清楚。我们的目标是研究三种不同 PDE（PDE2-4）在心脏兴奋-收缩偶联（ECC）中的作用。
在成年大鼠心室肌细胞中同时记录肌节缩短和 Ca2+瞬变，并通过 Western blot 分析确定 PKA 磷酸化的 ECC 蛋白。在基础条件下，选择性抑制 PDE2 或 PDE3 可引起 Ca2+瞬变、肌节缩短和肌钙蛋白 I 磷酸化的微小但显著增加，而 PDE4 抑制则没有影响。PDE3 抑制而不是 PDE2 或 PDE4 增加了肌球蛋白结合蛋白 C 的磷酸化。抑制 PDE2、3 或 4 均可增加肌球蛋白结合蛋白 C 的磷酸化，但对 L 型 Ca2+通道或兰尼碱受体磷酸化均无影响。PDE2 和 PDE3 或 PDE2 和 PDE4 的双重抑制与单独的 PDE 抑制相比进一步增加了 ECC，但当同时抑制 PDE3 和 PDE4 时，效果最强。这种组合还协同诱导了 ECC 蛋白磷酸化。β-肾上腺素能受体的亚最大刺激增加了 ECC，这种效应可通过 PDE 抑制增强，抑制强度 PDE4 = PDE3 > PDE2。在 ECC 蛋白磷酸化上获得了相同的结果。
我们的结果表明，PDE2、PDE3 和 PDE4 可在成年心肌细胞中差异调节 ECC。PDE2 和 PDE3 在调节基础心脏收缩和 Ca2+瞬变方面比 PDE4 发挥更重要的作用。然而，当 cAMP 水平升高时，例如在β-肾上腺素能刺激或 PDE3 抑制时，PDE4 变得至关重要。
