BACKGROUND:In heart failure, signaling downstream the β2-adrenergic receptor is critical. Sympathetic stimulation of β2-adrenergic receptor alters cAMP (cyclic adenosine 3′,5′-monophosphate) and triggers PKA (protein kinase A)-dependent phosphorylation of proteins that regulate cardiac function. cAMP levels are regulated in part by PDEs (phosphodiesterases). Several AKAPs (A kinase anchoring proteins) regulate cardiac function and are proposed as targets for precise pharmacology. AKAP12 is expressed in the heart and has been reported to directly bind β2-adrenergic receptor, PKA, and PDE4D. However, its roles in cardiac function are unclear.METHODS:cAMP accumulation in real time downstream of the β2-adrenergic receptor was detected for 60 minutes in live cells using the luciferase-based biosensor (GloSensor) in AC16 human-derived cardiomyocyte cell lines overexpressing AKAP12 versus controls. Cardiomyocyte intracellular calcium and contractility were studied in adult primary cardiomyocytes from male and female mice overexpressing cardiac AKAP12 (AKAP12^OX) and wild-type littermates post acute treatment with 100-nM isoproterenol (ISO). Systolic cardiac function was assessed in mice after 14 days of subcutaneous ISO administration (60 mg/kg per day). AKAP12 gene and protein expression levels were evaluated in left ventricular samples from patients with end-stage heart failure.RESULTS:AKAP12 upregulation significantly reduced total intracellular cAMP levels in AC16 cells through PDE8. Adult primary cardiomyocytes from AKAP12^OX mice had significantly reduced contractility and impaired calcium handling in response to ISO, which was reversed in the presence of the selective PDE8 inhibitor (PF-04957325). AKAP12^OX mice had deteriorated systolic cardiac function and enlarged left ventricles. Patients with end-stage heart failure had upregulated gene and protein levels of AKAP12.CONCLUSIONS:AKAP12 upregulation in cardiac tissue is associated with accelerated cardiac dysfunction through the AKAP12-PDE8 axis.

中文翻译：

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AKAP12 上调与 PDE8A 相关，加速心脏功能障碍

背景：在心力衰竭中，β2-肾上腺素受体下游的信号传导至关重要。 β2-肾上腺素能受体的交感神经刺激会改变 cAMP（环腺苷 3',5'-单磷酸）并触发调节心脏功能的蛋白的 PKA（蛋白激酶 A）依赖性磷酸化。 cAMP 水平部分受 PDE（磷酸二酯酶）调节。几种 AKAP（A 激酶锚定蛋白）可调节心脏功能，并被提议作为精确药理学的靶点。 AKAP12 在心脏中表达，据报道可直接结合 β2 肾上腺素受体、PKA 和 PDE4D。然而，其在心脏功能中的作用尚不清楚。 方法：在过表达AC16人源心肌细胞系中，使用基于荧光素酶的生物传感器（GloSensor）在活细胞中实时检测β2肾上腺素受体下游的cAMP积累60分钟。 AKAP12 与对照。研究人员在来自过度表达心脏 AKAP12 (AKAP12 ^OX )的雄性和雌性小鼠以及用 100 nM 异丙肾上腺素 (ISO) 急性治疗后的野生型同窝小鼠的成年原代心肌细胞中研究了心肌细胞的细胞内钙和收缩力。皮下注射 ISO（每天 60 毫克/公斤）14 天后，对小鼠的心脏收缩功能进行了评估。在终末期心力衰竭患者的左心室样本中评估 AKAP12 基因和蛋白表达水平。结果：AKAP12 上调通过 PDE8 显着降低 AC16 细胞中总细胞内 cAMP 水平。来自 AKAP12 ^OX小鼠的成年原代心肌细胞对 ISO 的反应显着降低了收缩性并损害了钙处理能力，而在选择性 PDE8 抑制剂 (PF-04957325) 的存在下，这种情况发生了逆转。 AKAP12 ^OX小鼠的心脏收缩功能恶化，左心室扩大。终末期心力衰竭患者的 AKAP12 基因和蛋白水平上调。结论：心脏组织中 AKAP12 的上调通过 AKAP12-PDE8 轴与加速心脏功能障碍相关。