Phadke Kavya, D'Anna Sergio, Torres Vega Estefania, Xiao Junhua, Lin Xianming, Zhang Mingliang, Sall Joseph, Liang Feng-Xia, Park David S, Cerrone Marina, Lundby Alicia, Delmar Mario, van van Opbergen Chantal J M
The Leon Charney Division of Cardiology, New York University Grossmann School of Medicine, New York, NY, USA.
Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
J Physiol. 2024 Oct 24. doi: 10.1113/JP286985.
Atrial arrhythmias occur in 20-40% of patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) and are associated with an increased risk of sustained ventricular arrhythmias and inappropriate implantable cardioverter-defibrillator shocks. The pathophysiology of atrial arrhythmias in ARVC remains unclear. Most cases of gene-positive ARVC are linked to pathogenic variants in the desmosomal gene plakophilin-2 (PKP2). Here, we test the hypothesis that loss of PKP2 expression leads to pro-arrhythmic changes in atrial cardiomyocytes. Atrial cells/tissue were obtained from a cardiac-specific, tamoxifen-activated model of PKP2 deficiency (PKP2cKO). By contrast to PKP2cKO ventricular myocytes, PKP2cKO atrial cardiomyocytes presented no significant differences in intracellular calcium (Ca ) transient dynamics, sarcoplasmic reticulum load or action potential morphology. PKP2cKO atrial cardiomyocytes showed elevated reactive oxygen species levels, increased frequency and amplitude of Ca sparks, and increased diastolic [Ca] compared to control; the latter two parameters were further increased by isoproterenol exposure and reversed by exposure to ryanodine receptor blocker dantrolene. We speculate that these isoproterenol-dependent effects may impact on the exercise-related atrial arrhythmia risk in ARVC patients. Despite absence of changes in Ca transient dynamics, PKP2cKO atrial cardiomyocytes showed enhanced sarcomere shortening and impaired sarcomere relaxation. Orthogonal transcriptomic analysis of human(GTEx) and PKP2cKO atrial tissue led to identification of 41 transcripts depending on PKP2 expression. Biochemical follow-up confirmed reduced abundance of sarcomeric protein myosin binding protein C, potentially playing a role in cellular shortening and relaxation changes observed. Our findings provide novel insights into the role of PKP2 in atrial myocardium with potential implications to therapeutic management of atrial fibrillation in patients with PKP2-related ARVC. KEY POINTS: Atrial arrhythmias occur in a large group of patients with arrhythmogenic right ventricular cardiomyopathy (ARVC), a cardiac disease mostly caused by pathogenic variants in the desmosomal gene plakophilin-2 (PKP2). Exercise is considered to be an independent risk factor for arrhythmias consequent to PKP2 deficiency. We show that loss of PKP2 expression affects cellular calcium handling and electrophysiology differently in left atrial vs. ventricular myocardium and causes extensive atrial fibrosis. PKP2-deficient atrial cardiomyocytes present increased spontaneous sarcoplasmic reticulum calcium release events, further enhanced by isoproterenol exposure and reversible by a ryanodine receptor blocker (dantrolene). In addition, PKP2-deficient atrial myocytes exhibit impaired relaxation and enhanced sarcomere shortening, most probably related to reduced abundance of myosin binding protein C. We speculate that cellular effects reported upon isoproterenol impact on the exercise-related atrial arrhythmia risk in ARVC patients. We further propose that therapeutic approaches aimed at mitigating ventricular damage may be effective to treat the atrial disease in ARVC.
20% - 40%的致心律失常性右室心肌病（ARVC）患者会发生房性心律失常，且其与持续性室性心律失常及不适当的植入式心律转复除颤器电击风险增加相关。ARVC中房性心律失常的病理生理学仍不清楚。大多数基因阳性的ARVC病例与桥粒蛋白盘状球蛋白2（PKP2）的致病变异有关。在此，我们检验了PKP2表达缺失导致心房心肌细胞发生促心律失常变化这一假说。心房细胞/组织取自心脏特异性、他莫昔芬激活的PKP2缺陷模型（PKP2cKO）。与PKP2cKO心室肌细胞不同，PKP2cKO心房心肌细胞在细胞内钙（Ca）瞬变动力学、肌浆网负荷或动作电位形态方面无显著差异。与对照组相比，PKP2cKO心房心肌细胞显示活性氧水平升高、Ca火花的频率和幅度增加以及舒张期[Ca]升高；后两个参数在暴露于异丙肾上腺素后进一步增加，而在暴露于兰尼碱受体阻滞剂丹曲林后逆转。我们推测这些依赖异丙肾上腺素的效应可能会影响ARVC患者与运动相关的房性心律失常风险。尽管Ca瞬变动力学没有变化，但PKP2cKO心房心肌细胞显示肌节缩短增强且肌节舒张受损。对人（GTEx）和PKP2cKO心房组织进行的正交转录组分析导致鉴定出41种依赖PKP2表达的转录本。生化后续研究证实肌节蛋白肌球蛋白结合蛋白C的丰度降低，这可能在观察到的细胞缩短和舒张变化中起作用。我们的研究结果为PKP2在心房心肌中的作用提供了新的见解，对PKP2相关ARVC患者房颤的治疗管理具有潜在意义。要点：大量致心律失常性右室心肌病（ARVC）患者会发生房性心律失常，ARVC是一种主要由桥粒基因盘状球蛋白2（PKP2）的致病变异引起的心脏病。运动被认为是PKP2缺乏导致心律失常发作的独立危险因素。我们表明，PKP2表达缺失对左心房与心室心肌细胞钙处理和电生理的影响不同，并导致广泛的心房纤维化。PKP2缺陷的心房心肌细胞自发肌浆网钙释放事件增加，在暴露于异丙肾上腺素后进一步增强，且可被兰尼碱受体阻滞剂（丹曲林）逆转。此外，PKP2缺陷的心房肌细胞舒张受损且肌节缩短增强，最可能与肌球蛋白结合蛋白C丰度降低有关。我们推测异丙肾上腺素对细胞的影响会影响ARVC患者与运动相关的房性心律失常风险。我们进一步提出，旨在减轻心室损伤的治疗方法可能对治疗ARVC中的心房疾病有效。
