Background:Arrhythmogenic right ventricular cardiomyopathy (ARVC) is characterized by high propensity to life-threatening arrhythmias and progressive loss of heart muscle. More than 40% of reported genetic variants linked to ARVC reside in the PKP2 gene, which encodes the PKP2 protein (plakophilin-2).Methods:We describe a comprehensive characterization of the ARVC molecular landscape as determined by high-resolution mass spectrometry, RNA sequencing, and transmission electron microscopy of right ventricular biopsy samples obtained from patients with ARVC with PKP2 mutations and left ventricular ejection fraction >45%. Samples from healthy relatives served as controls. The observations led to experimental work using multiple imaging and biochemical techniques in mice with a cardiac-specific deletion of Pkp2 studied at a time of preserved left ventricular ejection fraction and in human induced pluripotent stem cell–derived PKP2-deficient myocytes.Results:Samples from patients with ARVC present a loss of nuclear envelope integrity, molecular signatures indicative of increased DNA damage, and a deficit in transcripts coding for proteins in the electron transport chain. Mice with a cardiac-specific deletion of Pkp2 also present a loss of nuclear envelope integrity, which leads to DNA damage and subsequent excess oxidant production (O₂^.– and H₂O₂), the latter increased further under mechanical stress (isoproterenol or exercise). Increased oxidant production and DNA damage is recapitulated in human induced pluripotent stem cell–derived PKP2-deficient myocytes. Furthermore, PKP2-deficient cells release H₂O₂ into the extracellular environment, causing DNA damage and increased oxidant production in neighboring myocytes in a paracrine manner. Treatment with honokiol increases SIRT3 (mitochondrial nicotinamide adenine dinucleotide–dependent protein deacetylase sirtuin-3) activity, reduces oxidant levels and DNA damage in vitro and in vivo, reduces collagen abundance in the right ventricular free wall, and has a protective effect on right ventricular function.Conclusions:Loss of nuclear envelope integrity and subsequent DNA damage is a key substrate in the molecular pathology of ARVC. We show transcriptional downregulation of proteins of the electron transcript chain as an early event in the molecular pathophysiology of the disease (before loss of left ventricular ejection fraction <45%), which associates with increased oxidant production (O₂^.– and H₂O₂). We propose therapies that limit oxidant formation as a possible intervention to restrict DNA damage in ARVC.

中文翻译：

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核膜完整性的丧失和氧化剂产生的增加会导致缺乏 PKP2（ARVC 的分子底物）的成人心脏 DNA 损伤

背景：致心律失常性右室心肌病（ARVC）的特点是高度容易发生危及生命的心律失常和进行性心肌丧失。已报道的与 ARVC 相关的遗传变异超过 40% 存在于PKP2基因中，该基因编码 PKP2 蛋白 (plakophilin-2)。 方法：我们描述了通过高分辨率质谱、RNA 确定的 ARVC 分子景观的全面表征对从具有PKP2突变且左心室射血分数 > 45% 的ARVC 患者获得的右心室活检样本进行测序和透射电子显微镜检查。来自健康亲属的样本作为对照。这些观察结果导致使用多种成像和生化技术在左心室射血分数保留时研究的心脏特异性Pkp2缺失的小鼠和人诱导多能干细胞衍生的 PKP2 缺陷的肌细胞中进行实验工作。 结果：样品来自ARVC 患者出现核膜完整性丧失、DNA 损伤增加的分子特征以及电子传递链中蛋白质编码转录物的缺陷。心脏特异性缺失Pkp2的小鼠也会出现核膜完整性的丧失，从而导致 DNA 损伤和随后过量的氧化剂产生（O ₂ ^.–和 H ₂ O ₂），后者在机械应力（异丙肾上腺素或 H 2 O 2 ）下进一步增加。锻炼）。在人诱导多能干细胞衍生的 PKP2 缺陷型肌细胞中，氧化剂产量增加和 DNA 损伤得到了重现。此外，PKP2缺陷的细胞将H ₂ O ₂释放到细胞外环境中，以旁分泌方式引起DNA损伤并增加邻近肌细胞中氧化剂的产生。使用和厚朴酚治疗可增加 SIRT3（线粒体烟酰胺腺嘌呤二核苷酸依赖性蛋白脱乙酰酶 Sirtuin-3）活性，降低体外和体内氧化剂水平和 DNA 损伤，降低右心室游离壁中的胶原丰度，并对右心室具有保护作用结论：核膜完整性丧失和随后的 DNA 损伤是 ARVC 分子病理学的关键底物。我们发现电子转录链蛋白质的转录下调是该疾病分子病理生理学的早期事件（在左心室射血分数丧失<45%之前），这与氧化剂产生增加（O 2 _.–^和H ₂ O ₂）。我们提出限制氧化剂形成的疗法作为限制 ARVC 中 DNA 损伤的可能干预措施。