Calcific aortic valve disease (CAVD) is highly prevalent with marked morbidity and mortality rates and a lack of pharmaceutical treatment options because its mechanisms are unknown. Melatonin is reported to exert atheroprotective effects. However, whether melatonin protects against aortic valve calcification, a disease whose pathogenesis shares many similarities to that of atherosclerosis, and the underlying molecular mechanisms remain unknown. In this study, we found that the intragastric administration of melatonin for 24 weeks markedly ameliorated aortic valve calcification in high cholesterol diet (HCD)–treated ApoE^−/− mice, as evidenced by reduced thickness and calcium deposition in the aortic valve leaflets, improved echocardiographic parameters (decreased transvalvular peak jet velocity and increased aortic valve area), and decreased osteogenic differentiation marker (Runx2, osteocalcin, and osterix) expression in the aortic valves. Consistent with these in vivo data, we also confirmed the suppression of in vitro calcification by melatonin in hVICs. Mechanistically, melatonin reduced the level of CircRIC3, a procalcification circular RNA, which functions by acting as a miR‐204‐5p sponge to positively regulate the expression of the procalcification gene dipeptidyl peptidase‐4 (DPP4). Furthermore, CircRIC3 overexpression abolished the inhibitory effects of melatonin on hVIC osteogenic differentiation. Taken together, our results suggest that melatonin ameliorates aortic valve calcification via the regulation of CircRIC3/miR‐204‐5p/DPP4 signaling in hVICs; therefore, melatonin medication might be considered a novel pharmaceutical strategy for CAVD treatment.

中文翻译：

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褪黑激素通过调节瓣膜间质细胞中的环状 RNA CircRIC3/miR-204-5p/DPP4 信号传导来改善主动脉瓣钙化。

钙化性主动脉瓣疾病 (CAVD) 非常普遍，发病率和死亡率很高，并且由于其机制尚不清楚，因此缺乏药物治疗选择。据报道，褪黑激素具有动脉粥样硬化保护作用。然而，褪黑激素是否能预防主动脉瓣钙化，这种疾病的发病机制与动脉粥样硬化有许多相似之处，其潜在的分子机制仍然未知。在这项研究中，我们发现在高胆固醇饮食 (HCD) 治疗的 ApoE ^-/-中，胃内施用褪黑激素 24 周显着改善主动脉瓣钙化小鼠，如主动脉瓣叶中厚度减少和钙沉积所证明的那样，改善了超声心动图参数（跨瓣峰值射流速度降低和主动脉瓣面积增加），并降低了主动脉瓣中成骨分化标志物（Runx2、骨钙素和 osterix）的表达. 与这些体内数据一致，我们还证实了褪黑激素在 hVIC 中对体外钙化的抑制。从机制上讲，褪黑激素降低了 CircRIC3 的水平，CircRIC3 是一种前钙化环状 RNA，它通过充当 miR-204-5p 海绵来正向调节钙化前基因二肽基肽酶-4（DPP4）的表达。此外，CircRIC3 过表达消除了褪黑激素对 hVIC 成骨分化的抑制作用。综合起来，通过调节 hVIC 中的 CircRIC3/miR-204-5p/DPP4 信号；因此，褪黑激素药物可能被认为是 CAVD 治疗的新药物策略。