Background: Long non-coding RNAs (lncRNA) plasmacytoma variant translocation 1 (PVT1) has been shown to be associated with liver fibrosis. Nevertheless, the role of PVT1 in atrial fibrosis remains undefined. This study aims to elucidate the pathophysiological role of lncRNA PVT1 in the regulation of atrial fibrosis and to explore the underlying mechanism. Methods: Expression of PVT1, miR-128-sp, and Sp1 were examined in human atrial muscle tissues and angiotensin-II (Ang-II)-induced human atrial fibroblasts. Furthermore, the role of PVT1 in regulating atrial fibrosis in Ang-II-treated human atrial fibroblasts and Ang-II-induced atrial fibrosis in mice was investigated. Moreover, the interaction among PVT1, miR-128-3p, and Sp1 were examined using bioinformatics, expression correlation analysis, gain-or loss-offunction assays, RIP assays, and luciferase reporter assays. The involvement of transforming growth factor beta 1 (TGF-β1)/Smad pathway in this process was also explored. Results: PVT1 was increased in atrial muscle tissues from AF patients and positively with collagen I and collagen III. In vitro assay revealed that PVT1 overexpression facilitated the Ang-II-induced atrial fibroblasts proliferation, collagen production, and TGF-β1/Smad signaling activation, whereas PVT1 knockdown caused the opposite effect. In vivo assay further confirmed that PVT1 knockdown attenuated the Ang-II-induced mouse atrial fibrosis. Mechanically, PVT1 acted as a sponge for miR-128-3p to facilitate Sp1 expression, thereby activating the TGF-β1/Smad signaling pathway. Conclusion: LncRNA PVT1 promotes atrial fibrosis via miR-128-3p-SP1-TGF-β1-Smad axis in atrial fibrillation.

Abstract-LIM domain proteins are important regulators in cell growth, cell fate determination, cell differentiation, and remodeling of the cell cytoskeleton. LIM and cysteine-rich domains 1 (Lmcd1) is a novel protein that contain 2 LIM domains with regular spacing in the carboxy-terminal region. However, its roles in cardiac growth remain unknown. Here, we investigated whether Lmcd1 regulates cardiac hypertrophy in vitro and in vivo and elucidated the underlying molecular mechanisms. We used primary cultured cardiac myocytes and cardiac-specific Lmcd1 transgenic mice. In wild-type mice subjected to the aortic banding, cardiac hypertrophy was evident at 8 weeks. In transgenic mice, however, cardiac hypertrophy was significantly greater than that in wild-type mice, as estimated by heart weight:body weight ratio, cardiomyocyte area, and echocardiographic measurements, as well as cardiac atrial natriuretic peptide and B-type natriuretic peptide mRNA and protein levels. Our results further showed that cardiac fibrosis observed in wild-type aortic banding mice was augmented in transgenic aortic banding mice. Importantly, calcineurin activity and nuclear factor of activated T cells activation level were increased more in transgenic mice than those in wild-type mice after 8-week aortic banding. In vitro experiments in cardiac myocytes further revealed that angiotensin II-induced calcineurin activity and nuclear factor of activated T cells activation were enhanced by overexpression but blunted by downregulation of Lmcd1. In conclusion, our results suggest that Lmcd1 plays a critical role in the development of cardiac hypertrophy via activation of calcineurin/nuclear factor of activated T cells signaling pathway. Key Words: cardiac hypertrophy Ⅲ fibrosis Ⅲ Lmcd1 Ⅲ calcineurin Ⅲ NFAT C ardiac hypertrophy is a response of the myocardium to increased workload, characterized by an increase of myocardial mass and accumulation of extracellular matrix, leading to left ventricular (LV) dilatation, fibrosis, and impaired systolic function, and it potentates the development of ventricular arrhythmias, heart failure, and subsequent cardiovascular mortality. 1,2 Although initially a beneficial adaptive response, prolonged hypertrophy may result in ventricular dilatation and heart failure, which is increasing in prevalence and is a debilitating disease with high rates of mortality and morbidity. [3][4][5][6] However, antihypertensive therapies and aortic valve replacement are the only 2 treatments proven to effectively reverse both structural and functional cardiac abnormalities associated with pathological cardiac hypertrophy. Understanding the underlying processes regulating cardiac remodeling will allow us to identify specific new therapies to improve the long-term outcomes of pathological cardiac hypertrophy in patients.LIM domain proteins are well recognized as key components of the regulatory machinery of the cell and are important regulators in cell growth, cell fate determination, cell differentiation, and remodeling of the ce...

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