Background: Myocardial fibrosis is a hallmark of cardiac remodeling and functionally involved in heart failure development, a leading cause of deaths worldwide. Clinically, no therapeutic strategy is available that specifically attenuates maladaptive responses of cardiac fibroblasts, the effector cells of fibrosis in the heart. Therefore, our aim was to develop novel antifibrotic therapeutics based on naturally derived substance library screens for the treatment of cardiac fibrosis. Methods: Antifibrotic drug candidates were identified by functional screening of 480 chemically diverse natural compounds in primary human cardiac fibroblasts, subsequent validation, and mechanistic in vitro and in vivo studies. Hits were analyzed for dose-dependent inhibition of proliferation of human cardiac fibroblasts, modulation of apoptosis, and extracellular matrix expression. In vitro findings were confirmed in vivo with an angiotensin II–mediated murine model of cardiac fibrosis in both preventive and therapeutic settings, as well as in the Dahl salt-sensitive rat model. To investigate the mechanism underlying the antifibrotic potential of the lead compounds, treatment-dependent changes in the noncoding RNAome in primary human cardiac fibroblasts were analyzed by RNA deep sequencing. Results: High-throughput natural compound library screening identified 15 substances with antiproliferative effects in human cardiac fibroblasts. Using multiple in vitro fibrosis assays and stringent selection algorithms, we identified the steroid bufalin (from Chinese toad venom) and the alkaloid lycorine (from Amaryllidaceae species) to be effective antifibrotic molecules both in vitro and in vivo, leading to improvement in diastolic function in 2 hypertension-dependent rodent models of cardiac fibrosis. Administration at effective doses did not change plasma damage markers or the morphology of kidney and liver, providing the first toxicological safety data. Using next-generation sequencing, we identified the conserved microRNA 671-5p and downstream the antifibrotic selenoprotein P1 as common effectors of the antifibrotic compounds. Conclusions: We identified the molecules bufalin and lycorine as drug candidates for therapeutic applications in cardiac fibrosis and diastolic dysfunction.

Aims Cardiotoxicity leading to heart failure (HF) is a growing problem in many cancer survivors. As specific treatment strategies are not available, RNA discovery pipelines were employed and a new and powerful circular RNA (circRNA)-based therapy was developed for the treatment of doxorubicin-induced HF. Methods and results The circRNA sequencing was applied and the highly species-conserved circRNA insulin receptor (Circ-INSR) was identified, which participates in HF processes, including those provoked by cardiotoxic anti-cancer treatments. Chemotherapy-provoked cardiotoxicity leads to the down-regulation of Circ-INSR in rodents and patients, which mechanistically contributes to cardiomyocyte cell death, cardiac dysfunction, and mitochondrial damage. In contrast, Circ-INSR overexpression prevented doxorubicin-mediated cardiotoxicity in both rodent and human cardiomyocytes in vitro and in a mouse model of chronic doxorubicin cardiotoxicity. Breast cancer type 1 susceptibility protein (Brca1) was identified as a regulator of Circ-INSR expression. Detailed transcriptomic and proteomic analyses revealed that Circ-INSR regulates apoptotic and metabolic pathways in cardiomyocytes. Circ-INSR physically interacts with the single-stranded DNA-binding protein (SSBP1) mediating its cardioprotective effects under doxorubicin stress. Importantly, in vitro transcribed and circularized Circ-INSR mimics also protected against doxorubicin-induced cardiotoxicity. Conclusion Circ-INSR is a highly conserved non-coding RNA which is down-regulated during cardiotoxicity and cardiac remodelling. Adeno-associated virus and circRNA mimics-based Circ-INSR overexpression prevent and reverse doxorubicin-mediated cardiomyocyte death and improve cardiac function. The results of this study highlight a novel and translationally important Circ-INSR-based therapeutic approach for doxorubicin-induced cardiac dysfunction.

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Background The long noncoding RNA LIPCAR (Long Intergenic noncoding RNA Predicting CARdiac remodeling) has emerged as a promising biomarker in cardiac disease and cardiac remodeling. To determine whether LIPCAR levels help for a molecular phenotyping of chronic heart failure (HF) patients, this study assessed the association of LIPCAR with severity of the disease and its progression, and with risk of death or hospitalization in HF patients. Methods LIPCAR was measured in plasma of 967 HF patients with symptomatic heart failure participating in the Gruppo Italiano per lo Studio della Sopravvivenza nell'Insufficienza Cardiaca - Heart Failure (GISSI-HF) biohumoral sub-study. Results Plasma levels of LIPCAR were significantly associated with functional impairment as assessed by the New York Heart Association (NYHA) class, kidney function as reflected by estimated glomerular filtration rate, and creatinine, hemoglobin and mitral insufficiency. In females, these associations were more marked as compared to males. LIPCAR plasma levels were significantly related to the two cardiac markers, N-terminal pro-B type natriuretic peptide and high-sensitivity cardiac troponin T, but not to inflammatory markers such as high sensitivity C-reactive protein and pentraxin-3, nor to patient reported outcomes such as depression and quality of life. HF patients with high LIPCAR levels univariately showed significantly higher incidence of cardiovascular hospitalizations but not of death; after adjusting for covariates, no significant effects of LIPCAR were found for cardiovascular hospitalizations. Conclusion The circulating long noncoding RNA LIPCAR was increased in HF patients with higher NYHA class, impaired kidney function, and lower hemoglobin, which are indicators of patients’ overall state.

Non-coding RNAs have been shown to be involved in several pathological and physiological settings, including cardiovascular diseases and cardiac regeneration. In this Research Topic, the reports highlight the current knowledge and provide state-of-the-art data. In addition, obstacles and future Publisher's Note: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.