Erratum: LncRNA PFL contributes to cardiac fibrosis by acting as a competing endogenous RNA of let-7d: Erratum.

[This corrects the article DOI: 10.7150/thno.20846.].

SNX17 produces anti-arrhythmic effects by preserving functional SERCA2a protein in myocardial infarction.

BACKGROUND: Sorting nexin 17 (SNX17) is a critical cytoplasmic adaptor protein that regulates endosomal trafficking of membrane proteins to determine their recycling and/or degradation. The potential role of SNX17 in cardiovascular pathophysiology has not been reported. METHODS AND RESULTS: Cardiac arrhythmias were monitored using standard limb lead II electrocardiograph, and cardiac performances were determined by echocardiography in a rat model of myocardial infarction (MI) created by left anterior descending coronary artery ligation. We found that SNX17 was substantially downregulated in ischemic myocardium. The downregulation contributed to the cardiac electrical disturbances and contractile dysfunction as SNX17 replacement mitigated the detrimental alterations of MI hearts. Specifically, silence of SNX17 expression using RNA interference caused intracellular Ca2+ overload as revealed by the abnormal rise of resting [Ca2+]i and deceleration of Ca2+ decay, whereas SNX17 overexpression using vectors elicited the opposite effects. Moreover, the protein level of SERCA2a was significantly decreased by silencing SNX17. Immunohistochemistry indicated that SNX17 and SERCA2a were co-localized, and co-immunoprecipitation revealed the binding between the phox-homology domain of SNX17 and SERCA2a protein. Furthermore, lysosome inhibitor chloroquine prevented SNX17 silencing-induced reduction of SERCA2a protein level. CONCLUSION: Abnormal downregulation of SNX17 contributes to ischemic damages of cardiac electrophysiology and contractile function. SNX17 is an endogenous anti-arrhythmic factor acting by preserving functional SERCA2a protein in MI thereby offering a new strategy for the management of MI to alleviate ischemic myocardial injuries.

Cardiomyocyte Derived miR-328 Promotes Cardiac Fibrosis by Paracrinely Regulating Adjacent Fibroblasts.

BACKGROUND/AIMS: In our previous study, we demonstrated that elevated expression of miR-328 is a potent determinant of cardiac fibrosis during myocardial infarction (MI). In the present study, histological examination revealed progressive fibrosis in transgenic mice overexpressing cardiomyocyte-specific miR-328. This study investigated whether the transfer of miR-328 from cardiomyocytes (CMs) to cardiac fibroblasts (CFs) in a paracrine manner contributes to myocardial fibrosis. METHODS: Myocardial infarction was established by the occlusion of the left coronary artery. Masson's trichrome staining and collagen assays were used to evaluate the progression of fibrosis. The vesicles and translocation of miR-328 in a co-culture assay system were respectively observed using transmission electron microscopy (TEM) and immunofluorescence staining (IF). Real-time PCR was employed to detect the level of miR-328, Col1α1 and Col3α1. The protein expression of Col1α1, TGF-ßRIII, p-smad2/3 (phosphorylated-smad2/3) and TGF-ß1 were probed using western blot analysis. RESULTS: Cardiomyocyte-specific miR-328 overexpressing transgenic (TG) mice showed enhanced collagen deposition and provoked cardiac fibrosis by the activation of the TGF-ß1 pathway, and this effect was abrogated after knockdown of endogenous miR-328 in mice. Correspondingly, the expression of miR-328 was increased in CFs co-cultured with CMs transfected with miR-328 mimics, likely in a paracrine manner. The cardiomyocyte-mediated augmentation of miR-328 contributes to fibrogenesis in CFs, and this pro-fibrotic effect was reversed after the transfection of miR-328 inhibitor in CFs. CONCLUSION: A novel molecular mechanism for miR-328 derived from CMs as a paracrine signaling mediator of cardiac fibrogenesis further demonstrates that miR-328 is a potential therapeutic target.

Aspirin Reduces Cardiac Interstitial Fibrosis by Inhibiting Erk1/2-Serpine2 and P-Akt Signalling Pathways.

BACKGROUND/AIMS: Cardiac interstitial fibrosis is an abnormality of various cardiovascular diseases, including myocardial infarction, hypertrophy, and atrial fibrillation, and it can ultimately lead to heart failure. However, there is a lack of practical therapeutic approaches to treat fibrosis and reverse the damage to the heart. The purpose of this study was to investigate the effect of long-term aspirin administration on pressure overload-induced cardiac fibrosis in mice and reveal the underlying mechanisms of aspirin treatment. METHODS: C57BL/6 mice were subjected to transverse aortic constriction (TAC), and treated with 10 mg·kg-1·day-1 of aspirin for 4 weeks. Masson staining and a collagen content assay were used to detect the effects of aspirin on cardiac fibrosis in vivo and in vitro. Western blot and qRT-PCR were applied to examine the impact of aspirin on extracellular signal-regulated kinases (Erks), p-Akt/ß-catenin, SerpinE2, collagen I, and collagen III levels in the mice heart. RESULTS: Aspirin significantly suppressed the expression of α-smooth muscle actin (α-SMA; 1.19±0.19-fold) and collagen I (0.95±0.09-fold) in TAC mice. Aspirin, at doses of 100 and 1000 µM, also significantly suppressed angiotensin II-induced α-SMA and collagen I in cultured CFs. The enhanced phosphorylation of Erk1/2 caused by TAC (p-Erk1, 1.49±0.19-fold; p-Erk2, 1.96±0.68-fold) was suppressed by aspirin (p-Erk1, 1.04±0.15-fold; p-Erk2, 0.87±0.06-fold). SerpinE2 levels were suppressed via the Erk1/2 signalling pathway following treatment with aspirin (1.36±0.12-fold for TAC; 1.06±0.07-fold for aspirin+TAC). The p-Akt and ß-catenin levels were also significantly inhibited in vivo and in vitro. CONCLUSIONS: Our study reveals a novel mechanism by which aspirin alleviates pressure overload-induced cardiac interstitial fibrosis in TAC mice by suppressing the p-Erk1/2 and p-Akt/ß-catenin signalling pathways.

LncRNA PFL contributes to cardiac fibrosis by acting as a competing endogenous RNA of let-7d.

Rationale: Cardiac fibrosis is associated with various cardiovascular diseases and can eventually lead to heart failure. Dysregulation of long non-coding RNAs (lncRNAs) has recently been recognized as one of the key mechanisms involved in cardiac diseases. However, the potential roles and underlying mechanisms of lncRNAs in cardiac fibrosis have not been explicitly delineated. Methods and Results: Using a combination of in vitro and in vivo studies, we identified a lncRNA NONMMUT022555, which is designated as a pro-fibrotic lncRNA (PFL), and revealed that PFL is up-regulated in the hearts of mice in response to myocardial infarction (MI) as well as in the fibrotic cardiac fibroblasts (CFs). We found that knockdown of PFL by adenoviruses carrying shRNA attenuated cardiac interstitial fibrosis and improved ejection fraction (EF) and fractional shortening (FS) in MI mice. Further study showed that forced expression of PFL promoted proliferation, fibroblast-myofibroblast transition and fibrogenesis in mice CFs by regulating let-7d, whereas silencing PFL mitigated TGF-ß1-induced myofibroblast generation and fibrogenesis. More importantly, PFL acted as a competitive endogenous RNA (ceRNA) of let-7d, as forced expression of PFL reduced the expression and activity of let-7d. Moreover, let-7d levels were decreased in the MI mice and in fibrotic CFs. Inhibition of let-7d resulted in fibrogenesis in CFs, whereas forced expression of let-7d abated fibrogenesis through targeting platelet-activating factor receptor (Ptafr). Furthermore, overexpression of let-7d by adenoviruses carrying let-7d precursor impeded cardiac fibrosis and improved cardiac function in MI mice. Conclusion: Taken together, our study elucidated the role and mechanism of PFL in cardiac fibrosis, indicating the potential role of PFL inhibition as a novel therapy for cardiac fibrosis.

Overexpression of SerpinE2/protease nexin-1 Contribute to Pathological Cardiac Fibrosis via increasing Collagen Deposition.

Although increases in cardiovascular load (pressure overload) are known to elicit ventricular remodeling including cardiomyocyte hypertrophy and interstitial fibrosis, the molecular mechanisms of pressure overload or AngII -induced cardiac interstitial fibrosis remain elusive. In this study, serpinE2/protease nexin-1 was over-expressed in a cardiac fibrosis model induced by pressure-overloaded via transverse aortic constriction (TAC) in mouse. Knockdown of serpinE2 attenuates cardiac fibrosis in a mouse model of TAC. At meantime, the results showed that serpinE2 significantly were increased with collagen accumulations induced by AngII or TGF-ß stimulation in vitro. Intriguingly, extracellular collagen in myocardial fibroblast was reduced by knockdown of serpinE2 compared with the control in vitro. In stark contrast, the addition of exogenous PN-1 up-regulated the content of collagen in myocardial fibroblast. The MEK1/2- ERK1/2 signaling probably promoted the expression of serpinE2 via transcription factors Elk1 in myocardial fibroblast. In conclusion, stress-induced the ERK1/2 signaling pathway activation up-regulated serpinE2 expression, consequently led accumulation of collagen protein, and contributed to cardiac fibrosis.

Acetyl salicylic acid attenuates cardiac hypertrophy through Wnt signaling.

Ventricular hypertrophy is a powerful and independent predictor of cardiovascular morbid events. The vascular properties of low-dose acetyl salicylic acid (aspirin) provide cardiovascular benefits through the irreversible inhibition of platelet cyclooxygenase 1; however, the possible anti-hypertrophic properties and potential mechanism of aspirin have not been investigated in detail. In this study, healthy wild-type male mice were randomly divided into three groups and subjected to transverse aortic constriction (TAC) or sham operation. The TAC-operated mice were treated with the human equivalent of low-dose aspirin (10 mg·kg(-1)·d(-1)); the remaining mice received an equal amount of phosphate buffered saline with 0.65% ethanol, which was used as a vehicle. A cardiomyocyte hypertrophy model induced by angiotensin II (10 nmol·L(-1)) was treated with the human equivalent of low (10 or 100 µmol·L(-1)) and high (1000 µmol·L(-1)) aspirin concentrations in plasma. Changes in the cardiac structure and function were assessed through echocardiography and transmission electron microscopy. Gene expression was determined through RT-PCR and western blot analysis. Results indicated that aspirin treatment abrogated the increased thickness of the left ventricular anterior and posterior walls, the swelling of mitochondria, and the increased surface area in in vivo and in vitro hypertrophy models. Aspirin also normalized the upregulated hypertrophic biomarkers, ß-myosin heavy chain (ß-MHC), atrial natriuretic peptide (ANP), and b-type natriuretic peptide (BNP). Aspirin efficiently reversed the upregulation of ß-catenin and P-Akt expression and the TAC- or ANG II-induced downregulation of GSK-3ß. Therefore, low-dose aspirin possesses significant anti-hypertrophic properties at clinically relevant concentrations for anti-thrombotic therapy. The downregulation of ß-catenin and Akt may be the underlying signaling mechanism of the effects of aspirin.