HuR regulates phospholamban expression in isoproterenol-induced cardiac remodelling

RNA binding proteins as mediators of pathological cardiac remodeling

RNA binding proteins (RBPs) play a central in the post-transcriptional regulation of gene expression, which can account for up to 50% of all variations in protein expression within a cell. Following their binding to target RNAs, RBPs most typically confer changes in gene expression through modulation of alternative spicing, RNA stabilization/degradation, or ribosome loading/translation rate. All of these post-transcriptional regulatory processes have been shown to play a functional role in pathological cardiac remodeling, and a growing body of evidence is beginning to identify the mechanistic contribution of individual RBPs and their cardiac RNA targets. This review highlights the mechanisms of RBP-dependent post-transcriptional gene regulation in cardiomyocytes and fibroblasts and our current understanding of how RNA binding proteins functionally contribute to pathological cardiac remodeling.

Optimized New Shengmai Powder modulation of cAMP/Rap1A signaling pathway attenuates myocardial fibrosis in heart failure

BACKGROUND

Optimized New Shengmai Powder (ONSMP) is a traditional Chinese medicine formula with significant anti-heart failure and myocardial fibrosis effects, but the specific molecular biological mechanisms are not fully understood.

METHODS

In this study, we first used network pharmacology to analyze the ONSMP's active ingredients, core signaling pathways, and core targets. Second, calculate the affinity and binding modes of the ONSMP components to the core targets using molecular docking. Finally, the heart failure rat model was established by ligating the left anterior descending branch of the coronary artery and assessing the effect of ONSMP on myocardial fibrosis in heart failure using echocardiography, cardiac organ coefficients, heart failure markers, and pathological sections after 4 weeks of drug intervention. The cAMP level in rat myocardium was determined using Elisa, the α-SMA and FSP-1 positive expression determined by immunohistochemistry, and the protein and mRNA levels of the cAMP/Rap1A signaling pathway were detected by Western Blotting and quantitative real-time PCR, respectively.

RESULTS

The result shows that the possible mechanism of ONSMP in reducing myocardial fibrosis also includes the use of 12 active ingredients such as baicalin, vitamin D, resveratrol, tanshinone IIA, emodin, 15,16-dihydrotanshinone-i to regulate β1-AR, AC6, EPAC1, Rap1 A, STAT3, and CCND1 on the cAMP/Rap1A signaling pathway, thereby inhibiting the proliferation of cardiac fibroblasts and reduce the excessive secretion of collagen, effectively improve cardiac function and ventricular remodeling in heart failure rats.

CONCLUSION

This research shows that ONSMP can inhibit myocardial fibrosis and delay heart failure through the cAMP/Rap1A signaling pathway.

Valerenic acid attenuates pathological myocardial hypertrophy by promoting the utilization of multiple substrates in the mitochondrial energy metabolism

INTRODUCTION

Valerenic acid (VA) is a unique and biologically active component in Valeriana officinalis L., which has been reported to have a regulatory effect on the cardiovascular system. However, its therapeutic effects on pathological myocardial hypertrophy (PMH) and the underlying mechanisms are undefined.

OBJECTIVES

Our study aims to elucidate how VA improves PMH, and preliminarily discuss its mechanism.

METHODS

The efficacy of VA on PMH was confirmed by in vivo and in vitro experiments and the underlying mechanism was investigated by molecular dynamics (MD) simulations and specific siRNA interference.

RESULTS

VA enhanced cardiomyocyte fatty acid oxidation (FAO), inhibited hyper-activated glycolysis, and improved the unbalanced pyruvate-lactate axis. VA could significantly improve impaired mitochondrial function and reduce the triglyceride (TG) in the hypertrophic myocardium while reducing the lactate (LD) content. Molecular mechanistic studies showed that VA up-regulated the expression of peroxisome proliferator-activated receptor-α (PPARα) and downstream FAO-related genes including CD36, CPT1A, EHHADH, and MCAD. VA reduced the expression of ENO1 and PDK4, the key enzymes in glycolysis. Meanwhile, VA improved the pyruvate-lactate axis and promoted the aerobic oxidation of pyruvate by inhibiting LDAH and MCT4. MD simulations confirmed that VA can bind with the F273 site of PPARα, which proposes VA as a potential activator of the PPARα.

CONCLUSION

Our results demonstrated that VA might be a potent activator for the PPARα-mediated pathway. VA directly targets the PPARα and subsequently promotes energy metabolism to attenuate PMH, which can be applied as a potentially effective drug for the treatment of HF.

ZBTB20 Regulates SERCA2a Activity and Myocardial Contractility Through Phospholamban

BACKGROUND

Intracellular Ca2+ cycling determines myocardial contraction and relaxation in response to physiological demands. SERCA2a (sarcoplasmic/endoplasmic reticulum Ca2+-ATPase 2a) is responsible for the sequestration of cytosolic Ca2+ into intracellular stores during cardiac relaxation, and its activity is reversibly inhibited by PLN (phospholamban). However, the regulatory hierarchy of SERCA2a activity remains unclear.

METHODS

Cardiomyocyte-specific ZBTB20 knockout mice were generated by crossing ZBTB20flox mice with Myh6-Cre mice. Echocardiography, blood pressure measurements, Langendorff perfusion, histological analysis and immunohistochemistry, quantitative reverse transcription-PCR, Western blot analysis, electrophysiological measurements, and chromatin immunoprecipitation assay were performed to clarify the phenotype and elucidate the molecular mechanisms.

RESULTS

Specific ablation of ZBTB20 in cardiomyocyte led to a significant increase in basal myocardial contractile parameters both in vivo and in vitro, accompanied by an impairment in cardiac reserve and exercise capacity. Moreover, the cardiomyocytes lacking ZBTB20 showed an increase in sarcoplasmic reticular Ca2+ content and exhibited a remarkable enhancement in both SERCA2a activity and electrically stimulated contraction. Mechanistically, PLN expression was dramatically reduced in cardiomyocytes at the mRNA and protein levels by ZBTB20 deletion or silencing, and PLN overexpression could largely restore the basal contractility in ZBTB20-deficient cardiomyocytes.

CONCLUSIONS

These data point to ZBTB20 as a fine-tuning modulator of PLN expression and SERCA2a activity, thereby offering new perspective on the regulation of basal contractility in the mammalian heart.

Vericiguat alleviates ventricular remodeling and arrhythmias in mouse models of myocardial infarction via CaMKII signaling

AIMS

Maladaptive ventricular remodeling is a major cause of ventricular arrhythmias following myocardial infarction (MI) and adversely impacts the quality of life of affected patients. Vericiguat is a new soluble guanylate cyclase (sGC) activator with cardioprotective properties. However, its effects on MI-induced ventricular remodeling and arrhythmias are not fully comprehended; hence, our research evaluated the effect of vericiguat on mice post-MI.

MATERIALS AND METHODS

Mice were divided into four treatment groups: Sham, Sham+Veri, MI, and MI + Veri. For the MI groups and MI + Veri groups, the left anterior descending (LAD) coronary artery was occluded to induce MI. Conversely, the Sham group underwent mock surgery. Vericiguat was administered orally daily for 28 days to the Sham+Veri and MI + Veri groups. Additionally, H9c2 cells were cultured for further mechanistic studies. Assessment methods included echocardiography, pathological analysis, electrophysiological analysis, and Western blotting.

KEY FINDINGS

Vericiguat reduced cardiac dysfunction and infarct size after MI. It also mitigated MI-induced left ventricular fibrosis and cardiomyocyte apoptosis. Vericiguat normalized the expression of ion channel proteins (Kv4.3, Kv4.2, Kv2.1, Kv1.5, Kv7.1, KCNH2, Cav1.2) and the gap junction protein connexin 43, reducing the susceptibility to ventricular arrhythmia. Vericiguat significantly inhibited MI-induced calcium/calmodulin-dependent protein kinase II (CaMKII) pathway activation in mice.

SIGNIFICANCE

Vericiguat alleviated MI-induced left ventricular adverse remodeling and arrhythmias through modulation of the CamkII signaling pathway.

Molecular mechanisms mediate roflumilast protective effect against isoprenaline-induced myocardial injury

BACKGROUND

Myocardial necrosis is one of the most common cardiac and pathological diseases. Unfortunately, using the available medical treatment is not sufficient to rescue the myocardium. So that, we aimed in our model to study the possible cardioprotective effect of roflumilast (ROF) in an experimental model of induced myocardial injury using a toxic dose of isoprenaline (ISO) and detecting the role of vascular endothelial growth factor/endothelial nitric oxide synthase (VEGF/eNOS) and cyclic guanosine monophosphate/cyclic adenosine monophosphate/ sirtuin1 (cGMP/cAMP/SIRT1) signaling cascade.

MATERIALS AND METHODS

Animals were divided into five groups; control, ISO given group (150 mg/kg) i.p. on the 4th and 5th day, 3 ROF co-administered groups in different doses (0.25, 0.5, 1 mg/kg/day) for 5 days.

RESULTS

Our data revealed that ISO could induce cardiac toxicity as manifested by significant increases in troponin I, creatine kinase-MB (CK-MB), lactate dehydrogenase (LDH), malondialdehyde (MDA), tumor necrosis factor alpha (TNFα), and cleaved caspase-3 with toxic histopathological changes. Meanwhile, there were significant decreases in reduced glutathione (GSH), total antioxidant capacity (TAC), VEGF, eNOS, cGMP, cAMP and SIRT1. However, co-administration of ROF showed significant improvement and normalization of ISO induced cardiac damage.

CONCLUSION

We concluded that ROF successfully reduced ISO induced myocardial injury and this could be attributed to modulation of PDE4, VEGF/eNOS and cGMP/cAMP/SIRT1 signaling pathways with antioxidant, anti-inflammatory, and anti-apoptotic properties.

miR-455-5p promotes pathological cardiac remodeling via suppression of PRMT1-mediated Notch signaling pathway

Pathological cardiac remodeling plays an essential role in the progression of cardiovascular diseases, and numerous microRNAs have been reported to participate in pathological cardiac remodeling. However, the potential role of microRNA-455-5p (miR-455-5p) in this process remains to be elucidated. In the present study, we focused on clarifying the function and searching the direct target of miR-455-5p, as well as exploring its underlying mechanisms in pathological cardiac remodeling. We found that overexpression of miR-455-5p by transfection of miR-455-5p mimic in vitro or tail vain injection of miR-455-5p agomir in vivo provoked cardiac remodeling, whereas genetic knockdown of miR-455-5p attenuated the isoprenaline-induced cardiac remodeling. Besides, miR-455-5p directly targeted to 3'-untranslated region of protein arginine methyltransferase 1 (PRMT1) and subsequently downregulated PRMT1 level. Furthermore, we found that PRMT1 protected against cardiac hypertrophy and fibrosis in vitro. Mechanistically, miR-455-5p induced cardiac remodeling by downregulating PRMT1-induced asymmetric di-methylation on R1748, R1750, R1751 and R1752 of Notch1, resulting in suppression of recruitment of Presenilin, Notch1 cleavage, NICD releasing and Notch signaling pathway. Finally, circulating miR-455-5p was positively correlated with parameters of left ventricular wall thickening. Taken together, miR-455-5p plays a provocative role in cardiac remodeling via inactivation of the PRMT1-mediated Notch signaling pathway, suggesting miR-455-5p/PRMT1/Notch1 signaling axis as potential therapeutic targets for pathological cardiac remodeling.

PPP1R3A inhibits osteogenesis and negatively regulates intracellular calcium levels in calcific tendinopathy

Calcific tendinopathy (CT) is defined by the progressive accumulation of calcium crystals in tendonic regions that results in severe pain in patients. The etiology of CT is not fully elucidated. In this study, we elucidate the role of PPP1R3A in CT. A significant decrease in PPP1R3A expression was observed in CT patient tissues, which was further confirmed in tissues from a CT-induced rat model. Overexpression of PPP1R3A ex vivo reduced the expression of osteo/chondrogenic markers OCN and Sox9, improved tendon tissue architecture, and reduced intracellular Ca2+ levels. Overexpression of SERCA2 and knockdown of Piezo1 decreased expression of osteo/chondrogenic markers and intracellular calcium in PPP1R3A-knockdown tendon cells. Lastly, PPP1R3A expression was regulated at the posttranscriptional level by binding of HuR. Collectively, the present study indicates that PPP1R3A plays an important role in regulating calcium homeostasis in tendon cells via Piezo1/SERCA2, rendering it a promising target for therapeutic interventions of CT.

Integrative analysis of DNA methylome and transcriptome reveals epigenetic regulation of bisphenols-induced cardiomyocyte hypertrophy

Cardiac hypertrophy, a kind of cardiomyopathic abnormality, might trigger heart contractile and diastolic dysfunction, and even heart failure. Currently, bisphenols (BPs) including bisphenol A (BPA), and its alternatives bisphenol AF (BPAF), bisphenol F (BPF) and bisphenol S (BPS) are ubiquitously applied in various products and potentially possess high cardiovascular risks for humans. However, the substantial experimental evidences of BPs on heart function, and their structure-related effects on cardiomyocyte hypertrophy are still urgently needed. DNA methylation, a typical epigenetics, play key roles in BPs-induced transcription dysregulation, thereby affecting human health including cardiovascular system. Thus, in this study, we performed RNA-seq and reduced representation bisulfite sequencing (RRBS) to profile the landscapes of BPs-induced cardiotoxicity and to determine the key roles of DNA methylation in the transcription. Further, the capabilities of three BPA analogues, together with BPA, in impacting heart function and changing DNA methylation and transcription were compared. We concluded that similar to BPA, BPAF, BPF and BPS exposure deteriorated heart function in a mouse model, and induced cardiomyocyte hypertrophy in a H9c2 cell line. BPAF, BPF and BPS all played BPA-like roles in both transcriptive and methylated hierarchies. Moreover, we validated the expression levels of four cardiomyocyte hypertrophy related candidate genes, Psmc1, Piptnm2, Maz and Dusp18, which were all upregulated and with DNA hypomethylation. The findings on the induction of BPA analogues on cardiomyocyte hypertrophy and DNA methylation revealed their potential detrimental risks in heart function of humans.

Human antigen R regulates autophagic flux by stabilizing autophagy-associated mRNA in calcific aortic valve disease

AIMS

The incidence of calcific aortic valve disease (CAVD) has risen over the last decade and is expected to continue rising; however, pharmacological approaches have proven ineffective. In this study, we evaluated the role and underlying mechanisms of human antigen R (HuR)-mediated post-transcriptional regulation in CAVD.

METHODS AND RESULTS

We found that HuR was significantly upregulated in human calcified aortic valves and primary aortic valvular interstitial cells (VICs) following osteogenic stimulation. Subsequent functional studies revealed that HuR silencing ameliorated calcification both in vitro and in vivo. For the first time, we demonstrated that HuR directly interacted with the transcript of phosphatidylinositol-5-phosphate 4-kinase, type II, alpha (PIP4K2A), which mediates phosphatidylinositol signalling, facilitates autophagy, and acts as an mRNA stabilizer. HuR positively modulated PIP4K2A expression at the post-transcriptional level and consequently influenced the AKT/mTOR/ATG13 pathway to regulate autophagy and CAVD progression.

CONCLUSION

Our study provides new insights into the post-transcriptional regulatory role of HuR in modulating autophagy-positive factors to regulate the pathogenesis of CAVD. Our findings highlight the potential of HuR as an innovative therapeutic target in CAVD treatment.

Enhancement of Bottle Gourd Oil Activity via Optimized Self-Dispersing Lipid Formulations (SDLFs) to Mitigate Isoproterenol-Evoked Cardiac Toxicity in Rats via Modulating BMP, MMP2, and miRNA-21 and miRNA-23a Genes' Expression

Bottle gourd (BG) oil (family Cucurbitaceae) has several pharmacological activities including a reduction of the hazard of cardiovascular and atherosclerosis conditions. This work aimed to develop and optimize self-dispersing lipid formulations (SDLFs) of BG oil by applying a full 32 factorial design. The formulation variables (oil concentration and surfactant mixture ratio) showed an obvious impact on the characters of the prepared BG-SDLFs including droplet size (DS), polydispersity index (PDI), emulsification time (ET), and transmission percentage (Tr%). The optimum BG-SDLF composed of 30% oil and Tween 80/Cremophor® RH40 (1:1) showed good emulsification characteristics and a better drug release profile compared with BG oil. In vivo study in isoproterenol-injected rats showed that BG oil and the optimized BG-SDLF improved cardiac function, by elevating the miRNA-23a gene expression level and decreasing miRNA-21 gene expression. They also caused the inhibition of the plasma B-type natriuretic peptide (BNP), N-terminal proatrial natriuretic peptide (NT-pro-BNP), cystatin c, galectin-3, lipoprotein-associated phospholipase A2 (Lp-PLA2), matrix metallopeptidase 2 (MMP2), cardiac troponin I (cTnI), and cardiac troponin T (cTnT). Our study demonstrated that BG oil and the optimized BG-SDLF provided a cardioprotection against isoproterenol-induced cardiac toxicity with better results in groups treated with the optimized BG-SDLF.

Naringenin Attenuates Isoprenaline-Induced Cardiac Hypertrophy by Suppressing Oxidative Stress through the AMPK/NOX2/MAPK Signaling Pathway

Cardiac hypertrophy is accompanied by increased myocardial oxidative stress, and whether naringenin, a natural antioxidant, is effective in the therapy of cardiac hypertrophy remains unknown. In the present study, different dosage regimens (25, 50, and 100 mg/kg/d for three weeks) of naringenin (NAR) were orally gavaged in an isoprenaline (ISO) (7.5mg/kg)-induced cardiac hypertrophic C57BL/6J mouse model. The administration of ISO led to significant cardiac hypertrophy, which was alleviated by pretreatment with naringenin in both in vivo and in vitro experiments. Naringenin inhibited ISO-induced oxidative stress, as demonstrated by the increased SOD activity, decreased MDA level and NOX2 expression, and inhibited MAPK signaling. Meanwhile, after the pretreatment with compound C (a selective AMPK inhibitor), the anti-hypertrophic and anti-oxidative stress effects of naringenin were blocked, suggesting the protective effect of naringenin on cardiac hypertrophy. Our present study indicated that naringenin attenuated ISO-induced cardiac hypertrophy by regulating the AMPK/NOX2/MAPK signaling pathway.

Toll-like receptor-2 in cardiomyocytes and macrophages mediates isoproterenol-induced cardiac inflammation and remodeling

Heart failure (HF) is the leading cause of morbidity and mortality worldwide. Activation of the innate immune system initiates an inflammatory response during cardiac remodeling induced by isoproterenol (ISO). Here, we investigated whether Toll-like receptor-2 (TLR2) mediates ISO-induced inflammation, hypertrophy, and fibrosis. TLR2 was found to be increased in the heart tissues of mouse with HF under ISO challenge. Further, cardiomyocytes and macrophages were identified as the main cellular sources of the increased TLR2 levels in the model under ISO stimulation. The effect of TLR2 deficiency on ISO-induced cardiac remodeling was determined using TLR2 knockout mice and bone marrow transplantation models. In vitro studies involving ISO-treated cultured cardiomyocytes and macrophages showed that TLR2 knockdown significantly decreased ISO-induced cell inflammation and remodeling via MAPKs/NF-κB signaling. Mechanistically, ISO significantly increased the TLR2-MyD88 interaction in the above cells in a TLR1-dependent manner. Finally, DAMPs, such as HSP70 and fibronectin 1 (FN1), were found to be released from the cells under ISO stimulation, which further activated TLR1/2-Myd88 signaling and subsequently activated pro-inflammatory cytokine expression and cardiac remodeling. In summary, our findings suggest that TLR2 may be a target for the alleviation of chronic adrenergic stimulation-associated HF. In addition, this paper points out the possibility of TLR2 as a new target for heart failure under ISO stimulation.

SphK-produced S1P in somatic cells is indispensable for LH-EGFR signaling-induced mouse oocyte maturation

Germ cell division and differentiation require intimate contact and interaction with the surrounding somatic cells. Luteinizing hormone (LH) triggers epidermal growth factor (EGF)-like growth factors to promote oocyte maturation and developmental competence by activating EGF receptor (EGFR) in somatic cells. Here, we showed that LH-EGFR signaling-activated sphingosine kinases (SphK) in somatic cells. The activation of EGFR by EGF increased S1P and calcium levels in cumulus-oocyte complexes (COCs), and decreased the binding affinity of natriuretic peptide receptor 2 (NPR2) for natriuretic peptide type C (NPPC) to release the cGMP-mediated meiotic arrest. These functions of EGF were blocked by the SphK inhibitor SKI-II, which could be reversed by the addition of S1P. S1P also activated the Akt/mTOR cascade reaction in oocytes and promoted targeting protein for Xklp2 (TPX2) accumulation and oocyte developmental competence. Specifically depleting Sphk1/2 in somatic cells reduced S1P levels and impaired oocyte meiotic maturation and developmental competence, resulting in complete female infertility. Collectively, SphK-produced S1P in somatic cells serves as a functional transmitter of LH-EGFR signaling from somatic cells to oocytes: acting on somatic cells to induce oocyte meiotic maturation, and acting on oocytes to improve oocyte developmental competence.

SYNJ2BP Improves the Production of Lentiviral Envelope Protein by Facilitating the Formation of Mitochondrion-Associated Endoplasmic Reticulum Membrane

Equine infectious anemia virus (EIAV) and HIV are both members of the Lentivirus genus and are similar in major virological characters. EIAV endangers the horse industry. In addition, EIAV can also be used as a model for HIV research. The maturation of the lentiviral Env protein, which is necessary for viral entry, requires Env to be folded in the endoplasmic reticulum (ER). It is currently unclear how this process is regulated. Mitochondrion-associated endoplasmic reticulum membrane (MAM) is a specialized part of the close connection between the ER and mitochondria, and one of the main functions of MAM is to promote oxidative protein production in the ER. SYNJ2BP is one of the key proteins that make up the MAM, and we found that SYNJ2BP is essential for EIAV replication. We therefore constructed a SYNJ2BP knockout HEK293T cell line in which the number of MAMs is significantly reduced. Moreover, overexpression of SYNJ2BP could increase the number of MAMs. Our study demonstrates that SYNJ2BP can improve the infectivity of the EIAV virus with elevated production of the viral Env protein through increased MAM formation. Interestingly, SYNJ2BP was able to improve the production of not only EIAV Env but also HIV. Further investigation showed that MAMs can provide more ATP and calcium ions, which are essential factors for Env production, to the ER and can also reduce ER stress induced by HIV or EIAV Envs to increase the Env production level in cells. These results may help us to understand the key production mechanisms of lentiviral Env. IMPORTANCE Lentiviral Env proteins, which are rich in disulfide bonds, need to be fully folded in the ER; otherwise, misfolded Env proteins will induce ER stress and be degraded by ER-associated protein degradation (ERAD). To date, it is still unclear about Env production mechanism in the ER. MAM is the structure of closely connection between the ER and mitochondria. MAMs play important roles in the calcium steady state and oxidative stress, especially in the production of oxidative protein. For the first time, we found that SYNJ2BP can promote the production of lentiviral Env proteins by providing the ATP and calcium ions required for oxidative protein production in the ER and by reducing ER stress through facilitating formation of MAMs. These studies shed light on how MAMs improve lentiviral Env production, which will lay the foundation for the study of replication mechanisms in other lentiviruses from the perspective of the cellular organelle microenvironment.

Puerarin attenuates isoproterenol‑induced myocardial hypertrophy via inhibition of the Wnt/β‑catenin signaling pathway

Myocardial hypertrophy (MH) is an independent risk factor for cardiovascular disease, which in turn lead to arrhythmia or heart failure. Therefore, attention must be paid to formulation of therapeutic strategies for MH. Puerarin is a key bioactive ingredient isolated from Pueraria genera of plants that is beneficial for the treatment of MH. However, its molecular mechanism of action has not been fully determined. In the present study, 40 µM puerarin was demonstrated to be a safe dose for human AC16 cells using Cell Counting Kit‑8 assay. The protective effects of puerarin against MH were demonstrated in AC16 cells stimulated with isoproterenol (ISO). These effects were characterized by a significant decrease in surface area of cells (assessed using fluorescence staining) and mRNA and protein expression levels of MH‑associated biomarkers, including atrial and brain natriuretic peptide, assessed using reverse transcription‑quantitative PCR and western blotting, as well as β‑myosin heavy chain mRNA expression levels. Mechanistically, western blotting demonstrated that puerarin inhibited activation of the Wnt signaling pathway. Puerarin also significantly decreased phosphorylation of p65; this was mediated via crosstalk between the Wnt and NF‑κB signaling pathways. An inhibitor (Dickkopf‑1) and activator (IM‑12) of the Wnt signaling pathway were used to demonstrate that puerarin‑mediated effects alleviated ISO‑induced MH via the Wnt signaling pathway. The results of the present study demonstrated that puerarin pre‑treatment may be a potential therapeutic strategy for preventing ISO‑induced MH and managing MH in the future.

The RNA-binding protein HuR in human cancer: A friend or foe?

The RNA-binding proteins (RBPs) are critical trans factors that associate with specific cis elements present in mRNAs whose stability and translation are subject to regulation. The RBP Hu antigen R (HuR) is overexpressed in a wide variety of human cancers and serves as a prognostic factor of poor clinical outcome. HuR promotes tumorigenesis by interacting with a subset of oncogenic mRNAs implicated in different cancer hallmarks, and resistance to therapy. Reduction of HuR levels in cancer cells leads to tumor regression in mouse xenograft models. These findings prompt a working model whereby cancer cells use HuR, a master switch of multiple oncogenic mRNAs, to drive drug resistance and promote cell survival and metastasis, thus rendering the tumor cells with high cytoplasmic HuR more progressive and resistant to therapy. This review summarizes the roles of HuR in cancer and other diseases, therapeutic potential of HuR inhibition, and the current status of drug discovery on HuR.

Non-canonical features of microRNAs: paradigms emerging from cardiovascular disease

Research showing that microRNAs (miRNAs) are versatile regulators of gene expression has instigated tremendous interest in cardiovascular research. The overwhelming majority of studies are predicated on the dogmatic notion that miRNAs regulate the expression of specific target mRNAs by inhibiting mRNA translation or promoting mRNA decay in the RNA-induced silencing complex (RISC). These efforts mostly identified and dissected contributions of multiple regulatory networks of miRNA-target mRNAs to cardiovascular pathogenesis. However, evidence from studies in the past decade indicates that miRNAs also operate beyond this canonical paradigm, featuring non-conventional regulatory functions and cellular localizations that have a pathophysiological role in cardiovascular disease. In this Review, we highlight the functional relevance of atypical miRNA biogenesis and localization as well as RISC heterogeneity. Moreover, we delineate remarkable non-canonical examples of miRNA functionality, including direct interactions with proteins beyond the Argonaute family and their role in transcriptional regulation in the nucleus and in mitochondria. We scrutinize the relevance of non-conventional biogenesis and non-canonical functions of miRNAs in cardiovascular homeostasis and pathology, and contextualize how uncovering these non-conventional properties can expand the scope of translational research in the cardiovascular field and beyond.

An Evolutionarily Conserved AU-Rich Element in the 3' Untranslated Region of a Transcript Misannotated as a Long Noncoding RNA Regulates RNA Stability

One of the primary mechanisms of post-transcriptional gene regulation is the modulation of RNA stability. We recently discovered that LINC00675, a transcript annotated as a long noncoding RNA (lncRNA), is transcriptionally regulated by FOXA1 and encodes a highly conserved small protein that localizes to the endoplasmic reticulum, hence renamed as FORCP (FOXA1-regulated conserved small protein). Here, we show that the endogenous FORCP transcript is rapidly degraded and rendered unstable as a result of 3'UTR-mediated degradation. Surprisingly, although the FORCP transcript is a canonical nonsense-mediated decay (NMD) and microRNA (miRNA) target, we found that it is not degraded by NMD or miRNAs. Targeted deletion of an evolutionarily conserved region in the FORCP 3'UTR using CRISPR/Cas9 significantly increased the stability of the FORCP transcript. Interestingly, this region requires the presence of an immediate downstream 55-nt-long sequence for transcript stability regulation. Functionally, colorectal cancer cells lacking this conserved region expressed from the endogenous FORCP locus displayed decreased proliferation and clonogenicity. These data demonstrate that the FORCP transcript is destabilized via conserved elements within its 3'UTR and emphasize the need to interrogate the function of a given 3'UTR in its native context.

HuR-targeted agents: An insight into medicinal chemistry, biophysical, computational studies and pharmacological effects on cancer models

The Human antigen R (HuR) protein is an RNA-binding protein, ubiquitously expressed in human tissues, that orchestrates target RNA maturation and processing both in the nucleus and in the cytoplasm. A survey of known modulators of the RNA-HuR interactions is followed by a description of its structure and molecular mechanism of action - RRM domains, interactions with RNA, dimerization, binding modes with naturally occurring and synthetic HuR inhibitors. Then, the review focuses on HuR as a validated molecular target in oncology and briefly describes its role in inflammation. Namely, we show ample evidence for the involvement of HuR in the hallmarks and enabling characteristics of cancer, reporting findings from in vitro and in vivo studies; and we provide abundant experimental proofs of a beneficial role for the inhibition of HuR-mRNA interactions through silencing (CRISPR, siRNA) or pharmacological inhibition (small molecule HuR inhibitors).

O-ring-induced transverse aortic constriction (OTAC) is a new simple method to develop cardiac hypertrophy and heart failure in mice

Suture-based transverse aortic constriction (TAC) in mice is one of the most frequently used experimental models for cardiac pressure overload-induced heart failure. However, the incidence of heart failure in the conventional TAC depends on the operator's skill. To optimize and simplify this method, we proposed O-ring-induced transverse aortic constriction (OTAC) in mice. C57BL/6J mice were subjected to OTAC, in which an o-ring was applied to the transverse aorta (between the brachiocephalic artery and the left common carotid artery) and tied with a triple knot. We used different inner diameters of o-rings were 0.50 and 0.45 mm. Pressure overload by OTAC promoted left ventricular (LV) hypertrophy. OTAC also increased lung weight, indicating severe pulmonary congestion. Echocardiographic findings revealed that both OTAC groups developed LV hypertrophy within one week after the procedure and gradually reduced LV fractional shortening. In addition, significant elevations in gene expression related to heart failure, LV hypertrophy, and LV fibrosis were observed in the LV of OTAC mice. We demonstrated the OTAC method, which is a simple and effective cardiac pressure overload method in mice. This method will efficiently help us understand heart failure (HF) mechanisms with reduced LV ejection fraction (HFrEF) and cardiac hypertrophy.

Discovery of novel 4-phenylquinazoline-based BRD4 inhibitors for cardiac fibrosis

Bromodomain containing protein 4 (BRD4), as an epigenetic reader, can specifically bind to the acetyl lysine residues of histones and has emerged as an attractive therapeutic target for various diseases, including cancer, cardiac remodeling and heart failure. Herein, we described the discovery of hit 5 bearing 4-phenylquinazoline skeleton through a high-throughput virtual screen using 2,003,400 compound library (enamine). Then, structure-activity relationship (SAR) study was performed and 47 new 4-phenylquinazoline derivatives toward BRD4 were further designed, synthesized and evaluated, using HTRF assay set up in our lab. Eventually, we identified compound C-34, which possessed better pharmacokinetic and physicochemical properties as well as lower cytotoxicity against NRCF and NRCM cells, compared to the positive control JQ1. Using computer-based molecular docking and cellular thermal shift assay, we further verified that C-34 could target BRD4 at molecular and cellular levels. Furthermore, treatment with C-34 effectively alleviated fibroblast activation in vitro and cardiac fibrosis in vivo, which was correlated with the decreased expression of BRD4 downstream target c-MYC as well as the depressed TGF-β1/Smad2/3 signaling pathway. Taken together, our findings indicate that novel BRD4 inhibitor C-34 tethering a 4-phenylquinazoline scaffold can serve as a lead compound for further development to treat fibrotic cardiovascular disease.

MiRNA-339-5p promotes isoproterenol-induced cardiomyocyte hypertrophy by targeting VCP to activate the mTOR signaling

MicroRNAs (miRNAs) regulate multiple biological processes and participate in various cardiovascular diseases. This study aims to investigate the role of miR-339-5p in cardiomyocyte hypertrophy and the involved mechanism. Neonatal rat cardiomyocytes (NRCMs) were cultured and stimulated with isoproterenol (ISO). The hypertrophic responses were monitored by measuring the cell surface area and expression of hypertrophic markers including β-myosin heavy chain (β-MHC) and atrial natriuretic factor (ANF). Bioinformatic prediction tools and dual-luciferase reporter assay were performed to identify the target gene of miR-339-5p. Quantitative real-time polymerase chain reaction and western blot analysis were used to determine the levels of miR-339-5p and its downstream effectors. Our data showed that miR-339-5p was upregulated during cardiomyocyte hypertrophy triggered by ISO. MiR-339-5p overexpression resulted in enlargement of cell size and increased the levels of hypertrophic markers. In contrast, inhibition of miR-339-5p significantly attenuated ISO-induced hypertrophic responses of NRCMs. Valosin-containing protein (VCP), a suppressor of cardiac hypertrophy via inhibiting mechanistic target of rapamycin (mTOR) signaling, was validated as a target of miR-339-5p. MiR-339-5p suppressed VCP protein expression, leading to elevated phosphorylation of mTOR and ribosomal protein S6 kinase (S6K). VCP depletion activated the mTOR/S6K cascade and could compromise the anti-hypertrophic effects of miR-339-5p inhibitor. Additionally, the hypertrophic responses caused by miR-339-5p was alleviated in the presence of mTOR inhibitor rapamycin. In conclusion, our research revealed that miR-339-5p promoted ISO-induced cardiomyocyte hypertrophy by targeting VCP to activate the mTOR signaling, suggesting a promising therapeutic intervention by interfering miR-339-5p.

DNMT1-Induced miR-152-3p Suppression Facilitates Cardiac Fibroblast Activation in Cardiac Fibrosis

Novel insights into epigenetic control of cardiac fibrosis are now emerging. Cardiac fibroblasts (CFs) activation into myofibroblasts and the production of extracellular matrix (ECM) is the key to cardiac fibrosis development, but the specific mechanism is not fully understood. In the present study, we found that DNMT1 hypermethylation reduces the expression of microRNA-152-3p (miR-152-3p) and promotes Wnt1/β-catenin signaling pathway leading to CFs proliferation and activation. Cardiac fibrosis was produced by ISO, and the ISO was carried out according to the method described. CFs were harvested and cultured from SD neonatal rats and stimulated with TGF-β1. Importantly, DNMT1 resulted in the inhibition of miR-152-3p in activated CFs and both DNMT1 and miR-152-3p altered Wnt/β-catenin downstream protein levels. Over expression of DNMT1 and miR-152-3p inhibitors promotes proliferation of activating CFs. In addition, decreased methylation levels and over expression of miR-152-3p inhibited CFs proliferation. We determined that DNMT1 can methylate to miR-152-3p and demonstrated that expression of miR-152-3p inhibits CFs proliferation by inhibiting the Wnt1/β-catenin pathway. Our results stand out together DNMT1 methylation regulates miR-152-3p to slow the progression of cardiac fibrosis by inhibiting the Wnt1/β-catenin pathway.

Role of Circular RNAs in Cardiovascular Disease

Circular RNAs (circRNAs) have recently been identified as a new class of long noncoding RNAs with gene regulatory roles. These covalently closed transcripts are generated when the pre-mRNA splicing machinery back splices to join a downstream 5' splice site to an upstream 3' splice site. CircRNAs are naturally resistant to degradation by exonucleases and have long half-lives compared with their linear counterpart that potentially could serve as biomarkers for disease. Recent evidence highlights that circRNAs may play an essential role in cardiovascular injury and repair. However, our knowledge of circRNA is still in its infancy with limited direct evidence to suggest that circRNA may play critical roles in the mechanism and treatment of cardiac dysfunction. In this review, we focus on our current understanding of circRNA in the cardiovascular system.

Circular RNA in cardiovascular disease: Expression, mechanisms and clinical prospects

Circular RNAs (circRNAs) are a group of covalently closed, endogenous, non‐coding RNAs, which exist widely in human tissues including the heart. Increasing evidence has shown that cardiac circRNAs play crucial regulatory roles in cardiovascular diseases (CVDs). In this review, we aimed to provide a systemic understanding of circRNAs with a special emphasis on the cardiovascular system. We have summarized the current research on the classification, biogenesis and properties of circRNAs as well as their participation in the pathogenesis of CVDs. CircRNAs are conserved, stable and have specific spatiotemporal expression; thus, they have been accepted as a potential diagnostic marker or an incremental prognostic biomarker for CVDs.

Selective targeting of ubiquitination and degradation of PARP1 by E3 ubiquitin ligase WWP2 regulates isoproterenol-induced cardiac remodeling

The elevated expression of poly(ADP-ribose) polymerase-1 (PARP1) and increased PARP1 activity, namely, poly(ADP-ribosyl)ation (PARylation), have been observed in cardiac remodeling, leading to extreme energy consumption and myocardial damage. However, the mechanisms underlying the regulation of PARP1 require further study. WWP2, a HECT-type E3 ubiquitin ligase, is highly expressed in the heart, but its function there is largely unknown. Here, we clarified the role of WWP2 in the regulation of PARP1 and the impact of this regulatory process on cardiac remodeling. We determined that the knockout of WWP2 specifically in myocardium decreased the level of PARP1 ubiquitination and increased the effects of isoproterenol (ISO)-induced PARP1 and PARylation, in turn aggravating ISO-induced myocardial hypertrophy, heart failure, and myocardial fibrosis. Similar findings were obtained in a model of ISO-induced H9c2 cells with WWP2 knockdown, while the reexpression of WWP2 significantly increased PARP1 ubiquitination and decreased PAPR1 and PARylation levels. Mechanistically, coimmunoprecipitation results identified that WWP2 is a novel interacting protein of PARP1 and mainly interacts with its BRCT domain, thus mediating the degradation of PARP1 through the ubiquitin-proteasome system. In addition, lysine 418 (K418) and lysine 249 (K249) were shown to be of critical importance in regulating PARP1 ubiquitination and degradation by WWP2. These findings reveal a novel WWP2-PARP1 signal transduction pathway involved in controlling cardiac remodeling and may provide a basis for exploring new strategies for treating heart disorders related to cardiac remodeling.