Promotes Cardiomyocyte Hypertrophy Research Articles

YAP1-mediated dysregulation of ACE-ACE2 activity augments cardiac fibrosis upon induction of hyperglycemic stress

BackgroundDiabetic stress acts on the cardiac tissue to induce cardiac hypertrophy and fibrosis. Diabetes induced activated renin angiotensin system (RAS) has been reported to play a critical role in mediating cardiac hypertrophy and fibrosis. Angiotensin converting enzyme (ACE) in producing Angiotensin-II, promotes cardiomyocyte hypertrophy and fibrotic damage. ACE2, a recently discovered molecule structurally homologous to ACE, has been reported to be beneficial in reducing the effect of RAS driven pathologies. MethodsIn vivo diabetic mouse model was used and co-labelling immunostaining assay have been performed to analyse the fibrotic remodeling and involvement of associated target signaling molecules in mouse heart tissue. For in vitro analyses, qPCR and western blot experiments were performed in different groups for RNA and protein expression analyses. ResultsFibrosis markers were observed to be upregulated in the diabetic mouse heart tissue as well as in high glucose treated fibroblast and cardiomyocyte cells. Hyperglycemia induced overexpression of YAP1 leads to increased expression of β-catenin (CTNNB1) and ACE with downregulated ACE2 expression. The differential expression of ACE/ACE2 promotes TGFB1-SMAD2/3 pathway in the hyperglycemic cardiomyocyte and fibroblast resulting in increased cardiac fibrotic remodeling. ConclusionIn the following study, we have reported YAP1 modulates the RAS signaling pathway by inducing ACE and inhibiting ACE2 activity to augment cardiomyocyte hypertrophy and fibrosis in hyperglycemic condition. Furthermore, we have shown that hyperglycemia induced dysregulation of ACE-ACE2 activity by YAP1 promotes cardiac fibrosis through β-catenin/TGFB1 dependent pathway.

Morphological aspects of the heart of young rats subjected to high and medium intensity progressive resistance physical exercise protocols

Morphological aspects of the heart of young rats subjected to high and medium intensity progressive resistance physical exercise protocols

Down-regulation of the mitochondrial fusion protein Opa1/Mfn2 promotes cardiomyocyte hypertrophy in Su5416/hypoxia-induced pulmonary hypertension rats

BackgroundMaladaptive right ventricular (RV) remodeling is the most important pathological feature of pulmonary hypertension (PH), involving processes such as myocardial hypertrophy and fibrosis. A growing number of studies have shown that mitochondria-associated endoplasmic reticulum membranes (MAMs) are involved in various physiological and pathological processes, such as calcium homeostasis, lipid metabolism, inflammatory response, mitochondrial dynamics, and autophagy/mitophagy. The abnormal expression of MAMs-related factors is closely related to the occurrence and development of heart-related diseases. However, the role of MAM-related factors in the maladaptive RV remodeling of PH rats remains unclear. Methods and resultsWe first obtained the transcriptome data of RV tissues from PH rats induced by Su5416 combined with hypoxia treatment (SuHx) from the Gene Expression Omnibus (GEO) database. The results showed that two MAMs-related genes (Opa1 and Mfn2) were significantly down-regulated in RV tissues of SuHx rats, accompanied by significant up-regulation of cardiac hypertrophy-related genes (such as Nppb and Myh7). Subsequently, using the SuHx-induced PH rat model, we found that the downregulation of mitochondrial fusion proteins Opa1 and Mfn2 may be involved in maladaptive RV remodeling by accelerating mitochondrial dysfunction. Finally, at the cellular level, we found that overexpression of Opa1 and Mfn2 could inhibit hypoxia-induced mitochondrial fission and reduce ROS production in H9c2 cardiomyocytes, thereby retarded the progression of cardiomyocyte hypertrophy. ConclusionsThe down-regulation of mitochondrial fusion protein Opa1/Mfn2 can accelerate cardiomyocyte hypertrophy and then participate in maladaptive RV remodeling in SuHx-induced PH rats, which may be potential targets for preventing maladaptive RV remodeling.

Abstract P1173: Deciphering CITED4-dependent Signaling In The Heart Through Nascent Proteomics And Secretomics

Objective: Neuregulin-1 (Nrg1) promotes cardiomyocyte hypertrophy, survival, and cell cycle activity through ErbB signaling. It is investigated in clinical trials as a cardioprotective agent; however, its therapeutic use might be limited due to its pro-neoplastic potential for non-cardiomyocytes that makes targeted approaches necessary. High-throughput screening of hypertrophic agonists found that Nrg1 induces CITED4 (C4) expression. C4 is also upregulated in both physiological and pathological cardiac growth and necessary to prevent adverse remodeling in vivo. However, how C4 regulates Nrg1-signaling in the heart is yet unknown. Methods: We combined pulsed-SILAC labeling, click-chemistry and mass spectrometry that allows to capture immediate changes in the proteome and secretome after Nrg1 (12h and 24h) stimulation in siRNA-mediated C4-knockdown (C4KD) and control (ctr) NRVM and complemented this with established cell- and molecular biology techniques to validate and investigate cellular function and molecular signaling. Results: We confirmed dose-dependent C4 mRNA upregulation in response to Nrg1 stimulation in NRVM. Nrg1 downstream signaling through AKT was hindered in C4KD. Computational analysis comparing the nascent proteome after Nrg1 stimulation in C4KD and ctr NRVM revealed that C4 significantly regulates proteins responsible for translation, RNA processing and energy derivation. Consistent with previously observed development of cardiac fibrosis in C4 knockout mice in vivo , we found significant upregulation of TGFb2 in C4KD NRVM. We next confirmed the upregulation of TGFb2 and its downstream effectors in C4KD and ctr, while adenoviral overexpression of C4 led to reduced TGFb2 expression. Additionally, we found TGFb2 secretion increased from C4KD NRVM with Nrg1 stimulation in the nascent secretome. Conditioned media from C4KD NRVM led to an increased pro-fibrotic response in cardiac fibroblasts. In conclusion, nascent proteomics and secretomics help to elucidate C4-dependent Nrg1-signaling, which may be an important contribution toward our goal to identify targetable cardioprotective pathways in the heart.

Myristate induces mitochondrial fragmentation and cardiomyocyte hypertrophy through mitochondrial E3 ubiquitin ligase MUL1.

Introduction: Cardiovascular diseases, especially metabolic-related disorders, are progressively growing worldwide due to high-fat-containing foods, which promote a deleterious response at the cellular level, termed lipotoxicity, or lipotoxic stress. At the cardiac level, saturated fatty acids have been directly associated with cardiomyocyte lipotoxicity through various pathological mechanisms involving mitochondrial dysfunction, oxidative stress, and ceramide production, among others. However, integrative regulators connecting saturated fatty acid-derived lipotoxic stress to mitochondrial and cardiomyocyte dysfunction remain elusive. Methods: Here, we worked with a cardiomyocyte lipotoxicity model, which uses the saturated fatty acid myristate, which promotes cardiomyocyte hypertrophy and insulin desensitization. Results: Using this model, we detected an increase in the mitochondrial E3 ubiquitin ligase, MUL1, a mitochondrial protein involved in the regulation of growth factor signaling, cell death, and, notably, mitochondrial dynamics. In this context, myristate increased MUL1 levels and induced mitochondrial fragmentation, associated with the decrease of the mitochondrial fusion protein MFN2, and with the increase of the mitochondrial fission protein DRP1, two targets of MUL1. Silencing of MUL1 prevented myristate-induced mitochondrial fragmentation and cardiomyocyte hypertrophy. Discussion: These data establish a novel connection between cardiomyocytes and lipotoxic stress, characterized by hypertrophy and fragmentation of the mitochondrial network, and an increase of the mitochondrial E3 ubiquitin ligase MUL1.

4'‑O‑methylbavachalcone inhibits succinate induced cardiomyocyte hypertrophy via the NFATc4 pathway.

Pathological cardiac hypertrophy is an independent risk factor for complications such as arrhythmia, myocardial infarction, sudden mortality and heart failure. Succinate, an intermediate product of the Krebs cycle, is released into the bloodstream by cells; its levels increase with exacerbations of hypertension, myocardial and other tissue damage and metabolic disease. Succinate may also be involved in several metabolic pathways and mediates numerous pathological effects through its receptor, succinate receptor 1 (SUCNR1; previously known as GPR91). Succinate-induced activation of SUCNR1 has been reported to be related to cardiac hypertrophy, making SUCNR1 a potential target for treating cardiac hypertrophy. Traditional Chinese medicine (TCM) and its active ingredients have served important roles in improving cardiac functions and treating heart failure. The present study investigated whether 4'-O-methylbavachadone (MeBavaC), an active ingredient of the herbal remedy Fructus Psoraleae, which is often used in TCM and has protective effect on myocardial injury and hypertrophy induced by adriamycin, ischemia-reperfusion and sepsis, could ameliorate succinate-induced cardiomyocyte hypertrophy by inhibiting the NFATc4 pathway. Using immunofluorescence staining, reverse transcription-quantitative PCR, western blotting and molecular docking analysis, it was determined that succinate activated the calcineurin/NFATc4 and ERK1/2 pathways to promote cardiomyocyte hypertrophy. MeBavaC inhibited cardiomyocyte hypertrophy, nuclear translocation of NFATc4 and ERK1/2 signaling activation in succinate-induced cardiomyocytes. Molecular docking analysis revealed that MeBavaC interacts with SUCNR1 to form a relatively stable binding and inhibits the succinate-SUCNR1 interaction. The results demonstrated that MeBavaC suppressed cardiomyocyte hypertrophy by blocking SUCNR1 receptor activity and inhibiting NFATc4 and ERK1/2 signaling, which will contribute to the preclinical development of this compound.

Cardiomyocyte BRAF is a key signalling intermediate in cardiac hypertrophy in mice.

Cardiac hypertrophy is necessary for the heart to accommodate an increase in workload. Physiological, compensated hypertrophy (e.g. with exercise) is reversible and largely due to cardiomyocyte hypertrophy. Pathological hypertrophy (e.g. with hypertension) is associated with additional features including increased fibrosis and can lead to heart failure. RAF kinases (ARAF/BRAF/RAF1) integrate signals into the extracellular signal-regulated kinase 1/2 cascade, a pathway implicated in cardiac hypertrophy, and activation of BRAF in cardiomyocytes promotes compensated hypertrophy. Here, we used mice with tamoxifen-inducible cardiomyocyte-specific BRAF knockout (CM-BRAFKO) to assess the role of BRAF in hypertension-associated cardiac hypertrophy induced by angiotensin II (AngII; 0.8 mg/kg/d, 7 d) and physiological hypertrophy induced by phenylephrine (40 mg/kg/d, 7 d). Cardiac dimensions/functions were measured by echocardiography with histological assessment of cellular changes. AngII promoted cardiomyocyte hypertrophy and increased fibrosis within the myocardium (interstitial) and around the arterioles (perivascular) in male mice; cardiomyocyte hypertrophy and interstitial (but not perivascular) fibrosis were inhibited in mice with CM-BRAFKO. Phenylephrine had a limited effect on fibrosis but promoted cardiomyocyte hypertrophy and increased contractility in male mice; cardiomyocyte hypertrophy was unaffected in mice with CM-BRAFKO, but the increase in contractility was suppressed and fibrosis increased. Phenylephrine induced a modest hypertrophic response in female mice and, in contrast with the males, tamoxifen-induced loss of cardiomyocyte BRAF reduced cardiomyocyte size, had no effect on fibrosis and increased contractility. The data identify BRAF as a key signalling intermediate in both physiological and pathological hypertrophy in male mice, and highlight the need for independent assessment of gene function in females.

Chronic intermittent hypoxia accelerates cardiac dysfunction and cardiac remodeling during cardiac pressure overload in mice and can be alleviated by PHD3 overexpression.

Obstructive sleep apnea (OSA) accelerates the progression of chronic heart failure (CHF). OSA is characterized by chronic intermittent hypoxia (CIH), and CIH exposure accelerates cardiac systolic dysfunction and cardiac remodeling in a cardiac afterload stress mouse model. Mechanistic experiments showed that long-term CIH exposure activated hypoxia-inducible factor 1α (HIF-1α) expression in the mouse heart and upregulated miR-29c expression and that both HIF-1α and miR-29c simultaneously inhibited sarco-/endoplasmic reticulum calcium ATPase 2a (SERCA2a) expression in the mouse heart. Cardiac HIF-1α activation promoted cardiomyocyte hypertrophy. SERCA2a expression was suppressed in mouse heart in middle- and late-stage cardiac afterload stress, and CIH exposure further downregulated SERCA2a expression and accelerated cardiac systolic dysfunction. Prolyl hydroxylases (PHDs) are physiological inhibitors of HIF-1α, and PHD3 is most highly expressed in the heart. Overexpression of PHD3 inhibited CIH-induced HIF-1α activation in the mouse heart while decreasing miR-29c expression, stabilizing the level of SERCA2a. Although PHD3 overexpression did not reduce mortality in mice, it alleviated cardiac systolic dysfunction and cardiac remodeling induced by CIH exposure.

MiR-212 Promotes Cardiomyocyte Hypertrophy through Regulating Transcription Factor 7 Like 2.

To explore the role and possible mechanism of miRNA-212 in heart failure (HF). The rat model of abdominal aortic constriction was constructed, the changes of myocardial morphology were observed by hematoxylin-eosin (HE) staining, and the hypertrophy-related marker molecules were detected by quantitative real-time polymerase chain reaction (qRT-PCR). At the cellular level, phenylephrine and angiotensin II were added to induce cardiomyocyte hypertrophy. The overexpression of miR-212 adenovirus was constructed, and the expression of miR-212 was overexpressed, and its effect on cardiac hypertrophy (CH) was detected by immunofluorescence and qRT-PCR. Then, the mechanism of miR-212 regulating CH was verified by website prediction, luciferase reporter gene assay, qRT-PCR, and western blotting assay. In the successfully constructed rat model of abdominal aortic constriction and cardiomyocyte hypertrophy, ANP and myh7 were dramatically increased, myh6 expression was decreased, and miRNA-212 expression was increased. Overexpression of miRNA-212 in cardiomyocytes can promote cardiomyocyte hypertrophy, while knocking down miR-212 in cardiomyocytes can partially reverse cell hypertrophy. In addition, miR-212 targets TCF7L2 and inhibits the expression of this gene. miRNA-212 targets TCF7L2 and inhibits the expression of this gene, possibly through this pathway to promote cardiomyocyte hypertrophy.

Kallikrein-related peptidase-8 (KLK8) aggravated hypoxia-induced right ventricular hypertrophy by targeting P38 MAPK/P53 signaling pathway

Right ventricular (RV) hypertrophy and further heart failure are major co-morbidities, resulting in the premature death of patients with hypoxic pulmonary hypertension (HPH). The regulatory effects of kallikrein-related peptidase (KLK) family members on cardiac function have been extensively studied. However, to the best of the authors’ knowledge, the regulatory effects of KLK8 on RV hypertrophy caused by HPH have yet to be reported. The aim of the present study was to assess KLK8 expression in the RV tissue of HPH-modeled rats, and to further explore the effects and underlying mechanism of KLK8 in regulating the hypertrophy of hypoxia-induced H9c2 cardiomyocytes. In HPH model rats, increases in the right ventricle hypertrophy index, the right ventricular systolic pressure, cardiac output, as well as pulmonary artery wall thickness were observed. Western blot analysis revealed that KLK8 expression and MAPK/p53 signaling activity were enhanced in the RVs of rats in an RV HPH rat model. In hypoxia-induced H9c2 cardiomyocytes, KLK8 overexpression promoted cardiomyocyte hypertrophy, whereas KLK8 silencing showed the opposite results. KLK8 overexpression increased the expression levels of ventricular hypertrophy markers, including atrial natriuretic peptide, brain natriuretic peptide and myosin heavy chain 7, which were blocked upon addition of the p38 MAPK inhibitor, SB202190. Conversely, KLK8 silencing caused a decrease in the expression levels of the ventricular hypertrophy markers, which were further reduced via inhibition of the p38 MAPK/p53 signaling pathway. Taken together, the results of the present study have shown that KLK8 may subtly regulate RV hypertrophy, and therefore KLK8 may be a promising therapeutic target for treating HPH-induced RV hypertrophy.

Cardiomyocyte BRAF and type 1 RAF inhibitors promote cardiomyocyte and cardiac hypertrophy in mice in vivo.

The extracellular signal-regulated kinase 1/2 (ERK1/2) cascade promotes cardiomyocyte hypertrophy and is cardioprotective, with the three RAF kinases forming a node for signal integration. Our aims were to determine if BRAF is relevant for human heart failure, whether BRAF promotes cardiomyocyte hypertrophy, and if Type 1 RAF inhibitors developed for cancer (that paradoxically activate ERK1/2 at low concentrations: the ‘RAF paradox') may have the same effect. BRAF was up-regulated in heart samples from patients with heart failure compared with normal controls. We assessed the effects of activated BRAF in the heart using mice with tamoxifen-activated Cre for cardiomyocyte-specific knock-in of the activating V600E mutation into the endogenous gene. We used echocardiography to measure cardiac dimensions/function. Cardiomyocyte BRAFV600E induced cardiac hypertrophy within 10 d, resulting in increased ejection fraction and fractional shortening over 6 weeks. This was associated with increased cardiomyocyte size without significant fibrosis, consistent with compensated hypertrophy. The experimental Type 1 RAF inhibitor, SB590885, and/or encorafenib (a RAF inhibitor used clinically) increased ERK1/2 phosphorylation in cardiomyocytes, and promoted hypertrophy, consistent with a ‘RAF paradox' effect. Both promoted cardiac hypertrophy in mouse hearts in vivo, with increased cardiomyocyte size and no overt fibrosis. In conclusion, BRAF potentially plays an important role in human failing hearts, activation of BRAF is sufficient to induce hypertrophy, and Type 1 RAF inhibitors promote hypertrophy via the ‘RAF paradox'. Cardiac hypertrophy resulting from these interventions was not associated with pathological features, suggesting that Type 1 RAF inhibitors may be useful to boost cardiomyocyte function.

Free fatty acid receptor 2 promotes cardiomyocyte hypertrophy by activating STAT3 and GATA4

Free fatty acids (FFAs) play important roles in cardiovascular disease. Studies have shown that it is an important way for FAs to exert biological effects through their own receptors besides directly participating biochemical reaction in body. Free fatty acid receptor 2 (FFA2) can be activated by short-chain FAs and is involved in inflammatory reactions and lipid accumulation. Since the known pathological changes caused by FFA2 are also implicated in cardiac hypertrophy, we hypothesized that FFA2 might be pathogenic in cardiac hypertrophy. This paper showed that FFA2 expression significantly increased in cardiac hypertrophy in vivo and in vitro. FFA2 agonist 4-CMTB or TUG-1375 promoted the expression of the hypertrophy markers ANF and BNP and increased cell surface area in vitro, which was further strengthened by FFA2 overexpression, suggesting that FFA2 might contribute to cardiomyocyte hypertrophy. Furthermore, 4-CMTB treatment or FFA2 overexpression combined with 4-CMTB treatment elevated the phosphorylation and transcriptional activity of GATA4 and STAT3, which were inhibited by an ERK1/2 inhibitor, and GATA4 and STAT3 knockdown inhibited the elevation of hypertrophy biomarkers in cardiomyocytes treated with 4-CMTB. Taken together, these data indicate that FFA2 can enhance cardiomyocyte hypertrophy by activating STAT3 and GATA4 via ERK1/2, providing a potential new target for therapy.

KLK11 promotes the activation of mTOR and protein synthesis to facilitate cardiac hypertrophy

BackgroundCardiovascular diseases have become the leading cause of death worldwide, and cardiac hypertrophy is the core mechanism underlying cardiac defect and heart failure. However, the underlying mechanisms of cardiac hypertrophy are not fully understood. Here we investigated the roles of Kallikrein 11 (KLK11) in cardiac hypertrophy.MethodsHuman and mouse hypertrophic heart tissues were used to determine the expression of KLK11 with quantitative real-time PCR and western blot. Mouse cardiac hypertrophy was induced by transverse aortic constriction (TAC), and cardiomyocyte hypertrophy was induced by angiotensin II. Cardiac function was analyzed by echocardiography. The signaling pathway was analyzed by western blot. Protein synthesis was monitored by the incorporation of [3H]-leucine. Gene expression was analyzed by quantitative real-time PCR.ResultsThe mRNA and protein levels of KLK11 were upregulated in human hypertrophic hearts. We also induced cardiac hypertrophy in mice and observed the upregulation of KLK11 in hypertrophic hearts. Our in vitro experiments demonstrated that KLK11 overexpression promoted whereas KLK11 knockdown repressed cardiomyocytes hypertrophy induced by angiotensin II, as evidenced by cardiomyocyte size and the expression of hypertrophy-related fetal genes. Besides, we knocked down KLK11 expression in mouse hearts with adeno-associated virus 9. Knockdown of KLK11 in mouse hearts inhibited TAC-induced decline in fraction shortening and ejection fraction, reduced the increase in heart weight, cardiomyocyte size, and expression of hypertrophic fetal genes. We also observed that KLK11 promoted protein synthesis, the key feature of cardiomyocyte hypertrophy, by regulating the pivotal machines S6K1 and 4EBP1. Mechanism study demonstrated that KLK11 promoted the activation of AKT-mTOR signaling to promote S6K1 and 4EBP1 pathway and protein synthesis. Repression of mTOR with rapamycin blocked the effects of KLK11 on S6K1 and 4EBP1 as well as protein synthesis. Besides, rapamycin treatment blocked the roles of KLK11 in the regulation of cardiomyocyte hypertrophy.ConclusionsOur findings demonstrated that KLK11 promoted cardiomyocyte hypertrophy by activating AKT-mTOR signaling to promote protein synthesis.

RETRACTED ARTICLE: Indoleamine 2,3-Dioxygenase 1 (IDO1) Promotes Cardiac Hypertrophy via a PI3K-AKT-mTOR-Dependent Mechanism

Indoleamine 2,3-dioxygenase 1 (IDO1) is an enzyme for tryptophan metabolism, involved in immune cell differentiation/maturation and cancer biology. IDO1 is also expressed in cardiomyocytes, but its roles in the cardiovascular system are not fully understood. Here, we reported the functions of IDO1 during cardiac hypertrophy. Quantitative real-time PCR and Western blot experiments demonstrated the upregulation of IDO1 mRNA and protein levels in human and hypertrophic mouse hearts, as well as in angiotensin II (Ang II)-induced hypertrophic rat cardiomyocytes. IDO1 activity and metabolite product kynurenine were upregulated in rodent hypertrophic hearts and cardiomyocytes. Inhibition of IDO1 activity with PF-06840003 reduced Ang II-induced cardiac hypertrophy and rescued cardiac function in mice. siRNA-mediated knockdown of Ido1 repressed Ang II-induced growth in cardiomyocyte size and overexpression of hypertrophy-associated genes atrial natriuretic peptide (Anp or Nppa), brain natriuretic peptide (Bnp or Nppb), β-myosin heavy chain (β-Mhc or Myh7). By contrast, adenovirus-mediated rat Ido1 overexpression in cardiomyocytes promoted hypertrophic growth induced by Ang II. Mechanism analysis showed that IDO1 overexpression was associated with PI3K-AKT-mTOR signaling to activate the ribosomal protein S6 kinase 1 (S6K1), which promoted protein synthesis in Ang II-induced hypertrophy of rat cardiomyocytes. Finally, we provided evidence that inhibition of PI3K with pictilisib, AKT with perifosine, or mTOR with rapamycin, blocked the effects of IDO1 on protein synthesis and cardiomyocyte hypertrophy in Ang II-treated cells. Collectively, our findings identify that IDO1 promotes cardiomyocyte hypertrophy partially via PI3K-AKT-mTOR-S6K1 signaling.

MicroRNA-21-containing microvesicles from tubular epithelial cells promote cardiomyocyte hypertrophy

Background Cardiomyocyte hypertrophy has been reported as one of the important mechanisms for cardiovascular disease (CVD) in patients with chronic kidney disease (CKD). MiroRNA-21(miR-21) was determined to play an important role in myocardial hypertrophy. However, the role of microvesicles (MVs) containing miR-21 in CKD-related cardiomyocyte hypertrophy remains largely unexplored. Methods Renal tubular epithelial cells were stimulated by transforming growth factor (TGF-β1), and the conditioned medium was extracted by differential centrifugation. Renal tubular epithelial cells were labeled with Dil-C18 dye and the recipient cardiomyocytes were observed by fluorescence microscope. MiR-21 level in MVs was detected by qRT-PCR, and the length and diameter of cardiomyocytes were measured by microscope. BCA protein kit and ANP kit were used to detect the content of cell protein and the level of ANP. MiR-21 inhibitor was transfected into cardiomyocytes to observe the effect of miR-21 on myocardial hypertrophy. Results TGF-β1 could induce donor renal tubular epithelial cells to produce MVs and delivered into cardiomyocytes, followed by the diameter, protein concentration and ANP content of cardiomyocytes significantly increased. Meanwhile, MiR-21 levels were markedly increased in MVs isolated from donor renal tubular epithelial cells and recipient cardiomyocytes. Pre-transfection of miR-21 inhibitors could inhibit MV-induced cardiomyocyte hypertrophy. Conclusion Tubular cells could secrete miR-21 by MVs and deliver it into recipient cardiomyocytes to induce cardiomyocyte hypertrophy. It might shed a new light on the mechanism and treatment of CKD-related cardiac dysfunction.

The protective effects of the miR-129-5p/keap-1/Nrf2 axis on Ang II-induced cardiomyocyte hypertrophy.

BackgroundCardiac hypertrophy is a common pathological process in many cardiac diseases, and persistent cardiac hypertrophy is the main cause of heart failure and sudden cardiogenic death. Thus, it is essential to elucidate the mechanism of cardiac hypertrophy to ensure better prevention and treatment.MethodsThe Human cardiac myocytes (HCMs) were incubated with 100 nmol/L Ang II (Sigma) for 48 hours to induce the in vitro cardiomyocyte hypertrophy model. The [(3H])-leucine incorporation assay was used to evaluate cardiomyocytes hypertrophy. The activities of oxidative stress related enzymes superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA) and nitric oxide (NO) were detected using corresponding detection kits following standard protocol. Targeting relationship was verified through Bioinformatics analysis and luciferase reporter gene assay. The morphological change of cardiomyocyte was observed through immunofluorescence staining. Expressions of message ribonucleic acid (mRNA) and proteins were detected by quantitative real-time polymerase chain reaction and western blot, respectively.ResultsIn our study, the suppressed expression of micro ribonucleic acid (miRNA)-129-5p and the elevated expression of kelch-like ECH-associated protein 1 (keap-1) were found in the angiotensin II (Ang II)-induced cardiomyocyte hypertrophy model. MiR-129-5p effectively mimics suppressed Ang II-induced hypertrophic responses and oxidative stress. The results also showed that keap-1 was a target of miR-129-5p, and that the miR-129-5p inhibitor promoted cardiomyocyte hypertrophy and oxidative stress by elevating keap-1. Additionally, small interfering RNA (siRNA)-keap-1 activated the nuclear factor erythroid2-related factor 2 (Nrf2) pathway, while the miR-129-5p inhibitor inactivated the Nrf2 pathway by further elevating keap-1. The addition of the Nrf2 pathway activator NK-252 largely weakened the promoting effects of the miR-129-5p inhibitor on the progression of cardiomyocyte hypertrophy by suppressing oxidative stress.ConclusionsIn general, the results indicate that the overexpression of miRNA-129-5p protects against cardiomyocyte hypertrophy by targeting keap-1 via the Nrf2 pathway.

PRMT5 Prevents Cardiomyocyte Hypertrophy via Symmetric Dimethylating HoxA9 and Repressing HoxA9 Expression.

The present study reveals a link between protein arginine methyltransferase 5 (PRMT5) and Homebox A9 (HoxA9) in the regulation of cardiomyocyte hypertrophy. In cardiomyocyte hypertrophy induced by β-adrenergic receptor agonist isoprenaline (ISO), PRMT5 expression was decreased while HoxA9 was upregulated. Silencing of PRMT5 or inhibition of PRMT5 by its pharmacological inhibitor EPZ augmented the expressions of cardiomyocyte hypertrophic genes brain natriuretic peptide (BNP) and β-Myosin Heavy Chain (β-MHC), whereas overexpression of PRMT5 inhibited ISO-induced cardiomyocyte hypertrophy, suggesting that PRMT5 ameliorates cardiomyocyte hypertrophy. On the contrary, HoxA9 promoted cardiomyocyte hypertrophy, as implied by the gain-of-function and loss-of-function experiments. HoxA9 was involved in the regulation of PRMT5 in cardiomyocyte hypertrophy, since HoxA9 knockdown prevented si-RPMT5-induced cardiomyocyte hypertrophy, and HoxA9 expression impaired the anti-hypertrophic effect of PRMT5. Co-immunoprecipitation experiments revealed that there were physical interactions between PRMT5 and HoxA9. The symmetric dimethylation level of HoxA9 was decreased by ISO or EPZ treatment, suggesting that HoxA9 is methylated by PRMT5. Additionally, PRMT5 repressed the expression of HoxA9. Chromatin immunoprecipitation (ChIP) assay demonstrated that HoxA9 could bind to the promoter of BNP, and that this binding affinity was further enhanced by ISO or EPZ. In conclusion, this study suggests that PRMT5 symmetric dimethylates HoxA9 and represses HoxA9 expression, thus impairing its binding to BNP promoter and ultimately protecting against cardiomyocyte hypertrophy. These findings provide a novel insight of the mechanism underlying the cardiac protective effect of PRMT5, and suggest potential therapeutic strategies of PRMT5 activation or HoxA9 inhibition in treatment of cardiac hypertrophy.

Abstract 16383: Inhibition of Egfr Signalling Promotes Maladaptive Cardiac Remodelling in Hypertensive Heart Disease

Introduction: Epidermal growth factor (EGF) receptors (EGFRs: ERBB1-4) are activated by a family of ligands (e.g. EGF, Hb-EGF, EREG, TGFa), signaling through ERK1/2 and Akt to promote cell division and cancer. Antibody-based inhibition of ERBB2 in breast cancer can cause heart failure, but the role of other receptors and EGFR ligands in the heart, and potential cardiotoxicity of generic EGFR inhibitors is unclear. Hypothesis: We hypothesize that EGFR ligands play an important role in cardiac adaptation to hypertension, acting through EGFRs to promote adaptive remodelling. Methods & Results: EGF ligand/receptor mRNA expression was assessed in human failing hearts and normal controls (n=12/8). EGFRs were expressed at similar levels, but ligand expression differed with significant up- or downregulation of EGF/Hb-EGF vs EREG/TGFa, respectively, in failing hearts (p<0.05). EGF potently activated ERK1/2 and Akt (assessed by immunoblotting) in neonatal rat cardiomyocytes, leading to hypertrophy (p<0.05, n=4). The anti-cancer drug afatinib inhibits EGFRs. To assess the role of EGF signaling in cardiac adaptation to hypertension in vivo , C57Bl/6J mice (n=6) were treated with 0.8 mg/kg/d angiotensin II (AngII; 7d) ± 0.45 mg/kg/d afatinib. AngII promoted cardiac hypertrophy with increased left ventricular (LV) wall thickness (WT) and decreased LV internal diameter (ID; assessed by echocardiography). Afatinib enhanced AngII-induced hypertrophy with significantly increased WT:ID ratios (1.30-fold and 1.54-fold in diastole and systole, respectively; p<0.05) but inhibited AngII-induced increases in Nppb mRNA expression and cardiomyocyte cross-sectional area (208.80±9.78 vs 161.10±3.87μm 2 ; p<0.05). In contrast, Col1a1 mRNA expression was enhanced by afatinib, along with interstitial and perivascular fibrosis (3.21±0.38 vs 5.61±0.46, 0.98±0.06 vs 1.45±0.18 % area; p<0.05). Conclusion: EGFR signaling is modulated in human heart failure, promotes cardiomyocyte hypertrophy and is required for cardiac adaptation to hypertension. Since EGFR inhibition in hypertension prevents adaptive cardiomyocyte hypertrophy whilst promoting fibrosis, EGFR inhibitors are likely to cause cardiac dysfunction and be cardiotoxic in hypertensive patients.

Influence of high-intensity interval training and intermittent fasting on myocardium apoptosis pathway and cardiac morphology of healthy rats

AimTo evaluate the influence of intermittent fasting and high-intensity interval training (HIIT) on myocardial apoptosis signaling and cardiac morphological characteristics in healthy rats. MethodsMale Wistar rats (n = 60) were divided into four groups: sedentary control (SED-C), intermittent fasting (SED-IF), high-intensity interval training (HIIT-C), and high-intensity interval training plus intermittent fasting (HIIT-IF). SED-C and HIIT-C groups were treated daily with ad libitum chow; SED-IF and HIIT-IF received the same standard chow every other day. HIIT-C and HIIT-IF rats were submitted to an HIIT protocol five times a week for 12 weeks. At the end of the experiment, functional capacity, cardiac morphology, and expression of apoptosis signaling pathways-related proteins were analyzed. Key findingsHIIT increased cardiomyocyte cross-sectional area, collagen interstitial fraction, and the pro-apoptotic proteins AIF and caspase-3 expression, and reduced pro-apoptotic protein CYTC expression and the cleaved-to-non-cleaved PARP-1 ratio in myocardium. Intermittent fasting reduced cardiomyocyte cross-sectional area, collagen interstitial fraction, and expression of Bax, CYTC and cleaved PARP-1, and increased expression of the anti-apoptotic protein BCL-2. SMAC, ARC, and caspase-8 expression was not changed by HIIT or intermittent fasting. SignificanceHIIT promotes cardiomyocyte hypertrophy and interstitial fibrosis, and modulates the apoptosis signaling pathway in healthy rat myocardium. Intermittent fasting reduces pro-apoptotic and increases antiapoptotic signaling, besides attenuating HIIT-induced cardiomyocyte hypertrophy and myocardial interstitial fibrosis.

Abstract 507: Activation of the Classically Pro-Apoptotic Death Receptor 5 Promotes Physiological Hypertrophy and Cardiomyocyte Survival

Heart failure is hallmarked by a combination of cardiomyocyte hypertrophy and death. Apoptosis, one of the primary mechanisms of cell death, occurs through finely tuned extrinsic or intrinsic pathways. Of the mediators involved in extrinsic apoptotic signaling, some have been extensively studied, such as tumor necrosis factor ((TNF)-α), while others have been relatively untouched. One such receptor is Death Receptor 5 (DR5) which, along with its ligand TNF-Related Apoptosis Inducing Ligand (TRAIL), have recently been implicated as a biomarker in determining the progression and outcome in patients following multiple heart failure etiologies, suggesting a novel role of DR5 signaling in the heart. These studies suggest a potentially protective role for DR5 in the heart; however, the function of TRAIL/DR5 in the heart has been virtually unstudied. Our goal was to explore the role of TRAIL/DR5 in cardiomyocyte hypertrophy and survival with the hypothesis that DR5 promotes cardiomyocyte survival and growth through non-canonical mechanisms. Mice treated with the DR5 agonist bioymifi or a DR5 agonist antibody, MD5-1, were absent of cell death, while an increase in hypertrophy was observed without a decline in cardiac function. In isolated cardiomyocytes, this pro-hypertrophic phenotype was determined to operate through MMP-dependent cleavage of HB-EGFR, leading to transactivation of EGFR and ERK1/2 signaling. To determine the role of DR5 in heart failure, a chronic catecholamine administration model was used and DR5 activation was found to decrease cardiomyocyte death and cardiac fibrosis. ERK1/2, a well characterized pro-survival, pro-hypertrophic kinase is activated in the heart with DR5 agonist administration and may represent the mechanistic link through which DR5 is imparting cardioprotection. In summary, DR5 activation promotes cardiomyocyte hypertrophy and survival and prevents cardiac fibrosis via a non-canonical MMP-EGFR-ERK1/2 pathway. Taken together, these studies identify a previously undetermined role for DR5 in the heart and identify novel therapeutic target for the treatment of heart failure.