Regulation Of Cardiac Hypertrophy Research Articles

The crucial relationship between miRNA-27 and CSE/H2S, and the mechanism of action of GLP-1 in myocardial hypertrophy.

Cardiac hypertrophy is the most prevalent compensatory heart disease that ultimately leads to spontaneous heart failure. Mounting evidence suggests that microRNAs (miRs) and endogenous hydrogen sulfide (H2S) play a crucial role in the regulation of cardiac hypertrophy. In this study, we aimed to investigate whether inhibition of miR-27a could protect against cardiac hypertrophy by modulating H2S signaling. We established a model of cardiac hypertrophy by obtaining hypertrophic tissue from mice subjected to transverse aortic constriction (TAC) and from cells treated with angiotensin-II. Molecular alterations in the myocardium were quantified using quantitative real time PCR (qRT-PCR), Western blotting, and ELISA. Morphological changes were characterized by hematoxylin and eosin (HE) staining and Masson's trichrome staining. Functional myocardial changes were assessed using echocardiography. Our results demonstrated that miR-27a levels were elevated, while H2S levels were reduced in TAC mice and myocardial hypertrophy. Further luciferase and target scan assays confirmed that cystathionine-γ-lyase (CSE) was a direct target of miR-27a and was negatively regulated by it. Notably, enhancement of H2S expression in the heart was observed in mice injected with recombinant adeno-associated virus vector 9 (rAAV9)-anti-miR-27a and in cells transfected with a miR-27a inhibitor during cardiac hypertrophy. However, this effect was abolished by co-transfection with CSE siRNA and the miR-27a inhibitor. Conversely, injecting rAAV9-miR-27a yielded opposite results. Interestingly, our findings demonstrated that glucagon-like peptide-1 (GLP-1) agonists could mitigate myocardial damage by down-regulating miR-27a and up-regulating CSE. In summary, our study suggests that inhibition of miR-27a holds therapeutic promise for the treatment of cardiac hypertrophy by increasing H2S levels. Furthermore, our findings unveil a novel mechanism of GLP-1 agonists involving the miR-27a/H2S pathway in the management of cardiac hypertrophy.

Abstract 16957: PRKAG2 Directly Interacts With Myosin Heavy Chains to Modulate Myocyte Electrical and Morphological Changes in Cardiac Hypertrophy

Introduction: Mutations in the PRKAG2 gene cause a complex myocardial disorder characterized by hypertrophic cardiomyopathy (HCM) and conduction disturbances. While prior studies associated PRKAG2 -linked hypertrophy with increased glycogen storage, many HCM phenotypes in the disorder remain unexplained by this effect alone. We aimed to uncover the molecular mechanisms by which PRKAG2 mutations induce myocyte hypertrophy and electrical changes during cardiac development. Methods: We created transgenic zebrafish expressing WT (Tg WT ) and pathological mutant (Tg R299Q ) murine Prkag2 cDNA under a myocardium-specific promoter. Using these models, we studied the impact of Prkag2 variant on myocyte electrical activity, metabolism, and cytoarchitecture across cardiogenesis and in mature hearts. Results: Tg R299Q adult fish showed hypertrophic cardiomyocytes, swollen mitochondria, and shortened sarcomere length compared to Tg WT and WT, mirroring human HCM phenotypes. The glycogen content was elevated in adult hearts but not during early cardiogenesis. Despite the absence of glycogen accumulation at 6-day post fertilization, Tg R299Q hearts showed electrical abnormalities, including a reduced conduction velocity, decreased Ca 2+ amplitude, and prolonged action potential durations in both atria and ventricles, compared to Tg WT and WT. Co-immunoprecipitation and proximity ligation assay revealed physical interactions between Prkag2 and myosin heavy chain (MYH), with the R299Q variant enhancing this interaction and altering the subcellular localization of Prkag2 from mitochondria to sarcomeres. Knockdown of the fish homolog of MYH7 ( vmhcl ) restored the early electrical disturbances caused by Tg R299Q . This abnormal MYH-Prkag2 interaction disturbed mitochondria and sarcomere organization contributing to altered myocyte cytoarchitecture observed in Tg R299Q . Conclusions: Mutant PRKAG2 altered cardiac excitability and Ca 2+ handling during embryogenesis, preceding glycogen accumulation. Enhanced binding between Prkag2 and MYHs contributed to these early changes. Our study revealed a novel link between sarcomere proteins and metabolic regulators in cardiac hypertrophy, suggesting a new therapeutic avenue for treating HCM.

Palmitoylation-dependent regulation of cardiomyocyte Rac1 signaling activity and minor effects on cardiac hypertrophy

S-palmitoylation is a reversible lipid modification catalyzed by 23 S-acyltransferases with a conserved zinc finger aspartate-histidine-histidine-cysteine (zDHHC) domain that facilitates targeting of proteins to specific intracellular membranes. Here we performed a gain-of-function screen in the mouse and identified the Golgi-localized enzymes zDHHC3 and zDHHC7 as regulators of cardiac hypertrophy. Cardiomyocyte-specific transgenic mice overexpressing zDHHC3 show cardiac disease, and S-acyl proteomics identified the small GTPase Rac1 as a novel substrate of zDHHC3. Notably, cardiomyopathy and congestive heart failure in zDHHC3 transgenic mice is preceded by enhanced Rac1 S-palmitoylation, membrane localization, activity, downstream hypertrophic signaling, and concomitant induction of all Rho family small GTPases whereas mice overexpressing an enzymatically dead zDHHC3 mutant show no discernible effect. However, loss of Rac1 or other identified zDHHC3 targets Gαq/11 or galectin-1 does not diminish zDHHC3-induced cardiomyopathy, suggesting multiple effectors and pathways promoting decompensation with sustained zDHHC3 activity. Genetic deletion of Zdhhc3 in combination with Zdhhc7 reduces cardiac hypertrophy during the early response to pressure overload stimulation but not over longer time periods. Indeed, cardiac hypertrophy in response to 2weeks of angiotensin-II infusion is not diminished by Zdhhc3/7 deletion, again suggesting other S-acyltransferases or signaling mechanisms compensate to promote hypertrophic signaling. Taken together, these data indicate that the activity of zDHHC3 and zDHHC7 at the cardiomyocyte Golgi promote Rac1 signaling and maladaptive cardiac remodeling, but redundant signaling effectors compensate to maintain cardiac hypertrophy with sustained pathological stimulation in the absence of zDHHC3/7.

DEF6(differentially exprehomolog) exacerbates pathological cardiac hypertrophy via RAC1

Pathological cardiac hypertrophy involves multiple regulators and several signal transduction pathways. Currently, the mechanisms of it are not well understood. Differentially expressed in FDCP 6 homolog (DEF6) was reported to participate in immunity, bone remodeling, and cancers. The effects of DEF6 on pathological cardiac hypertrophy, however, have not yet been fully characterized. We initially determined the expression profile of DEF6 and found that DEF6 was upregulated in hypertrophic hearts and cardiomyocytes. Our in vivo results revealed that DEF6 deficiency in mice alleviated transverse aortic constriction (TAC)-induced cardiac hypertrophy, fibrosis, dilation and dysfunction of left ventricle. Conversely, cardiomyocyte-specific DEF6-overexpression aggravated the hypertrophic phenotype in mice under chronic pressure overload. Similar to the animal experiments, the in vitro data showed that adenovirus-mediated knockdown of DEF6 remarkably inhibited phenylephrine (PE)-induced cardiomyocyte hypertrophy, whereas DEF6 overexpression exerted the opposite effects. Mechanistically, exploration of the signal pathways showed that the mitogen-activated extracellular signal-regulated kinase 1/2 (MEK1/2)-extracellular signal-regulated kinase 1/2 (ERK1/2) cascade might be involved in the prohypertrophic effect of DEF6. Coimmunoprecipitation and GST (glutathione S-transferase) pulldown analyses demonstrated that DEF6 can directly interact with small GTPase Ras-related C3 botulinum toxin substrate 1 (Rac1), and the Rac1 activity assay revealed that the activity of Rac1 is altered with DEF6 expression in TAC-cardiac hypertrophy and PE-triggered cardiomyocyte hypertrophy. In the end, western blot and rescue experiments using Rac1 inhibitor NSC23766 and the constitutively active mutant Rac1(G12V) verified the requirement of Rac1 and MEK1/2-ERK1/2 activation for DEF6-mediated pathological cardiac hypertrophy. Our study substantiates that DEF6 acts as a deleterious regulator of cardiac hypertrophy by activating the Rac1 and MEK1/2-ERK1/2 signaling pathways, and suggests that DEF6 may be a potential treatment target for heart failure.

Cardiac-specific BACH1 ablation attenuates pathological cardiac hypertrophy by inhibiting the Ang II type 1 receptor expression and the Ca2+/CaMKII pathway.

BACH1 is upregulated in hypertrophic hearts, but its function in cardiac hypertrophy remains largely unknown. This research investigates the function and mechanisms of BACH1 in the regulation of cardiac hypertrophy. Male cardiac-specific BACH1 knockout mice or cardiac-specific BACH1 transgenic (BACH1-Tg) mice and their respective wild-type littermates developed cardiac hypertrophy induced by angiotensin II (Ang II) or transverse aortic constriction (TAC). Cardiac-specific BACH1 knockout in mice protected the hearts against Ang II- and TAC-induced cardiac hypertrophy and fibrosis, and preserved cardiac function. Conversely, cardiac-specific BACH1 overexpression markedly exaggerated cardiac hypertrophy and fibrosis and reduced cardiac function in mice with Ang II- and TAC-induced hypertrophy. Mechanistically, BACH1 silencing attenuated Ang II- and norepinephrine-stimulated calcium/calmodulin-dependent protein kinase II (CaMKII) signaling, the expression of hypertrophic genes, and hypertrophic growth of cardiomyocytes. Ang II stimulation promoted the nuclear localization of BACH1, facilitated the recruitment of BACH1 to the Ang II type 1 receptor (AT1R) gene promoter, and then increased the expression of AT1R. Inhibition of BACH1 attenuated Ang II-stimulated AT1R expression, cytosolic Ca2+ levels, and CaMKII activation in cardiomyocytes, whereas overexpression of BACH1 led to the opposite effects. The increased expression of hypertrophic genes induced by BACH1 overexpression upon Ang II stimulation was suppressed by CaMKII inhibitor KN93. The AT1R antagonist, losartan, significantly attenuated BACH1-mediated CaMKII activation and cardiomyocyte hypertrophy under Ang II stimulation in vitro. Similarly, Ang II-induced myocardial pathological hypertrophy, cardiac fibrosis, and dysfunction in BACH1-Tg mice were blunted by treatment with losartan. This study elucidates a novel important role of BACH1 in pathological cardiac hypertrophy by regulating the AT1R expression and the Ca2+/CaMKII pathway, and highlights potential therapeutic target in pathological cardiac hypertrophy. Transcription factor BACH1 is increased in failing human myocardium and hypertrophic human hearts. We revealed that cardiomyocyte-specific BACH1 ablation in mice protected the hearts against Ang II- and pressure overload-induced cardiac hypertrophy and fibrosis, and preserved cardiac function. BACH1 activated AT1R promoter activity under Ang II stimulation, and BACH1-mediated facilitation of cardiac hypertrophy under Ang II stimulation was regulated at least in part by AT1R expression. Moreover, BACH1 silencing attenuated the norepinephrine-stimulated CaMKII signaling pathway and hypertrophic growth of cardiomyocytes. Our findings suggest that BACH1 may pose a promising therapeutic target in pathological cardiac hypertrophy and heart failure.

Circ-sh3rf3/GATA-4/miR-29a regulatory axis in fibroblast-myofibroblast differentiation and myocardial fibrosis.

The transdifferentiation from cardiac fibroblasts to myofibroblasts is an important event in the initiation of cardiac fibrosis. However, the underlying mechanism is not fully understood. Circ-sh3rf3 (circular RNA SH3 domain containing Ring Finger 3) is a novel circular RNA which was induced in hypertrophied ventricles by isoproterenol hydrochloride, and our work has established that it is a potential regulator in cardiac hypertrophy, but whether circ-sh3rf3 plays a role in cardiac fibrosis remains unclear, especially in the conversion of cardiac fibroblasts into myofibroblasts. Here, we found that circ-sh3rf3 was down-regulated in isoproterenol-treated rat cardiac fibroblasts and cardiomyocytes as well as during fibroblast differentiation into myofibroblasts. We further confirmed that circ-sh3rf3 could interact with GATA-4 proteins and reduce the expression of GATA-4, which in turn abolishes GATA-4 repression of miR-29a expression and thus up-regulates miR-29a expression, thereby inhibiting fibroblast-myofibroblast differentiation and myocardial fibrosis. Our work has established a novel Circ-sh3rf3/GATA-4/miR-29a regulatory cascade in fibroblast-myofibroblast differentiation and myocardial fibrosis, which provides a new therapeutic target for myocardial fibrosis.

Crosstalk between PML and p53 in response to TGF-β1: A new mechanism of cardiac fibroblast activation.

Cardiac fibrosis is a common pathological cardiac remodeling in a variety of heart diseases, characterized by the activation of cardiac fibroblasts. Our previous study uncovered that promyelocytic leukemia protein (PML)-associated SUMO processes is a new regulator of cardiac hypertrophy and heart failure. The present study aimed to explore the role of PML in cardiac fibroblasts activation. Here we found that PML is significantly upregulated in cardiac fibrotic tissue and activated cardiac fibroblasts treated with transforming growth factor-β1 (TGF-β1). Gain- and loss-of-function experiments showed that PML impacted cardiac fibroblasts activation after TGF-β1 treatment. Further study demonstrated that p53 acts as the transcriptional regulator of PML, and participated in TGF-β1 induced the increase of PML expression and PML nuclear bodies (PML-NBs) formation. Knockdown or pharmacological inhibition of p53 produced inhibitory effects on the activation of cardiac fibroblasts. We further found that PML also may stabilize p53 through inhibiting its ubiquitin-mediated proteasomal degradation in cardiac fibroblasts. Collectively, this study suggests that PML crosstalk with p53 regulates cardiac fibroblasts activation, which provides a novel therapeutic strategy for cardiac fibrosis.

RCAN1 deficiency aggravates sepsis-induced cardiac remodeling and dysfunction by accelerating mitochondrial pathological fission.

Cardiac dysfunction and remodeling are serious complications of sepsis and are the main causes of death in sepsis. RCAN1 is a feedback regulator of cardiac hypertrophy. Here, we aim to investigate the role of RCAN1 in septic cardiomyopathy. Mice were randomly divided into control-WT, control-RCAN1-/-, LPS-induced WT and LPS-induced RCAN1-/- groups, some with Midiv-1 or KN93 treatment. The protein levels of RCAN1, p-ERK1/2, NFAT3, Drp1, p-Drp1, p-CaMKII in mouse hearts or cultured cardiomyocytes were determined by Western blotting. Myocardial function was assessed by echocardiography. Cardiac hypertrophy and fibrosis were detected by H&E and Masson's trichrome staining. Mitochondrial morphology was examined by transmission electron microscope. Serum level of LDH was detected by ELISA. Our data show that RCAN1 was downregulated in septic mouse heart and LPS-induced cardiomyocytes. RCAN1-/- mice showed a severe impairment of cardiac function, and increased myocardial hypertrophy and fibrosis. The protein levels of NFAT3 and p-ERK1/2 were significantly increased in the heart tissues of RCAN1-/- mice. Further, RCAN1 deficiency aggravated sepsis-induced cardiac mitochondrial injury as indicated by increased ROS production, pathological fission and the loss of mitochondrial membrane potential. Inhibition of fission with Mdivi-1 reversed LPS-induced cardiac hypertrophy, fibrosis and dysfunction in RCAN1-/- mice. Moreover, RCAN1 depletion promoted mitochondrial translocation of CaMKII, which enhanced fission and septic hypertrophy, while inhibition of CaMKII with KN93 reduced excessive fission, improved LPS-mediated cardiac remodeling and dysfunction in RCAN1-/- mice. Our finding demonstrated that RCAN1 deficiency aggravated mitochondrial injury and septic cardiomyopathy through activating CaMKII. RCAN1 serves as a novel therapeutic target for treatment of sepsis-related cardiac remodeling and dysfunction.

Doxorubicin-induced upregulation of follistatin-like 3 (FSTL3): a new therapeutic target

Abstract Introduction Doxorubicin (DOX) is among the most used anticancer drugs with associated cardiotoxicity. Follistatin-like 3 (FSTL3), a secreted member of the follistatins family that can selectively bind to members of the TGF-β superfamily, is involved in regulation of cardiac hypertrophy and heart failure. FSTL3 is also upregulated in breast and colorectal cancer tumours, is also an unfavourable prognostic indicator for various cancers. Purpose We aim to determine the dual role of FSTL3 in prevention of DOX-induced cardiotoxicity and synergistic anti-cancer effects. Methods Human cardiomyocytes (HCMs) were treated with DOX at 1uM (EC50) for 72 hours. Cell viability was assessed via CellTiter-Glo®. Secreted FSTL3 levels, as measured by ELISA (R&D systems). FSTL3 and TGF-β mRNA levels were measured by qPCR. Co-treatment of DOX with human anti-FSTL3 antibodies (Aviva Systems Biology) at 10ug/mL were introduced for 72hrs treatment. Results Secreted FSTL3 levels were significantly increased in DOX-treated HCMs at 72hrs compared to control (n=5, p<0.001). Consistently, FSTL3 and TGF-β mRNA levels, in collected HCMs were significantly increased in DOX-treated cells. Co-treatment of DOX with human anti-FSTL3 antibodies at 10ug/mL significantly improved HCM viability compared to IgG control group. Conversely, anti-FSTL3 antibodies provided synergistic anti-cancer effects with DOX: MCF-7 breast cancer cells were significantly reduced when co-treated with DOX and anti-FSTL3 antibody vs. IgG controls. Conclusion We show, for the first time, that: 1) FSTL3 is secreted directly from HCMs; 2) FSTL3 levels (both circulating and mRNA) is markedly elevated with DOX treatment; 3) neutralisation of FSTL3 in DOX-treated HCMs, restored HCM viability; and 4) exhibit synergistic anti-cancer effects with DOX. Taken together, FSTL3 is a potential target for dual anti-cancer and cardioprotective effects. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Heart Foundation of Australia Future Leader FellowshipsNSW Ministry of Health EMC FellowshipNSW Ministry of Health Translational Research Grant

G-protein coupled receptor 30 attenuates myocardial hypertrophy by reducing oxidative stress and apoptosis in Ang II-treated mice

G protein-coupled receptors (GPCRs) are the largest family of membrane receptors that mediate the effects of cardiac diseases. GPR30, also named G-protein-coupled estrogen receptor, shows beneficial effect on female patients with heart failure. This research aimed to probe the role and mechanism of GPR30 in myocardial hypertrophy. The model of cardiac hypertrophy was induced by infusion of angiotensin (Ang) II in mice, and was induced by Ang II treatment in neonatal rat cardiomyocyte (NRCM). The mouse model of myocardial hypertrophy was induced by angiotensin (Ang) Ⅱ, and the neonatal rat cardiomyocyte (NRCM) was induced by Ang Ⅱ treatment. GPR30 agonist G1 reduced cardiac hypertrophy induced by Ang II in mice, and reduced cardiac atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and β-myosin heavy chain (β-MHC) induced by Ang II. Ang Ⅱ treatment of myocardial fibrosis in mice was suppressed after administration of G1. GPR30 deficiency produced the opposite results. Oxidative stress and apoptosis were enhanced in the mice heart induced by Ang II, which were suppressed by G1 administration, but were further exacerbated after GPR30 deficiency. The outcomes demonstrated that GPR30 participated in the regulation of cardiac hypertrophy and fibrosis. Activation of GPR30 ameliorated cardiac hypertrophy and fibrosis by reducing oxidative stress and apoptosis.

Protections of transcription factor BACH2 and natural product myricetin against pathological cardiac hypertrophy and dysfunction.

Pathological hypertrophic myocardium under consistent adverse stimuli eventually can cause heart failure. This study aims to explore the role of BACH2, a member of the basic region leucine zipper transcription factor family, in cardiac hypertrophy and failure. Transverse aortic constriction surgery was operated to induce cardiac hypertrophy and failure in mice. BACH2 was overexpressed in mice through tail vein injection of AAV9-Bach2. Mice with systemic or cardiac-specific knockdown of Bach2 were adopted. Neonatal rat ventricular myocytes (NRVMs) were isolated and infected with lentivirus to overexpress Bach2 or transfected with siRNA to knock down Bach2. Our data showed that overexpression of BACH2 ameliorated TAC-induced cardiac hypertrophy and failure in mice and decreased isoproterenol (ISO)-triggered myocyte hypertrophy in NRVMs. Systemic or cardiac-specific knockdown of Bach2 worsened the cardiac hypertrophy and failure phenotype in mice. Further assays showed that BACH2 bound to the promotor region of Akap6 at the -600 to -587 site and repressed its expression, which functioned as a crucial scaffold for cardiac hypertrophy and failure signaling pathways. Small molecular natural product library screening suggested that myricetin could up-regulate expression of Bach2 and simultaneously suppress the transcriptional levels of hypertrophic marker genes Bnp and Myh7. Further studies showed that myricetin exerted a BACH2-dependent protective effect against cardiac hypertrophy in vivo and in vitro. Taken together, our findings demonstrated that BACH2 plays a crucial role in the regulation of cardiac hypertrophy and failure and can be a potential therapeutic target in the future.

MALAT1 regulates hypertrophy of cardiomyocytes by modulating the miR-181a/HMGB2 pathway.

Noncoding RNAs are important for the regulation of cardiac hypertrophy. The function of MALAT1 (a long noncoding mRNA), miR-181a, and HMGB2, their contribution to cardiac hypertrophy, and the regulatory relationship between them during this process remain unknown. In the present study, we treated primary cardiomyocytes with angiotensin II (Ang II) to mimic cardiac hypertrophy. MALAT1 expression was significantly downregulated in Ang II-treated cardiomyocytes compared with control cardiomyocytes. Ang II-induced cardiac hypertrophy was suppressed by overexpression of MALAT1 and promoted by genetic knockdown of MALAT1. A dual-luciferase reporter assay demonstrated that MALAT1 acted as a sponge for miR-181a and inhibited its expression during cardiac hypertrophy. Cardiac hypertrophy was suppressed by overexpression of an miR-181a inhibitor and enhanced by overexpression of an miR-181a mimic. HMGB2 was downregulated during cardiac hypertrophy and was identified as a target of miR-181a by bioinformatics analysis and a dual-luciferase reporter assay. miR-181a overexpression decreased the mRNA and protein levels of HMGB2. Rescue experiments indicated that MALAT1 overexpression reversed the effect of miR-181a on HMGB2 expression. In summary, the results of the present study show that MALAT1 acts as a sponge for miR-181a and thereby regulates expression of HMGB2 and development of cardiac hypertrophy. The novel MALAT1/miR-181a/HMGB2 axis might play a crucial role in cardiac hypertrophy and serve as a new therapeutic target.

Identification of a long noncoding RNA Gm17501 as a novel negative regulator of cardiac hypertrophy

Pathological cardiac hypertrophy is an independent risk factor for the development of heart failure. Long noncoding RNAs (lncRNAs), an emerging class of non-protein-coding transcripts, are involved in regulation of multiple cardiac diseases through diverse molecular mechanism, whereas the role of cytoplasmic lncRNAs in regulating cardiac hypertrophy remains unclear. In this study, we identified a novel and functional long noncoding RNA Gm17501, which was predominantly expressed in the cytoplasm of cardiomyocytes. The expression level of lncRNA Gm17501 was altered in cardiac hypertrophy induced by pressure overload and phenylephrine treatment. Moreover, lncRNA Gm17501 expression was decreased in the heart tissue of patients with heart failure. Silencing lncRNA Gm17501 aggravated cardiac hypertrophy under pathological stress. Inhibition of lncRNA Gm17501 did not alter the expression of nearby genes but decreased mRNA level of calcium handling proteins which were involved in cardiac contraction. Therefore, the cytoplasmic lncRNA Gm17501 might protect cardiomyocytes against hypertrophy, possibly by maintaining calcium signaling pathway.

On the road to discovering a new actor of cardiac pathological hypertrophy

Cardiac hypertrophy develops in response to hemodynamic overload, which can occur in hypertension and aortic stenosis. Maintenance of these pathological conditions eventually evolves into heart failure (HF) and death. O-GlcNAcylation, a post-translational modification of proteins, has been shown to drastically increase during cardiac hypertrophy development and to mediate maladaptive remodeling implicated in the progression of HF. Using mass spectrometry analysis, our lab recently identified several O-GlcNAcylated cardiac proteins that could be involved in such remodeling. Among them, O-GlcNAcylated protein 1 (OGP-1) looks to be a promising candidate. We investigated the role of OGP-1 in cardiac hypertrophy development. Change in OGP-1 expression was followed in neonatal rat cardiomyocytes (NRVM) treated with the pro-hypertrophic agent phenylephrine (PE) for 24 h. The same was done in vivo in two different hypertrophic mouse models, the first induced by Angiotensin II (Ang II) infusion for 5 to 14 days and the second promoted by transverse aortic constriction (TAC) for 2 to 6 weeks. The expression of OGP-1 was also evaluated in human hearts biopsies from different degree of cardiac remodeling. NRVM size was evaluated using α-actinin staining that labels sarcomeric Z-line. Pro-hypertrophic markers (ANP, BNP and β-MHC) were analyzed by quantitative PCR. The effect of OGP-1 overexpression and siRNA-mediated silencing was finally performed in NRVM. A significant decrease in OGP-1 expression was detected in both in vitro and in vivo rodent hypertrophic models. To evaluate the putative implication of OGP-1 in the regulation of cardiac hypertrophy, we repressed OGP-1 expression using siRNA in NRVM. We showed that OGP-1 knockdown induced a basal increase in cell size, similar to that found in PE-treated control cardiomyocytes, suggesting that OGP-1 repression may be sufficient to induce cardiomyocyte hypertrophy. Unexpectedly, the increase in cell size was not related to classical pro-hypertrophic pathways, ANP, BNP and β-MHC expression being unaffected. The other way round, OGP-1 overexpression prevented PE-induced NRVM hypertrophy. Our results underlie OGP-1 as a potential anti-hypertrophic protein and an interesting future target for the treatment of cardiac hypertrophy. Further investigations aim to identify the precise function of OGP-1 in the regulation of cardiac hypertrophy.

Epigenetic Reader Bromodomain Containing Protein 2 Facilitates Pathological Cardiac Hypertrophy via Regulating the Expression of Citrate Cycle Genes.

The bromodomain and extra-terminal domain proteins (BETs) family serve as epigenetic “readers”, which recognize the acetylated histones and recruit transcriptional regulator complexes to chromatin, eventually regulating gene transcription. Accumulating evidences demonstrate that pan BET inhibitors (BETi) confer protection against pathological cardiac hypertrophy, a precursor progress for developing heart failure. However, the roles of BET family members, except BRD4, remain unknown in pathological cardiac hypertrophy. The present study identified BRD2 as a novel regulator in cardiac hypertrophy, with a distinct mechanism from BRD4. BRD2 expression was elevated in cardiac hypertrophy induced by β-adrenergic agonist isoprenaline (ISO) in vivo and in vitro. Overexpression of BRD2 upregulated the expression of hypertrophic biomarkers and increased cell surface area, whereas BRD2 knockdown restrained ISO-induced cardiomyocyte hypertrophy. In vivo, rats received intramyocardial injection of adeno-associated virus (AAV) encoding siBRD2 significantly reversed ISO-induced pathological cardiac hypertrophy, cardiac fibrosis, and cardiac function dysregulation. The bioinformatic analysis of whole-genome sequence data demonstrated that a majority of metabolic genes, in particular those involved in TCA cycle, were under regulation by BRD2. Real-time PCR results confirmed that the expressions of TCA cycle genes were upregulated by BRD2, but were downregulated by BRD2 silencing in ISO-treated cardiomyocytes. Results of mitochondrial oxygen consumption rate (OCR) and ATP production measurement demonstrated that BRD2 augmented cardiac metabolism during cardiac hypertrophy. In conclusion, the present study revealed that BRD2 could facilitate cardiac hypertrophy through upregulating TCA cycle genes. Strategies targeting inhibition of BRD2 might suggest therapeutic potential for pathological cardiac hypertrophy and heart failure.

The lncRNA MIAT regulates CPT-1a mediated cardiac hypertrophy through m6A RNA methylation reading protein Ythdf2

sPathological cardiac hypertrophy is a key contributor in heart failure (HF). Long non-coding RNAs (lncRNAs) and N6-methyladenosine (m6A) modification play a vital role in cardiac hypertrophy respectively. Nevertheless, the interaction between lncRNA and m6A methylase in cardiac hypertrophy is scarcely reported. Here, we constructed a cardiac hypertrophy mouse model by transverse aortic constriction (TAC) surgery and H9c2 cell model by stimulating with AngII. We found that lncRNA MIAT mRNA level, and m6A RNA methylation reading protein Ythdf2 mRNA and protein levels, were significantly increased in the cardiac hypertrophy model both in vivo and vitro. MIAT or Ythdf2 overexpression aggravated cardiac hypertrophy, and vice versa. Through bioinformatics prediction, western blotting, FISH, RNA pull-down, and RIP, we found that MIAT bound to Ythdf2 and regulated its expression. Furthermore, we discovered that Ythdf2 function was a downstream of MIAT in cardiac hypertrophy. Finally, we found that MIAT was a necessary regulator of cardiac hypertrophy due to its regulation of the Ythdf2/PPARα/CPT-1a axis. This study indicated a new hypertrophic signaling pathway: MIAT/Ythdf2/PPARα/CPT-1a. The results provided a new understanding of the MIAT and m6A RNA methylation reading protein, Ythdf2, function and mechanism in cardiac hypertrophy and highlighted the potential therapeutic benefits in the heart.

Loss of m6A Methyltransferase METTL5 Promotes Cardiac Hypertrophy Through Epitranscriptomic Control of SUZ12 Expression.

Enhancement of protein synthesis from mRNA translation is one of the key steps supporting cardiomyocyte hypertrophy during cardiac remodeling. The methyltransferase-like5 (METTL5), which catalyzes m6A modification of 18S rRNA at position A1832, has been shown to regulate the efficiency of mRNA translation during the differentiation of ES cells and the growth of cancer cells. It remains unknown whether and how METTL5 regulates cardiac hypertrophy. In this study, we have generated a mouse model, METTL5-cKO, with cardiac-specific depletion of METTL5 in vivo. Loss function of METTL5 promotes pressure overload-induced cardiomyocyte hypertrophy and adverse remodeling. The regulatory function of METTL5 in hypertrophic growth of cardiomyocytes was further confirmed with both gain- and loss-of-function approaches in primary cardiomyocytes. Mechanically, METTL5 can modulate the mRNA translation of SUZ12, a core component of PRC2 complex, and further regulate the transcriptomic shift during cardiac hypertrophy. Altogether, our study may uncover an important translational regulator of cardiac hypertrophy through m6A modification.

Hdac8 Inhibitor Alleviates Transverse Aortic Constriction-Induced Heart Failure in Mice by Downregulating Ace1.

Background Heart failure is characterized by activation of the renin-angiotensin-aldosterone system, which is involved in the regulation of cardiac hypertrophy and hypertension. Recently, we reported that Hdac8 inhibition alleviates isoproterenol-induced and angiotensin II-induced cardiac hypertrophy or hypertension in mice. Here, the effect and regulatory mechanisms of the Hdac8 selective inhibitor PCI34051 on pressure overload-induced heart failure were examined. Methods and Results At week 6 posttransverse aortic constriction (TAC), mice were administered with PCI34051 (3, 10, or 30 mg/kg bodyweight/day) for 2 weeks. The therapeutic effects of PCI34051 on TAC-induced cardiac and lung hypertrophy were determined by examining the heart weight-to-bodyweight and lung weight-to-bodyweight ratios and the cross-sectional cardiomyocyte area. Echocardiography analysis revealed that PCI34051 mitigated TAC-induced decreased ejection fraction and fractional shortening. Additionally, the expression of Hdac8 was upregulated in the cardiac and pulmonary tissues of TAC mice. The expression levels of Ace1 and Agtr1 were upregulated, whereas those of Ace2 and Agtr2 were downregulated in TAC mice. PCI34051 treatment or Hdac8 knockdown alleviated inflammation as evidenced by Rela downregulation and Nfkbia upregulation in mice, as well as in cardiomyocytes, but not in cardiac fibroblasts. Hdac8 overexpression-induced Rela pathway activation was downregulated in Ace1 knockdown cells. Picrosirius red staining, real-time polymerase chain reaction, and western blotting analyses revealed that PCI34051 alleviated fibrosis and downregulated fibrosis-related genes. Moreover, PCI34051 or Hdac8 knockdown in rat cardiac fibroblasts alleviated cardiac fibrosis through the Tgfb1-Smad2/3 pathway. The results of overexpression and knockdown experiments revealed that Hdac8 and Ace1 promote inflammation and fibrosis. Conclusions Treatment with PCI34051 enhanced cardiac and lung functions in the TAC-induced heart failure mouse model. These data suggest that HDAC8 is a potential novel therapeutic target for heart failure accompanied by pathological lung diseases.

Doxorubicin-Induced Upregulation of Follistatin-Like 3 (FSTL3): A New Therapeutic Target

Doxorubicin (DOX) is among the most used anticancer drugs with associated cardiotoxicity. Follistatin-like 3 (FSTL3), a secreted member of the follistatins family that can selectively bind to members of the TGF-β superfamily, is involved in regulation of cardiac hypertrophy and heart failure. FSTL3 is also upregulated in breast and colorectal cancer tumours, is also an unfavourable prognostic indicator for various cancers. We aim to determine the dual role of FSTL3 in prevention of DOX-induced cardiotoxicity and synergistic anti-cancer effects.

JNK signaling-dependent regulation of histone acetylation are involved in anacardic acid alleviates cardiomyocyte hypertrophy induced by phenylephrine.

Cardiac hypertrophy is a complex process induced by the activation of multiple signaling pathways. We previously reported that anacardic acid (AA), a histone acetyltransferase (HAT) inhibitor, attenuates phenylephrine (PE)-induced cardiac hypertrophy by downregulating histone H3 acetylation at lysine 9 (H3K9ac). Unfortunately, the related upstream signaling events remained unknown. The mitogen-activated protein kinase (MAPK) pathway is an important regulator of cardiac hypertrophy. In this study, we explored the role of JNK/MAPK signaling pathway in cardiac hypertrophy induced by PE. The mice cardiomyocyte hypertrophy model was successfully established by treating cells with PE in vitro. This study showed that p-JNK directly interacts with HATs (P300 and P300/CBP-associated factor, PCAF) and alters H3K9ac. In addition, both the JNK inhibitor SP600125 and the HAT inhibitor AA attenuated p-JNK overexpression and H3K9ac hyperacetylation by inhibiting P300 and PCAF during PE-induced cardiomyocyte hypertrophy. Moreover, we demonstrated that both SP600125 and AA attenuate the overexpression of cardiac hypertrophy-related genes (MEF2A, ANP, BNP, and β-MHC), preventing cardiomyocyte hypertrophy and dysfunction. These results revealed a novel mechanism through which AA might protect mice from PE-induced cardiomyocyte hypertrophy. In particular, AA inhibits the effects of JNK signaling on HATs-mediated histone acetylation, and could therefore be used to prevent and treat pathological cardiac hypertrophy.