Pressure Overload-induced Pathological Cardiac Hypertrophy Research Articles

Histone methyltransferase MLL4 protects against pressure overload-induced heart failure via a THBS4-mediated protection in ER stress

Pressure overload-induced pathological cardiac hypertrophy eventually leads to heart failure (HF). Unfortunately, lack of effective targeted therapies for HF remains a challenge in clinical management. Mixed-lineage leukemia 4 (MLL4) is a member of the SET family of histone methyltransferase enzymes, which possesses histone H3 lysine 4 (H3K4)-specific methyltransferase activity. However, whether and how MLL4 regulates cardiac function is not reported in adult HF. Here we report that MLL4 is required for endoplasmic reticulum (ER) stress homeostasis of cardiomyocytes and protective against pressure overload-induced cardiac hypertrophy and HF. We observed that MLL4 is increased in the heart tissue of HF mouse model and HF patients. The cardiomyocyte-specific deletion of Mll4 (Mll4-cKO) in mice leads to aggravated ER stress and cardiac dysfunction following pressure overloading. MLL4 knockdown neonatal rat cardiomyocytes (NRCMs) also display accelerated decompensated ER stress and hypertrophy induced by phenylephrine (PE). The combined analysis of Cleavage Under Targets and Tagmentation sequencing (CUT&Tag-seq) and RNA sequencing (RNA-seq) data reveals that, silencing of Mll4 alters the chromatin landscape for H3K4me1 modification and gene expression patterns in NRCMs. Interestingly, the deficiency of MLL4 results in a marked reduction of H3K4me1 and H3K27ac occupations on Thrombospondin-4 (Thbs4) gene loci, as well as Thbs4 gene expression. Mechanistically, MLL4 acts as a transcriptional activator of Thbs4 through mono-methylation of H3K4 and further regulates THBS4-dependent ER stress response, ultimately plays a role in HF. Our study indicates that pharmacologically targeting MLL4 and ER stress might be a valid therapeutic approach to protect against cardiac hypertrophy and HF.

New insights into the effect of VMP1 on the treatment of pressure overload-induced pathological cardiac hypertrophy: Involving SERCA-regulated autophagic flux

Pathological cardiac hypertrophy is an adaptive reaction in response to pressure or volume overload. Autophagy is critical for damage caused by pathological cardiac hypertrophy. Vacuole membrane protein 1 (VMP1) is an endoplasmic reticulum (ER) transmembrane protein that is effective in activating autophagy. However, the role of VMP1 in pathological cardiac hypertrophy and its underlying mechanisms remain elusive. This study was designed to explore the potential mechanisms of VMP1 on pressure overload-induced pathological cardiac hypertrophy. In this work, abdominal aorta constriction (AAC) surgery was used to induce pathological cardiac hypertrophy in male C57BL/6 mice. H9C2 cardiomyocytes were treated with phenylephrine stimulation (PE) to induce the hypertrophic response. The in vivo results revealed that mice with AAC surgery caused pathological cardiac hypertrophy as evidenced by improved cardiac function according to multiple echocardiographic parameters. Moreover, elevated VMP1 expression was also observed in mice after AAC surgery. VMP1 knockdown aggravated changes in cardiac structure, cardiac dysfunction, and fibrosis. Meanwhile, VMP1 knockdown suppressed autophagy and endoplasmic reticulum calcium ATPase (SERCA) activity in heart tissues. H9C2 cardiomyocytes with VMP1 overexpression were used to investigate the specific mechanism of VMP1 in pathological cardiac hypertrophy, and VMP1 overexpression increased autophagic flux by upregulating SERCA activity. In conclusion, these findings revealed that VMP1 protected against pressure overload-induced pathological cardiac hypertrophy by inducing SERCA-regulated autophagic flux. Our results provide valuable insights regarding the pathophysiology of pathological cardiac hypertrophy and clues to a novel target for the treatment of pathological cardiac hypertrophy.

Deciphering transcriptional dynamics of cardiac hypertrophy and failure in a chamber-specific manner.

Pressure overload-induced pathological cardiac hypertrophy (CH) is a complexed and adaptive remodeling of the heart, predominantly involving an increase in cardiomyocyte size and thickening of ventricular walls. Over time, these changes can lead to heart failure (HF). However, the individual and shared biological mechanisms of both processes remain poorly understood. This study aimed to identify key genes and signaling pathways associated with CH and HF following aortic arch constriction (TAC) at four weeks and six weeks, respectively, and to investigate potential underlying molecular mechanisms in this dynamic transition from CH to HF at the whole cardiac transcriptome level. Initially, a total of 363, 482, and 264 differentially expressed genes (DEGs) for CH, and 317, 305, and 416 DEGs for HF were identified in the left atrium (LA), left ventricle (LV), and right ventricle (RV), respectively. These identified DEGs could serve as biomarkers for the two conditions in different heart chambers. Additionaly, two communal DEGs, elastin (ELN) and hemoglobin beta chain-beta S variant (HBB-BS), were found in all chambers, with 35 communal DEGs in the LA and LV and 15 communal DEGs in the LV and RV in both CH and HF. Functional enrichment analysis of these genes emphasized the crucial roles of the extracellular matrix and sarcolemma in CH and HF. Lastly, three groups of hub genes, including the lysyl oxidase (LOX) family, fibroblast growth factors (FGF) family, and NADH-ubiquinone oxidoreductase (NDUF) family, were determined to be essential genes of dynamic changes from CH to HF.

Gramine protects against pressure overload-induced pathological cardiac hypertrophy through Runx1-TGFBR1 signaling

BackgroundGramine, also named 3-(N,N-dimethylaminomethyl) indole, is a indole alkaloid. It is mainly extracted from various natural raw plants. Despite being the simplest 3-aminomethylindole, Gramine has broad pharmaceutical and therapeutic effects, such as vasodilatation, antioxidation, mitochondrial bioenergetics-related effects, and angiogenesis via modulation of TGFβ signaling. However, there is little information available about Gramine's role in heart disease, especially pathological cardiac hypertrophy. PurposeTo investigate Gramine's effect on pathological cardiac hypertrophy and clarify the mechanisms behind its action. MethodsIn the in vitro experiment, Gramine (25 μM or 50 μM) was used to investigate its role in Angiotensin II-induced primary neonatal rat cardiomyocytes (NRCMs) hypertrophy. In the in vivo experiment, Gramine (50 mg/kg or 100 mg/kg) was administrated to investigate its role in transverse aortic constriction (TAC) surgery mice. Additionally, we explored the mechanisms underlying these roles through Western blot, Real-time PCR, genome-wide transcriptomic analysis, chromatin immunoprecipitation and molecular docking studies. ResultsThe in vitro data demonstrated that Gramine treatment obviously improved primary cardiomyocyte hypertrophy induced by Angiotensin II, but had few effects on the activation of fibroblasts. The in vivo experiments indicated that Gramine significantly mitigated TAC-induced myocardial hypertrophy, interstitial fibrosis and cardiac dysfunction. Mechanistically, RNA sequencing and further bioinformatics analysis demonstrated that transforming growth factor β (TGFβ)-related signaling pathway was enriched significantly and preferentially in Gramine-treated mice as opposed to vehicle-treated mice during pathological cardiac hypertrophy. Moreover, this cardio-protection of Gramine was found to mainly involved in TGFβ receptor 1 (TGFBR1)- TGFβ activated kinase 1 (TAK1)-p38 MAPK signal cascade. Further exploration showed that Gramine restrained the up-regulation of TGFBR1 by binding to Runt-related transcription factor 1 (Runx1), thereby alleviating pathological cardiac hypertrophy. ConclusionOur findings provided a substantial body of evidence that Gramine possessed a potential druggability in pathological cardiac hypertrophy via suppressing the TGFBR1-TAK1-p38 MAPK signaling axis through interaction with transcription factor Runx1.

Ganoderma lucidum polysaccharides attenuates pressure-overload-induced pathological cardiac hypertrophy.

Pathological cardiac hypertrophy is an important risk factor for cardiovascular disease. However, drug therapies that can reverse the maladaptive process and restore heart function are limited. Ganoderma lucidum polysaccharides (GLPs) are one of the main active components of G. lucidum (Ganoderma lucidum), and they have various pharmacological effects. GLPs have been used as Chinese medicine prescriptions for clinical treatment. In this study, cardiac hypertrophy was induced by transverse aortic constriction (TAC) in mice. We found that GLPs ameliorate Ang II-induced cardiomyocyte hypertrophy in vitro and attenuate pressure overload-induced cardiac hypertrophy in vivo. Further research indicated that GLPs attenuated the mRNA levels of hypertrophic and fibrotic markers to inhibit cardiac hypertrophy through the PPARγ/PGC-1α pathway. Overall, these results indicate that GLPs inhibit cardiac hypertrophy through downregulating key genes for hypertrophy and fibrosis and attenuate pressure overload-induced pathological cardiac hypertrophy by activating PPARγ. This study provides important theoretical support for the potential of using GLPs to treat pathological myocardial hypertrophy and heart failure.

In Vivo Inhibition of miR-34a Modestly Limits Cardiac Enlargement and Fibrosis in a Mouse Model with Established Type 1 Diabetes-Induced Cardiomyopathy, but Does Not Improve Diastolic Function.

MicroRNA 34a (miR-34a) is elevated in the heart in a setting of cardiac stress or pathology, and we previously reported that inhibition of miR-34a in vivo provided protection in a setting of pressure overload-induced pathological cardiac hypertrophy and dilated cardiomyopathy. Prior work had also shown that circulating or cardiac miR-34a was elevated in a setting of diabetes. However, the therapeutic potential of inhibiting miR-34a in vivo in the diabetic heart had not been assessed. In the current study, type 1 diabetes was induced in adult male mice with 5 daily injections of streptozotocin (STZ). At 8 weeks post-STZ, when mice had established type 1 diabetes and diastolic dysfunction, mice were administered locked nucleic acid (LNA)-antimiR-34a or saline-control with an eight-week follow-up. Cardiac function, cardiac morphology, cardiac fibrosis, capillary density and gene expression were assessed. Diabetic mice presented with high blood glucose, elevated liver and kidney weights, diastolic dysfunction, mild cardiac enlargement, cardiac fibrosis and reduced myocardial capillary density. miR-34a was elevated in the heart of diabetic mice in comparison to non-diabetic mice. Inhibition of miR-34a had no significant effect on diastolic function or atrial enlargement, but had a mild effect on preventing an elevation in cardiac enlargement, fibrosis and ventricular gene expression of B-type natriuretic peptide (BNP) and the anti-angiogenic miRNA (miR-92a). A miR-34a target, vinculin, was inversely correlated with miR-34a expression, but other miR-34a targets were unchanged. In summary, inhibition of miR-34a provided limited protection in a mouse model with established type 1 diabetes-induced cardiomyopathy and failed to improve diastolic function. Given diabetes represents a systemic disorder with numerous miRNAs dysregulated in the diabetic heart, as well as other organs, strategies targeting multiple miRNAs and/or earlier intervention is likely to be required.

Novel genomic targets of valosin-containing protein in protecting pathological cardiac hypertrophy

Pressure overload-induced cardiac hypertrophy, such as that caused by hypertension, is a key risk factor for heart failure. However, the underlying molecular mechanisms remain largely unknown. We previously reported that the valosin-containing protein (VCP), an ATPase-associated protein newly identified in the heart, acts as a significant mediator of cardiac protection against pressure overload-induced pathological cardiac hypertrophy. Still, the underlying molecular basis for the protection is unclear. This study used a cardiac-specific VCP transgenic mouse model to understand the transcriptomic alterations induced by VCP under the cardiac stress caused by pressure overload. Using RNA sequencing and comprehensive bioinformatic analysis, we found that overexpression of the VCP in the heart was able to normalize the pressure overload-stimulated hypertrophic signals by activating G protein-coupled receptors, particularly, the olfactory receptor family, and inhibiting the transcription factor controlling cell proliferation and differentiation. Moreover, VCP overexpression restored pro-survival signaling through regulating alternative splicing alterations of mitochondrial genes. Together, our study revealed a novel molecular regulation mediated by VCP under pressure overload that may bring new insight into the mechanisms involved in protecting against hypertensive heart failure.

Abstract 11730: Endogenous MAFbx Mediates Cardiac Rupture After Myocardial Infarction in Mice

Rationale: Muscle atrophy F-box (MAFbx/atrogin-1), an E3 ubiquitin ligase, plays a critical role in mediating skeletal muscle atrophy and induces proteasomal degradation in cardiomyocytes. Loss of function of MAFbx inhibits pressure overload-induced pathological cardiac hypertrophy, in part through stabilization of IκB. The role of MAFbx in regulating cardiac remodeling following myocardial infarction (MI) remains unclear. Objective: We investigated the role of MAFbx in regulating cardiac remodeling following MI. Methods and Results: Permanent coronary ligation of the left coronary artery was applied to MAFbx knockout (KO) and wild-type (WT) mice. Expression of MAFbx in WT mice was significantly increased in the risk area of the LV after MI. The mortality rate due to cardiac rupture following MI was significantly decreased in MAFbx KO mice compared to WT mice (25.3% in KO mice (n=61) vs. 47.7% in WT mice (n=59) P=0.03). There was no difference in the infarct sizes 3 days after MI or the number of TUNEL-positive cardiomyocytes between MAFbx KO mice and WT mice. DNA microarray analyses revealed that the gene expression pattern in hearts after MI demonstrated clear clusters for MAFbx KO and WT. Interestingly, upregulation of matrix metalloproteinase (MMP)-9, interleukin 1β, proinflammatory cytokines, and NLRP3, an inflammasone component, were attenuated in MAFbx KO mice. MMP-9 activity was also decreased in MAFbx KO in the risk area 3 days after MI compared to in WT mice. Flow cytometry revealed that myocardial leukocyte infiltration one day after MI was suppressed in MAFbx KO mice. Immunofluorescence double-labeling showed that expression of NLRP3 in both cardiomyocytes and non-cardiomyocyte cells was decreased in MAFbx KO mice. Conclusions: These results suggest that MAFbx plays an important role in the excessive inflammation, including leukocyte infiltration, inflammasome formation, and production of proinflammatory cytokines, following MI. Inhibition of MAFbx reduces mortality due to cardiac rupture after MI, in part through decreased MMP9 activity and leukocyte infiltration.

Exercise preconditioning attenuates pressure overload-induced pathological cardiac hypertrophy: potential role of HSF1 and NF-κB p65 signaling

To observe the effect of exercise preconditioning (EP) on pressure overload-induced pathological cardiac hypertrophy and explore related mechanisms. Ten-week-old male Sprague-Dawley rats (n = 80) were randomly divided into four groups via random number table method: sham, TAC, EP + sham and EP + TAC. Two EP groups were subjected to 4 weeks of treadmill training, and followed by sham and TAC operations. Eight weeks after the surgery, mean arterial pressure (MAP), cardiac morphology, mRNA expressions of the B-type natriuretic peptide (BNP) and heat shock protein (HSP) 70 and protein expression of the BNP, heat shock transcription factor 1 (HSF1), HSP70, nuclear factor κB (NF-κB) p65, and interleukin-2 (IL-2) were examined. (1) Pathological cardiac hypertrophy index: eight weeks after TAC, MAP, heart size, HW/BW, cross-sectional area of the cardiomyocytes (CSA) and mRNA and protein expressions of BNP in the LV were all significantly higher in the TAC and EP + TAC groups than respective sham groups (all P < 0.05). HW/BW, CSA, and mRNA and protein expressions of BNP in the LV were significantly lower in EP + TAC group than in TAC group (all P < 0.05). (2) mRNA and protein expressions of HSF1 and HSP70 and nuclear HSF1 levels were significantly downregulated post TAC, however, EP treatment significantly increased the expression of HSF1 and nuclear HSF1 levels in TAC rats (all P < 0.05). (3) mRNA and protein expressions of NF-κB p65 and IL-2 were significantly increased in the TAC and EP + TAC groups compared with the respective sham groups (all P < 0.05), which were significantly downregulated in EP + TAC group compared to TAC group (all P < 0.05). EP could effectively reduce the cardiac hypertrophic responses induced by TAC possibly through upregulating the expressions of HSF1 and HSP70 and inhibiting the expression of NF-κB p65 and its nuclear translocation.

Hrd1 and ER-Associated Protein Degradation, ERAD, are Critical Elements of the Adaptive ER Stress Response in Cardiac Myocytes.

Hydroxymethyl glutaryl-coenzyme A reductase degradation protein 1 (Hrd1) is an endoplasmic reticulum (ER)-transmembrane E3 ubiquitin ligase that has been studied in yeast, where it contributes to ER protein quality control by ER-associated degradation (ERAD) of misfolded proteins that accumulate during ER stress. Neither Hrd1 nor ERAD has been studied in the heart, or in cardiac myocytes, where protein quality control is critical for proper heart function. The objective of this study were to elucidate roles for Hrd1 in ER stress, ERAD, and viability in cultured cardiac myocytes and in the mouse heart, in vivo. The effects of small interfering RNA-mediated Hrd1 knockdown were examined in cultured neonatal rat ventricular myocytes. The effects of adeno-associated virus-mediated Hrd1 knockdown and overexpression were examined in the hearts of mice subjected to pressure overload-induced pathological cardiac hypertrophy, which challenges protein-folding capacity. In cardiac myocytes, the ER stressors, thapsigargin and tunicamycin increased ERAD, as well as adaptive ER stress proteins, and minimally affected cell death. However, when Hrd1 was knocked down, thapsigargin and tunicamycin dramatically decreased ERAD, while increasing maladaptive ER stress proteins and cell death. In vivo, Hrd1 knockdown exacerbated cardiac dysfunction and increased apoptosis and cardiac hypertrophy, whereas Hrd1 overexpression preserved cardiac function and decreased apoptosis and attenuated cardiac hypertrophy in the hearts of mice subjected to pressure overload. Hrd1 and ERAD are essential components of the adaptive ER stress response in cardiac myocytes. Hrd1 contributes to preserving heart structure and function in a mouse model of pathological cardiac hypertrophy.

HSF1 and NF-κB p65 participate in the process of exercise preconditioning attenuating pressure overload-induced pathological cardiac hypertrophy

Pathological cardiac hypertrophy, often accompanied by hypertension, aortic stenosis and valvular defects, is typically associated with myocyte remodeling and cardiac dysfunction. Exercise preconditioning (EP) has been proven to enhance the tolerance of the myocardium to cardiac ischemia-reperfusion injury. However, the effects of EP in pathological cardiac hypertrophy are rarely reported. 10-wk-old male Sprague–Dawley rats (n = 80) were randomly divided into four groups: sham, TAC， EP + sham and EP + TAC. Two EP groups were subjected to 4 weeks of treadmill training, and the EP + TAC and TAC groups were followed by TAC operations. The sham and EP + sham groups underwent the same operation without aortic constriction. Eight weeks after the surgery, we evaluated the effects of EP by echocardiography, morphology, and histology and observed the expressions of the associated proteins. Compared with the respective control groups, hypertrophy-related indicators were significantly increased in the TAC and EP + TAC groups (p < 0.05). However, between the TAC and EP + TAC groups, all of these changes were effectively inhibited by EP treatment (p < 0.05). Furthermore, EP treatment upregulated the expression of HSF1 and HSP70, increased the HSF1 levels in the nuclear fraction, inhibited the expression of the NF-κB p65 subunit, decreased the NF-κB p65 subunit levels in the nuclear fraction, and reduced the IL2 levels in the myocardia of rats. EP could effectively reduce the cardiac hypertrophic responses induced by TAC and may play a protective role by upregulating the expressions of HSF1 and HSP70, activating HSF1 and then inhibiting the expression of NF-κB p65 and nuclear translocation.

Abstract 213: Fat Tissue specific Adipose Triglyceride Lipase as a major determinant for the development of pressure overload-induced heart failure

Introduction: Myocardial metabolism undergoes change in response to pathological cardiac hypertrophy (PH), characterized by increased reliance on glucose oxidation, decreased free fatty acid (FFA) oxidation and a loss of metabolic flexibility. Cardiac metabolism is influenced by other organs such as adipose tissue. Hence, we aimed to investigate the effect of Adipose Triglyceride Lipase (ATGL) in adipose tissue on the development of PH and heart failure (HF) in a pressure overload-induced cardiac hypertrophy model in mice. Methods: Male adipose tissue specific ATGL-knock out (atATGL-KO) and wild type mice (WT) underwent sham surgery (sham) or transverse aortic constriction (TAC). After 11 weeks, mice were sacrificed and organs were harvested. We performed echocardiography one week before and 11 weeks after surgery. Left ventricular mass (LVM), left ventricular mass/tibia length (LVM/TL) and ejection fraction (EF) were calculated. Beta-myosin heavy chain (β-MyHC) was measured in RNA of hearts. Insulin resistance was assessed by an intraperitoneal glucose tolerance test (GTT) and an insulin tolerance test (ITT). FFAs were measured in serum in total. Results: LVM and LVM/TL in WT was significantly higher compared to atATGL-KO after TAC (LVM/TL [mg/mm] WT-TAC: 18,0±2,2; atATGL-KO-TAC: 13,1±2,3; p&lt;0,01). The higher increase of LVM in WT was associated with a larger left ventricle internal diameter. Reduction of EF was significantly more pronounced in WT compared to atATGL-KO ([%] WT: 28,81±6,9 atATGL-KO: 42,39±4,5; p&lt;0,01). Beta-MyHC, a marker for PH, was markedly higher in WT-TAC than in atATGL-KO-TAC (WT-TAC: 11,3±3,6; atATGL-KO-TAC: 1.9±0,6; p&lt;0,01). While WT-TAC showed higher Serum FFA-levels than atATGL-KO-TAC ([mmol/l] WT-TAC: 0,97±0,086; atATGL-KO-TAC: 0,49±0,032; p&lt;0,001), GTT and ITT revealed a higher insulin sensitivity in atATGL-KO-TAC compared to WT-TAC. Conclusion: The present study demonstrates that atATGL is a crucial determinant for the development of pressure overload-induced PH and HI. The lack of ATGL in adipose tissue, the associated reduction of fatty acid release in the circulation and subsequent switches in cardiac energy substrates from free fatty acids to glucose are potential underlying mechanisms of this process.

Fibronectin contributes to pathological cardiac hypertrophy but not physiological growth

Ability of the heart to undergo pathological or physiological hypertrophy upon increased wall stress is critical for long-term compensatory function in response to increased workload demand. While substantial information has been published on the nature of the fundamental molecular signaling involved in hypertrophy, the role of extracellular matrix protein Fibronectin (Fn) in hypertrophic signaling is unclear. The objective of the study was to delineate the role of Fn during pressure overload-induced pathological cardiac hypertrophy and physiological growth prompted by exercise. Genetic conditional ablation of Fn in adulthood blunts cardiomyocyte hypertrophy upon pressure overload via attenuated activation of nuclear factor of activated T cells (NFAT). Loss of Fn delays development of heart failure and improves survival. In contrast, genetic deletion of Fn has no impact on physiological cardiac growth induced by voluntary wheel running. Down-regulation of the transcription factor c/EBPβ (Ccaat-enhanced binding protein β), which is essential for induction of the physiological growth program, is unaffected by Fn deletion. Nuclear NFAT translocation is triggered by Fn in conjunction with up-regulation of the fetal gene program and hypertrophy of cardiomyocytes in vitro. Furthermore, activation of the physiological gene program induced by insulin stimulation in vitro is attenuated by Fn, whereas insulin had no impact on Fn-induced pathological growth program. Fn contributes to pathological cardiomyocyte hypertrophy in vitro and in vivo via NFAT activation. Fn is dispensable for physiological growth in vivo, and Fn attenuates the activation of the physiological growth program in vitro.