Endogenous RBM4 prevents Ang II-induced cardiomyocyte hypertrophy via downregulating the expression of PTBP1

Aberrant gene expression in cardiomyocyte has been revealed to be the fundamental essence of pathological cardiac hypertrophy. However, the detailed mechanisms are not fully understood. The underlying regulators of gene expression involved in cardiac hypertrophy remain to be further identified. Here, we report that the RNA-binding protein RNA-binding motif protein 4 (RBM4) functions as an endogenic protector that is able to fight against cardiomyocyte hypertrophy in vitro. Under pro-hypertrophic stimulation of angiotensin II (Ang II), the protein level of RBM4 in cardiomyocyte and myocardium is elevated. Knockdown of RBM4 can further aggravate cardiomyocyte hypertrophy, while over-expression of RBM4 represses cardiomyocyte hypertrophy. Mechanistically, RBM4 is localized in the nucleus and down-regulates the expression of polypyrimidine tract-binding protein 1 (PTBP1), which has been shown to aggravate cardiomyocyte hypertrophy. In addition, we suggest that the up-regulation of RBM4 in cardiomyocyte hypertrophy is caused by N6-methyladenosine (m6A). Ang II induces m6A methylation of RBM4 mRNA, which further enhances the YTH domain-containing family protein 1 (YTHDF1)-mediated translation of RBM4. Thus, our results reveal a novel pathway consisting of m6A, RBM4 and PTBP1, which is involved in cardiomyocyte hypertrophy.

RICH1 is a novel key suppressor of isoproterenol‑ or angiotensin II‑induced cardiomyocyte hypertrophy

Cardiac hypertrophy is one of the key processes in the development of heart failure. Notably, small GTPases and GTPase‑activating proteins (GAPs) serve essential roles in cardiac hypertrophy. RhoGAP interacting with CIP4 homologs protein 1 (RICH1) is a RhoGAP that can regulate Cdc42/Rac1 and F‑actin dynamics. RICH1 is involved in cell proliferation and adhesion; however, to the best of our knowledge, its role in cardiac hypertrophy remains unknown. In the present study, the role of RICH1 in cardiomyocyte hypertrophy was assessed. Cell viability was analyzed using the Cell Counting Kit‑8 assay and cells surface area (CSA) was determined by cell fluorescence staining. Reverse transcription‑quantitative PCR and western blotting were used to assess the mRNA expression levels of hypertrophic marker genes, such as Nppa, Nppb and Myh7, and the protein expression levels of RICH1, respectively. RICH1 was shown to be downregulated in isoproterenol (ISO)‑ or angiotensin II (Ang II)‑treated H9c2 cells. Notably, overexpression of RICH1 attenuated the upregulation of hypertrophy‑related markers, such as Nppa, Nppb and Myh7, and the enlargement of CSA induced by ISO and Ang II. By contrast, the knockdown of RICH1 exacerbated these effects. These findings suggested that RICH1 may be a novel suppressor of ISO‑ or Ang II‑induced cardiomyocyte hypertrophy. The results of the present study will be beneficial to further studies assessing the role of RICH1 and its downstream molecules in inhibiting cardiac hypertrophy.

The function of tRNA-derived small RNAs in cardiovascular diseases

tRNA-derived small RNAs (tsRNAs) constitute a subgroup of small noncoding RNAs (ncRNAs) originating from tRNA molecules. Their rich content, evolutionary conservatism, high stability, and widespread existence makes them significant in disease research. These characteristics have positioned tsRNAs as key players in various physiological and pathological processes. tsRNA actively participates in regulating many cellular processes, such as cell death, proliferation, and metabolism. tsRNAs could be promising diagnostic markers for cardiovascular diseases (CVDs). tsRNAs have been identified in serums, suggesting their utility as early indicators for the diagnosis of CVDs. Moreover, the regulatory roles of tsRNAs in CVDs make them promising targets for therapeutic intervention. This review provides a succinct overview of the characteristics, classification, and regulatory functions of tsRNAs in the context of CVDs. By shedding light on the intricate roles of tsRNAs, this knowledge could pave the way for the development of innovative diagnostic tools and therapeutic strategies for CVDs.

ROCK1 deficiency preserves caveolar compartmentalization of signaling molecules and cell membrane integrity

In this study, we investigated the roles of ROCK1 in regulating structural and functional features of caveolae located at the cell membrane of cardiomyocytes, adipocytes, and mouse embryonic fibroblasts (MEFs) as well as related physiopathological effects. Caveolae are small bulb-shaped cell membrane invaginations, and their roles have been associated with disease conditions. One of the unique features of caveolae is that they are physically linked to the actin cytoskeleton that is well known to be regulated by RhoA/ROCKs pathway. In cardiomyocytes, we observed that ROCK1 deficiency is coincident with an increased caveolar density, clusters, and caveolar proteins including caveolin-1 and -3. In the mouse cardiomyopathy model with transgenic overexpressing Gαq in myocardium, we demonstrated the reduced caveolar density at cell membrane and reduced caveolar protein contents. Interestingly, coexisting ROCK1 deficiency in cardiomyocytes can rescue these defects and preserve caveolar compartmentalization of β-adrenergic signaling molecules including β1-adrenergic receptor and type V/VI adenylyl cyclase. In cardiomyocytes and adipocytes, we detected that ROCK1 deficiency increased insulin signaling with increased insulin receptor activation in caveolae. In MEFs, we identified that ROCK1 deficiency increased caveolar and total levels of caveolin-1 and cell membrane repair ability after mechanical or chemical disruptions. Together, these results demonstrate that ROCK1 can regulate caveolae plasticity and multiple functions including compartmentalization of signaling molecules and cell membrane repair following membrane disruption by mechanical force and oxidative damage. These findings provide possible molecular insights into the beneficial effects of ROCK1 deletion/inhibition in cardiomyocytes, adipocytes, and MEFs under certain diseased conditions.

Anserine, a Histidine-Containing Dipeptide, Suppresses Pressure Overload-Induced Systolic Dysfunction by Inhibiting Histone Acetyltransferase Activity of p300 in Mice

Anserine, an imidazole dipeptide, is present in the muscles of birds and fish and has various bioactivities, such as anti-inflammatory and anti-fatigue effects. However, the effect of anserine on the development of heart failure remains unknown. We cultured primary cardiomyocytes with 0.03 mM to 10 mM anserine and stimulated them with phenylephrine for 48 h. Anserine significantly suppressed the phenylephrine-induced increases in cardiomyocyte hypertrophy, ANF and BNP mRNA levels, and histone H3K9 acetylation. An in vitro histone acetyltransferase (HAT) assay showed that anserine directly suppressed p300-HAT activity with an IC50 of 1.87 mM. Subsequently, 8-week-old male C57BL/6J mice were subjected to transverse aortic constriction (TAC) and were randomly assigned to receive daily oral treatment with anserine-containing material, Marine Active® (60 or 200 mg/kg anserine) or vehicle for 8 weeks. Echocardiography revealed that anserine 200 mg/kg significantly prevented the TAC-induced increase in left ventricular posterior wall thickness and the decrease in left ventricular fractional shortening. Moreover, anserine significantly suppressed the TAC-induced acetylation of histone H3K9. These results indicate that anserine suppresses TAC-induced systolic dysfunction, at least in part, by inhibiting p300-HAT activity. Anserine may be used as a pharmacological agent for human heart failure therapy.

[Effect and mechanism of Linggui Zhugan Decoction in regulating Sig1R on AngⅡ-induced cardiomyocyte hypertrophy]

This study aims to explore the mechanism of Linggui Zhugan Decoction(LGZGD) in inhibiting Angiotensin Ⅱ(AngⅡ)-induced cardiomyocyte hypertrophy by regulating sigma-1 receptor(Sig1R). The model of H9c2 cardiomyocyte hypertrophy induced by AngⅡ in vitro was established by preparing LGZGD-containing serum and blank serum. H9c2 cells were divided into normal group, AngⅡ model group, 20% normal rat serum group(20% NSC), and 20% LGZGD-containing serum group. After the cells were incubated with AngⅡ(1 μmol·L~(-1)) or AngⅡ with serum for 72 h, the surface area of cardiomyocytes was detected by phalloidine staining, and the activities of Na~+-K~+-ATPase and Ca~(2+)-Mg~(2+)-ATPase were detected by micromethod. The mitochondrial Ca~(2+) levels were detected by flow cytometry, and the expression levels of atrial natriuretic peptide(ANP), brain natriuretic peptide(BNP), Sig1R, and inositol 1,4,5-triphosphate receptor type 2(IP_3R_2) were detected by Western blot. The expression of Sig1R was down-regulated by transfecting specific siRNA for investigating the efficacy of LGZGD-containing serum on cardiomyocyte surface area, Na~+-K~+-ATPase activity, Ca~(2+)-Mg~(2+)-ATPase activity, mitochondrial Ca~(2+), as well as ANP, BNP, and IP_3R_2 protein expressions. The results showed that compared with the normal group, AngⅡ could significantly increase the surface area of cardiomyocytes and the expression of ANP and BNP(P<0.01), and it could decrease the activities of Na~+-K~+-ATPase and Ca~(2+)-Mg~(2+)-ATPase, the concentration of mitochondrial Ca~(2+), and the expression of Sig1R(P<0.01). In addition, IP_3R_2 protein expression was significantly increased(P<0.01). LGZGD-containing serum could significantly decrease the surface area of cardiomyocytes and the expression of ANP and BNP(P<0.05, P<0.01), and it could increase the activities of Na~+-K~+-ATPase and Ca~(2+)-Mg~(2+)-ATPase, the concentration of mitochondrial Ca~(2+ )(P<0.01), and the expression of Sig1R(P<0.05). In addition, IP_3R_2 protein expression was significantly decreased(P<0.05). However, after Sig1R was down-regulated, the effects of LGZGD-containing serum were reversed(P<0.01). These results indicated that the LGZGD-containing serum could inhibit cardiomyocyte hypertrophy induced by AngⅡ, and its pharmacological effect was related to regulating Sig1R, promoting mitochondrial Ca~(2+ )inflow, restoring ATP synthesis, and protecting mitochondrial function.

Cardioprotective effects of Moku-boi-to and its impact on AngII-induced cardiomyocyte hypertrophy

Cardiomyocyte hypertrophy, induced by elevated levels of angiotensin II (AngII), plays a crucial role in cardiovascular diseases. Current therapeutic approaches aim to regress cardiac hypertrophy but have limited efficacy. Widely used Japanese Kampo medicines are highly safe and potential therapeutic agents. This study aims to explore the impact and mechanisms by which Moku-boi-to (MBT), a Japanese Kampo medicine, exerts its potential cardioprotective benefits against AngII-induced cardiomyocyte hypertrophy, bridging the knowledge gap and contributing to the development of novel therapeutic strategies. By evaluating the effects of six Japanese Kampo medicines with known cardiovascular efficiency on AngII-induced cardiomyocyte hypertrophy and cell death, we identified MBT as a promising candidate. MBT exhibited preventive effects against AngII-induced cardiomyocyte hypertrophy, cell death and demonstrated improvements in intracellular Ca2+ signaling regulation, ROS production, and mitochondrial function. Unexpectedly, experiments combining MBT with the AT1 receptor antagonist losartan suggested that MBT may target the AT1 receptor. In an isoproterenol-induced heart failure mouse model, MBT treatment demonstrated significant effects on cardiac function and hypertrophy. These findings highlight the cardioprotective potential of MBT through AT1 receptor-mediated mechanisms, offering valuable insights into its efficacy in alleviating AngII-induced dysfunction in cardiomyocytes. The study suggests that MBT holds promise as a safe and effective prophylactic agent for cardiac hypertrophy, providing a deeper understanding of its mechanisms for cardioprotection against AngII-induced dysfunction.

Effects of maternal hypothyroidism on postnatal cardiomyocyte proliferation and cardiac disease responses of the progeny

Maternal hypothyroidism (MH) could adversely affect the cardiac disease responses of the progeny. This study tested the hypothesis that MH reduces early postnatal cardiomyocyte (CM) proliferation so that the adult heart of MH progeny has a smaller number of larger cardiac myocytes, which imparts adverse cardiac disease responses following injury. Thyroidectomy (TX) was used to establish MH. The progeny from mice that underwent sham or TX surgery were termed Ctrl (control) or MH (maternal hypothyroidism) progeny, respectively. MH progeny had similar heart weight (HW) to body weight (BW) ratios and larger CM size consistent with fewer CMs at postnatal day 60 (P60) compared with Ctrl (control) progeny. MH progeny had lower numbers of EdU+, Ki67+, and phosphorylated histone H3 (PH3)+ CMs, which suggests they had a decreased CM proliferation in the postnatal timeframe. RNA-seq data showed that genes related to DNA replication were downregulated in P5 MH hearts, including bone morphogenetic protein 10 (Bmp10). Both in vivo and in vitro studies showed Bmp10 treatment increased CM proliferation. After transverse aortic constriction (TAC), the MH progeny had more severe cardiac pathological remodeling compared with the Ctrl progeny. Thyroid hormone (T4) treatment for MH mothers preserved their progeny's postnatal CM proliferation capacity and prevented excessive pathological remodeling after TAC. Our results suggest that CM proliferation during early postnatal development was significantly reduced in MH progeny, resulting in fewer CMs with hypertrophy in adulthood. These changes were associated with more severe cardiac disease responses after pressure overload.NEW & NOTEWORTHY Our study shows that compared with Ctrl (control) progeny, the adult progeny of mothers who have MH (MH progeny) had fewer CMs. This reduction of CM numbers was associated with decreased postnatal CM proliferation. Gene expression studies showed a reduced expression of Bmp10 in MH progeny. Bmp10 has been linked to myocyte proliferation. In vivo and in vitro studies showed that Bmp10 treatment of MH progeny and their myocytes could increase CM proliferation. Differences in CM number and size in adult hearts of MH progeny were linked to more severe cardiac structural and functional remodeling after pressure overload. T4 (synthetic thyroxine) treatment of MH mothers during their pregnancy, prevented the reduction in CM number in their progeny and the adverse response to disease stress.

STAT5b is a key effector of NRG-1/ERBB4-mediated myocardial growth

The growth factor Neuregulin-1 (NRG-1) regulates myocardial growth and is currently under clinical investigation as a treatment for heart failure. Here, we demonstrate in several in vitro and in vivo models that STAT5b mediates NRG-1/EBBB4-stimulated cardiomyocyte growth. Genetic and chemical disruption of the NRG-1/ERBB4 pathway reduces STAT5b activation and transcription of STAT5b target genes Igf1, Myc, and Cdkn1a in murine cardiomyocytes. Loss of Stat5b also ablates NRG-1-induced cardiomyocyte hypertrophy. Dynamin-2 is shown to control the cell surface localization of ERBB4 and chemical inhibition of Dynamin-2 downregulates STAT5b activation and cardiomyocyte hypertrophy. In zebrafish embryos, Stat5 is activated during NRG-1-induced hyperplastic myocardial growth, and chemical inhibition of the Nrg-1/Erbb4 pathway or Dynamin-2 leads to loss of myocardial growth and Stat5 activation. Moreover, CRISPR/Cas9-mediated knockdown of stat5b results in reduced myocardial growth and cardiac function. Finally, the NRG-1/ERBB4/STAT5b signaling pathway is differentially regulated at mRNA and protein levels in the myocardium of patients with pathological cardiac hypertrophy as compared to control human subjects, consistent with a role of the NRG-1/ERBB4/STAT5b pathway in myocardial growth.

Exosomes secreted from bone marrow mesenchymal stem cells suppress cardiomyocyte hypertrophy through Hippo-YAP pathway in heart failure

Mesenchymal stem cells-derived exosomes (MSCs-exosomes) reportedly possess cardioprotective effects. This study investigated the therapeutic potential and mechanisms of MSCs-exosomes on heart failure (HF). H9c2 cells were used to establish a cardiomyocyte hypertrophy model by angiotensin II (Ang II) treatment. Isolated MSCs-exosomes were identified by transmission electron microscope and CD63 detection. Apoptosis rate was measured by terminal deoxynucleotidyl transferase (TdT) dUTP Nick-End Labeling (TUNEL) assay. Levels of inflammatory factors [interleukin (IL)-1β, IL-4, IL-6, and tumor necrosis factor (TNF)-α] and brain natriuretic peptide (BNP) were determined by ELISA. Expression of apoptosis-related proteins [Bax, B-cell lymphoma-2 (Bcl-2), and caspase 3] and Hippo-Yes-associated protein (YAP) pathway-related proteins [YAP, phosphor (p)-YAP, and tafazzin (TAZ)] was detected by western blotting. Cardiomyocyte hypertrophy of H9c2 cells induced by Ang II was ameliorated by MSCs-exosomes treatment. MSCs-exosomes downregulated Bax and caspase 3 levels and upregulated Bcl-2 level in Ang II-induced H9c2 cells. MSCs-exosomes also reduced the levels of BNP, IL-1β, IL-4, IL-6, and TNF-α in Ang II-induced H9c2 cells. Meanwhile, p-YAP was downregulated and TAZ was upregulated after MSCs-exosomes administration. In conclusion, MSCs-exosomes alleviate the apoptosis and inflammatory response of cardiomyocyte via deactivating Hippo-YAP pathway in HF.

Lotus Bee Pollen Extract Inhibits Isoproterenol-Induced Hypertrophy via JAK2/STAT3 Signaling Pathway in Rat H9c2 Cells

Bee pollen possesses an anti-cardiomyocyte injury effect by reducing oxidative stress levels and inhibiting inflammatory response and apoptosis, but the possible effect mechanism has rarely been reported. This paper explores the effect of the extract of lotus bee pollen (LBPE) on cardiomyocyte hypertrophy (CH) and its mechanism. The main components of LBPE were identified via UPLC-QTOF MS. An isoproterenol-induced rat H9c2 CH model was subsequently used to evaluate the protection of LBPE on cells. LBPE (100, 250 and 500 μg∙mL^-1) reduced the surface area, total protein content and MDA content, and increased SOD activity and GSH content in CH model in a dose-dependent manner. Meanwhile, quantitative real-time PCR trials confirmed that LBPE reduced the gene expression levels of CH markers, pro-inflammatory cytokines and pro-apoptosis factors, and increased the Bcl-2 mRNA expression and Bcl-2/Bax ratio in a dose-dependent manner. Furthermore, target fishing, bioinformatics analysis and molecular docking suggested JAK2 could be a pivotal target protein for the main active ingredients in the LBPE against CH. Ultimately, Western blot (WB) trials confirmed that LBPE can dose-dependently inhibit the phosphorylation of JAK2 and STAT3. The results show that LBPE can protect against ISO-induced CH, possibly via targeting the JAK2/STAT3 pathway, also suggesting that LBPE may be a promising candidate against CH.

Pyrazole-Curcumin Suppresses Cardiomyocyte Hypertrophy by Disrupting the CDK9/CyclinT1 Complex

The intrinsic histone acetyltransferase (HAT), p300, has an important role in the development and progression of heart failure. Curcumin (CUR), a natural p300-specific HAT inhibitor, suppresses hypertrophic responses and prevents deterioration of left-ventricular systolic function in heart-failure models. However, few structure–activity relationship studies on cardiomyocyte hypertrophy using CUR have been conducted. To evaluate if prenylated pyrazolo curcumin (PPC) and curcumin pyrazole (PyrC) can suppress cardiomyocyte hypertrophy, cultured cardiomyocytes were treated with CUR, PPC, or PyrC and then stimulated with phenylephrine (PE). PE-induced cardiomyocyte hypertrophy was inhibited by PyrC but not PPC at a lower concentration than CUR. Western blotting showed that PyrC suppressed PE-induced histone acetylation. However, an in vitro HAT assay showed that PyrC did not directly inhibit p300-HAT activity. As Cdk9 phosphorylates both RNA polymerase II and p300 and increases p300-HAT activity, the effects of CUR and PyrC on the kinase activity of Cdk9 were examined. Phosphorylation of p300 by Cdk9 was suppressed by PyrC. Immunoprecipitation-WB showed that PyrC inhibits Cdk9 binding to CyclinT1 in cultured cardiomyocytes. PyrC may prevent cardiomyocyte hypertrophic responses by indirectly suppressing both p300-HAT activity and RNA polymerase II transcription elongation activity via inhibition of Cdk9 kinase activity.

GSK3β Serine 389 Phosphorylation Modulates Cardiomyocyte Hypertrophy and Ischemic Injury

Prior studies show that glycogen synthase kinase 3β (GSK3β) contributes to cardiac ischemic injury and cardiac hypertrophy. GSK3β is constitutionally active and phosphorylation of GSK3β at serine 9 (S9) inactivates the kinase and promotes cellular growth. GSK3β is also phosphorylated at serine 389 (S389), but the significance of this phosphorylation in the heart is not known. We analyzed GSK3β S389 phosphorylation in diseased hearts and utilized overexpression of GSK3β carrying ser→ala mutations at S9 (S9A) and S389 (S389A) to study the biological function of constitutively active GSK3β in primary cardiomyocytes. We found that phosphorylation of GSK3β at S389 was increased in left ventricular samples from patients with dilated cardiomyopathy and ischemic cardiomyopathy, and in hearts of mice subjected to thoracic aortic constriction. Overexpression of either GSK3β S9A or S389A reduced the viability of cardiomyocytes subjected to hypoxia-reoxygenation. Overexpression of double GSK3β mutant (S9A/S389A) further reduced cardiomyocyte viability. Determination of protein synthesis showed that overexpression of GSK3β S389A or GSK3β S9A/S389A increased both basal and agonist-induced cardiomyocyte growth. Mechanistically, GSK3β S389A mutation was associated with activation of mTOR complex 1 signaling. In conclusion, our data suggest that phosphorylation of GSK3β at S389 enhances cardiomyocyte survival and protects from cardiomyocyte hypertrophy.

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

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

Huoxue Qianyang Qutan recipe attenuates Ang II-induced cardiomyocyte hypertrophy by regulating reactive oxygen species production

Continuous and irreversible cardiac hypertrophy can induce cardiac maladaptation and cardiac remodeling, resulting in increased risk of developing cardiovascular diseases. The present study was conducted to investigate the therapeutic effect of Huoxue Qianyang Qutan recipe (HQQR) on angiotensin II (Ang II)-induced cardiomyocyte hypertrophy. Primary cardiomyocytes were isolated from the cardiac tissue of neonatal rats, followed by flow cytometry detection to confirm the proportion of primary cardiomyocytes. Cell Counting Kit-8 assay and immunofluorescence detection were performed to examine the effect of Ang II and HQQR on cardiomyocyte hypertrophy. Reactive oxygen species (ROS) and a series of metabolic indicators were quantified to investigate the effect of HQQR on Ang II-induced cardiomyocyte hypertrophy. Mitochondrial electron transport chain complex activity and related coding gene expression were determined to explore the effect of HQQR on mitochondrial function. HQQR significantly inhibited Ang II-induced cardiomyocyte hypertrophy and restored Ang II-induced ROS accumulation, metabolic indicators, and membrane potential levels. HQQR also regulated the mitochondrial function related to the sirtuin 1 pathway in Ang II-induced cardiomyocytes by increasing the activity of the mitochondrial electron transport chain complex and affecting the expression of genes encoding mitochondrial electron transport chain complex subunits. HQQR could alleviate Ang II-induced cardiomyocyte hypertrophy by modulating oxidative stress, accumulating ROS and increasing mitochondrial electron transport chain activity.

Yiqi Huoxue preserves heart function by upregulating the Sigma-1 receptor in rats with myocardial infarction

Yiqi Huoxue (YQHX) is widely used in traditional Chinese medical practice due to its reported cardioprotective effects. The aim of the present study was to investigate the mechanism underlying these effects of YQHX via the regulation of the Sigma-1 receptor. The Sigma-1 receptor is a chaperone protein located on the mitochondrion-associated endoplasmic reticulum (ER) membrane. It serves an important role in heart function by regulating intracellular Ca²⁺ homeostasis and enhancing cellular bioenergetics. In the present study, male Sprague Dawley rats with myocardial infarction (MI)-induced heart failure were used. MI rats were administered different treatments, including normal saline, YQHX and fluvoxamine, an agonist of the Sigma-1 receptor. Following four weeks of treatment, YQHX was revealed to improve heart function and attenuate myocardial hypertrophy in MI rats. Additionally, YQHX increased the ATP content and improved the mitochondrial ultrastructure in the heart tissues of MI rats in comparison with acontrol. Treatment was revealed to attenuate the decreased expression of the Sigma-1 receptor and increase the expression of inositol triphosphate type 2 receptors (IP₃R2) in MI rats. By exposing H9c2 cells to angiotensin II (Ang II), YQHX prevented cell hypertrophy and normalized the decreased ATP content. However, these positive effects were partially inhibited when the Sigma-1 receptor was knocked down via small interfering RNA transfection. The results of the present study suggested that the Sigma-1 receptor serves an important role in the cardioprotective efficacy of YQHX by increasing ATP content and attenuating cardiomyocyte hypertrophy.

Metformin attenuates angiotensin II-induced cardiomyocyte hypertrophy by upregulating the MuRF1 and MAFbx pathway

Pathological cardiac hypertrophy induced by aging and neurohumoral activation, such as angiotensin II (Ang II) activation, is an independent risk factor for heart failure. The muscle really interesting new gene-finger protein-1 (MuRF1) and muscle atrophy F-box (MAFbx) pathway has been previously reported to be an important mechanism underlying the pathogenesis of cardiac hypertrophy. Metformin is currently the first-line blood glucose-lowering agent that can be useful for the treatment of cardiovascular diseases. However, the potential role of metformin in the modulation of MuRF1 and MAFbx in cardiomyocyte hypertrophy remains poorly understood. The present study used H9c2 cells, a cardiomyocyte cell model. The surface area of cultured rat H9c2 myoblasts was measured and the expression levels of MuRF1 and MAFbx were quantified using western blot or reverse transcription-quantitative PCR. H9c2 cells were transfected with MuRF1 and MAFbx small interfering (si) RNA. The present study revealed that Ang II treatment significantly increased the cell surface area of model cardiomyocytes. Additionally, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) mRNA and protein expression was increased following this treatment. Ang II also downregulated MuRF1 and MAFbx protein and mRNA expression. In the H9C2, treatment with metformin attenuated hypertrophic remodeling. In addition, expression of ANP and BNP was significantly reduced in metformin-treated H9C2 cells. The results indicated that metformin increased the activity of MuRF1 and MAFbx and upregulated their expression, the knockdown of which resulted in deteriorative Ang II-induced cell hypertrophy, even following treatment with metformin. Taken together, data from the present study suggest that metformin can prevent cardiac hypertrophy through the MuRF1 and MAFbx pathways.

Selective loss of resident macrophage-derived insulin-like growth factor-1 abolishes adaptive cardiac growth to stress

Hypertension affects one-third of the world's population, leading to cardiac dysfunction that is modulated by resident and recruited immune cells. Cardiomyocyte growth and increased cardiac mass are essential to withstand hypertensive stress; however, whether immune cells are involved in this compensatory cardioprotective process is unclear. In normotensive animals, single-cell transcriptomics of fate-mapped self-renewing cardiac resident macrophages (RMs) revealed transcriptionally diverse cell states with a core repertoire of reparative gene programs, including high expression of insulin-like growth factor-1 (Igf1). Hypertension drove selective in situ proliferation and transcriptional activation of some cardiac RM states, directly correlating with increased cardiomyocyte growth. During hypertension, inducible ablation of RMs or selective deletion of RM-derived Igf1 prevented adaptive cardiomyocyte growth, and cardiac mass failed to increase, which led to cardiac dysfunction. Single-cell transcriptomics identified a conserved IGF1-expressing macrophage subpopulation in human cardiomyopathy. Here we defined the absolute requirement of RM-produced IGF-1 in cardiac adaptation to hypertension.

Replication Stress Response Modifies Sarcomeric Cardiomyopathy Remodeling

Background

Sarcomere gene mutations lead to cardiomyocyte hypertrophy and pathological myocardial remodeling. However, there is considerable phenotypic heterogeneity at both the cellular and the organ level, suggesting modifiers regulate the effects of these mutations. We hypothesized that sarcomere dysfunction leads to cardiomyocyte genotoxic stress, and this modifies pathological ventricular remodeling.

Methods and Results

Using a murine model deficient in the sarcomere protein, Mybpc3^−/− (cardiac myosin‐binding protein 3), we discovered that there was a surge in cardiomyocyte nuclear DNA damage during the earliest stages of cardiomyopathy. This was accompanied by a selective increase in ataxia telangiectasia and rad3‐related phosphorylation and increased p53 protein accumulation. The cause of the DNA damage and DNA damage pathway activation was dysregulated cardiomyocyte DNA synthesis, leading to replication stress. We discovered that selective inhibition of ataxia telangiectasia and rad3 related or cardiomyocyte deletion of p53 reduced pathological left ventricular remodeling and cardiomyocyte hypertrophy in Mybpc3^−/− animals. Mice and humans harboring other types of sarcomere gene mutations also had evidence of activation of the replication stress response, and this was associated with cardiomyocyte aneuploidy in all models studied.

Conclusions

Collectively, our results show that sarcomere mutations lead to activation of the cardiomyocyte replication stress response, which modifies pathological myocardial remodeling in sarcomeric cardiomyopathy.

Interactions between the ERK1/2 signaling pathway and PCAF play a key role in PE‑induced cardiomyocyte hypertrophy

Cardiomyocyte hypertrophy is a compensatory phase of chronic heart failure that is induced by the activation of multiple signaling pathways. The extracellular signal-regulated protein kinase (ERK) signaling pathway is an important regulator of cardiomyocyte hypertrophy. In our previous study, it was demonstrated that phenylephrine (PE)-induced cardiomyocyte hypertrophy involves the hyperacetylation of histone H3K9ac by P300/CBP-associated factor (PCAF). However, the upstream signaling pathway has yet to be fully identified. In the present study, the role of the extracellular signal-regulated protein kinase (ERK)1/2 signaling pathway in PE-induced cardiomyocyte hypertrophy was investigated. The mice cardiomyocyte hypertrophy model was successfully established by treating cells with PE in vitro. The results showed that phospho-(p-)ERK1/2 interacted with PCAF and modified the pattern of histone H3K9ac acetylation. An ERK inhibitor (U0126) and/or a histone acetylase inhibitor (anacardic acid; AA) attenuated the overexpression of phospho-ERK1/2 and H3K9ac hyperacetylation by inhibiting the expression of PCAF in PE-induced cardiomyocyte hypertrophy. Moreover, U0126 and/or AA could attenuate the overexpression of several biomarker genes related to cardiac hypertrophy (myocyte enhancer factor 2C, atrial natriuretic peptide, brain natriuretic peptide and β-myosin heavy chain) and prevented cardiomyocyte hypertrophy. These results revealed a novel mechanism in that AA protects against PE-induced cardiomyocyte hypertrophy in mice via the ERK1/2 signaling pathway, and by modifying the acetylation of H3K9ac. These findings may assist in the development of novel methods for preventing and treating hypertrophic cardiomyopathy.

Rutin Modulates MAPK Pathway Differently from Quercetin in Angiotensin II-Induced H9c2 Cardiomyocyte Hypertrophy

Rutin is a flavonoid with antioxidant property. It has been shown to exert cardioprotection against cardiomyocyte hypertrophy. However, studies regarding its antihypertrophic property are still lacking, whether it demonstrates similar antihypertrophic effect to its metabolite, quercetin. Hence, this study aimed to investigate the effects of both flavonoids on oxidative stress and mitogen-activated protein kinase (MAPK) pathway in H9c2 cardiomyocytes that were exposed to angiotensin II (Ang II) to induce hypertrophy. Cardiomyocytes were exposed to Ang II (600 nM) with or without quercetin (331 μM) or rutin (50 μM) for 24 h. A group given vehicle served as the control. The concentration of the flavonoids was chosen based on the reported effective concentration to reduce cell hypertrophy or cardiac injury in H9c2 cells. Exposure to Ang II increased cell surface area, intracellular superoxide anion level, NADPH oxidase and inducible nitric oxide synthase activities, and reduced cellular superoxide dismutase activity and nitrite level, which were similarly reversed by both rutin and quercetin. Rutin had no significant effects on phosphorylated proteins of extracellular signal-related kinases (ERK1/2) and p38 but downregulated phosphorylated c-Jun N-terminal kinases (JNK1/2), which were induced by Ang II. Quercetin, on the other hand, had significantly downregulated the phosphorylated proteins of ERK1/2, p38, and JNK1/2. The quercetin inhibitory effect on JNK1/2 was stronger than the rutin. In conclusion, both flavonoids afford similar protective effects against Ang II-induced cardiomyocyte hypertrophy, but they differently modulate MAPK pathway.

Inhibition of angiotensin II-induced hypertrophy and cardiac dysfunction by North American ginseng (Panax quinquefolius)

We determined whether North American ginseng (Panax quinquefolius L.) mitigates the effect of angiotensin II on hypertrophy and heart failure. Angiotensin II (0.3 mg/kg) was administered to rats for 2 or 4 weeks in the presence or absence of ginseng pretreatment. The effect of ginseng (10 μg/mL) on angiotensin II (100 nM) - induced hypertrophy was also determined in neonatal rat ventricular myocytes. We also determined effects of ginseng on fatty acid and glucose oxidation by measuring gene and protein expression levels of key factors. Angiotensin II treatment for 2 and 4 weeks induced cardiac hypertrophy as evidenced by increased heart weights, as well as the upregulation of the hypertrophy-related fetal gene expression levels, with all effects being abolished by ginseng. Ginseng also reduced abnormalities in left ventricular function as well as the angiotensin II-induced increased blood pressure. In myocytes, ginseng abolished the hypertrophic response to angiotensin II as assessed by surface area and gene expression of molecular markers of hypertrophy. Ginseng modulated angiotensin II-induced abnormalities in gene expression and protein levels of CD36, CPT1M, Glut4, and PDK4 in vivo and in vitro. In conclusion, ginseng suppresses angiotensin II-induced cardiac hypertrophy and dysfunction which is related to normalization of fatty acid and glucose oxidation.

ATPase Inhibitory Factor-1 Disrupts Mitochondrial Ca2+ Handling and Promotes Pathological Cardiac Hypertrophy through CaMKIIδ

ATPase inhibitory factor-1 (IF1) preserves cellular ATP under conditions of respiratory collapse, yet the function of IF1 under normal respiring conditions is unresolved. We tested the hypothesis that IF1 promotes mitochondrial dysfunction and pathological cardiomyocyte hypertrophy in the context of heart failure (HF). Methods and results: Cardiac expression of IF1 was increased in mice and in humans with HF, downstream of neurohumoral signaling pathways and in patterns that resembled the fetal-like gene program. Adenoviral expression of wild-type IF1 in primary cardiomyocytes resulted in pathological hypertrophy and metabolic remodeling as evidenced by enhanced mitochondrial oxidative stress, reduced mitochondrial respiratory capacity, and the augmentation of extramitochondrial glycolysis. Similar perturbations were observed with an IF1 mutant incapable of binding to ATP synthase (E55A mutation), an indication that these effects occurred independent of binding to ATP synthase. Instead, IF1 promoted mitochondrial fragmentation and compromised mitochondrial Ca2+ handling, which resulted in sarcoplasmic reticulum Ca2+ overloading. The effects of IF1 on Ca2+ handling were associated with the cytosolic activation of calcium-calmodulin kinase II (CaMKII) and inhibition of CaMKII or co-expression of catalytically dead CaMKIIδC was sufficient to prevent IF1 induced pathological hypertrophy. Conclusions: IF1 represents a novel member of the fetal-like gene program that contributes to mitochondrial dysfunction and pathological cardiac remodeling in HF. Furthermore, we present evidence for a novel, ATP-synthase-independent, role for IF1 in mitochondrial Ca2+ handling and mitochondrial-to-nuclear crosstalk involving CaMKII.

Angiotensin-(1-7) prevents T3-induced cardiomyocyte hypertrophy by upregulating FOXO3/SOD1/catalase and downregulating NF-ĸB

Clinical studies have shown a correlation between thyroid disorders and cardiac diseases. High levels of triiodothyronine (T3) induce cardiac hypertrophy, a risk factor for cardiac complications and heart failure. Previous results have demonstrated that angiotensin-(1-7) is able to block T3-induced cardiac hypertrophy; however, the molecular mechanisms involved in this event have not been fully elucidated. Here, we evidenced the contribution of FOXO3 signaling to angiotensin-(1-7) effects. Angiotensin-(1-7) treatment increased nuclear FOXO3 levels and reduced p-FOXO3 levels (inactive form) in isolated cardiomyocytes. Knockdown of FOXO3 by RNA silencing abrogated the antihypertrophic effect of angiotensin-(1-7). Increased expression of antioxidant enzymes superoxide dismutase 1 (SOD1 and catalase) and lower levels of reactive oxygen species and nuclear factor-κB (NF-κB) were observed after angiotensin-(1-7) treatment in vitro. Consistent with these results, transgenic rats overexpressing angiotensin-(1-7) displayed increased nuclear FOXO3 and SOD1 levels and reduced NF-κB levels in the heart. These results provide a new molecular mechanism responsible for the antihypertrophic effect of angiotensin-(1-7), which may contribute to future therapeutic targets.

Silencing of Sphingosine kinase 1 Affects Maturation Pathways in Mouse Neonatal Cardiomyocytes

Sphingosine kinase-1 (Sphk1) and its product, sphingosine-1-phosphate (S1P) are important regulators of cardiac growth and function. Numerous studies have reported that Sphk1/S1P signaling is essential for embryonic cardiac development and promotes pathological cardiac hypertrophy in adulthood. However, no studies have addressed the role of Sphk1 in postnatal cardiomyocyte (CM) development so far. The present study aimed to assess the molecular mechanism(s) by which Sphk1 silencing might influence CMs development and hypertrophy in vitro. Neonatal mouse CMs were transfected with siRNA against Sphk1 or negative control, and subsequently treated with 1 µM angiotensin II (AngII) or a control buffer for 24 h. The results of RNASeq analysis revealed that diminished expression of Sphk1 significantly accelerated neonatal CM maturation by inhibiting cell proliferation and inducing developmental pathways in the stress (AngII-induced) conditions. Importantly, similar effects were observed in the control conditions. Enhanced maturation of Sphk1-lacking CMs was further confirmed by the upregulation of the physiological hypertrophy-related signaling pathway involving Akt and downstream glycogen synthase kinase 3 beta (Gsk3β) downregulation. In summary, we demonstrated that the Sphk1 silencing in neonatal mouse CMs facilitated their postnatal maturation in both physiological and stress conditions.