Molecular targets and regulators of cardiac hypertrophy

HTR2A promotes the development of cardiac hypertrophy by activating PI3K-PDK1-AKT-mTOR signaling

5-Hydroxytryptamine receptor 2A (HTR2A) is a central regulator of fetal brain development and cognitive function in adults. However, the roles of HTR2A in the cardiovascular system are not fully understood. Here in this study, we explored the function of HTR2A in cardiac hypertrophy. Significantly, the expression levels of HTR2A mRNA and protein levels were upregulated in hypertrophic hearts of human patients. Besides, the expression of HTR2A was also upregulated in isoproterenol (ISO)-induced cardiac hypertrophy in the mouse. Next, the expression of HTR2A was knocked down with shRNA or overexpressed with adenovirus in neonatal rat cardiomyocytes, and ISO was used to induce cardiomyocyte hypertrophy. We showed that HTR2A knockdown repressed ISO-induced cardiomyocyte hypertrophy, which was demonstrated by decreased cardiomyocyte size and repressed expression of hypertrophic fetal genes (e.g., myosin heavy chain beta (β-Mhc), atrial natriuretic peptide (Anp), and brain natriuretic peptide (Bnp)). By contrast, HTR2A overexpression promoted cardiomyocyte hypertrophy. Of note, we observed that HTR2A promoted the activation (phosphorylation) of AKT-mTOR (mammalian target of rapamycin) signaling in cardiomyocytes, and repression of AKT-mTOR with perifosine or rapamycin blocked the effects of HTR2A on cardiomyocyte hypertrophy. Finally, we showed that HTR2A regulated AKT-mTOR signaling through activating the PI3K-PDK1 pathway, and inhibition of either PI3K or PDK1 blocked the roles of HTR2A in regulating AKT-mTOR signaling and cardiomyocyte hypertrophy. Altogether, these findings demonstrated that HTR2A activated PI3K-PDK1-AKT-mTOR signaling and promoted cardiac hypertrophy.

Low Plasma Volume and Increased Pressure Load Relate to Concentric Left Ventricular Remodeling After Preeclampsia: A Longitudinal Study

Background During uncomplicated pregnancy, left ventricular remodeling occurs in an eccentric way. In contrast, during preeclamptic gestation, the left ventricle hypertrophies concentrically, concurrent with loss in circulatory volume and increased blood pressure. Concentric cardiac structure persists in a substantial proportion of women and may be associated with pressure and volume load after preeclampsia. We hypothesize that low volume load, as indicated by plasma volume (PV) after preeclampsia and increased pressure load, is associated with remote concentric remodeling. Methods and Results In this longitudinal cohort study, we included 100 formerly preeclamptic women. Two visits were performed: at 0.8 years postpartum and at 4.8 years postpartum. During visit 1, we measured blood pressure and PV (I125 dilution technique, low PV ≤48 mL/kg lean body mass). During the second visit, we assessed cardiac geometry by cardiac ultrasound. Concentric remodeling was defined as relative wall thickness >0.42 and left ventricular mass index ≤95 g/m2. We adjusted multivariable analysis for primiparity, systolic blood pressure, PV mL/kg lean body mass, and antihypertensive medication at visit 1. Low PV is associated with remote concentric remodeling (odds ratio [OR], 4.37; 95% CI, 1.06-17.40; and adjusted OR, 4.67; 95% CI, 1.02-21.42). Arterial pressure load (systolic, diastolic, and mean arterial pressure) is also associated with development of concentric remodeling (OR, 1.15 [95% CI, 0.99-1.35]; OR, 1.24 [95% CI, 0.98-1.58]; and OR, 1.20 [95% CI, 0.98-1.47], respectively). Conclusions In former preeclamptic women, development toward left ventricular concentric remodeling is associated with low volume load and increased pressure load.

Arbutin Attenuates Isoproterenol-Induced Cardiac Hypertrophy by Inhibiting TLR-4/NF-κB Pathway in Mice

Arbutin is a glycoside reported for its anti-oxidant, anti-inflammatory and anti-tumor properties. However, the cardioprotective effect of Arbutin is not well established. The study aims to understand the effect of arbutin on isoproterenol (ISO)-induced cardiac hypertrophy in mice. The animals were pretreated with Arbutin for a week and ISO was administered for 10 days and then sacrificed. Cardiac injury markers such as creatinine kinase and lactate dehydrogenase concentrations were measured in the serum. The mRNA expression of cardiac hypertrophy markers namely atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) were measured using qRT-PCR. The levels of pro-inflammatory cytokines TNF-α and IL-6 were quantified by ELISA in isolated tissues and serum. Other tissue anti-oxidant parameters such as GST, GSH, SOD and TBARS were also measured. TUNEL assay was performed to detect apoptosis. Histology studies were performed using H & E and Masson trichome staining. Immunoblot analysis was used to quantify the protein expression of TLR-4 and NF-κB. ISO-alone-treated group showed significant increase in CK-MB, LDH along with increase in hypertrophic markers ANP and BNP, TNF-α and IL-6 levels in serum and tissues and increased cardiomyocyte apoptosis. Anti-oxidant parameters were significantly decreased and TLR-4 and NF-κB protein expression was found to be upregulated in comparison to the control group. Pretreatment with Arbutin-exhibited significant inhibition of TLR-4/NF-κB pathway with decreased levels of pro-inflammatory cytokines and enhanced myocardial anti-oxidant status. Our study demonstrated that pretreatment with Arbutin exhibits marked protective effects on ISO-induced cardiac hypertrophy in mice. Thus, Arbutin may be used as potential pharmacological interventions in the management of cardiac hypertrophy.

Inhibition of microRNA-146a attenuated heart failure in myocardial infarction rats

The aim of the present study was to determine the roles of microRNA (miR)-146a on myocardial infarction (MI)-induced heart failure and cardiac remodeling. Experiments were carried out in Sprague-Dawley rats treated with ligation of left coronary artery to induce heart failure, and in primary neonatal rat cardiac fibroblasts (CFs) and cardiomyocytes treated with angiotensin (Ang) II. Four weeks after MI, rats were injected with miR-146a antagomiR or agomiR via tail vein. After 2 weeks of injection, the rats were killed. In MI rats, left ventricle (LV) ejection fraction and fractional shortening were reduced, and LV volumes in diastole and systole were increased, which were reversed by miR-146a antagomiR, and further exacerbated after miR-146a agomiR treatment. Administration of miR-146a antagomiR improved the decreases of LV ±dp/dt_max and LV systolic pressure (LVSP), and the increase in LV end-diastolic pressure (LVEDP) of MI rats, but miR-146a agomiR deteriorated the LV ±dp/dt_max, LVSP and LVEDP. The increases in the levels of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), collagen I and collagen III in the heart, and ST2 and norepinephrine in the serum of MI rats were inhibited by miR-146a antagomiR, but aggravated after miR-146a agomiR treatment. The increases of collagen I and collagen III levels induced by Ang II in CFs, and the increases of ANP and BNP levels induced by Ang II in cardiomyocytes were inhibited by miR-146a antagomiR, but aggravated by miR-146a agomiR. These results demonstrated that inhibition of miR-146a improved cardiac dysfunction and cardiac remodeling in heart failure rats.

STEAP3 (Six-Transmembrane Epithelial Antigen of Prostate 3) Inhibits Pathological Cardiac Hypertrophy

Pathological cardiac hypertrophy is one of the major predictors and inducers of heart failure, the end stage of various cardiovascular diseases. However, the molecular mechanisms underlying pathogenesis of pathological cardiac hypertrophy remain largely unknown. Here, we provided the first evidence that STEAP3 (Six-Transmembrane Epithelial Antigen of Prostate 3) is a key negative regulator of this disease. We found that the expression of STEAP3 was reduced in pressure overload-induced hypertrophic hearts and phenylephrine-induced hypertrophic cardiomyocytes. In a transverse aortic constriction-triggered mouse cardiac hypertrophy model, STEAP3 deficiency remarkably deteriorated cardiac hypertrophy and fibrosis, whereas the opposite phenotype was observed in the cardiomyocyte-specific STEAP3 overexpressing mice. Accordingly, STEAP3 significantly mitigated phenylephrine-induced cell enlargement in primary neonatal rat cardiomyocytes. Mechanistically, via RNA-seq and immunoprecipitation-mass screening, we demonstrated that STEAP3 directly bond to Rho family small GTPase 1 and suppressed the activation of downstream mitogen-activated protein kinase-extracellular signal-regulated kinase signaling cascade. Remarkably, the antihypertrophic effect of STEAP3 was largely blocked by overexpression of constitutively active mutant Rac1 (G12V). Our study indicates that STEAP3 serves as a novel negative regulator of pathological cardiac hypertrophy by blocking the activation of the Rac1-dependent signaling cascade and may contribute to exploring effective therapeutic strategies of pathological cardiac hypertrophy treatment.

The Role of the NOD1/Rip2 Signaling Pathway in Myocardial Remodeling in Spontaneously Hypertensive Rats

BACKGROUND Chronic hypertension changes the function and structure of the heart and blood vessels. This study aimed to explore the role of the NOD1/Rip2 (nucleotide-binding oligomerization domain 1/receptor-interacting protein 2) signaling pathway in myocardial remodeling in spontaneously hypertensive rats (SHRs). MATERIAL AND METHODS Blood pressure was measured using a tail cuff. The cardiac structure was observed using echocardiography. Slices of the myocardium were stained with hematoxylin and eosin. The expression of NOD1 and Rip2 was detected using real-time polymerase chain reaction, western blot, and immunohistochemistry. The content and distribution of collagen in the myocardium were observed using Van Gieson staining. Enzyme-linked immunosorbent assay was used to detect the interleukin-1 (IL-1) concentrations. SHRs were treated with the NOD1 agonist iE-DAP and NOD1 inhibitor ML130. RESULTS The NOD1 agonist increased blood pressure in SHRs, and the NOD1 inhibitor decreased blood pressure; the interventricular septum thickness (IVST) and left ventricular posterior wall thickness (LVPWT) of the agonist-treated group were thicker than those of the control group, and the antagonist exerted the opposite effects. The levels of the NOD1 and Rip2 mRNAs and proteins, serum IL-1 concentration, and myocardial collagen volume fraction (CVF%) increased in SHRs in the NOD1 agonist group, but the levels of NOD1 and Rip2, serum IL-1 concentration, and myocardial collagen volume fraction (CVF%) decreased in SHRs in the NOD1 inhibitor group. CONCLUSIONS NOD1/Rip2 expression increased during the progression of myocardial remodeling in SHRs. The NOD1 agonist increased NOD1 expression and promoted myocardial remodeling, while the NOD1 antagonist reduced NOD1/Rip2 expression and protected against myocardial remodeling.

Time Course of Gene Expression Profile in Renal Ischemia and Reperfusion Injury in Mice

Ischemic renal failure is an inflammatory disease that can affect various organs, including the heart. The organ responds to the stimulus and undergoes tissue remodeling that can result in cardiac hypertrophy. This study aimed to characterize the cardiac global gene expression profile in renal ischemia/reperfusion (IR) model using microarray technology. To do that, left kidney ischemia was induced in male C57BL/6 mice for 60 minutes, followed by reperfusion (IR) for 5, 8, 15, or 20 days post ischemia (dpi). Total cardiac tissue RNA was extracted and hybridized to chips with 35,000 mouse genes. The GeneChip Mouse Genome 430 2.0 Array Expression chip (Affymetrix) was used, and CEL files generated were processed with DNA-Chip-Analyzer (dCHIP) software. Subsequent analysis considered only differences among groups of at least 1.2-fold (up or down) expression changes. Analyses of the samples indicated positive modulation of 17,413 genes and 405 pathways and negative modulation of 18,287 genes and 300 pathways. A narrower analysis of genes related to inflammation, metabolism, apoptosis, oxidative stress, and channels/ion transport was performance, and it was correlated with IR injury, corroborating previous data from literature. Renal IR induced a global shift in cardiac tissue gene expression; in particular, genes related to the inflammatory system and cardiomyocyte function were changed. The in-depth study of the cell signaling in the present study could stimulate the development of new therapeutic option to ameliorate the outcome of renal-IR-induced heart damage.

Carboxypeptidase A4 promotes cardiomyocyte hypertrophy through activating PI3K-AKT-mTOR signaling

Carboxypeptidase A4 (CPA4) is a member of the metallocarboxypeptidase family. Current studies have identified the roles of CPA4 in cancer biology and insulin sensitivity. However, the roles of CPA4 in other diseases are not known. In the present study, we investigated the roles of CPA4 in cardiac hypertrophy. The expression of CPA4 was significantly increased in the hypertrophic heart tissues of human patients and isoproterenol (ISO)-induced hypertrophic heart tissues of mice. We next knocked down Cpa4 with shRNA or overexpressed Cpa4 using adenovirus in neonatal rat cardiomyocytes and induced cardiomyocyte hypertrophy with ISO. We observed that Cpa4 overexpression promoted whereas Cpa4 knockdown reduced ISO-induced growth of cardiomyocyte size and overexpression of hypertrophy marker genes, such as myosin heavy chain β (β-Mhc), atrial natriuretic peptide (Anp), and brain natriuretic peptide (Bnp). Our further mechanism study revealed that the mammalian target of rapamycin (mTOR) signaling was activated by Cpa4 in cardiomyocytes, which depended on the phosphoinositide 3-kinase (PI3K)-AKT signaling. Besides, we showed that the PI3K-AKT-mTOR signaling was critically involved in the roles of Cpa4 during cardiomyocyte hypertrophy. Collectively, these results demonstrated that CPA4 is a regulator of cardiac hypertrophy by activating the PI3K-AKT-mTOR signaling, and CPA4 may serve as a promising target for the treatment of hypertrophic cardiac diseases.

Atrial remodeling and atrial fibrillation in acquired forms of cardiovascular disease

Atrial fibrillation (AF) is prevalent in common conditions and acquired forms of heart disease, including diabetes mellitus (DM), hypertension, cardiac hypertrophy, and heart failure. AF is also prevalent in aging. Although acquired heart disease is common in aging individuals, age is also an independent risk factor for AF. Importantly, not all individuals age at the same rate. Rather, individuals of the same chronological age can vary in health status from fit to frail. Frailty can be quantified using a frailty index, which can be used to assess heterogeneity in individuals of the same chronological age. AF is thought to occur in association with electrical remodeling due to changes in ion channel expression or function as well as structural remodeling due to fibrosis, myocyte hypertrophy, or adiposity. These forms of remodeling can lead to triggered activity and electrical re-entry, which are fundamental mechanisms of AF initiation and maintenance. Nevertheless, the underlying determinants of electrical and structural remodeling are distinct in different conditions and disease states. In this focused review, we consider the factors leading to atrial electrical and structural remodeling in human patients and animal models of acquired cardiovascular disease or associated risk factors. Our goal is to identify similarities and differences in the cellular and molecular bases for atrial electrical and structural remodeling in conditions including DM, hypertension, hypertrophy, heart failure, aging, and frailty.

Taurine attenuates isoproterenol-induced H9c2 cardiomyocytes hypertrophy by improving antioxidative ability and inhibiting calpain-1-mediated apoptosis

Pathological cardiac hypertrophy is ultimately accompanied by cardiomyocyte apoptosis. Apoptosis mainly related to calpain-1-mediated apoptotic pathways. Studies had proved that taurine can maintain heart health through antioxidation and antiapoptotic functions, but the effect of taurine on cardiac hypertrophy is still unclear. This study aimed to determine whether taurine could inhibit calpain-1-mediated mitochondria-dependent apoptotic pathways in isoproterenol (ISO)-induced hypertrophic cardiomyocytes. We found that taurine could inhibit the increase in cell surface area and reduce the protein expression levels of the hypertrophic markers atrial natriuretic peptide, brain natriuretic polypeptide, and β-myosin heavy chain. Taurine also reduced ROS, intracellular Ca²⁺ overload and mitochondrial membrane potential. Moreover, taurine inhibited cardiomyocyte apoptosis by decreasing the protein expression of calpain-1, Bax, t-Bid, cytosolic cytochrome c, Apaf-1, cleaved caspase-9 and cleaved caspase-3 and by enhancing calpastatin and Bcl-2 protein expression. Calpain-1 small interfering RNA transfection results showed similar antiapoptotic effects as the taurine prevention group. However, compared with the two treatments, taurine inhibited the expression of cleaved caspase-9 more significantly. Therefore, we believe that taurine prevents ISO-induced H9c2 cardiomyocyte hypertrophy by inhibiting oxidative stress, intracellular Ca²⁺ overload, the calpain-1-mediated mitochondria-dependent apoptotic pathway and cleaved caspase-9 levels.

Establishing a new human hypertrophic cardiomyopathy-specific model using human embryonic stem cells

Symptom of ventricular hypertrophy caused by cardiac troponin T (TNNT2) mutations is mild, while patients often showed high incidence of sudden cardiac death. The 92nd arginine to glutamine mutation (R92Q) of cTnT was one of the mutant hotspots in hypertrophic cardiomyopathy (HCM). However, there are no such human disease models yet. To solve this problem, we generated TNNT2 R92Q mutant hESC cell lines (heterozygote or homozygote) using TALEN mediated homologous recombination in this study. After directed cardiac differentiation, we found a relative larger cell size in both heterozygous and homozygous TNNT2 R92Q hESC-cardiomyocytes. Expression of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and sarcoplasmic reticulum Ca²⁺-ATPase2a (SERCA2a) were downregulated, while myocyte specific enhancer factor 2c (MEF2c) and the ratio of beta myosin to alpha myosin heavy chain (MYH7/MYH6) were increased in heterozygous TNNT2 R92Q hESC-cardiomyocytes. TNNT2 R92Q mutant cardiomyocytes exhibited efficient responses to heart-related pharmaceutical agents. We also found TNNT2 R92Q heterozygous mutant cardiomyocytes showed increased calcium sensitivity and contractility. Further, engineered heart tissues (EHTs) prepared by combining rat decellularized heart extracellular matrices with heterozygous R92Q mutant cardiomyocytes showed similar drug responses as to HCM patients and increased sensitivity to caspofungin-induced cardiotoxicity. Using RNA-sequencing of TNNT2 R92Q heterozygous mutant cardiomyocytes, we found dysregulation of calcium might participated in the early development of hypertrophy. Our hESC-derived TNNT2 R92Q mutant cardiomyocytes and EHTs are good in vitro human disease models for future disease studies and drug screening.

STVNa Attenuates Isoproterenol-Induced Cardiac Hypertrophy Response through the HDAC4 and Prdx2/ROS/Trx1 Pathways

Recent data show that cardiac hypertrophy contributes substantially to the overall heart failure burden. Mitochondrial dysfunction is a common feature of cardiac hypertrophy. Recent studies have reported that isosteviol inhibits myocardial ischemia-reperfusion injury in guinea pigs and H9c2 cells. This work investigated the protective mechanisms of isosteviol sodium (STVNa) against isoproterenol (Iso)-induced cardiac hypertrophy. We found that STVNa significantly inhibited H9c2 cell and rat primary cardiomyocyte cell surface, restored mitochondrial membrane potential (MMP) and morphological integrity, and decreased the expression of mitochondrial function-related proteins Fis1 and Drp1. Furthermore, STVNa decreased reactive oxygen species (ROS) levels and upregulated the expression of antioxidant factors, Thioredoxin 1 (Trx1) and Peroxiredoxin 2 (Prdx2). Moreover, STVNa restored the activity of histone deacetylase 4 (HDAC4) in the nucleus. Together, our data show that STVNa confers protection against Iso-induced myocardial hypertrophy primarily through the Prdx2/ROS/Trx1 signaling pathway. Thus, STVNA is a potentially effective treatment for cardiac hypertrophy in humans.

Effect of SKF‑96365 on cardiomyocyte hypertrophy induced by angiotensin II

Angiotensin II (Ang II) is an important bioactive peptide in the renin-angiotensin system, and it can contribute to cell proliferation and cardiac hypertrophy. Dysfunctions in transient receptor potential canonical (TRPC) channels are involved in many types of cardiovascular diseases. The aim of the present study was to investigate the role of the TRPC channel inhibitor SKF-96365 in cardiomyocyte hypertrophy induced by Ang II and the potential mechanisms of SKF-96365. H9c2 cells were treated with different concentrations of Ang II. The expression levels of cardiomyocyte hypertrophy markers and TRPC channel-related proteins were also determined. The morphology and surface area of the H9c2 cells, the expression of hypertrophic markers and TRPC channel-related proteins and the [³H] leucine incorporation rate were detected in the Ang II-treated H9c2 cells following treatment with the TRPC channel inhibitor SKF-96365. The intracellular Ca²⁺ concentration was tested by flow cytometry. The present results suggested that the surface area of H9c2 cells treated with Ang II was significantly increased compared with untreated H9c2 cells. The fluorescence intensity of α-actinin, the expression of hypertrophic markers and TRPC-related proteins, the [³H] leucine incorporation rate and the intracellular Ca²⁺ concentration were all markedly increased in the Ang II-treated H9c2 cells but decreased following SKF-96365 treatment. The present results suggested that Ang II induced cardiomyocyte hypertrophy in H9c2 cells and that the TRPC pathway may be involved in this process. Therefore, SKF-96365 can inhibit cardiomyocyte hypertrophy induced by Ang II by suppressing the TRPC pathway. The present results indicated that TRPC may be a therapeutic target for the development of novel drugs to treat cardiac hypertrophy.

Effects of Spaceflight on Human Induced Pluripotent Stem Cell-Derived Cardiomyocyte Structure and Function

With extended stays aboard the International Space Station (ISS) becoming commonplace, there is a need to better understand the effects of microgravity on cardiac function. We utilized human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) to study the effects of microgravity on cell-level cardiac function and gene expression. The hiPSC-CMs were cultured aboard the ISS for 5.5 weeks and their gene expression, structure, and functions were compared with ground control hiPSC-CMs. Exposure to microgravity on the ISS caused alterations in hiPSC-CM calcium handling. RNA-sequencing analysis demonstrated that 2,635 genes were differentially expressed among flight, post-flight, and ground control samples, including genes involved in mitochondrial metabolism. This study represents the first use of hiPSC technology to model the effects of spaceflight on human cardiomyocyte structure and function.

Deficiency of Cardiac Natriuretic Peptide Signaling Promotes Peripartum Cardiomyopathy-Like Remodeling in the Mouse Heart

BACKGROUND

The maternal circulatory system and hormone balance both change dynamically during pregnancy, delivery, and the postpartum period. Although atrial natriuretic peptides and brain natriuretic peptides produced in the heart control circulatory homeostasis through their common receptor, NPR1, the physiologic and pathophysiologic roles of endogenous atrial natriuretic peptide/brain natriuretic peptide in the perinatal period are not fully understood.

METHODS

To clarify the physiologic and pathophysiologic roles of the endogenous atrial natriuretic peptide/brain natriuretic peptide-NPR1 system during the perinatal period, the phenotype of female wild-type and conventional or tissue-specific Npr1-knockout mice during the perinatal period was examined, especially focusing on maternal heart weight, blood pressure, and cardiac function.

RESULTS

In wild-type mice, lactation but not pregnancy induced reversible cardiac hypertrophy accompanied by increases in fetal cardiac gene mRNAs and ERK1/2 (extracellular signaling-regulated kinase) phosphorylation. Npr1-knockout mice exhibited significantly higher plasma aldosterone level than did wild-type mice, severe cardiac hypertrophy accompanied by fibrosis, and left ventricular dysfunction in the lactation period. Npr1-knockout mice showed a high mortality rate over consecutive pregnancy-lactation cycles. In the hearts of Npr1-knockout mice during or after the lactation period, an increase in interleukin-6 mRNA expression, phosphorylation of signal transducer and activator of transcription 3, and activation of the calcineurin-nuclear factor of the activated T cells pathway were observed. Pharmacologic inhibition of the mineralocorticoid receptor or neuron-specific deletion of the mineralocorticoid receptor gene significantly ameliorated cardiac hypertrophy in lactating Npr1-knockout mice. Anti-interleukin-6 receptor antibody administration tended to reduce cardiac hypertrophy in lactating Npr1-knockout mice.

CONCLUSIONS

These results suggest that the characteristics of lactation-induced cardiac hypertrophy in wild-type mice are different from exercise-induced cardiac hypertrophy, and that the endogenous atrial natriuretic peptide/brain natriuretic peptide-NPR1 system plays an important role in protecting the maternal heart from interleukin-6-induced inflammation and remodeling in the lactation period, a condition mimicking peripartum cardiomyopathy.

Hypertrophic cardiomyopathy: genetics and clinical perspectives

Hypertrophic cardiomyopathy (HCM) is the most common inherited heart disease and defined by unexplained isolated progressive myocardial hypertrophy, systolic and diastolic ventricular dysfunction, arrhythmias, sudden cardiac death and histopathologic changes, such as myocyte disarray and myocardial fibrosis. Mutations in genes encoding for proteins of the contractile apparatus of the cardiomyocyte, such as β-myosin heavy chain and myosin binding protein C, have been identified as cause of the disease. Disease is caused by altered biophysical properties of the cardiomyocyte, disturbed calcium handling, and abnormal cellular metabolism. Mutations in sarcomere genes can also activate other signaling pathways via transcriptional activation and can influence non-cardiac cells, such as fibroblasts. Additional environmental, genetic and epigenetic factors result in heterogeneous disease expression. The clinical course of the disease varies greatly with some patients presenting during childhood while others remain asymptomatic until late in life. Patients can present with either heart failure symptoms or the first symptom can be sudden death due to malignant ventricular arrhythmias. The morphological and pathological heterogeneity results in prognosis uncertainty and makes patient management challenging. Current standard therapeutic measures include the prevention of sudden death by prohibition of competitive sport participation and the implantation of cardioverter-defibrillators if indicated, as well as symptomatic heart failure therapies or cardiac transplantation. There exists no causal therapy for this monogenic autosomal-dominant inherited disorder, so that the focus of current management is on early identification of asymptomatic patients at risk through molecular diagnostic and clinical cascade screening of family members, optimal sudden death risk stratification, and timely initiation of preventative therapies to avoid disease progression to the irreversible adverse myocardial remodeling stage. Genetic diagnosis allowing identification of asymptomatic affected patients prior to clinical disease onset, new imaging technologies, and the establishment of international guidelines have optimized treatment and sudden death risk stratification lowering mortality dramatically within the last decade. However, a thorough understanding of underlying disease pathogenesis, regular clinical follow-up, family counseling, and preventative treatment is required to minimize morbidity and mortality of affected patients. This review summarizes current knowledge about molecular genetics and pathogenesis of HCM secondary to mutations in the sarcomere and provides an overview about current evidence and guidelines in clinical patient management. The overview will focus on clinical staging based on disease mechanism allowing timely initiation of preventative measures. An outlook about so far experimental treatments and potential for future therapies will be provided.

Gender Differences in Cardiac Hypertrophy

Cardiac hypertrophy is an adaptive response to abnormal physiological and pathological stimuli, which can be classified into concentric and eccentric hypertrophy, induced by pressure overload or volume overload, respectively. In both physiological and pathological scenarios, females generally show a more favorable form of hypertrophy compared with their male counterparts. However once established, cardiac hypertrophy is a stronger risk factor for heart failure in females. Pre-menopausal women are better protected against cardiac hypertrophy compared with men, but this protection is abolished following menopause and is partially restored after estrogen replacement therapy. Estrogen exerts its protection by counteracting pro-hypertrophy signaling pathways, whereas androgen mostly plays an opposite role in cardiac hypertrophy. We here summarize the progress in the understanding of sexual dimorphisms in cardiac hypertrophy and highlight recent breakthroughs in the regulatory role of sex hormones and their intricate molecular networks, in order to shed light on gender-oriented therapeutic efficacy for pathological hypertrophy.

Selective Heart Irradiation Induces Cardiac Overexpression of the Pro-hypertrophic miR-212

Background: A deleterious, late-onset side effect of thoracic radiotherapy is the development of radiation-induced heart disease (RIHD). It covers a spectrum of cardiac pathology including also heart failure with preserved ejection fraction (HFpEF) characterized by left ventricular hypertrophy (LVH) and diastolic dysfunction. MicroRNA-212 (miR-212) is a crucial regulator of pathologic LVH via FOXO3-mediated pathways in pressure-overload-induced heart failure. We aimed to investigate whether miR-212 and its selected hypertrophy-associated targets play a role in the development of RIHD. Methods: RIHD was induced by selective heart irradiation (50 Gy) in a clinically relevant rat model. One, three, and nineteen weeks after selective heart irradiation, transthoracic echocardiography was performed to monitor cardiac morphology and function. Cardiomyocyte hypertrophy and fibrosis were assessed by histology at week 19. qRT-PCR was performed to measure the gene expression changes of miR-212 and forkhead box O3 (FOXO3) in all follow-up time points. The cardiac transcript level of other selected hypertrophy-associated targets of miR-212 including extracellular signal-regulated kinase 2 (ERK2), myocyte enhancer factor 2a (MEF2a), AMP-activated protein kinase, (AMPK), heat shock protein 40 (HSP40), sirtuin 1, (SIRT1), calcineurin A-alpha and phosphatase and tensin homolog (PTEN) were also measured at week 19. Cardiac expression of FOXO3 and phospho-FOXO3 were investigated at the protein level by Western blot at week 19. Results: In RIHD, diastolic dysfunction was present at every time point. Septal hypertrophy developed at week 3 and a marked LVH with interstitial fibrosis developed at week 19 in the irradiated hearts. In RIHD, cardiac miR-212 was overexpressed at week 3 and 19, and FOXO3 was repressed at the mRNA level only at week 19. In contrast, the total FOXO3 protein level failed to decrease in response to heart irradiation at week 19. Other selected hypertrophy-associated target genes failed to change at the mRNA level in RIHD at week 19. Conclusions: LVH in RIHD was associated with cardiac overexpression of miR-212. However, miR-212 seems to play a role in the development of LVH via FOXO3-independent mechanisms in RIHD. As a central regulator of pathologic remodeling, miR-212 might become a novel target for RIHD-induced LVH and heart failure.

Mechanical regulation of gene expression in cardiac myocytes and fibroblasts

The intact heart undergoes complex and multiscale remodelling processes in response to altered mechanical cues. Remodelling of the myocardium is regulated by a combination of myocyte and non-myocyte responses to mechanosensitive pathways, which can alter gene expression and therefore function in these cells. Cellular mechanotransduction and its downstream effects on gene expression are initially compensatory mechanisms during adaptations to the altered mechanical environment, but under prolonged and abnormal loading conditions, they can become maladaptive, leading to impaired function and cardiac pathologies. In this Review, we summarize mechanoregulated pathways in cardiac myocytes and fibroblasts that lead to altered gene expression and cell remodelling under physiological and pathophysiological conditions. Developments in systems modelling of the networks that regulate gene expression in response to mechanical stimuli should improve integrative understanding of their roles in vivo and help to discover new combinations of drugs and device therapies targeting mechanosignalling in heart disease.

The slow force response to stretch: Controversy and contradictions

When exposed to an abrupt stretch, cardiac muscle exhibits biphasic active force enhancement. The initial, instantaneous, force enhancement is well explained by the Frank-Starling mechanism. However, the cellular mechanisms associated with the second, slower phase remain contentious. This review explores hypotheses regarding this "slow force response" with the intention of clarifying some apparent contradictions in the literature. The review is partitioned into three sections. The first section considers pathways that modify the intracellular calcium handling to address the role of the sarcoplasmic reticulum in the mechanism underlying the slow force response. The second section focuses on extracellular calcium fluxes and explores the identity and contribution of the stretch-activated, non-specific, cation channels as well as signalling cascades associated with G-protein coupled receptors. The final section introduces promising candidates for the mechanosensor(s) responsible for detecting the stretch perturbation.

A severe clinical phenotype of Noonan syndrome with neonatal hypertrophic cardiomyopathy in the second case worldwide with RAF1 S259Y neomutation

Noonan syndrome and related disorders are a group of clinically and genetically heterogeneous conditions caused by mutations in genes of the RAS/MAPK pathway. Noonan syndrome causes multiple congenital anomalies, which are frequently accompanied by hypertrophic cardiomyopathy (HCM). We report here a Tunisian patient with a severe phenotype of Noonan syndrome including neonatal HCM, facial dysmorphism, severe failure to thrive, cutaneous abnormalities, pectus excavatum and severe stunted growth, who died in her eighth month of life. Using whole exome sequencing, we identified a de novo mutation in exon 7 of the RAF1 gene: c.776C > A (p.Ser259Tyr). This mutation affects a highly conserved serine residue, a main mediator of Raf-1 inhibition via phosphorylation. To our knowledge the c.776C > A mutation has been previously reported in only one case with prenatally diagnosed Noonan syndrome. Our study further supports the striking correlation of RAF1 mutations with HCM and highlights the clinical severity of Noonan syndrome associated with a RAF1 p.Ser259Tyr mutation.

Effects of heme oxygenase-1 upregulation on isoproterenol-induced myocardial infarction

The present study was designed to examine the effect of heme oxygenase-1 (HO-1) induction by cobalt protoporphyrin (CoPP) on the cardiac functions and morphology, electrocardiogram (ECG) changes, myocardial antioxidants (superoxide dismutase [SOD] and glutathione [GSH]), and expression of heat shock protein (Hsp) 70 and connexin 43 (Cx-43) in myocardial muscles in isoproterenol (ISO) induced myocardial infarction (MI). Thirty two adult male Sprague Dawely rats were divided into 4 groups (each 8 rats): normal control (NC) group, ISO group: received ISO at dose of 150 mg/kg body weight intraperitoneally (i.p.) for 2 successive days; ISO + Trizma group: received (ISO) and Trizma (solvent of CoPP) at dose of 5 mg/kg i.p. injection 2 days before injection of ISO, with ISO at day 0 and at day 2 after ISO injections; and ISO + CoPP group: received ISO and CoPP at a dose of 5 mg/kg dissolved in Trizma i.p. injection as Trizma. We found that, administration of ISO caused significant increase in heart rate, corrected QT interval, ST segment, cardiac enzymes (lactate dehydrogenase, creatine kinase-muscle/brain), cardiac HO-1, Hsp70 with significant attenuation in myocardial GSH, SOD, and Cx-43. On the other hand, administration of CoPP caused significant improvement in ECG parameters, cardiac enzymes, cardiac morphology; antioxidants induced by ISO with significant increase in HO-1, Cx-43, and Hsp70 expression in myocardium. In conclusions, we concluded that induction of HO-1 by CoPP ameliorates ISO-induced myocardial injury, which might be due to up-regulation of Hsp70 and gap junction protein (Cx-43).

Methamphetamine produces cardiac damage and apoptosis by decreasing melusin

Methamphetamine (METH) is an amphetamine-type drug that is highly addictive and widely abused. Many studies have shown that METH exposure causes severe damage not only to the nervous system but also to the cardiovascular system. Melusin protein is a mechanotransducer that plays an important role in maintaining normal heart function. However, the role of melusin in METH-induced cardiotoxicity has not yet been reported. We hypothesized that methamphetamine can produce cardiac damage and apoptosis by decreasing the quantity of melusin. To test this hypothesis, we determined the protein expression of melusin and apoptosis markers in METH-treated rats and primary rat cardiomyocytes. We also established a melusin-overexpressing cell model to assess the importance of melusin in maintaining antiapoptotic pathways. To confirm our findings from the in vitro and animal models, we also evaluated the apoptotic index of cardiomyocytes and the protein expression of apoptotic markers in postmortem heart tissues from deceased METH abusers and age-matched control subjects. The results showed that the apoptosis of cardiomyocytes was increased significantly and that the protein expression of melusin was decreased after exposure to METH in primary rat cardiomyocytes, in rats and in humans. METH treatment also decreased the expression of the downstream proteins FAK, IQGAP1, p-AKT, p-GSK3β, and p-ERK in primary rat cardiomyocytes and in vivo. After overexpression of melusin, the above effects were partially reversed in primary rat cardiomyocytes. We conclude that METH can produce cardiac damage and apoptosis by decreasing melusin, while melusin-activated signaling by phosphorylated AKT, phosphorylated GSK3β, and ERK may be resistant to methamphetamine-induced myocardial apoptosis.

SP1-SYNE1-AS1-miR-525-5p feedback loop regulates Ang-II-induced cardiac hypertrophy

Cardiac hypertrophy (CH) has become a huge threat to human health. Recent years, long noncoding RNAs (lncRNAs) have been studied in human diseases, including CH. According to bioinformatics analysis, 10 lncRNAs possibly involved in the progression of CH were screened out. Among which, lncRNA SYNE1 antisense RNA 1 (SYNE1-AS1) could be upregulated by Angiotensin II (Ang-II) in cardiomyocytes. Thus, we chose SYNE1-AS1 to do further study. To identify the biological function of SYNE1-AS1 in CH, SYNE1-AS1 was silenced in Ang-II-induced cardiomyocytes. Results of immunofluorescence staining demonstrated that increased cell surface area in Ang-II-induced cardiomyocytes was reduced by SYNE1-AS1 knockdown. Moreover, the hypertrophic responses were attenuated by SYNE1-AS1 knockdown. Mechanically, SYNE1-AS1 positively regulated Sp1 transcription factor (SP1) by sponging microRNA-525-5p (miR-525-5p). On the basis of previous reports, SP1 can transcriptionally activate lncRNAs. Therefore, we investigated the interaction between SP1 and SYNE1-AS1 promoter. Intriguingly, SYNE1-AS1 was activated by SP1. At last, rescue assays demonstrated the function of SP1-SYNE1-AS1 axis in CH. In conclusion, SP1-induced upregulation of lncRNA SYNE1-AS1 promoted CH via miR-525-5p/SP1 axis.

SIRT6 Suppresses NFATc4 Expression and Activation in Cardiomyocyte Hypertrophy

NFATc4, a member from the Nuclear Factor of Activated T cells (NFATs) transcription factor family, plays a pivotal role in the development of cardiac hypertrophy. NFATc4 is dephosphorylated by calcineurin and translocated from the cytoplasm to the nucleus to regulate the expression of hypertrophic genes, like brain natriuretic polypeptide (BNP). The present study identified SIRT6, an important subtype of NAD⁺ dependent class III histone deacetylase, to be a negative regulator of NFATc4 in cardiomyocyte hypertrophy. In phenylephrine (PE)-induced hypertrophic cardiomyocyte model, overexpression of SIRT6 by adenovirus infection or by plasmid transfection repressed the protein and mRNA expressions of NFATc4, elevated its phosphorylation level, prevented its nuclear accumulation, subsequently suppressed its transcriptional activity and downregulated its target gene BNP. By contrast, mutant of SIRT6 without deacetylase activity (H133Y) did not demonstrate these effects, suggesting that the inhibitory effect of SIRT6 on NFATc4 was dependent on its deacetylase activity. Moreover, the effect of SIRT6 overexpression on repressing BNP expression was reversed by NFATc4 replenishment, whereas the effect of SIRT6 deficiency on upregulating BNP was recovered by NFATc4 silencing. Mechanistically, interactions between SIRT6 and NFATc4 might possibly facilitate the deacetylation of NFATc4 by SIRT6, thereby preventing the activation of NFATc4. In conclusion, the present study reveals that SIRT6 suppresses the expression and activation of NFATc4. These findings provide more evidences of the anti-hypertrophic effect of SIRT6 and suggest SIRT6 as a potential therapeutic target for cardiac hypertrophy.

The long noncoding RNA XIST regulates cardiac hypertrophy by targeting miR-101

Cardiac hypertrophy and its resultant heart failure are among the most common causes of mortality, worldwide. Long noncoding RNAs (lncRNAs) are involved in diverse biological processes, and their vital role in the regulation of cardiac hypertrophy is increasingly being discovered. Nevertheless, the biological roles of lncRNA X-inactive specific transcript (XIST) in cardiac hypertrophy are scarcely reported, and the current study was designed to determine whether cardiac hypertrophy can be regulated by XIST and to elucidate the related mechanism. The animals were randomized to receive either an adeno-associated virus expressing XIST or control plasmid via a single bolus-tail vein injection. Two weeks later, hypertrophy was established by transverse aortic constriction (TAC) surgery. In vitro, H9c2 cells were used to explore the potential molecular mechanism of XIST in the regulation of phenylephrine (PE)-induced cardiomyocyte hypertrophy. A luciferase reporter assay and RNA immunoprecipitation were performed to explore the relationships among XIST, microRNA (miR)-101, and toll-like receptor 2 (TLR2). In this study, we demonstrated that the expression of XIST was significantly upregulated in hypertrophic mouse hearts and PE-treated cardiomyocytes. Then, we observed that knockdown of XIST attenuated PE-induced cardiomyocyte hypertrophy. Conversely, overexpression of XIST aggravated TAC-induced cardiac hypertrophy. Finally, we demonstrated that miR-101 was a direct target of XIST, whereas TLR2 was a target of miR-101. Rescue assays further confirmed that XIST promoted the progression of cardiac hypertrophy through competitively binding with miR-101 to enhance the expression of TLR2. Collectively, these in vivo and in vitro findings identify XIST as a necessary regulator of cardiac hypertrophy due to its regulation of the miR-101/TLR2 axis, suggesting that XIST might act as a therapeutic target for the treatment of cardiac hypertrophy and heart failure.

Identification of Crucial Genes and Pathways in Human Arrhythmogenic Right Ventricular Cardiomyopathy by Coexpression Analysis

As one common disease causing young people to die suddenly due to cardiac arrest, arrhythmogenic right ventricular cardiomyopathy (ARVC) is a disorder of heart muscle whose progression covers one complicated gene interaction network that influence the diagnosis and prognosis of it. In our research, differentially expressed genes (DEGs) were screened, and we established a weighted gene coexpression network analysis (WGCNA) and gene set net correlations analysis (GSNCA) for identifying crucial genes as well as pathways related to ARVC pathogenic mechanism (n = 12). In the research, the results demonstrated that there were 619 DEGs in total between non-failing donor myocardial samples and ARVC tissues (FDR < 0.05). WGCNA analysis identified the two gene modules (brown and turquoise) as being most significantly associated with ARVC state. Then the ARVC-related four key biological pathways (cytokine–cytokine receptor interaction, chemokine signaling pathway, neuroactive ligand receptor interaction, and JAK-STAT signaling pathway) and four hub genes (CXCL2, TNFRSF11B, LIFR, and C5AR1) in ARVC samples were further identified by GSNCA method. Finally, we used t-test and receiver operating characteristic (ROC) curves for validating hub genes, results showed significant differences in t-test and their AUC areas all greater than 0.8. Together, these results revealed that the new four hub genes as well as key pathways that might be involved into ARVC diagnosis. Even though further experimental validation is required for the implication by association, our findings demonstrate that the computational methods based on systems biology might complement the traditional gene-wide approaches, as such, might offer a new insight in therapeutic intervention within rare diseases of people like ARVC.

Inhibition of cardiac hypertrophy by aromadendrin through down-regulating NFAT and MAPKs pathways

Cardiac hypertrophy is a maladaptive response to pressure overload and it's an important risk factor for heart failure and other adverse cardiovascular events. Aromadendrin (ARO) has remarkable anti-lipid peroxidation efficacy and is a potential therapeutic medicine for the management of diabetes and cardiovascular diseases. In this study, we established the cardiac hypertrophy cell model in rat neonatal ventricular cardiomyocytes (RNVMs) with phenylephrine. The cell model was characterized by the increased protein synthesis and cardiomyocyte size, which can be normalized by ARO treatment in both concentration- and time-dependent manner. In transverse aortic constriction (TAC) induced cardiac hypertrophy model, ARO administration improved the impairment of cardiac function and alleviated the cardiac hypertrophy indicators, like ventricular mass/body weight, myocyte cross-sectional area, and the expression of ANP, BNP and Myh7. ARO treatment also suppressed the cardiac fibrosis and the correlated fibrogenic genes. Our further investigation revealed ARO could down-regulate pressure overload-induced Malondialdehyde (MDA) and 4-HNE expression, restore the decrease of GSH/GSSG ratio, meanwhile prevent nuclear translocation of NFAT and the activation of MAPKs pathways. Collectively, ARO has a protective effect against experimental cardiac hypertrophy in mice, suggesting its potential as a novel therapeutic drug for pathological cardiac hypertrophy.

Overexpression of small ubiquitin‑like modifier 2 ameliorates high glucose‑induced reductions in cardiomyocyte proliferation via the transforming growth factor‑β/Smad pathway

Hyperglycemia may induce diabetic cardiomyopathy (DC). In the current study, the mechanism underlying the alleviation of high glucose (HG)-induced impairments in the proliferation of H9c2 embryo cardiomyocyte proliferation by small ubiquitin-like modifier 2 (SUMO2) overexpression was investigated. H9c2 cell morphology was identified as classical long shuttle type by optical microscopy. The viability of HG-injured H9c2 cells was evaluated by a Cell Counting Kit-8 assay and the results indicated that viability was inhibited in a dose-dependent (5.6, 10, 20 and 30 mmol/l) and time-dependent (6, 12 and 24 h) manner. H9c2 cells treated with 20 mmol/l HG for 24 h were selected for subsequent experiments due to the extent of injury caused at a low density. Flow cytometry was conducted to confirm cell cycle arrest between G₁/S phases and apoptosis promotion in HG-injured H9c2 cells, and the subsequent alleviating effect of SUMO2 overexpression on these HG-induced effects. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis were performed to detect mRNA and protein expression levels of cell cycle-and apoptosis-associated factors. The results indicated that the expression ofthe cell cycle-associated factors CyclinA2 and C-Myc was upregulated, and cyclin-dependent kinase inhibitor 1a was downregulated. The expression of the apoptosis-associated factor Bcl-2 was upregulated, while Bcl-2-associated X and caspase-3 expression was downregulated, by SUMO2 overexpression. Furthermore, the effect of SUMO2 overexpression on the transforming growth factor (TGF)-β/Smad pathway was also determined using RT-qPCR and western blot analysis. The results indicated the mRNA and protein levels of TGF-β1 and Smad3 in HG-injured H9c2 cells were significantly decreased following SUMO2 overexpression. Thus, the results demonstrated that overexpression of SUMO2 may alleviate H9c2 cardiomyocyte cell cycle arrest and apoptosis promotion induced by HG via regulation of cell cycle- and apoptosis-associated factors, as well as inhibition of the TGF-β/Smad pathway. These results may therefore provide a novel strategy for the protection of cardiomyocytes and may aid the diagnosis and prognosis of patients with DC.

Cardiac remodeling and pre-eclampsia: an overview of microRNA expression patterns

Pre-eclampsia (PE) is strongly associated with heart failure (HF) later in life. During PE pregnancy, the left ventricle undergoes concentric remodeling which often persists after delivery. This aberrant remodeling can induce a molecular signature that can be evaluated in terms of microRNAs (miRNAs) and which may help to explain the associated increased risk of HF. For this review, we performed a literature search of PubMed (National Center for Biotechnology Information), identifying studies on miRNA expression in concentric remodeling and on miRNA expression in PE. The miRNA data were stratified based on origin (isolated from humans or animals and from tissue or the circulation) and both datasets compared in order to generate a list of miRNA expression patterns in concentric remodeling and in PE. The nine miRNAs identified in both concentric remodeling and PE-complicated pregnancy were: miR-1, miR-18, miR-21, miR-29b, miR-30, miR-125b, miR-181b, miR-195 and miR-499-5p. We found five of these miRNAs (miR-18, miR-21, miR-125b, miR-195 and miR-499-5p) to be upregulated in both PE pregnancy and cardiac remodeling and two (miR-1 and miR-30) to be downregulated in both; the remaining two miRNAs (miR-29b and miR-181b) showed upregulation during PE but downregulation in cardiac remodeling. This innovative approach may be a step towards finding relevant biomarkers for complicated pregnancy and elucidating their relationship with remote cardiovascular disease. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Protocatechuic aldehyde protects against isoproterenol-induced cardiac hypertrophy via inhibition of the JAK2/STAT3 signaling pathway

Protocatechuic aldehyde (PCA) is a natural compound found in the Chinese herb Salvia miltiorrhiza. It has been shown to possess multiple biological activities and to protect the cardiovascular system against oxidative stress, inflammation, and atherosclerosis. However, the potential effects of PCA on cardiac hypertrophy remain to be investigated. In this study, we showed that isoproterenol treatment (ISO, 10 μM for 24 h) induced significant hypertrophy in cultured neonatal rat cardiomyocytes, as manifested by enlargement of cell surface area (1.74-fold greater than that of the control, p < 0.05) and upregulation of hypertrophic gene markers (2.44- to 2.75-fold increase in ANF and β-MHC protein expression, p < 0.05). These ISO-induced hypertrophic responses were attenuated by PCA (50-200 μM, p < 0.05). Furthermore, intragastric administration of PCA (10-100 mg/kg/day) ameliorated cardiac hypertrophy in ISO-treated rats (1.5 mg/kg/day, s.c., for 7 days). PCA inhibited the abnormal changes in echocardiographic parameters and suppressed ISO-induced increase in cardiomyocyte cross-sectional area and collagen content (p < 0.05). It also ameliorated ISO-mediated elevation of HW/BW, LVW/BW, and HW/TL ratios (p < 0.05). Mechanistically, ISO facilitated JAK2 and STAT3 phosphorylation, increased STAT3 nuclear translocation, and enhanced STAT3 transcriptional activity. All these changes were attenuated by PCA. Taken together, these findings showed that PCA could protect against cardiac hypertrophy induced by ISO possibly via inhibition of the JAK2/STAT3 signaling pathway, suggesting the potential of PCA as a therapeutic candidate for hypertrophy-associated heart diseases.

S-Enantiomer of 19-Hydroxyeicosatetraenoic Acid Preferentially Protects Against Angiotensin II-Induced Cardiac Hypertrophy

We had recently demonstrated that the racemic mixture of 19-hydroxyeicosatetraenoic acid (19-HETE) protects against angiotensin II (Ang II)-induced cardiac hypertrophy. Therefore, the purpose of this study was to investigate whether the R- or S-enantiomer of 19-HETE confers cardioprotection against Ang II-induced cellular hypertrophy in RL-14 and H9c2 cells. Both cell lines were treated with vehicle or 10 μM Ang II in the absence and presence of 20 μM 19(R)-HETE or 19(S)-HETE for 24 hours. Thereafter, the level of midchain HETEs was determined using liquid chromatography-mass spectrometry. Gene- and protein-expression levels were measured using real-time polymerase chain reaction and Western blot analysis, respectively. The results showed that both 19(R)-HETE and 19(S)-HETE significantly decreased the metabolite formation rate of midchain HETEs, namely 8-, 9-, 12-, and 15-HETE, compared with control group, whereas the level of 5-HETE was selectively decreased by S-enantiomer. Moreover, both 19(R)-HETE and 19(S)-HETE significantly inhibited the catalytic activity of CYP1B1 and decreased the protein expression of 5- and 12-lipoxygenase (LOX) as well as cyclo-oxygenase-2 (COX-2). Notably, the decrease in 15-LOX protein expression was only mediated by 19(S)-HETE. Interestingly, both enantiomers protected against Ang II-induced cellular hypertrophy, as evidenced by a significant decrease in mRNA expression of β/α-myosin heavy chain ratio, atrial natriuretic peptide, and interleukins 6 and 8. Our data demonstrated that S-enantiomer of 19-HETE preferentially protected against Ang II-induced cellular hypertrophy by decreasing the level of midchain HETEs, inhibiting catalytic activity of CYP1B1, decreasing protein expression of LOX and COX-2 enzymes, and decreasing mRNA expression of IL-6 and IL-8.

Upregulation of lncRNA VDR/CASC15 induced by facilitates cardiac hypertrophy through modulating miR-432-5p/TLR4 axis

Sustained cardiac hypertrophy has threatened human health. With the development of human genome project, non-coding RNAs (ncRNAs) have attracted more and more attentions of researchers. As a subgroup of ncRNAs, long non-coding RNAs (lncRNAs) has been widely studied in human diseases, including cardiac hypertrophy. According to search results of bioinformatics website, lncRNA CASC15 potentially participates in the course of cardiac hypertrophy. According to the result of qRT-PCR, CASC15 expression was upregulated when cardiomyocytes were treated with Ang-II. Moreover, CASC15 was highly expressed in cardiac hypertrophic model. Upregulation of CASC15 was accompanied with some hypertrophic responses. To explore the specific biological function of CASC15 in cardiac hypertrophy, loss-of-function experiments were conducted in Ang-II-induced cardiomyocytes. Results of immunofluorence staining revealed that cell surface area enlarged by Ang-II was decreased when CASC15 was silenced. The expression levels of hypertrophic factors were attenuated by knockdown of CASC15. To detect the molecular mechanism by which CASC15 regulates the progression of cardiac hypertrophy, mechanism experiments were designed and carried out. It was found that CASC15 was activated by the transcription factor VDR. Furthermore, CASC15 can upregulate TLR4 by competitively binding miR-432-5p. In conclusion, Upregulation of lncRNA CASC15 induced by VDR facilitates cardiac hypertrophy via miR-432-5p/TLR4 axis.

TWEAK/Fn14 mediates atrial-derived HL-1 myocytes hypertrophy via JAK2/STAT3 signalling pathway

Atrial myocyte hypertrophy is one of the most important substrates in the development of atrial fibrillation (AF). The TWEAK/Fn14 axis is a positive regulator of cardiac hypertrophy in cardiomyopathy. This study therefore investigated the effects of Fn14 on atrial hypertrophy and underlying cellular mechanisms using HL‐1 atrial myocytes. In patients with AF, Fn14 protein levels were higher in atrial myocytes from atrial appendages, and expression of TWEAK was increased in peripheral blood mononuclear cells, while TWEAK serum levels were decreased. In vitro, Fn14 expression was up‐regulated in response to TWEAK treatment in HL‐1 atrial myocytes. TWEAK increased the expression of ANP and Troponin T, and Fn14 knockdown counteracted the effect. Inhibition of JAK2, STAT3 by specific siRNA attenuated TWEAK‐induced HL‐1 atrial myocytes hypertrophy. In conclusion, TWEAK/Fn14 axis mediates HL‐1 atrial myocytes hypertrophy partly through activation of the JAK2/STAT3 pathway.

Hypoxia-Induced Mitogenic Factor Promotes Cardiac Hypertrophy via Calcium-Dependent and Hypoxia-Inducible Factor-1α Mechanisms

HIMF (hypoxia-induced mitogenic factor/found in inflammatory zone 1/resistin like α) is a secretory and cytokine-like protein and serves as a critical stimulator of hypoxia-induced pulmonary hypertension. With a role for HIMF in heart disease unknown, we explored the possible roles for HIMF in cardiac hypertrophy by overexpressing and knocking down HIMF in cardiomyocytes and characterizing HIMF gene (himf) knockout mice. We found that HIMF mRNA and protein levels were upregulated in phenylephrine-stimulated cardiomyocyte hypertrophy and our mouse model of transverse aortic constriction-induced cardiac hypertrophy, as well as in human hearts with dilated cardiomyopathy. Furthermore, HIMF overexpression could induce cardiomyocyte hypertrophy, as characterized by elevated protein expression of hypertrophic biomarkers (ANP [atrial natriuretic peptide] and β-MHC [myosin heavy chain-β]) and increased cell-surface area compared with controls. Conversely, HIMF knockdown prevented phenylephrine-induced cardiomyocyte hypertrophy and himf ablation in knockout mice significantly attenuated transverse aortic constriction-induced hypertrophic remodeling and cardiac dysfunction. HIMF overexpression increased the cytosolic Ca²⁺ concentration and activated the CaN-NFAT (calcineurin-nuclear factor of activated T cell) and MAPK (mitogen-activated protein kinase) pathways; this effect could be prevented by reducing cytosolic Ca²⁺ concentration with L-type Ca²⁺ channel blocker nifedipine or inhibiting the CaSR (Ca²⁺ sensing receptor) with Calhex 231. Furthermore, HIMF overexpression increased HIF-1α (hypoxia-inducible factor) expression in neonatal rat ventricular myocytes, and HIMF knockout inhibited HIF-1α upregulation in transverse aortic constriction mice. Knockdown of HIF-1α attenuated HIMF-induced cardiomyocyte hypertrophy. In conclusion, HIMF has a critical role in the development of cardiac hypertrophy, and targeting HIMF may represent a potential therapeutic strategy.

Obesity-associated cardiac pathogenesis in broiler breeder hens: Pathological adaption of cardiac hypertrophy

Broiler hens consuming feed to appetite (ad libitum; AL) show increased mortality. Feed restriction (R) typically improves reproductive performance and livability of hens. Rapidly growing broilers can exhibit increased mortality due to cardiac insufficiency but it is unknown whether the increased mortality of non-R broiler hens is also due to cardiac compromise. To assess cardiac growth and physiology in fully mature birds, 45-week-old hens were either continued on R rations or assigned to AL feeding for 7 or 21 days. AL hens exhibited increased bodyweight, adiposity, absolute and relative heart weight, ventricular hypertrophy, and cardiac protein/DNA ratio by d 21 (P < 0.05). Increased heart weights due to hypertrophic growth was attributed to enhanced IGF-1-Akt-FoxO1 signaling and its downstream target, translation initiation factor 4E-BP1 in conjunction with down-regulation of ubiquitin ligase atrogin-1/MAFbx (P < 0.05). Reduced activation of cardiac AMPK and downstream activation of ACC-1 in parallel with increased cardiac nitric oxide levels, calcineurin activity, and MAPK activation in AL hens (P < 0.05) suggested that metabolic derangement develops along the cardiovascular remodeling. These indictors of cardiac maladaptive hypertrophic growth were further supported by uregulation of heart failure markers, BNP and MHC-β (P < 0.05). Hens allowed AL feeding for 70 d exhibited a higher incidence of mortality (40% vs. 10%) in association with ascites, pericardial effusion, and ventricle dilation. A higher incidence of irregular ECG patterns and rhythmicity consistent with persistently elevated systolic blood pressure and ventricle fibrosis were observed in AL hens (P < 0.05). These observations support the conclusion that AL feeding in broiler hens results in maladaptive cardiac hypertrophy that progresses to overt pathogenesis in contractility and thereby increases mortality. Feed restriction provides clear physiological benefit to heart function of adult broiler hens.

Salvia miltiorrhizaBurge (Danshen): a golden herbal medicine in cardiovascular therapeutics

Salvia miltiorrhiza Burge (Danshen) is an eminent medicinal herb that possesses broad cardiovascular and cerebrovascular protective actions and has been used in Asian countries for many centuries. Accumulating evidence suggests that Danshen and its components prevent vascular diseases, in particular, atherosclerosis and cardiac diseases, including myocardial infarction, myocardial ischemia/reperfusion injury, arrhythmia, cardiac hypertrophy and cardiac fibrosis. The published literature indicates that lipophilic constituents (tanshinone I, tanshinone IIa, tanshinone IIb, cryptotanshinone, dihydrotanshinone, etc) as well as hydrophilic constituents (danshensu, salvianolic acid A and B, protocatechuic aldehyde, etc) contribute to the cardiovascular protective actions of Danshen, suggesting a potential synergism among these constituents. Herein, we provide a systematic up-to-date review on the cardiovascular actions and therapeutic potential of major pharmacologically active constituents of Danshen. These bioactive compounds will serve as excellent drug candidates in small-molecule cardiovascular drug discovery. This article also provides a scientific rationale for understanding the traditional use of Danshen in cardiovascular therapeutics.

Cardiac-Specific Expression of ΔH2-R15 Mini-Dystrophin Normalized All Electrocardiogram Abnormalities and the End-Diastolic Volume in a 23-Month-Old Mouse Model of Duchenne Dilated Cardiomyopathy

Heart disease is a major health threat for Duchenne/Becker muscular dystrophy patients and carriers. Expression of a 6-8 kb mini-dystrophin gene in the heart holds promise to change the disease course dramatically. However, the mini-dystrophin gene cannot be easily studied with adeno-associated virus (AAV) gene delivery because the size of the minigene exceeds AAV packaging capacity. Cardiac protection of the ΔH2-R19 minigene was previously studied using the cardiac-specific transgenic approach. Although this minigene fully normalized skeletal muscle force, it only partially corrected electrocardiogram and heart hemodynamics in dystrophin-null mdx mice that had moderate cardiomyopathy. This study evaluated the ΔH2-R15 minigene using the same transgenic approach in mdx mice that had more severe cardiomyopathy. In contrast to the ΔH2-R19 minigene, the ΔH2-R15 minigene carries dystrophin spectrin-like repeats 16 to 19 (R16-19), a region that has been suggested to protect the heart in clinical studies. Cardiac expression of the ΔH2-R15 minigene normalized all aberrant electrocardiogram changes and improved hemodynamics. Importantly, it corrected the end-diastolic volume, an important diastolic parameter not rescued by ΔH2-R19 mini-dystrophin. It is concluded that that ΔH2-R15 mini-dystrophin is a superior candidate gene for heart protection. This finding has important implications in the design of the mini/micro-dystrophin gene for Duchenne cardiomyopathy therapy.

Z-disc protein CHAPb induces cardiomyopathy and contractile dysfunction in the postnatal heart

Aims

The Z-disc is a crucial structure of the sarcomere and is implicated in mechanosensation/transduction. Dysregulation of Z-disc proteins often result in cardiomyopathy. We have previously shown that the Z-disc protein Cytoskeletal Heart-enriched Actin-associated Protein (CHAP) is essential for cardiac and skeletal muscle development. Furthermore, the CHAP gene has been associated with atrial fibrillation in humans. Here, we studied the misregulated expression of CHAP isoforms in heart disease.

Methods and results

Mice that underwent transverse aortic constriction and calcineurin transgenic (Tg) mice, both models of experimental heart failure, displayed a significant increase in cardiac expression of fetal isoform CHAPb. To investigate whether increased expression of CHAPb postnatally is sufficient to induce cardiomyopathy, we generated CHAPb Tg mice under the control of the cardiac-specific αMHC promoter. CHAPb Tg mice displayed cardiac hypertrophy, interstitial fibrosis and enlargement of the left atrium at three months, which was more pronounced at the age of six months. Hypertrophy and fibrosis were confirmed by evidence of activation of the hypertrophic gene program (Nppa, Nppb, Myh7) and increased collagen expression, respectively. Connexin40 and 43 were downregulated in the left atrium, which was associated with delayed atrioventricular conduction. Tg hearts displayed both systolic and diastolic dysfunction partly caused by impaired sarcomere function evident from a reduced force generating capacity of single cardiomyocytes. This co-incided with activation of the actin signalling pathway leading to the formation of stress fibers.

Conclusion

This study demonstrated that the fetal isoform CHAPb initiates progression towards cardiac hypertrophy, which is accompanied by delayed atrioventricular conduction and diastolic dysfunction. Moreover, CHAP may be a novel therapeutic target or candidate gene for screening in cardiomyopathies and atrial fibrillation.

STAT3 Suppression Is Involved in the Protective Effect of SIRT6 Against Cardiomyocyte Hypertrophy

The activation of signal transducer and activator of transcription 3 (STAT3) is critical for the development of cardiac hypertrophy and heart failure. Sirtuin 6 (SIRT6) protects cardiomyocytes from hypertrophy. This study focused on the association between SIRT6 and STAT3 in the regulation of cardiomyocyte hypertrophy. In the phenylephrine (PE)-induced hypertrophic cardiomyocyte model and in the hearts of isoprenaline-induced cardiac hypertrophic rat model, the mRNA and protein expressions of STAT3 and its phosphorylated level at tyrosine 705 (P-STAT3) were significantly increased. By contrast, the deacetylation activity of SIRT6 was weakened without altering its protein expression. In addition, the nuclear localization of STAT3 and P-STAT3 was enhanced by PE, suggesting that STAT3 was activated in cardiomyocyte hypertrophy. Adenovirus infection-induced SIRT6 overexpression repressed the activation of STAT3 by decreasing its mRNA and protein levels, by suppressing its transcriptional activity, and by hindering the expressions of its target genes. Moreover, the effect of SIRT6 overexpression on eliminating PE-induced expressions of hypertrophic biomarkers, such as atrial natriuretic factor and brain natriuretic peptide, was reversed by STAT3 overexpression. Likewise, SIRT6 knockdown-induced upregulation of atrial natriuretic factor and brain natriuretic peptide was reversed by STAT3 silencing. These observations suggest that the antihypertrophic effect of SIRT6 involves STAT3 suppression. In conclusion, SIRT6 prevents PE-induced activation of STAT3 in cardiomyocyte hypertrophy; the inhibitory effect of SIRT6 on STAT3 contributes to cardiac protection.

The valosin-containing protein is a novel repressor of cardiomyocyte hypertrophy induced by pressure overload

Hypertension‐induced left ventricular hypertrophy (LVH) is an independent risk factor for heart failure. Regression of LVH has emerged as a major goal in the treatment of hypertensive patients. Here, we tested our hypothesis that the valosin‐containing protein (VCP), an ATPase associate protein, is a novel repressor of cardiomyocyte hypertrophy under the pressure overload stress. Left ventricular hypertrophy (LVH) was determined by echocardiography in 4‐month male spontaneously hypertensive rats (SHRs) vs. age‐matched normotensive Wistar Kyoto (WKY) rats. VCP expression was found to be significantly downregulated in the left ventricle (LV) tissues from SHRs vs. WKY rats. Pressure overload was induced by transverse aortic constriction (TAC) in wild‐type (WT) mice. At the end of 2 weeks, mice with TAC developed significant LVH whereas the cardiac function remained unchanged. A significant reduction of VCP at both the mRNA and protein levels in hypertrophic LV tissue was found in TAC WT mice compared to sham controls. Valosin‐containing protein VCP expression was also observed to be time‐ and dose‐dependently reduced in vitro in isolated neonatal rat cardiomyocytes upon the treatment of angiotensin II. Conversely, transgenic (TG) mice with cardiac‐specific overexpression of VCP showed a significant repression in TAC‐induced LVH vs. litter‐matched WT controls upon 2‐week TAC. TAC‐induced activation of the mechanistic target of rapamycin complex 1 (mTORC1) signaling observed in WT mice LVs was also significantly blunted in VCP TG mice. In conclusion, VCP acts as a novel repressor that is able to prevent cardiomyocyte hypertrophy from pressure overload by modulating the mTORC1 signaling pathway.

Rosiglitazone promotes cardiac hypertrophy and alters chromatin remodeling in isolated cardiomyocytes

Rosiglitazone is an anti-diabetic agent that raised a major controversy over its cardiovascular adverse effects. There is in vivo evidence that Rosiglitazone promotes cardiac hypertrophy by PPAR-γ-independent mechanisms. However, whether Rosiglitazone directly alters hypertrophic growth in cardiac cells is unknown. Chromatin remodeling by histone post-translational modifications has emerged as critical for many cardiomyopathies. Based on these observations, this study was initiated to investigate the cardiac hypertrophic effect of Rosiglitazone in a cellular model of primary neonatal rat cardiomyocytes (NRCM). We assessed whether the drug alters cardiac hypertrophy and its relationship with histone H3 phosphorylation. Our study showed that Rosiglitazone is a mild pro-hypertrophic agent. Rosiglitazone caused a significant increase in the release of brain natriuretic peptide (BNP) into the cell media and also increased cardiomyocytes surface area and atrial natriuretic peptide (ANP) protein expression significantly. These changes correlated with increased cardiac phosphorylation of p38 MAPK and enhanced phosphorylation of H3 at serine 10 globally and at one cardiac hypertrophic gene locus. These results demonstrate that Rosiglitazone causes direct cardiac hypertrophy in NRCM and alters H3 phosphorylation status. They suggest a new mechanism of Rosiglitazone cardiotoxicity implicating chromatin remodeling secondary to H3 phosphorylation, which activate the fetal cardiac gene program.

Contribution of Interleukin-6 to the Pathogenesis of Systemic Sclerosis

Systemic sclerosis (SSc) is a connective tissue disease of unknown etiology, manifesting in patients as tissue fibrosis, endothelial dysfunction, and inflammation. The disease is characterized by autoantibodies, a hallmark of autoimmunity. Various cytokines and growth factors are elevated in the systemic circulation and fibrotic lesions of patients with SSc. In particular, several studies over the past 2 decades have shown that interleukin-6 (IL-6) appears to be involved in the pathogenesis of SSc. Based on the association between aberrant IL-6 production and tissue fibrosis in patients with SSc, the anti-IL-6 receptor antibody, tocilizumab, is being investigated in clinical trials. This article reviews the biological features of IL-6 and the IL-6 receptor; the role of IL-6 in the pathogenesis of SSc; and the potential for IL-6 inhibition to be used in the treatment of patients with SSc.

GNAQ TT(-695/-694)GC Polymorphism Is Associated with Increased Gq Expression, Vascular Reactivity, and Myocardial Injury after Coronary Artery Bypass Surgery

BACKGROUND

Angiotensin II receptor type 1-mediated activation of the α-subunit of the heterotrimeric Gq protein evokes increased vasoconstriction and may promote hypertrophy-induced myocardial damage. The authors recently identified a TT(-695/-694)GC polymorphism in the human Gq promoter, the GC allele being associated with an increased prevalence of cardiac hypertrophy. In this article, the authors tested whether the TT(-695/-694)GC polymorphism is associated with differences in (1) myocardial Gq protein expression, (2) vascular reactivity, and (3) myocardial damage after coronary artery bypass grafting.

METHODS

Gq protein expression was measured in right atrial muscle from 55 patients undergoing coronary artery bypass grafting as were skin perfusion changes (n = 18; laser Doppler imaging), saphenous vein ring vascular reactivity (n = 50, organ bath) in response to angiotensin II, and myocardial damage (227 patients undergoing coronary artery bypass grafting), as assessed by postoperative cardiac troponin I concentration.

RESULTS

Myocardial Gq expression was greater in GC/GC genotypes (GC/GC vs.

TT/TT

1.27-fold change; P = 0.006). Skin perfusion after intradermal angiotensin II injection decreased only in GC/GC genotypes (P = 0.0002). Saphenous vein rings exposed to increasing angiotensin II concentrations showed an almost doubled maximum contraction in GC/GC compared with individuals with the TT/TT genotype (P = 0.022). In patients undergoing coronary artery bypass grafting, baseline cardiac ejection fraction was different (GC/GC: 55 ± 13%; GC/TT: 54 ± 14%; TT/TT: 48 ± 15%; P = 0.037) and postoperative peak cardiac troponin I was greater in patients with the GC/GC (11.5 ± 13.8 ng/ml) than in patients with the GC/TT (9.2 ± 9.2 ng/ml) or patients with the TT/TT genotype (6.6 ± 4.8 ng/ml, P = 0.015).

CONCLUSIONS

The GC/GC genotype of the TT(-695/-694)GC polymorphism is associated with increased Gq protein expression, augmented angiotensin II receptor type 1-related vasoconstriction, and increased myocardial injury after coronary artery bypass grafting, highlighting the impact of Gq genotype variation.

JAK2/STAT3 Pathway Was Associated with the Protective Effects of IL-22 On Aortic Dissection with Acute Lung Injury

Patients with aortic dissection (AD) may present acute lung injury (ALI) that may affect the prognosis. In this study, we aim to investigate the roles and mechanism of IL-22 in the pathogenesis of AD complicated with ALI. Six hundred and twenty-one AD patients were included, and the incidence of ALI and pulmonary CT findings were analyzed. Mouse ALI model was established through AngII, and then IL-22 injection and AG490 were given. The pathological changes, infiltration of inflammatory cells, and expression of STAT3 were determined. For the in vitro experiment, cultivated pulmonary microvascular endothelial cells (PMVECs) were treated by angiotensin II (AngII), followed by treating with IL-22 and/or AG490. The expression and migration of STAT3 was determined. Flow cytometry was carried out to evaluate the apoptosis. IL-22 contributed to the expression of STAT3 in lung tissues and attenuation of ALI. IL-22 obviously inhibited the apoptosis of PMVECs mediated by AngII and downregulated the expression and intranuclear transmission of STAT3. Such phenomenon was completely inhibited upon administration of AG490, an inhibitor of JAK2. Our data showed IL-22 contributed to the inhibition of PMVEC apoptosis mediated by AngII through activating the JAK2/STAT3 signaling pathway, which may attenuate the ALI induced by AngII.