Apoptosis in Heart Failure - The Role of the .BETA.-Adrenergic Receptor-Mediated Signaling Pathway and p53-Mediated Signaling Pathway in the Apoptosis of Cardiomyocytes -

The potential of herbal drugs to treat heart failure: The roles of Sirt1/AMPK

Heart failure (HF) is a highly morbid syndrome that seriously affects the physical and mental health of patients and generates an enormous socio-economic burden. In addition to cardiac myocyte oxidative stress and apoptosis, which are considered mechanisms for the development of HF, alterations in cardiac energy metabolism and pathological autophagy also contribute to cardiac abnormalities and ultimately HF. Silent information regulator 1 (Sirt1) and adenosine monophosphate-activated protein kinase (AMPK) are nicotinamide adenine dinucleotide (NAD+)-dependent deacetylases and phosphorylated kinases, respectively. They play similar roles in regulating some pathological processes of the heart through regulating targets such as peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), protein 38 mitogen-activated protein kinase (p38 MAPK), peroxisome proliferator-activated receptors (PPARs), and mammalian target of rapamycin (mTOR). We summarized the synergistic effects of Sirt1 and AMPK in the heart, and listed the traditional Chinese medicine (TCM) that exhibit cardioprotective properties by modulating the Sirt1/AMPK pathway, to provide a basis for the development of Sirt1/AMPK activators or inhibitors for the treatment of HF and other cardiovascular diseases (CVDs).

Exploring novel biomarkers in dilated cardiomyopathy‑induced heart failure by integrated analysis and in vitro experiments

Despite the availability of several effective and promising treatment methods, heart failure (HF) remains a significant public health concern that requires advanced therapeutic strategies and techniques. Dilated cardiomyopathy (DCM) is a crucial factor that contributes to the development and deterioration of HF. The aim of the present study was to identify novel biomarkers and biological pathways to enhance the diagnosis and treatment of patients with DCM-induced HF using weighted gene co-expression network analysis (WGCNA). A total of 24 co-expressed gene modules connected with DCM-induced HF were obtained by WGCNA. Among these, the blue module had the highest correlation with DCM-induced HF (r=0.91; P<0.001) and was enriched in the AGE-RAGE signaling pathway in diabetic complications, the p53 and MAPK signaling pathway, adrenergic signaling in cardiomyocytes, the Janus kinase-STAT signaling pathway and cGMP/PKG signaling. Eight key genes, including secreted protein acidic and rich in cysteine-related modular calcium-binding protein 2 (SMOC2), serpin family A member 3 (SERPINA3), myosin heavy chain 6 (MYH6), S100 calcium binding protein A9 (S100A9), tubulin α (TUBA)3E, TUBA3D, lymphatic vessel endothelial hyaluronic acid receptor 1 (LYVE1) and phospholipase C ε1 (PLCE1), were selected as the therapeutic targets of DCM-induced HF based on WGCNA and differentially expressed gene analysis. Immune cell infiltration analysis revealed that the proportion of naive B cells and CD4-activated memory T cells was markedly upregulated in DCM-induced HF tissues compared with tissues from healthy controls. Furthermore, reverse transcription-quantitative PCR in AC16 human cardiomyocyte cells treated with doxorubicin showed that among the eight key genes, only SERPINA3, MYH6, S100A9, LYVE1 and PLCE1 exhibited expression levels identical to those revealed by bioinformatics analysis, suggesting that these genes may be involved in the development of DCM-induced HF.

MicroRNAs target the PI3K/Akt/p53 and the Sirt1/Nrf2 signaling pathways in doxorubicin-induced cardiotoxicity

Doxorubicin (DOX) is used as a chemotherapeutic agent in the treatment of solid tumors. Irreversible cardiotoxicity is the major limitation in the clinical use of DOX. Several microRNAs (miRNAs) with diversified functions are identified that participate in exacerbating or suppressing DOX-induced cardiac damage. The miRNAs are small noncoding regulatory RNAs that modify the expression of the native genes. Studies have demonstrated that miRNAs by modifying the expression of proteins such as PTEN, Akt, and survivin can affect DOX-induced cardiac apoptosis. Moreover, miRNAs can modulate cardiac oxidative stress in DOX treatment through the posttranscriptional regulation of Sirt1, p66shc, and Nrf2 expressions. This manuscript has reviewed the regulation of the PI3K/Akt/p53 and the Sirt1/Nrf2 pathways by miRNAs in DOX-induced cardiotoxicity.

Metabolic remodeling of glycerophospholipids acts as a signature of dulaglutide and liraglutide treatment in recent-onset type 2 diabetes mellitus

Aims

As metabolic remodeling is a pathological characteristic in type 2 diabetes (T2D), we investigate the roles of newly developed long-acting glucagon-like peptide-1 receptor agonists (GLP-1RAs) such as dulaglutide and liraglutide on metabolic remodeling in patients with recent-onset T2D.

Methods

We recruited 52 cases of T2D and 28 control cases in this study. In the patient with T2D, 39 cases received treatment with dulaglutide and 13 cases received treatment with liraglutide. Using untargeted metabolomics analysis with broad-spectrum LC-MS, we tracked serum metabolic changes of the patients from the beginning to the end of follow-up (12th week).

Results

We identified 198 metabolites that were differentially expressed in the patients with T2D, compared to the control group, in which 23 metabolites were significantly associated with fasting plasma glucose. Compared to pre-treatment, a total of 46 and 45 differentially regulated metabolites were identified after treatments with dulaglutide and liraglutide, respectively, in which the most differentially regulated metabolites belong to glycerophospholipids. Furthermore, a longitudinal integration analysis concurrent with diabetes case-control status revealed that metabolic pathways, such as the insulin resistance pathway and type 2 diabetes mellitus, were enriched after dulaglutide and liraglutide treatments. Proteins such as GLP-1R, GNAS, and GCG were speculated as potential targets of dulaglutide and liraglutide.

Conclusions

In total, a metabolic change in lipids existed in the early stage of T2D was ameliorated after the treatments of GLP-1RAs. In addition to similar effects on improving glycemic control, remodeling of glycerophospholipid metabolism was identified as a signature of dulaglutide and liraglutide treatments.

Transcriptomic responses to cytotoxic drug cisplatin in water flea Daphnia magna

Cytotoxic drugs have been recognized by the European Union as the potential threat in the aquatic environment. As a typical cytotoxic drug, effects of long-term exposure to cisplatin at the environmentally relevant concentrations on the crustacean health and its molecular mechanism remain undetermined. In this study, the growth and reproduction of Daphnia magna resulting from cisplatin exposure were initially assessed. While the phenotypes were not altered in 2 μg L^-1, 20 μg L^-1, and 200 μg L^-1 treatment groups, cisplatin at 500 µg L^-1 significantly reduced the offspring number to 8-13 neonates in each brood, which was lower than 13-27 neonates in the control group. In addition to the delay in the time of first pregnancy, the body length was decreased by approximate 12.13% at day 7. Meanwhile, all daphnids died after exposure to 500 µg L^-1 cisplatin for 17 days. Transcriptome profiling bioassays were performed for 10 days to explore the alternation at the molecular level. Briefly, 980 (257 up- and 723 down-regulated), 429 (182 up- and 247 down-regulated) and 1984 (616 up-regulated and 1368 down-regulated) genes were differentially expressed (adj p < 0.05) in low (2 μg L^-1), medium (200 μg L^-1) and high (500 μg L^-1) cisplatin treatment groups, respectively. Differentially expressed genes were primarily enriched in the digestion and absorption, nerve conduction, endocrine interference, and circulatory related pathways. Specifically, the down-regulated digestive secretion and nutrient absorption and neuronal conduction pathways may lead to insufficient energy supply involved in growth and reproduction, and hinder ovarian development and cell growth. Down-regulation of ovarian steroids and relaxin signaling pathways may be related to the reduction of offspring number and delayed pregnancy, and reduced body length of D. magna may attribute to the enrichment of insulin secretion pathway. In addition, the death of D. magna may result from the reduced expression of genes in cardiomyocyte contraction and apoptosome processes. Taken together, this study revealed the potential toxic mechanism of cisplatin in a model water flea.

Investigation of the Potential Key Genes and the Multitarget Mechanisms of Polygonum cuspidatum against Heart Failure Based on Network Pharmacology and Experimental Validation

In this study, systematic pharmacology and bioinformatic approaches were employed to identify the potential targets of Polygonum cuspidatum (PC) for treating heart failure (HF). The active ingredients of PC were screened by using the TCMSP database, and HF-related genes were identified in the GEO database. Then, the herb-HF targeted-gene networks were constructed using Cytoscape software. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional analyses were performed to obtain the enriched molecular pathways associated with the pathogenesis of HF. Finally, in vitro experiment was performed to evidence network pharmacology analysis. 170 intersection genes were obtained, and key genes (FOXO3, NFKB1, and TNF) were identified. Besides, GO and KEGG findings indicated that PC treatment of HF was achieved via regulating apoptosis, IL-17 signaling pathway, TNF signaling pathway, response to oxidative stress, and response to reactive oxygen species. And cell experiment revealed that PC could decrease the expression of NFKB1 and TNF and increase the expression of FOXO3, SOD1, and GPX1 in H9C2 cells. These findings showed that the therapeutic mechanism of PC in the treatment of HF may be associated with the regulation of inflammation-related and oxidative stress-related genes.

Long Noncoding RNAs Involved in Cardiomyocyte Apoptosis Triggered by Different Stressors

Cardiomyocytes are essential to maintain the normal cardiac function. Ischemia, hypoxia, and drug stimulation can induce pathological apoptosis of cardiomyocytes which eventually leads to heart failure, arrhythmia, and other cardiovascular diseases. Understanding the molecular mechanisms that regulate cardiomyocyte apoptosis is of great significance for the prevention and treatment of cardiovascular diseases. In recent years, more and more evidences reveal that long noncoding RNAs (lncRNAs) play important regulatory roles in myocardial cell apoptosis. They can modulate the expression of apoptosis-related genes at post-transcriptional level by altering the translation efficacy of target mRNAs or functioning as a precursor for miRNAs or competing for miRNA-mediated inhibition. Moreover, reversing the abnormal expression of lncRNAs can attenuate and even reverse the pathological apoptosis of cardiomyocytes. Therefore, apoptosis-related lncRNAs may become a potential new field for studying cardiomyocyte apoptosis and provide new ideas for the treatment of cardiovascular diseases.

Mechanotranduction Pathways in the Regulation of Mitochondrial Homeostasis in Cardiomyocytes

Mitochondria are one of the most important organelles in cardiomyocytes. Mitochondrial homeostasis is necessary for the maintenance of normal heart function. Mitochondria perform four major biological processes in cardiomyocytes: mitochondrial dynamics, metabolic regulation, Ca²⁺ handling, and redox generation. Additionally, the cardiovascular system is quite sensitive in responding to changes in mechanical stress from internal and external environments. Several mechanotransduction pathways are involved in regulating the physiological and pathophysiological status of cardiomyocytes. Typically, the extracellular matrix generates a stress-loading gradient, which can be sensed by sensors located in cellular membranes, including biophysical and biochemical sensors. In subsequent stages, stress stimulation would regulate the transcription of mitochondrial related genes through intracellular transduction pathways. Emerging evidence reveals that mechanotransduction pathways have greatly impacted the regulation of mitochondrial homeostasis. Excessive mechanical stress loading contributes to impairing mitochondrial function, leading to cardiac disorder. Therefore, the concept of restoring mitochondrial function by shutting down the excessive mechanotransduction pathways is a promising therapeutic strategy for cardiovascular diseases. Recently, viral and non-viral protocols have shown potentials in application of gene therapy. This review examines the biological process of mechanotransduction pathways in regulating mitochondrial function in response to mechanical stress during the development of cardiomyopathy and heart failure. We also summarize gene therapy delivery protocols to explore treatments based on mechanical stress–induced mitochondrial dysfunction, to provide new integrative insights into cardiovascular diseases.

The role of the DFF40/CAD endonuclease in genomic stability

Maintenance of genomic stability in cells is primordial for cellular integrity and protection against tumor progression. Many factors such as ultraviolet light, oxidative stress, exposure to chemical reagents, particularly mutagens and radiation, can alter the integrity of the genome. Thus, human cells are equipped with many mechanisms that prevent these irreversible lesions in the genome, as DNA repair pathways, cell cycle checkpoints, and telomeric function. These mechanisms activate cellular apoptosis to maintain DNA stability. Emerging studies have proposed a new protein in the maintenance of genomic stability: the DNA fragmentation factor (DFF). The DFF40 is an endonuclease responsible of the oligonucleosomal fragmentation of the DNA during apoptosis. The lack of DFF in renal carcinoma cells induces apoptosis without oligonucleosomal fragmentation, which poses a threat to genetic information transfer between cancerous and healthy cells. In this review, we expose the link between the DFF and genomic instability as the source of disease development.

FABP4 inhibitor BMS309403 protects against hypoxia-induced H9c2 cardiomyocyte apoptosis through attenuating endoplasmic reticulum stress

Acute myocardial infarction is characterized by ischaemia-induced cardiomyocyte apoptosis, in which the endoplasmic reticulum (ER) stress plays an important role. The fatty acid-binding protein-4 (FABP4) has been implicated in regulating ER stress and apoptosis. Yet, whether FABP4 is involved in modulating cardiomyocyte apoptosis remains unclarified. By applying an in vitro model of hypoxia-induced apoptosis of H9c2 cardiomyocytes, we found that FABP4 expression was elevated upon hypoxia stimulation, which was further demonstrated to be transcriptionally activated by the hypoxia-inducible factor 1a (HIF-1α). In addition, the pharmacological inhibition of FABP4 with BMS309403 protected against hypoxia-induced apoptosis in cardiomyocytes, indicating that FABP4 induction is detrimental for cardiomyocyte survival under hypoxic condition. Moreover, BMS309403 attenuated ER stress in cardiomyocytes exposed to hypoxia, which, however, was reversed by tunicamycin, an ER stress activator. More importantly, the protective effect of BMS309403 on cardiomyocytes vanished in the presence of tunicamycin. Thus, these observations establish that FABP4 inhibitor BMS309403 reduces hypoxia-induced cardiomyocyte apoptosis through attenuating excessive ER stress, implying that FABP4 inhibition may be of clinical benefit for MI treatment.

Elevated intracellular cAMP concentration mediates growth suppression in glioma cells

Supressed levels of intracellular cAMP have been associated with malignancy. Thus, elevating cAMP through activation of adenylyl cyclase (AC) or by inhibition of phosphodiesterase (PDE) may be therapeutically beneficial. Here, we demonstrate that elevated cAMP levels suppress growth in C6 cells (a model of glioma) through treatment with forskolin, an AC activator, or a range of small molecule PDE inhibitors with differing selectivity profiles. Forskolin suppressed cell growth in a PKA-dependent manner by inducing a G₂/M phase cell cycle arrest. In contrast, trequinsin (a non-selective PDE2/3/7 inhibitor), not only inhibited cell growth via PKA, but also stimulated (independent of PKA) caspase-3/-7 and induced an aneuploidy phenotype. Interestingly, a cocktail of individual PDE 2,3,7 inhibitors suppressed cell growth in a manner analogous to forskolin but not trequinsin. Finally, we demonstrate that concomitant targeting of both AC and PDEs synergistically elevated intracellular cAMP levels thereby potentiating their antiproliferative actions.

Imbalance of ER and Mitochondria Interactions: Prelude to Cardiac Ageing and Disease?

Cardiac disease is still the leading cause of morbidity and mortality worldwide, despite some exciting and innovative improvements in clinical management. In particular, atrial fibrillation (AF) and heart failure show a steep increase in incidence and healthcare costs due to the ageing population. Although research revealed novel insights in pathways driving cardiac disease, the exact underlying mechanisms have not been uncovered so far. Emerging evidence indicates that derailed proteostasis (i.e., the homeostasis of protein expression, function and clearance) is a central component driving cardiac disease. Within proteostasis derailment, key roles for endoplasmic reticulum (ER) and mitochondrial stress have been uncovered. Here, we describe the concept of ER and mitochondrial stress and the role of interactions between the ER and mitochondria, discuss how imbalance in the interactions fuels cardiac ageing and cardiac disease (including AF), and finally assess the potential of drugs directed at conserving the interaction as an innovative therapeutic target to improve cardiac function.

Quercetin supports cell viability and inhibits apoptosis in cardiocytes by down-regulating miR-199a

Hypoxia-caused cardiocytes insults are closely correlated with ectopic expression of genes, which might be modulated by microRNAs (miRs). Quercetin exhibits a profound protective function against hypoxic damages in cardiomyocytes. Here, we aimed to investigate a possible underpinning. H9c2 cells were pre-administrated using quercetin before hypoxia treatment. The damages were assessed using viability, apoptosis and alteration of proteins associated with apoptosis and adenosine monophosphate-activated protein (AMPK) pathway. Transfection was conducted to enforce overexpression of miR-199a or silence of sirtuin 1 (sirt1) which were confirmed by qRT-PCR. Sirt1 protein was quantified by immunoblotting. A luciferase reporter was exploited to confirm the target relationship between miR-199a and sirt1 3'-untranslated region (3'-UTR). We found quercetin mitigated hypoxia-caused viability reduction and apoptosis with restoring apoptosis-associated protein and rescuing phosphorylation of AMPK. Quercetin flattened hypoxia-evoked overexpression of miR-199a. miR-199a abrogated the protective effects of quercetin against hypoxia-elicited damages. Quercetin elevated sirt1 which was repressed by hypoxia, while this effect was slight in miR-199a-overexpressed cells. miR-199a negatively mediated sirt1 expression through directly binding its 3'-UTR. Further, quercetin facilitated the phosphorylation of AMPK by up-regulating sirt1. Collectively, quercetin participated in repressing miR-199a which negatively modulated sirt1. Mechanically, through activating AMPK, quercetin protected cardiomyocytes cells against hypoxia-caused insults. Highlights Quercetin ameliorates hypoxia-evoked apoptosis and blockage of AMPK phosphorylation; The elevated miR-199a level is eased by quercetin, which might be a protective mechanism; Quercetin restores sirt1 level by repressing miR-199a expression; By mediating miR-199a and sirt1, AMPK phosphorylation is fortified by quercetin.

LncRNA RMRP accelerates hypoxia-induced injury by targeting miR-214-5p in H9c2 cells

OBJECTIVE

To elucidate the function of lncRNA RMRP in hypoxia-induced acute myocardial infarction (AMI) in vitro and explore its underlying mechanism.

METHODS

Hypoxic injury was confirmed by measurement of cell viability, LDH release, migration, invasion, and apoptosis in H9c2 cells. The interactions between RMRP and miR-214-5p as well as miR-214-5p and p53 were also investigated.

RESULTS

Hypoxia treatment significantly induced cell damage in H9c2 cells, accompanied with the up-regulation of RMRP expressions. Transfection of RMRP siRNA remarkably attenuated hypoxia-induced injury by enhancing cell viability, migration and invasion, and reducing cell apoptosis and LDH release; whereas, enforced expression of RMRP aggravated hypoxia-induced injury. Furthermore, RMRP served as an endogenous sponge for miR-214-5p, and its expression was negatively regulated by RMRP. The effects of RMRP knockdown on hypoxia-induced injury were further enhanced with miR-214-5p overexpression, but significantly abrogated with miR-214-5p silence. Moreover, p53 was verified as a direct target of miR-214-5p, and functional investigation revealed that RMRP regulated hypoxia-induced injury via modulating p53 signaling pathway, which was partially mediated by miR-214-5p.

CONCLUSION

Our findings demonstrated the novel molecular mechanism of RMRP/miR-214-5p/p53 axis on the regulation of hypoxia-induced myocardial injury in H9c2 cells, which might provide potential therapeutic targets for AMI treatment.

Translationally controlled tumor protein (TCTP) plays a pivotal role in cardiomyocyte survival through a Bnip3-dependent mechanism

Prevention of cardiomyocyte death is an important therapeutic strategy for heart failure. In this study, we focused on translationally controlled tumor protein (TCTP), a highly conserved protein that is expressed ubiquitously in mammalian tissues, including heart. TCTP plays pivotal roles in survival of certain cell types, but its function in cardiomyocytes has not been examined. We aimed to clarify the role of TCTP in cardiomyocyte survival and the underlying mechanism. Here, we demonstrated that downregulation of TCTP with siRNA induced cell death of cardiomyocytes with apoptotic and autophagic features, accompanied with mitochondrial permeability transition pore (mPTP) opening. TCTP loss did not induce cell death of cardiac fibroblasts. Bcl-2/adenovirus E1B 19-kDa interacting protein 3 (Bnip3) was found to mediate the TCTP-loss-induced cardiomyocyte death. In exploring the clinical significance of the TCTP expression in the heart, we found that DOX treatment markedly downregulated the protein expression of TCTP in cultured cardiomyocytes and in mouse heart tissue. Exogenous rescue of TCTP expression attenuated DOX-induced cardiomyocyte death. In mice, cardiomyocyte-specific overexpression of TCTP resulted in decreased susceptibility to DOX-induced cardiac dysfunction, accompanied with attenuated induction of Bnip3. Dihydroartemisinin, a pharmacological TCTP inhibitor, induced development of heart failure and cardiomyocyte death in control mice, but not in mice with cardiomyocyte-specific TCTP overexpression. Our findings revealed TCTP has a pivotal role in cardiomyocyte survival, at least in part through a Bnip3-dependent mechanism. TCTP could be considered as a candidate therapeutic target to prevent DOX-induced heart failure.

Cardiac Specific Knockout of p53 Decreases ER Stress-Induced Mitochondrial Damage

Endoplasmic reticulum (ER) stress contributes to cardiovascular disease including heart failure. Interactions between the ER and mitochondria during ER stress can impair the mitochondrial respiratory chain and increase cell injury. p53 is a tumor suppressor protein that regulates apoptosis. p53 contributes to the regulation of mitochondrial and ER interactions, especially during the progression of ER stress. The knockout (KO) of p53 leads to decreased injury in hearts following ischemia-reperfusion. We asked if KO of p53 can protect mitochondria during the induction of ER stress and decrease cell injury. Floxed p53 mice were crossed with mice carrying an α-myosin heavy chain cre to generate cardiac specific p53 KO mice. Thapsigargin (THAP) was used to induce ER stress in wild type (WT) and p53 KO mice. Mice were euthanized after 48 h THAP treatment. Cardiac mitochondria were isolated for functional measurement. TUNEL staining was used to assess myocyte death. In WT mice, THAP treatment decreased the rate of oxidative phosphorylation using pyruvate + malate as complex I substrates compared to vehicle-treated control. Complex I activity was also decreased in the THAP-treated WT mice. The rate of oxidative phosphorylation and complex I activity were not altered in THAP-treated p53 KO mice. The content of pyruvate dehydrogenase (PDH) α1 subunit was decreased in THAP-treated WT mice but not in p53 KO mice. ER stress led to a release of cytochrome c and apoptosis inducing factor from mitochondria into cytosol in WT but not in KO mice. Knockout of p53 also preserved mitochondrial bcl-2 content in THAP-treated mice. In WT mice, THAP treatment markedly increased cell death compared to vehicle treated hearts. In contrast, cell injury was decreased in THAP-treated p53 KO mice compared to corresponding wild type. Thus, KO of p53 decreased cell injury by protecting mitochondria during the ER stress.

Usefulness of Exchanged Protein Directly Activated by cAMP (Epac)1-Inhibiting Therapy for Prevention of Atrial and Ventricular Arrhythmias in Mice

BACKGROUND

It has been suggested that protein directly activated by cAMP (Epac), one of the downstream signaling molecules of β-adrenergic receptor (β-AR), may be an effective target for the treatment of arrhythmia. However, there have been no reports on the anti-arrhythmic effects or cardiac side-effects of Epac1 inhibitors in vivo. Methods and Results: In this study, the roles of Epac1 in the development of atrial and ventricular arrhythmias are examined. In addition, we examined the usefulness of CE3F4, an Epac1-selective inhibitor, in the treatment of the arrhythmias in mice. In Epac1 knockout (Epac1-KO) mice, the duration of atrial fibrillation (AF) was shorter than in wild-type mice. In calsequestrin2 knockout mice, Epac1 deficiency resulted in a reduction of ventricular arrhythmia. In both atrial and ventricular myocytes, sarcoplasmic reticulum (SR) Ca²⁺ leak, a major trigger of arrhythmias, and spontaneous SR Ca²⁺ release (SCR) were attenuated in Epac1-KO mice. Consistently, CE3F4 treatment significantly prevented AF and ventricular arrhythmia in mice. In addition, the SR Ca²⁺ leak and SCR were significantly inhibited by CE3F4 treatment in both atrial and ventricular myocytes. Importantly, cardiac function was not significantly affected by a dosage of CE3F4 sufficient to exert anti-arrhythmic effects.

CONCLUSIONS

These findings indicated that Epac1 is involved in the development of atrial and ventricular arrhythmias. CE3F4, an Epac1-selective inhibitor, prevented atrial and ventricular arrhythmias in mice.

The involvement of Nox4 in fine particulate matter exposure-induced cardiac injury in mice

Epidemiological studies have confirmed that ambient fine particulate matter (PM_2.5) exposure is associated with cardiovascular disease (CVD). However, the underlying mechanisms in PM_2.5 exposure-induced heart injury are largely unknown. It has been acknowledged that NADPH oxidase (Nox) 4 plays a critical role in CVD development. To investigate the acute effects of PM_2.5 on the mouse heart and the role of Nox4 in PM_2.5 exposure-induced cardiac injury, C57BL/6J mice were instilled with saline or 1.5, 3.0, 6.0 mg/kg BW PM_2.5 suspension for two weeks (five days per week). The levels of malondialdehyde (MDA), super oxide dismutase (SOD), inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNF-α) and interleukin (IL)-1β in heart supernatants were determined using related kits. The expression of Nox4, p67^phox, p47^phox and p22^phox in heart tissue was evaluated by immunofluorescence staining or Western blotting, respectively. Protein levels of p53, Bax, Bcl-2 and Caspase-3 in the heart were examined using immunohistochemical staining and Western blotting. TUNEL assay was used to measure myocardial apoptosis. PM_2.5 exposure leads to obvious cardiac injury. PM_2.5 exposure increases MDA level and iNOS activity, and decreases activity of SOD in heart supernatants of mice. High levels of TNF-α and IL-1β in heart supernatants of mice with PM_2.5 instillation were determined. Nox4 and Nox-associated subunits such as p67^phox, p47^phox and p22^phox expression levels were increased in heart tissue of mice after PM_2.5 exposure. Additionally, PM_2.5 exposure causes myocardial apoptosis in the mouse heart. This study suggested that Nox4 is involved in PM_2.5 exposure-induced cardiac injury in mice.

Weighted gene co‑expression network analysis in identification of key genes and networks for ischemic‑reperfusion remodeling myocardium

Acute myocardial infarction induces ventricular remodeling, which is implicated in dilated heart and heart failure. The pathogenical mechanism of myocardium remodeling remains to be elucidated. The aim of the present study was to identify key genes and networks for myocardium remodeling following ischemia-reperfusion (IR). First, the mRNA expression data from the National Center for Biotechnology Information database were downloaded to identify differences in mRNA expression of the IR heart at days 2 and 7. Then, weighted gene co-expression network analysis, hierarchical clustering, protein-protein interaction (PPI) network, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway were used to identify key genes and networks for the heart remodeling process following IR. A total of 3,321 differentially expressed genes were identified during the heart remodeling process. A total of 6 modules were identified through gene co-expression network analysis. GO and KEGG analysis results suggested that each module represented a different biological function and was associated with different pathways. Finally, hub genes of each module were identified by PPI network construction. The present study revealed that heart remodeling following IR is a complicated process, involving extracellular matrix organization, neural development, apoptosis and energy metabolism. The dysregulated genes, including SRC proto-oncogene, non-receptor tyrosine kinase, discs large MAGUK scaffold protein 1, ATP citrate lyase, RAN, member RAS oncogene family, tumor protein p53, and polo like kinase 2, may be essential for heart remodeling following IR and may be used as potential targets for the inhibition of heart remodeling following acute myocardial infarction.

In Silico Analysis of Differential Gene Expression in Three Common Rat Models of Diastolic Dysfunction

Standard therapies for heart failure with preserved ejection fraction (HFpEF) have been unsuccessful, demonstrating that the contribution of the underlying diastolic dysfunction pathophysiology differs from that of systolic dysfunction in heart failure and currently is far from being understood. Complicating the investigation of HFpEF is the contribution of several comorbidities. Here, we selected three established rat models of diastolic dysfunction defined by three major risk factors associated with HFpEF and researched their commonalities and differences. The top differentially expressed genes in the left ventricle of Dahl salt sensitive (Dahl/SS), spontaneous hypertensive heart failure (SHHF), and diabetes 1 induced HFpEF models were derived from published data in Gene Expression Omnibus and used for a comprehensive interpretation of the underlying pathophysiological context of each model. The diversity of the underlying transcriptomic of the heart of each model is clearly observed by the different panel of top regulated genes: the diabetic model has 20 genes in common with the Dahl/SS and 15 with the SHHF models. Advanced analytics performed in Ingenuity Pathway Analysis (IPA^®) revealed that Dahl/SS heart tissue transcripts triggered by upstream regulators lead to dilated cardiomyopathy, hypertrophy of heart, arrhythmia, and failure of heart. In the heart of SHHF, a total of 26 genes were closely linked to cardiovascular disease including cardiotoxicity, pericarditis, ST-elevated myocardial infarction, and dilated cardiomyopathy. IPA Upstream Regulator analyses revealed that protection of cardiomyocytes is hampered by inhibition of the ERBB2 plasma membrane-bound receptor tyrosine kinases. Cardioprotective markers such as natriuretic peptide A (NPPA), heat shock 27 kDa protein 1 (HSPB1), and angiogenin (ANG) were upregulated in the diabetes 1 induced model; however, the model showed a different underlying mechanism with a majority of the regulated genes involved in metabolic disorders. In conclusion, our findings suggest that multiple mechanisms may contribute to diastolic dysfunction and HFpEF, and thus drug therapies may need to be guided more by phenotypic characteristics of the cardiac remodeling events than by the underlying molecular processes.

Vidarabine, an anti-herpesvirus agent, prevents catecholamine-induced arrhythmias without adverse effect on heart function in mice

Sympathetic activation causes clinically important arrhythmias including atrial fibrillation (AF) and ventricular tachyarrhythmia. Although the usefulness of β-adrenergic receptor blockade therapy is widely accepted, its multiple critical side effects often prevent its initiation or continuation. The aim of this study is to determine the advantages of vidarabine, an adenylyl cyclase (AC)-targeted anti-sympathetic agent, as an alternative treatment for arrhythmia. We found that vidarabine, which we identified as a cardiac AC inhibitor, consistently shortens AF duration and reduces the incidence of sympathetic activation-induced ventricular arrhythmias. In atrial and ventricular myocytes, vidarabine inhibits adrenergic receptor stimulation-induced RyR2 phosphorylation, sarcoplasmic reticulum (SR) Ca²⁺ leakage, and spontaneous Ca²⁺ release from SR, the last of which has been considered as a potential arrhythmogenic trigger. Moreover, vidarabine also inhibits sympathetic activation-induced reactive oxygen species (ROS) production in cardiac myocytes. The pivotal role of vidarabine's inhibitory effect on ROS production with regard to its anti-arrhythmic property has also been implied in animal studies. In addition, as expected, vidarabine exerts an inhibitory effect on AC function, which is more potent in the heart than elsewhere. Indexes of cardiac function including ejection fraction and heart rate were not affected by a dosage of vidarabine sufficient to exert an anti-arrhythmic effect. These findings suggest that vidarabine inhibits catecholamine-induced AF or ventricular arrhythmia without deteriorating cardiac function in mice.

Modeling Human Cardiac Hypertrophy in Stem Cell-Derived Cardiomyocytes

Cardiac hypertrophy accompanies many forms of cardiovascular diseases. The mechanisms behind the development and regulation of cardiac hypertrophy in the human setting are poorly understood, which can be partially attributed to the lack of a human cardiomyocyte-based preclinical test system recapitulating features of diseased myocardium. The objective of our study is to determine whether human embryonic stem cell-derived cardiomyocytes (hESC-CMs) subjected to mechanical stretch can be used as an adequate in vitro model for studying molecular mechanisms of cardiac hypertrophy. We show that hESC-CMs subjected to cyclic stretch, which mimics mechanical overload, exhibit essential features of a hypertrophic state on structural, functional, and gene expression levels. The presented hESC-CM stretch approach provides insight into molecular mechanisms behind mechanotransduction and cardiac hypertrophy and lays groundwork for the development of pharmacological approaches as well as for discovering potential circulating biomarkers of cardiac dysfunction.

Cardiac voltage gated calcium channels and their regulation by β-adrenergic signaling

Voltage-gated calcium channels (VGCCs) are the predominant source of calcium influx in the heart leading to calcium-induced calcium release and ultimately excitation-contraction coupling. In the heart, VGCCs are modulated by the β-adrenergic signaling. Signaling through β-adrenergic receptors (βARs) and modulation of VGCCs by β-adrenergic signaling in the heart are critical signaling and changes to these have been significantly implicated in heart failure. However, data related to calcium channel dysfunction in heart failure is divergent and contradictory ranging from reduced function to no change in the calcium current. Many recent studies have highlighted the importance of functional and spatial microdomains in the heart and that may be the key to answer several puzzling questions. In this review, we have briefly discussed the types of VGCCs found in heart tissues, their structure, and significance in the normal and pathological condition of the heart. More importantly, we have reviewed the modulation of VGCCs by βARs in normal and pathological conditions incorporating functional and structural aspects. There are different types of βARs, each having their own significance in the functioning of the heart. Finally, we emphasize the importance of location of proteins as it relates to their function and modulation by co-signaling molecules. Its implication on the studies of heart failure is speculated.

Inducible and reversible phenotypes in a novel mouse model of Friedreich's Ataxia

Friedreich's ataxia (FRDA), the most common inherited ataxia, is caused by recessive mutations that reduce the levels of frataxin (FXN), a mitochondrial iron binding protein. We developed an inducible mouse model of Fxn deficiency that enabled us to control the onset and progression of disease phenotypes by the modulation of Fxn levels. Systemic knockdown of Fxn in adult mice led to multiple phenotypes paralleling those observed in human patients across multiple organ systems. By reversing knockdown after clinical features appear, we were able to determine to what extent observed phenotypes represent reversible cellular dysfunction. Remarkably, upon restoration of near wild-type FXN levels, we observed significant recovery of function, associated pathology and transcriptomic dysregulation even after substantial motor dysfunction and pathology were observed. This model will be of broad utility in therapeutic development and in refining our understanding of the relative contribution of reversible cellular dysfunction at different stages in disease.

Ursodeoxycholic acid protects cardiomyocytes against cobalt chloride induced hypoxia by regulating transcriptional mediator of cells stress hypoxia inducible factor 1α and p53 protein

In hepatocytes, ursodeoxycholic acid (UDCA) activates cell signalling pathways such as p53, intracellular calcium ([Ca²⁺ ]_i ), and sphingosine-1-phosphate (S1P)-receptor via Gα_i -coupled-receptor. Recently, UDCA has been shown to protect the heart against hypoxia-reoxygenation injury. However, it is not clear whether UDCA cardioprotection against hypoxia acts through a transcriptional mediator of cells stress, HIF-1α and p53. Therefore, in here, we aimed to investigate whether UDCA could protect cardiomyocytes (CMs) against hypoxia by regulating expression of HIF-1α, p53, [Ca²⁺ ]_i , and S1P-Gα_i -coupled-receptor. Cardiomyocytes were isolated from newborn rats (0-2 days), and hypoxia was induced by using cobalt chloride (CoCl₂ ). Cardiomyocytes were treated with UDCA and cotreated with either FTY720 (S1P-receptor agonist) or pertussis toxin (PTX; Gα_i inhibitor). Cells were subjected for proliferation assay, beating frequency, QuantiGene Plex assay, western blot, immunofluorescence, and calcium imaging. Our findings showed that UDCA counteracted the effects of CoCl₂ on cell viability, beating frequency, HIF-1α, and p53 protein expression. We found that these cardioprotection effects of UDCA were similar to FTY720, S1P agonist. Furthermore, we observed that UDCA protects CMs against CoCl₂ -induced [Ca²⁺ ]_i dynamic alteration. Pharmacological inhibition of the Gα_i -sensitive receptor did not abolish the cardioprotection of UDCA against CoCl₂ detrimental effects, except for cell viability and [Ca²⁺ ]_i . Pertussis toxin is partially effective in inhibiting UDCA protection against CoCl₂ effects on CM cell viability. Interestingly, PTX fully inhibits UDCA cardioprotection on CoCl₂ -induced [Ca²⁺ ]_i dynamic changes. We conclude that UDCA cardioprotection against CoCl₂ -induced hypoxia is similar to FTY720, and its actions are not fully mediated by the Gα_i -coupled protein sensitive pathways. Ursodeoxycholic acid is the most hydrophilic bile acid and is currently used to treat liver diseases. Recently, UDCA is shown to have a cardioprotection effects; however, the mechanism of UDCA cardioprotection is still poorly understood. The current data generated were the first to show that UDCA is able to inhibit the activation of HIF-1α and p53 protein during CoCl₂ -induced hypoxia in cardiomyocytes. This study provides an insight of UDCA mechanism in protecting cardiomyocytes against hypoxia.

The effect of exercise, resveratrol or their combination on Sarcopenia in aged rats via regulation of AMPK/Sirt1 pathway

Sarcopenia is an age-related syndrome characterized by progressive loss of muscle mass and function. Exercise is an important strategy to prolong life and increase muscle mass, and resveratrol has been shown a variety beneficial effects on skeletal muscle. In the present study, we investigated the potential efficacy of using short-term exercise (six weeks), resveratrol (150mg/kg/day), or combined exercise+resveratrol (150mg/kg/day) on gastrocnemius muscle mass, grip strength, cross-sectional area and microscopic morphology in aged rats, and explored the potential mechanism at the apoptosis level. Six months old SD rats were used as young control group and 24months old SD rats were adopted as aged group. After six weeks intervention, the data provide evidence that exercise, resveratrol or their combination significantly increase the relative grip strength and muscle mass in aged rats (P<0.05). Electron microscopy discovered a significant increase in sarcomere length, I-band and H-zone in aged rats (P<0.05), and exercise, resveratrol or their combination significantly reduced the increasement (P<0.05). Moreover, light microscopy revealed a significant increase on Feret's diameter and cross-sectional area (CSA) in aged rats (P<0.05), but exercise and resveratrol did not show significant effects on them (P>0.05). Furthermore, exercise, resveratrol or their combination significantly increased the expression of p-AMPK and SIRT1, decreased the expression of acetyl P53 and Bax/Bcl-2 ratio in aged rats (P<0.05). These findings show that aged rats show significant changes in gastrocnemius muscle morphology and ultrastructure, and the protective effects of exercise, resveratrol and their combination are probably associated with anti-apoptotic signaling pathways through activation of AMPK/Sirt1.

MiR-486 regulates cardiomyocyte apoptosis by p53-mediated BCL-2 associated mitochondrial apoptotic pathway

BACKGROUND

Cardiomyocyte apoptosis is a common pathological manifestation that occurs in several heart diseases. This study aimed to explore the mechanism of microRNA-486 (miR-486) in cardiomyocyte apoptosis by interfering with the p53-activated BCL-2 associated mitochondrial pathway.

METHODS

miR-486 mimics and inhibitors were transfected into the primary cardiomyocytes of suckling Sprague-Dawley rat pups, and H₂O₂ was used to induce apoptosis. Flow cytometry and TUNEL were both used to detect cardiomyocyte apoptosis, while the relative mRNA transcript and protein levels of miR-486, p53, Bbc3, BCL-2, and cleaved caspase-3 were detected using RT-PCR and western blot analysis, respectively.

RESULTS

miR-486 overexpression significantly decreased the expressions of p53, Bbc3 and cleaved caspase-3 (P < 0.05), and BCL-2 expression was significantly increased (P < 0.05), which in turn caused a significant decrease in the rate of cardiomyocyte apoptosis (P < 0.05). In contrast, miR-486 silencing resulted in an elevated rate of cardiomyocyte apoptosis (P < 0.05).

CONCLUSION

miR-486 may regulate cardiomyocyte apoptosis via p53-mediated BCL-2 associated mitochondrial apoptotic pathway. Therefore, up-regulating miR-486 expression in cardiomyocytes can effectively reduce the activation of the BCL-2 associated mitochondrial apoptotic pathway, consequently protecting cardiomyocytes.

Circulating microRNA-150-5p as a novel biomarker for advanced heart failure: A genome-wide prospective study

BACKGROUND

Circulating microRNAs (miRs) are promising biomarkers for heart failure (HF). Previous studies have provided inconsistent miR "signatures." The phenotypic and pathophysiologic heterogeneity of HF may have contributed to this inconsistency. In this study we assessed whether advanced HF (AHF) patients present a distinct miR signature compared with healthy subjects (HS) and mild to moderate HF (MHF) patients.

METHODS

The study consisted of 2 phases: a screening phase and a validation phase. In the screening phase, 752 miRs were profiled in HS and MHF and AHF patients (N = 15), using the real-time quantitative polymerase chain reaction (RT-qPCR) technique and global mean normalization. In the validation phase, the miRs found to be significantly dysregulated in AHF patients compared with both HS and MHF patients were validated in 15 HS, 25 patients with MHF and 29 with AHF, using RT-qPCR, and normalizing to exogenous (cel-miR-39) and endogenous controls.

RESULTS

In the screening phase, 5 miRs were found to be significantly dysregulated: -26a-5p; -145-3p; -150-5p; -485-3p; and -487b-3p. In the validation phase, miR-150-5p was confirmed to be significantly downregulated in AHF patients when compared with both HS and MHF patients, irrespective of the normalization method used. miR-26a-5p was confirmed to be significantly dysregulated only when normalized to cell-miR-39. Dysregulation of the other miRs could not be confirmed. miR-150-5p was significantly associated with maladaptive remodeling, disease severity and outcome.

CONCLUSIONS

Our data suggest miR-150-5p as a novel circulating biomarker for AHF. The association of miR-150-5p with maladaptive remodeling, disease severity and outcome supports the pathophysiologic relevance of downregulated miR-150-5p expression to AHF.

The role of Epac in the heart

As one of the most important second messengers, 3',5'-cyclic adenosine monophosphate (cAMP) mediates various extracellular signals including hormones and neurotransmitters, and induces appropriate responses in diverse types of cells. Since cAMP was formerly believed to transmit signals through only two direct target molecules, protein kinase A and the cyclic nucleotide-gated channel, the sensational discovery in 1998 of another novel direct effecter of cAMP [exchange proteins directly activated by cAMP (Epac)] attracted a great deal of scientific interest in cAMP signaling. Numerous studies on Epac have since disclosed its important functions in various tissues in the body. Recently, observations of genetically manipulated mice in various pathogenic models have begun to reveal the in vivo significance of previous in vitro or cellular-level findings. Here, we focused on the function of Epac in the heart. Accumulating evidence has revealed that both Epac1 and Epac2 play important roles in the structure and function of the heart under physiological and pathological conditions. Accordingly, developing the ability to regulate cAMP-mediated signaling through Epac may lead to remarkable new therapies for the treatment of cardiac diseases.

Hypoxic Preconditioning Inhibits Hypoxia-induced Apoptosis of Cardiac Progenitor Cells via the PI3K/Akt-DNMT1-p53 Pathway

Research has demonstrated that hypoxic preconditioning (HP) can enhance the survival and proliferation of cardiac progenitor cells (CPCs); however, the underlying mechanisms are not fully understood. Here, we report that HP of c-kit (+) CPCs inhibits p53 via the PI3K/Akt-DNMT1 pathway. First, CPCs were isolated from the hearts of C57BL/6 mice and further purified by magnetic-activated cell sorting. Next, these cells were cultured under either normoxia (H0) or HP for 6 hours (H6) followed by oxygen-serum deprivation for 24 hours (24h). Flow cytometric analysis and MTT assays revealed that hypoxia-preconditioned CPCs exhibited an increased survival rate. Western blot and quantitative real-time PCR assays showed that p53 was obviously inhibited, while DNMT1 and DNMT3β were both significantly up-regulated by HP. Bisulphite sequencing analysis indicated that DNMT1 and DNMT3β did not cause p53 promoter hypermethylation. A reporter gene assay and chromatin immunoprecipitation analysis further demonstrated that DNMT1 bound to the promoter locus of p53 in hypoxia-preconditioned CPCs. Together, these observations suggest that HP of CPCs could lead to p53 inhibition by up-regulating DNMT1 and DNMT3β, which does not result in p53 promoter hypermethylation, and that DNMT1 might directly repress p53, at least in part, by binding to the p53 promoter locus.

Anticancer Activity of γ-Bisabolene in Human Neuroblastoma Cells via Induction of p53-Mediated Mitochondrial Apoptosis

γ-Bisabolene has demonstrated antiproliferative activities against several human cancer cell lines. This study first discloses the antiproliferative and apoptosis induction activities of γ-bisabolene to human neuroblastoma TE671 cells. A CC50 value of γ-bisabolene was 8.2 μM to TE671 cells. Cell cycle analysis with PI staining showed γ-bisabolene elevating the sub-G1 fractions in a time-dependent manner. In addition, annexin V-FITC/PI staining showed γ-bisabolene significantly triggering early (annexin-V positive/PI negative) and late (annexin-V positive/PI positive) apoptosis in dose-dependent manners. γ-Bisabolene induced caspase 3/8/9 activation, intracellular ROS increase, and mitochondrial membrane potential decrease in apoptosis of human neuro-blastoma cells. Moreover, γ-bisabolene increased p53 phosphorylation and up-regulated p53-mediated apoptotic genes Bim and PUMA, as well as decreased the mRNA and protein levels of CK2α. Notably, the results indicated the involvement of CK2α-p53 pathways in mitochondria-mediated apoptosis of human neuroblastoma cells treated with γ-bisabolene. This study elucidated the apoptosis induction pathways of γ-bisabolene-treated neuroblastoma cells, in which could be useful for developing anti-neuroblastoma drugs.

Bromodomains: Structure, function and pharmacology of inhibition

Bromodomains are epigenetic readers of histone acetylation involved in chromatin remodeling and transcriptional regulation. The human proteome comprises 46 bromodomain-containing proteins with a total of 61 bromodomains, which, despite highly conserved structural features, recognize a wide array of natural peptide ligands. Over the past five years, bromodomains have attracted great interest as promising new epigenetic targets for diverse human diseases, including inflammation, cancer, and cardiovascular disease. The demonstration in 2010 that two small molecule compounds, JQ1 and I-BET762, potently inhibit proteins of the bromodomain and extra-terminal (BET) family with translational potential for cancer and inflammatory disease sparked intense efforts in academia and pharmaceutical industry to develop novel bromodomain antagonists for therapeutic applications. Several BET inhibitors are already in clinical trials for hematological malignancies, solid tumors and cardiovascular disease. Currently, the field faces the challenge of single-target selectivity, especially within the BET family, and of overcoming problems related to the development of drug resistance. At the same time, new trends in bromodomain inhibitor research are emerging, including an increased interest in non-BET bromodomains and a focus on drug synergy with established antitumor agents to improve chemotherapeutic efficacy. This review presents an updated view of the structure and function of bromodomains, traces the development of bromodomain inhibitors and their potential therapeutic applications, and surveys the current challenges and future directions of this vibrant new field in drug discovery.

Improved bioavailability of targeted Curcumin delivery efficiently regressed cardiac hypertrophy by modulating apoptotic load within cardiac microenvironment

Cardiomyocyte apoptosis acts as a prime modulator of cardiac hypertrophy leading to heart failure, a major cause of human mortality worldwide. Recent therapeutic interventions have focussed on translational applications of diverse pharmaceutical regimes among which, Curcumin (from Curcuma longa) is known to have an anti-hypertrophic potential but with limited pharmacological efficacies due to low aqueous solubility and poor bioavailability. In this study, Curcumin encapsulated by carboxymethyl chitosan (CMC) nanoparticle conjugated to a myocyte specific homing peptide was successfully delivered in bioactive form to pathological myocardium for effective regression of cardiac hypertrophy in a rat (Rattus norvegicus) model. Targeted nanotization showed higher cardiac bioavailability of Curcumin at a low dose of 5 mg/kg body weight compared to free Curcumin at 35 mg/kg body weight. Moreover, Curcumin/CMC-peptide treatment during hypertrophy significantly improved cardiac function by downregulating expression of hypertrophy marker genes (ANF, β-MHC), apoptotic mediators (Bax, Cytochrome-c) and activity of apoptotic markers (Caspase 3 and PARP); whereas free Curcumin in much higher dose showed minimal improvement during compromised cardiac function. Targeted Curcumin treatment significantly lowered p53 expression and activation in diseased myocardium via inhibited interaction of p53 with p300-HAT. Thus attenuated acetylation of p53 facilitated p53 ubiquitination and reduced the apoptotic load in hypertrophied cardiomyocytes; thereby limiting cardiomyocytes' need to enter the regeneration cycle during hypertrophy. This study elucidates for the first time an efficient targeted delivery regimen for Curcumin and also attributes towards probable mechanistic insight into its therapeutic potential as a cardio-protective agent for regression of cardiac hypertrophy.

Nuclear Translocation of Calpain-2 Mediates Apoptosis of Hypertrophied Cardiomyocytes in Transverse Aortic Constriction Rat

Apoptosis of cardiomyocytes plays an important role in the transition from cardiac hypertrophy to heart failure. Hypertrophied cardiomyocytes show enhanced susceptibility to apoptosis. Therefore, the aim of this study was to determine the susceptibility to apoptosis and its mechanism in hypertrophied cardiomyocytes using a rat model of transverse abdominal aortic constriction (TAC). Sixteen weeks of TAC showed compensatory and pathological hypertrophy in the left ventricle. TUNEL-positive nuclei were significantly increased in TAC with angiotensin II (Ang II) treatment. Calpain inhibitor, PD150606, effectively inhibited Ang II-induced apoptosis of hypertrophied cardiomyocytes. Ang II increased nuclear translocation of intracellular Ca(2+) activated calpain-2 in hypertrophied cardiomyocytes. Ang II enhanced the interaction between activated calpain-2 and Ca(2+)/calmodulin-dependent protein kinase II δB (CaMKIIδB), and promoted the degradation of CaMKIIδB by calpain-2 in the nuclei of hypertrophied cardiomyocytes. Consequently, the depressed CaMKIIδB downregulated the expression of antiapoptotic Bcl-2 leading to mitochondrial depolarization and release of cytochrome c led to apoptosis of hypertrophied cardiomyocytes. In conclusion, hypertrophied cardiomyocytes show increased susceptibility to apoptosis during Ang II stimulation via nuclear calpain-2 and CaMKIIδB pathway.

The important role of catestatin in cardiac remodeling

Catestatin (CST) was first discovered as a potent non-competitive and reversible inhibitor of catecholamine secretion. Recent reports on plasma CST level in heart diseases suggested a cardioprotective role for this peptide. Given that cardiac remodeling is the dominant pathologic process in cardiac dysfunction, we propose that CST participates in the regulation of concern pathways and contributes to the inhibition of cardiac remodeling. In this minireview, the potential mechanism of cardiac remodeling involving CST will be discussed from three aspects: hypertrophy, fibrosis, and apoptosis.

Molecular mechanisms and anti-cancer aspects of the medicinal phytochemicals rocaglamides (=flavaglines)

Rocaglamides (= flavaglines) are potent natural anti-cancer phytochemicals that inhibit cancer growth at nanomolar concentrations by the following mechanisms: (1) inhibition of translation initiation via inhibition of phosphorylation of the mRNA cap-binding eukaryotic translation initiation factor eIF4E and stabilization of RNA-binding of the translation initiation factor eIF4A in the eIF4F complex; (2) blocking cell cycle progression by activation of the ATM/ATR-Chk1/Chk2 checkpoint pathway; (3) inactivation of the heat shock factor 1 (HSF1) leading to up-regulation of thioredoxin-interacting protein (TXNIP) and consequent reduction of glucose uptake and (4) induction of apoptosis through activation of the MAPK p38 and JNK and inhibition of the Ras-CRaf-MEK-ERK signaling pathway. Besides the anti-cancer activities, rocaglamides are also shown to protect primary cells from chemotherapy-induced cell death and alleviate inflammation- and drug-induced injury in neuronal tissues. This review will focus on the recently discovered molecular mechanisms of the actions of rocaglamides and highlights the benefits of using rocaglamides in cancer treatment.

MicroRNA-133 modulates the β1-adrenergic receptor transduction cascade

RATIONALE

The sympathetic nervous system plays a fundamental role in the regulation of myocardial function. During chronic pressure overload, overactivation of the sympathetic nervous system induces the release of catecholamines, which activate β-adrenergic receptors in cardiomyocytes and lead to increased heart rate and cardiac contractility. However, chronic stimulation of β-adrenergic receptors leads to impaired cardiac function, and β-blockers are widely used as therapeutic agents for the treatment of cardiac disease. MicroRNA-133 (miR-133) is highly expressed in the myocardium and is involved in controlling cardiac function through regulation of messenger RNA translation/stability.

OBJECTIVE

To determine whether miR-133 affects β-adrenergic receptor signaling during progression to heart failure.

METHODS AND RESULTS

Based on bioinformatic analysis, β1-adrenergic receptor (β1AR) and other components of the β1AR signal transduction cascade, including adenylate cyclase VI and the catalytic subunit of the cAMP-dependent protein kinase A, were predicted as direct targets of miR-133 and subsequently validated by experimental studies. Consistently, cAMP accumulation and activation of downstream targets were repressed by miR-133 overexpression in both neonatal and adult cardiomyocytes following selective β1AR stimulation. Furthermore, gain-of-function and loss-of-function studies of miR-133 revealed its role in counteracting the deleterious apoptotic effects caused by chronic β1AR stimulation. This was confirmed in vivo using a novel cardiac-specific TetON-miR-133 inducible transgenic mouse model. When subjected to transaortic constriction, TetON-miR-133 inducible transgenic mice maintained cardiac performance and showed attenuated apoptosis and reduced fibrosis compared with control mice.

CONCLUSIONS

miR-133 controls multiple components of the β1AR transduction cascade and is cardioprotective during heart failure.

Time-Course of the Effects of QSYQ in Promoting Heart Function in Ameroid Constrictor-Induced Myocardial Ischemia Pigs

We aim to investigate the therapeutic effects of QSYQ on a pig myocardial ischemia (MI) model and to determine its mechanism of action. The MI model was induced by Ameroid constriction of the left anterior descending coronary (LAD) in Ba-Ma miniature pigs. Four groups were created: model group, digoxin group, QSYQ group, and sham-operated group. Heart function, Ang II, CGMP, TXB2, BNP, and cTnT were evaluated before (3 weeks after operation: 0 weeks) and at 2, 4, and 8 weeks after drug administration. After 8 weeks of administration, the pigs were sacrificed for cardiac injury measurements. Pigs with MI showed obvious histological changes, including BNP, cTnT, Ang II, CGRP, TXB2, and ET, deregulated heart function, and increased levels of apoptotic cells in myocardial tissue. Treatment with QSYQ improved cardiac remodeling by counteracting those events. The administration of QSYQ was accompanied by a restoration of heart function and of the levels of Ang II, CGRP, TXB2, ET BNP, and cTnT. In addition, QSYQ attenuated administration, reduced the apoptosis, and decreased the level of TNF- α and active caspase-3. In conclusion, administration of QSYQ could attenuate Ameroid constrictor induced myocardial ischemia, and TNF- α and active caspase-3 seemed to be the critical potential target of QSYQ.

Hesperetin attenuates mitochondria-dependent apoptosis in lipopolysaccharide-induced H9C2 cardiomyocytes

Apoptosis is closely associated with the occurrence and development of cardiovascular diseases and is considered as one of the crucial pathological processes of cardiomyopathy, sepsis, ischemia/reperfusion injury, myocardial infarction and heart failure. Hesperetin (HES), a flavanone glycoside found in citrus fruit peels, has been known to exhibit several key biological and pharmacological properties. Previous studies have demonstrated the anti-inflammatory, anti-oxidant and anti-tumor functions of HES. However, with regards to the pro- or anti-apoptotic functions of HES, there are several disagreements within the literature. To examine whether HES has protective effects in cardiac apoptosis, the present study examined the role of HES in lipopolysaccharide (LPS)-stimulated H9C2 cardiomyocytes, aiming to clarify the possible mechanisms underlying its effects. In the present study, HES reduced the percentage of viable apoptotic (VA) cells in a flow cytometry analysis. It had an anti-apoptosis function in LPS-stimulated H9C2 cells. To clarify whether HES alleviated LPS-stimulated apoptosis through the mitochondria-dependent intrinsic apoptotic pathway, certain indicators of this pathway were detected, including members of the caspase family. The data revealed that HES attenuated the activation of capase-3 and caspase-9. These results indicated HES has a mitochondria-dependent anti-apoptosis effect in LPS-stimulated H9C2 cells. To explore the possible mechanisms, the protein expression levels of certain markers in the possible signaling pathway were detected, including JNK and Bcl-2 family. As a result, HES downregulated the protein expression of Bax, upregulated the expression of Bcl-2 and attenuated the phosphorylation level of JNK. Therefore, the anti-apoptosis effects of HES were possibly mediated by the JNK/Bax signaling pathway. In conclusion, HES has a mitochondria-dependent anti-apoptosis effect in LPS-induced H9C2 cells via the JNK/Bax signaling pathway.

Crosstalk between AMPK activation and angiotensin II-induced hypertrophy in cardiomyocytes: the role of mitochondria

AMP-kinase (AMPK) activation reduces cardiac hypertrophy, although underlying molecular mechanisms remain unclear. In this study, we elucidated the anti-hypertrophic action of metformin, specifically, the role of the AMPK/eNOS/p53 pathway. H9c2 rat cardiomyocytes were treated with angiotensin II (AngII) for 24 hrs in the presence or absence of metformin (AMPK agonist), losartan [AngII type 1 receptor (AT1R) blocker], Nω-nitro-L-arginine methyl ester (L-NAME, pan-NOS inhibitor), splitomicin (SIRT1 inhibitor) or pifithrin-α (p53 inhibitor). Results showed that treatment with metformin significantly attenuated AngII-induced cell hypertrophy and death. Metformin attenuated AngII-induced activation (cleavage) of caspase 3, Bcl-2 down-regulation and p53 up-regulation. It also reduced AngII-induced AT1R up-regulation by 30% (P < 0.05) and enhanced AMPK phosphorylation by 99% (P < 0.01) and P-eNOS levels by 3.3-fold (P < 0.01). Likewise, losartan reduced AT1R up-regulation and enhanced AMPK phosphorylation by 54% (P < 0.05). The AMPK inhibitor, compound C, prevented AT1R down-regulation, indicating that metformin mediated its effects via AMPK activation. Beneficial effects of metformin and losartan converged on mitochondria that demonstrated high membrane potential (Δψ_m) and low permeability transition pore opening. Thus, this study demonstrates that the anti-hypertrophic effects of metformin are associated with AMPK-induced AT1R down-regulation and prevention of mitochondrial dysfunction through the SIRT1/eNOS/p53 pathway.

A low-dose β1-blocker effectively and safely slows the heart rate in patients with acute decompensated heart failure and rapid atrial fibrillation

OBJECTIVE

Recently, we reported that low-dose landiolol (1.5 µg·kg(-1)·min(-1)), an ultra-short-acting β-blocker, safely decreased the heart rate (HR) in patients with acute decompensated heart failure (ADHF) and sinus tachycardia, thereby improving cardiac function. We investigated whether low-dose landiolol effectively decreased the HR in ADHF patients with rapid atrial fibrillation (AF).

METHODS

We enrolled 23 ADHF patients with rapid AF (HR ≥120 beats·min(-1) and New York Heart Association class III-IV) and systolic heart failure (SHF: n = 12) or diastolic heart failure (DHF: n = 11) who received conventional therapy with diuretics, vasodilators, and/or low-dose inotropes. They were administered continuous intravenous infusion of low-dose landiolol (1.0-2.0 µg·kg(-1)·min(-1)), and their electrocardiograms and blood pressures were monitored for 24 h thereafter.

RESULTS

Two hours after starting landiolol, the HR was reduced significantly (22%), without a reduction in blood pressure, and remained constant thereafter. The HR reduction 2 h after landiolol administration was significantly greater in the DHF group than in the SHF group. No incidence of hypotension was recorded.

CONCLUSIONS

Digitalis or amiodarone is currently recommended for HR control in ADHF patients with rapid AF. Our results showed that continuous infusion of low-dose landiolol may also be useful as first-line therapy in these patients.

The AP-1 transcription factor c-Jun prevents stress-imposed maladaptive remodeling of the heart

Systemic hypertension increases cardiac workload and subsequently induces signaling networks in heart that underlie myocyte growth (hypertrophic response) through expansion of sarcomeres with the aim to increase contractility. However, conditions of increased workload can induce both adaptive and maladaptive growth of heart muscle. Previous studies implicate two members of the AP-1 transcription factor family, junD and fra-1, in regulation of heart growth during hypertrophic response. In this study, we investigate the function of the AP-1 transcription factors, c-jun and c-fos, in heart growth. Using pressure overload-induced cardiac hypertrophy in mice and targeted deletion of Jun or Fos in cardiomyocytes, we show that c-jun is required for adaptive cardiac hypertrophy, while c-fos is dispensable in this context. c-jun promotes expression of sarcomere proteins and suppresses expression of extracellular matrix proteins. Capacity of cardiac muscle to contract depends on organization of principal thick and thin filaments, myosin and actin, within the sarcomere. In line with decreased expression of sarcomere-associated proteins, Jun-deficient cardiomyocytes present disarrangement of filaments in sarcomeres and actin cytoskeleton disorganization. Moreover, Jun-deficient hearts subjected to pressure overload display pronounced fibrosis and increased myocyte apoptosis finally resulting in dilated cardiomyopathy. In conclusion, c-jun but not c-fos is required to induce a transcriptional program aimed at adapting heart growth upon increased workload.

Mitochondrial disruption occurs downstream from β-adrenergic overactivation by isoproterenol in differentiated, but not undifferentiated H9c2 cardiomyoblasts: differential activation of stress and survival pathways

β-Adrenergic receptor stimulation plays an important role in cardiomyocyte stress responses, which may result in apoptosis and cardiovascular degeneration. We previously demonstrated that toxicity of the β-adrenergic agonist isoproterenol on H9c2 cardiomyoblasts depends on the stage of cell differentiation. We now investigate β-adrenergic receptor downstream signaling pathways and stress responses that explain the impact of muscle cell differentiation on hyper-β-adrenergic stimulation-induced cytotoxicity. When incubated with isoproterenol, differentiated H9c2 muscle cells have increased cytosolic calcium, cyclic-adenosine monophosphate content and oxidative stress, as well as mitochondrial depolarization, increased superoxide anion, loss of subunits from the mitochondrial respiratory chain, decreased Bcl-xL content, increased p53 and phosphorylated-p66Shc as well as activated caspase-3. Undifferentiated H9c2 cells incubated with isoproterenol showed increased Bcl-xL protein and increased superoxide dismutase 2 which may act as protective mechanisms. We conclude that the differentiation of H9c2 is associated with differential regulation of stress responses, which impact the toxicity of several agents, namely those acting through β-adrenergic receptors and resulting in mitochondrial disruption in differentiated cells only.

Arsenic trioxide induces cardiac fibroblast apoptosis in vitro and in vivo by up-regulating TGF-β1 expression

Arsenic trioxide (As2O3; ATO) is clinically effective in treating acute promyelocytic leukemia (APL); however, it frequently causes cardiotoxic effects. This study was designed to investigate whether ATO could induce apoptosis of cardiac fibroblasts (CFs) that play very important roles in maintaining the structure integrity and function of the heart. Cardiac fibroblasts from guinea pigs administered with ATO (1mg/kgbw) were used to test the pro-apoptotic role of ATO in vivo. The current study demonstrated that ATO induced morphological characteristics of apoptosis and Caspase-3 activation in CFs of guinea pigs along with a significant up-regulation in TGF-β1 protein expression, Bax/Bcl-2 ratio and ERK1/2 phosphorylation. In vitro MTT assay showed that ATO remarkably reduced the viability of cultured cardiac fibroblasts (NRCFs) from neonatal rat in a concentration- and time-dependent manner. Consistent with the notions in vivo, ATO significantly induced the apoptosis in NRCFs, dramatically up-regulated TGF-β1 protein level and Bax/Bcl-2 ratio in a time-dependent fashion and activated Caspase-3 and ERK1/2. Finally, pretreatment with LY364947, an inhibitor of TGF-β signaling could apparently reverse these changes. We therefore conclude that TGF-β is functionally linked to ERK1/2 and that TGF-β signaling is responsible for ATO-induced CFs apoptosis, which provides a novel mechanism of ATO related cardiac toxicology.