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Cardiotoxicity is a serious challenge cancer patients face today. Various factors are involved in cardiotoxicity. Circular RNAs (circRNAs) are one of the effective factors in the occurrence and prevention of cardiotoxicity. circRNAs can lead to increased proliferation, apoptosis, and regeneration of cardiomyocytes by regulating the molecular pathways, as well as increasing or decreasing gene expression; some circRNAs have a dual role in cardiomyocyte regeneration or death. Identifying each of the pathways related to these processes can be effective on managing patients and preventing cardiotoxicity. In this study, an overview of the molecular pathways involved in cardiotoxicity by circRNAs and their effects on the downstream factors have been discussed. [ABSTRACT FROM AUTHOR]

New approach methodologies (NAMs) for predicting embryotoxicity and developmental toxicity are urgently needed for generating human relevant data, while reducing turnover time and costs, and alleviating ethical concerns related to the use of animal models. We have previously developed the PluriLum assay, a NKX2.5-reporter gene 3D model using human-induced pluripotent stem cells (hiPSCs) that are genetically modified to enable the assessment of adverse effects of chemicals on the early-stage embryo. Aiming at improving the predictive value of the PluriLum assay for future screening purposes, we sought to introduce standardization steps to the protocol, improving the overall robustness of the PluriLum assay, as well as a shortening of the assay protocol. First, we showed that the initial size of embryoid bodies (EBs) is crucial for a proper differentiation into cardiomyocytes and overall reproducibility of the assay. When the starting diameter of the EBs exceeds 500 µm, robust differentiation can be anticipated. In terms of reproducibility, exposure to the fungicide epoxiconazole at smaller initial diameters resulted in a larger variation of the derived data, compared to more reliable concentration–response curves obtained using spheroids with larger initial diameters. We further investigated the ideal length of the differentiation protocol, resulting in a shortening of the PluriLum assay by 24 h to 7 days. Following exposure to the teratogens all-trans and 13-cis retinoic acid, both cardiomyocyte contraction and measurement of NKX2.5-derived luminescence were recorded with a similar or increased sensitivity after 6 days of differentiation when compared to the original 7 days. Finally, we have introduced an efficient step for enzymatic dissociation of the EBs at assay termination. This allows for an even splitting of the individual EBs and testing of additional endpoints other than the NKX2.5-luciferase reporter, which was demonstrated in this work by the simultaneous assessment of ATP levels. In conclusion, we have introduced standardizations and streamlined the PluriLum assay protocol to improve its suitability as a NAM for screening of a large number of chemicals for developmental toxicity testing. [ABSTRACT FROM AUTHOR]

Hypercholesterolemia is one of the most important risk factors for cardiovascular diseases. However, it is mostly associated with vascular dysfunction and atherosclerotic lesions, while evidence of direct effects of hypercholesterolemia on cardiomyocytes and heart function is still incomplete and controversial. In this study, we assessed the direct effects of hypercholesterolemia on heart function and the electro-contractile properties of isolated cardiomyocytes. After 5 weeks, male Swiss mice fed with AIN-93 diet added with 1.25% cholesterol (CHO), developed an increase in total serum cholesterol levels and cardiomyocytes cholesterol content. These changes led to altered electrocardiographic records, with a shortening of the QT interval. Isolated cardiomyocytes displayed a shortening of the action potential duration with increased rate of depolarization, which was explained by increased IK, reduced ICa.L and altered INa voltage-dependent inactivation. Also, reduced diastolic [Ca2+]i was found with preserved adrenergic response and cellular contraction function. However, contraction of isolated hearts is impaired in isolated CHO hearts, before and after ischemia/reperfusion, although CHO heart was less susceptible to arrhythmic contractions. Overall, our results demonstrate that early hypercholesterolemia-driven increase in cellular cholesterol content is associated with direct modulation of the heart and cardiomyocytes' excitability, Ca2+ handling, and contraction. [ABSTRACT FROM AUTHOR]

The use of various model organisms has made a huge contribution to understanding the causes and mechanisms of disease development and the study of pathological processes occurring during the development of diseases of the human cardiovascular system, and, in particular, hypertrophic cardiomyopathy (HCM). The optimal solution in the study of primary molecular disturbances is the use of cellular models such as induced pluripotent stem cells (iPSCs), primary rodent cardiomyocytes (CMs), and immortalized lines. In this review, we have focused on the most commonly used cell models, including freshly isolated adult and neonatal rodent CMs, and on the commercially available immortalized cell lines (HL-1, AC16, and H9c2). In order to assess the adequacy of these lines as CM models for studying human myocardial pathologies, a comparative analysis of phenotypic characteristics (morphology, metabolism, calcium homeostasis, etc.) and the nuances of practical use (availability, response to hypertrophic inducers, transfection, etc.) was carried out. The latest published data on the use of these models to assess the pathogenicity of HCM-associated mutations, as well as to screen the effectiveness of developed therapeutic drugs, are also summarized. [ABSTRACT FROM AUTHOR]

Multiple RNAs have been involved in the progress of heart failure. However, the role of miR-1268a in heart failure is still unclear. The differentially expressed miRNAs in heart failure was analyzed based on GEO dataset GSE104150. AC16 cells were treated with Angiotensin II (Ang II) to explore the role of miR-1268a in heart failure. The web tool miRWalk was used to analyze the targets of miR-1268a. miR-1268a was up-regulated in Ang II-treated AC16 cells. Ang II treatment markedly inhibited cell proliferation, ATP production, fatty acid (FA) uptake and enhanced levels of HF markers BNP and ST2, and oxidative stress of AC16 cells. Notably, inhibition of miR-1268a eliminated the inhibiting effect of Ang II on cell proliferation, ATP production, FA uptake and decreased levels of BNP an ST2, and oxidative stress on AC16 cells. Furthermore, CD36 was a target of miR-1268a and the CD36 level was decreased by miR-1268a mimics but increased by miR-1268a inhibitor in AC16 cells. miR-1268a regulates FA metabolism and oxidative stress in myocardial cells by targeting CD36 in heart failure. [ABSTRACT FROM AUTHOR]

Tropical teleost fish Danio rerio is increasingly used as a model object for electrophysiological studies of human cardiac physiology and pathology. D. rerio is characterized by the similarity with humans in such functional parameters of the electrical activity of the heart as heart rate, action potential morphology, as well as in a set of ion currents depolarizing and repolarizing the cell membrane. D. rerio is easy to breed, easy to handle experimentally, and easy to genetically modify. This overview presents current data on the structural and functional organization of ion channels in D. rerio heart myocytes. [ABSTRACT FROM AUTHOR]

Background: Catecholamines are commonly used as therapeutic drugs in intensive care medicine to maintain sufficient organ perfusion during shock. However, excessive or sustained adrenergic activation drives detrimental cardiac remodeling and may lead to heart failure. Whether catecholamine treatment in absence of heart failure causes persistent cardiac injury, is uncertain. In this experimental study, we assessed the course of cardiac remodeling and recovery during and after prolonged catecholamine treatment and investigated the molecular mechanisms involved. Results: C57BL/6N wild-type mice were assigned to 14 days catecholamine treatment with isoprenaline and phenylephrine (IsoPE), treatment with IsoPE and subsequent recovery, or healthy control groups. IsoPE improved left ventricular contractility but caused substantial cardiac fibrosis and hypertrophy. However, after discontinuation of catecholamine treatment, these alterations were largely reversible. To uncover the molecular mechanisms involved, we performed RNA sequencing from isolated cardiomyocyte nuclei. IsoPE treatment resulted in a transient upregulation of genes related to extracellular matrix formation and transforming growth factor signaling. While components of adrenergic receptor signaling were downregulated during catecholamine treatment, we observed an upregulation of endothelin-1 and its receptors in cardiomyocytes, indicating crosstalk between both signaling pathways. To follow this finding, we treated mice with endothelin-1. Compared to IsoPE, treatment with endothelin-1 induced minor but longer lasting changes in cardiomyocyte gene expression. DNA methylation-guided analysis of enhancer regions identified immediate early transcription factors such as AP-1 family members Jun and Fos as key drivers of pathological gene expression following catecholamine treatment. Conclusions: The results from this study show that prolonged catecholamine exposure induces adverse cardiac remodeling and gene expression before the onset of left ventricular dysfunction which has implications for clinical practice. The observed changes depend on the type of stimulus and are largely reversible after discontinuation of catecholamine treatment. Crosstalk with endothelin signaling and the downstream transcription factors identified in this study provide new opportunities for more targeted therapeutic approaches that may help to separate desired from undesired effects of catecholamine treatment. [ABSTRACT FROM AUTHOR]

Background: Exosomes are involved in cell-to-cell communication in numerous diseases including cardiovascular diseases, neurological diseases. Little attention has been dedicated to exosomal circular RNAs in obstructive sleep apnea (OSA)-related cardiovascular diseases. The aim of this study was to explore the role of exosomal circular RNA ZNF292 (circZNF292) on AC16 cells exposure to intermittent hypoxia (IH). Methods: Exosome release inhibitor GW4869 was used to examine the effect of exosomes on IH-induced AC16 cells apoptosis. The expression of exosomal circZNF292 was detected by qRT-PCR in AC16 cells exposure to IH, and a luciferase reporter assay was conducted to confirm the connection between circZNF292 and miR-146a-5p. Exosomal circZNF292 was stably transfected with short hairpin RNAs (shRNAs) against circZNF292 and co-cultured with AC16 cells. The expression of miR-146a-5p and apoptosis-related protein was then measured to evaluate the effect of exosomal circZNF292. Results: We found that IH contributed to the AC16 cells apoptosis, and the administration of GW4869 increased the apoptosis of cardiomyocytes when exposed to IH. The expression of exosomal circZNF292 decreased and miR-146a-5p increased significantly in AC16 cells exposed to IH compared to normoxic conditions. Bioinformatics analysis predicted a circZNF292/miR-146a-5p axis in IH-induced cardiomyocytes apoptosis. The dual-luciferase reporter system validated the direct interaction of circZNF292 and miR-146a-5p. Knockdown of circZNF292 increased the expressions of miR-146a-5p and accelerated the AC16 cardiomyocytes apoptosis. Conclusions: The findings of this study suggested a novel mechanism by which exosomes transmit intrinsic regulatory signals to the myocardium through the exosomal circZNF292/miR-146a-5p axis. This finding highlights the potential of targeting this pathway as a therapeutic approach for treating cardiovascular diseases associated with OSA. [ABSTRACT FROM AUTHOR]

Ventricular arrhythmias are the leading cause of sudden cardiac death in patients after myocardial infarction (MI). Connexin43 (Cx43) is the most important gap junction channel-forming protein in cardiomyocytes. Dysfunction of Cx43 contributes to impaired myocardial conduction and the development of ventricular arrhythmias. Following an MI, Cx43 undergoes structural remodeling, including expression abnormalities, and redistribution. These alterations detrimentally affect intercellular communication and electrical conduction within the myocardium, thereby increasing the susceptibility to post-infarction ventricular arrhythmias. Emerging evidence suggests that post-translational modifications play essential roles in Cx43 regulation after MI. Therefore, Cx43-targeted management has the potential to be a promising protective strategy for the prevention and treatment of post infarction ventricular arrhythmias. In this article, we primarily reviewed the regulatory mechanisms of Cx43 mediated post-translational modifications on post-infarction ventricular arrhythmias. Furthermore, Cx43-targeted therapy have also been discussed, providing insights into an innovative treatment strategy for ventricular arrhythmias after MI. [ABSTRACT FROM AUTHOR]

The regenerative capacity of the adult mammalian heart remains a formidable challenge in biological research. Despite extensive investigations into the loss of regenerative potential during evolution and development, unlocking the mechanisms governing cardiomyocyte proliferation remains elusive. Two recent groundbreaking studies have provided fresh perspectives on mitochondrial-to-nuclear communication, shedding light on novel factors that regulate cardiomyocyte proliferation. The studies identified two mitochondrial processes, fatty acid oxidation and protein translation, as key players in restricting cardiomyocyte proliferation. Inhibition of these processes led to increased cell cycle activity in cardiomyocytes, mediated by reduction in H3k4me3 levels through accumulated α-ketoglutarate (αKG), and activation of the mitochondrial unfolded protein response (UPRmt), respectively. In this research highlight, we discuss the novel insights into mitochondrial-to-nuclear communication presented in these studies, the broad implications in cardiomyocyte biology and cardiovascular diseases, as well as the intriguing scientific questions inspired by the studies that may facilitate future investigations into the detailed molecular mechanisms of cardiomyocyte metabolism, proliferation, and mitochondrial-to-nuclear communications. [ABSTRACT FROM AUTHOR]

Diastolic heart failure (DHF), in which impaired ventricular filling leads to typical heart failure symptoms, represents over 50% of all heart failure cases and is linked with risk factors, including metabolic syndrome, hypertension, diabetes, and aging. A substantial proportion of patients with this disorder maintain normal left ventricular systolic function, as assessed by ejection fraction. Despite the high prevalence of DHF, no effective therapeutic agents are available to treat this condition, partially because the molecular mechanisms of diastolic dysfunction remain poorly understood. As such, by focusing on the underlying molecular and cellular processes contributing to DHF can yield new insights that can represent an exciting new avenue and propose a novel therapeutic approach for DHF treatment. This review discusses new developments from basic and clinical/translational research to highlight current knowledge gaps, help define molecular determinants of diastolic dysfunction, and clarify new targets for treatment. [ABSTRACT FROM AUTHOR]

Background: Cardiomyocyte apoptosis plays an important role in alcoholic cardiac injury. However, the association between calcium-sensing receptor (CaSR) and alcohol-induced cardiomyocyte apoptosis remain unclear. Therefore, we investigated the role and its moleculer mechanism of CaSR in rat cardiomyocyte apoptosis induced by alcohol. Methods: Alcohol-induced cardiomyocyte apoptosis in vivo and in vitro model of rats were applied in this study. The expression of CaSR, endoplasmic reticulum stress markers and apoptosis were tested by immunohistological staining, western blot, TUNEL and flow cytometry, respectively. [Ca2+]i were detected by confocal laser scanning microscopy. Results: Compared with the control group, alcohol intake (AI) led to abnormal arrangements of cardiomyocytes and obvious increase of myocardial apoptosis. Moreover, AI also significantly upregulated protein expression of CaSR, GRP94, caspase-12 and CHOP. Alcohol induced apoptosis of cultured cardiomyocytes of rats in a dose-dependent way. Activation of CaSR markedly enhanced cardiomyocyte apoptosis and ERS induced by alcohol, ERS inducer also significantly increased cardiomyocyte apoptosis without activating CaSR. Furthermore, GdCl3 augmented alcohol-induced increase of [Ca2+]i in cardiomyocytes, which was attenuated by NPS2390 but not 4-PBA pre-treatment. Conclusions: Alcohol could induce cardiomyocyte apoptosis in rats in vivo and in vitro, which was mediated probably via activating CaSR, and then ERS and the increase of the cytosolic [Ca2+]i. This provides a potential target for preventing cardiomyocyte apoptosis and cardiomyopathy induced by alochol. [ABSTRACT FROM AUTHOR]

TBC1 domain family member 25 (TBC1D25) is a crucial mediator of signal transduction involved in the development of several diseases. Particularly, a cardioprotective role of TBC1D25 has been raised due to its antagonistic action on cardiac hypertrophy. However, whether TBC1D25 protects the myocardium from ischemia–reperfusion injury has not been reported. This work aimed to determine the role of TBC1D25 in myocardial ischemia–reperfusion (MIR) injury and to explore the potential mechanisms involved. Marked decreases in TBC1D25 levels occurred in cardiomyocytes suffering hypoxia/reoxygenation (H/R) injury in vitro and myocardium tissues of rats with MIR injury in vivo. Cardiomyocytes overexpressing TBC1D25 were protected from apoptosis and inflammation triggered by H/R, whereas TBC1D25-deficient cardiomyocytes were more sensitive to H/R injury. Intramyocardial injection of recombinant adenovirus expressing TBC1D25 into rats reduced infarct size and cardiac injury triggered by MIR injury accompanied by decreased myocardial apoptosis and inflammation. A subsequent mechanistic investigation revealed that the signaling cascade of transforming growth factor-β–activated kinase 1 (TAK1)-c-Jun N-terminal kinase (JNK)/p38 mitogen-activated protein kinase (MAPK) activated under H/R or MIR conditions was markedly restrained by TBC1D25 overexpression. Moreover, TAK1 blockade remarkably reversed the TBC1D25 deficiency–induced aggravating effect on H/R injury. The work concludes that TBC1D25 protects against MIR injury through action on the TAK1-JNK/p38 MAPK signaling cascade. This work suggests TBC1D25 as a potential therapeutic target for MIR injury. [ABSTRACT FROM AUTHOR]

l-Carnitine (β-hydroxy-γ-trimethylaminobutyric acid, LC) is a crucial molecule for the mitochondrial oxidation of fatty acids. It facilitates the transport of long-chain fatty acids into the mitochondrial matrix. The reduction in LC levels during the aging process has been linked to numerous cardiovascular disorders, including contractility dysfunction, and disrupted intracellular Ca2+ homeostasis. The aim of this study was to examine the effects of long-term (7 months) LC administration on cardiomyocyte contraction and intracellular Ca2+ transients ([Ca2+]i) in aging rats. Male albino Wistar rats were randomly assigned to either the control or LC-treated groups. LC (50 mg/kg body weight/day) was dissolved in distilled water and orally administered for a period of 7 months. The control group received distilled water alone. Subsequently, ventricular single cardiomyocytes were isolated, and the contractility and Ca2+ transients were recorded in aging (18 months) rats. This study demonstrates, for the first time, a novel inotropic effect of long-term LC treatment on rat ventricular cardiomyocyte contraction. LC increased cardiomyocyte cell shortening and resting sarcomere length. Furthermore, LC supplementation led to a reduction in resting [Ca2+]i level and an increase in the amplitude of [Ca2+]i transients, indicative of enhanced contraction. Consistent with these results, decay time of Ca2+ transients also decreased significantly in the LC-treated group. The long-term administration of LC may help restore the Ca2+ homeostasis altered during aging and could be used as a cardioprotective medication in cases where myocyte contractility is diminished. [ABSTRACT FROM AUTHOR]

Coronary artery disease (CAD) as a major cardiovascular disease is the leading global cause of mortality, Klotho/FGF23 axis involved in development of cardiovascular disease, while the function and underlying mechanism of Klotho/FGF23 axis in CAD is unclear. Blood samples from 67 CAD patients with coronary artery bypass graft (CABG) surgery were collected, and the level of Klotho and FGF23 of those patients was measured by using an ELISA kit. Cardiomyocyte was isolated from 0 to 3 days Sprague Dawley (SD) rats. Expression of Klotho, FGF23 and the cardiomyocyte marker α-sarcomeric actin (α-SA), myosin heavy chain (MHC) and cardiac troponin I (cTnI) was assessed by immunofluorescence staining. Expression of Klotho and FGF23 mRNA was detected by qRT-PCR. Apoptosis and cell cycle were measured by flow cytometry. Cell viability was detected by using CCK-8. The protein expression of ERK/MAPK pathway related protein and cytokines production was measured by western blotting. The levels of Klotho in CAD patients increased after CABG surgery, while FGF23 decreased. Isolated cardiomyocyte morphology and structure were completed, and with stabilized beating within culture for 15 days, besides, α-SA, MHC, and cTnI proved positive. After transfected Lenti-Klotho and Lenti-FGF23 into isolated cardiomyocyte, fluorescence staining showed that the transfection was successful, and qRT-PCR results showed that the expression levels of Klotho and FGF23 mRNA significant increased compared with NEG (empty vector) group. Immunofluorescence staining results showed that compared with NEG group, there was a higher Klotho positive rate and lower FGF23 positive rate in Klotho overexpression (Klotho) group, while, there was a higher FGF23 positive rate and lower Klotho positive rate in FGF23 overexpression (FGF23) group. In addition, the expression of p-ERK1/2 and p-P38 increased in Klotho group but decreased in FGF23 group. Furthermore, overexpression of Klotho inhibited cardiomyocyte apoptosis, increased S phase fraction, promoted proliferation and elevated expression of transforming growth factor β1 (TGF-β1), nuclear factor-kappa B (NF-κB), angiotensin-II (AT-II), and activator protein-1 (AP-1), overexpression of FGF23 showed the opposite effect, however, ERK agonist (TPA) and inhibitor (U0126) reversed the effect caused by overexpression of Klotho and FGF23 separately. Klotho/FGF23 axis play a critical role in CAD progression through regulating ERK/MAPK pathway in Cardiomyocyte. [ABSTRACT FROM AUTHOR]

Introduction: Early afterdepolarizations (EADs) are secondary voltage depolarizations associated with reduced repolarization reserve (RRR) that can trigger lethal arrhythmias. Relating EADs to triggered activity is difficult to study, so the ability to suppress or provoke EADs would be experimentally useful. Here, we use computational simulations to assess the feasibility of subthreshold optogenetic stimulation modulating the propensity for EADs (cell-scale) and EAD-associated ectopic beats (organ-scale). Methods: We modified a ventricular ionic model by reducing rapid delayed rectifier potassium (0.25–0.1 × baseline) and increasing L-type calcium (1.0–3.5 × baseline) currents to create RRR conditions with varying severity. We ran simulations in models of single cardiomyocytes and left ventricles from post-myocardial infarction patient MRI scans. Optogenetic stimulation was simulated using either ChR2 (depolarizing) or GtACR1 (repolarizing) opsins. Results: In cell-scale simulations without illumination, EADs were seen for 164 of 416 RRR conditions. Subthreshold stimulation of GtACR1 reduced EAD incidence by up to 84.8% (25/416 RRR conditions; 0.1 μW/mm2); in contrast, subthreshold ChR2 excitation increased EAD incidence by up to 136.6% (388/416 RRR conditions; 50 μW/mm2). At the organ scale, we assumed simultaneous, uniform illumination of the epicardial and endocardial surfaces. GtACR1-mediated suppression (10–50 μW/mm2) and ChR2-mediated unmasking (50–100 μW/mm2) of EAD-associated ectopic beats were feasible in three distinct ventricular models. Conclusions: Our findings suggest that optogenetics could be used to silence or provoke both EADs and EAD-associated ectopic beats. Validation in animal models could lead to exciting new experimental regimes and potentially to novel anti-arrhythmia treatments. [ABSTRACT FROM AUTHOR]

Myocardial ischemia/reperfusion injury (I/RI) and ventricular remodeling are the critical pathological basis of heart failure. Danlou tablet (Dan) is a kind of Chinese patent medicine used in angina pectoris treatment in China. However, it remains unclear whether and how Dan could protect against cardiac remodeling after myocardial I/RI. In this study, both preventive and therapeutic administration of Dan attenuated ventricular remodeling and cardiac dysfunction at 3 weeks after myocardial I/RI. Dan inhibited Bax/Bcl2 ratio and Caspase3 cleavage in heart tissues and also inhibited apoptosis of human AC16 cells and neonatal rat cardiomyocytes stressed by oxygen and glucose deprivation/reperfusion. Mechanistically, Dan inhibited myocardial apoptosis through phosphorylating AKT and FoxO3a, thereby inhibiting downstream BIM and PUMA expressions. Collectively, these results demonstrate that Dan treatment is effective to protect against cardiac remodeling and dysfunction after myocardial I/RI and provide theoretical basis for its cardioprotection and clinical application in treating ischemic cardiac diseases. [ABSTRACT FROM AUTHOR]

Human umbilical cord–derived mesenchymal stem cells (hUC-MSCs) are used to regenerate the myocardium during cardiac repair after myocardial infarction. However, the regulatory mechanism underlying their ability to form mesodermal cells and differentiate into cardiomyocytes remains unclear. Here, we established a human-derived MSCs line isolated from healthy umbilical cords and established a cell model of the natural state to examine the differentiation of hUC-MSCs into cardiomyocytes. Quantitative RT-PCR, western blotting, immunofluorescence, flow cytometry, RNA Seq, and inhibitors of canonical Wnt signalling were used to detect the germ-layer markers T and MIXL1; the markers of cardiac progenitor cells MESP1, GATA4, and NKX2.5 and the cardiomyocyte-marker cTnT to identify the molecular mechanism associated with PYGO2, a key component of the canonical Wnt signalling pathway that regulates the formation of cardiomyocyte-like cells. We demonstrated that PYGO2 promotes the formation of mesodermal-like cells and their differentiation into cardiomyocytes through the hUC-MSC-dependent canonical Wnt signalling by promoting the early-stage entry of β-catenin into the nucleus. Surprisingly, PYGO2 did not alter the expression of the canonical-Wnt, NOTCH, or BMP signalling pathways during the middle–late stages. In contrast, PI3K-Akt signalling promoted hUC-MSCs formation and their differentiation into cardiomyocyte-like cells. To the best of our knowledge, this is the first study to demonstrate that PYGO2 uses a biphasic mechanism to promote cardiomyocyte formation from hUC-MSCs. [ABSTRACT FROM AUTHOR]

Mammalian cardiomyocytes (CMs) undergo maturation during postnatal heart development to meet the increased demands of growth. Here, we found that omentin-1, an adipokine, facilitates CM cell cycle arrest and metabolic maturation. Deletion of omentin-1 causes mouse heart enlargement and dysfunction in adulthood and CM maturation retardation in juveniles, including delayed cell cycle arrest and reduced fatty acid oxidation. Through RNA sequencing, molecular docking analysis, and proximity ligation assays, we found that omentin-1 regulates CM maturation by interacting directly with bone morphogenetic protein 7 (BMP7). Omentin-1 prevents BMP7 from binding to activin type II receptor B (ActRIIB), subsequently decreasing the downstream pathways mothers against DPP homolog 1 (SMAD1)/Yes-associated protein (YAP) and p38 mitogen-activated protein kinase (p38 MAPK). In addition, omentin-1 is required and sufficient for the maturation of human embryonic stem cell-derived CMs. Together, our findings reveal that omentin-1 is a pro-maturation factor for CMs that is essential for postnatal heart development and cardiac function maintenance. [ABSTRACT FROM AUTHOR]

Diabetes mellitus with hyperglycaemia is a major risk factor for malignant cardiac dysrhythmias. However, the underlying mechanisms remain unclear, especially during the embryonic developmental phase of the heart. This study investigated the effect of hyperglycaemia on the pulsatile activity of stem cell-derived cardiomyocytes. Mouse embryonic stem cells (mESCs) were differentiated into cardiac-like cells through embryoid body (EB) formation, in either baseline glucose or high glucose conditions. Action potentials (APs) were recorded using a voltage-sensitive fluorescent dye and gap junction activity was evaluated using scrape-loading lucifer yellow dye transfer assay. Molecular components were detected using immunocytochemistry and immunoblot analyses. High glucose decreased the spontaneous beating rate of EBs and shortened the duration of onset of quinidine-induced asystole. Furthermore, it altered AP amplitude, but not AP duration, and had no impact on neither the expression of the hyperpolarisation-activated cyclic nucleotide-gated isoform 4 (HCN4) channel nor on the EB beating rate response to ivabradine nor isoprenaline. High glucose also decreased both the intercellular spread of lucifer yellow within an EB and the expression of the cardiac gap junction protein connexin 43 as well as upregulated the expression of transforming growth factor beta 1 (TGF-β1) and phosphorylated Smad3. High glucose suppressed the autorhythmicity and gap junction conduction of mESC-derived cardiomyocytes, via mechanisms probably involving TGF-β1/Smad3 signalling. The results allude to glucotoxicity related proarrhythmic effects, with potential clinical implications in foetal diabetic cardiac disease. [ABSTRACT FROM AUTHOR]

Background: Metformin, a first-line oral anti-diabetic drug, has recently been reported to exert protective effect on various cardiovascular diseases. However, the potential role of metformin in ethanol-induced cardiomyocyte injury is still unknown. Therefore, this study was aimed to investigate the effect of metformin on ethanol-induced cardiomyocyte injury and its underlying mechanism. Methods and results: H9c2 cardiomyocytes were exposed to ethanol for 24 h to establish an ethanol-induced cardiomyocyte injury model, and followed by treatment with metformin in the presence or absence of Lapatinib (an ErbB2 inhibition). CCK8 and LDH assays demonstrated that metformin improved cell viability in cardiomyocytes exposed to ethanol. Furthermore, metformin suppressed cardiomyocyte apoptosis and reduced the expressions of apoptosis-related proteins (Bax and C-CAS-3). In addition, our results showed that metformin activated the AKT/Nrf2 pathway, and then promoted Nrf2 nuclear translocation and the transcription of its downstream antioxidant genes (HO-1, CAT and SOD2), thereby inhibiting oxidative stress. Interestingly, we found that ErbB2 protein expression was significantly inhibited in ethanol-treated cardiomyocytes, which was markedly reversed by metformin. In contrast, Lapatinib largely abrogated the activation of AKT/Nrf2 signaling by metformin, accompanied by the increases in oxidative stress and cardiomyocyte apoptosis, indicating that metformin prevented ethanol-induced cardiomyocyte injury in an ErbB2-dependent manner. Conclusion: In summary, our study provides the first evidence that metformin protects cardiomyocyte against ethanol-induced oxidative stress and apoptosis by activating ErbB2-mediated AKT/Nrf2 signaling. Thus, metformin may be a potential novel treatment approach for alcoholic cardiomyopathy. [ABSTRACT FROM AUTHOR]

Morroniside can prevent myocardial injury caused by ischemia and hypoxia, which can be used to treat acute myocardial infarction (AMI). Hypoxia can cause apoptosis and autophagic death of cardiomyocytes. Morroniside has the ability to inhibit apoptosis and autophagy. However, the relationship between Morroniside-protected cardiomyocytes and two forms of death is unclear. The effects of Morroniside on the proliferation, apoptosis level, and autophagic activity of rat cardiomyocyte line H9c2 under hypoxia were first observed. Next, the roles of Morroniside in the phosphorylation of JNK and BCL2, BCL2-Beclin1, and BCL2-Bax complexes as well as mitochondrial membrane potential in H9c2 cells were evaluated upon hypoxia. Finally, the significance of BCL2 or JNK in Morroniside-regulated autophagy, apoptosis, and proliferation in H9c2 cells was assessed by combining Morroniside and BCL2 competitive inhibitor (ABT-737) or JNK activator (Anisomycin). Our results showed that hypoxia promoted autophagy and apoptosis of H9c2 cells, and inhibited their proliferation. However, Morroniside could block the effect of hypoxia on H9c2 cells. In addition, Morroniside could inhibit JNK phosphorylation, BCL2 phosphorylation at the Ser70 and Ser87 sites, and the dissociation of BCL2-Beclin1 and BCL2-Bax complexes in H9c2 cells upon hypoxia. Moreover, the reduction of mitochondrial membrane potential in H9c2 cells caused by hypoxia was improved by Morroniside administration. Importantly, the inhibited autophagy, apoptosis, and promoted proliferation in H9c2 cells by Morroniside were reversed by the application of ABT-737 or Anisomycin. Overall, Morroniside inhibits Beclin1-dependent autophagic death and Bax-dependent apoptosis via JNK-mediated BCL2 phosphorylation, thereby improving the survival of cardiomyocytes under hypoxia. [ABSTRACT FROM AUTHOR]

The reperfusion of coronary artery blood supply is often accompanied by myocardial hypoxia/reperfusion (H/R) injury, and induced cardiomyocytes apoptosis. The activation of p38 can induce apoptosis, thereby aggravating the myocardial H/R injury. Metallothionein-2A (MT2A) has the functions of anti-apoptosis and protective effect through p38. However, it is not clear that MT2A may protect cardiomyocytes from H/R injury through p38 signaling pathway. Here, we constructed an H/R model for H9c2 cardiomyocytes to explore the protective effect of MT2A on cardiomyocytes apoptosis during the process of H/R through p38 signal pathway. The results revealed that both endogenously overexpressed MT2A and exogenously added MT2A can inhibit the active expression of p-p38 and cleaved caspase-3 under H/R. Based on our results, H/R induced cardiomyocytes apoptosis and activation of p38. And, MT2A can inhibit the active expression of caspase-3 and p38. We found that MT2A can protect cardiomyocytes apoptosis from H/R injury through p38 signaling pathway. [ABSTRACT FROM AUTHOR]

Autophagy plays various roles at different stages of ischemia reperfusion (I/R) injury in cardiomyocytes. It has been reported that tissue factor pathway inhibitor (TFPI) has a protective effect on I/R injury. This study aimed to determine the roles of TFPI in autophagy during the I/R injury process in cardiomyocytes and the possible mechanisms. An isolated hypoxia/reoxygenation (H/R) pattern of cardiomyocytes was established by the MIC101 system. The cell viability and oxidative stress of cardiomyocytes were detected by an MTT assay and ROS assay, respectively. The autophagy level was measured by Ad-mCherry-GFP-LC3B and MDC. We detected the expression levels of autophagy-related proteins by western blotting. After 2 h of hypoxia and 12 h of reoxygenation, the cardiomyocyte viability in the H/R group was significantly lower than that in the control group (p < 0.05) than in the H/R group. According to intracellular ROS production, the fluorescence intensity in the H/R group was enhanced compared with that in the negative control group, and it was weaker in the H/R + rTFPI group compared with the H/R group. The level of autophagy and the expression levels of autophagy-related proteins (LC3-II/LC3-I, Beclin-1 and PI3K) were markedly increased in the H/R group compared to the control group (p < 0.05) whereas the levels were markedly decreased in the H/R + rTFPI group compared to the H/R group (p < 0.05). TFPI could relieve cardiomyocyte injury by inhibiting the Class III PI3K/Beclin-1 pathway and oxidative stress; thus, TFPI decreased autophagy and protected cardiomyocytes induced by H/R injury. In conclusion, TFPI may be a new direction for the prevention of myocardial I/R injury. [ABSTRACT FROM AUTHOR]

Purpose: Glucocorticoids, which are widely prescribed around the world, cause cardiac remodeling in long-term treatment by triggering insulin resistance and increasing blood pressure. However, its role in cardiac remodeling remains unclear. Galectin-3 (gal-3) is a member of a beta-galactoside-binding animal lectins, upregulated as a result of insulin resistance and in the pressure-overloaded myocardium and regulate cardiac remodeling. We hypothesized that gal-3 may be upregulated in the myocardium with prolonged use of glucocorticoids and associated with cardiac hypertrophy. Methods: To examine the involvement of glucocorticoids in gal-3 levels in rat myocardium, sixteen female Wistar Albino rats were assigned to control (C; n = 8) and dexamethasone (Dex; n = 8) groups. Daily dexamethasone was injected subcutaneously for 28 days at a dose of 1 mg.kg−1. Control animals were injected with the same volume of saline. The body weight and heart weights were determined. Gal-3 levels in myocardium were determined by Western blot. Results: Our data shows that dexamethasone administration resulted in significant increase in heart weight (p < 0.05) and HW/BW ratios (p < 0.001) and 28 days of dexamethasone administration with the dose of 1 mg.kg−1 caused a twofold increase in the gal-3 expression in the left ventricle (p < 0.001). Conclusion: The finding of the current study is the first to show that dexamethasone causes an increase in gal-3 levels in myocardium. Our study provides an important step in the development of possible therapeutics by determining that dexamethasone causes an increase in gal-3 levels in the myocardium and raises awareness about the follow-up of patients receiving long-term glucocorticoid therapy. [ABSTRACT FROM AUTHOR]

To investigate the mechanism whereby sevoflurane (Sev) protects cardiomyocytes from hypoxia/reoxygenation (H/R) injury. The rat cardiomyocyte line H9C2 was exposed to hypoxia (1% oxygen) for 24 h, followed by reoxygenation for 2 h to construct a model of H/R injury. H9C2 was exposed to 2.4% Sev for 45 min before creating a hypoxic environment to observe the effect of Sev. MTT was taken to assess the viability of each group of cells, flow cytometry to detect cell apoptosis, and qRT-PCR or western blot to detect the expression of iron metabolism-related proteins and apoptosis-related proteins in the cells. And the kit determined the levels of total Fe and Fe2+ as well as factors related to oxidative stress in the cells. Administration of Sev significantly increased the cell viability of the H/R group while decreasing the expression of apoptosis-related proteins (Bax, cleaved caspase-3). Ferroportin 1 and mitochondrial ferritin, which are associated with iron metabolism, were considerably up-regulated by Sev, while iron regulatory protein 1, divalent metal transporter 1, and transferrin receptor 1 were significantly down-regulated in H/R cells. Additionally, Sev substantially reduced the levels of total Fe and Fe2+, reactive oxygen species, malondialdehyde, and 4-hydroxynonenal in H/R cells. In conclusion, Sev relieves H/R-induced cardiomyocyte injury by regulating iron homeostasis and ferroptosis. [ABSTRACT FROM AUTHOR]

Mechanical stimulation is capable of affecting cell apoptosis. Several studies have shown that the Bcl-2 gene family, including the Bcl-2 gene and Bax gene, plays an important role in apoptosis, as proteins produced by the Bcl-2 gene can inhibit apoptosis while proteins produced by the Bax gene can promote cell apoptosis. Understanding how mechanical stimulation alters the expression of apoptosis-related genes in cardiomyocytes can contribute to the development of ways to inhibit cardiomyocyte necrosis. Intermediate myocytes showed a clear transmural repolarization. The cytoskeleton changed slowly in the cytoplasm of cardiomyocytes. The high-frequency mechanical signal stimulation under caspase inhibitors had the lowest apoptotic rate of cardiomyocytes, and a comparison showed that the rate of necrosis of cardiomyocytes was lower in the high-frequency group than in the inhibitor group at different times. The expression of the Bcl-2 gene increased significantly after the stimulation of the high-frequency mechanical signal. Overall, the results suggest that high-frequency stimulation can effectively inhibit cardiomyocyte apoptosis. [ABSTRACT FROM AUTHOR]

Background: Heart failure is the leading cause of morbidity and mortality worldwide and is characterized by reduced cardiac function. Currently, cardiac transplantation therapy is applied for end-stage heart failure, but it is limited by the number of available donors. Methods and Results: Following an assessment of available literature, a narrative review was conducted to summarizes the current status and challenges of cardiac reprogramming for clinical application. Scientists have developed different regenerative treatment strategies for curing heart failure, including progenitor cell delivery and pluripotent cell delivery. Recently, a novel strategy has emerged that directly reprograms cardiac fibroblast into a functional cardiomyocyte. In this treatment, transcription factors are first identified to reprogram fibroblast into a cardiomyocyte. After that, microRNA and small molecules show great potential to optimize the reprogramming process. Some challenges regarding cell reprogramming in humans are conversion efficiency, virus utilization, immature and heterogenous induced cardiomyocytes, technical reproducibility issues, and physiological effects of depleted fibroblasts on myocardial tissue. Conclusion: Several strategies have shown positive results in direct cardiac reprogramming. However, direct cardiac reprogramming still needs improvement if it is used as a mainstay therapy in humans, and challenges need to be overcome before cardiac reprogramming can be considered a viable therapeutic strategy. Further advances in cardiac reprogramming studies are needed in cardiac regenerative therapy. [ABSTRACT FROM AUTHOR]

Arrhythmogenic cardiomyopathy (ACM) is one of the most common inherited cardiomyopathies, characterized by progressive fibrofatty replacement in the myocardium. However, the cellular origin of cardiac adipocytes in ACM remains largely unknown. Unraveling the cellular source of cardiac adipocytes in ACM would elucidate the underlying pathological process and provide a potential target for therapy. Herein, we generated an ACM mouse model by inactivating desmosomal gene desmoplakin in cardiomyocytes; and examined the adipogenic fates of several cell types in the disease model. The results showed that SOX9+, PDGFRa+, and PDGFRb+ mesenchymal cells, but not cardiomyocytes or smooth muscle cells, contribute to the intramyocardial adipocytes in the ACM model. Mechanistically, Bmp4 was highly expressed in the ACM mouse heart and functionally promoted cardiac mesenchymal-to-adipose transition in vitro. [ABSTRACT FROM AUTHOR]

Fibroblast growth factor 21 (FGF21) is a peptide hormone involved in energy homeostasis that protects against the development of obesity and diabetes in animal models. Its level is elevated in atherosclerotic cardiovascular diseases (CVD) in humans. However, little is known about the role of FGF21 in heart failure (HF). HF is a major global health problem with a prevalence that is predicted to rise, especially in ageing populations. Despite improved therapies, mortality due to HF remains high, and given its insidious onset, prediction of its development is challenging for physicians. The emergence of cardiac biomarkers to improve prediction, diagnosis, and prognosis of HF has received much attention over the past decade. Recent studies have suggested FGF21 is a promising biomarker candidate for HF. Preclinical research has shown that FGF21 is involved in the pathophysiology of HF through the prevention of oxidative stress, cardiac hypertrophy, and inflammation in cardiomyocytes. However, in the available clinical literature, FGF21 levels appear to be paradoxically raised in HF, potentially implying a FGF21 resistant state as occurs in obesity. Several potential confounding variables complicate the verdict on whether FGF21 is of clinical value as a biomarker. Further research is thus needed to evaluate whether FGF21 has a causal role in HF, and whether circulating FGF21 can be used as a biomarker to improve the prediction, diagnosis, and prognosis of HF. This review draws from preclinical and clinical studies to explore the role of FGF21 in HF. [ABSTRACT FROM AUTHOR]

The transverse-axial tubular system (tubular system) of cardiomyocytes plays a key role in excitation–contraction coupling. To determine the area of the tubular membrane in relation to the area of the surface membrane, indirect measurements through the determination of membrane capacitances are currently used in addition to microscopic methods. Unlike existing electrophysiological methods based on an irreversible procedure (osmotic shock), the proposed new approach uses a reversible short-term intermittent increase in the electrical resistance of the extracellular medium. The resulting increase in the lumen resistance of the tubular system makes it possible to determine separate capacitances of the tubular and surface membranes. Based on the analysis of the time course of the capacitive current, computational relations were derived to quantify the elements of the electrical equivalent circuit of the measured cardiomyocyte including both capacitances. The exposition to isotonic low-conductivity sucrose solution is reversible which is the main advantage of the proposed approach allowing repetitive measurements on the same cell under control and sucrose solutions. Experiments on rat ventricular cardiomyocytes (n = 20) resulted in the surface and tubular capacitance values implying the fraction of tubular capacitance/area of 0.327 ± 0.018. We conclude that the newly proposed method provides results comparable to the data obtained by the currently used detubulation method and, in addition, by being reversible, allows repeated evaluation of surface and tubular membrane parameters on the same cell. [ABSTRACT FROM AUTHOR]

Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) represent one of the most promising ways to treat cardiovascular diseases. High-purity cardiomyocytes (CM) from different cell sources could be obtained at present. However, the immature nature of these cardiomyocytes hinders its further clinical application. From immature to mature state, it involves structural, functional, and metabolic changes in cardiomyocytes. Generally, two types of culturing (2D and 3D) systems have been reported to induce cardiomyocyte maturation. 2D culture mainly achieves the maturation of cardiomyocytes through long-term culture, co-culture, supplementation of small molecule compounds, and the application of biophysical cues. The combined use of biomaterial's surface topography and biophysical cues also facilitates the maturation of cardiomyocytes. Cardiomyocyte maturation is a complex process involving many signaling pathways, and current methods fail to fully reproduce this process. Therefore, analyzing the signaling pathway network related to the maturation and producing hPSC-CMs with adult-like phenotype is a challenge. In this review, we summarized the structural and functional differences between hPSC-CMs and mature cardiomyocytes, and introduced various methods to induce cardiomyocyte maturation. [ABSTRACT FROM AUTHOR]

Junctophilin-2 (JP2) is a critical structural protein in the heart by stabilizing junctional membrane complexes between the plasma membrane and sarcoplasmic reticula responsible for precise Ca2+ regulation. Such complexes are essential for efficient cardiomyocyte contraction and adaptation to altered cardiac workload conditions. Mutations in the JPH2 gene that encodes JP2 are associated with inherited cardiomyopathies and arrhythmias, and disruption of JP2 function is lethal. Interestingly, cardiac stress promotes the proteolytic cleavage of JP2 that triggers the translocation of its N-terminal fragment into the nucleus to repress maladaptive gene transcription. We previously found that the central region of JP2 is responsible for mediating direct DNA binding interactions. Recent structural studies indicate that this region serves as a structural role in the cytosolic form of JP2 by folding into a single continuous α-helix. However, the structural basis of how this DNA-binding domain interacts with DNA is not known. Here, we report the backbone and sidechain assignments of the DNA-binding domain (residues 331-413) of mouse JP2. These assignments reveal that the JP2 DNA binding domain is an intrinsically disordered protein and contains two α-helices located in the C-terminal portion of the protein. Moreover, this protein binds to DNA in a similar manner to that shown previously by electrophoretic mobility shift assays. Therefore, these assignments provide a framework for further structural studies into the interaction of this JP2 domain with DNA for the elucidation of transcriptional regulation of stress-responsive genes as well as its role in the stabilization of junctional membrane complexes. [ABSTRACT FROM AUTHOR]

We investigated possible cardioprotective mechanisms of l-arginine coated nanoparticles (L-ACN) combined with swimming exercise (SE) in aging male rats considering heart and neural crest derivatives-expressed protein 2 (HAND2) and t-box transcription factor 5 (TBX5). Thirty-five male Wistar rats were randomly assigned into five groups: young, old, old + L-ACN, old + SE, and old + L-ACN + SE (n = 7 in each). l-arginine coated with chitosan nanoparticles was given to L-ACN groups via gavage at 500 mg/kg/day. SE groups performed a swimming exercise program 5 days per week for 6 weeks. The exercise program started with 20 min, gradually increasing to 60 min after four sessions, which was then constant until the completion of the training period. After the protocol completion, the rats were sacrificed, and the heart was fixed and frozen to carry out histological, immunohistochemistry (IHC), and gene expression analyses. The expression of HAND2 protein, HAND2 mRNA, and TBX5 mRNA of the heart tissue was significantly higher in the young group than in all older groups (P < 0.05). The old + L-ACN, old + SE, and old + L-ACN + SE groups showed a significant increase in these factors compared to the old group (P < 0.05). Nano-l-arginine supplement, along with swimming exercises, seems to have cardioprotective potential and improve cardiac function in old age by strengthening cardiomyocyte signaling, especially HAND2 and TBX5. However, more research is required, particularly on human samples. [ABSTRACT FROM AUTHOR]

This study aimed to explore the effects of Wenyang Zhenshuai granules (WZG) on the morphology of cardiomyocytes, cell viability, and the expression of key mitochondrial autophagy proteins in the doxorubicin-induced model of H9c2 cardiomyocyte injury. Cardiomyocytes were cultured for 44 h and divided into 4 groups: intact control, doxorubicin-injured cells (DOX), doxorubicin-injured cells treated with WZG (DOX+WZG), and doxorubicin-injured cells treated with valsartan (DOX+valsartan; reference group). The morphology of cardiomyocytes was analyzed under an inverted microscope; cardiomyocyte survival rate was determined by MTT assay. The expression of the key mitochondrial autophagy proteins (PINK1, parkin, LC3-II, and prohibitin-2) was analyzed by Western blotting. WZG down-regulated the expression of the key mitochondrial autophagy proteins in DOX-injured cells, which may be one of the important mechanisms for regulating ventricular remodeling and cardiomyocyte apoptosis. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Doxorubicin (DOX) is a potent chemotherapeutic agent; however, it causes severe heart injury via apoptosis induction in many patients. DOX-induced cardiotoxicity is attenuated by activated autophagy in the heart. We previously found that programmed cell death 1 (Pdcd1), an immune checkpoint receptor, inhibits DOX-induced cardiomyocyte apoptosis. In this study, we investigated whether autophagy contributes to the protective role of Pdcd1 against DOX-induced cardiomyocyte apoptosis. We also examined the role of Pdcd1 in DOX-induced apoptosis in cancer cells. Rat cardiomyocyte cell line H9c2 and human cancer cell lines K562 and MCF-7 were transfected with Pdcd1-encoding plasmid DNA to establish Pdcd1-overexpressing cells. Apoptosis and autophagy were determined using a luciferase assay. In H9c2 cells, DOX-induced apoptosis and viability reduction occurred through caspase activation. In particular, Pdcd1 overexpression activated the autophagy pathway through the inhibition of the mammalian target of rapamycin, a major negative regulator of autophagy. Moreover, it prevented DOX-induced cardiomyocyte apoptosis; a similar cardioprotection was observed when normal H9c2 cells (without Pdcd1 overexpression) were treated with rapamycin, an autophagy inducer, before the DOX treatment. Conversely, in cancer cells, Pdcd1 overexpression increased both basal and DOX-induced apoptosis. The role of Pdcd1 in DOX-induced apoptosis in cardiomyocytes and cancer cells was opposing. Pdcd1 signaling prevented DOX-induced apoptosis in cardiomyocytes, through autophagy induction; it enhanced DOX-induced apoptosis in cancer cells. Therefore, Pdcd1 could be a critical molecule for more effective and safer DOX chemotherapy. [ABSTRACT FROM AUTHOR]

Acute myocardial infarction (AMI) is a most serious cardiovascular disease. Increasing findings have indicated that circular RNAs (circRNAs) serve as competent biomarkers in the process of AMI. Herein, our study aimed to probe the functions of circ-SWT1 in cardiomyocyte injury after AMI. H2O2-induced human cardiomyocyte cell line AC16 were used for expression and function analyses. The levels of genes and proteins were detected by qRT-PCR and western blotting. Cell apoptosis was analyzed by flow cytometry and caspase3 activity analysis. The oxidative stress injury was evaluated by detecting the levels of reactive oxygen species (ROS), malondialdehyde and superoxide dismutase (SOD). Western blotting was used to detect the expressions of apoptosis-related markers and endoplasmic reticulum stress (ERS) markers. Dual-luciferase reporter, RIP and pull-down assays were applied to confirm the interaction between miR-192-5p and circ-SWT1 or SOD2. H2O2 treatment significantly decreased circ-SWT1 expression in cardiomyocytes, functionally, ectopic expression of circ-SWT1 attenuated H2O2-triggered apoptosis, oxidative stress and endoplasmic reticulum (ER) stress in cardiomyocytes in vitro. Mechanistically, circ-SWT1 competitively bound to miR-192-5p to relieve the repression of miR-192-5p on its target SOD2. Further rescue experiments showed that miR-192-5p upregulation reversed the inhibitory effects of circ-SWT1 on H2O2-induced cardiomyocyte injury. Moreover, miR-192-5p inhibition protected cardiomyocytes against H2O2-evoked apoptosis, oxidative stress and ER stress, which were abolished by SOD2 silencing. Circ-SWT1 ameliorates H2O2-induced apoptosis, oxidative stress and ER stress in cardiomyocytes via miR-192-5p/SOD2 axis, suggesting the potential involvement of circ-SWT1 in AMI process. [ABSTRACT FROM AUTHOR]

One of the most important side effects of chemotherapy is cardiovascular complications, such as cardiotoxicity. Many factors are involved in the pathogenesis of cardiotoxicity; one of the most important of which is long non-coding RNAs (lncRNAs). lncRNA has 200–1000 nucleotides. It is involved in important processes such as cell proliferation, regeneration and apoptosis; today it is used as a prognostic and diagnostic factor. A, various drugs by acting on lncRNAs can affect cells. Therefore, by accurately identifying IncRNAs function, we can play an effective role in preventing the development of cardiotoxicity-induced chemotherapy drugs, and use them as a therapeutic strategy to improve clinical symptoms and increase patient survival. [ABSTRACT FROM AUTHOR]

The release of extracellular vesicles (EVs) is increased under cellular stress and cardiomyocyte damaging conditions. However, whether the cardiomyocyte-derived EVs eventually reach the systemic circulation and whether their number in the bloodstream reflects cardiac injury, remains unknown. Wild type C57B/6 and conditional transgenic mice expressing green fluorescent protein (GFP) by cardiomyocytes were studied in lipopolysaccharide (LPS)-induced systemic inflammatory response syndrome (SIRS). EVs were separated both from platelet-free plasma and from the conditioned medium of isolated cardiomyocytes of the left ventricular wall. Size distribution and concentration of the released particles were determined by Nanoparticle Tracking Analysis. The presence of GFP + cardiomyocyte-derived circulating EVs was monitored by flow cytometry and cardiac function was assessed by echocardiography. In LPS-treated mice, systemic inflammation and the consequent cardiomyopathy were verified by elevated plasma levels of TNFα, GDF-15, and cardiac troponin I, and by a decrease in the ejection fraction. Furthermore, we demonstrated elevated levels of circulating small- and medium-sized EVs in the LPS-injected mice. Importantly, we detected GFP+ cardiomyocyte-derived EVs in the circulation of control mice, and the number of these circulating GFP+ vesicles increased significantly upon intraperitoneal LPS administration (P = 0.029). The cardiomyocyte-derived GFP+ EVs were also positive for intravesicular troponin I (cTnI) and muscle-associated glycogen phosphorylase (PYGM). This is the first direct demonstration that cardiomyocyte-derived EVs are present in the circulation and that the increased number of cardiac-derived EVs in the blood reflects cardiac injury in LPS-induced systemic inflammation (SIRS). [ABSTRACT FROM AUTHOR]

In heart failure, an increased abundance of post-translationally detyrosinated microtubules stiffens the cardiomyocyte and impedes its contractile function. Detyrosination promotes interactions between microtubules, desmin intermediate filaments, and the sarcomere to increase cytoskeletal stiffness, yet the mechanism by which this occurs is unknown. We hypothesized that detyrosination may regulate the growth and shrinkage of dynamic microtubules to facilitate interactions with desmin and the sarcomere. Through a combination of biochemical assays and direct observation of growing microtubule plus-ends in adult cardiomyocytes, we find that desmin is required to stabilize growing microtubules at the level of the sarcomere Z-disk, where desmin also rescues shrinking microtubules from continued depolymerization. Further, reducing detyrosination (i.e. tyrosination) below basal levels promotes frequent depolymerization and less efficient growth of microtubules. This is concomitant with tyrosination promoting the interaction of microtubules with the depolymerizing protein complex of end-binding protein 1 (EB1) and CAP-Gly domain-containing linker protein 1 (CLIP1/CLIP170). The dynamic growth and shrinkage of tyrosinated microtubules reduce their opportunity for stabilizing interactions at the Z-disk region, coincident with tyrosination globally reducing microtubule stability. These data provide a model for how intermediate filaments and tubulin detyrosination establish long-lived and physically reinforced microtubules that stiffen the cardiomyocyte and inform both the mechanism of action and therapeutic index for strategies aimed at restoring tyrosination for the treatment of cardiac disease. [ABSTRACT FROM AUTHOR]

Understanding how macrophages promote myocardial repair can help create new therapies for infarct repair. We aimed to determine what mechanisms underlie the reparative properties of macrophages. Cytokine arrays revealed that neonatal cardiac macrophages from the injured neonatal heart secreted high amounts of osteopontin (OPN). In vitro, recombinant OPN stimulated cardiac cell outgrowth, cardiomyocyte (CM) cell-cycle re-entry, and CM migration. In addition, OPN induced nuclear translocation of the cytoplasmatic yes-associated protein 1 (YAP1) and upregulated transcriptional factors and cell-cycle genes. Significantly, by blocking the OPN receptor CD44, we eliminated the effects of OPN on CMs. OPN also activated the proliferation and migration of non-CM cells: endothelial cells and cardiac mesenchymal stromal cells in vitro. Notably, the significant role of OPN in myocardial healing was demonstrated by impaired healing in OPN-deficient neonatal hearts. Finally, in the adult mice, a single injection of OPN into the border of the ischemic zone induced CM cell-cycle re-entry, improved scar formation, local and global cardiac function, and LV remodelling 30 days after MI. In summary, we have shown, for the first time, that recombinant OPN activates cell-cycle re-entry in CMs. In addition, recombinant OPN stimulates multiple cardiac cells and improves scar formation, LV remodelling, and regional and global function after MI. Therefore, we propose OPN as a new cell-free therapy to optimize infarct repair. [ABSTRACT FROM AUTHOR]

Cardiac contractile strength is recognised as being highly pH-sensitive, but less is known about the influence of pH on cardiac gene expression, which may become relevant in response to changes in myocardial metabolism or vascularization during development or disease. We sought evidence for pH-responsive cardiac genes, and a physiological context for this form of transcriptional regulation. pHLIP, a peptide-based reporter of acidity, revealed a non-uniform pH landscape in early-postnatal myocardium, dissipating in later life. pH-responsive differentially expressed genes (pH-DEGs) were identified by transcriptomics of neonatal cardiomyocytes cultured over a range of pH. Enrichment analysis indicated “striated muscle contraction” as a pH-responsive biological process. Label-free proteomics verified fifty-four pH-responsive gene-products, including contractile elements and the adaptor protein CRIP2. Using transcriptional assays, acidity was found to reduce p300/CBP acetylase activity and, its a functional readout, inhibit myocardin, a co-activator of cardiac gene expression. In cultured myocytes, acid-inhibition of p300/CBP reduced H3K27 acetylation, as demonstrated by chromatin immunoprecipitation. H3K27ac levels were more strongly reduced at promoters of acid-downregulated DEGs, implicating an epigenetic mechanism of pH-sensitive gene expression. By tandem cytoplasmic/nuclear pH imaging, the cardiac nucleus was found to exercise a degree of control over its pH through Na+/H+ exchangers at the nuclear envelope. Thus, we describe how extracellular pH signals gain access to the nucleus and regulate the expression of a subset of cardiac genes, notably those coding for contractile proteins and CRIP2. Acting as a proxy of a well-perfused myocardium, alkaline conditions are permissive for expressing genes related to the contractile apparatus. [ABSTRACT FROM AUTHOR]

Aluminum exposure can mediate either acute toxicity or chronic toxicity. Aluminum exerts toxic effects on the cardiovascular system, but there are few studies on its related mechanisms. In this study, we investigated the molecular mechanism of aluminum-induced oxidative damage and apoptosis in rat cardiomyocytes. Thirty-two male Wistar rats were randomly divided into four groups, including the control group (GC), low-dose group of aluminum exposure (GL), medium-dose group (GM), and high-dose group (GH), with eight rats in each group. The GL, GM, and GH groups were given 5, 10, and 20 mg/(kg·d) of AlCl3 solution by intraperitoneal injection, and the GC group received intraperitoneal injection of the same volume of normal saline (2 ml/rat/day), 5 times a week for 28 days. At the end of the experiment, the levels of aluminum, malondialdehyde (MDA), plasma lactate dehydrogenase (LDH), creatine kinase (CK), creatine kinase isoenzyme (CKMB), and alpha-hydroxybutyrate dehydrogenase (HBDH) were measured. The pathological changes of myocardium were observed by H&E staining. The apoptosis of cardiomyocytes was detected by TUNEL staining, and the expression of apoptosis-related proteins was determined by western blot. The results showed that the levels of CKMB and HBDH in the GM and GH groups were significantly higher than those in the GC group (P < 0.05). The content of aluminum in the myocardium and serum of the aluminum exposure groups was significantly higher than that of the GC group (P < 0.05). The level of MDA in the GM and GH groups was significantly higher than that in the GC group (P < 0.05). The pathological results showed that vacuolated and hypertrophied cardiomyocytes were found in aluminum exposure groups, especially in the GM and GH groups. The TUNEL staining showed that the apoptosis rate of the aluminum exposure groups was considerably higher than that of the GC group (P < 0.05). Western blot showed that the expression of Bcl-2, an anti-apoptotic protein, in cardiomyocytes of aluminum exposure groups was lower than that of the GC group (P < 0.05), while the levels of Bax and caspase-3 in the cardiomyocytes of the GM and GH groups were higher than those of the GC group (P < 0.05). The experimental results showed that aluminum could accumulate in myocardial tissues and cause damage to cardiomyocytes. It could induce oxidative stress damage by increasing the content of MDA in cardiomyocytes and trigger cardiomyocyte apoptosis by activating the pro-apoptotic proteins caspase-3 and Bax and reducing the anti-apoptotic protein Bcl-2. [ABSTRACT FROM AUTHOR]

Chronic alcohol consumption in adults can induce cardiomyopathy, arrhythmias, and heart failure. In newborns, prenatal alcohol exposure can increase the risk of congenital heart diseases. Understanding biological mechanisms involved in the long-term alcohol exposure-induced cardiotoxicity is pivotal to the discovery of therapeutic strategies. In this study, cardiomyocytes derived from human pluripotent stem cells (hiPSC-CMs) were treated with clinically relevant doses of ethanol for various durations up to 5 weeks. The treated cells were characterized for their cellular properties and functions, and global proteomic profiling was conducted to understand the molecular changes associated with long-term ethanol exposure. Increased cell death, oxidative stress, deranged Ca2+ handling, abnormal action potential, altered contractility, and suppressed structure development were observed in ethanol-treated cells. Many dysregulated proteins identified by global proteomic profiling were involved in apoptosis, heart contraction, and extracellular collagen matrix. In addition, several signaling pathways including the Wnt and TGFβ signaling pathways were affected due to long-term ethanol treatment. Therefore, chronic ethanol treatment of hiPSC-CMs induces cardiotoxicity, impairs cardiac functions, and alters protein expression and signaling pathways. This study demonstrates the utility of hiPSC-CMs as a novel model for chronic alcohol exposure study and provides the molecular mechanisms associated with long-term alcohol exposure in human cardiomyocytes. [ABSTRACT FROM AUTHOR]

It has been nearly 15 years since the discovery of human-induced pluripotent stem cells (iPSCs). During this time, differentiation methods to targeted cells have dramatically improved, and many types of cells in the human body can be currently generated at high efficiency. In the cardiovascular field, the ability to generate human cardiomyocytes in vitro with the same genetic background as patients has provided a great opportunity to investigate human cardiovascular diseases at the cellular level to clarify the molecular mechanisms underlying the diseases and discover potential therapeutics. Additionally, iPSC-derived cardiomyocytes have provided a powerful platform to study drug-induced cardiotoxicity and identify patients at high risk for the cardiotoxicity; thus, accelerating personalized precision medicine. Moreover, iPSC-derived cardiomyocytes can be sources for cardiac cell therapy. Here, we review these achievements and discuss potential improvements for the future application of iPSC technology in cardiovascular diseases. [ABSTRACT FROM AUTHOR]

The exposure of the developing foetal heart to hyperglycaemia in mothers with diabetes mellitus is a major risk factor for foetal cardiac complications that lead to heart failure. We studied the effects of hyperglycaemia on the layout of cardiac myofilament proteins in stem cell-derived cardiomyocytes and their possible underlying mechanisms. Mouse embryonic stem cells (mESCs) were differentiated into cardiac-like cells and cultured in media containing baseline- or high glucose concentrations. Cellular biomarkers were detected using Western blot analysis, immunocytochemistry, 5–ethynyl–2′-deoxyuridine (EdU) cell proliferation assay, and terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) assay. High glucose decreased the proportion of cardiac troponin T and α-actinin 2 positive mESCs as well as disrupted the α-actinin 2 striated pattern and the distribution of the cardiac myosin heavy chain α- and β isoforms. However, there was no alteration of the cellular EdU uptake nor the expression of the receptor of advanced glycation end-product (RAGE). High glucose also increased the presence of the oxidative stress marker nitrotyrosine as well as the number of TUNEL-stained nuclei in cardiac-like cells. Treatment with the antioxidant N-acetyl cysteine decreased the number of TUNEL-stained cells in high glucose and improved the α-actinin 2 striated pattern. Hyperglycaemia negatively impacted the expression and cellular organisation of cardiac myofilament proteins in mESC-derived cardiomyocytes through oxidative stress. The results add further insights into the pathophysiological mechanisms of cardiac contractile dysfunction in diabetic cardiac developmental disease. [ABSTRACT FROM AUTHOR]

Cardiovascular disorders (CAVDs) being a major concern over the past several years due to the huge number of morbidity and mortality worldwide, a number of studies have been done on the various aspects of cardiac problems. One of the various CAVDs is cardiovascular calcification. A number of investigations and research work have been done previously on the molecular mechanism of vascular and heart valve calcification but the mechanism of myocardial and cardiomyocyte calcification has remained uninvestigated. A number of case studies have shown the presence of calcific deposits in the myocardial/ventricular region of the heart in fetal condition as well as in individuals of different ages but no detailed studies have been done yet. In this study, we have mainly investigated the role of Forkhead box transcription factor FoxO1 and nuclear factor of activated T-cells NFATc3 in cardiomyocyte calcification. Our studies in H9c2 cardiomyocytes show that calcific deposition in cardiomyocytes does not occur in 15 d but upon osteogenic induction for 1 mo where FoxO1 expression gets reduced thereby increasing the expression of its downstream target NFATc3, thus increasing the expression of the osteogenic marker Runx2. Detailed studies on the molecular mechanism of cardiomyocyte calcification will help in finding out therapeutic strategies in the treatment of cardiac calcification. [ABSTRACT FROM AUTHOR]

Cell surface glycoproteins, which are good indicators of cellular types and biological function; are suited for cell evaluation. Tissue remodeling using various cells is a key feature of regenerative therapy. For artificial heart remodeling, a mixture of heart constituent cells has been investigated for organ assembly, however, the cellular characteristics remain unclear. In this study, the glycan profiles of human cardiomyocytes (HCMs), human cardiac fibroblasts (HCFs), and human vascular endothelial cells (ECs) were analyzed using evanescent-field lectin microarray analysis, a tool of glycan profiling, to clarify the required cellular characteristics. We found that ECs had more "α1-2fucose" and "core α1-6fucose" residues than other cells, and that "α2-6sialic acid" residue was more abundant in ECs and HCMs than in HCFs. HCFs showed higher abundance of "β-galactose" and "β-N-acetylgalactosamine" residues on N-glycan and O-glycan, respectively, compared to other cells. Interestingly, cardiac glycan profiles were insignificantly changed with cellular senescence. The residues identified in this study may participate in organ maintenance by contributing to the preservation of glycan components. Therefore, future studies should investigate the roles of glycans in optimal tissue remodeling since identifying cellular characteristics is important for the development of regenerative therapies. [ABSTRACT FROM AUTHOR]

Abstract—Homeodomain transcription factors play a significant role in mesenchymal stromal cells (MSCs). Previously, the role of Meis1, Pbx1 and Prep1 proteins from the TALE (Three Amino acid Loop Extension) family in adipocytic and osteogenic differentiation of mouse mesenchymal stromal cells was established. In this work, using ChIP-seq and bioinformatic analysis we investigated the binding pattern of PREP1 with the genomic DNA of human heart MSCs, identified nearby genes, and analyzed their ontology. The target genes of the PREP1 factor in cardiac MSCs have been established. Based on the results, the possible involvement of transcription factor PREP1 in the direct reprogramming of fibroblasts into cardiomyocytes is discussed. [ABSTRACT FROM AUTHOR]