Calcium cycling proteins and heart failure: mechanisms and therapeutics

FGF13 deficiency ameliorates calcium signaling abnormality in heart failure by regulating microtubule stability

Calcium signaling abnormality in cardiomyocytes, as a key mechanism, is closely associated with developing heart failure. Fibroblast growth factor 13 (FGF13) demonstrates important regulatory roles in the heart, but its association with cardiac calcium signaling in heart failure remains unknown. This study aimed to investigate the role and mechanism of FGF13 on calcium mishandling in heart failure. Mice underwent transaortic constriction to establish a heart failure model, which showed decreased ejection fraction, fractional shortening, and contractility. FGF13 deficiency alleviated cardiac dysfunction. Heart failure reduces calcium transients in cardiomyocytes, which were alleviated by FGF13 deficiency. Meanwhile, FGF13 deficiency restored decreased Cav1.2 and Serca2α expression and activity in heart failure. Furthermore, FGF13 interacted with microtubules in the heart, and FGF13 deficiency inhibited the increase of microtubule stability during heart failure. Finally, in isoproterenol-stimulated FGF13 knockdown neonatal rat ventricular myocytes (NRVMs), wildtype FGF13 overexpression, but not FGF13 mutant, which lost the binding site of microtubules, promoted calcium transient abnormality aggravation and Cav1.2 downregulation compared with FGF13 knockdown group. Generally, FGF13 deficiency improves abnormal calcium signaling by inhibiting the increased microtubule stability in heart failure, indicating the important role of FGF13 in cardiac calcium homeostasis and providing new avenues for heart failure prevention and treatment.

Global Proteomic Analysis Reveals Alterations in Differentially Expressed Proteins between Cardiopathic Lamin A/C Mutations

Lamin A/C (LMNA) is an important component of nuclear lamina. Mutations cause arrhythmia, heart failure, and sudden cardiac death. While LMNA-associated cardiomyopathy typically has an aggressive course that responds poorly to conventional heart failure therapies, there is variability in severity and age of penetrance between and even within specific mutations, which is poorly understood at the cellular level. Further, this heterogeneity has not previously been captured to mimic the heterozygous state, nor have the hundreds of clinical LMNA mutations been represented. Herein, we have overexpressed cardiopathic LMNA variants in HEK cells and utilized state-of-the-art quantitative proteomics to compare the global proteomic profiles of (1) aggregating Q353 K alone, (2) Q353 K coexpressed with WT, (3) aggregating N195 K coexpressed with WT, and (4) nonaggregating E317 K coexpressed with WT to help capture some of the heterogeneity between mutations. We analyzed each data set to obtain the differentially expressed proteins (DEPs) and applied gene ontology (GO) and KEGG pathway analyses. We found a range of 162 to 324 DEPs from over 6000 total protein IDs with differences in GO terms, KEGG pathways, and DEPs important in cardiac function, further highlighting the complexity of cardiac laminopathies. Pathways disrupted by LMNA mutations were validated with redox, autophagy, and apoptosis functional assays in both HEK 293 cells and in induced pluripotent stem cell derived cardiomyocytes (iPSC-CMs) for LMNA N195 K. These proteomic profiles expand our repertoire for mutation-specific downstream cellular effects that may become useful as druggable targets for personalized medicine approach for cardiac laminopathies.

RyR2 Stabilizer Attenuates Cardiac Hypertrophy by Downregulating TNF-α/NF-κB/NLRP3 Signaling Pathway through Inhibiting Calcineurin

The effect of Ryanodine receptor2 (RyR2) and its stabilizer on cardiac hypertrophy is not well known. C57/BL6 mice underwent transverse aortic contraction (TAC) or sham surgery were administered dantrolene, the RyR2 stabilizer, or control drug. Dantrolene significantly alleviated TAC-induced cardiac hypertrophy in mice, and RNA sequencing was performed implying calcineurin/NFAT3 and TNF-α/NF-κB/NLRP3 as critical signaling pathways. Further expression analysis and Western blot with heart tissue as well as neonatal rat cardiomyocyte (NRCM) model confirmed dantrolene decreases the activation of calcineurin/NFAT3 signaling pathway and TNF-α/NF-κB/NLRP3 signaling pathway, which was similar to FK506 and might be attenuated by calcineurin overexpression. The present study shows for the first time that RyR2 stabilizer dantrolene attenuates cardiac hypertrophy by inhibiting the calcineurin, therefore downregulating the TNF-α/NF-κB/NLRP3 pathway.

Compound SJ-12 attenuates streptozocin-induced diabetic cardiomyopathy by stabilizing SERCA2a

Heart failure (HF) is one of the major causes of death among diabetic patients. Although studies have shown that curcumin analog C66 can remarkably relieve diabetes-associated cardiovascular and kidney complications, the role of SJ-12, SJ-12, a novel curcumin analog, in diabetic cardiomyopathy and its molecular targets are unknown. 7-week-old male C57BL/6 mice were intraperitoneally injected with single streptozotocin (STZ) (160 mg/kg) to develop diabetic cardiomyopathy (DCM). The diabetic mice were then treated with SJ-12 via gavage for two months. Body weight, fast blood glucose, cardiac utrasonography, myocardial injury markers, pathological morphology of the heart, hypertrophic and fibrotic markers were assessed. The potential target of SJ-12 was evaluated via RNA-sequencing analysis. The O-GlcNAcylation levels of SP1 were detected via immunoprecipitation. SJ-12 effectively suppressed myocardial hypertrophy and fibrosis, thereby preventing heart dysfunction in mice with STZ-induced heart failure. RNA-sequencing analysis revealed that SJ-12 exerted its therapeutic effects through the modulation of the calcium signaling pathway. Furthermore, SJ-12 reduced the O-GlcNAcylation levels of SP1 by inhibiting O-linked N-acetylglucosamine transferase (OGT). Also, SJ-12 stabilized Sarcoplasmic/Endoplasmic Reticulum Calcium ATPase 2a (SERCA2a), a crucial regulator of calcium homeostasis, thus reducing hypertrophy and fibrosis in mouse hearts and cultured cardiomyocytes. However, the anti-fibrotic effects of SJ-12 were not detected in SERCA2a or OGT-silenced cardiomyocytes, indicating that SJ-12 can prevent DCM by targeting OGT-dependent O-GlcNAcylation of SP1.These findings indicate that SJ-12 can exert cardioprotective effects in STZ-induced mice by reducing the O-GlcNAcylation levels of SP1, thus stabilizing SERCA2a and reducing myocardial fibrosis and hypertrophy. Therefore, SJ-12 can be used for the treatment of diabetic cardiomyopathy.

Proteomic and cardiac dysregulation by representative perfluoroalkyl acids of different chemical speciation during early embryogenesis of zebrafish

Perfluoroalkyl acids (PFAAs) of different chemical speciation were previously found to cause diverse toxicity. However, the toxicological mechanisms depending on chemical speciation are still largely unknown. In this follow-up study, zebrafish embryos were acutely exposed to only one concentration at 4.67 μM of the acid and salt of representative PFAAs, including perfluorooctanoic acid (PFOA), perfluorobutane carboxylic acid (PFBA), and perfluorobutanesulfonic acid (PFBS), till 96 h post-fertilization (hpf), aiming to gain more mechanistic insights. High-throughput proteomics found that PFAA acid and salt exerted discriminative effects on protein expression pattern. Bioinformatic analyses based on differentially expressed proteins underlined the developmental cardiotoxicity of PFOA acid with regard to cardiac muscle contraction, vascular smooth muscle contraction, adrenergic signaling in cardiomyocytes, and multiple terms related to myocardial contraction. PFOA salt and PFBS acid merely disrupted the cardiac muscle contraction pathway, while cardiac muscle cell differentiation was significantly enriched in PFBA acid-exposed zebrafish larvae. Consistently, under PFAA exposure, especially PFOA and PFBS acid forms, transcriptional levels of key genes for cardiogenesis and the concentrations of troponin and epinephrine associated with myocardial contraction were significantly dysregulated. Moreover, a transgenic line Tg (my17: GFP) expressing green fluorescent protein in myocardial cells was employed to visualize the histopathology of developing heart. PFOA acid concurrently caused multiple deficits in heart morphogenesis and function, which were characterized by the significant increase in sinus venosus and bulbus arteriosus distance (SV-BA distance), the induction of pericardial edema, and the decrease in heart rate, further confirming the stronger toxicity of PFOA acid than the salt counterpart on heart development. Overall, this study highlighted the developmental cardiotoxicity of PFAAs, with potency ranking PFOA > PFBS > PFBA. The acid forms of PFAAs induced stronger cardiac toxicity than their salt counterparts, providing an additional insight into the structure-toxicity relationship.

Synthesis and biological evaluation of lycoctonine derivatives with cardiotonic and calcium channels inhibitory activities

In our previous study, a screening of a variety of lycotonine-type diterpenoid alkaloids were screened for cardiotonic activity revealed that lycoctonine had moderate cardiac effect. In this study, a series of structurally diverse of lycoctonine were synthesized by modifying on B-ring, D-ring, E-ring, F-ring, N-atom or salt formation on lycoctonine skeleton. We evaluated the cardiotonic activity of the derivatives by isolated frog heart, aiming to identify some compounds with significantly enhanced cardiac effects, among which compound 27 with a N-isobutyl group emerged as the most promising cardiotonic candidate. Furthermore, the cardiotonic mechanism of compound 27 was preliminarily investigated. The result suggested that the cardiotonic effect of compound 27 is related to calcium channels. Patch clamp technique confirmed that the compound 27 had inhibitory effects on CaV1.2 and CaV3.2, with inhibition rates of 78.52 % ± 2.26 % and 79.05 % ± 1.59 % at the concentration of 50 μM, respectively. Subsequently, the protective effect of 27 on H9c2 cells injury induced by cobalt chloride was tested. In addition, compound 27 can alleviate CoCl2-induced myocardial injury by alleviating calcium overload. These findings suggest that compound 27 was a new structural derived from lycoctonine, which may serve as a new lead compound for the treatment of heart failure.

Effect of photobiomodulation on alleviating primary dysmenorrhea caused by PGF2α

Photobiomodulation (PBM) has attracted widespread attention in suppressing various pain and inflammation. Primary dysmenorrhea (PD) primarily occurs in adolescents and adult females, and the limited effectiveness and side effects of conventional treatments have highlighted the urgent need to develop and identify new adjunct therapeutic strategies. In this work, the results of pain and PGs demonstrated that 850 nm, 630 nm, and 460 nm all exhibited pain inhibition, decreased PGF2α and upregulated PGE2, while 630 nm PBM has better effectiveness. Then to explore the underlying biological mechanisms of red light PBM on PD, we irradiated prostaglandin-F2α induced HUSM cells and found that low-level irradiance can restore intracellular calcium ion, ROS, ATP, and MMP levels to normal levels. And, red light enhanced cell viability and promoted cell proliferation for normal HUSM cells. Therefore, this study proposes that red light PBM may be a promising approach for the future clinical treatment of PD.

Synchronous force and Ca2+ measurements for repeated characterization of excitation-contraction coupling in human myocardium

Dysfunctional Ca2+ signaling affects the myocardial systole and diastole, may trigger arrhythmia and cause transcriptomic and proteomic modifications in heart failure. Thus, synchronous real-time measurement of Ca2+ and force is essential to investigate the relationship between contractility and Ca2+ signaling and the alteration of excitation-contraction coupling (ECC) in human failing myocardium. Here, we present a method for synchronized acquisition of intracellular Ca2+ and contraction force in long-term cultivated slices of human failing myocardium. Synchronous time series of contraction force and intracellular Ca2+ were used to calculate force-calcium loops and to analyze the dynamic alterations of ECC in response to various pacing frequencies, post-pause potentiation, high mechanical preload and pharmacological interventions in human failing myocardium. We provide an approach to simultaneously and repeatedly investigate alterations of contractility and Ca2+ signals in long-term cultured myocardium, which will allow detecting the effects of electrophysiological or pharmacological interventions on human myocardial ECC.

Current Approaches to Worsening Heart Failure: Pathophysiological and Molecular Insights

Worsening heart failure (WHF) is a severe and dynamic condition characterized by significant clinical and hemodynamic deterioration. It is characterized by worsening HF signs, symptoms and biomarkers, despite the achievement of an optimized medical therapy. It remains a significant challenge in cardiology, as it evolves into advanced and end-stage HF. The hyperactivation of the neurohormonal, adrenergic and renin-angiotensin-aldosterone system are well known pathophysiological pathways involved in HF. Several drugs have been developed to inhibit the latter, resulting in an improvement in life expectancy. Nevertheless, patients are exposed to a residual risk of adverse events, and the exploration of new molecular pathways and therapeutic targets is required. This review explores the current landscape of WHF, highlighting the complexities and factors contributing to this critical condition. Most recent medical advances have introduced cutting-edge pharmacological agents, such as guanylate cyclase stimulators and myosin activators. Regarding device-based therapies, invasive pulmonary pressure measurement and cardiac contractility modulation have emerged as promising tools to increase the quality of life and reduce hospitalizations due to HF exacerbations. Recent innovations in terms of WHF management emphasize the need for a multifaceted and patient-centric approach to address the complex HF syndrome.

Association of vectorcardiographic T-wave area with clinical and echocardiographic outcomes in cardiac resynchronization therapy

AIMS

Data on repolarization parameters in cardiac resynchronization therapy (CRT) are scarce. We investigated the association of baseline T-wave area, with both clinical and echocardiographic outcomes of CRT in a large, multi-centre cohort of CRT recipients. Also, we evaluated the association between the baseline T-wave area and QRS area.

METHODS AND RESULTS

In this retrospective study, 1355 consecutive CRT recipients were evaluated. Pre-implantation T-wave and QRS area were calculated from vectorcardiograms. Echocardiographic response was defined as a reduction of ≥15% in left ventricular end-systolic volume between 3 and 12 months after implantation. The clinical outcome was a combination of all-cause mortality, heart transplantation, and left ventricular assist device implantation. Left ventricular end-systolic volume reduction was largest in patients with QRS area ≥ 109 μVs and T-wave area ≥ 66 μVs compared with QRS area ≥ 109 μVs and T-wave area < 66 μVs (P = 0.004), QRS area < 109 μVs and T-wave area ≥ 66 μVs (P < 0.001) and QRS area < 109 μVs and T-wave area < 66 μVs (P < 0.001). Event-free survival rate was higher in the subgroup of patients with QRS area ≥ 109 μVs and T-wave area ≥ 66 μVs (n = 616, P < 0.001) and QRS area ≥ 109 μVs and T-wave area < 66 μVs (n = 100, P < 0.001) than the other subgroups. In the multivariate analysis, T-wave area remained associated with echocardiographic response (P = 0.008), but not with the clinical outcome (P = 0.143), when QRS area was included in the model.

CONCLUSION

Baseline T-wave area has a significant association with both clinical and echocardiographic outcomes after CRT. The association of T-wave area with echocardiographic response is independent from QRS area; the association with clinical outcome, however, is not.

Systolic heart failure induced by butylparaben in zebrafish is caused through oxidative stress and immunosuppression

Due to Butylparaben (BuP) widespread application in cosmetics, food, pharmaceuticals, and its presence as an environmental residue, human and animal exposure to BuP is common, potentially posing hazards to both human and animal health. Congenital heart disease is already a serious problem. However, the effects of BuP on the developing heart and its underlying mechanisms remain unclear. Here, zebrafish embryos were exposed to environmentally and human-relevant concentrations of BuP (0.6 mg/L, 1.2 mg/L, and 1.8 mg/L, calculated but not measured) at 6 h post-fertilization (hpf) and were treated until 72 hpf. Exposure to BuP led to cardiac morphological defects and cardiac dysfunction in zebrafish embryos, manifesting symptoms similar to systolic heart failure. The etiology of BuP-induced systolic heart failure in zebrafish embryos is multifactorial, including cardiomyocyte apoptosis, endocardial and atrioventricular valve damage, insufficient myocardial energy, impaired Ca2+ homeostasis, depletion of cardiac-resident macrophages, cardiac immune non-responsiveness, and cardiac oxidative stress. However, excessive accumulation of reactive oxygen species (ROS) in the cardiac region and cardiac immunosuppression (depletion of cardiac-resident macrophages and cardiac immune non-responsiveness) may be the predominant factors. In conclusion, this study indicates that BuP is a potential hazardous substance that can cause adverse effects on the developing heart and provides evidence and insights into the pathological mechanisms by which BuP leads to cardiac dysfunction. It may help to prevent the BuP-based congenital heart disease heart failure in human through ameliorating strategies and BuP discharge policies, while raising awareness to prevent the misuse of preservatives.

New drug discovery of cardiac anti-arrhythmic drugs: insights in animal models

Cardiac rhythm regulated by micro-macroscopic structures of heart. Pacemaker abnormalities or disruptions in electrical conduction, lead to arrhythmic disorders may be benign, typical, threatening, ultimately fatal, occurs in clinical practice, patients on digitalis, anaesthesia or acute myocardial infarction. Both traditional and genetic animal models are: In-vitro: Isolated ventricular Myocytes, Guinea pig papillary muscles, Patch-Clamp Experiments, Porcine Atrial Myocytes, Guinea pig ventricular myocytes, Guinea pig papillary muscle: action potential and refractory period, Langendorff technique, Arrhythmia by acetylcholine or potassium. Acquired arrhythmia disorders: Transverse Aortic Constriction, Myocardial Ischemia, Complete Heart Block and AV Node Ablation, Chronic Tachypacing, Inflammation, Metabolic and Drug-Induced Arrhythmia. In-Vivo: Chemically induced arrhythmia: Aconitine antagonism, Digoxin-induced arrhythmia, Strophanthin/ouabain-induced arrhythmia, Adrenaline-induced arrhythmia, and Calcium-induced arrhythmia. Electrically induced arrhythmia: Ventricular fibrillation electrical threshold, Arrhythmia through programmed electrical stimulation, sudden coronary death in dogs, Exercise ventricular fibrillation. Genetic Arrhythmia: Channelopathies, Calcium Release Deficiency Syndrome, Long QT Syndrome, Short QT Syndrome, Brugada Syndrome. Genetic with Structural Heart Disease: Arrhythmogenic Right Ventricular Cardiomyopathy/Dysplasia, Dilated Cardiomyopathy, Hypertrophic Cardiomyopathy, Atrial Fibrillation, Sick Sinus Syndrome, Atrioventricular Block, Preexcitation Syndrome. Arrhythmia in Pluripotent Stem Cell Cardiomyocytes. Conclusion: Both traditional and genetic, experimental models of cardiac arrhythmias' characteristics and significance help in development of new antiarrhythmic drugs.

Mitochondrial Calcium Overload Plays a Causal Role in Oxidative Stress in the Failing Heart

Heart failure is a serious global health challenge, affecting more than 6.2 million people in the United States and is projected to reach over 8 million by 2030. Independent of etiology, failing hearts share common features, including defective calcium (Ca2+) handling, mitochondrial Ca2+ overload, and oxidative stress. In cardiomyocytes, Ca2+ not only regulates excitation-contraction coupling, but also mitochondrial metabolism and oxidative stress signaling, thereby controlling the function and actual destiny of the cell. Understanding the mechanisms of mitochondrial Ca2+ uptake and the molecular pathways involved in the regulation of increased mitochondrial Ca2+ influx is an ongoing challenge in order to identify novel therapeutic targets to alleviate the burden of heart failure. In this review, we discuss the mechanisms underlying altered mitochondrial Ca2+ handling in heart failure and the potential therapeutic strategies.

Optical Mapping of Cardiomyocytes in Monolayer Derived from Induced Pluripotent Stem Cells

Optical mapping is a powerful imaging technique widely adopted to measure membrane potential changes and intracellular Ca2+ variations in excitable tissues using voltage-sensitive dyes and Ca2+ indicators, respectively. This powerful tool has rapidly become indispensable in the field of cardiac electrophysiology for studying depolarization wave propagation, estimating the conduction velocity of electrical impulses, and measuring Ca2+ dynamics in cardiac cells and tissues. In addition, mapping these electrophysiological parameters is important for understanding cardiac arrhythmia mechanisms. In this review, we delve into the fundamentals of cardiac optical mapping technology and its applications when applied to hiPSC-derived cardiomyocytes and discuss related advantages and challenges. We also provide a detailed description of the processing and analysis of optical mapping data, which is a crucial step in the study of cardiac diseases and arrhythmia mechanisms for extracting and comparing relevant electrophysiological parameters.

Cysteines 1078 and 2991 cross-linking plays a critical role in redox regulation of cardiac ryanodine receptor (RyR)

The most common cardiac pathologies, such as myocardial infarction and heart failure, are associated with oxidative stress. Oxidation of the cardiac ryanodine receptor (RyR2) Ca²⁺ channel causes spontaneous oscillations of intracellular Ca²⁺, resulting in contractile dysfunction and arrhythmias. RyR2 oxidation promotes the formation of disulfide bonds between two cysteines on neighboring RyR2 subunits, known as intersubunit cross-linking. However, the large number of cysteines in RyR2 has been a major hurdle in identifying the specific cysteines involved in this pathology-linked post-translational modification of the channel. Through mutagenesis of human RyR2 and in-cell Ca²⁺ imaging, we identify that only two cysteines (out of 89) in each RyR2 subunit are responsible for half of the channel's functional response to oxidative stress. Our results identify cysteines 1078 and 2991 as a redox-sensitive pair that forms an intersubunit disulfide bond between neighboring RyR2 subunits during oxidative stress, resulting in a pathological "leaky" RyR2 Ca²⁺ channel.

Engineering Alignment Has Mixed Effects on Human Induced Pluripotent Stem Cell Differentiated Cardiomyocyte Maturation

The potential of human induced pluripotent stem cell differentiated cardiomyocytes (hiPSC-CMs) is greatly limited by their functional immaturity. Strong relationships exist between cardiomyocyte (CM) structure and function, leading many in the field to seek ways to mature hiPSC-CMs by culturing on biomimetic substrates, specifically those that promote alignment. However, these in vitro models have so far failed to replicate the alignment that occurs during cardiac differentiation. We show that engineered alignment, incorporated before and during cardiac differentiation, affects hiPSC-CM electrochemical coupling and mitochondrial morphology. We successfully engineer alignment in differentiating human induced pluripotent stem cells (hiPSCs) as early as day 4. We uniquely apply optical redox imaging to monitor the metabolic changes occurring during cardiac differentiation. We couple this modality with cardiac-specific markers, which allows us to assess cardiac metabolism in heterogeneous cell populations. The engineered alignment drives hiPSC-CM differentiation toward the ventricular compact CM subtype and improves electrochemical coupling in the short term, at day 14 of differentiation. Moreover, we observe the glycolysis to oxidative phosphorylation switch throughout differentiation and CM development. On the subcellular scale, we note changes in mitochondrial morphology in the long term, at day 28 of differentiation. Our results demonstrate that cellular alignment accelerates hiPSC-CM maturity and emphasizes the interrelation of structure and function in cardiac development. We anticipate that combining engineered alignment with additional maturation strategies will result in improved development of mature CMs from hiPSCs and strongly improve cardiac tissue engineering.

Safety, Tolerability, and Pharmacokinetics of Recombinant Human Neuregulin-1 in Healthy Chinese Subjects

BACKGROUND

We investigated the safety, tolerability, and pharmacokinetics of intravenous recombinant human Neuregulin-1 (rhNRG-1), a DNA recombinant protein for the treatment of chronic heart failure, in healthy Chinese volunteers following single and multiple dose administration.

METHODS AND RESULTS

To evaluate the safety and tolerance after single-dosing escalation, 28 subjects were divided into six groups (0.2, 0.4, 0.8, 1.2, 1.6, and 2.4 μg/kg) to receive an intravenous (IV) infusion of rhNRG-1 over 10 min by a randomized, open-label design. Only the 1.2 μg/kg dose group obtained pharmacokinetic parameters: C_max was 7.645 (24.21) ng/mL, AUC_0-t was 97.088 (21.41) min·ng/mL. To assess the safety and pharmacokinetics after multiple-dosing, 32 subjects were divided into four groups (0.2, 0.4, 0.8, and 1.2 μg/kg) to receive a 10-min IV infusion of rhNRG-1 for five consecutive days. After multiple dosing of 1.2 μg/kg, the C_max value at day 5 was 8.838 (51.6) ng/mL and the AUC_0-t value at day 5 was 109.890 (32.99) min·ng/mL. RhNRG-1 is rapidly cleared from the blood and has a short t_1/2 of about 10 min. The adverse events related to rhNRG-1 mainly included flat or inverted T wave and gastrointestinal reactions, all of which were mild.

CONCLUSIONS

It is concluded that rhNRG-1 is safe and well tolerated in healthy Chinese subjects at the dosing levels used in this study. The severity and frequency of adverse events did not increase with the prolongation of administration time.

CLINICAL TRIAL REGISTRATION

Chinese Clinical Trial Registry ( http://www.chictr.org.cn ) Identifier No. ChiCTR2000041107.

Proteomics and phosphoproteomics of failing human left ventricle identifies dilated cardiomyopathy-associated phosphorylation of CTNNA3

The prognosis and treatment outcomes of heart failure (HF) patients rely heavily on disease etiology, yet the majority of underlying signaling mechanisms are complex and not fully elucidated. Phosphorylation is a major point of protein regulation with rapid and profound effects on the function and activity of protein networks. Currently, there is a lack of comprehensive proteomic and phosphoproteomic studies examining cardiac tissue from HF patients with either dilated dilated cardiomyopathy (DCM) or ischemic cardiomyopathy (ICM). Here, we used a combined proteomic and phosphoproteomic approach to identify and quantify more than 5,000 total proteins with greater than 13,000 corresponding phosphorylation sites across explanted left ventricle (LV) tissue samples, including HF patients with DCM vs. nonfailing controls (NFC), and left ventricular infarct vs. noninfarct, and periinfarct vs. noninfarct regions of HF patients with ICM. Each pair-wise comparison revealed unique global proteomic and phosphoproteomic profiles with both shared and etiology-specific perturbations. With this approach, we identified a DCM-associated hyperphosphorylation cluster in the cardiomyocyte intercalated disc (ICD) protein, αT-catenin (CTNNA3). We demonstrate using both ex vivo isolated cardiomyocytes and in vivo using an AAV9-mediated overexpression mouse model, that CTNNA3 phosphorylation at these residues plays a key role in maintaining protein localization at the cardiomyocyte ICD to regulate conductance and cell-cell adhesion. Collectively, this integrative proteomic/phosphoproteomic approach identifies region- and etiology-associated signaling pathways in human HF and describes a role for CTNNA3 phosphorylation in the pathophysiology of DCM.

Effects of bisphenols on lipid metabolism and neuro-cardiovascular toxicity in marine medaka larvae

Bisphenols are environmental endocrine disruptors that have detrimental effects on aquatic organisms. Using marine medaka larvae, this study explored the effects of bisphenol compounds [bisphenol A (BPA), bisphenol S (BPS), bisphenol F (BPF), and bisphenol AF (BPAF)] on the early growth and development of aquatic organisms. Marine medaka larvae were exposed to bisphenol compounds at concentrations of 0.05, 0.5, and 5 μM for 72 h, and changes in heartbeat rate, behavior, hormone levels, and gene expression were determined. Bisphenols were shown to have a toxic effect on the cardiovascular system of larvae and can cause neurotoxicity and endocrine disruption, such as changes to thyroid-related hormones. Functional enrichment showed that bisphenols mainly affect lipid metabolism and cardiac muscle contraction of larvae, which implied that the main toxic effects of bisphenols on marine medaka larvae targeted the liver and heart. This study provides a theoretical foundation for evaluating the toxicological effects of bisphenols on the early development of aquatic organisms.

Hydrogen sulfide regulates SERCA2a SUMOylation by S-Sulfhydration of SENP1 to ameliorate cardiac systole-diastole function in diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM) is a serious complication of diabetes mellitus that eventually progresses to heart failure. The sarco(endo)plasmic reticulum calcium ATPase 2a (SERCA2a), an important calcium pump in cardiomyocytes, is closely related to myocardial systolic-diastolic function. In mammalian cells, hydrogen sulfide (H₂S), as a second messenger, antioxidant, and sulfurizing agent, is involved in diverse biological processes. Despite the importance of H₂S for protection against DCM, the mechanisms remain poorly understood. The aim of the present study was to determine whether H₂S regulates intracellular calcium homeostasis by acting on SERCA2a to reduce cardiomyocyte apoptosis during DCM. Db/db mice were injected with NaHS for 18 weeks. Neonatal rat cardiomyocytes (NRCMs) were treated with high glucose, palmitate, oleate, and NaHS for 48 h. Compared to the NaHS-treated groups, in vivo and in vitro type 2 diabetic models both showed reduced intracellular H₂S content, reduced cystathionine γ-lyase (CSE) expression, impaired cardiac function, decreased SERCA2a expression and decreased SERCA2a activity, reduced SUMOylation of SERCA2a, increased sentrin-specific protease 1 (SENP1) expression, and disruption of calcium homeostasis leading to activation of the mitochondrial apoptosis pathway. Compared to the NaHS-treated type 2 diabetes cellular model, overexpression of SENP1 C683A reduced the S-sulfhydration of SENP1, reduced the SUMOylation of SERCA2a, reduced the increased expression and activity of SERCA2a, and induced mitochondrial apoptosis in cardiomyocytes. These results suggested that exogenous H₂S elevates SENP1 S-sulfhydration to increase SERCA2a SUMOylation, improve myocardial systolic-diastolic function, and decrease cardiomyocyte apoptosis in DCM.

Engineered cardiac tissue model of restrictive cardiomyopathy for drug discovery

Restrictive cardiomyopathy (RCM) is defined as increased myocardial stiffness and impaired diastolic relaxation leading to elevated ventricular filling pressures. Human variants in filamin C (FLNC) are linked to a variety of cardiomyopathies, and in this study, we investigate an in-frame deletion (c.7416_7418delGAA, p.Glu2472_Asn2473delinAsp) in a patient with RCM. Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) with this variant display impaired relaxation and reduced calcium kinetics in 2D culture when compared with a CRISPR-Cas9-corrected isogenic control line. Similarly, mutant engineered cardiac tissues (ECTs) demonstrate increased passive tension and impaired relaxation velocity compared with isogenic controls. High-throughput small-molecule screening identifies phosphodiesterase 3 (PDE3) inhibition by trequinsin as a potential therapy to improve cardiomyocyte relaxation in this genotype. Together, these data demonstrate an engineered cardiac tissue model of RCM and establish the translational potential of this precision medicine approach to identify therapeutics targeting myocardial relaxation.

Interaction between A-kinase anchoring protein 5 and protein kinase A mediates CaMKII/HDAC signaling to inhibit cardiomyocyte hypertrophy after hypoxic reoxygenation

We reported that A-kinase anchoring protein 5 (AKAP5) played a role in cardiomyocyte apoptosis after hypoxia-reoxygenation (H/R). The role of AKAP5 in cardiomyocyte hypertrophy has not been fully elucidated. Herein we investigated whether AKAP5 regulates cardiomyocyte hypertrophy through calcium/calmodulin-dependent protein kinase II (CaMKII). After H/R, deficiency of AKAP5 in H9C2 cardiomyocytes and neonatal rat cardiac myocytes activated CaMKII and stimulated cardiomyocyte hypertrophy. AKAP5 upregulation limited this. Low expression of AKAP5 increased CaMKII interaction with histone deacetylases 4/5 (HDAC4/5) and increased nuclear export of HDAC4/5. In addition, AKAP5 interactions with protein kinase A (PKA) and phospholamban (PLN) were diminished. Moreover, the phosphorylation of PLN was decreased, and intracellular calcium increased. Interference of this process with St-Ht31 increased CaMKII signaling, decreased PLN phosphorylation and promoted post-H/R cell hypertrophy. And PKA-anchoring deficient AKAP5ΔPKA could not attenuate hypoxia-reoxygenation-induced cardiomyocyte hypertrophy, but AKAP5 could. Altogether, AKAP5 downregulation exacerbated H/R-induced hypertrophy in cardiomyocytes. This was due to, in part, to less in AKAP5-PKA interaction and the accumulation of intracellular Ca²⁺ with a subsequent increase in CaMKII activity.

USP25 Ameliorates Pathological Cardiac Hypertrophy by Stabilizing SERCA2a in Cardiomyocytes

BACKGROUND

Pathological cardiac hypertrophy can lead to heart failure and is one of the leading causes of death globally. Understanding the molecular mechanism of pathological cardiac hypertrophy will contribute to the treatment of heart failure. DUBs (deubiquitinating enzymes) are essential to cardiac pathophysiology by precisely controlling protein function, localization, and degradation. This study set out to investigate the role and molecular mechanism of a DUB, USP25 (ubiquitin-specific peptidase 25), in pathological cardiac hypertrophy.

METHODS

The role of USP25 in myocardial hypertrophy was evaluated in murine cardiomyocytes in response to Ang II (angiotensin II) and transverse aortic constriction stimulation and in hypertrophic myocardium tissues of heart failure patients. Liquid chromotography with mass spectrometry/mass spectrometry analysis combined with Co-IP was used to identify SERCA2a (sarcoplasmic/endoplasmic reticulum Ca2+-ATPase 2A), an antihypertrophy protein, as an interacting protein of USP25. To clarify the molecular mechanism of USP25 in the regulation of SERCA2a, we constructed a series of mutant plasmids of USP25. In addition, we overexpressed USP25 and SERCA2a in the heart with adenoassociated virus serotype 9 vectors to validate the biological function of USP25 and SERCA2a interaction.

RESULTS

We revealed increased protein level of USP25 in murine cardiomyocytes subject to Ang II and transverse aortic constriction stimulation and in hypertrophic myocardium tissues of patients with heart failure. USP25 deficiency aggravated cardiac hypertrophy and cardiac dysfunction under Ang II and transverse aortic constriction treatment. Mechanistically, USP25 bound to SERCA2a directly via its USP (ubiquitin-specific protease) domain and cysteine at position 178 of USP25 exerts deubiquitination to maintain the stability of the SERCA2a protein by removing the K48 ubiquitin chain and preventing proteasomal pathway degradation, thereby maintaining calcium handling in cardiomyocytes. Moreover, restoration of USP25 expression via adenoassociated virus serotype 9 vectors in USP25^-/- mice attenuated Ang II-induced cardiac hypertrophy and cardiac dysfunction, whereas myocardial overexpression of SERCA2a could mimic the effect of USP25.

CONCLUSIONS

We confirmed that USP25 inhibited cardiac hypertrophy by deubiquitinating and stabilizing SERCA2a.

ABCB5+ mesenchymal stromal cells therapy protects from hypoxia by restoring Ca2+ homeostasis in vitro and in vivo

BACKGROUND

Hypoxia in ischemic disease impairs Ca²⁺ homeostasis and may promote angiogenesis. The therapeutic efficacy of mesenchymal stromal cells (MSCs) in peripheral arterial occlusive disease is well established, yet its influence on cellular Ca²⁺ homeostasis remains to be elucidated. We addressed the influence of ATP-binding cassette subfamily B member 5 positive mesenchymal stromal cells (ABCB5⁺ MSCs) on Ca²⁺ homeostasis in hypoxic human umbilical vein endothelial cells (HUVECs) in vitro and in vivo.

METHODS

Hypoxia was induced in HUVECs by Cobalt (II) chloride (CoCl₂) or Deferoxamine (DFO). Dynamic changes in the cytosolic- and endoplasmic reticulum (ER) Ca²⁺ and changes in reactive oxygen species were assessed by appropriate fluorescence-based sensors. Metabolic activity, cell migration, and tube formation were assessed by standard assays. Acute-on-chronic ischemia in Apolipoprotein E knock-out (ApoE^-/-) mice was performed by double ligation of the right femoral artery (DFLA). ABCB5⁺ MSC cells were injected into the ischemic limb. Functional recovery after DFLA and histology of gastrocnemius and aorta were assessed.

RESULTS

Hypoxia-induced impairment of cytosolic and ER Ca²⁺ were restored by ABCB5⁺ MSCs or their conditioned medium. Similar was found for changes in intracellular ROS production, metabolic activity, migratory ability and tube formation. The restoration was paralleled by an increased expression of the Ca²⁺ transporter Sarco-/endoplasmic reticulum ATPase 2a (SERCA2a) and the phosphorylation of Phospholamban (PLN). In acute-on-chronic ischemia, ABCB5⁺ MSCs treated mice showed a higher microvascular density, increased SERCA2a expression and PLN phosphorylation relative to untreated controls.

CONCLUSIONS

ABCB5⁺ MSCs therapy can restore cellular Ca²⁺ homeostasis, which may beneficially affect the angiogenic function of endothelial cells under hypoxia in vitro and in vivo.

Cardiac-Specific Expression of Cre Recombinase Leads to Age-Related Cardiac Dysfunction Associated with Tumor-like Growth of Atrial Cardiomyocyte and Ventricular Fibrosis and Ferroptosis

Transgenic expression of Cre recombinase driven by a specific promoter is normally used to conditionally knockout a gene in a tissue- or cell-type-specific manner. In αMHC-Cre transgenic mouse model, expression of Cre recombinase is controlled by the myocardial-specific α-myosin heavy chain (αMHC) promoter, which is commonly used to edit myocardial-specific genes. Toxic effects of Cre expression have been reported, including intro-chromosome rearrangements, micronuclei formation and other forms of DNA damage, and cardiomyopathy was observed in cardiac-specific Cre transgenic mice. However, mechanisms associated with Cardiotoxicity of Cre remain poorly understood. In our study, our data unveiled that αMHC-Cre mice developed arrhythmias and died after six months progressively, and none of them survived more than one year. Histopathological examination showed that αMHC-Cre mice had aberrant proliferation of tumor-like tissue in the atrial chamber extended from and vacuolation of ventricular myocytes. Furthermore, the αMHC-Cre mice developed severe cardiac interstitial and perivascular fibrosis, accompanied by significant increase of expression levels of MMP-2 and MMP-9 in the cardiac atrium and ventricular. Moreover, cardiac-specific expression of Cre led to disintegration of the intercalated disc, along with altered proteins expression of the disc and calcium-handling abnormality. Comprehensively, we identified that the ferroptosis signaling pathway is involved in heart failure caused by cardiac-specific expression of Cre, on which oxidative stress results in cytoplasmic vacuole accumulation of lipid peroxidation on the myocardial cell membrane. Taken together, these results revealed that cardiac-specific expression of Cre recombinase can lead to atrial mesenchymal tumor-like growth in the mice, which causes cardiac dysfunction, including cardiac fibrosis, reduction of the intercalated disc and cardiomyocytes ferroptosis at the age older than six months in mice. Our study suggests that αMHC-Cre mouse models are effective in young mice, but not in old mice. Researchers need to be particularly careful when using αMHC-Cre mouse model to interpret those phenotypic impacts of gene responses. As the Cre-associated cardiac pathology matched mostly to that of the patients, the model could also be employed for investigating age-related cardiac dysfunction.

Calcium and Reactive Oxygen Species Signaling Interplays in Cardiac Physiology and Pathologies

Mitochondria are key players in energy production, critical activity for the smooth functioning of energy-demanding organs such as the muscles, brain, and heart. Therefore, dysregulation or alterations in mitochondrial bioenergetics primarily perturb these organs. Within the cell, mitochondria are the major site of reactive oxygen species (ROS) production through the activity of different enzymes since it is one of the organelles with the major availability of oxygen. ROS can act as signaling molecules in a number of different pathways by modulating calcium (Ca²⁺) signaling. Interactions among ROS and calcium signaling can be considered bidirectional, with ROS regulating cellular Ca²⁺ signaling, whereas Ca²⁺ signaling is essential for ROS production. In particular, we will discuss how alterations in the crosstalk between ROS and Ca²⁺ can lead to mitochondrial bioenergetics dysfunctions and the consequent damage to tissues at high energy demand, such as the heart. Changes in Ca²⁺ can induce mitochondrial alterations associated with reduced ATP production and increased production of ROS. These changes in Ca²⁺ levels and ROS generation completely paralyze cardiac contractility. Thus, ROS can hinder the excitation-contraction coupling, inducing arrhythmias, hypertrophy, apoptosis, or necrosis of cardiac cells. These interplays in the cardiovascular system are the focus of this review.

A compartmentalized mathematical model of the β1- and β2-adrenergic signaling systems in ventricular myocytes from mouse in heart failure

Mouse models of heart failure are extensively used to research human cardiovascular diseases. In particular, one of the most common is the mouse model of heart failure resulting from transverse aortic constriction (TAC). Despite this, there are no comprehensive compartmentalized mathematical models that describe the complex behavior of the action potential, [Ca²⁺]_i transients, and their regulation by β₁- and β₂-adrenergic signaling systems in failing mouse myocytes. In this paper, we develop a novel compartmentalized mathematical model of failing mouse ventricular myocytes after TAC procedure. The model describes well the cell geometry, action potentials, [Ca²⁺]_i transients, and β₁- and β₂-adrenergic signaling in the failing cells. Simulation results obtained with the failing cell model are compared with those from the normal ventricular myocytes. Exploration of the model reveals the sarcoplasmic reticulum Ca²⁺ load mechanisms in failing ventricular myocytes. We also show a larger susceptibility of the failing myocytes to early and delayed afterdepolarizations and to a proarrhythmic behavior of Ca²⁺ dynamics upon stimulation with isoproterenol. The mechanisms of the proarrhythmic behavior suppression are investigated and sensitivity analysis is performed. The developed model can explain the existing experimental data on failing mouse ventricular myocytes and make experimentally testable predictions of a failing myocyte's behavior.

The role of subunit cooperativity on ryanodine receptor 2 calcium signaling

The ryanodine receptor type 2 (RyR2) is composed of four subunits that control calcium (Ca) release in cardiac cells. RyR2 serves primarily as a Ca sensor and can respond to rapid sub-millisecond pulses of Ca while remaining shut at resting concentrations. However, it is not known how the four subunits interact for the RyR2 to function as an effective Ca sensor. To address this question, and to understand the role of subunit cooperativity in Ca-mediated signal transduction, we have developed a computational model of the RyR2 composed of four interacting subunits. We first analyze the statistical properties of a single RyR2 tetramer, where each subunit can exist in a closed or open conformation. Our findings indicate that the number of subunits in the open state is a crucial parameter that dictates RyR2 kinetics. We find that three or four open subunits are required for the RyR2 to harness cooperative interactions to respond to sub-millisecond changes in Ca, while at the same time remaining shut at the resting Ca levels in the cardiac cell. If the required number of open subunits is lowered to one or two, the RyR2 cannot serve as a robust Ca sensor, as the large cooperativity required to stabilize the closed state prevents channel activation. Using this four-subunit model, we analyze the kinetics of Ca release from a RyR2 cluster. We show that the closure of a cluster of RyR2 channels is highly sensitive to the balance of cooperative interactions between closed and open subunits. Based on this result, we analyze how specific interactions between RyR2 subunits can induce persistent Ca leak from the sarcoplasmic reticulum (SR), which is believed to be arrhythmogenic. Thus, these results provide a framework to analyze how a pharmacologic or genetic modification of RyR2 subunit cooperativity can induce abnormal Ca cycling that can potentially lead to life-threatening arrhythmias.

Heart Failure And Type 2 Diabetes Mellitus: Neurohumoral, Histological And Molecular Interconnections

Heart failure (HF) is a global healthcare burden and a leading cause of morbidity and mortality worldwide. Type 2 diabetes mellitus (T2DM) appears to be one of the major risk factors that significantly worsen HF prognosis and increase the risk of fatal cardiovascular outcomes. Despite a great knowledge of pathophysiological mechanisms involved in HF development and progression, hospitalization rates in patients with HF and concomitant T2DM remain elevated. In this review, we discuss the complex interplay between systemic neurohumoral regulation and local cardiac mechanisms participating in myocardial remodeling and HF development in T2DM with special attention to cardiomyocyte energy metabolism, mitochondrial function and calcium metabolism, cardiomyocyte hypertrophy and death, extracellular matrix remodeling.

Cardiac-Specific Overexpression of Caveolin-1 in Rats With Ischemic Cardiomyopathy Improves Arrhythmogenicity and Cardiac Remodelling

BACKGROUND

Ischemic cardiomyopathy (ICM) is associated with electrical and structural remodelling, leading to arrhythmias. Caveolin-1 (Cav1) is a membrane protein involved in the pathogenesis of ischemic injury. Cav1 deficiency has been associated with arrhythmogenicity. The current study aimed to determine how Cav1 overexpression inhibits arrhythmias and cardiac remodelling in ICM.

METHODS

ICM was modelled using left anterior descending (LAD) artery ligation for 4 weeks. Cardiac-specific Cav1 overexpression in ICM on arrhythmias, excitation-contraction coupling, and cardiac remodelling were investigated using the intramyocardial injection of an adeno-associated virus serotype 9 (AAV-9) system, carrying a specific sequence expressing Cav1 (AAV^Cav1) under the cardiac troponin T (cTnT) promoter.

RESULTS

Cav1 overexpression decreased susceptibility to arrhythmias by upregulating gap junction connexin 43 (CX43) and reducing spontaneous irregular proarrhythmogenic Ca²⁺ waves in ventricular cardiomyocytes. It also alleviated ischemic injury-induced contractility weakness by improving Ca²⁺ cycling through normalizing Ca²⁺-handling protein levels and improving Ca²⁺ homeostasis. Masson stain and immunoblotting revealed that the deposition of excessive fibrosis was attenuated by Cav1 overexpression, inhibiting the transforming growth factor-β (TGF-β)/Smad2 signalling pathway. Coimmunoprecipitation assays demonstrated that the interaction between Cav1 and cSrc modulated CX43 expression and Ca²⁺-handling protein levels.

CONCLUSIONS

Cardiac-specific overexpression of Cav1 attenuated ventricular arrhythmia, improved Ca²⁺ cycling, and attenuated cardiac remodelling. These effects were attributed to modulation of CX43, normalized Ca²⁺-handling protein levels, improved Ca²⁺ homeostasis, and attenuated cardiac fibrosis.

The interplay between cardiac dyads and mitochondria regulated the calcium handling in cardiomyocytes

Calcium mishandling and mitochondrial dysfunction have been increasingly recognized as significant factors involved in the progression procedure of cardiomyopathy. Ca2+ mishandling could cause calcium-triggered arrhythmias, which could enhance force development and ATP consumption. Mitochondrial disorganization and dysfunction in cardiomyopathy could disturb the balance of energy catabolic and anabolic procedure. Close spatial localization and arrangement of structural among T-tubule, sarcoplasmic reticulum, mitochondria are important for Ca2+ handling. So that, we illustrate the regulating network between calcium handling and mitochondrial homeostasis, as well as its intracellular mechanisms in this review, which would be worthy to develop novel therapeutic strategy and restore the function of injured cardiomyocytes.

Induction of Cardiac Pathology: Endogenous versus Exogenous Nrf2 Upregulation

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a master regulator of the endogenous antioxidant response to reactive oxygen species as well as a controller of Phase II detoxification in response to xenobiotics. This amenity to specific external manipulation exploits the binding affinity of Nrf2 for its constitutive repressor and degradation facilitator Kelch-like erythroid cell-derived protein with CNC homology-associated protein 1 (Keap1). Derived from both natural and synthesized origins, these compounds have been extensively tested without definitive beneficial results. Unfortunately, multiple terminated trials have shown a negative side to Nrf2 with regard to cardiac pathologies while animal-based studies have demonstrated cardiomyocyte hypertrophy and heart failure after chronic Nrf2 upregulation. Putatively based on autophagic control of Nrf2 activity-modulating upstream factors, new evidence of miRNA involvement has added complexity to this mechanism. What follows is an extensive survey of Nrf2-regulating exogenous compounds that may promote cardiomyopathy, clinical trial evidence, and a comparison to exercise-induced factors that also upregulate Nrf2 while preventing cardiac pathologies.

Atrial Fibrillation Burden Specifically Determines Human Ventricular Cellular Remodeling

BACKGROUND

Atrial fibrillation (AF) can either be a consequence or an underlying mechanism of left ventricular systolic dysfunction. Patients included in the CASTLE-AF (Catheter Ablation vs. Standard Conventional Treatment in Patients With LV Dysfunction and AF) trial who suffered from AF and left ventricular systolic dysfunction benefited from an AF burden <50% after catheter ablation compared with those patients with an AF burden >50%.

OBJECTIVES

This analysis tried to explain the clinical findings of the CASTLE-AF trial regarding AF burden in a "back-to-bench" approach.

METHODS

To study the ventricular effects of different AF burdens, experiments were performed using human ventricular induced pluripotent stem cell-derived cardiomyocytes undergoing in vitro AF simulation. Epifluorescence microscopy, action potential measurements, and measurements of sarcomere regularity were conducted.

RESULTS

Induced pluripotent stem cell-derived cardiomyocytes stimulated with AF burden of 60% or higher displayed typical hallmarks of heart failure. Ca²⁺ transient amplitude was significantly reduced indicating negative inotropic effects. Action potential duration was significantly prolonged, which represents a potential trigger for arrhythmias. A significant decrease of sarcomere regularity could explain impaired cardiac contractility in patients with high AF burden. These effects were more pronounced after 7 days of AF simulation compared with 48 hours.

CONCLUSIONS

Significant functional and structural alterations occurred at the cellular level at a threshold of ∼50% AF burden as it was observed to be harmful in the CASTLE-AF trial. Therefore, these translational results may help to understand the findings of the CASTLE-AF trial.

Chai-Hu-San-Shen Capsule Ameliorates Ventricular Arrhythmia Through Inhibition of the CaMKII/FKBP12.6/RyR2/Ca2+ Signaling Pathway in Rats with Myocardial Ischemia

Ventricular arrhythmia is one of the main causes of sudden cardiac death, especially after myocardial ischemia. Previous studies have shown that Chai-Hu-San-Shen capsule (CHSSC) can reduce the incidence of ventricular arrhythmias following myocardial ischemia, however, the mechanisms of it are unclear. In present study, we explored the mechanism of CHSSC ameliorates ventricular arrhythmia following myocardial ischemia via inhibiting the CaMKII/FKBP12.6/RyR2/Ca²⁺ signaling pathway. In vivo, a myocardial ischemia rat model was established and treated with CHSSC to evaluate the therapeutic effect of CHSSC. In vitro, we established an ischemia model in H9C2 cells and treated with CHSSC, KN-93, or H-89. Then, intracellular Ca²⁺ content, the expression of RyR2, and the interaction between FKBP12.6 and RyR2 were detected. The results showed that CHSSC could delay the occurrence of ventricular arrhythmias and shorten the duration of ventricular arrhythmias. After myocardial ischemia, the intracellular Ca²⁺ content was increased, and CHSSC treatment mitigated this increase, down-regulated the levels of p-CaMKII, CaMKII, p-RyR2, and RyR2, and up-regulated the levels of p-RyR2 (Ser2808) and p-RyR2 (Ser2814). Co-immunoprecipitation showed an interaction between FKBP12.6 and RyR2, and CHSSC up-regulated the content of the FKBP12.6-RyR2 complex in ischemic cells. In conclusion, our study showed that CaMKII activation led to hyperphosphorylation of RyR2 (Ser2814) and RyR2 (Ser2808) during cardiomyocyte ischemia, which resulted in dissociation of the FKBP12.6-RyR2 complex, and increased intracellular Ca²⁺ content, which may contribute to the development of ventricular arrhythmias. CHSSC may reduce the incidence of ventricular arrhythmias following myocardial ischemia through inhibition of the CaMKII/RyR2/FKBP12.6/Ca²⁺ signaling pathway.

Ginsenoside Rb3 upregulates sarcoplasmic reticulum Ca2+-ATPase expression and improves the contractility of cardiomyocytes by inhibiting the NF-κB pathway

A causal relationship between ginsenoside Rb3 (G-Rb3) and improved inflammation and cardiac function has not been established. To determine which specific signaling pathways were involved in G-Rb3 improvement of inflammation and myocardial function. In vivo, we found that G-Rb3 decreased the levels of both nuclear factor κB (NF-κB p65) and CD45, an inflammatory marker. G-Rb3 also enhanced key proteins of the contraction unit (cardiac troponin protein I (cTnI) and α-actinin) to improve cardiac function. G-Rb3 inhibited NF-κB p65 nuclear translocation in vitro, as verified by western blot and IF. When NF-κB p65 was overexpressed, a decrease in cyclic nucleotide phosphodiesterase 3B (PDE3B) and SERCA2a expression, while no statistical significance was observed in the expressions of cAMP, PKA, and calcium/calmodulin-dependent protein kinase type II (CaMKⅡ) in each group. The NF-κB p65 plasmid blocked the SERCA2a promoter, as verified by the luciferase reporter system, and G-Rb3 truncated the NF-κB p65 block on the SERCA2a promoter. qPCR was also used to confirm that G-Rb3 increased the mRNA of SERCA2a. In conclusion, we confirmed that the mechanisms of G-Rb3 on ventricular systolic dysfunction causing inflammation are not via the cAMP/PKA pathway, but via suppressing the blockage of NF-κB p65 on the SERCA2a promoter and increasing the SERCA2a expression.

CRISPR/CAS9: A promising approach for the research and treatment of cardiovascular diseases

The development of gene-editing technology has been one of the biggest advances in biomedicine over the past two decades. Not only can it be used as a research tool to build a variety of disease models for the exploration of disease pathogenesis at the genetic level, it can also be used for prevention and treatment. This is done by intervening with the expression of target genes and carrying out precise molecular targeted therapy for diseases. The simple and flexible clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 gene-editing technology overcomes the limitations of zinc finger nucleases (ZFNs) and transcription activator-like effector nucleases (TALENs). For this reason, it has rapidly become a preferred method for gene editing. As a new gene intervention method, CRISPR/Cas9 has been widely used in the clinical treatment of tumours and rare diseases; however, its application in the field of cardiovascular diseases is currently limited. This article reviews the application of the CRISPR/Cas9 editing technology in cardiovascular disease research and treatment, and discusses the limitations and prospects of this technology.

Identification of a long noncoding RNA Gm17501 as a novel negative regulator of cardiac hypertrophy

Pathological cardiac hypertrophy is an independent risk factor for the development of heart failure. Long noncoding RNAs (lncRNAs), an emerging class of non-protein-coding transcripts, are involved in regulation of multiple cardiac diseases through diverse molecular mechanism, whereas the role of cytoplasmic lncRNAs in regulating cardiac hypertrophy remains unclear. In this study, we identified a novel and functional long noncoding RNA Gm17501, which was predominantly expressed in the cytoplasm of cardiomyocytes. The expression level of lncRNA Gm17501 was altered in cardiac hypertrophy induced by pressure overload and phenylephrine treatment. Moreover, lncRNA Gm17501 expression was decreased in the heart tissue of patients with heart failure. Silencing lncRNA Gm17501 aggravated cardiac hypertrophy under pathological stress. Inhibition of lncRNA Gm17501 did not alter the expression of nearby genes but decreased mRNA level of calcium handling proteins which were involved in cardiac contraction. Therefore, the cytoplasmic lncRNA Gm17501 might protect cardiomyocytes against hypertrophy, possibly by maintaining calcium signaling pathway.

Therapeutic Mechanism and Key Active Ingredients of Shenfu Injection in Sepsis: A Network Pharmacology and Molecular Docking Approach

At present, although the early treatment of sepsis is advocated, the treatment effect of sepsis is unsatisfactory, and the mortality rate remains high. Shenfu injection (SFI) has been used to treat sepsis with good clinical efficacy. Based on network pharmacology, this study adopted a new research strategy to identify the potential therapeutic targets and key active ingredients of SFI for sepsis from the perspective of the pathophysiology of sepsis. This analysis identified 28 active ingredients of SFI based on UHPLC-QQQ MS, including 18 ginsenosides and 10 aconite alkaloids. 59 targets were associated with the glycocalyx and sepsis pathways. Based on the number of targets related to the pathophysiological process of sepsis, we identified songorine, ginsenoside Rf, ginsenoside Re, and karacoline as the key active ingredients of SFI for the treatment of sepsis. According to the cluster analysis of MCODE and the validation on the GEO dataset, LGALS3, BCHE, AKT1, and IL2 were identified as the core targets. This study further explored the therapeutic mechanism and the key active ingredients of SFI in sepsis and provided candidate compounds for drug development.

STK25 inhibits PKA signaling by phosphorylating PRKAR1A

In the heart, protein kinase A (PKA) is critical for activating calcium handling and sarcomeric proteins in response to beta-adrenergic stimulation leading to increased myocardial contractility and performance. The catalytic activity of PKA is tightly regulated by regulatory subunits that inhibit the catalytic subunit until released by cAMP binding. Phosphorylation of type II regulatory subunits promotes PKA activation; however, the role of phosphorylation in type I regulatory subunits remain uncertain. Here, we utilize human induced pluripotent stem cell cardiomyocytes (iPSC-CMs) to identify STK25 as a kinase of the type Iα regulatory subunit PRKAR1A. Phosphorylation of PRKAR1A leads to inhibition of PKA kinase activity and increased binding to the catalytic subunit in the presence of cAMP. Stk25 knockout in mice diminishes Prkar1a phosphorylation, increases Pka activity, and augments contractile response to beta-adrenergic stimulation. Together, these data support STK25 as a negative regulator of PKA signaling through phosphorylation of PRKAR1A.

β-Adrenergic Receptor Desensitization/Down-Regulation in Heart Failure: A Friend or Foe?

Cardiac sympathetic activation, mediated by β-adrenergic receptors (β-ARs), normally increases cardiac contraction and relaxation. Accomplishing this task requires a physiological, concerted Ca²⁺ signaling, being able to increase Ca²⁺ release from sarcoplasmic reticulum (SR) in systole and speed up Ca²⁺ re-uptake in diastole. In heart failure (HF) myocardial β-ARs undergo desensitization/down-regulation due to sustained sympathetic adrenergic activation. β-AR desensitization/down-regulation diminishes adrenergic signaling and cardiac contractile reserve, and is conventionally considered to be detrimental in HF progression. Abnormal Ca²⁺ handling, manifested as cardiac ryanodine receptor (RyR2) dysfunction and diastolic Ca²⁺ leak (due to sustained adrenergic activation) also occur in HF. RyR2 dysfunction and Ca²⁺ leak deplete SR Ca²⁺ store, diminish Ca²⁺ release in systole and elevate Ca²⁺ levels in diastole, impairing both systolic and diastolic ventricular function. Moreover, elevated Ca²⁺ levels in diastole promote triggered activity and arrhythmogenesis. In the presence of RyR2 dysfunction and Ca²⁺ leak, further activation of the β-AR signaling in HF would worsen the existing abnormal Ca²⁺ handling, exacerbating not only cardiac dysfunction, but also ventricular arrhythmogenesis and sudden cardiac death. Thus, we conclude that β-AR desensitization/down-regulation may be a self-preserving, adaptive process (acting like an intrinsic β-AR blocker) protecting the failing heart from developing lethal ventricular arrhythmias under conditions of elevated sympathetic drive and catecholamine levels in HF, rather than a conventionally considered detrimental process. This also implies that medications simply enhancing β-AR signaling (like β-AR agonists) may not be so beneficial unless they can also correct dysfunctional Ca²⁺ handling in HF.

Synergistic and Attenuating Effect of Electroacupuncture on Aconitine in Improving Heart Failure and Its Calcium Regulation Mechanism

Objective

The objective is to observe the synergistic and attenuating effect of electroacupuncture (EA) on aconitine (ACO) in improving heart failure (HF) and to explore its underlying mechanism for calcium regulation.

Methods

Twenty-four male Sprague-Dawley rats were randomly divided into four groups: normal control (NC) (n = 6), HF(n = 6), ACO (n = 6), and ACO + EA (n = 6). The maximum rates of left ventricular pressure rising and declining (±dp/dtmax), arrhythmia, the left ventricular systolic pressure (LVSP), ejection fraction (LVEF), and fractional shortening (LVFS) were measured by physiological recorder and ultrasound, respectively. Protein expressions of sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase (SERCA2a), phospholamban (PLB), and Na⁺-Ca²⁺ exchange (NCX1) in the left ventricle tissue were detected by fluorescence immunoblotting.

Results

Compared with the NC group, LVSP, ±dp/dtmax, LVEF, and LVFS were decreased in the HF group; compared with the HF group, LVSP, ±dp/dtmax, LVEF, and LVFS were significantly increased in the ACO + EA group. Compared with the ACO group, the incidence and the degree of arrhythmia were significantly reduced in the ACO + EA group. Compared with the NC group, the activity of SERCA2a was decreased, and the expression of PLB and NCX1 was enhanced in the HF group; compared with the HF group and ACO group, the activity of SERCA2a was increased, and the expression of PLB and NCX1 was significantly attenuated in the ACO + EA group.

Conclusions

EA plays a synergistic and attenuated role in ACO improving HF, and the mechanism may be related to the enhancement of the SERCA2a activity and the decrease of the expression of PLB and NCX1 in cardiomyocytes.

Animal Models to Study Cardiac Arrhythmias

Cardiac arrhythmias are a significant cause of morbidity and mortality worldwide, accounting for 10% to 15% of all deaths. Although most arrhythmias are due to acquired heart disease, inherited channelopathies and cardiomyopathies disproportionately affect children and young adults. Arrhythmogenesis is complex, involving anatomic structure, ion channels and regulatory proteins, and the interplay between cells in the conduction system, cardiomyocytes, fibroblasts, and the immune system. Animal models of arrhythmia are powerful tools for studying not only molecular and cellular mechanism of arrhythmogenesis but also more complex mechanisms at the whole heart level, and for testing therapeutic interventions. This review summarizes basic and clinical arrhythmia mechanisms followed by an in-depth review of published animal models of genetic and acquired arrhythmia disorders.

Moving in the right direction: elucidating the mechanisms of interaction between flecainide and the cardiac ryanodine receptor

Flecainide is used to treat catecholaminergic polymorphic ventricular tachycardia (CPVT), an arrhythmia caused by disrupted cellular Ca²⁺ handling following β-adrenergic stimulation. The clinical efficacy of flecainide in this context involves complex effects on multiple ion channels that may be influenced by the disease state. A compelling narrative has been constructed around flecainide's nonselective block of sarcoplasmic reticulum (SR) lumen-to-cytoplasm Ca²⁺ release through intracellular calcium release channels (RyR2). However, ion fluxes across the SR membrane during heart contraction are bidirectional, and here, we review experimental evidence that flecainide's principal action on RyR2 involves the partial block of ion flow in the cytoplasm-to-lumen direction (i.e., flecainide inhibits RyR2-mediated SR 'countercurrent'). Experimental approaches that could advance new knowledge on the mechanism of RyR2 block by flecainide are proposed. Some impediments to progress in this area, that must be overcome to enable the development of superior drugs to treat CPVT, are also considered.

Targeting calcium-mediated inter-organellar crosstalk in cardiac diseases

INTRODUCTION

Abnormal calcium signaling between organelles such as the sarcoplasmic reticulum (SR), mitochondria and lysosomes is a key feature of heart diseases. Calcium serves as a secondary messenger mediating inter-organellar crosstalk, essential for maintaining the cardiomyocyte function.

AREAS COVERED

This article examines the available literature related to calcium channels and transporters involved in inter-organellar calcium signaling. The SR calcium-release channels ryanodine receptor type-2 (RyR2) and inositol 1,4,5-trisphosphate receptor (IP₃R), and calcium-transporter SR/ER-ATPase 2a (SERCA2a) are illuminated. The roles of mitochondrial voltage-dependent anion channels (VDAC), the mitochondria Ca²⁺ uniporter complex (MCUC), and the lysosomal H⁺/Ca²⁺ exchanger, two pore channels (TPC), and transient receptor potential mucolipin (TRPML) are discussed. Furthermore, recent studies showing calcium-mediated crosstalk between the SR, mitochondria, and lysosomes as well as how this crosstalk is dysregulated in cardiac diseases are placed under the spotlight.

EXPERT OPINION

Enhanced SR calcium release via RyR2 and reduced SR reuptake via SERCA2a, increased VDAC and MCUC-mediated calcium uptake into mitochondria, and enhanced lysosomal calcium-release via lysosomal TPC and TRPML may all contribute to aberrant calcium homeostasis causing heart disease. While mechanisms of this crosstalk need to be studied further, interventions targeting these calcium channels or combinations thereof might represent a promising therapeutic strategy.

Mitochondrial Ca2+ Homeostasis: Emerging Roles and Clinical Significance in Cardiac Remodeling

Mitochondria are the sites of oxidative metabolism in eukaryotes where the metabolites of sugars, fats, and amino acids are oxidized to harvest energy. Notably, mitochondria store Ca²⁺ and work in synergy with organelles such as the endoplasmic reticulum and extracellular matrix to control the dynamic balance of Ca²⁺ concentration in cells. Mitochondria are the vital organelles in heart tissue. Mitochondrial Ca²⁺ homeostasis is particularly important for maintaining the physiological and pathological mechanisms of the heart. Mitochondrial Ca²⁺ homeostasis plays a key role in the regulation of cardiac energy metabolism, mechanisms of death, oxygen free radical production, and autophagy. The imbalance of mitochondrial Ca²⁺ balance is closely associated with cardiac remodeling. The mitochondrial Ca²⁺ uniporter (mtCU) protein complex is responsible for the uptake and release of mitochondrial Ca²⁺ and regulation of Ca²⁺ homeostasis in mitochondria and consequently, in cells. This review summarizes the mechanisms of mitochondrial Ca²⁺ homeostasis in physiological and pathological cardiac remodeling and the regulatory effects of the mitochondrial calcium regulatory complex on cardiac energy metabolism, cell death, and autophagy, and also provides the theoretical basis for mitochondrial Ca²⁺ as a novel target for the treatment of cardiovascular diseases.

Autonomic Regulation of the Goldfish Intact Heart

Autonomic regulation plays a central role in cardiac contractility and excitability in numerous vertebrate species. However, the role of autonomic regulation is less understood in fish physiology. Here, we used Goldfish as a model to explore the role of autonomic regulation. A transmural electrocardiogram recording showed perfusion of the Goldfish heart with isoproterenol increased the spontaneous heart rate, while perfusion with carbamylcholine decreased the spontaneous heart rate. Cardiac action potentials obtained via sharp microelectrodes exhibited the same modifications of the spontaneous heart rate in response to isoproterenol and carbamylcholine. Interestingly, the duration of the cardiac action potentials lengthened in the presence of both isoproterenol and carbamylcholine. To evaluate cardiac contractility, the Goldfish heart was perfused with the Ca²⁺ indicator Rhod-2 and ventricular epicardial Ca²⁺ transients were measured using Pulsed Local Field Fluorescence Microscopy. Following isoproterenol perfusion, the amplitude of the Ca²⁺ transient significantly increased, the half duration of the Ca²⁺ transient shortened, and there was an observable increase in the velocity of the rise time and fall time of the Ca²⁺ transient, all of which are compatible with the shortening of the action potential induced by isoproterenol perfusion. On the other hand, carbamylcholine perfusion significantly reduced the amplitude of the Ca²⁺ transient and increased the half duration of the Ca²⁺ transient. These results are interesting because the effect of carbamylcholine is opposite to what happens in classically used models, such as mouse hearts, and the autonomic regulation of the Goldfish heart is strikingly similar to what has been observed in larger mammalian models resembling humans.

Alterations of sodium-hydrogen exchanger 1 function in response to SGLT2 inhibitors: what is the evidence?

This review summarizes and describes the current evidence addressing how sodium-glucose cotransporter 2 (SGLT2) inhibitors alter the function of sodium-hydrogen exchanger 1 (NHE-1), in association with their protective effects against adverse cardiovascular events. In the heart, SGLT2 inhibitors modulate the function of NHE-1 (either by direct inhibition or indirect attenuation of protein expression), which promotes cardiac contraction and an enhanced energy supply, in association with improved mitochondrial function, reduced inflammation/oxidative/endoplasmic reticulum stress, and attenuated fibrosis and apoptotic/autophagic cell death. The vasodilating effect of SGLT2 inhibitors has also been proposed due to NHE-1 inhibition. Moreover, platelet-expressed NHE-1 might serve as a target for SGLT2 inhibitors, since these drugs and selective NHE-1 inhibitors produce comparable activity against adenosine diphosphate-stimulated platelet activation. Overall, it is promising that the modulation of the functions of NHE-1 on the heart, blood vessels, and platelets may act as a contributing pathway for the cardiovascular benefits of SGLT2 inhibitors in diabetes and heart failure.