Advances in the understanding of excitation-contraction coupling: the pulsing quest for drugs against heart failure and arrhythmias

Proton pump inhibitors and cardiovascular risk: a critical review

Proton pump inhibitors (PPI) are widely used medications for gastrointestinal disorders. Recent research suggests a potential association between long-term PPI use and increased cardiovascular (CV) risk, creating a complex clinical dilemma. This review critically evaluates the current evidence for this association, considering the limitations of observational studies and the lack of definitive confirmation from randomized controlled trials.This review delves into the reported association between PPIs and adverse CV events, examining proposed mechanisms such as drug interactions, electrolyte imbalances induced by PPIs and their potential impact on cardiac and vascular function. Evidence suggests these mechanisms converge, with varying influence depending on patient populations.Clinicians require a risk-benefit analysis for each patient considering their CV risk profile. Alternative gastrointestinal therapies should be explored for high-bleeding risk patients. Medications with lower cytochrome-P450 interaction potential may be preferable among essential PPI users. Elucidating the specific mechanisms by which PPIs might influence CV health, assessing long-term vascular effects and investigating interactions with newer anticoagulant medications are crucial for future research.

Ongoing and Future Clinical Trials of Pharmacotherapy for Heart Failure

Increasing knowledge of the processes leading to heart failure (HF) has allowed significant developments in therapies for HF over the past few decades. Despite the evolution of HF treatment, it still places a large burden on patients and health care systems across the world.We used clinicaltrials.gov to gather information about clinical trials as of August 2023 studying pharmacotherapy for HF. We included interventional trials that were "active, not recruiting", "recruiting", or looking for participants but "not yet recruiting". In total, 119 studies met our criteria of ongoing clinical trials studying novel as well as currently approved HF pharmacotherapies. The major interventions were novel medications/already approved medications for other diseases 29 % (34 trials), sodium-glucose co-transporter inhibitors 21 % (25 trials), angiotensin receptor blocker-neprilysin inhibitors 10 % (12 trials), diuretics 14 % (17 trials) and mineralocorticoid receptor antagonists 5 % (6 trials). Ongoing research will aid in reducing the impact of HF and we summarize clinical trials leading the way to better HF treatment in this review.

Screening for Novel Type 2 Ryanodine Receptor Inhibitors by Endoplasmic Reticulum Ca2+ Monitoring

Type 2 ryanodine receptor (RyR2) is a Ca2+ release channel on the endoplasmic (ER)/sarcoplasmic reticulum that plays a central role in the excitation-contraction coupling in the heart. Hyperactivity of RyR2 has been linked to ventricular arrhythmias in patients with catecholaminergic polymorphic ventricular tachycardia and heart failure, where spontaneous Ca2+ release via hyperactivated RyR2 depolarizes diastolic membrane potential to induce triggered activity. In such cases, drugs that suppress RyR2 activity are expected to prevent the arrhythmias, but there is no clinically available RyR2 inhibitors at present. In this study, we searched for RyR2 inhibitors from a well-characterized compound library using a recently developed ER Ca2+-based assay, where the inhibition of RyR2 activity was detected by the increase in ER Ca2+ signals from R-CEPIA1er, a genetically encoded ER Ca2+ indicator, in RyR2-expressing HEK293 cells. By screening 1535 compounds in the library, we identified three compounds (chloroxylenol, methyl orsellinate, and riluzole) that greatly increased the ER Ca2+ signal. All of the three compounds suppressed spontaneous Ca2+ oscillations in RyR2-expressing HEK293 cells and correspondingly reduced the Ca2+-dependent [3H]ryanodine binding activity. In cardiomyocytes from RyR2-mutant mice, the three compounds effectively suppressed abnormal Ca2+ waves without substantial effects on the action-potential-induced Ca2+ transients. These results confirm that ER Ca2+-based screening is useful for identifying modulators of ER Ca2+ release channels and suggest that RyR2 inhibitors have potential to be developed as a new category of antiarrhythmic drugs. SIGNIFICANCE STATEMENT: We successfully identified three compounds having RyR2 inhibitory action from a well-characterized compound library using an endoplasmic reticulum Ca2+-based assay, and demonstrated that these compounds suppressed arrhythmogenic Ca2+ wave generation without substantially affecting physiological action-potential induced Ca2+ transients in cardiomyocytes. This study will facilitate the development of RyR2-specific inhibitors as a potential new class of drugs for life-threatening arrhythmias induced by hyperactivation of RyR2.

In Vivo Pharmacokinetic and Pharmacodynamic Properties of the Antiarrhythmic Molecule ent-Verticilide

The unnatural verticilide enantiomer (ent-verticilide) is a selective and potent inhibitor of cardiac ryanodine receptor (RyR2) calcium release channels and exhibits antiarrhythmic activity in a murine model of catecholaminergic polymorphic ventricular tachycardia (CPVT). To determine verticilide's pharmacokinetic and pharmacodynamic properties in vivo, we developed a bioassay to measure nat- and ent-verticilide in murine plasma and correlated plasma concentrations with antiarrhythmic efficacy in a mouse model of CPVT. nat-Verticilide rapidly degraded in plasma in vitro, showing >95% degradation within 5 minutes, whereas ent-verticilide showed <1% degradation over 6 hours. Plasma was collected from mice following intraperitoneal administration of ent-verticilide at two doses (3 mg/kg, 30 mg/kg). Peak C max and area under the plasma-concentration time curve (AUC) scaled proportionally to dose, and the half-life was 6.9 hours for the 3-mg/kg dose and 6.4 hours for the 30-mg/kg dose. Antiarrhythmic efficacy was examined using a catecholamine challenge protocol at time points ranging from 5 to 1440 minutes after intraperitoneal dosing. ent-Verticilide inhibited ventricular arrhythmias as early as 7 minutes after administration in a concentration-dependent manner, with an estimated potency (IC50) of 266 ng/ml (312 nM) and an estimated maximum inhibitory effect of 93.5%. Unlike the US Food and Drug Administration-approved pan-RyR blocker dantrolene, the RyR2-selective blocker ent-verticilide (30 mg/kg) did not reduce skeletal muscle strength in vivo. We conclude that ent-verticilide has favorable pharmacokinetic properties and reduces ventricular arrhythmias with an estimated potency in the nanomolar range, warranting further drug development. SIGNIFICANCE STATEMENT: ent-Verticilide has therapeutic potential to treat cardiac arrhythmias, but little is known about its pharmacological profile in vivo. The primary purpose of this study is to determine the systemic exposure and pharmacokinetics of ent-verticilide in mice and estimate its efficacy and potency in vivo. The current work suggests ent-verticilide has favorable pharmacokinetic properties and reduces ventricular arrhythmias with an estimated potency in the nanomolar range, warranting further drug development.

Pharmacological mechanism of natural drugs and their active ingredients in the treatment of arrhythmia via calcium channel regulation

Arrhythmia is characterized by abnormal heartbeat rhythms and frequencies caused by heart pacing and conduction dysfunction. Arrhythmia is the leading cause of death in patients with cardiovascular disease, with high morbidity and mortality rates, posing a serious risk to human health. Natural drugs and their active ingredients, such as matrine(MAT), tetrandrine(TET), dehydroevodiamine, tanshinone IIA, and ginsenosides, have been widely used for the treatment of atrial fibrillation, ventricular ectopic beats, sick sinus syndrome, and other arrhythmia-like diseases owing to their unique advantages. This review summarizes the mechanism of action of natural drugs and their active ingredients in the treatment of arrhythmia via the regulation of Ca²⁺, such as alkaloids, quinones, saponins, terpenoids, flavonoids, polyphenols, and lignan compounds, to provide ideas for the innovative development of natural drugs with potential antiarrhythmic efficacy.

Efficacy of the New Inotropic Agent Istaroxime in Acute Heart Failure

Current therapeutic strategies for acute heart failure (AHF) are based on traditional inotropic agents that are often associated with untoward effects; therefore, finding new effective approaches with a safer profile is dramatically needed. Istaroxime is a novel compound, chemically unrelated to cardiac glycosides, that is currently being studied for the treatment of AHF. Its effects are essentially related to its inotropic and lusitropic positive properties exerted through a dual mechanism of action: activation of the sarcoplasmic reticulum Ca2+ ATPase isoform 2a (SERCA2a) and inhibition of the Na+/K+-ATPase (NKA) activity. The advantages of istaroxime over the available inotropic agents include its lower arrhythmogenic action combined with its capability of increasing systolic blood pressure without augmenting heart rate. However, it has a limited half-life (1 hour) and is associated with adverse effects including pain at the injection site and gastrointestinal issues. Herein, we describe the main mechanism of action of istaroxime and we present a systematic overview of both clinical and preclinical trials testing this drug, underlining the latest insights regarding its adoption in clinical practice for AHF.

Bioengineering Strategies to Create 3D Cardiac Constructs from Human Induced Pluripotent Stem Cells

Human induced pluripotent stem cells (hiPSCs) can be used to generate various cell types in the human body. Hence, hiPSC-derived cardiomyocytes (hiPSC-CMs) represent a significant cell source for disease modeling, drug testing, and regenerative medicine. The immaturity of hiPSC-CMs in two-dimensional (2D) culture limit their applications. Cardiac tissue engineering provides a new promise for both basic and clinical research. Advanced bioengineered cardiac in vitro models can create contractile structures that serve as exquisite in vitro heart microtissues for drug testing and disease modeling, thereby promoting the identification of better treatments for cardiovascular disorders. In this review, we will introduce recent advances of bioengineering technologies to produce in vitro cardiac tissues derived from hiPSCs.

Glycation of ryanodine receptor in circulating lymphocytes predicts the response to cardiac resynchronization therapy

Finding reliable parameters to identify patients with heart failure (HF) that will respond to cardiac resynchronization therapy (CRT) represents a major challenge. We and others have observed post-translational modifications of Ryanodine Receptor (RyR) in several tissues (including skeletal muscle and circulating lymphocytes) of patients with advanced HF. We designed a prospective study to test the hypothesis that RyR1 glycation in circulating lymphocytes could predict CRT responsiveness in patients with non-ischemic HF. We enrolled 94 patients who underwent CRT and 30 individuals without HF, examining RyR1 glycation in peripheral lymphocytes at enrollment and after 1 year. We found that baseline RyR1 glycation independently predicts CRT response at 1 year after adjusting for age, diabetes, QRS duration and morphology, echocardiographic dyssynchrony, and hypertension. Moreover, RyR1 glycation in circulating lymphocytes significantly correlated with pathologic intracellular calcium leak. Taken together, our data show for the first time that RyR1 glycation in circulating lymphocytes represents a novel biomarker to predict CRT responsiveness.

Unilateral Acute Renal Ischemia-Reperfusion Injury Induces Cardiac Dysfunction through Intracellular Calcium Mishandling

Background: Acute renal failure (ARF) following renal ischemia-reperfusion (I/R) injury is considered a relevant risk factor for cardiac damage, but the underlying mechanisms, particularly those triggered at cardiomyocyte level, are unknown. Methods: We examined intracellular Ca²⁺ dynamics in adult ventricular cardiomyocytes isolated from C57BL/6 mice 7 or 15 days following unilateral renal I/R. Results: After 7 days of I/R, the cell contraction was significantly lower in cardiomyocytes compared to sham-treated mice. It was accompanied by a significant decrease in both systolic Ca²⁺ transients and sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA_2a) activity measured as Ca²⁺ transients decay. Moreover, the incidence of pro-arrhythmic events, measured as the number of Ca²⁺ sparks, waves or automatic Ca²⁺ transients, was greater in cardiomyocytes from mice 7 days after I/R than from sham-treated mice. Ca²⁺ mishandling related to systolic Ca²⁺ transients and contraction were recovered to sham values 15 days after I/R, but Ca²⁺ sparks frequency and arrhythmic events remained elevated. Conclusions: Renal I/R injury causes a cardiomyocyte Ca²⁺ cycle dysfunction at medium (contraction-relaxation dysfunction) and long term (Ca²⁺ leak), after 7 and 15 days of renal reperfusion, respectively.

IP3 receptor orchestrates maladaptive vascular responses in heart failure

Patients with heart failure (HF) have augmented vascular tone, which increases cardiac workload, impairing ventricular output and promoting further myocardial dysfunction. The molecular mechanisms underlying the maladaptive vascular responses observed in HF are not fully understood. Vascular smooth muscle cells (VSMCs) control vasoconstriction via a Ca2+-dependent process, in which the type 1 inositol 1,4,5-trisphosphate receptor (IP3R1) on the sarcoplasmic reticulum (SR) plays a major role. To dissect the mechanistic contribution of intracellular Ca2+ release to the increased vascular tone observed in HF, we analyzed the remodeling of IP3R1 in aortic tissues from patients with HF and from controls. VSMC IP3R1 channels from patients with HF and HF mice were hyperphosphorylated by both serine and tyrosine kinases. VSMCs isolated from IP3R1VSMC-/- mice exhibited blunted Ca2+ responses to angiotensin II (ATII) and norepinephrine compared with control VSMCs. IP3R1VSMC-/- mice displayed significantly reduced responses to ATII, both in vivo and ex vivo. HF IP3R1VSMC-/- mice developed significantly less afterload compared with HF IP3R1fl/fl mice and exhibited significantly attenuated progression toward decompensated HF and reduced interstitial fibrosis. Ca2+-dependent phosphorylation of the MLC by MLCK activated VSMC contraction. MLC phosphorylation was markedly increased in VSMCs from patients with HF and HF mice but reduced in VSMCs from HF IP3R1VSMC-/- mice and HF WT mice treated with ML-7. Taken together, our data indicate that VSMC IP3R1 is a major effector of increased vascular tone, which contributes to increased cardiac afterload and decompensation in HF.

Calcium Spark Detection and Event-Based Classification of Single Cardiomyocyte Using Deep Learning

Ca²⁺ sparks are the elementary Ca²⁺ release events in cardiomyocytes, altered properties of which lead to impaired Ca²⁺ handling and finally contribute to cardiac pathology under various diseases. Despite increasing use of machine-learning algorithms in deciphering the content of biological and medical data, Ca²⁺ spark images and data are yet to be deeply learnt and analyzed. In the present study, we developed a deep residual convolutional neural network method to detect Ca²⁺ sparks. Compared to traditional detection methods with arbitrarily defined thresholds to distinguish signals from noises, our new method detected more Ca²⁺ sparks with lower amplitudes but similar spatiotemporal distributions, thereby indicating that our new algorithm detected many very weak events that are usually omitted when using traditional detection methods. Furthermore, we proposed an event-based logistic regression and binary classification model to classify single cardiomyocytes using Ca²⁺ spark characteristics, which to date have generally been used only for simple statistical analyses and comparison between normal and diseased groups. Using this new detection algorithm and classification model, we succeeded in distinguishing wild type (WT) vs RyR2-R2474S^± cardiomyocytes with 100% accuracy, and vehicle vs isoprenaline-insulted WT cardiomyocytes with 95.6% accuracy. The model can be extended to judge whether a small number of cardiomyocytes (and so the whole heart) are under a specific cardiac disease. Thus, this study provides a novel and powerful approach for the research and application of calcium signaling in cardiac diseases.

Ion Channel Impairment and Myofilament Ca2+ Sensitization: Two Parallel Mechanisms Underlying Arrhythmogenesis in Hypertrophic Cardiomyopathy

Life-threatening ventricular arrhythmias are the main clinical burden in patients with hypertrophic cardiomyopathy (HCM), and frequently occur in young patients with mild structural disease. While massive hypertrophy, fibrosis and microvascular ischemia are the main mechanisms underlying sustained reentry-based ventricular arrhythmias in advanced HCM, cardiomyocyte-based functional arrhythmogenic mechanisms are likely prevalent at earlier stages of the disease. In this review, we will describe studies conducted in human surgical samples from HCM patients, transgenic animal models and human cultured cell lines derived from induced pluripotent stem cells. Current pieces of evidence concur to attribute the increased risk of ventricular arrhythmias in early HCM to different cellular mechanisms. The increase of late sodium current and L-type calcium current is an early observation in HCM, which follows post-translation channel modifications and increases the occurrence of early and delayed afterdepolarizations. Increased myofilament Ca²⁺ sensitivity, commonly observed in HCM, may promote afterdepolarizations and reentry arrhythmias with direct mechanisms. Decrease of K⁺-currents due to transcriptional regulation occurs in the advanced disease and contributes to reducing the repolarization-reserve and increasing the early afterdepolarizations (EADs). The presented evidence supports the idea that patients with early-stage HCM should be considered and managed as subjects with an acquired channelopathy rather than with a structural cardiac disease.