Cardiac ion channels

KCNIP2: A key regulator in cardiac electrophysiology and tumorigenesis

KCNIP2 (Kv Channel Interacting Protein 2), a regulatory protein of potassium channels, has been the focus of research in the context of cardiac electrophysiology and cardiac diseases. Recent studies have revealed that KCNIP2 expression has a significant impact on tumourigenesis. This review discusses the structure and function of KCNIP2, its involvement in cardiac electrical activity, and recent advancements in understanding its role in cardiac diseases, including myocardial hypertrophy, heart failure, and arrhythmias.It also reviews recent research on KCNIP2's role in tumors, offering insights into the molecular mechanisms underlying.

Autoimmune cardiac channelopathies and heart rhythm disorders: A contemporary review

Cardiac arrhythmias still represent a major health problem worldwide, at least in part because the fundamental pathogenic mechanisms are not fully understood, thus affecting the efficacy of therapeutic measures. In fact, whereas cardiac arrhythmias are in most cases due to structural heart diseases, the underlying cause remains elusive in a significant number of patients despite intensive investigations even including postmortem examination and molecular autopsy. A large body of data progressively accumulated during the last decade provides strong evidence that autoimmune mechanisms may be involved in a significant number of such unexplained or poorly explained cardiac arrhythmias. Several proarrhythmic anti-cardiac ion channel autoantibodies have been discovered, in all cases able to directly interfere with the electrophysiologic properties of the heart but leading to different arrhythmic phenotypes, including long QT syndrome, short QT syndrome, and atrioventricular block. These autoantibodies, which may develop independent of a history of autoimmune diseases, could help explain a percentage of arrhythmic events of unknown origin, thereby opening new frontiers for diagnosis and treatment of heart rhythm disorders. Based on this evidence, the novel term autoimmune cardiac channelopathies was coined in 2017. Since then, the interest in the field of cardioimmunology has shown a tumultuous growth, so much so that the number of arrhythmogenic anti-ion channel autoantibodies reported has significantly increased, also in association with not previously described arrhythmic phenotypes, such as atrial fibrillation, Brugada syndrome, and ventricular fibrillation/cardiac arrest. Thus, an updated reassessment of this topic, also highlighting perspectives and unmet needs, has become necessary and represents the main objective of this review.

One poison center's experience with "snake" firework ingestions

INTRODUCTION

"Snake" fireworks are a type of pyrotechnic device that, when ignited, burn and transform into a friable, snake-like structure. The inclusion of barium salts produces a green flame. Ingestion of these fireworks poses a risk of barium toxicity, which may result in hypokalemia, weakness, dysrhythmias, and respiratory distress.

METHODS

We evaluated firework-related cases at a single poison center between 2009 and 2023 and extracted those pertaining to snake fireworks. Cases were eligible for analysis if oral exposure was suspected or confirmed. Cases were excluded if there was no oral exposure, the missing firework was located after the initial call, or there was no longitudinal follow up after a suspected or witnessed exposure (that is, premature case closure). Pertinent details related to the exposure or those associated with barium toxicity were extracted and evaluated in a descriptive fashion.

RESULTS

Sixty-four cases met inclusion criteria. No deaths, dysrhythmias, weakness, or respiratory compromise were reported. All six children (9.3%) who were symptomatic had gastrointestinal complaints at initial contact with our poison center. Only two symptomatic patients had hypokalemia with the minimum serum potassium concentrations falling to 3.4 mmol/L and 2.1 mmol/L. Four additional patients developed mild hypokalemia (lowest 3.0 mmol/L) but no symptoms. The maximal latency after exposure until nadir potassium concentration was 8 h.

DISCUSSION

Oral exposures to snake fireworks occasionally resulted in mild symptomatic toxicity. The presence of symptoms did not appear to predict whether hypokalemia would develop. In the instances in which hypokalemia was present, or there was a notable downtrend in the serum potassium concentration, the repletion of potassium usually did not correlate with the extent of rebound.

CONCLUSION

In our case series, most children who had oral exposure to snake fireworks in an exploratory setting did not develop symptoms. Although severe toxicity reassuringly did not occur in our review, evaluation and monitoring are nevertheless prudent for symptomatic children.

Dysregulation of N-terminal acetylation causes cardiac arrhythmia and cardiomyopathy

N-terminal acetyltransferases including NAA10 catalyze N-terminal acetylation, an evolutionarily conserved co- and post-translational modification. However, little is known about the role of N-terminal acetylation in cardiac homeostasis. To gain insight into cardiac-dependent NAA10 function, we studied a previously unidentified NAA10 variant p.(Arg4Ser) segregating with QT-prolongation, cardiomyopathy, and developmental delay in a large kindred. Here, we show that the NAA10R4S variant reduced enzymatic activity, decreased NAA10-NAA15 complex formation, and destabilized the enzymatic complex N-terminal acetyltransferase A. In NAA10R4S/Y-induced pluripotent stem-cell-derived cardiomyocytes (iPSC-CMs), dysregulation of the late sodium and slow delayed rectifier potassium currents caused severe repolarization abnormalities, consistent with clinical QT prolongation. Engineered heart tissues generated from NAA10R4S/Y-iPSC-CMs had significantly decreased contractile force and sarcomeric disorganization, consistent with the pedigree's cardiomyopathic phenotype. Proteomic studies revealed dysregulation of metabolic pathways and cardiac structural proteins. We identified small molecule and genetic therapies that normalized the phenotype of NAA10R4S/Y-iPSC-CMs. Our study defines the roles of N-terminal acetylation in cardiac regulation and delineates mechanisms underlying QT prolongation, arrhythmia, and cardiomyopathy caused by NAA10 dysfunction.

Effect of dapagliflozin, a sodium-glucose co-transporter 2 inhibitor, on ventricular repolarization electrocardiographic parameters in type 2 diabetes patients: DAPA - ECG study

Background

Type 2 diabetes (T2DM) is a chronic metabolic disorder that affects approximately 10.5% of the world's population and is an independent risk factor for cardiovascular complications, including sudden cardiac death (SCD). Inhibitors of sodium-glucose co-transporter type 2 (iSGLT2), particularly dapagliflozin, have emerged as promising treatments in patients with T2DM and with heart failure and chronic kidney disease, demonstrating the ability to significantly reduce major cardiovascular events. However, the exact mechanisms that promote the observed benefits are still not fully understood.

Objective

In this study, we sought to understand the mechanisms associated with the benefits of dapagliflozin by evaluating various electrophysiological parameters of the electrocardiogram (ECG) in patients with T2DM. A randomized, multicenter, prospective study with 174 patients with T2DM divided into two groups: one receiving dapagliflozin plus optimized guideline directed medical therapy (GDMT) and the other optimized GDMT without SGLT2 inhibitors. Clinical, electrocardiographic, laboratory, and echocardiographic evaluations were performed initially and after three months. Descriptive and inferential statistics were used, with a significance level of 0.05.

Result

This study shows that in patients treated with dapagliflozin plus GDMT, a significant reduction in the duration of the interval from the peak of the T wave to the end of the T wave (TpTe), the QTc interval, and the ratio between the TpTe/QT intervals was observed, with no change in other electrocardiographic variables such as QT interval dispersion, JT peak interval, or changes in the QRS complex and T wave axes (QRS-T angle).

Conclusion

In patients with T2DM, dapagliflozin significantly shortened the TpTe and QTc intervals, as well as the TpTe/QT ratio. These results suggest a reduction in ventricular electrical remodeling, highlighting a potential cardioprotective effect of dapagliflozin.

Clinical trial registration

https://clinicaltrials.gov/study/NCT06721442, identifier NCT06721442.

Biomimetic Approaches in the Development of Optimised 3D Culture Environments for Drug Discovery in Cardiac Disease

Cardiovascular disease remains the leading cause of death worldwide, yet despite massive investment in drug discovery, the progress of cardiovascular drugs from lab to clinic remains slow. It is a complex, costly pathway from drug discovery to the clinic and failure becomes more expensive as a drug progresses along this pathway. The focus has begun to shift to optimisation of in vitro culture methodologies, not only because these must be undertaken are earlier on in the drug discovery pathway, but also because the principles of the 3Rs have become embedded in national and international legislation and regulation. Numerous studies have shown myocyte cell behaviour to be much more physiologically relevant in 3D culture compared to 2D culture, highlighting the advantages of using 3D-based models, whether microfluidic or otherwise, for preclinical drug screening. This review aims to provide an overview of the challenges in cardiovascular drug discovery, the limitations of traditional routes, and the successes in the field of preclinical models for cardiovascular drug discovery. It focuses on the particular role biomimicry can play, but also the challenges around implementation within commercial drug discovery.

Review of electrophysiological models to study membrane potential changes in breast cancer cell transformation and tumor progression

The transformation of normal breast cells into cancerous cells is a complex process influenced by both genetic and microenvironmental factors. Recent studies highlight the significant role of membrane potential (Vm) alterations in this transformation. Cancer cells typically exhibit a depolarized resting membrane potential (RMP) compared to normal cells, which correlates with increased cellular activity and more aggressive cancer behavior. These RMP and Vm changes are associated with altered ion channel activity, altered calcium dynamics, mitochondrial dysfunction, modified gap junction communication, and disrupted signaling pathways. Such fluctuations in RMP and Vm influence key processes in cancer progression, including cell proliferation, migration, and invasion. Notably, more aggressive subtypes of breast cancer cells display more frequent and pronounced Vm fluctuations. Understanding the electrical properties of cancer cells provides new insights into their behavior and offers potential therapeutic targets, such as ion channels and Vm regulation. This review synthesizes current research on how various factors modulate membrane potential and proposes an electrophysiological model of breast cancer cells based on experimental and clinical data from the literature. These findings may pave the way for novel pharmacological targets for clinicians, researchers, and pharmacologists in treating breast cancer.

Optical control of cardiac electrophysiology by the photochromic ligand azobupivacaine 2

BACKGROUND AND PURPOSE

Patients suffering from ischaemic heart disease and heart failure are at high risk of recurrent ventricular arrhythmias (VAs), eventually leading to sudden cardiac death. While high-voltage shocks delivered by an implantable defibrillator may prevent sudden cardiac death, these interventions themselves impair quality of life and raise both morbidity and mortality, which accentuates the need for developing novel defibrillation techniques.

EXPERIMENTAL APPROACH

Photopharmacology allows for reversible control of biological processes by light. When relying on synthetic and externally applied chromophores, it renders genetic modification of target cells dispensable and may hence be advantageous over optogenetic approaches. Here, the photochromic ligand azobupivacaine 2 (AB2) was probed as a modulator of cardiac electrophysiology in an ex vivo intact mouse heart model.

KEY RESULTS

By reversibly blocking voltage-gated Na+ and K+ channels, photoswitching of AB2 modulated both the ventricular effective refractory period and the conduction velocity in native heart tissue. Moreover, photoswitching of AB2 was able to convert VA into sinus rhythm.

CONCLUSION AND IMPLICATIONS

The present study provides the first proof of concept that AB2 enables gradual control of cardiac electrophysiology by light. AB2 may hence open the door to the development of an optical defibrillator based on photopharmacology.

Cardiomyocytes in Hypoxia: Cellular Responses and Implications for Cell-Based Cardiac Regenerative Therapies

Myocardial infarction (MI) is a severe hypoxic event, resulting in the loss of up to one billion cardiomyocytes (CMs). Due to the limited intrinsic regenerative capacity of the heart, cell-based regenerative therapies, which feature the implantation of stem cell-derived cardiomyocytes (SC-CMs) into the infarcted myocardium, are being developed with the goal of restoring lost muscle mass, re-engineering cardiac contractility, and preventing the progression of MI into heart failure (HF). However, such cell-based therapies are challenged by their susceptibility to oxidative stress in the ischemic environment of the infarcted heart. To maximize the therapeutic benefits of cell-based approaches, a better understanding of the heart environment at the cellular, tissue, and organ level throughout MI is imperative. This review provides a comprehensive summary of the cardiac pathophysiology occurring during and after MI, as well as how these changes define the cardiac environment to which cell-based cardiac regenerative therapies are delivered. This understanding is then leveraged to frame how cell culture treatments may be employed to enhance SC-CMs' hypoxia resistance. In this way, we synthesize both the complex experience of SC-CMs upon implantation and the engineering techniques that can be utilized to develop robust SC-CMs for the clinical translation of cell-based cardiac therapies.

Multifaceted Actions of Neurosteroids

Background and purpose

Neurosteroids modulate neuronal function and are promising therapeutic agents for neuropsychiatric disorders. Neurosteroid analogues are approved for treating postpartum depression and are of interest in other disorders. GABA-A receptors are well characterized targets of natural neurosteroids, but other biological pathways are likely relevant to therapeutic mechanisms and/or to off-target effects. We performed hypothesis-generating in silico analyses and broad in vitro biological screens to assess the range of actions of neurosteroids analogues of varying structural attributes.

Key Results

We employed in silico molecular similarity analysis and network pharmacology to elucidate likely targets. This analysis confirmed likely targets beyond GABA-A receptors. We then functionally screened 19 distinct neurosteroid structures across 78 targets representing interconnected signaling pathways, complemented with a limited screen of kinase activation. Results revealed unanticipated modulation of targets by neurosteroids with some structural selectivity. Many compounds-initiated androgen receptor translocation with little or no enantioselectivity. Modulation of multiple G-protein receptors was also unexpected.

Conclusions and implications

Neurosteroids are ascendant treatments in neuropsychiatry, but their full spectrum of actions remains unclear. This virtual and biological screening discovery approach opens new vistas for exploring mechanism of neurosteroids analogues. The multifaceted approach provides an unbiased, holistic exploration of the potential effects of neurosteroids across various molecular targets and provides a platform for future validation studies to aid drug discovery.

Differential Inhibition by Cenobamate of Canonical Human Nav1.5 Ion Channels and Several Point Mutants

Cenobamate is a new and highly effective antiseizure compound used for the treatment of adults with focal onset seizures and particularly for epilepsy resistant to other antiepileptic drugs. It acts on multiple targets, as it is a positive allosteric activator of γ-aminobutyric acid type A (GABAA) receptors and an inhibitor of neuronal sodium channels, particularly of the late or persistent Na+ current. We recently evidenced the inhibitory effects of cenobamate on the peak and late current component of the human cardiac isoform hNav1.5. The determined apparent IC50 values of 87.6 µM (peak) and 46.5 µM (late current) are within a clinically relevant range of concentrations (the maximal plasma therapeutic effective concentration for a daily dose of 400 mg in humans is 170 µM). In this study, we built a 3D model of the canonical hNav1.5 channel (UniProt Q14524-1) in open conformation using AlphaFold2, embedded it in a DPPC lipid bilayer, corrected the residue protonation state (pH 7.2) with H++, and added 2 Na+ ions in the selectivity filter. By molecular docking, we found the cenobamate binding site in the central cavity. We identified 10-point mutant variants in the binding site region and explored them via docking and MD. Mutants N1462K/Y (rs1064795922, rs199473614) and M1765R (rs752476527) (by docking) and N932S (rs2061582195) (by MD) featured higher predicted affinity than wild-type.

External low energy electromagnetic fields affect heart dynamics: surrogate for system synchronization, chaos control and cancer patient's health

All cells in the human body, including cancer cells, possess specific electrical properties crucial for their functions. These properties are notably different between normal and cancerous cells. Cancer cells are characterized by autonomous oscillations and damped electromagnetic field (EMF) activation. Cancer reduces physiological variability, implying a systemic disconnection that desynchronizes bodily systems and their inherent random processes. The dynamics of heart rate, in this context, could reflect global physiological network instability in the sense of entrainment. Using a medical device that employs an active closed-loop system, such as administering specifically modulated EMF frequencies at targeted intervals and at low energies, we can evaluate the periodic oscillations of the heart. This procedure serves as a closed-loop control mechanism leading to a temporary alteration in plasma membrane ionic flow and the heart's periodic oscillation dynamics. The understanding of this phenomenon is supported by computer simulations of a mathematical model, which are validated by experimental data. Heart dynamics can be quantified using difference logistic equations, and it correlates with improved overall survival rates in cancer patients.

Fine particulate matter‑induced cardiac developmental toxicity (Review)

Fine particulate matter (PM2.5) has become an important risk factor threatening human health. Epidemiological and toxicological investigations have revealed that PM2.5 not only leads to cardiovascular dysfunction, but it also gives rise to various adverse health effects on the human body, such as cardiovascular and cerebrovascular diseases, cancers, neurodevelopmental disorders, depression and autism. PM2.5 is able to penetrate both respiratory and placental barriers, thereby resulting in negative effects on fetal development. A large body of epidemiological evidences has suggested that gestational exposure to PM2.5 increases the incidence of congenital diseases in offspring, including congenital heart defects. In addition, animal model studies have revealed that gestational exposure to PM2.5 can disrupt normal heart development in offspring, although the potential molecular mechanisms have yet to be fully elucidated. The aim of the present review was to provide a brief overview of what is currently known regarding the molecular mechanisms underlying cardiac developmental toxicity in offspring induced by gestational exposure to PM2.5.

Pediatric flecainide pharmacogenomics: a roadmap to delivering precision-based care to pediatrics arrhythmias

Flecainide acetate is a Class 1c anti-arrhythmic with a potent sodium voltage gated channel blockade which is utilized for the second-line treatment of tachyarrhythmias in children and adults. Given its narrow therapeutic index, the individualization of drug therapy is of utmost importance for clinicians. Despite efforts to improve anti-arrhythmic drug therapy, there remain knowledge gaps regarding the impact of variation in the genes relevant to flecainide's disposition and response. This variability is compounded in developing children whose drug disposition and response pathways may remain immature. The purpose of this comprehensive review is to outline flecainide's disposition and response pathways while simultaneously highlighting opportunities for prospective investigation in the pediatric population.

Mechanistic Relevance of Ventricular Arrhythmias in Heart Failure with Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is increasing at an alarming rate worldwide, with limited effective therapeutic interventions in patients. Sudden cardiac death (SCD) and ventricular arrhythmias present substantial risks for the prognosis of these patients. Obesity is a risk factor for HFpEF and life-threatening arrhythmias. Obesity and its associated metabolic dysregulation, leading to metabolic syndrome, are an epidemic that poses a significant public health problem. More than one-third of the world population is overweight or obese, leading to an enhanced risk of incidence and mortality due to cardiovascular disease (CVD). Obesity predisposes patients to atrial fibrillation and ventricular and supraventricular arrhythmias-conditions that are caused by dysfunction in the electrical activity of the heart. To date, current therapeutic options for the cardiomyopathy of obesity are limited, suggesting that there is considerable room for the development of therapeutic interventions with novel mechanisms of action that will help normalize sinus rhythms in obese patients. Emerging candidates for modulation by obesity are cardiac ion channels and Ca-handling proteins. However, the underlying molecular mechanisms of the impact of obesity on these channels and Ca-handling proteins remain incompletely understood. Obesity is marked by the accumulation of adipose tissue, which is associated with a variety of adverse adaptations, including dyslipidemia (or abnormal systemic levels of free fatty acids), increased secretion of proinflammatory cytokines, fibrosis, hyperglycemia, and insulin resistance, which cause electrical remodeling and, thus, predispose patients to arrhythmias. Furthermore, adipose tissue is also associated with the accumulation of subcutaneous and visceral fat, which is marked by distinct signaling mechanisms. Thus, there may also be functional differences in the effects of the regional distribution of fat deposits on ion channel/Ca-handling protein expression. Evaluating alterations in their functional expression in obesity will lead to progress in the knowledge of the mechanisms responsible for obesity-related arrhythmias. These advances are likely to reveal new targets for pharmacological modulation. Understanding how obesity and related mechanisms lead to cardiac electrical remodeling is likely to have a significant medical and economic impact. Nevertheless, substantial knowledge gaps remain regarding HFpEF treatment, requiring further investigations to identify potential therapeutic targets. The objective of this study is to review cardiac ion channel/Ca-handling protein remodeling in the predisposition to metabolic HFpEF and arrhythmias. This review further highlights interleukin-6 (IL-6) as a potential target, cardiac bridging integrator 1 (cBIN1) as a promising gene therapy agent, and leukotriene B4 (LTB4) as an underappreciated pathway in future HFpEF management.

Identifying sex similarities and differences in structure and function of the sinoatrial node in the mouse heart

Background

The sinoatrial node (SN) generates the heart rate (HR). Its spontaneous activity is regulated by a complex interplay between the modulation by the autonomic nervous system (ANS) and intrinsic factors including ion channels in SN cells. However, the systemic and intrinsic regulatory mechanisms are still poorly understood. This study aimed to elucidate the sex-specific differences in heart morphology and SN function, particularly focusing on basal HR, expression and function of hyperpolarization-activated HCN4 and HCN1 channels and mRNA abundance of ion channels and mRNA abundance of ion channels contributing to diastolic depolarization (DD) and spontaneous action potentials (APs).

Methods

Body weight, heart weight and tibia length of 2- to 3-month-old male and female mice were measured. Conscious in-vivo HR of male and female mice was recorded via electrocardiography (ECG). Unconscious ex-vivo HR, stroke volume (SV) and ejection fraction (EF) were recorded via echocardiography. Ex-vivo HR was measured via Langendorff apparatus. Volume of atria, ventricles and whole hearts were measured from the ex-vivo hearts by microcomputed tomography (micro-CT). Immunohistochemistry targeting HCN4 and HCN1 was conducted in the SN and RA tissues from both male and female hearts. The funny current (I f) of SN cells in 1 nM and following wash-on of 1 μM isoproterenol (ISO) were recorded via whole cell patch clamp. The APs of SN tissue were recorded via sharp microelectrode and optical mapping of membrane voltage. The relative abundance of mRNAs was measured in male and female mice by qPCR.

Results

Heart weight to tibia length ratio and heart volume of females were significantly smaller than males. Unconscious in-vivo HR in male mice was higher than that in females. Conscious in-vivo HR, ex-vivo HR, SV, and EF showed no notable difference between male and female mice. Immunohistochemistry revealed HCN4, HCN1, and the sum of HCN4 and HCN1, expression in the SN was notably elevated compared with the RA in both male and females, but there was no sex difference in these channels expression. There were also no significant sex differences in the V 0.5 of I f in SN cells in the presence of 1 nM ISO, however wash-on 1 μM ISO in the same cells induced a significantly increased shift of V 0.5 to more positive voltages in males than in females. The expression of mRNA coding for adrenergic receptor beta-1 (Adrb1) and cholinergic receptors muscarinic 2 (chrm2) in male mice was higher compared with that in female mice. Early diastolic depolarization (EDD) rate in APs from peripheral SN (pSN) from male mice were higher than these in female mice. Mice of both sexes showed equivalent frequency of SN APs and spatial localization of the leading site in control, and similar significant response to ISO 100 nM superfusion.

Conclusion

Males display faster in-vivo HR, but not ex-vivo HR, than females associated with increased expression of Adrb1 in male versus female. This suggests a possible difference in the β-adrenergic modulation in males and females, possibly related to the greater ISO response of I f observed in cells from males. The role of hormonal influences or differential expression of other ion channels may explain these sex-specific variations in HR dynamics. Further investigations are necessary to pinpoint the precise molecular substrates responsible for these differences.

The endocannabinoid ARA-S facilitates the activation of cardiac Kv7.1/KCNE1 channels from different species

The endogenous endocannabinoid-like compound N-arachidonoyl-L-serine (ARA-S) facilitates activation of the human Kv7.1/KCNE1 channel and shortens a prolonged action potential duration and QT interval in guinea pig hearts. Hence, ARA-S is interesting to study further in cardiac models to explore the functional impact of such Kv7.1/KCNE1-mediated effects. To guide which animal models would be suitable for assessing ARA-S effects, and to aid interpretation of findings in different experimental models, it is useful to know whether Kv7.1/KCNE1 channels from relevant species respond similarly to ARA-S. To this end, we used the two-electrode voltage clamp technique to compare the effects of ARA-S on Kv7.1/KCNE1 channels from guinea pig, rabbit, and human Kv7.1/KCNE1, when expressed in Xenopus laevis oocytes. We found that the activation of Kv7.1/KCNE1 channels from all tested species was facilitated by ARA-S, seen as a concentration-dependent shift in the voltage-dependence of channel opening and increase in current amplitude and conductance over a broad voltage range. The rabbit channel displayed quantitatively similar effects as the human channel, whereas the guinea pig channel responded with more prominent increase in current amplitude and maximal conductance. This study suggests that rabbit and guinea pig models are both suitable for studying ARA-S effects mediated via Kv7.1/KCNE1.

Data-Driven Insights into the Association Between Oxidative Stress and Calcium-Regulating Proteins in Cardiovascular Disease

A growing body of biomedical literature suggests a bidirectional regulatory relationship between cardiac calcium (Ca2+)-regulating proteins and reactive oxygen species (ROS) that is integral to the pathogenesis of various cardiac disorders via oxidative stress (OS) signaling. To address the challenge of finding hidden connections within the growing volume of biomedical research, we developed a data science pipeline for efficient data extraction, transformation, and loading. Employing the CaseOLAP (Context-Aware Semantic Analytic Processing) algorithm, our pipeline quantifies interactions between 128 human cardiomyocyte Ca2+-regulating proteins and eight cardiovascular disease (CVD) categories. Our machine-learning analysis of CaseOLAP scores reveals that the molecular interfaces of Ca2+-regulating proteins uniquely associate with cardiac arrhythmias and diseases of the cardiac conduction system, distinguishing them from other CVDs. Additionally, a knowledge graph analysis identified 59 of the 128 Ca2+-regulating proteins as involved in OS-related cardiac diseases, with cardiomyopathy emerging as the predominant category. By leveraging a link prediction algorithm, our research illuminates the interactions between Ca2+-regulating proteins, OS, and CVDs. The insights gained from our study provide a deeper understanding of the molecular interplay between cardiac ROS and Ca2+-regulating proteins in the context of CVDs. Such an understanding is essential for the innovation and development of targeted therapeutic strategies.

QTc Interval: A frequently unrecognized electrocardiographic interval

The QT interval, an electrocardiographic temporal representation of the ventricular depolarization and repolarization, is an integral parameter that must be carefully evaluated to gather critical information regarding electrical instability that may cause malignant ventricular dysrhythmias or sudden cardiac death. The QT interval is affected by several inheritable and acquired factors, such as genetic mutations, electrolyte disturbances, and medication interactions. We strongly believe that prompt and accurate recognition of any QT interval abnormalities is critical in many clinical settings. This concise review article highlights the importance of accurate measurement of the QT interval, enhances understanding of the most prevalent factors yielding abnormalities within the QT interval and the prognostic value of the QT interval, as well as provides several key practical reminders for healthcare professionals to strengthen our clinical practice.

Genetic Code Expansion for Mechanistic Studies in Ion Channels: An (Un)natural Union of Chemistry and Biology

Ion channels play central roles in biology and human health by catalyzing the transmembrane flow of electrical charge. These proteins are ideal targets for genetic code expansion (GCE) methods because it is feasible to measure ion channel activity from miniscule amounts of protein and to analyze the resulting data via rigorous, established biophysical methods. In an ideal scenario, the encoding of synthetic, noncanonical amino acids via GCE allows the experimenter to ask questions inaccessible to traditional methods. For this reason, GCE has been successfully applied to a variety of ligand- and voltage-gated channels wherein extensive structural, functional, and pharmacological data exist. Here, we provide a comprehensive summary of GCE as applied to ion channels. We begin with an overview of the methods used to encode noncanonical amino acids in channels and then describe mechanistic studies wherein GCE was used for photochemistry (cross-linking; caged amino acids) and atomic mutagenesis (isosteric manipulation of charge and aromaticity; backbone mutation). Lastly, we cover recent advances in the encoding of fluorescent amino acids for the real-time study of protein conformational dynamics.

CardioGraph: a platform to study variations associated with familiar cardiopathies

BACKGROUND

Familiar cardiopathies are genetic disorders that affect the heart. Cardiologists face a significant problem when treating patients suffering from these disorders: most DNA variations are novel (i.e., they have not been classified before). To facilitate the analysis of novel variations, we present CardioGraph, a platform specially designed to support the analysis of novel variations and help determine whether they are relevant for diagnosis. To do this, CardioGraph identifies and annotates the consequence of variations and provides contextual information regarding which heart structures, pathways, and biological processes are potentially affected by those variations.

METHODS

We conducted our work through three steps. First, we define a data model to support the representation of the heterogeneous information. Second, we instantiate this data model to integrate and represent all the genomics knowledge available for familiar cardiopathies. In this step, we consider genomic data sources and the scientific literature. Third, the design and implementation of the CardioGraph platform. A three-tier structure was used: the database, the backend, and the frontend.

RESULTS

Three main results were obtained: the data model, the knowledge base generated with the instantiation of the data model, and the platform itself. The platform code has been included as supplemental material in this manuscript. Besides, an instance is publicly available in the following link: https://genomics-hub.pros.dsic.upv.es:3090 .

CONCLUSION

CardioGraph is a platform that supports the analysis of novel variations. Future work will expand the body of knowledge about familiar cardiopathies and include new information about hotspots, functional studies, and previously reported variations.

Dexmedetomidine vs. propofol on arrhythmia in cardiac surgery: a meta-analysis of randomized controlled trials

Background

Dexmedetomidine (DEX) and propofol are popular anesthetics, but it remains unknown whether DEX reduces the incidence of arrhythmias compared with propofol after cardiac surgery.

Methods

We performed a comprehensive search for RCTs (Randomized Controlled Trials) that compared the incidence of arrhythmias between DEX and propofol in adults who had undergone cardiac surgery across three databases (PubMed, Embase, the Cochrane Library), and ClinicalTrials.gov up to October 3, 2023. The primary outcome was ventricular arrhythmias, the secondary outcomes were bradycardia and atrial fibrillation (AF).

Results

Our analysis included 7 RCTs with 1,004 patients (mean age: 64.37, male: 71.11%) undergoing cardiac surgery, and the incidence of in-hospital arrhythmia was 22.01% (ventricular arrhythmias 2.75%, bradycardia 3.33%, AF 18.63%). Perioperative or postoperative use of DEX reduced the incidence of in-hospital ventricular arrhythmias [Odds Ratio (OR) 0.14, 95% Confidence Interval (CI) 0.03-0.66], but increased the risk of in-hospital bradycardia (OR 2.88, 95% CI 1.02-8.17) compared with propofol. The trial sequence analysis verified the adequacy of sample size and robustness of the ventricular arrhythmias and bradycardia. There was no significant reduced incidence of the use of DEX in the incidence of AF (OR 0.69, 95% CI 0.36-1.29). The GRADE assessment indicated a high certainty for ventricular arrhythmias and bradycardia and a moderate certainty for AF.

Conclusions

Our findings suggested the use of DEX reduces in-hospital ventricular arrhythmias but increases bradycardia incidence compared to propofol in adult patients undergoing cardiac surgery. Further studies are needed to assess the impact of dexmedetomidine on atrial fibrillation compared to propofol.

Systematic Review Registration

http://www.crd.york.ac.uk/prospero/ PROSPERO, identifier (CRD42023482193).

FGF4 and ascorbic acid enhance the maturation of induced cardiomyocytes by activating JAK2-STAT3 signaling

Direct cardiac reprogramming represents a novel therapeutic strategy to convert non-cardiac cells such as fibroblasts into cardiomyocytes (CMs). This process involves essential transcription factors, such as Mef2c, Gata4, Tbx5 (MGT), MESP1, and MYOCD (MGTMM). However, the small molecules responsible for inducing immature induced CMs (iCMs) and the signaling mechanisms driving their maturation remain elusive. Our study explored the effects of various small molecules on iCM induction and discovered that the combination of FGF4 and ascorbic acid (FA) enhances CM markers, exhibits organized sarcomere and T-tubule structures, and improves cardiac function. Transcriptome analysis emphasized the importance of ECM-integrin-focal adhesions and the upregulation of the JAK2-STAT3 and TGFB signaling pathways in FA-treated iCMs. Notably, JAK2-STAT3 knockdown affected TGFB signaling and the ECM and downregulated mature CM markers in FA-treated iCMs. Our findings underscore the critical role of the JAK2-STAT3 signaling pathway in activating TGFB signaling and ECM synthesis in directly reprogrammed CMs. Schematic showing FA enhances direct cardiac reprogramming and JAK-STAT3 signaling pathways underlying cardiomyocyte maturation.

Increased interleukin-6 levels are associated with atrioventricular conduction delay in severe COVID-19 patients

Background

Severely ill patients with coronavirus disease 2019 (COVID-19) show an increased risk of new-onset atrioventricular blocks (AVBs), associated with high rates of short-term mortality. Recent data suggest that the uncontrolled inflammatory activation observed in these patients, specifically interleukin (IL)-6 elevation, may play an important pathogenic role by directly affecting cardiac electrophysiology. The aim of our study was to assess the acute impact of IL-6 changes on electrocardiographic indices of atrioventricular conduction in severe COVID-19.

Methods

We investigated (1) the behavior of PR-interval and PR-segment in patients with severe COVID-19 during active phase and recovery, and (2) their association with circulating IL-6 levels over time.

Results

During active disease, COVID-19 patients showed a significant increase of PR-interval and PR-segment. Such atrioventricular delay was transient as these parameters rapidly normalized during recovery. PR-indices significantly correlated with circulating IL-6 levels over time. All these changes and correlations persisted also in the absence of laboratory signs of cardiac strain/injury or concomitant treatment with PR-prolonging drugs, repurposed or not.

Conclusions

Our study provides evidence that in patients with severe COVID-19 and high-grade systemic inflammation, IL-6 elevation is associated with a significant delay of atrioventricular conduction, independent of concomitant confounding factors. While transient, such alterations may enhance the risk of severe AVB and associated short-term mortality. Our data provide further support to current anti-inflammatory strategies for severe COVID-19, including IL-6 antagonists.

Association of same-day urinary phenol levels and cardiac electrical alterations: analysis of the Fernald Community Cohort

BACKGROUND

Exposure to phenols has been linked in animal models and human populations to cardiac function alterations and cardiovascular diseases, although their effects on cardiac electrical properties in humans remains to be established. This study aimed to identify changes in electrocardiographic (ECG) parameters associated with environmental phenol exposure in adults of a midwestern large cohort known as the Fernald Community Cohort (FCC).

METHODS

During the day of the first comprehensive medical examination, urine samples were obtained, and electrocardiograms were recorded. Cross-sectional linear regression analyses were performed.

RESULTS

Bisphenol A (BPA) and bisphenol F (BPF) were both associated with a longer PR interval, an indication of delayed atrial-to-ventricle conduction, in females (p < 0.05) but not males. BPA combined with BPF was associated with an increase QRS duration, an indication of delayed ventricular activation, in females (P < 0.05) but not males. Higher triclocarban (TCC) level was associated with longer QTc interval, an indication of delayed ventricular repolarization, in males (P < 0.01) but not females. Body mass index (BMI) was associated with a significant increase in PR and QTc intervals and ventricular rate in females and in ventricular rate in males. In females, the combined effect of being in the top tertile for both BPA urinary concentration and BMI was an estimate of a 10% increase in PR interval. No associations were found with the other phenols.

CONCLUSION

Higher exposure to some phenols was associated with alterations of cardiac electrical properties in a sex specific manner in the Fernald cohort. Our population-based findings correlate directly with clinically relevant parameters that are associated with known pathophysiologic cardiac conditions in humans.

An Updated Safety Review of the Relationship Between Atypical Antipsychotic Drugs, the QTc Interval and Torsades de Pointe As: Implications for Clinical Use

INTRODUCTION

The rising prevalence of psychiatric disorders has resulted in a significant increase in the use of antipsychotic medications. These agents may prolong the corrected QT interval (QTc), running the risk of precipitating ventricular arrhythmias, notably Torsades de Pointes (TdP). Current recommendations vary regarding the optimal approach to safe prescribing practices and QTc surveillance for antipsychotics. This review summarizes the current literature addressing these clinical concerns.

AREAS COVERED

The physiologic basis of the QTc interval, mechanisms underlying its susceptibility to pharmacological influence, specific risks associated with atypical antipsychotic agents, and recommendations for safe prescription practices. We performed a literature review using Pubmed and Embase databases, searching for 'antipsychotics' and 'torsades de pointes.'

EXPERT OPINION

Finding a safe and universally accepted protocol for prescribing antipsychotics remains a persistent challenge in medicine. Predictive models that integrate clinical history with demographic and ECG characteristics can help estimate an individual's susceptibility to therapy-associated risks, including QTc prolongation. Agents such as ziprasidone and iloperidone are significantly more likely to prolong the QTc interval compared to others such as brexpiprazole, cariprazine, olanzapine, and clozapine. A personalized approach using low-risk medications when clinically feasible, and at the lowest efficacious dose, offers a promising path toward safer antipsychotic prescribing.

Transcriptomic analysis reveals PC4's participation in thermotolerance of scallop Argopecten irradians irradians by regulating myocardial bioelectric activity

Rising ocean temperatures due to global warming pose a significant threat to the bay scallop aquaculture industry. Understanding the mechanisms of thermotolerance in bay scallops is crucial for developing thermotolerant breeds. Our prior research identified Arg0230340.1, part of the positive cofactor 4 (PC4) family, as a key gene associated with the thermotolerance index Arrhenius break temperature (ABT) in bay scallops. Further validation through RNA interference (RNAi) reinforced PC4's role in thermotolerance, offering a solid basis for investigating thermal response mechanisms in these scallops. In this study, we performed a comparative transcriptomic analysis on the temperature-sensitive hearts of bay scallops after siRNA-mediated RNAi targeting Arg0230340.1, to delve into the detailed molecular mechanism of PC4's participation in thermotolerance regulation. The analysis revealed that silencing Arg0230340.1 significantly reduced the expression of mitochondrial tRNA and rRNA, potentially affecting mitochondrial function and the heart's blood supply capacity. Conversely, the up-regulation of genes involved in energy metabolism, RNA polymerase II (RNAPII)-mediated basal transcription, and aminoacyl-tRNA synthesis pathways points to an intrinsic protective response, providing energy and substrates for damage repair and maintenance of essential functions under stress. GO and KEGG enrichment analyses indicated that the up-regulated genes were primarily associated with energy metabolism and spliceosome pathways, likely contributing to myocardial remodeling post-Arg0230340.1 knockdown. Down-regulated genes were enriched in ion channel pathways, particularly those for Na+, K+, and Ca2+ channels, whose dysfunction could disrupt normal myocardial bioelectric activity. The impaired cardiac performance resulting from RNAi targeting Arg0230340.1 reduced the cardiac workload in scallop hearts, thus affecting myocardial oxygen consumption and thermotolerance. We propose a hypothetical mechanism where PC4 down-regulation impairs cardiac bioelectric activity, leading to decreased thermotolerance in bay scallops, providing theoretical guidance for breeding thermotolerant scallop varieties and developing strategies for sustainable aquaculture in the face of long-term environmental changes.

Compartmentalization proteomics revealed endolysosomal protein network changes in a goat model of atrial fibrillation

Endolysosomes (EL) are known for their role in regulating both intracellular trafficking and proteostasis. EL facilitate the elimination of damaged membranes, protein aggregates, membranous organelles and play an important role in calcium signaling. The specific role of EL in cardiac atrial fibrillation (AF) is not well understood. We isolated atrial EL organelles from AF goat biopsies and conducted a comprehensive integrated omics analysis to study the EL-specific proteins and pathways. We also performed electron tomography, protein and enzyme assays on these biopsies. Our results revealed the upregulation of the AMPK pathway and the expression of EL-specific proteins that were not found in whole tissue lysates, including GAA, DYNLRB1, CLTB, SIRT3, CCT2, and muscle-specific HSPB2. We also observed structural anomalies, such as autophagic-vacuole formation, irregularly shaped mitochondria, and glycogen deposition. Our results provide molecular information suggesting EL play a role in AF disease process over extended time frames.

Looking both ways: Electroactive biomaterials with bidirectional implications for dynamic cell-material crosstalk

Cells exist in natural, dynamic microenvironmental niches that facilitate biological responses to external physicochemical cues such as mechanical and electrical stimuli. For excitable cells, exogenous electrical cues are of interest due to their ability to stimulate or regulate cellular behavior via cascade signaling involving ion channels, gap junctions, and integrin receptors across the membrane. In recent years, conductive biomaterials have been demonstrated to influence or record these electrosensitive biological processes whereby the primary design criterion is to achieve seamless cell-material integration. As such, currently available bioelectronic materials are predominantly engineered toward achieving high-performing devices while maintaining the ability to recapitulate the local excitable cell/tissue microenvironment. However, such reports rarely address the dynamic signal coupling or exchange that occurs at the biotic-abiotic interface, as well as the distinction between the ionic transport involved in natural biological process and the electronic (or mixed ionic/electronic) conduction commonly responsible for bioelectronic systems. In this review, we highlight current literature reports that offer platforms capable of bidirectional signal exchange at the biotic-abiotic interface with excitable cell types, along with the design criteria for such biomaterials. Furthermore, insights on current materials not yet explored for biointerfacing or bioelectronics that have potential for bidirectional applications are also provided. Finally, we offer perspectives aimed at bringing attention to the coupling of the signals delivered by synthetic material to natural biological conduction mechanisms, areas of improvement regarding characterizing biotic-abiotic crosstalk, as well as the dynamic nature of this exchange, to be taken into consideration for material/device design consideration for next-generation bioelectronic systems.

Association of same-day urinary phenol levels and cardiac electrical alterations: analysis of the Fernald Community Cohort

Background

Exposure to phenols has been linked in animal models and human populations to cardiac function alterations and cardiovascular diseases, although their effects on cardiac electrical properties in humans remains to be established. This study aimed to identify changes in electrocardiographic (ECG) parameters associated with environmental phenol exposure in adults of a midwestern large cohort known as the Fernald Community Cohort (FCC).

Methods

During the day of the first comprehensive medical examination, urine samples were obtained, and electrocardiograms were recorded. Cross-sectional linear regression analyses were performed.

Results

Bisphenol A (BPA) and bisphenol F (BPF) were both associated with a longer PR interval, an indication of delayed atrial-to-ventricle conduction, in females (p < 0.05) but not males. BPA combined with BPF was associated with an increase QRS duration, an indication of delayed ventricular activation, in females (P < 0.05) but not males. Higher triclocarban (TCC) level was associated with longer QTc interval, an indication of delayed ventricular repolarization, in males (P < 0.01) but not females. Body mass index (BMI) was associated with a significant increase in PR and QTc intervals and ventricular rate in females and in ventricular rate in males. In females, the combined effect of being in the top tertile for both BPA urinary concentration and BMI was an estimate of a 10% increase in PR interval. No associations were found with the other phenols.

Conclusion

Higher exposure to some phenols was associated with alterations of cardiac electrical properties in a sex specific manner in the Fernald cohort. Our population-based findings correlate directly with clinically relevant parameters that are associated with known pathophysiologic cardiac conditions in humans.

Quantifying the efficacy of voltage protocols in characterising ion channel kinetics: A novel information-theoretic approach

Voltage-clamp experiments are commonly utilised to characterise cellular ion channel kinetics. In these experiments, cells are stimulated using a known time-varying voltage, referred to as the voltage protocol, and the resulting cellular response, typically in the form of current, is measured. Parameters of models that describe ion channel kinetics are then estimated by solving an inverse problem which aims to minimise the discrepancy between the predicted response of the model and the actual measured cell response. In this paper, a novel framework to evaluate the information content of voltage-clamp protocols in relation to ion channel model parameters is presented. Additional quantitative information metrics that allow for comparisons among various voltage protocols are proposed. These metrics offer a foundation for future optimal design frameworks to devise novel, information-rich protocols. The efficacy of the proposed framework is evidenced through the analysis of seven voltage protocols from the literature. By comparing known numerical results for inverse problems using these protocols with the information-theoretic metrics, the proposed approach is validated. The essential steps of the framework are: (i) generate random samples of the parameters from chosen prior distributions; (ii) run the model to generate model output (current) for all samples; (iii) construct reduced-dimensional representations of the time-varying current output using proper orthogonal decomposition (POD); (iv) estimate information-theoretic metrics such as mutual information, entropy equivalent variance, and conditional mutual information using non-parametric methods; (v) interpret the metrics; for example, a higher mutual information between a parameter and the current output suggests the protocol yields greater information about that parameter, resulting in improved identifiability; and (vi) integrate the information-theoretic metrics into a single quantitative criterion, encapsulating the protocol's efficacy in estimating model parameters.

Telomerase is essential for cardiac differentiation and sustained metabolism of human cardiomyocytes

Telomeres as the protective ends of linear chromosomes, are synthesized by the enzyme telomerase (TERT). Critically short telomeres essentially contribute to aging-related diseases and are associated with a broad spectrum of disorders known as telomeropathies. In cardiomyocytes, telomere length is strongly correlated with cardiomyopathies but it remains ambiguous whether short telomeres are the cause or the result of the disease. In this study, we employed an inducible CRISPRi human induced pluripotent stem cell (hiPSC) line to silence TERT expression enabling the generation of hiPSCs and hiPSC-derived cardiomyocytes with long and short telomeres. Reduced telomerase activity and shorter telomere lengths of hiPSCs induced global transcriptomic changes associated with cardiac developmental pathways. Consequently, the differentiation potential towards cardiomyocytes was strongly impaired and single cell RNA sequencing revealed a shift towards a more smooth muscle cell like identity in the cells with the shortest telomeres. Poor cardiomyocyte function and increased sensitivity to stress directly correlated with the extent of telomere shortening. Collectively our data demonstrates a TERT dependent cardiomyogenic differentiation defect, highlighting the CRISPRi TERT hiPSCs model as a powerful platform to study the mechanisms and consequences of short telomeres in the heart and also in the context of telomeropathies.

BeatProfiler: Multimodal In Vitro Analysis of Cardiac Function Enables Machine Learning Classification of Diseases and Drugs

Goal: Contractile response and calcium handling are central to understanding cardiac function and physiology, yet existing methods of analysis to quantify these metrics are often time-consuming, prone to mistakes, or require specialized equipment/license. We developed BeatProfiler, a suite of cardiac analysis tools designed to quantify contractile function, calcium handling, and force generation for multiple in vitro cardiac models and apply downstream machine learning methods for deep phenotyping and classification. Methods: We first validate BeatProfiler's accuracy, robustness, and speed by benchmarking against existing tools with a fixed dataset. We further confirm its ability to robustly characterize disease and dose-dependent drug response. We then demonstrate that the data acquired by our automatic acquisition pipeline can be further harnessed for machine learning (ML) analysis to phenotype a disease model of restrictive cardiomyopathy and profile cardioactive drug functional response. To accurately classify between these biological signals, we apply feature-based ML and deep learning models (temporal convolutional-bidirectional long short-term memory model or TCN-BiLSTM). Results: Benchmarking against existing tools revealed that BeatProfiler detected and analyzed contraction and calcium signals better than existing tools through improved sensitivity in low signal data, reduction in false positives, and analysis speed increase by 7 to 50-fold. Of signals accurately detected by published methods (PMs), BeatProfiler's extracted features showed high correlations to PMs, confirming that it is reliable and consistent with PMs. The features extracted by BeatProfiler classified restrictive cardiomyopathy cardiomyocytes from isogenic healthy controls with 98% accuracy and identified relax90 as a top distinguishing feature in congruence with previous findings. We also show that our TCN-BiLSTM model was able to classify drug-free control and 4 cardiac drugs with different mechanisms of action at 96% accuracy. We further apply Grad-CAM on our convolution-based models to identify signature regions of perturbations by these drugs in calcium signals. Conclusions: We anticipate that the capabilities of BeatProfiler will help advance in vitro studies in cardiac biology through rapid phenotyping, revealing mechanisms underlying cardiac health and disease, and enabling objective classification of cardiac disease and responses to drugs.

Pharmacokinetics and Pharmacodynamics of Etripamil, an Intranasally Administered, Fast-Acting, Nondihydropyridine Calcium Channel Blocker

Etripamil, a fast-acting nondihydropyridine L-type calcium channel blocker, is under investigation for potential self-administration for the acute treatment of supraventricular tachyarrhythmias in a medically unsupervised setting. We report detailed pharmacokinetics and pharmacodynamics of intranasally administered etripamil in healthy adults from 2 Phase 1, randomized, double-blind studies: Study MSP-2017-1096 (sequential dose-escalation, crossover study design, n = 64) and NODE-102 (single dose, 4-way crossover study, n = 24). Validated bioanalytical assays determined plasma concentrations of etripamil and its inactive metabolite. Noncompartmental pharmacokinetic parameters were calculated. Pharmacodynamic parameters were determined for PR interval, blood pressure, and heart rate. Etripamil was rapidly absorbed intranasally, with time to maximal plasma concentration of 5-8.5 minutes, corresponding to a rapid greater than 10% increase in mean maximum PR interval from baseline within 4-7 minutes of doses of 60 mg or greater. Following peak plasma concentrations, systemic etripamil levels declined rapidly within the first 15 minutes following dosing and decreased more gradually thereafter. PR interval prolongation greater than 10% from baseline was generally sustained for about 45 minutes at doses of 60 mg or greater. The mean terminal half-life ranged from about 1.5 hours with 60 mg to about 2.5-3 hours for the 70- and 105-mg doses. Etripamil was generally well tolerated without symptomatic hypotension. Adverse events were primarily mild to moderate and related to the administration site; no serious adverse events or episodes of atrioventricular block occurred. Intranasal etripamil administration, at doses of 60 mg or greater, produced rapidly occurring slowing of atrioventricular nodal conduction with a limited duration of effect without hemodynamic or electrocardiographic safety signals in healthy volunteers.

Acute Adenoviral Infection Elicits an Arrhythmogenic Substrate Prior to Myocarditis

BACKGROUND

Viral cardiac infection represents a significant clinical challenge encompassing several etiological agents, disease stages, complex presentation, and a resulting lack of mechanistic understanding. Myocarditis is a major cause of sudden cardiac death in young adults, where current knowledge in the field is dominated by later disease phases and pathological immune responses. However, little is known regarding how infection can acutely induce an arrhythmogenic substrate before significant immune responses. Adenovirus is a leading cause of myocarditis, but due to species specificity, models of infection are lacking, and it is not understood how adenoviral infection may underlie sudden cardiac arrest. Mouse adenovirus type-3 was previously reported as cardiotropic, yet it has not been utilized to understand the mechanisms of cardiac infection and pathology.

METHODS

We have developed mouse adenovirus type-3 infection as a model to investigate acute cardiac infection and molecular alterations to the infected heart before an appreciable immune response or gross cardiomyopathy.

RESULTS

Optical mapping of infected hearts exposes decreases in conduction velocity concomitant with increased Cx43Ser368 phosphorylation, a residue known to regulate gap junction function. Hearts from animals harboring a phospho-null mutation at Cx43Ser368 are protected against mouse adenovirus type-3-induced conduction velocity slowing. Additional to gap junction alterations, patch clamping of mouse adenovirus type-3-infected adult mouse ventricular cardiomyocytes reveals prolonged action potential duration as a result of decreased IK1 and IKs current density. Turning to human systems, we find human adenovirus type-5 increases phosphorylation of Cx43Ser368 and disrupts synchrony in human induced pluripotent stem cell-derived cardiomyocytes, indicating common mechanisms with our mouse whole heart and adult cardiomyocyte data.

CONCLUSIONS

Together, these findings demonstrate that adenoviral infection creates an arrhythmogenic substrate through direct targeting of gap junction and ion channel function in the heart. Such alterations are known to precipitate arrhythmias and likely contribute to sudden cardiac death in acutely infected patients.

Perfluorooctanoic acid induces cardiac dysfunction in human induced pluripotent stem cell-derived cardiomyocytes

Perfluorooctanoic acid (PFOA), commonly found in drinking water, leads to widespread exposure through skin contact, inhalation, and ingestion, resulting in detectable levels of PFOA in the bloodstream. In this study, we found that exposure to PFOA disrupts cardiac function in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). We observed reductions in field and action potentials in hiPSC-CMs exposed to PFOA. Furthermore, PFOA demonstrated a dose-dependent inhibitory effect on various ion channels, including the calcium, sodium, and potassium channels. Additionally, we noted dose-dependent inhibition of the expression of these ion channels in hiPSC-CMs following exposure to PFOA. These findings suggest that PFOA exposure can impair cardiac ion channel function and decrease the transcription of genes associated with these channels, potentially contributing to cardiac dysfunction such as arrhythmias. Our study sheds light on the electrophysiological and epigenetic consequences of PFOA-induced cardiac dysfunction, underscoring the importance of further research on the cardiovascular effects of perfluorinated compounds (PFCs).

Essential Role of Anisotropy in Bioengineered Cardiac Tissue Models

As regulatory bodies encourage alternatives to animal testing, there is renewed interest in engineering disease models, particularly for cardiac tissues. The aligned organization of cells in the mammalian heart controls the electrical and ionic currents and its ability to efficiently circulate blood to the body. Although the development of engineered cardiac systems is rising, insights into the topographical aspects, in particular, the necessity to design in vitro cardiac models incorporating cues for unidirectional cell growth, is lacking. This review first summarizes the widely used methods to organize cardiomyocytes (CMs) unidirectionally and the ways to quantify the resulting cellular alignment. The behavior of CMs in response to alignment is described, with emphasis on their functions and underlying mechanisms. Lastly, the limitations of state-of-the-art techniques to modulate CM alignment in vitro and opportunities for further development in the future to improve the cardiac tissue models that more faithfully mimic the pathophysiological hallmarks are outlined. This review serves as a call to action for bioengineers to delve deeper into the in vivo role of cellular organization in cardiac muscle tissue and draw inspiration to effectively mimic in vitro for engineering reliable disease models.

HAND factors regulate cardiac lineage commitment and differentiation from human pluripotent stem cells

BACKGROUND

Transcription factors HAND1 and HAND2 (HAND1/2) play significant roles in cardiac organogenesis. Abnormal expression and deficiency of HAND1/2 result in severe cardiac defects. However, the function and mechanism of HAND1/2 in regulating human early cardiac lineage commitment and differentiation are still unclear.

METHODS

With NKX2.5eGFP H9 human embryonic stem cells (hESCs), we established single and double knockout cell lines for HAND1 and HAND2, respectively, whose cardiomyocyte differentiation efficiency could be monitored by assessing NKX2.5-eGFP+ cells with flow cytometry. The expression of specific markers for heart fields and cardiomyocyte subtypes was examined by quantitative PCR, western blot and immunofluorescence staining. Microelectrode array and whole-cell patch clamp were performed to determine the electrophysiological characteristics of differentiated cardiomyocytes. The transcriptomic changes of HAND knockout cells were revealed by RNA sequencing. The HAND1/2 target genes were identified and validated experimentally by integrating with HAND1/2 chromatin immunoprecipitation sequencing data.

RESULTS

Either HAND1 or HAND2 knockout did not affect the cardiomyocyte differentiation kinetics, whereas depletion of HAND1/2 resulted in delayed differentiation onset. HAND1 knockout biased cardiac mesoderm toward second heart field progenitors at the expense of first heart field progenitors, leading to increased expression of atrial and outflow tract cardiomyocyte markers, which was further confirmed by the appearance of atrial-like action potentials. By contrast, HAND2 knockout cardiomyocytes had reduced expression of atrial cardiomyocyte markers and displayed ventricular-like action potentials. HAND1/2-deficient hESCs were more inclined to second heart field lineage and its derived cardiomyocytes with atrial-like action potentials than HAND1 single knockout during differentiation. Further mechanistic investigations suggested TBX5 as one of the downstream targets of HAND1/2, whose overexpression partially restored the abnormal cardiomyocyte differentiation in HAND1/2-deficient hESCs.

CONCLUSIONS

HAND1/2 have specific and redundant roles in cardiac lineage commitment and differentiation. These findings not only reveal the essential function of HAND1/2 in cardiac organogenesis, but also provide important information on the pathogenesis of HAND1/2 deficiency-related congenital heart diseases, which could potentially lead to new therapeutic strategies.

Heart-on-a-chip systems with tissue-specific functionalities for physiological, pathological, and pharmacological studies

Recent advances in heart-on-a-chip systems hold great promise to facilitate cardiac physiological, pathological, and pharmacological studies. This review focuses on the development of heart-on-a-chip systems with tissue-specific functionalities. For one thing, the strategies for developing cardiac microtissues on heart-on-a-chip systems that closely mimic the structures and behaviors of the native heart are analyzed, including the imitation of cardiac structural and functional characteristics. For another, the development of techniques for real-time monitoring of biophysical and biochemical signals from cardiac microtissues on heart-on-a-chip systems is introduced, incorporating cardiac electrophysiological signals, contractile activity, and biomarkers. Furthermore, the applications of heart-on-a-chip systems in intelligent cardiac studies are discussed regarding physiological/pathological research and pharmacological assessment. Finally, the future development of heart-on-a-chip toward a higher level of systematization, integration, and maturation is proposed.

The new era of cardiovascular research: revolutionizing cardiovascular research with 3D models in a dish

Cardiovascular research has heavily relied on studies using patient samples and animal models. However, patient studies often miss the data from the crucial early stage of cardiovascular diseases, as obtaining primary tissues at this stage is impracticable. Transgenic animal models can offer some insights into disease mechanisms, although they usually do not fully recapitulate the phenotype of cardiovascular diseases and their progression. In recent years, a promising breakthrough has emerged in the form of in vitro three-dimensional (3D) cardiovascular models utilizing human pluripotent stem cells. These innovative models recreate the intricate 3D structure of the human heart and vessels within a controlled environment. This advancement is pivotal as it addresses the existing gaps in cardiovascular research, allowing scientists to study different stages of cardiovascular diseases and specific drug responses using human-origin models. In this review, we first outline various approaches employed to generate these models. We then comprehensively discuss their applications in studying cardiovascular diseases by providing insights into molecular and cellular changes associated with cardiovascular conditions. Moreover, we highlight the potential of these 3D models serving as a platform for drug testing to assess drug efficacy and safety. Despite their immense potential, challenges persist, particularly in maintaining the complex structure of 3D heart and vessel models and ensuring their function is comparable to real organs. However, overcoming these challenges could revolutionize cardiovascular research. It has the potential to offer comprehensive mechanistic insights into human-specific disease processes, ultimately expediting the development of personalized therapies.

Investigating Lycotoxin-An1a (An1a), a defense antiviral peptide from Alopecosa nagpag venom as prospective anti-dengue agent against DENV-2 NS2B-NS3 protease

Dengue fever is a global health concern with no effective therapy. Screening synthetic chemicals, animal-originated compounds, and phytocompounds against Dengue virus (DENV) targets has failed to find dengue antivirals. The current study examines animal drugs as antagonists against NS2B-NS3Pro, one of DENV's most promising therapeutic targets for dengue fever. Antiviral-Lycotoxin-An1a (An1a), a defence antiviral peptide isolated from the venom of Alopecosa nagpag, a toxic spider. Based on prior in vitro research, it was discovered that the venom peptide suppresses the action of DENV-2 NS2B-NS3Pro. An1a peptide with NS2B-NS3Pro wild type (WT) and two mutants (H51N and S135A) was tested for anti-dengue characteristics using in silico analysis. The WT NS2B-NS3Pro has a catalytic triad of His51, Asp75, and Ser135 in the active site, but the mutants have N51 instead of His51 and Ala135 instead of Ser135. The dynamic sites of the three proteases (WT, H51N, S135A) and the peptide toxin (An1a) were taken into account to achieve molecular docking of An1a with WT NS2B-NS3Pro in conjunction with H51N and S135A. Cluspro-2 performs rigid-flexible docking to predict peptide binding affinity, effectiveness, and inhibitory consistency. Since the ligand had a higher binding affinity, docking score, and molecular interaction network, MD simulations and MM-GBSA free energy calculations were used to investigate the stability of the three protein-peptide complexes. The computer-aided screening and manufacture of spider venom-based anti-dengue medicines yielded intriguing results in the preliminary studies. This study is significant in defining the ideal therapeutic candidate against dengue infections.

Cardiac maturation

The heart undergoes a dynamic maturation process following birth, in response to a wide range of stimuli, including both physiological and pathological cues. This process entails substantial re-programming of mitochondrial energy metabolism coincident with the emergence of specialized structural and contractile machinery to meet the demands of the adult heart. Many components of this program revert to a more "fetal" format during development of pathological cardiac hypertrophy and heart failure. In this review, emphasis is placed on recent progress in our understanding of the transcriptional control of cardiac maturation, encompassing the results of studies spanning from in vivo models to cardiomyocytes derived from human stem cells. The potential applications of this current state of knowledge to new translational avenues aimed at the treatment of heart failure is also addressed.

Computational Studies Show How the H463R Mutation Turns hKv1.5 into an Inactivation State

The KCNA5 gene provides the code for the α-subunit of the potassium channel Kv1.5. The genetic variant H463R in the Kv1.5 channel has been reported to cause a functional loss in atrial fibrillation (AF) patients. Understanding the mutations at a molecular level is key to developing improved therapeutics concerning cardiac hKv1.5 and hKv1.4 channels. Molecular dynamics and umbrella sampling free energy simulations are an effective tool to understand the mutation's effect on ion conduction, which we have employed and found that the hKv1.5[H463R] mutation imposes an energy barrier on the ion conduction pathway compared to the wild-type channel's ion free energy and pore structure. These results imply that the arginine mutation associated with the AF disease in particular modulates the inactivation process of hKv1.5. Kv1.4, encoded by the KCNA4 gene, is also present in the heart. Therefore, we considered simulation studies of the equivalent H507R mutation in the hKv1.4 channel and found that the mutation slightly reduces the ion conduction barrier in the ion conduction pathway, making it insignificant.

Intracellular K+ Limits T-cell Exhaustion and Preserves Antitumor Function

T cells are often compromised within cancers, allowing disease progression. We previously found that intratumoral elevations in extracellular K+, related to ongoing cell death, constrained CD8+ T-cell Akt-mTOR signaling and effector function. To alleviate K+-mediated T-cell dysfunction, we pursued genetic means to lower intracellular K+. CD8+ T cells robustly and dynamically express the Na+/K+ ATPase, among other K+ transporters. CRISPR-Cas9-mediated disruption of the Atp1a1 locus lowered intracellular K+ and elevated the resting membrane potential (i.e., Vm, Ψ). Despite compromised Ca2+ influx, Atp1a1-deficient T cells harbored tonic hyperactivity in multiple signal transduction cascades, along with a phenotype of exhaustion in mouse and human CD8+ T cells. Provision of exogenous K+ restored intracellular levels in Atp1a1-deficient T cells and prevented damaging levels of reactive oxygen species (ROS), and both antioxidant treatment and exogenous K+ prevented Atp1a1-deficient T-cell exhaustion in vitro. T cells lacking Atp1a1 had compromised persistence and antitumor activity in a syngeneic model of orthotopic murine melanoma. Translational application of these findings will require balancing the beneficial aspects of intracellular K+ with the ROS-dependent nature of T-cell effector function. See related Spotlight by Banuelos and Borges da Silva, p. 6.

Inherited Arrhythmias in the Pediatric Population: An Updated Overview

Pediatric cardiomyopathies (CMs) and electrical diseases constitute a heterogeneous spectrum of disorders distinguished by structural and electrical abnormalities in the heart muscle, attributed to a genetic variant. They rank among the main causes of morbidity and mortality in the pediatric population, with an annual incidence of 1.1-1.5 per 100,000 in children under the age of 18. The most common conditions are dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM). Despite great enthusiasm for research in this field, studies in this population are still limited, and the management and treatment often follow adult recommendations, which have significantly more data on treatment benefits. Although adult and pediatric cardiac diseases share similar morphological and clinical manifestations, their outcomes significantly differ. This review summarizes the latest evidence on genetics, clinical characteristics, management, and updated outcomes of primary pediatric CMs and electrical diseases, including DCM, HCM, arrhythmogenic right ventricular cardiomyopathy (ARVC), Brugada syndrome (BrS), catecholaminergic polymorphic ventricular tachycardia (CPVT), long QT syndrome (LQTS), and short QT syndrome (SQTS).

Casein Kinase 1 Phosphomimetic Mutations Negatively Impact Connexin-43 Gap Junctions in Human Pluripotent Stem Cell-Derived Cardiomyocytes

The transplantation of human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) has shown promise in preclinical models of myocardial infarction, but graft myocardium exhibits incomplete host-graft electromechanical integration and a propensity for pro-arrhythmic behavior. Perhaps contributing to this situation, hPSC-CM grafts show low expression of connexin 43 (Cx43), the major gap junction (GJ) protein, in ventricular myocardia. We hypothesized that Cx43 expression and function could be rescued by engineering Cx43 in hPSC-CMs with a series of phosphatase-resistant mutations at three casein kinase 1 phosphorylation sites (Cx43-S3E) that have been previously reported to stabilize Cx43 GJs and reduce arrhythmias in transgenic mice. However, contrary to our predictions, transgenic Cx43-S3E hPSC-CMs exhibited reduced Cx43 expression relative to wild-type cells, both at baseline and following ischemic challenge. Cx43-S3E hPSC-CMs showed correspondingly slower conduction velocities, increased automaticity, and differential expression of other connexin isoforms and various genes involved in cardiac excitation-contraction coupling. Cx43-S3E hPSC-CMs also had phosphorylation marks associated with Cx43 GJ internalization, a finding that may account for their impaired GJ localization. Taken collectively, our data indicate that the Cx43-S3E mutation behaves differently in hPSC-CMs than in adult mouse ventricular myocytes and that multiple biological factors likely need to be addressed synchronously to ensure proper Cx43 expression, localization, and function.

Creating Computational Models of Ion Channel Dynamics

Markov models are widely used to represent ion channel protein configurations as different states in the model's topology. Such models allow for dynamic simulation of ion channel kinetics through the simulated application of voltage potentials across a cell membrane. In this chapter, we present a general method for creating Markov models of ion channel kinetics using computational optimization alongside a fully featured example model of a cardiac potassium channel. Our methods cover designing training protocols, iteratively testing potential model topologies for structure identification, creation of algorithms for model simulation, as well as methods for assessing the quality of fit for a finalized model.

Nanoparticle Polymers Influence on Cardiac Health: Good or Bad for Cardiac Physiology?

Cardiovascular diseases (CVD) are one of the leading causes of death and morbidity worldwide. Lifestyle modifications, medications, and addressing epidemiological factors have long been at the forefront of targeting therapeutics for CVD. Treatments can be further complicated given the intersection of gender, age, unique comorbidities, and healthcare access, among many other factors. Therefore, expanding treatment and diagnostic modalities for CVD is absolutely necessary. Nanoparticles and nanomaterials are increasingly being used as therapeutic and diagnostic modalities in various disciplines of biomedicine. Nanoparticles have multiple ways of interacting with the cardiovascular system. Some of them alter cardiac physiology by impacting ion channels, whereas others influence ions directly or indirectly, improving cellular death via decreasing oxidative stress.  While embedding nanoparticles into therapeutics can help enhance healthy cardiovascular function in other scenarios, they can also impair physiology by increasing reactive oxidative species and leading to cardiotoxicity. This review explores different types of nanoparticles, their effects, and the applicable dosages to create a better foundation for understanding the current research findings.

Multi-site validation of a functional assay to adjudicate SCN5A Brugada Syndrome-associated variants

Brugada Syndrome (BrS) is an inheritable arrhythmia condition that is associated with rare, loss-of-function variants in the cardiac sodium channel gene, SCN5A. Interpreting the pathogenicity of SCN5A missense variants is challenging and ~79% of SCN5A missense variants in ClinVar are currently classified as Variants of Uncertain Significance (VUS). An in vitro SCN5A-BrS automated patch clamp assay was generated for high-throughput functional studies of NaV1.5. The assay was independently studied at two separate research sites - Vanderbilt University Medical Center and Victor Chang Cardiac Research Institute - revealing strong correlations, including peak INa density (R2=0.86). The assay was calibrated according to ClinGen Sequence Variant Interpretation recommendations using high-confidence variant controls (n=49). Normal and abnormal ranges of function were established based on the distribution of benign variant assay results. The assay accurately distinguished benign controls (24/25) from pathogenic controls (23/24). Odds of Pathogenicity values derived from the experimental results yielded 0.042 for normal function (BS3 criterion) and 24.0 for abnormal function (PS3 criterion), resulting in up to strong evidence for both ACMG criteria. The calibrated assay was then used to study SCN5A VUS observed in four families with BrS and other arrhythmia phenotypes associated with SCN5A loss-of-function. The assay revealed loss-of-function for three of four variants, enabling reclassification to likely pathogenic. This validated APC assay provides clinical-grade functional evidence for the reclassification of current VUS and will aid future SCN5A-BrS variant classification.