Inhibition of calcium/calmodulin (Ca2+ /CaM)-Calcium/calmodulin-dependent protein kinase II (CaMKII) axis reduces in vitro and ex vivo arrhythmias in experimental Chagas disease

Evaluation of Scalibor® deltamethrin collar chronic exposure in dogs

Deltamethrin is a pesticide used worldwide with several applications in the control of nuisance arthropods in homes, agriculture, against ectoparasites in dogs and livestock. Recent studies indicate that deltamethrin can induce cardiotoxicity. Therefore, this study aimed to evaluate the toxicity of deltamethrin in dogs through exposure to commercial collars over 8 months. Twenty healthy dogs were selected, 9 males and 11 females, weighing between 10 and 15 kg and aged between 1 and 8 years, with no history of intentional exposure to pyrethroids. Clinical, cardiological, and laboratory evaluations were performed monthly. The results demonstrate that exposure to deltamethrin 4 % via the dermal route, through a commercial collar, was safe for 8 months, with preserved cardiac electrocontractile function, assessed by electrocardiogram and echocardiogram. In addition, tracking of plasma biochemical markers did not indicate signs of cardiac, renal, or hepatic injury. Although deltamethrin 4 % collars demonstrated an acceptable safety profile regarding cardiovascular and laboratory evaluations, the occurrence of dermatological reactions in 25 % of the animals, which is a significant proportion, highlights the need for careful monitoring of dermatological reactions. Future investigations with different concentrations and longer periods are recommended to achieve a more comprehensive understanding of the long-term effects of deltamethrin, improving its safe application in veterinary medicine and promoting animal and human health.

Puerarin reduces susceptibility to ventricular arrhythmias and inhibits ferroptosis via Sirt1/Nrf2 signaling in high-fat-diet rats

Obesity is a significant risk factor for cardiac arrhythmias, and the ferroptosis is closely related to cardiac arrhythmias. This study aimed to investigate whether puerarin (Pue), a natural isoflavone, could reduce the susceptibility to ventricular arrhythmias (VAs) associated with obesity and inhibit ferroptosis, with a particular focus on the Sirt1/Nrf2 signaling pathway. Male rats were randomly divided into three groups: normal chow diet (NC), high-fat diet (HFD), and HFD with Pue treatment (100mg/kg, HFD + Pue). After 16 weeks, electrophysiological, structural, and molecular analysis were performed. Compared to the NC group, HFD rats exhibited prolonged QT interval and Tpeak-Tend interval, amplified transmural dispersion of ventricular repolarization, and increased susceptibility to VAs. Pue treatment significantly ameliorated these electrophysiological abnormalities and reduced VAs susceptibility. HFD rats showed cardiac hypertrophy, fibrosis, and inflammation, which were alleviated by Pue application. Cardiac lipid peroxidation, iron deposition, mitochondrial abnormality, and ferroptosis marker induction were observed in HFD rats. Further, treatment with Pue improved these alterations. Additionally, molecular docking analysis confirmed the interaction of Pue with Sirt1 and Nrf2. Furthermore, Pue treatment upregulated Sirt1 and Nrf2 expression in HFD rats, thereby reducing reactive oxygen species (ROS) generation and ferroptosis. Moreover, Pue protected cardiomyocytes against palmitic acid (PA)-induced injury by inhibiting ferroptosis via the Sirt1/Nrf2 pathway in H9c2 cells. Overall, our study shows for the first time that Pue reduces susceptibility to VAs and inhibits ferroptosis in HFD rats by modulating the Sirt1/Nrf2 signaling pathway, offering a potential therapeutic strategy for obesity-related cardiac arrhythmias.

Electrocontractile remodeling of isolated cardiomyocytes induced during early-stage hypercholesterolemia

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

Arrhythmogenic Manifestations of Chagas Disease: Perspectives From the Bench to Bedside

Chagas cardiomyopathy caused by infection with the intracellular parasite Trypanosoma cruzi is the most common and severe expression of human Chagas disease. Heart failure, systemic and pulmonary thromboembolism, arrhythmia, and sudden cardiac death are the principal clinical manifestations of Chagas cardiomyopathy. Ventricular arrhythmias contribute significantly to morbidity and mortality and are the major cause of sudden cardiac death. Significant gaps still exist in the understanding of the pathogenesis mechanisms underlying the arrhythmogenic manifestations of Chagas cardiomyopathy. This article will review the data from experimental studies and translate those findings to draw hypotheses about clinical observations. Human- and animal-based studies at molecular, cellular, tissue, and organ levels suggest 5 main pillars of remodeling caused by the interaction of host and parasite: immunologic, electrical, autonomic, microvascular, and contractile. Integrating these 5 remodeling processes will bring insights into the current knowledge in the field, highlighting some key features for future management of this arrhythmogenic disease.

Cardiac disturbances and changes in tissue cytokine levels in mice fed with a high-refined carbohydrate diet

AIMS

The consumption of highly refined carbohydrates increases systemic inflammatory markers, but its potential to exert direct myocardial inflammation is uncertain. Herein, we addressed the impact of a high-refined carbohydrate (HC) diet on mice heart and local inflammation over time.

MAIN METHODS

BALB/c mice were fed with a standard chow (control) or an isocaloric HC diet for 2, 4, or 8 weeks (HC groups), in which the morphometry of heart sections and contractile analyses by invasive catheterization and Langendorff-perfused hearts were assessed. Cytokines levels by ELISA, matrix metalloproteinase (MMP) activity by zymography, in situ reactive oxygen species (ROS) staining and lipid peroxidation-induced TBARS levels, were also determined.

KEY FINDINGS

HC diet fed mice displayed left ventricular hypertrophy and interstitial fibrosis in all times analyzed, which was confirmed by echocardiographic analyses of 8HC group. Impaired contractility indices of HC groups were observed by left ventricular catheterization, whereas ex vivo and in vitro indices of contraction under isoprenaline-stimulation were higher in HC-fed mice compared with controls. Peak levels of TNF-α, TGF-β, ROS, TBARS, and MMP-2 occur independently of HC diet time. However, a long-lasting local reduction of the anti-inflammatory cytokine IL-10 was found, which was linearly correlated to the decline of systolic function in vivo.

SIGNIFICANCE

Altogether, the results indicate that short-term consumption of HC diet negatively impacts the balance of anti-inflammatory defenses and proinflammatory/profibrotic mediators in the heart, which can contribute to HC diet-induced morphofunctional cardiac alterations.

Trypanosoma cruzi dysregulates expression profile of piRNAs in primary human cardiac fibroblasts during early infection phase

Trypanosoma cruzi, the etiological agent of Chagas Disease, causes severe morbidity, mortality, and economic burden worldwide. Though originally endemic to Central and South America, globalization has led to increased parasite presence in most industrialized countries. About 40% of infected individuals will develop cardiovascular, neurological, and/or gastrointestinal pathologies. Accumulating evidence suggests that the parasite induces alterations in host gene expression profiles in order to facilitate infection and pathogenesis. The role of regulatory gene expression machinery during T. cruzi infection, particularly small noncoding RNAs, has yet to be elucidated. In this study, we aim to evaluate dysregulation of a class of sncRNAs called piRNAs during early phase of T. cruzi infection in primary human cardiac fibroblasts by RNA-Seq. We subsequently performed in silico analysis to predict piRNA-mRNA interactions. We validated the expression of these selected piRNAs and their targets during early parasite infection phase by stem loop qPCR and qPCR, respectively. We found about 26,496,863 clean reads (92.72%) which mapped to the human reference genome. During parasite challenge, 441 unique piRNAs were differentially expressed. Of these differentially expressed piRNAs, 29 were known and 412 were novel. In silico analysis showed several of these piRNAs were computationally predicted to target and potentially regulate expression of genes including SMAD2, EGR1, ICAM1, CX3CL1, and CXCR2, which have been implicated in parasite infection, pathogenesis, and various cardiomyopathies. Further evaluation of the function of these individual piRNAs in gene regulation and expression will enhance our understanding of early molecular mechanisms contributing to infection and pathogenesis. Our findings here suggest that piRNAs play important roles in infectious disease pathogenesis and can serve as potential biomarkers and therapeutic targets.

Experimental hypothyroidism induces cardiac arrhythmias and ranolazine reverts and prevents the phenotype

AIMS

Hypothyroidism is associated with an increased risk of cardiovascular disease and enhanced susceptibility to arrhythmias. In our investigation, we evaluated the potential involvement of late sodium current (I_Na,late) in cardiac arrhythmias in an experimental murine model of hypothyroidism.

MAIN METHODS

Male Swiss mice were treated with methimazole (0.1 % w/vol, during 21 days) to induce experimental hypothyroidism before ECG, action potential (AP) and intracellular Ca²⁺ dynamics were evaluated. Susceptibility to arrhythmia was measured in vitro and in vivo.

KEY FINDINGS

The results revealed that hypothyroid animals presented ECG alterations (e.g. increased QTc) with the presence of spontaneous sustained ventricular tachycardia. These changes were associated with depolarized resting membrane potential in isolated cardiomyocytes and increased AP duration and dispersion at 90 % of the repolarization. Aberrant AP waveforms were related to increased Ca²⁺ sparks and out-of-pace Ca²⁺ waves. These changes were observed in a scenario of enhanced I_Na,late. Interestingly, ranolazine, a clinically used blocker of I_Na,late, restored the ECG alterations, reduced Ca²⁺ sparks and aberrant waves, decreased the in vitro events and the severity of arrhythmias observed in isolated cardiomyocytes from hypothyroid animals. Using the in vivo dobutamine + caffeine protocol, animals with hypothyroidism developed catecholaminergic bidirectional ventricular tachycardia, but pre-treatment with ranolazine prevented this.

SIGNIFICANCE

We concluded that animals with hypothyroidism have increased susceptibility to developing arrhythmias and ranolazine, a clinically used blocker of I_Na,late, is able to correct the arrhythmic phenotype.

The insecticide β-Cyfluthrin induces acute arrhythmic cardiotoxicity through interaction with NaV1.5 and ranolazine reverses the phenotype

β-Cyfluthrin, a class II Pyrethroid, is an insecticide used worldwide in agriculture, horticulture (field and protected crops), viticulture, and domestic applications. β-Cyfluthrin may impair the function of biological systems; however, little information is available about its potential cardiotoxic effect. Here, we explored the acute toxicity of β-Cyfluthrin in isolated heart preparations and its cellular basis, using isolated cardiomyocytes. Moreover, β-Cyfluthrin effects on the sodium current, especially late sodium current (INa-L), were investigated using HEK-293 cells transiently expressing human NaV1.5 channels. We report that β-Cyfluthrin raised INa-L in a dose-dependent manner. β-Cyfluthrin prolonged the repolarization of the action potential and triggered oscillations on its duration. Cardiomyocytes contraction and calcium dynamics were disrupted by the pesticide with a marked incidence of non-electronic stimulated contractions. The antiarrhythmic drug Ranolazine was able to reverse most of the phenotypes observed in isolated cells. Lastly, ventricular premature beats and long QT intervals were found during β-Cyfluthrin exposure, and Ranolazine was able to attenuate them. Overall, we demonstrated that β-Cyfluthrin can cause significant cardiac alterations and Ranolazine ameliorated the phenotype. Understanding the insecticides' impacts upon electromechanical properties of the heart is important for the development of therapeutic approaches to treat cases of pesticides intoxication.