Human Cardiac Myocytes Research Articles

Hypoxic-Normoxic Crosstalk Activates Pro-Inflammatory Signaling in Human Cardiac Fibroblasts and Myocytes in a Post-Infarct Myocardium on a Chip.

Myocardial infarctions locally deprive myocardium of oxygenated blood and cause immediate cardiac myocyte necrosis. Irreparable myocardium is then replaced with a scar through a dynamic repair process that is an interplay between hypoxic cells of the infarct zone and normoxic cells of adjacent healthy myocardium. In many cases, unresolved inflammation or fibrosis occurs for reasons that are incompletely understood, increasing the risk of heart failure. Crosstalk between hypoxic and normoxic cardiac cells is hypothesized to regulate mechanisms of repair after a myocardial infarction. To test this hypothesis, microfluidic devices are fabricated on 3D printed templates for co-culturing hypoxic and normoxic cardiac cells. This system demonstrates that hypoxia drives human cardiac fibroblasts toward glycolysis and a pro-fibrotic phenotype, similar to the anti-inflammatory phase of wound healing. Co-culture with normoxic fibroblasts uniquely upregulates pro-inflammatory signaling in hypoxic fibroblasts, including increased secretion of tumor necrosis factor alpha (TNF-α). In co-culture with hypoxic fibroblasts, normoxic human induced pluripotent stem cell (hiPSC)-derived cardiac myocytes also increase pro-inflammatory signaling, including upregulation of interleukin 6 (IL-6) family signaling pathway and increased expression of IL-6 receptor. Together, these data suggest that crosstalk between hypoxic fibroblasts and normoxic cardiac cells uniquely activates phenotypes that resemble the initial pro-inflammatory phase of post-infarct wound healing.

Study and optimization of the photobiomodulation effects induced on mitochondrial metabolic activity of human cardiomyocytes for different radiometric and spectral conditions

Photobiomodulation (PBM) represents a promising and powerful approach for non-invasive therapeutic interventions. This emerging field of research has gained a considerable attention due to its potential for multiple disciplines, including medicine, neuroscience, and sports medicine. While PBM has shown the ability to stimulate various cellular processes in numerous medical applications, the fine-tuning of treatment parameters, such as wavelength, irradiance, treatment duration, and illumination geometry, remains an ongoing challenge. Furthermore, additional research is necessary to unveil the specific mechanisms of action and establish standardized protocols for diverse clinical applications.Given the widely accepted understanding that mitochondria play a pivotal role in the PBM mechanisms, our study delves into a multitude of PBM illumination parameters while assessing the PBM's effects on the basis of endpoints reflecting the mitochondrial metabolism of human cardiac myocytes (HCM), that are known for their high mitochondrial density. These endpoints include: i) the endogenous production of protoporphyrin IX (PpIX), ii) changes in mitochondrial potential monitored by Rhodamine 123 (Rhod 123), iii) changes in the HCM's oxygen consumption, iv) the fluorescence lifetime of Rhod 123 in mitochondria, and v) alterations of the mitochondrial morphology. The good correlation observed between these different methods to assess PBM effects underscores that monitoring the endogenous PpIX production offers interesting indirect insights into the mitochondrial metabolic activity. This conclusion is important since many approved therapeutics and cancer detection approaches are based on the use of PpIX.Finally, this correlation strongly suggests that the PBM effects mentioned above have a common “fundamental” mechanistic origin.

Characterization of extracellular vesicles from patients with severe aortic stenosis undergoing transcatheter aortic valve implantation and assessment of their coagulation potential

Abstract Funding Acknowledgements None. Background The pathogenesis of aortic stenosis (AS) includes processes of inflammation and calcification. Patients with aortic stenosis have increased risk of stroke. The amount of circulating extracellular vesicles (EVs) is elevated in patients with severe AS and decreases following valve intervention. The function of these EVs in the clinical setting of severe AS is not fully known. Aim With flow cytometry characterize EVs in patients with severe AS before and after Transcatheter Aortic Valve Implantation (TAVI). To investigate whether these EVs have a procoagulant effects by themselves or when incubated with human aortic endothelial cells (hAoECs), human cardiac microvascular endothelial cells (hCMVEC), human cardiac myocytes (hCM) and spheroids of hCMVEC and hCM. Methods 25 patients with severe AS were included in the study and blood samples collected before and 2 months after TAVI. The CytoFLEX flow cytometer (Beckman Coulter) was used for characterization of surface antigens on purified EVs. 2D-cultures of hAoECs, hCMVEC and hCM were incubated with EVs (100 mg/mL) for 6 hours (h) and spheroids of hCM and hCMVEC with EVs for 48h. An inhouse assay determining Tissue Factor (TF) activity by means of FXa generation in cell lysates were utilized. TF activity in purified EVs alone was determined using Tissue Factor Activity Assay kit (Human, colorimetric) from abcam. Results We found an increased level of TF positive EVs, phosphatidylserine (PS) positive EVs as well as double positive PS / TF expressing EVs in AS patients before TAVI compared to healthy controls and reduction of PS+ and TF+/PS+ expressing EVs after TAVI (Fig 1). When analyzing TF activity by means of FXa generation we found no procoagulant effect in the purified EVs alone nor when incubating EVs with hAoEC or hCM. In contrast, we found an increased TF activity in hCMVEC and spheroids of hCM and hCMVEC after incubation with EVs from AS patients compared to healthy EVs. Conclusion Patients with AS have increased amount of EVs expressing typically procoagulant surface antigens. The EVs by themselves have no procoagulant activity. However, upon interaction with hCMVEC and spheroids, consisting of hCMVEC and hCM, EVs appear to induce procoagulant activity in the recipient cells thus suggesting a possible link to thromboembolic events in coronary arteries. Additional studies are warranted to elaborate the mechanism and function of these TF, PS and TF / PS positive EVs.

Antisense oligonucleotides as a potential therapeutic strategy in hypertrophic cardiomyopathy caused by MYBPC3 variants

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Sociedad Española de Cardiología Background/Introduction Non-sense or frameshift mutations in the MYBPC3 gene encoding cardiac myosin-binding protein C (cMyBP-C) are a major cause for inherited forms of Hypertrophic Cardiomyopathy (HCM), the most frequent inherited cardiac disease, affecting 0.2% of the general population and represents the leading cause for sudden cardiac death in young athletes. During the last decade, RNA-based therapeutic approaches have been studied for neuromuscular disorders and recently became to be considered to envision causal therapies for cardiomyopathies, utilizing antisense oligonucleotide mediated exon skipping, which attempts to reframe mutated mybpc3 transcripts, resulting in shortened but functional protein. MYBPC3 gene has a total of 34 coding exons and, exons 2, 22, and 24-27 are ideal targets for skipping. Purpose We aim to design and evaluate antisense oligonucleotides (AONs) for efficient exon-skipping in targeted MYBPC3 exons. Methods We designed two specific AONs to mask the MYBPC3 exon 26 and confirmed successfully mediated exon skipping without disrupting the MYBPC3 reading frame. We chose a previously identified MYBPC3 c.2671insG/p.R891Afs*160 variant in exon 26, which causes a frameshift mutation leading to truncated MYBPC3 in HCM. Primary Human Cardiac Myocytes (PHCM) (Promocell) were transfected with the splice-site targeting AONs. Results In this study we designed two chemically modified AONs (AON1 and AON2) through the addition of a 2′-O-methyl RNA phosphorothioate backbone, targeting exonic splicing enhancers (ESEs) or splice sites (SSs) can induce skipping of MYBPC3 exon 26. We evaluated AON1 (i26-3SS) and AON2 (ESE)-treated Primary Human Cardiac Myocytes (PHCM) show 26-27 exons skipping in comparison to control samples. The identity of the exon 26-27 skipped bands detected by RT-PCR was confirmed by Sanger sequencing and preservation of both nucleotide sequences of MYBPC3 exons 25 and 28 were observed. These results indicate that AONs specifically for mutated MYBPC3 target exons, expanding the framework of future advancements in the therapeutic potential of antisense-mediated exon skipping MYBPC3-based HCM. In addition, skipping exons 26 and 27 we eliminate a total of 22 possible exonic mutations, which represent 7.2% of the total known MYBPC3 exonic mutations. Conclusion(s) These results demonstrate that disruption of the MYBPC3 reading frame due to a truncating HCM mutation can be restored by exon skipping in cardiomyocytes in vitro indicating RNA-based strategies as a potential treatment option for HCM.Exon skipping scheme

Na/K-ATPase α1/Src Signaling Regulates Mitochondrial Metabolic Function and ROS Production in Human iPSC-derived Cardiomyocytes

Through an isoform specific mechanism, the Na/K-ATPase (NKA) α1 polypeptide-mediated regulation of Src kinase has emerged as a novel regulator of mitochondrial function in various cell types. Mitochondrial metabolism ensures adequate myocardial performance and adaptation to physiological demand. It is also a critical cellular determinant of cardiac repair and remodeling. To investigate the importance of the proposed NKA/Src regulatory signaling on cardiac mitochondrial metabolic function independently from the classic Na/K-ATPase enzymatic function, we used a gene targeting approach in cardiomyocytes. Human induced pluripotent stem cells (hiPSC) expressing a Src-signaling null mutant (A420P) form of NKA α1 were generated using CRISPR/Cas9-mediated genome editing. NKA isoform protein expression and enzymatic activity remained unchanged. However, baseline levels of Src and ERK1/2 phosphorylation were decreased by 55% and 80%, respectively in the A420P hiPSC (n=3, p<0.05). Both the WT and A420P hiPSC differentiated into cardiomyocytes (iCM) as assessed by morphology, spontaneous cell contraction, marker gene expression, and subcellular striations. Cell metabolism assessed by Seahorse extracellular flux analysis revealed significant reductions in basal and maximal rates of mitochondrial respiration (50%), spare respiratory capacity (50%), ATP production (60%), and coupling effciency (20%) (n=4, p<0.05). ROS production was monitored in live cells by measuring the oxidation of the CM-H2DCFDA dye using a fluorescence microscope. The slope of the ROS production rate curve was dramatically reduced in A420P iCM (80%, n=3, p<0.05). Protein carbonylation levels, analyzed by ELISA as markers of oxidative damage, were also decreased in A420P iCM (n=4, p<0.05). Taken together, these data provide genetic evidence for a role of NKA α1/Src in the tonic stimulation of basal mitochondrial metabolism and ROS production in human cardiac myocytes. This has potential significance in cardiometabolic diseases and suggests that targeting the NKA α1/Src signaling axis may offer a novel approach to address mitochondrial dysfunction. NIH Grant R15 HL145666, NIH Grant P20GM103434 to the West Virginia IDeA Network of Biomedical Research Excellence, and American Heart Association Postdoctoral Fellowship — 22POST917776 — to Marco T. Pessoa. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Modulating oxidative stress, apoptosis, and mitochondrial dysfunctions on cardiotoxicity induced by aluminum phosphide pesticide using resveratrol

The agricultural fumigant pesticide aluminum phosphide (AlP) is cardiotoxic. Water causes AlP to emit phosphine gas, a cardiac toxin that affects heart function and causes cardiogenic shock. AlP poisoning’s high fatality rate is due to cardiotoxicity. This study examines how resveratrol reduces oxidative stress, mitochondrial activity, and apoptosis in human cardiac myocyte (HCM) cells. After determining the optimal doses of resveratrol using the MTT test, HCM cells were subjected to a 24-h treatment of resveratrol following exposure to AlP (2.36 μM). The levels of reactive oxygen species (ROS), superoxide dismutase (SOD) activity, mitochondrial swelling, mitochondrial cytochrome c release, and mitochondrial membrane potential (MMP) in HCM cells were investigated. Also, the expression of Bax and Bcl-2, caspace-3 activity, and apoptosis were assessed. The present investigation revealed that AlP substantially increased the level of ROS and decreased SOD activation, which were significantly modulated by resveratrol in a dose-dependent manner. Moreover, AlP induced an elevation of mitochondrial swelling, cytochrome c release, and MMP collapse. Co-administration of resveratrol significantly reduced above mitochondrial markers. AlP also significantly upregulated BAX and downregulated Bcl-2 expression, elevated caspace-3 activity, and apoptosis. Resveratrol co-administration was able to meaningfully modulate the mentioned parameters and finally reduce apoptosis. In conclusion, resveratrol, via its pleotropic properties, significantly demonstrated cytoprotective effects on HCM cytotoxicity induced by AlP.

Mechanisms by which silencing long-stranded noncoding RNA KCNQ1OT1 alleviates myocardial ischemia/reperfusion injury (MI/RI)-induced cardiac injury via miR-377-3p/HMOX1

BackgroundThe key complication of myocardial infarction therapy is myocardial ischemia/reperfusion injury (MI/RI), and there is no effective treatment. The present study elucidates the mechanism of action of lncRNA KCNQ1OT1 in alleviating MI/RI and provides new perspectives and therapeutic targets for cardiac injury-related diseases.MethodsAn ischemia/reperfusion (I/R) injury model of human adult cardiac myocytes (HACMs) was constructed, and the expression of KCNQ1OT1 and miR-377-3p was determined by RT‒qPCR. The levels of related proteins were detected by western blot analysis. Cell proliferation was detected by a CCK-8 assay, and cell apoptosis and ROS content were determined by flow cytometry. SOD and MDA expression as well as Fe2+ changes were detected by related analysis kits. The target binding relationships between lncRNA KCNQ1OT1 and miR-377-3p as well as between miR-377-3p and heme oxygenase 1 (HMOX1) were verified by a dual-luciferase reporter gene assay.ResultsMyocardial ischemia‒reperfusion caused oxidative stress in HACMs, resulting in elevated ROS levels, increased Fe2+ levels, decreased cell viability, and increased LDH release (a marker of myocardial injury), and apoptosis. KCNQ1OT1 and HMOX1 were upregulated in I/R-induced myocardial injury, but the level of miR-377-3p was decreased. A dual-luciferase reporter gene assay indicated that lncRNA KCNQ1OT1 targets miR-377-3p and that miR-377-3p targets HMOX1. Inhibition of HMOX1 alleviated miR-377-3p downregulation-induced myocardial injury. Furthermore, lncRNA KCNQ1OT1 promoted the level of HMOX1 by binding to miR-377-3p and aggravated myocardial injury.ConclusionLncRNA KCNQ1OT1 aggravates ischemia‒reperfusion-induced cardiac injury via miR-377-3P/HMOX1.

Intracellular Dynamics of Human Cardiac Ventricular Myocyte: ORd Model

Human heart is elegantly articulated to mechanically contract in response to electrical excitation. Cardiac electrical activity may be described as a multiscale process from sub-cellular to cellular to tissue level. Ion movement at the cellular level through ion channels results in an action potential that propagates as an electrical wave in tissue. A first-principles-based mathematical description of the cellular-level dynamics of cardiac electrophysiological behavior provides a better understanding of the functioning of the heart. The mathematical models describing cellular dynamics often involve a coupled system of ordinary differential equations (ODEs) with variables including transmembrane voltage, ion concentrations and ion channel gating variables, whose evolution describes activation/inactivation of ion channels. In this study we discuss a mathematical model of the human ventricular myocyte (O’Hara–Rudy model), defined as a system of 41 ODEs, with variables involving membrane voltage, 29 gating variables describing activation of Na[Formula: see text], K[Formula: see text], Ca[Formula: see text] channels, 11 variables describing ion concentrations and Ca[Formula: see text] related flux. Runge–Kutta method with variable order and variable time step was adopted to solve the system numerically. We discuss the action potential (AP) profile of a healthy human ventricular myocyte and corresponding dominant ionic currents. We present a phase plot that describes the change in voltage and its rate as the system evolves over time. The phase plot seems to provide more details of the underlying events than the AP curve.

COX6A2 deficiency leads to cardiac remodeling in human pluripotent stem cell-derived cardiomyocytes

BackgroundCardiac remodeling is the initiating factor for the development of heart failure, which can result from various cardiomyopathies. Cytochrome c oxidase subunit 6A2 (COX6A2) is one of the components of cytochrome c oxidase that drives oxidative phosphorylation. The pathogenesis of myocardial remodeling caused by COX6A2 deficiency in humans remains unclear because there are no suitable research models. In this study, we established a COX6A2-deficient human cardiac myocyte (CM) model that mimics the human COX6A2 homozygous mutation and determined the effects of COX6A2 dysfunction and its underlying mechanism.MethodsA human COX6A2 homozygous knockout cardiomyocyte model was established by combining CRISPR/Cas9 gene editing technology and hiPSC-directed differentiation technology. Cell model phenotypic assays were done to characterize the pathological features of the resulting COX6A2-deficient cardiomyocytes.ResultsCOX6A2 gene knockout did not affect the pluripotency and differentiation efficiency of hiPSCs. Myocardial cells with a COX6A2 gene knockout showed abnormal energy metabolism, increased oxidative stress levels, abnormal calcium transport activity, and decreased contractility. In addition, L-carnitine and trimetazidine significantly improved energy metabolism in the COX6A2-deficient human myocardial model.ConclusionsWe have established a COX6A2-deficient human cardiomyocyte model that exhibits abnormal energy metabolism, elevated oxidative stress levels, abnormal calcium transport, and reduced contractility. This model represents an important tool to gain insight into the mechanism of action of energy metabolism disorders resulting in myocardial remodeling, elucidate the gene-phenotype relationship of COX6A2 deficiency, and facilitate drug screening.

The Na/K-ATPase α1/Src Signaling Axis Regulates Mitochondrial Metabolic Function and Redox Signaling in Human iPSC-Derived Cardiomyocytes.

Na/K-ATPase (NKA)-mediated regulation of Src kinase, which involves defined amino acid sequences of the NKA α1 polypeptide, has emerged as a novel regulatory mechanism of mitochondrial function in metazoans. Mitochondrial metabolism ensures adequate myocardial performance and adaptation to physiological demand. It is also a critical cellular determinant of cardiac repair and remodeling. To assess the impact of the proposed NKA/Src regulatory axis on cardiac mitochondrial metabolic function, we used a gene targeting approach in human cardiac myocytes. Human induced pluripotent stem cells (hiPSC) expressing an Src-signaling null mutant (A420P) form of the NKA α1 polypeptide were generated using CRISPR/Cas9-mediated genome editing. Total cellular Na/K-ATPase activity remained unchanged in A420P compared to the wild type (WT) hiPSC, but baseline phosphorylation levels of Src and ERK1/2 were drastically reduced. Both WT and A420P mutant hiPSC readily differentiated into cardiac myocytes (iCM), as evidenced by marker gene expression, spontaneous cell contraction, and subcellular striations. Total NKA α1-3 protein expression was comparable in WT and A420P iCM. However, live cell metabolism assessed functionally by Seahorse extracellular flux analysis revealed significant reductions in both basal and maximal rates of mitochondrial respiration, spare respiratory capacity, ATP production, and coupling efficiency. A significant reduction in ROS production was detected by fluorescence imaging in live cells, and confirmed by decreased cellular protein carbonylation levels in A420P iCM. Taken together, these data provide genetic evidence for a role of NKA α1/Src in the tonic stimulation of basal mitochondrial metabolism and ROS production in human cardiac myocytes. This signaling axis in cardiac myocytes may provide a new approach to counteract mitochondrial dysfunction in cardiometabolic diseases.

The cardioprotective effects of cerium oxide nanoparticles against the poisoning generated by aluminum phosphide pesticide: Controlling oxidative stress and mitochondrial damage

BackgroundAluminum phosphide (AlP) is a well-known toxic compound used as an agricultural pesticide to prevent insect damage to stored crops. However, even if just a small amount was consumed, it caused lasting harm to the human body and, in acute concentrations, death. The current study employed cerium oxide nanoparticles (CeO2 NPs) to reduce oxidative stress and various harmful outcomes of AlP poisoning. MethodsFollowing finding effective concentrations of CeO2 NPs via MTT assay, Human Cardiac Myocyte (HCM) cells were pre-treated with CeO2 NPs for 24 h. After that, they were exposed to 2.36 μM AlP. The activity of oxidative stress and mitochondrial biomarkers, including mitochondrial swelling, mitochondrial membrane potential, and cytochrome c release, were evaluated in HCM cells. Finally, the population of apoptotic and necrotic cells was assessed via flow cytometry. ResultsAfter 24 h, data revealed that all tested concentrations of CeO2 NPs were safe, and 25 and 50 μM of that were selected as effective concentrations. Oxidative stress markers (malondialdehyde, protein carbonyl, superoxide dismutase, and catalase) showed that CeO2 NPs could successfully decrease AlP poisoning due to their antioxidant characteristics. Mitochondrial markers were also recovered by pre-treatment of HCM cells with CeO2 NPs. Furthermore, pre-treating with CeO2 NPs could compensate for the reduction of live cells with AlP and cause a diminishing in the population of early and late apoptotic cells. ConclusionAs a result, it is evident that CeO2 NPs, through the recovery of oxidative stress and mitochondrial damages caused by AlP, reduce apoptosis and have therapeutic potentials on HCM cells.

Abstract P3048: Ppp1r1b-lncRNA Regulates Cardiomyocytes Differentiation Via Epigenetic Modulation Of Tbx5 Promoter

Introduction: Myogenic differentiation is essential to cardiac development as well as regeneration and repair in response to genetic lesions or injury in the context of cardiomyopathy and congenital heart defects (CHDs). We have previously shown that mouse Ppp1r1b-lncRNA modulates epigenetic features of myogenic master regulators through targeted interaction with histone-modifying complex and other co-factors. However, the molecular mechanisms that underlie human PPP1R1B-lncRNA -mediated regulation of cardiomyocyte differentiation remain unknown. Objectives: To elucidate the mechanisms by which human PPP1R1B-lncRNA regulates cardiomyocyte differentiation. Methods/Results: PPP1R1B-lncRNA possessed conserved function in promoting myogenic differentiation in human cardiac and skeletal myocytes and its expression was dysregulated in CHDs. Mechanistically, by silencing PPP1R1B-lncRNA , myogenic differentiation was impaired in PPP1R1B-lncRNA -deficient human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). The expressions of myogenic transcription factors, including GATA4 and TBX5 , as well as sarcomere proteins, including TNNT2 and MYOZ2, were significantly suppressed in PPP1R1B-lncRNA deficient hiPSC-CMs. Epigenetic analysis revealed increased H3K27 tri-methylation at TBX5 promoter in the PPP1R1B-lncRNA knockdown cardiac progenitors. PPP1R1B-lncRNA was found to bind to EZH2, the enzymatic core of the polycomb repressive complex (PRC2). Furthermore, chromatin isolation by RNA purification (ChIRP)-seq revealed enriched interaction of PPP1R1B-lncRNA with TBX5 , MEF2C, and GATA4 promoters. Meanwhile, chromatin immunoprecipitation (ChIP)-PCR demonstrated increased enrichments of EZH2 at TBX5 promoter in the PPP1R1B-lncRNA-depleted cells, resembling what was observed in the pre-differentiation state. Conclusions: Human PPP1R1B-lncRNA promotes cardiomyocyte differentiation via interactions with promoters of key cardiac transcription factors. PPP1R1B-lncRNA enhances chromatin accessibility at TBX5 promoter by interfering with PRC2 binding. Understanding PPP1R1B-lncRNA function in cardiomyocyte differentiation may lead to novel therapies for cardiopathies and CHDs.

Effect and mechanism of circHMGA2 on ferroptosis and pyroptosis in myocardial ischemia-reperfusion model CircHMGA2 exacerbates MI/R injury

Myocardial ischemia-reperfusion (MI/R) injury is a common and serious complication following reperfusion treatment for myocardial infarction (MI). Increasing evidence has verified the crucial role of circular RNAs (circRNAs) in the MI/R injury processes. The objective of this study was to investigate the effects and potential regulatory mechanisms of circHMGA2 on MI/R injury. Hypoxia/reoxygenation (H/R) models were established using human cardiac myocytes (HCMs) and mice models were induced by MI/R. The level of circHMGA2 was detected by RT-qPCR. Myocardial function was evaluated by the hemodynamic parameters, the activity of serum myocardial enzymes, HE staining and TUNEL assays. Cell proliferation was measured by CCK-8 assay. The ferrous ion (Fe2+) level was determined with an iron assay kit. Ferroptosis- and pyroptosis-related proteins were determined using western blotting. The levels of oxidative stress and inflammatory factors were analyzed using DCFH-DA staining or ELISA assays. CircHMGA2 was upregulated in H/R-induced HCMs and myocardial tissues of MI/R mice. In vitro, circHMGA2 knockdown attenuated the proliferation inhibition, restrained the ferroptosis and pyroptosis in H/R-induced HCMs. This regulatory mechanism may be associated with the suppression of NLRP3 pathway. In vivo, circHMGA2 depletion attenuated myocardial tissue damage of MI/R mice through inhibiting the oxidative stress and pyroptosis. Taken together, CircHMGA2 enhanced MI/R injury via promoting ferroptosis and pyroptosis, providing new insights into the treatment of MI/R injury.

Human induced pluripotent stem cell-derived cardiac myocytes and sympathetic neurons in disease modelling.

Human induced pluripotent stem cells (hiPSC) offer an unprecedented opportunity to generate model systems that facilitate a mechanistic understanding of human disease. Current differentiation protocols are capable of generating cardiac myocytes (hiPSC-CM) and sympathetic neurons (hiPSC-SN). However, the ability of hiPSC-derived neurocardiac co-culture systems to replicate the human phenotype in disease modelling is still in its infancy. Here, we adapted current methods for efficient and replicable induction of hiPSC-CM and hiPSC-SN. Expression of cell-type-specific proteins were confirmed by flow cytometry and immunofluorescence staining. The utility of healthy hiPSC-CM was tested with pressor agents to develop a model of cardiac hypertrophy. Treatment with angiotensin II (AngII) resulted in: (i) cell and nuclear enlargement, (ii) enhanced fetal gene expression, and (iii) FRET-activated cAMP responses to adrenergic stimulation. AngII or KCl increased intracellular calcium transients in hiPSC-SN. Immunostaining in neurocardiac co-cultures demonstrated anatomical innervation to myocytes, where myocyte cytosolic cAMP responses were enhanced by forskolin compared with monocultures. In conclusion, human iPSC-derived cardiac myocytes and sympathetic neurons replicated many features of the anatomy and (patho)physiology of these cells, where co-culture preparations behaved in a manner that mimicked key physiological responses seen in other mammalian systems. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.

Abstract 4771: Prevention of doxorubicin-induced cardiotoxicity by benfotiamine

Abstract Anthracyclines such as daunorubicin and doxorubicin (DOX) are currently used as chemotherapeutic agents in the prevention of various cancers including breast cancer, lung cancer, leukemia, and lymphoma. Although, anthracyclines are successful in controlling various cancers growth, the major drawback is the unwanted cardiotoxicity. Specifically, high doses of DOX used for the therapy of advanced cancers could cause life threating conditions. Therefore, specific interventions are required to decrease the cardiac toxicity associated with the DOX. Benfotiamine, a lipid soluble vitamin B1 derivative has shown be a potent anti-oxidant and anti-inflammatory agent. However, the efficacy of benfotiamine in the prevention of cardiotoxicity associated with the anthracyclines is not known. In this study, we examined the effect of benfotiamine in the prevention of DOX-induced cytotoxicity in the human umbilical vascular endothelial cells (HUVECs). Treatment of HUVECs with DOX caused significant endothelial cells death and benfotiamine in a concentration-dependent manner prevented the dox-induced endothelial cell death. Further, benfotiamine prevents the DOX-induced apoptosis in endothelial cells by preventing the activation of caspase-3. Benfotiamine also prevents DOX-induced reactive oxygen species generation. Our results also indicate that benfotiamine regulates DOX-induced expression of pro-apoptotic mediators such as BAD, phosphor-P53, and pro-caspase-3, and anti-apoptotic mediators such as BCL-2, BCL-x, IAPs, and HSP and others such as FADD, DR5, and SMAC/diablo. We plan to further explore how benfotiamine prevents DOX-induced cardiotoxicity using human cardiac myocytes and mouse models. Thus, based on our cell culture studies, benfotiamine through its potent anti-oxidative property could prevent endothelial cytotoxicity and suggests that it could be further developed as adjuvant therapy in controlling cardiotoxicity associated with the anthracycline chemotherapy. Citation Format: Justin R. Taylor, Kyra Harames. Prevention of doxorubicin-induced cardiotoxicity by benfotiamine. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4771.

Abstract 2592: Trypanasoma cruzi dystegulates piRNA computationally predicted to target proinflammatory molecules in Primary Human Cardiac Myocytes during Early Infection Phase

Abstract 2592: Trypanasoma cruzi dystegulates piRNA computationally predicted to target proinflammatory molecules in Primary Human Cardiac Myocytes during Early Infection Phase

Klotho Protein Decreases MMP-Mediated Degradation of Contractile Proteins during Ischaemia/Reperfusion Injury to the Cardiomyocytes

Ischaemia, followed by reperfusion, causes the generation of reactive oxygen species, overproduction of peroxynitrite, activation of matrix metalloproteinases (MMPs), and subsequently the degradation of heart contractile proteins in the cardiomyocytes. Klotho is a membrane-bound or soluble protein that regulates mineral metabolism and has antioxidative activity. This study aimed to examine the influence of Klotho protein on the MMP-mediated degradation of contractile proteins during ischaemia/reperfusion injury (IRI) to the cardiomyocytes. Human cardiac myocytes (HCM) underwent in vitro chemical IRI (with sodium cyanide and deoxyglucose), with or without the administration of recombinant Klotho protein. The expression of MMP genes, the expression and activity of MMP proteins, as well as the level of contractile proteins such as myosin light chain 1 (MLC1) and troponin I (TnI) in HCM were measured. Administration of Klotho protein resulted in a decreased activity of MMP-2 and reduced the release of MLC1 and TnI that followed in cells subjected to IRI. Thus, Klotho protein contributes to the inhibition of MMP-dependent degradation of contractile proteins and prevents injury to the cardiomyocytes during IRI.

LncRNA NEAT1 Downregulation Ameliorates the Myocardial Infarction of Mice by Regulating the miR-582-5p/F2RL2 Axis.

This study is aimed at effectively investigating the role of coagulation factor II thrombin receptor like 2 (F2RL2) in myocardial infarction (MI) as well as the upstream regulatory miRNA and lncRNA. Regulatory genes of F2RL2 were analyzed using StarBase and verified by dual-luciferase reporter assay. The MI mouse model was established. The left ventricular ejection fraction (EF) and fractional shortening (FS) were examined by echocardiography. The infarct area, pathological changes, and cell apoptosis in mouse myocardial tissue were evaluated using triphenyltetrazolium chloride and Evans blue, hematoxylin-eosin, and TUNEL staining assays. Oxygen-glucose deprivation- (OGD-) induced human cardiac myocytes (HCMs) were cultured and transfected. The cell viability, proliferation, and apoptosis were determined by CCK-8, EdU staining, and flow cytometry assays. The expressions of F2RL2, miR-582-5p, and nuclear paraspeckle assembly transcript 1 (NEAT1) in myocardial tissues and HCMs were quantified by qRT-PCR or Western blot. NEAT1 sponged miR-582-5p which targeted F2RL2. NEAT1 and F2RL2 were highly expressed while miR-582-5p was lowly expressed in MI mice. F2RL2 downregulation prevented the reduction in EF and SF and the elevation in infarct area and cell apoptosis of MI mice. Both F2RL2 and NEAT1 downregulations reversely modulated the decreased viability and proliferation and the increased apoptosis of OGD-induced HCMs, while miR-582-5p inhibitor did oppositely. NEAT1 silencing upregulated miR-582-5p level but downregulated F2RL2 level. miR-582-5p inhibitor upregulated the F2RL2 level. The role of NEAT1 silencing in OGD-induced HCMs was reversed by miR-582-5p inhibitor whose effect was further offset by F2RL2 downregulation. NEAT1 downregulation ameliorates MI by regulating the miR-582-5p/F2RL2 axis, providing novel biomarkers for MI treatment.

Abstract 12449: Inhibition of the Sodium Potassium ATPase Alpha 3 (ATP1A3) Pump Function Alters Repolarization Time and is Proarrhythmic in Cardiac Myocytes

Introduction: Inhibition of Na + /K + -ATPase (NKA) is arrhythmogenic, but the specific effect of alpha 3 NKA isoform (ATP1A3) inhibition is unknown. Variants in human ATP1A3 can lead to ventricular arrhythmias, yet the mechanism remains unknown. Hypothesis: Loss of NKA function results in shortening of QT interval and increased arrhythmia susceptibility due to intracellular Na+ and Ca2+ overload. Pharmacological inhibition of sodium-calcium exchanger (NCX) can rescue ECG parameter changes and arrhythmic phenotypes by reducing Ca2+ overload in the cell. Methods: Whole-cell patch clamp action potential recordings were conducted on induced pluripotent stem cell cardiomyocytes (iPSC-CMs) from an ostensibly healthy individual to measure action potential duration (APD) and presence of delayed after depolarizations (DADs). Cells were exposed to 10 -7 M ouabain and 10 -5 M ORM-10103 (a selective inhibitor of NCX). ECGs and in vivo intracardiac electrophysiology studies were performed in mice at 12-14 weeks of age after intraperitoneal drug administration of 5 μg/g ouabain and 10 μg/g ORM-10103. Results: APD recordings of iPSC-CMs demonstrated both shortening and lengthening of APD with ouabain exposure. In both models, DADs were found in 6 of 18 cells with ouabain treatment. These findings were rescued with pretreatment using ORM-10103, as 0 of 8 cells developed DADs. On mouse ECG recordings, ouabain led to QRS and QT prolongation. During programmed electrical stimulation, no arrhythmia was noted with vehicle-treated mice. Following ouabain administration, 2 in 12 mice developed induced monomorphic ventricular tachycardia. Pretreatment of ORM-10103 in mice did not rescue QRS and QT prolongation with ouabain administration. Conclusions: Pharmacologic inhibition of ATP1A3 variably altered cardiac repolarization time in a species-specific manner, yet was associated with a substrate for triggered arrhythmias. The arrhythmogenic phenotype was rescued with inhibition of NCX in human cardiac myocytes, suggesting that NCX plays a role in the arrhythmogenic mechanism of ATP1A3. However, these effects were not seen in murine cardiac myocytes. Exploration of specifies-specific differences in NKA isoform expression and cardiac repolarization is needed.

MiR-490-3p Alleviates Cardiomyocyte Injury via Targeting FOXO1.

MicroRNA-490-3p (miR-490-3p) plays a role in the pathogeneses of a variety of cardiovascular diseases. Bioinformatic analysis showed that miR-490-3p was downregulated in the myocardial tissues of mice with myocardial infarction (MI). Nevertheless, the functions and mechanisms of miR-490-3p in MI remain unclear. This study used an in-vitro model to investigate the role of miR-490-3p in MI. Human cardiac myocytes (HCMs) were cultured in a hypoxic environment. 3-(4,5)-Dimethylthiahiazo (-zy1)- 3,5-di-phenytetrazoliumromide (MTT) assay and flow cytometry were used to detect cell viability and apoptosis. The expression levels of forkhead box O1 (FOXO1) and miR-490-3p were detected by quantitative real-time PCR and Western blot. The levels of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), lactate dehydrogenase (LDH), cardiac troponin I (cTnI), and creatine kinase MB (CK-MB) were detected by enzyme-linked immunosorbent assay (ELISA). The targeted relationship between miR-490-3p and FOXO1 3'UTR was determined by a dual-luciferase reporter gene assay. miR-490-3p was significantly down-regulated in hypoxia-induced HCM cells, while FOXO1 was markedly up-regulated. miR-490-3p overexpression inhibited HCM cell inflammatory responses and injury after hypoxia treatment. FOXO1 was validated to be a direct target of miR- 490-3p, and its overexpression weakened the effects of miR-490-3p on cell viability, apoptosis, as well as inflammatory responses. miR-490-3p alleviates cardiomyocyte injury via targeting FOXO1 in MI.