tbuckley/cabot-search huggingface dataset:
Abstract Tu101: Measuring Fibrosis Progression in Duchenne Cardiomyopathy Using Cardiac Magnetic Resonance in mice
Authors: India Hawkins, Josh Mitchell, Adolfo Mauro, Nigeste Carter, Frank Corwin, Fadi Salloum, Frank Raucci
Journal: Circulation Research (2024)

Introduction: Transthoracic echocardiogram (TTE) is currently the gold standard for measuring cardiac function in mouse models of cardiomyopathy, however, it has its limitations. Challenges include poor acoustic windows, lower reproducibility, larger margin of error, and inability to accurately detect fibrosis. The detection of fibrosis is critical for assessing the severity of cardiac involvement and monitoring disease progression in Duchenne muscular dystrophy (DMD). Cardiac magnetic resonance imaging (CMR) can be used to more accurately measure cardiac function, chamber volumes, and tissue characterization to monitor the progression of fibrosis, including with parametric T1 mapping and late gadolinium enhancement (LGE). In this study, we have used a dystrophic mouse model (D2. mdx ) on the DBA/2J genetic background as a preclinical model of DMD. Hypothesis: We hypothesize that CMR can detect worsening cardiac function and signs of fibrosis in the left ventricle of D2. mdx mice compared to wildtype (DBA) controls. Methods: In a study group of 12 age-matched male mice (8 mdx, 4 DBA), CMR was performed with contrast to determine cardiac function and fibrotic developments in the heart. Results: D2. mdx mice displayed a higher left ventricular end-diastolic volume compared to DBA mice (32.8 ± 3.6 µL vs 27.4 ± 1.5 µL, p &lt; 0.05). Global longitudinal strain was decreased in D2. mdx compared to DBA mice (-11.0 ± 3.5% vs -18.2 ± 2.2%, p &lt; 0.05). Native T1 mapping (Fig 1A) showed significantly higher mean T1 times in D2. mdx mice compared to DBA controls (Fig 1B). LGE in the myocardium of the left ventricle was noted in 6 of 8 of the D2. mdx mice (Fig 1C), but not in DBA mice. Logistic regression modeling showed strong predictive value detecting LGE with increasing native T1 times (Fig 1D). Conclusion: CMR can detect tissue changes in D2. mdx myocardium representing fibrotic changes. Native T1 may be useful in longitudinal studies of antifibrotic therapies in these models.
Abstract Mo052: Electrocardiographic behavior, arrhythmias, and mortality in two calcium management strategies (cytoplasmic and mitochondrial) in hearts under ischemia.
Authors: Enio Vasques, Bruna Kim Vasques, JOSÉ GUSTAVO TAVARES, Francisco Sandro Menezes-Rodrigues, afonso caricati-neto, THIAGO Melo, Jose Eduardo Monteiro da Cunha, Tiago Rodrigues
Journal: Circulation Research (2024)

Background: The disruption of calcium homeostasis in ischemic hearts is determinant for triggering the arrhythmic phenomena and death. Interventions that act on calcium levels in cytoplasm and mitochondria might interrupt or minimize these outcomes. Trisulfate disaccharide (TD) acts by accelerating the sodium-calcium exchanger, decreasing cytosolic calcium levels. Ruthenium red (RuR) is a mitochondrial uniporter inhibitor that blocks calcium influx into mitochondria. Both agents can be useful in calcium overload elicited by myocardial ischemia (MI), modifying electrocardiographic (EKG) parameters that predict arrhythmia, arrhythmic phenomena, and cell death. Objectives: To compare the behavior of Tp-Te and QTc EKG intervals, arrhythmia rates, and mortality in ischemic hearts under the action of TD and RuR. Materials and Methods: Adult Wistar rats (n=24) were divided in 3 groups, i.e, Control: MI with no treatment (n=8), TD: MI treated with TD 0.2 mg/kg IV (n=8), and RuR:MI treated with RuR 1 mg/kg IV (n=8). Rats were monitored by EKG and submitted to surgical MI by ligation of anterior descending artery during 10 minutes followed by reperfusion thereafter. The Tp-Te and QT intervals were analyzed before and at 10 minutes of ischemia and 10 minutes after the onset of reperfusion. The incidence of arrhythmias and mortality were determined throughout the recording time. Results: The Tp-Te and QTc intervals increased during ischemia in all groups (Control, TD and RuR), which were normalized after 10 minutes reperfusion only in TD group. The observed arrhythmias (atrioventricular block, ventricular tachycardia, and torsade of pointes) had a higher incidence in the control group and the lower incidences, with statistically significant differences, were achieved in TD and RuR groups, whose incidence was similar in these both groups. Sustained arrhythmias led to a 50% mortality in the control group and 25% in RuR group. No mortality in TD group was observed. Conclusion: The strategy of decreasing cytosolic calcium levels by the action of TD has proved to be more effective than the blockade of mitochondrial calcium uptake by RuR, with further normalization of EKG parameters predictors of mortality, and absence of sustained arrhythmias and mortality, suggesting that the management of cytosolic calcium levels is more effective than only the management of mitochondrial calcium in MI model.
Abstract Mo072: Sustained Biological Pacemaker Activity Induced by AAV9-hTBX18
Authors: Rodrigo Miguel dos Santos, Thassio Mesquita, Lizbeth Sanchez, Liang Li, Eduardo Marban, Eugenio Cingolani
Journal: Circulation Research (2024)

Background: Sinoatrial node (SAN) dysfunction is a clinical disorder characterized by the inability of the SAN to maintain an appropriate heart rate (HR). Patients with this condition often need an electronic pacemaker. Although it is the current standard of care, devices can have complications. A biological pacemaker has been created by adenovirus expressing TBX18 as an alternative. Hypothesis: However, adenoviruses are immunogenic, limiting the duration of expression. We hypothesized that an AAV9 would promote prolonged TBX18 expression, induce somatic reprogramming in vivo, and sustained pacemaker activity. Methods: AAV9 containing GFP or TBX18 was directly injected into the myocardium of eight-week-old male Sprague Dawley rats (n=70) at low (1x10 9 GC), mid (1x10 10 GC) and high (1x10 11 GC) doses. Transient AV block was induced by tail vein injection of adenosine. A permanent complete AV block was induced by ablation of the his bundle. Hearts were harvested for optical mapping and mRNA analysis. Results: Six weeks after injection, all doses of AAV9-TBX18 had increased HR (low: 104±4, p=0.04; mid: 106±3.4, p=0.008; high: 103±4.1, p=0.04; vs GFP: 89±3 bpm) compared to AAV9-GFP when we induced AV block using adenosine. AAV9-GFP and -TBX18 mid dose injected rats underwent surgery to induce complete AV block. TBX18 group presented superior HR over the 24 hours monitored. 6-lead EKG analysis of the QRS axis in the frontal plane revealed that the ventricular ectopic beats from the AAV9-TBX18-injected group originated from the injection site. Activation maps further confirmed that the injection site originated those beats in TBX18-injected rats only. Successful reprogramming of adult ventricular myocytes into SAN-like cells was confirmed by transcriptional profiles with increased expression of TBX18 (2.2±0.5 FC, p&lt;0.0001) and Hcn2 (25.2±1.1 FC, p=0.02), and reduced Gja1 (-10.8±0.7 FC, p=0.005), Scn5a (-1.1±0.8 FC, p=0.01) and Nkx2.5 (-2.0±0.6 FC, p=0.004) relative to GFP. Conclusion: Collectively, these data indicate that the AAV-based somatic reprogramming induced by TBX18 leads to sustained biological pacemaker activity in rats with AV block. Long-term studies are needed to characterize the long-term effects of sustained TBX18 expression.
Abstract Mo057: Computational Modeling Reveals Enhanced Ca <sup>2+</sup> -Driven Arrhythmias in Female Patients with Atrial Fibrillation
Authors: Xianwei Zhang, Yixuan Wu, Charlotte Smith, William Louch, Stefano Morotti, Dobromir Dobrev, Eleonora Grandi, Haibo Ni
Journal: Circulation Research (2024)

Background and Aim: Substantial sex-based differences have been reported in atrial fibrillation (AF), with female patients experiencing worse symptoms, more complications from treatment, and greater risk of stroke and mortality. Recent studies revealed sex-specific alterations in AF-associated Ca 2+ dysregulation, whereby female myocytes more frequently exhibit proarrhythmic Ca 2+ -driven instabilities compared to male myocytes. Here, we aim to obtain a mechanistic understanding of the Ca 2+ -handling disturbances and Ca 2+ -driven arrhythmogenic events in males vs females and establish their responses to Ca 2+ -targeted interventions. Methods and Results: We incorporated known sex differences and AF-associated changes in the expression and phosphorylation of key Ca 2+ -handling proteins and in ultrastructural properties and dimensions of atrial myocytes into our recently developed 3D atrial myocyte model that couples electrophysiology with spatially detailed Ca 2+ -handling processes. Simulations show increased incidence of Ca 2+ sparks in female vs male myocytes in AF, in agreement with previous experimental reports. Additionally, our female model exhibited elevated propensity to developing pacing-induced spontaneous Ca 2+ releases (SCRs, Figure 1A,B ) and augmented beat-to-beat variability in action potential (AP)-elicited Ca 2+ transients compared with the male model ( Figure 1C ). Parameter sensitivity analysis uncovered precise arrhythmogenic contributions of each component that was implicated in sex and/or AF alterations ( Figure 2 ). Specifically, increased ryanodine receptor phosphorylation in female AF myocytes emerged as the major SCR contributor, while reduced L-type Ca 2+ current was protective against SCRs for male AF myocytes. Furthermore, simulations of Ca 2+ -targeted interventions identified potential strategies to attenuate Ca 2+ -driven arrhythmogenic events in female atria (e.g., t-tubule restoration, and inhibition of ryanodine receptor and sarcoplasmic/endoplasmic reticulum Ca 2+ -ATPase), and revealed enhanced efficacy when applied in combination. Conclusions: Our sex-specific computational models of human atrial myocytes uncover the increased female propensity to Ca 2+ -driven arrhythmogenic events vs male in AF, and identify combined Ca 2+ -targeted interventions as promising approaches to treat AF in female patients. Our study establishes that AF treatment may benefit from sex-dependent strategies informed by sex-specific mechanisms.
Abstract Mo056: Cholinergic Activation Suppresses Optogenetic Stimulation of Intrinsic Cardiac Catecholaminergic Neurons in Perfused Mouse Hearts
Authors: Rebekah Russo, Angel Moreno, David Mendelowitz, Matthew Kay
Journal: Circulation Research (2024)

Balance of cholinergic and catecholaminergic activation is necessary to maintain heart health. Interrogating the acute interaction of these autonomic pathways can be done using optogenetics via selective expression of channelrhodopsin (ChR2) within intrinsic cardiac neurons. We tested the hypothesis that cholinergic activation via exogenous acetylcholine (ACh) would suppress the beta-adrenergic heart rate (HR) acceleration induced by tyrosine hydroxylase (TH) neuron stimulation, with the prominence of AV block increasing with increased ACh concentration. ECGs were recorded during perfused heart studies using wild-type (WT) mice and transgenic mice that selectively expressed ChR2 in TH neurons that secrete norepinephrine (NE). HR responses were measured for WT while increasing [NE] and for TH by illuminating the right atrium (465nm, microLED) at a range duty cycles and frequencies. Duty cycles (at 5Hz) increasing from 5-50% caused proportional increases in HR however HR was unstable at duty cycles &gt;30%. At 20% duty cycle, HR increased by 39.43±6.79% (n=6). HR increased sigmoidally at frequencies from 2.5-15Hz (with 30ms pulse width) but HR was unstable at 15Hz. At 10Hz, heart rate increased by 64.24±13.47% (n=4). When comparing HR increases for TH (n=5) and WT+NE (n=4), optogenetic activation resulted in similar maximum HRs but drastically different rise times (7.6±1.25 vs 46.43±5.01 beats/sec, respectively). HR suppression at increasing doses of ACh was measured while perfusing WT hearts with NE and photostimulating TH hearts. The addition of ACh caused beta-adrenergic HR increases to diminish, eventually reaching below baseline HR. In WT+NE animals this occurred at 400nM ACh and in TH animals this did not occur until 1800nM ACh. As ACh increased in TH animals, onset of AV block occurred sooner and more prominently. In conclusion, optogenetic activation of TH neurons caused rapid HR acceleration that was suppressed by ACh at concentrations much higher than that required to suppress acceleration during NE perfusion. AV block also occurred more rapidly during TH neuron activation as [ACh] increased, demonstrating a time-dependent effect in the interaction of cholinergic and catecholaminergic activation.
Abstract We063: CD73 EXPRESSION ON NEUTROPHILS PROTECTS AGAINST CARDIOMYOCYTE DAMAGE DURING INVASIVE <i>STREPTOCOCCUS PNEUMONIAE</i> INFECTION
Authors: Manmeet Bhalla
Journal: Circulation Research (2024)

In recent years, Streptococcus pneumoniae (pneumococcus)-induced cardiac events have emerged as one of the most serious and life-threatening infection outcomes of invasive pneumococcal disease (IPD), leading to major adverse cardiac events (MACE) with high mortality rates. S. pneumoniae has the ability to invade myocardium and damage cardiomyocytes through the release of bacterial factors and formation of bacterial-filled cardiac microlesions. We previously found that polymorphonuclear cells (PMNs) or neutrophils are crucial for host defense against S. pneumoniae lung infection and that extracellular adenosine (EAD) production, by the exonucleosidase CD73, controlled the anti-bacterial functions of these cells. The objective of this study was to explore the role of PMNs and CD73 in cardiac damage during invasive pneumococcal infection. Upon intra-peritoneal ( i.p .) injection with TIGR4, an invasive pneumococcal strain, C57BL/6 mice showed an increased influx of PMNs into the cardiac tissue as determined by flow cytometry. However, the increased PMN numbers failed to contain bacterial burden in the heart and showed a positive correlation with serum levels of the cardiac damage marker Troponin-1 as determined through ELISA. Depletion of PMNs prior infection reduced pneumococcal burden in the heart and lowered the Troponin-1 levels suggesting that PMNs induce cardiac damage during infection. While exploring the mechanisms underlying the detrimental PMN response, we found that the late stage of IPD was associated with reduced CD73 expression on PMNs. The role of CD73 in regulating cardiac damage was tested in vivo using CD73 -/- mice which had significantly higher bacterial burden and cardiac damage compared to wild-type mice despite similar PMN numbers. The role of CD73 expression on PMNs was also tested ex vivo using the HL-1 cardiomyocyte cell line which showed increased LDH release upon S. pneumoniae infection in presence of CD73 -/- PMNs, a phenotype reversed by supplementation of exogenous adenosine. Similar iincreased damage in presence of CD73 -/- PMNs was seen with C57BL/6 Mouse Primary Cardiac Microvascular Endothelial Cells which lead to increased migration of beads across endothelium. Our findings suggest that dysregulation of CD73 on PMNs during invasive pneumococcal infection leads to an inability to control bacterial numbers and increased cardiac damage, and that the EAD-pathway can be a potential pharmacological target to limit disease severity.
Abstract Mo042: Poison Peptides May Contribute to Dysregulation of SERCA in Heart Failure
Authors: Taylor Phillips, Jacob Cunningham, Jaroslava Seflova, Ellen Cho, Seby Edassery, Elisa Bovo, Aleksey Zima, Jonathan Kirk, Seth Robia
Journal: Circulation Research (2024)

Proteolysis increases in heart disease, resulting in an accumulation of degraded membrane protein fragments in heart cells. Previous studies have shown that diverse hydrophobic alpha helices can bind and non-specifically inhibit the cardiac calcium pump SERCA. Thus, we hypothesized that partially degraded fragments of transmembrane proteins may directly inhibit SERCA or compete with native peptide regulators of the pump, like such as phospholamban. The resulting dysregulation of SERCA may contribute to calcium mishandling in heart failure. To test these hypotheses, purified cell membranes from non-failing or dilated cardiomyopathy human hearts were subjected to SDS-PAGE and mass spectrometry to identify protein fragments smaller than 26 kD. 1800 proteins were detected, of which 92 were upregulated &gt;3 fold in the failing heart samples, consistent with increased production of small fragments from these membrane proteins. 9 of the upregulated fragments containing transmembrane segments were selected for further analysis based on sequence hydrophobicity and structural similarity to endogenous micropeptide regulators of SERCA. Of these 9 fragments, 6 showed ER localization, suggesting potential for a toxic interaction with SERCA. The relative binding of these candidates to SERCA was quantified with FRET microscopy. Fragments of three membrane proteins (SEC61B, VAMP3, VAMP8) showed an avid interaction with SERCA. To measure SERCA inhibition, we utilized a calcium activity assay was performed usingin which HEK293T cells were transfected with SERCA, ryanodine receptor, candidate peptides and rCepia as an ER calcium indicator. ER-calcium level was normalized to minimum fluorescence after caffeine addition and an ionomycin induced maximum fluorescence after addition of ionomycin and calcium and caffeine induced minimum. Unregulated Candidate poison peptides were compared to SERCA alone and SERCA-PLB phospholamban controls were also performed. . SEC61B demonstrated the a strongest inhibition, most (similar to phospholamban, ) while VAMP3 and VAMP8’s effect was more modest. This type of non-nativeThus, we propose accumulation of toxic transmembrane peptide fragments may inhibition could be contributinginhibit SERCA and contribute to the calcium mishandling seen in heart failure. Future experiments will be performed to quantify the relative abundance of the fragments compared to endogenous regulatory micropeptides.
Abstract We048: Exon-skipping therapy can restore functional dystrophin attenuating calcium overload for DMD cardiomyopathy with mutations in actin-binding domain 1
Authors: Naoko Shiba, Xiao Yang, Masahiro Agata, Kohei Nagamine, Shin Kadota, Sato Mitsuto, Akinori Nakamura, Yuji Shiba
Journal: Circulation Research (2024)

Antisense oligonucleotide (AO)-mediated exon-skipping is a promising therapeutic strategy for Duchenne muscular dystrophy (DMD), which is caused by loss-of-function mutations in the DMD gene encoding Dp427m, leading to progressive cardiomyopathy. In-frame deletion of exons 3–9 (Δ3–9) manifesting asymptomatic or very mild clinical phenotype is an ideal goal for exon-skipping by targeting actin-binding domain 1 (ABD1); however, the efficacy of this therapy for DMD cardiomyopathy remains unclear. We compared three isogenic human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) expressing Δ3–9, frameshifting Δ3–7, and intact DMD. RNA-seq revealed high similarity between Δ3–9 and wild-type hiPSC-CMs. Furthermore, we observed electrophysiological alterations with accelerated CaMKII activation in Δ3–7 hiPSC-CMs compared to Δ3–9 and wild-type hiPSC-CMs, while Δ3–9 Dp427m was stably expressed, maintaining substantial binding to F-actin and retention of desmin. AOs targeting exon 8 efficiently induced exons 8–9 skipping to restore functional Dp427m and electrophysiological parameters in Δ3–7 hiPSC-CMs. Exon-skipping therapy converting the reading frame to Δ3–9 might be promising for DMD cardiomyopathy.
Abstract We064: Investigating the Cardioprotective Role of Neutrophil-Specific STING in Myocardial Ischemia/Reperfusion Injury
Authors: Maegan Brockman, Lanfang Wang, Triniti Scruggs, John Calvert, Rebecca Levit
Journal: Circulation Research (2024)

Introduction: Inflammation following myocardial ischemia/reperfusion injury (MI/R) plays a significant role in damaging cardiomyocytes and influencing infarct size, with neutrophils being the most rapid and numerous cells recruited to the myocardium post reperfusion. Single-cell RNA sequencing data identified neutrophils with upregulated type I interferon (IFN) signaling in the hearts of mice 24 hours post-MI/R. Aim: This study aims to address how the type I IFN neutrophil phenotype identified affects inflammation in MI/R. We hypothesize that neutrophils with upregulated type I IFN signaling are cardioprotective in MI/R. Methods: Male neutrophil-specific STING knockout (KO) mice underwent 60 minutes of ischemia followed by reperfusion for 24 hours. Immune cells were isolated from the left ventricle for flow cytometry. Subsequently, mice underwent 60 minutes of ischemia followed by reperfusion, and cardiac function was assessed two weeks-post reperfusion. Results: Flow cytometry revealed a significant decrease in the number of neutrophils in the myocardium of neutrophil-specific STING KO mice compared to wildtype mice after 24 hours of reperfusion (5.7x10 4 ± 1.0x10 4 ; 8.7x10 4 ± 1.9x10 4 , Two-way ANOVA, N=5-6, p=0.0006). Neutrophil-specific STING KO mice showed significant reduction in ejection fraction (29.2% ± 6.4) compared to wildtype mice (38.3% ± 6.7; Two-way ANOVA, N=4-5, p=0.036), and significantly increased left ventricular end systolic volume (4.39mm ± 0.48) compared to wildtype mice (3.59 ± 0.62; Two-way ANOVA, N=4-5, p=0.017), indicating impaired cardiac function in knockout mice. Conclusion: These data suggest that neutrophil STING plays a cardioprotective role in MI/R. These studies provide the foundation to further investigate the cardioprotective mechanisms behind neutrophil-specific STING. Identifying a novel cardioprotective mechanism could be a clinically feasible point of intervention to improve recovery after MI/R.