tbuckley/cabot-search huggingface dataset:
Abstract Mo079: Analyzing the Predicted Impact of Published SCN5A Variants in Juvenile-Onset Sick Sinus Syndrome
Authors: Snekha Rajasekaran, Aleksandra Foksinska, Camerron Crowder, Matthew Might
Journal: Circulation Research (2024)

Background: Sick sinus syndrome (SSS) is a cardiac condition caused by sinoatrial node dysfunction, leading to arrhythmias due to the inability to transmit signals properly to the upper chambers of the heart. While age-related degeneration of the sinoatrial node is the most common contributing factor to SSS, congenital disorders involving genetic variants can also lead to its development, even in pediatric patients. To explore the genetic basis of SSS in the pediatric population (age &lt; 19 years), we conducted a comprehensive review of case reports to identify associated genetic variants. Our focus centered on variants reported in the sodium channel protein type 5 subunit alpha ( SCN5A ) gene, which has been reported to contribute to various ventricular arrhythmias, including SSS. Methods: A comprehensive literature review of case reports of juvenile-onset SSS was conducted using PubTator/PubMed and the Online Mendelian Inheritance in Man (OMIM) database to identify SCN5A variants. Case reports were selected if they met the following criteria: at least one patient diagnosed with SSS at or under the age of 19 with a detected variant in the SCN5A gene. The structural effects of identified variants were assessed using the HOPE web service. Results: Data compiled from the literature review provided a total of 53 cases related to juvenile-onset SSS and the SCN5A gene. Among the reported patients, many exhibited multiple arrhythmogenic phenotypes alongside SSS, including progressive cardiac conduction disease, idiopathic ventricular tachycardia, and Brugada syndrome. The majority of identified variants were missense, although truncating and insertion/deletion variants were also documented. All three inheritance variations - heterozygous, homozygous, and compound heterozygous - were observed in this set of patients. Although many of the variants had some functional studies performed to determine their pathogenicity, some of the variants did not have a predicted impact. For these variants, we characterized the location and biochemical properties of the variants, comparing them to the variants with known functional impact. Conclusion: Future studies will explore the functional impact associated with the predicted variants through modeling specific mutations in SCN5A , using cardiomyocytes in vitro . Additionally, using further published studies and surveying the protein structure analysis of SCN5A variants will aid in characterizing those that are specific to SSS.
Abstract We089: Numb Family Proteins in Epicardium Regulate Epicardial Cells Differentiation and Ventricular Patterning During Development
Authors: Anika Nusrat, Luqi Zhao, Lianjie Miao, Mingfu Wu
Journal: Circulation Research (2024)

Background: Numb Family Proteins (NFPs), specifically two mammalian homologs Numb (denoted by Nb ) and Numblike (denoted by Nl ), have been evident to regulate essential cardiac functions during development. Previous studies reported NFPs as integral for epicardial cells (EpiCs) epithelial mesenchymal-transition (EMT). However, whether NFPs in epicardium regulate EpiCs differentiation to affect cardiac morphogenesis have not been explored. In this study, we investigated how NFPs in epicardium regulate EpiCs EMT and differentiation to modulate cardiac development and subsequently affect cardiac maintenance in adult stages. Method: Using mCherry:Numb knockin mouse model we observed enrichment of Numb in epicardium. We deleted Nb and Nl in epicardium via Tbx18 Cre/+ lineage and refer to this as EDKO. We harvested hearts at embryonic day 15.5/18.5 and assessed morphological and mechanistic differences between control and EDKOs. Conventional and Speckle tracking Echocardiography were used to examine adult heart structure and functions. Results: Our findings revealed that EDKO embryonic hearts display specific morphology with extended left ventricles. We found a surprising difference between female and male EDKOs in terms of survival to adulthood. Reduced EpiCs EMT and Cardiac Fibroblasts (CFs) migration distances, changes in CFs distribution have been observed in EDKO developing hearts. Reduced expression of smooth muscle cells (SMCs) and pericytes also was noticed in EDKOs. Strikingly, EDKO embryonic hearts show defects in ventricular compaction, ventricular wall patterning and in cell proliferation. Furthermore, when survived to adult stage, EDKO hearts revealed significant structural and functional changes over their aging. While digging into regulatory pathways, we found changes in Fibroblast growth factor receptors (Fgfrs)/p-Erk pathway and in activation of Notch1 in EDKO hearts. Conclusion: NFPs in epicardium regulate EpiCs differentiation into CFs and SMCs, and regulate ventricular wall morphogenesis during development. NFPs are also required to maintain cardiac structure and function at adult stages. Fgfrs/p-Erk pathway and Notch1 could be the possible mechanism behind cardiac morphogenetic regulation by NFPs in epicardium. Future aims: Further studies will identify downstream targets of NFPs’ regulation of EpiCs differentiation and ventricular wall patterning in embryonic hearts, and mechanistic pathways of epicardial NFPs’ role in adult hearts.
Abstract Mo078: Identifying Genetic Determinants of Phytosterol Levels: A Genome-Wide Association and Meta-Analysis Study Unveils a New Locus Influencing Campesterol Serum Concentrations
Authors: Jamil Alenbawi, Yasser Al-Sarraj, Umm-Kulthum Ismail Umlai, Ayat Kadhi, Nagham Hendi, Georges Nemer, Omar Albagha
Journal: Circulation Research (2024)

Background: Sitosterolemia, a rare inherited disorder, stems from mutations in the ABCG5/ABCG8 genes, which play a critical role in plant sterol transport. These genetic anomalies result in reduced phytosterol excretion, causing an accumulation in the body that can lead to serious health issues, such as premature coronary artery disease. Hypothesis: The study aimed to uncover the genetic determinants influencing plant sterol levels within the Middle East/North Africa (MENA) population, focusing on individuals from Qatar. It hypothesized that unique genetic variations might influence these levels, contributing to the development of sitosterolemia. Aims: To conduct the first genome-wide association study (GWAS) in the MENA region to identify genetic variants affecting plant sterol levels in the Qatari population, and to compare these findings with those from populations of European ancestry. Methods: The study utilized the Metabolon platform for analyzing serum levels of β-sitosterol and campesterol, combined with genome sequence data from the Qatar Genome Program. A trans-ancestry meta-analysis compared our findings with those from a large European cohort, while conditional analysis helped identify specific single nucleotide polymorphisms (SNPs) associated with these sterols. Results: The research identified two independent SNPs related to β-sitosterol ((rs145164937 and rs4299376) and two to campesterol (rs7598542 and rs75901165) in the Qatari population, alongside previously reported variants ( P &lt;5.0 ×10 -8 ) .Notably, one variant (rs75901165) was located in the Intraflagellar Transport 43 (IFT43) gene, diverging from the common ABCG5/8 locus. The study also supported the association of variants in the SCARB1 and ABO genes with sitosterolemia and assessed a polygenic risk score's efficacy based on European GWAS data in the Qatari cohort. Conclusion(s): The findings underscore the significance of conducting population-specific genetic research to understand better and manage conditions like sitosterolemia. This research highlights the importance of personalized treatment approaches for hyperlipidemia and the value of establishing comprehensive multi-omics databases tailored to specific populations.
Abstract We077: Mechanisms of T-lymphocyte Dysfunction in Dilated Cardiomyopathy Patients
Authors: Austin Angelotti, Shyam Bansal
Journal: Circulation Research (2024)

Preclinical studies have shown that T-cells infiltrate the heart during heart failure (HF), promoting remodeling. However, it remains unclear whether activated T-cells infiltrate the human failing hearts also. Importantly, cellular mechanisms that are involved in T-cell activation during human HF are unknown. To address this question, we analyzed published single-cell RNA sequencing data from patients with dilated cardiomyopathy (DCM) and compared it with control hearts. Our analysis focused on characterizing the gene expression of cardiac T-cells to uncover potential mechanisms underlying their role in human HF. We found that patients with DCM had significantly more cardiac CD3+ T-cells (%CD45+ cells; 35.5±5.9 vs 22.0±0.8 p &lt; 0.01), with gene signatures indicative of higher TCR dependent antigenic activation, proliferation, and exhaustion. Although there were no differences in the proportion of CD4+ helper and CD8+ cytotoxic T-cells between groups, patients with DCM had a higher proportion of activated (%CD45+ cells, 6.6±0.8 vs 3.1±0.3 p = 0.03) and proliferative CD4+ T-cells (%CD45+ cells, 8.0±0.8 vs 3.1±0.3 p &lt; 0.01). Additionally, genes involved in TNF and TGFβ signaling were significantly enriched in cardiac T-cells derived from patients with DCM (normalized enrichment scores = 2.35, p adj &lt; 0.01, and 1.72, p adj &lt; 0.01, respectively),consistent with preclinical studies published by us and others. Recently, we also showed that dysfunctional T-cells exhibit increased estrogenic signaling with activation of Estrogen Receptor (ER)α in mice. Thus, we also looked at estrogen signaling in T-cells infiltrated into the DCM hearts and found that, indeed, cardiac T-cells in DCM patients exhibit significant upregulation of genes involved in estrogen signaling (normalized enrichment score = 1.69, p adj &lt; 0.01). This comprehensive analysis, for the first time, shows that T-cells are antigenically activated, actively infiltrate the failing human hearts and exhibit increased estrogenic signaling during DCM, providing novel insights and potential avenues for targeted immunotherapies.
Abstract Tu103: SIRT2 Inhibition Decreases Glycolysis and Attenuates Hypertrophic Response in H9c2 Cardiomyocytes
Authors: Ezra Ketema, Muhammad Ahsan, Kaya Persad, Qiuyu Sun, Liyan Zhang, Gary Lopaschuk
Journal: Circulation Research (2024)

Introduction: Myocardial glycolysis increases in hypertrophic and failing hearts. Hyperacetylation also occurs in the failing heart, and many glycolytic enzymes are known to be subject to acetylation. However, it is generally considered that acetylation has inhibitory effects on glycolysis. As a result, it is not clear whether acetylation changes directly contribute to glycolysis changes in cardiac hypertrophy. We therefore determined whether changes in the acetylation of glycolytic enzymes and the activity of the cytosolic deacetylase SIRT2 regulate cardiac glycolysis. Methods: Glycolysis rates were directly measured in rat heart-derived H9c2 cardiomyocytes perfused with 5 mM [5- 3 H] glucose, 0.8 mM palmitate, and 4% bovine serum albumin. Before these metabolic measurements, H9c2 cells were treated with either a SIRT2 inhibitor (10 µM AGK2) or a vehicle for 24 hours. In separate experiments, SIRT2 was also knocked down in H9c2 cells using siRNA, followed by glycolysis rate determinations. The impact of SIRT2 inhibition or SIRT2 knockdown on the acetylation status of glycolytic enzyme was also assessed. Furthermore, the effects of SIRT2 inhibition on hypertrophic signalling were assessed by treating H9c2 cells with phenylephrine. Results: SIRT2 inhibition markedly decreased glycolysis rates in H9c2 cells compared to vehicle-treated cells (524±108 vs 2631±372 nmol . g dry wt -1. min -1 , p&lt;0.05). Similarly, SIRT2 knockdown resulted in a significant reduction in glycolysis rates compared to scrambled siRNA-treated H9c2 cells (745±31 vs 1659±168 nmol . g dry wt -1. min -1 , p&lt;0.05). The decrease in SIRT2 was accompanied by an increase in the acetylation status of the glycolytic enzyme glyceraldehyde phosphate dehydrogenase (GPDH). Moreover, a trend towards increased phosphofructokinase (PFK) acetylation was also observed in SIRT2 knockdown H9c2 cells compared to scrambled siRNA-treated cells. Lastly, AGK2 treatment also attenuated phenylephrine-mediated hypertrophic responses in H9c2 cells. Conclusions: Increased acetylation of glycolytic enzymes is associated with a decrease in glycolysis, and SIRT2 inhibition or deletion in H9c2 cells significantly decreases glycolysis rates and attenuates hypertrophy. SIRT2 may therefore contribute to the increased glycolysis seen in hypertrophy and heart failure.
Abstract We095: Using Human Cardiac Organoids to Elucidate the Cardioprotective Potential of Mitochondrial-Targeted Therapies in a Preclinical Model of Diabetic Cardiomyopathy
Authors: Alex Parker, Jarmon Lees, Jack Phang, Sonya Song, Shiang Lim, Miles De Blasio, Rebecca Ritchie
Journal: Circulation Research (2024)

Introduction: Mitochondrial dysregulation is implicated in many complications of type 2 diabetes (T2D). Mitochondrial-targeted therapies SkQ1, AP39 and SS31 limit renal T2D complications. We sought to obtain the first evidence of the cardioprotective potential of SkQ1, AP39 and SS31 in T2D, using a human induced pluripotent stem cell (iPSC)-derived 3D multicellular cardiac organoid model of diabetic cardiomyopathy. Methods: Human cardiac organoids (foreskin-2 cell-line) generated from human iPSC-derived cardiomyocytes, cardiac fibroblasts and endothelial cells were subjected to 5.55mM glucose (control) or T2D-like conditions (20mM glucose, fatty acids, endothelin-1 and cortisol) for 4 days with supplementation of either SkQ1 (50nM), AP39 (50nM) or SS31 (1µM) on day 2. On day 4, endpoint parameters were evaluated in cardiac organoids, including contractile function (captured via Olympus IX71), mitochondrial superoxide levels (MitoSOX assay), mitochondrial membrane potential (TMRM assay), and cellular injury (lactate dehydrogenase; LDH). Data are expressed as mean±SEM (fold control) with n =4-6 from 2-3 independent experiments. One-way ANOVA with Dunnett`s post hoc analysis was performed with P&lt;0.05 considered significant. Results: After 4 days, T2D-conditions increased total contraction duration (1.55±0.10-fold control), time-to-peak (1.71±0.11-fold control, indicative of systolic dysfunction) and relaxation duration (1.46±0.13-fold control, indicative of diastolic dysfunction) in cardiac organoids. All 3 functional parameters were attenuated by AP39 (to 1.15±0.06, 1.32±0.09 and 1.04±0.04-fold control, respectively), or by SS31 (to 1.10±0.05, 1.12±0.15 and 1.09±0.12-fold control, respectively; all P&lt;0.05), but not SkQ1. T2D-conditions increased mitochondrial superoxide (2.68±0.16-fold control), which was blunted by all 3 interventions, SkQ1 to 2.00±0.29, AP39 to 1.82±0.16 and SS31 to 1.89±0.17 (all P&lt;0.05). Cellular injury was evident in T2D cardiac organoids (2.07±0.23-fold control), which was again limited by SkQ1 (to 1.06±0.11), AP39 (to 1.18±0.09) or SS31 (to 1.08±0.07), all P&lt;0.05. Conclusion: These findings in human cardiac organoids highlight the cardioprotective potential of mitochondrial-targeted therapies to limit T2D-induced cardiac dysfunction, mitochondrial dysregulation and cellular injury, potentially facilitating clinical progression of candidates such as AP39 and SS31 as new therapies for patients with diabetic cardiomyopathy.
Abstract We054: Mitochondria-containing Extracellular Vesicles Mediate Heart Failure Sterile Inflammation
Authors: Dennis Wang, Kim Anh Huynh, Kevin O'Brien, Rong Tian
Journal: Circulation Research (2024)

Introduction: Sterile inflammation has long been postulated to exacerbate heart failure (HF); however, a lack of viable biological targets and thorough understanding of the underlying mechanism posed formidable challenges in the development of novel therapeutic interventions. Hypothesis: Given proinflammatory mitochondrial DNA (mtDNA) are known to be elevated in HF plasma; and that cells release mitochondrial components in extracellular vesicles, we hypothesize that proinflammatory circulating Mitochondria-containing Extracellular Vesicle (MitoEV) is a mediator of HF sterile inflammation. Methods/Results: Using plasma samples of 12 Stage-D HFrEF and 12 healthy participants, plasma microparticles (MP) are co-stained with mitochondrial- and cytoplasmic-specific markers then quantified by volume-metric flow analysis. We found that there are significantly more mitochondrial-cytoplasmic double-positive MP (designated MitoEV, accounts for &gt;70% of total MP) in HF relative to control. Next, using size-exclusion chromatography, we found MitoEV fractions are significantly more potent than soluble protein fractions to induce cytokine production in macrophage, implicating MitoEV as the source of HF plasma immunogenicity. Surface marker analysis by flow suggests that CD14+ monocytes is a major source of HF plasma MitoEV. Using THP-1 monocytes, we found that TLR9 activation by mtDNA results in injured mitochondria to be released as MitoEV (rather than removed by mitophagy), a pathway negatively regulated by beclin-1. Finally, boosting NAD by nicotinamide riboside preserves mitochondrial dysfunction and significantly reduces MitoEV release in primary monocytes. Conclusion: Our findings implicate circulating MitoEV released by monocytes upon mtDNA activation as a pivotal mediator of sterile inflammation in HF, demonstrating a promising avenue for potential therapeutic targeting. The study also provides a potential cellular mechanism to the anti-inflammatory effect of boosting NAD. Model: In HF circulation, mtDNA activates TLR9 of monocytes, injuring mitochondria, which are released as MitoEV (containing mtDNA) to amplify and propagate inflammation in an autocrine manner. Becn1, a key mediator of mitophagy, negatively regulates MitoEV release. Activated monocytes also release cytokines to further injure the heart, resulting in a vicious cycle. Boosting NAD protects against mtDNA-induced mitochondrial dysfunction, attenuates the MitoEV release, and ameliorates inflammation.
Abstract We075: Stimulator of Interferon Genes (STING) Regulates T Cell Fate in Cardiometabolic Heart Failure with Preserved Ejection Fraction (HFpEF)
Authors: Sasha Smolgovsky, Abraham Bayer, Ramona Emig, Zoie Magri, mark aronovitz, Kuljeet kaur, Alexander Poltorak, Robert Blanton, Pilar Alcaide
Journal: Circulation Research (2024)

Introduction: Combined obesity and hypertension alter the endoplasmic reticulum (ER) stress response by downregulating X-box binding protein 1 ( Xbp1 ) in T cells, which heightens T cell inflammatory potential and persistence in Heart Failure with Preserved Ejection Fraction (HFpEF), a prevalent syndrome with no cure. The ER protein Stimulator of Interferon Genes (STING), in concert with Xbp1 , coordinates T cell inflammation and death in other contexts, yet its role in the T cell inflammatory response in cardiometabolic HFpEF is unknown. Hypothesis: STING activation and dysregulated ER stress responses drive T cell inflammation in HFpEF by balancing T cell activation and persistence in response to combined comorbidities. Methods: C67BL/6J (wild type, WT) mice were fed high-fat diet/L-NAME (H/L) or standard chow (STD) for 5 weeks, and STING activation was measured in splenic CD4 + T cells by Western blotting. Splenic CD4 + T cells from WT or STING-deficient mice (STING -/- ) were activated with αCD3/αCD28 for 3 days in vitro , then treated with complete media (CM) or CM with 0.2 mM palmitate (abundant in dietary fat)/0.2 mM L-NAME (PALNA) for up to 48 hours. T cell gene expression, activation, and death were assessed using qPCR, flow cytometry, Western blotting, and Lionheart live-cell microscopy. Results: Mice fed H/L had significantly increased splenic T cell expression of phospho-STING, alongside decreased T cell Xbp1 expression and increased cardiac inflammation, compared to STD-fed mice. Ex vivo incubation of CD4 + T cells with PALNA significantly decreased Xbp1 gene expression and increased apoptosis, indicated by cleaved caspase-3 and cleaved poly (ADP-ribose) polymerase (PARP) expression, compared to cells in CM. However, the remaining live PALNA-treated cells showed higher expression of the activation protein CD69, and this was sustained over time, compared to cells in CM. Strikingly, live cell imaging revealed that STING -/- T cells had improved survival and decreased CD69 expression in response to PALNA compared to WT PALNA-treated cells. Conclusions: STING contributes to T cell inflammation in experimental cardiometabolic HFpEF by synergizing with dysregulated ER stress responses to promote the emergence of hyperactivated T cells.
Abstract We084: Deciphering the Molecular Code Underlining Postnatal Cardiomyocyte Maturation by an RNA Splicing Factor RBFox1
Authors: Jijun Huang, Josh Lee, Christoph Rau, Arash Pezhouman, Tomohiro Yokota, Hiromi Miwa, Matthew Feldman, Tsz Kin Kong, Ziyue Yang, Woan Ting Tay, Ivan Pushkarsky, Kyungsoo KIM, Shan Parikh, Shreya Udani, Boon Seng Soh, Chen Gao, Linsey Stiles, Orian Shirihai, Bjorn Knollmann, Reza Ardehali, Dino Di Carlo, Dale Abel, Yibin Wang
Journal: Circulation Research (2024)

Mammalian hearts undergo major changes after birth during the perinatal period. While several extrinsic factors such as mechanical load, electrical stimulation, hormones, and nutrients have been implicated in this process, the intrinsic regulatory circuit governing cardiomyocyte postnatal maturation is largely unknown. Importantly, stem-cell derived cardiomyocytes commonly exhibit immaturity which is a major limiting factor for their application as disease models or cell therapy agents. Therefore, uncovering the intrinsic regulatory mechanism of mammalian cardiomyocyte maturation has significant implications in both basic cardiac biology and cell-based therapy and disease modeling. In our recent analysis of the global transcriptome transition from neonatal to adult rat hearts, we found RNA splicing among the top changed pathways. Additionally, we found that expression of RBFox1, a cardiac enriched RNA splicing regulator, was significantly increased during the postnatal transition to adolescence. We further demonstrate that RBFox1 mediated post-transcriptional regulation has a potent effect to promote neonatal and stem-cell derived cardiomyocyte maturation. RNA-seq followed by Gene Ontology enrichment analysis showed that Rbfox1 led to differentially expressed genes enriched in cardiac contraction and conduction, sarcomere organization, K + ion import and muscle filament sliding, as well as differential isoform switches enriched in cardiac contraction and sarcomere structure. An evolutionarily conserved, temporal specific super enhancer exists upstream of cardiac Rbfox1 , which is occupied by active epigenetic markers in the postnatal period. We have identified the tissue and temporal transcriptional activity of this super enhancer in vitro and in vivo . Several binding motifs of transcription factors are predicted within it and a key DNA fragment was identified to be essential for enhancer activity. A transgenic mouse strain has been established to facilitate the tracing of myocyte maturation in vivo by constructing a reporter system driven by a 4xSuperEnhancer-Rbfox1Promoter-tdTomato construct. In conclusion, we propose a mechanism that RBFox1 is an intracellular regulator with tissue- and temporal-specific expression patterns that regulates cardiac maturation by promoting alternative splicing that fine tunes the genetic code.