Browsing by Subject "Cardiomyocyte"
Now showing 1 - 8 of 8
Results Per Page
Sort Options
Item F-box protein-32 down-regulates small-conductance calcium-activated potassium channel 2 in diabetic mouse atria(Elsevier, 2019-03-15) Ling, Tian-You; Yi, Fu; Lu, Tong; Wang, Xiao-Li; Sun, Xiaojing; Willis, Monte S.; Wu, Li-Qun; Shen, Win-Kuang; Adelman, John P.; Lee, Hon-Chi; Pathology and Laboratory Medicine, School of MedicineDiabetes mellitus (DM) is an independent risk factor for atrial fibrillation, but the underlying ionic mechanism for this association remains unclear. We recently reported that expression of the small-conductance calcium-activated potassium channel 2 (SK2, encoded by KCCN2) in atria from diabetic mice is significantly down-regulated, resulting in reduced SK currents in atrial myocytes from these mice. We also reported that the level of SK2 mRNA expression is not reduced in DM atria but that the ubiquitin-proteasome system (UPS), a major mechanism of intracellular protein degradation, is activated in vascular smooth muscle cells in DM. This suggests a possible role of the UPS in reduced SK currents. To test this possibility, we examined the role of the UPS in atrial SK2 down-regulation in DM. We found that a muscle-specific E3 ligase, F-box protein 32 (FBXO-32, also called atrogin-1), was significantly up-regulated in diabetic mouse atria. Enhanced FBXO-32 expression in atrial cells significantly reduced SK2 protein expression, and siRNA-mediated FBXO-32 knockdown increased SK2 protein expression. Furthermore, co-transfection of SK2 with FBXO-32 complementary DNA in HEK293 cells significantly reduced SK2 expression, whereas co-transfection with atrogin-1ΔF complementary DNA (a nonfunctional FBXO-32 variant in which the F-box domain is deleted) did not have any effects on SK2. These results indicate that FBXO-32 contributes to SK2 down-regulation and that the F-box domain is essential for FBXO-32 function. In conclusion, DM-induced SK2 channel down-regulation appears to be due to an FBXO-32-dependent increase in UPS-mediated SK2 protein degradation.Item Genome-wide analyses reveal the detrimental impacts of SARS-CoV-2 viral gene Orf9c on human pluripotent stem cell-derived cardiomyocytes(Cell Press, 2022) Liu, Juli; Zhang, Yucheng; Han, Lei; Guo, Shuai; Wu, Shiyong; Doud, Emma Helen; Wang, Cheng; Chen, Hanying; Rubart-von der Lohe, Michael; Wan, Jun; Yang, Lei; Pediatrics, School of MedicinePatients with coronavirus disease 2019 (COVID-19) commonly have manifestations of heart disease. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genome encodes 27 proteins. Currently, SARS-CoV-2 gene-induced abnormalities of human heart muscle cells remain elusive. Here, we comprehensively characterized the detrimental effects of a SARS-CoV-2 gene, Orf9c, on human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) by preforming multi-omic analyses. Transcriptomic analyses of hPSC-CMs infected by SARS-CoV-2 with Orf9c overexpression (Orf9cOE) identified concordantly up-regulated genes enriched into stress-related apoptosis and inflammation signaling pathways, and down-regulated CM functional genes. Proteomic analysis revealed enhanced expressions of apoptotic factors, whereas reduced protein factors for ATP synthesis by Orf9cOE. Orf9cOE significantly reduced cellular ATP level, induced apoptosis, and caused electrical dysfunctions of hPSC-CMs. Finally, drugs approved by the U.S. Food and Drug Administration, namely, ivermectin and meclizine, restored ATP levels and ameliorated CM death and functional abnormalities of Orf9cOE hPSC-CMs. Overall, we defined the molecular mechanisms underlying the detrimental impacts of Orf9c on hPSC-CMs and explored potentially therapeutic approaches to ameliorate Orf9c-induced cardiac injury and abnormalities.Item Impaired Reorganization of Centrosome Structure Underlies Human Infantile Dilated Cardiomyopathy(American Heart Association, 2023) Chun, Young Wook; Miyamoto, Matthew; Williams, Charles H.; Neitzel, Leif R.; Silver-Isenstadt, Maya; Cadar, Adrian G.; Fuller, Daniela T.; Fong, Daniel C.; Liu, Hanhan; Lease, Robert; Kim, Sungseek; Katagiri, Mikako; Durbin, Matthew D.; Wang, Kuo-Chen; Feaster, Tromondae K.; Sheng, Calvin C.; Neely, M. Diana; Sreenivasan, Urmila; Cortes-Gutierrez, Marcia; Finn, Aloke V.; Schot, Rachel; Mancini, Grazia M. S.; Ament, Seth A.; Ess, Kevin C.; Bowman, Aaron B.; Han, Zhe; Bichell, David P.; Su, Yan Ru; Hong, Charles C.; Pediatrics, School of MedicineBackground: During cardiomyocyte maturation, the centrosome, which functions as a microtubule organizing center in cardiomyocytes, undergoes dramatic structural reorganization where its components reorganize from being localized at the centriole to the nuclear envelope. This developmentally programmed process, referred to as centrosome reduction, has been previously associated with cell cycle exit. However, understanding of how this process influences cardiomyocyte cell biology, and whether its disruption results in human cardiac disease, remains unknown. We studied this phenomenon in an infant with a rare case of infantile dilated cardiomyopathy (iDCM) who presented with left ventricular ejection fraction of 18% and disrupted sarcomere and mitochondria structure. Methods: We performed an analysis beginning with an infant who presented with a rare case of iDCM. We derived induced pluripotent stem cells from the patient to model iDCM in vitro. We performed whole exome sequencing on the patient and his parents for causal gene analysis. CRISPR/Cas9-mediated gene knockout and correction in vitro were used to confirm whole exome sequencing results. Zebrafish and Drosophila models were used for in vivo validation of the causal gene. Matrigel mattress technology and single-cell RNA sequencing were used to characterize iDCM cardiomyocytes further. Results: Whole exome sequencing and CRISPR/Cas9 gene knockout/correction identified RTTN, the gene encoding the centrosomal protein RTTN (rotatin), as the causal gene underlying the patient's condition, representing the first time a centrosome defect has been implicated in a nonsyndromic dilated cardiomyopathy. Genetic knockdowns in zebrafish and Drosophila confirmed an evolutionarily conserved requirement of RTTN for cardiac structure and function. Single-cell RNA sequencing of iDCM cardiomyocytes showed impaired maturation of iDCM cardiomyocytes, which underlie the observed cardiomyocyte structural and functional deficits. We also observed persistent localization of the centrosome at the centriole, contrasting with expected programmed perinuclear reorganization, which led to subsequent global microtubule network defects. In addition, we identified a small molecule that restored centrosome reorganization and improved the structure and contractility of iDCM cardiomyocytes. Conclusions: This study is the first to demonstrate a case of human disease caused by a defect in centrosome reduction. We also uncovered a novel role for RTTN in perinatal cardiac development and identified a potential therapeutic strategy for centrosome-related iDCM. Future study aimed at identifying variants in centrosome components may uncover additional contributors to human cardiac disease.Item In situ three-dimensional reconstruction of mouse heart sympathetic innervation by two-photon excitation fluorescence imaging(2014-02-25) Freeman, Kim Renee; Rubart-von der Lohe, Michael; Atkinson, Simon; Hurley, Thomas D., 1961-; Gattone II, Vincent H.The sympathetic nervous system strongly modulates the contractile and electrical function of the heart. The anatomical underpinnings that enable a spatially and temporally coordinated dissemination of sympathetic signals within the cardiac tissue are only incompletely characterized. In this work we took the first step of unraveling the in situ 3D microarchitecture of the cardiac sympathetic nervous system. Using a combination of two-photon excitation fluorescence microscopy and computer-assisted image analyses, we reconstructed the sympathetic network in a portion of the left ventricular epicardium from adult transgenic mice expressing a fluorescent reporter protein in all peripheral sympathetic neurons. The reconstruction revealed several organizational principles of the local sympathetic tree that synergize to enable a coordinated and efficient signal transfer to the target tissue. First, synaptic boutons are aligned with high density along much of axon-cell contacts. Second, axon segments are oriented parallel to the main, i.e., longitudinal, axes of their apposed cardiomyocytes, optimizing the frequency of transmitter release sites per axon/per cardiomyocyte. Third, the local network was partitioned into branched and/or looped sub-trees which extended both radially and tangentially through the image volume. Fourth, sub-trees arrange to not much overlap, giving rise to multiple annexed innervation domains of variable complexity and configuration. The sympathetic network in the epicardial border zone of a chronic myocardial infarction was observed to undergo substantive remodeling, which included almost complete loss of fibers at depths >10 µm from the surface, spatially heterogeneous gain of axons, irregularly shaped synaptic boutons, and formation of axonal plexuses composed of nested loops of variable length. In conclusion, we provide, to the best of our knowledge, the first in situ 3D reconstruction of the local cardiac sympathetic network in normal and injured mammalian myocardium. Mapping the sympathetic network connectivity will aid in elucidating its role in sympathetic signal transmisson and processing.Item Modulation of cardiac fibrosis by Krüppel-like factor 6 through transcriptional control of thrombospondin 4 in cardiomyocytes(Oxford University Press, 2015-09-01) Sawaki, Daigo; Hou, Lianguo; Tomida, Shota; Sun, Junqing; Zhan, Hong; Aizawa, Kenichi; Son, Bo-Kyung; Kariya, Taro; Takimoto, Eiki; Otsu, Kinya; Conway, Simon J.; Manabe, Ichiro; Komuro, Issei; Friedman, Scott L.; Nagai, Ryozo; Suzuki, Toru; Department of Pediatrics, IU School of MedicineAIMS: Krüppel-like factors (KLFs) are a family of transcription factors which play important roles in the heart under pathological and developmental conditions. We previously identified and cloned Klf6 whose homozygous mutation in mice results in embryonic lethality suggesting a role in cardiovascular development. Effects of KLF6 on pathological regulation of the heart were investigated in the present study. METHODS AND RESULTS: Mice heterozygous for Klf6 resulted in significantly diminished levels of cardiac fibrosis in response to angiotensin II infusion. Intriguingly, a similar phenotype was seen in cardiomyocyte-specific Klf6 knockout mice, but not in cardiac fibroblast-specific knockout mice. Microarray analysis revealed increased levels of the extracellular matrix factor, thrombospondin 4 (TSP4), in the Klf6-ablated heart. Mechanistically, KLF6 directly suppressed Tsp4 expression levels, and cardiac TSP4 regulated the activation of cardiac fibroblasts to regulate cardiac fibrosis. CONCLUSION: Our present studies on the cardiac function of KLF6 show a new mechanism whereby cardiomyocytes regulate cardiac fibrosis through transcriptional control of the extracellular matrix factor, TSP4, which, in turn, modulates activation of cardiac fibroblasts.Item Myocardial polyploidization creates a barrier to heart regeneration in zebrafish(Elsevier, 2018-02-26) González-Rosa, Juan Manuel; Sharpe, Michka; Field, Dorothy; Soonpaa, Mark H.; Field, Loren J.; Burns, Caroline E.; Burns, C. Geoffrey; Pediatrics, School of MedicineCorrelative evidence suggests that polyploidization of heart muscle, which occurs naturally in post-natal mammals, creates a barrier to heart regeneration. Here, we move beyond a correlation by demonstrating that experimental polyploidization of zebrafish cardiomyocytes is sufficient to suppress their proliferative potential during regeneration. Initially, we determined that zebrafish myocardium becomes susceptible to polyploidization upon transient cytokinesis inhibition mediated by dominant-negative Ect2. Using a transgenic strategy, we generated adult animals containing mosaic hearts composed of differentially labeled diploid and polyploid-enriched cardiomyocyte populations. Diploid cardiomyocytes outcompeted their polyploid neighbors in producing regenerated heart muscle. Moreover, hearts composed of equivalent proportions of diploid and polyploid cardiomyocytes failed to regenerate altogether, demonstrating that a critical percentage of diploid cardiomyocytes is required to achieve heart regeneration. Our data identify cardiomyocyte polyploidization as a barrier to heart regeneration and suggest that mobilizing rare diploid cardiomyocytes in the human heart will improve its regenerative capacity.Item Phospholamban Regulates Nuclear Ca2+ Stores and Inositol 1,4,5-Trisphosphate Mediated Nuclear Ca2+ Cycling in Cardiomyocytes(Elsevier, 2018-10) Chen, Mu; Xu, Dongzhu; Wu, Adonis Z.; Kranias, Evangelia; Lin, Shien-Fong; Chen, Peng-Sheng; Chen, Zhenhui; Medicine, School of MedicineAIMS: Phospholamban (PLB) is the key regulator of the cardiac Ca2+ pump (SERCA2a)-mediated sarcoplasmic reticulum Ca2+ stores. We recently reported that PLB is highly concentrated in the nuclear envelope (NE) from where it can modulate perinuclear Ca2+ handling of the cardiomyocytes (CMs). Since inositol 1,4,5-trisphosphate (IP3) receptor (IP3R) mediates nuclear Ca2+ release, we examined whether the nuclear pool of PLB regulates IP3-induced nuclear Ca2+ handling. METHODS AND RESULTS: Fluo-4 based confocal Ca2+ imaging was performed to measure Ca2+ dynamics across both nucleus and cytosol in saponin-permeabilized CMs isolated from wild-type (WT) or PLB-knockout (PLB-KO) mice. At diastolic intracellular Ca2+ ([Ca2+]i = 100 nM), the Fab fragment of the monoclonal PLB antibody (anti-PLB Fab) facilitated the formation and increased the length of spontaneous Ca2+ waves (SCWs) originating from the nuclear region in CMs from WT but not from PLB-KO mice. We next examined nuclear Ca2+ activities at basal condition and after sequential addition of IP3, anti-PLB Fab, and the IP3R inhibitor 2-aminoethoxydiphenyl borate (2-APB) at a series of [Ca2+]i. In WT mice, at 10 nM [Ca2+]i where ryanodine receptor (RyR2) based spontaneous Ca2+ sparks rarely occurred, IP3 increased fluorescence amplitude (F/F0) of overall nuclear region to 1.19 ± 0.02. Subsequent addition of anti-PLB Fab significantly decreased F/F0 to 1.09 ± 0.02. At 50 nM [Ca2+]i, anti-PLB Fab not only decreased the overall nuclear F/F0 previously elevated by IP3, but also increased the amplitude and duration of spark-like nuclear Ca2+ release events. These nuclear Ca2+ releases were blocked by 2-APB. At 100 nM [Ca2+]i, IP3 induced short SCWs originating from nucleus. Anti-PLB Fab transformed those short waves into long SCWs with propagation from the nucleus into the cytosol. In contrast, neither nuclear nor cytosolic Ca2+ dynamics was affected by anti-PLB Fab in CMs from PLB-KO mice in all these conditions. Furthermore, in WT CMs pretreated with RyR2 blocker tetracaine, IP3 and anti-PLB Fab still increased the magnitude of nuclear Ca2+ release but failed to regenerate SCWs. Finally, anti-PLB Fab increased low Ca2+ affinity mag-fluo 4 fluorescence intensity in the lumen of NE of nuclei isolated from WT but not in PLB-KO mice. CONCLUSION: PLB regulates nuclear Ca2+ handling. By increasing Ca2+ uptake into lumen of the NE and perhaps other perinuclear membranes, the acute reversal of PLB inhibition decreases global Ca2+ concentration at rest in the nucleoplasm, and increases Ca2+ release into the nucleus, through mechanisms involving IP3R and RyR2 in the vicinity.Item SARS-CoV-2 viral genes Nsp6, Nsp8, and M compromise cellular ATP levels to impair survival and function of human pluripotent stem cell-derived cardiomyocytes(BMC, 2023-09-13) Liu, Juli; Wu, Shiyong; Zhang, Yucheng; Wang, Cheng; Liu, Sheng; Wan, Jun; Yang, Lei; Pediatrics, School of MedicineBackground: Cardiovascular complications significantly augment the overall COVID-19 mortality, largely due to the susceptibility of human cardiomyocytes (CMs) to SARS-CoV-2 virus. SARS-CoV-2 virus encodes 27 genes, whose specific impacts on CM health are not fully understood. This study elucidates the deleterious effects of SARS-CoV-2 genes Nsp6, M, and Nsp8 on human CMs. Methods: CMs were derived from human pluripotent stem cells (hPSCs), including human embryonic stem cells and induced pluripotent stem cells, using 2D and 3D differentiation methods. We overexpressed Nsp6, M, or Nsp8 in hPSCs and then applied whole mRNA-seq and mass spectrometry for multi-omics analysis. Co-immunoprecipitation mass spectrometry was utilized to map the protein interaction networks of Nsp6, M, and Nsp8 within host hiPSC-CMs. Results: Nsp6, Nsp8, and M globally perturb the transcriptome and proteome of hPSC-CMs. SARS-CoV-2 infection and the overexpression of Nsp6, Nsp8, or M coherently upregulated genes associated with apoptosis and immune/inflammation pathways, whereas downregulated genes linked to heart contraction and functions. Global interactome analysis revealed interactions between Nsp6, Nsp8, and M with ATPase subunits. Overexpression of Nsp6, Nsp8, or M significantly reduced cellular ATP levels, markedly increased apoptosis, and compromised Ca2+ handling in hPSC-CMs. Importantly, administration of FDA-approved drugs, ivermectin and meclizine, could restore ATP levels, thereby mitigating apoptosis and dysfunction in hPSC-CMs overexpressing Nsp6, Nsp8, or M. Conclusion: Overall, our findings uncover the extensive damaging effects of Nsp6, Nsp8, and M on hPSC-CMs, underlining the crucial role of ATP homeostasis in CM death and functional abnormalities induced by these SARS-CoV-2 genes, and reveal the potential therapeutic strategies to alleviate these detrimental effects with FDA-approved drugs.