Cardiology
Abstract
Gene mutations causing loss of dystrophin result in the severe muscle disease known as Duchenne muscular dystrophy (DMD). Despite efforts at genetic repair, DMD therapy remains largely palliative. Loss of dystrophin destabilizes the sarcolemmal membrane impacting mechanosensitive cation channels to increase calcium entry, promoting cell damage, and eventually muscle dysfunction. One putative channel is transient receptor potential canonical 6 (TRPC6) that we showed contributes to abnormal force and calcium stress-responses in mouse cardiomyocytes lacking dystrophin and haplodeficient in utrophin mdx/utrn+/- (HET). Here, we show in both HET and the far more severe homozygous mdx/utrn-/- (DKO) mouse that TRPC6 gene deletion or its selective pharmacologic inhibition (BI 749327) prolongs survival 2-3-fold, improving skeletal and cardiac muscle and bone defects. Gene pathways reduced by BI 749327 treatment most prominently regulate fat metabolism and TGFβ1 signaling. These results support the testing of TRPC6 inhibitors in human trials for other diseases as a novel DMD therapy.
Authors
Brian L. Lin, Joseph Y. Shin, William P.D. Jeffreys, Nadan Wang, Clarisse A. Lukban, Megan C. Moorer, Esteban Velarde, Olivia A. Hanselman, Seoyoung Kwon, Suraj Kannan, Ryan C. Riddle, Christopher W. Ward, Steven S. Pullen, Antonio Filareto, David A. Kass
Abstract
Obesity is an important risk factor for atrial fibrillation (AF), but a better mechanistic understanding of obesity-related atrial fibrillation is required. Serum glucocorticoid kinase 1 (SGK1) is a kinase positioned within multiple obesity-related pathways, and prior work has shown a pathologic role of SGK1 signaling in ventricular arrhythmias. We validated a mouse model of obesity-related AF using wild type mice fed a high fat diet. RNA sequencing of atrial tissue demonstrated substantial differences in gene expression, with enrichment of multiple SGK1-related pathways, and we confirmed upregulated of SGK1 transcription, activation, and signaling in obese atria. Mice expressing a cardiac specific dominant negative SGK1 were protected from obesity-related AF, through effects on atrial electrophysiology, action potential characteristics, structural remodeling, inflammation, and sodium current. Overall, this study demonstrates the promise of targeting SGK1 in a mouse model of obesity-related AF.
Authors
Aneesh Bapat, Guoping Li, Ling Xiao, Ashish Yeri, Maarten Hulsmans, Jana Grune, Masahiro Yamazoe, Maximillian J. Schloss, Yoshiko Iwamoto, Justin G. Tedeschi, Xinyu Yang, Matthias Nahrendorf, Anthony Rosenzweig, Patrick T. Ellinor, Saumya Das, David Milan
Abstract
Chitinase 3-like 1 (CHI3L1) is the prototypic chitinase-like protein mediating inflammation, cell proliferation, and tissue remodeling. Limited data suggests CHI3L1 is elevated in human pulmonary arterial hypertension (PAH) and is associated with disease severity. Despite its importance as a regulator of injury/repair responses, the relationship between CHI3L1 and pulmonary vascular remodeling is not well understood. We hypothesize that CHI3L1 and its signaling pathways contribute to the vascular remodeling responses that occur in pulmonary hypertension (PH). We examined the relationship of plasma CHI3L1 levels and severity of PH in patients with various forms of PH, including Group 1 PAH and Group 3 PH, and found that circulating levels of serum CHI3L1 were associated with worse hemodynamics and correlated directly with mean pulmonary artery pressure and pulmonary vascular resistance. We also used transgenic mice with constitutive knockout and inducible overexpression of CHI3L1 to examine its role in hypoxia-, monocrotaline-, and bleomycin-induced models of pulmonary vascular disease. In all 3 mouse models of pulmonary vascular disease, pulmonary hypertensive responses were mitigated in CHI3L1 null mice and accentuated in transgenic mice that overexpress CHI3L1. Finally, CHI3L1 alone was sufficient to induce pulmonary arterial smooth muscle cell proliferation, inhibit pulmonary vascular endothelial cell apoptosis, induce the loss of endothelial barrier function, and induce endothelial-to-mesenchymal transition. These findings demonstrate that CHI3L1 and its receptors play an integral role in pulmonary vascular disease pathobiology and may offer a novel target for the treatment PAH and PH associated with fibrotic lung disease.
Authors
Xiuna Sun, Erika Nakajima, Carmelissa Norbrun, Parand Sorkhdini, Alina Xiaoyu Yang, Dongqin Yang, Corey E. Ventetuolo, Julie Braza, Alexander Vang, Jason Aliotta, Debasree Banerjee, Mandy Pereira, Grayson Baird, Qing Lu, Elizabeth O. Harrington, Sharon Rounds, Chun Geun Lee, Hongwei Yao, Gaurav Choudhary, James R. Klinger, Yang Zhou
Abstract
Membrane instability and disruption underlie myriad acute and chronic disorders. Anxa6 encodes the membrane-associated protein annexin A6 and was identified as a genetic modifier of muscle repair and muscular dystrophy. To evaluate annexin A6’s role in membrane repair in vivo, we inserted sequences encoding green fluorescent protein (GFP) into the last coding exon of Anxa6. Heterozygous Anxa6gfp mice expressed a normal pattern of annexin A6 with reduced annexin A6GFP mRNA and protein. High-resolution imaging of wounded muscle fibers showed annexin A6GFP rapidly formed a repair cap at the site of injury. Injured cardiomyocytes and neurons also displayed repair caps after wounding, highlighting annexin A6–mediated repair caps as a feature in multiple cell types. Using surface plasmon resonance, we showed recombinant annexin A6 bound phosphatidylserine-containing lipids in a Ca2+- and dose-dependent fashion with appreciable binding at approximately 50 μM Ca2+. Exogenously added recombinant annexin A6 localized to repair caps and improved muscle membrane repair capacity in a dose-dependent fashion without disrupting endogenous annexin A6 localization, indicating annexin A6 promotes repair from both intracellular and extracellular compartments. Thus, annexin A6 orchestrates repair in multiple cell types, and recombinant annexin A6 may be useful in additional chronic disorders beyond skeletal muscle myopathies.
Authors
Alexis R. Demonbreun, Elena Bogdanovic, Lauren A. Vaught, Nina L. Reiser, Katherine S. Fallon, Ashlee M. Long, Claire C. Oosterbaan, Michele Hadhazy, Patrick G.T. Page, Prem Raj B. Joseph, Gabrielle Cowen, Alexander M. Telenson, Ammaarah Khatri, Katherine R. Sadleir, Robert Vassar, Elizabeth M. McNally
Abstract
Developmental cardiac tissue is regenerative while operating under low oxygen. After birth, ambient oxygen is associated with cardiomyocyte cell cycle exit and regeneration. Likewise, cardiac metabolism undergoes a shift with cardiac maturation. Whether there are common regulators of cardiomyocyte cell cycle linking metabolism to oxygen tension remains unknown. The objective of the study is to determine whether mitochondrial UCP2 is a metabolic oxygen sensor regulating cardiomyocyte cell cycle. Neonatal rat ventricular myocytes (NRVMs) under moderate hypoxia showed increased cell cycle activity and UCP2 expression. NRVMs exhibited a metabolic shift towards glycolysis, reduced citrate synthase, mtDNA, ΔΨm and DNA damage/oxidative stress while loss of UCP2 reversed this phenotype. Next, WT and UCP2KO mice kept under hypoxia for 4 weeks showed significant decline in cardiac function that was more pronounced in UCP2KO animals. Cardiomyocyte cell cycle activity was reduced while fibrosis and DNA damage was significantly increased in UCP2KO animals compared to WT under hypoxia. Mechanistically, UCP2 increased acetyl-CoA levels, histone acetylation and altered chromatin modifiers linking metabolism to cardiomyocyte cell cycle under hypoxia. Here, we show a novel role for mitochondrial UCP2 as an oxygen sensor regulating cardiomyocyte cell cycle activity, acetyl-CoA levels and histone acetylation in response to moderate hypoxia.
Authors
Vagner O.C. Rigaud, Clare Zarka, Justin Kurian, Daria Harlamova, Andrea Elia, Nicole Kasatkin, Jaslyn Johnson, Michael Behanan, Lindsay Kraus, Hannah Pepper, Nathaniel W. Snyder, Sadia Mohsin, Steven Houser, Mohsin Khan
Abstract
Cardiac fibrosis, a primary contributor to heart failure (HF) and sudden death, is considered an important target for HF therapy. However, the signaling pathways that govern cardiac fibroblast (CF) function during cardiac fibrosis have not been fully elucidated. Here, we found that a functionally unannotated human myocardial infarction (MI) associated gene, family with sequence similarity 114 member A1 (FAM114A1), is induced in failing human and mouse hearts compared to non-failing hearts. Homozygous knockout of Fam114a1 (Fam114a1–/–) in the mouse genome reduces cardiac hypertrophy and fibrosis while significantly restores cardiac function in angiotensin (Ang) II- and MI-induced HF mouse models. Fam114a1 deletion antagonizes Ang II-induced inflammation and oxidative stress. Using isolated mouse primary CFs in wild type and Fam114a1–/– mice, we found that FAM114A1 is a critical autonomous factor for CF proliferation, activation, and migration. We discovered that FAM114A1 interacts with angiotensin receptor-associated protein (AGTRAP) and regulates the expression of angiotensin type 1 receptor (AT1R) and downstream Ang II signaling transduction, and subsequently influences pro-fibrotic response. Using RNA-Seq in mouse primary CFs, we identified differentially expressed genes, including extracellular matrix proteins such as Adamts15. RNAi-mediated inactivation of Adamts15 attenuates CF activation and collagen deposition. Our results indicate that FAM114A1 regulates Ang II signaling and downstream pro-fibrotic and pro-inflammatory gene expression, thereby activating cardiac fibroblasts and augmenting pathological cardiac remodeling. These findings provide novel insights into the regulation of cardiac fibrosis and identify FAM114A1 as a new therapeutic target for the treatment of cardiac disease.
Authors
Kadiam C. Venkata Subbaiah, Jiangbin Wu, Wai Hong Wilson Tang, Peng Yao
Abstract
Loss-of-function (LOF) variants in SCN1B, encoding the voltage-gated sodium channel β1/β1B subunits, are linked to neurological and cardiovascular diseases. Scn1b-null mice have spontaneous seizures and ventricular arrhythmias and die by approximately 21 days after birth. β1/β1B Subunits play critical roles in regulating the excitability of ventricular cardiomyocytes and maintaining ventricular rhythmicity. However, whether they also regulate atrial excitability is unknown. We used neonatal Scn1b-null mice to model the effects of SCN1B LOF on atrial physiology in pediatric patients. Scn1b deletion resulted in altered expression of genes associated with atrial dysfunction. Scn1b-null hearts had a significant accumulation of atrial collagen, increased susceptibility to pacing induced atrial fibrillation (AF), sinoatrial node (SAN) dysfunction, and increased numbers of cholinergic neurons in ganglia that innervate the SAN. Atropine reduced the incidence of AF in null animals. Action potential duration was prolonged in null atrial myocytes, with increased late sodium current density and reduced L-type calcium current density. Scn1b LOF results in altered atrial structure and AF, demonstrating the critical role played by Scn1b in atrial physiology during early postnatal mouse development. Our results suggest that SCN1B LOF variants may significantly impact the developing pediatric heart.
Authors
Roberto Ramos-Mondragon, Nnamdi Edokobi, Samantha L. Hodges, Shuyun Wang, Alexandra A. Bouza, Chandrika Canugovi, Caroline Scheuing, Lena Juratli, William R. Abel, Sami F. Noujaim, Nageswara R. Madamanchi, Marschall S. Runge, Luis F. Lopez-Santiago, Lori L. Isom
Abstract
BACKGROUND. Sudden cardiac death (SCD) remains a worldwide public health problem in need of better noninvasive predictive tools. Current guidelines for primary preventive SCD therapies such as implantable cardioverter defibrillators (ICDs) are based on left ventricular ejection fraction (LVEF), but these are imprecise with fewer than 5% of ICDs delivering life-saving therapy per year. Impaired cardiac metabolism and ATP depletion cause arrhythmias in experimental models, but a link between arrhythmias and cardiac energetic abnormalities in people has not been explored, nor the potential for metabolically predicting clinical SCD risk. METHODS. We prospectively measured myocardial energy metabolism noninvasively with phosphorus magnetic resonance spectroscopy in patients with no history of significant arrhythmias prior to scheduled ICD implantation for primary prevention in the setting of reduced LVEF (≤35%). RESULTS. By two different analyses, low myocardial ATP significantly predicted the composite of subsequent appropriate ICD firings for life-threatening arrhythmias and cardiac death over ~10 years. Life-threatening arrhythmia risk was ~3-fold higher in low ATP patients and independent of established risk factors including LVEF. In patients with normal ATP, rates of appropriate ICD firings were several-fold lower than reported rates of ICD complications and inappropriate firings. CONCLUSION. These first data linking in vivo myocardial ATP depletion and subsequent significant arrhythmic events in people suggest an energetic component to clinical life-threatening ventricular arrhythmogenesis. The findings support investigation of metabolic strategies that limit ATP loss to treat or prevent life-threatening cardiac arrhythmias and herald non-invasive metabolic imaging as a complementary SCD risk stratification tool. TRIAL REGISTRATION. NCT00181233. FUNDING. This work was supported by DW Reynolds Foundation, the National Institutes of Health (grants HL61912, HL056882, HL103812, HL132181, HL140034), and the Russell H. Morgan (P.A.B.) and Clarence Doodeman (R.G.W.) Endowments at Johns Hopkins.
Authors
T. Jake Samuel, Shenghan Lai, Michael Schär, Katherine C. Wu, Angela M. Steinberg, An-Chi Wei, Mark Anderson, Gordon F. Tomaselli, Gary Gerstenblith, Paul A. Bottomley, Robert G. Weiss
Abstract
We have previously demonstrated that active immunization with the apolipoprotein B-100 (ApoB-100) peptide P210 reduces experimental atherosclerosis. To advance this immunization strategy to future clinical testing, we explored the possibility of delivering P210 as an antigen using nanoparticles, given this approach has now been used clinically. To that end, we first charactered the responses of T cells to P210 using PBMCs from human subjects with atherosclerotic cardiovascular disease (ASCVD). We then investigated the use of P210 in self-assembling peptide amphiphile micelles (P210-PAM) as a vaccine formulation to reduce atherosclerosis in ApoE-/- mice and its potential mechanisms of action. We also generated and characterized a humanized mouse model with chimeric HLA-A*02:01/Kb in ApoE-/- background to test the efficacy of P210-PAM immunization as a bridge for future clinical testing. P210 provoked T cell activation and memory response in PBMCs of human subjects with ASCVD. Dendritic cell uptake of P210-PAM and its co-staining with MHC-I molecules supported its use as a vaccine formulation. In ApoE-/- mice, immunization with P210-PAM dampened P210-specific CD4+ T cell proliferative response and CD8+ T cell cytolytic response, modulated macrophage phenotype, and significantly reduced aortic atherosclerosis. Potential clinical relevance of P210-PAM immunization was demonstrated by reduced atherosclerosis in the humanized ApoE-/- mouse model expressing chimeric HLA-A*02:01/Kb. Taken together, our data supports the experimental and translational use of P210-PAM as a potential vaccine candidate against human ASCVD.
Authors
Kuang-Yuh Chyu, Xiaoning Zhao, Jianchang Zhou, Paul C. Dimayuga, Nicole W.M. Lio, Bojan Cercek, Noah T. Trac, Eun Ji Chung, Prediman K. Shah
Abstract
Atrial fibrillation (AF), the most common sustained cardiac arrhythmia and a major risk factor for stroke, often arises through ectopic electrical impulses derived from the pulmonary veins (PV). Sequence variants in enhancers controlling expression of the transcription factor PITX2, which is expressed in the cardiomyocytes (CMs) of the PV and left atrium (LA), have been implicated in AF predisposition. Single nuclei multiomic profiling of RNA and analysis of chromatin accessibility combined with spectral clustering uncovered distinct PV- and LA-enriched CM cell states. Pitx2 mutant PV and LA CMs exhibited gene expression changes consistent with cardiac dysfunction through cell-type-distinct, PITX2-directed, cis-regulatory grammars controlling target gene expression. The perturbed network targets in each CM were enriched in distinct human AF-predisposition genes, suggesting combinatorial risk for AF-genesis. Our data further reveals that PV and LA Pitx2 mutant CMs signal to endothelial and endocardial cells through BMP10 signaling with pathogenic potential. This work provides a multiomic framework for interrogating the basis of AF-predisposition in the PV of humans.
Authors
Jeffrey D. Steimle, Francisco J. Grisanti Canozo, Minjun Park, Zachary A. Kadow, Md. Abul Hassan Samee, James F. Martin
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