The possible association between the membrane-associated guanylate kinase with inverted domain structure-1 (MAGI1) and inflammation has been suggested, but the molecular mechanisms underlying this link, especially during atherogenesis, remain unclear. In endothelial cells (ECs) exposed to disturbed flow (d-flow), p90 ribosomal S6 kinase (p90RSK) bound to MAGI1, causing MAGI1-S741 phosphorylation and sentrin/SUMO-specific protease 2 T368 phosphorylation-mediated MAGI1-K931 deSUMOylation. MAGI1-S741 phosphorylation upregulated EC activation via activating Rap1. MAGI1-K931 deSUMOylation induced both nuclear translocation of p90RSK-MAGI1 and ATF-6-MAGI1 complexes, which accelerated EC activation and apoptosis, respectively. Microarray screening revealed key roles for MAGI1 in the endoplasmic reticulum (ER) stress response. In this context, MAGI1 associated with activating transcription factor 6 (ATF-6). MAGI1 expression was upregulated in ECs and macrophages found in atherosclerotic-prone regions of mouse aortas as well as in the colonic epithelia and ECs of patients with inflammatory bowel disease. Further, reduced MAGI1 expression in Magi1–/+ mice inhibited d-flow–induced atherogenesis. In sum, EC activation and ER stress–mediated apoptosis are regulated in concert by two different types of MAGI1 posttranslational modifications, elucidating attractive drug targets for chronic inflammatory disease, particularly atherosclerosis.
Jun-ichi Abe, Kyung Ae Ko, Sivareddy Kotla, Yin Wang, Jesus Paez-Mayorga, Ik Jae Shin, Masaki Imanishi, Hang Thi Vu, Yunting Tao, Miguel M. Leiva-Juarez, Tamlyn N. Thomas, Jan L. Medina, Jong Hak Won, Yuka Fujii, Carolyn J. Giancursio, Elena McBeath, Ji-Hyun Shin, Liliana Guzman, Rei J. Abe, Jack Taunton, Naoki Mochizuki, William Faubion, John P. Cooke, Keigi Fujiwara, Scott E. Evans, Nhat-Tu Le
Following injury, leukocytes are released from hematopoietic organs and migrate to the site of damage to regulate tissue inflammation and repair, however leukocytes lacking β2-adrenergic receptor (β2AR) expression have marked impairments in these processes. β-blockade is a common strategy for the treatment of many cardiovascular etiologies, therefore the objective of our study was to assess the impact of prior β-blocker treatment on baseline leukocyte parameters and their responsiveness to acute injury. In a temporal and βAR isoform-dependent manner, chronic β-blocker infusion increased splenic vascular cell adhesion molecule-1 (VCAM-1) expression and leukocyte accumulation (monocytes/macrophages, mast cells and neutrophils) and decreased chemokine receptor 2 (CCR2) expression, migration of bone marrow cells (BMC) and peripheral blood leukocytes (PBL), as well as infiltration into the heart following acute cardiac injury. Further, CCR2 expression and migratory responsiveness was significantly reduced in the PBL of patients receiving β-blocker therapy compared to β-blocker-naïve patients. These results highlight the ability of chronic β-blocker treatment to alter baseline leukocyte characteristics that decrease their responsiveness to acute injury and suggest that prior β-blockade may act to reduce the severity of innate immune responses.
Laurel A. Grisanti, Claudio de Lucia, Toby P. Thomas, Aron Stark, John T. Strony, Valerie D. Myers, Remus Berretta, Daohai Yu, Celestino Sardu, Raffaele Marfella, Erhe Gao, Steven R. Houser, Walter J. Koch, Eman A. Hamad, Douglas G. Tilley
BACKGROUND. Spatial resolution in cardiac activation maps based on voltage measurement is limited by far-field interference. Precise characterization of electrical sources would resolve this limitation; however, practical charge-based cardiac mapping has not been achieved. METHODS. A prototype algorithm, developed from first principles of electrostatic field theory, derives charge density (CD) as a spatial representation of the true sources of the cardiac field. The algorithm processes multiple, simultaneous, noncontact voltage measurements within the cardiac chamber to inversely derive the global distribution of CD sources across the endocardial surface. RESULTS. Comparison of CD to an established computer-simulated model of atrial conduction demonstrated feasibility in terms of spatial, temporal, and morphologic metrics. Inverse reconstruction matched simulation with median spatial errors of 1.73 mm and 2.41 mm for CD and voltage, respectively. Median temporal error was less than 0.96 ms and morphologic correlation was greater than 0.90 for both CD and voltage. Activation patterns observed in human atrial flutter reproduced those established through contact maps, with a 4-fold improvement in resolution noted for CD over voltage. Global activation maps (charge density–based) are reported in atrial fibrillation with confirmed reduction of far-field interference. Arrhythmia cycle-length slowing and termination achieved through ablation of critical points demonstrated in the maps indicates both mechanistic and pathophysiological relevance. CONCLUSION. Global maps of cardiac activation based on CD enable classification of conduction patterns and localized nonpulmonary vein therapeutic targets in atrial fibrillation. The measurement capabilities of the approach have roles spanning deep phenotyping to therapeutic application. TRIAL REGISTRATION. ClinicalTrials.gov NCT01875614. FUNDING. The National Institute for Health Research (NIHR) Translational Research Program at Royal Papworth Hospital and Acutus Medical.
Andrew Grace, Stephan Willems, Christian Meyer, Atul Verma, Patrick Heck, Min Zhu, Xinwei Shi, Derrick Chou, Lam Dang, Christoph Scharf, Günter Scharf, Graydon Beatty
Hypertrophic cardiomyopathy (HCM) is triggered mainly by mutations in genes encoding sarcomeric proteins, but a significant proportion of patients lack a genetic diagnosis. We identified a novel mutation in the ryanodine receptor 2, RyR2-P1124L, in a patient from a genotype-negative HCM cohort. The aim of this study was to determine whether RyR2-P1124L triggers functional and structural alterations in isolated RyR2 channels and whole hearts. We found that P1124L induces significant conformational changes in the SPRY2 domain of RyR2. Recombinant RyR2-P1124L channels displayed a cytosolic loss-of-function phenotype, which contrasted with a higher sensitivity to luminal [Ca2+], indicating a luminal gain-of-function. Homozygous mice for RyR2-P1124L showed mild cardiac hypertrophy, similar to the human patient. This phenotype, evident at 1 yr of age, was accompanied by an increase in the expression of calmodulin (CaM). P1124L mice also showed higher susceptibility to arrhythmia at 8 mo of age, before the onset of hypertrophy. RyR2-P1124L has a distinct cytosolic loss-of-function and a luminal gain-of-function phenotype. This bifunctionally-divergent behavior triggers arrhythmias and structural cardiac remodeling, and involves overexpression of calmodulin as a potential hypertrophic mediator. This study is relevant to continue elucidating the possible causes of genotype-negative HCM and the role of RyR2 in cardiac hypertrophy.
Francisco J. Alvarado, J. Martijn Bos, Zhiguang Yuchi, Carmen R. Valdivia, Jonathan J. Hernandez, Yan-Ting Zhao, Dawn S. Henderlong, Yan Chen, Talia R. Booher, Cherisse A. Marcou, Filip Van Petegem, Michael J. Ackerman, Hector H. Valdivia
Sarcomeric disarray is a hallmark of gene mutations in patients with Hypertrophic Cardiomyopathy (HCM). However, it is unknown when detrimental sarcomeric changes first occur and whether they originate in the developing embryonic heart. Furthermore, Rho Kinase (ROCK) is a serine threonine protein kinase that is critical for regulating the function of several sarcomeric proteins and therefore, our aim was to determine if disruption of ROCK signalling during the earliest stages of heart development would disrupt the integrity of sarcomeres altering heart development and function. Using a mouse model in which the function of ROCK is specifically disrupted in embryonic cardiomyocytes we demonstrate a progressive cardiomyopathy that first appeared as sarcomeric disarray during cardiogenesis. This led to abnormalities in the structure of embryonic ventricular wall and compensatory cardiomyocyte hypertrophy during foetal development. This sarcomeric disruption and hypertrophy persisted throughout adult life, triggering left ventricular concentric hypertrophy with systolic dysfunction, and re-activation of foetal gene expression and cardiac fibrosis, all typical features of HCM. Taken together, our findings establish a novel mechanism for the developmental origin of the sarcomeric phenotype of HCM and suggest that variants in the ROCK genes or disruption of ROCK signalling could, in part, contribute to its pathogenesis.
Kate E. Bailey, Guy A. MacGowan, Simon Tual-Chalot, Lauren Phillips, Tim J. Mohun, Deborah J. Henderson, Helen M. Arthur, Simon D. Bamforth, Helen M. Phillips
Atherosclerosis is a leading cause of death worldwide in industrialized countries. Disease progression and regression are associated with different activation states of macrophages derived from inflammatory monocytes entering the plaques. The features of monocyte-to-macrophage transition and the full spectrum of macrophage activation states during either plaque progression or regression, however, are incompletely established. Here, we use a combination of single-cell RNA sequencing and genetic fate mapping to profile, for the first time to our knowledge, plaque cells derived from CX3CR1+ precursors in mice during both progression and regression of atherosclerosis. The analyses revealed a spectrum of macrophage activation states with greater complexity than the traditional M1 and M2 polarization states, with progression associated with differentiation of CXC3R1+ monocytes into more distinct states than during regression. We also identified an unexpected cluster of proliferating monocytes with a stem cell–like signature, suggesting that monocytes may persist in a proliferating self-renewal state in inflamed tissue, rather than differentiating immediately into macrophages after entering the tissue.
Jian-Da Lin, Hitoo Nishi, Jordan Poles, Xiang Niu, Caroline Mccauley, Karishma Rahman, Emily J. Brown, Stephen T. Yeung, Nikollaq Vozhilla, Ada Weinstock, Stephen A. Ramsey, Edward A. Fisher, P’ng Loke
Acute cardiorenal syndrome (CRS-1) is a morbid complication of acute cardiovascular disease. Heart-to-kidney signals transmitted by “cardiorenal connectors” have been postulated, but investigation into CRS-1 has been limited by technical limitations and a paucity of models. To address these limitations, we developed a translational model of CRS-1, cardiac arrest and cardiopulmonary resuscitation (CA/CPR), and now report findings from nanoscale mass spectrometry proteomic exploration of glomerular filtrate 2 hours after CA/CPR or sham procedure. Filtrate acquisition was confirmed by imaging, molecular weight and charge distribution, and exclusion of protein specific to surrounding cells. Filtration of proteins specific to the heart was detected following CA/CPR and confirmed with mass spectrometry performed using urine collections from mice with deficient tubular endocytosis. Cardiac LIM protein was a CA/CPR-specific filtrate component. Cardiac arrest induced plasma release of cardiac LIM protein in mice and critically ill human cardiac arrest survivors, and administration of recombinant cardiac LIM protein to mice altered renal function. These findings demonstrate that glomerular filtrate is accessible to nanoscale proteomics and elucidate the population of proteins filtered 2 hours after CA/CPR. The identification of cardiac-specific proteins in renal filtrate suggests a novel signaling mechanism in CRS-1. We expect these findings to advance understanding of CRS-1.
Rumie Wakasaki, Katsuyuki Matsushita, Kirsti Golgotiu, Sharon Anderson, Mahaba B. Eiwaz, Daniel J. Orton, Sang Jun Han, H. Thomas Lee, Richard D. Smith, Karin D. Rodland, Paul D. Piehowski, Michael P. Hutchens
BACKGROUND. Simultaneous noninvasively recorded skin sympathetic nerve activity (SKNA) and electrocardiogram (neuECG) can be used to estimate cardiac sympathetic tone. We tested the hypothesis that large and prolonged SKNA bursts are associated with temporal clustering arrhythmias. METHODS. We recorded neuECG in 10 patients (69 ± 10 years old) with atrial fibrillation (AF) episodes and in 6 patients (50 ± 13 years old) with ventricular tachycardia (VT) or fibrillation (VF) episodes. Clustering was defined by an arrhythmic episode followed within 1 minute by spontaneous recurrences of the same arrhythmia. The neuECG signals were bandpass filtered between 500–1000 Hz to display SKNA. RESULTS. There were 22 AF clusters, including 231 AF episodes from 6 patients, and 9 VT/VF clusters, including 99 VT/VF episodes from 3 patients. A total duration of SKNA bursts associated with AF was longer than that during sinus rhythm (78.9 min/hour [interquartile range (IQR) 17.5–201.3] vs. 16.3 min/hour [IQR 14.5–18.5], P = 0.022). The burst amplitude associated with AF in clustering patients was significantly higher than that in nonclustering patients (1.54 μV [IQR 1.35–1.89], n = 114, vs. 1.20 μV [IQR 1.05–1.42], n = 21, P < 0.001). The SKNA bursts associated with VT/VF clusters lasted 9.3 ± 3.1 minutes, with peaks that averaged 1.13 ± 0.38 μV as compared with 0.79 ± 0.11 μV at baseline (P = 0.041). CONCLUSION. Large and sustained sympathetic nerve activities are associated with the temporal clustering of AF and VT/VF. FUNDING. This study was supported in part by NIH grants R42DA043391 (THE), R56 HL71140, TR002208-01, R01 HL139829 (PSC), a Charles Fisch Cardiovascular Research Award endowed by Suzanne B. Knoebel of the Krannert Institute of Cardiology (TK and THE), a Medtronic-Zipes Endowment, and the Indiana University Health-Indiana University School of Medicine Strategic Research Initiative (PSC).
Takashi Kusayama, Juyi Wan, Anisiia Doytchinova, Johnson Wong, Ryan A. Kabir, Gloria Mitscher, Susan Straka, Changyu Shen, Thomas H. Everett IV, Peng-Sheng Chen
Iron deficiency is present in approximately 50% of heart failure (HF) patients. Large multi-center trials have shown that treatment of iron deficiency with intravenous iron benefits HF patients, but the underlying mechanisms are not known. To investigate the actions of iron deficiency on the heart, mice were fed an iron-depleted diet and some received intravenous ferric carboxymaltose (FCM), an iron supplementation used clinically. Iron-deficient animals became anemic and had reduced ventricular ejection fraction measured by magnetic resonance imaging. Ca2+ signaling, a pathway linked to the contractile deficit in failing hearts, was also significantly affected. Ventricular myocytes isolated from iron-deficient animals produced smaller Ca2+ transients from an elevated diastolic baseline, but had unchanged sarcoplasmic reticulum (SR) Ca2+-load, trigger L-type Ca2+ current or cytoplasmic Ca2+ buffering. Reduced fractional release from the SR was due to downregulated RyR2 channels, detected at protein and message level. The constancy of diastolic SR Ca2+-load is explained by reduced RyR2 permeability in combination with right-shifted SERCA activity due dephosphorylation of its regulator phospholamban. Supplementing iron levels with FCM restored normal Ca2+ signaling and ejection fraction. Thus, two Ca2+-handling proteins previously implicated in HF become functionally impaired in iron-deficiency anemia, but their activity is rescued by intravenous iron supplementation.
Yu Jin Chung, Antao Luo, Kyung Chan Park, Aminah Loonat, Samira Lakhal-Littleton, Peter A. Robbins, Pawel Swietach
Heart failure (HF) is associated in humans and mice with increased circulating levels of CXCL9 and CXCL10, chemokine ligands of the CXCR3 receptor, predominantly expressed on CD4+ T helper type 1 (Th1) cells. Chemokine engagement of receptors is required for T cell integrin activation and recruitment to sites of inflammation. Th1 cells drive adverse cardiac remodeling in pressure overload induced cardiac dysfunction, and mice lacking the integrin ligand ICAM-1 show defective T cell recruitment to the heart. Here, we show that CXCR3+ T cells infiltrate the heart in humans and mice with pressure overload induced cardiac dysfunction. Genetic deletion of CXCR3 disrupts CD4+ T cell heart infiltration and prevents adverse cardiac remodeling. We demonstrate that cardiac myeloid cells that include resident and infiltrated macrophages, and cardiac fibroblasts are the source of CXCL9 and CXCL10; which, mechanistically promote Th1 cell adhesion to ICAM-1 under shear conditions in a CXCR3-dependent manner. Our findings identify a previously unrecognized role for CXCR3 in Th1 cell recruitment into the heart in pressure overload induced cardiac dysfunction.
Njabulo Ngwenyama, Ane M. Salvador, Francisco Velázquez, Tania Nevers, Alexander Levy, Mark J. Aronovitz, Andrew D. Luster, Gordon S. Huggins, Pilar Alcaide
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