Aberrant expression of the cardiac gap junction protein connexin-43 (Cx43) has been suggested to play a role in the development of cardiac disease in the mdx mouse model of Duchenne muscular dystrophy (DMD), however a mechanistic understanding of this association is lacking. Here, we identified a reduction of phosphorylation of Cx43 serines S325/S328/S330 in human and mouse DMD hearts. We hypothesized that hypo-phosphorylation of Cx43 serine-triplet triggers pathological Cx43 redistribution to the lateral sides of cardiomyocytes (remodeling). Therefore, we generated knock-in mdx mice in which the Cx43 serine-triplet was replaced with either phospho-mimicking glutamic acids (mdxS3E) or non-phosphorylatable alanines (mdxS3A). The mdxS3E but not mdxS3A mice were resistant to Cx43 remodeling with a corresponding reduction of Cx43 hemichannel activity. MdxS3E cardiomyocytes displayed improved intracellular Ca2+ signaling and a reduction of NOX2/reactive oxygen species (ROS) production. Furthermore, mdxS3E mice were protected against inducible arrhythmias, related lethality and the development of cardiomyopathy. Inhibition of microtubule polymerization by colchicine reduced both NOX2/ROS and oxidized CaMKII, increased S325/S328/S330 phosphorylation and prevented Cx43 remodeling in mdx hearts. Together, these results demonstrate a mechanism of dystrophic Cx43-remodeling and suggest that targeting Cx43 may be a therapeutic strategy to prevent heart dysfunction and arrhythmias in DMD patients.
Eric Himelman, Mauricio A. Lillo, Julie Nouet, J. Patrick Gonzalez, Qingshi Zhao, Lai-Hua Xie, Hong Li, Tong Liu, Xander H.T. Wehrens, Paul D. Lampe, Glenn I. Fishman, Natalia Shirokova, Jorge E. Contreras, Diego Fraidenraich
Cantu Syndrome (CS) is a complex disorder caused by gain-of-function (GoF) mutations in ABCC9 and KCNJ8, which encode the SUR2 and Kir6.1 subunits, respectively, of vascular smooth muscle (VSM) KATP channels. CS includes dilated vasculature, marked cardiac hypertrophy, and other cardiovascular abnormalities. There is currently no targeted therapy, and it is unknown whether cardiovascular features can be reversed once manifest. Using combined transgenic and pharmacological approaches in a knock-in mouse model of CS, we have shown that reversal of vascular and cardiac phenotypes can be achieved (1) by genetic downregulation of KATP channel activity specifically in VSM, and (2) by chronic administration of the clinically-used KATP channel inhibitor, glibenclamide. These findings demonstrate (i) that VSM KATP channel GoF underlies CS cardiac enlargement, (ii) reversibility of CS-associated abnormalities and (iii) evidence of in vivo efficacy of glibenclamide as a therapeutic agent in CS.
Conor McClenaghan, Yan Huang, Zihan Yan, Theresa Harter, Carmen M. Halabi, Rod Chalk, Attila Kovacs, Gijs van Haaften, Maria S. Remedi, Colin G. Nichols
Sustained, indolent immune injury of the vasculature of a heart transplant limits long-term graft and recipient survival. This injury is mitigated by a poorly characterized, maladaptive repair response. Vascular endothelial cells respond to proangiogenic cues in the embryo by differentiation to specialized phenotypes, associated with expression of apelin. In the adult, the role of developmental proangiogenic cues in repair of the established vasculature is largely unknown. We found that human and minor histocompatibility–mismatched donor mouse heart allografts with alloimmune-mediated vasculopathy upregulated expression of apelin in arteries and myocardial microvessels. In vivo, loss of donor heart expression of apelin facilitated graft immune cell infiltration, blunted vascular repair, and worsened occlusive vasculopathy in mice. In vitro, an apelin receptor agonist analog elicited endothelial nitric oxide synthase activation to promote endothelial monolayer wound repair, and reduce immune cell adhesion. Thus, apelin acted as an autocrine growth cue to sustain vascular repair and mitigate the effects of immune injury. Treatment with an apelin receptor agonist after vasculopathy was established markedly reduced progression of arterial occlusion in mice. Together, these initial data identify proangiogenic apelin as a key mediator of coronary vascular repair and a pharmacotherapeutic target for immune-mediated injury of the coronary vasculature.
Andrew G. Masoud, Jiaxin Lin, Abul K. Azad, Maikel A. Farhan, Conrad Fischer, Lin F. Zhu, Hao Zhang, Banu Sis, Zamaneh Kassiri, Ronald B. Moore, Daniel Kim, Colin C. Anderson, John C. Vederas, Benjamin A. Adam, Gavin Y. Oudit, Allan G. Murray
Vascular Ehlers-Danlos syndrome (vEDS) is an autosomal-dominant connective tissue disorder caused by heterozygous mutations in the COL3A1 gene, which encodes the pro-alpha 1 chain of collagen III. Loss of structural integrity of the extracellular matrix is believed to drive the signs and symptoms of this condition, including spontaneous arterial dissection and/or rupture, the major cause of mortality. We created two mouse models of vEDS that carry heterozygous mutations in Col3a1 that encode glycine substitutions analogous to those found in patients, and showed that signaling abnormalities in the PLC/IP3/PKC/ERK pathway (phospholipase C/inositol 1,4,5-triphosphate/protein kinase C/extracellular signal-regulated kinase) are major mediators of vascular pathology.Treatment with pharmacologic inhibitors of ERK1/2 or PKC-beta prevented death due to spontaneous aortic rupture. Additionally, we found that pregnancy- and puberty-associated accentuation of vascular risk, also seen in vEDS patients, is rescued by attenuation of oxytocin and androgen signaling, respectively. Taken together, our results provide evidence that targetable signaling abnormalities contribute to the pathogenesis of vEDS, highlighting unanticipated therapeutic opportunities.
Caitlin J. Bowen, Juan Francisco Calderón Giadrosic, Zachary Burger, Graham Rykiel, Elaine C. Davis, Mark R. Helmers, Kelly Benke, Elena Gallo MacFarlane, Harry C. Dietz
Atrial fibrillation (AF), defined by disorganized atrial cardiac rhythm, is the most prevalent cardiac arrhythmia worldwide. Recent genetic studies have highlighted a major heritable component and identified numerous loci associated with AF risk, including the cardiogenic transcription factor genes TBX5, GATA4, and NKX2-5. We report that Tbx5 and Gata4 interact with opposite signs for atrial rhythm controls compared with cardiac development. Using mouse genetics, we found that AF pathophysiology caused by Tbx5 haploinsufficiency, including atrial arrhythmia susceptibility, prolonged action potential duration, and ectopic cardiomyocyte depolarizations, were all rescued by Gata4 haploinsufficiency. In contrast, Nkx2-5 haploinsufficiency showed no combinatorial effect. The molecular basis of the TBX5/GATA4 interaction included normalization of intra-cardiomyocyte calcium flux and expression of calcium channel genes Atp2a2 and Ryr2. Furthermore, GATA4 and TBX5 showed antagonistic interactions on an Ryr2 enhancer. Atrial rhythm instability caused by Tbx5 haploinsufficiency was rescued by a decreased dose of phospholamban, a sarco/endoplasmic reticulum Ca2+-ATPase inhibitor, consistent with a role for decreased sarcoplasmic reticulum calcium flux in Tbx5-dependent AF susceptibility. This work defines a link between Tbx5 dose, sarcoplasmic reticulum calcium flux, and AF propensity. The unexpected interactions between Tbx5 and Gata4 in atrial rhythm control suggest that evaluating specific interactions between genetic risk loci will be necessary for ascertaining personalized risk from genetic association data.
Brigitte Laforest, Wenli Dai, Leonid Tyan, Sonja Lazarevic, Kaitlyn M. Shen, Margaret Gadek, Michael T. Broman, Christopher R. Weber, Ivan P. Moskowitz
T cell autoreactivity is a hallmark of autoimmune diseases but can also benefit self-maintenance and foster tissue repair. Herein, we investigated whether heart-specific T cells exert salutary or detrimental effects in the context of myocardial infarction (MI), the leading cause of death worldwide. After screening more than 150 class-II-restricted epitopes, we found that myosin heavy chain alpha (MYHCA) was a dominant cardiac antigen triggering post-MI CD4+ T cell activation in mice. Transferred MYHCA614-629-specific CD4+ T (TCR-M) cells selectively accumulated in the myocardium and mediastinal lymph nodes (med-LN) of infarcted mice, acquired a Treg phenotype with a distinct pro-healing gene expression profile, and mediated cardioprotection. Myocardial Treg cells were also detected in autopsies from patients who suffered a MI. Noninvasive PET/CT imaging using a CXCR4 radioligand revealed enlarged med-LNs with increased cellularity in MI-patients. Notably, the med-LN alterations observed in MI patients correlated with the infarct size and cardiac function. Taken together, the results obtained in our study provide evidence showing that MI-context induces pro-healing T cell autoimmunity in mice and confirms the existence of an analogous heart/med-LN/T cell axis in MI patients.
Max Rieckmann, Murilo Delgobo, Chiara Gaal, Lotte Büchner, Philipp Steinau, Dan Reshef, Cristina Gil-Cruz, Ellis N. ter Horst, Malte Kircher, Theresa Reiter, Katrin G. Heinze, Hans W.M. Niessen, Paul A.J. Krijnen, Anja M. van der Laan, Jan J. Piek, Charlotte Koch, Hans-Jürgen Wester, Constantin Lapa, Wolfgang R. Bauer, Burkhard Ludewig, Nir Friedman, Stefan Frantz, Ulrich Hofmann, Gustavo Campos Ramos
Arrhythmogenic cardiomyopathy (ACM) is an inherited arrhythmia syndrome characterized by severe structural and electrical cardiac phenotypes, including myocardial fibrofatty replacement and sudden cardiac death. Clinical management of ACM is largely palliative, owing to an absence of therapies that target its underlying pathophysiology, which stems partially from our limited insight into the condition. Following identification of deceased ACM probands possessing ANK2 rare variants and evidence of ankyrin-B loss of function on cardiac tissue analysis, an ANK2 mouse model was found to develop dramatic structural abnormalities reflective of human ACM, including biventricular dilation, reduced ejection fraction, cardiac fibrosis, and premature death. Desmosomal structure and function appeared preserved in diseased human and murine specimens in the presence of markedly abnormal β-catenin expression and patterning, leading to identification of a previously unknown interaction between ankyrin-B and β-catenin. A pharmacological activator of the WNT/β-catenin pathway, SB-216763, successfully prevented and partially reversed the murine ACM phenotypes. Our findings introduce what we believe to be a new pathway for ACM, a role of ankyrin-B in cardiac structure and signaling, a molecular link between ankyrin-B and β-catenin, and evidence for targeted activation of the WNT/β-catenin pathway as a potential treatment for this disease.
Jason D. Roberts, Nathaniel P. Murphy, Robert M. Hamilton, Ellen R. Lubbers, Cynthia A. James, Crystal F. Kline, Michael H. Gollob, Andrew D. Krahn, Amy C. Sturm, Hassan Musa, Mona El-Refaey, Sara Koenig, Meriam Åström Aneq, Edgar T. Hoorntje, Sharon L. Graw, Robert W. Davies, Muhammad Arshad Rafiq, Tamara T. Koopmann, Shabana Aafaqi, Meena Fatah, David A. Chiasson, Matthew R.G. Taylor, Samantha L. Simmons, Mei Han, Chantal J.M. van Opbergen, Loren E. Wold, Gianfranco Sinagra, Kirti Mittal, Crystal Tichnell, Brittney Murray, Alberto Codima, Babak Nazer, Duy T. Nguyen, Frank I. Marcus, Nara Sobriera, Elisabeth M. Lodder, Maarten P. van den Berg, Danna A. Spears, John F. Robinson, Philip C. Ursell, Anna K. Green, Allan C. Skanes, Anthony S. Tang, Martin J. Gardner, Robert A. Hegele, Toon A.B. van Veen, Arthur A. M. Wilde, Jeff S. Healey, Paul M. L. Janssen, Luisa Mestroni, J. Peter van Tintelen, Hugh Calkins, Daniel P. Judge, Thomas J. Hund, Melvin M. Scheinman, Peter J. Mohler
About 1% of all newborns are affected by congenital heart disease (CHD). Recent findings identify aberrantly functioning cilia as a possible source for CHD. Faulty cilia also prevent the development of proper left-right asymmetry and cause heterotaxy, the incorrect placement of visceral organs. Intriguingly, signaling cascades such as mTor that influence mitochondrial biogenesis also affect ciliogenesis, and can cause heterotaxy-like phenotypes in zebrafish. Here, we identify levels of mitochondrial function as a determinant for ciliogenesis and a cause for heterotaxy. We detected reduced mitochondrial DNA content in biopsies of heterotaxy patients. Manipulation of mitochondrial function revealed a reciprocal influence on ciliogenesis and affected cilia-dependent processes in zebrafish, human fibroblasts and Tetrahymena thermophila. Exome analysis of heterotaxy patients revealed an increased burden of rare damaging variants in mitochondria-associated genes as compared to 1000 Genome controls. Knockdown of such candidate genes caused cilia elongation and ciliopathy-like phenotypes in zebrafish, which could not be rescued by RNA encoding damaging rare variants identified in heterotaxy patients. Our findings suggest that ciliogenesis is coupled to the abundance and function of mitochondria. Our data further reveal disturbed mitochondrial function as an underlying cause for heterotaxy-linked CHD and provide a mechanism for unexplained phenotypes of mitochondrial disease.
Martin D. Burkhalter, Arthi Sridhar, Pedro Sampaio, Raquel Jacinto, Martina S. Burczyk, Cornelia Donow, Max Angenendt, Competence Network for Congenital Heart Defects Investigators, Maja Hempel, Paul Walther, Petra Pennekamp, Heymut Omran, Susana S. Lopes, Stephanie M. Ware, Melanie Philipp
Exosomes, as functional paracrine units of therapeutic cells, can partially reproduce the reparative properties of their parental cells. The constitution of exosomes, as well as their biological activity, largely depends on the cells that secrete them. We isolated exosomes from explant-derived cardiac stromal cells from patients with heart failure (FEXO) or from normal donor hearts (NEXO) and compared their regenerative activities in vitro and in vivo. Patients in the FEXO group exhibited an impaired ability to promote endothelial tube formation and cardiomyocyte proliferation in vitro. Intramyocardial injection of NEXO resulted in structural and functional improvements in a murine model of acute myocardial infarction. In contrast, FEXO therapy exacerbated cardiac function and left ventricular remodeling. microRNA array and PCR analysis revealed dysregulation of miR-21-5p in FEXO. Restoring miR-21-5p expression rescued FEXO’s reparative function, whereas blunting miR-21-5p expression in NEXO diminished its therapeutic benefits. Further mechanistic studies revealed that miR-21-5p augmented Akt kinase activity through the inhibition of phosphatase and tensin homolog. Taken together, the heart failure pathological condition altered the miR cargos of cardiac-derived exosomes and impaired their regenerative activities. miR-21-5p contributes to exosome-mediated heart repair by enhancing angiogenesis and cardiomyocyte survival through the phosphatase and tensin homolog/Akt pathway.
Li Qiao, Shiqi Hu, Suyun Liu, Hui Zhang, Hong Ma, Ke Huang, Zhenhua Li, Teng Su, Adam Vandergriff, Junnan Tang, Tyler Allen, Phuong-Uyen Dinh, Jhon Cores, Qi Yin, Yongjun Li, Ke Cheng
BACKGROUND.l-Carnitine, an abundant nutrient in red meat, accelerates atherosclerosis in mice via gut microbiota–dependent formation of trimethylamine (TMA) and trimethylamine N-oxide (TMAO) via a multistep pathway involving an atherogenic intermediate, γ-butyrobetaine (γBB). The contribution of γBB in gut microbiota–dependent l-carnitine metabolism in humans is unknown. METHODS. Omnivores and vegans/vegetarians ingested deuterium-labeled l-carnitine (d3-l-carnitine) or γBB (d9-γBB), and both plasma metabolites and fecal polymicrobial transformations were examined at baseline, following oral antibiotics, or following chronic (≥2 months) l-carnitine supplementation. Human fecal commensals capable of performing each step of the l-carnitine→γBB→TMA transformation were identified. RESULTS. Studies with oral d3-l-carnitine or d9-γBB before versus after antibiotic exposure revealed gut microbiota contribution to the initial 2 steps in a metaorganismal l-carnitine→γBB→TMA→TMAO pathway in subjects. Moreover, a striking increase in d3-TMAO generation was observed in omnivores over vegans/vegetarians (>20-fold; P = 0.001) following oral d3-l-carnitine ingestion, whereas fasting endogenous plasma l-carnitine and γBB levels were similar in vegans/vegetarians (n = 32) versus omnivores (n = 40). Fecal metabolic transformation studies, and oral isotope tracer studies before versus after chronic l-carnitine supplementation, revealed that omnivores and vegans/vegetarians alike rapidly converted carnitine to γBB, whereas the second gut microbial transformation, γBB→TMA, was diet inducible (l-carnitine, omnivorous). Extensive anaerobic subculturing of human feces identified no single commensal capable of l-carnitine→TMA transformation, multiple community members that converted l-carnitine to γBB, and only 1 Clostridiales bacterium, Emergencia timonensis, that converted γBB to TMA. In coculture, E. timonensis promoted the complete l-carnitine→TMA transformation. CONCLUSION. In humans, dietary l-carnitine is converted into the atherosclerosis- and thrombosis-promoting metabolite TMAO via 2 sequential gut microbiota–dependent transformations: (a) initial rapid generation of the atherogenic intermediate γBB, followed by (b) transformation into TMA via low-abundance microbiota in omnivores, and to a markedly lower extent, in vegans/vegetarians. Gut microbiota γBB→TMA/TMAO transformation is induced by omnivorous dietary patterns and chronic l-carnitine exposure. TRIAL REGISTRATION. ClinicalTrials.gov NCT01731236. FUNDING. NIH and Office of Dietary Supplements grants HL103866, HL126827, and DK106000, and the Leducq Foundation.
Robert A. Koeth, Betzabe Rachel Lam-Galvez, Jennifer Kirsop, Zeneng Wang, Bruce S. Levison, Xiaodong Gu, Matthew F. Copeland, David Bartlett, David B. Cody, Hong J. Dai, Miranda K. Culley, Xinmin S. Li, Xiaoming Fu, Yuping Wu, Lin Li, Joseph A. DiDonato, W.H. Wilson Tang, Jose Carlos Garcia-Garcia, Stanley L. Hazen