scholarly journals Selective Connexin43 Inhibition Prevents Isoproterenol-Induced Arrhythmias and Lethality in Muscular Dystrophy Mice

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
J. Patrick Gonzalez ◽  
Jayalakshmi Ramachandran ◽  
Lai-Hua Xie ◽  
Jorge E. Contreras ◽  
Diego Fraidenraich
Keyword(s):  
Heart Failure ◽  
Muscular Dystrophy ◽  
Selective Inhibition ◽  
Cardiac Conduction ◽  
Peptide Mimetics ◽  
Wild Type ◽  
Protein Levels ◽  
Junction Protein ◽  
Life Threatening ◽  
Gap Junction Protein

Abstract Duchenne muscular dystrophy (DMD) is caused by an X-linked mutation that leads to the absence of dystrophin, resulting in life-threatening arrhythmogenesis and associated heart failure. We targeted the gap junction protein connexin43 (Cx43) responsible for maintaining cardiac conduction. In mild mdx and severe mdx:utr mouse models of DMD and human DMD tissues, Cx43 was found to be pathologically mislocalized to lateral sides of cardiomyocytes. In addition, overall Cx43 protein levels were markedly increased in mouse and human DMD heart tissues examined. Electrocardiography on isoproterenol challenged mice showed that both models developed arrhythmias and died within 24 hours, while wild-type mice were free of pathology. Administering peptide mimetics to inhibit lateralized Cx43 function prior to challenge protected mdx mice from arrhythmogenesis and death, while mdx:utr mice displayed markedly improved ECG scores. These findings suggest that Cx43 lateralization contributes significantly to DMD arrhythmogenesis and that selective inhibition may provide substantial benefit.

Abstract 255: Role of Connexin 43 in Muscular Dystrophy Cardiomyopathy

2016 ◽  
Vol 119 (suppl_1) ◽  
Author(s):  
J. Patrick Gonzalez ◽  
Jayalakshmi Ramachandran ◽  
Chifei Kang ◽  
Lai-Hua Xie ◽  
Natalia Shirokova ◽  
...  
Keyword(s):  
Heart Failure ◽  
Muscular Dystrophy ◽  
Mouse Models ◽  
Connexin 43 ◽  
Selective Inhibition ◽  
Cardiac Conduction ◽  
Mdx Mice ◽  
Wild Type ◽  
Junction Protein ◽  
Phosphorylation Pattern

Duchenne muscular dystrophy (DMD) is caused by an X-linked mutation that leads to the absence of dystrophin, resulting in life-threatening arrhythmogenesis and associated heart failure. The downstream events that lead to cardiomyopathy are largely unexplored. We unveiled a novel role for the gap junction protein connexin43 (Cx43) in maintaining cardiac conduction and ultimately in preventing heart failure from occurring in DMD. In mild mdx and severe mdx:utr mouse models of DMD, and human DMD tissues, Cx43 was found to be aberrantly upregulated and mislocalized to lateral sides of cardiomyocytes, with an abnormal phosphorylation pattern. We found that a triplet of serine residues, which plays a key role in a variety of cardiac pathologies, was hypophosphorylated in mdx relative to wild-type hearts. Electrocardiography on isoproterenol (Iso) challenged mice showed that both DMD mouse models developed arrhythmias and died within 24 hours, while wild-type mice were free of pathology. Administering peptide mimetic inhibitors of lateralized Cx43 channels prior to Iso challenge protected mdx mice from arrhythmogenesis and death. Cx43 copy number reduction in mdx:Cx43(+/-) mice not only ameliorated acute but also chronic, long-term symptoms of cardiomyopathy in mdx mice. Overall, our findings suggest that Cx43 lateralization contributes significantly to DMD cardiomyopathy and that selective inhibition of misplaced, upregulated channels may provide substantial benefit.

scholarly journals Catecholamine Surges Cause Cardiomyocyte Necroptosis via a RIPK1–RIPK3-Dependent Pathway in Mice

2021 ◽  
Vol 8 ◽  
Author(s):  
Penglong Wu ◽  
Mingqi Cai ◽  
Jinbao Liu ◽  
Xuejun Wang
Keyword(s):  
Heart Failure ◽  
Cardiac Injury ◽  
Underlying Mechanism ◽  
Selective Inhibitor ◽  
Blue Dye ◽  
Wild Type ◽  
Adrenergic Stimulation ◽  
Protein Levels ◽  
Regulated Necrosis ◽  
Dependent Pathway

Background: Catecholamine surges and resultant excessive β-adrenergic stimulation occur in a broad spectrum of diseases. Excessive β-adrenergic stimulation causes cardiomyocyte necrosis, but the underlying mechanism remains obscure. Necroptosis, a major form of regulated necrosis mediated by RIPK3-centered pathways, is implicated in heart failure; however, it remains unknown whether excessive β-adrenergic stimulation-induced cardiac injury involves necroptosis. Hence, we conducted the present study to address these critical gaps.Methods and Results: Two consecutive daily injections of isoproterenol (ISO; 85 mg/kg, s.c.) or saline were administered to adult mixed-sex mice. At 24 h after the second ISO injection, cardiac area with Evans blue dye (EBD) uptake and myocardial protein levels of CD45, RIPK1, Ser166-phosphorylated RIPK1, RIPK3, and Ser345-phosphorylated MLKL (p-MLKL) were significantly greater, while Ser321-phosphorylated RIPK1 was significantly lower, in the ISO-treated than in saline-treated wild-type (WT) mice. The ISO-induced increase of EBD uptake was markedly less in RIPK3−/− mice compared with WT mice (p = 0.016). Pretreatment with the RIPK1-selective inhibitor necrostatin-1 diminished ISO-induced increases in RIPK3 and p-MLKL in WT mice and significantly attenuated ISO-induced increases of EBD uptake in WT but not RIPK3−/− mice.Conclusions: A large proportion of cardiomyocyte necrosis induced by excessive β-adrenergic stimulation belongs to necroptosis and is mediated by a RIPK1–RIPK3-dependent pathway, identifying RIPK1 and RIPK3 as potential therapeutic targets for catecholamine surges.

Functional analysis of gap junctions in ovarian granulosa cells: distinct role for connexin43 in early stages of folliculogenesis

2003 ◽  
Vol 284 (4) ◽  
pp. C880-C887 ◽  
Author(s):  
Joanne E. I. Gittens ◽  
Abdul Amir Mhawi ◽  
Darcy Lidington ◽  
Yves Ouellette ◽  
Gerald M. Kidder
Keyword(s):  
Gap Junctions ◽  
Granulosa Cells ◽  
Significant Contribution ◽  
Ionic Current ◽  
Wild Type ◽  
Intercellular Coupling ◽  
Ovarian Granulosa Cells ◽  
Junction Protein ◽  
Gap Junction Protein

Ovarian granulosa cells are coupled via gap junctions containing connexin43 (Cx43 or α-1 connexin). In the absence of Cx43, granulosa cells stop growing in an early preantral stage. However, the fact that granulosa cells of mature follicles express multiple connexins complicated interpretation of this finding. The present experiments were designed to clarify the role of Cx43 vs. these other connexins in the earliest stages of folliculogenesis. Dye injection experiments revealed that granulosa cells from Cx43 knockout follicles are not coupled, and this was confirmed by ionic current injections. Furthermore, electron microscopy revealed that gap junctions are extremely rare in mutant granulosa cells. In contrast, mutant granulosa cells were able to form gap junctions with wild-type granulosa cells in a dye preloading assay. It was concluded that mutant granulosa cells contain a population of connexons, composed of an unidentified connexin, that do not normally contribute to gap junctions. Therefore, although Cx43 is not the only gap junction protein present in granulosa cells of early preantral follicles, it is the only one that makes a significant contribution to intercellular coupling.

scholarly journals NAD(P)H oxidase subunit p47phox is elevated, and p47phox knockout prevents diaphragm contractile dysfunction in heart failure

2015 ◽  
Vol 309 (5) ◽  
pp. L497-L505 ◽  
Author(s):  
Bumsoo Ahn ◽  
Adam W. Beharry ◽  
Gregory S. Frye ◽  
Andrew R. Judge ◽  
Leonardo F. Ferreira
Keyword(s):  
Heart Failure ◽  
Knockout Mice ◽  
Contractile Function ◽  
Isometric Force ◽  
Exercise Intolerance ◽  
Contractile Dysfunction ◽  
Wild Type ◽  
Shortening Velocity ◽  
Protein Levels ◽  
Specific Source

Patients with chronic heart failure (CHF) have dyspnea and exercise intolerance, which are caused in part by diaphragm abnormalities. Oxidants impair diaphragm contractile function, and CHF increases diaphragm oxidants. However, the specific source of oxidants and its relevance to diaphragm abnormalities in CHF is unclear. The p47phox-dependent Nox2 isoform of NAD(P)H oxidase is a putative source of diaphragm oxidants. Thus, we conducted our study with the goal of determining the effects of CHF on the diaphragm levels of Nox2 complex subunits and test the hypothesis that p47phox knockout prevents diaphragm contractile dysfunction elicited by CHF. CHF caused a two- to sixfold increase ( P < 0.05) in diaphragm mRNA and protein levels of several Nox2 subunits, with p47phox being upregulated and hyperphosphorylated. CHF increased diaphragm extracellular oxidant emission in wild-type but not p47phox knockout mice. Diaphragm isometric force, shortening velocity, and peak power were decreased by 20–50% in CHF wild-type mice ( P < 0.05), whereas p47phox knockout mice were protected from impairments in diaphragm contractile function elicited by CHF. Our experiments show that p47phox is upregulated and involved in the increased oxidants and contractile dysfunction in CHF diaphragm. These findings suggest that a p47phox-dependent NAD(P)H oxidase mediates the increase in diaphragm oxidants and contractile dysfunction in CHF.

scholarly journals Effect of Hook Subunit Concentration on Assembly and Control of Length of the Flagellar Hook ofSalmonella

1999 ◽  
Vol 181 (18) ◽  
pp. 5808-5813 ◽  
Author(s):  
Kazumasa Muramoto ◽  
Shigeru Makishima ◽  
Shin-Ichi Aizawa ◽  
Robert M. Macnab
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Basal Bodies ◽  
Wild Type ◽  
Hook Length ◽  
Capping Protein ◽  
Protein Levels ◽  
Junction Protein ◽  
And Control ◽  
Control Protein

ABSTRACT The flagellar hook of Salmonella is a filamentous polymer made up of subunits of the protein FlgE. Hook assembly is terminated when the length reaches about 55 nm. After our recent study of the effect of cellular levels of the hook length control protein FliK, we have now analyzed the effect of cellular levels of FlgE itself. When FlgE was overproduced in a wild-type strain, afliC (flagellin) mutant, or a fliD(hook-associated protein 2 [HAP2], filament capping protein) mutant, the hooks remained at the wild-type length. In a fliK (hook length control protein) mutant, which produces long hooks (polyhooks), the overproduction of FlgE resulted in extraordinarily long hooks (superpolyhooks). In a flgK (HAP1, first hook-filament junction protein) mutant or a flgL (HAP3, second hook-filament junction protein) mutant, the overproduction of FlgE also resulted in longer than normal hooks. Thus, at elevated hook protein levels not only FliK but also FlgK and FlgL are necessary for the proper termination of hook elongation. When FlgE was severely underproduced, basal bodies without hooks were often observed. However, those hooks that were seen were of wild-type length, demonstrating that FlgE underproduction decreases the probability of the initiation of hook assembly but not the extent of hook elongation.

Abstract 253: HSPB7 is Required for Maintaining the Intercalated Disc Structure to Prevent Cardiac Conduction System Failure in Mouse

2017 ◽  
Vol 121 (suppl_1) ◽  
Author(s):  
Wern-Chir Liao ◽  
Liang-Yi Juo ◽  
Yen-Hui Chen ◽  
Yu-Ting Yan
Keyword(s):  
Heart Failure ◽  
Gap Junction ◽  
Connexin 43 ◽  
Adherens Junction ◽  
Small Heat Shock Protein ◽  
Cardiac Conduction ◽  
Nucleotide Polymorphisms ◽  
Intercalated Disc ◽  
Junction Protein ◽  
And Function

HSPB7 is belonged to small heat-shock protein (HSPB) family and considered to function as a co-chaperone, which prevents protein aggregation and maintains protein structure. Single-nucleotide polymorphisms of HSPB7 associated with sporadic cardiomyopathy and heart failure have been identified in human patients. Additionally, HSPB7 is constitutively expressed in heart and rapidly increased in blood plasma after myocardial infarction, suggesting a functional role in the heart. In this study, we found that HSPB7 is highly colocalized with N-cadherin during the assembly and maturation of intercalated disc, suggesting that HSPB7 may involve in organizing and maintaining the cardiac cytoarchitecture. To elucidate the physiological function of HSPB7 in the adult heart, we generated a cardiac-specific inducible HSPB7 knockout mouse. Ablation of HSPB7 in the cardiomyocyte rapidly leads to heart failure, abnormal conduction properties and sudden arrhythmias death. Loss of HSPB7 did not cause significant changes in the organization of contractile proteins in sarcomeres, whereas severe abnormality in the intercalated disc was detected. The expression of connexin 43, a gap-junction protein located at the intercalated disc, was downregulated in HSPB7 knockout cardiomyocytes. Mislocalizations of desmoplakin (desmosomal proteins), and N-cadherin (adherens junction proteins) were also observed in the HSPB7 CKO hearts. Furthermore, filamin C, the interaction protein of HSPB7, was mislocalized and aggregated in HSPB7 mutant cardiomyocytes. The expressivity of the phenotype in the HSPB7 CKO mice is similar to human arrhythmogenic cardiomyopathy patients. Conclusively, we provide the first study characterizing HSPB7 as an intercalated disc protein. Our findings demonstrate that HSPB7 plays an essential role to maintain the structure and function of gap-junction complexes and intercalated disc and has vital implications for human heart disease.

Accelerated onset of heart failure in mice during pressure overload with chronically decreased SERCA2 calcium pump activity

2004 ◽  
Vol 286 (3) ◽  
pp. H1146-H1153 ◽  
Author(s):  
Jo El J. Schultz ◽  
Betty J. Glascock ◽  
Sandra A. Witt ◽  
Michelle L. Nieman ◽  
Kalpana J. Nattamai ◽  
...  
Keyword(s):  
Heart Failure ◽  
Cardiac Contractility ◽  
Pressure Overload ◽  
Left Ventricular ◽  
Wild Type ◽  
Human Heart Failure ◽  
Protein Levels ◽  
Plasmic Reticulum ◽  
Lv Mass ◽  
Pump Activity

We recently developed a mouse model with a single functional allele of Serca2 ( Serca2+/–) that shows impaired cardiac contractility and relaxation without overt heart disease. The goal of this study was to test the hypothesis that chronic reduction in sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA)2 levels in combination with an increased hemodynamic load will result in an accelerated pathway to heart failure. Age-matched wild-type and Serca2+/– mice were subjected to 10 wk of pressure overload via transverse aortic coarctation surgery. Cardiac hypertrophy and heart failure were assessed by echocardiography, gravimetry/histology, hemodynamics, and Western blotting analyses. Our results showed that ∼64% of coarcted Serca2+/– mice were in heart failure compared with 0% of coarcted wild-type mice ( P < 0.05). Overall, morbidity and mortality were greatly increased in Serca2+/– mice under pressure overload. Echocardiography assessment revealed a significant increase in left ventricular (LV) mass, and LV hypertrophy in coarcted Serca2+/– mice converted from a concentric to an eccentric pattern, similar to that seen in human heart failure. Coarcted Serca2+/– mice had decreased contractile/systolic and relaxation/diastolic performance and/or function compared with coarcted wild-type mice ( P < 0.05), despite a similar duration and degree of pressure overload. SERCA2a protein levels were significantly reduced (>50%) in coarcted Serca2+/– mice compared with noncoarcted and coarcted wild-type mice. Our findings suggest that reduction in SERCA2 levels in combination with an increased hemodynamic load results in an accelerated pathway to heart failure.

1264Genetic investigation of gap junction protein, alpha 5 of in Russian families with sick sinus syndrome

EP Europace ◽  
2020 ◽  
Vol 22 (Supplement_1) ◽  
Author(s):  
A Chernova ◽  
S Nikulina ◽  
V Maksimov
Keyword(s):  
Gap Junction ◽  
Germ Line ◽  
Vital Role ◽  
Cardiac Conduction ◽  
Control Group ◽  
Av Node ◽  
Connexin Gene ◽  
Junction Protein ◽  
A Cell ◽  
Gap Junction Protein

Abstract Background Connexin 40 (Cx40) is a gap-junction protein expressed in the heart where it mediates the coordinated electrical activation of the atria and ventricular conduction tissues, facilitates cell-to-cell adhesion, and provides pathways for direct intercellular communication. Recent studies have shown that Cx40 null mice have cardiac conduction abnormalities with a very high incidence of cardiac malformations in heterozygous (18%) and homozygous (33%) animals, indicating that Cx40 plays a vital role in cardiomorphogenesis.The process that mediates interactions between an AV node cell and its surroundings that contributes to the process of the AV node cell communicating with a bundle of His cell in cardiac conduction. Encompasses interactions such as signaling or attachment between one cell and another cell, between a cell and an extracellular matrix, or between a cell and any other aspect of its environment.  Methods This first study of SSS in a Russian population comprises the clinical and genetic investigation of 30 Russian families, including 67 members. The involvement of the Cx40 genes was investigated. The control group consisted of 615 patients without clinical ECG manifestations of cardiac diseases. All the examinees have undergone ECG, echocardioscopy, electrophysiological examination of the heart.  Results We conclude that polymorphism 44AG has mutation-specific effects on Cx40-related SSS.  Conclusions Mutation Cx40 impairs gap junction formation at cell-cell interfaces. This is the first demonstration of a germ line mutation in a connexin gene that emphasizes the importance of Cx40 in normal propagation in the specialized conduction system.  This study provides further evidence of the genetic heterogeneity of SSS.

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