Expression of the β (slow)-isoform of MHC in the adult  mouse heart causes dominant-negative functional effects

α- and β-myosin heavy chain (MHC), the two MHC isoforms expressed in the mammalian heart, differ quantitatively in their enzymatic activities. The MHC composition of the heart can change dramatically in response to numerous stimuli, leading to the hypothesis that changes in cardiac function can be caused by myosin isoform shifts. However, this hypothesis has remained unproven because the stimuli used to generate these shifts are complex and accompanied by many additional physiological changes, including alterations in cardiac mass and geometry. Adult mouse ventricles normally express only α-MHC (the faster motor). To determine whether genetic alteration of the MHC isoform composition in the adult mouse heart would result in changes in cardiac chamber mass and contractility, we established transgenic mouse lines that express a Myc-tagged β-MHC molecule (the slower motor) in adult ventricular tissue, one of which expreses 12% of its myosin as the transgene. There is no evidence of hypertrophy, induction of hypertrophic markers, and no histopathology. Myofibrillar Ca2+-activated ATPase activity is decreased by 23%, and Langendorff preparations demonstrate a significant 15% decrease in systolic function in transgenic hearts. These results suggest that even small shifts in the myosin isoform composition of the myocardium can result in physiologically significant changes in cardiac contractility and could be relevant to cardiovascular disease.

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NRSF-GNAO1 Pathway Contributes to the Regulation of Cardiac Ca 2+ Homeostasis

Circulation Research ◽

10.1161/circresaha.121.318898 ◽

2021 ◽

Author(s):

Hideaki Inazumi ◽

Koichiro Kuwahara ◽

Yasuaki Nakagawa ◽

Yoshihiro Kuwabara ◽

Takuro Numaga-Tomita ◽

...

Keyword(s):

Heart Failure ◽

Cardiac Dysfunction ◽

Molecular Mechanisms ◽

Systolic Function ◽

Expression Profiles ◽

Survival Rates ◽

Gene Expression Profiles ◽

Dominant Negative ◽

Mouse Heart ◽

Cardiac Gene

Background: During the development of heart failure, a fetal cardiac gene program is reactivated and accelerates pathological cardiac remodeling. We previously reported that a transcriptional repressor, neuron restrictive silencer factor (NRSF), suppresses the fetal cardiac gene program, thereby maintaining cardiac integrity. The underlying molecular mechanisms remains to be determined, however. Methods: We aim to elucidate molecular mechanisms by which NRSF maintains normal cardiac function. We generated cardiac-specific NRSF knockout mice and analyzed cardiac gene expression profiles in those mice and mice cardiac-specifically expressing a dominant-negative NRSF mutant. Results: We found that cardiac expression of Gαo, an inhibitory G protein encoded in humans by GNAO1, is transcriptionally regulated by NRSF and is increased in the ventricles of several mouse models of heart failure. Genetic knockdown of Gnao1 ameliorated the cardiac dysfunction and prolonged survival rates in these mouse heart failure models. Conversely, cardiac-specific overexpression of GNAO1 in mice was sufficient to induce cardiac dysfunction. Mechanistically, we observed that increasing Gαo expression increased surface sarcolemmal L-type Ca 2+ channel activity, activated Calcium/calmodulin-dependent kinase-II (CaMKII) signaling and impaired Ca 2+ handling in ventricular myocytes, which led to cardiac dysfunction. Conclusions: These findings shed light on a novel function of Gαo in the regulation of cardiac Ca 2+ homeostasis and systolic function and suggest Gαo may be an effective therapeutic target for the treatment of heart failure.

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Expression of Slow Skeletal Troponin I in Adult Mouse Heart Helps to Maintain the Left Ventricular Systolic Function During Respiratory Hypercapnia

Circulation Research ◽

10.1161/01.res.0000173849.68636.1e ◽

2005 ◽

Vol 97 (1) ◽

pp. 70-77 ◽

Cited By ~ 34

Author(s):

Dalia Urboniene ◽

Fernando A.L. Dias ◽

James R. Peña ◽

Lori A. Walker ◽

R. John Solaro ◽

...

Keyword(s):

Adult Mouse ◽

Troponin I ◽

Systolic Function ◽

Left Ventricular Systolic Function ◽

Left Ventricular ◽

Mouse Heart ◽

Ventricular Systolic Function ◽

Slow Skeletal Troponin I

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Abstract 1512: Heteromeric Assembly of HCN4 and C-Terminal Truncated HCN2 Subunits in the Generation of Cardiac Pacemaker (If) Channels

Circulation ◽

10.1161/circ.118.suppl_18.s_340-c ◽

2008 ◽

Vol 118 (suppl_18) ◽

Author(s):

Bin Ye ◽

Jeanne Nerbonne

Keyword(s):

Adult Mouse ◽

Cardiac Pacemaker ◽

Heart Association ◽

Dominant Negative ◽

Hek293 Cells ◽

Dominant Negative Mutant ◽

Mouse Heart ◽

Targeted Deletion ◽

Diastolic Depolarization ◽

Inward Currents

In sino-atrial and atrio-ventricular nodal cells, hyperpolarization- activated cyclic nucleotide-gated (HCN) cationic channels are expressed that carry inward currents, I f , contributing importantly to the diastolic depolarization critical for cardiac pacemaker functioning. Although previous studies have demonstrated myocardial expression of HCN2 and HCN4 subunits, the roles of these subunits in the generation of mature, functional I f channels remains unclear. In preliminary experiments, completed on transiently transfected HEK293 cells expressing wild type and dominant negative mutant HCN2 and HCN4 subunits, we find that HCN2 and HCN4 preferentially co-assemble to form heteromeric channels. In further studies focused on defining the molecular compositions of functional cardiac I f channels, we developed and validated C-and N-terminal HCN2 and HCN4 subunit specific antibodies and exploited these to identify the HCN subunits expressed in adult (mouse) heart and to immunoprecipitate cardiac HCN-encoded I f channel complexes. These experiments revealed that the HCN2 and HCN4 proteins co-immunoprecipitate from heart, In addition, Western blot experiments revealed that, although the full length HCN2 (105Da) and HCN4 (160Da) proteins are expressed in transiently transfected HEK293 cells and in adult (mouse) brain, the molecular weight of the HCN2 protein in the heart is reduced to about 60 kDa. In addition, the mature, 60 kDa HCN2 protein lacks the C-terminal cAMP binding domain. These observations likely explain the results of previous studies demonstrating that the targeted deletion of HCN2 does not affect the cAMP sensitivity of I f . In addition, taken together, these results demonstrate that functional myocardial I f channels reflect the heteromeric assembly of HCN2 and HCN4 subunits and further that the HCN4 subunit regulates cAMP-mediated regulation of I f channels. This research has received full or partial funding support from the American Heart Association, AHA National Center.

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DPP-4 inhibitor induces FGF21 expression via sirtuin 1 signaling and improves myocardial energy metabolism

Heart and Vessels ◽

10.1007/s00380-020-01711-z ◽

2020 ◽

Vol 36 (1) ◽

pp. 136-146

Author(s):

Nozomi Furukawa ◽

Norimichi Koitabashi ◽

Hiroki Matsui ◽

Hiroaki Sunaga ◽

Yogi Umbarawan ◽

...

Keyword(s):

Energy Metabolism ◽

Systolic Function ◽

Cardiac Fibroblasts ◽

Left Ventricular ◽

Sirtuin 1 ◽

Fibroblast Growth Factor 21 ◽

Mouse Heart ◽

Acid Uptake ◽

Dipeptidyl Peptidase 4 ◽

Fgf21 Expression

AbstractDipeptidyl peptidase-4 (DPP-4) inhibitors are widely used incretin-based therapy for the treatment of type 2 diabetes. We investigated the cardioprotective effect of a DPP-4 inhibitor, vildagliptin (vilda), on myocardial metabolism and cardiac performance under pressure overload. Mice were treated with either vehicle or vilda, followed by transverse aortic constriction (TAC). After 3 weeks of TAC, cardiac hypertrophy and impairment of systolic function were attenuated in vilda-treated mice. Pressure–volume analysis showed that vilda treatment significantly improved left-ventricular contractile efficiency in TAC heart. Myocardial energy substrate analysis showed that vilda treatment significantly increased glucose uptake as well as fatty acid uptake. Fibroblast growth factor 21 (FGF21), a peptide involved in the regulation of energy metabolism, increased in TAC heart and was further increased by vilda treatment. FGF21 was strongly expressed in cardiac fibroblasts than in cardiomyocytes in mouse heart after TAC with vilda treatment. Vilda treatment markedly induced FGF21 expression in human cardiac fibroblasts through a sirtuin (Sirt) 1-mediated pathway, suggesting that fibroblast-mediated FGF21 expression may regulate energy metabolism and exert vilda-mediated beneficial effects in stressed heart. Vilda induced a metabolic regulator, FGF21 expression in cardiac fibroblasts via Sirt1, and increased contractile efficiency in murine pressure-overloaded heart.

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Hyperlipidemia in pregnancy

Orvosi Hetilap ◽

10.1556/oh.2011.29108 ◽

2011 ◽

Vol 152 (19) ◽

pp. 753-757 ◽

Cited By ~ 1

Author(s):

Tatjána Ábel ◽

Anna Blázovics ◽

Márta Kemény ◽

Gabriella Lengyel

Keyword(s):

Cardiovascular Disease ◽

Acute Pancreatitis ◽

Cohort Studies ◽

Pregnant Women ◽

Breast Feeding ◽

Normal Pregnancy ◽

Large Cohort ◽

Physiological Changes ◽

Teratogenic Effects ◽

In Pregnancy

Physiological changes in lipoprotein levels occur in normal pregnancy. Women with hyperlipoproteinemia are advised to discontinue statins, fibrates already when they consider pregnancy up to and including breast-feeding the newborn, because of the fear for teratogenic effects. Hypertriglyceridemia in pregnancy can rarely lead to acute pancreatitis. Management of acute pancreatitis in pregnant women is similar to that used in non-pregnant patients. Further large cohort studies are needed to estimate the consequence of supraphysiologic hyperlipoproteinemia or extreme hyperlipoproteinemia in pregnancy on the risk for cardiovascular disease later in life. Orv. Hetil., 2011, 152, 753–757.

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Distribution and Structure-Function Relationship of Myosin Heavy Chain Isoforms in the Adult Mouse Heart

Journal of Biological Chemistry ◽

10.1074/jbc.m704574200 ◽

2007 ◽

Vol 282 (33) ◽

pp. 24057-24064 ◽

Cited By ~ 31

Author(s):

Maike Krenz ◽

Sakthivel Sadayappan ◽

Hanna E. Osinska ◽

Jeffrey A. Henry ◽

Samantha Beck ◽

...

Keyword(s):

Structure Function ◽

Myosin Heavy Chain ◽

Heavy Chain ◽

Adult Mouse ◽

Myosin Heavy Chain Isoforms ◽

Mouse Heart ◽

Structure Function Relationship ◽

Function Relationship ◽

Relationship Of

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Abstract 194: Phosphodiesterase 3 Controls Basal cGMP Levels And Regulates cGMP/cAMP Cross-talk In Adult Mouse Ventricular Cardiomyocytes

Circulation Research ◽

10.1161/res.113.suppl_1.a194 ◽

2013 ◽

Vol 113 (suppl_1) ◽

Author(s):

Konrad Götz ◽

Viacheslav Nikolaev

Keyword(s):

Cardiac Myocytes ◽

Cross Talk ◽

Adult Mouse ◽

Temporal Dynamics ◽

Cardiac Contractility ◽

Resonance Energy ◽

Direct Stimulation ◽

Specific Expression ◽

Cgmp Production ◽

Adult Cardiac Myocytes

PURPOSE: cGMP is an important second messenger which is involved in the regulation of cardiac contractility and pathological hypertrophy. In cardiomyocytes, signaling by cGMP is organized in microdomains and is considered cardioprotective. Especially in adult cardiac myocytes, measurements of cGMP have been challenging and little is known about the spatio-temporal dynamics of cGMP. Here we developed a transgenic mouse model to visualize cGMP dynamis in adult cardiac myocytes. Methods: We generated transgenic mice with cardiomyocyte-specific expression of a highly sensitive fluorescence resonance energy transfer (FRET)-based cGMP biosensor red cGES-DE5 and performed FRET measurements in freshly isolated adult mouse ventricular myocytes. To analyze cGMP/cAMP crosstalk, FRET experiments were performed in cardiomyocytes isolated from mice transgenically expressing the cAMP sensor Epac1-camps. Results: Basal cytosolic cGMP levels were very low (~10 nM), but could be markedly increased by stimulation with natriuretic peptides (CNP>>ANP). In contrast, direct stimulation of the soluble guanylyl cyclase (sGC) with NO-donors such as SNAP showed no effect. However, constitutive activity of this cyclase contributes to basal cGMP production, since a clear decrease of basal cGMP levels was observed after stimulation with the sGC inhibitor ODQ. This basal cGMP production is regulated by phosphodiesterase (PDE) activity. Unexpectedly, PDE3 is most important in controlling basal cGMP levels, whereas PDE2 and PDE5 are much less active. We could also show that cGMP pools produced by GC-B after CNP stimulation are mainly regulated by PDE3, so that the receptor and this PDE form one functional unit important for the regulation of cGMP/cAMP cross-talk. Conclusion: In summary, we performed the first FRET-based measurements of cGMP in adult cardiomyocytes and we could highlight the key role of PDE3 in the regulation of basal cGMP levels and cGMP/cAMP cross-talk.

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Right ventricular myocardial work: proof-of-concept for non-invasive assessment of right ventricular function

European Heart Journal - Cardiovascular Imaging ◽

10.1093/ehjci/jeaa261 ◽

2020 ◽

Author(s):

Steele C Butcher ◽

Federico Fortuni ◽

Jose M Montero-Cabezas ◽

Rachid Abou ◽

Mohammed El Mahdiui ◽

...

Keyword(s):

Cardiovascular Disease ◽

Stroke Volume ◽

Right Ventricular ◽

Systolic Function ◽

Stroke Volume Index ◽

Volume Index ◽

Left Ventricular Ejection ◽

Non Invasive ◽

Echocardiographic Parameters ◽

Global Work

Abstract Aims Right ventricular myocardial work (RVMW) is a novel method for non-invasive assessment of right ventricular (RV) function utilizing RV pressure–strain loops. This study aimed to explore the relationship between RVMW and invasive indices of right heart catheterization (RHC) in a cohort of patients with heart failure with reduced left ventricular ejection fraction (HFrEF), and to compare values of RVMW with those of a group of patients without cardiovascular disease. Methods and results Non-invasive analysis of RVMW was performed in 22 HFrEF patients [median age 63 (59–67) years] who underwent echocardiography and invasive RHC within 48 h. Conventional RV functional measurements, RV global constructive work (RVGCW), RV global work index (RVGWI), RV global wasted work (RVGWW), and RV global work efficiency (RVGWE) were analysed and compared with invasively measured stroke volume and stroke volume index. Non-invasive analysis of RVMW was also performed in 22 patients without cardiovascular disease to allow for comparison between groups. None of the conventional echocardiographic parameters of RV systolic function were significantly correlated with stroke volume or stroke volume index. In contrast, one of the novel indices derived non-invasively by pressure–strain loops, RVGCW, demonstrated a moderate correlation with invasively measured stroke volume and stroke volume index (r = 0.63, P = 0.002 and r = 0.59, P = 0.004, respectively). RVGWI, RVGCW, and RVGWE were significantly lower in patients with HFrEF compared to a healthy cohort, while values of RVGWW were significantly higher. Conclusion RVGCW is a novel parameter that provides an integrative analysis of RV systolic function and correlates more closely with invasively measured stroke volume and stroke volume index than other standard echocardiographic parameters.

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