Impaired relaxation is the main manifestation in transgenic mice expressing a restrictive cardiomyopathy mutation, R193H, in cardiac TnI

Transgenic mice were generated to express a restrictive cardiomyopathy (RCM) human cardiac troponin I (cTnI) R192H mutation in the heart (cTnI193His mice). The objective of this study was to assess cardiac function during the development of diastolic dysfunction and to gain insight into the pathophysiological impact of the RCM cTnI mutation. Cardiac function and pathophysiological changes were monitored in cTnI193His mice and wild-type littermates for a period of 12 mo. It progressed gradually from abnormal relaxation to diastolic dysfunction characterized with high-resolution echocardiography by a reversed E-to-A ratio, increased deceleration time, and prolonged isovolumetric relaxation time. At the age of 12 mo, cardiac output in cTnI193His mice was significantly declined, and some transgenic mice showed congestive heart failure. The negative impact of cTnI193His on ventricular contraction and relaxation was further demonstrated in isolated mouse working heart preparations. The main morphological change in cTnI193His myocytes was shortened cell length. Dobutamine stimulation increased heart rate in cTnI193His mice but did not improve CO. The cTnI193His mice had a phenotype similar to that in human RCM patients carrying the cTnI mutation characterized morphologically by enlarged atria and restricted ventricles and functionally by diastolic dysfunction and diastolic heart failure. The results demonstrate a critical role of the COOH-terminal domain of cTnI in the diastolic function of cardiac muscle.

Download Full-text

Abstract 843: Restrictive Cardiomyopathy Linked cTnI Mutation (K178E) Causes Severe Heart Failure and Early Mortality

Circulation ◽

10.1161/circ.118.suppl_18.s_623-c ◽

2008 ◽

Vol 118 (suppl_18) ◽

Author(s):

Pierre-Yves Jean-Charles ◽

Jianfeng Du ◽

Yuejin Li ◽

Nariman Gobara ◽

Xupei Huang

Keyword(s):

Heart Failure ◽

Transgenic Mice ◽

Diastolic Dysfunction ◽

Troponin I ◽

Severe Heart Failure ◽

Restrictive Cardiomyopathy ◽

Left Ventricular ◽

Early Mortality ◽

Cardiac Contraction ◽

Actin Binding

Multiple mutations in cardiac troponin I (cTnI) have been linked to the development of restrictive cardiomyopathy (RCM) in human patients. Among them, K178E mutation has the worst clinical phenotype. K178E mutation may influence the inhibitory function through actin binding since previous studies have shown that amino acids number 173–181 bind to actin and increase the inhibitory effect of TnI. We modeled the mutation of lysine 178→glutamate (K178E) in human cTnI by cardiac specific expression of the mutated protein (cTnI 179Glu in mouse sequence) in transgenic mice. Multiple lines were generated with varying degrees of expression to establish a dose relationship. Increased resting tension in isolated cardiac myocytes and decreased myofibrillar compliance were the main manifestations in cellular function measurements. In vivo cardiac function measured by high-resolution ultrasonic imaging and Doppler echocardiography revealed a significant diastolic dysfunction characterized with decrease of left ventricular end diastolic dimension (LVEDD), decreased cardiac ejection fraction (EF) and left ventricular faction of shortening (FS) as well as a decreased cardiac output (CO). Doppler measurements showed a restrictive left ventricular filling pattern, i.e. reversed E/A ratio; decreased deceleration time (DT); decreased isovolumic relaxation time (IVRT). Enlarged left and right atria was a dramatic sign, which was observed in most of the transgenic mice, and was developed early and fast (at age of 2–3 weeks). Severely affected lines developed a pathology similar to that observed in human restrictive cardiomyopathy patients who carry the same mutation and with a high early mortality. Our data indicate the causality of this mutation for diastolic dysfunction and heart failure and provide a useful animal model for further understanding the thin filament structure-function relationships and the physiological function of triponin in cardiac contraction and relaxation. (Supported by NIH GM073621 and AHA0715116B) This research has received full or partial funding support from the American Heart Association, AHA Greater Southeast Affiliate (Alabama, Florida, Georgia, Louisiana, Mississippi, Puerto Rico & Tennessee).

Download Full-text

Abstract 223: Troponin I Tyrosine Phosphorylation Modulation of Cardiac Function

Circulation Research ◽

10.1161/res.121.suppl_1.223 ◽

2017 ◽

Vol 121 (suppl_1) ◽

Author(s):

Elizabeth A Brundage ◽

Brendan Agatisa-Boyle ◽

Vikram Shettigar ◽

Jae-Hoon Chung ◽

Ziqing Qian ◽

...

Keyword(s):

Heart Failure ◽

Cardiac Function ◽

Diastolic Dysfunction ◽

Troponin I ◽

Heart Function ◽

Calcium Sensitivity ◽

Regulatory Proteins ◽

Myocardial Relaxation ◽

Kinase Phosphorylation ◽

Accelerated Relaxation

Heart failure results in depressed contraction and slowed relaxation, both of which limit heart function and contribute to the progression of heart disease. Currently there is no chronic therapy to accelerate relaxation and reverse the diastolic dysfunction present in heart failure. Myocardial relaxation is regulated by serine/threonine phosphorylation of key regulatory proteins. Tyrosine (Tyr) specific kinases are expressed in the heart but the Tyr phosphorylation of regulatory proteins to modulate heart function has not been demonstrated. To investigate the effects of Tyr kinase phosphorylation on cardiac contraction we employed a novel cell penetrating peptide to deliver a direct Tyr kinase activator into isolated adult myocytes. Results demonstrate Tyr kinases activation increases Tyr phosphorylation of the regulatory protein troponin I (TnI) at Tyr26. We have demonstrated that TnI Tyr26 phosphorylation is beneficial to cardiac health by decreasing calcium sensitivity and accelerating myofilament deactivation (key determinants in accelerating myocardial relaxation) and that TnI Tyr26 phosphorylation undergoes functional integration with TnI Ser23/24 resulting in further accelerated calcium dissociation (accelerated relaxation) without further decreased calcium sensitivity (no further depression of contraction). We now demonstrate TnI Tyr26 also undergoes novel signaling integration with TnI Ser23/24 phosphorylation increasing the rate of Tyr kinase mediated Tyr26 phosphorylation. For the first time we demonstrate tyrosine kinase phosphorylation of TnI at Tyr26 modulates cardiac function resulting in accelerated relaxation. Increasing TnI Tyr26 phosphorylation may therefore serve as a novel targeted mechanism for future therapeutic development to accelerate depressed myocardial relaxation and improve diastolic dysfunction in heart failure.

Download Full-text

p90 ribosomal S6 kinase 3 contributes to cardiac insufficiency in α-tropomyosin Glu180Gly transgenic mice

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00237.2013 ◽

2013 ◽

Vol 305 (7) ◽

pp. H1010-H1019 ◽

Cited By ~ 10

Author(s):

Catherine L. Passariello ◽

Marjorie Gayanilo ◽

Michael D. Kritzer ◽

Hrishikesh Thakur ◽

Zoharit Cozacov ◽

...

Keyword(s):

Heart Failure ◽

Transgenic Mice ◽

Cardiac Function ◽

Interstitial Fibrosis ◽

Cardiac Insufficiency ◽

S6 Kinase ◽

Transgenic Expression ◽

P90 Ribosomal S6 Kinase ◽

Ribosomal S6 Kinase

Myocardial interstitial fibrosis is an important contributor to the development of heart failure. Type 3 p90 ribosomal S6 kinase (RSK3) was recently shown to be required for concentric myocyte hypertrophy under in vivo pathological conditions. However, the role of RSK family members in myocardial fibrosis remains uninvestigated. Transgenic expression of α-tropomyosin containing a Glu180Gly mutation (TM180) in mice of a mixed C57BL/6:FVB/N background induces a cardiomyopathy characterized by a small left ventricle, interstitial fibrosis, and diminished systolic and diastolic function. Using this mouse model, we now show that RSK3 is required for the induction of interstitial fibrosis in vivo. TM180 transgenic mice were crossed to RSK3 constitutive knockout ( RSK3−/−) mice. Although RSK3 knockout did not affect myocyte growth, the decreased cardiac function and mild pulmonary edema associated with the TM180 transgene were attenuated by RSK3 knockout. The improved cardiac function was consistent with reduced interstitial fibrosis in the TM180; RSK3−/− mice as shown by histology and gene expression analysis, including the decreased expression of collagens. The specific inhibition of RSK3 should be considered as a potential novel therapeutic strategy for improving cardiac function and the prevention of sudden cardiac death in diseases in which interstitial fibrosis contributes to the development of heart failure.

Download Full-text

Long-term levosimendan treatment improves systolic function and myocardial relaxation in mice with cardiomyocyte-specific disruption of the Serca2 gene

Journal of Applied Physiology ◽

10.1152/japplphysiol.01044.2012 ◽

2013 ◽

Vol 115 (10) ◽

pp. 1572-1580 ◽

Cited By ~ 7

Author(s):

Vigdis Hillestad ◽

Frank Kramer ◽

Stefan Golz ◽

Andreas Knorr ◽

Kristin B. Andersson ◽

...

Keyword(s):

Gene Expression ◽

Heart Failure ◽

Cardiac Function ◽

Diastolic Dysfunction ◽

Systolic Function ◽

Cytosolic Calcium ◽

Left Ventricular ◽

Pressure Measurements ◽

Human Heart Failure

In human heart failure (HF), reduced cardiac function has, at least partly, been ascribed to altered calcium homeostasis in cardiomyocytes. The effects of the calcium sensitizer levosimendan on diastolic dysfunction caused by reduced removal of calcium from cytosol in early diastole are not well known. In this study, we investigated the effect of long-term levosimendan treatment in a murine model of HF where the sarco(endo)plasmatic reticulum ATPase ( Serca) gene is specifically disrupted in the cardiomyocytes, leading to reduced removal of cytosolic calcium. After induction of Serca2 gene disruption, these mice develop marked diastolic dysfunction as well as impaired contractility. SERCA2 knockout (SERCA2KO) mice were treated with levosimendan or vehicle from the time of KO induction. At the 7-wk end point, cardiac function was assessed by echocardiography and pressure measurements. Vehicle-treated SERCA2KO mice showed significantly diminished left-ventricular (LV) contractility, as shown by decreased ejection fraction, stroke volume, and cardiac output. LV pressure measurements revealed a marked increase in the time constant (τ) of isovolumetric pressure decay, showing impaired relaxation. Levosimendan treatment significantly improved all three systolic parameters. Moreover, a significant reduction in τ toward normalization indicated improved relaxation. Gene-expression analysis, however, revealed an increase in genes related to production of the ECM in animals treated with levosimendan. In conclusion, long-term levosimendan treatment improves both contractility and relaxation in a heart-failure model with marked diastolic dysfunction due to reduced calcium transients. However, altered gene expression related to fibrosis was observed.

Download Full-text

Abstract 1213: Cardiac Overexpression of Epac1 in Transgenic Mice Protects Heart from Lipopolysaccharide-induced Cardiac Dysfunction and Inhibits JAK-STAT Pathway

Circulation ◽

10.1161/circ.116.suppl_16.ii_246-b ◽

2007 ◽

Vol 116 (suppl_16) ◽

Author(s):

Satoshi Okumura ◽

Yunzhe Bai ◽

Meihua Jin ◽

Sayaka Suzuki ◽

Akiko Kuwae ◽

...

Keyword(s):

Heart Failure ◽

Cyclic Amp ◽

Transgenic Mice ◽

Cardiac Function ◽

Proinflammatory Cytokines ◽

Cardiac Dysfunction ◽

Left Ventricular ◽

Left Ventricular Ejection ◽

Ventricular Ejection Fraction ◽

Stat Pathway

The sympathetic nervous system and proinflammatory cytokines are believed to play independent roles in the pathophysiology of heart failure. However, the recent identification of Epac (exchange protein activated by cyclic AMP), a new cyclic AMP-binding protein that directly activates Rap1, have implicated that there may be a potential cross talk between the sympathetic and cytokine signals. In order to examine the role of Epac in cytokine signal to regulate cardiac function, we have generated transgenic mice expressing the human Epac1 gene under the control of alpha-cardiac myosin heavy chain promoter (Epac1-TG), and examined their response in lipopolysaccharide (LPS)-induced cardiac dysfunction, a well established model for sepsis-induced cardiac dysfunction. Sepsis-induced cardiac dysfunction results from the production of proinflammatory cytokines. At baseline, left ventricular ejection fraction (LVEF) was similar (TG vs. NTG, 67±1.7 vs. 69±2.1%, n =7–9). The degree of cardiac hypertrophy (LV(mg)/tibia(mm)) was also similar at 3 months old (TG vs. NTG 4.0±0.1 vs. 4.2±0.1, n =5–6), but it became slightly but significantly greater in Epac1-TG at 5 month old (TG vs. NTG 4.9±0.1 vs. 4.4±0.1, p< 0.05, n =5–7). LPS (5mg/kg) elicited a significant and robust reduction of LVEF in both Epac1-TG and NTG, but the magnitude of this decrease was much less in Epac1-TG at 6 hr after injection (TG vs. NTG 48±2.4 vs. 57±1.8%, p< 0.01, n =6–9). At 24 hr after injection, cardiac function was restored to the baseline in both Epac1-TG and NTG. We also examined the activation of JAK-STAT pathway at 24 hr after injection. The tyrosine phosphorylation of STAT1 (Tyr701) and STAT3 (Tyr705) in LV, which is an indicator of STAT activation, was reduced to a greater degree in Epac1-TG by 31±8.8% ( p< 0.05, n =4) and 29±5.9% ( p< 0.05, n =7), respectively, relative to that in NTG. Taken together, Epac1 protects the heart from the cytokine-induced cardiac dysfunction, at least in part, through the inhibition of the JAK-STAT pathway, suggesting the beneficial role played by sympathetic signal to antagonize proinflammatory cytokine signal in heart failure.

Download Full-text

Heart Failure–Related Hyperphosphorylation in the Cardiac Troponin I C Terminus Has Divergent Effects on Cardiac Function In Vivo

Circulation Heart Failure ◽

10.1161/circheartfailure.117.003850 ◽

2017 ◽

Vol 10 (9) ◽

Cited By ~ 3

Author(s):

Yuejin Li ◽

Guangshuo Zhu ◽

Nazareno Paolocci ◽

Pingbo Zhang ◽

Cyrus Takahashi ◽

...

Keyword(s):

Heart Failure ◽

Cardiac Function ◽

Cardiac Troponin ◽

Troponin I ◽

Cardiac Troponin I ◽

C Terminus

Download Full-text

Disruption of adenylyl cyclase type V does not rescue the phenotype of cardiac-specific overexpression of Gαq protein-induced cardiomyopathy

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.01208.2009 ◽

2010 ◽

Vol 299 (5) ◽

pp. H1459-H1467 ◽

Cited By ~ 9

Author(s):

Valeriy Timofeyev ◽

Cliff A. Porter ◽

Dipika Tuteja ◽

Hong Qiu ◽

Ning Li ◽

...

Keyword(s):

Heart Failure ◽

Protein Kinase C ◽

Protein Kinase ◽

Mouse Model ◽

Transgenic Mice ◽

Cardiac Function ◽

Adenylyl Cyclase ◽

Electrical Remodeling ◽

Kinase C ◽

Progressive Heart Failure

Adenylyl cyclase (AC) is the principal effector molecule in the β-adrenergic receptor pathway. ACV and ACVI are the two predominant isoforms in mammalian cardiac myocytes. The disparate roles among AC isoforms in cardiac hypertrophy and progression to heart failure have been under intense investigation. Specifically, the salutary effects resulting from the disruption of ACV have been established in multiple models of cardiomyopathy. It has been proposed that a continual activation of ACV through elevated levels of protein kinase C could play an integral role in mediating a hypertrophic response leading to progressive heart failure. Elevated protein kinase C is a common finding in heart failure and was demonstrated in murine cardiomyopathy from cardiac-specific overexpression of Gαq protein. Here we assessed whether the disruption of ACV expression can improve cardiac function, limit electrophysiological remodeling, or improve survival in the Gαq mouse model of heart failure. We directly tested the effects of gene-targeted disruption of ACV in transgenic mice with cardiac-specific overexpression of Gαq protein using multiple techniques to assess the survival, cardiac function, as well as structural and electrical remodeling. Surprisingly, in contrast to other models of cardiomyopathy, ACV disruption did not improve survival or cardiac function, limit cardiac chamber dilation, halt hypertrophy, or prevent electrical remodeling in Gαq transgenic mice. In conclusion, unlike other established models of cardiomyopathy, disrupting ACV expression in the Gαq mouse model is insufficient to overcome several parallel pathophysiological processes leading to progressive heart failure.

Download Full-text

Investigation of the Relationship Between Color M-Mode Early Diastolic Propagation Velocity and Left Ventricular Adverse Pressure Gradients

ASME 2010 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2010-19449 ◽

2010 ◽

Author(s):

Kelley C. Stewart ◽

Rahul Kumar ◽

John J. Charonko ◽

Pavlos P. Vlachos ◽

William C. Little

Keyword(s):

Heart Failure ◽

Diastolic Dysfunction ◽

Diastolic Heart Failure ◽

Diagnostic Techniques ◽

Left Ventricular Diastolic Dysfunction ◽

Left Ventricular ◽

Pressure Gradients ◽

Compensatory Mechanisms ◽

Ventricular Diastolic Dysfunction ◽

The Relationship

Left ventricular diastolic dysfunction (LVDD) and diastolic heart failure are conditions that affect the filling dynamics of the heart and affect 36% of patients diagnosed with congestive heart failure [1]. Although this condition is very prevalent, it currently remains difficult to diagnose due to inherent atrio-ventricular compensatory mechanisms including increased heart rate, increased left ventricular (LV) contractility, and increased left atrial pressure (LA). A greater comprehension of the governing flow physics in the left ventricle throughout the introduction of the heart’s compensatory mechanisms has great potential to substantially increase the understanding of the progression of diastolic dysfunction and in turn advance the diagnostic techniques.

Download Full-text

2007 Laennec Clinician/Educator Lecture—Unraveling the Mysteries of Diastology

Circulation ◽

10.1161/circ.116.suppl_16.ii_f-a ◽

2007 ◽

Vol 116 (suppl_16) ◽

Author(s):

Rick Nishimura

Keyword(s):

Heart Failure ◽

Diastolic Dysfunction ◽

Patient Care ◽

Hospital Admissions ◽

Critical Role ◽

Rapid Assessment ◽

Radionuclide Angiography ◽

Signs And Symptoms ◽

Diastolic Filling ◽

The Past

Diastolic dysfunction plays a critical role in the pathophysiology of producing signs and symptoms of heart failure. Heart failure with a normal ejection fraction (HFnlEF) is one of the leading causes of hospital admissions today and is associated with significant morbidity and mortality. It is thus important to understand the pathophysiology of diastolic dysfunction, which itself is a complex series of multiple interrelated events, including relaxation, suction, ventricular interaction, ventricular arterial coupling, pericardial restraint, and myocardial viscoelastic forces. It was difficult for the clinician to understand “diastology” in the past. Initial studies were limited to complex equations derived from animal models and were difficult to apply to patient care. The development of radionuclide angiography and Doppler echocardiography allowed noninvasive rapid assessment of volumetric filling and flow velocity curves, which began to provide insight into the complex process of diastolic filling for the clinician. As our understanding of diastology evolved over the past 2 decades, it has become clear that we now need to pursue new areas to understand this fascinating subject and apply it to patient care. These areas include the underlying mechanism HFnlEF (ventricular-vascular coupling versus true myocardial stiffness), relationship of rest versus exercise hemodynamics, and the complex ventricular fiber “twisting and shortening” of both contraction and relaxation.

Download Full-text

Role of Diastole in Left Ventricular Function, II: Diagnosis and Treatment

American Journal of Critical Care ◽

10.4037/ajcc2004.13.6.453 ◽

2004 ◽

Vol 13 (6) ◽

pp. 453-466 ◽

Cited By ~ 18

Author(s):

Shannan K. Hamlin ◽

Penelope S. Villars ◽

Joseph T. Kanusky ◽

Andrew D. Shaw

Keyword(s):

Heart Failure ◽

Diastolic Dysfunction ◽

Left Atrial ◽

Diastolic Heart Failure ◽

Systolic Heart Failure ◽

Clinical Signs ◽

Left Ventricular ◽

Exercise Intolerance ◽

Radiographic Findings ◽

Ventricular Compliance

Left ventricular diastolic dysfunction plays an important role in congestive heart failure. Although once thought to be lower, the mortality of diastolic heart failure may be as high as that of systolic heart failure. Diastolic heart failure is a clinical syndrome characterized by signs and symptoms of heart failure with preserved ejection fraction (0.50) and abnormal diastolic function. One of the earliest indications of diastolic heart failure is exercise intolerance followed by fatigue and, possibly, chest pain. Other clinical signs may include distended neck veins, atrial arrhythmias, and the presence of third and fourth heart sounds. Diastolic dysfunction is difficult to differentiate from systolic dysfunction on the basis of history, physical examination, and electrocardiographic and chest radiographic findings. Therefore, objective diagnostic testing with cardiac catheterization, Doppler echocardiography, and possibly measurement of serum levels of B-type natriuretic peptide is often required. Three stages of diastolic dysfunction are recognized. Stage I is characterized by reduced left ventricular filling in early diastole with normal left ventricular and left atrial pressures and normal compliance. Stage II or pseudonormalization is characterized by a normal Doppler echocardiographic transmitral flow pattern because of an opposing increase in left atrial pressures. This normalization pattern is a concern because marked diastolic dysfunction can easily be missed. Stage III, the final, most severe stage, is characterized by severe restrictive diastolic filling with a marked decrease in left ventricular compliance. Pharmacological therapy is tailored to the cause and type of diastolic dysfunction.

Download Full-text