scholarly journals Discrete effects of A57G-myosin essential light chain mutation associated with familial hypertrophic cardiomyopathy

2013 ◽  
Vol 305 (4) ◽  
pp. H575-H589 ◽  
Author(s):  
Katarzyna Kazmierczak ◽  
Ellena C. Paulino ◽  
Wenrui Huang ◽  
Priya Muthu ◽  
Jingsheng Liang ◽  
...  
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Light Chain ◽  
Left Ventricular ◽  
Compensatory Hypertrophy ◽  
Familial Hypertrophic Cardiomyopathy ◽  
Heart Weight ◽  
Myocardial Stiffness ◽  
Essential Light Chain

The functional consequences of the familial hypertrophic cardiomyopathy A57G (alanine-to-glycine) mutation in the myosin ventricular essential light chain (ELC) were assessed in vitro and in vivo using previously generated transgenic (Tg) mice expressing A57G-ELC mutant vs. wild-type (WT) of human cardiac ELC and in recombinant A57G- or WT-protein-exchanged porcine cardiac muscle strips. Compared with the Tg-WT, there was a significant increase in the Ca2+ sensitivity of force (ΔpCa50 ≅ 0.1) and an ∼1.3-fold decrease in maximal force per cross section of muscle observed in the mutant preparations. In addition, a significant increase in passive tension in response to stretch was monitored in Tg-A57G vs. Tg-WT strips indicating a mutation-induced myocardial stiffness. Consistently, the hearts of Tg-A57G mice demonstrated a high level of fibrosis and hypertrophy manifested by increased heart weight-to-body weight ratios and a decreased number of nuclei indicating an increase in the two-dimensional size of Tg-A57G vs. Tg-WT myocytes. Echocardiography examination showed a phenotype of eccentric hypertrophy in Tg-A57G mice, enhanced left ventricular (LV) cavity dimension without changes in LV posterior/anterior wall thickness. Invasive hemodynamics data revealed significantly increased end-systolic elastance, defined by the slope of the pressure-volume relationship, indicating a mutation-induced increase in cardiac contractility. Our results suggest that the A57G allele causes disease by means of a discrete modulation of myofilament function, increased Ca2+ sensitivity, and decreased maximal tension followed by compensatory hypertrophy and enhanced contractility. These and other contributing factors such as increased myocardial stiffness and fibrosis most likely activate cardiomyopathic signaling pathways leading to pathologic cardiac remodeling.

E22K mutation of RLC that causes familial hypertrophic cardiomyopathy in heterozygous mouse myocardium: effect on cross-bridge kinetics

2006 ◽  
Vol 291 (5) ◽  
pp. H2098-H2106 ◽  
Author(s):  
D. Dumka ◽  
J. Talent ◽  
I. Akopova ◽  
G. Guzman ◽  
D. Szczesna-Cordary ◽  
...  
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Light Chain ◽  
Left Ventricular ◽  
Familial Hypertrophic Cardiomyopathy ◽  
Time Resolved ◽  
Essential Light Chain ◽  
Cross Bridge ◽  
The Difference ◽  
Cross Bridges ◽  
The Times

Familial hypertrophic cardiomyopathy is a disease characterized by left ventricular and/or septal hypertrophy and myofibrillar disarray. It is caused by mutations in sarcomeric proteins, including the ventricular isoform of myosin regulatory light chain (RLC). The E22K mutation is located in the RLC Ca2+-binding site. We have studied transgenic (Tg) mouse cardiac myofibrils during single-turnover contraction to examine the influence of E22K mutation on 1) dissociation time (τ1) of myosin heads from thin filaments, 2) rebinding time (τ2) of the cross bridges to actin, and 3) dissociation time (τ3) of ADP from the active site of myosin. τ1 was determined from the increase in the rate of rotation of actin monomer to which a cross bridge was bound. τ2 was determined from the rate of anisotropy change of the recombinant essential light chain of myosin labeled with rhodamine exchanged for native light chain (LC1) in the cardiac myofibrils. τ3 was determined from anisotropy of muscle preloaded with a stoichiometric amount of fluorescent ADP. Cross bridges were induced to undergo a single detachment-attachment cycle by a precise delivery of stoichiometric ATP from a caged precursor. The times were measured in Tg-mutated (Tg-m) heart myofibrils overexpressing the E22K mutation of human cardiac RLC. Tg wild-type (Tg-wt) and non-Tg muscles acted as controls. τ1 was statistically greater in Tg-m than in controls. τ2 was shorter in Tg-m than in non-Tg, but the same as in Tg-wt. τ3 was the same in Tg-m and controls. To determine whether the difference in τ1 was due to intrinsic difference in myosin, we estimated binding of Tg-m and Tg-wt myosin to fluorescently labeled actin by measuring fluorescent lifetime and time-resolved anisotropy. No difference in binding was observed. These results suggest that the E22K mutation has no effect on mechanical properties of cross bridges. The slight increase in τ1 was probably caused by myofibrillar disarray. The decrease in τ2 of Tg hearts was probably caused by replacement of the mouse RLC for the human isoform in the Tg mice.

Chronic infarction decreases maximum cardiac work and sensitivity of heart to extracellular calcium

1985 ◽  
Vol 249 (1) ◽  
pp. H80-H87 ◽  
Author(s):  
E. Fellenius ◽  
C. A. Hansen ◽  
O. Mjos ◽  
J. R. Neely
Keyword(s):  
Adenine Nucleotides ◽  
Creatine Phosphate ◽  
Scar Tissue ◽  
Left Ventricular ◽  
Compensatory Hypertrophy ◽  
Tissue Mass ◽  
Pressure Development ◽  
Whole Heart

Rat hearts were infarcted in vivo by ligation of the left ventricular coronary artery to cause an initial 40% loss of viable tissue by weight. Due to compensatory hypertrophy of the surviving myocardium and progression of the infarct to scar tissue, the infarct represented approximately 25% by weight of the whole heart after 1 wk. After 1 or 3 wk, these infarcted hearts were removed and perfused in vitro by the working hearts technique. Ventricular pressure development and positive dP/dt were lower in infarcted hearts compared with sham-operated ones. O2 consumption and glucose utilization by viable tissue per unit pressure development was the same in normal and infarcted hearts. Levels of creatine phosphate and free creatine were decreased, but ATP and total adenine nucleotides were well maintained. The inotropic response to decreases in extracellular [Ca2+] was much greater in infarcted hearts than in sham controls. Prenalterol increased ventricular function proportionally more in infarcted than in the sham-operated hearts, suggesting that down regulation of beta receptors was not a problem. The infarcted hearts were much more sensitive to verapamil than control hearts. It is concluded that the depressed function of the noninfarcted tissue of chronically infarcted hearts is due in part to loss of functioning tissue mass and in part to decreased sensitivity to extracellular Ca2+.

scholarly journals A Novel Myosin Essential Light Chain Mutation Causes Hypertrophic Cardiomyopathy with Late Onset and Low Expressivity

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Paal Skytt Andersen ◽  
Paula Louise Hedley ◽  
Stephen P. Page ◽  
Petros Syrris ◽  
Johanna Catharina Moolman-Smook ◽  
...  
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Light Chain ◽  
Late Onset ◽  
Large Family ◽  
Left Ventricular ◽  
Cascade Screening ◽  
Essential Light Chain ◽  
Mutation Carriers ◽  
Genes Encoding ◽  
The Mean

Hypertrophic cardiomyopathy (HCM) is caused by mutations in genes encoding sarcomere proteins. Mutations inMYL3, encoding the essential light chain of myosin, are rare and have been associated with sudden death. Both recessive and dominant patterns of inheritance have been suggested. We studied a large family with a 38-year-old asymptomatic HCM-affected male referred because of a murmur. The patient had HCM with left ventricular hypertrophy (max WT 21 mm), a resting left ventricular outflow gradient of 36 mm Hg, and left atrial dilation (54 mm). Genotyping revealed heterozygosity for a novel missense mutation, p.V79I, inMYL3. The mutation was not found in 300 controls, and the patient had no mutations in 10 sarcomere genes. Cascade screening revealed a further nine heterozygote mutation carriers, three of whom had ECG and/or echocardiographic abnormalities but did not fulfil diagnostic criteria for HCM. The penetrance, if we consider this borderline HCM the phenotype of the p.V79I mutation, was 40%, but the mean age of the nonpenetrant mutation carriers is 15, while the mean age of the penetrant mutation carriers is 47. The mutation affects a conserved valine replacing it with a larger isoleucine residue in the region of contact between the light chain and the myosin lever arm. In conclusion,MYL3mutations can present with low expressivity and late onset.

Impact of exercise training on ventricular properties in a canine model of congestive heart failure

1997 ◽  
Vol 272 (3) ◽  
pp. H1382-H1390 ◽  
Author(s):  
K. Todaka ◽  
J. Wang ◽  
G. H. Yi ◽  
M. Knecht ◽  
R. Stennett ◽  
...  
Keyword(s):  
Heart Failure ◽  
Exercise Training ◽  
Heart Function ◽  
Systolic Pressure ◽  
Cardiac Pacing ◽  
Left Ventricular ◽  
Lv Function ◽  
Myocardial Stiffness

Exercise training improves functional class in patients with chronic heart failure (CHF) via effects on the periphery with no previously documented effect on intrinsic left ventricular (LV) properties. However, because methods used to evaluate in vivo LV function are limited, it is possible that some effects of exercise training on the failing heart have thus far eluded detection. Twelve dogs were instrumented for cardiac pacing and hemodynamic recordings. Hearts were paced rapidly for 4 wk. Six of the dogs received daily treadmill exercise (CHF(EX), 4.4 km/h, 2 h/day) concurrent with rapid pacing, while the other dogs remained sedentary (CHFs). Hemodynamic measurements taken in vivo at the end of 4 wk revealed relative preservation of maximum rate of pressure rise (2,540 +/- 440 vs. 1,720 +/- 300 mmHg/s, P < 0.05) and LV end-diastolic pressure (9 +/- 5 vs. 19 +/- 4 mmHg, P < 0.05) in CHF(EX) compared with CHFs. The hearts were then isolated and cross perfused for in vitro measurement of isovolumic pressure-volume relations; these results were compared with those of six normal dogs (N). Systolic function was similarly depressed in both groups of pacing animals [end-systolic elastance (Ees) values of 1.66 +/- 0.47 in CHFs, 1.77 +/- 0.38 in CHF(EX), and 3.05 +/- 0.81 mmHg/ml in N, with no changes in volume axis interceptors of the end-systolic pressure-volume relationship]. The diastolic myocardial stiffness constant, k, was elevated in CHFs and was normalized by exercise training (32 +/- 3 in CHFs, 21 +/- 3 in CHF(EX), 20 +/- 4 in N). Thus daily exercise training preserved in vivo hemodynamics during 4 wk of rapid cardiac pacing and was accompanied by a significant change in diastolic myocardial stiffness in vitro. These findings suggest that changes in heart function may contribute to the overall beneficial hemodynamic effects of exercise training in CHF by a significant effect on diastolic properties.

Abstract MP234: Novel Mybpc3 Variant Disrupts Myosin S2 Binding And Induces Heart Failure

2021 ◽  
Vol 129 (Suppl_1) ◽  
Author(s):  
Taejeong Song ◽  
Rohit Singh ◽  
Darshini Desai ◽  
Sheryl E Koch ◽  
Jack Rubinstein ◽  
...  
Keyword(s):  
Cardiac Function ◽  
Striated Muscle ◽  
Solid Phase ◽  
South Asians ◽  
Lipid Peroxide ◽  
Ventricular Volume ◽  
Left Ventricular ◽  
Heart Weight

Rationale: Cardiac m yosin binding protein-C regulates a ctomyosin interaction in striated muscle, but mutations in the MYBPC3 gene can lead to hypertrophic cardiomyopathy (HCM) as seen in some South Asians living in the USA carrying a novel variant wherein an aspartic acid is mutated to a valine at position 389 (D389V). Individuals and iPSC-derived cardiomyocytes carrying D389V display hypercontractility, indicating early onset of HCM. However, the mechanisms underlying the pathophysiology of this mutant in the context of HCM are unknown. Objective: To define the pathophysiological consequences D389V on myosin and cardiac function in vivo . Methods and Results: Compared with wild-type controls, our D389V knock-in homozygous mouse model showed decreased cardiac function by percentage of ejection fraction (-23%, P<0.01), but increased systolic left ventricular volume (+39%, P<0.01) at 3 and 6 months of age. Heart weight to tibia length ratio was significantly increased (+ 15%, P=0.05), demonstrating distinct pathogenicity. Using recombinant proteins carrying D389V substitution at the N-terminal MYBPC3 domains (rC0C2 D389V ), cosedimentation and solid-phase binding assays showed significantly reduced binding rate of rC0C2 D389V to the myosin S2 region (-55% and -23%, P<0.05, respectively), but in vitro actin motility over myosin increased 24% (P<0.05) compared to rC0C2 WT control, indicating a causal relationship between variant and decreased MYBPC3 binding to myosin. Human iPSC-derived D389V het cardiomyocytes display an increase in lipid peroxide and reactive oxygen species by +3- and +7-fold P<0.01, respectively, compared to noncarrier controls. Conclusion: D389V decreases interaction between MYBPC3 and myosin S2, causing reduced cardiac function and providing mechanistic evidence that it contributes to the etiology of HCM.

FC 064A RENAL-CARDIO INFLAMMATORY AXIS MEDIATES CARDIAC DYSFUNCTION IN CKD VIA IL-33-ST2: A NOVEL MECHANISM

2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
Alejandro Chade ◽  
Michael Hall ◽  
Deandra Fortenberry ◽  
Drew Bossier ◽  
Gene Bidwell
Keyword(s):  
Cardiac Fibrosis ◽  
Left Ventricular ◽  
Cellular Damage ◽  
Heart Weight ◽  
Swine Model ◽  
Renal Inflammation ◽  
Cardiac Abnormalities ◽  
Tnf Α

Abstract Background and Aims We developed a swine model of chronic kidney disease (CKD) that also display cardiac abnormalities associated with heart failure (HF). Inflammation contributes to progressive renal dysfunction and increases cardiovascular mortality of patients with CKD. Interleukin (IL)-33 is a tissue-derived nuclear cytokine from the IL family. IL-33 constitutively expressed but upregulated and released after cellular damage or necrotic cell death, acting as a pro-inflammatory cytokine. We hypothesize that IL-33 plays a prominent mechanistic role in renal-cardio pathophysiology in CKD. Method We induced CKD in 10 pigs via bilateral renovascular disease and dyslipidemia. We developed a renally-targeted biopolymer-fused peptide inhibitor of nuclear-factor kappa (NF-k)B (ELP-p50i) and show it blocks NFkB activity in vitro and in vivo. NF-kB is a key pro-inflammatory transcription factor upregulated in CKD and closely interacts with IL-33. Pigs were observed for 6 weeks, renal (multi-detector CT) and cardiac structure and function (echo) were quantified, then randomized to single intra-renal ELP-p50i or placebo (n=5 each), and studies repeated 8 weeks later. Blood was collected to measure circulating TNF-α, IL-33 and its specific decoy receptor soluble (s) ST2 (ELISA). Heart weights were measured after euthanasia, and renal and cardiac expression of ST2 and morphometric analyses were performed. Results Loss of renal function in CKD was accompanied by increased heart weight, left ventricular (LV) hypertrophy, diastolic dysfunction, abnormal LV strain, renal/cardiac fibrosis, circulating TNF-α, IL-33 but unchanged sST2, and increased renal/cardiac ST2 expression. Most of these changes were improved after intra-renal ELP-p50i and accompanied by augmented sST2, suggesting that inhibition of renal inflammation can attenuate cardiac abnormalities via augmented clearance of IL-33 (Figure). Conclusion Our study supports a prominent role for renal inflammation as a driving force for precursors of HF in CKD, proposing a renal-cardio inflammatory axis possibly mediated by NF-kB-TNF-α-IL-33/ST2 interactions. TNF-α can stimulate IL-33 as IL33 can activate NF-kB and TNF-α, extending this inflammatory loop in both the kidney and heart. We show that a translational renal anti-inflammatory strategy via targeted inhibition of renal NFkB inhibits this axis and improves renal and cardiac function, which may guide to new treatments targeting renal inflammation in CKD.

scholarly journals In Vivo Analysis of an Essential Myosin Light Chain Mutation Linked to Familial Hypertrophic Cardiomyopathy

2000 ◽  
Vol 87 (4) ◽  
pp. 296-302 ◽  
Author(s):  
Atsushi Sanbe ◽  
David Nelson ◽  
James Gulick ◽  
Elizabeth Setser ◽  
Hanna Osinska ◽  
...  
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Familial Hypertrophic Cardiomyopathy ◽  
In Vivo Analysis

Abstract 153: Inhibition of the 5-a-reductase Reduces Cardiac Hypertrophy and Improves Cardiac Function

2013 ◽  
Vol 113 (suppl_1) ◽  
Author(s):  
Carolin Zwadlo ◽  
Natali Froese ◽  
Johann Bauersachs ◽  
Joerg Heineke
Keyword(s):  
Cardiac Hypertrophy ◽  
Weight Ratio ◽  
Capillary Density ◽  
Left Ventricular ◽  
Heart Weight ◽  
Rat Cardiomyocytes ◽  
Male And Female ◽  
Female Mice

Objectives: Left ventricular hypertrophy (LVH) is an independent risk factor for increased cardiovascular mortality and a precursor of heart failure. Gender-specific differences point to a pivotal role of androgens in the development of pathological LVH. Dihydrotestosterone (DHT) is metabolized from testosterone via the enzyme 5-α-reductase. The 5-α-reductase is upregulated in the hypertrophied myocardium, leading to our assumption that DHT rather than testosterone is the crucial component in the development of LVH and might therefore constitute a potential therapeutic target. Methods: One week after transverse aortic constriction (TAC) or sham surgery male wild-type mice were treated for 2 weeks via an oralgastric tube with the 5-α-reductase inhibitor finasteride (daily dose 25mg/kg BW) or were left untreated (controls). Male and female transgenic Gαq (TG, a model of dilative cardiomyopathy) or non-transgenic mice were treated with finasteride for 6 weeks. Results: Cardiac hypertrophy after TAC was dramatically reduced by finasteride in male mice (heart weight/ body weight ratio, HW/BW in mg/g: control 6.65±0.35 versus finasteride treated 5.23±0.3; p<0.01). The reduced hypertrophy in these mice was accompanied by a reduction in cardiomyocyte diameter, ANP expression and fibrosis, but increased capillary density and Serca2a expression. Accordingly, finasteride also markedly reduced hypertrophy in isolated primary rat cardiomyocytes in vitro . Amelioration of hypertrophy by finasteride was associated with blunted activation of the prohypertrophic kinase mTOR in vitro and in vivo . Left ventricular dilation in male Gαq TG mice was markedly reduced by treatment with finasteride, which also led to an improvement in left ventricular function (determined as fractional area change in % by echocardiography: finasteride 44.72±1.71 vs. control 32.8±3.84, p<0.05) and a similar trend was observed in female mice. Interestingly, finasteride reduced pulmonary congestion in male and female mice alike. Conclusion: Finasteride treatment reduces hypertrophy and eccentric cardiac remodelling in mice, indicating a possible involvement of DHT in these processes as well as a potential benefit of 5-α-reductase inhibition in cardiac disease.

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