2-deoxy-ATP Alters Myosin Structure to Enhance Cross-Bridge Cycling and Improve Cardiac Function

Nowakowski, Sarah G.; Adamek, Nancy; Geeves, Michael A.; Kolwicz, Stephen C.; Murry, Charles E.; Daggett, Valerie; Regnier, Michael

doi:10.1016/j.bpj.2012.11.125

Cited by 4 publications

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“…Interestingly, even though contraction is stronger and faster, chemo-mechanical modelling suggests that the weaker hydrostatic interaction between dATP and myosin in the binding pocket (vs. ATP) may result in a faster release of the hydrolysis product dADP, thus the myosin detachment rate and relaxation is also faster. 20 Consequently, the kinetics of cell, tissue, and organ relaxation appear matched to the enhanced contractility. This is important, because an inotrope that impairs relaxation would offer substantially less benefit due to increased end-diastolic pressure and pulmonary congestion.…”

Section: Discussionmentioning

confidence: 99%

“…Expression of RNR using the cTnT promoter facilitates cardiomyocyte‐specific transcription and minimizes possible off‐target effects with a level of therapeutic specificity not achievable using small molecule drugs or gene therapies using constitutively expressed regulatory elements. Interestingly, even though contraction is stronger and faster, chemo‐mechanical modelling suggests that the weaker hydrostatic interaction between dATP and myosin in the binding pocket (vs. ATP) may result in a faster release of the hydrolysis product dADP, thus the myosin detachment rate and relaxation is also faster . Consequently, the kinetics of cell, tissue, and organ relaxation appear matched to the enhanced contractility.…”

Section: Discussionmentioning

confidence: 99%

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Ribonucleotide reductase‐mediated increase in dATP improves cardiac performance via myosin activation in a large animal model of heart failure

Kadota

Carey

Reinecke

et al. 2015

European J of Heart Fail

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Aims Heart failure remains a leading cause of morbidity, hospitalizations and deaths. We previously showed that overexpression of the enzyme ribonucleotide reductase (RNR) in cardiomyocytes increased levels of the myosin activator, 2-deoxy-adenosine triphosphate, catalyzed enhanced contraction and improved cardiac performance in rodent hearts. Here we used a swine model of myocardial infarction (MI) to test preliminarily a novel gene therapy for heart failure based on delivery of the human RNR enzyme complex under the control of a cardiac specific promoter via an adeno-associated virus serotype 6 vector - designated as BB-R12. Methods and Results We induced heart failure following MI in Yucatan minipigs by balloon occlusion of the left anterior descending artery. Two weeks later pigs received BB-R12 at one of three doses via antegrade coronary infusion. At two months post-treatment, left ventricular (LV) ejection fraction and systolic LV dimension (measured by echocardiography) improved significantly in the high-dose group, despite further deterioration in the saline controls. Hemodynamic parameters including LV end-diastolic pressure, +dP/dt, and −dP/dt all trended towards improvement in the high-dose group. We observed no difference in the histopathologic appearance of hearts or other organs from treated animals versus controls, nor did we encounter any safety or tolerability concerns following BB-R12 delivery. Conclusion These pilot results suggest cardiac-specific gene therapy using BB-R12 may reverse cardiac dysfunction by myosin activation in a large-animal heart failure model with no observed safety concerns. Thus further research into the therapeutic potential of BB-R12 for patients with chronic heart failure appears warranted.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Ribonucleotide reductase‐mediated increase in dATP improves cardiac performance via myosin activation in a large animal model of heart failure

Kadota

Carey

Reinecke

et al. 2015

European J of Heart Fail

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“…This results in translated structural changes on the actin binding surface that increase myosin affinity for actin. 36 We (ref. 14) and others 37,38 have shown that contractile activation is very dependent on initial cross-bridge binding and is highly cooperative.…”

Section: Discussionmentioning

confidence: 99%

AAV6-mediated Cardiac-specific Overexpression of Ribonucleotide Reductase Enhances Myocardial Contractility

et al. 2016

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Impaired systolic function, resulting from acute injury or congenital defects, leads to cardiac complications and heart failure. Current therapies slow disease progression but do not rescue cardiac function. We previously reported that elevating the cellular 2 deoxy-ATP (dATP) pool in transgenic mice via increased expression of ribonucleotide reductase (RNR), the enzyme that catalyzes deoxy-nucleotide production, increases myosin-actin interaction and enhances cardiac muscle contractility. For the current studies, we initially injected wild-type mice retro-orbitally with a mixture of adeno-associated virus serotype-6 (rAAV6) containing a miniaturized cardiac-specific regulatory cassette (cTnT(455)) composed of enhancer and promotor portions of the human cardiac troponin T gene (TNNT2) ligated to rat cDNAs encoding either the Rrm1 or Rrm2 subunit. Subsequent studies optimized the system by creating a tandem human RRM1-RRM2 cDNA with a P2A self-cleaving peptide site between the subunits. Both rat and human Rrm1/Rrm2 cDNAs resulted in RNR enzyme overexpression exclusively in the heart and led to a significant elevation of left ventricular (LV) function in normal mice and infarcted rats, measured by echocardiography or isolated heart perfusions, without adverse cardiac remodeling. Our study suggests that increasing RNR levels via rAAV-mediated cardiac-specific expression provide a novel gene therapy approach to potentially enhance cardiac systolic function in animal models and patients with heart failure.

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“…Our molecular dynamic simulations predict that dATP changes the charge exposure on loop 2[26], so it was possible that the effect of dATP could be MHC dependent. We have reported that dATP increases force and the rate of force development at all levels of Ca 2+ activation in demembranated cardiac preparations from normal and PTU treated rats, the latter of which express primarily β-MHC respectively [8].…”

Section: Discussionmentioning

confidence: 99%

2-Deoxy adenosine triphosphate improves contraction in human end-stage heart failure

Moussavi‐Harami

Razumova

Racca

et al. 2015

Journal of Molecular and Cellular Cardiology

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We are developing a novel treatment for heart failure by increasing myocardial 2 deoxy-ATP (dATP). Our studies in rodent models have shown that substitution of dATP for adenosine triphosphate (ATP) as the energy substrate in vitro or elevation of dATP in vivo increases myocardial contraction and that small increases in the native dATP pool of heart muscle are sufficient to improve cardiac function. Here we report, for the first time, the effect of dATP on human adult cardiac muscle contraction. We measured the contractile properties of chemically-demembranated multicellular ventricular wall preparations and isolated myofibrils from human subjects with end-stage heart failure. Isometric force was increased at both saturating and physiologic Ca2+ concentrations with dATP compared to ATP. This resulted in an increase in the Ca2+ sensitivity of force (pCa50) by 0.06 pCa units. The rate of force redevelopment (kTR) in demembranated wall muscle was also increased, as was the rate of contractile activation (kACT) in isolated myofibrils, indicating increased cross-bridge binding and cycling compared with ATP in failing human myocardium. These data suggest dATP could increase dP/dT and end systolic pressure in failing human myocardium. Importantly, even though the magnitude and rate of force development was increased, there was no increase in the time to 50% and 90% myofibril relaxation. These data, along with our previous studies in rodent models shows the promise of elevating myocardial dATP to enhance contraction and restore cardiac pump function. These data also support further pre-clinical evaluation of this new approach for treating heart failure.

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2-deoxy-ATP Alters Myosin Structure to Enhance Cross-Bridge Cycling and Improve Cardiac Function

Cited by 4 publications

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Ribonucleotide reductase‐mediated increase in dATP improves cardiac performance via myosin activation in a large animal model of heart failure

Ribonucleotide reductase‐mediated increase in dATP improves cardiac performance via myosin activation in a large animal model of heart failure

AAV6-mediated Cardiac-specific Overexpression of Ribonucleotide Reductase Enhances Myocardial Contractility

2-Deoxy adenosine triphosphate improves contraction in human end-stage heart failure

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