Chantal Allamargot

University of Iowa, Iowa City, Iowa, United States

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Publications (6)123.4 Total impact

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    ABSTRACT: Replying to F. Fieni et al. 513, http://dx.doi.org/10.1038/nature13626 (2014)In our Letter identifying mitochondrial CaMKII as a crucial component of a Ca(2+)-dependent process of heart disease, we used multiple methods to show that CaMKII modulates mitochondrial Ca(2+) homeostasis, as outlined below. First, we carried out electrophysiology of the mitochondrial calcium uniporter (MCU) current in mitoplasts. In our report we did not claim to measure capacitance of the mitoplast separately from the total capacitance of the mitoplast and pipette. Although we concede that the approach of Fieni et al. is preferable, we found that even after removing any correction for capacitance, dialysis with constitutively active CaMKII monomers increased MCU current whereas dialysis with catalytically dead CaMKII monomers did not.
    Nature 09/2014; 513(7519):E3. · 38.60 Impact Factor
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    ABSTRACT: Gene therapy using non-viral vectors that are safe and efficient in transfecting target cells is an effective approach to overcome the shortcomings of protein delivery of growth factors. The objective of this study was to develop and test a non-viral gene delivery system for bone regeneration utilizing a collagen scaffold to deliver polyethylenimine (PEI)-plasmid DNA (pDNA) [encoding platelet derived growth factor-B (PDGF-B)] complexes. The PEI-pPDGF-B complexes were fabricated at amine (N) to phosphate (P) ratio of 10 and characterized for size, surface charge, and in vitro cytotoxicity and transfection efficacy in human bone marrow stromal cells (BMSCs). The influence of the complex-loaded collagen scaffold on cellular attachment and recruitment was evaluated in vitro using microscopy techniques. The in vivo regenerative capacity of the gene delivery system was assessed in 5 mm diameter critical-sized calvarial defects in Fisher 344 rats. The complexes were ∼100 nm in size with a positive surface charge. Complexes prepared at an N/P ratio of 10 displayed low cytotoxicity as assessed by a cell viability assay. Confocal microscopy revealed significant proliferation of BMSCs on complex-loaded collagen scaffolds compared to empty scaffolds. In vivo studies showed significantly higher new bone volume/total volume (BV/TV) % in calvarial defects treated with the complex-activated scaffolds following 4 weeks of implantation (14- and 44-fold higher) when compared to empty defects or empty scaffolds, respectively. Together, these findings suggest that non-viral PDGF-B gene-activated scaffolds are effective for bone regeneration and are an attractive gene delivery system with significant potential for clinical translation.
    Biomaterials 10/2013; · 8.31 Impact Factor
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    ABSTRACT: Increased reactive oxygen species (ROS) contribute to asthma, but little is known about the molecular mechanisms connecting increased ROS with characteristic features of asthma. We show that enhanced oxidative activation of the Ca(2+)/calmodulin-dependent protein kinase (ox-CaMKII) in bronchial epithelium positively correlates with asthma severity and that epithelial ox-CaMKII increases in response to inhaled allergens in patients. We used mouse models of allergic airway disease induced by ovalbumin (OVA) or Aspergillus fumigatus (Asp) and found that bronchial epithelial ox-CaMKII was required to increase a ROS- and picrotoxin-sensitive Cl(-) current (ICl) and MUC5AC expression, upstream events in asthma progression. Allergen challenge increased epithelial ROS by activating NADPH oxidases. Mice lacking functional NADPH oxidases due to knockout of p47 and mice with epithelial-targeted transgenic expression of a CaMKII inhibitory peptide or wild-type mice treated with inhaled KN-93, an experimental small-molecule CaMKII antagonist, were protected against increases in ICl, MUC5AC expression, and airway hyperreactivity to inhaled methacholine. Our findings support the view that CaMKII is a ROS-responsive, pluripotent proasthmatic signal and provide proof-of-concept evidence that CaMKII is a therapeutic target in asthma.
    Science translational medicine 07/2013; 5(195):195ra97. · 10.76 Impact Factor
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    ABSTRACT: Myocardial cell death is initiated by excessive mitochondrial Ca(2+) entry causing Ca(2+) overload, mitochondrial permeability transition pore (mPTP) opening and dissipation of the mitochondrial inner membrane potential (ΔΨm). However, the signalling pathways that control mitochondrial Ca(2+) entry through the inner membrane mitochondrial Ca(2+) uniporter (MCU) are not known. The multifunctional Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is activated in ischaemia reperfusion, myocardial infarction and neurohumoral injury, common causes of myocardial death and heart failure; these findings suggest that CaMKII could couple disease stress to mitochondrial injury. Here we show that CaMKII promotes mPTP opening and myocardial death by increasing MCU current (I(MCU)). Mitochondrial-targeted CaMKII inhibitory protein or cyclosporin A, an mPTP antagonist with clinical efficacy in ischaemia reperfusion injury, equivalently prevent mPTP opening, ΔΨm deterioration and diminish mitochondrial disruption and programmed cell death in response to ischaemia reperfusion injury. Mice with myocardial and mitochondrial-targeted CaMKII inhibition have reduced I(MCU) and are resistant to ischaemia reperfusion injury, myocardial infarction and neurohumoral injury, suggesting that pathological actions of CaMKII are substantially mediated by increasing I(MCU). Our findings identify CaMKII activity as a central mechanism for mitochondrial Ca(2+) entry in myocardial cell death, and indicate that mitochondrial-targeted CaMKII inhibition could prevent or reduce myocardial death and heart failure in response to common experimental forms of pathophysiological stress.
    Nature 10/2012; · 38.60 Impact Factor
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    ABSTRACT: Excessive activation of β-adrenergic, angiotensin II, and aldosterone signaling pathways promotes mortality after myocardial infarction (MI), while antagonist drugs targeting these pathways are core therapies for treating post-MI patients. The multifunctional calcium/calmodulin-dependent protein kinase II (CaMKII) is activated by catecholamines and angiotensin II, and CaMKII inhibition prevents isoproterenol- and angiotensin II-mediated cardiomyopathy. Here we ask the hypothesis if aldosterone and CaMKII participated in common responses to MI by developing a mouse MI model supplemented by aldosterone infusion (MI+Aldo) to approximate plasma aldosterone levels measured in MI patients. We find that aldosterone exerts direct toxic actions on myocardium by oxidative activation of CaMKII, causing cardiac rupture and increased mortality in mice after MI (65.5% for aldosterone versus 31.0% for vehicle, P=0.007, n≥19 mice per treatment). Aldosterone oxidizes CaMKII by recruiting NADPH oxidase, and hyperactive CaMKII promotes matrix metalloproteinase 9 (MMP9) expression in cardiomyocytes. We find enhanced MMP9 expression in cardiomyocytes isolated from the MI region in MI+Aldo wildtype mice, suggesting that myocardial MMP9 may be essential for enhancing rupture in the MI+Aldo model. We also identified increased MMP9 from myocardium in the MI region of patients who died of MI-related cardiac rupture, but not in patients who died of MI without rupture, suggesting that our findings in mice were relevant to patients. Myocardial CaMKII inhibition, over-expression of methionine sulfoxide reductase A, an enzyme that reduces oxidized CaMKII, or NADPH oxidase knockout gave protection from aldosterone-enhanced post-MI cardiac rupture. These findings support the conclusion that oxidized myocardial CaMKII mediates cardiotoxic effects of aldosterone on cardiac matrix, establishing CaMKII as a nodal signal for the neurohumoral pathways associated with poor outcomes after MI. Our study provides a mechanic rationale for clinical testing of whether currently available aldosterone antagonist drugs administered immediately after the diagnosis of MI can reduce acute mortality, by minimizing the likelihood of myocardial rupture.
    American Heart Association Scientific Sessions 2011; 11/2011
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    ABSTRACT: Excessive activation of the β-adrenergic, angiotensin II (Ang II) and aldosterone signaling pathways promotes mortality after myocardial infarction, and antagonists targeting these pathways are core therapies for treating this condition. Catecholamines and Ang II activate the multifunctional Ca(2+)/calmodulin-dependent protein kinase II (CaMKII), the inhibition of which prevents isoproterenol-mediated and Ang II-mediated cardiomyopathy. Here we show that aldosterone exerts direct toxic actions on myocardium by oxidative activation of CaMKII, causing cardiac rupture and increased mortality in mice after myocardial infarction. Aldosterone induces CaMKII oxidation by recruiting NADPH oxidase, and this oxidized and activated CaMKII promotes matrix metalloproteinase 9 (MMP9) expression in cardiomyocytes. Myocardial CaMKII inhibition, overexpression of methionine sulfoxide reductase A (an enzyme that reduces oxidized CaMKII) or NADPH oxidase deficiency prevented aldosterone-enhanced cardiac rupture after myocardial infarction. These findings show that oxidized myocardial CaMKII mediates the cardiotoxic effects of aldosterone on the cardiac matrix and establish CaMKII as a nodal signal for the neurohumoral pathways associated with poor outcomes after myocardial infarction.
    Nature medicine 11/2011; 17(12):1610-8. · 27.14 Impact Factor