Cardiac CIP protein regulates dystrophic cardiomyopathy

Abstract Aims Duchenne muscular dystrophy (DMD) is an inherited devastating muscle disease with severe and often lethal cardiac complications. Emerging evidence suggests that the evolution of the pathology in DMD is accompanied by the accumulation of mitochondria with defective structure and function. Here, we investigate whether defects in the housekeeping autophagic pathway contribute to mitochondrial and metabolic dysfunctions in dystrophic cardiomyopathy. Methods and results We employed various biochemical and imaging techniques to assess mitochondrial structure and function as well as to evaluate autophagy, and specific mitochondrial autophagy (mitophagy), in hearts of mdx mice, an animal model of DMD. Our results indicate substantial structural damage of mitochondria and a significant decrease in ATP production in hearts of mdx animals, which developed cardiomyopathy. In these hearts, we also detected enhanced autophagy but paradoxically, mitophagy appeared to be suppressed. In addition, we found decreased levels of several proteins involved in the PINK1/PARKIN mitophagy pathway as well as an insignificant amount of PARKIN protein phosphorylation at the S65 residue upon induction of mitophagy. Conclusions Our results suggest faulty mitophagy in dystrophic hearts due to defects in the PINK1/PARKIN pathway.

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NADPH oxidase-2 inhibition restores contractility and intracellular calcium handling and reduces arrhythmogenicity in dystrophic cardiomyopathy

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00890.2013 ◽

2014 ◽

Vol 307 (5) ◽

pp. H710-H721 ◽

Cited By ~ 22

Author(s):

Daniel R. Gonzalez ◽

Adriana V. Treuer ◽

Guillaume Lamirault ◽

Vera Mayo ◽

Yenong Cao ◽

...

Keyword(s):

Nadph Oxidase ◽

Calcium Release ◽

Calcium Handling ◽

Mdx Mouse ◽

No Production ◽

Wild Type ◽

Intracellular Ca ◽

Dystrophic Cardiomyopathy ◽

The Impact ◽

Phospholamban Phosphorylation

Duchenne muscular dystrophy may affect cardiac muscle, producing a dystrophic cardiomyopathy in humans and the mdx mouse. We tested the hypothesis that oxidative stress participates in disrupting calcium handling and contractility in the mdx mouse with established cardiomyopathy. We found increased expression (fivefold) of the NADPH oxidase (NOX) 2 in the mdx hearts compared with wild type, along with increased superoxide production. Next, we tested the impact of NOX2 inhibition on contractility and calcium handling in isolated cardiomyocytes. Contractility was decreased in mdx myocytes compared with wild type, and this was restored toward normal by pretreating with apocynin. In addition, the amplitude of evoked intracellular Ca2+ concentration transients that was diminished in mdx myocytes was also restored with NOX2 inhibition. Total sarcoplasmic reticulum (SR) Ca2+ content was reduced in mdx hearts and normalized by apocynin treatment. Additionally, NOX2 inhibition decreased the production of spontaneous diastolic calcium release events and decreased the SR calcium leak in mdx myocytes. In addition, nitric oxide (NO) synthase 1 (NOS-1) expression was increased eightfold in mdx hearts compared with wild type. Nevertheless, cardiac NO production was reduced. To test whether this paradox implied NOS-1 uncoupling, we treated cardiac myocytes with exogenous tetrahydrobioterin, along with the NOX inhibitor VAS2870. These agents restored NO production and phospholamban phosphorylation in mdx toward normal. Together, these results demonstrate that, in mdx hearts, NOX2 inhibition improves the SR calcium handling and contractility, partially by recoupling NOS-1. These findings reveal a new layer of nitroso-redox imbalance in dystrophic cardiomyopathy.

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Early right ventricular fibrosis and reduction in biventricular cardiac reserve in the dystrophin-deficient mdx heart

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00485.2014 ◽

2015 ◽

Vol 308 (4) ◽

pp. H303-H315 ◽

Cited By ~ 17

Author(s):

Tatyana A. Meyers ◽

DeWayne Townsend

Keyword(s):

Right Ventricle ◽

Right Ventricular ◽

Cardiac Fibrosis ◽

Striated Muscle ◽

Mdx Mice ◽

Catheterization Technique ◽

Dystrophic Cardiomyopathy ◽

Systolic And Diastolic Function ◽

Ventricular Fibrosis ◽

The Right

Duchenne muscular dystrophy (DMD) is a progressive disease of striated muscle deterioration. Respiratory and cardiac muscle dysfunction are particularly clinically relevant because they result in the leading causes of death in DMD patients. Despite the clinical and physiological significance of these systems, little has been done to understand the cardiorespiratory interaction in DMD. We show here that prior to the onset of global cardiac dysfunction, dystrophin-deficient mdx mice have increased cardiac fibrosis with the right ventricle being particularly affected. Using a novel biventricular cardiac catheterization technique coupled with cardiac stress testing, we demonstrate that both the right and left ventricles have significant reductions in both systolic and diastolic function in response to dobutamine. Unstimulated cardiac function is relatively normal except for a significant reduction in the ventricular pressure transient duration compared with controls. These biventricular analyses also reveal the absence of a dobutamine-induced increase in isovolumic relaxation in the right ventricle of control hearts. Simultaneous assessment of biventricular pressure demonstrates a dobutamine-dependent enhancement of coupling between the ventricles in control mice, which is absent in mdx mice. Furthermore, studies probing the passive-extension properties of the left ventricle demonstrate that the mdx heart is significantly more compliant compared with age-matched C57BL/10 hearts, which have an age-dependent stiffening that is completely absent from dystrophic hearts. These new results indicate that right ventricular fibrosis is an early indicator of the development of dystrophic cardiomyopathy, suggesting a mechanism by which respiratory insufficiency may accelerate the development of heart failure in DMD.

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Engineered developmental niche enables predictive phenotypic screening in human dystrophic cardiomyopathy

10.1101/456301 ◽

2018 ◽

Author(s):

Jesse R. Macadangdang ◽

Jason W. Miklas ◽

Alec S.T. Smith ◽

Eunpyo Choi ◽

Winnie Leung ◽

...

Keyword(s):

Microelectrode Array ◽

Disease Modeling ◽

Contractile Function ◽

Calcium Content ◽

Cytosolic Calcium ◽

Biochemical Properties ◽

Directed Differentiation ◽

Dystrophic Cardiomyopathy ◽

Mitochondrial Capacity

ABSTRACTDirected differentiation of human pluripotent stem cells (hPSCs) into cardiomyocytes typically produces cells with structural, functional, and biochemical properties that most closely resemble those present in the fetal heart. Here we establish an in vitro engineered developmental cardiac niche to produce matured hPSC-derived cardiomyocytes (hPSC-CMs) with enhanced sarcomere development, electrophysiology, contractile function, mitochondrial capacity, and a more mature transcriptome. When this developmental cardiac niche was applied to dystrophin mutant hPSC-CMs, a robust disease phenotype emerged, which was not observed in non-matured diseased hPSC-CMs. Matured dystrophin mutant hPSC-CMs exhibited a greater propensity for arrhythmia as measured via beat rate variability, most likely due to higher resting cytosolic calcium content. Using a custom nanopatterned microelectrode array platform to screen functional output in hPSC-CMs exposed to our engineered developmental cardiac niche, we identified calcium channel blocker, nitrendipine, mitigated hPSC-CM arrhythmogenic behavior and correctly identified sildenafil as a false positive. Taken together, we demonstrate our developmental cardiac niche platform enables robust hPSC-CM maturation allowing for more accurate disease modeling and predictive drug screening.

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