Sarcolipin haploinsufficiency prevents dystrophic cardiomyopathy in mdx mice

Abstract

Background and Objective: Sarcolipin (SLN) is an inhibitor of sarco/endoplasmic reticulum (SR) Ca2+ ATPase (SERCA) and expressed at high levels in the ventricles of animal models for and patients with Duchenne muscular dystrophy (DMD). The goal of this study was to determine whether the germline ablation of SLN expression improves cardiac SERCA function, intracellular Ca2+ (Ca2+i) handling, and prevent cardiomyopathy in the mdx mouse model of DMD. Methods: The wildtype, mdx, SLN haploinsufficient mdx (mdx:sln+/-) and SLN deficient mdx (mdx:sln-/-) mice were used for this study. SERCA function and Ca2+i handling were determined by Ca2+ uptake assays and by measuring single-cell Ca2+ transients respectively. Age-dependent disease progression was determined by histopathological examinations and by echocardiography in 6, 12, and 20 months old mice. Gene expression changes in the ventricles of mdx:sln+/- mice were determined by RNA-Seq analysis. Results: SERCA function and Ca2+i cycling were improved in the ventricles of mdx:sln+/- mice. Fibrosis and necrosis were significantly decreased, and cardiac function was enhanced in the mdx:sln+/- mice until the study endpoint. The mdx:sln-/- mice also exhibited similar beneficial effects. RNA-Seq analysis identified distinct gene expression changes including the activation of the apelin pathway in the ventricles of mdx:sln+/- mice. Conclusions: Our findings suggest that reducing SLN expression is sufficient to improve cardiac SERCA function and Ca2+i cycling and prevent cardiomyopathy in mdx mice.

Abnormal Calcium Handling in Duchenne Muscular Dystrophy: Mechanisms and Potential Therapies

“…It has been shown that the levels of CSQ2 were drastically reduced in the heart of mdx mice (Lohan and Ohlendieck, 2004). However, we and others have shown that CSQ2 levels are unaltered in the hearts of mdx and mdx:utr −/− mice (Pertille et al, 2010;Voit et al, 2017;Mareedu et al, 2021). Surprisingly, CSQ2 expression is aberrantly increased in the fasttwitch muscles of mdx and mdx:utr −/− mice (Schneider et al, 2013;Voit et al, 2017).…”

“…Furthermore, AAVmediated SLN reduction normalized Ca 2+ i cycling and improved fusion and differentiation of dystrophin-deficient dog myoblasts (Niranjan et al, 2019). Our recent studies have demonstrated that reducing SLN expression is sufficient to restore cardiac SERCA function and Ca 2+ i cycling and to prevent the development of cardiomyopathy in mdx mice throughout their lifespan (Mareedu et al, 2021). To translate these findings into a therapeutic strategy, we also knocked down SLN expression in 1-monthold mdx:utr −/− mice via AAV-mediated RNA interference (Voit et al, 2017).…”

“…Irrespective of SERCA levels, SR Ca 2+ uptake is significantly reduced in dystrophin-deficient cardiac and skeletal muscles, indicating decreased SERCA function (Schneider et al, 2013;Voit et al, 2017;Wasala et al, 2020;Mareedu et al, 2021). Oxidative posttranslational modification has been shown to play an important role in SERCA activity in non-dystrophic heart diseases (Lancel et al, 2010;Horakova et al, 2013).…”

“…Little is known about the expression of MLN, DWORF, and SUMO-1 in dystrophin-deficient cardiac and skeletal muscles. It is worth pointing out that complete elimination of PLN exacerbates mdx cardiomyopathy (Law et al, 2018), whereas partial or complete elimination of SLN significantly reduces skeletal muscle disease and cardiomyopathy in mouse models of DMD (Voit et al, 2017;Mareedu et al, 2021).…”

Neuromuscular Development and Disease: Learning From in vitro and in vivo Models

“…The majority of our understanding of DMD has been derived from a range of preclinical animal models ( Wells, 2018 ) with the most common model being the mdx mouse which has a naturally occurring nonsense point mutation in exon 23 preventing dystrophin protein expression ( Manning and O’Malley, 2015 ). The mdx mice exhibit several expected disease features including fibrosis ( Gregorevic et al, 2008 ), respiratory dysfunction ( Burns et al, 2018 ), cardiomyopathy ( Mareedu et al, 2021 ), metabolic dysfunction ( Moore et al, 2020 ), and muscle weakness ( Barton et al, 2005 ). However, the mdx phenotype is milder and has a slower progression compared to clinical symptoms in DMD patients ( Dangain and Vrbova, 1984 ).…”