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1
Wehling, Michelle, Melissa J. Spencer, and James G. Tidball. "A nitric oxide synthase transgene ameliorates muscular dystrophy in mdx mice." Journal of Cell Biology 155, no. 1 (October 1, 2001): 123–32. http://dx.doi.org/10.1083/jcb.200105110.
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Dystrophin-deficient muscles experience large reductions in expression of nitric oxide synthase (NOS), which suggests that NO deficiency may influence the dystrophic pathology. Because NO can function as an antiinflammatory and cytoprotective molecule, we propose that the loss of NOS from dystrophic muscle exacerbates muscle inflammation and fiber damage by inflammatory cells. Analysis of transgenic mdx mice that were null mutants for dystrophin, but expressed normal levels of NO in muscle, showed that the normalization of NO production caused large reductions in macrophage concentrations in the mdx muscle. Expression of the NOS transgene in mdx muscle also prevented the majority of muscle membrane injury that is detectable in vivo, and resulted in large decreases in serum creatine kinase concentrations. Furthermore, our data show that mdx muscle macrophages are cytolytic at concentrations that occur in dystrophic, NOS-deficient muscle, but are not cytolytic at concentrations that occur in dystrophic mice that express the NOS transgene in muscle. Finally, our data show that antibody depletions of macrophages from mdx mice cause significant reductions in muscle membrane injury. Together, these findings indicate that macrophages promote injury of dystrophin-deficient muscle, and the loss of normal levels of NO production by dystrophic muscle exacerbates inflammation and membrane injury in muscular dystrophy.
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Spaulding, Hannah R., Tiffany Quindry, Kayleen Hammer, John C. Quindry, and Joshua T. Selsby. "Nutraceutical and pharmaceutical cocktails did not improve muscle function or reduce histological damage in D2-mdx mice." Journal of Applied Physiology 127, no. 4 (October 1, 2019): 1058–66. http://dx.doi.org/10.1152/japplphysiol.00162.2019.
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Progressive muscle injury and weakness are hallmarks of Duchenne muscular dystrophy. We showed previously that quercetin (Q) partially protected dystrophic limb muscles from disease-related injury. As quercetin activates PGC-1α through Sirtuin-1, an NAD+-dependent deacetylase, the depleted NAD+ in dystrophic skeletal muscle may limit quercetin efficacy; hence, supplementation with the NAD+ donor, nicotinamide riboside (NR), may facilitate quercetin efficacy. Lisinopril (Lis) protects skeletal muscle and improves cardiac function in dystrophin-deficient mice; therefore, it was included in this study to evaluate the effects of lisinopril used with quercetin and NR. Our purpose was to determine the extent to which Q, NR, and Lis decreased dystrophic injury. We hypothesized that Q, NR, or Lis alone would improve muscle function and decrease histological injury and when used in combination would have additive effects. Muscle function of 11-mo-old DBA (healthy), D2-mdx (dystrophin-deficient), and D2-mdx mice was assessed after treatment with Q, NR, and/or Lis for 7 mo. To mimic typical pharmacology of patients with Duchenne muscular dystrophy, a group was treated with prednisolone (Pred) in combination with Q, NR, and Lis. At 11 mo of age, dystrophin deficiency decreased specific tension and tetanic force in the soleus and extensor digitorum longus muscles and was not corrected by any treatment. Dystrophic muscle was more sensitive to contraction-induced injury, which was partially offset in the QNRLisPred group, whereas fatigue was similar between all groups. Treatments did not decrease histological damage. These data suggest that treatment with Q, NR, Lis, and Pred failed to adequately maintain dystrophic limb muscle function or decrease histological damage. NEW & NOTEWORTHY Despite a compelling rationale and previous evidence to the contrary in short-term investigations, quercetin, nicotinamide riboside, or Lisinopril, alone or in combination, failed to restore muscle function or decrease histological injury in dystrophic limb muscle from D2-mdx mice after long-term administration. Importantly, we also found that in the D2-mdx model, an emerging and relatively understudied model of Duchenne muscular dystrophy dystrophin deficiency caused profound muscle dysfunction and histopathology in skeletal muscle.
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Spaulding, HR, C. Ballmann, JC Quindry, MB Hudson, and JT Selsby. "Autophagy in the heart is enhanced and independent of disease progression in mus musculus dystrophinopathy models." JRSM Cardiovascular Disease 8 (January 2019): 204800401987958. http://dx.doi.org/10.1177/2048004019879581.
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Background Duchenne muscular dystrophy is a muscle wasting disease caused by dystrophin gene mutations resulting in dysfunctional dystrophin protein. Autophagy, a proteolytic process, is impaired in dystrophic skeletal muscle though little is known about the effect of dystrophin deficiency on autophagy in cardiac muscle. We hypothesized that with disease progression autophagy would become increasingly dysfunctional based upon indirect autophagic markers. Methods Markers of autophagy were measured by western blot in 7-week-old and 17-month-old control (C57) and dystrophic (mdx) hearts. Results Counter to our hypothesis, markers of autophagy were similar between groups. Given these surprising results, two independent experiments were conducted using 14-month-old mdx mice or 10-month-old mdx/Utrn± mice, a more severe model of Duchenne muscular dystrophy. Data from these animals suggest increased autophagosome degradation. Conclusion Together these data suggest that autophagy is not impaired in the dystrophic myocardium as it is in dystrophic skeletal muscle and that disease progression and related injury is independent of autophagic dysfunction.
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Whitehead, Nicholas P., Min Jeong Kim, Kenneth L. Bible, Marvin E. Adams, and Stanley C. Froehner. "A new therapeutic effect of simvastatin revealed by functional improvement in muscular dystrophy." Proceedings of the National Academy of Sciences 112, no. 41 (September 28, 2015): 12864–69. http://dx.doi.org/10.1073/pnas.1509536112.
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Duchenne muscular dystrophy (DMD) is a lethal, degenerative muscle disease with no effective treatment. DMD muscle pathogenesis is characterized by chronic inflammation, oxidative stress, and fibrosis. Statins, cholesterol-lowering drugs, inhibit these deleterious processes in ischemic diseases affecting skeletal muscle, and therefore have potential to improve DMD. However, statins have not been considered for DMD, or other muscular dystrophies, principally because skeletal-muscle-related symptoms are rare, but widely publicized, side effects of these drugs. Here we show positive effects of statins in dystrophic skeletal muscle. Simvastatin dramatically reduced damage and enhanced muscle function in dystrophic (mdx) mice. Long-term simvastatin treatment vastly improved overall muscle health inmdxmice, reducing plasma creatine kinase activity, an established measure of muscle damage, to near-normal levels. This reduction was accompanied by reduced inflammation, more oxidative muscle fibers, and improved strength of the weak diaphragm muscle. Shorter-term treatment protected against muscle fatigue and increasedmdxhindlimb muscle force by 40%, a value comparable to current dystrophin gene-based therapies. Increased force correlated with reduced NADPH Oxidase 2 protein expression, the major source of oxidative stress in dystrophic muscle. Finally, in oldmdxmice with severe muscle degeneration, simvastatin enhanced diaphragm force and halved fibrosis, a major cause of functional decline in DMD. These improvements were accompanied by autophagy activation, a recent therapeutic target for DMD, and less oxidative stress. Together, our findings highlight that simvastatin substantially improves the overall health and function of dystrophic skeletal muscles and may provide an unexpected, novel therapy for DMD and related neuromuscular diseases.
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Ng, Rainer, Joseph M. Metzger, Dennis R. Claflin, and John A. Faulkner. "Poloxamer 188 reduces the contraction-induced force decline in lumbrical muscles from mdx mice." American Journal of Physiology-Cell Physiology 295, no. 1 (July 2008): C146—C150. http://dx.doi.org/10.1152/ajpcell.00017.2008.
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Duchenne Muscular Dystrophy is a genetic disease caused by the lack of the protein dystrophin. Dystrophic muscles are highly susceptible to contraction-induced injury, and following contractile activity, have disrupted plasma membranes that allow leakage of calcium ions into muscle fibers. Because of the direct relationship between increased intracellular calcium concentration and muscle dysfunction, therapeutic outcomes may be achieved through the identification and restriction of calcium influx pathways. Our purpose was to determine the contribution of sarcolemmal lesions to the force deficits caused by contraction-induced injury in dystrophic skeletal muscles. Using isolated lumbrical muscles from dystrophic ( mdx) mice, we demonstrate for the first time that poloxamer 188 (P188), a membrane-sealing poloxamer, is effective in reducing the force deficit in a whole mdx skeletal muscle. A reduction in force deficit was also observed in mdx muscles that were exposed to a calcium-free environment. These results, coupled with previous observations of calcium entry into mdx muscle fibers during a similar contraction protocol, support the interpretation that extracellular calcium enters through sarcolemmal lesions and contributes to the force deficit observed in mdx muscles. The results provide a basis for potential therapeutic strategies directed at membrane stabilization of dystrophin-deficient skeletal muscle fibers.
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Watchko, Jon F., Terrence L. O'Day, and Eric P. Hoffman. "Functional characteristics of dystrophic skeletal muscle: insights from animal models." Journal of Applied Physiology 93, no. 2 (August 1, 2002): 407–17. http://dx.doi.org/10.1152/japplphysiol.01242.2001.
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Muscular dystrophies are a clinically and genetically heterogeneous group of disorders that show myofiber degeneration and regeneration. Identification of animal models of muscular dystrophy has been instrumental in research on the pathogenesis, pathophysiology, and treatment of these disorders. We review our understanding of the functional status of dystrophic skeletal muscle from selected animal models with a focus on 1) the mdx mouse model of Duchenne muscular dystrophy, 2) the Bio 14.6 δ-sarcoglycan-deficient hamster model of limb-girdle muscular dystrophy, and 3) transgenic null mutant murine lines of sarcoglycan (α, β, δ, and γ) deficiencies. Although biochemical data from these models suggest that the dystrophin-sarcoglycan-dystroglycan-laminin network is critical for structural integrity of the myofiber plasma membrane, emerging studies of muscle physiology suggest a more complex picture, with specific functional deficits varying considerably from muscle to muscle and model to model. It is likely that changes in muscle structure and function, downstream of the specific, primary biochemical deficiency, may alter muscle contractile properties.
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Reid, Andrea L., Yimin Wang, Adrienne Samani, Rylie M. Hightower, Michael A. Lopez, Shawn R. Gilbert, Lara Ianov, et al. "DOCK3 is a dosage-sensitive regulator of skeletal muscle and Duchenne muscular dystrophy-associated pathologies." Human Molecular Genetics 29, no. 17 (August 7, 2020): 2855–71. http://dx.doi.org/10.1093/hmg/ddaa173.
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Abstract DOCK3 is a member of the DOCK family of guanine nucleotide exchange factors that regulate cell migration, fusion and viability. Previously, we identified a dysregulated miR-486/DOCK3 signaling cascade in dystrophin-deficient muscle, which resulted in the overexpression of DOCK3; however, little is known about the role of DOCK3 in muscle. Here, we characterize the functional role of DOCK3 in normal and dystrophic skeletal muscle. Utilizing Dock3 global knockout (Dock3 KO) mice, we found that the haploinsufficiency of Dock3 in Duchenne muscular dystrophy mice improved dystrophic muscle pathologies; however, complete loss of Dock3 worsened muscle function. Adult Dock3 KO mice have impaired muscle function and Dock3 KO myoblasts are defective for myogenic differentiation. Transcriptomic analyses of Dock3 KO muscles reveal a decrease in myogenic factors and pathways involved in muscle differentiation. These studies identify DOCK3 as a novel modulator of muscle health and may yield therapeutic targets for treating dystrophic muscle symptoms.
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Cui, Chang-Hao, Taro Uyama, Kenji Miyado, Masanori Terai, Satoru Kyo, Tohru Kiyono, and Akihiro Umezawa. "Menstrual Blood-derived Cells Confer Human Dystrophin Expression in the Murine Model of Duchenne Muscular Dystrophy via Cell Fusion and Myogenic Transdifferentiation." Molecular Biology of the Cell 18, no. 5 (May 2007): 1586–94. http://dx.doi.org/10.1091/mbc.e06-09-0872.
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Duchenne muscular dystrophy (DMD), the most common lethal genetic disorder in children, is an X-linked recessive muscle disease characterized by the absence of dystrophin at the sarcolemma of muscle fibers. We examined a putative endometrial progenitor obtained from endometrial tissue samples to determine whether these cells repair muscular degeneration in a murine mdx model of DMD. Implanted cells conferred human dystrophin in degenerated muscle of immunodeficient mdx mice. We then examined menstrual blood–derived cells to determine whether primarily cultured nontransformed cells also repair dystrophied muscle. In vivo transfer of menstrual blood–derived cells into dystrophic muscles of immunodeficient mdx mice restored sarcolemmal expression of dystrophin. Labeling of implanted cells with enhanced green fluorescent protein and differential staining of human and murine nuclei suggest that human dystrophin expression is due to cell fusion between host myocytes and implanted cells. In vitro analysis revealed that endometrial progenitor cells and menstrual blood–derived cells can efficiently transdifferentiate into myoblasts/myocytes, fuse to C2C12 murine myoblasts by in vitro coculturing, and start to express dystrophin after fusion. These results demonstrate that the endometrial progenitor cells and menstrual blood–derived cells can transfer dystrophin into dystrophied myocytes through cell fusion and transdifferentiation in vitro and in vivo.
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Straub, Volker, Jill A. Rafael, Jeffrey S. Chamberlain, and Kevin P. Campbell. "Animal Models for Muscular Dystrophy Show Different Patterns of Sarcolemmal Disruption." Journal of Cell Biology 139, no. 2 (October 20, 1997): 375–85. http://dx.doi.org/10.1083/jcb.139.2.375.
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Genetic defects in a number of components of the dystrophin–glycoprotein complex (DGC) lead to distinct forms of muscular dystrophy. However, little is known about how alterations in the DGC are manifested in the pathophysiology present in dystrophic muscle tissue. One hypothesis is that the DGC protects the sarcolemma from contraction-induced damage. Using tracer molecules, we compared sarcolemmal integrity in animal models for muscular dystrophy and in muscular dystrophy patient samples. Evans blue, a low molecular weight diazo dye, does not cross into skeletal muscle fibers in normal mice. In contrast, mdx mice, a dystrophin-deficient animal model for Duchenne muscular dystrophy, showed significant Evans blue accumulation in skeletal muscle fibers. We also studied Evans blue dispersion in transgenic mice bearing different dystrophin mutations, and we demonstrated that cytoskeletal and sarcolemmal attachment of dystrophin might be a necessary requirement to prevent serious fiber damage. The extent of dye incorporation in transgenic mice correlated with the phenotypic severity of similar dystrophin mutations in humans. We furthermore assessed Evans blue incorporation in skeletal muscle of the dystrophia muscularis (dy/dy) mouse and its milder allelic variant, the dy2J/dy2J mouse, animal models for congenital muscular dystrophy. Surprisingly, these mice, which have defects in the laminin α2-chain, an extracellular ligand of the DGC, showed little Evans blue accumulation in their skeletal muscles. Taken together, these results suggest that the pathogenic mechanisms in congenital muscular dystrophy are different from those in Duchenne muscular dystrophy, although the primary defects originate in two components associated with the same protein complex.
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Reggio, Alessio, Marco Rosina, Natalie Krahmer, Alessandro Palma, Lucia Lisa Petrilli, Giuliano Maiolatesi, Giorgia Massacci, et al. "Metabolic reprogramming of fibro/adipogenic progenitors facilitates muscle regeneration." Life Science Alliance 3, no. 3 (February 4, 2020): e202000646. http://dx.doi.org/10.26508/lsa.202000660.
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In Duchenne muscular dystrophy (DMD), the absence of the dystrophin protein causes a variety of poorly understood secondary effects. Notably, muscle fibers of dystrophic individuals are characterized by mitochondrial dysfunctions, as revealed by a reduced ATP production rate and by defective oxidative phosphorylation. Here, we show that in a mouse model of DMD (mdx), fibro/adipogenic progenitors (FAPs) are characterized by a dysfunctional mitochondrial metabolism which correlates with increased adipogenic potential. Using high-sensitivity mass spectrometry–based proteomics, we report that a short-term high-fat diet (HFD) reprograms dystrophic FAP metabolism in vivo. By combining our proteomic dataset with a literature-derived signaling network, we revealed that HFD modulates the β-catenin–follistatin axis. These changes are accompanied by significant amelioration of the histological phenotype in dystrophic mice. Transplantation of purified FAPs from HFD-fed mice into the muscles of dystrophic recipients demonstrates that modulation of FAP metabolism can be functional to ameliorate the dystrophic phenotype. Our study supports metabolic reprogramming of muscle interstitial progenitor cells as a novel approach to alleviate some of the adverse outcomes of DMD.
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Chen, Yi-Wen, Po Zhao, Rehannah Borup, and Eric P. Hoffman. "Expression Profiling in the Muscular Dystrophies." Journal of Cell Biology 151, no. 6 (December 11, 2000): 1321–36. http://dx.doi.org/10.1083/jcb.151.6.1321.
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We used expression profiling to define the pathophysiological cascades involved in the progression of two muscular dystrophies with known primary biochemical defects, dystrophin deficiency (Duchenne muscular dystrophy) and α-sarcoglycan deficiency (a dystrophin-associated protein). We employed a novel protocol for expression profiling in human tissues using mixed samples of multiple patients and iterative comparisons of duplicate datasets. We found evidence for both incomplete differentiation of patient muscle, and for dedifferentiation of myofibers to alternative lineages with advancing age. One developmentally regulated gene characterized in detail, α-cardiac actin, showed abnormal persistent expression after birth in 60% of Duchenne dystrophy myofibers. The majority of myofibers (∼80%) remained strongly positive for this protein throughout the course of the disease. Other developmentally regulated genes that showed widespread overexpression in these muscular dystrophies included embryonic myosin heavy chain, versican, acetylcholine receptor α-1, secreted protein, acidic and rich in cysteine/osteonectin, and thrombospondin 4. We hypothesize that the abnormal Ca2+ influx in dystrophin- and α-sarcoglycan–deficient myofibers leads to altered developmental programming of developing and regenerating myofibers. The finding of upregulation of HLA-DR and factor XIIIa led to the novel identification of activated dendritic cell infiltration in dystrophic muscle; these cells mediate immune responses and likely induce microenvironmental changes in muscle. We also document a general metabolic crisis in dystrophic muscle, with large scale downregulation of nuclear-encoded mitochondrial gene expression. Finally, our expression profiling results show that primary genetic defects can be identified by a reduction in the corresponding RNA.
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Steen, Michelle S., Marvin E. Adams, Yan Tesch, and Stanley C. Froehner. "Amelioration of Muscular Dystrophy by Transgenic Expression of Niemann-Pick C1." Molecular Biology of the Cell 20, no. 1 (January 2009): 146–52. http://dx.doi.org/10.1091/mbc.e08-08-0811.
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Duchenne muscular dystrophy (DMD) and other types of muscular dystrophies are caused by the loss or alteration of different members of the dystrophin protein complex. Understanding the molecular mechanisms by which dystrophin-associated protein abnormalities contribute to the onset of muscular dystrophy may identify new therapeutic approaches to these human disorders. By examining gene expression alterations in mouse skeletal muscle lacking α-dystrobrevin (Dtna−/−), we identified a highly significant reduction of the cholesterol trafficking protein, Niemann-Pick C1 (NPC1). Mutations in NPC1 cause a progressive neurodegenerative, lysosomal storage disorder. Transgenic expression of NPC1 in skeletal muscle ameliorates muscular dystrophy in the Dtna−/− mouse (which has a relatively mild dystrophic phenotype) and in the mdx mouse, a model for DMD. These results identify a new compensatory gene for muscular dystrophy and reveal a potential new therapeutic target for DMD.
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Schertzer, Jonathan D., Chris van der Poel, Thea Shavlakadze, Miranda D. Grounds, and Gordon S. Lynch. "Muscle-specific overexpression of IGF-I improves E-C coupling in skeletal muscle fibers from dystrophic mdx mice." American Journal of Physiology-Cell Physiology 294, no. 1 (January 2008): C161—C168. http://dx.doi.org/10.1152/ajpcell.00399.2007.
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Duchenne muscular dystrophy (DMD) is a lethal X-linked disease caused by the absence of functional dystrophin. Abnormal excitation-contraction (E-C) coupling has been reported in dystrophic muscle fibers from mdx mice, and alterations in E-C coupling components may occur as a direct result of dystrophin deficiency. We hypothesized that muscle-specific overexpression of insulin-growth factor-1 (IGF-I) would reduce E-C coupling failure in mdx muscle. Mechanically skinned extensor digitorum longus muscle fibers from mdx mice displayed a faster decline in depolarization-induced force responses (DIFR); however, there were no differences in sarcoplasmic reticulum (SR)-mediated Ca2+ resequestration or in the properties of the contractile apparatus when compared with nondystrophic controls. The rate of DIFR decline was restored to control levels in fibers from transgenic mdx mice that overexpressed IGF-I in skeletal muscle ( mdx/IGF-I mice). Dystrophic muscles have a lower transcript level of a specific dihydropyridine receptor (DHPR) isoform, and IGF-I-mediated changes in E-C coupling were associated with increased transcript levels of specific DHPR isoforms involved in Ca2+ regulation. Importantly, IGF-I overexpression also increased the sensitivity of the contractile apparatus to Ca2+. The results demonstrate that IGF-I can ameliorate fundamental aspects of E-C coupling failure in dystrophic muscle fibers and that these effects are important for the improvements in cellular function induced by this growth factor.
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Amirouche, Adel, Vanessa E. Jahnke, John A. Lunde, Nathalie Koulmann, Damien G. Freyssenet, and Bernard J. Jasmin. "Muscle-specific microRNA-206 targets multiple components in dystrophic skeletal muscle representing beneficial adaptations." American Journal of Physiology-Cell Physiology 312, no. 3 (March 1, 2017): C209—C221. http://dx.doi.org/10.1152/ajpcell.00185.2016.
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Over the last several years, converging lines of evidence have indicated that miR-206 plays a pivotal role in promoting muscle differentiation and regeneration, thereby potentially impacting positively on the progression of neuromuscular disorders, including Duchenne muscular dystrophy (DMD). Despite several studies showing the regulatory function of miR-206 on target mRNAs in skeletal muscle cells, the effects of overexpression of miR-206 in dystrophic muscles remain to be established. Here, we found that miR-206 overexpression in mdx mouse muscles simultaneously targets multiple mRNAs and proteins implicated in satellite cell differentiation, muscle regeneration, and at the neuromuscular junction. Overexpression of miR-206 also increased the levels of several muscle-specific mRNAs/proteins, while enhancing utrophin A expression at the sarcolemma. Finally, we also observed that the increased expression of miR-206 in dystrophin-deficient mouse muscle decreased the production of proinflammatory cytokines and infiltration of macrophages. Taken together, our results show that miR-206 acts as a pleiotropic regulator that targets multiple key mRNAs and proteins expected to provide beneficial adaptations in dystrophic muscle, thus highlighting its therapeutic potential for DMD.
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Howlett, S. E., C. R. Triggle, and T. B. Hoekman. "Effects of noradrenaline, serotonin, and selected antagonists on the vascular smooth muscle of normal and dystrophic chickens." Canadian Journal of Physiology and Pharmacology 64, no. 5 (May 1, 1986): 545–49. http://dx.doi.org/10.1139/y86-090.
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The pathogenesis of the human muscular dystrophies is unknown, and several competing hypotheses have been proposed. The vascular hypothesis states that muscle fibre necrosis occurs in dystrophy as a result of transient muscle ischemia. Although abnormalities of the vascular system may be demonstrated in dystrophy, their role in pathogenesis remains obscure. The responses to serotonin (5-HT) and noradrenaline (NA) were examined in isolated ischiatic artery preparations from normal and genetically dystrophic chickens. The tension generated in response to 5-HT was greater in arteries from normal chickens than in arteries from dystrophic chickens, whereas responses to NA were similar. Analysis of the concentration–response relationships demonstrated that the dystrophic ischiatic artery was less sensitive to 5-HT than was the normal artery, although the sensitivity to NA was similar in both vessels. The results of this study are not consistent with the view that muscle fibre necrosis in avian dystrophy is a consequence of muscle anoxia. These data do demonstrate pharmacological differences between dystrophic avian arteries and arteries from normal chickens, but their presence may represent merely the expression of dystrophy in vascular smooth muscle.
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Gumerson, Jessica D., and Daniel E. Michele. "The Dystrophin-Glycoprotein Complex in the Prevention of Muscle Damage." Journal of Biomedicine and Biotechnology 2011 (2011): 1–13. http://dx.doi.org/10.1155/2011/210797.
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Muscular dystrophies are genetically diverse but share common phenotypic features of muscle weakness, degeneration, and progressive decline in muscle function. Previous work has focused on understanding how disruptions in the dystrophin-glycoprotein complex result in muscular dystrophy, supporting a hypothesis that the muscle sarcolemma is fragile and susceptible to contraction-induced injury in multiple forms of dystrophy. Although benign in healthy muscle, contractions in dystrophic muscle may contribute to a higher degree of muscle damage which eventually overwhelms muscle regeneration capacity. While increased susceptibility of muscle to mechanical injury is thought to be an important contributor to disease pathology, it is becoming clear that not all DGC-associated diseases share this supposed hallmark feature. This paper outlines experimental support for a function of the DGC in preventing muscle damage and examines the evidence that supports novel functions for this complex in muscle that when impaired, may contribute to the pathogenesis of muscular dystrophy.
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Dorchies, Olivier M., Stéphanie Wagner, Ophélie Vuadens, Katri Waldhauser, Timo M. Buetler, Pavel Kucera, and Urs T. Ruegg. "Green tea extract and its major polyphenol (−)-epigallocatechin gallate improve muscle function in a mouse model for Duchenne muscular dystrophy." American Journal of Physiology-Cell Physiology 290, no. 2 (February 2006): C616—C625. http://dx.doi.org/10.1152/ajpcell.00425.2005.
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Duchenne muscular dystrophy is a frequent muscular disorder caused by mutations in the gene encoding dystrophin, a cytoskeletal protein that contributes to the stabilization of muscle fiber membrane during muscle activity. Affected individuals show progressive muscle wasting that generally causes death by age 30. In this study, the dystrophic mdx 5Cv mouse model was used to investigate the effects of green tea extract, its major component (−)-epigallocatechin gallate, and pentoxifylline on dystrophic muscle quality and function. Three-week-old mdx 5Cv mice were fed for either 1 or 5 wk a control chow or a chow containing the test substances. Histological examination showed a delay in necrosis of the extensor digitorum longus muscle in treated mice. Mechanical properties of triceps suræ muscles were recorded while the mice were under deep anesthesia. Phasic and tetanic tensions of treated mice were increased, reaching values close to those of normal mice. The phasic-to-tetanic tension ratio was corrected. Finally, muscles from treated mice exhibited 30–50% more residual force in a fatigue assay. These results demonstrate that diet supplementation of dystrophic mdx 5Cv mice with green tea extract or (−)-epigallocatechin gallate protected muscle against the first massive wave of necrosis and stimulated muscle adaptation toward a stronger and more resistant phenotype.
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Anderson, Judy E. "Myotube phospholipid synthesis and sarcolemmal ATPase activity in dystrophic (mdx) mouse muscle." Biochemistry and Cell Biology 69, no. 12 (December 1, 1991): 835–41. http://dx.doi.org/10.1139/o91-124.
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Phospholipid incorporation of 32P by primary myotube cultures and the tissue activity of sarcolemmal Na+/K+-transporting ATPase were studied to determine whether the absence of dystrophin from dystrophic (mdx) muscle would affect membrane lipid synthesis and membrane function. The incorporation of 32P by phospholipid as a ratio with total protein was greater in cultured dystrophic cells compared with control cells. The mdx cells also incorporated more 32P than control cells into phosphatidylethanolamine, which is thought to increase prior to myoblast fusion, and less into phosphatidylserine, phosphatidylinositol, and lysophosphatidylchoiine. There was no difference in total protein content or [3H]leucine or 32P incorporation into the aqueous fraction of dystrophic and control cells, although dystrophic cells incorporated less [35S]methionine into protein than controls. Isolated sarcolemma from mdx skeletal muscle tissue demonstrated a consistently greater specific activity of ouabain-sensitive Na+/K+-transporting ATPase than sarcolemmal preparations from control skeletal muscle. These observations suggest that cytoskeletal changes such as dystrophin deficiency may alter the differentiation of membrane composition and function.Key words: muscular dystrophy, mdx, myogenesis, sarcolemma, ouabain-sensitive ATPase, phospholipid.
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Culligan, Kevin, Niamh Banville, Paul Dowling, and Kay Ohlendieck. "Drastic reduction of calsequestrin-like proteins and impaired calcium binding in dystrophic mdx muscle." Journal of Applied Physiology 92, no. 2 (February 1, 2002): 435–45. http://dx.doi.org/10.1152/japplphysiol.00903.2001.
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Although the reduction in dystrophin-associated glycoproteins is the primary pathophysiological consequence of the deficiency in dystrophin, little is known about the secondary abnormalities leading to x-linked muscular dystrophy. As abnormal Ca2+ handling may be involved in myonecrosis, we investigated the fate of key Ca2+ regulatory membrane proteins in dystrophic mdx skeletal muscle membranes. Whereas the expression of the ryanodine receptor, the dihydropyridine receptor, the Ca2+-ATPase, and calsequestrin was not affected, a drastic decline in calsequestrin-like proteins of 150–220 kDa was observed in dystrophic microsomes using one-dimensional immunoblotting, two-dimensional immunoblotting with isoelectric focusing, diagonal two-dimensional blotting technique, and immunoprecipitation. In analogy, overall Ca2+ binding was reduced in the sarcoplasmic reticulum of dystrophic muscle. The reduction in Ca2+ binding proteins might be directly involved in triggering impaired Ca2+ sequestration within the lumen of the sarcoplasmic reticulum. Thus disturbed sarcolemmal Ca2+ fluxes seem to influence overall Ca2+homeostasis, resulting in distinct changes in the expression profile of a subset of Ca2+ handling proteins, which might be an important factor in the progressive functional decline of dystrophic muscle fibers.
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Koenig, Xaver, Lena Rubi, Gerald J. Obermair, Rene Cervenka, Xuan B. Dang, Peter Lukacs, Stefan Kummer, et al. "Enhanced currents through L-type calcium channels in cardiomyocytes disturb the electrophysiology of the dystrophic heart." American Journal of Physiology-Heart and Circulatory Physiology 306, no. 4 (February 15, 2014): H564—H573. http://dx.doi.org/10.1152/ajpheart.00441.2013.
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Duchenne muscular dystrophy (DMD), induced by mutations in the gene encoding for the cytoskeletal protein dystrophin, is an inherited disease characterized by progressive muscle weakness. Besides the relatively well characterized skeletal muscle degenerative processes, DMD is also associated with cardiac complications. These include cardiomyopathy development and cardiac arrhythmias. The current understanding of the pathomechanisms in the heart is very limited, but recent research indicates that dysfunctional ion channels in dystrophic cardiomyocytes play a role. The aim of the present study was to characterize abnormalities in L-type calcium channel function in adult dystrophic ventricular cardiomyocytes. By using the whole cell patch-clamp technique, the properties of currents through calcium channels in ventricular cardiomyocytes isolated from the hearts of normal and dystrophic adult mice were compared. Besides the commonly used dystrophin-deficient mdx mouse model for human DMD, we also used mdx-utr mice, which are both dystrophin- and utrophin-deficient. We found that calcium channel currents were significantly increased, and channel inactivation was reduced in dystrophic cardiomyocytes. Both effects enhance the calcium influx during an action potential (AP). Whereas the AP in dystrophic mouse cardiomyocytes was nearly normal, implementation of the enhanced dystrophic calcium conductance in a computer model of a human ventricular cardiomyocyte considerably prolonged the AP. Finally, the described dystrophic calcium channel abnormalities entailed alterations in the electrocardiograms of dystrophic mice. We conclude that gain of function in cardiac L-type calcium channels may disturb the electrophysiology of the dystrophic heart and thereby cause arrhythmias.
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Pelosi, Laura, Laura Forcina, Carmine Nicoletti, Bianca Maria Scicchitano, and Antonio Musarò. "Increased Circulating Levels of Interleukin-6 Induce Perturbation in Redox-Regulated Signaling Cascades in Muscle of Dystrophic Mice." Oxidative Medicine and Cellular Longevity 2017 (2017): 1–10. http://dx.doi.org/10.1155/2017/1987218.
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Duchenne muscular dystrophy (DMD) is an X-linked genetic disease in which dystrophin gene is mutated, resulting in dysfunctional or absent dystrophin protein. The pathology of dystrophic muscle includes degeneration, necrosis with inflammatory cell invasion, regeneration, and fibrous and fatty changes. Nevertheless, the mechanisms by which the absence of dystrophin leads to muscle degeneration remain to be fully elucidated. An imbalance between oxidant and antioxidant systems has been proposed as a secondary effect of DMD. However, the significance and precise extent of the perturbation in redox signaling cascades is poorly understood. We report that mdx dystrophic mice are able to activate a compensatory antioxidant response at the presymptomatic stage of the disease. In contrast, increased circulating levels of IL-6 perturb the redox signaling cascade, even prior to the necrotic stage, leading to severe features and progressive nature of muscular dystrophy.
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Hitaka, T., T. Mizutani, K. Watanabe, and T. Totsuka. "The high content of natural suppressor serine tRNA in dystrophic mouse muscle." Biochemical Journal 266, no. 1 (February 15, 1990): 201–6. http://dx.doi.org/10.1042/bj2660201.
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In order to gain an insight into the pathogenesis of mouse muscular dystrophy, we investigated the natural suppressor serine tRNA. The natural suppressor seryl-tRNA was distinguished from the other seryl-tRNAs on the basis of its specific property of being converted into phosphoseryl-tRNA by a tRNA kinase. On a wet-weight basis, the content of total tRNA in dystrophic muscles was 47% of that in normal muscles. Although the serine-accepting activities of tRNA were similar in muscles of 3-month-old dystrophic and normal mice, the ratio of [32P]phosphoseryl-tRNA (suppressor tRNA) to the total serine tRNA was significantly enhanced in dystrophic muscles compared with that in normal muscles. This high content of suppressor tRNA in dystrophic muscles was further confirmed by dot-blot hybridization experiments with the DNA probes CGTAGTCGGCAGGAT and CGCCCGAAAGGTGGAA for major tRNA(IGASer) and suppressor tRNA respectively. At the early postnatal age of 3 weeks, when only a week had elapsed since the first manifestation of the dystrophic symptom (hindleg dragging), the ratio of suppressor tRNA to major tRNAs in dystrophic hindleg muscles was abnormally increased. Thereafter it decreased with age in normal mice but remained almost unchanged in dystrophic mice. Consequently, at 3 months old, it was 1.7 times higher in dystrophic than in normal mice. The suppressor tRNA is now accepted to play a role in the synthesis of glutathione peroxidase. The present study showed that the content of this enzyme was abnormally elevated in dystrophic mice. Previously we had demonstrated that the docosahexaenoic (C22:6) acid content in phospholipids was decreased, possibly resulting from the enhanced oxidative milieu caused by the dystrophic condition. Thus far, the findings suggest that an increase in the contents of suppressor tRNA and glutathione peroxidase in dystrophic muscle may have been secondarily induced by such a highly oxidative state in the dystrophic condition. However, it is difficult to exclude the possibility that the natural suppressor tRNA plays a primary role in the pathogenesis of muscular dystrophies.
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Echigoya, Yusuke, Akinori Nakamura, Tetsuya Nagata, Nobuyuki Urasawa, Kenji Rowel Q. Lim, Nhu Trieu, Dharminder Panesar, et al. "Effects of systemic multiexon skipping with peptide-conjugated morpholinos in the heart of a dog model of Duchenne muscular dystrophy." Proceedings of the National Academy of Sciences 114, no. 16 (April 3, 2017): 4213–18. http://dx.doi.org/10.1073/pnas.1613203114.
Full textAbstract:
Duchenne muscular dystrophy (DMD) is a lethal genetic disorder caused by an absence of the dystrophin protein in bodywide muscles, including the heart. Cardiomyopathy is a leading cause of death in DMD. Exon skipping via synthetic phosphorodiamidate morpholino oligomers (PMOs) represents one of the most promising therapeutic options, yet PMOs have shown very little efficacy in cardiac muscle. To increase therapeutic potency in cardiac muscle, we tested a next-generation morpholino: arginine-rich, cell-penetrating peptide-conjugated PMOs (PPMOs) in the canine X-linked muscular dystrophy in Japan (CXMDJ) dog model of DMD. A PPMO cocktail designed to skip dystrophin exons 6 and 8 was injected intramuscularly, intracoronarily, or intravenously into CXMDJ dogs. Intravenous injections with PPMOs restored dystrophin expression in the myocardium and cardiac Purkinje fibers, as well as skeletal muscles. Vacuole degeneration of cardiac Purkinje fibers, as seen in DMD patients, was ameliorated in PPMO-treated dogs. Although symptoms and functions in skeletal muscle were not ameliorated by i.v. treatment, electrocardiogram abnormalities (increased Q-amplitude and Q/R ratio) were improved in CXMDJ dogs after intracoronary or i.v. administration. No obvious evidence of toxicity was found in blood tests throughout the monitoring period of one or four systemic treatments with the PPMO cocktail (12 mg/kg/injection). The present study reports the rescue of dystrophin expression and recovery of the conduction system in the heart of dystrophic dogs by PPMO-mediated multiexon skipping. We demonstrate that rescued dystrophin expression in the Purkinje fibers leads to the improvement/prevention of cardiac conduction abnormalities in the dystrophic heart.
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Srivastava, Niraj Kumar, Somnath Mukherjee, and Vijay Nath Mishra. "Metabolic Disturbance in Patients with Muscular Dystrophy and Reflection of Altered Enzyme Activity in Dystrophic Muscle: One Critical View." Journal of Biomedical Research & Environmental Sciences 1, no. 8 (December 2020): 393–403. http://dx.doi.org/10.37871/jbres1171.
Full textAbstract:
Muscular dystrophies are inherited myogenic diseases and considered by progressive muscle wasting and weakness with variable distribution and severity. The essential characteristics of muscular dystrophies are selective involvement, significant wasting and weakness of muscles. The most common and frequent types of muscular dystrophies are Duchenne Muscular Dystrophy (DMD), Becker Muscular Dystrophy (BMD), Facioscapulohumeral Dystrophy (FSHD) and Limb Girdle Muscular Dystrophy (LGMD). Metabolic disturbance is observed in muscular dystrophy patients (DMD, BMD, FSHD and LGMD-2B). Alteration in the level of metabolites (BCAA, Glu/ Gln, Ace, alanine, glucose, histidine, propionate, tyrosine and fumarate) in dystrophic muscle reflects the alteration in the activity of enzymes. Collectively, these observations propose that there is alteration in the rate of glycolysis, TCA cycle, fatty acid oxidation, gluconeogenesis pathway and protein metabolism (catabolism & anabolism) in the muscular dystrophy patients. Metabolic disturbance, further provide the explanation about the pathophysiology of muscular dystrophy.
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Hughes, K. J., A. Rodriguez, K. M. Flatt, S. Ray, A. Schuler, B. Rodemoyer, V. Veerappan, et al. "Physical exertion exacerbates decline in the musculature of an animal model of Duchenne muscular dystrophy." Proceedings of the National Academy of Sciences 116, no. 9 (February 12, 2019): 3508–17. http://dx.doi.org/10.1073/pnas.1811379116.
Full textAbstract:
Duchenne muscular dystrophy (DMD) is a genetic disorder caused by loss of the protein dystrophin. In humans, DMD has early onset, causes developmental delays, muscle necrosis, loss of ambulation, and death. Current animal models have been challenged by their inability to model the early onset and severity of the disease. It remains unresolved whether increased sarcoplasmic calcium observed in dystrophic muscles follows or leads the mechanical insults caused by the muscle’s disrupted contractile machinery. This knowledge has important implications for patients, as potential physiotherapeutic treatments may either help or exacerbate symptoms, depending on how dystrophic muscles differ from healthy ones. Recently we showed how burrowing dystrophic (dys-1) C. elegans recapitulate many salient phenotypes of DMD, including loss of mobility and muscle necrosis. Here, we report that dys-1 worms display early pathogenesis, including dysregulated sarcoplasmic calcium and increased lethality. Sarcoplasmic calcium dysregulation in dys-1 worms precedes overt structural phenotypes (e.g., mitochondrial, and contractile machinery damage) and can be mitigated by reducing calmodulin expression. To learn how dystrophic musculature responds to altered physical activity, we cultivated dys-1 animals in environments requiring high intensity or high frequency of muscle exertion during locomotion. We find that several muscular parameters (e.g., size) improve with increased activity. However, longevity in dystrophic animals was negatively associated with muscular exertion, regardless of effort duration. The high degree of phenotypic conservation between dystrophic worms and humans provides a unique opportunity to gain insight into the pathology of the disease as well as the initial assessment of potential treatment strategies.
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Yeadon, J. E., H. Lin, S. M. Dyer, and S. J. Burden. "Dystrophin is a component of the subsynaptic membrane." Journal of Cell Biology 115, no. 4 (November 15, 1991): 1069–76. http://dx.doi.org/10.1083/jcb.115.4.1069.
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A subsynaptic protein of Mr approximately 300 kD is a major component of Torpedo electric organ postsynaptic membranes and copurifies with the AChR and the 43-kD subsynaptic protein. mAbs against this protein react with neuromuscular synapses in higher vertebrates, but not at synapses in dystrophic muscle. The Torpedo 300-kD protein comigrates in SDS-PAGE with murine dystrophin and reacts with antibodies against murine dystrophin. The sequence of a partial cDNA isolated by screening an expression library with mAbs against the Torpedo 300-kD protein shows striking homology to mammalian dystrophin, and in particular to the b isoform of dystrophin. These results indicate that dystrophin is a component of the postsynaptic membrane at neuromuscular synapses and raise the possibility that loss of dystrophin from synapses in dystrophic muscle may have consequences that contribute to muscular dystrophy.
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Vieira, Natassia M., Janelle M. Spinazzola, Matthew S. Alexander, Yuri B. Moreira, Genri Kawahara, Devin E. Gibbs, Lillian C. Mead, Sergio Verjovski-Almeida, Mayana Zatz, and Louis M. Kunkel. "Repression of phosphatidylinositol transfer protein α ameliorates the pathology of Duchenne muscular dystrophy." Proceedings of the National Academy of Sciences 114, no. 23 (May 22, 2017): 6080–85. http://dx.doi.org/10.1073/pnas.1703556114.
Full textAbstract:
Duchenne muscular dystrophy (DMD) is a progressive muscle wasting disease caused by X-linked inherited mutations in the DYSTROPHIN (DMD) gene. Absence of dystrophin protein from the sarcolemma causes severe muscle degeneration, fibrosis, and inflammation, ultimately leading to cardiorespiratory failure and premature death. Although there are several promising strategies under investigation to restore dystrophin protein expression, there is currently no cure for DMD, and identification of genetic modifiers as potential targets represents an alternative therapeutic strategy. In a Brazilian golden retriever muscular dystrophy (GRMD) dog colony, two related dogs demonstrated strikingly mild dystrophic phenotypes compared with those typically observed in severely affected GRMD dogs despite lacking dystrophin. Microarray analysis of these “escaper” dogs revealed reduced expression of phosphatidylinositol transfer protein-α (PITPNA) in escaper versus severely affected GRMD dogs. Based on these findings, we decided to pursue investigation of modulation of PITPNA expression on dystrophic pathology in GRMD dogs, dystrophin-deficient sapje zebrafish, and human DMD myogenic cells. In GRMD dogs, decreased expression of Pitpna was associated with increased phosphorylated Akt (pAkt) expression and decreased PTEN levels. PITPNA knockdown by injection of morpholino oligonucleotides in sapje zebrafish also increased pAkt, rescued the abnormal muscle phenotype, and improved long-term sapje mutant survival. In DMD myotubes, PITPNA knockdown by lentiviral shRNA increased pAkt and increased myoblast fusion index. Overall, our findings suggest PIPTNA as a disease modifier that accords benefits to the abnormal signaling, morphology, and function of dystrophic skeletal muscle, and may be a target for DMD and related neuromuscular diseases.
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van Westering, Tirsa L. E., Henrik J. Johansson, Britt Hanson, Anna M. L. Coenen-Stass, Yulia Lomonosova, Jun Tanihata, Norio Motohashi, et al. "Mutation-independent Proteomic Signatures of Pathological Progression in Murine Models of Duchenne Muscular Dystrophy." Molecular & Cellular Proteomics 19, no. 12 (September 29, 2020): 2047–67. http://dx.doi.org/10.1074/mcp.ra120.002345.
Full textAbstract:
The absence of the dystrophin protein in Duchenne muscular dystrophy (DMD) results in myofiber fragility and a plethora of downstream secondary pathologies. Although a variety of experimental therapies are in development, achieving effective treatments for DMD remains exceptionally challenging, not least because the pathological consequences of dystrophin loss are incompletely understood. Here we have performed proteome profiling in tibialis anterior muscles from two murine DMD models (mdx and mdx52) at three ages (8, 16, and 80 weeks of age), all n = 3. High-resolution isoelectric focusing liquid chromatography-tandem MS (HiRIEF-LC–MS/MS) was used to quantify the expression of 4974 proteins across all 27 samples. The two dystrophic models were found to be highly similar, whereas multiple proteins were differentially expressed relative to WT (C57BL/6) controls at each age. Furthermore, 1795 proteins were differentially expressed when samples were pooled across ages and dystrophic strains. These included numerous proteins associated with the extracellular matrix and muscle function that have not been reported previously. Pathway analysis revealed multiple perturbed pathways and predicted upstream regulators, which together are indicative of cross-talk between inflammatory, metabolic, and muscle growth pathways (e.g. TNF, INFγ, NF-κB, SIRT1, AMPK, PGC-1α, PPARs, ILK, and AKT/PI3K). Upregulation of CAV3, MVP and PAK1 protein expression was validated in dystrophic muscle by Western blot. Furthermore, MVP was upregulated during, but not required for, the differentiation of C2C12 myoblasts suggesting that this protein may affect muscle regeneration. This study provides novel insights into mutation-independent proteomic signatures characteristic of the dystrophic phenotype and its progression with aging.
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Sarkozy, Anna, Mariacristina Scoto, Francesco Muntoni, and Joana Domingos. "Dystrophinopathies and Limb-Girdle Muscular Dystrophies." Neuropediatrics 48, no. 04 (April 20, 2017): 262–72. http://dx.doi.org/10.1055/s-0037-1601860.
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AbstractMuscular dystrophies are a heterogeneous group of inherited diseases. The natural history of these disorders along with their management have changed mainly due to a better understanding of their pathophysiology, the evolution of standards of care, and new treatment options. Dystrophinopathies include both Duchenne's and Becker's muscular dystrophies, but in reality they are a spectrum of muscle diseases caused by mutations in the gene that encodes the protein dystrophin. Duchenne's muscular dystrophy is the most common form of inherited muscle disease of childhood. The current standards of care considerably prolong independent ambulation and survival. Several therapeutic options either aiming at substituting/correcting the primary protein defect or limiting the progression of the dystrophic process are currently being explored in clinical trials.Limb-girdle muscular dystrophies (LGMDs) are rare and heterogeneous conditions, characterized by weakness and wasting of the pelvic and shoulder girdle muscles. Originally classified into dominant and recessive, > 30 genetic forms of LGMDs are currently recognized. Further understanding of the pathogenic mechanisms of LGMD will help identifying novel therapeutic approaches that can be tested in clinical trials.
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Iyer, Shama R., Sameer B. Shah, Christopher W. Ward, Joseph P. Stains, Espen E. Spangenburg, Eric S. Folker, and Richard M. Lovering. "Differential YAP nuclear signaling in healthy and dystrophic skeletal muscle." American Journal of Physiology-Cell Physiology 317, no. 1 (July 1, 2019): C48—C57. http://dx.doi.org/10.1152/ajpcell.00432.2018.
Full textAbstract:
Mechanical forces regulate muscle development, hypertrophy, and homeostasis. Force-transmitting structures allow mechanotransduction at the sarcolemma, cytoskeleton, and nuclear envelope. There is growing evidence that Yes-associated protein (YAP) serves as a nuclear relay of mechanical signals and can induce a range of downstream signaling cascades. Dystrophin is a sarcolemma-associated protein, and its absence underlies the pathology in Duchenne muscular dystrophy. We tested the hypothesis that the absence of dystrophin in muscle would result in reduced YAP signaling in response to loading. Following in vivo contractile loading in muscles of healthy (wild-type; WT) mice and mice lacking dystrophin ( mdx), we performed Western blots of whole and fractionated muscle homogenates to examine the ratio of phospho (cytoplasmic) YAP to total YAP and nuclear YAP, respectively. We show that in vivo contractile loading induced a robust increase in YAP expression and its nuclear localization in WT muscles. Surprisingly, in mdx muscles, active YAP expression was constitutively elevated and unresponsive to load. Results from qRT-PCR analysis support the hyperactivation of YAP in vivo in mdx muscles, as evidenced by increased gene expression of YAP downstream targets. In vitro assays of isolated myofibers plated on substrates with high stiffness showed YAP nuclear labeling for both genotypes, indicating functional YAP signaling in mdx muscles. We conclude that while YAP signaling can occur in the absence of dystrophin, dystrophic muscles have altered mechanotransduction, whereby constitutively active YAP results in a failure to respond to load, which could be attributed to the increased state of “pre-stress” with increased cytoskeletal and extracellular matrix stiffness.
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Carberry, Steven, Margit Zweyer, Dieter Swandulla, and Kay Ohlendieck. "Profiling of Age-Related Changes in theTibialis AnteriorMuscle Proteome of the mdx Mouse Model of Dystrophinopathy." Journal of Biomedicine and Biotechnology 2012 (2012): 1–11. http://dx.doi.org/10.1155/2012/691641.
Full textAbstract:
X-linked muscular dystrophy is a highly progressive disease of childhood and characterized by primary genetic abnormalities in the dystrophin gene. Senescent mdx specimens were used for a large-scale survey of potential age-related alterations in the dystrophic phenotype, because the established mdx animal model of dystrophinopathy exhibits progressive deterioration of muscle tissue with age. Since the mdxtibialis anteriormuscle is a frequently used model system in muscular dystrophy research, we employed this particular muscle to determine global changes in the dystrophic skeletal muscle proteome. The comparison of mdx mice aged 8 weeks versus 22 months by mass-spectrometry-based proteomics revealed altered expression levels in 8 distinct protein species. Increased levels were shown for carbonic anhydrase, aldolase, and electron transferring flavoprotein, while the expressions of pyruvate kinase, myosin, tropomyosin, and the small heat shock protein Hsp27 were found to be reduced in aged muscle. Immunoblotting confirmed age-dependent changes in the density of key muscle proteins in mdx muscle. Thus, segmental necrosis in mdxtibialis anteriormuscle appears to trigger age-related protein perturbations due to dystrophin deficiency. The identification of novel indicators of progressive muscular dystrophy might be useful for the establishment of a muscle subtype-specific biomarker signature of dystrophinopathy.
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Sitzia, Clementina, Andrea Farini, Federica Colleoni, Francesco Fortunato, Paola Razini, Silvia Erratico, Alessandro Tavelli, et al. "Improvement of Endurance of DMD Animal Model Using Natural Polyphenols." BioMed Research International 2015 (2015): 1–17. http://dx.doi.org/10.1155/2015/680615.
Full textAbstract:
Duchenne muscular dystrophy (DMD), the most common form of muscular dystrophy, is characterized by muscular wasting caused by dystrophin deficiency that ultimately ends in force reduction and premature death. In addition to primary genetic defect, several mechanisms contribute to DMD pathogenesis. Recently, antioxidant supplementation was shown to be effective in the treatment of multiple diseases including muscular dystrophy. Different mechanisms were hypothesized such as reduced hydroxyl radicals, nuclear factor-κB deactivation, and NO protection from inactivation. Following these promising evidences, we investigated the effect of the administration of a mix of dietary natural polyphenols (ProAbe) on dystrophic mdx mice in terms of muscular architecture and functionality. We observed a reduction of muscle fibrosis deposition and myofiber necrosis together with an amelioration of vascularization. More importantly, the recovery of the morphological features of dystrophic muscle leads to an improvement of the endurance of treated dystrophic mice. Our data confirmed that ProAbe-based diet may represent a strategy to coadjuvate the treatment of DMD.
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Yu, Lu, Xiaoli Zhang, Yexin Yang, Dan Li, Kaiyuan Tang, Zifan Zhao, Wanwan He, et al. "Small-molecule activation of lysosomal TRP channels ameliorates Duchenne muscular dystrophy in mouse models." Science Advances 6, no. 6 (February 2020): eaaz2736. http://dx.doi.org/10.1126/sciadv.aaz2736.
Full textAbstract:
Duchenne muscular dystrophy (DMD) is a devastating disease caused by mutations in dystrophin that compromise sarcolemma integrity. Currently, there is no treatment for DMD. Mutations in transient receptor potential mucolipin 1 (ML1), a lysosomal Ca2+ channel required for lysosomal exocytosis, produce a DMD-like phenotype. Here, we show that transgenic overexpression or pharmacological activation of ML1 in vivo facilitates sarcolemma repair and alleviates the dystrophic phenotypes in both skeletal and cardiac muscles of mdx mice (a mouse model of DMD). Hallmark dystrophic features of DMD, including myofiber necrosis, central nucleation, fibrosis, elevated serum creatine kinase levels, reduced muscle force, impaired motor ability, and dilated cardiomyopathies, were all ameliorated by increasing ML1 activity. ML1-dependent activation of transcription factor EB (TFEB) corrects lysosomal insufficiency to diminish muscle damage. Hence, targeting lysosomal Ca2+ channels may represent a promising approach to treat DMD and related muscle diseases.
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Schertzer, Jonathan D., James G. Ryall, and Gordon S. Lynch. "Systemic administration of IGF-I enhances oxidative status and reduces contraction-induced injury in skeletal muscles of mdx dystrophic mice." American Journal of Physiology-Endocrinology and Metabolism 291, no. 3 (September 2006): E499—E505. http://dx.doi.org/10.1152/ajpendo.00101.2006.
Full textAbstract:
The absence of dystrophin and resultant disruption of the dystrophin glycoprotein complex renders skeletal muscles of dystrophic patients and dystrophic mdx mice susceptible to contraction-induced injury. Strategies to reduce contraction-induced injury are of critical importance, because this mode of damage contributes to the etiology of myofiber breakdown in the dystrophic pathology. Transgenic overexpression of insulin-like growth factor-I (IGF-I) causes myofiber hypertrophy, increases force production, and can improve the dystrophic pathology in mdx mice. In contrast, the predominant effect of continuous exogenous administration of IGF-I to mdx mice at a low dose (1.0–1.5 mg·kg−1·day−1) is a shift in muscle phenotype from fast glycolytic toward a more oxidative, fatigue-resistant, slow muscle without alterations in myofiber cross-sectional area, muscle mass, or maximum force-producing capacity. We found that exogenous administration of IGF-I to mdx mice increased myofiber succinate dehydrogenase activity, shifted the overall myosin heavy chain isoform composition toward a slower phenotype, and, most importantly, reduced contraction-induced damage in tibialis anterior muscles. The deficit in force-producing capacity after two damaging lengthening contractions was reduced significantly in tibialis anterior muscles of IGF-I-treated (53 ± 4%) compared with untreated mdx mice (70 ± 5%, P < 0.05). The results provide further evidence that IGF-I administration can enhance the functional properties of dystrophic skeletal muscle and, compared with results in transgenic mice or virus-mediated overexpression, highlight the disparities in different models of endocrine factor delivery.
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Srivastava, U. S., E. A. Sugden, P. K. Majumdar, M. L. Thakur, and G. M. Bhatnagar. "Biochemical changes in progressive muscular dystrophy. XIV. Skeletal muscle myosin mRNA translatability in dystrophic mice." Biochemistry and Cell Biology 65, no. 9 (September 1, 1987): 833–41. http://dx.doi.org/10.1139/o87-108.
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Variations in the content and translatability of the poly(A)+ RNA and mRNA molecules coding for myosin (M) were studied in the hind leg muscles of genetically dystrophic mice. The poly(A)+ RNA content of total skeletal muscle failed to increase normally during progression of the disease. M mRNA, isolated from dystrophic murine muscle poly(A)+ RNA, was mostly found to be associated with the 26S RNA species. The translation of M mRNA in an in vitro heterologous wheat germ system was lower at 8 and 16 weeks in the dystrophic group as compared with the controls. Analysis of the translation products via sodium dodecyl sulfate – polyacrylamide gel electrophoresis, autoradiography, and densitometric autoradiographic tracing demonstrated the gradual disappearance of a protein band corresponding to M, the major component of skeletal muscle. cDNA was synthesized, using M mRNA that was isolated and purified from normal and dystrophic mouse muscle as a template. Total radioactivity was measured in some cDNA fractions produced from normal and dystrophic mouse muscle, while other fractions were utilized for separation and sizing of cDNA by disc gel electrophoresis. The cDNA from normal muscle was hybridized with M mRNA from normal and 16-week-old dystrophic mouse muscles. The cDNA probe, hybridization experiments, and studies involving the content and synthesis of M mRNA suggest that murine muscular dystrophy elicited a shorter species of mRNA or shorter sequences of the same species of mRNA coding for M. Not all poly(A)+ mRNA sequences coding for M, found in control mice, were present in their dystrophic counterparts. In conclusion, it appears that murine muscular dystrophy produces a shorter species of pre-M mRNA via decreased polynucleotide elongation.
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Koenig, Xaver, Janine Ebner, and Karlheinz Hilber. "Voltage-Dependent Sarcolemmal Ion Channel Abnormalities in the Dystrophin-Deficient Heart." International Journal of Molecular Sciences 19, no. 11 (October 23, 2018): 3296. http://dx.doi.org/10.3390/ijms19113296.
Full textAbstract:
Mutations in the gene encoding for the intracellular protein dystrophin cause severe forms of muscular dystrophy. These so-called dystrophinopathies are characterized by skeletal muscle weakness and degeneration. Dystrophin deficiency also gives rise to considerable complications in the heart, including cardiomyopathy development and arrhythmias. The current understanding of the pathomechanisms in the dystrophic heart is limited, but there is growing evidence that dysfunctional voltage-dependent ion channels in dystrophin-deficient cardiomyocytes play a significant role. Herein, we summarize the current knowledge about abnormalities in voltage-dependent sarcolemmal ion channel properties in the dystrophic heart, and discuss the potentially underlying mechanisms, as well as their pathophysiological relevance.
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Jakubiec-Puka, Anna, Donatella Biral, Kazimierz Krawczyk, and Romeo Betto. "Ultrastructure of diaphragm from dystrophic alpha-sarcoglycan-null mice." Acta Biochimica Polonica 52, no. 2 (June 30, 2005): 453–60. http://dx.doi.org/10.18388/abp.2005_3459.
Full textAbstract:
alpha-Sarcoglycan is a 50 kDa single-pass transmembrane glycoprotein exclusively expressed in striated muscle that, together with beta-, gamma-, and delta-sarcoglycan, forms a sub-complex at the muscle fibre cell membrane. The sarcoglycans are components of the dystrophin-associated glycoprotein (DAG) complex which forms a mechanical link between the intracellular cytoskeleton and extracellular matrix. The DAG complex function is to protect the muscle membrane from the stress of contractile activity and as a structure for the docking of signalling proteins. Genetic defects of DAG components cause muscular dystrophies. A lack or defects of alpha-sarcoglycan causes the severe type 2D limb girdle muscular dystrophy. alpha-Sarcoglycan-null (Sgca-null) mice develop progressive muscular dystrophy similar to the human disorder. This animal model was used in the present work for an ultrastructural study of diaphragm muscle. Diaphragm from Sgca-null mouse presents a clear dystrophic phenotype, with necrosis, regeneration, fibre hypertrophy and splitting, excess of collagen and fatty infiltration. Some abnormalities were also observed, such as centrally located nuclei of abnormal shape, fibres containing inclusion bodies within the contractile structure, and fibres with electron-dense material dispersed over almost the entire cell. Additionally, unusual interstitial cells of uncertain identity were detected within muscle fibres. The abnormal ultrastructure of the diaphragm from Sgca-null mice is discussed.
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Pákozdy, Á., M. Leschnik, B. Nell, U. Kolm, Z. Virányi, B. Belényi, M. Molnár, and T. Bilzer. "Myotonic dystrophy in two European grey wolves ( Canis lupus )." Acta Veterinaria Hungarica 55, no. 1 (March 1, 2007): 87–95. http://dx.doi.org/10.1556/avet.55.2007.1.9.
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Two related European Grey wolves ( Canis lupus ) with the history of muscle stiffness beginning at 2 weeks of age were examined in this study. Muscle tone and muscle mass were increased in both animals. Muscle stiffness was worsened by stress so that the animals fell into lateral recumbency. Blood chemistry revealed mildly increased serum creatine kinase activity. Abnormal potentials typical of myotonic discharges were recorded by electromyography. Cataract, first-degree atrioventricular (AV) block and inhomogeneous myocardial texture by ultrasound suggested extramuscular involvement. Myopathology demonstrated dystrophic signs in the muscle biopsy specimen. The presumptive diagnosis based on the in vivo findings was myotonic dystrophy. Immunochemistry of the striated muscles revealed focal absence of dystrophin 1 and beta-dystroglycan in both cases. Cardiac and ophthalmologic involvement suggested a disorder very similar to a human form of myotonic dystrophy. This is the first description of myotonic dystrophy in wolves.
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Kiriaev, Leonit, Sindy Kueh, John W. Morley, Kathryn N. North, Peter J. Houweling, and Stewart I. Head. "Branched fibers from old fast-twitch dystrophic muscles are the sites of terminal damage in muscular dystrophy." American Journal of Physiology-Cell Physiology 314, no. 6 (June 1, 2018): C662—C674. http://dx.doi.org/10.1152/ajpcell.00161.2017.
Full textAbstract:
A striking pathological feature of dystrophinopathies is the presence of morphologically abnormal branched skeletal muscle fibers. The deterioration of muscle contractile function in Duchenne muscular dystrophy is accompanied by both an increase in number and complexity of these branched fibers. We propose that when number and complexity of branched fibers reaches a critical threshold, or “tipping point,” the branches in and of themselves are the site of contraction-induced rupture. In the present study, we use the dystrophic mdx mouse and littermate controls to study the prediseased dystrophic fast-twitch extensor digitorum longus (EDL) muscle at 2–3 wk, the peak myonecrotic phase at 6–9 wk, and finally, “old,” at 58–112 wk. Using a combination of isolated muscle function contractile measurements coupled with single-fiber imaging and confocal microscope imaging of cleared whole muscles, we identified a distinct pathophysiology, acute fiber rupture at branch nodes, which occurs in “old” fast-twitch EDL muscle approaching the end stage of the dystrophinopathy muscle disease, where the EDL muscles are entirely composed of complexed branched fibers. This evidence supports our concept of “tipping point” where the number and extent of fiber branching reach a level where the branching itself terminally compromises muscle function, irrespective of the absence of dystrophin.
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Hayes, Alan, and David A. Williams. "Contractile properties of clenbuterol-treatedmdx muscle are enhanced by low-intensity swimming." Journal of Applied Physiology 82, no. 2 (February 1, 1997): 435–39. http://dx.doi.org/10.1152/jappl.1997.82.2.435.
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Hayes, Alan, and David A. Williams. Contractile properties of clenbuterol-treated mdxmuscle are enhanced by low-intensity swimming. J. Appl. Physiol. 82(2): 435–439, 1997.—The β2-agonist clenbuterol has potent anabolic properties in normal and denervated muscle and, as such, may be of use in muscle wasting diseases such as muscular dystrophy. However, potential side effects such as the transformation of the fiber type pool toward increased proportions of fast-twitch fibers must be balanced with the beneficial anabolic properties. In the present report, we clearly show that extensor digitorum longus and soleus muscles from dystrophic mdxmice exposed to a combination of clenbuterol and low-intensity endurance swimming exercise did not undergo the slow- to fast-twitch fiber transformations caused by clenbuterol administration alone, yet increases in the force-generating capacity of the soleus (30–40%) that resulted from the clenbuterol treatment were maintained after the swimming program. The increased sensitivity of dystrophin-deficient dystrophic muscle to clenbuterol and low-intensity exercise that is evident in this study may have therapeutic implications in the treatment of muscle wasting diseases.
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Matsumura, Cíntia Yuri, Ana Paula Tiemi Taniguti, Adriana Pertille, Humberto Santo Neto, and Maria Julia Marques. "Stretch-activated calcium channel protein TRPC1 is correlated with the different degrees of the dystrophic phenotype in mdx mice." American Journal of Physiology-Cell Physiology 301, no. 6 (December 2011): C1344—C1350. http://dx.doi.org/10.1152/ajpcell.00056.2011.
Full textAbstract:
In Duchenne muscular dystrophy (DMD) and in the mdx mouse model of DMD, the lack of dystrophin is related to enhanced calcium influx and muscle degeneration. Stretch-activated channels (SACs) might be directly involved in the pathology of DMD, and transient receptor potential cation channels have been proposed as likely candidates of SACs. We investigated the levels of transient receptor potential canonical channel 1 (TRPC1) and the effects of streptomycin, a SAC blocker, in muscles showing different degrees of the dystrophic phenotype. Mdx mice (18 days old, n = 16) received daily intraperitoneal injections of streptomycin (182 mg/kg body wt) for 18 days, followed by removal of the diaphragm, sternomastoid (STN), biceps brachii, and tibialis anterior muscles. Control mdx mice ( n = 37) were injected with saline. Western blot analysis showed higher levels of TRPC1 in diaphragm muscle compared with STN and limb muscles. Streptomycin reduced creatine kinase and prevented exercise-induced increases of total calcium and Evans blue dye uptake in diaphragm and in STN muscles. It is suggested that different levels of the stretch-activated calcium channel protein TRPC1 may contribute to the different degrees of the dystrophic phenotype seen in mdx mice. Early treatment designed to regulate the activity of these channels may ameliorate the progression of dystrophy in the most affected muscle, the diaphragm.
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Niebrój-Dobosz, Irena, and Irena Hausmanowa-Petrusewicz. "The involvement of oxidative stress in determining the severity and progress of pathological processes in dystrophin-deficient muscles." Acta Biochimica Polonica 52, no. 2 (May 25, 2005): 449–52. http://dx.doi.org/10.18388/abp.2005_3458.
Full textAbstract:
In both forms of muscular dystrophy, the severe Duchenne's muscular dystrophy (DMD) with lifespan shortened to about 20 years and the milder Becker dystrophy (BDM) with normal lifespan, the gene defect is located at chromosome locus Xp21. The location is the same in the experimental model of DMD in the mdx mice. As the result of the gene defect a protein called dystrophin is either not synthesized, or is produced in traces. Although the structure of this protein is rather well established there are still many controversies about the dystrophin function. The most accepted suggestion supposes that it stabilizes sarcolemma in the course of the contraction-relaxation cycle. Solving the problem of dystrophin function is a prerequisite for introduction of an effective therapy. Among the different factors which might be responsible for the appearance and progress of dystrophic changes in muscles there is an excessive action of oxidative stress. In this review data indicating the influence of oxidative stress on the severity of the pathologic processes in dystrophy are discussed. Several pieces of data indicating the action of oxidative damage to different macromolecules in DMD/BDM are presented. Special attention is devoted to the degree of oxidative damage to muscle proteins, the activity of neuronal nitric oxide synthase (nNOS) and their involvement in defining the severity of the dystrophic processes. It is indicated that the severity of the morbid process is related to the degree of oxidative damage to muscle proteins and the decrease of the nNOS activity in muscles. Estimation of the degree of the destructive action of oxidative stress in muscular dystrophy may be a useful marker facilitating introduction of an effective antioxidant therapy and regulation of nNOS activity.
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Wieneke, Sascha, Peter Heimann, Sigalit Leibovitz, Uri Nudel, and Harald Jockusch. "Acute pathophysiological effects of muscle-expressed Dp71 transgene on normal and dystrophic mouse muscle." Journal of Applied Physiology 95, no. 5 (November 2003): 1861–66. http://dx.doi.org/10.1152/japplphysiol.00326.2003.
Full textAbstract:
products of the dystrophin gene range from the 427-kDa full-length dystrophin to the 70.8-kDa Dp71. Dp427 is expressed in skeletal muscle, where it links the actin cytoskeleton with the extracellular matrix via a complex of dystrophin-associated proteins (DAPs). Dystrophin deficiency disrupts the DAP complex and causes muscular dystrophy in humans and the mdx mouse. Dp71, the major nonmuscle product, consists of the COOH-terminal part of dystrophin, including the binding site for the DAP complex but lacks binding sites for microfilaments. Dp71 transgene (Dp71tg) expressed in mdx muscle restores the DAP complex but does not prevent muscle degeneration. In wild-type (WT) mouse muscle, Dp71tg causes a mild muscular dystrophy. In this study, we tested, using isolated extensor digitorum longus muscles, whether Dp71tg exerts acute influences on force generation and sarcolemmal stress resistance. In WT muscles, there was no effect on isometric twitch and tetanic force generation, but with a cytomegalovirus promotor-driven transgene, contraction with stretch led to sarcolemmal ruptures and irreversible loss of tension. In MDX muscle, Dp71tg reduced twitch and tetanic tension but did not aggravate sarcolemmal fragility. The adverse effects of Dp71 in muscle are probably due to its competition with dystrophin and utrophin (in MDX muscle) for binding to the DAP complex.
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Saotome, Masao, Yuji Yoshitomi, Shunichi Kojima, and Morio Kuramochi. "Dilated Cardiomyopathy of Becker-Type Muscular Dystrophy with Exon 4 Deletion." Angiology 52, no. 5 (May 2001): 343–47. http://dx.doi.org/10.1177/000331970105200508.
Full textAbstract:
The authors report a 47-year-old man with Becker-type muscular dystrophy presenting with dilated cardiomyopathy. Left ventriculography showed diffuse severe hypokinesia: left ventric ular end-diastolic volume index 193 mL/m2, left ventricular end-systolic volume index 143 mL/m 2, and left ventricular ejection fraction 26%. Skeletal muscle biopsy demonstrated a dystrophic process. Genetic analysis revealed a deletion of exon 4. There was a difference in immunos taining pattern between skeletal muscles and cardiac muscles. Severe cardiac dysfunction in this case may be associated with the damage in dystrophin-deficient fibers.
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Raimondo, Theresa M., and David J. Mooney. "Anti-inflammatory nanoparticles significantly improve muscle function in a murine model of advanced muscular dystrophy." Science Advances 7, no. 26 (June 2021): eabh3693. http://dx.doi.org/10.1126/sciadv.abh3693.
Full textAbstract:
Chronic inflammation contributes to the pathogenesis of all muscular dystrophies. Inflammatory T cells damage muscle, while regulatory T cells (Tregs) promote regeneration. We hypothesized that providing anti-inflammatory cytokines in dystrophic muscle would promote proregenerative immune phenotypes and improve function. Primary T cells from dystrophic (mdx) mice responded appropriately to inflammatory or suppressive cytokines. Subsequently, interleukin-4 (IL-4)– or IL-10–conjugated gold nanoparticles (PA4, PA10) were injected into chronically injured, aged, mdx muscle. PA4 and PA10 increased T cell recruitment, with PA4 doubling CD4+/CD8− T cells versus controls. Further, 50% of CD4+/CD8− T cells were immunosuppressive Tregs following PA4, versus 20% in controls. Concomitant with Treg recruitment, muscles exhibited increased fiber area and fourfold increases in contraction force and velocity versus controls. The ability of PA4 to shift immune responses, and improve dystrophic muscle function, suggests that immunomodulatory treatment may benefit many genetically diverse muscular dystrophies, all of which share inflammatory pathology.
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Mázala, Davi A. G., Robert W. Grange, and Eva R. Chin. "The role of proteases in excitation-contraction coupling failure in muscular dystrophy." American Journal of Physiology-Cell Physiology 308, no. 1 (January 1, 2015): C33—C40. http://dx.doi.org/10.1152/ajpcell.00267.2013.
Full textAbstract:
Duchenne muscular dystrophy (DMD) is one of the most frequent types of muscular dystrophy. Alterations in intracellular calcium (Ca2+) handling are thought to contribute to the disease severity in DMD, possibly due to the activation of Ca2+-activated proteases. The purpose of this study was twofold: 1) to determine whether prolonged excitation-contraction (E-C) coupling disruption following repeated contractions is greater in animals lacking both dystrophin and utrophin ( mdx/Utr−/−) compared with mice lacking only dystrophin ( mdx); and 2) to assess whether protease inhibition can prevent E-C coupling failure following repeated tetani in these dystrophic mouse models. Excitation-contraction coupling was assessed using Fura-2 ratio, as an index of intracellular free Ca2+ concentration, in response to electrical stimulation of single muscle fibers from the flexor digitorum brevis muscle. Resting Fura-2 ratio was higher in dystrophic compared with control (Con) fibers, but peak Fura-2 ratios during stimulation were similar in dystrophic and Con fibers. One hour after a series of repeated tetani, peak Fura-2 ratios were reduced by 30 ± 5.6%, 23 ± 2%, and 36 ± 3.1% in mdx, mdx/Utr+/−, and mdx/Utr−/−, respectively, with the greatest reduction in mdx/Utr−/− fibers ( P < 0.05). Protease inhibition attenuated this decrease in peak Fura-2 ratio. These data indicate that E-C coupling impairment after repeated contractions is greatest in fibers lacking both dystrophin and utrophin and that prevention of protease activation can mitigate the prolonged E-C coupling impairment. These data further suggest that acute protease inhibition may be useful in reducing muscle weakness in DMD.
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Niranjan, Nandita, Satvik Mareedu, Yimin Tian, Kasun Kodippili, Nadezhda Fefelova, Antanina Voit, Lai-Hua Xie, Dongsheng Duan, and Gopal J. Babu. "Sarcolipin overexpression impairs myogenic differentiation in Duchenne muscular dystrophy." American Journal of Physiology-Cell Physiology 317, no. 4 (October 1, 2019): C813—C824. http://dx.doi.org/10.1152/ajpcell.00146.2019.
Full textAbstract:
Reduction in the expression of sarcolipin (SLN), an inhibitor of sarco(endo)plasmic reticulum (SR) Ca2+-ATPase (SERCA), ameliorates severe muscular dystrophy in mice. However, the mechanism by which SLN inhibition improves muscle structure remains unclear. Here, we describe the previously unknown function of SLN in muscle differentiation in Duchenne muscular dystrophy (DMD). Overexpression of SLN in C2C12 resulted in decreased SERCA pump activity, reduced SR Ca2+ load, and increased intracellular Ca2+ ([Formula: see text]) concentration. In addition, SLN overexpression resulted in altered expression of myogenic markers and poor myogenic differentiation. In dystrophin-deficient dog myoblasts and myotubes, SLN expression was significantly high and associated with defective [Formula: see text] cycling. The dystrophic dog myotubes were less branched and associated with decreased autophagy and increased expression of mitochondrial fusion and fission proteins. Reduction in SLN expression restored these changes and enhanced dystrophic dog myoblast fusion during differentiation. In summary, our data suggest that SLN upregulation is an intrinsic secondary change in dystrophin-deficient myoblasts and could account for the [Formula: see text] mishandling, which subsequently contributes to poor myogenic differentiation. Accordingly, reducing SLN expression can improve the [Formula: see text] cycling and differentiation of dystrophic myoblasts. These findings provide cellular-level supports for targeting SLN expression as a therapeutic strategy for DMD.
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Betts, Corinne A., Aarti Jagannath, Tirsa LE van Westering, Melissa Bowerman, Subhashis Banerjee, Jinhong Meng, Maria Sofia Falzarano, et al. "Dystrophin involvement in peripheral circadian SRF signalling." Life Science Alliance 4, no. 10 (August 13, 2021): e202101014. http://dx.doi.org/10.26508/lsa.202101014.
Full textAbstract:
Absence of dystrophin, an essential sarcolemmal protein required for muscle contraction, leads to the devastating muscle-wasting disease Duchenne muscular dystrophy. Dystrophin has an actin-binding domain, which binds and stabilises filamentous-(F)-actin, an integral component of the RhoA-actin-serum-response-factor-(SRF) pathway. This pathway plays a crucial role in circadian signalling, whereby the suprachiasmatic nucleus (SCN) transmits cues to peripheral tissues, activating SRF and transcription of clock-target genes. Given dystrophin binds F-actin and disturbed SRF-signalling disrupts clock entrainment, we hypothesised dystrophin loss causes circadian deficits. We show for the first time alterations in the RhoA-actin-SRF-signalling pathway, in dystrophin-deficient myotubes and dystrophic mouse models. Specifically, we demonstrate reduced F/G-actin ratios, altered MRTF levels, dysregulated core-clock and downstream target-genes, and down-regulation of key circadian genes in muscle biopsies from Duchenne patients harbouring an array of mutations. Furthermore, we show dystrophin is absent in the SCN of dystrophic mice which display disrupted circadian locomotor behaviour, indicative of disrupted SCN signalling. Therefore, dystrophin is an important component of the RhoA-actin-SRF pathway and novel mediator of circadian signalling in peripheral tissues, loss of which leads to circadian dysregulation.
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Vandebrouck, Clarisse, Dominique Martin, Monique Colson-Van Schoor, Huguette Debaix, and Philippe Gailly. "Involvement of TRPC in the abnormal calcium influx observed in dystrophic (mdx) mouse skeletal muscle fibers." Journal of Cell Biology 158, no. 6 (September 16, 2002): 1089–96. http://dx.doi.org/10.1083/jcb.200203091.
Full textAbstract:
Duchenne muscular dystrophy results from the lack of dystrophin, a cytoskeletal protein associated with the inner surface membrane, in skeletal muscle. The absence of dystrophin induces an abnormal increase of sarcolemmal calcium influx through cationic channels in adult skeletal muscle fibers from dystrophic (mdx) mice. We observed that the activity of these channels was increased after depletion of the stores of calcium with thapsigargin or caffeine. By analogy with the situation observed in nonexcitable cells, we therefore hypothesized that these store-operated channels could belong to the transient receptor potential channel (TRPC) family. We measured the expression of TRPC isoforms in normal and mdx adult skeletal muscles fibers, and among the seven known isoforms, five were detected (TRPC1, 2, 3, 4, and 6) by RT-PCR. Western blot analysis and immunocytochemistry of normal and mdx muscle fibers demonstrated the localization of TRPC1, 4, and 6 proteins at the plasma membrane. Therefore, an antisense strategy was used to repress these TRPC isoforms. In parallel with the repression of the TRPCs, we observed that the occurrence of calcium leak channels was decreased to one tenth of its control value (patch-clamp technique), showing the involvement of TRPC in the abnormal calcium influx observed in dystrophic fibers.
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Nogami, Ken'ichiro, Yusuke Maruyama, Fusako Sakai-Takemura, Norio Motohashi, Ahmed Elhussieny, Michihiro Imamura, Satoshi Miyashita, et al. "Pharmacological activation of SERCA ameliorates dystrophic phenotypes in dystrophin-deficient mdx mice." Human Molecular Genetics 30, no. 11 (April 5, 2021): 1006–19. http://dx.doi.org/10.1093/hmg/ddab100.
Full textAbstract:
Abstract Duchenne muscular dystrophy (DMD) is an X-linked genetic disorder characterized by progressive muscular weakness because of the loss of dystrophin. Extracellular Ca2+ flows into the cytoplasm through membrane tears in dystrophin-deficient myofibers, which leads to muscle contracture and necrosis. Sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) takes up cytosolic Ca2+ into the sarcoplasmic reticulum, but its activity is decreased in dystrophic muscle. Here, we show that an allosteric SERCA activator, CDN1163, ameliorates dystrophic phenotypes in dystrophin-deficient mdx mice. The administration of CDN1163 prevented exercise-induced muscular damage and restored mitochondrial function. In addition, treatment with CDN1163 for 7 weeks enhanced muscular strength and reduced muscular degeneration and fibrosis in mdx mice. Our findings provide preclinical proof-of-concept evidence that pharmacological activation of SERCA could be a promising therapeutic strategy for DMD. Moreover, CDN1163 improved muscular strength surprisingly in wild-type mice, which may pave the new way for the treatment of muscular dysfunction.