RESUMO
BACKGROUND: A healthy heart is able to modify its function and increase relaxation through post-translational modifications of myofilament proteins. While there are known examples of serine/threonine kinases directly phosphorylating myofilament proteins to modify heart function, the roles of tyrosine (Y) phosphorylation to directly modify heart function have not been demonstrated. The myofilament protein TnI (troponin I) is the inhibitory subunit of the troponin complex and is a key regulator of cardiac contraction and relaxation. We previously demonstrated that TnI-Y26 phosphorylation decreases calcium-sensitive force development and accelerates calcium dissociation, suggesting a novel role for tyrosine kinase-mediated TnI-Y26 phosphorylation to regulate cardiac relaxation. Therefore, we hypothesize that increasing TnI-Y26 phosphorylation will increase cardiac relaxation in vivo and be beneficial during pathological diastolic dysfunction. METHODS: The signaling pathway involved in TnI-Y26 phosphorylation was predicted in silico and validated by tyrosine kinase activation and inhibition in primary adult murine cardiomyocytes. To investigate how TnI-Y26 phosphorylation affects cardiac muscle, structure, and function in vivo, we developed a novel TnI-Y26 phosphorylation-mimetic mouse that was subjected to echocardiography, pressure-volume loop hemodynamics, and myofibril mechanical studies. TnI-Y26 phosphorylation-mimetic mice were further subjected to the nephrectomy/DOCA (deoxycorticosterone acetate) model of diastolic dysfunction to investigate the effects of increased TnI-Y26 phosphorylation in disease. RESULTS: Src tyrosine kinase is sufficient to phosphorylate TnI-Y26 in cardiomyocytes. TnI-Y26 phosphorylation accelerates in vivo relaxation without detrimental structural or systolic impairment. In a mouse model of diastolic dysfunction, TnI-Y26 phosphorylation is beneficial and protects against the development of disease. CONCLUSIONS: We have demonstrated that tyrosine kinase phosphorylation of TnI is a novel mechanism to directly and beneficially accelerate myocardial relaxation in vivo.
Assuntos
Cálcio , Troponina I , Camundongos , Animais , Fosforilação , Troponina I/genética , Cálcio/metabolismo , Processamento de Proteína Pós-Traducional , Contração Miocárdica/fisiologia , Miofibrilas/metabolismo , Proteínas Tirosina Quinases , Tirosina/metabolismo , Tirosina/farmacologiaRESUMO
Troponin I (TnI) is a key regulator of cardiac contraction and relaxation with TnI Ser-23/24 phosphorylation serving as a myofilament mechanism to modulate cardiac function. Basal cardiac TnI Ser-23/24 phosphorylation is high such that both increased and decreased TnI phosphorylation may modulate cardiac function. While the effects of increasing TnI Ser-23/24 phosphorylation on heart function are well established, the effects of decreasing TnI Ser-23/24 phosphorylation are not clear. To understand the in vivo role of decreased TnI Ser-23/24 phosphorylation, mice expressing TnI with Ser-23/24 mutated to alanine (TnI S23/24A) that lack the ability to be phosphorylated at these residues were subjected to echocardiography and pressure-volume hemodynamic measurements in the absence or presence of physiological (pacing increasing heart rate or adrenergic stimulation) or pathological (transverse aortic constriction (TAC)) stress. In the absence of pathological stress, the lack of TnI Ser-23/24 phosphorylation impaired systolic and diastolic function. TnI S23/24A mice also had an impaired systolic and diastolic response upon stimulation increased heart rate and an impaired adrenergic response upon dobutamine infusion. Following pathological cardiac stress induced by TAC, TnI S23/24A mice had a greater increase in ventricular mass, worse diastolic function, and impaired systolic and diastolic function upon increasing heart rate. These findings demonstrate that mice lacking the ability to phosphorylate TnI at Ser-23/24 have impaired in vivo systolic and diastolic cardiac function, a blunted cardiac reserve and a worse response to pathological stress supporting decreased TnI Ser23/24 phosphorylation is a modulator of these processes in vivo.
Assuntos
Cardiopatias , Troponina I , Camundongos , Animais , Fosforilação , Troponina I/metabolismo , Camundongos Transgênicos , Contração Miocárdica , Adrenérgicos/farmacologia , Cálcio/metabolismoRESUMO
Suppressing mineralocorticoid receptor (MR) activity with MR antagonists is therapeutic for chronic skeletal muscle pathology in Duchenne muscular dystrophy (DMD) mouse models. Although mechanisms underlying clinical MR antagonist efficacy for DMD cardiomyopathy and other cardiac diseases are defined, mechanisms in skeletal muscles are not fully elucidated. Myofiber MR knockout improves skeletal muscle force and a subset of dystrophic pathology. However, MR signaling in myeloid cells is known to be a major contributor to cardiac efficacy. To define contributions of myeloid MR in skeletal muscle function and disease, we performed parallel assessments of muscle pathology, cytokine levels, and myeloid cell populations resulting from myeloid MR genetic knockout in muscular dystrophy and acute muscle injury. Myeloid MR knockout led to lower levels of C-C motif chemokine receptor 2 (CCR2)-expressing macrophages, resulting in sustained myofiber damage after acute injury of normal muscle. In acute injury, myeloid MR knockout also led to increased local muscle levels of the enzyme that produces the endogenous MR agonist aldosterone, further supporting important contributions of MR signaling in normal muscle repair. In muscular dystrophy, myeloid MR knockout altered cytokine levels differentially between quadriceps and diaphragm muscles, which contain different myeloid populations. Myeloid MR knockout led to higher levels of fibrosis in dystrophic diaphragm. These results support important contributions of myeloid MR signaling to skeletal muscle repair in acute and chronic injuries and highlight the useful information gained from cell-specific genetic knockouts to delineate mechanisms of pharmacological efficacy.
Assuntos
Diafragma/metabolismo , Macrófagos/metabolismo , Doenças Musculares/metabolismo , Distrofia Muscular de Duchenne/metabolismo , Músculo Quadríceps/metabolismo , Receptores de Mineralocorticoides/metabolismo , Aldosterona/metabolismo , Animais , Compostos de Bário , Cloretos , Citocinas/genética , Citocinas/metabolismo , Diafragma/imunologia , Diafragma/patologia , Modelos Animais de Doenças , Feminino , Fibrose , Macrófagos/imunologia , Masculino , Camundongos Endogâmicos mdx , Camundongos Knockout , Doenças Musculares/induzido quimicamente , Doenças Musculares/imunologia , Doenças Musculares/patologia , Distrofia Muscular de Duchenne/genética , Distrofia Muscular de Duchenne/imunologia , Distrofia Muscular de Duchenne/patologia , Músculo Quadríceps/imunologia , Músculo Quadríceps/patologia , Receptores CCR2/genética , Receptores CCR2/metabolismo , Receptores de Mineralocorticoides/genética , Transdução de SinaisRESUMO
Duchenne muscular dystrophy (DMD) is a genetic, degenerative, striated muscle disease exacerbated by chronic inflammation. Mdx mice in the genotypic DMD model poorly represent immune-mediated pathology observed in patients. Improved understanding of innate immunity in dystrophic muscles is required to develop specific anti-inflammatory treatments. Here, inflammation in mdx mice and the more fibrotic utrn+/-;mdx Het model was comprehensively investigated. Unbiased analysis showed that mdx and Het mice contain increased levels of numerous chemokines and cytokines, with further increased in Het mice. Chemokine and chemokine receptor gene expression levels were dramatically increased in 4-week-old dystrophic quadriceps muscles, and to a lesser extent in diaphragm during the early injury phase, and had a small but consistent increase at 8 and 20 weeks. An optimized direct immune cell isolation method prevented loss of up to 90% of macrophages with density-dependent centrifugation previously used for mdx flow cytometry. Het quadriceps contain higher proportions of neutrophils and infiltrating monocytes than mdx, and higher percentages of F4/80Hi, but lower percentages of F4/80Lo cells and patrolling monocytes compared with Het diaphragms. These differences may restrict regenerative potential of dystrophic diaphragms, increasing pathologic severity. Fibrotic and inflammatory gene expression levels are higher in myeloid cells isolated from Het compared with mdx quadriceps, supporting Het mice may represent an improved model for testing therapeutic manipulation of inflammation in DMD.
Assuntos
Distrofina/metabolismo , Inflamação/metabolismo , Músculo Esquelético/patologia , Distrofia Muscular Animal/patologia , Distrofia Muscular de Duchenne/patologia , Animais , Inflamação/patologia , Macrófagos/metabolismo , Camundongos Transgênicos , Monócitos/metabolismo , Músculo Esquelético/metabolismo , Distrofia Muscular Animal/metabolismo , Distrofia Muscular de Duchenne/metabolismo , Músculos Respiratórios/metabolismo , Músculos Respiratórios/patologiaRESUMO
Mineralocorticoid receptor (MR) drugs have been used clinically for decades to treat cardiovascular diseases. MR antagonists not only show preclinical efficacy for heart in Duchenne muscular dystrophy (DMD) models but also improve skeletal muscle force and muscle membrane integrity. The mechanisms of action of MR antagonists in skeletal muscles are entirely unknown. Since MR are present in many cell types in the muscle microenvironment, it is critical to define cell-intrinsic functions in each cell type to ultimately optimize antagonist efficacy for use in the widest variety of diseases. We generated a new conditional knockout of MR in myofibers and quantified cell-intrinsic mechanistic effects on functional and histological parameters in a DMD mouse model. Skeletal muscle MR deficiency led to improved respiratory muscle force generation and less deleterious fibrosis but did not reproduce MR antagonist efficacy on membrane susceptibility to induced damage. Surprisingly, acute application of MR antagonist to muscles led to improvements in membrane integrity after injury independent of myofiber MR. These data demonstrate that MR antagonists are efficacious to dystrophic skeletal muscles through both myofiber intrinsic effects on muscle force and downstream fibrosis and extrinsic functions on membrane stability. MR antagonists may therefore be applicable for treating more general muscle weakness and possibly other conditions that result from cell injuries.
Assuntos
Antagonistas de Receptores de Mineralocorticoides/uso terapêutico , Músculo Esquelético/patologia , Distrofia Muscular de Duchenne/patologia , Animais , Membrana Celular/efeitos dos fármacos , Membrana Celular/fisiologia , Modelos Animais de Doenças , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos mdx , Força Muscular/efeitos dos fármacos , Músculo Esquelético/imunologia , Músculo Esquelético/metabolismo , Músculo Esquelético/fisiopatologia , Distrofia Muscular de Duchenne/tratamento farmacológico , Distrofia Muscular de Duchenne/metabolismo , Distrofia Muscular de Duchenne/fisiopatologia , Receptores de Mineralocorticoides/genética , Receptores de Mineralocorticoides/metabolismo , Espironolactona/uso terapêuticoRESUMO
FDA-approved mineralocorticoid receptor (MR) antagonists are used to treat heart failure. We have recently demonstrated efficacy of MR antagonists for skeletal muscles in addition to heart in Duchenne muscular dystrophy mouse models and that mineralocorticoid receptors are present and functional in skeletal muscles. The goal of this study was to elucidate the underlying mechanisms of MR antagonist efficacy on dystrophic skeletal muscles. We demonstrate for the first time that infiltrating myeloid cells clustered in damaged areas of dystrophic skeletal muscles have the capacity to produce the natural ligand of MR, aldosterone, which in excess is known to exacerbate tissue damage. Aldosterone synthase protein levels are increased in leukocytes isolated from dystrophic muscles compared with controls and local aldosterone levels in dystrophic skeletal muscles are increased, despite normal circulating levels. All genes encoding enzymes in the pathway for aldosterone synthesis are expressed in muscle-derived leukocytes. 11ß-HSD2, the enzyme that inactivates glucocorticoids to increase MR selectivity for aldosterone, is also increased in dystrophic muscle tissues. These results, together with the demonstrated preclinical efficacy of antagonists, suggest MR activation is in excess of physiological need and likely contributes to the pathology of muscular dystrophy. This study provides new mechanistic insight into the known contribution of myeloid cells to muscular dystrophy pathology. This first report of myeloid cells having the capacity to produce aldosterone may have implications for a wide variety of acute injuries and chronic diseases with inflammation where MR antagonists may be therapeutic.
Assuntos
Insuficiência Cardíaca/tratamento farmacológico , Antagonistas de Receptores de Mineralocorticoides/administração & dosagem , Músculo Esquelético/efeitos dos fármacos , Distrofia Muscular de Duchenne/tratamento farmacológico , 11-beta-Hidroxiesteroide Desidrogenase Tipo 2/biossíntese , 11-beta-Hidroxiesteroide Desidrogenase Tipo 2/genética , Aldosterona/metabolismo , Animais , Citocromo P-450 CYP11B2/biossíntese , Citocromo P-450 CYP11B2/genética , Modelos Animais de Doenças , Coração/efeitos dos fármacos , Coração/fisiopatologia , Insuficiência Cardíaca/metabolismo , Insuficiência Cardíaca/patologia , Humanos , Camundongos , Músculo Esquelético/patologia , Distrofia Muscular de Duchenne/genética , Distrofia Muscular de Duchenne/patologia , Células Mieloides/efeitos dos fármacos , Células Mieloides/patologiaRESUMO
Angiotensin-converting enzyme inhibitors (ACEi) and mineralocorticoid receptor (MR) antagonists are FDA-approved drugs that inhibit the renin-angiotensin-aldosterone system (RAAS) and are used to treat heart failure. Combined treatment with the ACEi lisinopril and the nonspecific MR antagonist spironolactone surprisingly improves skeletal muscle, in addition to heart function and pathology in a Duchenne muscular dystrophy (DMD) mouse model. We recently demonstrated that MR is present in all limb and respiratory muscles and functions as a steroid hormone receptor in differentiated normal human skeletal muscle fibers. The goals of the current study were to begin to define cellular and molecular mechanisms mediating the skeletal muscle efficacy of RAAS inhibitor treatment. We also compared molecular changes resulting from RAAS inhibition with those resulting from the current DMD standard-of-care glucocorticoid treatment. Direct assessment of muscle membrane integrity demonstrated improvement in dystrophic mice treated with lisinopril and spironolactone compared with untreated mice. Short-term treatments of dystrophic mice with specific and nonspecific MR antagonists combined with lisinopril led to overlapping gene-expression profiles with beneficial regulation of metabolic processes and decreased inflammatory gene expression. Glucocorticoids increased apoptotic, proteolytic, and chemokine gene expression that was not changed by RAAS inhibitors in dystrophic mice. Microarray data identified potential genes that may underlie RAAS inhibitor treatment efficacy and the side effects of glucocorticoids. Direct effects of RAAS inhibitors on membrane integrity also contribute to improved pathology of dystrophic muscles. Together, these data will inform clinical development of MR antagonists for treating skeletal muscles in DMD.
Assuntos
Membrana Celular/efeitos dos fármacos , Antagonistas de Receptores de Mineralocorticoides/administração & dosagem , Proteínas Musculares/metabolismo , Distrofias Musculares/tratamento farmacológico , Distrofias Musculares/metabolismo , Sistema Renina-Angiotensina/efeitos dos fármacos , Inibidores da Enzima Conversora de Angiotensina/administração & dosagem , Animais , Membrana Celular/patologia , Relação Dose-Resposta a Droga , Regulação da Expressão Gênica/efeitos dos fármacos , Lisinopril/administração & dosagem , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Distrofias Musculares/patologia , Espironolactona/administração & dosagem , Resultado do TratamentoRESUMO
Mineralocorticoid and glucocorticoid receptors are closely related steroid hormone receptors that regulate gene expression through many of the same hormone response elements. However, their transcriptional activities and effects in skeletal muscles are largely unknown. We recently identified mineralocorticoid receptors (MR) in skeletal muscles after finding that combined treatment with the angiotensin-converting enzyme inhibitor lisinopril and MR antagonist spironolactone was therapeutic in Duchenne muscular dystrophy mouse models. The glucocorticoid receptor (GR) agonist prednisolone is the current standard-of-care treatment for Duchenne muscular dystrophy because it prolongs ambulation, likely due to its anti-inflammatory effects. However, data on whether glucocorticoids have a beneficial or detrimental direct effect on skeletal muscle are controversial. Here, we begin to define the gene expression profiles in normal differentiated human skeletal muscle myotubes treated with MR and GR agonists and antagonists. The MR agonist aldosterone and GR agonist prednisolone had highly overlapping gene expression profiles, supporting the notion that prednisolone acts as both a GR and MR agonist that may have detrimental effects on skeletal muscles. Co-incubations with aldosterone plus either nonspecific or selective MR antagonists, spironolactone or eplerenone, resulted in similar numbers of gene expression changes, suggesting that both drugs can block MR activation to a similar extent. Eplerenone treatment alone decreased a number of important muscle-specific genes. This information may be used to develop biomarkers to monitor clinical efficacy of MR antagonists or GR agonists in muscular dystrophy, develop a temporally coordinated treatment with both drugs, or identify novel therapeutics with more specific downstream targets.
Assuntos
Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/metabolismo , Receptores de Glucocorticoides/agonistas , Receptores de Glucocorticoides/antagonistas & inibidores , Receptores de Mineralocorticoides/agonistas , Adolescente , Adulto , Aldosterona/farmacologia , Western Blotting , Células Cultivadas , Eplerenona , Humanos , Masculino , Distrofia Muscular de Duchenne , Prednisolona/farmacologia , Espironolactona/análogos & derivados , Espironolactona/farmacologia , Adulto JovemRESUMO
Early treatment with heart failure drugs lisinopril and spironolactone improves skeletal muscle pathology in Duchenne muscular dystrophy (DMD) mouse models. The angiotensin converting enzyme inhibitor lisinopril and mineralocorticoid receptor (MR) antagonist spironolactone indirectly and directly target MR. The presence and function of MR in skeletal muscle have not been explored. MR mRNA and protein are present in all tested skeletal muscles from both wild-type mice and DMD mouse models. MR expression is cell autonomous in both undifferentiated myoblasts and differentiated myotubes from mouse and human skeletal muscle cultures. To test for MR function in skeletal muscle, global gene expression analysis was conducted on human myotubes treated with MR agonist (aldosterone; EC50 1.3 nM) or antagonist (spironolactone; IC50 1.6 nM), and 53 gene expression differences were identified. Five differences were conserved in quadriceps muscles from dystrophic mice treated with spironolactone plus lisinopril (IC50 0.1 nM) compared with untreated controls. Genes down-regulated more than 2-fold by MR antagonism included FOS, ANKRD1, and GADD45B, with known roles in skeletal muscle, in addition to NPR3 and SERPINA3, bona fide targets of MR in other tissues. MR is a novel drug target in skeletal muscle and use of clinically safe antagonists may be beneficial for muscle diseases.
Assuntos
Aldosterona/farmacologia , Lisinopril/farmacologia , Fibras Musculares Esqueléticas/metabolismo , Proteínas Musculares , Receptores de Melanocortina , Espironolactona/farmacologia , Animais , Linhagem Celular , Humanos , Camundongos , Proteínas Musculares/agonistas , Proteínas Musculares/antagonistas & inibidores , Proteínas Musculares/metabolismo , Doenças Musculares/tratamento farmacológico , Doenças Musculares/metabolismo , Receptores de Melanocortina/agonistas , Receptores de Melanocortina/antagonistas & inibidores , Receptores de Melanocortina/metabolismoRESUMO
INTRODUCTION: We tested how a treadmill exercise program influences oxygen consumption, oxidative stress, and exercise capacity in the mdx mouse, a model of Duchenne muscular dystrophy. METHODS: At age 4 weeks mdx mice were subjected to 4 weeks of twice-weekly treadmill exercise. Sedentary mdx and wild-type mice served as controls. Oxygen consumption, time to exhaustion, oxidative stress, and myofiber damage were assessed. RESULTS: At age 4 weeks, there was a significant difference in exercise capacity between mdx and wild-type mice. After exercise, mdx mice had lower basal oxygen consumption and exercise capacity, but similar maximal oxygen consumption. Skeletal muscle from these mice displayed increased oxidative stress. Collagen deposition was higher in exercised versus sedentary mice. CONCLUSIONS: Exercised mdx mice exhibit increased oxidative stress, as well as deficits in exercise capacity, baseline oxygen consumption, and increased myofiber fibrosis. Muscle Nerve 54: 110-117, 2016.
Assuntos
Distrofia Muscular de Duchenne/reabilitação , Miofibrilas/metabolismo , Miofibrilas/patologia , Estresse Oxidativo/fisiologia , Condicionamento Físico Animal/métodos , Animais , Colágeno/metabolismo , Modelos Animais de Doenças , Espectroscopia de Ressonância de Spin Eletrônica , Feminino , Glutationa/metabolismo , Dissulfeto de Glutationa/metabolismo , Hidroxiprolina/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos mdx , Distrofia Muscular de Duchenne/genética , Estresse Oxidativo/genética , Consumo de Oxigênio/genética , Consumo de Oxigênio/fisiologiaRESUMO
Duchenne muscular dystrophy (DMD) is a devastating muscle disease caused by the absence of functional dystrophin. There are multiple ongoing clinical trials for DMD that are testing gene therapy treatments consisting of adeno-associated viral (AAV) vectors carrying miniaturized versions of dystrophin optimized for function, termed micro-dystrophins (µDys). Utrophin, the fetal homolog of dystrophin, has repeatedly been reported to be upregulated in human DMD muscle as a compensatory mechanism, but whether µDys displaces full-length utrophin is unknown. In this study, dystrophin/utrophin-deficient mice with transgenic overexpression of full-length utrophin in skeletal muscles were systemically administered low doses of either AAV6-CK8e-Hinge3-µDys (µDysH3) or AAV6-CK8e-µDys5 (µDys5). We used immunofluorescence to qualitatively assess the localization of µDys with transgenic utrophin and neuronal nitric oxide synthase (nNOS) in quadriceps muscles. µDys protein resulting from both gene therapies co-localized at myofiber membranes with transgenic utrophin. We also confirmed the sarcolemmal co-localization of nNOS with µDys5, but not with transgenic utrophin expression or µDysH3. Transgenic utrophin expression and µDys proteins produced from both therapies stabilize the dystrophin-glycoprotein complex as observed by sarcolemmal localization of ß-dystroglycan. This study suggests that µDys gene therapy will likely not inhibit any endogenous compensation by utrophin in DMD muscle.
Assuntos
Distrofina , Fibras Musculares Esqueléticas , Animais , Humanos , Camundongos , Distrofina/genética , Utrofina/genética , Músculo Esquelético , Terapia GenéticaRESUMO
Introduction: Duchenne muscular dystrophy (DMD) is a fatal striated muscle degenerative disease. DMD is caused by loss of dystrophin protein, which results in sarcolemmal instability and cycles of myofiber degeneration and regeneration. Pathology is exacerbated by overactivation of infiltrating immune cells and fibroblasts, which leads to chronic inflammation and fibrosis. Mineralocorticoid receptors (MR), a type of nuclear steroid hormone receptors, are potential therapeutic targets for DMD. MR antagonists show clinical efficacy on DMD cardiomyopathy and preclinical efficacy on skeletal muscle in DMD models. Methods: We have previously generated myofiber and myeloid MR knockout mouse models to dissect cell-specific functions of MR within dystrophic muscles. Here, we compared skeletal muscle gene expression from both knockouts to further define cell-type specific signaling downstream from MR. Results: Myeloid MR knockout increased proinflammatory and profibrotic signaling, including numerous myofibroblast signature genes. Tenascin C was the most highly upregulated fibrotic gene in myeloid MR-knockout skeletal muscle and is a component of fibrosis in dystrophic skeletal muscle. Surprisingly, lysyl oxidase (Lox), canonically a collagen crosslinker, was increased in both MR knockouts, but did not localize to fibrotic regions of skeletal muscle. Lox localized within myofibers, including only a region of quadriceps muscles. Lysyl oxidase like 1 (Loxl1), another Lox family member, was increased only in myeloid MR knockout muscle and localized specifically to fibrotic regions. Discussion: This study suggests that MR signaling in the dystrophic muscle microenvironment involves communication between contributing cell types and modulates inflammatory and fibrotic pathways in muscle disease.
Assuntos
Cardiomiopatias/terapia , Cardiomiopatia Dilatada/etiologia , Distrofia Muscular Animal/genética , Distrofia Muscular de Duchenne/genética , Animais , Cardiomiopatia Dilatada/terapia , Fármacos Cardiovasculares/uso terapêutico , Claudina-5/deficiência , Claudina-5/genética , Progressão da Doença , Método Duplo-Cego , Avaliação Pré-Clínica de Medicamentos , Distrofina/deficiência , Distrofina/genética , Regulação da Expressão Gênica , Terapia Genética , Insuficiência Cardíaca/tratamento farmacológico , Insuficiência Cardíaca/etiologia , Insuficiência Cardíaca/prevenção & controle , Humanos , Camundongos , Camundongos Endogâmicos mdx , Antagonistas de Receptores de Mineralocorticoides/uso terapêutico , Distrofia Muscular Animal/complicações , Distrofia Muscular de Duchenne/complicações , Ensaios Clínicos Controlados Aleatórios como Assunto , Pesquisa Translacional Biomédica , Utrofina/deficiência , Utrofina/genéticaRESUMO
Cachexia contributes to nearly a third of all cancer deaths, yet the mechanisms underlying skeletal muscle wasting in this syndrome remain poorly defined. We report that tumor-induced alterations in the muscular dystrophy-associated dystrophin glycoprotein complex (DGC) represent a key early event in cachexia. Muscles from tumor-bearing mice exhibited membrane abnormalities accompanied by reduced levels of dystrophin and increased glycosylation on DGC proteins. Wasting was accentuated in tumor mdx mice lacking a DGC but spared in dystrophin transgenic mice that blocked induction of muscle E3 ubiquitin ligases. Furthermore, DGC deregulation correlated positively with cachexia in patients with gastrointestinal cancers. Based on these results, we propose that, similar to muscular dystrophy, DGC dysfunction plays a critical role in cancer-induced wasting.
Assuntos
Caquexia/metabolismo , Proteínas Associadas à Distrofina/fisiologia , Distrofina/fisiologia , Glicoproteínas/fisiologia , Neoplasias/metabolismo , Adulto , Idoso , Animais , Caquexia/complicações , Distrofina/metabolismo , Proteínas Associadas à Distrofina/metabolismo , Feminino , Efeito Fundador , Humanos , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos mdx , Camundongos Transgênicos , Pessoa de Meia-Idade , Músculo Esquelético/metabolismo , Músculo Esquelético/patologia , Atrofia Muscular/metabolismo , Atrofia Muscular/patologia , Neoplasias/complicações , Neoplasias/patologia , Ubiquitina-Proteína Ligases/metabolismoRESUMO
Identification of new molecular targets in heart failure could ultimately have a substantial positive impact on both the health and financial aspects of treating the large heart failure population. We originally identified reduced levels of the cell junction protein claudin-5 specifically in heart in the dystrophin/utrophin-deficient (Dmd(mdx);Utrn(-/-)) mouse model of muscular dystrophy and cardiomyopathy, which demonstrates physiological hallmarks of heart failure. We then showed that at least 60% of cardiac explant samples from patients with heart failure resulting from diverse etiologies also have reduced claudin-5 levels. These claudin-5 reductions were independent of changes in other cell junction proteins previously linked to heart failure. The goal of this study was to determine whether sustaining claudin-5 levels is sufficient to prevent the onset of histological and functional indicators of heart failure. Here, we show the proof-of-concept rescue experiment in the Dmd(mdx);Utrn(-/-) model, in which claudin-5 reductions were originally identified. Expression of claudin-5 4 weeks after a single administration of recombinant adeno-associated virus (rAAV) containing a claudin-5 expression cassette prevented the onset of physiological hallmarks of cardiomyopathy and improved histological signs of cardiac damage. This experiment demonstrates that claudin-5 may represent a novel treatment target for prevention of heart failure.
Assuntos
Cardiomiopatias/prevenção & controle , Claudina-5/genética , Claudina-5/metabolismo , Insuficiência Cardíaca/prevenção & controle , Distrofia Muscular Animal/metabolismo , Miocárdio/metabolismo , Animais , Dependovirus/genética , Modelos Animais de Doenças , Distrofina/genética , Técnicas de Transferência de Genes , Insuficiência Cardíaca/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Distrofia Muscular Animal/genética , Utrofina/deficiência , Utrofina/genética , Utrofina/metabolismoRESUMO
Micro-dystrophin gene replacement therapies for Duchenne muscular dystrophy (DMD) are currently in clinical trials, but have not been thoroughly investigated for their efficacy on cardiomyopathy progression to heart failure. We previously validated Fiona/dystrophin-utrophin-deficient (dko) mice as a DMD cardiomyopathy model that progresses to reduced ejection fraction indicative of heart failure. Adeno-associated viral (AAV) vector delivery of an early generation micro-dystrophin prevented cardiac pathology and functional decline through 1 year of age in this new model. We now show that gene therapy using a micro-dystrophin optimized for skeletal muscle efficacy (AAV-µDys5), and which is currently in a clinical trial, is able to fully prevent cardiac pathology and cardiac strain abnormalities and maintain normal (>45%) ejection fraction through 18 months of age in Fiona/dko mice. Early treatment with AAV-µDys5 prevents inflammation and fibrosis in Fiona/dko hearts. Collagen in cardiac fibrotic scars becomes more tightly packed from 12 to 18 months in Fiona/dko mice, but the area of fibrosis containing tenascin C does not change. Increased tight collagen correlates with unexpected improvements in Fiona/dko whole-heart function that maintain impaired cardiac strain and strain rate. This study supports micro-dystrophin gene therapy as a promising intervention for preventing DMD cardiomyopathy progression.
RESUMO
BACKGROUND: Nearly universal cardiomyopathy in Duchenne muscular dystrophy (DMD) contributes to heart failure and death. Because DMD patients show myocardial fibrosis well before functional impairment, we postulated that earlier treatment using drugs with antifibrotic effect may be beneficial. METHODS AND RESULTS: Three groups of 10 utrn(+/-);mdx, or "het" mice, deficient for dystrophin and haploinsufficient for utrophin with skeletal myopathy and cardiomyopathy that closely mimics clinical DMD were studied. One het group received spironolactone and lisinopril starting at 8 weeks of life (het-treated-8); a second received the same starting at 4 weeks of life (het-treated-4), and the third het group was untreated. At 20 weeks, all mice had normal ejection fractions though circumferential strain rate was abnormal (-0.21±0.08) in untreated hets. This improved to -0.40±0.07 in het-treated-8 mice (P=0.003) and further improved to -0.56±0.10 in het-treated-4 mice (P=0.014 for het-treated-4 versus het-treated-8). Treated mice showed less cardiomyocyte damage, with a 44% reduction in intracardiomyocyte serum immunoglobulin G localization in het-treated-8 mice (P<0.0001) and a further 53% reduction in het-treated-4 mice (P=0.0003 versus het-treated-8); matrix metalloproteinases were similarly reduced. Cardiac, limb, and diaphragm function by ex vivo muscle testing remained at 80% of normal with early treatment compared to a decline to 40% of normal skeletal muscle function without treatment. CONCLUSIONS: These findings offer clinically available medications with proven antifibrotic effect as a new therapeutic strategy in DMD. Early initiation greatly attenuated myocardial disease and, for the first time with these drugs, improved skeletal myopathy. Thus, early initiation of such agents warrants further clinical evaluation to maintain ambulatory, respiratory, and cardiac function for patients with DMD and related myopathies.
Assuntos
Lisinopril/farmacologia , Músculo Esquelético/patologia , Distrofia Muscular de Duchenne/tratamento farmacológico , Distrofia Muscular de Duchenne/patologia , Miocárdio/patologia , Espironolactona/farmacologia , Animais , Técnicas de Imagem Cardíaca , Cardiomiopatias/tratamento farmacológico , Cardiomiopatias/patologia , Cardiotônicos/farmacologia , Modelos Animais de Doenças , Diuréticos/farmacologia , Isoproterenol/farmacologia , Imageamento por Ressonância Magnética , Camundongos , Camundongos Endogâmicos mdxRESUMO
Duchenne muscular dystrophy (DMD) is a striated muscle degenerative disease due to loss of functional dystrophin protein. Loss of dystrophin results in susceptibility of muscle membranes to damage, leading to muscle degeneration and continuous inflammation and fibrosis that further exacerbate pathology. Long-term glucocorticoid receptor (GR) agonist treatment, the current standard-of-care for DMD, modestly improves prognosis but has serious side effects. The mineralocorticoid receptor (MR), a ligand-activated transcription factor present in many cell types, has been implicated as a therapeutic target for DMD. MR antagonists (MRAs) have fewer side effects than GR agonists and are used clinically for heart failure. MRA efficacy has recently been demonstrated for DMD cardiomyopathy and in preclinical studies, MRAs also alleviate dystrophic skeletal muscle pathology. MRAs lead to improvements in muscle force and membrane stability and reductions in degeneration, inflammation, and fibrosis in dystrophic muscles. Myofiber-specific MR knockout leads to most of these improvements, supporting an MR-dependent mechanism of action, but MRAs additionally stabilize myofiber membranes in an MR-independent manner. Immune cell MR signaling in dystrophic and acutely injured normal muscle contributes to wound healing, and myeloid-specific MR knockout is detrimental. More research is needed to fully elucidate MR signaling in striated muscle microenvironments. Direct comparisons of genomic and non-genomic effects of glucocorticoids and MRAs on skeletal muscles and heart will contribute to optimal temporal use of these drugs, since they compete for binding conserved receptors. Despite the advent of genetic medicines, therapies targeting inflammation and fibrosis will be necessary to achieve optimal patient outcomes.
RESUMO
Mineralocorticoid receptor antagonists (MRAs) slow cardiomyopathy in patients with Duchenne muscular dystrophy (DMD) and improve skeletal muscle pathology and function in dystrophic mice. However, glucocorticoids, known antiinflammatory drugs, remain a standard of care for DMD, despite substantial side effects. Exact mechanisms underlying mineralocorticoid receptor (MR) signaling contribution to dystrophy are unknown. Whether MRAs affect inflammation in dystrophic muscles and how they compare with glucocorticoids is unclear. The MRA spironolactone and glucocorticoid prednisolone were each administered for 1 week to dystrophic mdx mice during peak skeletal muscle necrosis to compare effects on inflammation. Both drugs reduced cytokine levels in mdx quadriceps, but prednisolone elevated diaphragm cytokines. Spironolactone did not alter myeloid populations in mdx quadriceps or diaphragms, but prednisolone increased F4/80hi macrophages. Both spironolactone and prednisolone reduced inflammatory gene expression in myeloid cells sorted from mdx quadriceps, while prednisolone additionally perturbed cell cycle genes. Spironolactone also repressed myeloid expression of the gene encoding fibronectin, while prednisolone increased its expression. Overall, spironolactone exhibits antiinflammatory properties without altering leukocyte distribution within skeletal muscles, while prednisolone suppresses quadriceps cytokines but increases diaphragm cytokines and pathology. Antiinflammatory properties of MRAs and different limb and respiratory muscle responses to glucocorticoids should be considered when optimizing treatments for patients with DMD.