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1.
Free Radic Biol Med ; 219: 112-126, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38574978

RESUMO

The purpose of this study was to identify causes of quadriceps muscle weakness in facioscapulohumeral muscular dystrophy (FSHD). To this aim, we evaluated quadriceps muscle and fat volumes by magnetic resonance imaging and their relationships with muscle strength and oxidative stress markers in adult patients with FSHD (n = 32) and healthy controls (n = 7), and the effect of antioxidant supplementation in 20 of the 32 patients with FSHD (n = 10 supplementation and n = 10 placebo) (NCT01596803). Compared with healthy controls, the dominant quadriceps strength and quality (muscle strength per unit of muscle volume) were decreased in patients with FSHD. In addition, fat volume was increased, without changes in total muscle volume. Moreover, in patients with FSHD, the lower strength of the non-dominant quadriceps was associated with lower muscle quality compared with the dominant muscle. Antioxidant supplementation significantly changed muscle and fat volumes in the non-dominant quadriceps, and muscle quality in the dominant quadriceps. This was associated with improved muscle strength (both quadriceps) and antioxidant response. These findings suggest that quadriceps muscle strength decline may not be simply explained by atrophy and may be influenced also by the muscle intrinsic characteristics. As FSHD is associated with increased oxidative stress, supplementation might reduce oxidative stress and increase antioxidant defenses, promoting changes in muscle function.


Assuntos
Antioxidantes , Suplementos Nutricionais , Força Muscular , Distrofia Muscular Facioescapuloumeral , Estresse Oxidativo , Músculo Quadríceps , Humanos , Distrofia Muscular Facioescapuloumeral/tratamento farmacológico , Distrofia Muscular Facioescapuloumeral/fisiopatologia , Distrofia Muscular Facioescapuloumeral/metabolismo , Distrofia Muscular Facioescapuloumeral/dietoterapia , Distrofia Muscular Facioescapuloumeral/patologia , Estresse Oxidativo/efeitos dos fármacos , Antioxidantes/administração & dosagem , Antioxidantes/metabolismo , Antioxidantes/uso terapêutico , Masculino , Feminino , Força Muscular/efeitos dos fármacos , Adulto , Pessoa de Meia-Idade , Músculo Quadríceps/metabolismo , Músculo Quadríceps/patologia , Músculo Quadríceps/fisiopatologia , Músculo Quadríceps/efeitos dos fármacos , Imageamento por Ressonância Magnética , Tecido Adiposo/metabolismo , Tecido Adiposo/efeitos dos fármacos
2.
Nutrients ; 15(7)2023 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-37049513

RESUMO

In patients with facioscapulohumeral muscular dystrophy (FSHD), a rare genetic neuromuscular disease, reduced physical performance is associated with lower blood levels of vitamin C, zinc, selenium, and increased oxidative stress markers. Supplementation of vitamin C, vitamin E, zinc, and selenium improves the quadriceps' physical performance. Here, we compared the nutritional status of 74 women and 85 men with FSHD. Calorie intake was lower in women with FSHD than in men. Moreover, we assessed vitamin C, vitamin E, zinc, copper, and selenium intakes in diet and their concentrations in the plasma. Vitamin E, copper, and zinc intake were lower in women with FSHD than in men, whereas plasma vitamin C, copper levels, and copper/zinc ratio were higher in women with FSHD than in men. The dietary intake and plasma concentrations of the studied vitamins and minerals were not correlated in both sexes. A well-balanced and varied diet might not be enough in patients with FSHD to correct the observed vitamin/mineral deficiencies. A low energy intake is a risk factor for suboptimal intake of proteins, vitamins, and minerals that are important for protein synthesis and other metabolic pathways and that might contribute to progressive muscle mass loss. Antioxidant supplementation and higher protein intake seem necessary to confer protection against oxidative stress and skeletal muscle mass loss.


Assuntos
Distrofia Muscular Facioescapuloumeral , Selênio , Masculino , Humanos , Feminino , Distrofia Muscular Facioescapuloumeral/metabolismo , Estado Nutricional , Cobre , Vitaminas , Vitamina E , Ácido Ascórbico , Vitamina A , Zinco
3.
Clin Chim Acta ; 544: 117328, 2023 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-37031784

RESUMO

BACKGROUND AND AIMS: Muscle mass (MM) impairment observed in facioscapulohumeral muscular dystrophy (FSHD) may bias estimated glomerular filtration rate (eGFR) based on creatinine (eGFRcreat). eGFR based on cystatin C (eGFRcys), produced by all nucleated cells, should be an interesting alternative. Main objectives were to compare eGFRcreat and eGRFcys for chronic kidney disease (CKD) staging and for annual eGFR evolution. Secondary objective was to analyse creatinine, cystatin C with measured MM. MATERIAL AND METHODS: During 4 years, 159 FSHD patients having one or more creatinine and cystatin C measurements (total samples: n = 379), with MM determination by bio-impedancemetry during their follow-up were included. eGFR were determined with CKD-Epi and EKFC equations. RESULTS: On first examination samples, mean eGFRcys was significantly lower than mean eGFRcreat of 25.5 and 17.9 ml/min/1.73 m2 using CKD-Epi and EKFC equations, respectively. 53.5% (CKD-Epi) and 59.1% (EKFC) of agreement were obtained when using eGFRcys instead of eGFRcreat with reclassifications occurring mainly towards more severe stages. Age was correlated with cystatin C but not with creatinine, MM was correlated with creatinine but not with cystatin C. eGFR decreases > 1 ml/min/1.73 m2 were more important when using eGFRcys instead of eGFRcreat (CKD-Epi: 37.5 vs 15.4%, p < 0.001; EKFC: 34.6 vs 20.2%, p < 0.01). CONCLUSION: Cystatin C which is independent of MM appears as a promising candidate biomarker for CKD diagnosis and follow-up in FSHD patient.


Assuntos
Distrofia Muscular Facioescapuloumeral , Insuficiência Renal Crônica , Humanos , Distrofia Muscular Facioescapuloumeral/diagnóstico , Cistatina C , Creatinina , Taxa de Filtração Glomerular , Rim
4.
Redox Biol ; 56: 102450, 2022 10.
Artigo em Inglês | MEDLINE | ID: mdl-36030628

RESUMO

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant disorder characterized by progressive muscle weakness. Adenine nucleotide translocator 1 (ANT1), the only 4q35 gene involved in mitochondrial function, is strongly expressed in FSHD skeletal muscle biopsies. However, its role in FSHD is unclear. In this study, we evaluated ANT1 overexpression effects in primary myoblasts from healthy controls and during Xenopus laevis organogenesis. We also compared ANT1 overexpression effects with the phenotype of FSHD muscle cells and biopsies. Here, we report that the ANT1 overexpression-induced phenotype presents some similarities with FSHD muscle cells and biopsies. ANT1-overexpressing muscle cells showed disorganized morphology, altered cytoskeletal arrangement, enhanced mitochondrial respiration/glycolysis, ROS production, oxidative stress, mitochondrial fragmentation and ultrastructure alteration, as observed in FSHD muscle cells. ANT1 overexpression in Xenopus laevis embryos affected skeletal muscle development, impaired skeletal muscle, altered mitochondrial ultrastructure and led to oxidative stress as observed in FSHD muscle biopsies. Moreover, ANT1 overexpression in X. laevis embryos affected heart structure and mitochondrial ultrastructure leading to cardiac arrhythmia, as described in some patients with FSHD. Overall our data suggest that ANT1 could contribute to mitochondria dysfunction and oxidative stress in FSHD muscle cells by modifying their bioenergetic profile associated with ROS production. Such interplay between energy metabolism and ROS production in FSHD will be of significant interest for future prospects.


Assuntos
Distrofia Muscular Facioescapuloumeral , Translocador 1 do Nucleotídeo Adenina/genética , Translocador 1 do Nucleotídeo Adenina/metabolismo , Humanos , Desenvolvimento Muscular , Músculo Esquelético/metabolismo , Distrofia Muscular Facioescapuloumeral/genética , Distrofia Muscular Facioescapuloumeral/patologia , Mioblastos/metabolismo , Espécies Reativas de Oxigênio/metabolismo
5.
Cell Death Differ ; 28(1): 123-138, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-32661288

RESUMO

SEPN1-related myopathy (SEPN1-RM) is a muscle disorder due to mutations of the SEPN1 gene, which is characterized by muscle weakness and fatigue leading to scoliosis and life-threatening respiratory failure. Core lesions, focal areas of mitochondria depletion in skeletal muscle fibers, are the most common histopathological lesion. SEPN1-RM underlying mechanisms and the precise role of SEPN1 in muscle remained incompletely understood, hindering the development of biomarkers and therapies for this untreatable disease. To investigate the pathophysiological pathways in SEPN1-RM, we performed metabolic studies, calcium and ATP measurements, super-resolution and electron microscopy on in vivo and in vitro models of SEPN1 deficiency as well as muscle biopsies from SEPN1-RM patients. Mouse models of SEPN1 deficiency showed marked alterations in mitochondrial physiology and energy metabolism, suggesting that SEPN1 controls mitochondrial bioenergetics. Moreover, we found that SEPN1 was enriched at the mitochondria-associated membranes (MAM), and was needed for calcium transients between ER and mitochondria, as well as for the integrity of ER-mitochondria contacts. Consistently, loss of SEPN1 in patients was associated with alterations in body composition which correlated with the severity of muscle weakness, and with impaired ER-mitochondria contacts and low ATP levels. Our results indicate a role of SEPN1 as a novel MAM protein involved in mitochondrial bioenergetics. They also identify a systemic bioenergetic component in SEPN1-RM and establish mitochondria as a novel therapeutic target. This role of SEPN1 contributes to explain the fatigue and core lesions in skeletal muscle as well as the body composition abnormalities identified as part of the SEPN1-RM phenotype. Finally, these results point out to an unrecognized interplay between mitochondrial bioenergetics and ER homeostasis in skeletal muscle. They could therefore pave the way to the identification of biomarkers and therapeutic drugs for SEPN1-RM and for other disorders in which muscle ER-mitochondria cross-talk are impaired.


Assuntos
Retículo Endoplasmático/metabolismo , Mitocôndrias/metabolismo , Proteínas Musculares/metabolismo , Doenças Musculares/metabolismo , Selenoproteínas/metabolismo , Adolescente , Adulto , Animais , Cálcio/metabolismo , Criança , Retículo Endoplasmático/genética , Metabolismo Energético , Feminino , Homeostase , Humanos , Masculino , Camundongos , Camundongos Knockout , Pessoa de Meia-Idade , Fibras Musculares Esqueléticas/metabolismo , Fibras Musculares Esqueléticas/patologia , Proteínas Musculares/genética , Doenças Musculares/genética , Doenças Musculares/patologia , Oxirredução , Selenoproteínas/genética , Adulto Jovem
6.
Brain ; 135(Pt 4): 1115-27, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22418739

RESUMO

The skeletal muscle ryanodine receptor is an essential component of the excitation-contraction coupling apparatus. Mutations in RYR1 are associated with several congenital myopathies (termed RYR1-related myopathies) that are the most common non-dystrophic muscle diseases of childhood. Currently, no treatments exist for these disorders. Although the primary pathogenic abnormality involves defective excitation-contraction coupling, other abnormalities likely play a role in disease pathogenesis. In an effort to discover novel pathogenic mechanisms, we analysed two complementary models of RYR1-related myopathies, the relatively relaxed zebrafish and cultured myotubes from patients with RYR1-related myopathies. Expression array analysis in the zebrafish disclosed significant abnormalities in pathways associated with cellular stress. Subsequent studies focused on oxidative stress in relatively relaxed zebrafish and RYR1-related myopathy myotubes and demonstrated increased oxidant activity, the presence of oxidative stress markers, excessive production of oxidants by mitochondria and diminished survival under oxidant conditions. Exposure to the antioxidant N-acetylcysteine reduced oxidative stress and improved survival in the RYR1-related myopathies human myotubes ex vivo and led to significant restoration of aspects of muscle function in the relatively relaxed zebrafish, thereby confirming its efficacy in vivo. We conclude that oxidative stress is an important pathophysiological mechanism in RYR1-related myopathies and that N-acetylcysteine is a successful treatment modality ex vivo and in a vertebrate disease model. We propose that N-acetylcysteine represents the first potential therapeutic strategy for these debilitating muscle diseases.


Assuntos
Acetilcisteína/uso terapêutico , Antioxidantes/uso terapêutico , Doenças Musculares/tratamento farmacológico , Doenças Musculares/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Canal de Liberação de Cálcio do Receptor de Rianodina/metabolismo , Acetofenonas/farmacologia , Animais , Animais Geneticamente Modificados , Comportamento Animal , Modelos Animais de Doenças , Inibidores Enzimáticos/farmacologia , Humanos , Indometacina/farmacologia , Larva , Análise em Microsséries , Microscopia Eletrônica de Transmissão , Mitocôndrias/ultraestrutura , Contração Muscular/genética , Fibras Musculares Esqueléticas/efeitos dos fármacos , Fibras Musculares Esqueléticas/metabolismo , Fibras Musculares Esqueléticas/patologia , Fibras Musculares Esqueléticas/ultraestrutura , Proteínas Musculares/genética , Proteínas Musculares/metabolismo , Doenças Musculares/genética , Doenças Musculares/patologia , Mutação/genética , Estresse Oxidativo/genética , Canal de Liberação de Cálcio do Receptor de Rianodina/genética , Peixe-Zebra
7.
PLoS One ; 6(8): e23094, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-21858002

RESUMO

Selenium is an essential trace element and selenoprotein N (SelN) was the first selenium-containing protein shown to be directly involved in human inherited diseases. Mutations in the SEPN1 gene, encoding SelN, cause a group of muscular disorders characterized by predominant affection of axial muscles. SelN has been shown to participate in calcium and redox homeostasis, but its pathophysiological role in skeletal muscle remains largely unknown. To address SelN function in vivo, we generated a Sepn1-null mouse model by gene targeting. The Sepn1(-/-) mice had normal growth and lifespan, and were macroscopically indistinguishable from wild-type littermates. Only minor defects were observed in muscle morphology and contractile properties in SelN-deficient mice in basal conditions. However, when subjected to challenging physical exercise and stress conditions (forced swimming test), Sepn1(-/-) mice developed an obvious phenotype, characterized by limited motility and body rigidity during the swimming session, as well as a progressive curvature of the spine and predominant alteration of paravertebral muscles. This induced phenotype recapitulates the distribution of muscle involvement in patients with SEPN1-Related Myopathy, hence positioning this new animal model as a valuable tool to dissect the role of SelN in muscle function and to characterize the pathophysiological process.


Assuntos
Proteínas Musculares/fisiologia , Músculo Esquelético/fisiopatologia , Doenças Musculares/fisiopatologia , Selenoproteínas/fisiologia , Animais , Modelos Animais de Doenças , Embrião de Mamíferos/embriologia , Embrião de Mamíferos/metabolismo , Feminino , Regulação da Expressão Gênica no Desenvolvimento , Immunoblotting , Masculino , Camundongos , Camundongos da Linhagem 129 , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Atividade Motora , Contração Muscular/genética , Contração Muscular/fisiologia , Proteínas Musculares/genética , Proteínas Musculares/metabolismo , Músculo Esquelético/anormalidades , Músculo Esquelético/patologia , Doenças Musculares/genética , Doenças Musculares/metabolismo , Fenótipo , Carbonilação Proteica , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Selenoproteínas/genética , Selenoproteínas/metabolismo , Estresse Psicológico/fisiopatologia , Estresse Psicológico/psicologia , Natação/psicologia
8.
Proc Natl Acad Sci U S A ; 107(44): 19090-5, 2010 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-20956306

RESUMO

MyoD, a master regulator of myogenesis, exhibits a circadian rhythm in its mRNA and protein levels, suggesting a possible role in the daily maintenance of muscle phenotype and function. We report that MyoD is a direct target of the circadian transcriptional activators CLOCK and BMAL1, which bind in a rhythmic manner to the core enhancer of the MyoD promoter. Skeletal muscle of Clock(Δ19) and Bmal1(-/-) mutant mice exhibited ∼30% reductions in normalized maximal force. A similar reduction in force was observed at the single-fiber level. Electron microscopy (EM) showed that the myofilament architecture was disrupted in skeletal muscle of Clock(Δ19), Bmal1(-/-), and MyoD(-/-) mice. The alteration in myofilament organization was associated with decreased expression of actin, myosins, titin, and several MyoD target genes. EM analysis also demonstrated that muscle from both Clock(Δ19) and Bmal1(-/-) mice had a 40% reduction in mitochondrial volume. The remaining mitochondria in these mutant mice displayed aberrant morphology and increased uncoupling of respiration. This mitochondrial pathology was not seen in muscle of MyoD(-/-) mice. We suggest that altered expression of both Pgc-1α and Pgc-1ß in Clock(Δ19) and Bmal1(-/-) mice may underlie this pathology. Taken together, our results demonstrate that disruption of CLOCK or BMAL1 leads to structural and functional alterations at the cellular level in skeletal muscle. The identification of MyoD as a clock-controlled gene provides a mechanism by which the circadian clock may generate a muscle-specific circadian transcriptome in an adaptive role for the daily maintenance of adult skeletal muscle.


Assuntos
Fatores de Transcrição ARNTL/metabolismo , Proteínas CLOCK/metabolismo , Mitocôndrias Musculares/metabolismo , Desenvolvimento Muscular/fisiologia , Músculo Esquelético/metabolismo , Proteína MyoD/metabolismo , Fatores de Transcrição ARNTL/genética , Animais , Proteínas CLOCK/genética , Relógios Circadianos/fisiologia , Tomografia com Microscopia Eletrônica , Perfilação da Expressão Gênica , Regulação da Expressão Gênica/fisiologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Knockout , Mitocôndrias Musculares/genética , Mitocôndrias Musculares/ultraestrutura , Músculo Esquelético/ultraestrutura , Proteína MyoD/genética , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo , Transativadores/biossíntese , Transativadores/genética , Fatores de Transcrição
9.
Antioxid Redox Signal ; 12(7): 893-904, 2010 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-19769461

RESUMO

Healthy cells continually produce low levels of reactive oxygen species (ROS), which are buffered by multiple antioxidant systems. Imbalance between ROS production and elimination results in oxidative stress, which has been implicated in aging and in numerous human diseases, including cancer and diabetes. Selenoproteins are a family of proteins that contain the amino acid selenocysteine, encoded by an in-frame UGA. Those selenoproteins whose function is identified are catalytically active in redox processes, representing one of the main enzymatic antioxidant systems and important mediators of the beneficial role of selenium in human health. Nevertheless, the function of most selenoproteins remains unknown; this included Selenoprotein N (SelN), the only selenoprotein directly associated with a human genetic disease. Mutations of the SelN gene cause SEPN1-related myopathy, a particular early-onset muscle disorder. Recent studies have identified SelN as a key protein in cell protection against oxidative stress and redox-related calcium homeostasis. Furthermore, an effective ex vivo treatment of SelN deficiency has been identified, paving the way to a clinical therapy. In this review we discuss the physiological and pathophysiological role of SelN and the interest of SEPN1-related myopathy as a model paradigm to understand and target therapeutically other selenoproteins involved in human health and disease.


Assuntos
Cálcio/metabolismo , Homeostase , Estresse Oxidativo , Selenoproteínas/metabolismo , Transdução de Sinais/fisiologia , Antioxidantes/metabolismo , Humanos , Doenças Musculares/fisiopatologia , Óxido Nítrico/metabolismo , Oxirredução , Espécies Reativas de Oxigênio/metabolismo , Selenoproteínas/genética
10.
Ann Neurol ; 65(6): 677-86, 2009 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-19557870

RESUMO

OBJECTIVE: Mutations of the selenoprotein N gene (SEPN1) cause SEPN1-related myopathy (SEPN1-RM), a novel early-onset muscle disorder formerly divided into four different nosological categories. Selenoprotein N (SelN) is the only selenoprotein involved in a genetic disease; its function being unknown, no treatment is available for this potentially lethal disorder. Our objective was to clarify the role of SelN and the pathophysiology of SEPN1-RM to identify therapeutic targets. METHODS: We established and analyzed an ex vivo model of SelN deficiency using fibroblast and myoblast primary cultures from patients with null SEPN1 mutations. DCFH assay, OxyBlot, Western blot, Fura-2, and cell survival studies were performed to measure intracellular oxidant activity, oxidative stress markers, calcium handling, and response to exogenous treatments. RESULTS: SelN-depleted cells showed oxidative/nitrosative stress manifested by increased intracellular oxidant activity (reactive oxygen species and nitric oxide) and/or excessive oxidation of proteins, including the contractile proteins actin and myosin heavy chain II in myotubes. SelN-devoid myotubes showed also Ca(2+) homeostasis abnormalities suggesting dysfunction of the redox-sensor Ca(2+) channel ryanodine receptor type 1. Furthermore, absence of SelN was associated with abnormal susceptibility to H(2)O(2)-induced oxidative stress, demonstrated by increased cell death. This cell phenotype was restored by pretreatment with the antioxidant N-acetylcysteine. INTERPRETATION: SelN plays a key role in redox homeostasis and human cell protection against oxidative stress. Oxidative/nitrosative stress is a primary pathogenic mechanism in SEPN1-RM, which can be effectively targeted ex vivo by antioxidants. These findings pave the way to SEPN1-RM treatment, which would represent a first specific pharmacological treatment for a congenital myopathy.


Assuntos
Antioxidantes/uso terapêutico , Proteínas Musculares/fisiologia , Doenças Musculares/fisiopatologia , Doenças Musculares/terapia , Estresse Oxidativo , Selenoproteínas/fisiologia , Adolescente , Células Cultivadas , Criança , Pré-Escolar , Feminino , Marcação de Genes , Homeostase/genética , Humanos , Masculino , Proteínas Musculares/deficiência , Proteínas Musculares/genética , Doenças Musculares/metabolismo , Doenças Musculares/patologia , Mutação/genética , Oxirredução , Estresse Oxidativo/genética , Selenoproteínas/deficiência , Selenoproteínas/genética
11.
Hum Mutat ; 30(3): 411-6, 2009 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-19067361

RESUMO

Mutations in SEPN1 result in a spectrum of early-onset muscle disorders referred to as SEPN1-related myopathy. The SEPN1 gene encodes selenoprotein N (SelN), which contains the amino acid selenocysteine (Sec). Incorporation of Sec occurs due to redefinition of a UGA codon during translation. Efficient insertion requires a Sec insertion sequence (SECIS) in the 3'UTR and, for at least a subset of selenoprotein genes, a Sec redefinition element (SRE) located adjacent to the UGA codon. We report the effect of three novel and one previously reported point mutation in the SelN SRE element on Sec insertion efficiency. Notably, the previously reported mutation c.1397G>A (p.R466Q), which weakens the secondary structure of the SRE element, reduces Sec insertion efficiency and SelN RNA levels. Muscle from patients with this mutation have negligible levels of SelN protein. This data highlights the importance of the SRE element during SelN expression and illustrates a novel molecular mechanism by which point mutations may lead to SEPN1-related myopathy.


Assuntos
Proteínas Musculares/genética , Doenças Musculares/genética , Mutação , Selenocisteína/metabolismo , Selenoproteínas/genética , Regiões 3' não Traduzidas/genética , Sequência de Bases , Western Blotting , Linhagem Celular , Células Cultivadas , Códon de Terminação/genética , Fibroblastos/metabolismo , Fibroblastos/patologia , Expressão Gênica , Humanos , Luciferases de Vaga-Lume/genética , Luciferases de Vaga-Lume/metabolismo , Proteínas Musculares/metabolismo , Doenças Musculares/metabolismo , Doenças Musculares/patologia , Mutação Puntual , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Sequências Reguladoras de Ácido Nucleico/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Selenoproteínas/metabolismo , Transfecção
12.
J Appl Physiol (1985) ; 104(3): 694-9, 2008 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-18187611

RESUMO

Tumor necrosis factor-alpha (TNF) diminishes specific force of skeletal muscle. To address the mechanism of this response, we tested the hypothesis that TNF acts via the type 1 (TNFR1) receptor subtype to increase oxidant activity and thereby depress myofibrillar function. Experiments showed that a single intraperitoneal dose of TNF (100 microg/kg) increased cytosolic oxidant activity (P < 0.05) and depressed maximal force of male ICR mouse diaphragm by approximately 25% within 1 h, a deficit that persisted for 48 h. Pretreating animals with the antioxidant Trolox (10 mg/kg) lessened oxidant activity (P < 0.05) and abolished contractile losses in TNF-treated muscle (P < 0.05). Genetic TNFR1 deficiency prevented the rise in oxidant activity and fall in force stimulated by TNF; type 2 TNF receptor deficiency did not. TNF effects on muscle function were evident at the myofibrillar level. Chemically permeabilized muscle fibers from TNF-treated animals had lower maximal Ca2+-activated force (P < 0.02) with no change in Ca2+ sensitivity or shortening velocity. We conclude that TNF acts via TNFR1 to stimulate oxidant activity and depress specific force. TNF effects on force are caused, at least in part, by decrements in function of calcium-activated myofibrillar proteins.


Assuntos
Diafragma/metabolismo , Contração Muscular , Força Muscular , Miofibrilas/metabolismo , Estresse Oxidativo , Receptores Tipo I de Fatores de Necrose Tumoral/metabolismo , Transdução de Sinais , Fator de Necrose Tumoral alfa/metabolismo , Animais , Antioxidantes/farmacologia , Cálcio/metabolismo , Cromanos/farmacologia , Diafragma/efeitos dos fármacos , Diafragma/inervação , Estimulação Elétrica , Injeções Intraperitoneais , Masculino , Camundongos , Camundongos Endogâmicos ICR , Camundongos Knockout , Contração Muscular/efeitos dos fármacos , Força Muscular/efeitos dos fármacos , Miofibrilas/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Receptores Tipo I de Fatores de Necrose Tumoral/deficiência , Receptores Tipo I de Fatores de Necrose Tumoral/genética , Receptores Tipo II do Fator de Necrose Tumoral/metabolismo , Transdução de Sinais/efeitos dos fármacos , Fatores de Tempo , Fator de Necrose Tumoral alfa/administração & dosagem
13.
J Appl Physiol (1985) ; 102(3): 956-64, 2007 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-17110517

RESUMO

Antigravity muscles atrophy and weaken during prolonged mechanical unloading caused by bed rest or spaceflight. Unloading also induces oxidative stress in muscle, a putative cause of weakness. We tested the hypothesis that dietary supplementation with Bowman-Birk inhibitor concentrate (BBIC), a soy protein extract, would oppose these changes. Adult mice were fed a diet supplemented with 1% BBIC during hindlimb unloading for up to 12 days. Soleus muscles of mice fed the BBIC-supplemented diet weighed less, developed less force per cross-sectional area, and developed less total force after unloading than controls. BBIC supplementation was protective, blunting decrements in soleus muscle weight and force. Cytosolic oxidant activity was assessed using 2',7'-dichlorofluorescin diacetate. Oxidant activity increased in unloaded muscle, peaking at 3 days and remaining elevated through 12 days of unloading. Increases in oxidant activity correlated directly with loss of muscle mass and were abolished by BBIC supplementation. In vitro assays established that BBIC directly buffers reactive oxygen species and also inhibits serine protease activity. We conclude that dietary supplementation with BBIC protects skeletal muscle during prolonged unloading, promoting redox homeostasis in muscle fibers and blunting atrophy-induced weakness.


Assuntos
Debilidade Muscular/prevenção & controle , Músculo Esquelético/efeitos dos fármacos , Atrofia Muscular/prevenção & controle , Estresse Oxidativo/efeitos dos fármacos , Inibidor da Tripsina de Soja de Bowman-Birk/uso terapêutico , Inibidores da Tripsina/uso terapêutico , Animais , Antioxidantes/farmacologia , Comportamento Animal , Peso Corporal , Citosol/metabolismo , Elevação dos Membros Posteriores , Masculino , Camundongos , Camundongos Endogâmicos ICR , Contração Muscular , Fadiga Muscular , Músculo Esquelético/metabolismo , Inibidores de Proteases/farmacologia , Fatores de Tempo , Inibidor da Tripsina de Soja de Bowman-Birk/farmacologia , Inibidores da Tripsina/farmacologia
14.
Muscle Nerve ; 34(3): 298-303, 2006 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-16718687

RESUMO

Skeletal muscle of patients with Duchenne-type muscular dystrophy and mdx mice exhibits elevated activity of the transcription factor NF-kappaB (nuclear factor-kappaB), which may play a role in muscle catabolism. We measured skeletal muscle NF-kappaB activity in mdx mice at three ages (10 days, 4 weeks, and 8 weeks) to test the hypothesis that NF-kappaB activity is elevated in an age-dependent manner in these mice. In addition, we tested the hypothesis that NF-kappaB activity could be reduced in mdx skeletal muscle by dietary supplementation with curcumin (1% w/v) or by fatiguing muscle contractions. We found that NF-kappaB activity was elevated at 4 and 8 weeks of age but not at 10 days, and was resistant to inhibition by either fatiguing contractions or dietary curcumin. We conclude that NF-kappaB activity is elevated in dystrophic skeletal muscle in an age-related manner and is resistant to inhibition by physiological and pharmacological means. These findings are consistent with a role for NF-kappaB activation in dystrophic muscle wasting but suggest that predicted interventions such as exercise or inhibitors of the early steps in the NF-kappa activation pathway may not be effective and that targeted research is needed to identify novel therapeutic strategies.


Assuntos
Curcumina/farmacologia , Inibidores Enzimáticos/farmacologia , Contração Muscular/efeitos dos fármacos , Distrofia Muscular Animal/tratamento farmacológico , Distrofia Muscular de Duchenne/tratamento farmacológico , NF-kappa B/metabolismo , Animais , Modelos Animais de Doenças , Técnicas In Vitro , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos mdx , Contração Muscular/fisiologia , Atrofia Muscular/tratamento farmacológico , Atrofia Muscular/fisiopatologia , Distrofia Muscular Animal/fisiopatologia , Distrofia Muscular de Duchenne/fisiopatologia
15.
J Appl Physiol (1985) ; 100(2): 399-405, 2006 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-16166238

RESUMO

Phospholipase A2 (PLA2) activity supports production of reactive oxygen species (ROS) by mammalian cells. In skeletal muscle, endogenous ROS modulate the force of muscle contraction. We tested the hypothesis that skeletal muscle cells constitutively express the calcium-independent PLA2 (iPLA2) isoform and that iPLA2 modulates both cytosolic oxidant activity and contractile function. Experiments utilized differentiated C2C12 myotubes and a panel of striated muscles isolated from adult mice. Muscle preparations were processed for measurement of mRNA by real-time PCR, protein by immunoblot, cytosolic oxidant activity by the dichlorofluorescein oxidation assay, and contractile function by in vitro testing. We found that iPLA2 was constitutively expressed by all muscles tested (myotubes, diaphragm, soleus, extensor digitorum longus, gastrocnemius, heart) and that mRNA and protein levels were generally similar among muscles. Selective iPLA2 blockade by use of bromoenol lactone (10 microM) decreased cytosolic oxidant activity in myotubes and intact soleus muscle fibers. iPLA2 blockade also inhibited contractile function of unfatigued soleus muscles, shifting the force-frequency relationship rightward and depressing force production during acute fatigue. Each of these changes could be reproduced by selective depletion of superoxide anions using superoxide dismutase (1 kU/ml). These findings suggest that constitutively expressed iPLA2 modulates oxidant activity in skeletal muscle fibers by supporting ROS production, thereby influencing contractile properties and fatigue characteristics.


Assuntos
Músculo Esquelético/enzimologia , Fosfolipases A/metabolismo , Animais , Linhagem Celular , Citosol/enzimologia , Sequestradores de Radicais Livres/farmacologia , Fosfolipases A2 do Grupo VI , Técnicas In Vitro , Masculino , Camundongos , Camundongos Endogâmicos ICR , Contração Muscular , Fadiga Muscular , Fibras Musculares Esqueléticas/efeitos dos fármacos , Fibras Musculares Esqueléticas/enzimologia , Músculo Esquelético/citologia , Músculo Esquelético/efeitos dos fármacos , Miocárdio/enzimologia , Naftalenos/farmacologia , Oxirredução , Inibidores de Fosfodiesterase/farmacologia , Fosfolipases A/antagonistas & inibidores , Fosfolipases A/genética , Fosfolipases A2 , Pironas/farmacologia , RNA Mensageiro/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Músculos Respiratórios/enzimologia , Superóxido Dismutase/farmacologia
16.
Aviat Space Environ Med ; 75(7): 581-8, 2004 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-15267079

RESUMO

INTRODUCTION: Prolonged mechanical unloading induces skeletal muscle weakness, a major problem following extended bed rest or spaceflight. Antioxidants are reported to partially inhibit the weakness caused by limb immobilization. The current study tested allopurinol, a xanthine oxidase inhibitor with antioxidant properties, for its capacity to protect the function of unloaded antigravity muscles. METHODS: Adult mice conditioned by 12 d of hindlimb suspension, with or without allopurinol 50 mg x kg(-1) x d(-1), were compared with freely ambulating controls. Animals were anesthetized and soleus muscles were isolated for ex vivo analyses. RESULTS: Relative to control muscles, unloading decreased soleus weight (-44%; p < 0.05) and cross-sectional area (-38%; p < 0.05), increased cytosolic oxidant activity (-46%; p < 0.01), decreased absolute tetanic force (e.g., -64% at 250 Hz; p < 0.001 ) and force/area (-35%; p < 0.01), and increased passive compliance of the unstimulated muscle (p < 0.05). Allopurinol administration blunted the effects of unloading, partially inhibiting losses of absolute force (p < 0.05) and force/area (p < 0.05) without affecting muscle atrophy. The drug also blunted compliance changes in the passive muscle (p < 0.05). DISCUSSION: Allopurinol does not inhibit atrophy of skeletal muscle caused by prolonged unloading. However, allopurinol does lessen the contractile dysfunction caused by unloading, an action that may have potential benefit for astronauts and bedridden individuals.


Assuntos
Alopurinol/farmacologia , Antioxidantes/farmacologia , Sequestradores de Radicais Livres/farmacologia , Elevação dos Membros Posteriores , Contração Muscular/efeitos dos fármacos , Atrofia Muscular/prevenção & controle , Animais , Inibidores Enzimáticos/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos ICR , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/fisiologia , Xantina Oxidase/antagonistas & inibidores
17.
Am J Physiol Regul Integr Comp Physiol ; 287(4): R698-705, 2004 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-15178539

RESUMO

Free radicals are produced continuously by skeletal muscle fibers. Extracellular release of reactive oxygen species (ROS) and nitric oxide (NO) derivatives has been demonstrated, but little is known about intracellular oxidant regulation. We used a fluorescent oxidant probe, 2',7'-dichlorofluorescin (DCFH), to assess net oxidant activity in passive muscle fiber bundles isolated from mouse diaphragm and studied in vitro. We tested the following three hypotheses. 1) Net oxidant activity is decreased by muscle cooling. 2) CO(2) exposure depresses intracellular oxidant activity. 3) Muscle-derived ROS and NO both contribute to overall oxidant activity. Our results indicate that DCFH oxidation was diminished by cooling muscle fibers from 37 degrees C to 23 degrees C (P < 0.001). The rate of DCFH oxidation correlated positively with CO(2) exposure (0-10%; P < 0.05) and negatively with concurrent changes in pH (7.0-8.5; P < 0.05). Separate exposures to anti-ROS enzymes (superoxide dismutase, 1 kU/ml; catalase, 1 kU/ml), a glutathione peroxidase mimetic (ebselen, 30 microM), NO synthase inhibitors (N(omega)-nitro-l-arginine methyl ester, 1 mM; N(omega)-monomethyl-l-arginine, 1 mM), or an NO scavenger (hemoglobin, 1 microM) each inhibited DCFH oxidation (P < 0.05). Oxidation was increased by hydrogen peroxide, 100 microM, an NO donor (NOC-22, 400 microM), or the substrate for NO synthase (l-arginine, 5 mM). We conclude that net oxidant activity in resting muscle fibers is 1) decreased at subphysiological temperatures, 2) increased by CO(2) exposure, and 3) influenced by muscle-derived ROS and NO derivatives to similar degrees.


Assuntos
Dióxido de Carbono/farmacologia , Fibras Musculares Esqueléticas/metabolismo , Músculo Esquelético/metabolismo , Óxido Nítrico/fisiologia , Oxidantes/metabolismo , Animais , Antioxidantes/farmacologia , Azóis/farmacologia , Catalase/metabolismo , Citosol/metabolismo , Corantes Fluorescentes , Peróxido de Hidrogênio/farmacologia , Processamento de Imagem Assistida por Computador , Técnicas In Vitro , Indicadores e Reagentes , Isoindóis , Masculino , Camundongos , Camundongos Endogâmicos ICR , Fibras Musculares Esqueléticas/enzimologia , Músculo Esquelético/citologia , Músculo Esquelético/enzimologia , Compostos Organosselênicos/farmacologia , Oxidantes/farmacologia , Espécies Reativas de Oxigênio/metabolismo , Superóxido Dismutase/metabolismo , Temperatura
18.
J Appl Physiol (1985) ; 97(5): 1740-5, 2004 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-15208298

RESUMO

This study tested the hypothesis that skeletal muscle contraction activates nuclear factor-kappaB (NF-kappaB), a putative regulator of muscle protein breakdown. Muscle biopsies were obtained from the vastus lateralis of healthy humans before, immediately after, and 1 h after fatiguing resistance exercise of the lower limbs. Biopsies were analyzed for nuclear NF-kappaB DNA binding activity by using electrophoretic mobility shift assay. NF-kappaB activity, measured immediately after exercise, was less than preexercise activity; after 1-h recovery, activity returned to preexercise levels. In follow-up studies in adult mice, basal NF-kappaB activity varied among individual muscles. NF-kappaB activity in diaphragm fiber bundles was decreased after a 10-min bout of fatiguing tetanic contractions in vitro. NF-kappaB activity in soleus was increased by 12 days of unloading by hindlimb suspension; this increase was reversed by 10 min of fatiguing exercise. These data provide no support for our original hypothesis. Instead, acute fatiguing exercise appears to decrease NF-kappaB activity in muscle under a variety of conditions.


Assuntos
DNA/metabolismo , Exercício Físico/fisiologia , Fadiga Muscular/fisiologia , Músculo Esquelético/metabolismo , NF-kappa B/metabolismo , Adulto , Animais , Diafragma/metabolismo , Feminino , Membro Posterior , Elevação dos Membros Posteriores , Humanos , Perna (Membro) , Fígado/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos ICR , Fatores de Tempo
19.
Clin Physiol Funct Imaging ; 23(3): 149-54, 2003 May.
Artigo em Inglês | MEDLINE | ID: mdl-12752557

RESUMO

We compared the changes in compound muscle mass action potential (M-wave) recorded in vastus lateralis in response to hyperbaric hyperoxia (HBO) in nine combat divers who dived daily while breathing 100% O2 or O2-enriched mixture (O2 divers) to those measured in eight recreational divers who dived occasionally using compressed air/21% O2 (air divers). The O2 divers completed a 6-h HBO exposure in which the inspired oxygen pressure (PiO2) varied from 1.15 to 2.7 absolute atmospheres (ATA), PiO2 being maintained at 1.15 ATA throughout the first 2-h period, whereas the air divers only completed a 2-h HBO exposure with PiO2 constant at 1.15 ATA. Before HBO exposure, there were no intergroup differences between baseline M-wave characteristics (amplitude and duration), but the conduction time was significantly shorter in O2 divers compared with air divers. After 90 min of HBO (1.15 ATA) the air divers demonstrated neuromuscular hyperexcitability, as evidenced by an increased M-wave amplitude (13%, P<0.01 versus baseline), shortened M-wave duration (5%, P<0.05 versus baseline), and reduced conduction time (5%, P<0.01 versus baseline). In O2 divers, similar HBO-induced M-wave changes were only observed when PiO2 was greater than 1.50 ATA. We conclude that HBO elicites neuromuscular hyperexcitability, attenuated in elite O2 divers.


Assuntos
Potenciais de Ação/fisiologia , Mergulho/fisiologia , Eletromiografia/métodos , Oxigenoterapia Hiperbárica/métodos , Músculo Esquelético/fisiologia , Condução Nervosa/fisiologia , Junção Neuromuscular/fisiologia , Adulto , Humanos , Hiperóxia/fisiopatologia , Militares , Músculo Esquelético/fisiopatologia , Junção Neuromuscular/fisiopatologia , Transmissão Sináptica/fisiologia , Coxa da Perna/fisiologia
20.
Muscle Nerve ; 26(2): 194-200, 2002 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-12210382

RESUMO

It has previously been shown that both hypoxemia and nitric oxide (NO) synthase blockade depress the activation of group IV muscle afferents after muscle stimulation (MS). In the present study, we questioned whether hypoxemia exerts a specific inhibitory influence, independently from its effects on endogenous NO formation. This hypothesis was tested in two groups of anesthetized rabbits in which we examined the effects of hypoxemia, and then of subsequent NO synthase blockade by N(G)-nitro-L-arginine methyl ester (L-NAME), and vice versa. In each protocol, group IV afferent activity was recorded from the resting tibialis anterior muscle and after 3-min periods of MS that elicited a significant decrease in muscle force. NO synthase blockade in normoxemia suppressed the group IV afferent response to MS, and hypoxemia alone significantly reduced the post-MS activation of these nerve afferents (+18% vs. +28% in normoxemia). In hypoxemic rabbits, further NO synthase blockade abolished the post-MS activation of group IV afferents. Moreover, when hypoxemia followed the NO synthase blockade, MS significantly reduced the discharge of group IV afferents (-28%). Thus, while these muscle afferents are activated after fatiguing muscle contractions when the endogenous NO production is present, they are deactivated by hypoxemia when NO production is blocked. We conclude that endogenous NO production and hypoxemia exert opposite effects on the activation of the group IV afferents. Our data anticipate the neuromuscular side effects of treatments using exogenous NO or drugs acting on endogenous NO production.


Assuntos
Hipóxia/metabolismo , Músculo Esquelético/inervação , Neurônios Aferentes/metabolismo , Óxido Nítrico/metabolismo , Animais , Inibidores Enzimáticos/farmacologia , Fadiga Muscular/fisiologia , Músculo Esquelético/fisiologia , NG-Nitroarginina Metil Éster/farmacologia , Neurônios Aferentes/efeitos dos fármacos , Óxido Nítrico Sintase/antagonistas & inibidores , Óxido Nítrico Sintase/metabolismo , Nitroarginina/farmacologia , Coelhos
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