Immobilization-induced activation of key proteolytic systems in skeletal muscles is prevented by a mitochondria-targeted antioxidant

2013 ◽  
Vol 115 (4) ◽  
pp. 529-538 ◽  
Author(s):  
Erin E. Talbert ◽  
Ashley J. Smuder ◽  
Kisuk Min ◽  
Oh Sung Kwon ◽  
Hazel H. Szeto ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Atrophy ◽  
Skeletal Muscles ◽  
Mammalian Target Of Rapamycin ◽  
Skeletal Muscle Atrophy ◽  
Muscle Disuse ◽  
Mitochondrial Ros ◽  
Disuse Muscle Atrophy ◽  
Muscle Fiber Atrophy ◽  
First Time

Long periods of skeletal muscle disuse result in muscle fiber atrophy, and mitochondrial production of reactive oxygen species (ROS) appears to be a required signal for the increase in protein degradation that occurs during disuse muscle atrophy. The experiments detailed here demonstrate for the first time in limb muscle that the inactivity-induced increases in E3 ligase expression and autophagy biomarkers result from increases in mitochondrial ROS emission. Treatment of animals with a mitochondrial-targeted antioxidant also prevented the disuse-induced decrease in anabolic signaling (Akt/mammalian target of rapamycin signaling) that is normally associated with prolonged inactivity in skeletal muscles. Additionally, our results confirm previous findings that treatment with a mitochondrial-targeted antioxidant is sufficient to prevent casting-induced skeletal muscle atrophy, mitochondrial dysfunction, and activation of the proteases calpain and caspase-3. Collectively, these data reveal that inactivity-induced increases in mitochondrial ROS emission play a required role in activation of key proteolytic systems and the downregulation of important anabolic signaling molecules in muscle fibers exposed to prolonged inactivity.

Role of SIRT2 in regulating the dexamethasone-activated autophagy pathway in skeletal muscle atrophy

2021 ◽  
Author(s):  
Ziqiu HAN ◽  
Cen CHANG ◽  
Weiyi ZHU ◽  
Yanlei ZHANG ◽  
Jing ZHENG ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Atrophy ◽  
Skeletal Muscles ◽  
Weight Ratio ◽  
Beclin 1 ◽  
C2c12 Cells ◽  
Skeletal Muscle Atrophy ◽  
Time To Exhaustion ◽  
Endurance Capacity ◽  
Polymerase Chain Reaction Inhibition

The proteolytic autophagy system is involved in a major regulatory pathway in dexamethasone (Dex)-induced muscle atrophy. Sirtuin 2 (SIRT2) is known to participate in modulating autophagy signaling, exerting effects in skeletal muscle atrophy. We aimed to determine the effects of SIRT2 on autophagy in Dex-induced myoatrophy. Mice were randomly divided into the normal, Dex, and sirtinol groups. C2C12 cells were differentiated into myotubes and transfected with short hairpin (sh)-Sirt2-green fluorescent protein (GFP) or Sirt2-GFP lentivirus. To evaluate the mass and function of skeletal muscles, we measured the myofiber cross-sectional area, myotube size, gastrocnemius muscle wet weight/body weight ratio (%), and time-to-exhaustion. The SIRT2, myosin heavy chain (MyHC), LC3, and Beclin-1 expression levels were detected by western blotting and quantitative reverse transcription-polymerase chain reaction. Inhibition of SIRT2 markedly attenuated the muscle mass and endurance capacity. The same phenotype was observed in Sirt2-shRNA-treated myotubes, as evidenced by their decreased size. Conversely, SIRT2 overexpression alleviated Dex-induced myoatrophy in vitro. Moreover, SIRT2 negatively regulated the expression of the LC3b and Beclin-1 in skeletal muscles. These findings suggested that SIRT2 activation protects myotubes against Dex-induced atrophy through the inhibition of the autophagy system; this phenomenon may potentially serve as a target for treating glucocorticoid-induced myopathy.

scholarly journals Two Weeks of Smoking Cessation Reverse Cigarette Smoke-Induced Skeletal Muscle Atrophy and Mitochondrial Dysfunction in Mice

2020 ◽  
Author(s):  
Tom Tanjeko Ajime ◽  
Jef Serré ◽  
Rob C I Wüst ◽  
Guy Anselme Mpaka Messa ◽  
Chiel Poffé ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Smoking Cessation ◽  
Mitochondrial Dysfunction ◽  
Muscle Mass ◽  
Muscle Atrophy ◽  
Skeletal Muscles ◽  
Skeletal Muscle Atrophy ◽  
Limb Muscle ◽  
Male Mice ◽  
And Function

Abstract Introduction Apart from its adverse effects on the respiratory system, cigarette smoking also induces skeletal muscle atrophy and dysfunction. Whether short-term smoking cessation can restore muscle mass and function is unknown. We, therefore, studied the impact of 1- and 2-week smoking cessation on skeletal muscles in a mouse model. Methods Male mice were divided into four groups: Air-exposed (14 weeks); cigarette smoke (CS)-exposed (14 weeks); CS-exposed (13 weeks) followed by 1-week cessation; CS-exposed (12 weeks) followed by 2 weeks cessation to examine exercise capacity, physical activity levels, body composition, muscle function, capillarization, mitochondrial function and protein expression in the soleus, plantaris, and diaphragm muscles. Results CS-induced loss of body and muscle mass was significantly improved within 1 week of cessation due to increased lean and fat mass. Mitochondrial respiration and protein levels of the respiratory complexes in the soleus were lower in CS-exposed mice, but similar to control values after 2 weeks of cessation. Exposing isolated soleus muscles to CS extracts reduced mitochondrial respiration that was reversed after removing the extract. While physical activity was reduced in all groups, exercise capacity, limb muscle force, fatigue resistance, fiber size and capillarization, and diaphragm cytoplasmic HIF-1α were unaltered by CS-exposure. However, CS-induced diaphragm atrophy and increased capillary density were not seen after 2 weeks of smoking cessation. Conclusion In male mice, 2 weeks of smoking cessation reversed smoking-induced mitochondrial dysfunction, limb muscle mass loss, and diaphragm muscle atrophy, highlighting immediate benefits of cessation on skeletal muscles. Implications Our study demonstrates that CS-induced skeletal muscle mitochondrial dysfunction and atrophy are significantly improved by 2 weeks of cessation in male mice. We show for the first time that smoking cessation as short as 1 to 2 weeks is associated with immediate beneficial effects on skeletal muscle structure and function with the diaphragm being particularly sensitive to CS-exposure and cessation. This could help motivate smokers to quit smoking as early as possible. The knowledge that smoking cessation has potential positive extrapulmonary effects is particularly relevant for patients referred to rehabilitation programs and those admitted to hospitals suffering from acute or chronic muscle deterioration yet struggling with smoking cessation.

scholarly journals Effects of Nandrolone in the Counteraction of Skeletal Muscle Atrophy in a Mouse Model of Muscle Disuse: Molecular Biology and Functional Evaluation

PLoS ONE ◽  
2015 ◽  
Vol 10 (6) ◽  
pp. e0129686 ◽  
Author(s):  
Giulia Maria Camerino ◽  
Jean-François Desaphy ◽  
Michela De Bellis ◽  
Roberta Francesca Capogrosso ◽  
Anna Cozzoli ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Molecular Biology ◽  
Mouse Model ◽  
Muscle Atrophy ◽  
Skeletal Muscle Atrophy ◽  
Functional Evaluation ◽  
Muscle Disuse

scholarly journals FOXO signaling is required for disuse muscle atrophy and is directly regulated by Hsp70

2010 ◽  
Vol 298 (1) ◽  
pp. C38-C45 ◽  
Author(s):  
Sarah M. Senf ◽  
Stephen L. Dodd ◽  
Andrew R. Judge
Keyword(s):  
Skeletal Muscle ◽  
Muscle Atrophy ◽  
Muscle Fiber ◽  
Muscle Wasting ◽  
Dominant Negative ◽  
Disuse Muscle Atrophy ◽  
Rat Soleus Muscle ◽  
Muscle Fiber Atrophy ◽  
Fiber Atrophy

The purpose of the current study was to determine whether heat shock protein 70 (Hsp70) directly regulates forkhead box O (FOXO) signaling in skeletal muscle. This aim stems from previous work demonstrating that Hsp70 overexpression inhibits disuse-induced FOXO transactivation and prevents muscle fiber atrophy. However, although FOXO is sufficient to cause muscle wasting, no data currently exist on the requirement of FOXO signaling in the progression of physiological muscle wasting, in vivo. In the current study we show that specific inhibition of FOXO, via expression of a dominant-negative FOXO3a, in rat soleus muscle during disuse prevented >40% of muscle fiber atrophy, demonstrating that FOXO signaling is required for disuse muscle atrophy. Subsequent experiments determined whether Hsp70 directly regulates FOXO3a signaling when independently activated in skeletal muscle, via transfection of FOXO3a. We show that Hsp70 inhibits FOXO3a-dependent transcription in a gene-specific manner. Specifically, Hsp70 inhibited FOXO3a-induced promoter activation of atrogin-1, but not MuRF1. Further studies showed that a FOXO3a DNA-binding mutant can activate MuRF1, but not atrogin-1, suggesting that FOXO3a activates these two genes through differential mechanisms. In summary, FOXO signaling is required for physiological muscle atrophy and is directly inhibited by Hsp70.

scholarly journals Mitochondrial-targeted antioxidants protect skeletal muscle against immobilization-induced muscle atrophy

2011 ◽  
Vol 111 (5) ◽  
pp. 1459-1466 ◽  
Author(s):  
Kisuk Min ◽  
Ashley J. Smuder ◽  
Oh-sung Kwon ◽  
Andreas N. Kavazis ◽  
Hazel H. Szeto ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Skeletal Muscle ◽  
Muscle Atrophy ◽  
Muscle Fibers ◽  
Skeletal Muscle Atrophy ◽  
Ros Production ◽  
Oxygen Species ◽  
Mitochondrial Ros ◽  
Protease Activation ◽  
Limb Immobilization

Prolonged periods of muscular inactivity (e.g., limb immobilization) result in skeletal muscle atrophy. Although it is established that reactive oxygen species (ROS) play a role in inactivity-induced skeletal muscle atrophy, the cellular pathway(s) responsible for inactivity-induced ROS production remain(s) unclear. To investigate this important issue, we tested the hypothesis that elevated mitochondrial ROS production contributes to immobilization-induced increases in oxidative stress, protease activation, and myofiber atrophy in skeletal muscle. Cause-and-effect was determined by administration of a novel mitochondrial-targeted antioxidant (SS-31) to prevent immobilization-induced mitochondrial ROS production in skeletal muscle fibers. Compared with ambulatory controls, 14 days of muscle immobilization resulted in significant muscle atrophy, along with increased mitochondrial ROS production, muscle oxidative damage, and protease activation. Importantly, treatment with a mitochondrial-targeted antioxidant attenuated the inactivity-induced increase in mitochondrial ROS production and prevented oxidative stress, protease activation, and myofiber atrophy. These results support the hypothesis that redox disturbances contribute to immobilization-induced skeletal muscle atrophy and that mitochondria are an important source of ROS production in muscle fibers during prolonged periods of inactivity.

scholarly journals Low Levels of Serum Tryptophan Underlie Skeletal Muscle Atrophy

Nutrients ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 978 ◽  
Author(s):  
Soranobu Ninomiya ◽  
Nobuhiko Nakamura ◽  
Hiroshi Nakamura ◽  
Taku Mizutani ◽  
Yuto Kaneda ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Atrophy ◽  
Skeletal Muscles ◽  
B Cell Lymphoma ◽  
Tryptophan Metabolism ◽  
Skeletal Muscle Atrophy ◽  
C2c12 Myoblast ◽  
Standard Diet ◽  
Deficient Diet ◽  
Low Levels

Sarcopenia is a poor prognosis factor in some cancer patients, but little is known about the mechanisms by which malignant tumors cause skeletal muscle atrophy. Tryptophan metabolism mediated by indoleamine 2,3-dioxygenase is one of the most important amino acid changes associated with cancer progression. Herein, we demonstrate the relationship between skeletal muscles and low levels of tryptophan. A positive correlation was observed between the volume of skeletal muscles and serum tryptophan levels in patients with diffuse large B-cell lymphoma. Low levels of tryptophan reduced C2C12 myoblast cell proliferation and differentiation. Fiber diameters in the tibialis anterior of C57BL/6 mice fed a tryptophan-deficient diet were smaller than those in mice fed a standard diet. Metabolomics analysis revealed that tryptophan-deficient diet downregulated glycolysis in the gastrocnemius and upregulated the concentrations of amino acids associated with the tricarboxylic acid cycle. The weights and muscle fiber diameters of mice fed the tryptophan-deficient diet recovered after switching to the standard diet. Our data showed a critical role for tryptophan in regulating skeletal muscle mass. Thus, the tryptophan metabolism pathway may be a promising target for preventing or treating skeletal muscle atrophies.

scholarly journals Skeletal muscle denervation causes skeletal muscle atrophy through a pathway that involves both Gadd45a and HDAC4

2013 ◽  
Vol 305 (7) ◽  
pp. E907-E915 ◽  
Author(s):  
Kale S. Bongers ◽  
Daniel K. Fox ◽  
Scott M. Ebert ◽  
Steven D. Kunkel ◽  
Michael C. Dyle ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Atrophy ◽  
Muscle Fiber ◽  
Molecular Mechanisms ◽  
Skeletal Muscle Atrophy ◽  
Muscle Denervation ◽  
Mrna Induction ◽  
Convergence Point ◽  
Muscle Fiber Atrophy ◽  
Fiber Atrophy

Skeletal muscle denervation causes muscle atrophy via complex molecular mechanisms that are not well understood. To better understand these mechanisms, we investigated how muscle denervation increases growth arrest and DNA damage-inducible 45α ( Gadd45a) mRNA in skeletal muscle. Previous studies established that muscle denervation strongly induces Gadd45a mRNA, which increases Gadd45a, a small myonuclear protein that is required for denervation-induced muscle fiber atrophy. However, the mechanism by which denervation increases Gadd45a mRNA remained unknown. Here, we demonstrate that histone deacetylase 4 (HDAC4) mediates induction of Gadd45a mRNA in denervated muscle. Using mouse models, we show that HDAC4 is required for induction of Gadd45a mRNA during muscle denervation. Conversely, forced expression of HDAC4 is sufficient to increase skeletal muscle Gadd45a mRNA in the absence of muscle denervation. Moreover, Gadd45a mediates several downstream effects of HDAC4, including induction of myogenin mRNA, induction of mRNAs encoding the embryonic nicotinic acetylcholine receptor, and, most importantly, skeletal muscle fiber atrophy. Because Gadd45a induction is also a key event in fasting-induced muscle atrophy, we tested whether HDAC4 might also contribute to Gadd45a induction during fasting. Interestingly, however, HDAC4 is not required for fasting-induced Gadd45a expression or muscle atrophy. Furthermore, activating transcription factor 4 (ATF4), which contributes to fasting-induced Gadd45a expression, is not required for denervation-induced Gadd45a expression or muscle atrophy. Collectively, these results identify HDAC4 as an important regulator of Gadd45a in denervation-induced muscle atrophy and elucidate Gadd45a as a convergence point for distinct upstream regulators during muscle denervation and fasting.

scholarly journals Various Jobs of Proteolytic Enzymes in Skeletal Muscle during Unloading: Facts and Speculations

2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
E. V. Kachaeva ◽  
B. S. Shenkman
Keyword(s):  
Skeletal Muscle ◽  
Muscle Atrophy ◽  
Skeletal Muscles ◽  
Proteolytic Enzymes ◽  
Disuse Atrophy ◽  
Muscle Degeneration ◽  
Muscle Adaptation ◽  
Signaling Systems ◽  
Disuse Muscle Atrophy ◽  
Postural Muscles

Skeletal muscles, namely, postural muscles, as soleus, suffer from atrophy under disuse. Muscle atrophy development caused by unloading differs from that induced by denervation or other stimuli. Disuse atrophy is supposed to be the result of shift of protein synthesis/proteolysis balance towards protein degradation increase. Maintaining of the balance involves many systems of synthesis and proteolysis, whose activation leads to muscle adaptation to disuse rather than muscle degeneration. Here, we review recent data on activity of signaling systems involved in muscle atrophy development under unloading and muscle adaptation to the lack of support.

scholarly journals Nox2 Inhibition Regulates Stress Response and Mitigates Skeletal Muscle Fiber Atrophy during Simulated Microgravity

2021 ◽  
Vol 22 (6) ◽  
pp. 3252
Author(s):  
John M. Lawler ◽  
Jeffrey M. Hord ◽  
Pat Ryan ◽  
Dylan Holly ◽  
Mariana Janini Gomes ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Stress Response ◽  
Muscle Atrophy ◽  
Muscle Fiber ◽  
Skeletal Muscle Atrophy ◽  
Positive Staining ◽  
Angiotensin Ii Receptor ◽  
Mechanical Unloading ◽  
Muscle Fiber Atrophy ◽  
Fiber Atrophy

Insufficient stress response and elevated oxidative stress can contribute to skeletal muscle atrophy during mechanical unloading (e.g., spaceflight and bedrest). Perturbations in heat shock proteins (e.g., HSP70), antioxidant enzymes, and sarcolemmal neuronal nitric oxidase synthase (nNOS) have been linked to unloading-induced atrophy. We recently discovered that the sarcolemmal NADPH oxidase-2 complex (Nox2) is elevated during unloading, downstream of angiotensin II receptor 1, and concomitant with atrophy. Here, we hypothesized that peptidyl inhibition of Nox2 would attenuate disruption of HSP70, MnSOD, and sarcolemmal nNOS during unloading, and thus muscle fiber atrophy. F344 rats were divided into control (CON), hindlimb unloaded (HU), and hindlimb unloaded +7.5 mg/kg/day gp91ds-tat (HUG) groups. Unloading-induced elevation of the Nox2 subunit p67phox-positive staining was mitigated by gp91ds-tat. HSP70 protein abundance was significantly lower in HU muscles, but not HUG. MnSOD decreased with unloading; however, MnSOD was not rescued by gp91ds-tat. In contrast, Nox2 inhibition protected against unloading suppression of the antioxidant transcription factor Nrf2. nNOS bioactivity was reduced by HU, an effect abrogated by Nox2 inhibition. Unloading-induced soleus fiber atrophy was significantly attenuated by gp91ds-tat. These data establish a causal role for Nox2 in unloading-induced muscle atrophy, linked to preservation of HSP70, Nrf2, and sarcolemmal nNOS.

scholarly journals Mitochondrial signaling contributes to disuse muscle atrophy

2012 ◽  
Vol 303 (1) ◽  
pp. E31-E39 ◽  
Author(s):  
Scott K. Powers ◽  
Michael P. Wiggs ◽  
Jose A. Duarte ◽  
A. Murat Zergeroglu ◽  
Haydar A. Demirel
Keyword(s):  
Skeletal Muscle ◽  
Mechanical Ventilation ◽  
Muscle Atrophy ◽  
Prolonged Mechanical Ventilation ◽  
Therapeutic Interventions ◽  
Skeletal Muscle Atrophy ◽  
Future Research ◽  
Primary Role ◽  
Mitochondrial Signaling ◽  
Disuse Muscle Atrophy

It is well established that long durations of bed rest, limb immobilization, or reduced activity in respiratory muscles during mechanical ventilation results in skeletal muscle atrophy in humans and other animals. The idea that mitochondrial damage/dysfunction contributes to disuse muscle atrophy originated over 40 years ago. These early studies were largely descriptive and did not provide unequivocal evidence that mitochondria play a primary role in disuse muscle atrophy. However, recent experiments have provided direct evidence connecting mitochondrial dysfunction to muscle atrophy. Numerous studies have described changes in mitochondria shape, number, and function in skeletal muscles exposed to prolonged periods of inactivity. Furthermore, recent evidence indicates that increased mitochondrial ROS production plays a key signaling role in both immobilization-induced limb muscle atrophy and diaphragmatic atrophy occurring during prolonged mechanical ventilation. Moreover, new evidence reveals that, during denervation-induced muscle atrophy, increased mitochondrial fragmentation due to fission is a required signaling event that activates the AMPK-FoxO3 signaling axis, which induces the expression of atrophy genes, protein breakdown, and ultimately muscle atrophy. Collectively, these findings highlight the importance of future research to better understand the mitochondrial signaling mechanisms that contribute to disuse muscle atrophy and to develop novel therapeutic interventions for prevention of inactivity-induced skeletal muscle atrophy.

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