Aging does not alter the mechanosensitivity of the p38, p70S6k, and JNK2 signaling pathways in skeletal muscle

2005 ◽  
Vol 98 (4) ◽  
pp. 1562-1566 ◽  
Author(s):  
Troy A. Hornberger ◽  
R. D. Mateja ◽  
E. R. Chin ◽  
J. L. Andrews ◽  
K. A. Esser
Keyword(s):  
Skeletal Muscle ◽  
Signaling Pathways ◽  
Ex Vivo ◽  
Mechanical Stimuli ◽  
S6 Kinase ◽  
Diminished Capacity ◽  
Ribosomal S6 Kinase ◽  
Passive Stretch ◽  
Old Mice ◽  
Dependent Mechanism

The capacity for skeletal muscle to recover its mass following periods of unloading (regrowth) has been reported to decline with age. Although the mechanisms responsible for the impaired regrowth are not known, it has been suggested that aged muscles have a diminished capacity to sense and subsequently respond to a given amount of mechanical stimuli (mechanosensitivity). To test this hypothesis, extensor digitorum longus muscles from young (2–3 mo) and old (26–27 mo) mice were subjected to intermittent 15% passive stretch (ex vivo) as a source of mechanical stimulation and analyzed for alterations in the phosphorylation of stress-activated protein kinase (p38), ribosomal S6 kinase (p70S6k), and the p54 jun N-terminal kinase (JNK2). The results indicated that the average magnitude of specific tension (mechanical stimuli) induced by 15% stretch was similar in muscles from young and old mice. Young and old muscles also revealed similar increases in the magnitude of mechanically induced p38, p70S6k (threonine/serine 421/424 and threonine 389), and JNK2 phosphorylation. In addition, coincubation experiments demonstrated that the release of locally acting growth factors was not sufficient for the induction of JNK2 phosphorylation, suggesting that JNK2 was activated by a mechanical rather than a mechanical/growth factor-dependent mechanism. Taken together, the results of this study demonstrate that aging does not alter the mechanosensitivity of the p38, p70S6k, and JNK2 signaling pathways in skeletal muscle.

scholarly journals RESTORATION OF HYPOXIA SIGNALING IMPROVES AGING-ASSOCIATED LOSS OF SKELETAL MUSCLE REGENERATIVE POTENTIAL

2019 ◽  
Vol 3 (Supplement_1) ◽  
pp. S730-S731
Author(s):  
Kodi Udeh ◽  
Bin Li ◽  
Yori Endo ◽  
Adriana Panayi ◽  
Dharaniya Sakthivel ◽  
...  
Keyword(s):  
Gene Expression ◽  
Skeletal Muscle ◽  
Ex Vivo ◽  
Post Injury ◽  
Cross Sectional ◽  
Protein Levels ◽  
Aryl Hydrocarbon ◽  
Ability To Regenerate ◽  
Old Mice ◽  
Hypoxia Signaling

Abstract Skeletal muscle retains the ability to regenerate throughout life, but this decreases significantly with aging. The present study investigates whether aging-associated loss of muscle hypoxia signaling limits regenerative potential. Utilizing young (3 months) and old (22-24 months) mice, skeletal muscle from old mice exhibited a 40% decline in the cross-sectional area (CSA) of newly regenerating fibers following cryoinjury at day 10 (p < 0.01) post-injury as compared to young. Focused PCR array demonstrated a greater than 3-fold decline in expression of the majority of hypoxia signaling genes. In particular, aryl hydrocarbon receptor nuclear translocator (ARNT), which is required for downstream hypoxia signaling and the transcription of hypoxia response genes, is 5-fold lower for both gene expression (p < 0.01) and protein levels (p < 0.01) in old versus young mice. To determine the effects of ARNT on muscle regeneration, we utilized a genetically modified mouse which results in an 80% decrease in ARNT gene expression following activation, specifically in skeletal muscle. Compared to littermate controls, mice with a muscle specific knockdown of ARNT (mKO ARNT) exhibit a 30% decline in regenerating fiber sizes at day 10 (p < 0.01) following cryoinjury, without any loss of regenerative potential in FACS isolated satellite cells ex vivo. Administration of a pharmacologic hypoxia activator, ML228, induced a 30% increase in regenerating fiber CSA in both old mice and mKO ARNT mice (p < 0.01) as compared to treatment with vehicle control. These data suggest hypoxia signaling declines with aging in skeletal muscle and activation of hypoxia signaling may promote regeneration.

scholarly journals Passive stretch regulates skeletal muscle glucose uptake independent of nitric oxide synthase

2019 ◽  
Vol 126 (1) ◽  
pp. 239-245 ◽  
Author(s):  
Jarrod P. Kerris ◽  
Andrew C. Betik ◽  
Jinhua Li ◽  
Glenn K. McConell
Keyword(s):  
Nitric Oxide ◽  
Skeletal Muscle ◽  
Nitric Oxide Synthase ◽  
Glucose Uptake ◽  
Signaling Pathways ◽  
Mechanical Strain ◽  
Passive Stretching ◽  
Skeletal Muscle Glucose Uptake ◽  
Oxide Synthase ◽  
Passive Stretch

Skeletal muscle contraction increases glucose uptake via an insulin-independent mechanism. Signaling pathways arising from mechanical strain are activated during muscle contractions, and mechanical strain in the form of passive stretching stimulates glucose uptake. However, the exact mechanisms regulating stretch-stimulated glucose uptake are not known. Since nitric oxide synthase (NOS) has been implicated in the regulation of glucose uptake during ex vivo and in situ muscle contractions and during exercise, and NO is increased with stretch, we examined whether the increase in muscle glucose uptake during stretching involves NOS. We passively stretched isolated extensor digitorum longus muscles (15 min at ~100–130 mN) from control mice and mice lacking either neuronal NOSµ (nNOSµ) or endothelial NOS (eNOS) isoforms, as well as used pharmacological inhibitors of NOS. Stretch significantly increased muscle glucose uptake appoximately twofold ( P < 0.05), and this was unaffected by the presence of the NOS inhibitors NG-monomethyl-l-arginine (100 µM) or NG-nitro-l-arginine methyl ester (100 µM). Similarly, stretch-stimulated glucose uptake was not attenuated by deletion of either eNOS or nNOSµ isoforms. Furthermore, stretching failed to increase skeletal muscle NOS enzymatic activity above resting levels. These data clearly demonstrate that stretch-stimulated skeletal muscle glucose uptake is not dependent on NOS. NEW & NOTEWORTHY Passive stretching is known to activate muscle glucose uptake through mechanisms that partially overlap with contraction. We report that genetic knockout of endothelial nitric oxide synthase (NOS) or neuronal NOS or pharmacological NOS inhibition does not affect stretch-stimulated glucose uptake. Passive stretch failed to increase NOS activity above resting levels. This information is important for the study of signaling pathways that regulate stretch-stimulated glucose uptake and indicate that NOS should be excluded as a potential signaling factor in this regard.

scholarly journals Androgens induce growth of the limb skeletal muscles in a rapamycin-insensitive manner

2018 ◽  
Vol 315 (4) ◽  
pp. R721-R729 ◽  
Author(s):  
Michael L. Rossetti ◽  
David H. Fukuda ◽  
Bradley S. Gordon
Keyword(s):  
Skeletal Muscle ◽  
Fiber Type ◽  
Muscle Growth ◽  
Total Protein Content ◽  
Cross Sectional ◽  
S6 Kinase ◽  
Mechanistic Target Of Rapamycin ◽  
Ribosomal S6 Kinase

Signaling through the mechanistic target of rapamycin complex 1 (mTORC1) has been well defined as an androgen-sensitive transducer mediating skeletal muscle growth in vitro; however, this has yet to be tested in vivo. As such, male mice were subjected to either sham or castration surgery and allowed to recover for 7 wk to induce atrophy of skeletal muscle. Then, castrated mice were implanted with either a control pellet or a pellet that administered rapamycin (~2.5 mg·kg−1·day−1). Seven days postimplant, a subset of castrated mice with control pellets and all castrated mice with rapamycin pellets were given once weekly injections of nandrolone decanoate (ND) to induce muscle growth over a six-week period. Effective blockade of mTORC1 by rapamycin was noted in the skeletal muscle by the inability of insulin to induce phosphorylation of ribosomal S6 kinase 1 70 kDa (Thr389) and uncoordinated-like kinase 1 (Ser757). While castration reduced tibialis anterior (TA) mass, muscle fiber cross-sectional area, and total protein content, ND administration restored these measures to sham levels in a rapamycin-insensitive manner. Similar findings were also observed in the plantaris and soleus, suggesting this rapamycin-insensitive effect was not specific to the TA or fiber type. Androgen-mediated growth was not due to changes in translational capacity. Despite these findings in the limb skeletal muscle, rapamycin completely prevented the ND-mediated growth of the heart. In all, these data indicate that mTORC1 has a limited role in the androgen-mediated growth of the limb skeletal muscle; however, mTORC1 was necessary for androgen-mediated growth of heart muscle.

scholarly journals Altered Extracellular Signal-Regulated Kinase Signaling and Glycogen Metabolism in Skeletal Muscle from p90 Ribosomal S6 Kinase 2 Knockout Mice

2001 ◽  
Vol 21 (1) ◽  
pp. 81-87 ◽  
Author(s):  
Scott D. Dufresne ◽  
Christian Bjørbæk ◽  
Karim El-Haschimi ◽  
Yi Zhao ◽  
William G. Aschenbach ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Knockout Mice ◽  
Muscle Glycogen ◽  
Glycogen Synthase ◽  
S6 Kinase ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal ◽  
P90 Ribosomal S6 Kinase ◽  
Ribosomal S6 Kinase ◽  
Glycogen Synthase Activity

ABSTRACT The p90 ribosomal S6 kinase (RSK), a cytosolic substrate for the extracellular signal-regulated kinase (ERK), is involved in transcriptional regulation, and one isoform (RSK2) has been implicated in the activation of glycogen synthase by insulin. To determine RSK2 function in vivo, mice lacking a functional rsk2 gene were generated and studied in response to insulin and exercise, two potent stimulators of the ERK cascade in skeletal muscle. RSK2 knockout (KO) mice weigh 10% less and are 14% shorter than wild-type (WT) mice. They also have impaired learning and coordination. Hindlimb skeletal muscles were obtained from mice 10, 15, or 30 min after insulin injection or immediately after strenuous treadmill exercise for 60 min. While insulin and exercise significantly increased ERK phosphorylation in skeletal muscle from both WT and KO mice, the increases were twofold greater in the KO animals. This occurred despite 27% lower ERK2 protein expression in skeletal muscle of KO mice. KO mice had 18% less muscle glycogen in the fasted basal state, and insulin increased glycogen synthase activity more in KO than WT mice. The enhanced insulin-stimulated increases in ERK and glycogen synthase activities in KO mice were not associated with higher insulin receptor or with IRS1 tyrosine phosphorylation or with IRS1 binding to phosphatidylinositol 3-kinase. However, insulin-stimulated serine phosphorylation of Akt was significantly higher in the KO animals. c-fos mRNA was increased similarly in muscle from WT and KO mice in response to insulin (2.5-fold) and exercise (15-fold). In conclusion, RSK2 likely plays a major role in feedback inhibition of the ERK pathway in skeletal muscle. Furthermore, RSK2 is not required for activation of muscle glycogen synthase by insulin but may indirectly modulate muscle glycogen synthase activity and/or glycogen content by other mechanisms, possibly through regulation of Akt. RSK2 knockout mice may be a good animal model for the study of Coffin-Lowry syndrome.

scholarly journals Purification and characterization of a novel ribosomal S6 kinase from skeletal muscle of insulin-treated rats.

1994 ◽  
Vol 269 (10) ◽  
pp. 7816-7823
Author(s):  
Y.J. Hei ◽  
S.L. Pelech ◽  
X. Chen ◽  
J. Diamond ◽  
J.H. McNeill
Keyword(s):  
Skeletal Muscle ◽  
Purification And Characterization ◽  
S6 Kinase ◽  
Ribosomal S6 Kinase

scholarly journals Mutation of the PDK1 PH Domain Inhibits Protein Kinase B/Akt, Leading to Small Size and Insulin Resistance

2008 ◽  
Vol 28 (10) ◽  
pp. 3258-3272 ◽  
Author(s):  
Jose R. Bayascas ◽  
Stephan Wullschleger ◽  
Kei Sakamoto ◽  
Juan M. García-Martínez ◽  
Carol Clacher ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Protein Kinase ◽  
Signaling Pathways ◽  
Protein Kinase B ◽  
Ph Domain ◽  
S6 Kinase ◽  
Downstream Signaling ◽  
Insulin Resistant ◽  
Ribosomal S6 Kinase ◽  
Mtor Complex 1

ABSTRACT PDK1 activates a group of kinases, including protein kinase B (PKB)/Akt, p70 ribosomal S6 kinase (S6K), and serum and glucocorticoid-induced protein kinase (SGK), that mediate many of the effects of insulin as well as other agonists. PDK1 interacts with phosphoinositides through a pleckstrin homology (PH) domain. To study the role of this interaction, we generated knock-in mice expressing a mutant of PDK1 incapable of binding phosphoinositides. The knock-in mice are significantly small, insulin resistant, and hyperinsulinemic. Activation of PKB is markedly reduced in knock-in mice as a result of lower phosphorylation of PKB at Thr308, the residue phosphorylated by PDK1. This results in the inhibition of the downstream mTOR complex 1 and S6K1 signaling pathways. In contrast, activation of SGK1 or p90 ribosomal S6 kinase or stimulation of S6K1 induced by feeding is unaffected by the PDK1 PH domain mutation. These observations establish the importance of the PDK1-phosphoinositide interaction in enabling PKB to be efficiently activated with an animal model. Our findings reveal how reduced activation of PKB isoforms impinges on downstream signaling pathways, causing diminution of size as well as insulin resistance.

Hyperactivation of RAP1 and JAK/STAT Signaling Pathways Contributes to Fibrosis during the Formation of Nasal Capsular Contraction

2021 ◽  
pp. 1-12
Author(s):  
Meng Wu ◽  
Ming Li ◽  
Hong-Ju Xie ◽  
Hong-Wei Liu
Keyword(s):  
Signaling Pathways ◽  
Type I Collagen ◽  
Ex Vivo ◽  
Capsular Contracture ◽  
Silicone Implant ◽  
Type I ◽  
Loss Of Function ◽  
Sequencing Data ◽  
Functional Changes ◽  
Stat Signaling

Silicone implant-based augmentation rhinoplasty or mammoplasty induces capsular contracture, which has been acknowledged as a process that develops an abnormal fibrotic capsule associated with the immune response to allogeneic materials. However, the signaling pathways leading to the nasal fibrosis remain poorly investigated. We aimed to explore the molecular mechanism underlying the pathogenesis of nasal capsular contracture, with a specific research interest in the signaling pathways involved in fibrotic development at the advanced stage of contracture. By examining our recently obtained RNA sequencing data and global gene expression profiling between grade II and grade IV nasal capsular tissues, we found that both the RAP1 and JAK/STAT signaling pathways were hyperactive in the contracted capsules. This was verified on quantitative real-time PCR which demonstrated upregulation of most of the representative component signatures in these pathways. Loss-of-function assays through siRNA-mediated Rap1 silencing and/or small molecule-directed inhibition of JAK/STAT pathway in ex vivo primary nasal fibroblasts caused a series of dramatic behavioral and functional changes, including decreased cell viability, increased apoptosis, reduced secretion of proinflammatory cytokines, and synthesis of type I collagen, compared to control cells, and indicating the essential role of the RAP1 and JAK/STAT signaling pathways in nasal capsular fibrosis. Our results sheds light on targeting downstream signaling pathways for the prevention and therapy of silicone implant-induced nasal capsular contracture.

scholarly journals Global Deletion of 11β-HSD1 Prevents Muscle Wasting Associated with Glucocorticoid Therapy in Polyarthritis

2021 ◽  
Vol 22 (15) ◽  
pp. 7828
Author(s):  
Justine M. Webster ◽  
Michael S. Sagmeister ◽  
Chloe G. Fenton ◽  
Alex P. Seabright ◽  
Yu-Chiang Lai ◽  
...  
Keyword(s):  
Rheumatoid Arthritis ◽  
Skeletal Muscle ◽  
Chronic Inflammation ◽  
Muscle Atrophy ◽  
Muscle Wasting ◽  
Ex Vivo ◽  
Glucocorticoid Therapy ◽  
Knock Out ◽  
Fiber Size ◽  
Anti Inflammatory

Glucocorticoids provide indispensable anti-inflammatory therapies. However, metabolic adverse effects including muscle wasting restrict their use. The enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11β-HSD1) modulates peripheral glucocorticoid responses through pre-receptor metabolism. This study investigates how 11β-HSD1 influences skeletal muscle responses to glucocorticoid therapy for chronic inflammation. We assessed human skeletal muscle biopsies from patients with rheumatoid arthritis and osteoarthritis for 11β-HSD1 activity ex vivo. Using the TNF-α-transgenic mouse model (TNF-tg) of chronic inflammation, we examined the effects of corticosterone treatment and 11β-HSD1 global knock-out (11βKO) on skeletal muscle, measuring anti-inflammatory gene expression, muscle weights, fiber size distribution, and catabolic pathways. Muscle 11β-HSD1 activity was elevated in patients with rheumatoid arthritis and correlated with inflammation markers. In murine skeletal muscle, glucocorticoid administration suppressed IL6 expression in TNF-tg mice but not in TNF-tg11βKO mice. TNF-tg mice exhibited reductions in muscle weight and fiber size with glucocorticoid therapy. In contrast, TNF-tg11βKO mice were protected against glucocorticoid-induced muscle atrophy. Glucocorticoid-mediated activation of catabolic mediators (FoxO1, Trim63) was also diminished in TNF-tg11βKO compared to TNF-tg mice. In summary, 11β-HSD1 knock-out prevents muscle atrophy associated with glucocorticoid therapy in a model of chronic inflammation. Targeting 11β-HSD1 may offer a strategy to refine the safety of glucocorticoids.

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