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Wang Y, Lu J, Liu Y. Skeletal Muscle Regeneration in Cardiotoxin-Induced Muscle Injury Models. Int J Mol Sci 2022; 23:ijms232113380. [PMID: 36362166 PMCID: PMC9657523 DOI: 10.3390/ijms232113380] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 10/27/2022] [Accepted: 10/28/2022] [Indexed: 11/06/2022] Open
Abstract
Skeletal muscle injuries occur frequently in daily life and exercise. Understanding the mechanisms of regeneration is critical for accelerating the repair and regeneration of muscle. Therefore, this article reviews knowledge on the mechanisms of skeletal muscle regeneration after cardiotoxin-induced injury. The process of regeneration is similar in different mouse strains and is inhibited by aging, obesity, and diabetes. Exercise, microcurrent electrical neuromuscular stimulation, and mechanical loading improve regeneration. The mechanisms of regeneration are complex and strain-dependent, and changes in functional proteins involved in the processes of necrotic fiber debris clearance, M1 to M2 macrophage conversion, SC activation, myoblast proliferation, differentiation and fusion, and fibrosis and calcification influence the final outcome of the regenerative activity.
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2
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Waldemer-Streyer RJ, Kim D, Chen J. Muscle cell-derived cytokines in skeletal muscle regeneration. FEBS J 2022; 289:6463-6483. [PMID: 35073461 PMCID: PMC9308828 DOI: 10.1111/febs.16372] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 01/13/2022] [Accepted: 01/21/2022] [Indexed: 12/14/2022]
Abstract
Regeneration of the mammalian adult skeletal muscle is a well-orchestrated process regulated by multiple proteins and signalling pathways. Cytokines constitute a major class of regulators of skeletal myogenesis. It is well established that infiltrating immune cells at the site of muscle injury secrete cytokines, which play critical roles in the myofibre repair and regeneration process. In the past 10-15 years, skeletal muscle itself has emerged as a prolific producer of cytokines. Much attention in the field has been focused on the endocrine effects of muscle-secreted cytokines (myokines) on metabolic regulation. However, ample evidence suggests that muscle-derived cytokines also regulate myogenic differentiation and muscle regeneration in an autocrine manner. In this review, we survey cytokines that meet two criteria: (a) evidence of expression by muscle cells; (b) evidence demonstrating a myogenic function. Dozens of cytokines representing several major classes make up this group, and together they regulate all steps of the myogenic process. How such a large array of cytokines coordinate their signalling to form a regulatory network is a fascinating, pressing question. Functional studies that can distinguish the source of the cytokines in vivo are also much needed in order to facilitate exploration of their full therapeutic potential.
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Affiliation(s)
| | | | - Jie Chen
- Department of Cell & Developmental Biology, University of Illinois at Urbana-Champaign, 601 S. Goodwin Ave., Urbana, IL 61801
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3
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Miyake T, McDermott JC. Nucleolar localization of c-Jun. FEBS J 2021; 289:748-765. [PMID: 34499807 DOI: 10.1111/febs.16187] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 08/09/2021] [Accepted: 09/06/2021] [Indexed: 01/20/2023]
Abstract
Nucleoli are well defined for their function in ribosome biogenesis, but only a small fraction of the nucleolar proteome has been characterized. Here, we report that the proto-oncogene, c-Jun, is targeted to the nucleolus. Using live cell imaging in myogenic cells, we document that the c-Jun basic domain contains a unique, evolutionarily conserved motif that determines nucleolar targeting. Fos family Jun dimer partners, such as Fra2, while nuclear, do not co-localize with c-Jun in the nucleolus. A point mutation in c-Jun that mimics Fra2 (M260E) in its Nucleolar Localization sequence (NoLS) results in loss of c-Jun nucleolar targeting while still preserving nuclear localization. Fra2 can sequester c-Jun in the nucleoplasm, indicating that the stoichiometric ratio of heterodimeric partners regulates c-Jun nucleolar targeting. Finally, nucleolar localization of c-Jun modulates nucleolar architecture and ribosomal RNA accumulation. These studies highlight a novel role for Jun family proteins in the nucleolus, having potential implications for a diverse array of AP-1-regulated cellular processes.
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Affiliation(s)
- Tetsuaki Miyake
- Department of Biology, York University, Toronto, ON, Canada.,Muscle Health Research Centre (MHRC), York University, Toronto, ON, Canada.,Centre for Research in Biomolecular Interactions (CRBI), York University, Toronto, ON, Canada
| | - John C McDermott
- Department of Biology, York University, Toronto, ON, Canada.,Muscle Health Research Centre (MHRC), York University, Toronto, ON, Canada.,Centre for Research in Biomolecular Interactions (CRBI), York University, Toronto, ON, Canada.,Centre for Research in Mass Spectrometry (CRMS), York University, Toronto, ON, Canada
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4
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Maintenance of the Undifferentiated State in Myogenic Progenitor Cells by TGFβ Signaling is Smad Independent and Requires MEK Activation. Int J Mol Sci 2020; 21:ijms21031057. [PMID: 32033454 PMCID: PMC7038076 DOI: 10.3390/ijms21031057] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 01/28/2020] [Accepted: 02/04/2020] [Indexed: 12/12/2022] Open
Abstract
Transforming growth factor β (TGFβ) is a pluripotent cytokine and regulates a myriad of biological processes. It has been established that TGFβ potently inhibits skeletal muscle differentiation; however, the molecular mechanism is not clearly defined. Previously, we reported that inhibition of the TGFβ canonical pathway by an inhibitory Smad, Smad7, does not reverse this effect on differentiation, suggesting that activation of receptor Smads (R-Smads) by TGFβ is not responsible for repression of myogenesis. In addition, pharmacological blockade of Smad3 activation by TGFβ did not reverse TGFβ's inhibitory effect on myogenesis. In considering other pathways, we observed that TGFβ potently activates MEK/ERK, and a pharmacological inhibitor of MEK reversed TGFβ's inhibitory effect on myogenesis, as indicated by a myogenin promoter-reporter gene, sarcomeric myosin heavy chain accumulation, and phenotypic myotube formation. Furthermore, we found that c-Jun, a known potent repressor of myogenesis, which is coincidently also a down-stream target of MEK/ERK signaling, was phosphorylated and accumulates in the nucleus in response to TGFβ activation. Taken together, these observations support a model in which TGFβ activates a MEK/ERK/c-Jun pathway to repress skeletal myogenesis, maintaining the pluripotent undifferentiated state in myogenic progenitors.
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5
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Au ED, Desai AP, Koniaris LG, Zimmers TA. The MEK-Inhibitor Selumetinib Attenuates Tumor Growth and Reduces IL-6 Expression but Does Not Protect against Muscle Wasting in Lewis Lung Cancer Cachexia. Front Physiol 2017; 7:682. [PMID: 28149280 PMCID: PMC5241300 DOI: 10.3389/fphys.2016.00682] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Accepted: 12/22/2016] [Indexed: 01/06/2023] Open
Abstract
Cachexia, or wasting of skeletal muscle and fat, afflicts many patients with chronic diseases including cancer, organ failure, and AIDS. Muscle wasting reduces quality of life and decreases response to therapy. Cachexia is caused partly by elevated inflammatory cytokines, including interleukin-6 (IL-6). Others and we have shown that IL-6 alone is sufficient to induce cachexia both in vitro and in vivo. The mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK) inhibitor Selumetinib has been tested in clinical trials for various cancers. Moreover, Selumetinib has also been shown to inhibit the production of IL-6. In a retrospective analysis of a phase II clinical trial in advanced cholangiocarcinoma, patients treated with Selumetinib experienced significant gains in skeletal muscle vs. patients receiving standard therapy. However, the use of Selumetinib as a treatment for cachexia has yet to be investigated mechanistically. We sought to determine whether MEK inhibition could protect against cancer-induced cachexia in mice. In vitro, Selumetinib induced C2C12 myotube hypertrophy and nuclear accretion. Next we tested Selumetinib in the Lewis lung carcinoma (LLC) model of cancer cachexia. Treatment with Selumetinib reduced tumor mass and reduced circulating and tumor IL-6; however MEK inhibition did not preserve muscle mass. Similar wasting was seen in limb muscles of Selumetinib and vehicle-treated LLC mice, while greater fat and carcass weight loss was observed with Selumetinib treatment. As well, Selumetinib did not block wasting in C2C12 myotubes treated with LLC serum. Taken together, out results suggest that this MEK inhibitor is not protective in LLC cancer cachexia despite lowering IL-6 levels, and further that it might exacerbate tumor-induced weight loss. Differences from other studies might be disease, species or model-specific.
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Affiliation(s)
- Ernie D Au
- Department of Surgery, Indiana University School of MedicineIndianapolis, IN, USA; Department of Biochemistry and Molecular Biology, Indiana University School of MedicineIndianapolis, IN, USA; Indiana University Simon Cancer CenterIndianapolis, IN, USA
| | - Aditya P Desai
- Department of Surgery, Indiana University School of MedicineIndianapolis, IN, USA; Indiana University Simon Cancer CenterIndianapolis, IN, USA
| | - Leonidas G Koniaris
- Department of Surgery, Indiana University School of MedicineIndianapolis, IN, USA; Indiana University Simon Cancer CenterIndianapolis, IN, USA; IUPUI Center for Cachexia Research, Innovation and TherapyIndianapolis, IN, USA
| | - Teresa A Zimmers
- Department of Surgery, Indiana University School of MedicineIndianapolis, IN, USA; Department of Biochemistry and Molecular Biology, Indiana University School of MedicineIndianapolis, IN, USA; Indiana University Simon Cancer CenterIndianapolis, IN, USA; IUPUI Center for Cachexia Research, Innovation and TherapyIndianapolis, IN, USA; Department of Otolaryngology, Head and Neck Surgery, Indiana University School of MedicineIndianapolis, IN, USA; Department of Anatomy and Cell Biology, Indiana University School of MedicineIndianapolis, IN, USA
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6
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Costamagna D, Mommaerts H, Sampaolesi M, Tylzanowski P. Noggin inactivation affects the number and differentiation potential of muscle progenitor cells in vivo. Sci Rep 2016; 6:31949. [PMID: 27573479 PMCID: PMC5004166 DOI: 10.1038/srep31949] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Accepted: 07/28/2016] [Indexed: 10/25/2022] Open
Abstract
Inactivation of Noggin, a secreted antagonist of Bone Morphogenetic Proteins (BMPs), in mice leads, among others, to severe malformations of the appendicular skeleton and defective skeletal muscle fibers. To determine the molecular basis of the phenotype, we carried out a histomorphological and molecular analysis of developing muscles Noggin(-/-) mice. We show that in 18.5 dpc embryos there is a marked reduction in muscle fiber size and a failure of nuclei migration towards the cell membrane. Molecularly, the absence of Noggin results in an increased BMP signaling in muscle tissue as shown by the increase in SMAD1/5/8 phosphorylation, concomitant with the induction of BMP target genes such as Id1, 2, 3 as well as Msx1. Finally, upon removal of Noggin, the number of mesenchymal Pax7(+) muscle precursor cells is reduced and they are more prone to differentiate into adipocytes in vitro. Thus, our results highlight the importance of Noggin/BMP balance for myogenic commitment of early fetal progenitor cells.
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Affiliation(s)
- Domiziana Costamagna
- Translational Cardiomyology Lab, Stem Cell Biology and Embryology, Dept. Development and Regeneration, KU Leuven, Belgium.,Laboratory of Experimental Medicine and Clinical Pathology, Dept. Clinical and Biological Sciences, University of Turin, Italy
| | - Hendrik Mommaerts
- Department of Development and Regeneration, Laboratory for Developmental and Stem Cell Biology, Skeletal Biology and Engineering Research Centre, KU Leuven, Belgium
| | - Maurilio Sampaolesi
- Translational Cardiomyology Lab, Stem Cell Biology and Embryology, Dept. Development and Regeneration, KU Leuven, Belgium.,Division of Human Anatomy, Dept. of Public Health, Experimental and Forensic Medicine, University of Pavia, Italy
| | - Przemko Tylzanowski
- Department of Development and Regeneration, Laboratory for Developmental and Stem Cell Biology, Skeletal Biology and Engineering Research Centre, KU Leuven, Belgium.,Department of Biochemistry and Molecular Biology, Medical University, Lublin, Poland
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7
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Hunt LC, White J. The Role of Leukemia Inhibitory Factor Receptor Signaling in Skeletal Muscle Growth, Injury and Disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 900:45-59. [DOI: 10.1007/978-3-319-27511-6_3] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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8
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Sharma M, Juvvuna PK, Kukreti H, McFarlane C. Mega roles of microRNAs in regulation of skeletal muscle health and disease. Front Physiol 2014; 5:239. [PMID: 25018733 PMCID: PMC4072100 DOI: 10.3389/fphys.2014.00239] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Accepted: 06/10/2014] [Indexed: 01/01/2023] Open
Abstract
Skeletal muscle is a dynamic tissue with remarkable plasticity. Skeletal muscle growth and regeneration are highly organized processes thus it is not surprising that a high degree of complexity exists in the regulation of these processes. Recent discovery of non-coding microRNAs (miRNAs) has prompted extensive research in understanding the roles of these molecules in skeletal muscle. Research so far shows that miRNAs play a very significant role at every aspect of muscle biology. Besides muscle growth, development, and regeneration miRNAs are also involved in the pathology of muscle diseases and metabolism. In this review, recent advancements in miRNA function during myogenesis, exercise, atrophy, aging, and dystrophy are discussed.
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Affiliation(s)
- Mridula Sharma
- Department of Biochemistry, YLL School of Medicine, National University of Singapore Singapore, Singapore
| | - Prasanna Kumar Juvvuna
- Department of Biochemistry, YLL School of Medicine, National University of Singapore Singapore, Singapore
| | - Himani Kukreti
- Department of Biochemistry, YLL School of Medicine, National University of Singapore Singapore, Singapore
| | - Craig McFarlane
- Brenner Centre for Molecular Medicine, Singapore Institute for Clinical Sciences (ASTAR) Singapore, Singapore
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9
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Jang YN, Baik EJ. JAK-STAT pathway and myogenic differentiation. JAKSTAT 2014; 2:e23282. [PMID: 24058805 PMCID: PMC3710318 DOI: 10.4161/jkst.23282] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Revised: 12/13/2012] [Accepted: 12/14/2012] [Indexed: 11/19/2022] Open
Abstract
Myogenic differentiation plays an important role in muscle regeneration and is regulated by two transcription factor families, MRFs and MEF2, which induce differentiation of myoblasts through expression of the muscle-specific gene, myogenin. In addition, many intracellular signaling pathways are also involved in myogenic differentiation, including p38 MAPK, ERK/MAPK and PI3K/AKT. The JAK-STAT pathway is activated by various cytokines and positively or negatively regulates the differentiation of myoblasts. JAK1 plays a notable role in proliferation; whereas, JAK2 and JAK3 function mainly in differentiation. The STATs, molecules downstream of JAK, regulate myogenesis. With JAK1, STAT1 promotes proliferation, while STAT3 has a dual effect on proliferation and differentiation. The JAK-STAT negative regulator, SOCS, is also associated with myogenesis; although, its role is controversial. In this review, we will discuss the role of the JAK-STAT pathway on myogenic differentiation.
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Affiliation(s)
- You-Na Jang
- Department of Physiology; Chronic Inflammatory Disease Research Center; Ajou University School of Medicine; Suwon, Korea
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10
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Dong ZL, Wang Y, Li TF, Zheng SJ, Kong YQ, Lan YL, Guo JL, Fu SG. p42/p44 mitogen-activated protein kinases inhibit atrial natriuretic peptide mRNA transcription in gp130-mediated hypertrophic ventricular myocytes. ASIAN PAC J TROP MED 2014; 7:216-20. [DOI: 10.1016/s1995-7645(14)60024-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 01/15/2014] [Accepted: 02/15/2014] [Indexed: 11/26/2022] Open
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11
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Yin S, Wu H, Lv J, Wu X, Zhang Y, Du J, Zhang Y. SHP-1 arrests mouse early embryo development through downregulation of Nanog by dephosphorylation of STAT3. PLoS One 2014; 9:e86330. [PMID: 24466030 PMCID: PMC3897670 DOI: 10.1371/journal.pone.0086330] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Accepted: 12/07/2013] [Indexed: 01/14/2023] Open
Abstract
Src-homology protein tyrosine phosphatase-1 (SHP-1) is a protein tyrosine phosphatase that is implicated in the regulation of growth, differentiation, survival, apoptosis and proliferation of hematopoietic cells and other cell types. Here, we found that SHP-1 is involved in regulation of early embryonic development. Embryos overexpressing SHP-1 were mainly arrested at the 8-cell stage, and Nanog mRNA expression was first observed in the morulae that showed down-regulation of SHP-1. These results suggested an antagonistic relationship between SHP-1 and Nanog during early embryonic development. Next, the specific mechanism was examined in mouse F9 embryonal carcinoma cells. We confirmed that signal transducer and activator of transcription 3 (STAT3) was a substrate for SHP-1 by co-immunoprecipitation. Using overexpression and knockdown strategies, we found that SHP-1 participated in regulation of Nanog expression. Furthermore, site mutation of STAT3 was performed to confirm that SHP-1 was responsible for rapid STAT3 dephosphorylation and a decrease of Nanog expression in F9 cells. These findings suggest that SHP-1 plays a crucial role during early embryonic development. Thus, SHP-1 may function as a key regulator for Nanog that specifically demarcates the nascent epiblast, coincident with the domain of X chromosome reprogramming.
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Affiliation(s)
- Songna Yin
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China
- Key Laboratory of Animal Biotechnology, Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi, China
| | - Haibo Wu
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China
- Key Laboratory of Animal Biotechnology, Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi, China
| | - Jiaxing Lv
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China
- Key Laboratory of Animal Biotechnology, Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi, China
| | - Xinying Wu
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China
- Key Laboratory of Animal Biotechnology, Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi, China
| | - Yan Zhang
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China
- Key Laboratory of Animal Biotechnology, Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi, China
| | - Juan Du
- Key Laboratory of Animal Biotechnology, Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi, China
- College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China
| | - Yong Zhang
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China
- Key Laboratory of Animal Biotechnology, Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi, China
- * E-mail:
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12
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Downregulation of the cardiotrophin-1 gene expression by valsartan and spironolactone in hypertrophied heart rats in vivo and rat cardiomyocyte H9c2 cell line in vitro: a novel mechanism of cardioprotection. J Cardiovasc Pharmacol 2013; 61:337-44. [PMID: 23288202 DOI: 10.1097/fjc.0b013e318283a565] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The incidence, prevalence, and hospitalization rates associated with heart failure (HF) are projected to increase substantially in the world. Among all medications used clinically to treat HF, valsartan (VAL) and spironolactone (SPL) have been shown to reduce morbidity and mortality. Recently, a novel cardiac gene cardiotrophin-1 (CT-1) has been shown to play a crucial role in the pathogenesis of HF. However, the ability of VAL and SPL to modulate the expression of CT-1 has not been investigated yet. Therefore, healthy and isoproterenol (ISO)-induced hypertrophy adult male Wistar albino rats were treated with either VAL or SPL for 14 days. Thereafter, cardiac markers of cardiotoxicity and hypertrophy, creatine kinase, heart weight/body weight ratio, and atrial natriuretic peptide mRNA levels were measured. In addition, CT-1 mRNA and protein levels were determined by real-time polymerase chain reaction and Western blot analysis. Our results showed that the increases in all HF markers, creatine kinase, heart weight/body weight ratio, and atrial natriuretic peptide mRNA levels in ISO-treated rats were significantly restored to their normal levels by VAL and SPL. In addition, induction of cardiac hypertrophy by ISO caused remarkable induction in CT-1 mRNA and protein expression levels by approximately 3.5- and 3-fold, respectively. Importantly, VAL and SPL significantly decreased the induction of CT-1 gene at the mRNA and protein levels in heart hypertrophied rats. On the other hand, treatment of cardiac-derived rat myoblast H9c2 cells with VAL and SPL significantly decreased angiotensin II-induced CT-1 mRNA levels through transcriptional mechanism, as demonstrated by the effect of transcription inhibitor, actinomycin D. In conclusion, VAL and SPL exhibited their cardioprotective effect through inhibiting the expression of CT-1 gene in cardiac hypertrophied rats.
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13
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Ge Y, Waldemer RJ, Nalluri R, Nuzzi PD, Chen J. RNAi screen reveals potentially novel roles of cytokines in myoblast differentiation. PLoS One 2013; 8:e68068. [PMID: 23844157 PMCID: PMC3699544 DOI: 10.1371/journal.pone.0068068] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Accepted: 05/24/2013] [Indexed: 01/08/2023] Open
Abstract
Cytokines are cell-secreted signaling molecules that modulate various cellular functions, with the best-characterized roles in immune responses. The expression of numerous cytokines in skeletal muscle tissues and muscle cells has been reported, but their function in skeletal myogenesis, the formation of skeletal muscle, has been largely underexplored. To systematically examine the potential roles of cytokines in skeletal myogenesis, we undertook an RNAi screen of 134 mouse cytokine genes for their involvement in the differentiation of C2C12 myoblasts. Our results have uncovered 29 cytokines as strong candidates for novel myogenic regulators, potentially conferring positive and negative regulation at distinct stages of myogenesis. These candidates represent a diverse collection of cytokine families, including interleukins, TNF-related factors, and chemokines. Our findings suggest the fundamental importance of cytokines in the cell-autonomous regulation of myoblast differentiation, and may facilitate future identification of novel therapeutic targets for improving muscle regeneration and growth in health and diseases.
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Affiliation(s)
- Yejing Ge
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Rachel J. Waldemer
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Ramakrishna Nalluri
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Paul D. Nuzzi
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Jie Chen
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
- * E-mail:
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14
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Alli NS, Yang EC, Miyake T, Aziz A, Collins-Hooper H, Patel K, McDermott JC. Signal-dependent fra-2 regulation in skeletal muscle reserve and satellite cells. Cell Death Dis 2013; 4:e692. [PMID: 23807221 PMCID: PMC3702306 DOI: 10.1038/cddis.2013.221] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Activator protein-1 (AP-1) is a ubiquitous transcription factor that paradoxically also has some tissue-specific functions. In skeletal muscle cells, we document that the AP-1 subunit, Fra-2, is expressed in the resident stem cells (Pax7-positive satellite cells) and also in the analogous undifferentiated ‘reserve' cell population in myogenic cultures, but not in differentiated myofiber nuclei. Silencing of Fra-2 expression enhances the expression of differentiation markers such as muscle creatine kinase and myosin heavy chain, indicating a possible role of Fra-2 in undifferentiated myogenic progenitor cells. We observed that Fra-2 is a target of cytokine-mediated extracellular signal-regulated kinase-1/2 signaling in cultured muscle cells, and extensive mass spectrometry and mutational analysis identified S320 and T322 as regulators of Fra-2 protein stability. Interestingly, Fra-2 S320 phosphorylation occurs transiently in activated satellite cells and is extinguished in myogenin-positive differentiating cells. Thus, cytokine-mediated Fra-2 expression and stabilization is linked to regulation of myogenic progenitor cells having implications for the molecular regulation of adult muscle stem cells and skeletal muscle regeneration.
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Affiliation(s)
- N S Alli
- Department of Biology, York University, 4700 Keele Street, Toronto, Ontario, Canada
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15
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Muñoz-Cánoves P, Scheele C, Pedersen BK, Serrano AL. Interleukin-6 myokine signaling in skeletal muscle: a double-edged sword? FEBS J 2013; 280:4131-48. [PMID: 23663276 PMCID: PMC4163639 DOI: 10.1111/febs.12338] [Citation(s) in RCA: 480] [Impact Index Per Article: 43.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Revised: 04/25/2013] [Accepted: 05/07/2013] [Indexed: 12/19/2022]
Abstract
Interleukin (IL)-6 is a cytokine with pleiotropic functions in different tissues and organs. Skeletal muscle produces and releases significant levels of IL-6 after prolonged exercise and is therefore considered as a myokine. Muscle is also an important target of the cytokine. IL-6 signaling has been associated with stimulation of hypertrophic muscle growth and myogenesis through regulation of the proliferative capacity of muscle stem cells. Additional beneficial effects of IL-6 include regulation of energy metabolism, which is related to the capacity of actively contracting muscle to synthesize and release IL-6. Paradoxically, deleterious actions for IL-6 have also been proposed, such as promotion of atrophy and muscle wasting. We review the current evidence for these apparently contradictory effects, the mechanisms involved and discuss their possible biological implications.
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Affiliation(s)
- Pura Muñoz-Cánoves
- Cell Biology Group, Department of Experimental and Health Sciences, Pompeu Fabra University (UPF), Institució Catalana de Recerca i Estudis Avançats (ICREA), CIBER on Neurodegenerative diseases (CIBERNED), Barcelona, Spain.
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16
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Ge Y, Waldemer RJ, Nalluri R, Nuzzi PD, Chen J. Flt3L is a novel regulator of skeletal myogenesis. J Cell Sci 2013; 126:3370-9. [PMID: 23704355 DOI: 10.1242/jcs.123950] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Various cues initiate multiple signaling pathways to regulate the highly coordinated process of skeletal myogenesis. Myoblast differentiation comprises a series of ordered events starting with cell cycle withdrawal and ending with myocyte fusion, with each step probably controlled by multiple extracellular signals and intracellular signaling pathways. Here we report the identification of Fms-like tyrokine kinase 3 ligand (Flt3L) signaling as a novel regulator of skeletal myogenesis. Flt3L is a multifunctional cytokine in immune cells, but its involvement in skeletal muscle formation has not been reported. We found that Flt3L is expressed in C2C12 myoblasts, with levels increasing throughout differentiation. Knockdown of Flt3L, or its receptor Flt3, suppresses myoblast differentiation, which is rescued by recombinant Flt3L or Flt3, respectively. Differentiation is not rescued, however, by recombinant ligand when the receptor is knocked down, or vice versa, suggesting that Flt3L and Flt3 function together. Flt3L knockdown also inhibits differentiation in mouse primary myoblasts. Both Flt3L and Flt3 are highly expressed in nascent myofibers during muscle regeneration in vivo, and Flt3L siRNA impairs muscle regeneration, validating the physiological significance of Flt3L function in myogenesis. We have identified a cellular mechanism for the myogenic function of Flt3L, as we show that Flt3L promotes cell cycle exit that is necessary for myogenic differentiation. Furthermore, we identify Erk as a relevant target of Flt3L signaling during myogenesis, and demonstrate that Flt3L suppresses Erk signaling through p120RasGAP. In summary, our work reveals an unexpected role for an immunoregulatory cytokine in skeletal myogenesis and a new myogenic pathway.
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Affiliation(s)
- Yejing Ge
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, 601 S. Goodwin Avenue B107, Urbana, IL 61801, USA
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17
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Vu V, Liu Y, Sen S, Xu A, Sweeney G. Delivery of adiponectin gene to skeletal muscle using ultrasound targeted microbubbles improves insulin sensitivity and whole body glucose homeostasis. Am J Physiol Endocrinol Metab 2013; 304:E168-75. [PMID: 23132298 PMCID: PMC3543570 DOI: 10.1152/ajpendo.00493.2012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Numerous studies have shown that adiponectin confers antidiabetic effects via both insulin-like and insulin-sensitizing actions. The majority of adiponectin in circulation is derived from adipocytes; however, other tissues such as skeletal muscle can produce adiponectin. This study was designed to investigate the functional significance of adiponectin produced by skeletal muscle. We encapsulated the adiponectin gene in lipid-coated microspheres filled with octafluoropropane gas that were injected into the systemic circulation and destroyed within the microvasculature of skeletal muscle using ultrasound. We first demonstrated safe and successful targeting of luciferase and green fluorescent protein reporter genes to skeletal muscle using this approach and then confirmed efficient overexpression of adiponectin mRNA and oligomeric protein forms. Glucose tolerance test indicated that overexpression of adiponectin in skeletal muscle was able to improve glucose intolerance induced by feeding mice a high-fat diet (HFD), and this correlated with improved skeletal muscle insulin signaling. We then performed hyperinsulinemic-euglycemic clamp studies and demonstrated that adiponectin overexpression attenuated the decreases in glucose infusion rate, glucose disposal, and increase in glucose appearance induced by HFD. Ultrasound-targeted microbubble destruction (UTMD) delivery of adiponectin to skeletal muscle also enhanced serum adiponectin levels and improved hepatic insulin sensitivity. In conclusion, our data show that UTMD efficiently delivers adiponectin to skeletal muscle and that this improves insulin sensitivity and glucose homeostasis.
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Affiliation(s)
- Vivian Vu
- Department of Biology, York University, Toronto, Canada
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Hoene M, Runge H, Häring HU, Schleicher ED, Weigert C. Interleukin-6 promotes myogenic differentiation of mouse skeletal muscle cells: role of the STAT3 pathway. Am J Physiol Cell Physiol 2013; 304:C128-36. [DOI: 10.1152/ajpcell.00025.2012] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Myogenic differentiation of skeletal muscle cells is characterized by a sequence of events that include activation of signal transducer and activator of transcription 3 (STAT3) and enhanced expression of its target gene Socs3. Autocrine effects of IL-6 may contribute to the activation of the STAT3-Socs3 cascade and thus to myogenic differentiation. The importance of IL-6 and STAT3 for the differentiation process was studied in C2C12 cells and in primary mouse wild-type and IL-6−/− skeletal muscle cells. In differentiating C2C12 myoblasts, the upregulation of IL-6 mRNA expression and protein secretion started after increased phosphorylation of STAT3 on tyrosine 705 and increased mRNA expression of Socs3 was observed. Knockdown of STAT3 and IL-6 mRNA in differentiating C2C12 myoblasts impaired the expression of the myogenic markers myogenin and MyHC IIb and subsequently myotube fusion. However, the knockdown of IL-6 did not prevent the induction of STAT3 tyrosine phosphorylation. The IL-6-independent activation of STAT3 was verified in differentiating primary IL-6−/− myoblasts. The phosphorylation of STAT3 and the expression levels of STAT3, Socs3, and myogenin during differentiation were comparable in the primary myoblasts independent of the genotype. However, IL-6−/− cells failed to induce MyHC IIb expression to the same level as in wild-type cells and showed reduced myotube formation. Supplementation of IL-6 could partially restore the fusion of IL-6−/− cells. These data demonstrate that IL-6 depletion during myogenic differentiation does not reduce the activation of the STAT3-Socs3 cascade, while IL-6 and STAT3 are both necessary to promote myotube fusion.
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Affiliation(s)
- Miriam Hoene
- Division of Pathobiochemistry and Clinical Chemistry, University Tuebingen, Tuebingen, Germany
- Paul Langerhans Institute Tuebingen, Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Centre Munich, University Tuebingen, Tuebingen, Germany
| | - Heike Runge
- Division of Pathobiochemistry and Clinical Chemistry, University Tuebingen, Tuebingen, Germany
| | - Hans Ulrich Häring
- Division of Endocrinology, Diabetology, Angiology, Nephrology, and Clinical Chemistry, Department of Internal Medicine, University Tuebingen, Tuebingen, Germany; and
- Paul Langerhans Institute Tuebingen, Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Centre Munich, University Tuebingen, Tuebingen, Germany
| | - Erwin D. Schleicher
- Division of Pathobiochemistry and Clinical Chemistry, University Tuebingen, Tuebingen, Germany
- Paul Langerhans Institute Tuebingen, Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Centre Munich, University Tuebingen, Tuebingen, Germany
| | - Cora Weigert
- Division of Pathobiochemistry and Clinical Chemistry, University Tuebingen, Tuebingen, Germany
- Paul Langerhans Institute Tuebingen, Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Centre Munich, University Tuebingen, Tuebingen, Germany
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19
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Andres-Mateos E, Mejias R, Soleimani A, Lin BM, Burks TN, Marx R, Lin B, Zellars RC, Zhang Y, Huso DL, Marr TG, Leinwand LA, Merriman DK, Cohn RD. Impaired skeletal muscle regeneration in the absence of fibrosis during hibernation in 13-lined ground squirrels. PLoS One 2012; 7:e48884. [PMID: 23155423 PMCID: PMC3498346 DOI: 10.1371/journal.pone.0048884] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2012] [Accepted: 10/02/2012] [Indexed: 02/06/2023] Open
Abstract
Skeletal muscle atrophy can occur as a consequence of immobilization and/or starvation in the majority of vertebrates studied. In contrast, hibernating mammals are protected against the loss of muscle mass despite long periods of inactivity and lack of food intake. Resident muscle-specific stem cells (satellite cells) are known to be activated by muscle injury and their activation contributes to the regeneration of muscle, but whether satellite cells play a role in hibernation is unknown. In the hibernating 13-lined ground squirrel we show that muscles ablated of satellite cells were still protected against atrophy, demonstrating that satellite cells are not involved in the maintenance of skeletal muscle during hibernation. Additionally, hibernating skeletal muscle showed extremely slow regeneration in response to injury, due to repression of satellite cell activation and myoblast differentiation caused by a fine-tuned interplay of p21, myostatin, MAPK, and Wnt signaling pathways. Interestingly, despite long periods of inflammation and lack of efficient regeneration, injured skeletal muscle from hibernating animals did not develop fibrosis and was capable of complete recovery when animals emerged naturally from hibernation. We propose that hibernating squirrels represent a new model system that permits evaluation of impaired skeletal muscle remodeling in the absence of formation of tissue fibrosis.
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Affiliation(s)
- Eva Andres-Mateos
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Rebeca Mejias
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Arshia Soleimani
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Brian M. Lin
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Tyesha N. Burks
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Ruth Marx
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Benjamin Lin
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Richard C. Zellars
- Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
| | - Yonggang Zhang
- Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
| | - David L. Huso
- Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Tom G. Marr
- Hiberna Corporation, Boulder, Colorado, United States of America
| | - Leslie A. Leinwand
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado, United States of America
| | - Dana K. Merriman
- Department of Biology and Microbiology, University of Wisconsin, Oshkosh, Wisconsin, United States of America
| | - Ronald D. Cohn
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
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20
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Hunt LC, Upadhyay A, Jazayeri JA, Tudor EM, White JD. An anti-inflammatory role for leukemia inhibitory factor receptor signaling in regenerating skeletal muscle. Histochem Cell Biol 2012; 139:13-34. [PMID: 22926285 DOI: 10.1007/s00418-012-1018-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/08/2012] [Indexed: 11/30/2022]
Abstract
Skeletal muscle regeneration in pathology and following injury requires the coordinated actions of inflammatory cells and myogenic cells to remove damaged tissue and rebuild syncytial muscle cells, respectively. Following contusion injury to muscle, the cytokine leukemia inhibitor factor (LIF) is up-regulated and knockout of Lif negatively impacts on morphometric parameters of muscle regeneration. Although it was speculated that LIF regulates muscle regeneration through direct effects on myogenic cells, the inflammatory effects of LIF have not been examined in regenerating skeletal muscle. Therefore, the expression and function of LIF was examined using the antagonist MH35-BD during specific inflammatory and myogenic stages of notexin-induced muscle regeneration in mice. LIF protein and mRNA were up-regulated in two distinct phases following intramuscular injection of notexin into tibialis anterior muscles. The first phase of LIF up-regulation coincided with the increased expression of pro-inflammatory cytokines; the second phase coincided with myogenic differentiation and formation of new myotubes. Administration of the LIF receptor antagonist MH35-BD during the second phase of LIF up-regulation had no significant effects on transcript expression of genes required for myogenic differentiation or associated with inflammation; there were no significant differences in morphometric parameters of the regenerating muscle. Conversely, when MH35-BD was administered during the acute inflammatory phase, increased gene transcripts for the pro-inflammatory cytokines Tnf (Tumor necrosis factor), Il1b (Interleukin-1β) and Il6 (Interleukin-6) alongside an increase in the number of Ly6G positive neutrophils infiltrating the muscle were observed. This was followed by a reduction in Myog (Myogenin) mRNA, which is required for myogenic differentiation, and the subsequent number of myotubes formed was significantly decreased in MH35-BD-treated groups compared to sham. Thus, antagonism of the LIF receptor during the inflammatory phase of skeletal muscle regeneration appeared to induce an inflammatory response that inhibited subsequent myotube formation. We propose that the predominant role of LIF in skeletal muscle regeneration appears to be in regulating the inflammatory response rather than directly effecting myogenic cells.
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Affiliation(s)
- Liam C Hunt
- Faculty of Veterinary Science, University of Melbourne, Flemington road, Parkville, VIC 3010, Australia
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21
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Miyake T, McDermott JC, Gramolini AO. A method for the direct identification of differentiating muscle cells by a fluorescent mitochondrial dye. PLoS One 2011; 6:e28628. [PMID: 22174849 PMCID: PMC3235136 DOI: 10.1371/journal.pone.0028628] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Accepted: 11/11/2011] [Indexed: 11/18/2022] Open
Abstract
Identification of differentiating muscle cells generally requires fixation, antibodies directed against muscle specific proteins, and lengthy staining processes or, alternatively, transfection of muscle specific reporter genes driving GFP expression. In this study, we examined the possibility of using the robust mitochondrial network seen in maturing muscle cells as a marker of cellular differentiation. The mitochondrial fluorescent tracking dye, MitoTracker, which is a cell-permeable, low toxicity, fluorescent dye, allowed us to distinguish and track living differentiating muscle cells visually by epi-fluorescence microscopy. MitoTracker staining provides a robust and simple detection strategy for living differentiating cells in culture without the need for fixation or biochemical processing.
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Affiliation(s)
- Tetsuaki Miyake
- Department of Physiology, University of Toronto, Best Institute Medical Research, Toronto, Canada
- * E-mail: (AOG); (TM)
| | | | - Anthony O. Gramolini
- Department of Physiology, University of Toronto, Best Institute Medical Research, Toronto, Canada
- * E-mail: (AOG); (TM)
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22
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Muscle wasting and impaired myogenesis in tumor bearing mice are prevented by ERK inhibition. PLoS One 2010; 5:e13604. [PMID: 21048967 PMCID: PMC2965098 DOI: 10.1371/journal.pone.0013604] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2010] [Accepted: 09/28/2010] [Indexed: 01/06/2023] Open
Abstract
Background The onset of cachexia is a frequent feature in cancer patients. Prominent characteristic of this syndrome is the loss of body and muscle weight, this latter being mainly supported by increased protein breakdown rates. While the signaling pathways dependent on IGF-1 or myostatin were causally involved in muscle atrophy, the role of the Mitogen-Activated-Protein-Kinases is still largely debated. The present study investigated this point on mice bearing the C26 colon adenocarcinoma. Methodology/Principal Findings C26-bearing mice display a marked loss of body weight and muscle mass, this latter associated with increased phosphorylated (p)-ERK. Administration of the ERK inhibitor PD98059 to tumor bearers attenuates muscle depletion and weakness, while restoring normal atrogin-1 expression. In C26 hosts, muscle wasting is also associated with increased Pax7 expression and reduced myogenin levels. Such pattern, suggestive of impaired myogenesis, is reversed by PD98059. Increased p-ERK and reduced myosin heavy chain content can be observed in TNFα-treated C2C12 myotubes, while decreased myogenin and MyoD levels occur in differentiating myoblasts exposed to the cytokine. All these changes are prevented by PD98059. Conclusions/Significance These results demonstrate that ERK is involved in the pathogenesis of muscle wasting in cancer cachexia and could thus be proposed as a therapeutic target.
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23
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Oncostatin M inhibits myoblast differentiation and regulates muscle regeneration. Cell Res 2010; 21:350-64. [PMID: 20956996 DOI: 10.1038/cr.2010.144] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Oncostatin M (OSM) is a cytokine of the interleukin-6 family and plays important roles during inflammation. However, its roles in myoblast differentiation and muscle regeneration remain unexplored. We show here that OSM potently inhibited myoblast differentiation mainly by activating the JAK1/STAT1/STAT3 pathway. OSM downregulated myocyte enhancer-binding factor 2A (MEF2A), upregulated the expression of Id1 and Id2, and inhibited the transcriptional activity of MyoD and MEF2. In addition, OSM also enhanced the expression of STAT3 and OSM receptor, which constituted a positive feedback loop to further amplify OSM-induced signaling. Moreover, we found that STAT1 physically associated with MEF2 and repressed its transcriptional activity, which could account for the OSM-mediated repression of MEF2. Although undetectable in normal muscles in vivo, OSM was rapidly induced on muscle injury and then promptly downregulated just before the majority of myoblasts differentiate. Prolonged expression of OSM in muscles compromised the regeneration process without affecting myoblast proliferation, suggesting that OSM functions to prevent proliferating myoblasts from premature differentiation during the early phase of muscle regeneration.
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24
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Hamrick MW, Herberg S, Arounleut P, He HZ, Shiver A, Qi RQ, Zhou L, Isales CM, Mi QS. The adipokine leptin increases skeletal muscle mass and significantly alters skeletal muscle miRNA expression profile in aged mice. Biochem Biophys Res Commun 2010; 400:379-83. [PMID: 20800581 DOI: 10.1016/j.bbrc.2010.08.079] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2010] [Accepted: 08/23/2010] [Indexed: 02/05/2023]
Abstract
Age-associated loss of muscle mass, or sarcopenia, contributes directly to frailty and an increased risk of falls and fractures among the elderly. Aged mice and elderly adults both show decreased muscle mass as well as relatively low levels of the fat-derived hormone leptin. Here we demonstrate that loss of muscle mass and myofiber size with aging in mice is associated with significant changes in the expression of specific miRNAs. Aging altered the expression of 57 miRNAs in mouse skeletal muscle, and many of these miRNAs are now reported to be associated specifically with age-related muscle atrophy. These include miR-221, previously identified in studies of myogenesis and muscle development as playing a role in the proliferation and terminal differentiation of myogenic precursors. We also treated aged mice with recombinant leptin, to determine whether leptin therapy could improve muscle mass and alter the miRNA expression profile of aging skeletal muscle. Leptin treatment significantly increased hindlimb muscle mass and extensor digitorum longus fiber size in aged mice. Furthermore, the expression of 37 miRNAs was altered in muscles of leptin-treated mice. In particular, leptin treatment increased the expression of miR-31 and miR-223, miRNAs known to be elevated during muscle regeneration and repair. These findings suggest that aging in skeletal muscle is associated with marked changes in the expression of specific miRNAs, and that nutrient-related hormones such as leptin may be able to reverse muscle atrophy and alter the expression of atrophy-related miRNAs in aging skeletal muscle.
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Affiliation(s)
- Mark W Hamrick
- Department of Cellular Biology and Anatomy, Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA 30912, USA.
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Abstract
In the "canonical" view of transforming growth factor beta (TGF-beta) signaling, Smad7 plays an inhibitory role. While Smad7 represses Smad3 activation by TGF-beta, it does not reverse the inhibitory effect of TGF-beta on myogenesis, suggesting a different function in myogenic cells. We previously reported a promyogenic role of Smad7 mediated by an interaction with MyoD. Based on this association, we hypothesized a possible nuclear function of Smad7 independent of its role at the level of the receptor. We therefore engineered a chimera of Smad7 with a nuclear localization signal (NLS), which serves to prevent and therefore bypass binding to the TGF-beta receptor while concomitantly constitutively localizing Smad7 to the nucleus. This Smad7-NLS did not repress Smad3 activation by TGF-beta but did retain its ability to enhance myogenic gene activation and phenotypic myogenesis, indicating that the nuclear, receptor-independent function of Smad7 is sufficient to promote myogenesis. Furthermore, Smad7 physically interacts with MyoD and antagonizes the repressive effects of active MEK on MyoD. Reporter and myogenic conversion assays indicate a pivotal regulation of MyoD transcriptional properties by the balance between Smad7 and active MEK. Thus, Smad7 has a nuclear coactivator function that is independent of TGF-beta signaling and necessary to promote myogenic differentiation.
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26
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McLoon LK. A new role for satellite cells: control of reinnervation after muscle injury by semaphorin 3A. Focus on "Possible implication of satellite cells in regenerative motoneuritogenesis: HGF upregulates neural chemorepellent Sema3A during myogenic differentiation". Am J Physiol Cell Physiol 2009; 297:C227-30. [PMID: 19535512 DOI: 10.1152/ajpcell.00256.2009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Linda K McLoon
- Department of Ophthalmology and Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA.
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