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Cao J, Verma SK, Jaworski E, Mohan S, Nagasawa CK, Rayavara K, Sooter A, Miller SN, Holcomb RJ, Powell MJ, Ji P, Elrod ND, Yildirim E, Wagner EJ, Popov V, Garg NJ, Routh AL, Kuyumcu-Martinez MN. RBFOX2 is critical for maintaining alternative polyadenylation patterns and mitochondrial health in rat myoblasts. Cell Rep 2021; 37:109910. [PMID: 34731606 PMCID: PMC8600936 DOI: 10.1016/j.celrep.2021.109910] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 07/22/2021] [Accepted: 10/08/2021] [Indexed: 12/16/2022] Open
Abstract
RBFOX2, which has a well-established role in alternative splicing, is linked to heart diseases. However, it is unclear whether RBFOX2 has other roles in RNA processing that can influence gene expression in muscle cells, contributing to heart disease. Here, we employ both 3'-end and nanopore cDNA sequencing to reveal a previously unrecognized role for RBFOX2 in maintaining alternative polyadenylation (APA) signatures in myoblasts. RBFOX2-mediated APA modulates mRNA levels and/or isoform expression of a collection of genes, including contractile and mitochondrial genes. Depletion of RBFOX2 adversely affects mitochondrial health in myoblasts, correlating with disrupted APA of mitochondrial gene Slc25a4. Mechanistically, RBFOX2 regulation of Slc25a4 APA is mediated through consensus RBFOX2 binding motifs near the distal polyadenylation site, enforcing the use of the proximal polyadenylation site. In sum, our results unveil a role for RBFOX2 in fine-tuning expression of mitochondrial and contractile genes via APA in myoblasts relevant to heart diseases.
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Affiliation(s)
- Jun Cao
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Sunil K Verma
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Elizabeth Jaworski
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Stephanie Mohan
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Chloe K Nagasawa
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Kempaiah Rayavara
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Amanda Sooter
- School of Medicine, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Sierra N Miller
- Center for Addiction Research, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Richard J Holcomb
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Mason J Powell
- School of Medicine, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Ping Ji
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Nathan D Elrod
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Eda Yildirim
- Department of Cell Biology, Duke University School of Medicine, Durham, NC 27708, USA
| | - Eric J Wagner
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA; Sealy Centre for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Vsevolod Popov
- Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Nisha J Garg
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Andrew L Routh
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA; Sealy Centre for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Muge N Kuyumcu-Martinez
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA; Department of Neuroscience, Cell biology and Anatomy, University of Texas Medical Branch, Galveston, TX 77555, USA.
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2
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Ramírez Hurtado AL, Martínez FV, Diaz Galindo CA, Cuellar KG, Villareal Reyna SZ, Sánchez Herrera DP, Rodríguez González J. Noisy stimulation effect in calcium dynamics on cardiac cells. Exp Cell Res 2020; 396:112319. [PMID: 33039368 DOI: 10.1016/j.yexcr.2020.112319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 10/05/2020] [Accepted: 10/07/2020] [Indexed: 11/24/2022]
Abstract
Noise is present in nature, and it affects the nervous and cardiovascular system. Noise added to stimuli may change the performance of excitable cells. In this paper, we study the effect of noise on the two main heart cell types: pacemaker and myocardial cells. This study investigates whether noise can induce changes in calcium dynamics on the two main heart cell types: pacemaker and myocardial cells, when stimuli with periodic electrical signals are disturbed by Gaussian white noise. Calcium dynamic parameters were obtained using imaging signals. Our results show that low intensities of noise favor amplitude and raise rate calcium dynamics, although our results show that the pacemaker cells are not affected by a noisy stimulus. Altogether, these findings suggest that noise plays a key role in calcium dynamics.
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Affiliation(s)
- Alberto Luis Ramírez Hurtado
- Centro de Investigación y de Estudios Avanzados del I.P.N - Unidad Monterrey, Vía del Conocimiento 201, Parque de Investigación e Innovación Tecnológica, C.P.: 66600, Apodaca, Nuevo León, Mexico
| | - Fernando Villafranca Martínez
- Centro de Investigación y de Estudios Avanzados del I.P.N - Unidad Monterrey, Vía del Conocimiento 201, Parque de Investigación e Innovación Tecnológica, C.P.: 66600, Apodaca, Nuevo León, Mexico
| | - Carlos Alberto Diaz Galindo
- Centro de Investigación y de Estudios Avanzados del I.P.N - Unidad Monterrey, Vía del Conocimiento 201, Parque de Investigación e Innovación Tecnológica, C.P.: 66600, Apodaca, Nuevo León, Mexico
| | - Karen Garza Cuellar
- Centro de Investigación y de Estudios Avanzados del I.P.N - Unidad Monterrey, Vía del Conocimiento 201, Parque de Investigación e Innovación Tecnológica, C.P.: 66600, Apodaca, Nuevo León, Mexico
| | - Sandra Zue Villareal Reyna
- Centro de Investigación y de Estudios Avanzados del I.P.N - Unidad Monterrey, Vía del Conocimiento 201, Parque de Investigación e Innovación Tecnológica, C.P.: 66600, Apodaca, Nuevo León, Mexico
| | - Daniel Paulo Sánchez Herrera
- Centro de Investigación y de Estudios Avanzados del I.P.N - Unidad Monterrey, Vía del Conocimiento 201, Parque de Investigación e Innovación Tecnológica, C.P.: 66600, Apodaca, Nuevo León, Mexico.
| | - Jesús Rodríguez González
- Centro de Investigación y de Estudios Avanzados del I.P.N - Unidad Monterrey, Vía del Conocimiento 201, Parque de Investigación e Innovación Tecnológica, C.P.: 66600, Apodaca, Nuevo León, Mexico.
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3
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Billah M, Ridiandries A, Allahwala UK, Mudaliar H, Dona A, Hunyor S, Khachigian LM, Bhindi R. Remote Ischemic Preconditioning induces Cardioprotective Autophagy and Signals through the IL-6-Dependent JAK-STAT Pathway. Int J Mol Sci 2020; 21:ijms21051692. [PMID: 32121587 PMCID: PMC7084188 DOI: 10.3390/ijms21051692] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2020] [Revised: 02/19/2020] [Accepted: 02/27/2020] [Indexed: 02/08/2023] Open
Abstract
Autophagy is a cellular process by which mammalian cells degrade and assist in recycling damaged organelles and proteins. This study aimed to ascertain the role of autophagy in remote ischemic preconditioning (RIPC)-induced cardioprotection. Sprague Dawley rats were subjected to RIPC at the hindlimb followed by a 30-min transient blockade of the left coronary artery to simulate ischemia reperfusion (I/R) injury. Hindlimb muscle and the heart were excised 24 h post reperfusion. RIPC prior to I/R upregulated autophagy in the rat heart at 24 h post reperfusion. In vitro, autophagy inhibition or stimulation prior to RIPC, respectively, either ameliorated or stimulated the cardioprotective effect, measured as improved cell viability to mimic the preconditioning effect. Recombinant interleukin-6 (IL-6) treatment prior to I/R increased in vitro autophagy in a dose-dependent manner, activating the Janus kinase/signal transducers and activators of transcription (JAK-STAT) pathway without affecting the other kinase pathways, such as p38 mitogen-activated protein kinases (MAPK), and glycogen synthase kinase 3 Beta (GSK-3β) pathways. Prior to I/R, in vitro inhibition of the JAK-STAT pathway reduced autophagy upregulation despite recombinant IL-6 pre-treatment. Autophagy is an essential component of RIPC-induced cardioprotection that may upregulate autophagy through an IL-6/JAK-STAT-dependent mechanism, thus identifying a potentially new therapeutic option for the treatment of ischemic heart disease.
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Affiliation(s)
- Muntasir Billah
- Department of Cardiology, Kolling Institute of Medical Research, Northern Sydney Local Health District, St Leonards, NSW 2065, Australia; (A.R.); (U.K.A.); (H.M.); (A.D.); (S.H.); (R.B.)
- Sydney Medical School Northern, University of Sydney, Sydney, NSW 2006, Australia
- School of Life Sciences, Independent University Bangladesh, Dhaka 1229, Bangladesh
- Correspondence:
| | - Anisyah Ridiandries
- Department of Cardiology, Kolling Institute of Medical Research, Northern Sydney Local Health District, St Leonards, NSW 2065, Australia; (A.R.); (U.K.A.); (H.M.); (A.D.); (S.H.); (R.B.)
- Sydney Medical School Northern, University of Sydney, Sydney, NSW 2006, Australia
| | - Usaid K Allahwala
- Department of Cardiology, Kolling Institute of Medical Research, Northern Sydney Local Health District, St Leonards, NSW 2065, Australia; (A.R.); (U.K.A.); (H.M.); (A.D.); (S.H.); (R.B.)
- Sydney Medical School Northern, University of Sydney, Sydney, NSW 2006, Australia
| | - Harshini Mudaliar
- Department of Cardiology, Kolling Institute of Medical Research, Northern Sydney Local Health District, St Leonards, NSW 2065, Australia; (A.R.); (U.K.A.); (H.M.); (A.D.); (S.H.); (R.B.)
| | - Anthony Dona
- Department of Cardiology, Kolling Institute of Medical Research, Northern Sydney Local Health District, St Leonards, NSW 2065, Australia; (A.R.); (U.K.A.); (H.M.); (A.D.); (S.H.); (R.B.)
| | - Stephen Hunyor
- Department of Cardiology, Kolling Institute of Medical Research, Northern Sydney Local Health District, St Leonards, NSW 2065, Australia; (A.R.); (U.K.A.); (H.M.); (A.D.); (S.H.); (R.B.)
| | - Levon M. Khachigian
- Vascular Biology and Translational Research, School of Medical Sciences, University of New South Wales, Sydney, NSW 2052, Australia;
| | - Ravinay Bhindi
- Department of Cardiology, Kolling Institute of Medical Research, Northern Sydney Local Health District, St Leonards, NSW 2065, Australia; (A.R.); (U.K.A.); (H.M.); (A.D.); (S.H.); (R.B.)
- Sydney Medical School Northern, University of Sydney, Sydney, NSW 2006, Australia
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4
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Billah M, Ridiandries A, Rayner BS, Allahwala UK, Dona A, Khachigian LM, Bhindi R. Egr-1 functions as a master switch regulator of remote ischemic preconditioning-induced cardioprotection. Basic Res Cardiol 2019; 115:3. [PMID: 31823016 DOI: 10.1007/s00395-019-0763-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Accepted: 11/27/2019] [Indexed: 12/15/2022]
Abstract
Despite improved treatment options myocardial infarction (MI) is still a leading cause of mortality and morbidity worldwide. Remote ischemic preconditioning (RIPC) is a mechanistic process that reduces myocardial infarction size and protects against ischemia reperfusion (I/R) injury. The zinc finger transcription factor early growth response-1 (Egr-1) is integral to the biological response to I/R, as its upregulation mediates the increased expression of inflammatory and prothrombotic processes. We aimed to determine the association and/or role of Egr-1 expression with the molecular mechanisms controlling the cardioprotective effects of RIPC. This study used H9C2 cells in vitro and a rat model of cardiac ischemia reperfusion (I/R) injury. We silenced Egr-1 with DNAzyme (ED5) in vitro and in vivo, before three cycles of RIPC consisting of alternating 5 min hypoxia and normoxia in cells or hind-limb ligation and release in the rat, followed by hypoxic challenge in vitro and I/R injury in vivo. Post-procedure, ED5 administration led to a significant increase in infarct size compared to controls (65.90 ± 2.38% vs. 41.00 ± 2.83%, p < 0.0001) following administration prior to RIPC in vivo, concurrent with decreased plasma IL-6 levels (118.30 ± 4.30 pg/ml vs. 130.50 ± 1.29 pg/ml, p < 0.05), downregulation of the cardioprotective JAK-STAT pathway, and elevated myocardial endothelial dysfunction. In vitro, ED5 administration abrogated IL-6 mRNA expression in H9C2 cells subjected to RIPC (0.95 ± 0.20 vs. 6.08 ± 1.40-fold relative to the control group, p < 0.05), resulting in increase in apoptosis (4.76 ± 0.70% vs. 2.23 ± 0.34%, p < 0.05) and loss of mitochondrial membrane potential (0.57 ± 0.11% vs. 1.0 ± 0.14%-fold relative to control, p < 0.05) in recipient cells receiving preconditioned media from the DNAzyme treated donor cells. This study suggests that Egr-1 functions as a master regulator of remote preconditioning inducing a protective effect against myocardial I/R injury through IL-6-dependent JAK-STAT signaling.
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Affiliation(s)
- M Billah
- Department of Cardiology, Kolling Institute, Northern Sydney Local Health District, Level 12, Royal North Shore Hospital, Cnr Reserve Rd and Westbourne, St Leonards, NSW, 2065, Australia.
- Sydney Medical School Northern, University of Sydney, Sydney, NSW, 2006, Australia.
- School of Life Sciences, Independent University Bangladesh, Dhaka, Bangladesh.
| | - A Ridiandries
- Department of Cardiology, Kolling Institute, Northern Sydney Local Health District, Level 12, Royal North Shore Hospital, Cnr Reserve Rd and Westbourne, St Leonards, NSW, 2065, Australia
- Sydney Medical School Northern, University of Sydney, Sydney, NSW, 2006, Australia
| | - B S Rayner
- Inflammation Group, Heart Research Institute, University of Sydney, Sydney, NSW, Australia
| | - U K Allahwala
- Department of Cardiology, Kolling Institute, Northern Sydney Local Health District, Level 12, Royal North Shore Hospital, Cnr Reserve Rd and Westbourne, St Leonards, NSW, 2065, Australia
- Sydney Medical School Northern, University of Sydney, Sydney, NSW, 2006, Australia
| | - A Dona
- Department of Cardiology, Kolling Institute, Northern Sydney Local Health District, Level 12, Royal North Shore Hospital, Cnr Reserve Rd and Westbourne, St Leonards, NSW, 2065, Australia
- Sydney Medical School Northern, University of Sydney, Sydney, NSW, 2006, Australia
| | - L M Khachigian
- Vascular Biology and Translational Research, School of Medical Sciences, University of New South Wales, Sydney, Australia
| | - R Bhindi
- Department of Cardiology, Kolling Institute, Northern Sydney Local Health District, Level 12, Royal North Shore Hospital, Cnr Reserve Rd and Westbourne, St Leonards, NSW, 2065, Australia
- Sydney Medical School Northern, University of Sydney, Sydney, NSW, 2006, Australia
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5
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Kaynak Bayrak G, Gümüşderelioğlu M. Construction of cardiomyoblast sheets for cardiac tissue repair: comparison of three different approaches. Cytotechnology 2019; 71:819-833. [PMID: 31236767 PMCID: PMC6663965 DOI: 10.1007/s10616-019-00325-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Accepted: 06/20/2019] [Indexed: 12/27/2022] Open
Abstract
Recently, cell sheet engineering has emerged as one of the most accentuated approaches of tissue engineering and cardiac tissue is the pioneering application area of cell sheets with clinical use. In this study, we cultured rat cardiomyoblasts (H9C2 cell line) to obtain cell sheets by using three different approaches; using (1) thermo-responsive tissue culture plates, (2) high cell seeding density/high serum content and (3) ascorbic acid treatment. To compare the outcomes of three methods, morphologic examination, immunofluorescent stainings and live/dead cell assay were performed and the effects of serum concentration and ascorbic acid treatment on cardiac gene expressions were examined. The results showed that cardiomyoblast sheets were successfully obtained in all approaches without losing their integrity and viability. Also, the results of RT-PCR analysis showed that the types of tissue culture surface, cell seeding density, serum concentration and ascorbic acid treatment affect cardiac gene expressions of cells in cell sheets. Although three methods were succeeded, ascorbic acid treatment was found as the most rapid and effective method to obtain cell sheets with cardiac characteristics.
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Affiliation(s)
| | - Menemşe Gümüşderelioğlu
- Bioengineering Department, Hacettepe University, Ankara, Turkey.
- Chemical Engineering Department, Hacettepe University, Ankara, Turkey.
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6
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Walsh KB, Li H, Koley G. Graphene alters the properties of voltage-gated Ca
2+
channels in rat cardiomyocytes. Biomed Phys Eng Express 2018. [DOI: 10.1088/2057-1976/aad0cd] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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7
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Lenčo J, Lenčová-Popelová O, Link M, Jirkovská A, Tambor V, Potůčková E, Stulík J, Šimůnek T, Štěrba M. Proteomic investigation of embryonic rat heart-derived H9c2 cell line sheds new light on the molecular phenotype of the popular cell model. Exp Cell Res 2015; 339:174-86. [DOI: 10.1016/j.yexcr.2015.10.020] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Revised: 10/20/2015] [Accepted: 10/23/2015] [Indexed: 01/15/2023]
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8
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Angel-Ambrocio AH, Soto-Acosta R, Tammineni ER, Carrillo ED, Bautista-Carbajal P, Hernández A, Sánchez JA, del Angel RM. An embryonic heart cell line is susceptible to dengue virus infection. Virus Res 2015; 198:53-8. [DOI: 10.1016/j.virusres.2015.01.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 01/07/2015] [Indexed: 10/24/2022]
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9
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Alpha1a-adrenoceptor genetic variant induces cardiomyoblast-to-fibroblast-like cell transition via distinct signaling pathways. Cell Signal 2014; 26:1985-97. [PMID: 24835978 DOI: 10.1016/j.cellsig.2014.05.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Revised: 05/08/2014] [Accepted: 05/09/2014] [Indexed: 12/21/2022]
Abstract
The role of naturally occurring human α1a-Adrenergic Receptor (α1aAR) genetic variants associated with cardiovascular disorders is poorly understood. Here, we present the novel findings that expression of human α1aAR-247R (247R) genetic variant in cardiomyoblasts leads to transition of cardiomyoblasts into a fibroblast-like phenotype, evidenced by morphology and distinct de novo expression of characteristic genes. These fibroblast-like cells exhibit constitutive, high proliferative capacity and agonist-induced hypertrophy compared with cells prior to transition. We demonstrate that constitutive, synergistic activation of EGFR, Src and ERK kinases is the potential molecular mechanism of this transition. We also demonstrate that 247R triggers two distinct EGFR transactivation-dependent signaling pathways: 1) constitutive Gq-independent β-arrestin-1/Src/MMP/EGFR/ERK-dependent hyperproliferation and 2) agonist-induced Gq- and EGFR/STAT-dependent hypertrophy. Interestingly, in cardiomyoblasts agonist-independent hyperproliferation is MMP-dependent, but in fibroblast-like cells it is MMP-independent, suggesting that expression of α1aAR genetic variant in cardiomyocytes may trigger extracellular matrix remodeling. Thus, these novel findings demonstrate that EGFR transactivation by α1aAR-247R leads to hyperproliferation, hypertrophy and alterations in cardiomyoblasts, suggesting that these unique genetically-mediated alterations in signaling pathways and cellular function may lead to myocardial fibrosis. Such extracellular matrix remodeling may contribute to the genesis of arrhythmias in certain types of heart failure.
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10
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Digoxin and ouabain induce the efflux of cholesterol via liver X receptor signalling and the synthesis of ATP in cardiomyocytes. Biochem J 2012; 447:301-11. [PMID: 22845468 DOI: 10.1042/bj20120200] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Cardioactive glycosides exert positive inotropic effects on cardiomyocytes through the inhibition of Na(+)/K(+)-ATPase. We showed previously that in human hepatoma cells, digoxin and ouabain increase the rate of the mevalonate cascade and therefore have Na(+)/K(+)-ATPase-independent effects. In the present study we found that they increase the expression and activity of 3-hydroxy-3 methylglutaryl-CoA reductase and the synthesis of cholesterol in cardiomyocytes, their main target cells. Surprisingly this did not promote intracellular cholesterol accumulation. The glycosides activated the liver X receptor transcription factor and increased the expression of ABCA1 (ATP-binding cassette protein A1) transporter, which mediates the efflux of cholesterol and its delivery to apolipoprotein A-I. By increasing the synthesis of ubiquinone, another derivative of the mevalonate cascade, digoxin and ouabain simultaneously enhanced the rate of electron transport in the mitochondrial respiratory chain and the synthesis of ATP. Mice treated with digoxin showed lower cholesterol and higher ubiquinone content in their hearts, and a small increase in their serum HDL (high-density lipoprotein) cholesterol. The results of the present study suggest that cardioactive glycosides may have a role in the reverse transport of cholesterol and in the energy metabolism of cardiomyocytes.
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Wobus AM, Rohwedel J, Maltsev V, Hescheler J. In vitro cellular models for cardiac development and pharmacotoxicology. Toxicol In Vitro 2012; 9:477-88. [PMID: 20650116 DOI: 10.1016/0887-2333(95)00023-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Permanent cultures of cardiac cells described so far have limited value for studying cell biology and pharmacology of the developing heart because of the loss of proliferative capacity and cardiac-specific properties of cardiomyocytes during long-term cultivation. Pluripotent embryonic carcinoma (EC) and embryonic stem (ES) cells cultivated as permanent lines offer a new approach for studying cardiogenic differentiation in vitro. We describe cardiogenesis in vitro by differentiating EC and ES cells by way of embryo-like aggregates (embryoid bodies) into spontaneously beating cardiomyocytes. During cardiomyocyte differentiation three distinct developmental stages were defined by expression of specific action potentials and ionic currents measured by the whole-cell patch-clamp technique. Whereas early differentiated cardiomyocytes are characterized by action potentials and ionic currents typical for early pacemaker cells, terminally differentiated cardiomyocytes show action potentials and ionic currents inherent to ventricular-, atrial- or sinus nodal-like cells. These functional characteristics are in accordance with the expression of alpha- and beta-cardiac myosin heavy chain at early differentiation stages and the additional expression of ventricular-specific MLC-2V and atrial-specific ANF genes at terminal stages demonstrated by reverse transcription polymerase chain reaction (RT-PCR) analysis. Pharmacological studies performed by measuring chronotropic responses and by analysing the Ca(2+) channel activity correspond to data obtained with cardiac cells from living organisms. For testing the influence of exogenous compounds on cardiac differentiation the teratogenic compound retinoic acid (RA) was applied during distinct stages of embryoid body development. A temporally controlled influence of RA on cardiac differentiation and expression of cardiac-specific genes was found. We conclude that ES cell-derived cardiomyocytes provide an excellent cellular model to study early cardiac development and to perform pharmacological and embryotoxicological investigations.
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Affiliation(s)
- A M Wobus
- Institute of Plant Genetics and Crop Plant Research, D-06466 Gatersleben, Germany
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12
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Xu S, Han P, Huang M, Wu JC, Chang C, Tsao PS, Yue P. In vivo, ex vivo, and in vitro studies on apelin's effect on myocardial glucose uptake. Peptides 2012; 37:320-6. [PMID: 22906703 DOI: 10.1016/j.peptides.2012.08.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Revised: 08/02/2012] [Accepted: 08/02/2012] [Indexed: 12/31/2022]
Abstract
Apelin is an endogenous peptide hormone recently implicated in glucose homeostasis. However, whether apelin affects glucose uptake in myocardial tissue remains undetermined. In this study, we utilized in vivo, ex vivo and in vitro methods to study apelin's effect on myocardial glucose uptake. Pyroglutamated apelin-13 (2mg/kg/day) was administered to C57BL6/J mice for 7 days. In vivo myocardial glucose uptake was measured by FDG-PET scanning, and GLUT4 translocation was assessed by immunofluorescence imaging. For in vitro studies, differentiated H9C2 cardiomyoblasts were exposed to pyroglutamated apelin-13 (100 nM) for 2h. To test their involvement in apelin-stimulated myocardial glucose uptake, the energy sensing protein kinase AMPK were inhibited by pharmacologic inhibition (compound C) and RNA interference. IRS-1 phosphorylation was assessed by western blotting using an antibody directed against IRS-1 Ser-789-phosphorylated form. We found that apelin increased myocardial glucose uptake and GLUT4 membrane translocation in C57BL6/J mice. Apelin was also sufficient to increase glucose uptake in H9C2 cells. Apelin-mediated glucose uptake was significantly decreased by AMPK inhibition. Finally, apelin increased IRS-1 Ser-789 phosphorylation in an AMPK-dependent manner. The results of our study demonstrated that apelin increases myocardial glucose uptake through a pathway involving AMPK. Apelin also facilitates IRS-1 Ser-789 phosphorylation, suggesting a novel mechanism for its effects on glucose uptake.
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Affiliation(s)
- Shiming Xu
- Department of Medicine/Cardiovascular Medicine, Stanford University School of Medicine, 300 Pasteur Dr, Stanford, CA 94305, United States
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13
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Lynn EG, Stevens MV, Wong RP, Carabenciov D, Jacobson J, Murphy E, Sack MN. Transient upregulation of PGC-1alpha diminishes cardiac ischemia tolerance via upregulation of ANT1. J Mol Cell Cardiol 2010; 49:693-8. [PMID: 20600099 DOI: 10.1016/j.yjmcc.2010.06.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Revised: 06/18/2010] [Accepted: 06/18/2010] [Indexed: 12/20/2022]
Abstract
Prolonged cardiac overexpression of the mitochondrial biogenesis regulatory transcriptional coactivator PGC-1alpha disrupts cardiac contractile function and its genetic ablation limits cardiac capacity to enhance workload. In contrast, transient induction of PGC-1alpha alleviates neuronal cell oxidative stress and enhances skeletal myotube anti-oxidant defenses. We explored whether transient upregulation of PGC-1alpha in the heart protects against ischemia-reperfusion injury. The transient induction of PGC-1alpha in the cardiac-restricted inducible PGC-1alpha transgenic mouse, increased PGC-1alpha protein levels 5-fold. Following 25 min of ischemia and 2h of reperfusion on a Langendorff perfusion apparatus, contractile recovery and the rate pressure product was significantly blunted in mice overexpressing PGC-1alpha vs. controls. Affymetrix gene array analysis showed a 3-fold PGC-1alpha-mediated upregulation of adenine nucleotide translocase 1 (ANT1). As ANT1 upregulation induces cardiomyocyte cell death we investigated whether the induction of ANT1 by PGC-1alpha contributes to this enhanced ischemia-stress susceptibility. Infection with adenovirus harboring PGC-1alpha into cardiac-derived H9c2 cells significantly upregulates ANT1 without changing basal cell viability. In response to anoxia-reoxygenation injury cell death is significantly increased following PGC-1alpha overexpression. This detrimental effect is abolished following siRNA knockdown of ANT1. Similarly, the attenuation of ANT-1 in the presence of PGC-1alpha overexpression preserves the mitochondrial membrane potential in response to hydrogen-peroxide stress. Interestingly, the isolated knockdown of ANT1 also protects H9c2 cells from anoxia-reoxygenation injury. Taken together these data suggest that transient induction of PGC-1alpha in the murine heart decreases ischemia-reperfusion contractile recovery and diminishes anoxia-reoxygenation tolerance in H9c2 cells. These adverse phenotypes appear to be mediated, in part, by PGC-1alpha induced upregulation of ANT1.
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Affiliation(s)
- Edward G Lynn
- Translational Medicine Branch, NHLBI, NIH, Bethesda, MD 20892-1454, USA
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14
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Benitah JP, Alvarez JL, Gómez AM. L-type Ca(2+) current in ventricular cardiomyocytes. J Mol Cell Cardiol 2009; 48:26-36. [PMID: 19660468 DOI: 10.1016/j.yjmcc.2009.07.026] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Revised: 07/09/2009] [Accepted: 07/27/2009] [Indexed: 12/24/2022]
Abstract
L-type Ca(2+) channels are mediators of Ca(2+) influx and the regulatory events accompanying it and are pivotal in the function and dysfunction of ventricular cardiac myocytes. L-type Ca(2+) channels are located in sarcolemma, including the T-tubules facing the sarcoplasmic reticulum junction, and are activated by membrane depolarization, but intracellular Ca(2+)-dependent inactivation limits Ca(2+) influx during action potential. I(CaL) is important in heart function because it triggers excitation-contraction coupling, modulates action potential shape and is involved in cardiac arrhythmia. L-type Ca(2+) channels are multi-subunit complexes that interact with several molecules involved in their regulations, notably by beta-adrenergic signaling. The present review highlights some of the recent findings on L-type Ca(2+) channel function, regulation, and alteration in acquired pathologies such as cardiac hypertrophy, heart failure and diabetic cardiomyopathy, as well as in inherited arrhythmic cardiac diseases such as Timothy and Brugada syndromes.
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15
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Liu X, Liu W, Yang L, Xia B, Li J, Zuo J, Li X. Increased connexin 43 expression improves the migratory and proliferative ability of H9c2 cells by Wnt-3a overexpression. Acta Biochim Biophys Sin (Shanghai) 2007; 39:391-8. [PMID: 17558443 DOI: 10.1111/j.1745-7270.2007.00296.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The change of connexin 43 (Cx43) expression and the biological behaviors of Cx43 in rat heart cell line H9c2, expressing Wnt-3a (wingless-type MMTV integration site family, member 3A), were evaluated in the present study. Plasmid pcDNA3.1/Wnt-3a was constructed and transferred into H9c2 cells. The cell model Wnt-3a(+)-H9c2 steadily expressing Wnt-3a was obtained. Compared with H9c2 and pcDNA3.1-H9c2 cells, the expression of Cx43 in Wnt-3a(+)-H9c2 cells was clearly increased, the proliferation of Wnt-3a(+)-H9c2 cells was significantly changed, and cell migration abilities were also improved(P<0.05). In comparison with H9c2 and pcDNA3.1-H9c2 cells, the G2 phase of the cell cycle increased by 11% in Wnt-3a(+)-H9c2 cells. Thus, Wnt-3a overexpression is associated with an increase in Cx43 expression and altered migratory and proliferative activity in H9c2 cells. Cx43 might be one of the downstream target genes regulated by Wnt-3a.
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Affiliation(s)
- Xiaoyu Liu
- Department of Cellular and Genetic Medicine, Shanghai Medical College, Fudan University, Shanghai 200032, China
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16
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Sardão VA, Oliveira PJ, Holy J, Oliveira CR, Wallace KB. Vital imaging of H9c2 myoblasts exposed to tert-butylhydroperoxide--characterization of morphological features of cell death. BMC Cell Biol 2007; 8:11. [PMID: 17362523 PMCID: PMC1831770 DOI: 10.1186/1471-2121-8-11] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2006] [Accepted: 03/16/2007] [Indexed: 11/10/2022] Open
Abstract
Background When exposed to oxidative conditions, cells suffer not only biochemical alterations, but also morphologic changes. Oxidative stress is a condition induced by some pro-oxidant compounds, such as by tert-butylhydroperoxide (tBHP) and can also be induced in vivo by ischemia/reperfusion conditions, which is very common in cardiac tissue. The cell line H9c2 has been used as an in vitro cellular model for both skeletal and cardiac muscle. Understanding how these cells respond to oxidative agents may furnish novel insights into how cardiac and skeletal tissues respond to oxidative stress conditions. The objective of this work was to characterize, through vital imaging, morphological alterations and the appearance of apoptotic hallmarks, with a special focus on mitochondrial changes, upon exposure of H9c2 cells to tBHP. Results When exposed to tBHP, an increase in intracellular oxidative stress was detected in H9c2 cells by epifluorescence microscopy, which was accompanied by an increase in cell death that was prevented by the antioxidants Trolox and N-acetylcysteine. Several morphological alterations characteristic of apoptosis were noted, including changes in nuclear morphology, translocation of phosphatidylserine to the outer leaflet of the cell membrane, and cell blebbing. An increase in the exposure period or in tBHP concentration resulted in a clear loss of membrane integrity, which is characteristic of necrosis. Changes in mitochondrial morphology, consisting of a transition from long filaments to small and round fragments, were also detected in H9c2 cells after treatment with tBHP. Bax aggregates near mitochondrial networks were formed after short periods of incubation. Conclusion Vital imaging of alterations in cell morphology is a useful method to characterize cellular responses to oxidative stress. In the present work, we report two distinct patterns of morphological alterations in H9c2 cells exposed to tBHP, a pro-oxidant agent frequently used as model to induce oxidative stress. In particular, dynamic changes in mitochondrial networks could be visualized, which appear to be centrally involved in how these cells respond to oxidative stress. The data also indicate that the cause of H9c2 cell death following tBHP exposure is increased intracellular oxidative stress.
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Affiliation(s)
- Vilma A Sardão
- Center for Neurosciences and Cellular Biology, University of Coimbra, Coimbra, Portugal
| | - Paulo J Oliveira
- Center for Neurosciences and Cellular Biology, University of Coimbra, Coimbra, Portugal
| | - Jon Holy
- Department of Anatomy, Microbiology and Pathology, University of Minnesota-Medical School, Duluth, USA
| | - Catarina R Oliveira
- Center for Neurosciences and Cellular Biology, University of Coimbra, Coimbra, Portugal
| | - Kendall B Wallace
- Department of Biochemistry and Molecular Biology, University of Minnesota-Medical Medical School, Duluth, USA
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17
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Kanaya H, Takeya R, Takeuchi K, Watanabe N, Jing N, Sumimoto H. Fhos2, a novel formin-related actin-organizing protein, probably associates with the nestin intermediate filament. Genes Cells 2005; 10:665-78. [PMID: 15966898 DOI: 10.1111/j.1365-2443.2005.00867.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Fhos1 is a mammalian formin-family protein, and functions as an organizer of the actin microfilament. Here we have cloned human and mouse cDNAs for a novel Fhos homolog, designated Fhos2. The messages for Fhos2 are expressed in the heart, kidney, and brain, where the Fhos1 mRNAs are not abundant. Two splice variants of Fhos2 exist in a tissue-specific manner; the longer variant Fhos2L is the major form in the heart, whereas the kidney and brain predominantly express Fhos2S that encodes a shorter protein. Over-expression of an active form of the two Fhos2 variants, as well as that of Fhos1, induces the formation of actin stress fibers in HeLa cells, suggesting that Fhos2 acts as an actin-organizing protein. Biochemical analysis using rat cardiomyoblastic H9c2 (2-1) cells reveals that endogenous Fhos2 is enriched in the intermediate filament fraction. Consistent with this, Fhos2 localizes to the nestin intermediate filament but not to other cytoskeletons, as demonstrated by staining of H9c2 (2-1) cells with anti-Fhos2 antibodies. Furthermore, Fhos2 is present in nestin-expressing neuroepithelial cells of the fetal rat brain. Thus, Fhos2 not only has the actin-organizing activity but also associates with nestin, which may imply a Fhos2-mediated link between the nestin intermediate filament and actin microfilament.
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Affiliation(s)
- Hideki Kanaya
- Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
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18
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Pagano M, Naviglio S, Spina A, Chiosi E, Castoria G, Romano M, Sorrentino A, Illiano F, Illiano G. Differentiation of H9c2 cardiomyoblasts: The role of adenylate cyclase system. J Cell Physiol 2004; 198:408-16. [PMID: 14755546 DOI: 10.1002/jcp.10420] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The adenylate cyclase (AC)/cAMP/cAMP-dependent protein kinase pathway controls many biological phenomena. The molecular mechanisms by which cAMP induces alternative commitment towards differentiation or proliferation are not still completely known. The differentiation of myoblast cell lines into myocytes/myotubes represents a well-established model of skeletal muscle differentiation. We analyzed the AC/cAMP pathway during terminal differentiation of H9c2 myoblasts. When cultured in low-serum containing medium, H9c2 myoblasts exit the cell cycle and differentiate into myocytes/myotubes. A key step of this process is the expression of myogenin, an essential transcription factor for the terminal differentiation into myocytes. During this phenomenon we observed a decrease in both cAMP levels and AC activity, which suggests a functional negative role of cAMP on the differentiation process of H9c2 cells. 8-Br-cAMP and other cAMP-elevating agents, such as forskolin, IBMX, and isoproterenol, negatively affected skeletal muscle differentiation of H9c2 myoblasts. Both AC activity down-regulation and intracellular cAMP reduction were accompanied by significant variations in the levels of membrane proteins belonging to the AC system (AC catalytic subunit, G(alphai-1), G(alphas)). The functional relationship between intracellular cAMP content and protein levels of AC system is discussed.
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Affiliation(s)
- M Pagano
- Department of Biochemistry and Biophysics "F. Cedrangolo", School of Medicine, Second University of Naples, Naples, Italy
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19
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Pang L, Koren G, Wang Z, Nattel S. Tissue-specific expression of two human Ca(v)1.2 isoforms under the control of distinct 5' flanking regulatory elements. FEBS Lett 2003; 546:349-54. [PMID: 12832067 DOI: 10.1016/s0014-5793(03)00629-x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Transcriptional regulation may be important for L-type Ca(2+) channel alpha(1C) subunit (Ca(v)1.2) gene expression. In this study, we found two human Ca(v)1.2 isoforms, one strongly and selectively expressed in heart and the other with apparently ubiquitous expression. The promoter for the cardiac isoform has an 'initiator' sequence, and is active in neonatal cardiomyocytes but not in cardiac fibroblasts, H9C2 cells, human aorta-vascular smooth muscle and HEK293 cells. The promoter for the ubiquitously expressed isoform is of the 'housekeeping' type and is active in all cell types examined. These data indicate specific expression patterns of two human Ca(v)1.2 isoforms under the control of distinct 5' flanking regulatory sequences.
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Affiliation(s)
- Li Pang
- Department of Medicine, Montreal Heart Institute, and University of Montreal, 5000 Belanger St East, Montreal, QC, Canada H1T 1C8
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20
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Saito M, Sakiyama K, Shiota T, Ito M. Isoproterenol produces a rapid increase in sialidase activity in rat heart tissue and cardiomyocyte-derived H9c2 cells in culture. FEBS Lett 2003; 542:105-8. [PMID: 12729907 DOI: 10.1016/s0014-5793(03)00359-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The effects of isoproterenol on sialidase activity in rat cardiomyocytes were examined. Administration of isoproterenol to rats (0.2 or 2 mg/kg body weight) produced an increase in sialidase activity in total membrane fraction of heart tissue within 120 min (121+/-13% of the control at 120 min after administration of 0.2 mg isoproterenol/kg, n=5, P<0.05). Sialidase activity in cardiomyocyte-derived H9c2 cells was also increased by treatment with isoproterenol (10 microM) for 60 min. The effect of isoproterenol on sialidase activity was amplified by the addition of 3-isobutyl-1-methylxanthine (IBMX). Sialidase activity in H9c2 cells was elevated by treatment with dibutyryl cAMP plus IBMX without isoproterenol. The content of N-acetylneuraminic acid in cells decreased by 22% after treatment with isoproterenol plus IBMX. These results suggest that sialidase activity in rat cardiomyocytes is regulated by beta-adrenergic stimulators via a cAMP-dependent process. The increased activity of sialidase may account for the reduction of sialic acid content of cells.
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Affiliation(s)
- Megumi Saito
- Department of Clinical Pharmacology and Therapeutics, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Shizuoka 422-8526, Japan.
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21
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Wang W, Hino N, Yamasaki H, Aoki T, Ochi R. KV2.1 K+ channels underlie major voltage-gated K+ outward current in H9c2 myoblasts. THE JAPANESE JOURNAL OF PHYSIOLOGY 2002; 52:507-14. [PMID: 12617756 DOI: 10.2170/jjphysiol.52.507] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The H9c2 clonal cell line derived from embryonic rat ventricle is an in vitro model system for cardiac and skeletal myocytes. We used the whole-cell patch clamp technique to characterize the electrophysiological and pharmacological properties of an outward K+ current (IK(V)) and determined its molecular correlate in H9c2 myoblasts. IK(V) was activated by threshold depolarization to -30 mV, and its current amplitude and rate of activation increased with further depolarizations. IK(V) inactivated slowly with a time constant of 1-2 s, and the V(0.5) for steady-state inactivation was -37.9 +/- 4.6 mV (n = 10). Tetraethylammonium and quinidine suppressed IK(V) with IC(50)'s of 3.7 mM and 11.6 microM, respectively. Using RT-PCR analysis we found that the K(V )2.1 gene is the most abundantly expressed among genes for K(V)1.2, 1.4, 1.5, 2.1, 4.2, and 4.3, and by Western blotting we confirmed the synthesis of the K(V)2.1 alpha-subunit protein. We conclude that IK(V), the predominant voltage-gated outward current in H9c2 myoblasts, flows through the channels comprised of the K(V)2.1-subunit gene product.
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Affiliation(s)
- Wei Wang
- Department of Physiology, Juntendo University School of Medicine, Hongo 2-1-1, Tokyo, 113-8421 Japan
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22
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Hasselbaink DM, Roemen THM, van der Vusse GJ. Protein acylation in the cardiac muscle like cell line, H9c2. Mol Cell Biochem 2002; 239:101-12. [PMID: 12479575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2023]
Abstract
Besides serving as oxidisable substrates, fatty acids (FA) are involved in co- and post-translational modification of proteins (protein acylation). Despite the high rate of fatty acid utilisation in the heart, information on protein acylation in cardiac muscle is scarce. To explore this subject in more detail, we used the H9c2 cell line as an experimental model. After incubation with 3H-palmitate or 3H-myristate, cells were lysed and proteins precipitated, followed by extensive delipidation. The delipidated proteins were subjected to SDS-PAGE and transferred to nitro-cellulose prior to autoradiography. In addition, TLC was used to separate the various lipid classes. The first aspect we addressed was the extent of protein acylation as a function of time, relative to fatty acid incorporation into various lipid classes. Cells were incubated for 30 min, 1 h and 2 h with 100 microCi palmitate (PA, 2.3 nmol) or 125 microCi myristate (MA, 2.5 nmol). Palmitoylation increased from 0.48 +/- 0.25 to 1.25 +/- 0.56 microCi/mg protein between 30 min to 2 h, while myristoylation increased from 0.25 +/- 0.12 to 0.77 +/- 0.36 microCi/mg protein. Furthermore, delipidated proteins subjected to autoradiography showed that a set of distinct proteins was labelled with 3H-palmitate. Incorporation into phospholipids (PL) increased from 40-60% of the total amount of radio-labelled PA or MA supplied between 30 min and 2 h. Only the FA pool differed between MA and PA, with a higher FA content present after incubations with MA. Second, we investigated palmitoylation and incorporation into cellular lipids as a function of the amount of PA applied. Palmitoylation showed saturation at high PA concentrations. The percentage incorporation of 3H-PA in the various lipids depended on the amount of PA added: a decline in the PL pool with a concomitant increase in the size of the diacylglycerol pool at high PA concentrations. Third, inhibition of palmitoylation by cerulenin and tunicamycin was investigated. While both were able to inhibit palmitoylation, cerulenin also inhibited the incorporation of PA into various lipid classes, indicating differences in inhibitory action.
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Affiliation(s)
- Danny M Hasselbaink
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands
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23
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Klugbauer N, Welling A, Specht V, Seisenberger C, Hofmann F. L-type Ca2+ channels of the embryonic mouse heart. Eur J Pharmacol 2002; 447:279-84. [PMID: 12151019 DOI: 10.1016/s0014-2999(02)01850-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In the heart, where Ca(2+) influx across the sarcolemma is essential for contraction, L-type Ca(2+) channels represent the major entry pathway of Ca(2+). Mice with a homozygous deletion of the L-type Ca(v)1.2 Ca(2+) channel gene die before day 14.5 p.c. Electrophysiological and pharmacological investigations on Ca(v)1.2-/- cardiomyocytes demonstrated that contractions depended on the influx of Ca(2+) through an L-type-like Ca(2+) channel. We analyzed now the expression pattern of various L-type Ca(2+) channels. Amplification of the alternative exons 1a and 1b revealed that embryonic cardiac cells express both Ca(v)1.2a and Ca(v)1.2b subunits. Reverse transcriptase-polymerase chain reaction (RT-PCR) amplifications indicated the expression of Ca(v)1.1 and Ca(v)1.3 in about a 1:10 ratio in Ca(v)1.2-/- embryos. Two different amino termini of the Ca(v)1.3 cDNA were found in the embryonic heart, which both gave rise to functional channels. Ca(v)1.3(1a) and Ca(v)1.3(1b) channels have similar current kinetics and voltage-dependencies as described for Ca(v)1.3(8A) channels [J. Biol. Chem. 276 (2001) 22100], but the properties of Ca(v)1.3(1a) or Ca(v)1.3(1b) channels are different from that of the L-type-like current in Ca(v)1.2-/- cardiomyocytes. The I(Ba) of Ca(v)1.3(1a) was blocked by the dihydropyridine nisoldipine with an IC(50) value of 0.13 microM at a holding potential of -80 mV. In embryonic Ca(v)1.2+/+ cardiomyocytes, I(Ba) was blocked by nisoldipine with an IC(50) value of 0.1 microM. Although the expressed Ca(v)1.3 channel has a similar affinity for nisoldipine as Ca(v)1.2+/+ cardiomyocytes, the L-type-like Ca(2+) channel found in Ca(v)1.2+/+ and -/- cardiomyocytes is not identical with the new Ca(v)1.3 splice variants.
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Affiliation(s)
- Norbert Klugbauer
- Institut für Pharmakologie und Toxikologie der Technischen Universität München, Biedersteiner Str. 29, 80802 Munich, Germany.
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24
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Hamano T, Kobayashi K, Sakairi T, Hayashi M, Mutai M. Peroxisome proliferator-activated receptor alpha (PPAR alpha) agonist, WY-14,643, increased transcription of myosin light chain-2 in cardiomyocytes. J Toxicol Sci 2001; 26:275-84. [PMID: 11871124 DOI: 10.2131/jts.26.275] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Peroxisome proliferator-activated receptors (PPARs) are nuclear hormone receptors that can be activated by xenobiotics and natural fatty acids. To assess the potential physiological activity of PPAR ligands on cardiac muscular cells, the effects of PPAR alpha agonist, WY-14,643, on both rat hearts and a rat cardiomyocyte cell line (H9c2 cells) were investigated. Male F344 rats were fed a diet containing WY-14,643 at a concentration of 100 ppm for 26 weeks. Cardiac muscular hypertrophy was revealed by morphometric analysis in which the diameter of the muscular fibers in WY-14,643-treated rats was larger than those of control rats. Using H9c2 cells in vitro, the protein content per cell was increased in a dose-dependent manner with the treatment of WY-14,643. The transcription of myosin light chain-2 (MLC-2), a parameter of myocardial hypertrophy, was increased in H9c2 cells transfected with the rat MLC-2/luciferase fusion gene by WY-14,643 as well as other peroxisome proliferators, clofibrate and di(2-ethylhexyl) phthalate. In addition, accumulation of myosin light chain protein was confirmed in H9c2 cells treated with WY-14,643 at 10 micrograms/ml for 7 days or more by immunohistochemistry. These results suggest that PPAR alpha ligands have a potential to regulate MLC-2, which is a contractile protein in cardiomyocytes and may play a part of role in the pathogenesis of cardiac hypertrophy.
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Affiliation(s)
- T Hamano
- Toxicology Laboratory, Mitsubishi Pharma Co., 100-5 Yana, Kisarazu-shi, Chiba 292-0812, Japan
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25
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Van Nieuwenhoven FA, Martin X, Heijnen VV, Cornelussen RN, Snoeckx LH. HSP70-mediated acceleration of translational recovery after stress is independent of ribosomal RNA synthesis. Eur J Cell Biol 2001; 80:586-92. [PMID: 11675934 DOI: 10.1078/0171-9335-00192] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
HSP70 is known to protect cells against stressful events. In the present study, the hypothesis was investigated that elevated HSP70 levels protect RNA polymerase I during stress, leading to decreased inhibition of ribosomal RNA (rRNA) synthesis and accelerated recovery of protein translation after stress. To this end, transcriptional and translational activity was studied in H9c2 cells during recovery after a severe heat treatment (SHT, 1 h 45 degrees C) in the presence of elevated HSP70 levels. The latter was achieved by heat pretreatment or by adenovirus-mediated hsp70 gene transfer. Rates of transcription and translation were determined by measuring cellular 3H-labelled uridine and leucine incorporation, respectively. The two types of pretreatment did not affect basal rates of transcription and translation, immediately before SHT. During SHT, both transcriptional and translational rates dropped to less than 10% of basal levels in pretreated as well as non-pretreated cells. Two and four h after SHT, both transcriptional and translational rates were significantly higher in HSP70-overexpressing cells compared to non-pretreated cells. However, immediately after SHT, transcription rates were similarly depressed in non-pretreated and pretreated cells, showing that increased levels of HSP70 did not protect RNA polymerase I activity during SHT. Thus, the HSP70-mediated acceleration of translational recovery is not preceded in time by an enhanced recovery of rRNA synthesis. Therefore, the HSP70-mediated early recovery of protein synthesis after heat stress is independent of rRNA synthesis.
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Affiliation(s)
- F A Van Nieuwenhoven
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, The Netherlands.
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26
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Seisenberger C, Specht V, Welling A, Platzer J, Pfeifer A, Kühbandner S, Striessnig J, Klugbauer N, Feil R, Hofmann F. Functional embryonic cardiomyocytes after disruption of the L-type alpha1C (Cav1.2) calcium channel gene in the mouse. J Biol Chem 2000; 275:39193-9. [PMID: 10973973 DOI: 10.1074/jbc.m006467200] [Citation(s) in RCA: 198] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The L-type alpha(1C) (Ca(v)1.2) calcium channel is the major calcium entry pathway in cardiac and smooth muscle. We inactivated the Ca(v)1.2 gene in two independent mouse lines that had indistinguishable phenotypes. Homozygous knockout embryos (Ca(v)1. 2-/-) died before day 14.5 postcoitum (p.c.). At day 12.5 p.c., the embryonic heart contracted with identical frequency in wild type (+/+), heterozygous (+/-), and homozygous (-/-) Ca(v)1.2 embryos. Beating of isolated embryonic cardiomyocytes depended on extracellular calcium and was blocked by 1 microm nisoldipine. In (+/+), (+/-), and (-/-) cardiomyocytes, an L-type Ba(2+) inward current (I(Ba)) was present that was stimulated by Bay K 8644 in all genotypes. At a holding potential of -80 mV, nisoldipine blocked I(Ba) of day 12.5 p.c. (+/+) and (+/-) cells with two IC(50) values of approximately 0.1 and approximately 1 microm. Inhibition of I(Ba) of (-/-) cardiomyocytes was monophasic with an IC(50) of approximately 1 microm. The low affinity I(Ba) was also present in cardiomyocytes of homozygous alpha(1D) (Ca(v)1.3) knockout embryos at day 12.5 p.c. These results indicate that, up to day 14 p.c., contraction of murine embryonic hearts requires an unidentified, low affinity L-type like calcium channel.
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MESH Headings
- 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester/pharmacology
- Animals
- Barium/metabolism
- Calcium Channel Agonists/pharmacology
- Calcium Channel Blockers/pharmacology
- Calcium Channels, L-Type/genetics
- Calcium Channels, L-Type/physiology
- Cell Line
- DNA, Complementary/metabolism
- Dose-Response Relationship, Drug
- Electrophysiology
- Exons
- Genetic Vectors
- Genotype
- Heart/embryology
- Homozygote
- Inhibitory Concentration 50
- Ions
- Kinetics
- Mice
- Mice, Knockout
- Models, Genetic
- Myocardium/cytology
- Nisoldipine/pharmacology
- Phenotype
- RNA/metabolism
- Time Factors
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Affiliation(s)
- C Seisenberger
- Institut für Pharmakologie und Toxikologie, TU München, Biedersteiner Strasse 29, D-80802 München, Germany
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27
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Szalai G, Csordás G, Hantash BM, Thomas AP, Hajnóczky G. Calcium signal transmission between ryanodine receptors and mitochondria. J Biol Chem 2000; 275:15305-13. [PMID: 10809765 DOI: 10.1074/jbc.275.20.15305] [Citation(s) in RCA: 181] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Control of energy metabolism by increases of mitochondrial matrix [Ca(2+)] ([Ca(2+)](m)) may represent a fundamental mechanism to meet the ATP demand imposed by heart contractions, but the machinery underlying propagation of [Ca(2+)] signals from ryanodine receptor Ca(2+) release channels (RyR) to the mitochondria remains elusive. Using permeabilized cardiac (H9c2) cells we investigated the cytosolic [Ca(2+)] ([Ca(2+)](c)) and [Ca(2+)](m) signals elicited by activation of RyR. Caffeine, Ca(2+), and ryanodine evoked [Ca(2+)](c) spikes that often appeared as frequency-modulated [Ca(2+)](c) oscillations in these permeabilized cells. Rapid increases in [Ca(2+)](m) and activation of the Ca(2+)-sensitive mitochondrial dehydrogenases were synchronized to the rising phase of the [Ca(2+)](c) spikes. The RyR-mediated elevations of global [Ca(2+)](c) were in the submicromolar range, but the rate of [Ca(2+)](m) increases was as large as it was in the presence of 30 microm global [Ca(2+)](c). Furthermore, RyR-dependent increases of [Ca(2+)](m) were relatively insensitive to buffering of [Ca(2+)](c) by EGTA. Therefore, RyR-driven rises of [Ca(2+)](m) appear to result from large and rapid increases of perimitochondrial [Ca(2+)]. The falling phase of [Ca(2+)](c) spikes was followed by a rapid decay of [Ca(2+)](m). CGP37157 slowed down relaxation of [Ca(2+)](m) spikes, whereas cyclosporin A had no effect, suggesting that activation of the mitochondrial Ca(2+) exchangers accounts for rapid reversal of the [Ca(2+)](m) response with little contribution from the permeability transition pore. Thus, rapid activation of Ca(2+) uptake sites and Ca(2+) exchangers evoked by RyR-mediated local [Ca(2+)](c) signals allow mitochondria to respond rapidly to single [Ca(2+)](c) spikes in cardiac cells.
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Affiliation(s)
- G Szalai
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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28
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Ménard C, Pupier S, Mornet D, Kitzmann M, Nargeot J, Lory P. Modulation of L-type calcium channel expression during retinoic acid-induced differentiation of H9C2 cardiac cells. J Biol Chem 1999; 274:29063-70. [PMID: 10506158 DOI: 10.1074/jbc.274.41.29063] [Citation(s) in RCA: 143] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The molecular mechanisms underlying the developmental regulation of L-type voltage-dependent Ca(2+) channels (VDCCs) are still unknown. In this study, we have characterized the expression patterns of skeletal (alpha(1S)) and cardiac (alpha(1C)) L-type VDCCs during cardiogenic differentiation in H9C2 cells that derived from embryonic rat heart. We report that chronic treatment of H9C2 cells with 10 nM all-trans-retinoic acid (all-trans-RA) enhanced cardiac Ca(2+) channel expression, as demonstrated by reverse transcription-polymerase chain reaction, immunoblotting, and indirect immunofluorescence studies, as well as patch-clamp experiments. In addition, RA treatment prevented expression of functional skeletal L-type VDCCs, which were restricted to myotubes that spontaneously appear in control H9C2 cultures undergoing myogenic transdifferentiation. The use of specific skeletal and cardiac markers indicated that RA, by preventing myogenic transdifferentiation, preserves cardiac differentiation of this cell line. Altogether, we provide evidence that cardiac and skeletal subtype-specific L-type Ca(2+) channels are relevant functional markers of differentiated cardiac and skeletal myocytes, respectively. In conclusion, our data demonstrate that in vitro RA stimulates cardiac (alpha(1C)) L-type Ca(2+) channel expression, therefore supporting the hypothesis that the RA pathway might be involved in the tissue specific expression of Ca(2+) channels in mature cardiac cells.
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Affiliation(s)
- C Ménard
- IGH-CNRS UPR 1142, 141 rue de la Cardonille, 34396 Montpellier cedex 05, France
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29
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Wang W, Watanabe M, Nakamura T, Kudo Y, Ochi R. Properties and expression of Ca2+-activated K+ channels in H9c2 cells derived from rat ventricle. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:H1559-66. [PMID: 10330239 DOI: 10.1152/ajpheart.1999.276.5.h1559] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
H9c2 is a clonal myogenic cell line derived from embryonic rat ventricle that can serve as a surrogate for cardiac or skeletal muscle in vitro. Using whole cell clamp with H9c2 myotubes, we observed that depolarizing pulses activated slow outward K+ currents and then slow tail currents. The K+ currents were abolished in a Ca2+-free external solution, indicating that they were Ca2+-activated K+ currents. They were blocked by apamin, a small-conductance Ca2+-activated K+ (SK) channel antagonist (IC50 = 6.2 nM), and by d-tubocurarine (IC50 = 49.4 microM). Activation of SK channels exhibited a bell-shaped voltage dependence that paralleled the current-voltage relation for L-type Ca2+ currents (ICa,L). ICa,L exhibited a slow time course similar to skeletal ICa, L, were unaffected by apamin, and were only slightly depressed by d-tubocurarine. RT-PCR analysis of the mRNAs revealed that rSK3, but not rSK1 or rSK2, was expressed in H9c2 myotubes but not in myoblasts. These results suggest that rSK3 channels are expressed in H9c2 myotubes and are primarily activated by ICa,L directly or indirectly via Ca2+-induced Ca2+ release from sarcoplasmic reticulum.
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Affiliation(s)
- W Wang
- Department of Physiology, Juntendo University School of Medicine, Tokyo 113-8421, Japan
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30
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Van Nieuwenhoven FA, Luiken JJ, De Jong YF, Grimaldi PA, Van der Vusse GJ, Glatz JF. Stable transfection of fatty acid translocase (CD36) in a rat heart muscle cell line (H9c2). J Lipid Res 1998. [DOI: 10.1016/s0022-2275(20)32502-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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31
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Chaloin L, Vidal P, Lory P, Méry J, Lautredou N, Divita G, Heitz F. Design of carrier peptide-oligonucleotide conjugates with rapid membrane translocation and nuclear localization properties. Biochem Biophys Res Commun 1998; 243:601-8. [PMID: 9480855 DOI: 10.1006/bbrc.1997.8050] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Peptides containing a hydrophobic motif associated with a nuclear localization signal separated by various linkers were synthesized in solid phase. The hydrophobic sequence corresponds either to a signal peptide sequence or to a fragment of the fusion peptide of GP41 while the hydrophilic sequence is that of a nuclear localization signal. The C-termini of these peptides bear a cysteamide group that was linked to a fluorescent probe. This allowed the cellular localization of the probe to be determined as a function of the peptide sequences. The labeled peptides were then incubated with fibroblasts. Using N-biotinylated derivatives we confirmed by indirect immunofluorescence that the observed localizations corresponds to those of the peptides. The presence of a linker appears to play a role in the cellular localization. One of these peptides was successfully used to target fluorescent oligodeoxynucleotides into living cells demonstrating improved cell delivery of peptide-oligodeoxynucleotide conjugates.
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Affiliation(s)
- L Chaloin
- Centre de Recherche de Biochimie Macromoléculaire, ERS 155 1919, Montpellier, France
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32
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Hoch B, Haase H, Schulze W, Hagemann D, Morano I, Krause EG, Karczewski P. Differentiation-dependent expression of cardiac δ-CaMKII isoforms. J Cell Biochem 1998. [DOI: 10.1002/(sici)1097-4644(19980201)68:2<259::aid-jcb12>3.0.co;2-a] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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33
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Péréon Y, Navarro J, Hamilton M, Booth FW, Palade P. Chronic stimulation differentially modulates expression of mRNA for dihydropyridine receptor isoforms in rat fast twitch skeletal muscle. Biochem Biophys Res Commun 1997; 235:217-22. [PMID: 9196066 DOI: 10.1006/bbrc.1997.6753] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
This study examined the effects of low frequency chronic stimulation on expression of the mRNA encoding the two isoforms of the alpha1 subunit of the dihydropyridine receptor (DHPR) calcium channel, a critical component of skeletal muscle excitation-contraction coupling. RNase protection assay was used to determine alteration in isoform expression in 5-day, 9-day and 13-day chronically stimulated rat tibialis anterior muscle, and to compare it with soleus and extensor digitorum longus muscles. Low frequency chronic stimulation was associated not only with a significant decrease in the mRNA level of the skeletal isoform of the DHPR, but also with a significant increase in the mRNA level of the cardiac isoform of the DHPR, the overwhelming majority of which was the adult splice variant. Significant levels of cardiac DHPR mRNA expression were also found in normal adult slow twitch soleus muscle. These findings raise the question of a potential role for the cardiac DHPR in certain adult skeletal muscles.
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Affiliation(s)
- Y Péréon
- Department of Physiology and Biophysics, University of Texas Medical Branch, Galveston 77555-0641, USA
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34
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Taouil K, Féray JC, Brunet J, Christen MO, Garay RP, Hannaert P. Inhibition by xipamide of amiloride-induced acidification in cultured rat cardiocytes. Eur J Pharmacol 1997; 324:289-94. [PMID: 9145785 DOI: 10.1016/s0014-2999(97)00087-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The diuretic drug xipamide improves myocardial relaxation in hypertensive patients with left ventricular hypertrophy, but its mechanism of action is unknown. Here, xipamide was tested in cultured rat heart myogenic H9c2 cells and newborn cardiomyocytes for its effects on cell acidification (and Ca2+ mobilization). In H9c2 cells, blocking Na+/H+ exchange with amiloride (2 mM) provoked cell acidification with rate = 0.82 +/- 0.17 pH units/h (n = 6). Xipamide 1 microM maximally inhibited 50 +/- 7% (n = 9) of cell acidification. The action of xipamide required the presence of HCO3- and was antagonized by the HCO3(-)-transport blocker DIDS (4,4'-diisothiocyanostilbene-2.2'-disulfonic acid). Conversely, the carbonic anhydrase (EC 4.2.1.1) inhibitor acetazolamide failed to prevent xipamide action. Finally, xipamide was without significant effect on the Ca2+ signals induced by endothelin-1, vasopressin or the Ca2+ ionophore ionomycin. In newborn rat cardiomyocytes, xipamide reduced amiloride-induced cell acidification at similar concentrations as in H9c2 cardiocytes, but with a slightly higher extent of maximal inhibition (70-80%). In conclusion, xipamide reduced amiloride-dependent cell acidification in the rat heart myogenic H9c2 cell line and in newborn rat cultured cardiomyocytes. This action of xipamide seems to be related to a complex interaction with DIDS-sensitive HCO3- movements. Prevention of cell acidification by xipamide could be involved in the beneficial effects of this compound in myocardial relaxation and left ventricle filling in hypertensive patients with left ventricular hypertrophy.
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Affiliation(s)
- K Taouil
- INSERM U400, Faculté de Médecine de Créteil, France
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35
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Klamut HJ, Bosnoyan-Collins LO, Worton RG, Ray PN. A muscle-specific enhancer within intron 1 of the human dystrophin gene is functionally dependent on single MEF-1/E box and MEF-2/AT-rich sequence motifs. Nucleic Acids Res 1997; 25:1618-25. [PMID: 9092671 PMCID: PMC146611 DOI: 10.1093/nar/25.8.1618] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
In previous studies we have described a 5.0 kb Hin dIII fragment downstream of muscle exon 1 that exhibits properties consistent with a muscle-specific transcriptional enhancer. The goal of this study has been to identify the sequence elements responsible for muscle-specific enhancer activity. Functional studies indicated that this enhancer is active in pre- and post-differentiated H9C2(2-1) myoblasts but functions poorly in L6 and C2C12 myotubes. The core enhancer region was delimited to a 195 bp Spe I- Acc I fragment and sequence analysis identified three MEF-1/E box and two MEF-2/AT-rich motifs as potential muscle-specific regulatory domains. EMSA competition and DNase footprinting indicated that sequences within a 30 bp region containing single adjoining MEF-1/E box and MEF-2/AT-rich motifs are target binding sites for trans -acting factors expressed in H9C2(2-1) myotubes but not in L6 or C2C12 myotubes. Site-specific mutations within these motifs resulted in a significant reduction in enhancer activity in H9C2(2-1) myotubes. These results suggest that the mechanisms governing DMD gene expression in muscle are similar to those identified in other muscle-specific genes. However, the myogenic profile of enhancer activity and trans -acting factor binding suggests a more specialized role for this enhancer that is consistent with its potential involvement in dystrophin gene regulation in cardiac muscle.
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Affiliation(s)
- H J Klamut
- Division of Experimental Therapeutics, Ontario Cancer Institute and Department of Medical Biophysics, University of Toronto, Princess Margaret Hospital, 610 University Avenue, Toronto, Ontario M5G 2M9, Canada.
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