101
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Quarles EK, Dai DF, Tocchi A, Basisty N, Gitari L, Rabinovitch PS. Quality control systems in cardiac aging. Ageing Res Rev 2015; 23:101-15. [PMID: 25702865 PMCID: PMC4686341 DOI: 10.1016/j.arr.2015.02.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2014] [Revised: 02/02/2015] [Accepted: 02/12/2015] [Indexed: 12/31/2022]
Abstract
Cardiac aging is an intrinsic process that results in impaired cardiac function, along with cellular and molecular changes. These degenerative changes are intimately associated with quality control mechanisms. This review provides a general overview of the clinical and cellular changes which manifest in cardiac aging, and the quality control mechanisms involved in maintaining homeostasis and retarding aging. These mechanisms include autophagy, ubiquitin-mediated turnover, apoptosis, mitochondrial quality control and cardiac matrix homeostasis. Finally, we discuss aging interventions that have been observed to impact cardiac health outcomes. These include caloric restriction, rapamycin, resveratrol, GDF11, mitochondrial antioxidants and cardiolipin-targeted therapeutics. A greater understanding of the quality control mechanisms that promote cardiac homeostasis will help to understand the benefits of these interventions, and hopefully lead to further improved therapeutic modalities.
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Affiliation(s)
- Ellen K Quarles
- University of Washington School of Medicine, Department of Pathology, Box 357470, Seattle, WA 98195-7470, United States.
| | - Dao-Fu Dai
- University of Washington School of Medicine, Department of Pathology, Box 357470, Seattle, WA 98195-7470, United States.
| | - Autumn Tocchi
- University of Washington School of Medicine, Department of Pathology, Box 357470, Seattle, WA 98195-7470, United States.
| | - Nathan Basisty
- University of Washington School of Medicine, Department of Pathology, Box 357470, Seattle, WA 98195-7470, United States.
| | - Lemuel Gitari
- University of Washington School of Medicine, Department of Pathology, Box 357470, Seattle, WA 98195-7470, United States.
| | - Peter S Rabinovitch
- University of Washington School of Medicine, Department of Pathology, Box 357470, Seattle, WA 98195-7470, United States.
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102
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Conte S, Katayama S, Vesterlund L, Karimi M, Dimitriou M, Jansson M, Mortera-Blanco T, Unneberg P, Papaemmanuil E, Sander B, Skoog T, Campbell P, Walfridsson J, Kere J, Hellström-Lindberg E. Aberrant splicing of genes involved in haemoglobin synthesis and impaired terminal erythroid maturation in SF3B1 mutated refractory anaemia with ring sideroblasts. Br J Haematol 2015; 171:478-90. [PMID: 26255870 PMCID: PMC4832260 DOI: 10.1111/bjh.13610] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Accepted: 06/25/2015] [Indexed: 02/06/2023]
Abstract
Refractory anaemia with ring sideroblasts (RARS) is distinguished by hyperplastic inefficient erythropoiesis, aberrant mitochondrial ferritin accumulation and anaemia. Heterozygous mutations in the spliceosome gene SF3B1 are found in a majority of RARS cases. To explore the link between SF3B1 mutations and anaemia, we studied mutated RARS CD34+ marrow cells with regard to transcriptome sequencing, splice patterns and mutational allele burden during erythroid differentiation. Transcriptome profiling during early erythroid differentiation revealed a marked up‐regulation of genes involved in haemoglobin synthesis and in the oxidative phosphorylation process, and down‐regulation of mitochondrial ABC transporters compared to normal bone marrow. Moreover, mis‐splicing of genes involved in transcription regulation, particularly haemoglobin synthesis, was confirmed, indicating a compromised haemoglobinization during RARS erythropoiesis. In order to define the phase during which erythroid maturation of SF3B1 mutated cells is most affected, we assessed allele burden during erythroid differentiation in vitro and in vivo and found that SF3B1 mutated erythroblasts showed stable expansion until late erythroblast stage but that terminal maturation to reticulocytes was significantly reduced. In conclusion, SF3B1 mutated RARS progenitors display impaired splicing with potential downstream consequences for genes of key importance for haemoglobin synthesis and terminal erythroid differentiation.
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Affiliation(s)
- Simona Conte
- Karolinska Institutet, Department of Medicine (Huddinge), Centre for Hematology and Regenerative Medicine, Stockholm, Sweden
| | - Shintaro Katayama
- Karolinska Institutet, Department of Biosciences and Nutrition and Center for Innovative Medicine, Stockholm, Sweden
| | - Liselotte Vesterlund
- Karolinska Institutet, Department of Biosciences and Nutrition and Center for Innovative Medicine, Stockholm, Sweden
| | - Mohsen Karimi
- Karolinska Institutet, Department of Medicine (Huddinge), Centre for Hematology and Regenerative Medicine, Stockholm, Sweden
| | - Marios Dimitriou
- Karolinska Institutet, Department of Medicine (Huddinge), Centre for Hematology and Regenerative Medicine, Stockholm, Sweden
| | - Monika Jansson
- Karolinska Institutet, Department of Medicine (Huddinge), Centre for Hematology and Regenerative Medicine, Stockholm, Sweden
| | - Teresa Mortera-Blanco
- Karolinska Institutet, Department of Medicine (Huddinge), Centre for Hematology and Regenerative Medicine, Stockholm, Sweden
| | - Per Unneberg
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm, Sweden
| | - Elli Papaemmanuil
- Cancer Genetics & Genomics, The Wellcome Trust Sanger Institute, Hinxton, Cambridge, UK
| | - Birgitta Sander
- Karolinska Institutet, Department of Laboratory Medicine, Division of Pathology, Stockholm, Sweden
| | - Tiina Skoog
- Karolinska Institutet, Department of Biosciences and Nutrition and Center for Innovative Medicine, Stockholm, Sweden
| | - Peter Campbell
- Cancer Genetics & Genomics, The Wellcome Trust Sanger Institute, Hinxton, Cambridge, UK
| | - Julian Walfridsson
- Karolinska Institutet, Department of Medicine (Huddinge), Centre for Hematology and Regenerative Medicine, Stockholm, Sweden
| | - Juha Kere
- Karolinska Institutet, Department of Biosciences and Nutrition and Center for Innovative Medicine, Stockholm, Sweden
| | - Eva Hellström-Lindberg
- Karolinska Institutet, Department of Medicine (Huddinge), Centre for Hematology and Regenerative Medicine, Stockholm, Sweden
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103
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Forini F, Nicolini G, Iervasi G. Mitochondria as key targets of cardioprotection in cardiac ischemic disease: role of thyroid hormone triiodothyronine. Int J Mol Sci 2015; 16:6312-36. [PMID: 25809607 PMCID: PMC4394534 DOI: 10.3390/ijms16036312] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 03/10/2015] [Accepted: 03/12/2015] [Indexed: 12/30/2022] Open
Abstract
Ischemic heart disease is the major cause of mortality and morbidity worldwide. Early reperfusion after acute myocardial ischemia has reduced short-term mortality, but it is also responsible for additional myocardial damage, which in the long run favors adverse cardiac remodeling and heart failure evolution. A growing body of experimental and clinical evidence show that the mitochondrion is an essential end effector of ischemia/reperfusion injury and a major trigger of cell death in the acute ischemic phase (up to 48–72 h after the insult), the subacute phase (from 72 h to 7–10 days) and chronic stage (from 10–14 days to one month after the insult). As such, in recent years scientific efforts have focused on mitochondria as a target for cardioprotective strategies in ischemic heart disease and cardiomyopathy. The present review discusses recent advances in this field, with special emphasis on the emerging role of the biologically active thyroid hormone triiodothyronine (T3).
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Affiliation(s)
- Francesca Forini
- CNR Institute of Clinical Physiology, Via G. Moruzzi 1, Pisa 56124, Italy.
| | - Giuseppina Nicolini
- CNR Institute of Clinical Physiology, Via G. Moruzzi 1, Pisa 56124, Italy.
- Tuscany Region G. Monasterio Foundation, Via G. Moruzzi 1, Pisa 56124, Italy.
| | - Giorgio Iervasi
- CNR Institute of Clinical Physiology, Via G. Moruzzi 1, Pisa 56124, Italy.
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104
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Mitofusin 2-deficiency suppresses cell proliferation through disturbance of autophagy. PLoS One 2015; 10:e0121328. [PMID: 25781899 PMCID: PMC4363693 DOI: 10.1371/journal.pone.0121328] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 01/30/2015] [Indexed: 12/20/2022] Open
Abstract
Mitofusin2 (Mfn2), a mitochondrial outer membrane protein serving primarily as a mitochondrial fusion protein, has multiple functions in regulating cell biological processes. Defects of Mfn2 were found in diabetes, obesity, and neurodegenerative diseases. In the present study, we found that knockdown of Mfn2 by shRNA led to impaired autophagic degradation, inhibited mitochondrial oxygen consumption rate and cell glycolysis, reduced ATP production, and suppressed cell proliferation. Inhibition of autophagic degradation mimicked Mfn2-deficiency mediated cell proliferation suppression, while enhancement of autophagosome maturation restored the suppressed cell proliferation by Mfn2-deficiency. Thus, our findings revealed the role of Mfn2 in regulating cell proliferation and mitochondrial metabolism, and shed new light on understanding the mechanisms of Mfn2 deficiency related diseases.
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105
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Westermeier F, Navarro-Marquez M, López-Crisosto C, Bravo-Sagua R, Quiroga C, Bustamante M, Verdejo HE, Zalaquett R, Ibacache M, Parra V, Castro PF, Rothermel BA, Hill JA, Lavandero S. Defective insulin signaling and mitochondrial dynamics in diabetic cardiomyopathy. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:1113-8. [PMID: 25686534 DOI: 10.1016/j.bbamcr.2015.02.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2014] [Revised: 01/21/2015] [Accepted: 02/08/2015] [Indexed: 12/20/2022]
Abstract
Diabetic cardiomyopathy (DCM) is a common consequence of longstanding type 2 diabetes mellitus (T2DM) and encompasses structural, morphological, functional, and metabolic abnormalities in the heart. Myocardial energy metabolism depends on mitochondria, which must generate sufficient ATP to meet the high energy demands of the myocardium. Dysfunctional mitochondria are involved in the pathophysiology of diabetic heart disease. A large body of evidence implicates myocardial insulin resistance in the pathogenesis of DCM. Recent studies show that insulin signaling influences myocardial energy metabolism by impacting cardiomyocyte mitochondrial dynamics and function under physiological conditions. However, comprehensive understanding of molecular mechanisms linking insulin signaling and changes in the architecture of the mitochondrial network in diabetic cardiomyopathy is lacking. This review summarizes our current understanding of how defective insulin signaling impacts cardiac function in diabetic cardiomyopathy and discusses the potential role of mitochondrial dynamics.
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Affiliation(s)
- Francisco Westermeier
- Advanced Center for Chronic Diseases (ACCDiS), Faculty of Chemical & Pharmaceutical Sciences & Faculty of Medicine, University of Chile, Santiago, Chile
| | - Mario Navarro-Marquez
- Advanced Center for Chronic Diseases (ACCDiS), Faculty of Chemical & Pharmaceutical Sciences & Faculty of Medicine, University of Chile, Santiago, Chile
| | - Camila López-Crisosto
- Advanced Center for Chronic Diseases (ACCDiS), Faculty of Chemical & Pharmaceutical Sciences & Faculty of Medicine, University of Chile, Santiago, Chile
| | - Roberto Bravo-Sagua
- Advanced Center for Chronic Diseases (ACCDiS), Faculty of Chemical & Pharmaceutical Sciences & Faculty of Medicine, University of Chile, Santiago, Chile
| | - Clara Quiroga
- Advanced Center for Chronic Diseases (ACCDiS), Faculty of Chemical & Pharmaceutical Sciences & Faculty of Medicine, University of Chile, Santiago, Chile
| | - Mario Bustamante
- Advanced Center for Chronic Diseases (ACCDiS), Faculty of Chemical & Pharmaceutical Sciences & Faculty of Medicine, University of Chile, Santiago, Chile
| | - Hugo E Verdejo
- Advanced Center for Chronic Diseases (ACCDiS), Faculty of Medicine, Pontifical Catholic University of Chile, Santiago, Chile
| | - Ricardo Zalaquett
- Advanced Center for Chronic Diseases (ACCDiS), Faculty of Medicine, Pontifical Catholic University of Chile, Santiago, Chile
| | - Mauricio Ibacache
- Anesthesiology Division, Faculty of Medicine, Pontifical Catholic University of Chile, Santiago, Chile
| | - Valentina Parra
- Advanced Center for Chronic Diseases (ACCDiS), Faculty of Chemical & Pharmaceutical Sciences & Faculty of Medicine, University of Chile, Santiago, Chile; Internal Medicine Division of Cardiology, Dallas, TX, USA; Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Pablo F Castro
- Advanced Center for Chronic Diseases (ACCDiS), Faculty of Medicine, Pontifical Catholic University of Chile, Santiago, Chile
| | - Beverly A Rothermel
- Internal Medicine Division of Cardiology, Dallas, TX, USA; Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Joseph A Hill
- Internal Medicine Division of Cardiology, Dallas, TX, USA; Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Sergio Lavandero
- Advanced Center for Chronic Diseases (ACCDiS), Faculty of Chemical & Pharmaceutical Sciences & Faculty of Medicine, University of Chile, Santiago, Chile; Internal Medicine Division of Cardiology, Dallas, TX, USA; Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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106
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Abstract
Mitochondrial fitness is central to heart health. In many cell types, mitochondria are dynamic, interconnected filamentous networks. By comparison, mitochondria of healthy postmitotic adult cardiomyocytes are shortened, round, hypodynamic organelles. Mitochondrial networks are absent in cardiomyocytes; fission, fusion, and organelle mobility are not normally observed. Nevertheless, mitochondrial fission factor Drp1 and fusion factors Mfn1, Mfn2, and Opa1 are abundant and indispensable in adult hearts. Here, we review recent insights into roles for mitochondrial dynamics factors not strictly related to morphometric remodeling, advancing the argument that fission and fusion of cardiomyocyte mitochondria support surveillance, sequestration, and mitophagic removal of damaged organelles.
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Affiliation(s)
- Moshi Song
- Center for Pharmacogenomics, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63108, USA
| | - Gerald W Dorn
- Center for Pharmacogenomics, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63108, USA.
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107
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Baker MJ, Palmer CS, Stojanovski D. Mitochondrial protein quality control in health and disease. Br J Pharmacol 2014; 171:1870-89. [PMID: 24117041 DOI: 10.1111/bph.12430] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Revised: 08/28/2013] [Accepted: 09/01/2013] [Indexed: 12/13/2022] Open
Abstract
Progressive mitochondrial dysfunction is linked with the onset of many age-related pathologies and neurological disorders. Mitochondrial damage can come in many forms and be induced by a variety of cellular insults. To preserve organelle function during biogenesis or times of stress, multiple surveillance systems work to ensure the persistence of a functional mitochondrial network. This review provides an overview of these processes, which collectively contribute to the maintenance of a healthy mitochondrial population, which is critical for cell physiology and survival.
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Affiliation(s)
- Michael J Baker
- Department of Biochemistry and Molecular Biology and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, VIC, Australia; ARC Centre of Excellence for Coherent X-ray Science, Melbourne, VIC, Australia
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108
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Astragalus polysaccharide suppresses doxorubicin-induced cardiotoxicity by regulating the PI3k/Akt and p38MAPK pathways. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2014; 2014:674219. [PMID: 25386226 PMCID: PMC4216718 DOI: 10.1155/2014/674219] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 09/11/2014] [Indexed: 01/02/2023]
Abstract
Background. Doxorubicin, a potent chemotherapeutic agent, is associated with acute and chronic cardiotoxicity, which is cumulatively dose-dependent. Astragalus polysaccharide (APS), the extract of Astragalus membranaceus with strong antitumor and antiglomerulonephritis activity, can effectively alleviate inflammation. However, whether APS could ameliorate chemotherapy-induced cardiotoxicity is not understood. Here, we investigated the protective effects of APS on doxorubicin-induced cardiotoxicity and elucidated the underlying mechanisms of the protective effects of APS. Methods. We analyzed myocardial injury in cancer patients who underwent doxorubicin chemotherapy and generated a doxorubicin-induced neonatal rat cardiomyocyte injury model and a mouse heart failure model. Echocardiography, reactive oxygen species (ROS) production, TUNEL, DNA laddering, and Western blotting were performed to observe cell survival, oxidative stress, and inflammatory signal pathways in cardiomyocytes. Results. Treatment of patients with the chemotherapeutic drug doxorubicin led to heart dysfunction. Doxorubicin reduced cardiomyocyte viability and induced C57BL/6J mouse heart failure with concurrent elevated ROS generation and apoptosis, which, however, was attenuated by APS treatment. In addition, there was profound inhibition of p38MAPK and activation of Akt after APS treatment. Conclusions. These results demonstrate that APS could suppress oxidative stress and apoptosis, ameliorating doxorubicin-mediated cardiotoxicity by regulating the PI3k/Akt and p38MAPK pathways.
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109
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New insights into the role of mitochondrial dynamics and autophagy during oxidative stress and aging in the heart. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2014; 2014:210934. [PMID: 25132912 PMCID: PMC4124219 DOI: 10.1155/2014/210934] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Revised: 06/05/2014] [Accepted: 06/18/2014] [Indexed: 12/26/2022]
Abstract
The heart is highly sensitive to the aging process. In the elderly, the heart tends to become hypertrophic and fibrotic. Stiffness increases with ensuing systolic and diastolic dysfunction. Aging also affects the cardiac response to stress. At the molecular level, the aging process is associated with accumulation of damaged proteins and organelles, partially due to defects in protein quality control systems. The accumulation of dysfunctional and abnormal mitochondria is an important pathophysiological feature of the aging process, which is associated with excessive production of reactive oxygen species. Mitochondrial fusion and fission and mitochondrial autophagy are crucial mechanisms for maintaining mitochondrial function and preserving energy production. In particular, mitochondrial fission allows for selective segregation of damaged mitochondria, which are afterward eliminated by autophagy. Unfortunately, recent evidence indicates that mitochondrial dynamics and autophagy are progressively impaired over time, contributing to the aging process. This suggests that restoration of these mechanisms could delay organ senescence and prevent age-associated cardiac diseases. Here, we discuss the current understanding of the close relationship between mitochondrial dynamics, mitophagy, oxidative stress, and aging, with a particular focus on the heart.
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110
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Wu Z, Zhu Y, Cao X, Sun S, Zhao B. Mitochondrial toxic effects of Aβ through mitofusins in the early pathogenesis of Alzheimer's disease. Mol Neurobiol 2014; 50:986-96. [PMID: 24710686 DOI: 10.1007/s12035-014-8675-z] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2013] [Accepted: 03/11/2014] [Indexed: 12/16/2022]
Abstract
Mitochondrial dysfunction has been implicated in the pathogenesis of Alzheimer's disease (AD). However, it is obscure how amyloid-beta (Aβ) can impair mitochondria in the early stage of AD pathology. Using PrP-hAPP/hPS1 double-transgenic AD mouse model, we find that abnormal mitochondrial morphology and damaged mitochondrial structure in hippocampal neurons appear in the early stage of AD-like disease development. We also find consistent mitochondrial abnormalities in the SH-SY5Y cells, which express amyloid precursor protein (APP) Swedish mutation (APPsw) and have been used as a cell model of the early-onset AD. Significant changes of mitofusin GTPases (Mfn1 and Mfn2) were detected both in the PrP-hAPP/hPS1 brains and SH-SY5Y cells. Moreover, our results show that Aβ accumulation in neurons of PrP-hAPP/hPS1 mice can affect the neurogenesis prior to plaque formation. These findings suggest that mitochondrial impairment is a very early event in AD pathogenesis and abnormal expression of Mfn1 and Mfn2 caused by excessive intracellular Aβ is the possible molecular mechanism. Interestingly, L-theanine has significant effects on regulating mitochondrial fusion proteins in SH-SY5Y (APPsw) cells. Overall, our results not only suggest a new early mechanism of AD pathogenesis but also propose a preventive candidate, L-theanine, for the treatment of AD.
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Affiliation(s)
- Zhaofei Wu
- State Key Laboratory of Brain and Cognitive Sciences, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing, 100101, China
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111
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Marín-García J, Akhmedov AT, Moe GW. Mitochondria in heart failure: the emerging role of mitochondrial dynamics. Heart Fail Rev 2014; 18:439-56. [PMID: 22707247 DOI: 10.1007/s10741-012-9330-2] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Over the past decade, mitochondria have emerged as critical integrators of energy production, generation of reactive oxygen species (ROS), multiple cell death, and signaling pathways in the constantly beating heart. Clarification of the molecular mechanisms, underlying mitochondrial ROS generation and ROS-induced cell death pathways, associated with cardiovascular diseases, by itself remains an important aim; more recently, mitochondrial dynamics has emerged as an important active mechanism to maintain normal mitochondria number and morphology, both are necessary to preserve cardiomyocytes integrity. The two opposing processes, division (fission) and fusion, determine the cell type-specific mitochondrial morphology, the intracellular distribution and activity. The tightly controlled balance between fusion and fission is of particular importance in the high energy demanding cells, such as cardiomyocytes, skeletal muscles, and neuronal cells. A shift toward fission will lead to mitochondrial fragmentation, observed in quiescent cells, while a shift toward fusion will result in the formation of large mitochondrial networks, found in metabolically active cardiomyocytes. Defects in mitochondrial dynamics have been associated with various human disorders, including heart failure, ischemia reperfusion injury, diabetes, and aging. Despite significant progress in our understanding of the molecular mechanisms of mitochondrial function in the heart, further focused research is needed to translate this knowledge into the development of new therapies for various ailments.
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Affiliation(s)
- José Marín-García
- The Molecular Cardiology and Neuromuscular Institute, 75 Raritan Ave., Highland Park, NJ 08904, USA.
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112
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Mitofusin 1 is negatively regulated by microRNA 140 in cardiomyocyte apoptosis. Mol Cell Biol 2014; 34:1788-99. [PMID: 24615014 DOI: 10.1128/mcb.00774-13] [Citation(s) in RCA: 102] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
MicroRNAs (miRNAs) are a class of small noncoding RNAs that mediate posttranscriptional gene silencing. Mitochondrial fission participates in the induction of apoptosis. It remains largely unknown whether miRNAs can regulate mitochondrial fission. Reactive oxygen species and doxorubicin could induce mitochondrial fission and apoptosis in cardiomyocytes. Concomitantly, mitofusin 1 (Mfn1) was downregulated, whereas miRNA 140 (miR-140) was upregulated upon apoptotic stimulation. We investigated whether Mfn1 and miR-140 play a functional role in mitochondrial fission and apoptosis. Ectopic expression of Mfn1 attenuated mitochondrial fission and apoptosis. Knockdown of miR-140 inhibited mitochondrial fission. Our results further revealed that knockdown of miR-140 was able to reduce myocardial infarct sizes in an animal model. We observed that miR-140 could suppress the expression of Mfn1, and it exerted its effect on mitochondrial fission and apoptosis through targeting Mfn1. Our data revealed that mitochondrial fission occurs in cardiomyocytes and can be counteracted by Mfn1. However, the function of Mfn1 is negatively regulated by miR-140. Our present work suggests that Mfn1 and miR-140 are integrated into the program of cardiomyocyte apoptosis.
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113
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Bereiter-Hahn J. Mitochondrial dynamics in aging and disease. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 127:93-131. [PMID: 25149215 DOI: 10.1016/b978-0-12-394625-6.00004-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Mitochondria are self-replicating organelles but nevertheless strongly depend on supply coded in nuclear genes. They serve many physiological demands in living cells. Supply of the cytoplasm with ATP and engagement in Ca(2+) regulation belong to the main functions of mitochondria. In large eukaryotic cells, in particular in neurons, with their long dendrites and axons, mitochondria have to move to the sites of their action. This trafficking involves several motor molecules and mechanisms to sense the sites of requirements of mitochondria. With aging and as a consequence of some diseases, mitochondrial components may be rendered dysfunctional, and mtDNA mutations arise during the course of replication and by the action of reactive oxygen species. Mutants in motor molecules engaged in trafficking and in the machinery of fusion and fission are causing severe deficiencies on the cellular level; they support neurodegeneration and, thus, cause many diseases. Frequent fusion and fission events mediate the elimination of impaired parts from mitochondria which finally will be degraded by autophagosomes. Extensive fusion provides a basis for functional complementation. Mobility of proteins and small molecules within the mitochondria is necessary to reach the functional goals of fusion and fission, although cristae and a large fraction of proteins of the respiratory complexes proved to be stable for hours after fusion and perform slow exchange of material.
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Affiliation(s)
- Jürgen Bereiter-Hahn
- Institute for Cell Biology and Neurosciences, Goethe University Frankfurt am Main, Frankfurt am Main, Germany
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114
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Hwang SJ, Kim W. Mitochondrial dynamics in the heart as a novel therapeutic target for cardioprotection. Chonnam Med J 2013; 49:101-7. [PMID: 24400211 PMCID: PMC3881204 DOI: 10.4068/cmj.2013.49.3.101] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Revised: 11/23/2013] [Accepted: 11/25/2013] [Indexed: 01/05/2023] Open
Abstract
Traditionally, mitochondria have been regarded solely as energy generators for cells; however, accumulating data have demonstrated that these complex organelles play a variety of roles within the cardiomyocyte that extend beyond this classic function. Mitochondrial dynamics involves mitochondrial movements and morphologic alterations by tethering, fusion, and fission, which depend on cellular energy requirements and metabolic status. Many studies have indicated that mitochondrial dynamics may be a fundamental component of the maintenance of normal cellular homeostasis and cardiac function. Mitochondrial dynamics is controlled by the protein machinery responsible for mitochondrial fusion and fission, but cardiomyocytes are densely packed as part of an intricate cytoarchitecture for efficient and imbalanced contraction; thus, mitochondrial dynamics in the adult heart are restricted and occur more slowly than in other organs. Cardiac mitochondrial dynamics is important for cardiac physiology in diseased conditions such as ischemia-reperfusion (IR) injury. Changes in mitochondrial morphology through modulation of the expression of proteins regulating mitochondrial dynamics demonstrates the beneficial effects on cardiac performance after IR injury. Thus, accurately defining the roles of mitochondrial dynamics in the adult heart can guide the identification and development of novel therapeutic targets for cardioprotection. Further studies should be performed to establish the exact mechanisms of mitochondrial dynamics.
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Affiliation(s)
- Seung Joon Hwang
- Division of Cardiology, Department of Internal Medicine, Kyung Hee University Hospital, Kyung Hee University School of Medicine, Seoul, Korea
| | - Weon Kim
- Division of Cardiology, Department of Internal Medicine, Kyung Hee University Hospital, Kyung Hee University School of Medicine, Seoul, Korea
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115
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Huntington's disease induced cardiac amyloidosis is reversed by modulating protein folding and oxidative stress pathways in the Drosophila heart. PLoS Genet 2013; 9:e1004024. [PMID: 24367279 PMCID: PMC3868535 DOI: 10.1371/journal.pgen.1004024] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Accepted: 10/29/2013] [Indexed: 11/19/2022] Open
Abstract
Amyloid-like inclusions have been associated with Huntington's disease (HD), which is caused by expanded polyglutamine repeats in the Huntingtin protein. HD patients exhibit a high incidence of cardiovascular events, presumably as a result of accumulation of toxic amyloid-like inclusions. We have generated a Drosophila model of cardiac amyloidosis that exhibits accumulation of PolyQ aggregates and oxidative stress in myocardial cells, upon heart-specific expression of Huntingtin protein fragments (Htt-PolyQ) with disease-causing poly-glutamine repeats (PolyQ-46, PolyQ-72, and PolyQ-102). Cardiac expression of GFP-tagged Htt-PolyQs resulted in PolyQ length-dependent functional defects that included increased incidence of arrhythmias and extreme cardiac dilation, accompanied by a significant decrease in contractility. Structural and ultrastructural analysis of the myocardial cells revealed reduced myofibrillar content, myofibrillar disorganization, mitochondrial defects and the presence of PolyQ-GFP positive aggregates. Cardiac-specific expression of disease causing Poly-Q also shortens lifespan of flies dramatically. To further confirm the involvement of oxidative stress or protein unfolding and to understand the mechanism of PolyQ induced cardiomyopathy, we co-expressed expanded PolyQ-72 with the antioxidant superoxide dismutase (SOD) or the myosin chaperone UNC-45. Co-expression of SOD suppressed PolyQ-72 induced mitochondrial defects and partially suppressed aggregation as well as myofibrillar disorganization. However, co-expression of UNC-45 dramatically suppressed PolyQ-72 induced aggregation and partially suppressed myofibrillar disorganization. Moreover, co-expression of both UNC-45 and SOD more efficiently suppressed GFP-positive aggregates, myofibrillar disorganization and physiological cardiac defects induced by PolyQ-72 than did either treatment alone. Our results demonstrate that mutant-PolyQ induces aggregates, disrupts the sarcomeric organization of contractile proteins, leads to mitochondrial dysfunction and increases oxidative stress in cardiomyocytes leading to abnormal cardiac function. We conclude that modulation of both protein unfolding and oxidative stress pathways in the Drosophila heart model can ameliorate the detrimental PolyQ effects, thus providing unique insights into the genetic mechanisms underlying amyloid-induced cardiac failure in HD patients. Huntington's disease (HD) is associated with amyloid-like inclusions in the brain and heart, and accumulation of amyloid protein is associated with neurodegeneration and cardiomyopathy. Recent studies suggest that HD patients show increased susceptibility to cardiac failure. However, the mechanisms by which disease-causing poly-glutamine repeats (PolyQ) cause heart dysfunction in these patients are unclear. We have developed a novel Drosophila heart model that exhibits significant GFP-positive aggregates upon HD-causing PolyQ expression in myocardial cells resulting in PolyQ length-dependent physiological defects. Modulation of protein folding and oxidative stress pathways in this system reduced the number of aggregates and reversed the cardiac dysfunction in response to expression of disease-causing PolyQ. The ability to explore PolyQ-associated mechanisms of cardiomyopathy in a genetically tractable whole organism, Drosophila melanogaster, promises to provide novel insights into the relationship between amyloid accumulation and heart dysfunction. Our findings not only impact the understanding of PolyQ-induced cardiomyopathy but also other human cardiac diseases associated with oxidative stress, mitochondrial defects and protein homeostasis.
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Relationship between the expressions of mitofusin-2 and procollagen in uterosacral ligament fibroblasts of postmenopausal patients with pelvic organ prolapse. Eur J Obstet Gynecol Reprod Biol 2013; 174:141-5. [PMID: 24361166 DOI: 10.1016/j.ejogrb.2013.11.024] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Revised: 11/07/2013] [Accepted: 11/28/2013] [Indexed: 11/21/2022]
Abstract
OBJECTIVES To compare the mRNA and protein expressions of mitochondrial fusion protein-2 (mitofusin-2, Mfn2), and procollagen 1A1/1A2/3A1 in uterosacral ligament fibroblasts of postmenopausal patients with or without pelvic organ prolapse (POP). The effect of Mfn2 on the expression of procollagen in fibroblasts was also investigated. STUDY DESIGN Thirty-seven POP patients and 23 non-POP postmenopausal patients were included in the POP (study) and non-POP (control) groups, respectively. Laser capture microdissection (LCM) was combined with quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting to detect the mRNA and protein expressions of Mfn2, and types I and III procollagen in uterosacral ligament fibroblasts of the two groups, and the differences in expression levels were compared between the groups. The correlation between Mfn2 and procollagens was also investigated. RESULTS Fibroblasts were successfully isolated from frozen sections of the uterosacral ligament using LCM. The results of qRT-PCR and western blot showed that the expressions of types I and III procollagen were significantly lower and those of Mfn2 were significantly higher in the POP group than in the non-POP group (p<0.05, all). In POP, opposite trends of protein expression changes of Mfn2 and procollagens were observed along with the duration of postmenopause (P<0.05), while this was not the case in POP accompanied by stress urinary incontinence and frequency of vaginal delivery (P>0.05). The expressions of type I and III procollagen were negatively associated with Mfn2 in POP patients (-1<r<0, P<0.001, all). CONCLUSIONS Mfn2 expression changed along with the duration of postmenopause and had a negative association with the expression of procollagens. Our results suggest that the Mfn2 protein may affect the synthesis of procollagen of fibroblasts in postmenopausal patients with POP. Changes in Mfn2 and procollagen expression may play a role in the development of POP.
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Chen KH, Dasgupta A, Ding J, Indig FE, Ghosh P, Longo DL. Role of mitofusin 2 (Mfn2) in controlling cellular proliferation. FASEB J 2013; 28:382-94. [PMID: 24081906 DOI: 10.1096/fj.13-230037] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
It has been reported that Mitofusin2 (Mfn2) inhibits cell proliferation when overexpressed. We wanted to study the role of endogenous Mfn2 in cell proliferation, along with the structural features of Mfn2 that influence its mitochondrial localization and control of cell proliferation. Mfn2-knockdown clones of a B-cell lymphoma cell line BJAB exhibited an increased rate of cell proliferation. A 2-fold increase in cell proliferation was also observed in Mfn2-knockout mouse embryonic fibroblast (MEF) cells as compared with the control wild-type cells, and the proliferative advantage of the knockout MEF cells was blocked on reintroduction of the Mfn2 gene. Mfn2 exerts its antiproliferative effect by acting as an effector molecule of Ras, resulting in the inhibition of the Ras-Raf-ERK signaling pathway. Furthermore, both the N-terminal (aa 1-264) and the C-terminal (aa 265-757) fragments of Mfn2 blocked cell proliferation through distinct mechanisms: the N-terminal-mediated inhibition was due to its interaction with Raf-1, whereas the C-terminal fragment of Mfn2 inhibited cell proliferation by interacting with Ras. The inhibition of proliferation by the N-terminal fragment was independent of its mitochondrial localization. Collectively, our data provide new insights regarding the role of Mfn2 in controlling cellular proliferation.
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Affiliation(s)
- Kuang-Hueih Chen
- 2Lymphocyte Cell Biology Unit, Laboratory of Genetics, National Institute on Aging, National Institutes of Health, Biomedical Research Center, 251 Bayview Blvd., Baltimore, MD 21224, USA. P.G.,
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Lin C, Guo X, Lange S, Liu J, Ouyang K, Yin X, Jiang L, Cai Y, Mu Y, Sheikh F, Ye S, Chen J, Ke Y, Cheng H. Cypher/ZASP is a novel A-kinase anchoring protein. J Biol Chem 2013; 288:29403-13. [PMID: 23996002 DOI: 10.1074/jbc.m113.470708] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PKA signaling is important for the post-translational modification of proteins, especially those in cardiomyocytes involved in cardiac excitation-contraction coupling. PKA activity is spatially and temporally regulated through compartmentalization by protein kinase A anchoring proteins. Cypher/ZASP, a member of PDZ-LIM domain protein family, is a cytoskeletal protein that forms multiprotein complexes at sarcomeric Z-lines. It has been demonstrated that Cypher/ZASP plays a pivotal structural role in the structural integrity of sarcomeres, and several of its mutations are associated with myopathies including dilated cardiomyopathy. Here we show that Cypher/ZASP, interacting specifically with the type II regulatory subunit RIIα of PKA, acted as a typical protein kinase A anchoring protein in cardiomyocytes. In addition, we show that Cypher/ZASP itself was phosphorylated at Ser(265) and Ser(296) by PKA. Furthermore, the PDZ domain of Cypher/ZASP interacted with the L-type calcium channel through its C-terminal PDZ binding motif. Expression of Cypher/ZASP facilitated PKA-mediated phosphorylation of the L-type calcium channel in vitro. Additionally, the phosphorylation of the L-type calcium channel at Ser(1928) induced by isoproterenol was impaired in neonatal Cypher/ZASP-null cardiomyocytes. Moreover, Cypher/ZASP interacted with the Ser/Thr phosphatase calcineurin, which is a phosphatase for the L-type calcium channel. Taken together, our data strongly suggest that Cypher/ZASP not only plays a structural role for the sarcomeric integrity, but is also an important sarcomeric signaling scaffold in regulating the phosphorylation of channels or contractile proteins.
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Affiliation(s)
- Changsong Lin
- From the Department of Pathology and Pathophysiology, Program in Molecular Cell Biology, Zhejiang University School of Medicine, Hangzhou 310058, China
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Mfn2 modulates the UPR and mitochondrial function via repression of PERK. EMBO J 2013; 32:2348-61. [PMID: 23921556 DOI: 10.1038/emboj.2013.168] [Citation(s) in RCA: 320] [Impact Index Per Article: 29.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Accepted: 07/03/2013] [Indexed: 12/11/2022] Open
Abstract
Mitofusin 2 (Mfn2) is a key protein in mitochondrial fusion and it participates in the bridging of mitochondria to the endoplasmic reticulum (ER). Recent data indicate that Mfn2 ablation leads to ER stress. Here we report on the mechanisms by which Mfn2 modulates cellular responses to ER stress. Induction of ER stress in Mfn2-deficient cells caused massive ER expansion and excessive activation of all three Unfolded Protein Response (UPR) branches (PERK, XBP-1, and ATF6). In spite of an enhanced UPR, these cells showed reduced activation of apoptosis and autophagy during ER stress. Silencing of PERK increased the apoptosis of Mfn2-ablated cells in response to ER stress. XBP-1 loss-of-function ameliorated autophagic activity of these cells upon ER stress. Mfn2 physically interacts with PERK, and Mfn2-ablated cells showed sustained activation of this protein kinase under basal conditions. Unexpectedly, PERK silencing in these cells reduced ROS production, normalized mitochondrial calcium, and improved mitochondrial morphology. In summary, our data indicate that Mfn2 is an upstream modulator of PERK. Furthermore, Mfn2 loss-of-function reveals that PERK is a key regulator of mitochondrial morphology and function.
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Abstract
SIGNIFICANCE Mitochondria are dynamic organelles capable of changing their shape and distribution by undergoing either fission or fusion. Changes in mitochondrial dynamics, which is under the control of specific mitochondrial fission and fusion proteins, have been implicated in cell division, embryonic development, apoptosis, autophagy, and metabolism. Although the machinery for modulating mitochondrial dynamics is present in the cardiovascular system, its function there has only recently been investigated. In this article, we review the emerging role of mitochondrial dynamics in cardiovascular health and disease. RECENT ADVANCES Changes in mitochondrial dynamics have been implicated in vascular smooth cell proliferation, cardiac development and differentiation, cardiomyocyte hypertrophy, myocardial ischemia-reperfusion injury, cardioprotection, and heart failure. CRITICAL ISSUES Many of the experimental studies investigating mitochondrial dynamics in the cardiovascular system have been confined to cardiac cell lines, vascular cells, or neonatal cardiomyocytes, in which mitochondria are distributed throughout the cytoplasm and are free to move. However, in the adult heart where mitochondrial movements are restricted by their tightly-packed distribution along myofibrils or beneath the subsarcolemma, the relevance of mitochondrial dynamics is less obvious. The investigation of transgenic mice deficient in cardiac mitochondrial fission or fusion proteins should help elucidate the role of mitochondrial dynamics in the adult heart. FUTURE DIRECTIONS Investigating the role of mitochondrial dynamics in cardiovascular health and disease should result in the identification of novel therapeutic targets for treating patients with cardiovascular disease, the leading cause of death and disability globally.
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Affiliation(s)
- Sang-Bing Ong
- Skaggs School of Pharmacy & Pharmaceutical Sciences, University of California, San Diego, San Diego, CA, USA
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Astragalus polysaccharides suppress ICAM-1 and VCAM-1 expression in TNF-α-treated human vascular endothelial cells by blocking NF-κB activation. Acta Pharmacol Sin 2013; 34:1036-42. [PMID: 23728723 DOI: 10.1038/aps.2013.46] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Accepted: 03/14/2013] [Indexed: 12/28/2022] Open
Abstract
AIM To investigate the effects Astragalus polysaccharides (APS) on tumor necrosis factor (TNF)-α-induced inflammatory reactions in human umbilical vein endothelial cells (HUVECs) and to elucidate the underlying mechanisms. METHODS HUVECs were treated with TNF-α for 24 h. The amounts of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) were determined with Western blotting. HUVEC viability and apoptosis were detected using cell viability assay and Hoechst staining, respectively. Reactive oxygen species (ROS) production was measured by DHE staining. Monocyte and HUVEC adhesion assay was used to detect endothelial cell adhesive function. NF-κB activation was detected with immunofluorescence. RESULTS TNF-α (1-80 ng/mL) caused dose- and time-dependent increases of ICAM-1 and VCAM-1 expression in HUVECs, accompanied by significant augmentation of IκB phosphorylation and NF-κB translocation into the nuclei. Pretreatment with APS (10 and 50 μg/mL) significantly attenuated TNFα-induced upregulation of ICAM-1 VCAM-1 and NF-κB translocation. Moreover, APS significantly reduced apoptosis, ROS generation and adhesion function damage in TNF-α-treated HUVECs. CONCLUSION APS suppresses TNFα-induced adhesion molecule expression by blocking NF-κB signaling and inhibiting ROS generation in HUVECs. The results suggest that APS may be used to treat and prevent endothelial cell injury-related diseases.
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Tbx20 functions as an important regulator of estrogen-mediated cardiomyocyte protection during oxidative stress. Int J Cardiol 2013; 168:3704-14. [PMID: 23871353 DOI: 10.1016/j.ijcard.2013.06.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Revised: 04/26/2013] [Accepted: 06/15/2013] [Indexed: 01/17/2023]
Abstract
BACKGROUND As a transcription factor mainly expressed in cardiovascular system, T-box 20 (Tbx20) plays an important role in embryonic cardiovascular system development and adult heart function. Here, we determined the mechanism by which Tbx20 regulates cardiomyocyte apoptosis and cardiomyopathies. METHODS We analyzed Tbx20 expression levels and apoptosis rates in normal and heart failure human autopsy heart samples. Female C57BL/6 mice were ovariectomized and treated with 17β-estradiol to determine Tbx20 expression levels. ROS production, TUNEL, DNA laddering, qRT-PCR, Western blot, immunohistochemistry and ChIP analyses were performed on male C57BL/6 transverse aortic constriction-induced heart failure samples and on neonatal rat ventricular myocytes that were treated with H2O2 to investigate the role of Tbx20 in estrogen-mediated heart protection. RESULTS Tbx20 expression was down regulated during heart failure, accompanied by elevated cardiomyocyte apoptotic levels in humans and mice. H2O2 led to a concurrent decrease in Tbx20 expression and increase in apoptosis in cultured neonatal rat cardiomyocytes. Tbx20 overexpression reduced H2O2-induced cardiomyocyte apoptosis and was associated with a profound inhibition of p38MAPK, Bax and caspase3 and the activation of Bcl-2. Estrogen was able to protect cardiomyocytes from H2O2-induced apoptosis by upregulating Tbx20 expression in a concentration-dependent manner. Tbx20 silencing increased oxidative stress-induced apoptosis in H9c2 cells. Moreover, Tbx20 directly regulated Esrra expression to enhance the heart-protective effect of estrogen. CONCLUSIONS These results indicate that Tbx20 functions as an important regulator of estrogen-mediated cardiomyocyte protection during oxidative stress, suggesting that estorgen-Tbx20-ERR-α may represent a crucial regulatory cascade and a potential therapeutic target for heart failure.
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Redpath CJ, Bou Khalil M, Drozdzal G, Radisic M, McBride HM. Mitochondrial hyperfusion during oxidative stress is coupled to a dysregulation in calcium handling within a C2C12 cell model. PLoS One 2013; 8:e69165. [PMID: 23861961 PMCID: PMC3704522 DOI: 10.1371/journal.pone.0069165] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Accepted: 06/11/2013] [Indexed: 01/04/2023] Open
Abstract
Atrial Fibrillation is the most common sustained cardiac arrhythmia worldwide harming millions of people every year. Atrial Fibrillation (AF) abruptly induces rapid conduction between atrial myocytes which is associated with oxidative stress and abnormal calcium handling. Unfortunately this new equilibrium promotes perpetuation of the arrhythmia. Recently, in addition to being the major source of oxidative stress within cells, mitochondria have been observed to fuse, forming mitochondrial networks and attach to intracellular calcium stores in response to cellular stress. We sought to identify a potential role for rapid stimulation, oxidative stress and mitochondrial hyperfusion in acute changes to myocyte calcium handling. In addition we hoped to link altered calcium handling to increased sarcoplasmic reticulum (SR)-mitochondrial contacts, the so-called mitochondrial associated membrane (MAM). We selected the C2C12 murine myotube model as it has previously been successfully used to investigate mitochondrial dynamics and has a myofibrillar system similar to atrial myocytes. We observed that rapid stimulation of C2C12 cells resulted in mitochondrial hyperfusion and increased mitochondrial colocalisation with calcium stores. Inhibition of mitochondrial fission by transfection of mutant DRP1K38E resulted in similar effects on mitochondrial fusion, SR colocalisation and altered calcium handling. Interestingly the effects of 'forced fusion' were reversed by co-incubation with the reducing agent N-Acetyl cysteine (NAC). Subsequently we demonstrated that oxidative stress resulted in similar reversible increases in mitochondrial fusion, SR-colocalisation and altered calcium handling. Finally, we believe we have identified that myocyte calcium handling is reliant on baseline levels of reactive oxygen species as co-incubation with NAC both reversed and retarded myocyte response to caffeine induced calcium release and re-uptake. Based on these results we conclude that the coordinate regulation of mitochondrial fusion and MAM contacts may form a point source for stress-induced arrhythmogenesis. We believe that the MAM merits further investigation as a therapeutic target in AF-induced remodelling.
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Affiliation(s)
- Calum J Redpath
- Cellular Electrophysiology Laboratory, University of Ottawa Heart Institute, University of Ottawa, Ottawa, ON, Canada.
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Chen Y, Lv L, Jiang Z, Yang H, Li S, Jiang Y. Mitofusin 2 protects hepatocyte mitochondrial function from damage induced by GCDCA. PLoS One 2013; 8:e65455. [PMID: 23755235 PMCID: PMC3675030 DOI: 10.1371/journal.pone.0065455] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Accepted: 04/24/2013] [Indexed: 01/15/2023] Open
Abstract
Mitochondrial impairment is hypothesized to contribute to the pathogenesis of chronic cholestatic liver diseases. Mitofusin 2 (Mfn2) regulates mitochondrial morphology and signaling and is involved in the development of numerous mitochondrial-related diseases; however, a functional role for Mfn2 in chronic liver cholestasis which is characterized by increased levels of toxic bile acids remain unknown. Therefore, the aims of this study were to evaluate the expression levels of Mfn2 in liver samples from patients with extrahepatic cholestasis and to investigate the role Mfn2 during bile acid induced injury in vitro. Endogenous Mfn2 expression decreased in patients with extrahepatic cholestasis. Glycochenodeoxycholic acid (GCDCA) is the main toxic component of bile acid in patients with extrahepatic cholestasis. In human normal hepatocyte cells (L02), Mfn2 plays an important role in GCDCA-induced mitochondrial damage and changes in mitochondrial morphology. In line with the mitochondrial dysfunction, the expression of Mfn2 decreased significantly under GCDCA treatment conditions. Moreover, the overexpression of Mfn2 effectively attenuated mitochondrial fragmentation and reversed the mitochondrial damage observed in GCDCA-treated L02 cells. Notably, a truncated Mfn2 mutant that lacked the normal C-terminal domain lost the capacity to induce mitochondrial fusion. Increasing the expression of truncated Mfn2 also had a protective effect against the hepatotoxicity of GCDCA. Taken together, these findings indicate that the loss of Mfn2 may play a crucial role the pathogenesis of the liver damage that is observed in patients with extrahepatic cholestasis. The findings also indicate that Mfn2 may directly regulate mitochondrial metabolism independently of its primary fusion function. Therapeutic approaches that target Mfn2 may have protective effects against hepatotoxic of bile acids during cholestasis.
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Affiliation(s)
- Yongbiao Chen
- Department of Hepatobiliary Surgery, Fuzhou General Hospital, Fuzhou, China
- * E-mail: (YC); (YJ)
| | - Lizhi Lv
- Department of Hepatobiliary Surgery, Fuzhou General Hospital, Fuzhou, China
| | - Zhelong Jiang
- Department of Hepatobiliary Surgery, Fuzhou General Hospital, Fuzhou, China
| | - Hejun Yang
- Department of Hepatobiliary Surgery, Fuzhou General Hospital, Fuzhou, China
| | - Song Li
- Department of Hepatobiliary Surgery, Fuzhou General Hospital, Fuzhou, China
| | - Yi Jiang
- Department of Hepatobiliary Surgery, Fuzhou General Hospital, Fuzhou, China
- * E-mail: (YC); (YJ)
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Lu ZQ, Tang LM, Zhao GJ, Yao YM, Zhu XM, Dong N, Yu Y. Overactivation of mitogen-activated protein kinase and suppression of mitofusin-2 expression are two independent events in high mobility group box 1 protein-mediated T cell immune dysfunction. J Interferon Cytokine Res 2013; 33:529-41. [PMID: 23697559 DOI: 10.1089/jir.2012.0054] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
High mobility group box 1 protein (HMGB1), a critical proinflammatory cytokine, has recently been identified to be an immunostimulatory signal involved in sepsis-related immune dysfunction when released extracellularly, but the potential mechanism involved remains elusive. Here, we showed that the treatment with HMGB1 in vitro inhibited T lymphocyte immune response and expression of mitofusin-2 (Mfn-2; a member of the mitofusin family) in a dose- and time-dependent manner. Upregulation of Mfn-2 expression attenuated the suppressive effect of HMGB1 on T cell immune function. The phosphorylation of both extracellular signal-regulated kinase (ERK)1/2 and p38 mitogen-activated protein kinase (MAPK) was markedly upregulated by treating with high amount of HMGB1, while pretreatment with ERK1/2 and p38 MAPK-specific inhibitors (U0126 and SB203580) could attenuate suppression of T cell immune function and nuclear factor of activated T cell (NFAT) activation induced by HMGB1, respectively. HMGB1-induced activity of ERK1/2 and p38 was not fully inhibited in the presence of U0126 or SB203580. Interestingly, overexpression of Mfn-2 had no marked effect on HMGB1-mediated activation of MAPK, but could attenuate the suppressive effect of HMGB1 on the activity of NFAT. Thus, the mechanisms involved in HMGB1-induced T cell immune dysfunction in vitro at least partly include suppression of Mfn-2 expression, overactivation of ERK1/2, p38 MAPK, and intervention of NFAT activation, while the protective effect of Mfn-2 on T cell immune dysfunction induced by HMGB1 is dependent on other signaling pathway associated with NFAT, but not MAPK. Taken together, we conclude that overactivation of MAPK and suppression of Mfn-2 expression are two independent events in HMGB1-mediated T cell immune dysfunction.
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Affiliation(s)
- Zhong-qiu Lu
- Emergency Department, The First Affiliated Hospital of Wenzhou Medical College, Wenzhou, P. R. China.
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Piquereau J, Caffin F, Novotova M, Lemaire C, Veksler V, Garnier A, Ventura-Clapier R, Joubert F. Mitochondrial dynamics in the adult cardiomyocytes: which roles for a highly specialized cell? Front Physiol 2013; 4:102. [PMID: 23675354 PMCID: PMC3650619 DOI: 10.3389/fphys.2013.00102] [Citation(s) in RCA: 161] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Accepted: 04/23/2013] [Indexed: 11/17/2022] Open
Abstract
Mitochondrial dynamics is a recent topic of research in the field of cardiac physiology. The study of mechanisms involved in the morphological changes and in the mobility of mitochondria is legitimate since the adult cardiomyocytes possess numerous mitochondria which occupy at least 30% of cell volume. However, architectural constraints exist in the cardiomyocyte that limit mitochondrial movements and communication between adjacent mitochondria. Still, the proteins involved in mitochondrial fusion and fission are highly expressed in these cells and could be involved in different processes important for the cardiac function. For example, they are required for mitochondrial biogenesis to synthesize new mitochondria and for the quality-control of the organelles. They are also involved in inner membrane organization and may play a role in apoptosis. More generally, change in mitochondrial morphology can have consequences in the functioning of the respiratory chain, in the regulation of the mitochondrial permeability transition pore (MPTP), and in the interactions with other organelles. Furthermore, the proteins involved in fusion and fission of mitochondria are altered in cardiac pathologies such as ischemia/reperfusion or heart failure (HF), and appear to be valuable targets for pharmacological therapies. Thus, mitochondrial dynamics deserves particular attention in cardiac research. The present review draws up a report of our knowledge on these phenomena.
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Affiliation(s)
- Jerome Piquereau
- Department of Signaling and Cardiac Pathophysiology, U-769, INSERM Châtenay-Malabry, France ; IFR141, Université Paris-Sud Châtenay-Malabry, France
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Wappler EA, Institoris A, Dutta S, Katakam PVG, Busija DW. Mitochondrial dynamics associated with oxygen-glucose deprivation in rat primary neuronal cultures. PLoS One 2013; 8:e63206. [PMID: 23658809 PMCID: PMC3642144 DOI: 10.1371/journal.pone.0063206] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Accepted: 04/02/2013] [Indexed: 12/29/2022] Open
Abstract
Our objective was to investigate the mitochondrial dynamics following oxygen-glucose deprivation (OGD) in cultured rat cortical neurons. We documented changes in morphology, protein expression, and DNA levels in mitochondria following OGD and examined the roles of mitochondrial fission [dynamin-related protein 1 (Drp1), fission protein-1 (Fis1)] and fusion [mitofusin-1 (Mfn1), mitofusin-2 (Mfn2), and optic atrophy-1 protein (OPA1)] proteins on mitochondrial biogenesis and morphogenesis. We tested the effects of two Drp1 blockers [15-deoxy-Δ12,14-Prostaglandin J2 (PGJ2) and Mitochondrial Division Inhibitor (Mdivi-1)] on mitochondrial dynamics and cell survival. One hour of OGD had minimal effects on neuronal viability but mitochondria appeared condensed. Three hours of OGD caused a 60% decrease in neuronal viability accompanied by a transition from primarily normal/tubular and lesser number of rounded mitochondria during normoxia to either poorly labeled or small and large rounded mitochondria. The percentage of rounded mitochondria remained the same. The mitochondrial voltage-dependent anion channel, Complex V, and mitoDNA levels increased after OGD associated with a dramatic reduction in Drp1 expression, less reduction in Mfn2 expression, an increase in Mfn1 expression, with no changes in either OPA1 or Fis1. Although PGJ2 increased polymerization of Drp1, it did not reduce cell death or alter mitochondrial morphology following OGD and Mdivi-1 did not protect neurons against OGD. In summary, mitochondrial biogenesis and maintained fusion occurred in neurons along with mitochondrial fission following OGD; thus Mfn1 but not Drp1 may be a major regulator of these processes.
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Affiliation(s)
- Edina A Wappler
- Department of Pharmacology, Tulane University School of Medicine, New Orleans, Louisiana, United States of America.
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Verdejo HE, del Campo A, Troncoso R, Gutierrez T, Toro B, Quiroga C, Pedrozo Z, Munoz JP, Garcia L, Castro PF, Lavandero S. Mitochondria, myocardial remodeling, and cardiovascular disease. Curr Hypertens Rep 2013; 14:532-9. [PMID: 22972531 DOI: 10.1007/s11906-012-0305-4] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The process of muscle remodeling lies at the core of most cardiovascular diseases. Cardiac adaptation to pressure or volume overload is associated with a complex molecular change in cardiomyocytes which leads to anatomic remodeling of the heart muscle. Although adaptive at its beginnings, the sustained cardiac hypertrophic remodeling almost unavoidably ends in progressive muscle dysfunction, heart failure and ultimately death. One of the features of cardiac remodeling is a progressive impairment in mitochondrial function. The heart has the highest oxygen uptake in the human body and accordingly it has a large number of mitochondria, which form a complex network under constant remodeling in order to sustain the high metabolic rate of cardiac cells and serve as Ca(2+) buffers acting together with the endoplasmic reticulum (ER). However, this high dependence on mitochondrial metabolism has its costs: when oxygen supply is threatened, high leak of electrons from the electron transport chain leads to oxidative stress and mitochondrial failure. These three aspects of mitochondrial function (Reactive oxygen species signaling, Ca(2+) handling and mitochondrial dynamics) are critical for normal muscle homeostasis. In this article, we will review the latest evidence linking mitochondrial morphology and function with the process of myocardial remodeling and cardiovascular disease.
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Affiliation(s)
- Hugo E Verdejo
- Centro Estudios Moleculares de la Célula, Facultad Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile
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129
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Yuan M, Li J, Lv J, Mo X, Yang C, Chen X, Liu Z, Liu J. Polydatin (PD) inhibits IgE-mediated passive cutaneous anaphylaxis in mice by stabilizing mast cells through modulating Ca2+ mobilization. Toxicol Appl Pharmacol 2012. [DOI: 10.10.1016/j.taap.2012.08.024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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130
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Yuan M, Li J, Lv J, Mo X, Yang C, Chen X, Liu Z, Liu J. Polydatin (PD) inhibits IgE-mediated passive cutaneous anaphylaxis in mice by stabilizing mast cells through modulating Ca²⁺ mobilization. Toxicol Appl Pharmacol 2012; 264:462-9. [PMID: 22959927 DOI: 10.1016/j.taap.2012.08.024] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Revised: 08/22/2012] [Accepted: 08/23/2012] [Indexed: 12/11/2022]
Abstract
Mast cells play a key role in the pathogenesis of asthma and are a promising target for therapeutic intervention in asthma. This study investigated the effects of polydatin (PD), a resveratrol glucoside, on mast cell degranulation upon cross-linking of the high-affinity IgE receptors (FcεRI), as well as the anti-allergic activity of PD in vivo. Herein, we demonstrated that PD treatment for 30 min suppressed FcεRI-mediated mast cell degranulation in a dose-dependent manner. Concomitantly, PD significantly decreased FcεRI-mediated Ca²⁺ increase in mast cells. The suppressive effects of PD on FcεRI-mediated Ca²⁺ increase were largely inhibited by using LaCl₃ to block the Ca²⁺ release-activated Ca²⁺ channels (CRACs). Furthermore, PD significantly inhibited Ca²⁺ entry through CRACs evoked by thapsigargin (TG). Knocking down protein expression of Orai1, the pore-forming subunit of CRACs, significantly decreased PD suppression of FcεRI-induced intracellular Ca²⁺ influx and mast cell degranulation. In a mouse model of mast cell-dependent passive cutaneous anaphylaxis (PCA), in vivo PD administration suppressed mast cell degranulation and inhibited anaphylaxis. Taken together, our data indicate that PD stabilizes mast cells by suppressing FcεRI-induced Ca²⁺ mobilization mainly through inhibiting Ca²⁺ entry via CRACs, thus exerting a protective effect against PCA.
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Affiliation(s)
- Meichun Yuan
- Department of Pathophysiology, School of Medicine, Shenzhen University, Shenzhen 518060, China
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131
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Abstract
Mitochondria are dynamic organelles that continually undergo fusion and fission. These opposing processes work in concert to maintain the shape, size, and number of mitochondria and their physiological function. Some of the major molecules mediating mitochondrial fusion and fission in mammals have been discovered, but the underlying molecular mechanisms are only partially unraveled. In particular, the cast of characters involved in mitochondrial fission needs to be clarified. By enabling content mixing between mitochondria, fusion and fission serve to maintain a homogeneous and healthy mitochondrial population. Mitochondrial dynamics has been linked to multiple mitochondrial functions, including mitochondrial DNA stability, respiratory capacity, apoptosis, response to cellular stress, and mitophagy. Because of these important functions, mitochondrial fusion and fission are essential in mammals, and even mild defects in mitochondrial dynamics are associated with disease. A better understanding of these processes likely will ultimately lead to improvements in human health.
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Affiliation(s)
- David C Chan
- Division of Biology and the Howard Hughes Medical Institute, California Institute of Technology, Pasadena, California 91125, USA.
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132
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Abstract
Parkinson's disease is a debilitating disorder characterized by a progressive loss of dopaminergic neurons caused by programmed cell death. The aim of this review is to provide an up-to-date summary of the major programmed cell death pathways as they relate to PD. For a long time, programmed cell death has been synonymous with apoptosis but there now is evidence that other types of programmed cell death exist, such as autophagic cell death or programmed necrosis, and that these types of cell death are relevant to PD. The pathways and signals covered here include namely the death receptors, BCL-2 family, caspases, calpains, cdk5, p53, PARP-1, autophagy, mitophagy, mitochondrial fragmentation, and parthanatos. The review will present evidence from postmortem PD studies, toxin-induced models (especially MPTP/MPP+, 6-hydroxydopamine and rotenone), and from α-synuclein, LRRK2, Parkin, DJ-1, and PINK1 genetic models of PD, both in vitro and in vivo.
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Affiliation(s)
- Katerina Venderova
- University of the Pacific, Thomas J. Long School of Pharmacy, Department of Physiology and Pharmacology, Stockton, CA 95211, USA.
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133
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Gao Q, Wang XM, Ye HW, Yu Y, Kang PF, Wang HJ, Guan SD, Li ZH. Changes in the expression of cardiac mitofusin-2 in different stages of diabetes in rats. Mol Med Rep 2012; 6:811-4. [PMID: 22825027 DOI: 10.3892/mmr.2012.1002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Accepted: 07/13/2012] [Indexed: 11/05/2022] Open
Abstract
The aim of this study was to investigate the role of mitofusin-2 (Mfn2) in different stages of diabetes in rats and to analyze the related mechanism(s). A diabetic model in SD rats was induced by a single intraperitoneal injection of 55 mg/kg streptozoticin (STZ). The hearts were isolated from diabetes mellitus (DM) rats at the fourth week (DM4W), eighth week (DM8W) and twelfth week (DM12W) and fasting blood glucose (FBG) levels and the ratio of heart weight to body weight (HW/BW) were measured. Malondialdehyde (MDA) content, superoxide dismutase (SOD) and caspase 3 activities were measured. The expression of Mfn2 of the left anterior myocardium at the mRNA level was detected using RT‑PCR. In contrast to the normal group, in the DM4W, DM8W and DM12W groups, there was a significant increase in the FBG levels, but no difference among the DM4W, DM8W and DM12W groups. The HW/BW ratio as well as the MDA content were increased, while SOD activity was reduced. Caspase‑3 activity was increased, while the expression of Mfn-2 mRNA levels was reduced. In addition, with the development of diabetic cardiomyopathy, the contents of MDA and caspase 3 were increased, whereas SOD activity and Mfn-2 mRNA levels were further reduced. In conclusion, our results indicated that with the development of diabetes, the expression of cardiac Mfn2 has showed a decrease, which may be associated with the decrease of antioxidant ability and progression of apoptosis.
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Affiliation(s)
- Qin Gao
- Department of Physiology, Bengbu Medical College, Bengbu 233030, PR China
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134
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Papanicolaou KN, Phillippo MM, Walsh K. Mitofusins and the mitochondrial permeability transition: the potential downside of mitochondrial fusion. Am J Physiol Heart Circ Physiol 2012; 303:H243-55. [PMID: 22636681 DOI: 10.1152/ajpheart.00185.2012] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Mitofusins (Mfn-1 and Mfn-2) are transmembrane proteins that bind and hydrolyze guanosine 5'-triphosphate to bring about the merging of adjacent mitochondrial membranes. This event is necessary for mitochondrial fusion, a biological process that is critical for organelle function. The broad effects of mitochondrial fusion on cell bioenergetics have been extensively studied, whereas the local effects of mitofusin activity on the structure and integrity of the fusing mitochondrial membranes have received relatively little attention. From the study of fusogenic proteins, theoretical models, and simulations, it has been noted that the fusion of biological membranes is associated with local perturbations on the integrity of the membrane that present in the form of lipidic holes which open on the opposing bilayers. These lipidic holes represent obligate intermediates that make the fusion process thermodynamically more favorable and at the same time induce leakage to the fusing membranes. In this perspectives article we present the relevant evidence selected from a spectrum of membrane fusion/leakage models and attempt to couple this information with observations conducted with cardiac myocytes or mitochondria deficient in Mfn-1 and Mfn-2. More specifically, we argue in favor of a situation whereby mitochondrial fusion in cardiac myocytes is coupled with outer mitochondrial membrane destabilization that is opportunistically employed during the process of mitochondrial permeability transition. We hope that these insights will initiate research on this new hypothesis of mitochondrial permeability transition regulation, a poorly understood mitochondrial function with significant consequences on myocyte survival.
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Affiliation(s)
- Kyriakos N Papanicolaou
- Whitaker Cardiovascular Institute, Boston University School of Medicine, Massachusetts, 02118, USA
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135
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Zhao T, Huang X, Han L, Wang X, Cheng H, Zhao Y, Chen Q, Chen J, Cheng H, Xiao R, Zheng M. Central role of mitofusin 2 in autophagosome-lysosome fusion in cardiomyocytes. J Biol Chem 2012; 287:23615-25. [PMID: 22619176 DOI: 10.1074/jbc.m112.379164] [Citation(s) in RCA: 165] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In the heart, autophagy has been implicated in cardioprotection and ischemia-reperfusion tolerance, and the dysregulation of autophagy is associated with the development of heart failure. Mitochondrial dynamic proteins are profoundly involved in autophagic processes, especially the initiation and formation of autophagosomes, but it is not clear whether they play any role in cardiac autophagy. We previously reported that mitofusin 2 (MFN2), a mitochondrial outer membrane protein, serves as a major determinant of cardiomyocyte apoptosis mediated by oxidative stress. Here, we reveal a novel and essential role of MFN2 in mediating cardiac autophagy. We found that specific deletion of MFN2 in cardiomyocytes caused extensive accumulation of autophagosomes. In particular, the fusion of autophagosomes with lysosomes, a critical step in autophagic degradation, was markedly retarded without altering the formation of autophagosomes and lysosomes in response to ischemia-reperfusion stress. Importantly, MFN2 co-immunoprecipitated with RAB7 in the heart, and starvation further increased it. Knockdown of MFN2 by shRNA prevented, whereas re-expression of MFN2 restored, the autophagosome-lysosome fusion in neonatal cardiomyocytes. Hearts from cardiac-specific MFN2 knock-out mice had abnormal mitochondrial and cellular metabolism and were vulnerable to ischemia-reperfusion challenge. Our study defined a novel and essential role of MFN2 in the cardiac autophagic process by mediating the maturation of autophagy at the phase of autophagosome-lysosome fusion; deficiency of MFN2 caused multiple molecular and functional defects that undermined cardiac reserve and gradually led to cardiac vulnerability and dysfunction.
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Affiliation(s)
- Ting Zhao
- Institute of Molecular Medicine, State Key Laboratory of Biomembrane and Membrane Biotechnology, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
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136
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Antico Arciuch VG, Elguero ME, Poderoso JJ, Carreras MC. Mitochondrial regulation of cell cycle and proliferation. Antioxid Redox Signal 2012; 16:1150-80. [PMID: 21967640 PMCID: PMC3315176 DOI: 10.1089/ars.2011.4085] [Citation(s) in RCA: 294] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Revised: 10/03/2011] [Accepted: 10/03/2011] [Indexed: 01/01/2023]
Abstract
Eukaryotic mitochondria resulted from symbiotic incorporation of α-proteobacteria into ancient archaea species. During evolution, mitochondria lost most of the prokaryotic bacterial genes and only conserved a small fraction including those encoding 13 proteins of the respiratory chain. In this process, many functions were transferred to the host cells, but mitochondria gained a central role in the regulation of cell proliferation and apoptosis, and in the modulation of metabolism; accordingly, defective organelles contribute to cell transformation and cancer, diabetes, and neurodegenerative diseases. Most cell and transcriptional effects of mitochondria depend on the modulation of respiratory rate and on the production of hydrogen peroxide released into the cytosol. The mitochondrial oxidative rate has to remain depressed for cell proliferation; even in the presence of O₂, energy is preferentially obtained from increased glycolysis (Warburg effect). In response to stress signals, traffic of pro- and antiapoptotic mitochondrial proteins in the intermembrane space (B-cell lymphoma-extra large, Bcl-2-associated death promoter, Bcl-2 associated X-protein and cytochrome c) is modulated by the redox condition determined by mitochondrial O₂ utilization and mitochondrial nitric oxide metabolism. In this article, we highlight the traffic of the different canonical signaling pathways to mitochondria and the contributions of organelles to redox regulation of kinases. Finally, we analyze the dynamics of the mitochondrial population in cell cycle and apoptosis.
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Affiliation(s)
| | - María Eugenia Elguero
- Laboratory of Oxygen Metabolism, University of Buenos Aires, University Hospital, Buenos Aires, Argentina
| | - Juan José Poderoso
- Laboratory of Oxygen Metabolism, University of Buenos Aires, University Hospital, Buenos Aires, Argentina
- Department of Internal Medicine, School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
- CONICET, Buenos Aires, Argentina
| | - María Cecilia Carreras
- Laboratory of Oxygen Metabolism, University of Buenos Aires, University Hospital, Buenos Aires, Argentina
- CONICET, Buenos Aires, Argentina
- Department of Clinical Biochemistry, INFIBIOC and School of Pharmacy and Biochemistry, University of Buenos Aires, Buenos Aires, Argentina
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137
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Ngoh GA, Papanicolaou KN, Walsh K. Loss of mitofusin 2 promotes endoplasmic reticulum stress. J Biol Chem 2012; 287:20321-32. [PMID: 22511781 DOI: 10.1074/jbc.m112.359174] [Citation(s) in RCA: 144] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The outer mitochondrial membrane GTPase mitofusin 2 (Mfn2) is known to regulate endoplasmic reticulum (ER) shape in addition to its mitochondrial fusion effects. However, its role in ER stress is unknown. We report here that induction of ER stress with either thapsigargin or tunicamycin in mouse embryonic fibroblasts leads to up-regulation of Mfn2 mRNA and protein levels with no change in the expression of the mitochondrial shaping factors Mfn1, Opa1, Drp1, and Fis1. Genetic deletion of Mfn2 but not Mfn1 in mouse embryonic fibroblasts or cardiac myocytes in mice led to an increase in the expression of the ER chaperone proteins. Genetic ablation of Mfn2 in mouse embryonic fibroblasts amplified ER stress and exacerbated ER stress-induced apoptosis. Deletion of Mfn2 delayed translational recovery through prolonged eIF2α phosphorylation associated with decreased GADD34 and p58(IPK) expression and elevated C/EBP homologous protein induction at late time points. These changes in the unfolded protein response were coupled to increased cell death reflected by augmented caspase 3/7 activity, lactate dehydrogenase release from cells, and an increase in propidium iodide-positive nuclei in response to thapsigargin or tunicamycin treatment. In contrast, genetic deletion of Mfn1 did not affect ER stress-mediated increase in ER chaperone synthesis or eIF2α phosphorylation. Additionally, ER stress-induced C/EBP homologous protein, GADD34, and p58(IPK) induction and cell death were not affected by loss of Mfn1. We conclude that Mfn2 but not Mfn1 is an ER stress-inducible protein that is required for the proper temporal sequence of the ER stress response.
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Affiliation(s)
- Gladys A Ngoh
- Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
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138
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Ong SB, Gustafsson AB. New roles for mitochondria in cell death in the reperfused myocardium. Cardiovasc Res 2011; 94:190-6. [PMID: 22108916 DOI: 10.1093/cvr/cvr312] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Mitochondria play an important role in regulating the life and death of cells. They provide the cell with energy via oxidative phosphorylation but can quickly turn into death-promoting organelles in response to stress by disrupting adenosine triphosphate synthesis, releasing pro-death proteins, and producing reactive oxygen species. Due to their high-energy requirement, cardiac myocytes are abundant in mitochondria and as a result, particularly vulnerable to mitochondrial defects. Myocardial ischaemia and reperfusion are associated with mitochondrial dysfunction and cell death. Therefore, future therapies will focus on preserving mitochondrial integrity and function in hopes of minimizing the impact of ischaemia/reperfusion (I/R) injury. It is well established that myocardial I/R activates both necrosis and apoptosis, and that blocking either process reduces the levels of injury. However, recent studies have demonstrated that alterations in mitochondrial dynamics or clearance of mitochondria via autophagy also can contribute to cell death in the myocardium. In this review, we will discuss these new developments and their impact on the role of cardiac mitochondria in cell death following reperfusion in the heart.
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Affiliation(s)
- Sang-Bing Ong
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, La Jolla, CA 92093-0758, USA
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139
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Chen Y, Liu Y, Dorn GW. Mitochondrial fusion is essential for organelle function and cardiac homeostasis. Circ Res 2011; 109:1327-31. [PMID: 22052916 DOI: 10.1161/circresaha.111.258723] [Citation(s) in RCA: 394] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
RATIONALE Mitochondria constitute 30% of myocardial mass. Mitochondrial fusion and fission appear essential for health of most tissues. Mitochondrial fission occurs in neonatal cardiomycyte and is implicated in cardiomyocyte death. Mitochondrial fusion has not been observed in postmitotic myocytes of adult hearts, and its occurrence and function in this context are controversial. OBJECTIVE Determine the consequences on organelle and organ function of disrupting cardiomyocyte mitochondrial fusion in vivo. METHODS AND RESULTS The murine mfn1 and mfn2 genes, encoding mitofusins (Mfn) 1 and 2 that mediate mitochondrial tethering and outer mitochondrial membrane fusion, were interrupted by Cre-mediated excision of essential exons in neonatal (Nkx2.5-Cre) and adult (MYH6 modified estrogen receptor-Cre-modified estrogen receptor plus tamoxifen or Raloxifene) hearts. Embryonic combined Mfn1/Mfn2 ablation was lethal after e9.5. Conditional combined Mfn1/Mfn2 ablation in adult hearts induced mitochondrial fragmentation, cardiomyocyte and mitochondrial respiratory dysfunction, and rapidly progressive and lethal dilated cardiomyopathy. Before heart failure developed, cardiomyocyte shortening and calcium cycling were unaffected by absence of Mfn1 and Mfn2. Based on the time course over which fusion-defective mitochondrial size decreases, a mitochondrial fusion/fission cycle in adult mouse hearts occurs approximately every 16 days. CONCLUSIONS Mitochondrial fusion in adult cardiac myocytes is necessary to maintain normal mitochondrial morphology and is essential for normal cardiac respiratory and contractile function. Interruption of mitochondrial fusion causes lethal cardiac failure at a time corresponding to 3 or 4 cycles of unopposed mitochondrial fission.
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Affiliation(s)
- Yun Chen
- Center for Pharmacogenomics, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA.
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140
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Saks V, Kuznetsov AV, Gonzalez-Granillo M, Tepp K, Timohhina N, Karu-Varikmaa M, Kaambre T, Dos Santos P, Boucher F, Guzun R. Intracellular Energetic Units regulate metabolism in cardiac cells. J Mol Cell Cardiol 2011; 52:419-36. [PMID: 21816155 DOI: 10.1016/j.yjmcc.2011.07.015] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Revised: 06/20/2011] [Accepted: 07/18/2011] [Indexed: 12/30/2022]
Abstract
This review describes developments in historical perspective as well as recent results of investigations of cellular mechanisms of regulation of energy fluxes and mitochondrial respiration by cardiac work - the metabolic aspect of the Frank-Starling law of the heart. A Systems Biology solution to this problem needs the integration of physiological and biochemical mechanisms that take into account intracellular interactions of mitochondria with other cellular systems, in particular with cytoskeleton components. Recent data show that different tubulin isotypes are involved in the regular arrangement exhibited by mitochondria and ATP-consuming systems into Intracellular Energetic Units (ICEUs). Beta II tubulin association with the mitochondrial outer membrane, when co-expressed with mitochondrial creatine kinase (MtCK) specifically limits the permeability of voltage-dependent anion channel for adenine nucleotides. In the MtCK reaction this interaction changes the regulatory kinetics of respiration through a decrease in the affinity for adenine nucleotides and an increase in the affinity for creatine. Metabolic Control Analysis of the coupled MtCK-ATP Synthasome in permeabilized cardiomyocytes showed a significant increase in flux control by steps involved in ADP recycling. Mathematical modeling of compartmentalized energy transfer represented by ICEUs shows that cyclic changes in local ADP, Pi, phosphocreatine and creatine concentrations during contraction cycle represent effective metabolic feedback signals when amplified in the coupled non-equilibrium MtCK-ATP Synthasome reactions in mitochondria. This mechanism explains the regulation of respiration on beat to beat basis during workload changes under conditions of metabolic stability. This article is part of a Special Issue entitled "Local Signaling in Myocytes."
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Affiliation(s)
- Valdur Saks
- Laboratory of Bioenergetics, National Institute of Chemical Physics and Biophysics, Tallinn, Estonia.
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141
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Abstract
Mitochondria are highly dynamic organelles, capable of undergoing constant fission and fusion events, forming networks. These dynamic events allow the transmission of chemical and physical messengers and the exchange of metabolites within the cell. In this article we review the signaling mechanisms controlling mitochondrial fission and fusion, and its relationship with cell bioenergetics, especially in the heart. Furthermore we also discuss how defects in mitochondrial dynamics might be involved in the pathogenesis of metabolic cardiac diseases.
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142
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Sun Z, Zhang J, Zhang J, Chen C, Du Q, Chang L, Cao C, Zheng M, Garcia-Barrio MT, Chen YE, Xiao RP, Mao J, Zhu X. Rad GTPase induces cardiomyocyte apoptosis through the activation of p38 mitogen-activated protein kinase. Biochem Biophys Res Commun 2011; 409:52-7. [PMID: 21549102 DOI: 10.1016/j.bbrc.2011.04.104] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Accepted: 04/22/2011] [Indexed: 11/28/2022]
Abstract
Rad is a member of a subclass of small GTP-binding proteins, the RGK family. In the present study we investigated the role of Rad protein in regulating cardiomyocyte viability. DNA fragmentation and TUNEL assays demonstrated that Rad promoted rat neonatal cardiomyocyte apoptosis. Rad silencing fully blocked serum deprivation induced apoptosis, indicating Rad is necessary for trigger cardiomyocyte apoptosis. Rad overexpression caused a dramatic decrease of the anti-apoptotic molecule Bcl-x(L), whereas Bcl-x(L) overexpression protected cardiomyocytes against Rad-induced apoptosis. Rad-triggered apoptosis was mediated by the activation of p38 MAPK. The p38 blocker SB203580 effectively protected cardiomyocytes against Rad-evoked apoptosis.
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Affiliation(s)
- Zhongcui Sun
- Department of Cardiology, Peking University Third Hospital, Beijing, China
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143
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Camara AKS, Bienengraeber M, Stowe DF. Mitochondrial approaches to protect against cardiac ischemia and reperfusion injury. Front Physiol 2011; 2:13. [PMID: 21559063 PMCID: PMC3082167 DOI: 10.3389/fphys.2011.00013] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Accepted: 03/24/2011] [Indexed: 12/18/2022] Open
Abstract
The mitochondrion is a vital component in cellular energy metabolism and intracellular signaling processes. Mitochondria are involved in a myriad of complex signaling cascades regulating cell death vs. survival. Importantly, mitochondrial dysfunction and the resulting oxidative and nitrosative stress are central in the pathogenesis of numerous human maladies including cardiovascular diseases, neurodegenerative diseases, diabetes, and retinal diseases, many of which are related. This review will examine the emerging understanding of the role of mitochondria in the etiology and progression of cardiovascular diseases and will explore potential therapeutic benefits of targeting the organelle in attenuating the disease process. Indeed, recent advances in mitochondrial biology have led to selective targeting of drugs designed to modulate or manipulate mitochondrial function, to the use of light therapy directed to the mitochondrial function, and to modification of the mitochondrial genome for potential therapeutic benefit. The approach to rationally treat mitochondrial dysfunction could lead to more effective interventions in cardiovascular diseases that to date have remained elusive. The central premise of this review is that if mitochondrial abnormalities contribute to the etiology of cardiovascular diseases (e.g., ischemic heart disease), alleviating the mitochondrial dysfunction will contribute to mitigating the severity or progression of the disease. To this end, this review will provide an overview of our current understanding of mitochondria function in cardiovascular diseases as well as the potential role for targeting mitochondria with potential drugs or other interventions that lead to protection against cell injury.
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Affiliation(s)
- Amadou K S Camara
- Department of Anesthesiology, Medical College of Wisconsin Milwaukee, WI, USA
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144
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Papanicolaou KN, Khairallah RJ, Ngoh GA, Chikando A, Luptak I, O'Shea KM, Riley DD, Lugus JJ, Colucci WS, Lederer WJ, Stanley WC, Walsh K. Mitofusin-2 maintains mitochondrial structure and contributes to stress-induced permeability transition in cardiac myocytes. Mol Cell Biol 2011; 31:1309-28. [PMID: 21245373 PMCID: PMC3067905 DOI: 10.1128/mcb.00911-10] [Citation(s) in RCA: 295] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Revised: 09/10/2010] [Accepted: 12/17/2010] [Indexed: 11/20/2022] Open
Abstract
Mitofusin-2 (Mfn-2) is a dynamin-like protein that is involved in the rearrangement of the outer mitochondrial membrane. Research using various experimental systems has shown that Mfn-2 is a mediator of mitochondrial fusion, an evolutionarily conserved process responsible for the surveillance of mitochondrial homeostasis. Here, we find that cardiac myocyte mitochondria lacking Mfn-2 are pleiomorphic and have the propensity to become enlarged. Consistent with an underlying mild mitochondrial dysfunction, Mfn-2-deficient mice display modest cardiac hypertrophy accompanied by slight functional deterioration. The absence of Mfn-2 is associated with a marked delay in mitochondrial permeability transition downstream of Ca(2+) stimulation or due to local generation of reactive oxygen species (ROS). Consequently, Mfn-2-deficient adult cardiomyocytes are protected from a number of cell death-inducing stimuli and Mfn-2 knockout hearts display better recovery following reperfusion injury. We conclude that in cardiac myocytes, Mfn-2 controls mitochondrial morphogenesis and serves to predispose cells to mitochondrial permeability transition and to trigger cell death.
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Affiliation(s)
- Kyriakos N. Papanicolaou
- Whitaker Cardiovascular Institute, Boston University School of Medicine, 715 Albany Street, W611, Boston, Massachusetts 02118, Division of Cardiology and Department of Medicine, University of Maryland, 20 Penn Street, HSF2, Room S022, Baltimore, Maryland 21201, Cardiovascular Medicine Section and Myocardial Biology Unit, Boston University Medical Center, 715 Albany Street, X704, Boston, Massachusetts 02118, Center for Biomedical Engineering and Technology, University of Maryland Baltimore, 725 W. Lombard Street, Baltimore, Maryland 21201
| | - Ramzi J. Khairallah
- Whitaker Cardiovascular Institute, Boston University School of Medicine, 715 Albany Street, W611, Boston, Massachusetts 02118, Division of Cardiology and Department of Medicine, University of Maryland, 20 Penn Street, HSF2, Room S022, Baltimore, Maryland 21201, Cardiovascular Medicine Section and Myocardial Biology Unit, Boston University Medical Center, 715 Albany Street, X704, Boston, Massachusetts 02118, Center for Biomedical Engineering and Technology, University of Maryland Baltimore, 725 W. Lombard Street, Baltimore, Maryland 21201
| | - Gladys A. Ngoh
- Whitaker Cardiovascular Institute, Boston University School of Medicine, 715 Albany Street, W611, Boston, Massachusetts 02118, Division of Cardiology and Department of Medicine, University of Maryland, 20 Penn Street, HSF2, Room S022, Baltimore, Maryland 21201, Cardiovascular Medicine Section and Myocardial Biology Unit, Boston University Medical Center, 715 Albany Street, X704, Boston, Massachusetts 02118, Center for Biomedical Engineering and Technology, University of Maryland Baltimore, 725 W. Lombard Street, Baltimore, Maryland 21201
| | - Aristide Chikando
- Whitaker Cardiovascular Institute, Boston University School of Medicine, 715 Albany Street, W611, Boston, Massachusetts 02118, Division of Cardiology and Department of Medicine, University of Maryland, 20 Penn Street, HSF2, Room S022, Baltimore, Maryland 21201, Cardiovascular Medicine Section and Myocardial Biology Unit, Boston University Medical Center, 715 Albany Street, X704, Boston, Massachusetts 02118, Center for Biomedical Engineering and Technology, University of Maryland Baltimore, 725 W. Lombard Street, Baltimore, Maryland 21201
| | - Ivan Luptak
- Whitaker Cardiovascular Institute, Boston University School of Medicine, 715 Albany Street, W611, Boston, Massachusetts 02118, Division of Cardiology and Department of Medicine, University of Maryland, 20 Penn Street, HSF2, Room S022, Baltimore, Maryland 21201, Cardiovascular Medicine Section and Myocardial Biology Unit, Boston University Medical Center, 715 Albany Street, X704, Boston, Massachusetts 02118, Center for Biomedical Engineering and Technology, University of Maryland Baltimore, 725 W. Lombard Street, Baltimore, Maryland 21201
| | - Karen M. O'Shea
- Whitaker Cardiovascular Institute, Boston University School of Medicine, 715 Albany Street, W611, Boston, Massachusetts 02118, Division of Cardiology and Department of Medicine, University of Maryland, 20 Penn Street, HSF2, Room S022, Baltimore, Maryland 21201, Cardiovascular Medicine Section and Myocardial Biology Unit, Boston University Medical Center, 715 Albany Street, X704, Boston, Massachusetts 02118, Center for Biomedical Engineering and Technology, University of Maryland Baltimore, 725 W. Lombard Street, Baltimore, Maryland 21201
| | - Dushon D. Riley
- Whitaker Cardiovascular Institute, Boston University School of Medicine, 715 Albany Street, W611, Boston, Massachusetts 02118, Division of Cardiology and Department of Medicine, University of Maryland, 20 Penn Street, HSF2, Room S022, Baltimore, Maryland 21201, Cardiovascular Medicine Section and Myocardial Biology Unit, Boston University Medical Center, 715 Albany Street, X704, Boston, Massachusetts 02118, Center for Biomedical Engineering and Technology, University of Maryland Baltimore, 725 W. Lombard Street, Baltimore, Maryland 21201
| | - Jesse J. Lugus
- Whitaker Cardiovascular Institute, Boston University School of Medicine, 715 Albany Street, W611, Boston, Massachusetts 02118, Division of Cardiology and Department of Medicine, University of Maryland, 20 Penn Street, HSF2, Room S022, Baltimore, Maryland 21201, Cardiovascular Medicine Section and Myocardial Biology Unit, Boston University Medical Center, 715 Albany Street, X704, Boston, Massachusetts 02118, Center for Biomedical Engineering and Technology, University of Maryland Baltimore, 725 W. Lombard Street, Baltimore, Maryland 21201
| | - Wilson S. Colucci
- Whitaker Cardiovascular Institute, Boston University School of Medicine, 715 Albany Street, W611, Boston, Massachusetts 02118, Division of Cardiology and Department of Medicine, University of Maryland, 20 Penn Street, HSF2, Room S022, Baltimore, Maryland 21201, Cardiovascular Medicine Section and Myocardial Biology Unit, Boston University Medical Center, 715 Albany Street, X704, Boston, Massachusetts 02118, Center for Biomedical Engineering and Technology, University of Maryland Baltimore, 725 W. Lombard Street, Baltimore, Maryland 21201
| | - W. Jonathan Lederer
- Whitaker Cardiovascular Institute, Boston University School of Medicine, 715 Albany Street, W611, Boston, Massachusetts 02118, Division of Cardiology and Department of Medicine, University of Maryland, 20 Penn Street, HSF2, Room S022, Baltimore, Maryland 21201, Cardiovascular Medicine Section and Myocardial Biology Unit, Boston University Medical Center, 715 Albany Street, X704, Boston, Massachusetts 02118, Center for Biomedical Engineering and Technology, University of Maryland Baltimore, 725 W. Lombard Street, Baltimore, Maryland 21201
| | - William C. Stanley
- Whitaker Cardiovascular Institute, Boston University School of Medicine, 715 Albany Street, W611, Boston, Massachusetts 02118, Division of Cardiology and Department of Medicine, University of Maryland, 20 Penn Street, HSF2, Room S022, Baltimore, Maryland 21201, Cardiovascular Medicine Section and Myocardial Biology Unit, Boston University Medical Center, 715 Albany Street, X704, Boston, Massachusetts 02118, Center for Biomedical Engineering and Technology, University of Maryland Baltimore, 725 W. Lombard Street, Baltimore, Maryland 21201
| | - Kenneth Walsh
- Whitaker Cardiovascular Institute, Boston University School of Medicine, 715 Albany Street, W611, Boston, Massachusetts 02118, Division of Cardiology and Department of Medicine, University of Maryland, 20 Penn Street, HSF2, Room S022, Baltimore, Maryland 21201, Cardiovascular Medicine Section and Myocardial Biology Unit, Boston University Medical Center, 715 Albany Street, X704, Boston, Massachusetts 02118, Center for Biomedical Engineering and Technology, University of Maryland Baltimore, 725 W. Lombard Street, Baltimore, Maryland 21201
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145
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Yu H, Guo Y, Mi L, Wang X, Li L, Gao W. Mitofusin 2 inhibits angiotensin II-induced myocardial hypertrophy. J Cardiovasc Pharmacol Ther 2010; 16:205-11. [PMID: 21106870 DOI: 10.1177/1074248410385683] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND OBJECTIVES Myocardial hypertrophy is a common clinical finding leading to heart failure and sudden death. Mitofusin 2 (Mfn2), a hyperplasia suppressor protein, is downregulated in hypertrophic heart. This study examined the role of Mfn2 in myocardial hypertrophy and its potential signal pathway. METHODS AND RESULTS In in vitro studies, neonatal cardiac myocytes were isolated and cultured. Incubation of cultured cardiomycytes with angiotensin II (Ang II) inhibited gene expression of Mfn2; induced cell hypertrophy and protein synthesis; and activated protein kinase Akt. Pretreatment of cells with AdMfn2-a replication-deficient adenoviral vector encoding rat Mfn2 gene-upregulated Mfn2 expression and subsequently attenuated Ang II-induced cell hypertrophy; protein synthesis; and Akt activation. In in vivo studies, direct gene delivery of AdMfn2 into myocardium decreased the infusion of Ang II-induced atrial natriuretic factor (ANF, a hypertrophic marker) expression and cardiomyocyte cross-sectional area. Consistently, upregulation of Mfn2 in myocardium decreased the thicknesses of anterior and posterior walls of left ventricle (LV) and the ratio of LV mass/body weight in Ang II-treated rats. Of note, AdGFP (control for AdMfn2) did not affect the effects of Ang II in vitro or in vivo. CONCLUSIONS Upregulation of Mfn2 inhibits Ang II-induced myocardial hypertrophy. In this process, inhibition of Akt activation seems to play a significant role. These findings indicate Mfn2 is a critical protein in modulating myocyte hypertrophy.
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Affiliation(s)
- Haiyi Yu
- Department of Cardiology, Peking University Third Hospital and Key Laboratory of Molecular Cardiovascular Sciences Ministry of Education, Beijing, PR China
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146
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Dorn GW, Scorrano L. Two close, too close: sarcoplasmic reticulum-mitochondrial crosstalk and cardiomyocyte fate. Circ Res 2010; 107:689-99. [PMID: 20847324 DOI: 10.1161/circresaha.110.225714] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Mitochondria are key organelles in cell life whose dysfunction is associated with a variety of diseases. Their crucial role in intermediary metabolism and energy conversion makes them a preferred target in tissues, such as the heart, where the energetic demands are very high. In the cardiomyocyte, the spatial organization of mitochondria favors their interaction with the sarcoplasmic reticulum, thereby offering a mechanism for Ca(2+)-mediated crosstalk between these 2 organelles. Recently, the molecular basis for this interaction has begun to be unraveled, and we are learning how endoplasmic reticulum-mitochondrial interactions are often exploited by death signals, such as proapoptotic Bcl-2 family members, to amplify the cell death cascade. Here, we review our present understanding of the structural basis and the functional consequences of the close interaction between sarcoplasmic reticulum and mitochondria on cardiomyocyte function and death.
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Affiliation(s)
- Gerald W Dorn
- Washington University Center for Pharmacogenomics, Campus Box 8220, 660 S Euclid Ave, St Louis, MO 63110, USA.
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147
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Krüppel-like factor 4 interacts with p300 to activate mitofusin 2 gene expression induced by all-trans retinoic acid in VSMCs. Acta Pharmacol Sin 2010; 31:1293-302. [PMID: 20711222 DOI: 10.1038/aps.2010.96] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
AIM To elucidate how krüppel-like factor 4 (KLF4) activates mitofusin 2 (mfn-2) expression in all-trans retinoic acid (ATRA)-induced vascular smooth muscle cell (VSMC) differentiation. METHODS The mfn-2 promoter-reporter constructs and the KLF4 acetylation-deficient or phosphorylation-deficient mutants were constructed. Adenoviral vector of KLF4-mediated overexpression and Western blot analysis were used to determine the effect of KLF4 on mfn-2 expression. The luciferase assay and chromatin immunoprecipitation were used to detect the transactivation of KLF4 on mfn-2 gene expression. Co-immunoprecipitation and GST pull-down assays were used to determine the modification of KLF4 and interaction of KLF4 with p300 in VSMCs. RESULTS KLF4 mediated ATRA-induced mfn-2 expression in VSMCs. KLF4 bound directly to the mfn-2 promoter and activated its transcription. ATRA increased the interaction of KLF4 with p300 by inducing KLF4 phosphorylation via activation of JNK and p38 MAPK signaling. KLF4 acetylation by p300 increased its activity to transactivate the mfn-2 promoter. CONCLUSION ATRA induces KLF4 acetylation by p300 and increases the ability of KLF4 to transactivate the mfn-2 promoter in VSMCs.
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148
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Zheng M, Xiao RP. Role of mitofusin 2 in cardiovascular oxidative injury. J Mol Med (Berl) 2010; 88:987-91. [PMID: 20824264 DOI: 10.1007/s00109-010-0675-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Revised: 08/16/2010] [Accepted: 08/16/2010] [Indexed: 01/27/2023]
Abstract
Mitochondria are highly dynamic organelles with constant shape changes regulated by fusion and fission events. In addition to regulating mitochondrial morphology, mitochondrial fusion/fission is involved in fundamental mitochondrial biological processes, including mitochondrial metabolism, energization, respiration, mitochondrial membrane potential, and mtDNA stability. Dysfunction of mitochondrial dynamics has been implicated in various human diseases, especially in neurodegenerative diseases. Emerging evidence indicates that impaired expression of mitochondrial fusion proteins or their malfunction participates in oxidative stress-induced cardiovascular injury. This review will focus on recent advances of mitochondrial fusion in regulating various cellular processes in cardiovascular system.
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Affiliation(s)
- Ming Zheng
- Institute of Molecular Medicine, Peking University, Beijing, 100871, People's Republic of China
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149
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Abstract
Mitochondria are dynamic and are able to interchange their morphology between elongated interconnected mitochondrial networks and a fragmented disconnected arrangement by the processes of mitochondrial fusion and fission, respectively. Changes in mitochondrial morphology are regulated by the mitochondrial fusion proteins (mitofusins 1 and 2, and optic atrophy 1) and the mitochondrial fission proteins (dynamin-related peptide 1 and mitochondrial fission protein 1) and have been implicated in a variety of biological processes including embryonic development, metabolism, apoptosis, and autophagy, although the majority of studies have been largely confined to non-cardiac cells. Despite the unique arrangement of mitochondria in the adult heart, emerging data suggest that changes in mitochondrial morphology may be relevant to various aspects of cardiovascular biology-these include cardiac development, the response to ischaemia-reperfusion injury, heart failure, diabetes mellitus, and apoptosis. Interestingly, the machinery required for altering mitochondrial shape in terms of the mitochondrial fusion and fission proteins are all present in the adult heart, but their physiological function remains unclear. In this article, we review the current developments in this exciting new field of mitochondrial biology, the implications for cardiovascular physiology, and the potential for discovering novel therapeutic strategies for treating cardiovascular disease.
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Affiliation(s)
- Sang-Bing Ong
- The Hatter Cardiovascular Institute, University College, London WC1E 6HX, UK
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150
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Mutation of the protein kinase A phosphorylation site influences the anti-proliferative activity of mitofusin 2. Atherosclerosis 2010; 211:216-23. [DOI: 10.1016/j.atherosclerosis.2010.02.012] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2009] [Revised: 02/05/2010] [Accepted: 02/08/2010] [Indexed: 11/23/2022]
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