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Oralova V, Matalova E, Killinger M, Knopfova L, Smarda J, Buchtova M. Osteogenic Potential of the Transcription Factor c-MYB. Calcif Tissue Int 2017; 100:311-322. [PMID: 28012106 DOI: 10.1007/s00223-016-0219-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Accepted: 12/10/2016] [Indexed: 12/30/2022]
Abstract
The transcription factor c-MYB is a well-known marker of undifferentiated cells such as haematopoietic cell precursors, but recently it has also been observed in differentiated cells that produce hard tissues. Our previous findings showed the presence of c-MYB in intramembranous bones and its involvement in the chondrogenic steps of endochondral ossification, where the up-regulation of early chondrogenic markers after c-myb overexpression was observed. Since we previously detected c-MYB in osteoblasts, we aimed to analyse the localisation of c-MYB during later stages of endochondral bone formation and address its function during bone matrix production. c-MYB-positive cells were found in the chondro-osseous junction zone in osteoblasts of trabecular bone as well as deeper in the zone of ossification in cells of spongy bone. To experimentally evaluate the osteogenic potential of c-MYB during endochondral bone formation, micromasses derived from embryonic mouse limb buds were established. Nuclear c-MYB protein expression was observed in long-term micromasses, especially in the areas around nodules. c-myb overexpression induced the expression of osteogenic-related genes such as Bmp2, Comp, Csf2 and Itgb1. Moreover, alizarin red staining and osteocalcin labelling promoted mineralised matrix production in c-myb-overexpressing cultures, whereas downregulation of c-myb by siRNA reduced mineralised matrix production. In conclusion, c-Myb plays a role in the osteogenesis of long bones by inducing osteogenic genes and causing the enhancement of mineral matrix production. This action of the transcription factor c-Myb might be of interest in the future for the establishment of novel approaches to tissue regeneration.
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Affiliation(s)
- V Oralova
- Institute of Animal Physiology and Genetics, v.v.i., Czech Academy of Sciences, Veveri 97, 602 00, Brno, Czech Republic.
- Evolutionary Developmental Biology, Ghent University, Ghent, Belgium.
| | - E Matalova
- Institute of Animal Physiology and Genetics, v.v.i., Czech Academy of Sciences, Veveri 97, 602 00, Brno, Czech Republic
- Department of Physiology, University of Veterinary and Pharmaceutical Sciences, Brno, Czech Republic
| | - M Killinger
- Institute of Animal Physiology and Genetics, v.v.i., Czech Academy of Sciences, Veveri 97, 602 00, Brno, Czech Republic
- Department of Experimental Biology, Masaryk University, Brno, Czech Republic
| | - L Knopfova
- Department of Experimental Biology, Masaryk University, Brno, Czech Republic
- International Clinical Research Center, St. Anne's University Hospital, Brno, Czech Republic
| | - J Smarda
- Department of Experimental Biology, Masaryk University, Brno, Czech Republic
| | - M Buchtova
- Institute of Animal Physiology and Genetics, v.v.i., Czech Academy of Sciences, Veveri 97, 602 00, Brno, Czech Republic
- Department of Experimental Biology, Masaryk University, Brno, Czech Republic
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2
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Yu X, Liu W, Fan Z, Qian F, Zhang D, Han Y, Xu L, Sun G, Qi J, Zhang S, Tang M, Li J, Chai R, Wang H. c-Myb knockdown increases the neomycin-induced damage to hair-cell-like HEI-OC1 cells in vitro. Sci Rep 2017; 7:41094. [PMID: 28112219 PMCID: PMC5253735 DOI: 10.1038/srep41094] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Accepted: 12/14/2016] [Indexed: 12/17/2022] Open
Abstract
c-Myb is a transcription factor that plays a key role in cell proliferation, differentiation, and apoptosis. It has been reported that c-Myb is expressed within the chicken otic placode, but whether c-Myb exists in the mammalian cochlea, and how it exerts its effects, has not been explored yet. Here, we investigated the expression of c-Myb in the postnatal mouse cochlea and HEI-OC1 cells and found that c-Myb was expressed in the hair cells (HCs) of mouse cochlea as well as in cultured HEI-OC1 cells. Next, we demonstrated that c-Myb expression was decreased in response to neomycin treatment in both cochlear HCs and HEI-OC1 cells, suggesting an otoprotective role for c-Myb. We then knocked down c-Myb expression with shRNA transfection in HEI-OC1 cells and found that c-Myb knockdown decreased cell viability, increased expression of pro-apoptotic factors, and enhanced cell apoptosis after neomycin insult. Mechanistic studies revealed that c-Myb knockdown increased cellular levels of reactive oxygen species and decreased Bcl-2 expression, both of which are likely to be responsible for the increased sensitivity of c-Myb knockdown cells to neomycin. This study provides evidence that c-Myb might serve as a new target for the prevention of aminoglycoside-induced HC loss.
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Affiliation(s)
- Xiaoyu Yu
- Otolaryngology-Head and Neck Surgery, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, China
- Shandong Provincial Key Laboratory of Otology, Jinan, China
| | - Wenwen Liu
- Otolaryngology-Head and Neck Surgery, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, China
- Shandong Provincial Key Laboratory of Otology, Jinan, China
| | - Zhaomin Fan
- Otolaryngology-Head and Neck Surgery, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, China
| | - Fuping Qian
- Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Institute of Life Sciences, Southeast University, Nanjing 210096, China
- Co-innovation Center of Neuroregeneration, Nantong University, Nantong 226001, China
| | - Daogong Zhang
- Otolaryngology-Head and Neck Surgery, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, China
| | - Yuechen Han
- Otolaryngology-Head and Neck Surgery, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, China
| | - Lei Xu
- Otolaryngology-Head and Neck Surgery, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, China
| | - Gaoying Sun
- Otolaryngology-Head and Neck Surgery, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, China
- Shandong Provincial Key Laboratory of Otology, Jinan, China
| | - Jieyu Qi
- Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Institute of Life Sciences, Southeast University, Nanjing 210096, China
- Co-innovation Center of Neuroregeneration, Nantong University, Nantong 226001, China
| | - Shasha Zhang
- Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Institute of Life Sciences, Southeast University, Nanjing 210096, China
- Co-innovation Center of Neuroregeneration, Nantong University, Nantong 226001, China
| | - Mingliang Tang
- Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Institute of Life Sciences, Southeast University, Nanjing 210096, China
- Co-innovation Center of Neuroregeneration, Nantong University, Nantong 226001, China
| | - Jianfeng Li
- Otolaryngology-Head and Neck Surgery, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, China
- Shandong Provincial Key Laboratory of Otology, Jinan, China
| | - Renjie Chai
- Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Institute of Life Sciences, Southeast University, Nanjing 210096, China
- Co-innovation Center of Neuroregeneration, Nantong University, Nantong 226001, China
- Department of Otolaryngology Head and Neck Surgery, Zhongda Hospital, Southeast University, Nanjing 210096, China
| | - Haibo Wang
- Otolaryngology-Head and Neck Surgery, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, China
- Shandong Provincial Key Laboratory of Otology, Jinan, China
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Oralová V, Matalová E, Janečková E, Drobná Krejčí E, Knopfová L, Šnajdr P, Tucker AS, Veselá I, Šmarda J, Buchtová M. Role of c-Myb in chondrogenesis. Bone 2015; 76:97-106. [PMID: 25845979 DOI: 10.1016/j.bone.2015.02.031] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Revised: 02/20/2015] [Accepted: 02/21/2015] [Indexed: 12/22/2022]
Abstract
The Myb locus encodes the c-Myb transcription factor involved in controlling a broad variety of cellular processes. Recently, it has been shown that c-Myb may play a specific role in hard tissue formation; however, all of these results were gathered from an analysis of intramembranous ossification. To investigate a possible role of c-Myb in endochondral ossification, we carried out our study on the long bones of mouse limbs during embryonic development. Firstly, the c-myb expression pattern was analyzed by in situ hybridization during endochondral ossification of long bones. c-myb positive areas were found in proliferating as well as hypertrophic zones of the growth plate. At early embryonic stages, localized expression was also observed in the perichondrium and interdigital areas. The c-Myb protein was found in proliferating chondrocytes and in the perichondrium of the forelimb bones (E14.5-E17.5). Furthermore, protein was detected in pre-hypertrophic as well as hypertrophic chondrocytes. Gain-of-function and loss-of-function approaches were used to test the effect of altered c-myb expression on chondrogenesis in micromass cultures established from forelimb buds of mouse embryos. A loss-of-function approach using c-myb specific siRNA decreased nodule formation, as well as downregulated the level of Sox9 expression, a major marker of chondrogenesis. Transient c-myb overexpression markedly increased the formation of cartilage nodules and the production of extracellular matrix as detected by intense staining with Alcian blue. Moreover, the expression of early chondrogenic genes such as Sox9, Col2a1 and activity of a Col2-LUC reporter were increased in the cells overexpressing c-myb while late chondrogenic markers such as Col10a1 and Mmp13 were not significantly changed or were downregulated. Taken together, the results of this study demonstrate that the c-Myb transcription factor is involved in the regulation and promotion of endochondral bone formation.
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Affiliation(s)
- V Oralová
- Institute of Animal Physiology and Genetics CAS, v.v.i., Brno, Czech Republic; Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic.
| | - E Matalová
- Institute of Animal Physiology and Genetics CAS, v.v.i., Brno, Czech Republic; Department of Physiology, University of Veterinary and Pharmaceutical Sciences, Brno, Czech Republic
| | - E Janečková
- Institute of Animal Physiology and Genetics CAS, v.v.i., Brno, Czech Republic; Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - E Drobná Krejčí
- Institute of Anatomy, Charles University, Prague, Czech Republic
| | - L Knopfová
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - P Šnajdr
- Institute of Anatomy, Charles University, Prague, Czech Republic
| | - A S Tucker
- Department of Craniofacial Development and Stem Cell Biology, King's College London, London, UK
| | - I Veselá
- Department of Anatomy, Histology and Embryology, University of Veterinary and Pharmaceutical Sciences, Brno, Czech Republic
| | - J Šmarda
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - M Buchtová
- Institute of Animal Physiology and Genetics CAS, v.v.i., Brno, Czech Republic; Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
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Chromatin methylation and cardiovascular aging. J Mol Cell Cardiol 2015; 83:21-31. [DOI: 10.1016/j.yjmcc.2015.02.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 01/20/2015] [Accepted: 02/12/2015] [Indexed: 12/26/2022]
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Veselá B, Svandová E, Smarda J, Matalová E. Mybs in mouse hair follicle development. Tissue Cell 2014; 46:352-5. [PMID: 25064514 DOI: 10.1016/j.tice.2014.06.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Revised: 05/23/2014] [Accepted: 06/18/2014] [Indexed: 11/18/2022]
Abstract
The Myb transcription factors are involved in essential cellular processes, such as cell proliferation, differentiation and cell death. Biological functions carried out by specific Myb proteins are distinct. Hair follicles are ectodermal-derived organs with cycling character of the growth resulting from the presence of somatic stem cells. In this study, we followed the expression of the Myb proteins in developing hair follicles and in the hair follicle stem cell niche by immunofluorescence staining. During hair follicle development, B-Myb was present in a few cells located in the area of cell division; c-Myb was abundant postanally in dividing cells but also in keratinizing zone. In addition, c-Myb was also detected in cells under the hair follicle bulge. These findings indicate possible involvement of c-Myb in regulation of activated stem cells leaving the niche.
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Affiliation(s)
- B Veselá
- Institute of Animal Physiology and Genetics CAS, v.v.i., Brno, Czech Republic; Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic.
| | - E Svandová
- Institute of Animal Physiology and Genetics CAS, v.v.i., Brno, Czech Republic; Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - J Smarda
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - E Matalová
- Institute of Animal Physiology and Genetics CAS, v.v.i., Brno, Czech Republic; Department of Physiology, University of Veterinary and Pharmaceutical Sciences, Brno, Czech Republic
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Causes and Consequences of Age-Related Changes in DNA Methylation: A Role for ROS? BIOLOGY 2014; 3:403-25. [PMID: 24945102 PMCID: PMC4085615 DOI: 10.3390/biology3020403] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Revised: 05/28/2014] [Accepted: 05/31/2014] [Indexed: 01/15/2023]
Abstract
Recent genome-wide analysis of C-phosphate-G (CpG) sites has shown that the DNA methylome changes with increasing age, giving rise to genome-wide hypomethylation with site‑specific incidences of hypermethylation. This notion has received a lot of attention, as it potentially explains why aged organisms generally have a higher risk of age-related diseases. However, very little is known about the mechanisms that could cause the occurrence of these changes. Moreover, there does not appear to be a clear link between popular theories of aging and alterations in the methylome. Some of the most fruitful of these theories attribute an important role to reactive oxygen species, which seem to be responsible for an increase in oxidative damage to macromolecules, such as DNA, during the lifetime of an organism. In this review, the connection between changes in DNA methylation and these reactive oxygen species is discussed, as well as the effect of these changes on health. Deeper insights into the nature, causes and consequences of the aging methylome might provide a deeper understanding of the molecular mechanisms of aging and eventually contribute to the development of new diagnostic and therapeutic tools.
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Heyn H, Moran S, Esteller M. Aberrant DNA methylation profiles in the premature aging disorders Hutchinson-Gilford Progeria and Werner syndrome. Epigenetics 2012; 8:28-33. [PMID: 23257959 PMCID: PMC3549877 DOI: 10.4161/epi.23366] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
DNA methylation gradiently changes with age and is likely to be involved in aging-related processes with subsequent phenotype changes and increased susceptibility to certain diseases. The Hutchinson-Gilford Progeria (HGP) and Werner Syndrome (WS) are two premature aging diseases showing features of common natural aging early in life. Mutations in the LMNA and WRN genes were associated to disease onset; however, for a subset of patients the underlying causative mechanisms remain elusive. We aimed to evaluate the role of epigenetic alteration on premature aging diseases by performing comprehensive DNA methylation profiling of HGP and WS patients. We observed profound changes in the DNA methylation landscapes of WRN and LMNA mutant patients, which were narrowed down to a set of aging related genes and processes. Although of low overall variance, non-mutant patients revealed differential DNA methylation at distinct loci. Hence, we propose DNA methylation to have an impact on premature aging diseases.
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Affiliation(s)
- Holger Heyn
- Cancer Epigenetics and Biology Program (PEBC), Bellvitge Biomedical Research Institute (IDIBELL), Barcelona, Catalonia, Spain
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Lungova V, Buchtova M, Janeckova E, Tucker AS, Knopfova L, Smarda J, Matalova E. Localization of c-MYB in differentiated cells during postnatal molar and alveolar bone development. Eur J Oral Sci 2012; 120:495-504. [DOI: 10.1111/j.1600-0722.2012.01004.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/01/2012] [Indexed: 12/12/2022]
Affiliation(s)
| | | | | | - Abigail S. Tucker
- Department of Craniofacial Development and Stem Cell Biology, and Department of Orthodontics; KCL; London; UK
| | - Lucia Knopfova
- Department of Experimental Biology; Faculty of Science; Masaryk University; Brno; Czech Republic
| | - Jan Smarda
- Department of Experimental Biology; Faculty of Science; Masaryk University; Brno; Czech Republic
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Bhattarai G, Lee YH, Lee NH, Yun JS, Hwang PH, Yi HK. c-myb mediates inflammatory reaction against oxidative stress in human breast cancer cell line, MCF-7. Cell Biochem Funct 2011; 29:686-93. [DOI: 10.1002/cbf.1808] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Revised: 08/15/2011] [Accepted: 08/24/2011] [Indexed: 12/23/2022]
Affiliation(s)
- Govinda Bhattarai
- Department of Oral Biochemistry, Institute of Oral-Bio Science and BK21 Program; School of Dentistry, Chonbuk National University; Joenju; Korea
| | - Young-Hee Lee
- Department of Oral Biochemistry, Institute of Oral-Bio Science and BK21 Program; School of Dentistry, Chonbuk National University; Joenju; Korea
| | - Nan-Hee Lee
- Department of Oral Biochemistry, Institute of Oral-Bio Science and BK21 Program; School of Dentistry, Chonbuk National University; Joenju; Korea
| | - Ji-Soo Yun
- Molecular Science and Technology Research Center; Ajou University; Suwon; Korea
| | - Pyoung-Han Hwang
- Department of Pediatrics; Chonbuk National Medical School, Chonbuk National University; Joenju; Korea
| | - Ho-Keun Yi
- Department of Oral Biochemistry, Institute of Oral-Bio Science and BK21 Program; School of Dentistry, Chonbuk National University; Joenju; Korea
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Matalová E, Buchtová M, Tucker AS, Bender TP, Janečková E, Lungová V, Balková S, Smarda J. Expression and characterization of c-Myb in prenatal odontogenesis. Dev Growth Differ 2011; 53:793-803. [PMID: 21762405 DOI: 10.1111/j.1440-169x.2011.01287.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The transcription factor c-Myb is involved in the control of cell proliferation, survival and differentiation. As these processes accompany the morphogenesis of developing teeth, this work investigates the possible role of c-Myb during odontogenesis. Analysis of the expression of c-Myb in the monophyodont mouse was followed by similar analysis in a diphyodont species, the pig, which has a dentition more closely resembling that of the human. The distribution of c-Myb was correlated with the pattern of proliferation and apoptosis and the tooth phenotype of c-Myb mutant mice was also assessed. In the mouse, c-Myb expression was detected throughout prenatal development of the first molar tooth. Negative temporospatial correlation was found between c-Myb expression and apoptosis, while c-Myb expression positively correlated with proliferation. c-Myb-positive cells, however, were more abundant than the proliferating cell nuclear antigen positive cells, suggesting other roles of c-Myb in odontogenesis. In the minipig, in contrast to the mouse, there was an asymmetrical arrangement of c-Myb positive cells, with a higher presence on the labial side of the tooth germ and dental lamina. A cluster of negative cells was situated in the mesenchyme close to the tooth bud. At later stages, the number of positive cells decreased and these cells were situated in the upper part of the dental papilla in the areas of future cusp formation. The expression of c-Myb in both species was strong in the odontoblasts and ameloblasts at the stage of dentin and enamel production suggesting a possible novel role of c-Myb during tooth mineralization.
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Affiliation(s)
- Eva Matalová
- Institute of Animal Physiology and Genetics, v.v.i., Academy of Sciences of the Czech Republic.
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c-myb has a character of oxidative stress resistance in aged human diploid fibroblasts: regulates SAPK/JNK and Hsp60 pathway consequently. Biogerontology 2009; 11:267-74. [PMID: 19707884 DOI: 10.1007/s10522-009-9244-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2009] [Accepted: 08/13/2009] [Indexed: 01/26/2023]
Abstract
This study examined whether c-myb acts as a survival molecule in aged cells. A previous in vitro ageing model suggested that aged cells have a higher cell capacity for survival after exposure to oxidative stress, which involves blockage of the translocation of Hsp60 from the mitochondria to the cytoplasm followed by SAPK/JNK inactivation, than young cells. In human diploid fibroblasts (HDFs), c-myb expression increased gradually with ageing, and this increase had a significant influence on the cell survival capacity after exposure to oxidative stress. To clarify the role of c-myb in oxidative stress, young cells under 21 passages, which lacked c-myb expression, were transfected with adenovirus-mediated c-myb for express c-myb. These c-myb-over-expressed young cells showed increased cell viability upon exposure to oxidative stress to a similar extent to that of the aged cells. In addition, these c-myb-over-expressed young cells did not exhibit SAPK/JNK activation, Hsp60 displacement and cytochrome C release, as was observed in aged cells. The aged cells that had c-myb suppressed using siRNA c-myb showed reduced cell viability and increased apoptosis in a manner to that observed in young cells. From this study, c-myb blocked SAPK/JNK and Hsp60 translocation upon exposure to oxidative stress. This result suggests that c-myb might act as a modulator of cell survival in the ageing process by suppressing apoptosis in aged cells.
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Comparison of ionized calcium-binding adapter molecule 1 immunoreactivity of the hippocampal dentate gyrus and CA1 region in adult and aged dogs. Neurochem Res 2008; 33:1309-15. [PMID: 18270819 DOI: 10.1007/s11064-007-9584-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2007] [Accepted: 12/27/2007] [Indexed: 10/22/2022]
Abstract
Similarities between age-related changes in the canine and human brain have resulted in the general acceptance of the canine brain as a model of human brain aging. The hippocampus is essentially required for intact cognitive ability and appears to be particularly vulnerable to the aging process. We observed changes in ionized calcium-binding adapter molecule 1 (Iba-1, a microglial marker) immunoreactivity and protein levels in the hippocampal dentate gyrus and CA1 region of adult (2-3 years) and aged (10-12 years) dogs. We also observed the interferon-gamma (IFN-gamma), a pro-inflammatory cytokine, protein levels in these groups. In the dentate gyrus and CA1 region of the adult dog, Iba-1 immunoreactive microglia were well distributed and their processes were highly ramified. However, in the aged dog, the processes of Iba-1 immunoreactive microglia were hypertrophied in the dentate gyrus. Moreover, Iba-1 protein level in the dentate gyrus in the aged dog was higher than in the adult dog. IFN-gamma expression was increased in the dentate gyrus homogenates of aged dogs than adult dogs. In addition, we found that some neurons were positive to Fluoro-Jade B (a marker for neuronal degeneration) in the dentate polymorphic layer, but not in the hippocampal CA1 region in the aged dog. These results suggest that Iba-1 immunoreactive microglia are hypertrophied in the dentate gyrus in the aged dog.
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