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Gado M, Baschant U, Hofbauer LC, Henneicke H. Bad to the Bone: The Effects of Therapeutic Glucocorticoids on Osteoblasts and Osteocytes. Front Endocrinol (Lausanne) 2022; 13:835720. [PMID: 35432217 PMCID: PMC9008133 DOI: 10.3389/fendo.2022.835720] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Accepted: 02/10/2022] [Indexed: 02/06/2023] Open
Abstract
Despite the continued development of specialized immunosuppressive therapies in the form of monoclonal antibodies, glucocorticoids remain a mainstay in the treatment of rheumatological and auto-inflammatory disorders. Therapeutic glucocorticoids are unmatched in the breadth of their immunosuppressive properties and deliver their anti-inflammatory effects at unparalleled speed. However, long-term exposure to therapeutic doses of glucocorticoids decreases bone mass and increases the risk of fractures - particularly in the spine - thus limiting their clinical use. Due to the abundant expression of glucocorticoid receptors across all skeletal cell populations and their respective progenitors, therapeutic glucocorticoids affect skeletal quality through a plethora of cellular targets and molecular mechanisms. However, recent evidence from rodent studies, supported by clinical data, highlights the considerable role of cells of the osteoblast lineage in the pathogenesis of glucocorticoid-induced osteoporosis: it is now appreciated that cells of the osteoblast lineage are key targets of therapeutic glucocorticoids and have an outsized role in mediating their undesirable skeletal effects. As part of this article, we review the molecular mechanisms underpinning the detrimental effects of supraphysiological levels of glucocorticoids on cells of the osteoblast lineage including osteocytes and highlight the clinical implications of recent discoveries in the field.
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Affiliation(s)
- Manuel Gado
- Center for Regenerative Therapies TU Dresden, Technische Universität Dresden, Dresden, Germany
| | - Ulrike Baschant
- Department of Medicine III, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- Center for Healthy Aging, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Lorenz C. Hofbauer
- Center for Regenerative Therapies TU Dresden, Technische Universität Dresden, Dresden, Germany
- Department of Medicine III, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- Center for Healthy Aging, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Holger Henneicke
- Center for Regenerative Therapies TU Dresden, Technische Universität Dresden, Dresden, Germany
- Department of Medicine III, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- Center for Healthy Aging, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- *Correspondence: Holger Henneicke,
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Dos-Santos ALA, Dick CF, Lopes LR, Rocco-Machado N, Muzi-Filho H, Freitas-Mesquita AL, Paes-Vieira L, Vieyra A, Meyer-Fernandes JR. Tartrate-resistant phosphatase type 5 in Trypanosoma cruzi is important for resistance to oxidative stress promoted by hydrogen peroxide. Exp Parasitol 2019; 205:107748. [PMID: 31442453 DOI: 10.1016/j.exppara.2019.107748] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 08/01/2019] [Accepted: 08/19/2019] [Indexed: 11/28/2022]
Abstract
Trypanosoma cruzi (the causative agent of Chagas disease) presents a complex life cycle that involves adaptations in vertebrate and invertebrate hosts. As a protozoan parasite of hematophagous insects and mammalian hosts, T. cruzi is exposed to reactive oxygen species (ROS). To investigate the functionality of T. cruzi tartrate-resistant acid phosphatase type 5 (TcACP5), we cloned, superexpressed and purified the enzyme. Purified TcACP5 exhibited a Vmax and apparent Km for pNPP hydrolysis of 7.7 ± 0.2 nmol pNP × μg-1 × h-1 and 169.3 ± 22.6 μM, respectively. The pH dependence was characterized by sharp maximal activity at pH 5.0, and inhibition assays demonstrated its sensitivity to acid phosphatase inhibitors. Similar activities were obtained with saturating concentrations of P-Ser and P-Thr as substrates. The enzyme metabolizes hydrogen peroxide (H2O2) in vitro, and parasites superexpressing this enzyme were more resistant to oxidative stress promoted by H2O2. Taken together, these results suggest that TcACP5 plays a central role in phosphoryl transfer and redox reactions.
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Affiliation(s)
- André L A Dos-Santos
- Leopoldo De Meis Medical Biochemistry Institute, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; National Institute of Science and Technology for Structural Biology and Bioimaging (INBEB), Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Claudia F Dick
- Leopoldo De Meis Medical Biochemistry Institute, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; Carlos Chagas Filho Biophysics Institute, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; National Institute of Science and Technology for Structural Biology and Bioimaging (INBEB), Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Leandro R Lopes
- Leopoldo De Meis Medical Biochemistry Institute, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; Paulo de Góes Microbiology Institute, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; National Institute of Science and Technology for Structural Biology and Bioimaging (INBEB), Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Nathália Rocco-Machado
- Leopoldo De Meis Medical Biochemistry Institute, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; National Institute of Science and Technology for Structural Biology and Bioimaging (INBEB), Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Humberto Muzi-Filho
- Carlos Chagas Filho Biophysics Institute, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; National Center for Structural Biology and Bioimaging (CENABIO), Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Anita L Freitas-Mesquita
- Leopoldo De Meis Medical Biochemistry Institute, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; National Institute of Science and Technology for Structural Biology and Bioimaging (INBEB), Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Lisvane Paes-Vieira
- Leopoldo De Meis Medical Biochemistry Institute, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; National Institute of Science and Technology for Structural Biology and Bioimaging (INBEB), Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Adalberto Vieyra
- Carlos Chagas Filho Biophysics Institute, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; National Center for Structural Biology and Bioimaging (CENABIO), Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; Graduate Program in Translational Biomedicine, Grande Rio University, Duque de Caxias, Brazil
| | - José Roberto Meyer-Fernandes
- Leopoldo De Meis Medical Biochemistry Institute, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; National Institute of Science and Technology for Structural Biology and Bioimaging (INBEB), Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
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Diao F, Chen K, Wang Y, Li Y, Xu W, Lu J, Chen YX. Involvement of small G protein RhoB in the regulation of proliferation, adhesion and migration by dexamethasone in osteoblastic cells. PLoS One 2017; 12:e0174273. [PMID: 28323887 PMCID: PMC5360316 DOI: 10.1371/journal.pone.0174273] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Accepted: 03/06/2017] [Indexed: 12/02/2022] Open
Abstract
Long-term exposure to therapeutic doses of glucocorticoids (GCs) results in bone remodeling, which frequently causes osteoporosis and fracture healing retardation because of the abnormality of osteoblastic proliferation and differentiation. The mechanisms of GCs’ effect on osteoblasts are largely unknown. In this present study, we found that dexamethasone (Dex) could induce the expression of the small G protein, RhoB, in mRNA and protein levels in the osteoblast-derived osteosarcoma cell lines MG-63. The up-regulation of RhoB mRNA by Dex mainly occurs at posttranscriptional level by increasing its mRNA stability through PI-3K/Akt and p38 mitogen-activated protein kinase signaling pathways. Over-expression of RhoB in MG-63 cells magnified while down-regulation of RhoB level by RNA interference impaired Dex-induced growth inhibition but not differentiation. What’s more, over-expression of RhoB mimicked the effect of Dex on cell adhesion and migration. And interfering RhoB expression partially suppressed Dex-induced pro-adhesion and anti-migration in MG-63 cells. In conclusion, these results indicate that RhoB plays an important role in the pathological effect of Dex on osteoblastic growth and migration, which is a part of the mechanisms of GCs’ adverse effect on bone remodeling.
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Affiliation(s)
- Fei Diao
- Department of Pathophysiology, Second Military Medical University, Shanghai, China
| | - Kangyao Chen
- Department of Orthopedics, Changhai Hospital affiliated to Second Military Medical University, Shanghai, China
- Department of -Orthopedics, Fuzhou Second Hospital affiliated to Xiamen University, Fuzhou, Fujian Province, China
| | - Yan Wang
- Department of Pathophysiology, Second Military Medical University, Shanghai, China
| | - Yidong Li
- Department of Pathophysiology, Second Military Medical University, Shanghai, China
| | - Weidong Xu
- Department of Orthopedics, Changhai Hospital affiliated to Second Military Medical University, Shanghai, China
| | - Jian Lu
- Department of Pathophysiology, Second Military Medical University, Shanghai, China
- * E-mail: (JL); (YXC)
| | - Yu-Xia Chen
- Department of Pathophysiology, Second Military Medical University, Shanghai, China
- * E-mail: (JL); (YXC)
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Frenkel B, White W, Tuckermann J. Glucocorticoid-Induced Osteoporosis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015. [PMID: 26215995 DOI: 10.1007/978-1-4939-2895-8_8] [Citation(s) in RCA: 100] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Osteoporosis is among the most devastating side effects of glucocorticoid (GC) therapy for the management of inflammatory and auto-immune diseases. Evidence from both humans and mice indicate deleterious skeletal effects within weeks of pharmacological GC administration, both related and unrelated to a decrease in bone mineral density (BMD). Osteoclast numbers and bone resorption are also rapidly increased, and together with osteoblast inactivation and decreased bone formation, these changes lead the fastest loss in BMD during the initial disease phase. Bone resorption then decreases to sub-physiological levels, but persistent and severe inhibition of bone formation leads to further bone loss and progressively increased fracture risk, up to an order of magnitude higher than that observed in untreated individuals. Bone forming osteoblasts are thus considered the main culprits in GC-induced osteoporosis (GIO). Accordingly, we focus this review primarily on deleterious effects on osteoblasts: inhibition of cell replication and function and acceleration of apoptosis. Mediating these adverse effects, GCs target pivotal regulatory mechanisms that govern osteoblast growth, differentiation and survival. Specifically, GCs inhibit growth factor pathways, including Insulin Growth Factors, Growth Hormone, Hepatocyte Growth/Scatter Factor and IL6-type cytokines. They also inhibit downstream kinases, including PI3-kinase and the MAP kinase ERK, the latter attributable in part to direct transcriptional stimulation of MAP kinase phosphatase 1. Most importantly, however, GCs inhibit the Wnt signaling pathway, which plays a pivotal role in osteoblast replication, function and survival. They transcriptionally stimulate expression of Wnt inhibitors of both the Dkk and Sfrp families, and they induce reactive oxygen species (ROS), which result in loss of ß-catenin to ROS-activated FoxO transcription factors. Identification of dissociated GCs, which would suppress the immune system without causing osteoporosis, is proving more challenging than initially thought, and GIO is currently managed by co-treatment with bisphosphonates or PTH. These drugs, however, are not ideally suited for GIO. Future therapeutic approaches may aim at GC targets such as those mentioned above, or newly identified targets including the Notch pathway, the AP-1/Il11 axis and the osteoblast master regulator RUNX2.
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Affiliation(s)
- Baruch Frenkel
- Department of Orthopaedic Surgery, Keck School of Medicine, Institute for Genetic Medicine, University of Southern California, 2250 Alcazar Street, CSC-240, Los Angeles, CA, 90033, USA,
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Liu C, Wang X, Zhang H, Xie X, Liu P, Liu Y, Jani PH, Lu Y, Chen S, Qin C. Immortalized Mouse Floxed Fam20c Dental Papillar Mesenchymal and Osteoblast Cell Lines Retain Their Primary Characteristics. J Cell Physiol 2015; 230:2581-7. [PMID: 25833681 DOI: 10.1002/jcp.25008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 03/30/2015] [Indexed: 12/18/2022]
Abstract
Fam20c is essential for the normal mineralization of dentin and bone. The generation of odontoblast and osteoblast cell lines carrying floxed Fam20c allele can offer valuable tools for the study of the roles of Fam20c in the mineralization of dentin and bone. The limited capability of the primary odontoblasts and osteoblasts to proliferate necessitates the development of odontoblast and osteoblast cell lines serving as substitutes for the study of differentiation and mineralization of the odontoblasts and osteoblasts. In this study, we established and characterized immortalized mouse floxed Fam20c dental papilla mesenchymal and osteoblast cell lines. The isolated primary mouse floxed Fam20c dental papilla mesenchymal cells and osteoblasts were immortalized by the infection of lentivirus containing Simian Virus 40 T-antigen (SV40 T-Ag). The immortalization of floxed Fam20c dental papilla mesenchymal cells and osteoblasts was verified by the long-term passages and genomic integration of SV40 T-Ag. The immortalized floxed Fam20c dental papilla mesenchymal and osteoblast cell lines not only proliferated at a high rate and retained the morphology of their primary counterparts, but also preserved the dentin and bone specific gene expression as the primary dental papilla mesenchymal cells and osteoblasts did. Consistently, the capability of the primary floxed Fam20c dental papilla mesenchymal cells and osteoblasts to mineralize was also inherited by the immortalized dental papilla mesenchymal and osteoblast cell lines. Thus, we have successfully generated the immortalized mouse floxed Fam20c dental papilla mesenchymal and osteoblast cell lines.
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Affiliation(s)
- Chao Liu
- Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry, Dallas, Texas
| | - Xiaofang Wang
- Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry, Dallas, Texas
| | - Hua Zhang
- Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry, Dallas, Texas
| | - Xiaohua Xie
- Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry, Dallas, Texas.,Department of Endodontics, The Institute of Hard Tissue Development and Regeneration, the 2nd Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Peihong Liu
- Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry, Dallas, Texas.,Department of Periodontics, Harbin Medical University School of Stomatology, Harbin, China
| | - Ying Liu
- Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry, Dallas, Texas
| | - Priyam H Jani
- Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry, Dallas, Texas
| | - Yongbo Lu
- Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry, Dallas, Texas
| | - Shuo Chen
- Department of Pediatric Dentistry, Dental School, The University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - Chunlin Qin
- Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry, Dallas, Texas
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Sanderson M, Sadie-Van Gijsen H, Hough S, Ferris WF. The Role of MKP-1 in the Anti-Proliferative Effects of Glucocorticoids in Primary Rat Pre-Osteoblasts. PLoS One 2015; 10:e0135358. [PMID: 26263165 PMCID: PMC4532462 DOI: 10.1371/journal.pone.0135358] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Accepted: 07/21/2015] [Indexed: 12/04/2022] Open
Abstract
Glucocorticoid (GC)-induced osteoporosis has been attributed to a GC-induced suppression of pre-osteoblast proliferation. Our previous work identified a critical role for mitogen-activated protein kinase (MAPK) phosphatase-1 (MKP-1) in mediating the anti-proliferative effects of GCs in immortalized pre-osteoblasts, but we subsequently found that MKP-1 null mice were not protected against the pathological effects of GCs on bone. In order to reconcile this discrepancy, we have assessed the effects of GCs on proliferation, activation of the MAPK ERK1/2 and MKP-1 expression in primary adipose-derived stromal cells (ADSCs) and ADSC-derived pre-osteoblasts (ADSC-OBs). ADSCs were isolated by means of collagenase digestion from adipose tissue biopsies harvested from adult male Wistar rats. ADSC-OBs were prepared by treating ADSCs with osteoblast differentiation media for 7 days. The effects of increasing concentrations of the GC dexamethasone on basal and mitogen-stimulated cell proliferation were quantified by tritiated thymidine incorporation. ERK1/2 activity was measured by Western blotting, while MKP-1 expression was quantified on both RNA and protein levels, using semi-quantitative real-time PCR and Western blotting, respectively. GCs were strongly anti-proliferative in both naïve ADSCs and ADSC-OBs, but had very little effect on mitogen-induced ERK1/2 activation and did not upregulate MKP-1 protein expression. These findings suggest that the anti-proliferative effects of GCs in primary ADSCs and ADSC-OBs in vitro do not require the inhibition of ERK1/2 activation by MKP-1, which is consistent with our in vivo findings in MKP-1 null mice.
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Affiliation(s)
- Micheline Sanderson
- Division of Endocrinology, Department of Medicine, Faculty of Medicine and Health Sciences, Stellenbosch University Tygerberg Campus, Parow, South Africa
| | - Hanél Sadie-Van Gijsen
- Division of Endocrinology, Department of Medicine, Faculty of Medicine and Health Sciences, Stellenbosch University Tygerberg Campus, Parow, South Africa
| | - Stephen Hough
- Division of Endocrinology, Department of Medicine, Faculty of Medicine and Health Sciences, Stellenbosch University Tygerberg Campus, Parow, South Africa
| | - William F. Ferris
- Division of Endocrinology, Department of Medicine, Faculty of Medicine and Health Sciences, Stellenbosch University Tygerberg Campus, Parow, South Africa
- * E-mail:
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Jain A, Wordinger RJ, Yorio T, Clark AF. Role of the alternatively spliced glucocorticoid receptor isoform GRβ in steroid responsiveness and glaucoma. J Ocul Pharmacol Ther 2014; 30:121-7. [PMID: 24506296 DOI: 10.1089/jop.2013.0239] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Glucocorticoid (GC)-induced ocular hypertension (OHT) is a serious side effect of GC therapy in susceptible individuals. This OHT is due to increased aqueous humor (AH) outflow resistance in the trabecular meshwork (TM) caused by GC-mediated changes in TM structure and function. GCs may also play a role in the development of primary open-angle glaucoma (POAG). Elevated cortisol levels in the AH or enhanced GC sensitivity may be one of the reasons for elevated intraocular pressure in POAG patients. The GC OHT responder population is at greater risk of developing POAG compared with non-responders. We recently have gained insight into the molecular mechanisms responsible for this differential GC responsiveness, which is attributed to differences in GC receptor isoform expression in the TM. This article summarizes current knowledge on alternative GC receptor splicing to generate GC receptor alpha (GRα) and GRβ and their roles in the regulation of GC responsiveness in normal and glaucoma TM.
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Affiliation(s)
- Ankur Jain
- 1 Department of Cell Biology and Immunology, University of North Texas Health Science Center , Fort Worth, Texas
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Abstract
Glucocorticoids (GCs) are frequently prescribed pharmacological agents most notably for their immunosuppressive effects. Endogenous GCs mediate biological processes such as energy metabolism and tissue development. At the cellular level, GCs bind to the glucocorticoid receptor (GR), a cytosolic protein that translocates to the nuclei and functions to alter transcription upon ligand binding. Among a long list of genes activated by GCs is the glucocorticoid-induced leucine zipper (GILZ). GC-induced GILZ expression has been well established in lymphocytes and mediates GC-induced apoptosis. Unlike lymphocytes, cardiomyocytes respond to GCs by gaining resistance against apoptosis. We determined GILZ expression in cardiomyocytes in vivo and in vitro. Expression of GILZ in mouse hearts as a result of GC administration was confirmed by Western blot analyses. GCs induced dose- and time-dependent elevation of GILZ expression in primary cultured rat cardiomyocytes, with dexamethasone (Dex) as low as 0.1 μM being effective. Time course analysis indicated that GILZ protein levels increased at 8 h and peaked at 48 h after exposure to 1 μM Dex. H9c2(2-1) cell line showed a similar response of GILZ induction by Dex as primary cultured rat cardiomyocytes, providing a convenient model for studying the biological significance of GILZ expression. With corticosterone (CT), an endogenous form of corticosteroids in rodents, 0.1-2.5 μM was found to induce GILZ in H9c2(2-1) cells. Time course analysis with 1 μM CT indicated induction of GILZ at 6 h with peak expression at 18 h. Inhibition of the GR by mifepristone led to blunting of GILZ induction by GCs. Our data demonstrate GILZ induction in cardiomyocytes both in vivo and in vitro by GCs, pointing to H9c2(2-1) cells as a valid model for studying the biological function of GILZ in cardiomyocytes.
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Ma Y, Nyman JS, Tao H, Moss HH, Yang X, Elefteriou F. β2-Adrenergic receptor signaling in osteoblasts contributes to the catabolic effect of glucocorticoids on bone. Endocrinology 2011; 152:1412-22. [PMID: 21266510 PMCID: PMC3060633 DOI: 10.1210/en.2010-0881] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The sympathetic nervous system is a physiological regulator of bone homeostasis. Autonomic nerves are indeed present in bone, bone cells express the β2-adrenergic receptors (β2AR), and pharmacological or genetic disruption of sympathetic outflow to bone induces bone gain in rodents. These recent findings implied that conditions that affect β2AR signaling in osteoblasts and/or sympathetic drive to bone may contribute to bone diseases. In this study, we show that dexamethasone stimulates the expression of the β2AR in differentiated primary calvarial osteoblasts, as measured by an increase in Adrβ2 mRNA and β2AR protein level after short-term dexamethasone treatment. Isoproterenol-induced cAMP accumulation and the expression of the β2AR target gene Rankl were also significantly increased after dexamethasone pretreatment, indicating that dexamethasone promotes the responsiveness of differentiated osteoblasts to adrenergic stimulation. These in vitro results led to the hypothesis that glucocorticoid-induced bone loss, provoked by increased endogenous or high-dose exogenous glucocorticoids given for the treatment of inflammatory diseases, might, at least in part, be mediated by increased sensitivity of bone-forming cells to the tonic inhibitory effect of sympathetic nerves on bone formation or their stimulatory effect on bone resorption. Supporting this hypothesis, both pharmacological and genetic β2AR blockade in mice significantly reduced the bone catabolic effect of high-dose prednisolone in vivo. This study emphasizes the importance of sympathetic nerves in the regulation of bone homeostasis and indicates that this neuroskeletal signaling axis can be modulated by hormones or drugs and contribute to enhance pathological bone loss.
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Affiliation(s)
- Yun Ma
- Department of Medicine, Vanderbilt University, 2215 Garland Avenue, MRB IV, Room 1225E, Nashville, Tennessee 37232-0575, USA
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Diefenbacher M, Sekula S, Heilbock C, Maier JV, Litfin M, van Dam H, Castellazzi M, Herrlich P, Kassel O. Restriction to Fos family members of Trip6-dependent coactivation and glucocorticoid receptor-dependent trans-repression of activator protein-1. Mol Endocrinol 2008; 22:1767-80. [PMID: 18535250 DOI: 10.1210/me.2007-0574] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The term activator protein (AP)-1 describes homodimeric and heterodimeric transcription factors composed of members of the Jun, Fos, and cAMP response element-binding protein (CREB)/activating transcription factor (ATF) families of proteins. Distinct AP-1 dimers, for instance the prototypical c-Jun:c-Fos and c-Jun:ATF2 dimers, are differentially regulated by signaling pathways and bind related yet distinct response elements in the regulatory regions of AP-1 target genes. Little is known about the dimer-specific regulation of AP-1 activity at the promoter of its target genes. We have previously shown that nTrip6, the nuclear isoform of the LIM domain protein Trip6, acts as an AP-1 coactivator. Moreover, nTrip6 is an essential component of glucocorticoid receptor (GR)-mediated trans-repression of AP-1, in that it mediates the tethering of GR to the promoter-bound AP-1. We have now discovered a striking specificity of nTrip6 actions determined by the binding preference of its LIM domains. We show that nTrip6 interacts only with Fos family members. Consequently, nTrip6 is a selective coactivator for AP-1 dimers containing Fos. nTrip6 also assembles activated GR to c-Jun:c-Fos-driven promoters. Neither nTrip6 nor GR are recruited to a promoter occupied by c-Jun:ATF2. Thus, only Fos-containing dimers are trans-repressed by GR. Thus, the dimer composition of AP-1 determines the mechanism of both the positive and negative regulation of AP-1 transcriptional activity. Interestingly, on a second level of action, GR represses the increase in transcriptional activity of c-Jun:ATF2 induced by c-Jun N-terminal kinase (JNK)-dependent phosphorylation. This repression depends on GR-mediated induction of MAPK phosphatase 1 (MKP-1) expression, which results in c-Jun N-terminal kinase inactivation.
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Affiliation(s)
- Markus Diefenbacher
- Institut für Toxikologie und Genetik, Forschungszentrum Karlsruhe, Hermann-von-Helmholtz Platz 1, D- 76344 Eggenstein-Leopoldshafen, Germany
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Espina B, Liang M, Russell RGG, Hulley PA. Regulation of bim in glucocorticoid-mediated osteoblast apoptosis. J Cell Physiol 2008; 215:488-96. [PMID: 18064628 DOI: 10.1002/jcp.21335] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Osteoblasts undergo apoptosis both in vitro and in vivo in response to high dose glucocorticoid (GC) treatment. However, the molecular mechanisms remain elusive, hindering the prevention and treatment of this side-effect. Apoptosis was induced by dexamethasone (Dex) in murine MBA-15.4 osteoblasts within 24-48 h of treatment. We found dose- and time-dependent upregulation of Bim protein, a pro-apoptotic Bcl-2 family member, with highest levels at 24-48 h for 1 microM Dex. This was also observed in primary human bone marrow stromal cells. Bim is subjected to stringent transcriptional and post-translational regulation in osteoblasts. Bim mRNA was upregulated in response to 1 microM Dex; both cycloheximide and the GC receptor antagonist, RU486, prevented Dex-induction of Bim protein, indicating transcriptional regulation involving the GC receptor. The proteasome inhibitor, MG132, potently increased Bim protein levels. Bim was also upregulated in osteoblasts undergoing apoptosis in response to serum deprivation and matrix detachment. Gene silencing experiments show that short interference RNA (siRNA) specific for Bim or the downstream effector Bax both reduced apoptosis induced by Dex in osteoblastic cells. These findings suggest that Bim is a novel regulator of osteoblast apoptosis and may be a therapeutic target.
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Affiliation(s)
- B Espina
- The Botnar Research Centre, Oxford Institute of Musculoskeletal Sciences, Nuffield Department of Orthopaedic Surgery, Oxford, UK.
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Conradie MM, de Wet H, Kotze DDR, Burrin JM, Hough FS, Hulley PA. Vanadate prevents glucocorticoid-induced apoptosis of osteoblasts in vitro and osteocytes in vivo. J Endocrinol 2007; 195:229-40. [PMID: 17951534 PMCID: PMC2173947 DOI: 10.1677/joe-07-0217] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Skeletal mass is maintained by a balance between formation and resorption, cell proliferation and apoptosis. In vitro, glucocorticoids (GCs) decrease extracellular signal-regulated kinases (ERK) activation by mitogens, thus inhibiting osteoblast proliferation. Both ERK activity and proliferation are restored by co-treatment with the protein tyrosine phosphatase inhibitor, vanadate. Since ERK signalling may also be anti-apoptotic, we explored the effects of vanadate on GC-induced apoptosis in vitro and in vivo. Apoptosis in MBA-15.4 pre-osteoblasts increased from 6 h and remained up to eightfold higher through 6 days of 10(- 6) M dexamethasone (Dex) treatment. Co-incubation with 10(- 7) M vanadate markedly reduced apoptosis at all time points. Vanadate also prevented GC-induced poly-ADP-ribose polymerase cleavage. We assessed the transcriptional profiles of seven anti-apoptotic proteins (Bcl-2, Bcl-X(L), inhibitors of apoptosis protein-1 (IAP-1), IAP-2, X-linked IAP (XIAP), Fas-associated death-domain-like IL-1beta-converting enzyme-inhibitory protein (FLIP(Long)) and FLIP(Short)) in osteoblasts subjected to various stimuli using real-time quantitative PCR. Although these anti-apoptotic genes responded to different mitogenic conditions, Dex failed to repress their expression, and in fact significantly up-regulated Bcl-X(L), IAP-2 and XIAP. Dex may therefore induce apoptosis by up-regulating pro-apoptotic gene expression. We have previously demonstrated that rats treated with GC develop low formation osteoporosis (bone histomorphometry and DEXA) and skeletal fragility (breaking strength) that were largely prevented by co-treatment with vanadate. We report here that vertebrae from rats treated with 3.5 mg/kg per day methylprednisolone for 9 weeks showed increased incidence of terminal deoxynucleotidyl transferase-mediated biotin-dUTP nick end-labelling-positive apoptotic osteocytes, which was reduced by vanadate co-treatment. We conclude that vanadate prevents GC-induced apoptosis of pre-osteoblasts in vitro and osteocytes in vivo, and this may contribute to its bone-sparing effects in vivo.
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Affiliation(s)
- M M Conradie
- Division of Endocrinology and Metabolism, Department of Medicine, Faculty of Health Sciences, University of StellenboschTygerbergSouth Africa
| | - H de Wet
- Division of Endocrinology and Metabolism, Department of Medicine, Faculty of Health Sciences, University of StellenboschTygerbergSouth Africa
| | - D D R Kotze
- Division of Endocrinology and Metabolism, Department of Medicine, Faculty of Health Sciences, University of StellenboschTygerbergSouth Africa
| | - J M Burrin
- Department of Endocrinology, St Bart's Hospital, University of LondonLondonUK
| | - F S Hough
- Division of Endocrinology and Metabolism, Department of Medicine, Faculty of Health Sciences, University of StellenboschTygerbergSouth Africa
| | - P A Hulley
- Division of Endocrinology and Metabolism, Department of Medicine, Faculty of Health Sciences, University of StellenboschTygerbergSouth Africa
- Institute of Musculoskeletal Sciences, Botnar Research Centre, Nuffield Orthopaedic Centre, University of OxfordHeadington, Oxford OX3 7LDUK
- (Correspondence should be addressed to P A Hulley; )
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14
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Buse P, Maiyar AC, Failor KL, Tran S, Leong MLL, Firestone GL. The stimulus-dependent co-localization of serum- and glucocorticoid-regulated protein kinase (Sgk) and Erk/MAPK in mammary tumor cells involves the mutual interaction with the importin-alpha nuclear import protein. Exp Cell Res 2007; 313:3261-75. [PMID: 17692313 PMCID: PMC3422670 DOI: 10.1016/j.yexcr.2007.07.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2007] [Revised: 06/21/2007] [Accepted: 07/03/2007] [Indexed: 01/04/2023]
Abstract
In Con8 rat mammary epithelial tumor cells, indirect immunofluorescence revealed that Sgk (serum- and glucocorticoid-regulated kinase) and Erk/MAPK (extracellular signal-regulated protein kinase/mitogen activated protein kinase) co-localized to the nucleus in serum-treated cells and to the cytoplasmic compartment in cells treated with the synthetic glucocorticoid dexamethasone. Moreover, the subcellular distribution of the importin-alpha nuclear transport protein was similarly regulated in a signal-dependent manner. In vitro GST-pull down assays revealed the direct interaction of importin-alpha with either Sgk or Erk/MAPK, while RNA interference knockdown of importin-alpha expression disrupted the localization of both Sgk and Erk into the nucleus of serum-treated cells. Wild type or kinase dead forms of Sgk co-immunoprecipitated with Erk/MAPK from either serum- or dexamethasone-treated mammary tumor cells, suggesting the existence of a protein complex containing both kinases. In serum-treated cells, nucleus residing Sgk and Erk/MAPK were both hyperphosphorylated, indicative of their active states, whereas, in dexamethasone-treated cells Erk/MAPK, but not Sgk, was in its inactive hypophosphorylated state. Treatment with a MEK inhibitor, which inactivates Erk/MAPK, caused the relocalization of both Sgk and ERK to the cytoplasm. We therefore propose that the signal-dependent co-localization of Sgk and Erk/MAPK mediated by importin-alpha represents a new pathway of signal integration between steroid and serum/growth factor-regulated pathways.
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Affiliation(s)
- Patricia Buse
- Department of Molecular and Cell Biology and The Cancer Research Laboratory, University of California at Berkeley, Berkeley, CA 94720-3200, USA
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15
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Horsch K, de Wet H, Schuurmans MM, Allie-Reid F, Cato ACB, Cunningham J, Burrin JM, Hough FS, Hulley PA. Mitogen-activated protein kinase phosphatase 1/dual specificity phosphatase 1 mediates glucocorticoid inhibition of osteoblast proliferation. Mol Endocrinol 2007; 21:2929-40. [PMID: 17761948 PMCID: PMC2838148 DOI: 10.1210/me.2007-0153] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Steroid-induced osteoporosis is a common side effect of long-term treatment with glucocorticoid (GC) drugs. GCs have multiple systemic effects that may influence bone metabolism but also directly affect osteoblasts by decreasing proliferation. This may be beneficial at low concentrations, enhancing differentiation. However, high-dose treatment produces a severe deficit in the proliferative osteoblastic compartment. We provide causal evidence that this effect of GC is mediated by induction of the dual-specificity MAPK phosphatase, MKP-1/DUSP1. Excessive MKP-1 production is both necessary and sufficient to account for the impaired osteoblastic response to mitogens. Overexpression of MKP-1 after either GC treatment or transfection ablates the mitogenic response in osteoblasts. Knockdown of MKP-1 using either immunodepletion of MKP-1 before in vitro dephosphorylation assay or short interference RNA transfection prevents inactivation of ERK by GCs. Neither c-jun N-terminal kinase nor p38 MAPK is activated by the mitogenic cocktail in 20% fetal calf serum, but their activation by a DNA-damaging agent (UV irradiation) was inhibited by either GC treatment or overexpression of MKP-1, indicating regulation of all three MAPKs by MKP-1 in osteoblasts. However, an inhibitor of the MAPK/ERK kinase-ERK pathway inhibited osteoblast proliferation whereas inhibitors of c-jun N-terminal kinase or p38 MAPK had no effect, suggesting that ERK is the MAPK that controls osteoblast proliferation. Regulation of ERK by MKP-1 provides a novel mechanism for control of osteoblast proliferation by GCs.
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Affiliation(s)
- Kay Horsch
- Division of Endocrinology and Metabolism, Department of Medicine, University of Stellenbosch, Stellenbosch 7505, South Africa
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16
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Expression profiling of Dexamethasone-treated primary chondrocytes identifies targets of glucocorticoid signalling in endochondral bone development. BMC Genomics 2007; 8:205. [PMID: 17603917 PMCID: PMC1929075 DOI: 10.1186/1471-2164-8-205] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2007] [Accepted: 07/01/2007] [Indexed: 01/27/2023] Open
Abstract
Background Glucocorticoids (GCs) are widely used anti-inflammatory drugs. While useful in clinical practice, patients taking GCs often suffer from skeletal side effects including growth retardation in children and adolescents, and decreased bone quality in adults. On a physiological level, GCs have been implicated in the regulation of chondrogenesis and osteoblast differentiation, as well as maintaining homeostasis in cartilage and bone. We identified the glucocorticoid receptor (GR) as a potential regulator of chondrocyte hypertrophy in a microarray screen of primary limb bud mesenchyme micromass cultures. Some targets of GC regulation in chondrogenesis are known, but the global effects of pharmacological GC doses on chondrocyte gene expression have not been comprehensively evaluated. Results This study systematically identifies a spectrum of GC target genes in embryonic growth plate chondrocytes treated with a synthetic GR agonist, dexamethasone (DEX), at 6 and 24 hrs. Conventional analysis of this data set and gene set enrichment analysis (GSEA) was performed. Transcripts associated with metabolism were enriched in the DEX condition along with extracellular matrix genes. In contrast, a subset of growth factors and cytokines were negatively correlated with DEX treatment. Comparing DEX-induced gene expression data to developmental changes in gene expression in micromass cultures revealed an additional layer of complexity in which DEX maintains the expression of certain chondrocyte marker genes while inhibiting factors that promote vascularization and ultimately ossification of the cartilaginous template. Conclusion Together, these results provide insight into the mechanisms and major molecular classes functioning downstream of DEX in primary chondrocytes. In addition, comparison of our data with microarray studies of DEX treatment in other cell types demonstrated that the majority of DEX effects are tissue-specific. This study provides novel insights into the effects of pharmacological GC on chondrocyte gene transcription and establishes the foundation for subsequent functional studies.
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17
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St-Pierre B, Cooper M, Jiang Z, Zacksenhaus E, Egan SE. Dynamic regulation of the Stra13/Sharp/Dec bHLH repressors in mammary epithelium. Dev Dyn 2004; 230:124-30. [PMID: 15108316 DOI: 10.1002/dvdy.20013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Mammary gland development is a dynamic process involving cyclical proliferation, cellular differentiation, and cell death. In this study, we have determined that expression of the Stra13/Sharp/Dec basic helix-loop-helix (bHLH) family is dynamically regulated in mammary epithelium. In cultured HC11 cells, epidermal growth factor (EGF) treatment rapidly induces Stra13 protein accumulation, which is blocked by the synthetic glucocorticoid, dexamethasone. Neither the induction of Stra13 by EGF nor its repression by dexamethasone correlates with changes in Stra13 mRNA levels. During mouse mammary gland development in vivo, Stra13 is highly expressed in epithelial ducts during puberty, and strongly induced in both ducts and alveoli during early involution, while the related Sharp-1 gene is highly expressed only during late stages of involution. Together, these data indicate that Stra13/Dec/Sharp-family bHLH repressors are dynamically regulated during mammary gland development and may function to regulate apoptosis in this tissue.
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Affiliation(s)
- Benoit St-Pierre
- Programs in Cancer Research and Developmental Biology, The Hospital for Sick Children, and Department of Molecular and Medical Genetics, The University of Toronto, Toronto, Ontario, Canada
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18
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Xu D, Makkinje A, Kyriakis JM. Gene 33 is an endogenous inhibitor of epidermal growth factor (EGF) receptor signaling and mediates dexamethasone-induced suppression of EGF function. J Biol Chem 2004; 280:2924-33. [PMID: 15556944 DOI: 10.1074/jbc.m408907200] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We report a mechanism by which the adapter protein Gene 33 (also called RALT and MIG6) regulates epidermal growth factor receptor (EGFR) signaling. We find that Gene 33 inhibits EGFR autophosphorylation and specifically blunts epidermal growth factor (EGF)-induced activation and/or phosphorylation of Ras, ERK, JNK, Akt/PKB, and retinoblastoma protein. The Ack homology domain of Gene 33, which contains the previously identified EGFR binding domain, is both necessary and sufficient for this inhibition of EGFR autophosphorylation. The endogenous Gene 33 polypeptide is induced by EGF, platelet-derived growth factor, serum, and dexamethasone (Dex) in Rat 2 rat fibroblasts. Dex induces Gene 33 expression and inhibits EGFR phosphorylation and EGF signaling. RNA interference-mediated silencing of Gene 33 significantly reverses this effect. Overexpression of Gene 33 completely blocks EGF-induced protein and DNA synthesis in Rat 2 cells, whereas gene 33 RNA interference substantially enhances EGF-induced protein and DNA synthesis in Rat 2 cells. Our results indicate that Gene 33 is a physiological feedback inhibitor of the EGFR, functioning to inhibit EGFR phosphorylation and all events induced by EGFR activation. Our results also indicate a role for Gene 33 in the suppression, by Dex, of EGF signaling pathways. We propose that Gene 33 may function in the cross-talk between EGF signaling and other mitogenic and/or stress signaling pathways.
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MESH Headings
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/physiology
- Adenoviridae/genetics
- Amino Acid Sequence
- Animals
- Blotting, Northern
- Blotting, Western
- Carrier Proteins/genetics
- Carrier Proteins/physiology
- Cell Line
- DNA, Complementary/metabolism
- Dexamethasone/pharmacology
- Electrophoresis, Polyacrylamide Gel
- Epidermal Growth Factor/metabolism
- ErbB Receptors/metabolism
- Extracellular Signal-Regulated MAP Kinases/metabolism
- Glucocorticoids/pharmacology
- Glutathione Transferase/metabolism
- Guanosine Triphosphate/chemistry
- Humans
- Immunoprecipitation
- Intracellular Signaling Peptides and Proteins
- Models, Genetic
- Molecular Sequence Data
- Oligonucleotides/chemistry
- Phosphorylation
- Platelet-Derived Growth Factor/metabolism
- Protein Binding
- Protein Structure, Tertiary
- RNA Interference
- RNA, Double-Stranded/chemistry
- Rats
- Sequence Homology, Amino Acid
- Serine/chemistry
- Signal Transduction
- Time Factors
- Transfection
- Tumor Suppressor Proteins
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Affiliation(s)
- Dazhong Xu
- Molecular Cardiology Research Institute, Tufts-New England Medical Center and Department of Medicine, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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19
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Sakai A, Han J, Cato ACB, Akira S, Li JD. Glucocorticoids synergize with IL-1beta to induce TLR2 expression via MAP Kinase Phosphatase-1-dependent dual Inhibition of MAPK JNK and p38 in epithelial cells. BMC Mol Biol 2004; 5:2. [PMID: 15125785 PMCID: PMC419700 DOI: 10.1186/1471-2199-5-2] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2003] [Accepted: 05/04/2004] [Indexed: 11/16/2022] Open
Abstract
Background Despite the importance of glucocorticoids in suppressing immune and inflammatory responses, their role in enhancing host immune and defense response against invading bacteria is poorly understood. Toll-like receptor 2 (TLR2) has recently gained importance as one of the major host defense receptors. The increased expression of TLR2 in response to bacteria-induced cytokines has been thought to be crucial for the accelerated immune response and resensitization of epithelial cells to invading pathogens. Results We show that IL-1β, a key proinflammatory cytokine, greatly up-regulates TLR2 expression in human epithelial cells via a positive IKKβ-IκBα-dependent NF-κB pathway and negative MEKK1-MKK4/7-JNK1/2 and MKK3/6-p38 α/β pathways. Glucocorticoids synergistically enhance IL-1β-induced TLR2 expression via specific up-regulation of the MAP kinase phosphatase-1 that, in turn, leads to dephosphorylation and inactivation of both MAPK JNK and p38, the negative regulators for TLR2 induction. Conclusion These results indicate that glucocorticoids not only suppress immune and inflammatory response, but also enhance the expression of the host defense receptor, TLR2. Thus, our studies may bring new insights into the novel role of glucocorticoids in orchestrating and optimizing host immune and defense responses during bacterial infections and enhance our understanding of the signaling mechanisms underlying the glucocorticoid-mediated attenuation of MAPK.
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Affiliation(s)
- Akihiro Sakai
- Gonda Department of Cell and Molecular Biology, House Ear Institute, and the Department of Otolaryngology, University of Southern California, Los Angeles, CA 90057, USA
| | - Jiahuai Han
- Department of Immunology, the Scripps Research Institute, La Jolla, CA 92037, USA
| | - Andrew CB Cato
- Forschungszentrum Karlsruhe, Institute of Toxicology & Genetics, P.O. Box 3640, D-76021 Karlsruhe, Germany
| | - Shizuo Akira
- Department of Host Defense, Research Institute for Microbial Diseases, Osaka University, CREST of Japan Science and Technology Corporation, 3-1 Yamada-oka, Suita, Osaka 565-0871, Japan
| | - Jian-Dong Li
- Gonda Department of Cell and Molecular Biology, House Ear Institute, and the Department of Otolaryngology, University of Southern California, Los Angeles, CA 90057, USA
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20
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Hulley P, Davison A. Regulation of tyrosine phosphorylation cascades by phosphatases: What the actions of vanadium teach us. ACTA ACUST UNITED AC 2003. [DOI: 10.1002/jtra.10040] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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21
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Engelbrecht Y, de Wet H, Horsch K, Langeveldt CR, Hough FS, Hulley PA. Glucocorticoids induce rapid up-regulation of mitogen-activated protein kinase phosphatase-1 and dephosphorylation of extracellular signal-regulated kinase and impair proliferation in human and mouse osteoblast cell lines. Endocrinology 2003; 144:412-22. [PMID: 12538600 PMCID: PMC2820733 DOI: 10.1210/en.2002-220769] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
A central feature of glucocorticoid (GC)-induced osteoporosis is decreased bone formation, secondary to decreased numbers of functional osteoblasts. We find that ERK activity is essential for serum-induced osteoblast proliferation in vitro because inhibition of MAPK/ERK kinase activity by U0126 completely abolished both serum-induced activation of ERK and proliferation of mouse (MBA-15.4) and human (MG-63) osteoblast cell lines. Dexamethasone (Dex) rapidly (<2 h) inhibits the sustained phase of ERK activation, required for nuclear shift and mitogenesis. This inhibition is reversed by cotreatment with the protein synthesis inhibitor, cycloheximide, and by the GC receptor antagonist, RU486, suggesting a classical transcriptional mechanism. Phosphatase activity was up-regulated by Dex treatment, and inhibition of ERK activity by Dex was also reversed by the protein tyrosine phosphatase inhibitor, vanadate. Coupled with the rapidity of Dex action, this indicates immediate-early gene phosphatase involvement, and we therefore used quantitative, real-time PCR to examine expression profiles of the dual-specificity MAPK phosphatases, MKP-1 and MKP-3. MKP-1, but not MKP-3, mRNA expression was 10-fold up-regulated in both mouse and human osteoblast cell lines within 30 min of Dex treatment and remained elevated for 24 h. MKP-1 protein was also markedly up-regulated following 1-8 h of Dex treatment, and this correlated precisely with dephosphorylation of ERK. Cell proliferation was impaired by Dex treatment, and this was reversed by both RU486 and vanadate. Therefore, MKP-1 up-regulation provides a novel and rapid mechanism, whereby GCs inhibit osteoblast proliferation.
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Affiliation(s)
- Y Engelbrecht
- Endocrinology and Metabolism Unit, Department of Internal Medicine, University of Stellenbosch, Tygerberg 7505, Cape Town, South Africa
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22
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Lasa M, Abraham SM, Boucheron C, Saklatvala J, Clark AR. Dexamethasone causes sustained expression of mitogen-activated protein kinase (MAPK) phosphatase 1 and phosphatase-mediated inhibition of MAPK p38. Mol Cell Biol 2002; 22:7802-11. [PMID: 12391149 PMCID: PMC134716 DOI: 10.1128/mcb.22.22.7802-7811.2002] [Citation(s) in RCA: 270] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The stress-activated protein kinase p38 stabilizes a number of mRNAs encoding inflammatory mediators, such as cyclooxygenase 2 (Cox-2). In HeLa cells the anti-inflammatory glucocorticoid dexamethasone destabilizes Cox-2 mRNA by inhibiting p38 function. Here we demonstrate that this effect is phosphatase dependent. Furthermore, in HeLa cells dexamethasone induced the sustained expression of mitogen-activated protein kinase phosphatase 1 (MKP-1), a potent inhibitor of p38 function. The inhibition of p38 and the induction of MKP-1 by dexamethasone occurred with similar dose dependence and kinetics. No other known p38 phosphatases were induced by dexamethasone, and other cell types which failed to express MKP-1 also failed to inhibit p38 in response to dexamethasone. The proinflammatory cytokine interleukin 1 (IL-1) induced MKP-1 expression in a p38-dependent manner and acted synergistically with dexamethasone to induce MKP-1 expression. In HeLa cells treated with IL-1 or IL-1 and dexamethasone, the dynamics of p38 activation mirrored the expression of MKP-1. These observations suggest that MKP-1 participates in a negative-feedback loop which regulates p38 function and that dexamethasone may inhibit proinflammatory gene expression in part by inducing MKP-1 expression.
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Affiliation(s)
- Marina Lasa
- Kennedy Institute of Rheumatology Division, Imperial College Faculty of Medicine, London W6 8LH, United Kingdom
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23
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Sharma SK, Carew TJ. Inclusion of phosphatase inhibitors during Western blotting enhances signal detection with phospho-specific antibodies. Anal Biochem 2002; 307:187-9. [PMID: 12137799 DOI: 10.1016/s0003-2697(02)00008-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Shiv K Sharma
- Department of Neurobiology and Behavior, McGaugh Hall, University of California at Irvine, 92697, USA
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24
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Rubin J, Murphy TC, Fan X, Goldschmidt M, Taylor WR. Activation of extracellular signal-regulated kinase is involved in mechanical strain inhibition of RANKL expression in bone stromal cells. J Bone Miner Res 2002; 17:1452-60. [PMID: 12162499 DOI: 10.1359/jbmr.2002.17.8.1452] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Mechanical input is known to regulate skeletal mass. In vitro, application of strain inhibits osteoclast formation by decreasing expression of the ligand RANKL in bone stromal cells, but the mechanism responsible for this down-regulation is unknown. In experiments here, application of 1.8% equibiaxial strain for 6 h reduced vitamin D-stimulated RANKL mRNA expression by nearly one-half in primary bone stromal cells. Application of strain caused a rapid activation of ERK1/2, which returned to baseline by 60 minutes. Adding the ERK1/2 inhibitor PD98059 30 minutes before strain delivery prevented the strain effect on RANKL mRNA expression, suggesting that activation of ERK1/2 was required for transduction of the mechanical force. Mechanical strain also activated N-terminal Jun kinase (JNK) that, in contrast, did not return to baseline during 24 h of continuous strain. This suggests that JNK may represent an accessory pathway for mechanical transduction in bone cells. Our data indicate that strain modulation of RANKL expression involves activation of MAPK pathways.
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Affiliation(s)
- Janet Rubin
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, USA
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25
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Hulley PA, Conradie MM, Langeveldt CR, Hough FS. Glucocorticoid-induced osteoporosis in the rat is prevented by the tyrosine phosphatase inhibitor, sodium orthovanadate. Bone 2002; 31:220-9. [PMID: 12110438 DOI: 10.1016/s8756-3282(02)00807-4] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Glucocorticoid-induced osteoporosis is characterized by decreased osteoblast numbers and a marked impairment of new bone formation. We found that, in vitro, dexamethasone inhibits both preosteoblast proliferation and mitogenic kinase activity in response to mitogens, and that inhibition of protein tyrosine phosphatases (PTPs) using sodium orthovanadate prevents this. Therefore, dexamethasone may act by either upregulating antiproliferative PTPs or downregulating promitogenic tyrosine-phosphorylated substrates. In this study, osteoporosis was induced in 3.5-month-old rats by subcutaneous injection with methylprednisolone 3.5 mg/kg per day for 9 weeks. Rats were treated with steroid alone or in combination with 0.5 mg/mL sodium orthovanadate, administered continuously in drinking water. Steroid-treated bones were significantly (p < 0.005) osteopenic (according to dual-energy X-ray absorptiometry) and physically weaker (p < 0.05) than controls. Quantitative bone histology confirmed a significant decrease in osteoid surfaces (p < 0.001), osteoblast numbers (p < 0.05), and rate of bone formation (p < 0.001). Concomitant treatment with vanadate largely prevented the densitometric, histologic, and physical abnormalities induced by prednisolone. This study supports our finding that PTPs are central to the negative regulation of osteoblast proliferation by glucocorticoids and, furthermore, suggests that PTP inhibitors such as sodium orthovanadate should be considered as novel anabolic agents for the treatment of steroid-induced osteoporosis.
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Affiliation(s)
- P A Hulley
- Department of Endocrinology and Metabolism, University of Stellenbosch Medical School, Tygerberg, Cape Town, South Africa.
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26
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Kassel O, Sancono A, Krätzschmar J, Kreft B, Stassen M, Cato AC. Glucocorticoids inhibit MAP kinase via increased expression and decreased degradation of MKP-1. EMBO J 2001; 20:7108-16. [PMID: 11742987 PMCID: PMC125780 DOI: 10.1093/emboj/20.24.7108] [Citation(s) in RCA: 370] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Glucocorticoids inhibit the proinflammatory activities of transcription factors such as AP-1 and NF-kappa B as well as that of diverse cellular signaling molecules. One of these signaling molecules is the extracellular signal-regulated kinase (Erk-1/2) that controls the release of allergic mediators and the induction of proinflammatory cytokine gene expression in mast cells. The mechanism of inhibition of Erk-1/2 activity by glucocorticoids is unknown. Here we report a novel dual action of glucocorticoids for this inhibition. Glucocorticoids increase the expression of the MAP kinase phosphatase-1 (MKP-1) gene at the promoter level, and attenuate proteasomal degradation of MKP-1, which we report to be triggered by activation of mast cells. Both induction of MKP-1 expression and inhibition of its degradation are necessary for glucocorticoid-mediated inhibition of Erk-1/2 activation. In NIH-3T3 fibroblasts, although glucocorticoids up-regulate the MKP-1 level, they do not attenuate the proteasomal degradation of this protein and consequently they are unable to inhibit Erk-1/2 activity. These results identify MKP-1 as essential for glucocorticoid-mediated control of Erk-1/2 activation and unravel a novel regulatory mechanism for this anti-inflammatory drug.
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Affiliation(s)
| | | | - Jörn Krätzschmar
- Forschungszentrum Karlsruhe, Institute of Toxicology and Genetics, PO Box 3640, D-76021 Karlsruhe,
Schering AG, D-13342 Berlin and Institute of Immunology, Johannes Gutenberg University, Obere Zahlbacher Strasse 65, D-55101 Mainz, Germany Corresponding author e-mail:
| | - Bertolt Kreft
- Forschungszentrum Karlsruhe, Institute of Toxicology and Genetics, PO Box 3640, D-76021 Karlsruhe,
Schering AG, D-13342 Berlin and Institute of Immunology, Johannes Gutenberg University, Obere Zahlbacher Strasse 65, D-55101 Mainz, Germany Corresponding author e-mail:
| | - Michael Stassen
- Forschungszentrum Karlsruhe, Institute of Toxicology and Genetics, PO Box 3640, D-76021 Karlsruhe,
Schering AG, D-13342 Berlin and Institute of Immunology, Johannes Gutenberg University, Obere Zahlbacher Strasse 65, D-55101 Mainz, Germany Corresponding author e-mail:
| | - Andrew C.B. Cato
- Forschungszentrum Karlsruhe, Institute of Toxicology and Genetics, PO Box 3640, D-76021 Karlsruhe,
Schering AG, D-13342 Berlin and Institute of Immunology, Johannes Gutenberg University, Obere Zahlbacher Strasse 65, D-55101 Mainz, Germany Corresponding author e-mail:
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Son GH, Geum D, Jung H, Kim K. Glucocorticoid inhibits growth factor-induced differentiation of hippocampal progenitor HiB5 cells. J Neurochem 2001; 79:1013-21. [PMID: 11739613 DOI: 10.1046/j.1471-4159.2001.00634.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the present study, we investigated the effect of glucocorticoid on neuronal differentiation of hippocampal progenitor HiB5 cells. Dexamethasone (DEX), a synthetic glucocorticoid, inhibited platelet-derived growth factor (PDGF)-induced differentiation of HiB5 cells. The inhibitory effect of DEX was antagonized by RU486, a glucocorticoid receptor (GR) antagonist, indicating the GR-mediated processes. Nestin mRNA level was decreased and midsize neurofilament (NF-M) mRNA level was increased as a function of neuronal differentiation. DEX significantly blocked PDGF-induced down-regulation of nestin mRNA level, and up-regulation of NF-M mRNA level, which were similar to those of undifferentiated cells. DEX inhibited PDGF-induced activation of cyclic AMP-responsive element binding protein (CREB) and AP-1, suggesting that glucocorticoid interfered with signal transduction cascades linking the PDGF receptor and downstream transcription factors. Indeed, DEX reduced PDGF-induced phosphorylation of extracellular signal-regulated kinases 1/2 (ERK1/2). Tyrosine phosphatase inhibitor reversed the effect of DEX on ERK1/2. In accordance with this finding, blockage of ERK1/2 signaling pathway with PD098059, a potent inhibitor for Ras/ERK pathway, mimicked the inhibitory effect of DEX on differentiation processes. Taken together, these results indicate that glucocorticoid inhibits PDGF-induced differentiation of hippocampal progenitor HiB5 cells by inhibiting the ERK1/2 signaling cascade via a tyrosine phosphatase-dependent mechanism.
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Affiliation(s)
- G H Son
- Development and Neuroendocrine Research Laboratory, School of Biological Sciences, Seoul National University, Seoul, Korea
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Brenner KA, Corbett SA, Schwarzbauer JE. Regulation of fibronectin matrix assembly by activated Ras in transformed cells. Oncogene 2000; 19:3156-63. [PMID: 10918570 DOI: 10.1038/sj.onc.1203626] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Fibronectin extracellular matrix plays a critical role in the microenvironment of cells. Loss of this matrix frequently accompanies oncogenic transformation, allowing changes in cell growth, morphology, and tissue organization. The HT1080 human fibrosarcoma cell line is deficient in formation of fibronectin matrix fibrils but assembly can be induced by the glucocorticoid dexamethasone. Here we show that fibronectin assembly can also be restored by stimulation of alpha5beta1 integrin with activating antibody or with Mn2+ suggesting that integrin activity is reduced in these cells. While dexamethasone promoted actin stress fiber formation, actin filaments remained cortical following Mn2+ treatment showing that the dexamethasone effect is not due solely to cytoskeletal changes. HT1080 cells have one activated allele of N-ras and PD98059 inhibition of signaling from Ras through ERK increased fibronectin matrix accumulation. Conversely, the p38 MAP kinase inhibitor SB203580 blocked induction of matrix and increased ERK phosphorylation. Thus, two MAP kinase pathways contribute to the control of integrin-mediated fibronectin assembly. ERK activity and fibronectin assembly were linked in three different ras-transformed cell lines but not in SV40- or RSV-transformed cells indicating that oncogenic Ras uses a distinct mechanism to down-regulate cell-fibronectin interactions.
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Affiliation(s)
- K A Brenner
- Department of Molecular Biology, Princeton University, New Jersey 08544, USA
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Tian L, Philp JA, Shipston MJ. Glucocorticoid block of protein kinase C signalling in mouse pituitary corticotroph AtT20 D16:16 cells. J Physiol 1999; 516 ( Pt 3):757-68. [PMID: 10200423 PMCID: PMC2269291 DOI: 10.1111/j.1469-7793.1999.0757u.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
1. The regulation of large conductance calcium- and voltage-activated potassium (BK) currents by activation of the protein kinase C (PKC) and glucocorticoid signalling pathways was investigated in AtT20 D16:16 clonal mouse anterior pituitary corticotroph cells. 2. Maximal activation of PKC using the phorbol esters, 4beta-phorbol 12-myristate, 13-acetate (PMA), phorbol 12, 13 dibutyrate (PDBu) and 12-deoxyphorbol 13-phenylacetate (dPPA) elicited a rapid, and sustained, inhibition of the outward steady-state voltage- and calcium- dependent potassium current predominantly carried through BK channels. 3. The effect of PMA was blocked by the PKC inhibitors bisindolylmaleimide I (BIS; 100 nM) and chelerythrine chloride (CHE; 25 microM) and was not mimicked by the inactive phorbol ester analogue 4alpha-PMA. 4. PMA had no significant effect on the 1 mM tetraethylammonium (TEA)-insensitive outward current or pharmacologically isolated, high voltage-activated calcium current. 5. PMA had no significant effect on steady-state outward current in cells pre-treated for 2 h with 1 microM of the glucocorticoid agonist dexamethasone. Dexamethasone had no significant effect on steady-state outward current amplitude or sensitivity to 1 mM TEA and did not block PMA-induced translocation of the phorbol ester-sensitive PKC isoforms, PKCalpha and PKCepsilon, to membrane fractions. 6. Taken together these data suggest that in AtT20 D16:16 corticotroph cells BK channels are important targets for PKC action and that glucocorticoids inhibit PKC signalling downstream of PKC activation.
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Affiliation(s)
- L Tian
- Membrane Biology Group, Department of Biomedical Sciences, University of Edinburgh, Medical School, Teviot Place, Edinburgh EH8 9AG, UK
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30
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Börcsök I, Schairer HU, Sommer U, Wakley GK, Schneider U, Geiger F, Niethard FU, Ziegler R, Kasperk CH. Glucocorticoids regulate the expression of the human osteoblastic endothelin A receptor gene. J Exp Med 1998; 188:1563-73. [PMID: 9802968 PMCID: PMC2212506 DOI: 10.1084/jem.188.9.1563] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/1998] [Revised: 08/24/1998] [Indexed: 01/23/2023] Open
Abstract
The endothelial cell-derived peptide endothelin 1 (ET1) stimulates cell proliferation and differentiated functions of human osteoblastic cells (HOC), and HOC constitutively express the endothelin A receptor (ETRA). Therefore, ET1 may play an important role in the regulation of bone cell metabolism. As glucocorticoids (GC) exert a profound influence on bone metabolism and increase the effects of ET1 on bone cell metabolism in vitro, the effects of GC on ETRA expression in HOC were investigated. Dexamethasone (DEX) increased ETRA mRNA levels in a dose- and time-dependent fashion. The effects of dexamethasone, prednisolone, and deflazacort on the increase of ETRA mRNA levels correlate positively with their binding affinity to the GC receptor. Scatchard analysis of ET1 binding data to HOC revealed that DEX increased the binding capacity for ET1 from 25,300 to 62,800 binding sites per osteoblastic cell, leading to an enhanced mitogenic effect of ET1 on HOC after preincubation with DEX. Transiently transfected primary HOC with a reporter gene construct, containing the 5'-flanking region of the ETRA gene fused to luciferase gene, showed a promoter-dependent expression of the reporter gene and the induction of reporter gene expression by DEX treatment. Total RNA extracts of femoral head biopsies with osteonecrotic lesions from GC-treated patients showed threefold higher ETRA mRNA levels compared with extracts of bone biopsies from patients with traumatically induced osteonecrosis and coxarthrosis. Furthermore, GC treatment increased plasma ET1 levels by 50% compared with pretreatment values. These findings suggest that GC induced upregulation of ETRA, and ET1 plasma levels enhance ET1's anabolic action on bone cell metabolism. Increased ET1 concentrations may also impair bone perfusion by vasoconstriction in a metabolically activated skeletal region.
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Affiliation(s)
- I Börcsök
- Department of Medicine, Ruprecht-Karls-University of Heidelberg, D-69115 Heidelberg, Germany
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Condino-Neto A, Whitney C, Newburger PE. Dexamethasone But Not Indomethacin Inhibits Human Phagocyte Nicotinamide Adenine Dinucleotide Phosphate Oxidase Activity by Down-Regulating Expression of Genes Encoding Oxidase Components. THE JOURNAL OF IMMUNOLOGY 1998. [DOI: 10.4049/jimmunol.161.9.4960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Abstract
We investigated the effects of dexamethasone or indomethacin on the NADPH oxidase activity, cytochrome b558 content, and expression of genes encoding the components gp91-phox and p47-phox of the NADPH oxidase system in the human monocytic THP-1 cell line, differentiated with IFN-γ and TNF-α, alone or in combination, for up to 7 days. IFN-γ and TNF-α, alone or in combination, caused a significant up-regulation of the NADPH oxidase system as reflected by an enhancement of the PMA-stimulated superoxide release, cytochrome b558 content, and expression of gp91-phox and p47-phox genes on both days 2 and 7 of cell culture. Noteworthy was the tremendous synergism between IFN-γ and TNF-α for all studied parameters. Dexamethasone down-regulated the NADPH oxidase system of cytokine-differentiated THP-1 cells as assessed by an inhibition on the PMA-stimulated superoxide release, cytochrome b558 content, and expression of the gp91-phox and p47-phox genes. The nuclear run-on assays indicated that dexamethasone down-regulated the NADPH oxidase system at least in part by inhibiting the transcription of gp91-phox and p47-phox genes. Indomethacin inhibited only the PMA-stimulated superoxide release of THP-1 cells differentiated with IFN-γ and TNF-α during 7 days. None of the other parameters was affected by indomethacin. We conclude that dexamethasone down-regulates the NADPH oxidase system at least in part by inhibiting the expression of genes encoding the gp91-phox and p47-phox components of the NADPH oxidase system.
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Affiliation(s)
- Antonio Condino-Neto
- *Center for Investigation in Pediatrics, State University of Campinas Medical School, Campinas, Brazil; and
| | - Constance Whitney
- †Department of Pediatrics and the Cancer Center, University of Massachusetts Medical Center, Worcester, MA 01655
| | - Peter E. Newburger
- †Department of Pediatrics and the Cancer Center, University of Massachusetts Medical Center, Worcester, MA 01655
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