101
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Gong H, Jarzynka MJ, Cole TJ, Lee JH, Wada T, Zhang B, Gao J, Song WC, DeFranco DB, Cheng SY, Xie W. Glucocorticoids antagonize estrogens by glucocorticoid receptor-mediated activation of estrogen sulfotransferase. Cancer Res 2008; 68:7386-93. [PMID: 18794126 PMCID: PMC6551207 DOI: 10.1158/0008-5472.can-08-1545] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Glucocorticoids and estrogens are two classes of steroid hormones that have essential but distinct physiologic functions. Estrogens also represent a risk factor for breast cancer. It has been suggested that glucocorticoids can attenuate estrogen responses, but the mechanism by which glucocorticoids inhibit estrogenic activity is unknown. In this study, we show that activation of glucocorticoid receptor (GR) by dexamethasone (DEX) induced the expression and activity of estrogen sulfotransferase (SULT1E1 or EST), an enzyme important for the metabolic deactivation of estrogens, because sulfonated estrogens fail to activate the estrogen receptor. Treatment with DEX lowered circulating estrogens, compromised uterine estrogen responses, and inhibited estrogen-dependent breast cancer growth in vitro and in a xenograft model. We further showed that the mouse and human SULT1E1 genes are transcriptional targets of GR and deletion of Sult1e1/Est in mice abolished the DEX effect on estrogen responses. These findings have revealed a novel nuclear receptor-mediated and metabolism-based mechanism of estrogen deprivation, which may have implications in therapeutic development for breast cancers. Because glucocorticoids and estrogens are widely prescribed drugs, our results also urge caution in avoiding glucocorticoid-estrogen interactions in patients.
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MESH Headings
- Animals
- Breast Neoplasms/drug therapy
- Breast Neoplasms/enzymology
- Breast Neoplasms/genetics
- Breast Neoplasms/pathology
- Cell Growth Processes/drug effects
- Cell Growth Processes/physiology
- Cell Line, Tumor
- Dexamethasone/pharmacology
- Enzyme Activation
- Estradiol/pharmacology
- Estrogen Antagonists/pharmacology
- Estrogens/blood
- Female
- Humans
- Liver/drug effects
- Liver/enzymology
- Mice
- Mice, Inbred C57BL
- Mice, Nude
- Neoplasms, Hormone-Dependent/drug therapy
- Neoplasms, Hormone-Dependent/enzymology
- Neoplasms, Hormone-Dependent/metabolism
- Neoplasms, Hormone-Dependent/pathology
- RNA, Messenger/biosynthesis
- RNA, Messenger/genetics
- Receptors, Glucocorticoid/genetics
- Receptors, Glucocorticoid/metabolism
- Sulfotransferases/biosynthesis
- Sulfotransferases/genetics
- Sulfotransferases/metabolism
- Transcription, Genetic
- Uterus/drug effects
- Uterus/enzymology
- Uterus/metabolism
- Xenograft Model Antitumor Assays
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Affiliation(s)
- Haibiao Gong
- Center for Pharmacogenetics and Department of Pharmaceutical Sciences, Monash University, Clayton, Victoria, Australia
| | - Michael J. Jarzynka
- University of Pittsburgh Cancer Institute and Department of Pathology, Monash University, Clayton, Victoria, Australia
| | - Timothy J. Cole
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
| | - Jung Hoon Lee
- Center for Pharmacogenetics and Department of Pharmaceutical Sciences, Monash University, Clayton, Victoria, Australia
| | - Taira Wada
- Center for Pharmacogenetics and Department of Pharmaceutical Sciences, Monash University, Clayton, Victoria, Australia
| | - Bin Zhang
- Center for Pharmacogenetics and Department of Pharmaceutical Sciences, Monash University, Clayton, Victoria, Australia
| | - Jie Gao
- Center for Pharmacogenetics and Department of Pharmaceutical Sciences, Monash University, Clayton, Victoria, Australia
| | - Wen-Chao Song
- Institute for Translational Medicine and Therapeutics and Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
| | - Donald B. DeFranco
- Department of Pharmacology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Shi-Yuan Cheng
- University of Pittsburgh Cancer Institute and Department of Pathology, Monash University, Clayton, Victoria, Australia
| | - Wen Xie
- Center for Pharmacogenetics and Department of Pharmaceutical Sciences, Monash University, Clayton, Victoria, Australia
- Department of Pharmacology, University of Pittsburgh, Pittsburgh, Pennsylvania
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102
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Lin WY, Hu YJ, Lee YH. Hepatocyte nuclear factor-1alpha regulates glucocorticoid receptor expression to control postnatal body growth. Am J Physiol Gastrointest Liver Physiol 2008; 295:G542-51. [PMID: 18583462 PMCID: PMC2536778 DOI: 10.1152/ajpgi.00081.2008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Hepatocyte nuclear factor 1alpha (HNF-1alpha) is a homeodomain-containing transcription factor and is important in postnatal growth and development in mice. In the HNF-1alpha-deficient liver, the expressions of a large set of growth hormone (GH)-responsive genes were significantly downregulated. By analyzing various HNF-1alpha mutant mice, we disclosed a mechanism by which hepatic HNF-1alpha regulates the expression of GH-responsive genes that are crucial for growth and development. We found that HNF-1alpha is required for the normal expression of glucocorticoid receptor (GR) specifically in livers. In the liver, GR, together with STAT5, is known to mediate the GH action by transactivating the GH-responsive genes that function in body growth and development. We further demonstrated that HNF-1alpha modulated GR gene expression by directly transactivating the GR gene promoter via a cryptic regulatory element located 3 bp upstream of the translation start site in exon 2 of the GR gene locus.
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Affiliation(s)
- Wan-Yi Lin
- Laboratory of Molecular Pathology, Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Yu-Jie Hu
- Laboratory of Molecular Pathology, Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Ying-Hue Lee
- Laboratory of Molecular Pathology, Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
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103
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Van der Linden SC, Heringa MB, Man HY, Sonneveld E, Puijker LM, Brouwer A, Van der Burg B. Detection of multiple hormonal activities in wastewater effluents and surface water, using a panel of steroid receptor CALUX bioassays. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2008; 42:5814-20. [PMID: 18754514 DOI: 10.1021/es702897y] [Citation(s) in RCA: 184] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
It is generally known that there are compounds present in the aquatic environment that can disturb endocrine processes, for example via interaction with the endogenous hormone receptors. Most research so far has focused on compounds that bind to the estrogen and/or androgen receptor, but ligands for other hormone receptors might also be present. In this study, a newly completed panel of human cell derived CALUX reporter gene bioassays was utilized to test water extracts for estrogen (ER), as well as androgen (AR), progesterone (PR), and glucocorticoid (GR) receptor mediated transactivation activity. Effluents from industry, hospital, and municipal sewage treatment plants, as well as tap water and different sources of surface water were tested. The CALUX reporter gene panel showed high sensitivity and specificity to known agonists, enabling discrimination between different receptor based endocrine responses present in the aquatic environment. Our results clearly showed the presence of agonistic activity on the ER, as well as on the AR, PR, and GR in the raw and wastewater and surface water extracts. However, no hormone receptor-mediated transactivation was detected in the drinking water or in the blank water. The levels of estrogenic activity were 0.2-0.5 ng E2-equiv/L for surface water and 0.4-1.0 ng E2-equiv/L for municipal effluents, which was consistent with previous studies. Surprisingly, the other hormonal activities were found to be present in similar or much higher levels. Most notably, glucocorticoid-like activity was detected in all samples, at surprisingly high levels ranging from 0.39-1.3 ng Dex-equiv/L in surface water and 11-243 ng Dex-equiv/L in effluents. When regarding the fact that dexamethasone in the GR CALUX bioassay is a factor 12 more potent than the natural hormone cortisol, results expressed as cortisol equivalents would range up to 2900 ng cortisol equiv/L. Further studies are needed to establish the identity of the active compounds and to understand the significance of the level of activities with regard to human and ecotoxicological risks.
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104
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Chen W, Dang T, Blind RD, Wang Z, Cavasotto CN, Hittelman AB, Rogatsky I, Logan SK, Garabedian MJ. Glucocorticoid receptor phosphorylation differentially affects target gene expression. Mol Endocrinol 2008; 22:1754-66. [PMID: 18483179 DOI: 10.1210/me.2007-0219] [Citation(s) in RCA: 205] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The glucocorticoid receptor (GR) is phosphorylated at multiple sites within its N terminus (S203, S211, S226), yet the role of phosphorylation in receptor function is not understood. Using a range of agonists and GR phosphorylation site-specific antibodies, we demonstrated that GR transcriptional activation is greatest when the relative phosphorylation of S211 exceeds that of S226. Consistent with this finding, a replacement of S226 with an alanine enhances GR transcriptional response. Using a battery of compounds that perturb different signaling pathways, we found that BAPTA-AM, a chelator of intracellular divalent cations, and curcumin, a natural product with antiinflammatory properties, reduced hormone-dependent phosphorylation at S211. This change in GR phosphorylation was associated with its decreased nuclear retention and transcriptional activation. Molecular modeling suggests that GR S211 phosphorylation promotes a conformational change, which exposes a novel surface potentially facilitating cofactor interaction. Indeed, S211 phosphorylation enhances GR interaction with MED14 (vitamin D receptor interacting protein 150). Interestingly, in U2OS cells expressing a nonphosphorylated GR mutant S211A, the expression of IGF-binding protein 1 and interferon regulatory factor 8, both MED14-dependent GR target genes, was reduced relative to cells expressing wild-type receptor across a broad range of hormone concentrations. In contrast, the induction of glucocorticoid-induced leucine zipper, a MED14-independent GR target, was similar in S211A- and wild-type GR-expressing cells at high hormone levels, but was reduced in S211A cells at low hormone concentrations, suggesting a link between GR phosphorylation, MED14 involvement, and receptor occupancy. Phosphorylation also affected the magnitude of repression by GR in a gene-selective manner. Thus, GR phosphorylation at S211 and S226 determines GR transcriptional response by modifying cofactor interaction. Furthermore, the effect of GR S211 phosphorylation is gene specific and, in some cases, dependent upon the amount of activated receptor.
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Affiliation(s)
- Weiwei Chen
- Department of Pharmacology, and the NYU Cancer Institute, NYU School of Medicine, 550 First Avenue, New York, New York 10016, USA
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105
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van der Laan S, Meijer OC. Pharmacology of glucocorticoids: Beyond receptors. Eur J Pharmacol 2008; 585:483-91. [DOI: 10.1016/j.ejphar.2008.01.060] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2007] [Revised: 01/11/2008] [Accepted: 01/24/2008] [Indexed: 11/28/2022]
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106
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Rocha Viegas L, Hoijman E, Beato M, Pecci A. Mechanisms involved in tissue-specific apopotosis regulated by glucocorticoids. J Steroid Biochem Mol Biol 2008; 109:273-8. [PMID: 18424036 DOI: 10.1016/j.jsbmb.2008.03.007] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Physiological cell turnover is under the control of a sharp and dynamic balance of different homeostatic mechanisms such as the equilibrium between cell proliferation and cell death. These mechanisms play an important role in maintaining normal tissue function and architecture. It is well known that apoptosis is the prevalent mode of physiological cell loss in most tissues. Steroid hormones like glucocorticoids have been identified as key signals controlling cell turnover by modulating programmed cell death in a tissue- and cell-specific manner. In this sense, several reports have demonstrated that glucocorticoids are able to induce apoptosis in cells of the hematopoietic system such as monocytes, macrophages, and T lymphocytes. In contrast, they protect against apoptotic signals evoked by cytokines, cAMP, tumor suppressors, in glandular cells such as the mammary gland epithelia, endometrium, hepatocytes, ovarian follicular cells, and fibroblasts. Although several studies have provided significant information on hormone-dependent apoptosis in an specific tissue, a clearly defined pathway that mediates cell death in response to glucocorticoids in different cell types is still misunderstood. The scope of this review is held to those mechanisms by which glucocorticoids control apoptosis, emphasizing tissue-specific expression of genes that are involved in the apoptotic pathway.
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Affiliation(s)
- Luciana Rocha Viegas
- Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Cdad. Universitaria, Pab. II, C1428EGA Buenos Aires, Argentina
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107
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Yang JQ, Rüdiger JJ, Hughes JM, Goulet S, Gencay-Cornelson MM, Borger P, Tamm M, Roth M. Cell Density and Serum Exposure Modify the Function of the Glucocorticoid Receptor C/EBP Complex. Am J Respir Cell Mol Biol 2008; 38:414-22. [DOI: 10.1165/rcmb.2007-0079oc] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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108
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Blind R, Garabedian MJ. Differential recruitment of glucocorticoid receptor phospho-isoforms to glucocorticoid-induced genes. J Steroid Biochem Mol Biol 2008; 109:150-7. [PMID: 18304804 PMCID: PMC2699583 DOI: 10.1016/j.jsbmb.2008.01.002] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2007] [Revised: 10/25/2007] [Accepted: 01/15/2008] [Indexed: 11/18/2022]
Abstract
The human glucocorticoid receptor (GR) is phosphorylated on its N-terminus at three major sites (S203, S211 and S226) within activation function 1 (AF1). Although GR has been shown to assemble at glucocorticoid responsive elements (GREs) in the presence of hormone, the timing and specificity of GR phospho-isoform recruitment to receptor target genes has not been established. Using chromatin immunoprecipitation (ChIP) and GR phosphorylation site-specific antibodies, we examined GR phospho-isoform recruitment to several glucocorticoid-induced genes including tyrosine aminotransferase (tat) and sulfonyltransferase-1A1 (sult) in rat hepatoma cells, and the glucocorticoid-induced leucine zipper (gilz) gene in human U2OS cells. GR P-S211 and GR P-S226 isoforms were efficiently recruited to the tat, sult and gilz GREs in a hormone-dependent manner. In contrast, the GR P-S203 isoform displayed no significant recruitment to any GREs of the genes analyzed, consistent with its lack of nuclear accumulation. Interestingly, the kinetics of GR P-S211 and GR P-S226 recruitment differed among genes. Our findings indicate that GR phospho-isoforms selectively occupy GR target genes, and suggests gene specific requirements for GR phosphorylation in receptor-dependent transcriptional activation.
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Affiliation(s)
- Raymond Blind
- Department of Microbiology, NYU Cancer Institute, NYU School of Medicine, 550 First Avenue, New York, N.Y. 10016
- Department of Pharmacology, NYU Cancer Institute, NYU School of Medicine, 550 First Avenue, New York, N.Y. 10016
| | - Michael J. Garabedian
- Department of Microbiology, NYU Cancer Institute, NYU School of Medicine, 550 First Avenue, New York, N.Y. 10016
- Department of Urology, NYU Cancer Institute, NYU School of Medicine, 550 First Avenue, New York, N.Y. 10016
- Corresponding author: Phone: 212 263-7662, FAX: 212 263-8276,
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109
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Affiliation(s)
- Kamal A S Al-Shoumer
- Division of Endocrinology, Faculty of Medicine, Kuwait University and Mubarak Al-Kabeer Hospital, Kuwait.
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110
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De Bosscher K, Van Craenenbroeck K, Meijer OC, Haegeman G. Selective transrepression versus transactivation mechanisms by glucocorticoid receptor modulators in stress and immune systems. Eur J Pharmacol 2008; 583:290-302. [PMID: 18289525 DOI: 10.1016/j.ejphar.2007.11.076] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2007] [Revised: 09/28/2007] [Accepted: 11/12/2007] [Indexed: 12/14/2022]
Abstract
Glucocorticoids control immune homeostasis and regulate stress responses in the human body to a large extent via the glucocorticoid receptor. This transcription factor can modulate gene expression either through direct DNA binding (mainly resulting in transactivation) or independent of DNA binding (in the majority of cases resulting in transrepression). The aim of this review is to discuss the mechanistic basis and applicability of different glucocorticoid receptor modulators in various affections, ranging from immune disorders to mental dysfunctions.
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Affiliation(s)
- Karolien De Bosscher
- Laboratory of Eukaryotic Gene Expression & Signal Transduction (LEGEST), Department of Molecular Biology, Ghent University, K.L. Ledeganckstraat 35, 9000 Gent, Belgium.
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111
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Chebotaev DV, Yemelyanov AY, Lavker RM, Budunova IV. Epithelial Cells in the Hair Follicle Bulge do not Contribute to Epidermal Regeneration after Glucocorticoid-Induced Cutaneous Atrophy. J Invest Dermatol 2007; 127:2749-58. [PMID: 17657244 DOI: 10.1038/sj.jid.5700992] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
One of the major adverse effects of glucocorticoid therapy is cutaneous atrophy, often followed by the development of resistance to steroids. It is accepted that epithelial stem cells (SCs) located in the hair follicle bulge divide during times of epidermal proliferative need. We determined whether follicular epithelial SCs and their transit amplifying progeny were stimulated to proliferate in response to the chronic application of glucocorticoid fluocinolone acetonide (FA). After first two applications of FA, keratinocyte proliferation in the interfollicular epidermis (IFE) and hair follicles was minimal and resulted in significant epidermal hypoplasia. We observed that a 50% depletion of the interfollicular keratinocyte population triggered a proliferative response. Unexpectedly, less than 2% of the proliferating keratinocytes were located in the bulge region of the hair follicle, whereas 82% were in IFE. It is known that cell desensitization to glucocorticoids is mediated via temporary decrease of glucocorticoid receptor (GR) expression. We found that GR expression was significantly decreased in IFE keratinocytes after each FA treatment. In contrast, many bulge keratinocytes retained GR in the nucleus. Our results indicate that bulge keratinocytes, including follicular SCs, are more sensitive to the antiproliferative effect of glucocorticoids than basal keratinocytes, possibly due to the incomplete process of desensitization.
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Affiliation(s)
- Dmitry V Chebotaev
- Department of Dermatology, Northwestern University, Chicago, Illinois 60611, USA
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112
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Chebotaev D, Yemelyanov A, Budunova I. The mechanisms of tumor suppressor effect of glucocorticoid receptor in skin. Mol Carcinog 2007; 46:732-40. [PMID: 17538956 DOI: 10.1002/mc.20349] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Glucocorticoid hormones exert a tumor suppressor effect in different experimental models, including mouse skin carcinogenesis. The glucocorticoid control of cellular functions is mediated via the glucocorticoid receptor (GR), a well-known transcription factor that regulates genes by DNA-binding dependent transactivation, and DNA-binding independent transrepression through negative interaction with other transcription factors. In this perspective, we analyze known mechanisms that underlie the anticancer effect of GR signaling, including effects on cell growth, differentiation, apoptosis, and angiogenesis. We also discuss a novel mechanism for the tumor suppressor effect of the GR in skin: through the regulation of the number and status of follicular epithelial stem cells (SC), which are a target cell population for skin carcinogenesis. Our studies on keratin5.GR transgenic animals that are resistant to skin carcinogenesis, demonstrated that the GR diminishes the number of follicular epithelial SCs, reduces their proliferative and survival potential and affects the expression of follicular SC "signature" genes. The analysis of global effect of the GR on gene expression in follicular epithelial SCs, basal keratinocytes, and mouse skin tumors provided an unexpected evidence that gene transrepression by GR plays an important role in the maintenance of SC and in inhibition of skin carcinogenesis by this steroid hormone receptor. It is known that antiinflammatory effect of glucocorticoids is chiefly mediated by GR transrepression. Thus, our findings suggest the similarity between the mechanisms of antiinflammatory and anticancer effects of the GR signaling. We discuss the potential clinical applications of our findings in light of drug discovery programs focused on the development of selective GR modulators that preferentially induce GR transrepression.
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Affiliation(s)
- Dmitry Chebotaev
- Department of Dermatology, Feinberg Medical School, Northwestern University, Chicago, Illinois 60611, USA
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113
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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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114
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Jin XC, Lu YF, Yang XF, Ma L, Li BM. Glucocorticoid receptors in the basolateral nucleus of amygdala are required for postreactivation reconsolidation of auditory fear memory. Eur J Neurosci 2007; 25:3702-12. [PMID: 17610589 DOI: 10.1111/j.1460-9568.2007.05621.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
It is well known that initial consolidation requires de novo gene transcription and protein synthesis in order for memory to become stable. The consolidated memory again becomes labile and temporarily sensitive to disruption when retrieved, requiring a reconsolidation process to become permanent. Although it is well established that glucocorticoid receptors (GR) in the basolateral nucleus of amygdala (BLA) are required for consolidation of fear memory, little is known about their role in reconsolidation of fear memory. In the present study, we first examined the effect of a GR antagonist on postconditioning consolidation of auditory fear memory (AFM). Intra-BLA infusion of the GR antagonist RU486 0 h postconditioning impaired long-term AFM, leaving short-term AFM intact. RU486 had no effect if infusion was performed 6 h postconditioning. We then investigated the effect of the RU486 treatment on postretrieval reconsolidation of AFM. Severe amnesia took place when RU486 was infused into the BLA 0 h postretrieval (reactivation) of AFM, regardless of whether the retrieval was performed 1 day or 10 days postconditioning. RU486 produced no amnesia if the memory retrieval was omitted or if the drug was administered 6 h postretrieval. Treatment with RU486 0 h postretrieval produced no deficit in postretrieval short-term memory but impaired postretrieval long-term memory, and the amnesia exhibited no spontaneous recovery 6 days after retrieval. The present results provide strong evidence that glucocorticoid receptors in the BLA are required for reconsolidation as well as consolidation of AFM.
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Affiliation(s)
- Xin-Chun Jin
- Institute of Neurobiology, Institutes of Brain Science, Fudan University, 138 Yi Xue Yuan Road, Shanghai 200032, China
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115
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Zhu J, Gong JY, Goodman OB, Cartegni L, Nanus DM, Shen R. Bombesin attenuates pre-mRNA splicing of glucocorticoid receptor by regulating the expression of serine-arginine protein p30c (SRp30c) in prostate cancer cells. BIOCHIMICA ET BIOPHYSICA ACTA 2007; 1773:1087-94. [PMID: 17540466 PMCID: PMC1939980 DOI: 10.1016/j.bbamcr.2007.04.016] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2007] [Revised: 04/17/2007] [Accepted: 04/20/2007] [Indexed: 11/19/2022]
Abstract
Although glucocorticoids are frequently administered to patients with hormone refractory prostate cancer, their therapeutic effectiveness is limited by the development of glucocorticoid resistance. The molecular mechanisms of glucocorticoid resistance are unknown but are believed to involve neuropeptide growth factors and cytokines. We examined the functional interaction between bombesin and dexamethasone in PC-3 cells and found that bombesin could act as a survival factor by interfering with dexamethasone-mediated growth inhibition. Because glucocorticoids exert their effects through glucocorticoid receptors (GRs), we measured the expression of GR alpha and GR beta isoforms in the presence of bombesin. Western blotting and real time PCR revealed bombesin induced expression of GR beta, but not GR alpha. Because GR isoforms are generated by alternative splicing of a common GR gene, we examined the expression of serine-arginine (SR) proteins involved in alternative splicing, and found that the expression of SRp30 was induced by bombesin in PC-3 cells. To characterize the role of SRp30 in splicing of GR isoforms, siRNAs specific to various SRp30 isoforms were transfected into PC-3 cells. We found that suppression of SRp30c expression by siRNA specifically antagonized bombesin's effect on glucocorticoid-mediated inhibition of PC cells, suggesting that bombesin-induced expression of SRp30c affects GR pre-mRNA splicing, leading to increased GR beta expression and contributing to glucocorticoid resistance in PC cells.
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Affiliation(s)
- Jin Zhu
- Department of Urology, Weill Medical College of Cornell University and New York Presbyterian Hospital, New York, NY
| | - Jun Y. Gong
- Department of Urology, Weill Medical College of Cornell University and New York Presbyterian Hospital, New York, NY
| | - Oscar B. Goodman
- Department of Medicine, Weill Medical College of Cornell University and New York Presbyterian Hospital, New York, NY
| | - Luca Cartegni
- Department of Molecular Pharmacology and Chemistry, Memorial Sloan Kettering Cancer Center, New York, NY
| | - David M. Nanus
- Department of Urology, Weill Medical College of Cornell University and New York Presbyterian Hospital, New York, NY
- Department of Medicine, Weill Medical College of Cornell University and New York Presbyterian Hospital, New York, NY
| | - Ruoqian Shen
- Department of Urology, Weill Medical College of Cornell University and New York Presbyterian Hospital, New York, NY
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116
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Sánchez-Vega B, Krett N, Rosen ST, Gandhi V. Glucocorticoid receptor transcriptional isoforms and resistance in multiple myeloma cells. Mol Cancer Ther 2007; 5:3062-70. [PMID: 17172408 DOI: 10.1158/1535-7163.mct-06-0344] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Although glucocorticoids play an important role in the treatment of multiple myeloma, some patients do not respond or develop resistance. The glucocorticoid receptor (GR), a single gene, mediates the effects of glucocorticoids. Using a model system of a multiple myeloma cell line sensitive to glucocorticoids and its early and late resistant variants, we have analyzed mutations in the GR gene, detected the presence of different transcriptional isoforms, quantified their levels of expression, and identified the promoters that regulate their expression. Levels of GR transcripts were comparable with the expression of total GR protein. Development of resistance correlates with an overall reduction in GR mRNA levels. This decrease in GR levels is neither due to mutation of the gene nor due to methylation. GRalpha is the predominant isoform in the sensitive cell line decreasing in expression in the early resistant cells and virtually undetectable in late resistant cells. GR-P is expressed at equivalent levels in both sensitive and early resistant cells, whereas in the late resistant cells, GR-P is the predominant isoform. GR-A is only expressed in the early resistant cell line. GRbeta is the least expressed isoform in all cell lines. Interestingly, the level of expression of exon 1-exon 2 RNA fragments remains similar in sensitive and resistant cell lines. Resistant cells became sensitive to glucocorticoids after GRalpha transfection. In conclusion, we show different patterns of expression of the GR isoforms and provide evidence that a decline in the expression of GRalpha may be associated with development of resistance.
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Affiliation(s)
- Beatriz Sánchez-Vega
- Department of Experimental Therapeutics, University of Texas M.D. Anderson Cancer Center, Box 71, 1515 Holcombe Boulevard, Houston, TX 77030, USA
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117
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Lagrèze WA. Steroide bei Sehnerverkrankungen? Ophthalmologe 2007; 104:517-20. [PMID: 17486348 DOI: 10.1007/s00347-007-1525-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Diseases of the optic nerve are the third most common cause of blindness in Germany. Common optic nerve diseases include optic nerve neuritis and traumatic optic neuropathy. These diseases are often treated with steroids. In the case of traumatic optic neuropathy, recent results indicate that such treatment is not of value, and can even be dangerous due to the side effects if the doses are high. Based on current results, the value of high dose steroid treatment for optic nerve neuritis is also questionable.
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Affiliation(s)
- W A Lagrèze
- Universitäts-Augenklinik Freiburg, 79106, Freiburg.
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118
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Hardy RS, Filer A, Cooper MS, Parsonage G, Raza K, Hardie DL, Rabbitt EH, Stewart PM, Buckley CD, Hewison M. Differential expression, function and response to inflammatory stimuli of 11beta-hydroxysteroid dehydrogenase type 1 in human fibroblasts: a mechanism for tissue-specific regulation of inflammation. Arthritis Res Ther 2007; 8:R108. [PMID: 16846535 PMCID: PMC1779419 DOI: 10.1186/ar1993] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2006] [Revised: 05/22/2006] [Accepted: 06/19/2006] [Indexed: 11/10/2022] Open
Abstract
Stromal cells such as fibroblasts play an important role in defining tissue-specific responses during the resolution of inflammation. We hypothesized that this involves tissue-specific regulation of glucocorticoids, mediated via differential regulation of the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). Expression, activity and function of 11β-HSD1 was assessed in matched fibroblasts derived from various tissues (synovium, bone marrow and skin) obtained from patients with rheumatoid arthritis or osteoarthritis. 11β-HSD1 was expressed in fibroblasts from all tissues but mRNA levels and enzyme activity were higher in synovial fibroblasts (2-fold and 13-fold higher mRNA levels in dermal and synovial fibroblasts, respectively, relative to bone marrow). Expression and activity of the enzyme increased in all fibroblasts following treatment with tumour necrosis factor-α or IL-1β (bone marrow: 8-fold and 37-fold, respectively, compared to vehicle; dermal fibroblasts: 4-fold and 14-fold; synovial fibroblasts: 7-fold and 31-fold; all P < 0.01 compared with vehicle). Treatment with IL-4 or interferon-γ was without effect, and there was no difference in 11β-HSD1 expression between fibroblasts (from any site) obtained from patients with rheumatoid arthritis or osteoarthritis. In the presence of 100 nmol/l cortisone, IL-6 production – a characteristic feature of synovial derived fibroblasts – was significantly reduced in synovial but not dermal or bone marrow fibroblasts. This was prevented by co-treatment with an 11β-HSD inhibitor, emphasizing the potential for autocrine activation of glucocorticoids in synovial fibroblasts. These data indicate that differences in fibroblast-derived glucocorticoid production (via the enzyme 11β-HSD1) between cells from distinct anatomical locations may play a key role in the predeliction of certain tissues to develop persistent inflammation.
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Affiliation(s)
- Rowan S Hardy
- Division of Medical Sciences, Institute of Biomedical Research, The University of Birmingham Medical School, Birmingham, UK
| | - Andrew Filer
- Division of Immunity and Infection, Institute of Biomedical Research, The University of Birmingham Medical School, Birmingham, UK
| | - Mark S Cooper
- Division of Medical Sciences, Institute of Biomedical Research, The University of Birmingham Medical School, Birmingham, UK
| | - Greg Parsonage
- Division of Immunity and Infection, Institute of Biomedical Research, The University of Birmingham Medical School, Birmingham, UK
| | - Karim Raza
- Division of Immunity and Infection, Institute of Biomedical Research, The University of Birmingham Medical School, Birmingham, UK
| | - Debbie L Hardie
- Division of Immunity and Infection, Institute of Biomedical Research, The University of Birmingham Medical School, Birmingham, UK
| | - Elizabeth H Rabbitt
- Division of Medical Sciences, Institute of Biomedical Research, The University of Birmingham Medical School, Birmingham, UK
| | - Paul M Stewart
- Division of Medical Sciences, Institute of Biomedical Research, The University of Birmingham Medical School, Birmingham, UK
| | - Christopher D Buckley
- Division of Immunity and Infection, Institute of Biomedical Research, The University of Birmingham Medical School, Birmingham, UK
| | - Martin Hewison
- Division of Endocrinology, Diabetes and Metabolism, Cedars-Sinai Medical Center, Los Angeles, California, USA
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119
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Wang Z, Chen W, Kono E, Dang T, Garabedian MJ. Modulation of glucocorticoid receptor phosphorylation and transcriptional activity by a C-terminal-associated protein phosphatase. Mol Endocrinol 2006; 21:625-34. [PMID: 17185395 DOI: 10.1210/me.2005-0338] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The glucocorticoid receptor (GR) is phosphorylated at three major sites on its N terminus (S203, S211, and S226), and phosphorylation modulates GR-regulatory functions in vivo. We examined the phosphorylation site interdependence, the contribution of the receptor C-terminal ligand-binding domain, and the participation of protein phosphatases in GR N-terminal phosphorylation and gene expression. We found that GR phosphorylation at S203 was greater when S226 was not phosphorylated and vice versa, indicative of intersite dependency. We also observed that a GR derivative lacking the ligand-binding domain, which no longer binds the heat shock protein 90 (Hsp90) complex, exhibits increased GR phosphorylation at all three sites as compared with the full-length receptor. A GR mutation (F602S) that produces a receptor less dependent on Hsp90 for function as well as treatment with the Hsp90 inhibitor geldanamycin also increased basal GR phosphorylation at a subset of sites. Pharmacological inhibition of serine/threonine protein phosphatases increased GR basal phosphorylation. Likewise, a reduction in protein phosphatase 5 protein levels enhanced GR phosphorylation at a subset of sites and selectively reduced the induction of endogenous GR target genes. Together, our findings suggest that GR undergoes a phosphorylation/dephosphorylation cycle that maintains steady-state receptor phosphorylation at a low basal level in the absence of ligand. Our findings also suggest that the ligand-dependent increase in GR phosphorylation results, in part, from the dissociation of a ligand-binding domain-linked protein phosphatase(s), and that changes in the intracellular concentration of protein phosphatase 5 differentially affect GR target gene expression.
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Affiliation(s)
- Zhen Wang
- Department of Microbiology, New York University Cancer Institute, New York University School of Medicine, 550 First Avenue, New York, New York 10016, USA
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120
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Singer TD, Raptis S, Sathiyaa R, Nichols JW, Playle RC, Vijayan MM. Tissue-specific modulation of glucocorticoid receptor expression in response to salinity acclimation in rainbow trout. Comp Biochem Physiol B Biochem Mol Biol 2006; 146:271-8. [PMID: 17215158 DOI: 10.1016/j.cbpb.2006.11.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2006] [Revised: 11/03/2006] [Accepted: 11/04/2006] [Indexed: 11/25/2022]
Abstract
While studies clearly point to a role for cortisol signaling in seawater adaptation, very little is known about salinity impact on glucocorticoid receptor (GR) expression in fish. To this end, we investigated the temporal GR expression in the gill and liver of rainbow trout (Oncorhynchus mykiss) to salinity exposure. Trout were subjected to gradual salinity increases (11 ppt for 1 d, 17 ppt for 2 d and 23 ppt for 2 d) over a five day period. Gill Na(+), K(+)-ATPase alpha-subunit mRNA showed a transient elevation with salinity exposure, while gill cystic fibrosis transmembrane conductance regulator mRNA was not significantly affected by salinity. Liver PEPCK transcript levels showed a transient increase at day 1, but not at day 3 or day 5 of salinity exposure, while the activity of this enzyme was significantly depressed at all time points. Liver glycogen content was also significantly reduced by salinity exposure compared to the freshwater group. Gill GR transcript levels were 3-fold greater upon salinity exposure and this level was maintained over the 5 day period, while gill GR protein content remained unchanged except for a significant drop at day 1 of salinity exposure. Liver GR transcript levels showed no significant change with salinity exposure, while GR protein content was transiently elevated at day 3, but not at day 1 or day 5 of salinity exposure. The tissue-specific GR transcript response in the gill leads us to hypothesize a role for osmosensory signal transduction pathway in the regulation of GR expression in fish. Collectively, salinity exposure modulates GR expression and glucocorticoid signaling in rainbow trout.
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Affiliation(s)
- Thomas D Singer
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
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Goecke IA, Alvarez C, Henríquez J, Salas K, Molina ML, Ferreira A, Gatica H. Methotrexate regulates the expression of glucocorticoid receptor alpha and beta isoforms in normal human peripheral mononuclear cells and human lymphocyte cell lines in vitro. Mol Immunol 2006; 44:2115-23. [PMID: 17118450 DOI: 10.1016/j.molimm.2006.07.303] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2006] [Revised: 07/22/2006] [Accepted: 07/24/2006] [Indexed: 12/01/2022]
Abstract
MTX is an effective therapy for autoimmune-inflammatory diseases. The mechanisms that mediate these actions are not completely clear. It is accepted that many of these effects are mediated through the release of adenosine with the activation of the adenosine receptor A2. MTX is used as a steroid sparing agent. An improved in vitro GC cell sensitivity in GC insensitive asthma patients has been demonstrated after MTX treatment. Most GC actions are mediated by the GCR. The effect of MTX on GCRs expression has not been previously evaluated. Therefore, we evaluate if MTX regulates the expression of glucocorticoid receptors, increasing the expression of the active receptor (GCR alpha) and/or decreasing the expression of the dominant negative receptor (GCR beta). We show that MTX increases the mRNA and protein levels of GCR alpha and decreases or leaves unchanged the protein expression of the GCR beta in CEM cells in culture. This effect was also observed in other lymphocytes (Jurkat and Raji) and in PBMNC from healthy volunteers. We also show that upon MTX treatment PBMC from normal volunteers exhibit a higher sensitivity to DEX inhibition on LPS-induced TNF alpha release. To explore if these actions are mediated by adenosine through the adenosine receptor A2 we evaluate the effect of adenosine on the GCRs expression and the effect of an A2 receptor blocker (DMPX) on MTX effects on GCRs expression. Our results show that adenosine does not mimic and DMPX can enhance MTX effects on these receptors. We conclude that MTX increases the GCR alpha/GCR beta ratio of expression in lymphocytes which could mediate its previously reported effects in improving cell glucocorticoid sensitivity. These actions are not mediated by the adenosine receptor A2.
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Affiliation(s)
- I Annelise Goecke
- Rheumatology Service, Internal Medicine Department, Clinical Hospital, University of Chile, Santos Dumont 999, Santiago, Chile.
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122
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Dexamethasone stimulates expression of C-type Natriuretic Peptide in chondrocytes. BMC Musculoskelet Disord 2006; 7:87. [PMID: 17116261 PMCID: PMC1660540 DOI: 10.1186/1471-2474-7-87] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2006] [Accepted: 11/20/2006] [Indexed: 11/29/2022] Open
Abstract
Background Growth of endochondral bones is regulated through the activity of cartilaginous growth plates. Disruption of the physiological patterns of chondrocyte proliferation and differentiation – such as in endocrine disorders or in many different genetic diseases (e.g. chondrodysplasias) – generally results in dwarfism and skeletal defects. For example, glucocorticoid administration in children inhibits endochondral bone growth, but the molecular targets of these hormones in chondrocytes remain largely unknown. In contrast, recent studies have shown that C-type Natriuretic Peptide (CNP) is an important anabolic regulator of cartilage growth, and loss-of-function mutations in the human CNP receptor gene cause dwarfism. We asked whether glucocorticoids could exert their activities by interfering with the expression of CNP or its downstream signaling components. Methods Primary mouse chondrocytes in monolayer where incubated with the synthetic glucocorticoid Dexamethasone (DEX) for 12 to 72 hours. Cell numbers were determined by counting, and real-time PCR was performed to examine regulation of genes in the CNP signaling pathway by DEX. Results We show that DEX does influence expression of key genes in the CNP pathway. Most importantly, DEX significantly increases RNA expression of the gene encoding CNP itself (Nppc). In addition, DEX stimulates expression of Prkg2 (encoding cGMP-dependent protein kinase II) and Npr3 (natriuretic peptide decoy receptor) genes. Conversely, DEX was found to down-regulate the expression of the gene encoding its receptor, Nr3c1 (glucocorticoid receptor), as well as the Npr2 gene (encoding the CNP receptor). Conclusion Our data suggest that the growth-suppressive activities of DEX are not due to blockade of CNP signaling. This study reveals a novel, unanticipated relationship between glucocorticoid and CNP signaling and provides the first evidence that CNP expression in chondrocytes is regulated by endocrine factors.
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123
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Xu D, Buehner A, Xu J, Lambert T, Nekl C, Nielsen MK, Zhou Y. A polymorphic glucocorticoid receptor in a mouse population may explain inherited altered stress response and increased anxiety‐type behaviors. FASEB J 2006; 20:2414-6. [PMID: 17012242 DOI: 10.1096/fj.06-5926fje] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A polymorphic glucocorticoid receptor (GR(Qn)) with an expanded CAG track and two silent mutations, when compared with the sequence of other isoform (GR(wt)), is found in two outbred mouse lines that were produced by selection for high (SH) or low (SL) stress response from high or low heat loss lines of mice, respectively. The GR(Qn) allele, which is also found in 5 of 16 commonly used inbred mouse lines, had a much higher frequency in SL mice; the GR(wt/wt) was found only in the SH line. Both GR(Qn/Qn) and GR(wt/Qn) mice had a much weaker corticosterone response to stress than the GR(wt/wt) mice. Assessment of open field activity revealed that GR(Qn/Qn) and GR(wt/Qn) mice exhibited significantly lower velocity and locomotor activity, less time in the center, and much longer duration in corner zones than the GR(wt/wt) mice. The increased anxiety-type behaviors of the GR(Qn/Qn) and GR(wt/Qn) mice were confirmed by the "elevated plus maze" test in which GR(Qn/Qn) and GR(wt/Qn) mice spent significantly less time in the "open arm" and longer duration in the "closed arm," than GR(wt/wt) mice. These results suggest this GR polymorphism plays a role in complex mechanisms leading to lower corticosterone response to stress, and may also be associated with decreased locomotive and increased anxiety-type behaviors in mice.
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Affiliation(s)
- Dongsheng Xu
- Department of Veterinary and Biomedical Science, University of Nebraska-Lincoln, Lincoln, NE 68588-0665, USA
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124
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Turner JD, Schote AB, Macedo JA, Pelascini LPL, Muller CP. Tissue specific glucocorticoid receptor expression, a role for alternative first exon usage? Biochem Pharmacol 2006; 72:1529-37. [PMID: 16930562 DOI: 10.1016/j.bcp.2006.07.005] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2006] [Revised: 07/04/2006] [Accepted: 07/11/2006] [Indexed: 01/28/2023]
Abstract
The CpG island upstream of the GR is highly structured and conserved at least in all the animal species that have been investigated. Sequence alignment of these CpG islands shows inter-species homology ranging from 64 to 99%. This 3.1kb CpG rich region upstream of the GR exon 2 encodes 5' untranslated mRNA regions. These CpG rich regions are organised into multiple first exons and, as we and others have postulated, each with its own promoter region. Alternative mRNA transcript variants are obtained by the splicing of these alternative first exons to a common acceptor site in the second exon of the GR. Exon 2 contains an in-frame stop codon immediately upstream of the ATG start codon to ensure that this 5' heterogeneity remains untranslated, and that the sequence and structure of the GR is unaffected. Tissue specific differential usage of exon 1s has been observed in a range of human tissues, and to a lesser extent in the rat and mouse. The GR expression level is tightly controlled within each tissue or cell type at baseline and upon stimulation. We suggest that no single promoter region may be capable of containing all the necessary promoter elements and yet preserve the necessary proximity to the transcription initiation site to produce such a plethora of responses. Thus we further suggest that alternative first exons each under the control of specific transcription factors control both the tissue specific GR expression and are involved in the tissue specific GR transcriptional response to stimulation. Spreading the necessary promoter elements over multiple promoter regions, each with an associated alternative transcription initiation site would appear to vastly increase the capacity for transcriptional control of GR.
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Affiliation(s)
- Jonathan D Turner
- Institute of Immunology, Laboratoire National de Santé, 20A rue Auguste Lumière, L-1950 Luxembourg, Grand Duchy of Luxembourg
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125
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Ito K, Chung KF, Adcock IM. Update on glucocorticoid action and resistance. J Allergy Clin Immunol 2006; 117:522-43. [PMID: 16522450 DOI: 10.1016/j.jaci.2006.01.032] [Citation(s) in RCA: 278] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2006] [Revised: 01/25/2006] [Accepted: 01/25/2006] [Indexed: 12/11/2022]
Abstract
Extensive development of inhaled and oral glucocorticoids has resulted in highly potent molecules that have been optimized to target activity to the lung and minimize systemic exposure. These have proved highly effective for most asthmatic subjects, but despite these developments, there are a number of subjects with asthma who fail to respond to even high doses of inhaled or even oral glucocorticoids. Advances in delineating the fundamental mechanisms of glucocorticoid pharmacology, especially the concepts of transactivation and transrepression and cofactor recruitment, have resulted in better understanding of the molecular mechanisms whereby glucocorticoids suppress inflammation. The existence of multiple mechanisms underlying glucocorticoid insensitivity raises the possibility that this might indeed reflect different diseases with a common phenotype, and studies examining the efficacy of potential new agents should be targeted toward subgroups of patients with severe corticosteroid-resistant asthma who clearly require effective new drugs and other approaches to improved asthma control.
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Affiliation(s)
- Kazuhiro Ito
- Cell and Molecular Biology, Airways Disease Section, National Heart and Lung Institute, Imperial College London, UK
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126
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Zeissig S, Fromm A, Mankertz J, Zeitz M, Fromm M, Schulzke JD. Restoration of ENaC expression by glucocorticoid receptor transfection in human HT-29/B6 colon cells. Biochem Biophys Res Commun 2006; 344:1065-70. [PMID: 16643850 DOI: 10.1016/j.bbrc.2006.04.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2006] [Accepted: 04/03/2006] [Indexed: 11/30/2022]
Abstract
The epithelial sodium channel (ENaC) controls colonic sodium absorption. So far, investigation of ENaC was limited by an unexplained lack of steroid-dependent ENaC expression in cultured intestinal cells, which we aimed to resolve. HT-29/B6 cells constitutively expressed the alpha-ENaC subunit, while beta- and gamma-ENaC subunits could not be detected due to deficient basal as well as corticosteroid-induced transcription. This was due to a lack of expression of both activating and inhibiting isoforms of glucocorticoid receptor (GR-alpha, -beta) and mineralocorticoid receptor. Stable transfection of GR-alpha restored intestine-specific glucocorticoid upregulation of beta- and gamma-ENaC in HT-29/B6 cells, which was followed by intact targeting of ENaC channels to the apical cell membrane and dose-dependent induction of electrogenic sodium absorption. In conclusion, ENaC deficiency is due to a lack of steroid receptors and not the consequence of a crypt-like phenotype of cultured intestinal cells. By stable GR transfection we obtained a model, in which ENaC regulation can be studied.
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Affiliation(s)
- Sebastian Zeissig
- Department of Gastroenterology, Charité, Campus Benjamin Franklin, Berlin, Germany.
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127
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Takahashi H, Sakamoto T, Hyodo S, Shepherd BS, Kaneko T, Grau EG. Expression of glucocorticoid receptor in the intestine of a euryhaline teleost, the Mozambique tilapia (Oreochromis mossambicus): Effect of seawater exposure and cortisol treatment. Life Sci 2006; 78:2329-35. [PMID: 16376384 DOI: 10.1016/j.lfs.2005.09.050] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2005] [Accepted: 09/20/2005] [Indexed: 11/21/2022]
Abstract
Cortisol plays an important role in controlling intestinal water and ion transport in teleosts possibly through glucocorticoid receptor (GR) and/or mineralocorticoid receptor. To better understand the role of GR in the teleost intestine, in a euryhaline tilapia, Oreochromis mossambicus, we examined (1) the intestinal localizations of GR; (2) the effects of environmental salinity challenge and cortisol treatment on GR mRNA expression. The mRNA abundance of GR in the posterior intestinal region of tilapia was found to be higher than that in the anterior and middle intestine. In the posterior intestine, GR appears to be localized in the mucosal layer. GR mRNA levels in the posterior intestine were elevated after exposure of freshwater fish to seawater for 7 days following an increase in plasma cortisol. Similarly, cortisol implantation in freshwater tilapia for 7 days elevated the intestinal GR mRNA. These results indicate that seawater acclimation is accompanied by upregulation of GR mRNA abundance in intestinal tissue, possibly as a consequence of the elevation of cortisol levels. In contrast, a single intraperitoneal injection of cortisol into freshwater tilapia decreased intestinal GR mRNA. This downregulation of the GR mRNA by cortisol suggests a dual mode of autoregulation of GR expression by cortisol.
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Affiliation(s)
- Hideya Takahashi
- Ushimado Marine Laboratory, Graduate School of Natural Science and Technology, Okayama University, Ushimado, Setouchi, Okayama, 701-4303, Japan
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128
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Alexander SPH, Mathie A, Peters JA. Steroid hormone. Br J Pharmacol 2006. [DOI: 10.1038/sj.bjp.0706483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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129
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Scutt N, Rolf CG, Scutt A. Glucocorticoids inhibit tenocyte proliferation and Tendon progenitor cell recruitment. J Orthop Res 2006; 24:173-82. [PMID: 16435354 DOI: 10.1002/jor.20030] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Corticosteroid injection is commonly used to treat tendon injuries but is often associated with tendon rupture and impaired tendon healing. The effects of dexamethasone on tenocytes have been studied in vitro but only using high concentrations of dexamethasone in monolayer cultures of tenocytes over short periods of time. We have therefore investigated the effects of physiological and pharmacological concentrations of dexamethasone on monolayer cultures of tenocytes over extended time periods. We have also used fibroblastic-colony forming unit cultures to examine the effects of dexamethasone on a progenitor cell population located in tendons. Culturing tenocytes in the presence of dexamethasone for a period of 24 days resulted in a concentration-related decrease in cell number and collagen synthesis as compared to control cultures. This effect was time dependent with cell number in both dexamethasone-treated and control cultures leveling off after 14 days with the control cultures reaching higher cell densities. In contrast in control cultures, collagen accumulation continued to increase until week 4, whereas in the presence of dexamethasone, this tended to level off after 14 days. To study the role of progenitor cell recruitment, the effects of dexamethasone were investigated using the fibroblastic-colony forming unit assay. Treatment with dexamethasone at concentrations of 0.1 nM to 10 microM leads to a progressive reduction in mean colony size as compared to control cultures. Colony number remained constant at concentrations below 10 nM but fell progressively at concentrations above this. In conclusion, dexamethasone reduces both cell number and collagen synthesis in tenocyte cultures in a concentration-dependent manner by both direct effects on tenocyte proliferation and collagen accumulation, and also by modulating the recruitment of tendon progenitor cells.
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Affiliation(s)
- Nanette Scutt
- Sheffield Centre for Sports Medicine, Division of Clinical Sciences South, University of Sheffield Medical School, Sheffield, United Kingdom
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130
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Goecke A, Guerrero J. Glucocorticoid receptor beta in acute and chronic inflammatory conditions: clinical implications. Immunobiology 2005; 211:85-96. [PMID: 16446173 DOI: 10.1016/j.imbio.2005.11.002] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2005] [Accepted: 09/29/2005] [Indexed: 01/02/2023]
Abstract
Glucocorticoids (GC) are hormones with a wide variety of actions, including profound anti-inflammatory/immunosuppressive effects. Their actions are mediated by an intracellular receptor called the glucocorticoid receptor (GCR). The classical GCR that mediates the hormone response is called GCR alpha. Recently however, many GCR isotypes have been described. A defective GC action has been proposed as an etio-pathogenic mechanism for the development of inflammatory/autoimmune diseases. Inadequate GC actions may have multiple causes such as: defective hypothalamic-pituitary-adrenal axis function, GC export from cells, hormone metabolization into inactive compounds and modifications of the GC receptor, among others. In 1995, a dominant negative effect of a GC receptor isotype termed beta was described; starting a still unsolved controversy about the role of GCR beta as an inducer of GC resistance in certain pathological conditions. The present article will review the data about a possible role for GCR beta in the development of GC resistance in inflammatory diseases. This review will especially focus on the role of the GCR beta in rheumatoid arthritis and in septic shock as examples of a chronic inflammatory disease and an acute systemic inflammatory condition. Original data supporting possible hyperexpression of GCR beta in both conditions will be shown.
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Affiliation(s)
- Annelise Goecke
- Rheumatology Service, Internal Medicine Department, Clinical Hospital, University of Chile, Santiago, Chile.
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132
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DeRijk R, de Kloet ER. Corticosteroid receptor genetic polymorphisms and stress responsivity. Endocrine 2005; 28:263-70. [PMID: 16388115 DOI: 10.1385/endo:28:3:263] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2005] [Accepted: 07/13/2005] [Indexed: 11/11/2022]
Abstract
A fundamental question in the neuroendocrinology of stress-related psychopathology is why some individuals flourish and others perish under similar adverse conditions. In this contribution we focus on the variants of mineralocorticorticoid (MR) and glucocorticoid receptors (GR) that operate in balance and coordinate behavioral, autonomic, and neuroendocrine response patterns involved in homeostasis and health. In the GR-gene, three single nucleotide polymorphism (SNPs) have been associated with changes in metabolic profile and cardiovascular parameters: the ER22/23EK with a favorable and the N363S and the Bcl1 with a more adverse profile. Importantly, the N363S and the Bcl1 are found to increase cortisol responses to a psychosocial stressor. As a result, the whole body will suffer from overexposure with possible adverse effects on metabolism, cardiovascular control, immune function, and behavior. Also in the MR gene, variants are being identified that are associated with dysregulated autonomic, behavioral, and neuroendocrine responses. The data suggest that these MR and GR variants contribute to individual differences in resilience and vulnerability to stressors, and that these receptors therefore are potential drug targets for recovery of homeostasis and health.
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MESH Headings
- Adaptation, Physiological
- Humans
- Hydrocortisone/metabolism
- Polymorphism, Single Nucleotide/genetics
- Receptors, Glucocorticoid/genetics
- Receptors, Glucocorticoid/metabolism
- Receptors, Mineralocorticoid/genetics
- Receptors, Mineralocorticoid/metabolism
- Stress, Physiological/genetics
- Stress, Physiological/metabolism
- Stress, Psychological/genetics
- Stress, Psychological/metabolism
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Affiliation(s)
- Roel DeRijk
- Department of Psychiatry, Leiden University Medical Center, 2300 RC, Leiden, The Netherlands
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133
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Davies S, Dai D, Pickett G, Leslie KK. Gene regulation profiles by progesterone and dexamethasone in human endometrial cancer Ishikawa H cells. Gynecol Oncol 2005; 101:62-70. [PMID: 16289307 DOI: 10.1016/j.ygyno.2005.09.054] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2005] [Revised: 09/13/2005] [Accepted: 09/22/2005] [Indexed: 01/31/2023]
Abstract
OBJECTIVE Progesterone and glucocorticoids such as dexamethasone mediate distinct biological functions, yet they bind to receptors that recognize the same consensus DNA response element. In breast cancer, progestins are associated with the incidence and progression of tumors, whereas glucocorticoids are growth-suppressive in mammary cancer cells; the differential effects of these two steroids are less well understood in the hormone-dependent disease cancer of the uterine endometrium. We set out to identify genes that are regulated by progesterone through progesterone receptors and dexamethasone through glucocorticoid receptors in a well-differentiated human endometrial cancer cell line. METHODS PR- and GR-positive Ishikawa H endometrial cancer cells were treated with vehicle, dexamethasone (100 nM) or progesterone (100 nM) for 2 h, 6 h, 12 h and 24 h, and RNA was isolated. Affymetrix microarrays were performed using the human HG-U133A chip, querying the expression of 22,000 genes. Expression of genes of particular interest was confirmed by real-time RT-PCR. RESULTS Expression analysis demonstrated that dexamethasone and progesterone regulate overlapping but distinct sets of genes and presumably exert many similar but also unique biological effects. Using real-time RT-PCR, we confirmed three particular genes of interest: the transcript for cysteine 1 (legumain), a gene associated with metastasis, that is strongly downregulated by progesterone, upstream c-fos relating transcription factor-2 (USF-2), an anti-proliferative factor that is induced by both progesterone and dexamethasone and N-cadherin, a cellular adhesion molecule downregulated by dexamethasone. CONCLUSION These studies provide new insight into the effects of progesterone and dexamethasone in endometrial cancer cells and provide an extensive list of regulated pathways which can be assessed in the future as biomarkers and molecular targets for new therapies. Taken together, our findings indicate that progesterone and dexamethasone are primarily growth inhibitors in Ishikawa H endometrial cancer cells.
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Affiliation(s)
- Suzy Davies
- Reproductive Molecular Biology Laboratory, Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, The University of New Mexico Health Sciences Center, Albuquerque, NM 87131-5286, USA
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134
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Koubovec D, Ronacher K, Stubsrud E, Louw A, Hapgood JP. Synthetic progestins used in HRT have different glucocorticoid agonist properties. Mol Cell Endocrinol 2005; 242:23-32. [PMID: 16125839 DOI: 10.1016/j.mce.2005.07.001] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2005] [Revised: 06/29/2005] [Accepted: 07/06/2005] [Indexed: 10/25/2022]
Abstract
The synthetic progestins, medroxyprogesterone acetate (MPA) and norethisterone acetate (NET-EN or NET-A), are widely used as female contraceptive agents and in hormone replacement therapy (HRT). Competitive binding revealed that MPA displays a higher relative binding affinity than NET-A and progesterone (prog) for the human GR (Kd of 4.2 nM for dexamethasone (dex) and Ki's of 10.8, 270 and 215 nM for MPA, NET-A and prog, respectively). Furthermore, MPA displays much greater glucocorticoid (GC) transactivation agonist potency than NET-A or prog (EC50s of 1.1, 7.2, >1000 and 280 nM for dex, MPA, NET-A and prog, respectively) and much greater GC agonist potency for transrepression than NET-A or prog (EC50s of 0.21, 2.7, >100 and 26 nM for dex, MPA, NET-A and prog, respectively). In addition, MPA induces phosphorylation of the GR at Ser 211 to a much greater extent than NET-A or prog and protects the GR from partial trypsin digestion in vitro to a much greater extent than NET-A or prog at saturating concentrations. Together these results suggest that the differences in biological activity of the progestins are not merely due to differences in their affinity for the GR but also due to the induction of different conformational changes in the liganded-GR. MPA and NET-A therefore display very different GC-like properties compared to each other and to prog, and are likely to exhibit different side effects via the GR.
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Affiliation(s)
- Dominique Koubovec
- Department of Biochemistry, University of Stellenbosch, Private Bag X1, Matieland, Stellenbosch 7602, South Africa
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135
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Moraes LA, Paul-Clark MJ, Rickman A, Flower RJ, Goulding NJ, Perretti M. Ligand-specific glucocorticoid receptor activation in human platelets. Blood 2005; 106:4167-75. [PMID: 16131566 DOI: 10.1182/blood-2005-04-1723] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Few studies have addressed the effects of classical anti-inflammatory glucocorticoids on platelet function. Here, we report for the first time that human platelets contain the glucocorticoid receptor (GR) as identified by a combination of biochemical and functional techniques. Ligand-binding studies revealed the presence of a high- and low-affinity binding site for [3H]-dexamethasone in platelets. The 2 GR ligands prednisolone and dexamethasone competed for [3H]-dexamethasone binding, as did the mineralocorticoid aldosterone. However, while prednisolone (1-10 microM) reduced adenosine diphosphate (ADP, 4 microM) and thromboxane A2 receptor agonist U46619 induced platelet aggregation (up to 75%), dexamethasone had no effect. The inhibition produced by prednisolone was reversed by preincubation with the GR antagonist mifepristone (10 microM; RU486), suggesting the functional importance of the ligand-receptor complex. In addition, prednisolone caused a marked (approximately 50%) reduction in thromboxane B2 levels, whereas dexamethasone was without effect. The apparently anomalous binding data were clarified by the fact that washed platelets (1) contained mineralocorticoid receptor and that (2) it was associated with GR. Taken together, our data suggest that platelet GR forms a heterodimeric complex with the mineralocorticoid receptor that is susceptible to differential activation by specific receptor ligands.
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Affiliation(s)
- Leonardo A Moraes
- The William Harvey Research Institute, Charterhouse Square, London EC1M 6BQ, United Kingdom
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136
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Phuc Le P, Friedman JR, Schug J, Brestelli JE, Parker JB, Bochkis IM, Kaestner KH. Glucocorticoid receptor-dependent gene regulatory networks. PLoS Genet 2005; 1:e16. [PMID: 16110340 PMCID: PMC1186734 DOI: 10.1371/journal.pgen.0010016] [Citation(s) in RCA: 173] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2005] [Accepted: 06/16/2005] [Indexed: 12/23/2022] Open
Abstract
While the molecular mechanisms of glucocorticoid regulation of transcription have been studied in detail, the global networks regulated by the glucocorticoid receptor (GR) remain unknown. To address this question, we performed an orthogonal analysis to identify direct targets of the GR. First, we analyzed the expression profile of mouse livers in the presence or absence of exogenous glucocorticoid, resulting in over 1,300 differentially expressed genes. We then executed genome-wide location analysis on chromatin from the same livers, identifying more than 300 promoters that are bound by the GR. Intersecting the two lists yielded 53 genes whose expression is functionally dependent upon the ligand-bound GR. Further network and sequence analysis of the functional targets enabled us to suggest interactions between the GR and other transcription factors at specific target genes. Together, our results further our understanding of the GR and its targets, and provide the basis for more targeted glucocorticoid therapies.
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Affiliation(s)
- Phillip Phuc Le
- Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Joshua R Friedman
- Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
- Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Jonathan Schug
- Center for Bioinformatics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - John E Brestelli
- Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - J. Brandon Parker
- Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Irina M Bochkis
- Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Klaus H Kaestner
- Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
- *To whom correspondence should be addressed. E-mail:
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137
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Cascallana JL, Bravo A, Donet E, Leis H, Lara MF, Paramio JM, Jorcano JL, Pérez P. Ectoderm-targeted overexpression of the glucocorticoid receptor induces hypohidrotic ectodermal dysplasia. Endocrinology 2005; 146:2629-38. [PMID: 15746257 DOI: 10.1210/en.2004-1246] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Hypohidrotic ectodermal dysplasia is a human syndrome defined by maldevelopment of one or more ectodermal-derived tissues, including the epidermis and cutaneous appendices, teeth, and exocrine glands. The molecular bases of this pathology converge in a dysfunction of the transcription factor nuclear factor of the kappa-enhancer in B cells (NF-kappaB), which is essential to epithelial homeostasis and development. A number of mouse models bearing disruptions in NF-kappaB signaling have been reported to manifest defects in ectodermal derivatives. In ectoderm-targeted transgenic mice overexpressing the glucocorticoid receptor (GR) [keratin 5 (K5)-GR mice], the NF-kappaB activity is greatly decreased due to functional antagonism between GR and NF-kappaB. Here, we report that K5-GR mice exhibit multiple epithelial defects in hair follicle, tooth, and palate development. Additionally, these mice lack Meibomian glands and display underdeveloped sweat and preputial glands. These phenotypic features appear to be mediated specifically by ligand-activated GR because the synthetic analog dexamethasone induced similar defects in epithelial morphogenesis, including odontogenesis, in wild-type mice. We have focused on tooth development in K5-GR mice and found that an inhibitor of steroid synthesis partially reversed the abnormal phenotype. Immunostaining revealed reduced expression of the inhibitor of kappaB kinase subunits, IKKalpha and IKKgamma, and diminished p65 protein levels in K5-GR embryonic tooth, resulting in a significantly reduced kappaB-binding activity. Remarkably, altered NF-kappaB activity elicited by GR overexpression correlated with a dramatic decrease in the protein levels of DeltaNp63 in tooth epithelia without affecting Akt, BMP4, or Foxo3a. Given that many of the 170 clinically distinct ectodermal dysplasia syndromes still remain without cognate genes, deciphering the molecular mechanisms of this mouse model with epithelial NF-kappaB and p63 dysfunction may provide important clues to understanding the basis of other ectodermal dysplasia syndromes.
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Affiliation(s)
- Jose Luis Cascallana
- Department of Animal Pathology, Veterinary Faculty, University of Santiago de Compostela, E-27002 Lugo, Spain
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138
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Czock D, Keller F, Rasche FM, Häussler U. Pharmacokinetics and pharmacodynamics of systemically administered glucocorticoids. Clin Pharmacokinet 2005; 44:61-98. [PMID: 15634032 DOI: 10.2165/00003088-200544010-00003] [Citation(s) in RCA: 557] [Impact Index Per Article: 29.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Glucocorticoids have pleiotropic effects that are used to treat diverse diseases such as asthma, rheumatoid arthritis, systemic lupus erythematosus and acute kidney transplant rejection. The most commonly used systemic glucocorticoids are hydrocortisone, prednisolone, methylprednisolone and dexamethasone. These glucocorticoids have good oral bioavailability and are eliminated mainly by hepatic metabolism and renal excretion of the metabolites. Plasma concentrations follow a biexponential pattern. Two-compartment models are used after intravenous administration, but one-compartment models are sufficient after oral administration.The effects of glucocorticoids are mediated by genomic and possibly nongenomic mechanisms. Genomic mechanisms include activation of the cytosolic glucocorticoid receptor that leads to activation or repression of protein synthesis, including cytokines, chemokines, inflammatory enzymes and adhesion molecules. Thus, inflammation and immune response mechanisms may be modified. Nongenomic mechanisms might play an additional role in glucocorticoid pulse therapy. Clinical efficacy depends on glucocorticoid pharmacokinetics and pharmacodynamics. Pharmacokinetic parameters such as the elimination half-life, and pharmacodynamic parameters such as the concentration producing the half-maximal effect, determine the duration and intensity of glucocorticoid effects. The special contribution of either of these can be distinguished with pharmacokinetic/pharmacodynamic analysis. We performed simulations with a pharmacokinetic/pharmacodynamic model using T helper cell counts and endogenous cortisol as biomarkers for the effects of methylprednisolone. These simulations suggest that the clinical efficacy of low-dose glucocorticoid regimens might be increased with twice-daily glucocorticoid administration.
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Affiliation(s)
- David Czock
- Division of Nephrology, University Hospital Ulm, Robert-Koch-Str. 8, Ulm 89081, Germany
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139
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Chen QM, Alexander D, Sun H, Xie L, Lin Y, Terrand J, Morrissy S, Purdom S. Corticosteroids inhibit cell death induced by doxorubicin in cardiomyocytes: induction of antiapoptosis, antioxidant, and detoxification genes. Mol Pharmacol 2005; 67:1861-73. [PMID: 15755911 DOI: 10.1124/mol.104.003814] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Psychological or physical stress induces an elevation of corticosteroids in the circulating system. We report here that corticosterone (CT) protects cardiomyocytes from apoptotic cell death induced by doxorubicin (Dox), an antineoplastic drug known to induce cardiomyopathy possibly through reactive oxygen species production. The cytoprotection induced by CT is within the range of physiologically relevant doses. The lowest dose tested, 0.1 microM (or 3.5 microg/dl), inhibited apoptosis by approximately 25% as determined by caspase activity. With 1 microM CT, cardiomyocytes gain a cytoprotective effect after 8 h of incubation and remain protected for at least 72 h. Hydrocortisone, cortisone, dexamethasone, and aldosterone but not androstenedione or cholesterol also induced cytoprotection. Analyses of 20,000 gene expression sequences using Affymetrix high-density oligonucleotide array found that CT caused up-regulation of 140 genes and down-regulation of 108 genes over 1.5-fold. Among the up-regulated genes are bcl-xL, metallothioneins, glutathione peroxidase-3, and glutathione S-transferases. Western blot analyses revealed that CT induced an elevation of bcl-xL but not bcl-2 or proapoptotic factors bax, bak, and bad. Inhibiting the expression of bcl-xL reduced the cytoprotective effect of CT. Our data suggest that CT induces a cytoprotective effect on cardiomyocytes in association with reprogramming gene expression and induction of bcl-xL gene.
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Affiliation(s)
- Qin M Chen
- Department of Pharmacology, University of Arizona, 1501 N. Campbell Avenue, Tucson, AZ 85724, USA.
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140
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Abstract
Stress has profound effects on brain structure and function, but the underlying mechanisms are still poorly understood. Recent studies imply that neuronal cell adhesion molecules of the immunoglobulin superfamily--NCAM and L1--are important mediators of the effects of stress on the brain. Chronic stress regimes that lead to hippocampal atrophy and spatial-learning impairment in rodents simultaneously induce a pattern of changes in cell adhesion molecule expression that fits with a role for these molecules in stress-induced neuronal damage and neuroprotective mechanisms. These findings highlight cell adhesion molecules as potential therapeutic targets to treat stress-related cognitive disturbances.
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Affiliation(s)
- Carmen Sandi
- Laboratory of Behavioral Genetics, Brain Mind Institute, Swiss Federal Institute of Technology, EPFL, CH-1015 Lausanne, Switzerland.
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141
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Sturm A, Bury N, Dengreville L, Fagart J, Flouriot G, Rafestin-Oblin ME, Prunet P. 11-deoxycorticosterone is a potent agonist of the rainbow trout (Oncorhynchus mykiss) mineralocorticoid receptor. Endocrinology 2005; 146:47-55. [PMID: 15486226 DOI: 10.1210/en.2004-0128] [Citation(s) in RCA: 166] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The teleost fish are thought to lack the mineralocorticoid hormone aldosterone but possess mineralocorticoid receptor (MR) homologs. Here we describe the characterization of two rainbow trout (Oncorhynchus mykiss) MRs, called rtMRa and rtMRb. The open reading frame of rtMRa cDNA encoded a protein of 1041 amino acids. The rtMRb predicted protein sequence is similar, differing in only 10 amino acids in the nonconserved A/B domain and lacking a three-amino acid insertion between the two zinc fingers of the C domain. Expression of rtMR mRNA (sum of both forms), measured in juvenile trout by real-time RT-PCR, shows that the transcripts are ubiquitous. Expression was significantly higher in brain than the other tissues studied (eye, trunk kidney, head kidney, gut, gills, liver, spleen, ovary, heart, white muscle, skin). Hormonal stimulation of receptor transactivation activity was studied in COS-7 cells transiently cotransfected with receptor cDNA and a mouse mammary tumor virus-luciferase reporter. The mineralocorticoids 11-deoxycorticosterone and aldosterone were more potent enhancers of rtMRa transcriptional activity (EC50 = 1.6 +/- 0.5 x 10(-10) and 1.1 +/- 0.4 x 10(-10) M, respectively) than the glucocorticoids cortisol and 11-deoxycortisol (EC50 = 1.1 +/- 0.3 x 10(-9) and 3.7 +/- 1.9 x 10(-9) M, respectively). A similar response was observed in transactivation assays with rtMRb. These results are discussed in the view of reported circulating levels of corticosteroids in trout.
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Affiliation(s)
- A Sturm
- Station Commune de Recherche en Ichtyophysiologie, Biodiversité et Environnement, Institut National de la Recherche Agonomique, Institut Fedératif de Recherche 98, 35042 Rennes, France
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142
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Schoneveld OJLM, Gaemers IC, Lamers WH. Mechanisms of glucocorticoid signalling. ACTA ACUST UNITED AC 2004; 1680:114-28. [PMID: 15488991 DOI: 10.1016/j.bbaexp.2004.09.004] [Citation(s) in RCA: 215] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2004] [Revised: 09/10/2004] [Accepted: 09/13/2004] [Indexed: 10/26/2022]
Abstract
It has become increasingly clear that glucocorticoid signalling not only comprises the binding of the glucocorticoid receptor (GR) to its response element (GRE), but also involves indirect regulation glucocorticoid-responsive genes by regulating or interacting with other transcription factors. In addition, they can directly regulate gene expression by binding to negative glucocorticoid response elements (nGREs), to simple GREs, to GREs, or to GREs and GRE half sites (GRE1/2s) that are part of a regulatory unit. A response unit allows a higher level of glucocorticoid induction than simple GREs and, in addition, allows the integration of tissue-specific information with the glucocorticoid response. Presumably, the complexity of such a glucocorticoid response unit (GRU) depends on the number of pathways that integrate at this unit. Because GRUs are often located at distant sites relative to the transcription-start site, the GRU has to find a way to communicate with the basal-transcription machinery. We propose that the activating signal of a distal enhancer can be relayed onto the transcription-initiation complex by coupling elements located proximal to the promoter.
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Affiliation(s)
- Onard J L M Schoneveld
- AMC Liver Center, Academic Medical Center, University of Amsterdam, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands
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143
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Pardee K, Reinking J, Krause H. Nuclear Hormone Receptors, Metabolism, and Aging: What Goes Around Comes Around. ACTA ACUST UNITED AC 2004; 2004:re8. [PMID: 15564562 DOI: 10.1126/sageke.2004.47.re8] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Previous studies have linked the mysterious and inevitable process of aging to essential processes such as metabolism, maturation, and fecundity. Each of these processes is controlled to a large extent by nuclear hormone receptors (NHRs). NHRs also play important roles in the control of periodical processes, the most recently implicated being circadian rhythm. This Review stresses the mounting evidence for tight relationships between each of these NHR-regulated processes and the processes of aging.
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Affiliation(s)
- Keith Pardee
- Banting and Best Department of Medical Research, University of Toronto, Charles H. Best Institute, Toronto, Ontario, Canada
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144
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Melo MR, Faria CDC, Melo KC, Rebouças NA, Longui CA. Real-time PCR quantitation of glucocorticoid receptor alpha isoform. BMC Mol Biol 2004; 5:19. [PMID: 15507144 PMCID: PMC529441 DOI: 10.1186/1471-2199-5-19] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2004] [Accepted: 10/26/2004] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND The expression of glucocorticoid-receptor (GR) seems to be a key mechanism in the regulation of glucocorticoid (GC) sensitivity and is potentially involved in cases of GC resistance or hypersensitivity. The aim of this study is to describe a method for quantitation of GR alpha isoform (GRalpha) expression using real-time PCR (qrt-PCR) with analytical capabilities to monitor patients, offering standard-curve reproducibility as well as intra- and inter-assay precision. RESULTS Standard-curves were constructed by employing standardized Jurkat cell culture procedures, both for GRalpha and BCR (breakpoint cluster region), as a normalizing gene. We evaluated standard-curves using five different sets of cell culture passages, RNA extraction, reverse transcription, and qrt-PCR quantification. Intra-assay precision was evaluated using 12 replicates of each gene, for 2 patients, in a single experiment. Inter-assay precision was evaluated on 8 experiments, using duplicate tests of each gene for two patients. Standard-curves were reproducible, with CV (coefficient of variation) of less than 11%, and Pearson correlation coefficients above 0,990 for most comparisons. Intra-assay and inter-assay were 2% and 7%, respectively. CONCLUSION This is the first method for quantitation of GRalpha expression with technical characteristics that permit patient monitoring, in a fast, simple and robust way.
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Affiliation(s)
- Murilo R Melo
- Pediatric Endocrinology Unit, Irmandade da Santa Casa de Misericórdia de São Paulo, Brazil
| | - Cláudia DC Faria
- Pediatric Endocrinology Unit, Irmandade da Santa Casa de Misericórdia de São Paulo, Brazil
| | - Keli C Melo
- Pediatric Endocrinology Unit, Irmandade da Santa Casa de Misericórdia de São Paulo, Brazil
| | - Nancy A Rebouças
- Department of Physiology, Biomedical Sciences Institute, University of São Paulo, Brazil
| | - Carlos A Longui
- Pediatric Endocrinology Unit, Irmandade da Santa Casa de Misericórdia de São Paulo, Brazil
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145
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Purton JF, Monk JA, Liddicoat DR, Kyparissoudis K, Sakkal S, Richardson SJ, Godfrey DI, Cole TJ. Expression of the glucocorticoid receptor from the 1A promoter correlates with T lymphocyte sensitivity to glucocorticoid-induced cell death. THE JOURNAL OF IMMUNOLOGY 2004; 173:3816-24. [PMID: 15356129 DOI: 10.4049/jimmunol.173.6.3816] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Glucocorticoid (GC) hormones cause pronounced T cell apoptosis, particularly in immature thymic T cells. This is possibly due to tissue-specific regulation of the glucocorticoid receptor (GR) gene. In mice the GR gene is transcribed from five separate promoters designated: 1A, 1B, 1C, 1D, and 1E. Nearly all cells express GR from promoters 1B-1E, but the activity of the 1A promoter has only been reported in the whole thymus or lymphocyte cell lines. To directly assess the role of GR promoter use in sensitivity to glucocorticoid-induced cell death, we have compared the activity of the GR 1A promoter with GC sensitivity in different mouse lymphocyte populations. We report that GR 1A promoter activity is restricted to thymocyte and peripheral lymphocyte populations and the cortex of the brain. The relative level of expression of the 1A promoter to the 1B-1E promoters within a lymphocyte population was found to directly correlate with susceptibility to GC-induced cell death, with the extremely GC-sensitive CD4+CD8+ thymocytes having the highest levels of GR 1A promoter activity, and the relatively GC-resistant alphabetaTCR+CD24(int/low) thymocytes and peripheral T cells having the lowest levels. DNA sequencing of the mouse GR 1A promoter revealed a putative glucocorticoid-response element. Furthermore, GR 1A promoter use and GR protein levels were increased by GC treatment in thymocytes, but not in splenocytes. These data suggest that tissue-specific differences in GR promoter use determine T cell sensitivity to glucocorticoid-induced cell death.
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Affiliation(s)
- Jared F Purton
- Department of Microbiology and Immunology, University of Melbourne, Parkville, Victoria, Australia
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146
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Abstract
Inhaled and intranasal glucocorticoids are the most common and effective drugs for controlling symptoms and airway inflammation in respiratory diseases such as asthma, allergic rhinitis, and nasal polyposis. The last few years have seen a growing understanding of the mechanisms of glucocorticoid action and, in particular, the receptor that mediates glucocorticoid actions, the glucocorticoid receptor (GR). In this revision we present an update on the GR gene, the expression and regulation of its gene products, namely GRalpha and GRbeta, as well as their alterations in pathological states. GRalpha is responsible for the induction and repression of target genes, it is expressed in virtually all human cells and tissues, and its expression is known to be downregulated by glucocorticoids. GRbeta has been found to act as a dominant negative inhibitor of GRalpha-mediated transactivation in in vitro studies with transfected cells, but it does not appear to have a significant inhibitory effect on GRalpha-mediated transrepression. In addition, for most tissues the expression of GRbeta, at least at the mRNA level, is extremely low compared with that of GRalpha. Some pro-inflammatory cytokines appear to upregulate the expression of GRbeta, and increased GRbeta expression has been reported in diseases associated with glucocorticoid resistance or insensitivity, such as bronchial asthma, nasal polyposis, and ulcerative colitis. However, the possible role of GRbeta in modulating glucocorticoid sensitivity and/or resistance in vivo has been highly debated and it is not yet clear.
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Affiliation(s)
- L Pujols
- Institut d'Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain
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147
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Torrego A, Pujols L, Roca-Ferrer J, Mullol J, Xaubet A, Picado C. Glucocorticoid Receptor Isoforms α and β inin VitroCytokine-induced Glucocorticoid Insensitivity. Am J Respir Crit Care Med 2004; 170:420-5. [PMID: 15184204 DOI: 10.1164/rccm.200308-1143oc] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
We stimulated peripheral blood mononuclear cells from 14 healthy subjects, 14 patients with stable asthma, and 13 patients with unstable asthma with interleukin (IL)-2 and IL-4 to induce glucocorticoid insensitivity and we examined the relationship between insensitivity and the expression of glucocorticoid receptor (GR) isoforms. Results are expressed as IC(50) (nanomolar) values (means +/- SD) in proliferation assays and as 10(3) cDNA molecules per microgram of total RNA (means +/- SD) in real-time polymerase chain reaction analysis. Cells from patients with unstable asthma were less sensitive (316 +/- 7 nM) to dexamethasone antiproliferative effects than those from healthy control subjects (102 +/- 4 nM, p < 0.05) and patients with stable asthma (107 +/- 2 nM, p < 0.05). Coincubation with IL-2 and IL-4 repressed the inhibitory effect of dexamethasone on proliferation in all groups (unstable: 851 +/- 47 nM, p < 0.01; stable: 912 +/- 52 nM, p = 0.001; control subjects: 537 +/- 45 nM, p = 0.001). GR-alpha mRNA baseline expression was higher in patients with unstable asthma [(1.95 +/- 0.40) x 10(3) cDNA molecules/microg total RNA, p < 0.05] than in patients with stable asthma [(1.46 +/- 0.35) x 10(3) cDNA molecules/microg total RNA] and healthy subjects [(1.35 +/- 0.25) x 10(3) cDNA molecules/microg total RNA]. GR-beta mRNA was 600 times lower than GR-alpha in the three groups. Coincubation with IL-2 and IL-4 significantly increased GR-alpha mRNA expression in the three groups (p < 0.01), but caused no significant change in GR-beta mRNA. GR-alpha, but not GR-beta, protein was detected at baseline and after cytokine exposure. Our data do not support the hypothesis that increased GR-beta expression can contribute to cytokine-induced glucocorticoid insensitivity.
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Affiliation(s)
- Alfons Torrego
- Servei de Pneumologia, Hospital Clínic, Villarroel 170, 08036 Barcelona, Spain
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148
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Yoon SW, Park IY, Sohn BH, Lee J, Yeo WH, Lee YI. A new compound from Micromonospora sp. SA246, 9-hydroxycrisamicin-A, activates hepatitis B virus replication. Biochem Biophys Res Commun 2004; 319:859-65. [PMID: 15184062 DOI: 10.1016/j.bbrc.2004.05.061] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2004] [Indexed: 12/18/2022]
Abstract
A new compound from Micromonospora sp. SA246, 9-hydroxycrisamicin-A (9-HCA-A), showed potential for activating hepatitis B virus (HBV) replication. To define the mechanism of 9-HCA-A, we used HepG2 2.2.15 cells which support HBV replication. 9-HCA-A activated HBV replication, increased episomal and integrated HBV DNA content, and increased secretions of HBV antigens (HBsAg and HBeAg) into culture medium. 9-HCA-A also activated HBV transcription in Hep2 2.2.15 cell line. To examine transcriptional control mechanisms, we analyzed the effect of 9-HCA-A on four different HBV promoters (Core, PreS1, PreS2, and X) in hepatoma cell line. 9-HCA-A responsive element was located at HBx promoter. By EMSA, we showed that 9-HCA-A activated the HBx promoter by detaching the 9-HCA-A responsive element binding protein (9H-REBP). Protein phosphatase (PP2A1) treatment detaches the 9H-REBP from the HBx promoter, similar to 9-HCA-A, while protein kinase A treatment does not detach the 9H-REBP from the HBx promoter. Our results showed that 9H- REBP functions as a repressor of HBV replication while 9-HCA-A activated protein phosphatase released the BP on the HBx promoter, thus activating HBV replication.
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Affiliation(s)
- Seok Won Yoon
- Liver Cell Signal Transduction Laboratory, Bioscience Research Division, Korea Research Institute of Bioscience and Biotechnology, P.O. Box 115, Yusong, Taejon 305-600, Republic of Korea
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149
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Bhargava A, Pearce D. Mechanisms of mineralocorticoid action: determinants of receptor specificity and actions of regulated gene products. Trends Endocrinol Metab 2004; 15:147-53. [PMID: 15109612 DOI: 10.1016/j.tem.2004.03.009] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The mineralocorticoid receptor (MR) and its close cousin, the glucocorticoid receptor (GR), share considerable structural and functional similarity, including indistinguishable DNA binding properties, yet they mediate distinct physiological responses in some tissues. Specificity is determined by their distinct interactions with other protein factors and modification by peptides, including the small ubiquitin modifier SUMO1. Serum and glucocorticoid-regulated kinase 1 (sgk1) is one key target gene of both MR and GR, and encodes a serine-threonine kinase that stimulates the apical membrane localization of the epithelial sodium channel ENaC. Sgk1 exerts its effects, at least in part, by inhibiting an isoform of the ENaC inhibitory ubiquitin ligase Nedd4-2. This review briefly summarizes two areas of mineralocorticoid research: molecular determinants of MR specificity, and the role of Sgk1 in mediating the effects of aldosterone on epithelial Na(+) transport.
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Affiliation(s)
- Aditi Bhargava
- Departments of Medicine and Cellular and Molecular Pharmacology, Box 2140, N272C Genentach Hall, University of California, San Francisco, CA 94143-2140, USA
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150
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Hyde GN, Seale AP, Grau EG, Borski RJ. Cortisol rapidly suppresses intracellular calcium and voltage-gated calcium channel activity in prolactin cells of the tilapia (Oreochromis mossambicus). Am J Physiol Endocrinol Metab 2004; 286:E626-33. [PMID: 14656715 DOI: 10.1152/ajpendo.00088.2003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cortisol was previously shown to rapidly (10-20 min) reduce the release of prolactin (PRL) from pituitary glands of tilapia (Oreochromis mossambicus). This inhibition of PRL release by cortisol is accompanied by rapid reductions in (45)Ca(2+) and cAMP accumulation. Cortisol's early actions occur through a protein synthesis-independent pathway and are mimicked by a membrane-impermeable analog. The signaling pathway that mediates rapid, nongenomic membrane effects of glucocorticoids is poorly understood. Using the advantageous characteristics of the teleost pituitary gland from which a nearly pure population of PRL cells can be isolated and incubated in defined medium, we examined whether cortisol rapidly reduces intracellular free calcium (Ca(i)(2+)) and suppresses L-type voltage-gated ion channel activity in events that lead to reduced PRL release. Microspectrofluorometry, used in combination with the Ca(2+)-sensitive dye fura 2 revealed that cortisol reversibly reduces basal and hyposmotically induced Ca(i)(2+) within seconds (P < 0.001) in dispersed pituitary cells. Somatostatin, a peptide known to inhibit PRL release through a membrane receptor-coupled mechanism, similarly reduces Ca(i)(2+). Under depolarizing [K(+)], the L-type calcium channel agonist BAY K 8644, a factor known to delay the closing of L-type Ca(2+) channels, stimulates PRL release in a concentration-dependent fashion (P < 0.01). Cortisol (and somatostatin) blocks BAY K 8644-induced PRL release (P < 0.01; 30 min), well within the time course over which its actions occur, independent of protein synthesis and at the level of the plasma membrane. Results indicate that cortisol inhibits tilapia PRL release through rapid reductions in Ca(i)(2+) that likely involve an attenuation of Ca(2+) entry through L-type voltage-gated Ca(2+) channels. These results provide further evidence that glucocorticoids rapidly modulate hormone secretion via a membrane-associated mechanism similar to that observed with the fast effects of peptides and neurotransmitters.
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MESH Headings
- 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester/antagonists & inhibitors
- 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester/pharmacology
- Animals
- Anti-Inflammatory Agents/pharmacology
- Calcium/metabolism
- Calcium Channel Agonists/pharmacology
- Calcium Channel Blockers
- Calcium Channels, L-Type/drug effects
- Calcium Radioisotopes
- Cyclic AMP/metabolism
- Electrophoresis, Polyacrylamide Gel
- Fura-2
- Hormone Antagonists/pharmacology
- Hydrocortisone/pharmacology
- In Vitro Techniques
- Ion Channel Gating/drug effects
- Ion Channel Gating/physiology
- Male
- Osmotic Pressure
- Pituitary Gland, Anterior/cytology
- Pituitary Gland, Anterior/drug effects
- Pituitary Gland, Anterior/metabolism
- Prolactin/physiology
- Somatostatin/pharmacology
- Tilapia/physiology
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Affiliation(s)
- Gregory N Hyde
- Department of Zoology, North Carolina State University, Box 7617, Raleigh, NC 27695-7617, USA
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