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M Dexamethasone (m + dexamethasone)
Selected AbstractsDexamethasone alters F-actin architecture and promotes cross-linked actin network formation in human trabecular meshwork tissueCYTOSKELETON, Issue 2 2005Abbot F. Clark Abstract Elevated intraocular pressure is an important risk factor for the development of glaucoma, a leading cause of irreversible blindness. This ocular hypertension is due to increased hydrodynamic resistance to the drainage of aqueous humor through specialized outflow tissues, including the trabecular meshwork (TM) and the endothelial lining of Schlemm's canal. We know that glucocorticoid therapy can cause increased outflow resistance and glaucoma in susceptible individuals, that the cytoskeleton helps regulate aqueous outflow resistance, and that glucocorticoid treatment alters the actin cytoskeleton of cultured TM cells. Our purpose was to characterize the actin cytoskeleton of cells in outflow pathway tissues in situ, to characterize changes in the cytoskeleton due to dexamethasone treatment in situ, and to compare these with changes observed in cell culture. Human ocular anterior segments were perfused with or without 10,7 M dexamethasone, and F-actin architecture was investigated by confocal laser scanning microscopy. We found that outflow pathway cells contained stress fibers, peripheral actin staining, and occasional actin "tangles." Dexamethasone treatment caused elevated IOP in several eyes and increased overall actin staining, with more actin tangles and the formation of cross-linked actin networks (CLANs). The actin architecture in TM tissues was remarkably similar to that seen in cultured TM cells. Although CLANs have been reported previously in cultured cells, this is the first report of CLANs in tissue. These cytoskeletal changes may be associated with increased aqueous humor outflow resistance after ocular glucocorticoid treatment. Cell Motil. Cytoskeleton 60:83,95, 2005. © 2004 Wiley-Liss, Inc. [source] Adenovirus-mediated BMP2 expression in human bone marrow stromal cellsJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 1 2001Elizabeth A. Olmsted Abstract Recombinant adenoviral vectors have been shown to be potential new tools for a variety of musculoskeletal defects. Much emphasis in the field of orthopedic research has been placed on developing systems for the production of bone. This study aims to determine the necessary conditions for sustained production of high levels of active bone morphogenetic protein 2 (BMP2) using a recombinant adenovirus type 5 (Ad5BMP2) capable of eliciting BMP2 synthesis upon infection and to evaluate the consequences for osteoprogenitor cells. The results indicate that high levels (144 ng/ml) of BMP2 can be produced in non-osteoprogenitor cells (A549 cell line) by this method and the resultant protein appears to be three times more biologically active than the recombinant protein. Surprisingly, similar levels of BMP2 expression could not be achieved after transduction with Ad5BMP2 of either human bone marrow stromal cells or the mouse bone marrow stromal cell line W20-17. However, human bone marrow stromal cells cultured with 1 ,M dexamethasone for four days, or further stimulated to become osteoblast-like cells with 50 ,g/ml ascorbic acid, produced high levels of BMP2 upon Ad5BMP2 infection as compared to the undifferentiated cells. The increased production of BMP2 in adenovirus transduced cells following exposure to 1 ,M dexamethasone was reduced if the cells were not given 50 ,g/ml ascorbic acid. When bone marrow stromal cells were allowed to become confluent in culture prior to differentiation, BMP2 production in response to Ad5BMP2 infection was lost entirely. Furthermore, the increase in BMP2 synthesis seen during differentiation was greatly decreased when Ad5BMP2 was administered prior to dexamethasone treatment. In short, the efficiency of adenovirus mediated expression of BMP2 in bone marrow stromal cells appears to be dependent on the differentiation state of these cells. J. Cell. Biochem. 82: 11,21, 2001. © 2001 Wiley-Liss, Inc. [source] Dexamethasone up-regulates type II IL-1 receptor in mouse primary activated astrocytesJOURNAL OF NEUROCHEMISTRY, Issue 3 2001F. Pousset Brain astrocytes play a pivotal role in the brain response to inflammation. They express IL-1 receptors including the type I IL-1 receptor (IL-1RI) that transduces IL-1 signals in cooperation with the IL-1 receptor accessory protein (IL-1RAcP) and the type II IL-1 receptor (IL-1RII) that functions as a decoy receptor. As glucocorticoid receptors are expressed on astrocytes, we hypothesized that glucocorticoids regulate IL-1 receptors expression. IL-1,-activated mouse primary astrocytes were treated with 10,6 M dexamethasone, and IL-1 receptors were studied at the mRNA and protein levels. Using RT-PCR, IL-1RI and IL-1RII but not IL-1RAcP mRNAs were found to be up-regulated by dexamethasone in a time-dependent manner. Dexamethasone (Dex), but not progesterone, had no effect on IL-1RI but strongly increased IL-1RII mRNA expression. Binding studies revealed an increase in the number of IL-1RII binding sites under the effect of Dex, but no change in affinity. These findings support the concept that glucocorticoids have important regulatory effect on the response of astrocytes to IL-1. [source] Early osteoblastic differentiation induced by dexamethasone enhances adenoviral gene delivery to marrow stromal cellsJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 2 2004Jeremy S. Blum Abstract We investigated the implications of induced osteogenic differentiation on gene delivery in multipotent rat marrow stromal cells (MSCs). Prior to genetic manipulation cells were cultured with or without osteogenic supplements (5 ± 10,8 M dexamethasone, 160 ,M l-ascorbic acid 2-phosphate, and 10 mM ,-glycerophosphate). Comparison of liposome, retroviral, and adenoviral vectors demonstrated that all three vectors could mediate gene delivery to primary rat MSCs. When these vectors were applied in the absence or presence of osteogenic supplements, we found that MSCs differentiated prior to transduction with adenovirus type 5 vectors produced a 300% increase in transgene expression compared to MSCs that were not exposed to osteogenic supplements. This differentiation effect appeared specific to adenoviral mediated gene delivery, since there was minimal increase in retroviral gene delivery and no increase in liposome gene delivery when MSCs were treated with osteogenic supplements. In addition, we also determined this increase in transgene production to occur at a higher concentration of dexamethasone (5 ± 10,8 M) in the culture medium of MSCs prior to adenoviral transduction. We found that this increased transgene production could be extended to the osteogenic protein, human bone morphogenetic protein 2 (hBMP-2). When delivered by an adenoviral vector, hBMP-2 transgene production could be increased from 1.4 ng/105 cells/3 days to 4.3 ng/105 cells/3 days by culture of MSCs with osteogenic supplements prior to transduction. These results indicate that the utility of MSCs as a therapeutic protein delivery mechanism through genetic manipulation can be enhanced by pre-culture of these cells with dexamethasone. © 2003 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source] Expression of receptor activator of NF-kappa B ligand and osteoprotegerin in culture of human periodontal ligament cellsJOURNAL OF PERIODONTAL RESEARCH, Issue 6 2002Tomokazu Hasegawa The receptor activator of NF-kappa B ligand (RANKL) and its decoy receptor, osteoprotegerin (OPG), are the important proteins implicated in osteoclastogenesis. In this study, we investigated the expressions of RANKL and OPG in cultured human periodontal ligament (PDL) cells and their roles in osteoclastogenesis. Northern blotting revealed that the OPG mRNA was down-regulated remarkably by application of 10,8 m one-alpha, 25-dihydroxyvitamin D3[1,25-(OH)2D3] and 10,7 m dexamethasone (Dex). In contrast, RANKL mRNA was up-regulated by the same treatment. Western blotting demonstrated decrease of OPG by the application of 1,25-(OH)2D3 and Dex. Tartrate-resistant acid phosphatase-positive multinuclear cells were markedly induced when the PDL cells were cocultured with mouse bone marrow cells in the presence of an anti-OPG antibody together with 1,25-(OH)2D3 and Dex. These results indicate that PDL cells synthesize both RANKL and OPG and that inactivation of OPG may play a key role in the differentiation of osteoclasts. [source] New pOp/LhG4 vectors for stringent glucocorticoid-dependent transgene expression in ArabidopsisTHE PLANT JOURNAL, Issue 6 2005Judith Craft Summary To facilitate glucocorticoid-inducible transgene expression from the pOp promoter in Arabidopsis the ligand-binding domain of a rat glucocorticoid receptor (GR LBD) was fused to the amino terminus of the synthetic transcription factor LhG4 to generate LhGR-N. Fusions bearing the GR LBD at other positions in LhG4 exhibited incomplete repression or inefficient induction. LhGR-N was stringently repressed in the absence of exogenous glucocorticoid but was fully activated by addition of 2 ,m dexamethasone which resulted in 1000-fold increase in GUS reporter activity. Half maximal induction was achieved with 0.2 ,m dexamethasone. Reporter transcripts were detectable within 2 h of dexamethasone application and peaked 4,10 h later. Neither LhGR-N nor dexamethasone affected seedling development although ethanol retarded development when used as a solvent for dexamethasone. The efficiency of the pOp target promoter was improved 10- to 20-fold by incorporating six copies of the ideal lac operator with sufficient inter-operator spacing to allow simultaneous occupancy. Introduction of the TMV , sequence into the 5,UTR resulted in a further 10-fold increase in dexamethasone-inducible reporter activity and an increase in the induction factor to 104. Although promoters containing the TMV , sequence exhibited slightly increased basal expression levels in the absence of dexamethasone, stringent regulation of the cytokinin biosynthetic gene ipt was achieved with all promoters. Despite the severity of the induced ipt phenotypes, transcripts for the KNOX homoeodomain transcription factors BREVIPEDICELLUS and SHOOTMERISTEMLESS were not significantly increased within 48 h of dexamethasone application to seedlings. 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