Control of gene expression by glucocorticoid hormones

Evaluation of Orbital Lymphoproliferative and Inflammatory Disorders by Gene Expression Analysis

Non-specific orbital inflammation (NSOI) and IgG4-related orbital disease (IgG4-ROD) are often challenging to differentiate. Furthermore, it is still uncertain how chronic inflammation, such as IgG4-ROD, can lead to mucosa-associated lymphoid tissue (MALT) lymphoma. Therefore, we aimed to evaluate the diagnostic value of gene expression analysis to differentiate orbital autoimmune diseases and elucidate genetic overlaps. First, we established a database of NSOI, relapsing NSOI, IgG4-ROD and MALT lymphoma patients of our orbital center (2000−2019). In a consensus process, three typical patients of the above mentioned three groups (mean age 56.4 ± 17 years) at similar locations were selected. Afterwards, RNA was isolated using the RNeasy FFPE kit (Qiagen) from archived paraffin-embedded tissues. The RNA of these 12 patients were then subjected to gene expression analysis (NanoString nCounter®), including a total of 1364 target genes. The most significantly upregulated and downregulated genes were used for a machine learning algorithm to distinguish entities. This was possible with a high probability (p < 0.0001). Interestingly, gene expression patterns showed a characteristic overlap of lymphoma with IgG4-ROD and NSOI. In contrast, IgG4-ROD shared only altered expression of one gene regarding NSOI. To validate our potential biomarker genes, we isolated the RNA of a further 48 patients (24 NSOI, 11 IgG4-ROD, 13 lymphoma patients). Then, gene expression pattern analysis of the 35 identified target genes was performed using a custom-designed CodeSet to assess the prediction accuracy of the multi-parameter scoring algorithms. They showed high accuracy and good performance (AUC ROC: IgG4-ROD 0.81, MALT 0.82, NSOI 0.67). To conclude, genetic expression analysis has the potential for faster and more secure differentiation between NSOI and IgG4-ROD. MALT-lymphoma and IgG4-ROD showed more genetic similarities, which points towards progression to lymphoma.

Betamethasone induces potent immunosuppression and reduces HIV infection in a PBMC in vitro model

Genital inflammation is an established risk factor for increased HIV acquisition risk. Certain HIV-exposed seronegative populations, who are naturally resistant to HIV infection, have an immune quiescent phenotype defined by reduced immune activation and inflammatory cytokines at the genital tract. Therefore, the aim of this study was to create an immune quiescent environment using immunomodulatory drugs to mitigate HIV infection. Using an in vitro peripheral blood mononuclear cell (PBMC) model, we found that inflammation was induced using phytohemagglutinin and Toll-like receptor (TLR) agonists Pam3CSK4 (TLR1/2), lipopolysaccharide (LPS) (TLR4) and R848 (TLR7/8). After treatment with anti-inflammatory drugs, ibuprofen (IBF) and betamethasone (BMS), PBMCs were exposed to HIV NL4-3 AD8. Multiplexed ELISA was used to measure 28 cytokines to assess inflammation. Flow cytometry was used to measure immune activation (CD38, HLA-DR and CCR5) and HIV infection (p24 production) of CD4+ T cells. BMS potently suppressed inflammation (soluble cytokines, p<0.05) and immune activation (CD4+ T cells, p<0.05). BMS significantly reduced HIV infection of CD4+ T cells only in the LPS (0.98%) and unstimulated (1.7%) conditions (p<0.02). In contrast, IBF had minimal anti-inflammatory and immunosuppressive but no anti-HIV effects. BMS demonstrated potent anti-inflammatory effects, regardless of stimulation condition. Despite uniform immunosuppression, BMS differentially affected HIV infection according to the stimulation conditions, highlighting the complex nature of these interactions. Together, these data underscore the importance of interrogating inflammatory signaling pathways to identify novel drug targets to mitigate HIV infection.

A decline in female baboon hypothalamo-pituitary-adrenal axis activity anticipates aging

Stressors that disrupt homeostasis advance aging. Glucocorticoids regulate multiple processes that determine the aging trajectory. Debate exists regarding life-course circulating glucocorticoid concentrations. Rodent and nonhuman primate studies indicate circulating glucocorticoids fall from early life. We measured fasting morning cortisol in 24 female baboons (6-21 years, human equivalent ~18-70). We also quantified hypothalamic paraventricular nuclear (PVN) arginine vasopressin (AVP), corticotropin-releasing hormone, steroid receptors, and pituitary proopiomelanocortin immunohistochemically in 14 of these females at 6-13 years. We identified significant age-related 1) linear fall in cortisol and PVN AVP from as early as 6 years; 2) increased PVN glucocorticoid and mineralocorticoid receptors; 3) increased PVN 11β-hydroxysteroid dehydrogenase 1 and 2, regulators of local cortisol production, and 4) decreased pituitary proopiomelanocortin. Our data identify increased age-related negative feedback and local PVN cortisol production as potential mechanisms decreasing PVN drive to hypothalamo-pituitary-adrenal axis activity that result in the age-related circulating cortisol fall. Further studies are needed to determine whether the cortisol fall 1) causes aging, 2) protects by slowing aging, or 3) is an epiphenomenon unrelated to aging processes. We conclude that aging processes are best studied by linear life-course analysis beginning early in life.

New insights into the functional mechanisms and clinical applications of the kallikrein-related peptidase family

The Kallikrein-related peptidase (KLK) family consists of fifteen conserved serine proteases that form the largest contiguous cluster of proteases in the human genome. While primarily recognized for their clinical utilities as potential disease biomarkers, new compelling evidence suggests that this family plays a significant role in various physiological processes, including skin desquamation, semen liquefaction, neural plasticity, and body fluid homeostasis. KLK activation is believed to be mediated through highly organized proteolytic cascades, regulated through a series of feedback loops, inhibitors, auto-degradation and internal cleavages. Gene expression is mainly hormone-dependent, even though transcriptional epigenetic regulation has also been reported. These regulatory mechanisms are integrated with various signaling pathways to mediate multiple functions. Dysregulation of these pathways has been implicated in a large number of neoplastic and non-neoplastic pathological conditions. This review highlights our current knowledge of structural/phylogenetic features, functional role and regulatory/signaling mechanisms of this important family of enzymes.

Rapid nongenomic inhibitory effects of glucocorticoids on phagocytosis and superoxide anion production by macrophages

Traditionally, steroid hormone effects have been described as a result of the modulation of nuclear transcription, thus triggering genomic events that are responsible for physiological effects. Despite early observations of rapid steroid effects that were incompatible with this theory, nongenomic steroid effects have been widely recognized only recently. However, the nongenomic effect of glucocorticoid (GC) on anti-inflammation and immunosuppression has not been reported. Macrophages play important roles in inflammation and the immune response. The present experiment selected macrophages as experimental cells to explore the nongenomic effects and possible mechanisms of GCs on phagocytosis and superoxide anion production. Phagocytosis by macrophages was detected by the neutral red uptake assay. The superoxide anions were measured by cytochrome C reduction assay. It was found that both 10(-4) and 10(-5) mol/L corticosterone (CORT) rapidly inhibited uptake of neutral red by macrophages in less than 30 min, and the inhibition by the former was stronger than that of the latter. CORT (10(-4) to 10(-10) mol/L) rapidly inhibited superoxide anion production by macrophages in less than 30 min. The above-mentioned effects were insensitive to the GC-receptor antagonist mifepristone (RU486) and the translation inhibitor actidione. CORT coupled to bovine serum albumin (BSA-CORT) was able to mimic the rapid inhibitory effects of CORT. The results indicated that CORT could rapidly inhibit phagocytosis and superoxide anion production by mouse peritoneal macrophages in vitro in less than 30 min by a rapid, nongenomic mechanism, which contributes to the anti-inflammatory and immunosuppressive actions of GCs. These data shed a new light on the clinical application of GCs.

Regulation by glucocorticoids of cell differentiation and insulin-like growth factor binding protein production in cultured fetal rat nasal chondrocytes

Glucocorticoids (GCs) modulate insulin-like growth factor action in cartilage through mechanisms that are complex and insufficiently defined, especially in the context of cranio-facial growth. Because the family of IGF-binding proteins (IGFBP-1 to -6) is important in the regulation of IGF availability and bioactivity, we examined the effect of GCs on chondrocyte differentiation in correlation with IGFBP production in cultured fetal rat chondrocytes isolated from nasal septum cartilage of fetal rat. Dexamethasone (DEX) effects were tested before and at the onset of extracellular matrix maturation. DEX induced a dose-dependent increase in the size of cartilage nodule formed, (45)Ca incorporation into extracellular matrix, alkaline phosphatase activity, and sulfatation of glycosaminoglycans, maximal effects being obtained with a 10-mM DEX concentration. The IGFBPs produced by cultured chondrocytes were characterized in culture medium which had been conditioned for 24 h under serum-free conditions by these cells. Western ligand blotting with a mixture of [(125)I]IGF-I and -II revealed bands of 20, 24, 29, a 31-32 kDa doublet and a 39-41 kDa triplet which were differently regulated by DEX. Immunoblotting showed that following DEX exposure, IGFBP-3 and -6 were up-regulated whereas IGFBP-2, -5, and the 24 kDa band were down-regulated. The effect of DEX on both differentiation and IGFBP production showed a same dependence, and developed when extracellular matrix maturation had been just induced. The results obtained in this chondrocyte culture system show that production of IGFBPs is modulated by DEX at physiological concentrations thus regulating IGF availability and action, a control which could promote the primordial role of the rat nasal septum in craniofacial growth.

Energy metabolism, stress hormones and neural recovery from cerebral ischemia/hypoxia

All the advancements in the understanding of the molecular and cellular processes leading to the great investments in developing neuroprotection against cerebral ischemic/hypoxic damage cannot obscure the simple fact that exhaustion of energy supplies is still at the basis of this disorder. Much has been investigated and postulated over the years about the quick collapse of energy metabolism that follows oxygen and glucose deprivation in the brain. Anaerobic glycolysis, recognized as a pathway of paramount importance in keeping energy supplies, although, at bare minimum, has also presented a dilemma-a significant increase in lactate production during ischemia/hypoxia (IH). The dogma of lactate as a useless end product of anaerobic glycolysis and its postulated role as a detrimental player in the demise of the ischemic cell has persisted for the past quarter of a century. This persistence is due to, at least in part, the well-documented phenomenon termed "the glucose paradox of cerebral ischemia," the unexplained aggravation of postischemic neuronal damage by preischemic hyperglycemia. Recent studies have questioned the deleterious effect of lactic acid, while others even have offered the possibility that this monocarboxylate serves as an aerobic energy substrate during recovery from IH. Reviewed here are studies published over the past few years along with some key older papers on the topic of energy metabolism and recovery of neural tissue from IH. New insights gained from both in vitro and in vivo studies on energy metabolism of the ischemic/hypoxic brain should improve our understanding of this key metabolic process and the chances of protecting this organ from the consequences of energy deprivation.

Cortisol suppresses prolactin release through a non-genomic mechanism involving interactions with the plasma membrane

In the classical theory of steroid hormone action, steroids diffuse through the membrane and alter transcription of specific genes resulting in synthesis of proteins important for modulating cell function. Most often, steroids work solely through the genome to exert their physiological actions in a process that normally takes hours or days to occur. In tilapia (Oreochromis mossambicus), cortisol inhibits prolactin (PRL) release within 10-20 min in vitro. This action is accompanied by similarly rapid reductions in cellular Ca(2+) and cAMP levels, second messengers known to transduce the membrane effects of peptide hormones. We further examined whether cortisol might inhibit PRL release through a non-genomic, membrane-associated mechanism using the protein synthesis inhibitor, cycloheximide, and a membrane impermeant form of cortisol, cortisol-21 hemisuccinate BSA (HEF/BSA). Cycloheximide (2 and 10 microg/ml) was ineffective in overcoming PRL release induced by hyposmotic medium or that inhibited by cortisol over 4 h static incubations. These dosages reduced protein synthesis as measured by amino acid incorporation in pituitaries by 75 and 99%, respectively. During 4-h incubation, HEF/BSA and HEF significantly reduced PRL release in a dose-dependent fashion. These studies suggest that cortisol inhibits PRL release through a plasma membrane-associated, protein-synthesis independent (non-genomic) pathway.

Nongenomic membrane actions of glucocorticoids in vertebrates

For decades, it was widely assumed that glucocorticoids (GCs) work solely through changes in gene expression to exert their physiological actions, a process that normally takes several hours to occur. However, recent evidence indicates that GCs might also act at the membrane through specific receptors to exert multiple rapid effects on various tissues and cells. GCs modulate hormone secretion, neuronal excitability, behavior, cell morphology, carbohydrate metabolism and other processes within seconds or minutes. These early actions occur independent of the genome and are transduced by the same biochemical effector pathways responsible for mediating rapid responses to neurotransmitters. The biological significance of most rapid GC effects are not well understood, but many might be related to the important functions that this hormone plays in modulating stress responses.

Ontogeny of intestinal nutrient transport

Children born prematurely lack the ability to digest and to absorb nutrients at rates compatible with their nutritional needs. As a result, total parenteral nutrition may need to be given. While this nutritional support may be life-saving, the baby who receives this therapy is exposed to the risks of possible sepsis, catheter dysfunction, and liver disease. The rodent model of postnatal development provides a useful framework to investigate some of the cellular features of human intestinal development. The up-regulation of intestinal gene expression and precocious development of intestinal nutrient absorption can be achieved by providing growth factor(s) or by modifying the composition of the maternal diet during pregnancy and nursing or the weaning diet of the infant. Accelerating the digestive and absorptive functions of the intestine would thereby allow for the maintenance of infant nutrition through oral food intake, and might possibly eliminate the need for, and risks of, total parenteral nutrition. Accordingly, this review was undertaken to focus on the adaptive processes available to the intestine, to identify what might be the signals for and mechanisms of the modified nutrient absorption, and to speculate on approaches that need to be studied as means to possibly accelerate the adaptive processes in ways which would be beneficial to the newborn young.Key words: absorption, adaptation, diet, peptides.

The stressful condition as a nutritionally dependent adaptive dichotomy

The injured body manifests a cascade of cytokine-induced metabolic events aimed at developing defense mechanisms and tissue repair. Rising concentrations of counterregulatory hormones work in concert with cytokines to generate overall insulin and insulin-like growth factor 1 (IGF-1), postreceptor resistance and energy requirements grounded on lipid dependency. Salient features are self-sustained hypercortisolemia persisting as long as cytokines are oversecreted and down-regulation of the hypothalamo-pituitary-thyroid axis stabilized at low basal levels. Inhibition of thyroxine 5'-deiodinating activity (5'-DA) accounts for the depressed T3 values associated with the sparing of both N and energy-consuming processes. Both the liver and damaged territories adapt to stressful signals along up-regulated pathways disconnected from the central and peripheral control systems. Cytokines stimulate liver 5'-DA and suppress the synthesis of transthyretin (TTR), causing the drop of retinol-binding protein (RBP) and the leakage of increased amounts of T4 and retinol in free form. TTR and RBP thus work as prohormonal reservoirs of precursor molecules which need to be converted into bioactive derivatives (T3 and retinoic acids) to reach transcriptional efficiency. The converting steps (5'-DA and cellular retinol-binding protein-I) are activated by T4 and retinol, themselves operating as limiting factors of positive feedback loops. Healthy adults with normal macrophage functioning and liver parenchymal integrity, who submitted to a stress of medium severity, are characterized by TTR-RBP plasma levels reduced by half and an estimated ten-fold increase in free ligand disposal to target cells during the days ensuing injury. This transient hyperthyroid and hyperretinoid climate creates a second defense line strengthening and fine-tuning the effects primarily initiated by cytokines. The suicidal behavior of thyroxine-binding globulin (TBG), corticosteroid-binding globulin (CBG), and IGFBP-3 allows the occurrence of peak endocrine and mitogenic influences at the site of inflammation. The production rate of TTR by the liver is the main determinant of both the hepatic release and blood transport of holoRBP, which explains why poor nutritional status concomitantly impairs thyroid- and retinoid-dependent acute-phase responses, hindering the stressed body to appropriately face the survival crisis. The prognostic significance of low TT4 blood levels may be assigned to the exhaustion of extrathyroidal hormonal pools normally stored in liver and plasma but markedly shrunken in protein-depleted states. These data offer new insights into the mechanisms whereby preexisting malnutrition and stressful complications are interrelated, emphasizing the pivotal role played by TTR in that context.

Insulin inhibition of glucocorticoid-stimulated gene transcription: requirement for an insulin response element?

The glucocorticoid hormone receptor binds to regulatory elements of target genes and activates transcription through interactions with coactivators. For a subset of genes, glucocorticoid receptor activity is inhibited by insulin. The present paper analyzes recent data on the molecular mechanisms whereby insulin exerts this antiglucocorticoid effect. Two models are proposed. In the first model insulin controls the activity of an insulin-responsive factor bound to an insulin-responsive DNA element. In a second model, insulin targets a non-DNA bound coactivator of the glucocorticoid receptor. Here, the gene-specificity of the effect of insulin is conferred by the combined action of the glucocorticoid receptor, of DNA-bound transcription factors and of coactivators, which form a higher order structure that binds to a DNA sequence called glucocorticoid/insulin responsive unit.

Corticosteroid regulation of ion channel conductances and mRNA levels in individual hippocampal CA1 neurons

Overexposure to corticosteroid hormones is harmful to hippocampal neuronal integrity, likely by perturbation of calcium homeostasis. To identify molecular mechanisms at the single-cell level, we characterized mRNA expression corresponding to voltage- and ligand-gated Ca channels in individual dissociated CA1 neurons in response to long-term corticosterone (CORT) exposure. Predominant mineralocorticoid receptor occupation (ADC-LO group) resulted in low levels of P/Q- and L-type Ca channel mRNAs, high levels of GluR-2 versus GluR-1, and a high ratio of NMDAR-2A to NMDAR-2B mRNA. Corresponding alterations in protein expression were consistent with the restriction of Ca influx. In contrast, additional glucocorticoid receptor occupation (ADC-HI group) altered the expression of these mRNAs in a manner consistent with enhanced Ca influx; interestingly, qualitatively similar alterations were seen in control ADX neurons. Electrophysiological data from the same neurons indicate that Ca current amplitudes also are modulated by CORT, although on a shorter time scale. Finally, principal components analysis (PCA) suggests that neuronal AMPA and NMDA receptor composition may be regulated by MR and GR activation in a complex manner. Therefore, our data implicate molecular events by which CORT may regulate Ca influx into CA1 hippocampal neurons.

Corticosteroid regulation of ion channel conductances and mRNA levels in individual hippocampal CA1 neurons

Overexposure to corticosteroid hormones is harmful to hippocampal neuronal integrity, likely by perturbation of calcium homeostasis. To identify molecular mechanisms at the single-cell level, we characterized mRNA expression corresponding to voltage- and ligand-gated Ca channels in individual dissociated CA1 neurons in response to long-term corticosterone (CORT) exposure. Predominant mineralocorticoid receptor occupation (ADC-LO group) resulted in low levels of P/Q- and L-type Ca channel mRNAs, high levels of GluR-2 versus GluR-1, and a high ratio of NMDAR-2A to NMDAR-2B mRNA. Corresponding alterations in protein expression were consistent with the restriction of Ca influx. In contrast, additional glucocorticoid receptor occupation (ADC-HI group) altered the expression of these mRNAs in a manner consistent with enhanced Ca influx; interestingly, qualitatively similar alterations were seen in control ADX neurons. Electrophysiological data from the same neurons indicate that Ca current amplitudes also are modulated by CORT, although on a shorter time scale. Finally, principal components analysis (PCA) suggests that neuronal AMPA and NMDA receptor composition may be regulated by MR and GR activation in a complex manner. Therefore, our data implicate molecular events by which CORT may regulate Ca influx into CA1 hippocampal neurons.

Chronic loss of glucocorticoids following adrenalectomy down-regulates the expression of glucocorticoid receptor mRNA in the rat forebrain

In the negative feedback model, loss of endogenous glucocorticoids up-regulates the expression of glucocorticoid receptor mRNA. To elucidate further the effect of chronic lack of glucocorticoids on the expression of glucocorticoid receptor mRNA and protein, in situ hybridization and immunohistochemical methods were used to examine the long-term alteration of glucocorticoid receptor mRNA and its immunoreactivity in the forebrain of adrenalectomized rats. Constant lack of glucocorticoids resulted in marked decrease in the expression of glucocorticoid receptor mRNA and disappearance of glucocorticoid receptor immunoreactivity in many forebrain structures. In particular, in the suprapyramidal blade of the hippocampal granule cell layer and cerebral cortex, many cells showed almost no glucocorticoid receptor mRNA signals. These results suggest that long-term loss of endogenous glucocorticoids down-regulates the levels of glucocorticoid receptor mRNA, leading to reduction in the synthesis of glucocorticoid receptors in the rat forebrain. Therefore, the presence of endogenous glucocorticoids is vital to the continued expression of glucocorticoid receptor mRNA.

The hydrocortisone-induced transcriptional down-regulation of beta-galactoside alpha2,6-sialyltransferase in the small intestine of suckling rats is suppressed by mifepristone (RU-38.486)

The progressive loss of sialic acids of the brush-border membrane glycoproteins is one of the major biochemical changes which occur in the rat small intestine during the transition from suckling to weaning, and this process is speeded up by an injection of glucocorticoids to the suckling animals. We used the rat liver beta-galactoside alpha2,6-sialyltransferase (ST6(N), EC 2.4.99.1) cDNA as a probe to examine the mRNA level of this enzyme in the small intestine of both suckling (13-day-old) and weaned (25-day-old) rats. In the ileum of suckling rats, the ST6(N) mRNA level was about four times higher than in the jejunum, whereas the membrane-bound enzyme activity was less than two times higher. In comparison with the controls, hydrocortisone treatment significantly decreased the level of this transcript and of the corresponding enzyme activity in both segments of the small intestine of suckling rats. Additionally, the antiglucocorticoid mifepristone (RU-38.486) suppressed the effect of hydrocortisone. The expression of ST6(N) mRNA in the small intestine of weaned (25-day-old) rats was several times lower than that in suckling (13-day-old) rats, and was unresponsive to hydrocortisone as well as to mifepristone. These results indicate that the glucocorticoid-induced transcriptional down-regulation of ST6(N) expression in the small intestine of suckling rats is mediated via the glucocorticoid receptor pathway, and support the notion that alterations in sialylation of brush-border membrane glycoconjugates occurring upon weaning are the result of a lower expression of ST6(N).

Coordinate expression of beta-galactoside alpha 2,6-sialyltransferase mRNA and enzyme activity in suckling rat jejunum cultured in different media: transcriptional induction by dexamethasone

In attempting to elucidate the molecular basis of the expression of alpha 2,6-sialyltransferase (alpha 2,6-ST) in jejunal explants of 7-day-old rats during cultivation, the total jejunal RNA was analysed by hybridization using a cDNA clone encoding rat liver alpha 2,6-ST. Under cultivation in both serum-free and serum-containing media jejunal alpha 2,6-ST mRNA closely paralleled the bound (100,000 g pellet) as well as the soluble (100,000 g supernatant) alpha 2,6-ST activity, the correlation coefficients being 0.976 and 0.816, respectively. Dexamethasone (Dx) treatment enhanced alpha 2,6-ST mRNA and membrane-bound alpha 2,6-ST activity in close correlation. Jejunal alpha 2,6-ST mRNA is sensitive to actinomycin D and is lost with apparently identical kinetics in Dx-stimulated and control explants, suggesting that regulation by Dx may be exerted by altering the rate of mRNA synthesis. Dx-dependent activation resulted in elevation of the 4.3-Kb mRNA and can be inhibited by the antiglucocorticoid onapristone, demonstrating the participation of the glucocorticoid receptor pathway.

Differential regulation of adrenocorticoid receptors in the hippocampus and spinal cord of adrenalectomized rats

Using multiple polymerase chain reaction assay and cytosolic receptor binding assay we studied type I, mineralocorticoid receptor (MR), and type II, glucocorticoid receptor (GR), adrenocorticoid receptors expression in rat hippocampus and spinal cord, at various times after adrenalectomy: 12 hr, 24 hr, 3 days, and 1 week. Analysis of the data demonstrates that in hippocampus the expression of MR and GR mRNA was not significantly affected by adrenalectomy. On the contrary, Bmax of MR was significantly increased at each time post-surgery, with only slight modifications of Kd. Bmax and Kd for GR showed a significant increase after 3 days and 1 week. In the spinal cord, MR mRNA was increased 12 hr after adrenalectomy, reaching a maximum at 3 days. Bmax of MR was also significantly increased after 3 days, whereas its Kd remained unchanged for the entire duration of the the study. Both GR mRNA and binding parameters were poorly affected by adrenalectomy. The results of the present experiments demonstrate that the absence of adrenocortical hormones influences differentially MR and GR expression in hippocampus and spinal cord, suggesting the existence of various and independent mechanisms of regulation of adrenocorticoid receptor.

Interferons up-regulate with different potency HLA class I antigen expression in M14 human melanoma cell line. Possible interaction with glucocorticoid hormones

The relative potency of interferon alpha (IFN alpha), interferon beta (IFN beta), and interferon gamma (IFN gamma) in inducing the expression of HLA class I antigens, as well as their capacity to counteract the inhibition induced by glucocorticoid hormones on HLA class I antigen expression, were analysed in the human melanoma cell line M14, both at membrane and at mRNA level. The data obtained indicate that (a) IFN enhance with different potency (IFN gamma > IFN beta > IFN alpha) the expression of HLA class I antigens in M14 cells, (b) prednisone inhibits HLA class I antigen expression, (c) glucocorticoid hormones, when associated with IFN alpha or IFN gamma, inhibit the HLA class I enhancement induced by IFN alone, and, finally, (c) the association between 1 microM prednisone or 1 microM deflazacort and IFN beta seems to potentiate the enhancing capacity of IFN on the expression of HLA class I molecules at the mRNA level. These findings, if confirmed, might indicate that IFN and glucocorticoid hormones are not mutually exclusive in the management of human melanoma.

Mechanisms of neuronal plasticity as analyzed at the single cell level

This chapter has highlighted how correlates of neuronal plasticity such as electrophysiological responsiveness and changes in gene expression may be examined in defined CNS regions as well as in single cells. The ability to simultaneously measure the mRNA levels for hundreds of different genes, to clone novel genes, and to characterize the physiology and morphology of the cell promises to provide insight into molecular mechanisms of plasticity. The importance of understanding how one gene product changes relative to another (coordinated changes) as well as subcellular distribution of mRNAs cannot be overstated. It is only through an analysis of both the molecular and cellular processes associated with plasticity that a thorough understanding of the mechanisms of neuronal plasticity can be gained.

Glucocorticoid regulation of calcitonin receptor in mouse osteoclast-like multinucleated cells

Abundant multinucleated cells (MNCs) are formed in cocultures of mouse osteoblastic cells and marrow cells in the presence of 1 alpha, 25-dihydroxyvitamin D3 [1 alpha, 25(OH)2D3], and these cells have the properties of osteoclasts (OCs). In this study using the mammalian OCs, we tried to clarify the role of glucocorticoids (GCs) in calcitonin receptors (CTR) and CT-responsive cAMP production in OCs. Dexamethasone (DEX) dose and time dependently enhanced the specific binding of [125I]salmon calcitonin (sCT). When the MNCs were preincubated with DEX for 24 h, the effect was evident at 10(-9) M and the maximum effect was obtained at 10(-7) M. The effect developed over 12-48 h at doses of 10(-9) and 10(-6) M DEX. The numbers of CTR-positive mononuclear cells and MNCs were not altered by the DEX treatment. Prednisolone and triamcinolone reproduced the DEX effect, but 17 beta-estradiol, progesterone, testosterone, aldosterone, and 1 alpha, 25(OH)2D3 did not. RU486, a GC receptor antagonist, attenuated the effect of DEX to enhance the specific binding of [125I]sCT. From a Scatchard plot analysis, DEX enhanced CTR number (212 +/- 64%) with a minimal change in the affinity to sCT. Autoradiographic studies using [125I]sCT showed that DEX enhanced the density of the grains on the tartrate-resistant acid phosphatase (TRAP)-positive MNCs and mononuclear cells, but not on other types of cells. DEX preincubation also enhanced sCT-stimulated but not prostaglandin E2- or forskolin-stimulated cAMP production.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal steroid receptors: interactions with brain neuropeptide systems in relation to nutrient intake and metabolism

The glucocorticoid, corticosterone (CORT), is believed to have an important function in modulating nutrient ingestion and metabolism. Recent evidence described in this review suggests that the effects of this adrenal hormone are mediated through two steroid receptor subtypes, the type I mineralocorticoid receptor and the type II glucocorticoid receptor. These receptors, which have different affinities for CORT, respond to different levels of circulating hormone. They mediate distinct effects of the steroid, which can be distinguished by the specific nutrient ingested and by the particular period of the circadian cycle. Under normal physiological conditions, the type I receptor is tonically activated, either by low basal levels of circulating CORT (0.5-2 microgram %) normally available across the circadian cycle or possibly by the mineralocorticoid aldosterone. This type I activation is required for the maintenance of fat ingestion and fat deposition that occurs during most meals of the feeding cycle. In contrast, the type II receptor is phasically activated by moderate levels of CORT (2-10 micrograms %) normally reached during the circadian peak. Activation of this receptor is required for the natural surge in carbohydrate ingestion and metabolism that is essential at the onset of the active feeding cycle when the body's glycogen stores are at their nadir, and gluconeogenesis is needed to maintain blood glucose levels. This receptor is also activated during periods of increased energy requirements, such as, after exercise and food restriction, when CORT levels rise further (> 10 micrograms %) and when its catabolic effects on fat and protein stores predominate to provide additional substrates for glucose homeostasis. These functions of CORT on fat and carbohydrate balance are mediated, in part, by type I and type II receptors located within the hypothalamic paraventricular nucleus, which is known to have key functions in controlling nutrient intake and metabolism, as well as circulating CORT levels. Moreover, the type II receptors within this nucleus, in addition to the arcuate nucleus, may interact positively with the peptide, neuropeptide Y, and the catecholamine, norepinephrine, both of which act to enhance natural carbohydrate feeding and CORT release at the onset of the natural feeding cycle. Thus, under normal conditions, endogenous CORT has a primary function in controlling nutrient ingestion and metabolism over the natural circadian cycle, through the coordinated action of the type I and type II steroid receptor systems. Through this action, CORT has impact on total caloric intake and body weight gain over the long term.(ABSTRACT TRUNCATED AT 400 WORDS)

Immunocytochemical localization of glucocorticoid receptor in rat skin

The aim of the present study was to map immunohistochemically the distribution of the glucocorticoid receptor (GR) in rat skin. Nuclear GR-like immunoreactivity (LI) was found in both epidermis and dermis. In the epidermis, the basal cell layer showed an intense immunoreaction; the lower part of the spinous layer was also labelled. In the dermis, the fibroblasts as well as the sweat glands, sebocytes and adipocytes were GR-immunoreactive (IR). In the root sheath of the hair follicle the staining was most intensive in the outer layer. The endothelial cells comprising the smooth muscle cells of the blood vessels, as well as the arrector pili muscle, showed GR-LI. In the peripheral nerves, the immunoreaction was localized to the nuclei of the Schwann cells and in the perineurial fibroblasts. Mast cells did not show nuclear GR-LI. Based on our immunocytochemical findings that several cell types of the skin are GR-IR, the variable physiological and pharmacological effects of glucocorticoids are easier to understand.

Morphology, growth, and gene expression in five newly isolated murine hepatocellular tumor cell lines

Five murine hepatocellular tumor cell lines (HepM-1-5) were isolated and grown in a synthetic medium added with hormones, growth factors and/or serum. The morphology of these lines ranged from a nearly homogeneous epithelial-like shape (HepM-2) to a stromal appearance (HepM-1). The remaining lines displayed a mixed morphology. For their proliferation all of the cell lines retained a clear dependence on the extracellular calcium level and hormonal and/or serum growth factors and, rather homogeneously, they did not express the albumin, alpha-fetoprotein (with the exception of HepM-2 cells), tyrosine aminotransferase, and ornithine transcarbamylase genes, whereas they all exhibited discrete levels of the ornithine aminotransferase mRNA. Only HepM-3 and HepM-5 lines expressed the procollagen type I gene.

Modulation of ecto-nucleoside triphosphate pyrophosphatase activity of human osteoblast-like bone cells by 1 alpha,25-dihydroxyvitamin D3, 24R,25-dihydroxyvitamin D3, parathyroid hormone, and dexamethasone

Extracellular inorganic pyrophosphate (PPi) is involved in the regulation of mineralization, and there is evidence that the cell surface enzyme, NTP pyrophosphatase, is a major source of this metabolite in bone. Osteotrophic agents that influence bone turnover may exert their effects, in part, by modulating the activity of ecto-NTP pyrophosphatase in bone cells. We investigated the effect of 1, 25(OH)2 D3, 24, 25(OH)2D3, dexamethasone, and parathyroid hormone (PTH) on the activity of this enzyme in cultured human trabecular bone-derived osteoblast-like cells. 1,25(OH)2D3 at 10(-11)-10(-9) M induced a dose- and time-dependent increase in activity (at 96 h; maximum 10(-9) M, p < 0.001), whereas higher concentrations (10(-8) and 10(-7) M) had no effect. In contrast, 24,25(OH)2D3 was effective only at 10(-8) and 10(-6) M (at 96 h; p < 0.01). Dexamethasone (10(-9)-10(-7) M) caused a dose-dependent decrease in ecto-NTP pyrophosphatase activity (10(-7) M, p < 0.001); concentrations higher than 10(-7) M did not evoke greater inhibition. This effect became apparent by 48 h and was significantly enhanced after 72 h. The response to dexamethasone was attenuated by cycloheximide, indicating a requirement for de novo protein synthesis. Interestingly, the stimulatory effect of 10(-9) M 1,25(OH)2D3 on ecto-NTP pyrophosphatase activity was significantly enhanced in the presence of dexamethasone (10(-9)-10(-7) M). Human PTH(1-34) and bovine PTH(1-34) in the range 10(-10)-10(-7) M had no effect on enzyme activity over a 72 h period.(ABSTRACT TRUNCATED AT 250 WORDS)

Bombesin receptor gene expression in rat pancreatic acinar AR42J cells: transcriptional regulation by glucocorticoids

BACKGROUND/AIMS

This study investigated the correlation between glucocorticoid-regulated gene expression of the bombesin receptor (BR) and cellular sensitivity to bombesin stimulation in the rat pancreatic acinar cell line AR42J.

METHODS

BR gene expression was assessed using a cloned complementary DNA probe and radioligand binding assays. Intracellular Ca2+ mobilization was assessed by dual wavelength spectrophotometry using fura-2 in single cells.

RESULTS

Dexamethasone resulted in a rapid dose- and time-dependent decrease of BR messenger RNA levels with maximal inhibition to 25% +/- 2% of controls (n = 4) after 6 hours of hormone treatment. BR messenger RNA half-life was approximately 120 minutes and was not affected by dexamethasone pretreatment; nuclear run-on analysis showed a decreased transcription rate of the BR to approximately 25% of control after hormonal treatment. Radioligand binding studies showed a time-dependent decrease of specific bombesin binding to 25% +/- 8% of control after 48 hours of hormone treatment. Down-regulation of BR gene expression by dexamethasone resulted in a time- and dose-dependent decrease of intracellular Ca2+ mobilization after bombesin stimulation compared with untreated controls.

CONCLUSIONS

Glucocorticoids decrease BR gene transcription. The subsequent decrease in cellular BR number renders AR42J cells less sensitive for bombesin-stimulated intracellular Ca2+ mobilization.

Effect of dexamethasone on the peptic activity of gastric lumen and mucosa

Dexamethasone (9 alpha-fluoro-16 alpha methyl-11 beta,17 alpha,21-trihydroxy-1,4-pregnadiene-3,20-dione-21-phosphate), a synthetic glucocorticoid, has a dual role on pepsinogen content of the gastric lumen and mucosa as measured by its peptic activity. Following stimulation the luminal peptic activity gradually decreases after 6 hr, then returns to basal levels at 18 hr and by 24 hr is inhibited by 50%. The luminal peptic activity induced by the secretory compound mercaptomethylimidazole (MMI) is also decreased. Dexamethasone effect on both basal and MMI-induced peptic activity can be reproduced by cycloheximide or puromycin, translational blockers of protein synthesis. This drug also has an independent time and dose-dependent inhibitory effect on gastric mucosal peptic activity which does not correlate with increased peptic activity of the lumen. Dexamethasone appears to be more effective than hydrocortisone and corticosterone in inhibiting the basal peptic activity of both lumen and mucosa. The inhibitory effect of this drug on tissue peptic activity is not mediated through induction of any inhibitory protein as evidenced by the insensitivity of the effect to actinomycin D. Studies on [14C]phenylalanine incorporation into gastric protein indicate that the effect of dexamethasone on tissue pepsinogen content is not due to a generalized block of protein synthesis.

Dexamethasone induces chondrogenesis in organoid culture of cell mixtures from mouse embryos

The effect of dexamethasone on morphogenesis and differentiation of cells obtained from mouse embryos grown at high density in vitro was investigated. Cells from decapitated mouse embryos of day 10 to day 13 were isolated by enzymatic treatment and grown at high density at the medium/air interface in organoid culture. After 28 days in culture, organoid-like structures such as vesicles, gland-like structures and cell aggregates had developed, dependent on the stage of the embryos. After the addition of 10(-7) M dexamethasone, cartilage had formed in cultures of cells from day-10, -11 and -12 embryos. It was maximal in cultures of day-11 cells and rare in day-10 cells. No cartilage was found in cultures of day-13 cells. Cartilage induction was similar in cultures treated with 10(-6) and 10(-7) M dexamethasone, but clearly less in cultures treated with 10(-8) M. Only minute amounts of cartilage were detectable after dexamethasone treatment of cells obtained from decapitated embryos (day-11 and -12) whose limb buds had been cut off. In organoid cultures of pure limb bud cells, 10(-7) M dexamethasone had no influence on chondrogenesis. The results indicate that the cells inducible to form cartilage by dexamethasone originate from the limb buds. Glucocorticoid induction of chondrogenesis has not been described in vivo. The dependency of both chondrogenesis and expression of glucocorticoid receptor on cell density in vitro may be the cause for this effect.

Glucocorticoid-mediated muscle atrophy: alterations in transcriptional activity of skeletal muscle nuclei

Glucocorticoid-induced muscle atrophy is associated with a decrease in the level of protein synthesis and a loss of RNA. This paper reports the behaviour of RNA polymerase I- and RNA polymerase II-directed transcription (EC 2.7.7.6) in nuclei isolated from skeletal muscles of rats given a catabolic dose of dexamethasone acetate (5 mg per Kg body weight) over a period of 4 days. Both activities were altered by the dexamethasone treatment. In the case of RNA polymerase I-mediated transcription there was a loss of template-engaged enzymes indicating the existence of an inhibition of initiation of transcription while the rate of elongation of bound enzymes was unaltered. The number of RNA polymerase II-chromatin bound enzymes was increased, but the mean polynucleotide elongation rate was reduced. The possibility that glucocorticoids may impair the elongation stage of transcription in skeletal muscle by increasing the frequency of premature termination of transcripts is discussed. No evidence was obtained for any increase in ribonuclease activity in muscle nuclei of dexamethasone-treated animals.

Thyroid hormone and glucocorticoid regulation of receptor and target gene mRNAs in pituitary GH3 cells

We have examined the effects of triiodothyronine (T3), in dose-response and time-course studies, on T3 receptor (T3R) alpha and beta and glucocorticoid receptor (GR) mRNAs in rate pituitary GH3 cells, in parallel with T3 actions on expression of the growth hormone (GH) target gene. Modulatory influences of dexamethasone (dex) on T3 action were studied by treatment with dex before and during T3 treatment. T3 treatment (1-100 nM) for 24 h reduced T3R alpha mRNA, while the presence of dex (1 microM) enhanced the T3 effect on T3R alpha mRNA and induced T3 inhibition of T3R beta mRNA. Stimulatory effects of T3 treatment on GH mRNA and release were seen in the face of inhibition of T3R mRNAs; these effects on GH were also enhanced by the presence of dex. T3 treatment for 24 h increased GR mRNA; this effect was inhibited by the presence of dex. We next examined the influence of dex on GR and T3R alpha and beta mRNAs, in parallel with effects of dex on the prolactin (PRL) target gene. Modulatory influences of T3 on dex action were studied by treatment of cells with T3 before and during dex treatment. Treatment with dex (0.1-10 microM) for 24 h reduced GR mRNA, an action enhanced by the presence of T3 (100 nM). Dex treatment resulted in inhibition of PRL mRNA and release despite parallel inhibition of GR mRNA by dex; these effects were enhanced by the presence of T3. In contrast to actions on GR, dex has no effect on T3R mRNAs. These effects of T3 and dex on receptor mRNAs suggest that glucocorticoid modulation of T3 action is not related to direct actions on T3R synthesis. In contrast, the mechanism of T3 modulation of glucocorticoid action may be due in part to alteration of GR mRNA expression. Effects of T3 and dex on target gene expression were observed in the presence of parallel reduction of their respective receptor mRNAs. This provides new evidence that interactions between these hormones are likely to be mediated by mechanisms other than regulation of receptor gene expression.

Isolation of a cDNA clone, encoding a human beta-galactoside binding protein, overexpressed during glucocorticoid-induced cell death

In this report we describe the isolation and characterization of a cDNA clone overexpressed tenfold during the induction of apoptosis in the glucocorticoid-sensitive human leukaemia cell line CEM C7. This clone was shown by DNA sequence analysis to represent the human HL14 gene, encoding a beta-galactoside binding protein, the mouse homologue of which has recently been reported to act as a cell growth inhibitory factor.

New elements of glucocorticoid-receptor binding sites of hormone-regulated genes

The structure of the DNA regions recognized by glucocorticoid-receptor complexes (GIRC) was analyzed using frequency matrices and a modified perceptron method. Some complementary conservative elements which may modulate the efficiency of GIRC binding were found at both sides of the previously established conserved nucleotide sequence (core) (Beato, M. et al. (1987) J. Steroid Biochem. 27, 9-14). A criterion based on the concurrent use of several perceptron matrices to search for the potential GIRC binding site sequences has been worked out. By applying this criterion 73 sites were identified in 28 sequences of glucocorticoid regulated genes and 7 sites were identified in 26 sequences independent from glucocorticoid regulation.

Regulation of the glucocorticoid receptor in fetal rat lung during development

The effect of the synthetic glucocorticoid betamethasone on the regulation of the glucocorticoid receptor mRNA and on receptor protein was studied in fetal rat lung during development. Using a glucocorticoid receptor cRNA probe, glucocorticoid receptor mRNA was examined by Northern blot hybridization and by solution hybridization. A monoclonal antibody against the glucocorticoid receptor was used to study regulation of the receptor protein by the Western immunoblotting technique. In fetal rat lungs, of 16-21 days of gestation, as well as in adult lungs, betamethasone treatment resulted in a significant decrease of glucocorticoid receptor mRNA to 50-65% of the control level. In contrast, betamethasone treatment did not down-regulate the receptor protein in rat lungs of 16-19 days of gestation, whereas a decrease of glucocorticoid receptor protein to 40-60% of control was seen in lungs of 21 days of gestation, in postnatal and adult lung. These results provide data for a change in regulation in vivo of the glucocorticoid receptor by its homologous ligand in fetal rat lung during development.

Cortisol reduces plasticity in the kitten visual cortex

We investigated the effect of elevated levels of cortisol on plasticity in the visual cortex of the cat. Animals were given daily injections of cortisol i.m. for 20 days starting around 35 days of age. After 10 days they were monocularly deprived, and after an additional 10 days recordings were made from the visual cortex to construct an ocular dominance histogram. The results were compared with those from normal animals of the same age, and with animals monocularly deprived for the same period but not treated with cortisol. Cortisol reduced the ocular dominance shift in a dose-dependent manner, but did not totally abolish it even at the highest doses used. Two other series of animals were recorded, one slightly later in the critical period and one slightly earlier, with care taken to give cortisol before the animals were exposed to light in the morning. In both cases, cortisol reduced the ocular dominance shift but did not abolish it. To interpret these results, we measured levels of plasma cortisol in normal cats of various ages. Average levels were fairly constant between birth and 12 months of age (0.5-1 microgram/dl), and increased slightly after that, but there was a large variation between animals. Thus elevated levels of cortisol can have a substantial effect on plasticity in the visual cortex of the cat, but the decline of the critical period for plasticity between 6 weeks and 3-5 months of age does not seem to be due to a rise in cortisol levels during this time.

Receptor-mediated prednisolone pharmacodynamics in rats: model verification using a dose-sparing regimen

Our receptor/gene-mediated model of corticosteroid action was tested and extended by examining the pharmacokinetics/dynamics of multiple low doses vs. a single higher dose of intravenously administered prednisolone in adrenalectomized male Wistar rats. Low-dose rats received 3 bolus doses (5 mg/kg) of prednisolone at 0, 0.5 and 1.0 hr. High-dose animals were given a single 25 mg/kg dose of prednisolone. Both regimens were expected to produce equivalent net responses based on model predictions. Control rats were not dosed. The profiles of free hepatic cytosolic glucocorticoid receptors and the hepatic tyrosine aminotransferase (TAT) enzyme were examined. Plasma prednisolone concentrations showed bi-exponential decline for both doses using pooled animal data. Clearance of total plasma prednisolone was 4.16 and 3.21 L/hr per kg in low- and high-dose groups. Volume of distribution at steady state (approximately 1.50 L/kg) and central volume (approximately 0.6 L/kg) were similar for both groups. Receptor levels from 5-16 hr stabilized at 64% of the 0-hr control value. Receptor and TAT profiles were essentially superimposable for both dosing groups. Our previous model was used to simultaneously describe prednisolone plasma concentrations, hepatic receptors, and TAT activity. The ability of total plasma prednisolone (Cp), corticosteroid binding globulin (CBG)-free plasma prednisolone (CCBG), and free plasma prednisolone (CF) to describe the kinetics/dynamics were examined. The CF values produced optimum fitting of all receptor data. The similarity of the two dosing groups supports the view that appropriately timed doses of a steroid can be used in an optimally efficacious manner by first filling all receptor sites and then replacing steroid as receptors are expected to recycle from nuclear/DNA binding sites as the steroid is eliminated.

Dexamethasone-induced plasminogen activator inhibitor: characterization, purification, and preparation of monoclonal antibodies

The effects of dexamethasone on protein synthesis were studied in human fibrosarcoma (HT-1080) cells. Dexamethasone induced a new protein of 46 kD which was rapidly secreted into the medium, while neither progesterone nor estradiol would induce the synthesis of this protein and only a small increase in its amount could be seen in the presence of testosterone. The 46 kD protein was partially purified by ammonium sulfate precipitation and gel filtration and mouse monoclonal antibodies to it were produced in mouse hybrid cells. Altogether 13 positive clones were found, of which six reacted only with native and seven reacted with the unreduced 46 kD protein in Western blotting. It was possible by using polyclonal antibodies to plasminogen activator inhibitor type I (PAI-1) and purified plasminogen activator inhibitor type I to confirm that the 46 kD protein purified and characterized here was PAI-1. In addition, the 46 kD protein clearly inhibited plasminogen activation, thus further confirming that protein isolated was an inhibitor of plasminogen activator. Since the induction of PAI-1 by dexamethasone was very extensive, it is possible that glucocorticoids regulate proteolysis and fibrinolysis in vivo by increasing the amount of the inhibitor of plasminogen activator and thus preventing the activation of plasminogen to plasmin. The reduction of activation of plasminogen to plasmin by glucocorticoid-induced inhibitor could be of great importance, e.g., in various blistering diseases, in metastases from malignant cells, and in the migration of inflammatory cells.

The influence of vitamin B6 on the structure and function of the glucocorticoid receptor

Pyridoxal phosphate influences several properties of steroid hormone receptors in vitro, but its role in vivo has not been clearly established. In an effort to address this issue, we have investigated the in vivo effects of vitamin B6 on the physical properties and biological function of the human glucocorticoid receptor. We demonstrate that vitamin B6 treatment of whole cells in culture produces an alteration in the isoelectric point of the receptor, as well as changes in the steroid and DNA binding capacities. Furthermore, glucocorticoid dependent transcriptional activation properties of the receptor are also altered by modulation of the vitamin B6 status. High concentrations of vitamin B6 suppress activation of transcription, while vitamin deficiency enhances responsiveness to steroid hormone. Together, these studies imply a physiological role for vitamin B6 in glucocorticoid hormone action.

Glucocorticoid receptors and enzyme induction in the spinal cord of rats: effects of acute transection

The spinal cord is a glucocorticoid-responsive tissue, as demonstrated by hormonal effects on enzyme induction and by the presence of type II and type I glucocorticoid receptors in cytoplasmic extracts of this CNS region. Using microdissection techniques, we have found in the present investigation that glucocorticoid type II receptors are the most abundant class detected in gray (ventral and dorsal horns) and white (lateral funiculus) matter and that the distribution of type II sites among these regions was quantitatively similar. Type I sites were also quantified, with a slight prevalence in gray matter as opposed to white matter. Furthermore, stimulation of an inducible enzyme, ornithine decarboxylase (ODC), was found in ventral horn and lateral funiculus but not in dorsal horn after administration of dexamethasone (DEX), a type II receptor ligand. We also found that surgical transection of the spinal cord, while markedly increasing ODC activity per se, did not prevent the stimulatory effect of DEX administration on ODC activity measured in the lumbar enlargement of the spinal cord located below the surgical lesion. Taken together, the results suggest a direct effect of glucocorticoids on ODC activity in the spinal cord of rats, probably mediated by glucocorticoid receptors (type II) found in target cells of the ventral horn and lateral funiculus. The results also indicate that glucocorticoid receptors of the dorsal horn were not involved in ODC induction, and a function for these receptors awaits the results of further experimentation.

Charting of type II glucocorticoid receptor-like immunoreactivity in the rat central nervous system

The rat brain and spinal cord have been mapped for Type II glucocorticoid receptor-like immunoreactivity in neurons and glia, using a monoclonal antibody, BUGR2, which recognizes an epitope close to the DNA-binding domain of the rat Type II receptor. The study revealed a widespread distribution of Type II-like immunoreactive neurons and glia, and a heterogeneity of densities and intensities of immunoreactive elements. Our results corresponded to a large extent with previous immunocytochemical mapping using Ig2a, a monoclonal antibody against a different epitope in the variable domain, with some notable differences in the hippocampus, hypothalamus and cerebellum. There was also a good correlation between immunocytochemical mapping and binding studies, [3H]steroid autoradiography and mRNA localization of the Type II receptor.

Stabilization of glucocorticoid-receptor interactions in vitro by removal of RNA bound to receptor complexes in vivo

The dissociation of the steroid from glucocorticoid-receptor-RNA complexes at 5 degrees C was evaluated in cytosolic and nuclear extracts prepared from Hela cells crosslinked in vivo with glutaraldehyde. Sample treatment with catalytically active RNase A prevented the dissociation of the steroid which was induced by sample dilution with buffer. Dilution of the extracts with boiled cytosol, instead, stabilized steroid-receptor interactions. We conclude that some heat-stable factor should be also associated with glucocorticoid-receptor-RNA complexes from crosslinked cells, stabilizing steroid-receptor interactions, and we propose that it could counteract the labilizing effect of RNA.

Additive effects of dexamethasone and calcium on the calcitonin mRNA level in adrenalectomized rats

Northern hybridizations were used to evaluate the effects of dexamathasone and calcium on calcitonin mRNA levels in adrenalectomized female rats. Two weeks after adrenalectomy, a 3.6-fold decrease in the calcitonin mRNA level was observed (28% vs 100% in sham-operated controls). After 5 days of dexamethasone treatment (1.5 mg/kg b. wt), a 2.6-fold rise in calcitonin mRNA occurred in adrenalectomized rats (73% vs 28%). This increment was higher when dexamethasone treated animals were injected with calcium (100% vs 73%). The effect of calcium on the calcitonin mRNA level of adrenalectomized rats treated or not with dexamethasone was similar, and additive in the former case. Our data suggest that calcium and dexamethasone elevate calcitonin mRNA by two different mechanisms.

Glucocorticoids inhibit prostaglandin synthesis not only at the level of phospholipase A2 but also at the level of cyclo-oxygenase/PGE isomerase

1. Prostanoid synthesis was induced in bone marrow-derived macrophages by addition of exogenous arachidonic acid to the cell cultures. When the cells were preincubated with dexamethasone (10(-7) and 10(-6) M) overnight, prostaglandin synthesis was inhibited by 66.5 +/- 2.8% and 56.7 +/- 2.9% (mean +/- s.d.; n = 3) respectively. 2. Endogenous membrane bound phospholipase A2 was measured with labelled phospholipids used as substrates. The enzyme activity with phosphatidylcholine and phosphatidylethanolamine as substrates was inhibited by 27.0 +/- 8.3% and 23.3 +/- 11.1% (n = 4) respectively, in dexamethasone-treated macrophages compared to control cells. Neither the distribution of radiolabelled arachidonic acid among the different phospholipid species nor the release of arachidonic acid from prelabelled cells were significantly impaired by pretreatment of the macrophages with dexamethasone (1 microM). 3. The enzyme activity of the cyclo-oxygenase/prostaglandin E (PGE) isomerase was measured in cell membranes from control cells and dexamethasone-treated cells. It was inhibited by 40.0 +/- 8.4% (n = 4) in dexamethasone-treated cells as compared to control cells. Thus, glucocorticoids inhibit not only phospholipase A2 in these cells, but predominantly inhibit arachidonic acid metabolism subsequent to its release from phospholipids.

Pharmacokinetics and pharmacodynamic modeling of direct suppression effects of methylprednisolone on serum cortisol and blood histamine in human subjects

Pharmacodynamic models for "directly suppressive" effects of methylprednisolone are based on the premise that receptor interactions of steroids are followed by immediate suppression of either the circadian secretion of cortisol or the constant rate recirculation of histamine-containing basophils that persists until inhibitory concentrations of methylprednisolone disappear. Methylprednisolone doses of 0, 10, 20, and 40 mg were given as the 21-succinate sodium salt in a balanced crossover study to six normal men. Plasma steroid concentrations and blood histamine were measured simultaneously. Both forms of methylprednisolone exhibited linear kinetic parameters. One dynamic model quantitates the baseline circadian pattern and the decline and return of cortisol with similar parameter estimates for all three dose levels. A similar model describes the monoexponential decline and the log-linear return to steady-state baseline of blood histamine. Similar inhibitory concentration values for both effects approximated the equilibrium dissociation constant of in vitro steroid receptor binding. The new models are more physiologically appropriate for these steroid effects than three other models that are commonly employed in pharmacodynamics. Steroid effects generally appear to be receptor mediated with either nongene immediate responses or gene-mediated delayed effects. These models allow quantitation of the rapid effects of steroids with simple equations and common fitted parameters for all steroid dose levels.

Molecular changes associated with induction of cell death in a human T-cell leukaemia line: putative nucleases identified as histones

Following treatment of the human T-cell leukaemia line, CEM-C7, with the glucocorticoid, dexamethasone, a rapid decrease in viability occurred after 40 h which coincided with fragmentation of DNA in these cells. A similar pattern of DNA fragmentation was observed when these cells were gamma-irradiated or treated with cycloheximide. Distinct morphological changes occurred after treatment, indicating a form of cell death, regulated from within, termed apoptosis. A set of nuclear proteins ranging in size from 10-18 kDa appeared by 40 h following treatment with dexamethasone. Treatment of cells with gamma-irradiation or cycloheximide also produced the same protein pattern. This set of proteins, and a doublet approximately 55 kDa in size, had apparent nuclease activity which was not observed in untreated cells. However, protein microsequencing of these bands in the 10-18 kDa region revealed that they were histone proteins. These results cast doubt on a recent report which provided evidence that these proteins were induced nucleases.