Showing papers on "Glucocorticoid published in 2002"

Chronic Psychological Stress and the Regulation of Pro-Inflammatory Cytokines: A Glucocorticoid-Resistance Model

Abstract: This study examined whether chronic stress impairs the immune system’s capacity to respond to hormonal signals that terminate inflammation. Fifty healthy adults were studied; half were parents of cancer patients, and half were parents of healthy children. Parents of cancer patients reported more psychological distress than parents of healthy children. They also had flatter diurnal slopes of cortisol secretion, primarily because of reduced output during the morning hours. There was also evidence that chronic stress impaired the immune system’s response to anti-inflammatory signals: The capacity of a synthetic glucocorticoid hormone to suppress in vitro production of the pro-inflammatory cytokine interleukin-6 was diminished among parents of cancer patients. Findings suggest a novel pathway by which chronic stress might alter the course of inflammatory disease.

Interaction between glucocorticoid hormones, stress and psychostimulant drugs.

Abstract: In this review we summarize data obtained from animal studies showing that glucocorticoid hormones have a facilitatory role on behavioural responses to psychostimulant drugs such as locomotor activity, self-administration and relapse. These behavioural effects of glucocorticoids involve an action on the meso-accumbens dopamine system, one of the major systems mediating the addictive properties of drugs of abuse. The effects of glucocorticoids in the nucleus accumbens are site-specific; these hormones modify dopamine transmission in only the shell of this nucleus without modifying it in the core. Studies with corticosteroid receptor antagonists suggest that the dopaminergic effects of these hormones depend mostly on glucocorticoid, not on mineralocorticoid receptors. These data suggest that an increase in glucocorticoid hormones, through an action on mesolimbic dopamine neurons, could increase vulnerability to drug abuse. We also discuss the implications of this finding with respect to the physiological role of glucocorticoids. It is proposed that an increase in glucocorticoids, by activating the reward pathway, could counteract the aversive effects of stress. During chronic stress, repeated increases in glucocorticoids and dopamine would result in sensitization of the reward system. This sensitized state, which can persist after the end of the stress, would render the subject more responsive to drugs of abuse and consequently more vulnerable to the development of addiction.

p38 Mitogen-activated protein kinase–induced glucocorticoid receptor phosphorylation reduces its activity: Role in steroid-insensitive asthma

Abstract: Background: Although glucocorticoids are the most effective treatment for chronic inflammatory diseases, such as asthma, some patients show a poor response. IL-2 combined with IL-4 can alter glucocorticoid receptor (GR) ligand-binding affinity and modulate glucocorticoid function. Objective: We sought to confirm the altered ligand-binding affinity in a distinct group of steroid-dependent asthmatic subjects and examine the mechanism by which IL-2 and IL-4 modify the ligand-binding affinity of the GR. Methods: We examined PBMCs from healthy subjects, subjects with mild asthma, and steroid-dependent subjects with severe asthma using dexamethasone-binding assays and Western blot analysis of GR and phosphorylated activated transcription factor 2 expression. GR phosphorylation was measured after orthophosphate labeling and immunoprecipitation and cytokine production by means of ELISA. Results: GR ligand-binding affinity was reduced in the nucleus but not in the cytoplasm of steroid-dependent asthmatic subjects compared with that seen in healthy subjects (dissociation constant, 39.8 ± 4.6 vs 6.79 ± 0.8 nmol/L). This difference in ligand-binding affinity could be mimicked by IL-2 and IL-4 cotreatment and was blocked by the p38 mitogen-activated kinase (MAPK) inhibitor SB203580. Activation of p38 MAPK by IL-2 and IL-4, as shown by means of phosphorylation of activated transcription factor 2, resulted in GR phosphorylation and reduced dexamethasone repression of LPS-stimulated GM-CSF release. p38 MAPK phosphorylation of CD2 + T cells occurred on serine residues. The ability of dexamethasone to modulate IL-10 release was also inhibited by IL-2 and IL-4 cotreatment. These effects were also inhibited by SB203580. Conclusion: These data show that p38 MAPK inhibitors may have potential in reversing glucocorticoid insensitivity and reestablishing the beneficial effects of glucocorticoids in patients with severe asthma. (J Allergy Clin Immunol 2002;109:649-57.)

Mechanisms of glucocorticoid action in bone.

Abstract: Glucocorticoids cause profound effects on bone cell replication, differentiation, and function. Glucocorticoids increase bone resorption by stimulating osteoclastogenesis by increasing the expression of RANK ligand and decreasing the expression of its decoy receptor, osteoprotegerin. In accordance with the increase in bone resorption, glucocorticoids stimulate the expression of collagenase 3 by posttranscriptional mechanisms. The most significant effect of glucocorticoids in bone is an inhibition of bone formation. This is because of a decrease in the number of osteoblasts and their function. The decrease in cell number is secondary to a decrease in osteoblastic cell replication and differentiation, and an increase in the apoptosis of mature osteoblasts. Glucocorticoids decrease osteoblastic function directly and indirectly through the modulation of growth factor expression, receptor binding, or binding protein levels. Clinically, patients with glucocorticoid-induced osteoporosis (GIOP) develop bone loss in the first few months of glucocorticoid exposure, and modest doses of glucocorticoids increase the risk of fractures of the spine and hip. Bisphosphonates inhibit bone resorption and prevent and revert the bone loss that follows glucocorticoid exposure. Anabolic agents, such as parathyroid hormone, stimulate bone formation and can increase bone mass in GIOP.

A Polymorphism in the Glucocorticoid Receptor Gene, Which Decreases Sensitivity to Glucocorticoids In Vivo, Is Associated With Low Insulin and Cholesterol Levels

Abstract: We investigated whether a polymorphism in codons 22 and 23 of the glucocorticoid (GC) receptor gene [GAGAGG(GluArg) → GAAAAG(GluLys)] is associated with altered GC sensitivity, anthropometric parameters, cardiovascular risk factors, and sex steroid hormones. In a subgroup of 202 healthy elderly subjects of the Rotterdam Study, we identified 18 heterozygotes (8.9%) for the 22/23EK allele (ER22/23EK carriers). In the highest age group, the number of ER22/23EK carriers was higher (67–82 years, 12.9%) than in the youngest age group (53–67 years, 4.9%; P < 0.05). Two dexamethasone (DEX) suppression tests with 1 and 0.25 mg DEX were performed, and serum cortisol and insulin concentrations were compared between ER22/23EK carriers and noncarriers. After administration of 1 mg DEX, the ER22/23EK group had higher serum cortisol concentrations (54.8 ± 18.3 vs. 26.4 ± 1.4 nmol/l, P < 0.0001), as well as a smaller decrease in cortisol (467.0 ± 31.7 vs. 484.5 ± 10.3 nmol/l, P < 0.0001). ER22/23EK carriers had lower fasting insulin concentrations ( P < 0.001), homeostasis model assessment- insulin resistance (IR) (index of IR, P < 0.05), and total ( P < 0.02) and LDL cholesterol concentrations ( P < 0.01). Our data suggest that carriers of the 22/23EK allele are relatively more resistant to the effects of GCs with respect to the sensitivity of the adrenal feedback mechanism than noncarriers, resulting in a better metabolic health profile.

The Glucocorticoid Receptor: Coding a Diversity of Proteins and Responses through a Single Gene

Abstract: The ability of natural and synthetic glucocorticoids to elicit numerous and diverse physiological responses is remarkable. How the product of a single gene can participate in such a myriad of cell- and tissue-specific pathways has remained largely unknown. The last several years have seen increased description of glucocorticoid receptor (GR) protein isoforms. Here we review the current state of knowledge regarding naturally occurring GR isoforms and discuss how this array of receptor species generates the diversity associated with the glucocorticoid response. We propose that the multiplicity of receptor forms have unique tissue- specific actions on the downstream biology providing a mechanism to create GR signaling networks.

Prolonged methylprednisolone treatment suppresses systemic inflammation in patients with unresolving acute respiratory distress syndrome: evidence for inadequate endogenous glucocorticoid secretion and inflammation-induced immune cell resistance to glucocorticoids.

Abstract: Nuclear factor-kappaB (NF-kappaB) and glucocorticoid receptor-alpha (GR-alpha) have diametrically opposed functions in regulating inflammation. We investigated whether unresolving acute respiratory distress syndrome (ARDS) is associated with systemic inflammation- induced glucocorticoid resistance and whether prolonged methylprednisolone administration accelerates the suppression of systemic inflammatory indices and normalizes the sensitivity of the immune system to glucocorticoids. Patients enrolled into a randomized trial evaluating prolonged methylprednisolone administration in unresolving ARDS had serial plasma samples collected before and after randomization. In the plasma, we measured the concentrations of tumor necrosis factor-alpha (TNF-alpha), interleukins (IL) IL-1beta and IL-6, adrenocorticotropic hormone (ACTH), and cortisol. The ability of patient plasma to influence the NF-kappaB and GR-signal transduction systems of normal peripheral blood leukocytes (PBL) was examined. Patients treated with methylprednisolone had progressive and sustained reductions of TNF-alpha, IL-1beta, IL-6, ACTH, and cortisol concentrations over time. Normal PBL exposed to plasma samples collected during methylprednisolone exhibited significant progressive increases in all aspects of GR-mediated activity and significant reductions in NF-kappaB DNA-binding and transcription of TNF-alpha and IL-1beta. These findings provide support for the presence of endogenous glucocorticoid inadequacy in the control of inflammation and systemic inflammation-induced peripheral glucocorticoid resistance in ARDS. Prolonged methylprednisolone administration accelerated the resolution of both systemic inflammation and peripheral acquired glucocorticoid resistance in ARDS.

Functional PPAR-gamma receptor is a novel therapeutic target for ACTH-secreting pituitary adenomas.

Abstract: Adrenocorticotrophic hormone (ACTH)-secreting pituitary tumors are associated with high morbidity due to excess glucocorticoid production. No suitable drug therapies are currently available, and surgical excision is not invariably curative. Here we demonstrate immunoreactive expression of the nuclear hormone receptor peroxisome proliferator-activated receptor-gamma (PPAR-gamma) exclusively in normal ACTH-secreting human anterior pituitary cells: PPAR-gamma was abundantly expressed in all of six human ACTH-secreting pituitary tumors studied. PPAR-gamma activators induced G0/G1 cell-cycle arrest and apoptosis and suppressed ACTH secretion in human and murine corticotroph tumor cells. Development of murine corticotroph tumors, generated by subcutaneous injection of ACTH-secreting AtT20 cells, was prevented in four of five mice treated with the thiazolidinedione compound rosiglitazone, and ACTH and corticosterone secretion was suppressed in all treated mice. Based on these findings, thiazolidinediones may be an effective therapy for Cushing disease

Cyclooxygenase-2 induction in cerebral cortex: an intracellular response to synaptic excitation.

Abstract: We have characterised the induction of the mitogen-inducible form of cyclooxygenase, COX-2, in the rat cerebral cortex in response to excitotoxin injection into the nucleus basalis. This model is associated with intense stimulation of the ascending pathway to the cerebral cortex, seizure activity, and subsequent ipsilateral cortical induction of various immediate early genes (IEGs), including c-fos, c-jun, and zif268, and ornithine decarboxylase enzyme activity and mRNA, all of which processes are sensitive to treatment with the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801. In this study we show that excitotoxin injection also causes a marked induction of COX-2 mRNA in ipsilateral cortex detectable at 1 h and peaking at 4 h, where COX-2 mRNA levels were 19 times those in unoperated animals. Levels of COX-2 mRNA remained significantly elevated at 24 h. The early induction of COX-2 at 1 h was also seen in sham-operated animals, but at 4 h the COX-2 mRNA level was significantly increased (4.4-fold) in animals injected with excitotoxin compared with sham-operated animals. The induction at this time point (4 h) was explored pharmacologically and found to be significantly attenuated by treatment with MK-801 (1.5 mg/kg), lamotrigine (10 mg/kg), which prevents presynaptic glutamate release by blocking voltage-sensitive Na + channels, and the glucocorticoid dexamethasone (3 mg/kg), which has an indirect inhibitory effect on phospholipase A 2 and COX activity. These results demonstrate that the induction of COX-2 mRNA occurs by two distinct mechanisms : the rapid and transient response to tissue damage and a second delayed and more substantial response, which is initiated by excitotoxin stimulation and is mediated by presynaptic glutamate release, NMDA receptor activation, and subsequent phospholipase A 2 activity. We propose a model to demonstrate the similarities between COX-2 and IEG mRNA induction and highlight possible mechanistic differences in the nature of the induction by the phospholipase A 2 pathway.

Osteoblastic 11β‐Hydroxysteroid Dehydrogenase Type 1 Activity Increases With Age and Glucocorticoid Exposure

Abstract: The risk of glucocorticoid-induced osteoporosis increases substantially with age but there is considerable individual variation. In recent studies we have shown that the effects of glucocorticoids on bone are dependent on autocrine actions of the enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1); expression of 11beta-HSD1 in osteoblasts (OBs) facilitates local synthesis of active glucocorticoids with consequent effects on osteoblastic proliferation and differentiation. Using primary cultures of human OBs, we have now characterized the age-specific variation in osteoblastic 11beta-HSD1 and defined enzyme kinetics and regulation using natural and therapeutic glucocorticoids. 11beta-HSD1 reductase activity (cortisone to cortisol conversion) was recognized in all OB cultures and correlated positively with age (r = 0.58 with all cultures, p < 0.01, and n = 18; r = 0.87 with calcaneal-derived cultures, p < 0.001, and n = 14). Glucocorticoid treatment caused a time- and dose-dependent increase in 11beta-HSD1 activity over control (e.g., dexamethasone [DEX; 1 microM], 2.6-fold +/- 0.5 (mean +/- SE), p < 0.001, and n = 16; cortisol (100 nM), 1.7-fold +/- 0.1, p < 0.05, and n = 14). Similar increases in 11beta-HSD1 mRNA expression were indicated using real-time quantitative reverse-transcription polymerase chain reaction (RT-PCR) analyses (3.5-fold with DEX, p < 0.01; 2.5-fold with cortisol, p < 0.05). The capacity of 11beta-HSD1 to metabolize the synthetic glucocorticoids prednisone and prednisolone was investigated in human OBs (hOBs) and fetal kidney-293 cells stably transfected with human 11beta-HSD1 cDNA. Transfected cells and hOBs were able to interconvert prednisone and prednisolone with reaction kinetics indistinguishable from those for cortisone and cortisol. To assess the in vivo availability of substrates for osteoblastic 11beta-HSD1, plasma cortisone and prednisone levels were measured in normal males before and after oral prednisolone (5 mg). The 9:00 a.m. serum cortisone levels were 110 +/- 5 nmol/liter and prednisone levels peaked at 78 +/- 23 nmol/liter 120 minutes after administration of prednisolone. Thus, therapeutic use of steroids increases substrate availability for 11beta-HSD1 in bone. These studies indicate that activation of glucocorticoids at an autocrine level within bone is likely to play an important role in the age-related decrease in bone formation and increased risk of glucocorticoid-induced osteoporosis.

Abnormal cortisol metabolism and tissue sensitivity to cortisol in patients with glucose intolerance

Abstract: Recent evidence suggests that increased cortisol secretion, altered cortisol metabolism, and/or increased tissue sensitivity to cortisol may link insulin resistance, hypertension, and obesity. Whether these changes are important in type 2 diabetes mellitus (DM) is unknown. We performed an integrated assessment of glucocorticoid secretion, metabolism, and action in 25 unmedicated lean male patients with hyperglycemia (20 with type 2 diabetes and 5 with impaired glucose intolerance by World Health Organization criteria) and 25 healthy men, carefully matched for body mass index, age, and blood pressure. Data are mean +/- SE. Patients with hyperglycemia (DM) had higher HbA(1c) (6.9 +/- 0.2% vs. 6.0 +/- 0.1%, P < 0.0001) and triglycerides. Cortisol secretion was not different, as judged by 0900 h plasma cortisol and 24 h total urinary cortisol metabolites. However, the proportion of cortisol excreted as 5alpha- and 5beta-reduced metabolites was increased in DM patients. Following an oral dose of cortisone 25 mg, generation of plasma cortisol by hepatic 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD 1) was impaired in DM patients (area under the curve, 3617 +/- 281 nM.2 h vs. 4475 +/- 228; P < 0.005). In contrast, in sc gluteal fat biopsies from 17 subjects (5 DM and 12 controls) in vitro 11beta-HSD 1 activity was not different (area under the curve, 128 +/- 56% conversion.30 h DM vs. 119 +/- 21, P = 0.86). Sensitivity to glucocorticoids was increased in DM patients both centrally (0900 h plasma cortisol after overnight 250 micro g oral dexamethasone 172 +/- 16 nM vs. 238 +/- 20 nM, P < 0.01) and peripherally (more intense forearm dermal blanching following overnight topical beclomethasone; 0.56 +/- 0.92 ratio to vehicle vs. 0.82 +/- 0.69, P < 0.05). In summary, in patients with glucose intolerance, cortisol secretion, although normal, is inappropriately high given enhanced central and peripheral sensitivity to glucocorticoids. Normal 11beta-HSD 1 activity in adipose tissue with impaired hepatic conversion of cortisone to cortisol suggests that tissue-specific changes in 11beta-HSD 1 activity in hyperglycemia differ from those in primary obesity but may still be susceptible to pharmacological inhibition of the enzyme to reduce intracellular cortisol concentrations. Thus, altered cortisol action occurs not only in obesity and hypertension but also in glucose intolerance, and could therefore contribute to the link between these multiple cardiovascular risk factors.

Increased Glucocorticoid Receptor Expression in Human Skeletal Muscle Cells May Contribute to the Pathogenesis of the Metabolic Syndrome

Abstract: Altered glucocorticoid hormone action may contribute to the etiology of the metabolic syndrome, but the molecular mechanisms are poorly defined. Tissue sensitivity to glucocorticoid is regulated by expression of the glucocorticoid receptor (GR)-alpha and 11beta-hydroxysteroid dehydrogenase type I (11beta-HSD1)-mediated intracellular synthesis of active cortisol from inactive cortisone. We have analyzed GRalpha and 11beta-HSD1 expression in skeletal myoblasts from men (n = 14) with contrasting levels of insulin sensitivity (euglycemic clamp measurements of insulin-dependent glucose disposal rate), blood pressure, and adiposity. Positive associations were evident between myoblast expression of GRalpha under basal conditions and levels of insulin resistance (r(2) = 0.34, P < 0.05), BMI (r(2) = 0.49, P < 0.01), percent body fat (r(2) = 0.34, P < 0.02), and blood pressure (r(2) = 0.86, P < 0.001). Similar associations were evident when myoblasts were incubated with physiological levels of cortisol (P < 0.01 for all). Importantly, GRalpha expression was unaffected by variations in in vivo concentrations of insulin, IGF-1, or glucose concentrations. In common with the GR, 11beta-HSD1 expression in myoblasts incubated with physiological concentrations of cortisol in vitro was positively associated with levels of insulin resistance (r(2) = 0.68, P < 0.001), BMI (r(2) = 0.63, P < 0.005), and blood pressure (r(2) = 0.27, P < 0.05). Regulation of GRalpha and 11beta-HSD1 by cortisol was abolished by the GR antagonist RU38486. In summary, our data suggest that raised skeletal muscle cell expression of GRalpha and 11beta -HSD1-mediated regulation of intracellular cortisol may play a fundamental role in mechanisms contributing to the pathogenesis of the metabolic syndrome.

Electroconvulsive seizures increase hippocampal neurogenesis after chronic corticosterone treatment

Abstract: Major depression is often associated with elevated glucocorticoid levels. High levels of glucocorticoids reduce neurogenesis in the adult rat hippocampus. Electroconvulsive seizures (ECS) can enhance neurogenesis, and we investigated the effects of ECS in rats where glucocorticoid levels were elevated in order to mimic conditions seen in depression. Rats given injections of corticosterone or vehicle for 21 days were at the end of this period treated with either a single or five daily ECSs. Proliferating cells were labelled with bromodeoxyuridine (BrdU). After 3 weeks, BrdU-positive cells in the dentate gyrus were quantified and analyzed for co-labelling with the neuronal marker neuron-specific nuclear protein (NeuN). In corticosterone-treated rats, neurogenesis was decreased by 75%. This was counteracted by a single ECS. Multiple ECS further increased neurogenesis and no significant differences in BrdU/NeuN positive cells were detected between corticosterone- and vehicle-treated rats given five ECS. Approximately 80% of the cells within the granule cell layer and 10% of the hilar cells were double-labelled with BrdU and NeuN. We therefore conclude that electroconvulsive seizures can increase hippocampal neurogenesis even in the presence of elevated levels of glucocorticoids. This further supports the hypothesis that induction of neurogenesis is an important event in the action of antidepressant treatment.

Clinical review 151: The role of parathyroid hormone in the pathogenesis of glucocorticoid-induced osteoporosis: a re-examination of the evidence

Abstract: One of the most important of the secondary causes of osteoporosis is chronic exposure to glucocorticoids, which are used for an extraordinarily large number of disorders. The adverse effects of hypercortisolism on bone metabolism were recognized more than half a century ago (1). Today, glucocorticoid exposure in the context of medicinal use has become far more common than excess endogenous exposure (Cushing’s syndrome). Glucocorticoid-induced osteoporosis (GIO) is the third most common cause of osteoporosis, trailing only postmenopausal and age-related osteoporosis (2). As many as 50% of individuals on chronic glucocorticoid therapy will suffer an osteoporotic fracture (3). Recently, a large-scale retrospective cohort study by Van Staa et al. (4) in England clearly demonstrated that fracture risk is increased across virtually the entire dosage range of oral glucocorticoids. A large number of subjects with a history of glucocorticoid exposure (n 244,235) were matched to the same number of control patients who had no history of glucocorticoid exposure. The average age of the subjects was 57 yr; respiratory diseases were the common indication for therapy, being prescribed in 40% of the patients (4). Referent to nonglucocorticoid users, subjects with a history of glucocorticoid therapy had significantly greater risk for fractures at the spine (rr 2.6), the hip (rr 1.6), and at any nonvertebral site (rr 1.3). The magnitude of the fracture risk was directly related to dosage, with subjects receiving as little as 2.5 mg of prednisolone at significantly greater risk than control subjects (4). Bone loss from glucocorticoid use was also found to occur rapidly, within the first 3 months of treatment. A similarly precipitous loss of bone mass has also been observed prospectively when glucocorticoids are used in the setting of organ transplantation (5, 6), and in other clinical situations (7–10). Even inhaled steroids have been implicated as a cause of bone loss (11, 12). The cardinal feature of GIO on skeletal dynamics is a reduction in bone formation. Bone formation is inhibited, in part, through a decrease in osteoblast life span and function. Histomorphometric studies demonstrate a marked reduction in indices of bone formation, such as reduced mineral apposition rate and prolonged mineralization lag time. The amount of bone that is replaced in each remodeling cycle can be reduced by as much as 30% (13–17). Biochemical markers of bone formation, osteocalcin and bone-specific alkaline phosphatase, are suppressed. In addition to this primary suppressive effect on bone formation, glucocorticoids also induce an early phase of accelerated bone resorption (18). Osteoclast number and activity increase, along with an increase in the fraction of eroded bone surface (14, 15). Biochemical markers of bone resorption, urinary N-telopeptide and pyridinoline cross-link excretion, rise during early glucocorticoid exposure (17, 19, 20). This early phase of glucocorticoid use, therefore, can be associated with rapid bone loss due to both reduced bone formation and accelerated bone resorption. With continued use of glucocorticoids, the rapid rate of osteoclast-mediated bone resorption slows (14), but suppression of bone formation continues as the dominant skeletal dynamic. Thus, bone loss is progressive because bone resorption chronically exceeds bone formation. Although bone loss due to glucocorticoid use tends to be diffuse, the axial skeleton is targeted preferentially. The cancellous bones of the vertebral spine are typically affected, whereas cortical bone sites of the appendicular skeleton (i.e. forearm) are affected to a lesser extent (21, 22). Spontaneous fractures of the vertebrae or ribs are common complications of GIO (23).

Glucocorticoid Induces Apoptosis in Rat Leydig Cells

Abstract: The aim of the present study was to investigate whether glucocorticoid induces apoptosis in rat Leydig cells. To determine whether there are developmental differences in glucocorticoid sensitivity, Leydig cells were isolated at distinct stages of their differentiation [mesenchymal-like progenitors (PLC), immature Leydig cells (ILC), and adult Leydig cells (ALC)] from 21-, 35-, and 90-d-old Sprague Dawley rats, respectively. Glucocorticoid induction of apoptosis was evaluated after both in vitro and in vivo exposures. In the first set of experiments, PLC, ILC, and ALC were treated with 100 nM corticosterone (CORT) for either 4 or 24 h in vitro and then assessed for labeling with the apoptotic marker annexin V. PLC exposed to CORT had levels of annexin V-fluorescein isothiocyanate labeling that were unchanged relative to control values at both time points (P > 0.05). In contrast, CORT-treated ILC and ALC had increased frequencies of apoptosis: in ALC, a 22.1 +/- 1.7% incidence after 4 h and 30.5 +/- 2.3% after 24 h compared with 7.4 +/- 0.8% in untreated controls (P < 0.05). Similar trends were observed for ILC. Ultrastructural analysis confirmed that the increase in annexin V labeling was associated with characteristic signs of apoptosis, including nuclear fragmentation and formation of apoptotic bodies. A second line of experiments examined whether apoptosis was evident in purified Leydig cells after administration of CORT in vivo. Male rats were subjected to bilateral adrenalectomy and were treated with CORT by ip injection twice daily at doses ranging from 2.5-7.5 mg/100 g BW starting 3 d after surgery. The frequency of Leydig cell apoptosis was measured at 12, 24, 48, and 72 h after the first injection. Administration of the 2.5-mg dose raised circulating CORT 5-10 times above normal basal concentrations, and LH levels sampled at these times were not altered in the treated animals. Increased Leydig cell apoptosis was measurable after 24 h of treatment, with an incidence of 21.1 +/- 1.8% in ALC compared with 5.7 +/- 0.8% in untreated controls (P < 0.05). Sharp reductions in immunocytochemical staining intensity were observed in the treated animals for a Leydig cell marker, 11beta-hydroxysteroid dehydrogenase, which occurred concurrently with decreased serum T levels. This was consistent with the hypothesis that CORT-mediated induction of apoptosis leads to declines in Leydig cell numbers, thereby affecting T production. These results suggest that excessive exposure to CORT initiates apoptosis in rat Leydig cells, potentially contributing to suppression of circulating T levels during stress and other conditions in which glucocorticoid concentrations are elevated.

Short day lengths augment stress-induced leukocyte trafficking and stress-induced enhancement of skin immune function.

Abstract: Environmental conditions influence the onset and severity of infection and disease. Stressful conditions during winter may weaken immune function and further compromise survival by means of hypothermia, starvation, or shock. To test the hypothesis that animals may use photoperiod to anticipate the onset of seasonal stressors and adjust immune function, we evaluated glucocorticoids and the distribution of blood leukocytes in Siberian hamsters (Phodopus sungorus) exposed to long day lengths (i.e., summer) or short day (SD) lengths (i.e., winter) at baseline and during acute stress. We also investigated the influence of photoperiod and acute stress on a delayed-type hypersensitivity response in the skin. SDs increased glucocorticoid concentrations and the absolute number of circulating blood leukocytes, lymphocytes, T cells, and natural killer cells at baseline in hamsters. During stressful challenges, it appears beneficial for immune cells to exit the blood and move to primary immune defense areas such as the skin, in preparation for potential injury or infection. Acute (2 h) restraint stress induced trafficking of lymphocytes and monocytes out of the blood. This trafficking occurred more rapidly in SDs compared to long days. Baseline delayed-type hypersensitivity responses were enhanced during SDs; this effect was augmented by acute stress and likely reflected more rapid redistribution of leukocytes out of the blood and into the skin. These results suggest that photoperiod may provide a useful cue by which stressors in the environment may be anticipated to adjust the repertoire of available immune cells and increase survival likelihood.

Positive effects of glucocorticoids on T cell function by up-regulation of IL-7 receptor alpha.

Abstract: Despite the effects of glucocorticoids on immune function, relatively little is known about glucocorticoid-inducible genes and how their products may regulate lymphocyte function. Using DNA microarray technology to analyze gene expression in PBMC from healthy donors, we identified IL-7Ralpha as a glucocorticoid-inducible gene. This observation was confirmed at the mRNA and protein levels. Conversely, TCR signaling decreased IL-7Ralpha expression, and the relative strength of signaling between these two receptors determined the final IL-7Ralpha levels. The up-regulation of IL-7Ralpha by glucocorticoids was associated with enhanced IL-7-mediated signaling and function. Moreover, IL-7-mediated inhibition of apoptosis at increasing concentrations of glucocorticoids is consistent with enhanced cell sensitivity to IL-7 following glucocorticoid exposure. These observations provide a mechanism by which glucocorticoids may have a positive influence on T cell survival and function.

Prenatal programming of postnatal endocrine responses by glucocorticoids

Abstract: Epidemiological studies have led to the hypothesis that a major component of the risk of diseases such as hypertension, coronary heart disease and non-insulin-dependent diabetes (the 'metabolic syndrome') is established before birth. Although the underlying mechanisms of this 'programming' of disease have not yet been conclusively determined, a reduced fetal nutrient supply as a consequence of poor placental function or unbalanced maternal nutrition is strongly implicated. It has been proposed that one outcome of suboptimal nutrition is exposure of the fetus to excess glucocorticoids, which restrict fetal growth and programme permanent alterations in its cardiovascular, endocrine and metabolic systems. This review focuses on the effects of endogenous and exogenous glucocorticoid exposure in utero on postnatal hypothalamo-pituitary-adrenal (HPA) axis activity, both in humans and experimental animals. The physiological consequences and proposed underlying molecular and cellular mechanisms are discussed. Current data indicate that key targets for programming may include not only the HPA axis but also glucocorticoid receptor gene and 11beta-hydroxysteroid dehydrogenase type 2 (11betaHSD2) gene expression in a range of tissues.

The effect of prenatal betamethasone administration on postnatal ovine hypothalamic-pituitary-adrenal function.

Abstract: Prenatal exposure to glucocorticoids is associated with alterations in fetal growth and endocrine function. However, few studies have examined the effects of clinically relevant doses of glucocorticoids on postnatal hypothalamic–pituitary–adrenal (HPA) function. To determine the effects of maternal or fetal betamethasone administration (0·5 mg/kg maternal or estimated fetal weight) on postnatal HPA function at 6 months and 1 year postnatal age, pregnant ewes were randomized into the following treatment groups: no treatment (n=6); maternal saline (n=6); single maternal betamethasone (M1) (n=6); repeated maternal betamethasone (M4) (n=6); fetal saline (n=5); single fetal betamethasone (n=6) and repeated fetal betamethasone (F4) (n=6). Single injections were given at 104 days of gestation and repeated injections at 104, 111, 118 and 125 days. Lambs were born spontaneously and the ACTH and cortisol responses to i.v. corticotropinreleasing hormone (CRH) (0·5 µg/kg) plus arginine vasopressin (AVP) (0·1 µg/kg) were measured at 6 months and 1 year postnatally. At 6 months postnatal age, neither maternal nor fetal prenatal betamethasone administration altered significantly the ACTH and cortisol responses to CRH+AVP. However, in animals at 1 year postnatal age, a previous single injection of betamethasone to the mother (M1) resulted in significantly elevated basal and stimulated cortisol levels (P<0·05), without significant change in the ACTH response. In contrast, betamethasone administration to the fetus resulted in significantly attenuated ACTH responses to CRH+AVP at 1 year compared with control animals (P<0·05), but these were not associated with any significant changes in basal or stimulated cortisol levels. All control animals exhibited a significant increase in peak ACTH responses to CRH+AVP between 6 months and 1 year postnatal age (P<0·05). After prenatal betamethasone (F4, M4) the difference in peak ACTH response between animals at 6 months and 1 year postnatal age was abolished. We conclude that in sheep between 6 months and 1 year postnatal age, HPA function undergoes developmental changes that are influenced by prenatal glucocorticoid exposure. Furthermore, the effects of glucocorticoid on postnatal HPA responses may vary according to the time in gestation that the steroid was administered, and whether it was given directly into the

Different glucocorticoids vary in their genomic and non-genomic mechanism of action in A549 cells.

Abstract: We have examined the effects of 12 glucocorticoids as inhibitors of A549 cell growth. Other than cortisone and prednisone, all the glucocorticoids inhibited cell growth and this was strongly correlated (r=0.91) with inhibition of prostaglandin (PG)E(2) formation. The molecular mechanism by which the active steroids prevented PGE(2) synthesis was examined and three groups were identified. Group A drugs did not inhibit arachidonic acid release but inhibited the induction of COX2. Group B drugs were not able to inhibit the induction of COX2 but inhibited arachidonic acid release through suppression of cPLA(2) activation. Group C drugs were apparently able to bring about both effects. The inhibitory actions of all steroids was dependent upon glucocorticoid receptor occupation since RU486 reversed their effects. However, group A acted through the NF-kappaB pathway to inhibit COX2 as the response was blocked by the inhibitor geldanamycin which prevents dissociation of GR and the effect was blocked by APDC, the NF-kappaB inhibitor. On the other hand, the group B drugs were not inhibited by NF-kappaB inhibitors or geldanamycin but their effect was abolished by the src inhibitor PP2. Group C drugs depended on both pathways. In terms of PGE(2) generation, there is clear evidence of two entirely separate mechanisms of glucocorticoid action, one of which correlates with NF-kappaB mediated genomic actions whilst the other, depends upon rapid effects on a cell signalling system which does not require dissociation of GR. The implications for these findings are discussed.