Glucocorticoid

About: Glucocorticoid is a research topic. Over the lifetime, 14073 publications have been published within this topic receiving 646556 citations. The topic is also known as: glucocorticosteroid & glucocorticoids.

Role of Transcriptional Activation of IκBα in Mediation of Immunosuppression by Glucocorticoids

Abstract: Glucocorticoids are potent immunosuppressive drugs, but their mechanism is poorly understood. Nuclear factor kappa B (NF-κB), a regulator of immune system and inflammation genes, may be a target for glucocorticoid-mediated immunosuppression. The activation of NF-κB involves the targeted degradation of its cytoplasmic inhibitor, IκBα, and the translocation of NF-κB to the nucleus. Here it is shown that the synthetic glucocorticoid dexamethasone induces the transcription of the IκBα gene, which results in an increased rate of IκBα protein synthesis. Stimulation by tumor necrosis factor causes the release of NF-κB from IκBα. However, in the presence of dexamethasone this newly released NF-κB quickly reassociates with newly synthesized IκBα, thus markedly reducing the amount of NF-κB that translocates to the nucleus. This decrease in nuclear NF-κB is predicted to markedly decrease cytokine secretion and thus effectively block the activation of the immune system.

Novel mechanisms of glucocorticoid resistance in childhood acute lymphoblastic leukemia.

Abstract: 2458 Despite dramatic improvements in treatment over the past 40 years, acute lymphoblastic leukemia (ALL) remains one of the most common causes of death from disease in childhood. Glucocorticoids are among the most effective agents used in the treatment of lymphoid malignancies, and patient response to treatment is an important determinant of long-term outcome in childhood ALL. In spite of its clinical significance, the molecular basis of glucocorticoid resistance is still poorly understood. The aim of this study was to develop an experimental model system to define clinically relevant mechanisms of glucocorticoid resistance in childhood ALL. An in vivo model of childhood ALL has been developed in our laboratory, using patient biopsies established as xenografts in immune-deficient nonobese diabetic severe-combined immunodeficient (NOD/SCID) mice. This model is highly representative of the human disease (Lock et al., Blood, 99: 4100-4108, 2002). The in vivo responses of these xenografts to the glucocorticoid dexamethasone (DEX) correlated significantly with patient outcome (p 1 μM) in xenografts from six patients, five of whom died of their disease. In contrast, four DEX-sensitive xenografts (IC50 values 2-fold in sensitive xenografts within 8 hours of treatment. In contrast, Bim induction was dramatically attenuated in DEX-resistant xenografts. These results have identified a clinically significant and novel mechanism of glucocorticoid resistance in childhood ALL, which occurs downstream of receptor-ligand interactions, but upstream of the signalling pathway resulting in Bim induction and apoptosis.

Cortisol levels during human aging predict hippocampal atrophy and memory deficits.

Abstract: Elevated glucocorticoid levels produce hippocampal dysfunction and correlate with individual deficits in spatial learning in aged rats. Previously we related persistent cortisol increases to memory impairments in elderly humans studied over five years. Here we demonstrate that aged humans with significant prolonged cortisol elevations showed reduced hippocampal volume and deficits in hippocampus-dependent memory tasks compared to normal-cortisol controls. Moreover, the degree of hippocampal atrophy correlated strongly with both the degree of cortisol elevation over time and current basal cortisol levels. Therefore, basal cortisol elevation may cause hippocampal damage and impair hippocampus-dependent learning and memory in humans.

Anti-inflammatory actions of glucocorticoids : molecular mechanisms

Abstract: 1. Glucocorticoids are widely used for the suppression of inflammation in chronic inflammatory diseases such as asthma, rheumatoid arthritis, inflammatory bowel disease and autoimmune diseases, all of which are associated with increased expression of inflammatory genes. The molecular mechanisms involved in this anti-inflammatory action of glucocorticoids is discussed, particularly in asthma, which accounts for the highest clinical use of these agents. 2. Glucocorticoids bind to glucocorticoid receptors in the cytoplasm which then dimerize and translocate to the nucleus, where they bind to glucocorticoid response elements (GRE) on glucocorticoid-responsive genes, resulting in increased transcription. Glucocorticoids may increase the transcription of genes coding for anti-inflammatory proteins, including lipocortin-1, interleukin-10, interleukin-1 receptor antagonist and neutral endopeptidase, but this is unlikely to account for all of the widespread anti-inflammatory actions of glucocorticoids. 3. The most striking effect of glucocorticoids is to inhibit the expression of multiple inflammatory genes (cytokines, enzymes, receptors and adhesion molecules). This cannot be due to a direct interaction between glucocorticoid receptors and GRE, as these binding sites are absent from the promoter regions of most inflammatory genes. It is more likely to be due to a direct inhibitory interaction between activated glucocorticoid receptors and activated transcription factors, such as nuclear factor-kappa B and activator protein-1, which regulate the inflammatory gene expression. 4. It is increasingly recognized that glucocorticoids change the chromatin structure. Glucocorticoid receptors also interact with CREB-binding protein (CBP), which acts as a co-activator of transcription, binding several other transcription factors that compete for binding sites on this molecule. Increased transcription is associated with uncoiling of DNA wound around histone and this is secondary to acetylation of the histone residues by the enzymic action of CBP. Glucocorticoids may lead to deacetylation of histone, resulting in tighter coiling of DNA and reduced access of transcription factors to their binding sites, thereby suppressing gene expression. 5. Rarely patients with chronic inflammatory diseases fail to respond to glucocorticoids, although endocrine function of steroids is preserved. This may be due to excessive formation of activator protein-1 at the inflammatory site, which consumes activated glucocorticoid receptors so that they are not available for suppressing inflammatory genes. 6. This new understanding of glucocorticoid mechanisms may lead to the development of novel steroids with less risk of side effects (which are due to the endocrine and metabolic actions of steroids). 'Dissociated' steroids which are more active in transrepression (interaction with transcription factors) than transactivation (GRE binding) have now been developed. Some of the transcription factors that are inhibited by glucocorticoid, such as nuclear factor-kappa B, are also targets for novel anti-inflammatory therapies.