Dataset Information

Inhibition of histone deacetylase 2 expression by elevated glucocorticoid receptor beta in steroid-resistant asthma.

ABSTRACT:

Rationale

Cross-talk between glucocorticoid receptors and histone deacetylases (HDACs) under steroid-insensitive conditions has not been explored.

Objectives

To evaluate expression and interaction of HDACs with glucocorticoid receptor isoforms in bronchoalveolar lavage and peripheral blood mononuclear cells from steroid-resistant versus steroid-sensitive patients with asthma.

Methods

Expression of HDACs 1 through 11 was measured by real-time polymerase chain reaction in primary cells and in the DO11.10 cell line, designed to overexpress glucocorticoid receptor β. Glucocorticoid receptor β expression was inhibited in bronchoalveolar lavage cells by small interfering RNA. Human HDAC2 promoter fragments were cloned into a luciferase reporter vector, and transiently transfected with glucocorticoid receptor α- and β-encoding plasmids into the cells. Luciferase activity was then assayed in response to glucocorticoids.

Measurements and main results

Levels of HDAC2 mRNA, but not other histone deacetylases, were significantly decreased in bronchoalveolar lavage cells but not in peripheral blood mononuclear cells from steroid-resistant patients with asthma. Overexpression of glucocorticoid receptor β in DO11.10 cells selectively reduced HDAC2 mRNA and protein levels. Silencing of glucocorticoid receptor β in bronchoalveolar lavage cells from patients with asthma significantly increased HDAC2 mRNA. Luciferase activity assays with HDAC2 promoter reporter constructs identified two glucocorticoid-inducible regions in the HDAC2 promoter. Promoter activity was increased more than fourfold in dexamethasone-treated cells cotransfected with glucocorticoid receptor α. Cotransfection of glucocorticoid receptor β abolished this effect in a dose-dependent manner.

Conclusions

Glucocorticoid receptor β controls expression of histone deacetylase 2 by inhibiting glucocorticoid response elements in its promoter. This highlights a novel mechanism by which glucocorticoid receptor β promotes steroid insensitivity (Li et al.: J Allergy Clin Immunol 2009;123:S146; and Li et al.: J Allergy Clin Immunol 2010;125:AB104).

SUBMITTER: Li LB

PROVIDER: S-EPMC2970859 | biostudies-literature | 2010 Oct

REPOSITORIES: biostudies-literature

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Publications

Inhibition of histone deacetylase 2 expression by elevated glucocorticoid receptor beta in steroid-resistant asthma.

Li Ling-Bo LB Leung Donald Y M DY Martin Richard J RJ Goleva Elena E

American journal of respiratory and critical care medicine 20100610 7

<h4>Rationale</h4>Cross-talk between glucocorticoid receptors and histone deacetylases (HDACs) under steroid-insensitive conditions has not been explored.<h4>Objectives</h4>To evaluate expression and interaction of HDACs with glucocorticoid receptor isoforms in bronchoalveolar lavage and peripheral blood mononuclear cells from steroid-resistant versus steroid-sensitive patients with asthma.<h4>Methods</h4>Expression of HDACs 1 through 11 was measured by real-time polymerase chain reaction in pri ...[more]

PMID: 20538962

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Project description:BackgroundRegulation or restoration of therapeutic sensitivity to glucocorticoids is important in patients with steroid-resistant asthma. Spleen tyrosine kinase (Syk) is activated at high levels in asthma patients and mouse models, and small-molecule Syk inhibitors such as R406 show potent anti-inflammatory effects in the treatment of immune inflammatory diseases. Several downstream signaling molecules of Syk are involved in the glucocorticoid response, so we hypothesized that R406 could restore sensitivity to dexamethasone in severe steroid-resistant asthma. Objective: To discover the role of the Syk inhibitor R406 in glucocorticoid resistance in severe asthma. Methods: Steroid-resistant asthma models were induced by exposure of C57BL/6 mice to house dust mite (HDM) and β-glucan and by TNF-α administration to the bronchial epithelial cell line BEAS-2B. We evaluated the role of the Syk inhibitor R406 in dexamethasone (Dex)-insensitive airway inflammation. Pathological alterations and cytokines in the lung tissues and inflammatory cells in BALF were assessed. We examined the effects of Dex or R406 alone and in combination on the phosphorylation of MAPKs, glucocorticoid receptor (GR) and Syk, as well as the transactivation and transrepression induced by Dex in mouse lung tissues and BEAS-2B cells. Results: Exposure to HDM and β-glucan induced steroid-resistant airway inflammation. The Syk inhibitor R406 plus Dex significantly reduced airway inflammation compared with Dex alone. Additionally, TNF-α-induced IL-8 production in BEAS-2B cells was not completely inhibited by Dex, while R406 markedly promoted the anti-inflammatory effect of Dex. Compared with Dex alone, R406 enhanced Dex-mediated inhibition of the phosphorylation of MAPKs and GR-Ser226 induced by allergens or TNF-α in vivo and in vitro. Moreover, R406 also restored the impaired expression and nuclear translocation of GRα induced by TNF-α. Then, the activation of NF-κB and decreased HDAC2 activity in the asthmatic model were further regulated by R406, as well as the expression of GILZ. Conclusions: The Syk inhibitor R406 improves sensitivity to dexamethasone by modulating GR. This study provides a reference for the development of drugs to treat severe steroid-resistant asthma.

Project description:BackgroundAcetylation of heat shock protein 90 (Hsp90) regulates downstream hormone signaling via the glucocorticoid receptor (GR), but the role of this molecular mechanism in stress homeostasis is poorly understood. We tested whether acetylation of Hsp90 in the brain predicts and modulates the behavioral sequelae of a mouse model of social stress.MethodsMice subjected to chronic social defeat stress were stratified into resilient and vulnerable subpopulations. Hypothalamic-pituitary-adrenal axis function was probed using a dexamethasone/corticotropin-releasing factor test. Measurements of Hsp90 acetylation, Hsp90-GR interactions, and GR translocation were performed in the dorsal raphe nucleus. To manipulate Hsp90 acetylation, we pharmacologically inhibited histone deacetylase 6, a known deacetylase of Hsp90, or overexpressed a point mutant that mimics the hyperacetylated state of Hsp90 at lysine K294.ResultsLower acetylated Hsp90, higher GR-Hsp90 association, and enhanced GR translocation were observed in dorsal raphe nucleus of vulnerable mice after chronic social defeat stress. Administration of ACY-738, a histone deacetylase 6-selective inhibitor, led to Hsp90 hyperacetylation in brain and in neuronal culture. In cell-based assays, ACY-738 increased the relative association of Hsp90 with FK506 binding protein 51 versus FK506 binding protein 52 and inhibited hormone-induced GR translocation. This effect was replicated by overexpressing the acetylation-mimic point mutant of Hsp90. In vivo, ACY-738 promoted resilience to chronic social defeat stress, and serotonin-selective viral overexpression of the acetylation-mimic mutant of Hsp90 in raphe neurons reproduced the behavioral effect of ACY-738.ConclusionsHyperacetylation of Hsp90 is a predictor and causal molecular determinant of stress resilience in mice. Brain-penetrant histone deacetylase 6 inhibitors increase Hsp90 acetylation and modulate GR chaperone dynamics offering a promising strategy to curtail deleterious socioaffective effects of stress and glucocorticoids.

Dataset Information

Inhibition of histone deacetylase 2 expression by elevated glucocorticoid receptor beta in steroid-resistant asthma.

Rationale

Objectives

Methods

Measurements and main results

Conclusions

Publications

Inhibition of histone deacetylase 2 expression by elevated glucocorticoid receptor beta in steroid-resistant asthma.

Similar Datasets

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