Department of Pediatrics, National Jewish Health, Denver, CO 80206, USA.
Am J Respir Crit Care Med. 2010 Oct 1;182(7):877-83. doi: 10.1164/rccm.201001-0015OC. Epub 2010 Jun 10.
Cross-talk between glucocorticoid receptors and histone deacetylases (HDACs) under steroid-insensitive conditions has not been explored.
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.
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.
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.
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).
在类固醇不敏感的情况下，糖皮质激素受体和组蛋白去乙酰化酶（HDACs）之间的串扰尚未得到探索。
评估糖皮质激素受体同工型在支气管肺泡灌洗液和外周血单个核细胞中与 HDACs 的表达和相互作用，这些细胞来自类固醇耐药与类固醇敏感的哮喘患者。
通过实时聚合酶链反应测量原发性细胞和设计过度表达糖皮质激素受体β的 DO11.10 细胞系中 HDACs1 到 11 的表达。用小干扰 RNA 抑制支气管肺泡灌洗细胞中的糖皮质激素受体β表达。克隆人 HDAC2 启动子片段到荧光素酶报告载体中，并将编码糖皮质激素受体α和β的质粒瞬时转染到细胞中。然后检测糖皮质激素对荧光素酶活性的影响。
来自类固醇耐药哮喘患者的支气管肺泡灌洗液细胞中，但不是外周血单个核细胞中，HDAC2mRNA 的水平显著降低，但不是其他组蛋白去乙酰化酶。糖皮质激素受体β在 DO11.10 细胞中的过度表达选择性地降低了 HDAC2mRNA 和蛋白水平。哮喘患者支气管肺泡灌洗液细胞中糖皮质激素受体β 的沉默显著增加了 HDAC2mRNA。用 HDAC2 启动子报告构建体进行荧光素酶活性测定，在 HDAC2 启动子中鉴定出两个糖皮质激素诱导区域。在用地塞米松处理的细胞中转染糖皮质激素受体α后，启动子活性增加了四倍以上。糖皮质激素受体β以剂量依赖性方式完全消除了这种效应。
糖皮质激素受体β通过抑制其启动子中的糖皮质激素反应元件来控制组蛋白去乙酰化酶 2 的表达。这突出了糖皮质激素受体β促进类固醇不敏感的一种新机制（Li 等人：J Allergy Clin Immunol 2009；123：S146；和 Li 等人：J Allergy Clin Immunol 2010；125：AB104）。
