Division of Molecular and Systems Toxicology, Department of Pharmaceutical Sciences, University of Basel, Klingelbergstrasse 50, CH-4056 Basel, Switzerland.
J Neuroinflammation. 2012 Nov 28;9:260. doi: 10.1186/1742-2094-9-260.
Microglia, the resident macrophage-like cells in the brain, regulate innate immune responses in the CNS to protect neurons. However, excessive activation of microglia contributes to neurodegenerative diseases. Corticosteroids are potent modulators of inflammation and mediate their effects by binding to mineralocorticoid receptors (MR) and glucocorticoid receptors (GR). Here, the coordinated activities of GR and MR on the modulation of the nuclear factor-κB (NF-κB) pathway in murine BV-2 microglial cells were studied.
BV-2 cells were treated with different corticosteroids in the presence or absence of MR and GR antagonists. The impact of the glucocorticoid-activating enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) was determined by incubating cells with 11-dehydrocorticosterone, with or without selective inhibitors. Expression of interleukin-6 (IL-6), tumor necrosis factor receptor 2 (TNFR2), and 11β-HSD1 mRNA was analyzed by RT-PCR and IL-6 protein expression by ELISA. NF-κB activation and translocation upon treatment with various corticosteroids were visualized by western blotting, immunofluorescence microscopy, and translocation assays.
GR and MR differentially regulate NF-κB activation and neuroinflammatory parameters in BV-2 cells. By converting inactive 11-dehydrocorticosterone to active corticosterone, 11β-HSD1 essentially modulates the coordinated action of GR and MR. Biphasic effects were observed for 11-dehydrocorticosterone and corticosterone, with an MR-dependent potentiation of IL-6 and tumor necrosis factor-α (TNF-α) expression and NF-κB activation at low/moderate concentrations and a GR-dependent suppression at high concentrations. The respective effects were confirmed using the MR ligand aldosterone and the antagonist spironolactone as well as the GR ligand dexamethasone and the antagonist RU-486. NF-κB activation could be blocked by spironolactone and the inhibitor of NF-κB translocation Cay-10512. Moreover, an increased expression of TNFR2 was observed upon treatment with 11-dehydrocorticosterone and aldosterone, which was reversed by 11β-HSD1 inhibitors and/or spironolactone and Cay-10512.
A tightly coordinated GR and MR activity regulates the NF-κB pathway and the control of inflammatory mediators in microglia cells. The balance of GR and MR activity is locally modulated by the action of 11β-HSD1, which is upregulated by pro-inflammatory mediators and may represent an important feedback mechanism involved in resolution of inflammation.
小胶质细胞是大脑中常驻的巨噬细胞样细胞，可调节中枢神经系统中的固有免疫反应以保护神经元。然而，小胶质细胞的过度激活会导致神经退行性疾病。皮质类固醇是炎症的有效调节剂，通过与盐皮质激素受体 (MR) 和糖皮质激素受体 (GR) 结合来发挥作用。在这里，研究了 MR 和 GR 对鼠 BV-2 小胶质细胞中核因子-κB (NF-κB) 途径的调节的协调作用。
用不同的皮质类固醇处理 BV-2 细胞，同时存在或不存在 MR 和 GR 拮抗剂。通过孵育细胞用 11-去氢皮质酮，以及选择性抑制剂，来确定糖皮质激素激活酶 11β-羟甾脱氢酶 1 (11β-HSD1) 的作用。通过 RT-PCR 和 ELISA 分析白细胞介素-6 (IL-6)、肿瘤坏死因子受体 2 (TNFR2) 和 11β-HSD1 mRNA 的表达。用 Western blot、免疫荧光显微镜和转位测定法观察用各种皮质类固醇处理后 NF-κB 的激活和转位。
GR 和 MR 以不同的方式调节 BV-2 细胞中的 NF-κB 激活和神经炎症参数。通过将无活性的 11-去氢皮质酮转化为活性皮质酮，11β-HSD1 实际上调节了 GR 和 MR 的协调作用。对于 11-去氢皮质酮和皮质酮观察到双相作用，在低/中浓度下，MR 依赖性增强了 IL-6 和肿瘤坏死因子-α (TNF-α) 的表达和 NF-κB 的激活，而在高浓度下，GR 依赖性抑制了它们。使用 MR 配体醛固酮和拮抗剂螺内酯以及 GR 配体地塞米松和拮抗剂 RU-486 证实了各自的作用。NF-κB 的激活可以被螺内酯和 NF-κB 转位抑制剂 Cay-10512 阻断。此外，用 11-去氢皮质酮和醛固酮处理观察到 TNFR2 的表达增加，这可以通过 11β-HSD1 抑制剂和/或螺内酯和 Cay-10512 逆转。
GR 和 MR 的紧密协调活动调节了小胶质细胞中 NF-κB 途径和炎症介质的控制。GR 和 MR 活性的平衡受 11β-HSD1 的作用局部调节，11β-HSD1 受促炎介质上调，可能代表参与炎症消退的重要反馈机制。
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