Department of Medical Science, Graduate School of East-West Medical Science, East-West Integrated Medical Science Research Center, Kyung Hee University, Yongin-si 446-701, Korea.
Can J Physiol Pharmacol. 2009 Jun;87(6):440-7. doi: 10.1139/y09-027.
Prolonged stress results in elevation of glucocorticoid (GC) hormones, which can have deleterious effects in the brain. The hippocampus, which has a high concentration of glucocorticoid receptors, is especially vulnerable to increasing levels of GCs. GCs have been suggested to endanger hippocampal neurons by exacerbating the excitotoxic glutamate-calcium-reactive oxygen species (ROS) cascade. In an effort to reveal the mechanisms underlying GC-mediated hippocampal neurotoxicity, we aimed to clarify the molecular pathway of GC-induced ROS increase by using organotypic hippocampal slice cultures. Assays for ROS, using 2',7'-dichlorodihydrofluorescein diacetate fluorescence, showed that treatment of synthetic GC, dexamethasone (DEX) significantly enhanced ROS levels. Time course and dose response analyses indicated that peak amount of ROS was generated at 4 h after treatment with 50 micromol/L DEX. By contrast, other steroid hormones, progesterone and estradiol did not influence ROS production. N-acetyl-L-cysteine completely suppressed ROS produced by DEX. Propidium iodide staining exhibited prominent cell death in the hippocampal layer after 96 h of DEX treatment. RU486, a GC receptor antagonist, almost completely blocked the effect of DEX on ROS production and cell death, indicating that DEX-induced ROS overproduction and hippocampal death are mediated via GC receptors. Real-time reverse transcriptase PCR analysis demonstrated that after DEX treatment the level of glutathione peroxidase mRNA was decreased whereas that of NADPH oxidase mRNA was significantly enhanced. These findings suggest that excess GCs cause hippocampal damage by regulating genes involved in ROS generation.
长期的压力会导致糖皮质激素（GC）水平升高，这会对大脑产生有害影响。海马体中糖皮质激素受体的浓度很高，因此特别容易受到 GC 水平升高的影响。GC 被认为通过加剧兴奋性谷氨酸-钙-活性氧（ROS）级联反应来危害海马神经元。为了揭示 GC 介导的海马神经毒性的机制，我们旨在通过使用器官型海马切片培养物来阐明 GC 诱导的 ROS 增加的分子途径。使用 2'，7'-二氯二氢荧光素二乙酸酯荧光法进行的 ROS 测定表明，合成 GC 地塞米松（DEX）处理显著增强了 ROS 水平。时程和剂量反应分析表明，ROS 的峰值量在 50 μmol/L DEX 处理后 4 小时产生。相比之下，其他类固醇激素孕酮和雌二醇不会影响 ROS 的产生。N-乙酰-L-半胱氨酸完全抑制了 DEX 产生的 ROS。碘化丙啶染色显示，DEX 处理 96 小时后海马层有明显的细胞死亡。GC 受体拮抗剂 RU486 几乎完全阻断了 DEX 对 ROS 产生和细胞死亡的影响，表明 DEX 诱导的 ROS 产生过多和海马死亡是通过 GC 受体介导的。实时逆转录 PCR 分析表明，DEX 处理后谷胱甘肽过氧化物酶 mRNA 的水平降低，而 NADPH 氧化酶 mRNA 的水平显著增强。这些发现表明，过量的 GC 通过调节参与 ROS 生成的基因导致海马损伤。
