Mechanism of glucocorticoid-induced oxidative stress in rat hippocampal slice cultures.
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.
You
Jung-Man
JM
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.
Yun
Su-Jin
SJ
Nam
Kyong Nyon
KN
Kang
Chulhun
C
Won
Ran
R
Lee
Eunjoo H
EH
D000818:Animals; D000831:Animals, Newborn; D000975:Antioxidants / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D003907:Dexamethasone / Q000009:adverse effects / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005470:Fluorometry; D005938:Glucocorticoids / Q000009:adverse effects / Q000494:pharmacology*; D006624:Hippocampus / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D018613:Microscopy, Confocal; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D020258:Neurotoxicity Syndromes / Q000209:etiology / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects* / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000975:Antioxidants; D005938:Glucocorticoids; D017382:Reactive Oxygen Species; D003907:Dexamethasone