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KMID : 1204320080240020263
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Laboratory Animal Research
2008 Volume.24 No. 2 p.263 ~ p.266
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17β-Estradiol Regulates Nitric Oxide Synthase Expression in Ischemic Brain Injury
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Koh Phil-Ok
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Abstract
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Estradiol prevents neuronal cell death in ischemic brain injury. It is known that nitric oxide is produced by three nitric oxide synthases (NOS), endothelial NOS (eNOS), neuronal NOS (nNOS), and inducible NOS (iNOS). eNOS produces NO with neuroprotective effects, whereas iNOS produces NO with cytotoxic effects. This study investigated the levels of NOS isoforms induced by estradiol in ischemic brain injury. Adult female rats were ovariectomized and treated with estradiol prior to middle cerebral artery occlusion (MCAO). Brain tissues were collected at 24 hr after MCAO. We have previously reported that estradiol significantly reduces infarct size and decreases the number of TUNEL positive cells in the cerebral cortex. Western blot analysis was used to evaluate the levels of eNOS, iNOS, and nNOS. The level of iNOS increased in oil-treated animals and estradiol prevented the injury-induced increase of iNOS. In contrast to iNOS levels, eNOS decreased in oil-treated animals and estradiol prevented the injury-induced decrease of eNOS. However, nNOS levels were consistently maintained in both oil- and estradiol-treated animals. In addition, estradiol prevents the injury-induced an increase of cleaved PARP levels. This study provides further evidence that estradiol exerts a neuroprotective effect and the up- and down-regulation of NOS isoforms by estradiol may contribute to the neuroprotective effects.
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KEYWORD
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Estradiol, neuroprotection, NOS
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