Estradiol reduces activity of the blood-brain barrier Na-K-Cl cotransporter and decreases edema formation in permanent middle cerebral artery occlusion

Martha E O'Donnell, Tina I. Lam, Lien Q. Tran, Shahin Foroutan, Steven E. Anderson

Research output: Contribution to journalArticle

80 Scopus citations

Abstract

Estrogen has been shown to protect against stroke-induced brain damage, yet the mechanism is unknown. During the early hours of stroke, cerebral edema forms as increased transport of Na and Cl from blood into brain occurs across an intact blood-brain barrier (BBB). We showed previously that a luminal BBB Na-K-Cl cotransporter is stimulated by hypoxia and arginine vasopressin (AVP), factors present during cerebral ischemia, and that inhibition of the cotransporter by intravenous bumetanide greatly reduces edema in rats subjected to permanent middle cerebral artery occlusion (MCAO). The present study was conducted to determine whether estrogen protects in stroke at least in part by reducing activity of the BBB cotransporter, thereby decreasing edema formation. Ovariectomized rats were subjected to 210 mins of permanent MCAO after 7-day or 30-min pretreatment with 17Β-estradiol and then brain swelling and 2,3,5-triphenyltetrazolium chloride staining were assessed as measures of brain edema and lesion volume, respectively. Diffusion-weighed imaging was used to monitor permanent MCAO-induced decreases in apparent diffusion coefficient (ADC) values, an index of changes in brain water distribution and mobility. Na-K-Cl cotransporter activity of cerebral microvascular endothelial cells (CMECs) was assessed as bumetanide-sensitive K influx and cotransporter abundance by Western blot analysis after estradiol treatment. Estradiol significantly decreased brain swelling and lesion volume and attenuated the decrease in ADC values during permanent MCAO. Estradiol also abolished CMEC cotransporter stimulation by chemical hypoxia or AVP and decreased cotransporter abundance. These findings support the hypothesis that estrogen attenuates stimulation of BBB Na-K-Cl cotransporter activity, reducing edema formation during stroke.

Original languageEnglish (US)
Pages (from-to)1234-1249
Number of pages16
JournalJournal of Cerebral Blood Flow and Metabolism
Volume26
Issue number10
DOIs
StatePublished - Oct 18 2006

Keywords

  • Blood-brain barrier
  • Brain edema
  • Cerebral ischemia
  • Cotransport
  • Estrogen
  • Stroke

ASJC Scopus subject areas

  • Endocrinology
  • Neuroscience(all)
  • Endocrinology, Diabetes and Metabolism

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