title: Rapid nontranscriptional activation of endothelial nitric oxide synthase mediates increased cerebral blood flow and stroke protection by corticosteroids.
abstract: Many cellular responses to corticosteroids involve the transcriptional modulation of target genes by the glucocorticoid receptor (GR). A rapid, non-nuclear effect of GR was found to mediate neuroprotection. High-dose corticosteroids (20 mg/kg intraperitoneally), given within 2 hours of transient cerebral ischemia, acutely increased endothelial nitric oxide synthase (eNOS) activity, augmented regional cerebral blood flow (CBF) by 40% to 50%, and reduced cerebral infarct size by 32%. These neuroprotective effects of corticosteroids were abolished by the GR antagonist RU486 and by inhibition of phosphatidylinositol 3-kinase (PI3K), and were absent in eNOS(-/-) mice. To determine the mechanism by which GR activated eNOS, we measured the effect of corticosteroids on PI3K and the protein kinase Akt. In a ligand-dependent manner, GR activated PI3K and Akt in vitro and in vivo caused NO-dependent vasodilation, which was blocked by cotreatment with RU486 or the PI3K inhibitor LY294002 but not by transcriptional inhibitors. Indeed, a mutant GR, which cannot dimerize and bind to DNA, still activated PI3K and Akt in response to corticosteroids. These findings indicate that non-nuclear GR rapidly activates eNOS through the PI3K/Akt pathway and suggest that this mechanism mediates the acute neuroprotective effects of corticosteroids through augmentation of CBF.
authors.affiliation: Cardiovascular Division, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Florian P
authors.initials: FP
authors.lastname: Limbourg
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Huang
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Plumier
authors.forename: Tommaso
authors.initials: T
authors.lastname: Simoncini
authors.forename: Masayuki
authors.initials: M
authors.lastname: Fujioka
authors.forename: Jan
authors.initials: J
authors.lastname: Tuckermann
authors.forename: Günther
authors.initials: G
authors.lastname: Schütz
authors.forename: Michael A
authors.initials: MA
authors.lastname: Moskowitz
authors.forename: James K
authors.initials: JK
authors.lastname: Liao
mesh_terms: D000305:Adrenal Cortex Hormones / Q000627:therapeutic use*; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002417:Cattle; D002478:Cells, Cultured; D002544:Cerebral Infarction / Q000517:prevention & control*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D002522:Chlorocebus aethiops; D017931:DNA Primers; D004730:Endothelium, Vascular / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic; D017930:Genes, Reporter; D006801:Humans; D002546:Ischemic Attack, Transient / Q000201:enzymology / Q000503:physiopathology; D051379:Mice; D008815:Mice, Inbred Strains; D018696:Neuroprotective Agents; D019001:Nitric Oxide Synthase / Q000235:genetics*; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011965:Receptors, Glucocorticoid / Q000502:physiology; D011994:Recombinant Proteins / Q000378:metabolism; D020521:Stroke / Q000517:prevention & control*; D014162:Transfection
chemical_list: D000305:Adrenal Cortex Hormones; D017931:DNA Primers; D018696:Neuroprotective Agents; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D019869:Phosphatidylinositol 3-Kinases; D011965:Receptors, Glucocorticoid; D011994:Recombinant Proteins; C496314:NOS3 protein, human; C496315:Nos3 protein, mouse