title: Glucocorticoid insensitivity at the hypoxic blood-brain barrier can be reversed by inhibition of the proteasome.
abstract: OBJECTIVE
  Glucocorticoids potently stabilize the blood-brain barrier and ameliorate tissue edema in certain neoplastic and inflammatory disorders of the central nervous system, but they are largely ineffective in patients with acute ischemic stroke. The reasons for this discrepancy are unresolved.
  
  
  METHODS
  To address the molecular basis for the paradox unresponsiveness of the blood-brain barrier during hypoxia, we used murine brain microvascular endothelial cells exposed to O(2)/glucose deprivation as an in vitro model. In an in vivo approach, mice were subjected to transient middle cerebral artery occlusion to induce brain infarctions. Blood-brain barrier damage and edema formation were chosen as surrogate markers of glucocorticoid sensitivity in the presence or absence of proteasome inhibitors.
  
  
  RESULTS
  O(2)/glucose deprivation reduced the expression of tight junction proteins and transendothelial resistance in murine brain microvascular endothelial cells in vitro. Dexamethasone treatment failed to reverse these effects during hypoxia. Proteasome-dependent degradation of the glucocorticoid receptor impaired glucocorticoid receptor transactivation thereby preventing physiological glucocorticoid activity. Inhibition of the proteasome, however, fully restored the blood-brain barrier stabilizing properties of glucocorticoid during O(2)/glucose deprivation. Importantly, mice treated with the proteasome inhibitor Bortezomib in combination with steroids several hours after stroke developed significantly less brain edema and functional deficits, whereas respective monotherapies were ineffective.
  
  
  CONCLUSIONS
  We for the first time show that inhibition of the proteasome can overcome glucocorticoid resistance at the hypoxic blood-brain barrier. Hence, combined treatment strategies may help to combat stroke-induced brain edema formation in the future and prevent secondary clinical deterioration.
authors.affiliation: University of Würzburg, Department of Neurology, Josef-Schneider-Strasse 11, D-97080 Würzburg, Germany. chistoph.kleinschnitz@mail.uni-wuerzburg.de
authors.forename: Christoph
authors.initials: C
authors.lastname: Kleinschnitz
authors.forename: Kinga
authors.initials: K
authors.lastname: Blecharz
authors.forename: Timo
authors.initials: T
authors.lastname: Kahles
authors.forename: Tobias
authors.initials: T
authors.lastname: Schwarz
authors.forename: Peter
authors.initials: P
authors.lastname: Kraft
authors.forename: Kerstin
authors.initials: K
authors.lastname: Göbel
authors.forename: Sven G
authors.initials: SG
authors.lastname: Meuth
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Burek
authors.forename: Thomas
authors.initials: T
authors.lastname: Thum
authors.forename: Guido
authors.initials: G
authors.lastname: Stoll
authors.forename: Carola
authors.initials: C
authors.lastname: Förster
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier / Q000187:drug effects* / Q000201:enzymology* / Q000473:pathology; D015687:Cell Hypoxia / Q000187:drug effects / Q000502:physiology; D002461:Cell Line, Transformed; D004195:Disease Models, Animal; D018432:Drug Resistance, Multiple / Q000502:physiology; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D005938:Glucocorticoids / Q000494:pharmacology* / Q000627:therapeutic use; D020925:Hypoxia-Ischemia, Brain / Q000150:complications / Q000188:drug therapy* / Q000201:enzymology*; D051379:Mice; D009924:Organ Culture Techniques; D011480:Protease Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D046988:Proteasome Endopeptidase Complex / Q000502:physiology; D061988:Proteasome Inhibitors; D020521:Stroke / Q000188:drug therapy / Q000201:enzymology; D016896:Treatment Outcome
chemical_list: D005938:Glucocorticoids; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D046988:Proteasome Endopeptidase Complex