title: Loss of shear stress induces leukocyte-mediated cytokine release and blood-brain barrier failure in dynamic in vitro blood-brain barrier model.
abstract: Brain ischemia is associated with an acute release of pro-inflammatory cytokines, notably TNF-alpha and IL-6 and failure of the blood-brain barrier. Shear stress, hypoxia-hypoglycemia, and blood leukocytes play a significant role in blood-brain barrier failure during transient or permanent ischemia. However, these mechanisms have not been studied as independent variables for in vitro ischemia. The present study, using a dynamic in vitro blood-brain barrier model, showed that flow cessation/reperfusion under normoxia-normoglycemia or hypoxia-hypoglycemia without blood leukocytes in the luminal perfusate had a modest, transient effect on cytokine release and blood-brain barrier permeability. By contrast, exposure to normoxic-normoglycemic flow cessation/reperfusion with blood leukocytes in the luminal perfusate led to a significant increase in TNF-alpha and IL-6, accompanied by biphasic blood-brain barrier opening. Enhanced permeability was partially prevented with an anti-TNF-alpha antibody. In leukocyte-free cartridges, the same levels of IL-6 had no effect, while TNF-alpha caused a moderate increase in blood-brain barrier permeability, suggesting that blood leukocytes are the prerequisite for cytokine release and blood-brain barrier failure during reduction or cessation of flow. These cells induce release of TNF-alpha early after ischemia/reperfusion; TNF-alpha triggers release of IL-6, since blockade of TNF-alpha prevents IL-6 release, whereas blockade of IL-6 induces TNF-alpha release. Pre-treatment of blood leukocytes with the cyclooxygenase (COX) inhibitor, ibuprofen, inhibited cytokine release and completely preserved blood-brain barrier permeability during the reperfusion period. In conclusion, loss of flow (flow cessation/reperfusion) independent of hypoxia-hypoglycemia plays a significant role in blood-brain barrier failure by stimulating leukocyte-mediated inflammatory mechanisms.
authors.affiliation: Department of Neurological Surgery, Cerebrovascular Research Center, Cleveland, Ohio 44195, USA. bengezl@ccf.org
authors.forename: Ljiljana
authors.initials: L
authors.lastname: Krizanac-Bengez
authors.forename: Marc R
authors.initials: MR
authors.lastname: Mayberg
authors.forename: Edwin
authors.initials: E
authors.lastname: Cunningham
authors.forename: Mohammed
authors.initials: M
authors.lastname: Hossain
authors.forename: Stephen
authors.initials: S
authors.lastname: Ponnampalam
authors.forename: Fiona E
authors.initials: FE
authors.lastname: Parkinson
authors.forename: Damir
authors.initials: D
authors.lastname: Janigro
mesh_terms: D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D001786:Blood Glucose / Q000378:metabolism; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000502:physiology*; D002545:Brain Ischemia / Q000378:metabolism; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology; D007052:Ibuprofen / Q000494:pharmacology; D015850:Interleukin-6 / Q000378:metabolism*; D007962:Leukocytes / Q000166:cytology / Q000378:metabolism*; D008297:Male; D008954:Models, Biological; D010539:Permeability; D051381:Rats; D017207:Rats, Sprague-Dawley; D015424:Reperfusion; D033081:Shear Strength; D013314:Stress, Mechanical; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D001786:Blood Glucose; D015850:Interleukin-6; D014409:Tumor Necrosis Factor-alpha; D007052:Ibuprofen