title: Effects of interleukin-6 on the expression of tight junction proteins in isolated cerebral microvessels from yearling and adult sheep.
abstract: OBJECTIVE
  The blood-brain barrier is a selective diffusion barrier between brain parenchyma and the intravascular compartment. Tight junctions are integral components of the blood-brain barrier. Pro-inflammatory cytokines are important in the pathogenesis of brain injury and could modify the protein constituents of tight junctions. We hypothesized that interleukin-6 (IL-6) downregulates key protein constituents of endothelial tight junctions (e.g. occludin and claudin-5).
  
  
  METHODS
  We examined the effects of IL-6 on tight junction protein expression using an in vitro blood-brain barrier model. We isolated microvessels from yearling and adult ovine cerebral cortex and placed them into culture with IL-6 concentrations of 0 (control, phosphate-buffered saline), 1, 10, and 100 ng/ml for 24 h. Cerebral microvessels were harvested, Western immunoblot performed for occludin and claudin-5, densitometry performed, and results expressed as a ratio to control values.
  
  
  RESULTS
  Western immunoblot analysis showed that treatment with 100 ng/ml of IL-6, but not the lower concentrations, reduced (p < 0.05) occludin expression in microvessels from yearling and adult sheep and claudin-5 in microvessels from adult sheep. However, treatment with 10 ng/ml of IL-6 increased claudin-5 in microvessels from yearling sheep. The percent of lactate dehydrogenase released from the microvessels into the surrounding media was not increased by IL-6 treatment, suggesting that the reductions in tight junction proteins did not result from cell death. Treatment of adult cerebral cortical microvessels with IL-6 preincubated with anti-IL-6 monoclonal antibodies partially attenuated the reduction in claudin-5.
  
  
  CONCLUSIONS
  We conclude that IL-6 modulates tight junction protein expression in cerebral cortical microvessels from yearling and adult sheep.
authors.affiliation: Department of Pediatrics, The Alpert Medical School of Brown University, Women and Infants Hospital of Rhode Island, Providence, RI 02905-2499, USA.
authors.forename: Susan S
authors.initials: SS
authors.lastname: Cohen
authors.forename: May
authors.initials: M
authors.lastname: Min
authors.forename: Erin E
authors.initials: EE
authors.lastname: Cummings
authors.forename: Xiaodi
authors.initials: X
authors.lastname: Chen
authors.forename: Grazyna B
authors.initials: GB
authors.lastname: Sadowska
authors.forename: Surendra
authors.initials: S
authors.lastname: Sharma
authors.forename: Barbara S
authors.initials: BS
authors.lastname: Stonestreet
mesh_terms: D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D000906:Antibodies / Q000494:pharmacology; D002540:Cerebral Cortex / Q000166:cytology*; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects*; D066298:In Vitro Techniques; D015850:Interleukin-6 / Q000276:immunology / Q000494:pharmacology*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D055806:Microvessels / Q000187:drug effects*; D012756:Sheep; D062725:Tight Junction Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000906:Antibodies; D015850:Interleukin-6; D062725:Tight Junction Proteins; D007770:L-Lactate Dehydrogenase