Effects of Interleukin-6 on the Expression of Tight Junction Proteins in Isolated Cerebral Microvessels from Yearling and Adult Sheep

Objectives: 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 IL6, but not the lower concentrations, reduced (p < 0.05) Received: December 14, 2012 Accepted after revision: March 4, 2013 Published online: July 18, 2013 Barbara S. Stonestreet, MD The Alpert Medical School of Brown University, Department of Pediatrics Women and Infants Hospital of Rhode Island 101 Dudley Street, Providence, RI 02905-2499 (USA) E-Mail bstonestreet @ wihri.org © 2013 S. Karger AG, Basel 1021–7401/13/0205–0264$38.00/0