1. ¹Department of Neurosurgery, University of Michigan Medical School, Ann Arbor, Michigan, USA
2. ²Department of Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
3. ³Department of Pathology, University of Michigan Medical School, Ann Arbor, Michigan, USA

Correspondence: Dr AV Andjelkovic, Departments of Neurosurgery and Pathology, University of Michigan Medical School, R5550 Kresge I, Ann Arbor, MI 48109-0532, USA. E-mail: anuskaa@umich.edu

Received 27 May 2005; Revised 27 July 2005; Accepted 18 August 2005; Published online 28 September 2005.

Abstract

The chemokine CCL2 is considered as one of the main effectors driving postischemic infiltration of monocytes into the brain parenchyma. New experimental data, however, suggest that CCL2 could also participate in blood–brain barrier (BBB) 'opening' during the transmigration of monocytes. The current study examines the role of CCL2 in regulating BBB permeability after ischemia in vitro. To address this issue, an in vitro BBB model (coculture of astrocytes and brain endothelial cells) was subjected to 5 h of oxygen glucose deprivation, followed by reoxgenation (in vitro ischemia/reperfusion (I/R)) for 0 to 48 h. During reperfusion, there was a biphasic enhancement of barrier permeability, with a 200-fold increase in barrier permeability to FITC-albumin at 6 h and a further period of disruption around 24 h. The latter coincided with increased secretion of CCL2 by both astrocytes and brain endothelial cells and increased levels of the CCL2 receptor, CCR2. Applying antisense oligonucleotide or neutralizing antibody to block CCL2 significantly decreased I/R-induced enhancement of BBB permeability (approximately twofold) and redistribution of tight-junction (TJ) proteins (occludin, zonula occluden-1, 2, claudin-5). Similarly, absence of CCR2 from endothelial cells caused stabilization of TJ complexes and decreased the permeability of brain endothelial barrier during in vitro I/R. These data suggest CCL2/CCR2 has an important role in regulating brain endothelial permeability and might be a potential novel therapeutic target for stroke.