Cytokine regulation of MCP-1 expression in brain and retinal microvascular endothelial cells

Chemokines have a pivotal role in the selective mediation and amplification of inflammation. The CNS vascular endothelial cells, which form part of the blood-brain barrier (BBB) and blood-retinal barrier (BRB), are ideally situated to present chemokines to circulating lymphocytes leading to their recruitment. Monocyte-chemoattractant protein-1 (MCP-1), also known as CCL2, a potent chemoattractant of T cells and monocytes, has been implicated in inflammatory and angio-proliferative brain and retinal disease. In this study, MCP-1 expression by CNS endothelial cells was investigated in vitro. Rat brain (GP8/3.9) and retinal (JG2/1) vascular endothelial cell lines expressed MCP-1 constitutively in vitro as assessed by immunocytochemistry and enzyme linked immunosorbant assay (ELISA). Upregulation of secreted MCP-1 was observed following activation with the pro-inflammatory cytokines TNF-alpha, IL-1 beta and IFN-gamma, and was reduced following dexamethasone treatment. Functional chemotactic activity of brain and retinal endothelial cell supernatants was demonstrated in an in vitro chemotaxis assay, which was inhibited by anti-MCP-1 antibodies. These findings suggest that endothelial cell-derived MCP-1 plays a key role in leukocyte recruitment across the blood-brain and blood-retinal barriers in vivo.