Expression of the β-chemokines RANTES and MIP-1β by human brain microvessel endothelial cells in primary culture

The mechanisms that regulate inflammatory cell recruitment across the blood-brain barrier (BBB) during CNS inflammation have not been fully characterized. Likely players in this process include the chemokines, small secondary messengers of inflammation capable of subset-specific leukocyte activation and chemoattraction. Primary cultures of human brain microvessel endothelial cells (HBMEC) were examined for their in vitro expression of the beta chemokines RANTES and MIP-le. Untreated HBMEC expressed low levels of RANTES and MIP-1 beta RNA that were significantly upregulated following cytokine treatment. Parallel studies performed on human umbilical Vein endothelial cells (HUVEC) showed induction of RANTES but not MIP-1 beta RNA. Following stimulation with LPS, TNF-alpha, IFN-gamma, and IL-1 beta alone or in combination, HBMEC released significant amounts of RANTES and MIP-1 beta into the culture supernatants. RANTES secretion by HUVEC could be induced only with TNF-alpha/IFN-gamma. Both RANTES and MIP-1 beta were detected by immunocytochemistry on the apical and basal surfaces of HBMEC, as well as bound to basal lamina-like material under the basal cell surface. Cytokine stimulation induced significant increase of RANTES and MIP-1 beta molecules associated with the EC surface and subendothelial matrix. The expression of RANTES and MIP-1 beta by HBMEC suggests that these chemokines may play an important role in mediating inflammatory responses and leukocyte trafficking across the BBB.