3>Functional expression of CXCR3 in cultured mouse and human astrocytes and microglia<

It has been established recently that inflammation of the central nervous system (CNS) is accompanied by an expression of chemokines within the CNS. Several lines of evidence suggest that chemokines within the CNS initiate and orchestrate the infiltration of the inflamed brain by blood leukocytes. In line with this assump-tion is the finding that glial cells expressing the chemokine ligands CXCL10 and CXCL9 accompany the presence of CXCR3 positive T-cells in the CNS in demyeli-nating diseases. It is also known that endogenous cells of the CNS express functional chemokine receptors, raising the possibility that chemokines may be involved in intercellular signaling between brain cells during brain inflammation. Since it was shown recent-ly that CXCL10, but also CCL21 expression is induced rapidly in damaged neurons it seemed of interest to investigate whether CXCR3 is expressed in brain cells. Astrocytes and microglia from neonatal mouse brain and adult human brain were grown in culture and investigated for CXCR3 expression by the means of various techniques. RT-PCR experiments and in situ hybridization analysis revealed that astrocytes and microglia from both mouse and human sources express CXCR3 mRNA. Protein expression of CXCR3 in all cell types was detected by immunocy-tochemistry. Moreover, stimulation of cultured glial cells with chemokine ligands for CXCR3 induced intracellular calcium transients and chemotaxis, indicating the functional expression of CXCR3. These results indicate that glial cells in culture functionally express the chemokine receptor CXCR3. Since damaged neurons rapidly induce the expression of chemokines that activate CXCR3 it is suggested that glial expression of CXCR3 might contribute to an intercellular signaling system in the CNS related to patho-logical conditions