Differential expression of fibronectin, tenascin-C and NCAMs in cultured hippocampal astrocytes activated by kainate, bacterial lipopolysaccharide or basic fibroblast growth factor

Different reports demonstrated that reactive glial cells express increased amounts of adhesion and matrix molecules. Despite a wealth of information on the expression of these molecules during development and after lesion, very little is known of how this expression is regulated. In the present report we used Western blots and immunocytochemistry to investigate the expression of neural cell adhesion molecule (NCAM), fibronectin and tenascin-C in cultured astrocytes from rat hippocampus. The effects of three different extracellular signals were analyzed: the glutamatergic receptor agonist kainic acid, the basic fibroblast growth factor (bFGF) and the bacterial lipopolysaccharide. Each treatment had a specific pattern of glial activation and differentially modified the expression of these proteins. Treatment of astrocytes with kainic acid resulted in an increase of tenascin-C, a decrease of fibronectin and a shift of NCAMs isoforms: NCAM 140 and PSA-NCAM (polysialic acid-rich NCAMs) were increased while NCAM 120 was decreased. bFGF increased fibronectin, tenascin-C and NCAM 120 while decreasing PSA-NCAM. Finally, the treatment of astrocytes with lipopolysaccharide induced a significant increase of fibronectin, tenascin-C and NCAM 120 but did not modify the expression of NCAM 140 and PSA-NCAM. These data suggest different mechanisms for modulation of cell surface interactions. They suggest that glial activation by bFGF and lipopolysaccharide are associated with an increase of the adhesive properties, while kainate action is rather associated with a decrease of the adhesiveness of astrocytes. (C) 1997 Elsevier Science B.V.