Phosphorylation of vasodilator-stimulated phosphoprotein: a consequence ofnitric oxide and cGMP mediated signal transduction in brain capillary endothelial cells and astrocytes

Then is contradictory information on the relevance of nitric oxide (NO) and cGMP for the function of brain capillary endothelial cells (BCEC) forming the blood-brain barrier (BBB). Therefore, NO/cGMP-mediated signal transduct ion was investigated in cell cultures of BCEC and of astrocytes (AC) induci ng BBB properties in BCEC. Constitutive, Ca2+-activated isoforms of NO synt hase (NOS) were found in BCEC (endothelial NOS: eNOS) and in AC (neuronal N OS: nNOS), leading to increased NO release after incubation with the Ca2+-i onophore A23187. Both cell types expressed inducible NOS (iNOS) after incub ation with cytokines. Soluble guanylate cyclase (sGC) was detected in both cell types. NO-dependent cGMP formation were observed in BCEC and, less pro nounced, in AC. Furthermore, both cell types formed cGMP independently of N O via stimulation of particulate guanylate cyclase (pGC). cGMP-dependent pr otein kinase (PKG) type II, but not type II, was expressed in BCEC and AC. In BCEC, vasodilator-stimulated phosphoprotein (VASP) was detected, an esta blished substrate of PKG and associated with microfilaments and cell-cell c ontacts. Phosphorylation of VASP was intensified by increased intracellular cGMP concentrations. The results indicate that BCEC and, to a smaller degr ee, AC can form NO and cCMP in response to different stimuli. In BCEC, NO/c GMP-dependent phosphorylation of VASP is demonstrated, thus providing a pos sibility of influencing cell-cell contacts. (C) 1999 Elsevier Science B.V. All rights reserved.