Mutual regulation between serine and nitric oxide metabolism in human glioblastoma cells.

D-Serine indirectly caused dose- and time-dependent inhibition of neuronal nitric oxide synthase (nNOS) without affecting endothelial nitric oxide synthase (eNOS) in human glioblastoma cell line U87. Activity Of D-amino acid oxidase (DAAO), catalyzing the oxidative deamination of 14 D-amino acid, was enhanced by NO in a dose-dependent manner. Recently, we have reported that serine racemase (SR) is inhibited by NO and activated by D-serine through nitrosylation and denitrosylation, respectively [K. Shoji, S. Mariotto, A.R. Ciampa, H. Suzuki, Regulation of serine racemase activity by D-serine and nitric oxide in human glioblastoma cells, Neurosci. Lett., in press]. Thus, the metabolism of both D-serine and NO in U87 cells is functionally correlated in a complex manner. Suppression of NO production by D-serine in U87 cells contrasts its known action in enhancing nNOS in neurons. (c) 2005 Elsevier Ireland Ltd. All rights reserved.