Evidence for the presence of N-acetylaspartylglutamate in cultured oligodendrocytes and LPS activated microglia

The levels of N-acetylaspartylglutamate (NAAG) were determined by HPLC in untreated or lipopolysaccharide (LPS) activated pure astrocyte, oligodendrocyte, and microglial cultures derived from developing rat brain. Oligodendrocyte cultures expressed 1.52±0.12 nmol/ μg protein of NAAG, whereas astrocyte cultures (0.04±0.08 nmol/ μg protein) and untreated microglial cultures (0.05±0.09 nmol/ μg protein) contained only trace amounts of the dipeptide. After stimulation of microglial cultures for 24 h with LPS, NAAG levels increased significantly to 0.37±0.12 SD nmol/ μg protein. NAAG levels in astrocyte and oligodendrocyte cultures remained unchanged after LPS treatment. The findings indicate that NAAG is localized to specific glial cell types. Further our results suggest that NAAG biosynthesis is induced in microglia, activated by specific stimuli.