Purines, including ATP and adenosine (ADO), are important neurotransmitters in the CNS. Purine release and metabolism are contributed by astrocytes and microglia. Previously, we showed that fibroblast growth factor 2 (FGF2) modulates purine metabolisms in cultured astrocytes. However, the modulation of purine metabolisms in microglia is unclear. In this study, we investigated the expressions and activities of purine metabolic enzymes in cultured astrocytes and microglia and the effects of FGF2 on them.
Cultured astrocytes and microglia from rat cortex were treated with FGF2. The expressions of enzymes were measured by real-time PCR. Enzymatic activities were measured by incubation with solution containing ATP, AMP or ADO and measurement of metabolites with HPLC.
The expressions of NTPDase1, CD73 and ADA were higher in microglia than astrocytes, while that of NTPDase2 was higher in astrocytes. The activities of NTPDases, CD73 and ADA were also higher in microglia. FGF2 increased CD73 and ADA, and decreased NTPDase2 in astrocytes, whereas did not affect any enzymes in microglia. In addition, FGF2 phosphorylated ERK and JNK, and dephosphorylated STAT3 in astrocytes, while phosphorylated only ERK in microglia.
These results indicate that microglia have higher purine metabolisms compared to astrocytes, although FGF2 modulates it only in astrocytes. These differences may be attributed to the difference in intracellular signaling pathways.