EFFECTS OF PROTEIN-KINASE-C ACTIVATION ON PROSTAGLANDIN PRODUCTION AND CYCLOOXYGENASE MESSENGER-RNA LEVELS IN OVINE ASTROGLIA

We examined effects of protein kinase C (PKC) activation by phorbol di butyrate (PDB) on prostaglandin production in astroglia. Astroglia wer e cultured from sheep fetal cortex and grown in Eagle's basal media su pplemented with 10% fetal calf serum (BME-C). prostaglandin F-2 alpha (PGF(2 alpha)) levels in media were determined at 2-24 hours after exp osure to PDB. PDB increased production of PGF(2 alpha) at 10(-8)M and 10(-6)M. In addition, PDB increased the ratio of membrane to cytosolic PKC. Coapplication of H7 [1-(5-isoquinolinylsulfonyl)-2-methyl-pipera zine] (10(-4)M) with PDB (10(-6)M) inhibited PDB-induced PGF(2 alpha) production. To investigate the role of protein synthesis in increased prostaglandin production by PDB, astroglia were coincubated with actin omycin D (1 mg/ml) or cycloheximide (10 mg/ml). At 4 hrs, both actinom ycin D and cycloheximide inhibited increases in PGF(2 alpha) in respon se to PDB application. In addition, COX-2 mRNA levels and COX activity levels were examined. PDB increased COX-2 mRNA levels by 2 hours, and COX activity tripled after 12 hr exposure to PDB. In addition, the in crease in COX activity was blocked by cycloheximide. In summary, PKC a ctivation promotes enhanced prostaglandin production via an increase i n COX synthesis.