Induction of COX-2 and PGE(2) biosynthesis by LL-1 beta is mediated by PKCand mitogen-activated protein kinases in murine astrocytes

1 Interleukin-1 (IL-1) is an important mediator of immunoinflammatory respo nses in the brain. In the present study, we examined whether prostaglandin E-2 (PGE(2)) production after IL-1 beta stimulation is dependent upon activ ation of protein kinases in astroglial cells. 2 Astrocyte cultures stimulated with IL-1 beta or the phorbol ester, PMA si gnificantly increased PGE(2) secretion. The stimulatory action of IL-1 beta on PGE(2) production was totally abolished by NS-398, a specific inhibitor of cyclo-oxygenase-2 activity, as well as by the protein synthesis inhibit or cycloheximide, and the glucocorticoid dexamethasone. Furthermore, IL-1 b eta induced the expression of COX-2 mRNA. This occurred early at 2 h, with a maximum at 4 h and declined at 12 h. IL-1 beta treatment also induced the expression of COX-2 protein as determined by immunoblot analysis. In that case the expression of the protein remained high at least up to 12 h. 3 Treatment of cells with protein kinase C inhibitors (H-7, bisindolylmalei mide and calphostin C) inhibited IL-1 beta stimulation of PGE(2). In additi on, PKC-depleted astrocyte cultures by overnight treatment with PMA no long er responded to PMA or IL-1. The ablation of the effects of PMA and IL-1 be ta on PGE, production, likely results from down-regulation of phorbol ester sensitive-PKC isoenzymes. Immunoblot analysis demonstrated the translocati on of the conventional isoform cPKC-alpha from cytosol to membrane followin g treatment with IL-1 beta. 4 In addition. IL-1 beta treatment led to activation of extracellular signa l-regulated kinase (ERK1/2) and p38 subgroups of MAP kinases in astroglial cells. Interestingly, the inhibition of ERK kinase with PD 98059, as well a s the inhibition of p38 MAPK with SE 203580, prevented IL-1 beta-induced PG E, release. 5 ERK1/2 activation by IL-1 beta was sensitive to inhibition by the PKC inh ibitor bisindolylmalei rmde suggesting that ERK. phosphorylation is a downs tream signal of PKC activation. 6 These results suggest key roles for PKC a s well as for ERK1/2, and p38 MAP kinase cascades in the biosynthesis of PG E(2), likely by regulating the induction of cyclo-oxygenase-2, in IL-1 beta -stimulated astroglial cells.