TRANSIENT EXPRESSION OF PROSTAGLANDIN ENDOPEROXIDE SYNTHASE-2 DURING MOUSE MACROPHAGE ACTIVATION

We investigated regulation of macrophage prostaglandin production duri ng activation by interferon gamma (IFN-gamma) and lipopolysaccharide ( LPS). An in vitro model was established using the mouse macrophage-lik e cell line RAW 264.7. Cells were cultivated in the presence of IFN-ga mma and LPS for up to 48 h and changes in the secretion of nitric oxid e (NO.) and tumor necrosis factor alpha (TNF-alpha) were observed as a ctivation markers. Under these conditions a prompt and strong increase in PGE(2) production was found in the first 8 h followed by nearly co nstant generation of PGE(2) during the next 40 h. In contrast, the act ivity of prostaglandin endoperoxide synthase (PGHS), measured as PGE(2 ) production of microsomal protein fractions, was also increased, but reached a clear maximum at 24 h. Recently a second form of PGHS was cl oned (PGHS-2) and specific antibodies and mRNA probes for both isoform s are available. PGHS-2 enzyme was expressed maximally after 24- h of activation whereas PGHS-1. was not influenced. In the presence of IFN- gamma and LPS, PGHS-2 mRNA expression reached a maximum at 8 h but PGH S-1 mRNA was not induced during the whole time period. These data indi cate that changes in PG synthesis following macrophage activation are due to regulation of PGHS-2 expression.