text: Tumour necrosis factor-alpha-dependent regulation of prostaglandin endoperoxide synthase-2.
  Tumour necrosis factor alpha (TNF-alpha)-mediated regulation of prostaglandin endoperoxide synthase-2 (PGHS-2) mRNA levels was examined in murine fibrosarcoma MCA-101 cells. We demonstrated that the formation of prostaglandin E2 (PGE2) is highly dependent on the expression of PGHS-2 enzyme in these cells. TNF-alpha-induced PGE2 production was evident after 12 h and was associated with a significant TNF-alpha-mediated increase in PGHS-2 immunoreactive protein. A specific PGHS-2 inhibitor, NS-398, completely abolished the TNF-alpha-mediated increase in PGE2 production, suggesting that the PGE2 formed in response to TNF-alpha was derived from PGHS-2. TNF-alpha-mediated PGHS-2 mRNA accumulation was observed at 1 h, remained elevated for 24 h, and was blocked by actinomycin D, indicating that TNF-alpha increases PGHS-2 gene transcription. A significant post-transcriptional mechanism also contributed to the increased PGHS-2 mRNA accumulation as the mRNA half-life was approximately 4-5 h in TNF-alpha-stimulated cells. Inhibition of protein tyrosine phosphatases (PTPs) and protein tyrosine kinases (PTKs) inhibited the TNF-alpha-mediated increase in PGHS-2 mRNA levels. We suggest that PTPs and PTKs play a role in the transcriptional and/or post-transcriptional mechanisms that contribute to the regulation of the PGHS-2 gene by TNF-alpha.