Differential regulation of cyclooxygenase-2 (COX-2) mRNA stability by interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) in human in vitro differentiated macrophages

Cyclooxygenase-2 (COX-2) is a highly inducible gene in macrophages by pro-i nflammatory cytokines. A major mechanism for cytokine-induced COX-2 express ion is stabilization of COX-2 mRNA. In this study, we examined the inductio n of COX-2 expression by interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) in human primary in vitro differentiated macrophag es. IL-1 beta (5 ng/mL) or TNF-alpha (1 ng/mL) induced up to an similar to 40-fold increase of COX-2 mRNA in macrophages during a 2 to 2.5-hr incubati on. Run-off experiments demonstrated that cytokine stimulation had only a m ild effect on the COX-2 transcription rate (similar to 10-40% increase). Th e translation blocker cycloheximide (CHM) (10 mg/mL) superinduced COX-2 mRN A during 2 hr of incubation and further stabilized the COX 2 mRNA (T-1/2 > 4 hr). The CHM-superinduced COX-2 mRNA was subject to a rapid degradation a fter removal of CHM (T-1/2 < 1 hr). Both IL-1 beta and TNF-alpha stabilized cytokine induced COX-2 mRNA (T-1/2 greater than or equal to 2 hr). Maximal stabilization of COX 2 mRNA after a short-term stimulation required the co ntinued presence of IL-1 beta in the medium. Long-term treatment of TNF-alp ha destabilized the induced COX-2 mRNA. Cells simultaneously treated with b oth IL-1 beta and TNF-alpha had a reduced induction of COX-2, IL-1 beta, an d IL-6 mRNA. In transcription-arrested cells, the translation blocker purom ycin affected the TNF-alpha-induced stabilization and destabilization of CO X-2 mRNA, but not the IL-1 beta-induced stabilization. The studies suggest that positive and negative regulation of mRNA stability may play a major ro le in cytokine mediated COX-2 induction in human macrophages. TNF-alpha map play both pro inflammatory and protective roles during inflammation by reg ulation of pro-inflammatory gene transcripts. BIOCHEM PHARMACOL 59;2:187-19 4, 2000. (C) 1999 Elsevier Science Inc.