Interleukin-1β elevates cyclooxygenase-2 protein level and enzyme activity via increasing its mRNA stability in human endometrial stromal cells: An effect mediated by extracellularly regulated kinases 1 and 2

We investigated the regulation of PG production in human endometrial stromal cells (ESC) by IL-1β. We found that cyclooxygenase-2 (COX-2) mRNA and protein levels and PGE₂ production in ESC were significantly increased by IL-1β. COX-2 mRNA, protein, and PGE2 levels in IL-1β-treated ESC were decreased by a PKA inhibitor, a nuclear factor (NF-κB) inhibitor, and an ERK1/2 inhibitor, but not by a p38 MAPK inhibitor or a PKC inhibitor, suggesting the possible involvement of PKA, NF-κB, and/or the ERK1/2 signaling pathway(s) in IL-1β-mediated COX-2 gene induction in ESC. We then transiently transfected deletion mutants of the COX-2 promoter fused to the luciferase reporter gene and variants of -360/+56 bp promoter construct carrying different site-directed mutations of selected cis-acting elements. We determined that a NF-κB site (-222/-213 bp), a nuclear factor for IL-6 expression site (NF-IL6, -132/-124 bp), and a cAMP response element (-59/-52 bp) were essential for the baseline COX-2 gene promoter regulation. The addition of IL-1β, however, did not affect the activity of these COX-2 promoter constructs. To investigate the potential effects of IL-1β on COX-2 mRNA stability, ESC were treated with actinomycin D, a general transcription inhibitor, in the absence or presence of IL-1β. We found that 1) IL-1β significantly increased COX-2 mRNA stability; 2) continuous transcription was not required to sustain the IL-1β-induced COX-2 mRNA levels; and 3) COX-2 mRNA was highly unstable in the absence of IL-1β. Additionally, we found that the ERK1/2 signaling pathway was essential for stabilizing COX-2 mRNA. We conclude that levels of COX-2 mRNA, protein, and enzyme activity in ESC are controlled by various signaling pathways, including PKA, ERK1/2, and NF-κB. Moreover, posttranscriptional mRNA stability is an important mechanism for IL-1β-induced elevation of COX-2 expression in ESC.