Inhibition of IL-1β-dependent prostaglandin E2 release by antisense microsomal prostaglandin E synthase 1 oligonucleotides in A549 cells

The metabolism of arachidonic acid through the cyclooxygenase pathway is a highly regulated cellular process that results in the formation of PGH2. This unstable intermediate can be enzymatically metabolized to PGE2 by the actions of a microsomal 17 kDa PGE synthase (mPGES1). Treatment of A549 cells with IL-1β for 24 h resulted in a twofold increase in mPGES1 mRNA, protein expression, and PGES specific activity. To understand the relationship between expression of mPGES1 and PGE2 formation, IL-1β treated cells were incubated with increasing concentrations of antisense oligonucleotides (ASO) and their effects compared to cells treated with reverse sense oligonucleotides (RSO) designed against the ATG translation initiation codon of mPGES1. Incubation with ASO resulted in a 44% reduction in mRNA expression level as compared to RSO-treated cells. Microsomal preparations isolated from ASO- and RSO-treated cells were analyzed for their ability to convert PGH2 to PGE2 in the presence 2.5 mM reduced glutathione. An approximate 50% reduction (ASO: 1.8 nmol/min/mg, RSO: 3.7 nmol/min/mg) in PGES activity, protein expression by immunodetection, and extracellular PGE2 release was detected in these samples. As a control in these studies, the protein levels of COX2 and secreted IL-8 were quantified; no change in these levels was observed. These results demonstrate the direct association between mPGES1 expression, its enzymatic activity, and total PGE2 production following an inflammatory stimulus.