Non-steroidal anti-inflammatory drugs increase MRP4 expression in an endometriotic epithelial cell line in a PPARa dependent manner

OBJECTIVE: Endometriosis is a debilitating disease characterized by chronic inflammation. The transporter multidrug resistance-associated protein 4 (MRP4/ABCC4) is expressed in human endometrial tissue; it is overexpressed in ectopic endometrial tissue, and is modulated by the anti-inflammatory lipid Lipoxin A4 (LXA4). Recently, it was demonstrated that aspirin induces platelet MRP4 over-expression, through genomic modulation in megakaryocytes. Since patients with endometriosis frequently use aspirin or other non-aspirin Non-Steroidal Anti-Inflammatory Drugs (NSAIDs), the aim of this study was to verify whether aspirin and other NSAIDs enhance MRP4 expression in 12Z human endometriotic epithelial cells and whether this was peroxisome proliferator-activated receptor alpha (PPARa) dependent. MATERIALS AND METHODS: MRP4 and PPARa expression was analyzed by Q-RT-PCR using TaqMan® Master Mix and TaqMan® Assay Reagents (Life Technologies, Monza, Italy) and Western blot. RESULTS: In 12Z cells, aspirin and other NSAIDs enhanced MRP4 mRNA and protein expression; these treatments also induced PPARa expression. Aspirin and diclofenac-induced increases in MRP4 expression were not observed in cells where PPARa was knocked down using siRNA. NSAIDs-induced MRP4 expression was correlated with augmented PGE2 secretion, indicating functional relevance. CONCLUSIONS: MRP4 expression was increased in cells treated with NSAIDs and the nuclear receptor PPARa is involved. Elevated PGE2 levels in cell supernatants correlate with its increased transport by MRP4 after NSAID treatment. More importantly, we provide evidence that in endometriotic epithelial cells aspirin and non-aspirin NSAIDs treatments alter gene expression.