Nonsteroidal anti-inflammatory drugs in-vitro and in-vivo treatment and Multidrug Resistance Protein 4 expression in human platelets

Platelet Multidrug Resistance Protein 4 (MRP4)-overexpression has a role in reducing aspirin action in patients after by-pass surgery. Aspirin induces platelet MRP4 over-expression, through megakaryocytes genomic modulation. Aim of our work was to verify whether other non-steroidal antiinflammatory drugs (NSAIDs) enhance platelet MRP4 expression and evaluate platelet function in patients who overexpressed MRP4. We evaluatedMRP4-mRNA in a human megakacaryoblastic cell line (DAMI), treated with both COX-2 inhibitor (celecoxib) and traditional NSAIDs (diclofenac and naproxen). Osteoarthritis patients, who reported to take NSAIDs twice aweek for at least four continuousweeks and a control population,who didn't take any drugs during the previous month, were enrolled.We evaluated platelet MRP4 amount, by both mRNA levels and protein expression (Western-Blot) and ADP induced platelet aggregation. DAMI cells treated with celecoxib, diclofenac, and naproxen showed a significant increase in MRP4-mRNA expression compared to the mock culture. Osteoarthritis patient platelets presented a higher expression ofMRP4 (both atmRNA and protein levels) and an increase in ADP-induced platelet aggregation compared to the control population. NSAIDtreatment induced plateletMRP4 overexpression. Osteoarthritis patients,who overexpressMRP4, showed platelet hyper-reactivity. These evidences could explain in part the increased cardiovascular risk present during NSAID treatment.