title: Dual effects of nimesulide, a COX-2 inhibitor, in human platelets.
abstract: Nimesulide (CAS 51803-78-2) has been shown to exert marked anti-inflammatory effect in several in vivo models of inflammation. Since nimesulide is considered to be a selective inhibitor of COX-2, it has not been studied in detail in relation to its mechanistic effects on platelets, which express COX-1. This study was conducted to investigate the effects of nimesulide in platelet aggregation. We show that nimesulide (1-100 microM) inhibited platelet aggregation induced by adrenaline (20-200 microM). It also inhibited thromboxane A2 (TXA2) formation by platelets at low concentration (IC50; 1 microM). However, much lower concentrations of nimesulide (0.01-0.1 microM) potentiated the aggregatory response of subthreshold concentrations of adrenaline (0.2-2 microM). Such an effect was blocked by Ca2+-channel blockers, verapamil and diltiazem (IC50: 7 and 46 microM, respectively), nitric oxide donor, SNAP (IC50; 2 microM) and cinchonine (10 nM) but not by genistein (up to 10 microM). These results are indicative of the concentration-dependent dual effects of nimesulide on human platelet aggregation. The synergistic effect of low doses of nimesulide and adrenaline seems to be mediated through inhibition of multiple signalling pathways.
authors.affiliation: Department of Physiology and Pharmacology, The Aga Khan University Medical College, Karachi, Pakistan. arshad.saeed@aku.edu
authors.forename: S A
authors.initials: SA
authors.lastname: Saeed
authors.forename: M N
authors.initials: MN
authors.lastname: Afzal
authors.forename: B H
authors.initials: BH
authors.lastname: Shah
mesh_terms: D001792:Blood Platelets / Q000187:drug effects* / Q000502:physiology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology*; D004110:Diltiazem / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004837:Epinephrine / Q000494:pharmacology; D006801:Humans; D020030:Nitric Oxide Donors / Q000494:pharmacology; D010396:Penicillamine / Q000031:analogs & derivatives / Q000494:pharmacology; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D013449:Sulfonamides / Q000494:pharmacology*; D013928:Thromboxane A2 / Q000037:antagonists & inhibitors; D014700:Verapamil / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D016861:Cyclooxygenase Inhibitors; D020030:Nitric Oxide Donors; D010975:Platelet Aggregation Inhibitors; C110881:S-nitro-N-acetylpenicillamine; D013449:Sulfonamides; D013928:Thromboxane A2; D014700:Verapamil; D004110:Diltiazem; D010396:Penicillamine; C012655:nimesulide; D004837:Epinephrine