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Cyclooxygenase and lipoxygenase metabolite synthesis by polymorphonuclear neutrophils: in vitro effect of dipyrone
Abstract:
Functional activity of polymorphonuclear neutrophils (PMN) is associated with the metabolism of Arachidonic Acid (AA) released from membrane phospholipids. In this study the in vitro effect of dipyrone, a non steroidal anti-inflammatory drug, on the production of AA metabolites through cyclooxygenase (CO) and lipoxygenase (LO) pathways by stimulated PMN has been investigated. PMN isolated by counterflow centrifuge elutriator were greater than 98% pure and viable. Metabolite production was evaluated by RIA of Thromboxane A2 (TxA2), Prostaglandin E2 (PGE2), Leukotriene B2 (LTB4) and Leukotriene C4 (LTC4) after PMN stimulation with calcium ionophore A 23187 (20 microM). The levels of beta-thromboglobulin (RIA) lower than 5 ng/ml allowed us to rule out activation of residual contaminant platelets. In these experimental conditions, in the absence of dipyrone the products (ng/10(6) cells) of AA metabolism were LTB4 (3.51 +/- 0.22), LTC4 (0.81 +/- 0.08), TxB2 (0.144 +/- 0.025) and PGE2 (0.150 +/- 0.017). Incubation with dipyrone induced changes of PGE2 and TXB2 production in a dose dependent fashion (r = 0.83 and r = 0.87, p less than 0.001), obtaining already at the lowest drug concentration (5 micrograms/ml) a significant inhibition (33 and 40% for TxB2 and PGE2 p less than 0.005). No significant changes of LTB4 and LTC4 production have been observed. The results of this study indicate that dipyrone relevantly affects CO metabolite synthesis by stimulated PMN at concentrations comparable to those reached in therapeutic use. The inhibition of PGE2 synthesis which is present in inflamed tissues and actively participates in inflammatory reactions, could contribute to the therapeutic anti-inflammatory action of dipyrone.
Insights
Dipyrone, a non-steroidal anti-inflammatory drug, inhibits cyclooxygenase (CO) pathway metabolites, Thromboxane A2 (TxA2) and Prostaglandin E2 (PGE2), in polymorphonuclear neutrophils (PMN). This suggests a mechanism for dipyrone's anti-inflammatory effects.
Area of Science:
- Immunopharmacology
- Inflammation Research
- Eicosanoid Metabolism
Background:
- Polymorphonuclear neutrophils (PMN) play a crucial role in inflammation.
- PMN activity is linked to Arachidonic Acid (AA) metabolism via cyclooxygenase (CO) and lipoxygenase (LO) pathways.
- Understanding drug effects on these pathways is key to developing anti-inflammatory therapies.
Purpose of the Study:
- To investigate the in vitro effects of dipyrone on AA metabolite production by stimulated human PMN.
- To determine dipyrone's impact on CO and LO pathways in PMN.
- To correlate dipyrone's metabolite modulation with its anti-inflammatory action.
Main Methods:
- Human PMN isolated using counterflow centrifuge elutriator (>98% purity and viability).
- PMN stimulated with calcium ionophore A 23187 (20 microM).
- Quantification of AA metabolites (Thromboxane A2, Prostaglandin E2, Leukotriene B4, Leukotriene C4) using RIA.
Main Results:
- Dipyrone significantly inhibited Prostaglandin E2 (PGE2) and Thromboxane A2 (TxA2) production in a dose-dependent manner.
- Inhibition of PGE2 and TxA2 was observed at low dipyrone concentrations (5 micrograms/ml), with 33-40% reduction (p < 0.005).
- No significant changes in Leukotriene B4 (LTB4) or Leukotriene C4 (LTC4) production were detected.
Conclusions:
- Dipyrone affects CO metabolite synthesis in stimulated PMN at therapeutically relevant concentrations.
- Inhibition of PGE2, a key mediator in inflammation, likely contributes to dipyrone's anti-inflammatory efficacy.
- Dipyrone's selective action on the CO pathway warrants further investigation for its therapeutic applications.