Salicylate metabolites inhibit cyclooxygenase-2-dependent prostaglandin E-2 synthesis in murine macrophages

The poor cyclooxygenase (COX) inhibitor and major aspirin metabolite salicy lic acid is known to exert analgesic and anti-inflammatory effects by still unidentified mechanisms. In RAW 264.7 macrophages, lipopolysaccharide (LPS )-induced COX-2-dependent synthesis of prostaglandin E-2 (PGE(2)) was suppr essed by aspirin (IC50 of 5.35 mu M), whereas no significant inhibition was observed in the presence of sodium salicylate and the salicylate metabolit e salicyluric acid at concentrations up to 100 mu M. However, the salicylat e metabolite gentisic acid (2,5-dihydroxybenzoic acid; 10-100 mu M) and sal icyl-coenzyme A (100 mu M), the intermediate product in the formation of sa licyluric acid from salicylic acid, significantly suppressed LPS-induced PG E(2) production. In contrast, gamma-resorcylic acid (2,6-dihydroxybenzoic a cid) as well as unconjugated coenzyme A failed to affect prostanoid synthes is, implying that the para-substitution of hydroxy groups and the activated coenzyme A thioester are important for COX-2 inhibition. Using realtime RT -PCR, none of the salicylate derivatives tested were found to interfere wit h COX-2 expression. Overall, our results suggest that certain metabolites o f salicylic acid may contribute to the pharmacological action of its parent compound by inhibiting COX-2-dependent PGE(2) formation at sites of inflam mation. (C) 2000 Academic Press.