Interference of α-alkyl-substituted pirinixic acid derivatives with neutrophil functions and signalling pathways

Pirinixic acid (Wy-14,643) is an agonist of the peroxisome proliferator-activated receptor (PPAR) subtype α exhibiting beneficial effects in various inflammation-related processes in a slow, long-termed fashion. We recently showed that α-substituted pirinixic acid derivatives are agonists of PPARα and act as dual inhibitors of 5-lipoxygenase (5-LO, EC 1.13.11.34) and the microsomal prostaglandin E2 synthase-1 (EC 5.3.99.3). Here, we explored short-term effects of α-substituted pirinixic acid derivatives on typical neutrophil functions evoked by the agonist N-formyl-methionyl-leucyl-phenylalanine (fMLP) including leukotriene formation, generation of reactive oxygen species, and release of human leukocyte elastase (EC 3.4.21.37), and we investigated the modulation of related signalling pathways. Pirinixic acid derivatives that are substituted with alkyl residues in α-position of the carboxylic group and with a 6-aminoquinoline residue at the pyrimidine moiety cause inhibition of leukotriene formation, reactive oxygen species formation, and leukocyte elastase release in response to fMLP. In parallel, Ca2+ mobilisation and the phosphorylation (activation) of p38 mitogen-activated protein kinase was significantly reduced, whereas phosphorylation of the extracellular signal-regulated kinase-2 was unaffected. Pirinixic acid itself was not or only marginally active in all these assays. Conclusively, targeted structural modification of pirinixic acid leads to bioactive compounds that display immediate anti-inflammatory properties in human neutrophils with potential therapeutic value.