Lipoxin A_2 and aspirin-triggered 15-epi-lipoxin A_4 inhibit peroxynitrite formation, NF-kB and AP-1 activation, and IL-8 gene expression in human leukocytes

摘要

Lipoxin A_4 (LXA_4) and aspirin-triggered 15-epi-LXA_4 (ATL) are emerging as endogenous braking signals for neutrophil-mediated tissue injury. Recent studies indicate that peroxynitrite (ONOO~-) may function as an intracellular signal for the production of IL-8, a potent proinflammatory cytokine in human leukocytes. In this study, we evaluated the impact of the metabolically stable analogues of LXA_4/ATL on lipopolysaccharide (LPS)-induced ONOO-formation and ONOO~--mediated IL-8 gene expression in human leukocytes. At nanomolar concentrations, LXA_4 analogues markedly reduced LPS-stimulated superoxide formation, evoked increases in intracellular diamino-fluorescein fluorescence (an indicator of NO formation), and consequently reduced ONOO~-formation in isolated neutrophils, as well as in neutrophils, mono-cytes, and lymphocytes, in whole blood. LXA_4/ATL analogues attenuated nuclear accumulation of activator protein-1 and nuclear factor-kB in both polymorphonuclear and mononuclear leukocytes and inhibited IL-8 mRNA expression and IL-8 release by 50-65% in response to LPS. The LXA_4 inhibitory responses were concentration dependent and were not shared by 15-deoxy-LXA_4. None of the LXA_4 analogues studied affected neutrophil survival, nor reversed the apoptosis delaying action of LPS in neutrophils. In addition, LXA_4 analogues had no significant effect on exogenous ONOO~-induced IL-8 gene and protein expression. These findings suggest that by attenuating ONOO~- formation, LXA_4 and ATL can oppose ONOO~- signaling in leukocytes and provide a rationale for using stable synthetic analogues as antiinflammatory compounds in vivo.