Lipoxin A4and aspirin-triggered 15-epi-lipoxin A4inhibit peroxynitrite formation, NF-κB and AP-1 activation, and IL-8 gene expression in human leukocytes

Abstract

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, monocytes, and lymphocytes, in whole blood. LXA 4/ATL analogues attenuated nuclear accumulation of activator protein-1 and nuclear factor-κB 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.