A Stable Aspirin-Triggered Lipoxin A4 Analog Blocks Phosphorylation of Leukocyte-Specific Protein 1 in Human

Lipoxins and their aspirin-triggered 15-epimers are endogenous anti-inflammatory agents that block neutrophil chemotaxis in vitro and inhibit neutrophil influx in several models of acute inflammation. In this study, we examined the effects of 15-epi-16-(p-fluoro)-phenoxy-lipoxin A4 methyl ester, an aspirin-triggered lipoxin A4-stable analog (ATLa), on the protein phosphorylation pattern of human neutrophils. Neutrophils stimulated with the chemoattractant fMLP were found to exhibit intense phosphor-ylation of a 55-kDa protein that was blocked by ATLa (10–50 nM). This 55-kDa protein was identified as leukocyte-specific protein 1, a downstream component of the p38-MAPK cascade in neutrophils, by mass spectrometry, Western blotting, and immuno-precipitation experiments. ATLa (50 nM) also reduced phosphorylation/activation of several components of the p38-MAPK pathway in these cells (MAPK kinase 3/MAPK kinase 6, p38-MAPK, MAPK-activated protein kinase-2). These results indicate that ATLa exerts its anti-inflammatory effects, at least in part, by blocking activation of the p38-MAPK cascade in neutrophils, which is known to promote chemotaxis and other proinflammatory responses by these cells. The Journal of Immunology, 2004, 173: 2091–2098. L ipoxins are endogenous anti-inflammatory lipid mediatorsthat promote the resolution of inflammation. Biosynthesisof these lipid mediators in humans requires cell-cell in-teractions and is highly influenced by the presence of certain cy-tokines and aspirin (reviewed in Refs. 1–3). Monocytes, eosino-phils, and airway-epithelial cells can convert arachidonate int