Neutrophil-mediated changes in vascular permeability are inhibited by topical application of aspirin-triggered 15-epi-lipoxin A4 and novel lipoxin B4 stable analogues

Neutrophil (PMN) activation is critical in inflammation and reperfusion injury, suggesting that PMN-directed therapies may be of clinical use. Here, leukotriene B-4 (LTB4)-induced PMN influx in ear skin was equivalent between 5-lipoxygenase knockout and wild-type mice, To explore actions of lipoxin (LX) in PMN-mediated tissue injury, we prepared several novel LX stable analogues, including analogues of LXA(4) and aspirin-triggered 15-epi-LXA(4) as well as LXB4, and examined their impact in PMN infiltration and vascular permeability. Each applied topically to mouse ears inhibited dramatically PMN-mediated increases in vascular permeability (IC50 range of 13-26 nmol) with a rank order of 15(R/S)-methyl-LXA(4) > 16-para-fluoro-phenoxy-LXA(4) similar to 5(S)-methyl-LXB4 greater than or equal to 16-phenoxy-LXA(4) > 5(R)-methyl-LXB4. These LX mimetics were as potent as an LTB, receptor antagonist, yet results from microphysiometry with mouse leukocytes indicated that they do not act as LTB, receptor level antagonists. In addition, within 24 h of delivery, > 90% were cleared from ear biopsies, Neither IL-8, FMLP, C5a, LTD4, nor platelet-activating factor act topically to promote PMN influx. When applied with LTB4, PGE(2) enhanced sharply both infiltration and vascular permeability, which were inhibited by a fluorinated stable analogue of aspirin-triggered LX. These results indicate that mimetics of LXs and aspirin-triggered 15-epi-LXA(4) are topically active in this model and are potent inhibitors of both PMN infiltration and PMN-mediated vascular injury.