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From the * Center for Experimental Therapeutics and Reperfusion Injury, Department of Anesthesia,
and the Lipoxins are bioactive eicosanoids that are immunomodulators. In human myeloid cells, lipoxin
(LX) A4 actions are mediated by interaction with a G protein-coupled receptor. To explore
functions of LXA4 and aspirin-triggered 5(S),6(R),15(R)-trihydroxy-7,9,13-trans-11-cis-eicosatetraenoic acid (15-epi-LXA4) in vivo, we cloned and characterized a mouse LXA4 receptor
(LXA4R). When expressed in Chinese hamster ovary cells, the mouse LXA4R showed specific
binding to [3H]LXA4 (Kd
Renal Division, Department of Medicine, Brigham and Women's Hospital, Harvard Medical
School, Boston, Massachusetts 02115; and the § Department of Chemistry, University of Southern
California, Los Angeles, California 90089
1.5 nM), and with LXA4 activated GTP hydrolysis. Mouse
LXA4R mRNA was most abundant in neutrophils. In addition to LXA4 and 15-epi-LXA4,
bioactive LX stable analogues competed with both [3H]LXA4 and [3H]leukotriene D4 (LTD4)-
specific binding in vitro to neutrophils and endothelial cells, respectively. Topical application
of LXA4 analogues and novel aspirin-triggered 15-epi-LXA4 stable analogues to mouse ears
markedly inhibited neutrophil infiltration in vivo as assessed by both light microscopy and reduced myeloperoxidase activity in skin biopsies. The 15(R)-16-phenoxy-17,18, 19,20-tetranorLXA4 methyl ester (15-epi-16-phenoxy-LXA4), an analogue of aspirin triggered 15-epi-LXA4, and
15(S)-16-phenoxy-17,18,19,20-tetranor-LXA4 methyl ester (16-phenoxy-LXA4) were each as
potent as equimolar applications of the anti-inflammatory, dexamethasone. Thus, we identified
murine LXA4R, which is highly expressed on murine neutrophils, and showed that both LXA4
and 15-epi-LXA4 stable analogues inhibit neutrophil infiltration in the mouse ear model of inflammation. These findings provide direct in vivo evidence for an anti-inflammatory action for
both aspirin-triggered LXA4 and LXA4 stable analogues and their site of action in vivo.
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