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LXA4, aspirin-triggered 15-epi-LXA4, and their analogs selectively downregulate PMN azurophilic degranulation
A T Gewirtz1, V V Fokin, N A Petasis
1Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, Georgia, USA. agewirt@emory.edu
Abstract:
The eicosanoid lipoxin A4 (LXA4) is biosynthesized in vivo by cells present at inflammatory sites and appears to be an endogenous anti-inflammatory mediator. Further, in the presence of aspirin, the 15-epimer of LXA4 (15-epi-LXA4) is biosynthesized and may mediate some of aspirin's desirable bioactions. LXA4, 15-epi-LXA4, and their stable analogs inhibit inflammation in established animal models, indicating that these compounds may be useful for treating inflammatory disease states. To investigate the cellular mechanisms by which these lipid mediators downregulate inflammation, we investigated whether these eicosanoids could influence receptor-mediated degranulation of human neutrophils, an event thought to play a major causative role in several inflammatory disease states. LXA4, 15-epi-LXA4, and their stable analogs potently (IC50 < 1 nM) and selectively downregulated neutrophil release of azurophilic granule contents but did not affect other neutrophil secretory functions. Thus the cellular basis of action of these natural off-switches to inflammation appears to involve downregulation of neutrophil azurophilic granule release.
Insights
Lipoxin A4 (LXA4) and its aspirin-triggered epimer (15-epi-LXA4) are potent anti-inflammatory mediators. These compounds selectively inhibit neutrophil degranulation, offering a cellular mechanism for their therapeutic potential in inflammatory diseases.
Area of Science:
- Biochemistry
- Immunology
- Pharmacology
Background:
- Lipoxin A4 (LXA4) is an endogenous anti-inflammatory mediator produced at inflammatory sites.
- Aspirin can induce the biosynthesis of 15-epi-LXA4, potentially mediating some of aspirin's beneficial effects.
- LXA4, 15-epi-LXA4, and their analogs show anti-inflammatory activity in animal models.
Purpose of the Study:
- To investigate the cellular mechanisms by which LXA4 and 15-epi-LXA4 exert their anti-inflammatory effects.
- To determine if these eicosanoids influence receptor-mediated degranulation of human neutrophils.
Main Methods:
- Investigated the effect of LXA4, 15-epi-LXA4, and stable analogs on human neutrophil degranulation.
- Assessed the selective impact on the release of azurophilic granule contents.
Main Results:
- LXA4, 15-epi-LXA4, and stable analogs potently inhibited neutrophil release of azurophilic granule contents (IC50 < 1 nM).
- These eicosanoids selectively downregulated azurophilic granule release without affecting other neutrophil secretory functions.
Conclusions:
- The anti-inflammatory action of LXA4 and 15-epi-LXA4 involves the selective downregulation of neutrophil azurophilic granule release.
- These findings elucidate a key cellular mechanism for the anti-inflammatory properties of these eicosanoids, supporting their therapeutic potential.