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J Allergy Clin Immunol. 1999 Jul;104(1):153-62.

PGE 2 and dibutyryl cyclic adenosine monophosphate prolong eosinophil survival in vitro.

Author information

1
Asthma and Allergy Research Institute and Department of Medicine, University of Western Australia, Perth, Australia.

Abstract

BACKGROUND:

Apoptosis represents a mechanism by which the accumulation and inflammatory potential of eosinophils in asthma might be limited. Mediators derived from the airway epithelium may influence the rate of eosinophil apoptosis.

OBJECTIVE:

We have investigated the effects on eosinophil apoptosis of 3 mediators that are likely to be produced by the airway epithelium, namely PGE2, TNF-alpha, and nitric oxide.

METHODS:

Peripheral blood eosinophils from healthy adult volunteers were purified by density gradient centrifugation and negative immunomagnetic selection. Eosinophils were cultured for 16 or 40 hours with PGE2 (10 nmol/L), dibutyryl cyclic adenosine monophosphate (AMP; 100 micromol/L), TNF-alpha (500 U/mL), the nitric oxide donors, S-nitroso-N-acetylpenicillamine (100 micromol/L), and 2,2;-(hydroxynitrosohydrazono)bis-ethanamine (1 mmol/L), or dibutyryl cyclic guanosine monophosphate (100 micromol/L). Control cultures consisted of untreated, IL5-treated (100 U/mL), and anti-Fas-treated (400 ng/mL) cells. Eosinophil apoptosis was assessed by flow cytometric analysis of annexin V-FITC binding to externalized phosphatidylserine, by electrophoresis of phosphorus 32 end-labeled DNA fragments, and by flow cytometric assessment of hypodiploid DNA with propidium iodide.

RESULTS:

PGE2 and cyclic AMP inhibited spontaneous eosinophil apoptosis at both 16 and 40 hours as did the PGEP2 receptor agonist, 11-deoxy PGE1, at 40 hours, but these effects were not inhibited by a protein kinase A antagonist. TNF-alpha delayed apoptosis in eosinophil cultures at 16 hours, whereas S-nitroso- N-acetylpenicillamine, 2, 2;-(hydroxynitrosohydrazono)bis-ethanamine, and cyclic guanosine monophosphate had little effect. Anti-Fas had little effect on spontaneous eosinophil apoptosis but significantly reduced the inhibitory effects of PGE2, cyclic AMP, and TNF-alpha. Assessments of apoptosis by DNA fragmentation gave similar but quantitatively less sensitive results.

CONCLUSION:

Inhibition of spontaneous eosinophil apoptosis by PGE2 appears to be mediated by EP2 receptors but is not protein kinase A dependent. By enhancing eosinophil survival, PGE2 may increase the proinflammatory potential of these cells in chronic asthma.

PMID:
10400853
DOI:
10.1016/s0091-6749(99)70127-2
[Indexed for MEDLINE]

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