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Lung tissue eosinophils may be cleared through luminal entry rather than apoptosis: effects of steroid treatment

In English

Författare

Summary, in English

Spontaneous or steroid-induced eosinophil apoptosis occurring in vitro has not been demonstrated in lung tissues in vivo. This study examines cell apoptosis in rat lungs using the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) technique and transmission electron microscopy (TEM). After establishing sustained lung edema and eosinophilia by challenge with Sephadex beads intratracheally, budesonide treatment was started intratracheally. Sephadex alone increased the total number of apoptotic cells, which were not efficiently engulfed by macrophages or other cells, in vivo. Yet apoptotic tissue eosinophils were exceedingly rare (1 of 360 TEM-analyzed eosinophils). By contrast, approximately 20% of eosinophils in the airway lumen were apoptotic, and unengulfed. Budesonide promptly inhibited edema but 3 d of steroid treatment were required to reduce the established tissue eosinophilia. Not at any time point did budesonide induce eosinophil apoptosis (0 of 318 TEM-analyzed tissue eosinophils). We conclude that (1) eosinophil apoptosis can occur but is a rare event in vivo in respiratory tract tissues; (2) airway tissue eosinophils, rather than undergoing apoptosis, are eliminated by migration into airway lumen followed by apoptosis and mucociliary clearance; (3) anti-inflammatory steroid treatment may not increase eosinophil apoptosis in vivo nor may it affect the luminal entry of eosinophils; (4) steroids permit elimination of eosinophils into airway lumen and slowly resolve established lung eosinophilia.

Publiceringsår

2001

Språk

Engelska

Sidor

1948-1956

Publikation/Tidskrift/Serie

American Journal of Respiratory and Critical Care Medicine

Volym

164

Issue

10

Dokumenttyp

Artikel i tidskrift

Förlag

American Thoracic Society

Ämne

  • Respiratory Medicine and Allergy

Nyckelord

  • steroids
  • apoptosis
  • eosinophils
  • transmission electron microscopy

Status

Published

Forskningsgrupp

  • Lung Biology
  • Airway Inflammation and Immunology

ISBN/ISSN/Övrigt

  • ISSN: 1535-4970