Recurrent asthma attacks may accelerate airway remodeling
MedWire News: Recurrent asthma attacks may aggravate airway remodeling, say Japanese researchers who found that acute attacks are associated with hypersecretion of epidermal growth factor (EGF) and amphiregulin in the airways.
Writing in the Journal of Allergy and Clinical Immunology, Yoshimichi Okayama (Nihon University Graduate School of Medical Science, Tokyo) and team explain: “EGF receptor ligands, such as EGF and amphiregulin, may play key roles in tissue remodeling in asthma.”
However, they add that “the kinetics of EGF and amphiregulin secretion in the airway after an acute asthma attack and the effect of prolonged airway exposure to these ligands on airway remodeling are unknown.”
To investigate, the researchers used enzyme-linked-immunosorbent serologic assay to examine EGF and amphiregulin levels in sputum samples collected from 14 hospitalized children during an asthma attack, 13 stable asthmatic children, eight healthy control children, and seven children with respiratory tract infections.
The team also assessed the effects of EGF and amphiregulin on the proliferation and/or differentiation of normal human bronchial epithelial (NHBE) cells, bronchial smooth muscle cells (BSMC), and normal human lung fibroblasts (NHLF).
Analysis revealed that sputum levels of EGF were significantly higher in children hospitalized for an acute asthma attack than in those from any of the other groups, and remained so for around a week until the recovery phase.
Among hospitalized patients, amphiregulin levels were only elevated throughout the duration of the acute attack and subsequently returned to similar levels to those observed in the other non-hospitalized children.
The researchers also found that elevated EGF was associated with proliferation of NHBE cells, BSMC, and NHLF, whereas elevated amphiregulin was only associated with NHBE cell proliferation. Prolonged exposure of NHBE cells to EGF and amphiregulin induced mucous cell metaplasia in an interleukin-13–independent manner.
Okayama and team conclude: “These data indicate that EGF and amphiregulin are hypersecreted in the airway of subjects with acute severe asthma both during and after an acute asthma attack.”
They add: “Prevention of acute asthma attacks may be crucial to preventing progression of airway remodeling in the asthmatic airway.”
MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2009
By Mark Cowen