Extracellular matrix regulates enhanced eotaxin expression in asthmatic airway smooth muscle cells.
BACKGROUND
Altered airway smooth muscle (ASM) function and enrichment of the extracellular matrix (ECM) with fibronectin and collagen are key features of asthma. Previously, we have reported these ECM proteins enhance ASM synthetic function.


OBJECTIVE
We compared ASM cultured from endobronchial biopsies from subjects with and without asthma to assess if asthmatic cells were hypersecretory and determined whether the underlying mechanism involved autocrine ECM production.


METHODS
Cells from subjects with and without asthma were cultured on plastic or in plates precoated with ECM proteins. Cytokine production was evaluated by enzyme-linked immunosorbent assay and by reverse transcriptase-polymerase chain reaction. Function-blocking integrin antibodies were used to identify integrin involvement.


RESULTS
Baseline eotaxin and its production after stimulation with interleukin (IL)-13, IL-1beta, or tumor necrosis factor-alpha was increased (2.5- to 6.0-fold) in ASM cells cultured from subjects with asthma compared with healthy subjects. When seeded on ECM from asthmatic ASM, IL-13-dependent eotaxin release from healthy or asthmatic ASM was enhanced compared with culture on healthy ECM. The ECM substrates fibronectin and type I collagen each enhanced IL-13-dependent eotaxin release, and Western immunoblot indicated that fibronectin expression was higher in asthmatic ASM cells. Integrin-blocking antibodies revealed that alpha5beta1 was required for more than 50% of the enhanced IL-13-dependent eotaxin release by ASM cells from subjects with asthma, whereas alpha2beta1 or alphavbeta3 neutralization lacked effect.


CONCLUSIONS
The data indicate that ASM cells cultured from subjects with asthma are hypersecretory compared with cells from healthy donors and that autocrine fibronectin secretion acting via alpha5beta1 in part underlies this effect.
Chan
Vivien
V
King's College London School of Medicine, MRC and Asthma UK Centre in Allergic Mechanisms of Asthma, Thomas Guy House, Guy's Hospital Campus, London SE1 9RT, UK.
Burgess
Janette K
JK
Ratoff
Jonathan C
JC
O'connor
Brian J
BJ
Greenough
Anne
A
Lee
Tak H
TH
Hirst
Stuart J
SJ
D000328:Adult; D000368:Aged; D001249:Asthma / Q000378:metabolism*; D015153:Blotting, Western; D002478:Cells, Cultured; D054413:Chemokine CCL11; D019742:Chemokines, CC / Q000378:metabolism*; D024042:Collagen Type I / Q000378:metabolism; D005109:Extracellular Matrix / Q000502:physiology*; D005260:Female; D005353:Fibronectins / Q000378:metabolism; D006801:Humans; D016023:Integrins / Q000378:metabolism; D018793:Interleukin-13 / Q000378:metabolism; D008297:Male; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation / Q000502:physiology
C515456:CCL11 protein, human; D054413:Chemokine CCL11; D019742:Chemokines, CC; D024042:Collagen Type I; D005353:Fibronectins; D016023:Integrins; D018793:Interleukin-13