Differential deposition of fibronectin by asthmatic bronchial epithelial cells.
Altered ECM protein deposition is a feature in asthmatic airways. Fibronectin (Fn), an ECM protein produced by human bronchial epithelial cells (HBECs), is increased in asthmatic airways. This study investigated the regulation of Fn production in asthmatic or nonasthmatic HBECs and whether Fn modulated HBEC proliferation and inflammatory mediator secretion. The signaling pathways underlying transforming growth factor (TGF)-β1-regulated Fn production were examined using specific inhibitors for ERK, JNK, p38 MAPK, phosphatidylinositol 3 kinase, and activin-like kinase 5 (ALK5). Asthmatic HBECs deposited higher levels of Fn in the ECM than nonasthmatic cells under basal conditions, whereas cells from the two groups had similar levels of Fn mRNA and soluble Fn. TGF-β1 increased mRNA levels and ECM and soluble forms of Fn but decreased cell proliferation in both cells. The rate of increase in Fn mRNA was higher in nonasthmatic cells. However, the excessive amounts of ECM Fn deposited by asthmatic cells after TGF-β1 stimulation persisted compared with nonasthmatic cells. Inhibition of ALK5 completely prevented TGF-β1-induced Fn deposition. Importantly, ECM Fn increased HBEC proliferation and IL-6 release, decreased PGE2 secretion, but had no effect on VEGF release. Soluble Fn had no effect on cell proliferation and inflammatory mediator release. Asthmatic HBECs are intrinsically primed to produce more ECM Fn, which when deposited into the ECM, is capable of driving remodeling and inflammation. The increased airway Fn may be one of the key driving factors in the persistence of asthma and represents a novel, therapeutic target.
Respiratory Cellular and Molecular Biology Group, Woolcock Institute of Medical Research, Sydney, New South Wales, Australia; Discipline of Pharmacology, Sydney Medical School, The University of Sydney, New South Wales, Australia; and qi.ge@sydney.edu.au.
Qi
Q
Ge
Respiratory Cellular and Molecular Biology Group, Woolcock Institute of Medical Research, Sydney, New South Wales, Australia;
Qingxiang
Q
Zeng
Respiratory Cellular and Molecular Biology Group, Woolcock Institute of Medical Research, Sydney, New South Wales, Australia;
Gavin
G
Tjin
Royal Prince Alfred Hospital, Sydney, New South Wales, Australia.
Edmund
E
Lau
Respiratory Cellular and Molecular Biology Group, Woolcock Institute of Medical Research, Sydney, New South Wales, Australia; Discipline of Pharmacology, Sydney Medical School, The University of Sydney, New South Wales, Australia; and.
Judith L
JL
Black
Respiratory Cellular and Molecular Biology Group, Woolcock Institute of Medical Research, Sydney, New South Wales, Australia; Discipline of Pharmacology, Sydney Medical School, The University of Sydney, New South Wales, Australia; and.
Brian G G
BG
Oliver
Respiratory Cellular and Molecular Biology Group, Woolcock Institute of Medical Research, Sydney, New South Wales, Australia; Discipline of Pharmacology, Sydney Medical School, The University of Sydney, New South Wales, Australia; and.
Janette K
JK
Burgess
D001249:Asthma / Q000378:metabolism* / Q000473:pathology; D001980:Bronchi / Q000473:pathology; D049109:Cell Proliferation; D002470:Cell Survival; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000378:metabolism*; D005353:Fibronectins / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D020545:Respiratory Mucosa / Q000473:pathology; D053773:Transforming Growth Factor beta1 / Q000502:physiology
D005353:Fibronectins; D053773:Transforming Growth Factor beta1
ECM protein; IL-6; TGF-β1; airway epithelial cell; asthma; fibronectin