Constitutive ALK5-independent c-Jun N-terminal kinase activation contributes to endothelin-1 overexpression in pulmonary fibrosis: evidence of an autocrine endothelin loop operating through the endothelin A and B receptors.
The signal transduction mechanisms generating pathological fibrosis are almost wholly unknown. Endothelin-1 (ET-1), which is up-regulated during tissue repair and fibrosis, induces lung fibroblasts to produce and contract extracellular matrix. Lung fibroblasts isolated from scleroderma patients with chronic pulmonary fibrosis produce elevated levels of ET-1, which contribute to the persistent fibrotic phenotype of these cells. Transforming growth factor beta (TGF-beta) induces fibroblasts to produce and contract matrix. In this report, we show that TGF-beta induces ET-1 in normal and fibrotic lung fibroblasts in a Smad-independent ALK5/c-Jun N-terminal kinase (JNK)/Ap-1-dependent fashion. ET-1 induces JNK through TAK1. Fibrotic lung fibroblasts display constitutive JNK activation, which was reduced by the dual ETA/ETB receptor inhibitor, bosentan, providing evidence of an autocrine endothelin loop. Thus, ET-1 and TGF-beta are likely to cooperate in the pathogenesis of pulmonary fibrosis. As elevated JNK activation in fibrotic lung fibroblasts contributes to the persistence of the myofibroblast phenotype in pulmonary fibrosis by promoting an autocrine ET-1 loop, targeting the ETA and ETB receptors or constitutive JNK activation by fibrotic lung fibroblasts is likely to be of benefit in combating chronic pulmonary fibrosis.
Shi-Wen
Xu
X
Centre for Rheumatology, Department of Medicine, Royal Free and University College Medical School, Rowland Hill Street, London NW3 2PF, United Kingdom.
Rodríguez-Pascual
Fernando
F
Lamas
Santiago
S
Holmes
Alan
A
Howat
Sarah
S
Pearson
Jeremy D
JD
Dashwood
Michael R
MR
du Bois
Roland M
RM
Denton
Christopher P
CP
Black
Carol M
CM
Abraham
David J
DJ
Leask
Andrew
A
D000199:Actins / Q000096:biosynthesis; D030201:Activin Receptors, Type I / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D065130:Endothelin A Receptor Antagonists; D065131:Endothelin B Receptor Antagonists; D019332:Endothelin-1 / Q000378:metabolism*; D004789:Enzyme Activation; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D017346:Protein Serine-Threonine Kinases; D011658:Pulmonary Fibrosis / Q000378:metabolism*; D044022:Receptor, Endothelin A / Q000378:metabolism*; D044023:Receptor, Endothelin B / Q000378:metabolism*; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism*; D051785:Smad Proteins / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000494:pharmacology
D000199:Actins; D065130:Endothelin A Receptor Antagonists; D065131:Endothelin B Receptor Antagonists; D019332:Endothelin-1; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D018125:Receptors, Transforming Growth Factor beta; D051785:Smad Proteins; D018808:Transcription Factor AP-1; D016212:Transforming Growth Factor beta; D017346:Protein Serine-Threonine Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D030201:Activin Receptors, Type I; D000077293:Receptor, Transforming Growth Factor-beta Type I; C000625841:TGFBR1 protein, human; C000625842:Tgfbr1 protein, mouse