PGE(2) inhibition of TGF-beta1-induced myofibroblast differentiation is Smad-independent but involves cell shape and adhesion-dependent signaling.
Myofibroblasts are pathogenic in pulmonary fibrotic disease due to their exuberant production of matrix rich in collagen that interferes with gas exchange and the ability of these cells to contract and distort the alveolar space. Transforming growth factor-beta1 (TGF-beta1) is a well-known inducer of myofibroblast differentiation. TGF-beta1-induced transformation of fibroblasts to apoptosis-resistant myofibroblasts is adhesion-dependent and focal adhesion kinase (FAK)-mediated. Prostaglandin E(2) (PGE(2)) inhibits this differentiation via E prostanoid receptor 2 (EP2) signaling and cAMP elevation, but whether PGE(2) does so by interfering with TGF-beta1 signaling is unknown. Thus we examined the effects of PGE(2) in the presence and absence of TGF-beta1 stimulation on candidate signaling pathways in human lung fibroblasts. We now demonstrate that PGE(2) does not interfere with TGF-beta1-induced Smad phosphorylation or its translocation to the nucleus. Rather, PGE(2) has dramatic effects on cell shape and cytoskeletal architecture and disrupts the formation of appropriate focal adhesions. PGE(2) treatment diminishes TGF-beta1-induced phosphorylation of paxillin, STAT-3, and FAK and, in turn, limits activation of the protein kinase B (PKB/Akt) pathway. These alterations do not, however, result in increased apoptosis within the first 24 h of treatment. Interestingly, the effects of PGE(2) stimulation alone do not always mirror the effects of PGE(2) in the presence of TGF-beta1, indicating that the context for EP2 signaling is different in the presence of TGF-beta1. Taken together, our results demonstrate that PGE(2) has the potential to limit TGF-beta1-induced myofibroblast differentiation via adhesion-dependent, but Smad-independent, pathways.
Thomas
Peedikayil E
PE
Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine, University of Michigan, Ann Arbor, MI 48109-2200, USA.
Peters-Golden
Marc
M
White
Eric S
ES
Thannickal
Victor J
VJ
Moore
Bethany B
BB
D000199:Actins / Q000378:metabolism; D000527:Alprostadil / Q000031:analogs & derivatives / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D048430:Cell Shape / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism; D003599:Cytoskeleton / Q000187:drug effects / Q000502:physiology; D015232:Dinoprostone / Q000378:metabolism / Q000494:pharmacology*; D005347:Fibroblasts / Q000166:cytology* / Q000378:metabolism; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism; D006801:Humans; D008168:Lung / Q000166:cytology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D051419:Paxillin / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D051785:Smad Proteins / Q000378:metabolism*; D051899:Smad2 Protein / Q000378:metabolism; D051900:Smad3 Protein / Q000378:metabolism; D051901:Smad4 Protein / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*
D000199:Actins; D051419:Paxillin; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; C497796:SMAD4 protein, human; D051785:Smad Proteins; D051899:Smad2 Protein; D051900:Smad3 Protein; D051901:Smad4 Protein; D053773:Transforming Growth Factor beta1; D003094:Collagen; D051416:Focal Adhesion Protein-Tyrosine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D000527:Alprostadil; C048491:butaprost; D015232:Dinoprostone