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1-Induced Myofibroblast Differentiation Is SMAD-Independent but Involves Cell Shape and Adhesion-Dependent Signaling
1 Internal Medicine, University of Michigan, Ann Arbor, Michigan, United States; Divison Pulmonary Critical Care Medicine, University Michigan, Ann Arbor, Michigan, United States
2 Divison Pulmonary Critical Care Medicine, University Michigan, Ann Arbor, Michigan, United States; Internal Medicine, University of Michigan, Ann Arbor, Michigan, United States
3 Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan, United States
4 Internal Medicine, University of Michigan, Ann Arbor`, Michigan, United States; Divison Pulmonary Critical Care Medicine, University Michigan, Ann Arbor, Michigan, United States
* To whom correspondence should be addressed. E-mail: bmoore{at}umich.edu.
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-
1 (TGF-
1) is a well known inducer of myofibroblast differentiation. TGF-
1-induced transformation of fibroblasts to apoptosis-resistant myofibroblasts is adhesion-dependent and focal adhesion kinase (FAK)-mediated. Prostaglandin E2 (PGE2 ) inhibits this differentiation via E prostanoid receptor 2 (EP2) signaling and cyclic adenosine monophosphate (cAMP) elevation, but whether PGE2 does so by interfereing with TGF-
1 signaling is unknown. Thus, we examined the effects of PGE2 in the presence and absence of TGF-
1 stimulation on candidate signaling pathways in human lung fibroblasts. We now demonstrate that PGE2 does not interfere with TGF-
1-induced SMAD phosphorylation or its translocation to the nucleus. Rather, PGE2 has dramatic effects on cell shape and cytoskeletal architecture and disrupts the formation of appropriate focal adhesions. PGE2 treatment diminishes TGF-
1-induced phosphorylation of paxillin, STAT-3 and FAK and in turn limits activation of the pro-survival 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 PGE2 stimulation alone do not always mirror the effects of PGE2 in the presence of TGF-
1, indicating that the context for EP2 signaling is different in the presence of TGF-
1. Taken together, our results demonstrate that PGE2 has the potential to limit TGF-
1-induced myofibroblast differentiation via adhesion-dependent, but SMAD-independent pathways.
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