The antifibrotic effects of plasminogen activation occur via prostaglandin E2 synthesis in humans and mice
Kristy A. Bauman, Scott H. Wettlaufer, Katsuhide Okunishi, Kevin M. Vannella, Joshua S. Stoolman, Steven K. Huang, Anthony J. Courey, Eric S. White, Cory M. Hogaboam, Richard H. Simon, Galen B. Toews, Thomas H. Sisson, Bethany B. Moore, Marc Peters-Golden
Kristy A. Bauman, Scott H. Wettlaufer, Katsuhide Okunishi, Kevin M. Vannella, Joshua S. Stoolman, Steven K. Huang, Anthony J. Courey, Eric S. White, Cory M. Hogaboam, Richard H. Simon, Galen B. Toews, Thomas H. Sisson, Bethany B. Moore, Marc Peters-Golden
View: Text | PDF
Research Article Pulmonology

The antifibrotic effects of plasminogen activation occur via prostaglandin E2 synthesis in humans and mice

Abstract

Plasminogen activation to plasmin protects from lung fibrosis, but the mechanism underlying this antifibrotic effect remains unclear. We found that mice lacking plasminogen activation inhibitor–1 (PAI-1), which are protected from bleomycin-induced pulmonary fibrosis, exhibit lung overproduction of the antifibrotic lipid mediator prostaglandin E2 (PGE2). Plasminogen activation upregulated PGE2 synthesis in alveolar epithelial cells, lung fibroblasts, and lung fibrocytes from saline- and bleomycin-treated mice, as well as in normal fetal and adult primary human lung fibroblasts. This response was exaggerated in cells from Pai1–/– mice. Although enhanced PGE2 formation required the generation of plasmin, it was independent of proteinase-activated receptor 1 (PAR-1) and instead reflected proteolytic activation and release of HGF with subsequent induction of COX-2. That the HGF/COX-2/PGE2 axis mediates in vivo protection from fibrosis in Pai1–/– mice was demonstrated by experiments showing that a selective inhibitor of the HGF receptor c-Met increased lung collagen to WT levels while reducing COX-2 protein and PGE2 levels. Of clinical interest, fibroblasts from patients with idiopathic pulmonary fibrosis were found to be defective in their ability to induce COX-2 and, therefore, unable to upregulate PGE2 synthesis in response to plasmin or HGF. These studies demonstrate crosstalk between plasminogen activation and PGE2 generation in the lung and provide a mechanism for the well-known antifibrotic actions of the fibrinolytic pathway.

Authors

Kristy A. Bauman, Scott H. Wettlaufer, Katsuhide Okunishi, Kevin M. Vannella, Joshua S. Stoolman, Steven K. Huang, Anthony J. Courey, Eric S. White, Cory M. Hogaboam, Richard H. Simon, Galen B. Toews, Thomas H. Sisson, Bethany B. Moore, Marc Peters-Golden

×

Figure 8

Lack of effect of PAR-1 agonist and antagonist peptides on PGE2 production and COX-2 expression in IMR-90 cells.

Options: View larger image (or click on image) Download as PowerPoint
Lack of effect of PAR-1 agonist and antagonist peptides on PGE2 producti...
(A) IMR-90 cells in SFM were treated with the PAR-1 agonist peptide TFLLRN (100 μM) for 18 hours; n = 3. (B) IMR-90 cells in SFM were treated with plasmin (100 mU/ml) with and without the PAR-1 antagonist peptide FLLRN (antag; 100 μM) for 18 hours; n = 3. Where plasmin and FLLRN were coincubated, the antagonist was added 10 minutes before the plasmin. Lysates were harvested, and COX-2 protein expression was determined by immunoblot analysis and densitometry using α-tubulin as a loading control. Medium was removed from the cells for PGE2 determination. COX-2 immunoblots in A and B are derived from the same experiments, so that differences in densitometric units accurately reflect differences between plasmin (B) and no-plasmin control (A) conditions. None of the comparisons shown represent statistically significant differences. Blots in both A and B are composed from two lanes that were run on the same gel but were noncontiguous.