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
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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

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Figure 9

Plasmin induces IMR-90 cell COX-2 expression and PGE2 synthesis in an HGF-dependent manner.

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Plasmin induces IMR-90 cell COX-2 expression and PGE2 synthesis in an HG...
(A) IMR-90 cells in SFM were treated with plasmin (50 mU/ml) for 2, 4, 9, 18, and 24 hours. Total HGF was determined by ELISA and normalized to levels measured in cells incubated with SFM alone; n = 3, *P < 0.05 versus control. At 2 hours, the mean absolute concentration of HGF was 6.12 ng/ml. (B) IMR-90 cells in SFM were treated with HGF (1 or 10 ng/ml) for 18 hours. Lysates were harvested for COX-2 protein expression as determined by immunoblot analysis and densitometry using α-tubulin as a loading control; n = 3, *P = 0.05 versus control (SFM alone). (C) IMR-90 cells in SFM were treated with plasmin (50 mU/ml), plasmin with an HGF receptor blocking antibody (20 μg/ml), or plasmin with a nonspecific IgG (control IgG; 20 μg/ml) for 18 hours (n = 3). PGE2 was determined and normalized for cellular protein. *P < 0.05 versus control (SFM alone). (D) IMR-90 cells in SFM were treated with PLG (200 mU/ml) for 2, 4, 9, 18, and 24 hours. Lysates were harvested for COX-2 protein expression (inverted triangles) as determined by immunoblot analysis and densitometry using α-tubulin as a loading control. Media was harvested, and PGE2 (squares) and HGF (circles) were determined and normalized to cellular protein. Data are expressed relative to SFM control and are from 1 experiment representative of 2.