Ligation of protease-activated receptor 1 enhances αv β6 integrin–dependent TGF-β activation and promotes acute lung injury
R. Gisli Jenkins, Xiao Su, George Su, Christopher J. Scotton, Eric Camerer, Geoffrey J. Laurent, George E. Davis, Rachel C. Chambers, Michael A. Matthay, Dean Sheppard
R. Gisli Jenkins, Xiao Su, George Su, Christopher J. Scotton, Eric Camerer, Geoffrey J. Laurent, George E. Davis, Rachel C. Chambers, Michael A. Matthay, Dean Sheppard
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Research Article Pulmonology

Ligation of protease-activated receptor 1 enhances αv β6 integrin–dependent TGF-β activation and promotes acute lung injury

Abstract

Activation of latent TGF-β by the αvβ6 integrin is a critical step in the development of acute lung injury. However, the mechanism by which αvβ6-mediated TGF-β activation is regulated has not been identified. We show that thrombin, and other agonists of protease-activated receptor 1 (PAR1), activate TGF-β in an αvβ6 integrin–specific manner. This effect is PAR1 specific and is mediated by RhoA and Rho kinase. Intratracheal instillation of the PAR1-specific peptide TFLLRN increases lung edema during high-tidal-volume ventilation, and this effect is completely inhibited by a blocking antibody against the αvβ6 integrin. Instillation of TFLLRN during high-tidal-volume ventilation is associated with increased pulmonary TGF-β activation; however, this is not observed in Itgb6–/– mice. Furthermore, Itgb6–/– mice are also protected from ventilator-induced lung edema. We also demonstrate that pulmonary edema and TGF-β activity are similarly reduced in Par1–/– mice following bleomycin-induced lung injury. These results suggest that PAR1-mediated enhancement of αvβ6-dependent TGF-β activation could be one mechanism by which activation of the coagulation cascade contributes to the development of acute lung injury, and they identify PAR1 and the αvβ6 integrin as potential therapeutic targets in this condition.

Authors

R. Gisli Jenkins, Xiao Su, George Su, Christopher J. Scotton, Eric Camerer, Geoffrey J. Laurent, George E. Davis, Rachel C. Chambers, Michael A. Matthay, Dean Sheppard

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Figure 2

Stimulation of lung epithelial cells with a PAR1 agonist leads to αv β6 -dependent TGF-β activation.

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Stimulation of lung epithelial cells with a PAR1 agon...
(A) IMLE cells were cocultured with TML cells and stimulated with increasing doses of SFLLRN, and luciferase activity from the TGF-β–responsive plasminogen activator inhibitor-1 promoter was measured. IMLE cells expressing human WT β6 (black bars) were compared with IMLE cells that had no cell surface β6 (white bars), and both were also stimulated with increasing doses of SFLLRN in the presence of αvβ6 blocking antibody (IMLE β6-positive, dark gray bars; IMLE β6-negative, light gray bars). (B) To determine the proportion of TGF-β expression that was mediated by αvβ6 in epithelial cell cultures, IMLE cells and normal human bronchial epithelial (NHBE) cells were stimulated with 10 μM of SFLLRN (gray bars), in the absence or presence of an αvβ6 blocking antibody (black bars) or a pan–TGF-β blocking antibody (white bars), in coculture with TML cells, and luciferase activity was measured. All experiments were performed in triplicate, and the mean + SEM is shown. Results are a representative example of at least 2 identical independent experiments.