Thrombin Enhances Lung Fibroblast Proliferation in Bleomycin-induced Pulmonary Fibrosis

Abstract

To clarify the role of thrombin in fibroblast growth and the development of pulmonary fibrosis in bleomycin-induced interstitial lung disease, we examined the relationship of thrombin activity to fibroblast growth-stimulating activity (FGA) in bronchoalveolar lavage (BAL) fluid from bleomycin-treated rats. Male Wistar rats were given a single intratracheal injection of bleomycin, BAL was performed 2, 6, and 15 days later, and the BAL fluid was assayed for thrombin activity and FGA. Higher FGA than the control value was detected in the BAL fluid from rats on day 6 after bleomycin administration. In bleomycin-treated rats, thrombin activity in the BAL fluid was significantly elevated on day 2 and maximal on day 6. The FGA of the BAL fluid from bleomycin-treated rats on day 6 was significantly decreased by its treatment with various thrombin inhibitors, such as alpha 1-protease inhibitor, antithrombin III, hirudin, and MD-805. In our assay, purified rat thrombin also showed FGA in vitro, and its FGA was inhibited by the same concentrations of these thrombin inhibitors as those inhibiting the activity in the BAL fluid. On ammonium sulfate fractionation, most of the thrombin activity was recovered in the fraction of 35 to 50% saturation in which most of the FGA was detected. These results suggest that the FGA of the BAL fluid from bleomycin-treated rats was at least partly due to thrombin is responsible, at least in part, for fibroblast growth and pulmonary fibrosis in bleomycin-induced interstitial lung disease.

Thrombin Increases Lung Fibroblast Survival while Promoting Alveolar Epithelial Cell Apoptosis via the Endoplasmic Reticulum Stress Marker, CCAAT Enhancer–Binding Homologous Protein

“…In addition to its role in hemostasis, thrombin also mediates a number of biological responses relevant to inflammatory and tissue repair responses, predominantly via PAR-1-dependent mechanisms. Our group and others have previously shown that thrombin activity is increased in bronchoalveolar lavage fluid from patients with SSc-ILD and in bleomycin-induced pulmonary fibrosis models of ILDs (19,20). In this study, we demonstrate that thrombin increases expression of CHOP in primary AECs and A549 cells, and that the thrombin receptor, PAR-1, colocalizes with CHOP in SSc-ILD lung.…”

“…A number of reports have demonstrated that thrombin activity is increased in bronchoalveolar lavage fluid obtained from patients with SSc-ILD, as well as in experimental models of bleomycininduced pulmonary fibrosis (19,20). Thrombin, mostly through proteaseactivated receptor (PAR)-1, can modulate tissue repair by stimulating differentiation of normal fibroblasts to a myofibroblast phenotype, promoting adhesion and proliferation of endothelial cells and inducing secretion of several profibrotic factors, such as transforming growth factorb and connective tissue growth factor (21)(22)(23).…”

Bleomycin‐induced lung injury assessed noninvasively and in spontaneously breathing rats by proton MRI

“…Evidence from the literature suggests that the major fibroproliferative phase induced by BLM in rats and mice occurs within the first week following its administration and that this process coexists with inflammation (14,21,29,30). Histological examinations of rats (1,26) have shown an elevated presence of inflammatory cells and cytokines at four days and a further increment at six days after BLM-treatment, as well as protein-rich granular-textured edema in the alveolar spaces.…”

From clot to collagen: coagulation peptides in interstitial lung disease

“…Similar findings have also been reported for animal models of fibrosis. For example, thrombin has been shown to be increased and act as a potent fibroblast mitogen in BAL fluid obtained from rats developing fibrosis following bleomycin administration [10]. More recently, TF expression was shown to be increased at sites characterized by persistent fibrin deposition and fibroproliferation in mice following a similar administration of bleomycin [11].…”