Antiinflammatory and antifibrotic effects of the oral direct thrombin inhibitor dabigatran etexilate in a murine model of interstitial lung disease.
ABSTRACT Activation of the coagulation cascade leading to generation of thrombin has been documented extensively in various forms of lung injury, including that associated with systemic sclerosis. We previously demonstrated that the direct thrombin inhibitor dabigatran inhibits thrombin-induced profibrotic signaling in lung fibroblasts. This study was undertaken to test whether dabigatran etexilate attenuates lung injury in a murine model of interstitial lung disease.
Lung injury was induced in female C57BL/6 mice by a single intratracheal instillation of bleomycin. Dabigatran etexilate was given as supplemented chow beginning on day 1 of bleomycin instillation (early treatment, study of antiinflammatory effect) or on day 8 following bleomycin instillation (late treatment, study of antifibrotic effect). Mice were killed 2 weeks or 3 weeks after bleomycin instillation, and lung tissue, bronchoalveolar lavage (BAL) fluid, and plasma were investigated.
Both early treatment and late treatment with dabigatran etexilate attenuated the development of bleomycin-induced pulmonary fibrosis. Dabigatran etexilate significantly reduced thrombin activity and levels of transforming growth factor β1 in BAL fluid, while simultaneously reducing the number of inflammatory cells and protein concentrations. Histologically evident lung inflammation and fibrosis were significantly decreased in dabigatran etexilate-treated mice. Additionally, dabigatran etexilate reduced collagen, connective tissue growth factor, and α-smooth muscle actin expression in mice with bleomycin-induced lung fibrosis, whereas it had no effect on basal levels of these proteins.
Inhibition of thrombin using the oral direct thrombin inhibitor dabigatran etexilate has marked antiinflammatory and antifibrotic effects in a bleomycin model of pulmonary fibrosis. Our data provide preclinical information about the feasibility and efficacy of dabigatran etexilate as a new therapeutic approach for the treatment of interstitial lung disease.
[show abstract] [hide abstract]
ABSTRACT: Platelet-derived growth factor (PDGF) isoforms play a major role in stimulating the replication, survival, and migration of myofibroblasts during the pathogenesis of fibrotic diseases. During fibrogenesis, PDGF is secreted by a variety of cell types as a response to injury, and many pro-inflammatory cytokines mediate their mitogenic effects via the autocrine release of PDGF. PDGF action is determined by the relative expression of PDGF alpha-receptors (PDGFRalpha) and beta-receptors (PDGFRbeta) on the surface of myofibroblasts. These receptors are induced during fibrogenesis, thereby amplifying biological responses to PDGF isoforms. PDGF action is also modulated by extracellular binding proteins and matrix molecules. This review summarizes the literature on the role of PDGF and its receptors in the development of fibrosis in a variety of organ systems, including lung, liver, kidney, and skin.Cytokine & Growth Factor Reviews 09/2004; 15(4):255-73. · 7.81 Impact Factor
[show abstract] [hide abstract]
ABSTRACT: To evaluate the effect of anticoagulant therapy on the survival of patients with idiopathic pulmonary fibrosis (IPF). Prospective study. Five hospitals located in the Miyagi prefecture in Japan, including a university hospital, a Red Cross hospital, two public general hospitals, and a municipal hospital. Fifty-six patients with IPF (mean age, 69.4 years; range, 47 to 89) admitted to the hospitals from April 2001 to April 2004. Patients were assigned to receive prednisolone alone or prednisolone plus anticoagulant therapy. The anticoagulants included oral warfarin in an outpatient setting and low-molecular-weight heparin for rehospitalized patients with severely progressive respiratory failure. There was no difference in baseline characteristics, including age, gender, clinical condition, pulmonary function, and plasma d-dimer level between the non-anticoagulant group and the anticoagulant group. The overall survival and hospitalization-free periods were assessed. There was a significant difference between survival curves of the non-anticoagulant group and the anticoagulant group, with a 2.9 hazard ratio (p = 0.04, Cox regression model). There was no significant difference in the probability of a hospitalization-free period between groups. The major cause of clinical deterioration was acute exacerbation during follow-up in the present study. Therefore, the mortality and plasma d-dimer levels in patients with an acute exacerbation were also assessed. The mortality associated with acute exacerbations of IPF in the anticoagulant group was significantly reduced compared to that in the non-anticoagulant group (18% vs 71%, respectively; p = 0.008, Fisher Exact Test). Furthermore, the plasma d-dimer levels in patients who died were significantly higher than those in survivors during acute exacerbation of IPF (3.3 +/- 2.3 microg/mL vs 0.9 +/- 0.7 microg/mL, p < 0.0001). Histologic analysis performed in three patients who died due to an exacerbation of IPF in the non-anticoagulant group demonstrated the features of usual interstitial pneumonia and acute lung injury. Our data suggested that plasma d-dimer levels are associated with mortality in patients with an acute exacerbation of IPF, and that anticoagulant therapy has a beneficial effect on survival in patients with IPF.Chest 10/2005; 128(3):1475-82. · 5.25 Impact Factor
Article: Thrombin differentiates normal lung fibroblasts to a myofibroblast phenotype via the proteolytically activated receptor-1 and a protein kinase C-dependent pathway.[show abstract] [hide abstract]
ABSTRACT: Myofibroblasts are ultrastructurally and metabolically distinctive fibroblasts that express smooth muscle (SM)-alpha actin and are associated with various fibrotic lesions. The present study was undertaken to investigate the myofibroblast phenotype that appears after activation of normal lung fibroblasts by thrombin. We demonstrate that thrombin induces smooth muscle-alpha actin expression and rapid collagen gel contraction by normal lung fibroblasts via the proteolytically activated receptor-1 and independent of transforming growth factor-beta pathway. Using antisense oligonucleotides we demonstrate that a decreased level of PKCepsilon abolishes SM-alpha actin expression and collagen gel contraction induced by thrombin in normal lung fibroblasts. Inhibition of PKCepsilon translocation also abolishes thrombin-induced collagen gel contraction, SM-alpha actin increase, and its organization by normal lung fibroblasts, suggesting that activation of PKCepsilon is required for these effects. In normal lung fibroblasts PKCepsilon binds to SM-alpha actin after thrombin treatment, but in activated fibroblasts derived from scleroderma lung they associate even in untreated cells. This suggests that SM-alpha actin may serve as a substrate for PKCepsilon in lung fibroblasts when activated by thrombin. We propose that thrombin differentiates normal lung fibroblasts to a myofibroblast phenotype via a PKC-dependent pathway. Thrombin-induced differentiation of normal lung fibroblasts to a myofibroblast phenotype resembles the phenotype observed in scleroderma lung fibroblasts. Therefore, we conclude that chronic exposure to thrombin after microvascular injury leads to activation of normal lung fibroblasts and to the appearance of a myofibroblast phenotype in vivo. Our study provides novel, compelling evidence that thrombin is an important mediator of the interstitial lung fibrosis associated with scleroderma.Journal of Biological Chemistry 12/2001; 276(48):45184-92. · 4.77 Impact Factor