Pleural inflammation and pleuropulmonary fibrosis may progress to irreversible thoracic dysfunction with significant morbidity and mortality. Pleural injury activates pleural mesothelial cells (PMCs) to express plasminogen activator inhibitor (PAI)-1 and inhibits fibrinolysis, promotes pleural inflammation and fibrosis. PAI-1 knockdown was reported to ablate bleomycin-induced lung fibrosis by inhibiting epithelial to mesenchymal transition (EMT). Thrombin triggers proteinase-activated receptors (PARs), induces EMT and increases PAI-1 synthesis in endothelial cells, and direct thrombin inhibition attenuates lung fibrosis. All indicate that both PAI-1 and thrombin are essential in inflammation and fibrosis. However, the role of thrombin in pleural inflammation and pleuropulmonary fibrosis and whether PAI-1 is implicated in thrombin-induced fibrogenesis have never been investigated. Our preliminary data demonstrated that thrombin increased PAI-1 expression via PAR-1/JNK/AP-1 signaling, and induced α-SMA expression and collagen synthesis in human PMCs. PAI-1 siRNA repressed thrombin-induced JNK phosphorylation, α-SMA and collagen production in PMCs. Moreover, the pleural levels of thrombin and PAI-1 were significantly elevated and correlated in inflammatory effusions and pleural fibrosis. Central hypothesis is that thrombin induces PMCs to elaborate PAI-1 that mediates fibrogenesis in inflammatory effusions. Specific Aim 1: To explore the thrombin-induced PAI-1 expression, EMT and collagen synthesis in PMCs, the activated receptors and signalings and the implication mechanism of PAI-1 in vitro (1st year). Hypothesis 1: Thrombin induces PAI-1 expression and then activates EMT and collagen synthesis 1.1. To measure the expression of PAI-1, α-SMA and collagen in PMCs induced by thrombin. 1.2. To find the activated thrombin receptors and signalings in thrombin–induced PAI-1 expression 1.3. To study the role of PAI-1 in regulation of thrombin–induced α-SMA and collagen expression Specific Aim 2: To define the clinical implication of thrombin and PAI-1 in patients with inflammatory pleural effusions and pleuropulmonary fibrosis (2nd year). Hypothesis 2: Thrombin and PAI-1 correlate with pleuropulmonary fibrosis and predict outcomes. 2.1. To measure and compare the protein levels and gene expression (mRNA) of thrombin, PAI-1, in pleural fluids among patients with inflammatory pleural effusions and pleuropulmonary fibrosis. 2.2. Link the protein levels and gene expression (mRNA) of thrombin, PAI-1, α-SMA and collagen in pleural fluids with clinical data to find a predictive biomarker. 2.3. To conduct a randomized, double blind, placebo-controlled trial with inhibitors of thrombin or PAI-1 for treatment of inflammatory pleural effusions and pleuropulmonary fibrosis. Specific Aim 3: To define the role of PAI-1 in regulation of thrombin-induced pleural inflammation and pleuropulmonary fibrosis in vivo. (3rd years). Hypothesis 3: PAI-1 mediates thrombin-induced pleuropulmonary fibrosis in vivo. 3.1 To measure the thrombin and PAI-1 levels and pleuropulmonary fibrosis in thrombin gene transfected murine models. 3.2. To examine the effect of PAI-1 siRNA on pleuropulmonary fibrosis in thrombin gene transfected murine models 3.3. To assess EMT and pleuropulmonary fibrosis in the thrombin-treated PAI-1-knockout mice.
|Effective start/end date||8/1/16 → 7/31/17|
- epithelial to mesenchymal transition
- plasminogen activator inhibitor-1
- pleural mesothelial cell
- pleuropulmonary fibrosis