Thrombin Upregulates PAI-1 and Mesothelial-Mesenchymal Transition Through PAR-1 and Contributes to Tuberculous Pleural Fibrosis.

Cheng-Ying Hsieh,Joen-Rong Sheu,Wei-Lin Chen,Chi-Li Chung,Chih-Hao Yang,Jie-Heng Tsai

doi:10.3390/ijms20205076

Abstract

Thrombin is an essential procoagulant and profibrotic mediator. However, its implication in tuberculous pleural effusion (TBPE) remains unknown. The effusion thrombin and plasminogen activator inhibitor-1 (PAI-1) levels were measured among transudative pleural effusion (TPE, n = 22) and TBPE (n = 24) patients. Pleural fibrosis, identified as radiological residual pleural thickening (RPT) and shadowing, was measured at 12-month follow-up. Moreover, in vivo and in vitro effects of thrombin on PAI-1 expression and mesothelial–mesenchymal transition (MMT) were assessed. We demonstrated the effusion thrombin levels were significantly higher in TBPE than TPE, especially greater in TBPE patients with RPT > 10mm than those without, and correlated positively with PAI-1 and pleural fibrosis area. In carbon black/bleomycin-treated mice, knockdown of protease-activated receptor-1 (PAR-1) markedly downregulated α-smooth muscle actin (α-SMA) and fibronectin, and attenuated pleural fibrosis. In pleural mesothelial cells (PMCs), thrombin concentration-dependently increased PAI-1, α-SMA, and collagen I expression. Specifically, Mycobacterium tuberculosis H37Ra (MTBRa) induced thrombin production by PMCs via upregulating tissue factor and prothrombin, and PAR-1 silencing considerably abrogated MTBRa−stimulated PAI-1 expression and MMT. Consistently, prothrombin/PAR-1 expression was evident in the pleural mesothelium of TBPE patients. Conclusively, thrombin upregulates PAI-1 and MMT and may contribute to tuberculous pleural fibrosis. Thrombin/PAR-1 inhibition may confer potential therapy for pleural fibrosis.

Highlights

Tuberculosis (TB) remains a major global public health issue [1]
All patients with TPE were diagnosed with congestive heart failure, and to explore the profibrotic role of thrombin in tuberculous pleural effusion (TBPE), the TBPE patients were categorized into residual pleural thickening (RPT) ≤ 10 mm (n = 14) and RPT > 10 mm (n = 10) groups, based on the chest radiograph at the end of 12-month follow-up
In order to elucidate the cause of raised production of thrombin in TBPE, we examined the effect of Mycobacterium tuberculosis H37Ra (MTBRa) on tissue factor (TF) and prothrombin expression in pleural mesothelial cells (PMCs), and found that MTBRa significantly increased the mRNA and protein expression of TF and prothrombin in a concentration-dependent manner (Figure 6B–D), which may further trigger the coagulation cascade and raised the level of thrombin

Summary

Introduction

Tuberculosis (TB) remains a major global public health issue [1]. Tuberculous pleural effusion (TBPE) is the most common extrapulmonary TB and often complicates with residual pleural fibrosis that results in pulmonary restriction and dyspnea [2]. TBPE, caused by tuberculous pleural injury, is enriched with inflammatory cells, various cytokines, and coagulation factors [3]. PMCs elaborate tissue factor (TF) to activate coagulation and produce plasminogen activator inhibitor-1 (PAI-1) to suppress fibrinolysis, resulting in pleural fibrin deposition [7,8]. Recent in vitro and in vivo studies showed that, upon pleural injury, PMCs undergo mesothelial–mesenchymal transition (MMT) into myofibroblasts and secrete excess ECM to develop pleural fibrosis [9,10]. All these findings indicate that PAI-1 overexpression and mmT in PMCs are essential in pleural fibrogenesis. A recent animal study reported that PAI-1 deficiency paradoxically promotes pleural injury, mmT and organization, which highlight the key role of PAI-1 in tissue repair and merit further investigations [11]

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