Inhibition of Plasminogen Activator Inhibitor-1 Expression in Smoke-Exposed Alveolar Type II Epithelial Cells Attenuates Epithelial-Mesenchymal Transition / 결핵및호흡기질환

BACKGROUND: Smoking is a risk factor for idiopathic pulmonary fibrosis (IPF), but the mechanism of the association remains obscure. There is evidence demonstrating that plasminogen activator inhibitor-1 (PAI-1) is involved in the progression of pulmonary fibrosis. This study was to determine whether the administration of small interfering RNA (siRNA) targeting PAI-1 or PAI-1 inhibitor to the cigarette smoking extract (CSE)-exposed rat alveolar type II epithelial cells (ATII cells) limits the epithelial-mesenchymal transition (EMT). METHODS: ATII cells were isolated from lung of SD-rat using percoll gradient method and cultured with 5% CSE. The EMT was determined from the ATII cells by measuring the real-time RT PCR and western blotting after the PAI-1 siRNA transfection to the cells and after administration of tiplaxtinin, an inhibitor of PAI-1. The effect of PAI-1 inhibitor was also evaluated in the bleomycin-induced rats. RESULTS: PAI-1 was overexpressed in the smoking exposed ATII cells and was directly associated with EMT. The EMT from the ATII cells was suppressed by PAI-1 siRNA transfection or administration of tiplaxtinin. Signaling pathways for EMT by smoking extract were through the phosphorylation of SMAD2 and ERK1/2, and finally Snail expression. Tiplaxtinin also suppressed the pulmonary fibrosis and PAI-1 expression in the bleomycin-induced rats. CONCLUSION: Our data shows that CSE induces rat ATII cells to undergo EMT by PAI-1 via SMAD2-ERK1/2-Snail activation. This suppression of EMT by PAI-1 siRNA transfection or PAI-1 inhibitor in primary type II alveolar epithelial cells might be involved in the attenuation of bleomycin-induced pulmonary fibrosis in rats.

Inhibitory effect of receptor for advanced glycation end products (RAGE) on the TGF-beta-induced alveolar epithelial to mesenchymal transition

Idiopathic pulmonary fibrosis (IPF) is a lethal parenchymal lung disease characterized by myofibroblast proliferation. Alveolar epithelial cells (AECs) are thought to produce myofibroblasts through the epithelial to mesenchymal transition (EMT). Receptor for advanced glycation end products (RAGE) is a member of the immunoglobulin superfamily of cell surface receptors whose activation is associated with renal fibrosis during diabetes and liver fibrosis. RAGE is expressed at low basal levels in most adult tissues except the lung. In this study, we evaluated the interaction of ligand advanced glycation end products (AGE) with RAGE during the epithelial to myofibroblast transition in rat AECs. Our results indicate that AGE inhibited the TGF-beta-dependent alveolar EMT by increasing Smad7 expression, and that the effect was abolished by RAGE siRNA treatment. Thus, the induction of Smad7 by the AGE-RAGE interaction limits the development of pulmonary fibrosis by inhibiting TGF-beta-dependent signaling in AECs.

Inhibitory effect of CXC chemokine receptor 4 antagonist AMD3100 on bleomycin induced murine pulmonary fibrosis

CXC chemokine receptor 4 (CXCR4), which binds the stromal cell-derived factor-1 (SDF-1), has been shown to play a critical role in mobilizing the bone marrow (BM)-derived stem cells and inflammatory cells. We studied the effects of AMD3100, CXCR4 antagonist, on a murine bleomycin-induced pulmonary fibrosis model. Treatment of mice with AMD3100 in bleomycin-treated mice resulted in the decrease of SDF-1 in bronchoalveolar lavage (BAL) fluids at an early stage and was followed by the decrease of fibrocytes in the lung. AMD3100 treatment decreased the SDF-1 mRNA expression, fibrocyte numbers in the lung at an early stage (day 3) and CXCR4 expression at the later stage (day 7 and 21) after bleomycin injury. The collagen content and pulmonary fibrosis were significantly attenuated by AMD3100 treatment in later stage of bleomycin injury. AMD3100 treatment also decreased the murine mesenchymal and hematopoietic stem cell chemotaxis when either in the stimulation with bleomycin treated lung lysates or SDF-1 in vitro. In BM stem cell experiments, the phosphorylation of p38 MAPK which was induced by SDF-1 was significantly blocked by addition of AMD3100. Our data suggest that AMD3100 might be effective in preventing the pulmonary fibrosis by inhibiting the fibrocyte mobilization to the injured lung via blocking the SDF-1/CXCR4 axis.

IP-10 Decreases TNF-alpha Induced MUC5AC Expression in Human Airway Epithelial Cells: a Possible Relation with Little Sputum Production in Idiopathic Pulmonary Fibrosis / 결핵및호흡기질환

BACKGROUND: IPF is characterized by chronic, fibrosing inflammatory lung disease of unknown etiology. Typical symptoms of IPF are exertional dyspnea with nonproductive cough. Why patients with typical IPF have dry cough rather than productive cough, is unknown. IP-10 plays an important regulatory role in leukocyte trafficking into the lung. The present study investigated the effect of IP-10 in the pathogenesis of dry cough rather than productive cough in IPF patients. METHODS: IP-10 concentration was measured by ELISA from BALF of IPF patients. To evaluate the role of IP-10 in mucin expression, the expression of the MUC5AC mucin gene was measured in NCI-H292 cells, a human pulmonary mucoepidermoid carcinoma cell line, after stimulation by TNF-alpha with or without IP-10 pretreatment. EGFR-MAPK expression was also examined as a possible mechanism. RESULTS: IP-10 levels were significantly higher in the BALF of IPF patients compared to healthy controls. IP-10 pretreatment reduced TNF-alpha induced MUC5AC mucin expression by inhibiting the EGFR-MAPK signal transduction pathway in NCI-H292 cells. CONCLUSION: These findings suggest that little mucus production in IPF patients might be attributable to IP-10 overproduction, which inhibits the EGFR-MAPK signal transduction pathway required for MUC5AC mucin gene expression.