IQGAP1 Regulates Actin Polymerization and Contributes to Bleomycin-Induced Lung Fibrosis.

We previously found IQ motif containing GTPase activating protein (IQGAP1) to be consistently elevated in lung fibroblasts (LF) isolated from patients with scleroderma (systemic sclerosis, SSc)-associated interstitial lung disease (ILD) and reported that IQGAP1 contributed to SSc by regulating expression and organization of α-smooth muscle actin (SMA) in LF. The aim of this study was to compare the development of ILD in the presence and absence of IQGAP1. Pulmonary fibrosis was induced in IQGAP1 knockout (KO) and wild-type (WT) mice by a single-intratracheal instillation of bleomycin. Two and three weeks later, mice were euthanized and investigated. We observed that the IQGAP1 KO mouse was characterized by a reduced rate of actin polymerization with reduced accumulation of actin in the lung compared to the WT mouse. After exposure to bleomycin, the IQGAP1 KO mouse demonstrated decreased contractile activity of LF, reduced expression of SMA, TGFß, and collagen, and lowered overall fibrosis scores compared to the WT mouse. The numbers of inflammatory cells and expression of pro-inflammatory cytokines in lung tissue were not significantly different between IQGAP1 KO and WT mice. We conclude that IQGAP1 plays an important role in the development of lung fibrosis induced by bleomycin, and the absence of IQGAP1 reduces the contractile activity of lung fibroblast and bleomycin-induced pulmonary fibrosis. Thus, IQGAP1 may be a potential target for novel anti-fibrotic therapies for lung fibrosis.

Antifibrotic efficacy of nintedanib in a cellular model of systemic sclerosis-associated interstitial lung disease.

OBJECTIVES: Nintedanib is approved for the treatment of idiopathic pulmonary fibrosis (IPF) and was demonstrated to slow disease progression in patients with IPF by reducing decline in forced vital capacity by 50%. Recently, nintedanib has been reported to exert anti-fibrotic activity on systemic sclerosis (scleroderma, SSc) skin fibroblasts and to diminish skin and lung fibrosis in mouse models. The goal of the present study was to determine the effects of nintedanib on a cellular model of SSc-associated interstitial lung disease (ILD). METHODS: Study was performed using lung fibroblasts (LF) isolated from five patients with SSc-ILD and from three control subjects. RESULTS: Nintedanib inhibited LF proliferation and migration in a concentration- and time-dependent manner. The proliferation rate of LF stimulated with PDGF in the presence of nintedanib was reduced 1.9-fold within 24 h as compared to cells stimulated with PDGF alone. Migration of SSc-ILD LF incubated with 100 nM nintedanib was reduced from 62.8±12.5% to 39.1±9.0% in the presence of PDGF and from 38.2±7.9% to 26.6±7.2% in serum-free medium. Nintedanib attenuated PDGF-induced Ca2+ efflux, reduced α-SMA promoter activity and α-SMA protein expression. Furthermore, nintedanib blocked PDGF-induced differentiation of normal LF to myofibroblasts, reduced production of collagen and fibronectin, and decreased contractility of SSc-ILD LF in both floating and fixed collagen gels. CONCLUSIONS: Our data demonstrate significant antifibrotic efficacy of nintedanib in SSc-ILD LF suggesting that nintedanib has the potential not only to prevent but also to reverse the increased activity of LF consequently attenuating excessive lung fibrosis observed in SSc-ILD.

Transforming growth factor ß1 (TGFß1)-induced CD44V6-NOX4 signaling in pathogenesis of idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a progressive clinical syndrome of fatal outcome. The lack of information about the signaling pathways that sustain fibrosis and the myofibroblast phenotype has prevented the development of targeted therapies for IPF. Our previous study showed that isolated fibrogenic lung fibroblasts have high endogenous levels of the hyaluronan receptor, CD44V6 (CD44 variant containing exon 6), which enhances the TGFß1 autocrine signaling and induces fibroblasts to transdifferentiate into myofibroblasts. NADPH oxidase 4 (NOX4) enzyme, which catalyzes the reduction of O2 to hydrogen peroxide (H2O2), has been implicated in the cardiac and lung myofibroblast phenotype. However, whether CD44V6 regulates NOX4 to mediate tissue repair and fibrogenesis is not well-defined. The present study assessed the mechanism of how TGF-ß-1-induced CD44V6 regulates the NOX4/reactive oxygen species (ROS) signaling that mediates the myofibroblast differentiation. Specifically, we found that NOX4/ROS regulates hyaluronan synthesis and the transcription of CD44V6 via an effect upon AP-1 activity. Further, CD44V6 is part of a positive-feedback loop with TGFß1/TGFßRI signaling that acts to increase NOX4/ROS production, which is required for myofibroblast differentiation, myofibroblast differentiation, myofibroblast extracellular matrix production, myofibroblast invasion, and myofibroblast contractility. Both NOX4 and CD44v6 are up-regulated in the lungs of mice subjected to experimental lung injury and in cases of human IPF. Genetic (CD44v6 shRNA) or a small molecule inhibitor (CD44v6 peptide) targeting of CD44v6 abrogates fibrogenesis in murine models of lung injury. These studies support a function for CD44V6 in lung fibrosis and offer proof of concept for therapeutic targeting of CD44V6 in lung fibrosis disorders.

Overexpression of c-Met and CD44v6 receptors contributes to autocrine TGF-ß1 signaling in interstitial lung disease.

The hepatocyte growth factor (HGF) and the HGF receptor Met pathway are important in the pathogenesis of interstitial lung disease (ILD). Alternatively spliced isoforms of CD44 containing variable exon 6 (CD44v6) and its ligand hyaluronan (HA) alter cellular function in response to interaction between CD44v6 and HGF. TGF-ß1 is the crucial cytokine that induces fibrotic action in ILD fibroblasts (ILDFbs). We have identified an autocrine TGF-ß1 signaling that up-regulates both Met and CD44v6 mRNA and protein expression. Western blot analysis, flow cytometry, and immunostaining revealed that CD44v6 and Met colocalize in fibroblasts and in tissue sections from ILD patients and in lungs of bleomycin-treated mice. Interestingly, cell proliferation induced by TGF-ß1 is mediated through Met and CD44v6. Further, cell proliferation mediated by TGF-ß1/CD44v6 is ERK-dependent. In contrast, action of Met on ILDFb proliferation does not require ERK but does require p38(MAPK). ILDFbs were sorted into CD44v6(+)/Met(+) and CD44v6(-)/Met(+) subpopulations. HGF inhibited TGF-ß1-stimulated collagen-1 and α-smooth muscle cell actin expression in both of these subpopulations by interfering with TGF-ß1 signaling. HGF alone markedly stimulated CD44v6 expression, which in turn regulated collagen-1 synthesis. Our data with primary lung fibroblast cultures with respect to collagen-1, CD44v6, and Met expressions were supported by immunostaining of lung sections from bleomycin-treated mice and from ILD patients. These results define the relationships between CD44v6, Met, and autocrine TGF-ß1 signaling and the potential modulating influence of HGF on TGF-ß1-induced CD44v6-dependent fibroblast function in ILD fibrosis.

Thrombin increases lung fibroblast survival while promoting alveolar epithelial cell apoptosis via the endoplasmic reticulum stress marker, CCAAT enhancer-binding homologous protein.

Apoptosis of alveolar epithelial cells (AECs) and survival of lung fibroblasts are critical events in the pathogenesis of pulmonary fibrosis; however, mechanisms underlying the apoptosis of AECs and the resistance of lung fibroblasts to apoptosis remain obscure. Herein, we demonstrate that the fate of these two cell types depends on the expression of CCAAT enhancer-binding homologous protein (CHOP). We observed that thrombin, which is overexpressed in scleroderma (SSc; systemic sclerosis) and other interstitial lung diseases (ILDs), increases the expression of CHOP in primary AECs and in A549 cells via an Ets1-dependent pathway. In addition, thrombin activates caspase-3 in AECs and induces apoptosis of these cells in a CHOP-dependent manner. In contrast, thrombin decreases endoplasmic reticulum stress-induced CHOP in lung fibroblasts through Myc-dependent mechanisms and protects such cells from apoptosis. Furthermore, when lung fibroblasts are transfected with recombinant CHOP, they then undergo apoptosis, even in the presence of thrombin, suggesting that CHOP signaling pathways are downstream of thrombin. In accordance with the differential effects of thrombin on AECs and lung fibroblasts, we observed strong expression of CHOP in AECs in fibrotic lung tissue isolated from patients with SSc-associated ILD (SSc-ILD), but not in lung myofibroblasts nor in normal lung tissue. Expression of CHOP in SSc lung is accompanied by positive staining for the thrombin receptor, protease-activated receptor-1, and for terminal deoxynucleotidyl transferase dUTP nick end labeling, suggesting roles for both thrombin and CHOP in AEC apoptosis in SSc-ILD. We conclude that regulation of CHOP by thrombin directs AECs toward apoptosis while promoting survival of lung fibroblasts, ultimately contributing to the persistent fibroproliferation seen in SSc-ILD and other fibrosing lung diseases.

Recent advances in understanding the pathogenesis of scleroderma-interstitial lung disease.

Systemic sclerosis (scleroderma, SSc) is a heterogeneous autoimmune connective tissue disease of unknown etiology. Interstitial lung disease (ILD) is a frequent complication, and a significant contributor to morbidity and mortality among SSc patients. SSc-ILD most commonly occurs within 10 years of diagnosis, and may be seen in patients with either the limited or diffuse cutaneous subset of SSc. SSc-ILD is a multifaceted disease process in which different factors and pathways are involved. Aberrant function of a variety of lung cells, cytokines, growth factors, peptides, and bioactive proteins, in combination with genetic and epigenetic regulators, have crucial functions in the pathogenesis of this disease. Here we present our view on recent advances regarding the pathogenesis of SSc-ILD.

Critical Role of LMCD1 in Promoting Profibrotic Characteristics of Lung Myofibroblasts in Experimental and Scleroderma-Associated Lung Fibrosis.

OBJECTIVE: Interstitial lung disease (ILD) is a serious complication and leading cause of mortality in patients with systemic sclerosis (SSc). In this study, we explored the role of LIM and cysteine-rich domains protein 1 (LMCD1) as a novel factor in the pathogenesis of SSc-related ILD (SSc-ILD). METHODS: The expression and effects of LMCD1 were studied in lung tissue samples and fibroblasts from SSc-ILD patients and control subjects as well as in lung tissue samples from animal models. RESULTS: LMCD1 was consistently elevated in lung tissue samples and in fibroblasts isolated from SSc-ILD patients as compared to controls. Additionally, LMCD1 was found to be highly expressed in the lung in the fibroblast-specific protein (FSP)-driven, constitutively active transforming growth factor ß receptor type I (TGFßR1) transgenic mouse model of ILD and the bleomycin-induced mouse model of ILD. In lung fibroblasts from SSc-ILD patients, LMCD1 is an essential factor for the TGFß-induced generation of type I collagen, fibronectin, and α-smooth muscle actin (α-SMA). Depletion of LMCD1 by small interfering RNA reduced the expression of extracellular matrix proteins and lowered transcriptional activity and expression of α-SMA, as well as decreased the proliferation and contractile activity of SSc-ILD lung fibroblasts. In dense fibrotic areas of affected lung tissue, lung LMCD1 colocalized with α-SMA. In cultured scleroderma lung fibroblasts, LMCD1 colocalized and interacted with serum response factor which mediates LMCD1-induced contractile activity of lung fibroblasts. CONCLUSION: Our study identifies LMCD1 as a profibrotic molecule contributing to the activation of myofibroblasts and the persistent fibroproliferation observed in SSc-ILD. Thus, LMCD1 may be a potential novel therapeutic target for patients with SSc-ILD.

Antiinflammatory and antifibrotic effects of the oral direct thrombin inhibitor dabigatran etexilate in a murine model of interstitial lung disease.

OBJECTIVE: 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. METHODS: 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. RESULTS: 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 ß1 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. CONCLUSION: 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.

Differential DNA Methylation Landscape in Skin Fibroblasts from African Americans with Systemic Sclerosis.

The etiology and reasons underlying the ethnic disparities in systemic sclerosis (SSc) remain unknown. African Americans are disproportionally affected by SSc and yet are underrepresented in research. The aim of this study was to comprehensively investigate the association of DNA methylation levels with SSc in dermal fibroblasts from patients of African ancestry. Reduced representation bisulfite sequencing (RRBS) was performed on primary dermal fibroblasts from 15 SSc patients and 15 controls of African ancestry, and over 3.8 million CpG sites were tested for differential methylation patterns between cases and controls. The dermal fibroblasts from African American patients exhibited widespread reduced DNA methylation. Differentially methylated CpG sites were most enriched in introns and intergenic regions while depleted in 5' UTR, promoters, and CpG islands. Seventeen genes and eleven promoters showed significant differential methylation, mostly in non-coding RNA genes and pseudogenes. Gene set enrichment analysis (GSEA) and gene ontology (GO) analyses revealed an enrichment of pathways related to interferon signaling and mesenchymal differentiation. The hypomethylation of DLX5 and TMEM140 was accompanied by these genes' overexpression in patients but underexpression for lncRNA MGC12916. These data show that differential methylation occurs in dermal fibroblasts from African American patients with SSc and identifies novel coding and non-coding genes.

Progression of Interstitial Lung Disease in Systemic Sclerosis: The Importance of Pneumoproteins Krebs von den Lungen 6 and CCL18.

OBJECTIVE: To investigate the relationship between Krebs von den Lungen 6 (KL-6) and CCL18 levels and the severity and progression of systemic sclerosis (SSc)-related interstitial lung disease (ILD). METHODS: Patients enrolled in the Scleroderma Lung Study II (cyclophosphamide [CYC] versus mycophenolate mofetil [MMF]) were included. Baseline and 12-month plasma samples were analyzed by enzyme-linked immunosorbent assay to assess CCL18 and KL-6 levels. The forced vital capacity (FVC) and the diffusing capacity for carbon monoxide (DLco) were measured every 3 months. Joint models were created to investigate the relationship between baseline CCL18 and KL-6 levels and the course of the FVC and DLco over 1 year according to treatment arm. RESULTS: Baseline KL-6 and CCL18 levels each correlated with the extent of radiographic fibrosis. Levels of both CCL18 and KL-6 declined significantly at 1 year. In both treatment arms (n = 71 for CYC, n = 62 for MMF), a higher baseline KL-6 level predicted progression of ILD based on the course of FVC (P = 0.024 for CYC; P = 0.005 for MMF) and DLco (P < 0.001 for CYC; P = 0.004 for MMF) over 1 year. A higher baseline CCL18 level predicted progression of ILD based on the course of the FVC (P < 0.001 for CYC; P = 0.007 for MMF) and DLco (P = 0.001 for CYC; P < 0.001 for MMF) over 1 year, as well as mortality (P = 0.0008 for CYC arm only). CONCLUSION: In a rigorously conducted clinical trial for SSc-related ILD, KL-6 and CCL18 levels correlated with ILD severity and declined with immunosuppression. Patients with higher baseline KL-6 and CCL18 levels were more likely to experience disease progression despite treatment. KL-6 and CCL18 levels could be used to identify patients with a progressive ILD phenotype who may benefit from a more aggressive initial treatment approach.

Establishment of an indirect ELISA for detection of the novel antifibrotic peptide M10.

OBJECTIVE: M10 is a ten amino acid peptide generated from the intracellular cytoplasmic tail of the hepatocyte growth factor (HGF) receptor c-Met following cleavage by caspase-3. Recently we reported that M10 interacts with Smad2 and demonstrates antifibrotic properties in vitro and in vivo and can be advanced into a novel antifibrotic remedy. The current study was undertaken to develop an immunoassay to measure M10 concentration in biological specimens. EXPERIMENTAL DESIGN: An Indirect Enzyme-Linked Immunosorbent Assay (ELISA) for detection of M10 in biological fluids was developed using pharmaceutical grade synthetic M10 as a calibrator and commercially available anti-c-Met C12 antibody. RESULTS: M10 ELISA specifically detected in plasma M10, but not a scrambled peptide, following a single intraperitoneal administration of M10 (1mg/kg) to mice. The detection limit was 9.6 ng/ml, and the measuring limit was between 15 ng/ml and 200 ng/ml. The recovery limits of M10 were between 80% and 120%; intra-assay coefficient of variation was between 5.3% and 6.3%; inter-assay coefficient of variation was between 5.0% and 8.0% over the buffer concentration tested in the range from 15 ng /ml to 250 ng /ml. The peak of M10 concentration following a single intraperitoneal injection (1mg/kg) was achieved within 6 hours and declined to minimal levels by 48 hours. The experimentally obtained half-life for M10 was comparable to the theoretically predicted half-life for M10. CONCLUSIONS: We have established a highly sensitive ELISA to detect the antifibrotic peptide M10 in plasma samples, which should prove to be a novel tool to study the pharmacokinetics and efficacy of M10 in the treatment of fibroproliferative disorders.

Novel lung imaging biomarkers and skin gene expression subsetting in dasatinib treatment of systemic sclerosis-associated interstitial lung disease.

BACKGROUND: There are no effective treatments or validated clinical response markers in systemic sclerosis (SSc). We assessed imaging biomarkers and performed gene expression profiling in a single-arm open-label clinical trial of tyrosine kinase inhibitor dasatinib in patients with SSc-associated interstitial lung disease (SSc-ILD). METHODS: Primary objectives were safety and pharmacokinetics. Secondary outcomes included clinical assessments, quantitative high-resolution computed tomography (HRCT) of the chest, serum biomarker assays and skin biopsy-based gene expression subset assignments. Clinical response was defined as decrease of >5 or >20% from baseline in the modified Rodnan Skin Score (MRSS). Pulmonary function was assessed at baseline and day 169. RESULTS: Dasatinib was well-tolerated in 31 patients receiving drug for a median of nine months. No significant changes in clinical assessments or serum biomarkers were seen at six months. By quantitative HRCT, 65% of patients showed no progression of lung fibrosis, and 39% showed no progression of total ILD. Among 12 subjects with available baseline and post-treatment skin biopsies, three were improvers and nine were non-improvers. Improvers mapped to the fibroproliferative or normal-like subsets, while seven out of nine non-improvers were in the inflammatory subset (p = 0.0455). Improvers showed stability in forced vital capacity (FVC) and diffusing capacity for carbon monoxide (DLCO), while both measures showed a decline in non-improvers (p = 0.1289 and p = 0.0195, respectively). Inflammatory gene expression subset was associated with higher baseline HRCT score (p = 0.0556). Non-improvers showed significant increase in lung fibrosis (p = 0.0313). CONCLUSIONS: In patients with SSc-ILD dasatinib treatment was associated with acceptable safety profile but no significant clinical efficacy. Patients in the inflammatory gene expression subset showed increase in skin fibrosis, decreasing pulmonary function and worsening lung fibrosis during the study. These findings suggest that target tissue-specific gene expression analyses can help match patients and therapeutic interventions in heterogeneous diseases such as SSc, and quantitative HRCT is useful for assessing clinical outcomes. TRIAL REGISTRATION: Clinicaltrials.gov NCT00764309.

M10, a caspase cleavage product of the hepatocyte growth factor receptor, interacts with Smad2 and demonstrates antifibrotic properties in vitro and in vivo.

Hepatocyte growth factor receptor, also known as cellular mesenchymal-epithelial transition factor (c-MET, MET), is an important antifibrotic molecule that protects various tissues, including lung, from injury and fibrosis. The intracellular cytoplasmic tail of MET contains a caspase-3 recognition motif "DEVD-T" that on cleavage by caspase-3 generates a 10-amino acid peptide, TRPASFWETS, designated as "M10". M10 contains at its N-terminus the uncharged amino acid proline (P) directly after a cationic amino acid arginine (R) which favors the transport of the peptide through membranes. M10, when added to cell culture medium, remains in the cytoplasm and nuclei of cells for up to 24 hours. M10 effectively decreases collagen in both scleroderma and TGFß-stimulated normal lung and skin fibroblasts. M10 interacts with the Mad Homology 2 domain of Smad2 and inhibits TGFß-induced Smad2 phosphorylation, suggesting that the antifibrotic effects of M10 are mediated in part by counteracting Smad-dependent fibrogenic pathways. In the bleomycin murine model of pulmonary fibrosis, M10 noticeably reduced lung inflammation and fibrosis. Ashcroft fibrosis scores and lung collagen content were significantly lower in bleomycin-treated mice receiving M10 as compared with bleomycin-treated mice receiving scrambled peptide. We conclude that M10 peptide interacts with Smad2 and demonstrates strong antifibrotic effects in vitro and in vivo in an animal model of lung fibrosis and should be considered as a potential therapeutic agent for systemic sclerosis and other fibrosing diseases.

D1398G Variant of MET Is Associated with Impaired Signaling of Hepatocyte Growth Factor in Alveolar Epithelial Cells and Lung Fibroblasts.

Pulmonary fibrosis represents the terminal stage of a diverse group of lung diseases including scleroderma associated interstitial lung disease. The molecular mechanisms underlying the pathogenesis of lung fibrosis are not well understood and there is a great need for more effective treatment for this lethal disease. We recently discovered a small fragment of hepatocyte growth factor (HGF) receptor MET as a peptide designated "M10," with strong antifibrotic properties. Furthermore, we showed that aspartic acid at position 1398 of MET is essential for M10 generation. The current study was undertaken to investigate the D1398G variant of MET in which aspartic acid at position 1398 was mutated to glycine resulting in loss of M10. We demonstrate that lung fibroblasts, A549, and primary alveolar epithelial cells (AEC) expressing D1398G MET exhibit reduced auto-phosphorylation on tyrosine residues and reduced activation of Ras and MAPK. HGF treatment of scleroderma lung fibroblasts as well as HGF treatment of TGFß-treated normal lung fibroblasts transfected with wild type MET is associated with decreased collagen, connective tissue growth factor (CTGF, CCN2) and smooth muscle α-actin (SMA). However, HGF has no such effects in cells transfected with MET D1398G. Cisplatin- and FasL-induced apoptosis is significantly reduced in AEC transfected with MET wild type, but not in AEC transfected with MET D1398G. We conclude that the D1398G variant of MET is associated with compromised phosphorylation and impaired HGF signaling in lung fibroblasts and AEC, two cell types implicated in the pathogenesis of pulmonary fibrosis associated with scleroderma. Ongoing studies will explore the frequency of this variant and its relationship to pulmonary outcomes in scleroderma patients.

The PPARγ Agonist Rosiglitazone Is Antifibrotic for Scleroderma Lung Fibroblasts: Mechanisms of Action and Differential Racial Effects.

We present novel data demonstrating that the expression of PPARγ is reduced in lung fibroblasts from black SSc-ILD patients as compared to white patients. Activating PPARγ with the agonist rosiglitazone increased the expression of MMP-1 and inhibited collagen type I in lung fibroblasts isolated from white, but not black, SSc-ILD patients. Blocking the c-Met receptor abolishes rosiglitazone's effects on collagen and MMP-1 in lung fibroblasts isolated from white SSc-ILD patients, while augmenting the expression of the c-Met receptor in fibroblasts from black SSc-ILD patients replicates the effects of rosiglitazone seen in whites. We conclude that PPARγ agonists warrant consideration as potential antifibrotic drugs in patients with SSc-ILD. Differential therapeutic effects might be anticipated especially relative to racial differences and the functional expression of the c-Met receptor.

Coagulation and autoimmunity in scleroderma interstitial lung disease.

OBJECTIVES: Interstitial lung disease in systemic sclerosis (SSc-ILD) is often an irreversible and progressive fibrosing process that now is the leading cause of scleroderma-related deaths. In this review we present our current understanding of the role played by coagulation and particularly by thrombin in autoimmune-mediated tissue injury and fibrosis, mainly as it relates to SSc-ILD. METHODS: We used PubMed to search for articles published up to October 2010 for keywords referring to autoimmunity, coagulation, pulmonary fibrosis, and scleroderma. RESULTS: SSc-ILD is an autoimmune disease associated with lymphocyte activation and release of various cytokines and growth factors. The production of autoantibodies is a central feature in SSc. Activation of the coagulation cascade with release of thrombin is 1 of the earliest events following tissue injury. Thrombin contributes to autoimmune responses by activating of pathogenic Th2 lymphocyte profile in SSc. Thrombin also modulates tissue repair responses, stimulates transformation of epithelial cells, endothelial cells, and fibroblasts into myofibroblast phenotype, and induces secretion of several pro-immune and profibrotic factors, which serve as antigens for pathogenic autoantibodies production in SSc-ILD. CONCLUSIONS: The identification of links between autoimmunity and coagulation would provide new insights into the pathogenesis of pulmonary fibrosis associated with autoimmune diseases and further acknowledge the importance of thrombin in the development of SSc-ILD.

Dabigatran, a direct thrombin inhibitor, demonstrates antifibrotic effects on lung fibroblasts.

OBJECTIVE: Myofibroblasts are the principal mesenchymal cells responsible for tissue remodeling, collagen deposition, and the restrictive nature of lung parenchyma associated with pulmonary fibrosis. We previously reported that thrombin activates protease-activated receptor 1 (PAR-1) and induces a myofibroblast phenotype in normal lung fibroblasts resembling the phenotype of scleroderma lung myofibroblasts. We undertook this study to investigate whether a selective direct thrombin inhibitor, dabigatran, interferes with signal transduction in human lung fibroblasts induced by thrombin and mediated via PAR-1. METHODS: Lung fibroblast proliferation was analyzed using the Quick Cell Proliferation Assay. Expression and organization of alpha-smooth muscle actin (alpha-SMA) was studied by immunofluorescence staining and immunoblotting. Contractile activity of lung fibroblasts was measured by a collagen gel contraction assay. Connective tissue growth factor (CTGF) and type I collagen expression was analyzed on Western blots. RESULTS: Dabigatran, at concentrations of 50-1,000 ng/ml, inhibited thrombin-induced cell proliferation, alpha-SMA expression and organization, and the production of collagen and CTGF in normal lung fibroblasts. Moreover, when treated with dabigatran (1 microg/ml), scleroderma lung myofibroblasts produced 6-fold less alpha-SMA, 3-fold less CTGF, and 2-fold less type I collagen compared with untreated cells. CONCLUSION: Dabigatran restrains important profibrotic events in lung fibroblasts and warrants study as a potential antifibrotic drug for the treatment of fibrosing lung diseases such as scleroderma lung disease and idiopathic pulmonary fibrosis.

Proteomic analysis of CTGF-activated lung fibroblasts: identification of IQGAP1 as a key player in lung fibroblast migration.

Connective tissue growth factor (CTGF, CCN2) is overexpressed in lung fibroblasts isolated from patients with interstitial lung disease (ILD) and systemic sclerosis (SSc, scleroderma) and is considered to be a molecular marker of fibrosis. To understand the significance of elevated CTGF, we investigated the changes in lung fibroblast proteome in response to CTGF overexpression. Using 2-dimensional gel electrophoresis followed by in-gel proteolytic digestion and mass spectrometric analysis, we identified 13 proteins affected by CTGF. Several of the CTGF-induced proteins, such as pro-alpha (I) collagen and cytoskeletal proteins vinculin, moesin, and ezrin, are known to be elevated in pulmonary fibrosis, whereas 9 of 13 proteins have not been studied in pulmonary fibrosis and are, therefore, novel CTGF-responsive molecules that may have important roles in ILD. Our study demonstrates that 1 of the novel CTGF-induced proteins, IQ motif containing GTPase activating protein (IQGAP) 1, is elevated in lung fibroblasts isolated from scleroderma patients with ILD. IQGAP1 is a scaffold protein that plays a pivotal role in regulating migration of endothelial and epithelial cells. Scleroderma lung fibroblasts and normal lung fibroblasts treated with CTGF demonstrated increased rate of migration in a wound healing assay. Depletion of IQGAP1 expression by small interfering RNA inhibited CTGF-induced migration and MAPK ERK1/2 phosphorylation in lung fibroblasts. MAPK inhibitor U0126 decreased CTGF-induced cell migration and did not interfere with CTGF-induced IQGAP1 expression, suggesting that MAPK pathway is downstream of IQGAP1. These findings further implicate the importance of CTGF in lung tissue repair and fibrosis and propose that CTGF-induced migration of lung fibroblasts to the damaged tissue is mediated via IQGAP1 and MAPK signaling pathways.