Tissue factor expression and fibrin deposition in the lungs of patients with idiopathic pulmonary fibrosis and systemic sclerosis

Lipid nanoparticles for pulmonary fibrosis: A comprehensive review

Idiopathic pulmonary fibrosis (IPF) is a fatal progressive and irreversible ailment associated with the proliferation of fibroblast and accumulation of extracellular matrix (ECM) with gradual scarring of lung tissue. Despite several research studies, the treatments available are not efficient enough for the reversal of the disease and are constantly in progress. No drugs other than Pirfenidone and Nintedanib have been approved for the treatment of IPF, necessitating the exploration of novel therapeutic strategies. Recently, lipid-based nanoparticles (LNPs) have drawn more attention because of their potential to enhance the solubility of drugs, cross biological barriers of the lungs and specifically target lung fibrotic tissues, overcoming various challenges in treating IPF. LNPs offer a versatile platform to encapsulate a wide range of drugs, both hydrophilic and lipophilic, improving their bioavailability, allowing sustained release and reducing toxicity, which radiates their significant role in addressing the complexities of IPF. This review summarizes the pathogenesis and conventional treatment of idiopathic pulmonary fibrosis, along with their drawbacks. The review focuses on different types of lipid-based nanoparticles that have been tested in the treatment of idiopathic pulmonary fibrosis, including nanoemulsions, liposomes, solid lipid nanoparticles, nanostructured lipid carriers, niosomes and lipid-polymer hybrid nanoparticles. The review also highlights the future prospects that can offer a potential approach for developing novel strategies to treat idiopathic pulmonary fibrosis.

Usefulness of Combined Measurement of Surfactant Protein D, Thrombin-Antithrombin III Complex, D-Dimer, and Plasmin-α2 Plasmin Inhibitor Complex in Acute Exacerbation of Interstitial Lung Disease: A Retrospective Cohort Study

Background/Objectives: The coagulation cascade due to tissue damage is considered to be one of the causes of poor prognostic outcomes in patients with acute exacerbations of interstitial lung disease (AE-ILD). This study aimed to confirm coagulopathy in AE-ILD by evaluating the differences in the clinical characteristics of coagulation/fibrinolysis markers between stable ILD and AE-ILD. Methods: Overall, 81 patients were enrolled in this retrospective study and categorized into the following two groups: a chronic ILD group comprising 63 outpatients and an acute ILD group comprising 18 inpatients diagnosed with AE-ILD. Serum markers, including thrombin-antithrombin III complex (TAT), D-dimer, plasmin-α2 plasmin inhibitor complex (PIC), and surfactant protein D (SP-D), were compared between the groups. Results: Among the 18 patients with acute ILD, 17 did not meet the International Society of Thrombosis and Hemostasis scoring system for disseminated intravascular coagulation. In acute ILD, the SP-D levels were statistically significantly positively correlated with TAT, D-dimer, and PIC levels, while the Krebs von den Lungen 6 (KL-6) levels showed no correlation with any of these coagulation/fibrinolytic markers. A positive correlation was observed between SP-D levels and TAT, D-dimer, and PIC levels in acute ILD. Serum TAT, D-dimer, and PIC all showed good area under the receiver operating characteristic (ROC) curve (AUC) values in ROC analysis for the diagnosis of acute ILD. Conclusions: In the clinical setting of AE-ILD, it may be important to focus not only on alveolar damage markers such as SP-D but also on coagulation/fibrinolytic markers including TAT, D-dimer, and PIC.

Beyond epithelial damage: vascular and endothelial contributions to idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive scarring disease of the lung with poor survival. The incidence and mortality of IPF are rising, but treatment remains limited. Currently, two drugs can slow the scarring process but often at the expense of intolerable side effects, and without substantially changing overall survival. A better understanding of mechanisms underlying IPF is likely to lead to improved therapies. The current paradigm proposes that repetitive alveolar epithelial injury from noxious stimuli in a genetically primed individual is followed by abnormal wound healing, including aberrant activity of extracellular matrix-secreting cells, with resultant tissue fibrosis and parenchymal damage. However, this may underplay the importance of the vascular contribution to fibrogenesis. The lungs receive 100% of the cardiac output, and vascular abnormalities in IPF include (a) heterogeneous vessel formation throughout fibrotic lung, including the development of abnormal dilated vessels and anastomoses; (b) abnormal spatially distributed populations of endothelial cells (ECs); (c) dysregulation of endothelial protective pathways such as prostacyclin signaling; and (d) an increased frequency of common vascular and metabolic comorbidities. Here, we propose that vascular and EC abnormalities are both causal and consequential in the pathobiology of IPF and that fuller evaluation of dysregulated pathways may lead to effective therapies and a cure for this devastating disease.

Vorapaxar proven to be a promising candidate for pulmonary fibrosis by intervening in the PAR1/JAK2/STAT1/3 signaling pathway-an experimental in vitro and vivo study

Idiopathic pulmonary fibrosis (IPF) is a lethal lung disease, and its 5-year mortality rate is even higher than the mortality rate of some cancers. Fibrosis can cause irreversible damage to lung structure and function. Treatment options for IPF remain limited, and there is an urgent need to develop effective therapeutic drugs. Protease activated receptor-1 (PAR-1) is a G-protein-coupled receptor and is considered a potential target for the treatment of fibrotic diseases. Vorapaxar is a clinically approved PAR-1 antagonist for cardiovascular protection. The purpose of this study was to explore the potential effect and mechanism of Vorapaxar on pulmonary fibrosis in vivo and in vitro. In the experimental animal model, Vorapaxar can effectively alleviate bleomycin (BLM)-induced pulmonary fibrosis. Treatment with 2.5, 5 or 10 mg/kg Vorapaxar once a day reduced the degree of fibrosis in a dose-dependent manner. The expression of fibronectin, collagen and α smooth muscle actin decreased significantly at the messenger RNA (mRNA) and protein levels in treated mice. In vitro, our results showed that Vorapaxar could inhibit the activation of fibroblasts induced by thrombin in a dose-dependent manner. In terms of mechanism, Vorapaxar inhibits the signal transduction of JAK2/STAT1/3 by inhibiting the activation of protease activated receptor 1, which reduces the expression of HSP90β and the interaction between HSP90β and transforming growth factor-β (TGFβ) receptor II and inhibits the TGFβ/Smad signaling pathway. In conclusion, Vorapaxar inhibits the activation of pulmonary fibroblasts induced by thrombin by targeting protease activated receptor 1 and alleviates BLM-induced pulmonary fibrosis in mice.

Extensive and Persistent Extravascular Dermal Fibrin Deposition Characterizes Systemic Sclerosis

Systemic sclerosis (SSc) is an autoimmune disease characterized by progressive multiorgan fibrosis. While the cause of SSc remains unknown, a perturbed vasculature is considered a critical early step in the pathogenesis. Using fibrinogen as a marker of vascular leakage, we found extensive extravascular fibrinogen deposition in the dermis of both limited and diffuse systemic sclerosis disease, and it was present in both early and late-stage patients. Based on a timed series of excision wounds, retention on the fibrin deposit of the splice variant domain, fibrinogen αEC, indicated a recent event, while fibrin networks lacking the αEC domain were older. Application of this timing tool to SSc revealed considerable heterogeneity in αEC domain distribution providing unique insight into disease activity. Intriguingly, the fibrinogen-αEC domain also accumulated in macrophages. These observations indicate that systemic sclerosis is characterized by ongoing vascular leakage resulting in extensive interstitial fibrin deposition that is either continually replenished and/or there is impaired fibrin clearance. Unresolved fibrin deposition might then incite chronic tissue remodeling.

HER2 drives lung fibrosis by activating a metastatic cancer signature in invasive lung fibroblasts

Progressive tissue fibrosis, including idiopathic pulmonary fibrosis (IPF), is characterized by excessive recruitment of fibroblasts to sites of tissue injury and unremitting extracellular matrix deposition associated with severe morbidity and mortality. However, the molecular mechanisms that control progressive IPF have yet to be fully determined. Previous studies suggested that invasive fibroblasts drive disease progression in IPF. Here, we report profiling of invasive and noninvasive fibroblasts from IPF patients and healthy donors. Pathway analysis revealed that the activated signatures of the invasive fibroblasts, the top of which was ERBB2 (HER2), showed great similarities to those of metastatic lung adenocarcinoma cancer cells. Activation of HER2 in normal lung fibroblasts led to a more invasive genetic program and worsened fibroblast invasion and lung fibrosis, while antagonizing HER2 signaling blunted fibroblast invasion and ameliorated lung fibrosis. These findings suggest that HER2 signaling may be a key driver of fibroblast invasion and serve as an attractive target for therapeutic intervention in IPF.

The Therapeutic Potential of Anticoagulation in Organ Fibrosis

Fibrosis, also known as organ scarring, describes a pathological stiffening of organs or tissues caused by increased synthesis of extracellular matrix (ECM) components. In the past decades, mounting evidence has accumulated showing that the coagulation cascade is directly associated with fibrotic development. Recent findings suggest that, under inflammatory conditions, various cell types (e.g., immune cells) participate in the coagulation process causing pathological outcomes, including fibrosis. These findings highlighted the potential of anticoagulation therapy as a strategy in organ fibrosis. Indeed, preclinical and clinical studies demonstrated that the inhibition of blood coagulation is a potential intervention for the treatment of fibrosis across all major organs (e.g., lung, liver, heart, and kidney). In this review, we aim to summarize our current knowledge on the impact of components of coagulation cascade on fibrosis of various organs and provide an update on the current development of anticoagulation therapy for fibrosis.

Contracting scars from fibrin drops

This paper describes a microscale fibroplasia and contraction model that is based on fibrin-embedded lung fibroblasts and provides a convenient visual readout of fibrosis. Cell-laden fibrin microgel drops are formed by aqueous two-phase microprinting. The cells deposit extracellular matrix (ECM) molecules such as collagen while fibrin is gradually degraded. Ultimately, the cells contract the collagen-rich matrix to form a compact cell-ECM spheroid. The size of the spheroid provides the visual readout of the extent of fibroplasia. Stimulation of this wound-healing model with the profibrotic cytokine TGF-β1 leads to an excessive scar formation response that manifests as increased collagen production and larger cell-ECM spheroids. Addition of drugs also shifted the scarring profile: the FDA-approved fibrosis drugs (nintedanib and pirfenidone) and a PAI-1 inhibitor (TM5275) significantly reduced cell-ECM spheroid size. Not only is the assay useful for evaluation of antifibrotic drug effects, it is relatively sensitive; one of the few in vitro fibroplasia assays that can detect pirfenidone effects at submillimolar concentrations. Although this paper focuses on lung fibrosis, the approach opens opportunities for studying a broad range of fibrotic diseases and for evaluating antifibrotic therapeutics.

Coagulation Factor-XII induces interleukin-6 by primary lung fibroblasts: A role in idiopathic pulmonary fibrosis?

Background The mechanisms driving idiopathic pulmonary fibrosis (IPF) remain undefined, however it is postulated that coagulation imbalances may play a role. The impact of blood-derived clotting factors, including factor XII (FXII) has not been investigated in the context of IPF. Methods Plasma levels of FXII were measured by ELISA in patients with IPF and age-matched healthy donors. Expression of FXII in human lung tissue was quantified using multiplex immunohistochemistry and western blotting. Mechanistic investigation of FXII activity was assessed in vitro on primary lung fibroblasts using qPCR and specific receptor/FXII inhibition. The functional outcome of FXII on fibroblast migration was examined by high-content image analysis. Findings Compared to 35 healthy donors, plasma levels of FXII were not higher in IPF (n=27, p>0·05). Tissue FXII was elevated in IPF (n=11) and increased numbers of FXII+ cells were found in IPF (n=8) lung tissue compared to non-diseased controls (n=6, p<0·0001). Activated FXII induced IL6 mRNA and IL-6 protein in fibroblasts that was blocked by anti-FXII antibody, CSL312. FXII-induced IL-6 production via PAR-1 and NF-kB. FXII induced migration of fibroblasts in a concentration-dependent manner. Interpretation FXII is normally confined to the circulation but leaks from damaged vessels into the lung interstitium in IPF where it 1) induces IL-6 production and 2) enhances migration of resident fibroblasts, critical events that drive chronic inflammation and therefore, contribute to fibrotic disease progression. Targeting FXII-induced fibroblastic processes in IPF may ameliorate pulmonary fibrosis. Funding National Health and Medical Research Council CRE in Lung Fibrosis and CSL Ltd.

Diagnostic Impact of Radiological Findings and Extracellular Vesicles: Are We Close to Radiovesicolomics?

Simple Summary

Over the years, diagnostic tests such as in radiology and flow cytometry have become more and more powerful in the constant struggle against different pathologies, some of which are life-threatening. The possibility of using these “weapons” in a conjugated manner could result in higher healing and prevention rates, and a decrease in late diagnosis diseases. Different correlations among pathologies, extracellular vesicles (EVs), and radiological findings were recently demonstrated by many authors. Together with the increasing importance of “omics” sciences, and artificial intelligence in this new century, the perspective of a new research field called “radiovesicolomics” could be the missing link, enabling a different approach to disease diagnosis and treatment.

Abstract

Currently, several pathologies have corresponding and specific diagnostic and therapeutic branches of interest focused on early and correct detection, as well as the best therapeutic approach. Radiology never ceases to develop newer technologies in order to give patients a clear, safe, early, and precise diagnosis; furthermore, in the last few years diagnostic imaging panoramas have been extended to the field of artificial intelligence (AI) and machine learning. On the other hand, clinical and laboratory tests, like flow cytometry and the techniques found in the “omics” sciences, aim to detect microscopic elements, like extracellular vesicles, with the highest specificity and sensibility for disease detection. If these scientific branches started to cooperate, playing a conjugated role in pathology diagnosis, what could be the results? Our review seeks to give a quick overview of recent state of the art research which investigates correlations between extracellular vesicles and the known radiological features useful for diagnosis.

Associations of D-Dimer with Computed Tomographic Lung Abnormalities, Serum Biomarkers of Lung Injury, and Forced Vital Capacity: MESA Lung Study

Rationale: The coagulation cascade may play a role in the pathogenesis of interstitial lung disease through increased production of thrombin and fibrin deposition. Whether circulating coagulation cascade factors are linked to lung inflammation and scarring among community-dwelling adults is unknown. Objectives: To test the hypothesis that higher baseline D-dimer concentrations are associated with markers of early lung injury and scarring. Methods: Using the MESA (Multi-Ethnic Study of Atherosclerosis) cohort (n = 6,814), we examined associations of baseline D-dimer concentrations with high attenuation areas from examination 1 (2000-2002; n = 6,184) and interstitial lung abnormalities from examination 5 computed tomographic (CT) scans (2010-2012; n = 2,227), and serum MMP-7 (matrix metalloproteinase-7) and SP-A (surfactant protein-A) from examination 1 (n = 1,098). We examined longitudinal change in forced vital capacity (FVC) from examinations 3-6 (2004-2018, n = 3,562). We used linear logistic regression and linear mixed models to examine associations and adjust for potential confounders. Results: The mean (standard deviation) age of the cohort was 62 (10) years, and the D-dimer concentration was 0.35 (0.69) ug/ml. For every 10% increase in D-dimer concentration, there was an increase in high attenuation area percentage of 0.27 (95% confidence interval (CI), 0.08-0.47) after adjustment for covariates. Associations were stronger among those older than 65 years (P values for interaction < 0.001). A 10% increase in D-dimer concentration was associated with an odds ratio of 1.05 for interstitial lung abnormalities (95% CI, 0.99-1.11). Higher D-dimer concentrations were associated with higher serum MMP-7 and a faster decline in FVC. D-dimer was not associated with SP-A. Conclusions: Higher D-dimer concentrations were associated with a greater burden of lung parenchymal abnormalities detected on CT scan, MMP-7, and FVC decline among community-dwelling adults.

Venous Thromboembolic Disease in Chronic Inflammatory Lung Diseases: Knowns and Unknowns

Persistent inflammation within the respiratory tract underlies the pathogenesis of numerous chronic pulmonary diseases. There is evidence supporting that chronic lung diseases are associated with a higher risk of venous thromboembolism (VTE). However, the relationship between lung diseases and/or lung function with VTE is unclear. Understanding the role of chronic lung inflammation as a predisposing factor for VTE may help determine the optimal management and aid in the development of future preventative strategies. We aimed to provide an overview of the relationship between the most common chronic inflammatory lung diseases and VTE. Asthma, chronic obstructive pulmonary disease, interstitial lung diseases, or tuberculosis increase the VTE risk, especially pulmonary embolism (PE), compared to the general population. However, high suspicion is needed to diagnose a thrombotic event early as the clinical presentation inevitably overlaps with respiratory disorders. PE risk increases with disease severity and exacerbations. Hence, hospitalized patients should be considered for thromboprophylaxis administration. Conversely, all VTE patients should be asked for lung comorbidities before determining anticoagulant therapy duration, as those patients are at increased risk of recurrent PE episodes rather than DVT. Further research is needed to understand the underlying pathophysiology of in-situ thrombosis in those patients.

The ER Stress/UPR Axis in Chronic Obstructive Pulmonary Disease and Idiopathic Pulmonary Fibrosis

Cellular protein homeostasis in the lungs is constantly disrupted by recurrent exposure to various external and internal stressors, which may cause considerable protein secretion pressure on the endoplasmic reticulum (ER), resulting in the survival and differentiation of these cell types to meet the increased functional demands. Cells are able to induce a highly conserved adaptive mechanism, known as the unfolded protein response (UPR), to manage such stresses. UPR dysregulation and ER stress are involved in numerous human illnesses, such as metabolic syndrome, fibrotic diseases, and neurodegeneration, and cancer. Therefore, effective and specific compounds targeting the UPR pathway are being considered as potential therapies. This review focuses on the impact of both external and internal stressors on the ER in idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD) and discusses the role of the UPR signaling pathway activation in the control of cellular damage and specifically highlights the potential involvement of non-coding RNAs in COPD. Summaries of pathogenic mechanisms associated with the ER stress/UPR axis contributing to IPF and COPD, and promising pharmacological intervention strategies, are also presented.

Efficacy of recombinant human soluble thrombomodulin for acute exacerbation of idiopathic pulmonary fibrosis: A systematic review and meta-analysis

Idiopathic pulmonary fibrosis (IPF) is a chronic fibrosing lung disease of unknown etiology. Recombinant human soluble thrombomodulin (rhTM) is used for the management of acute exacerbation (AE) of IPF. The present review aimed to summarize the evidence and perform a meta-analysis of the efficacy and safety of rhTM in the management of AE-IPF. An electronic search of titles and abstracts published until 31st August 2019 was performed in the PubMed, Biomed Central, Scopus and Embase databases. Studies comparing rhTM-treated and control subjects with AE-IPF and assessing mortality and adverse events were included. Six studies met the inclusion criteria. A total of 145 patients received rhTM, while 146 patients served as controls. The meta-analysis indicated that rhTM resulted in a reduction in 28-day [odds ratio (OR), 0.25; 95% CI, 0.08-0.77; P=0.02; I²=0%] and 90-day mortality (OR, 0.29; 95% CI, 0.17-0.49; P<0.00001; I²=0%) compared with the controls. Adverse events were pooled and no difference was determined between rhTM and control groups (OR, 1.07; 95% CI, 0.45-2.51; P=0.88; I²=0%). It was indicated that administration of rhTM may reduce the short-term mortality in patients with AE-IPF; however, the quality of evidence was not high. The drug appears to be safe without any enhanced risk of adverse events, although high-quality randomized controlled trials with a large sample size are required to further support its use in the treatment of IPF.

Highlights of high-resolution computed tomography imaging in evaluation of complications and co-morbidities in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) represents a condition included in the heterogeneous group of interstitial lung diseases without known causes. The recent ATS/ERS/JRS/ALAT guidelines and the white paper published by the Fleischner Society have well-defined diagnosis and management of idiopathic pulmonary fibrosis. Idiopathic pulmonary fibrosis management is complex because it is also influenced by several co-morbidities and complications. The new frontier in idiopathic pulmonary fibrosis is represented by the effort to understand the complex mechanism of the pathogenesis and progression of disease in order to predict several consequences and co-morbidities. In our review, we tried to distinguish co-morbidities from complications of idiopathic pulmonary fibrosis. In each complication, we have reviewed the existing literature and we have emphasized the complex pathobiological pathway which links the progression of idiopathic pulmonary fibrosis to the development of the complication itself. For every co-morbidity, we tried to identify share common risk factors which explain the coexistence of idiopathic pulmonary fibrosis with its co-morbidities. We then analyzed high-resolution computed tomography (CT) aspects of co-morbidities and complications of idiopathic pulmonary fibrosis that the radiologist should be aware of. In this review, we focused on the role of high-resolution CT imaging in the evaluation of co-morbidities and complications in idiopathic pulmonary fibrosis because their early diagnosis and treatment could change the prognosis in patients with idiopathic pulmonary fibrosis. We have also pointed out that in some cases the final combined quantitative CT tools and conventional visual CT score would allow to get an accurate analysis and quantification of disease progression, co-morbidities, and complications of idiopathic pulmonary fibrosis in order to improve staging systems in idiopathic pulmonary fibrosis.

Intestinal proteomic analysis of a novel non-human primate model of experimental colitis reveals signatures of mitochondrial and metabolic dysfunction

Animal models recapitulating features of chronic colitis, such as ulcerative colitis, Crohn's disease, or HIV infection, are critical to study disease pathogenesis and test novel therapeutics. In this study, we used a proteomics approach to explore the molecular intestinal response in two rhesus macaque (RM) animal models of experimentally induced colitis using dextran sulfate sodium (DSS) and simian immunodeficiency virus (SIV) infection. Proteomic analysis detected more than 2500 proteins in colonic tissue collected from 30 RMs. Differential protein expression analysis revealed a protein expression pattern in DSS-treated RMs resembling the proteome of human ulcerative colitis. In a group of 12 DSS-treated RMs compared to 6 with no treatment, decrease in expression of proteins related to mitochondrial energy metabolism, including fatty acid metabolism was noted, while innate immune activation pathways, including complement and coagulation proteins were upregulated. SIV infection of RMs resulted in increased innate immune responses related to viral defense. Proteomic signatures of barrier damage were apparent in both DSS treatment or SIV infection. These results demonstrate that DSS treatment in a non-human primate model resembles features of human ulcerative colitis, making this a promising tool to study important immunological mechanisms in inflammatory bowel disease.

Hematopoietic protease nexin-1 protects against lung injury by preventing thrombin signaling in mice

Coagulation and fibrinolytic system deregulation has been implicated in the development of idiopathic pulmonary fibrosis, a devastating form of interstitial lung disease. We used intratracheal instillation of bleomycin to induce pulmonary fibrosis in mice and analyzed the role of serine protease inhibitor E2 (serpinE2)/protease nexin-1 (PN-1), a tissue serpin that exhibits anticoagulant and antifibrinolytic properties. PN-1 deficiency was associated, after bleomycin challenge, with a significant increase in mortality, as well as a marked increase in active thrombin in bronchoalveolar lavage fluids, an overexpression of extracellular matrix proteins, and an accumulation of inflammatory cells in the lungs. Bone marrow transplantation experiments showed that protective PN-1 was derived from hematopoietic cell compartment. A pharmacological strategy using the direct thrombin inhibitor argatroban reversed the deleterious effects of PN-1 deficiency. Concomitant deficiency of the thrombin receptor protease-activated receptor 4 (PAR4) abolished the deleterious effects of PN-1 deficiency in hematopoietic cells. These data demonstrate that prevention of thrombin signaling by PN-1 constitutes an important endogenous mechanism of protection against lung fibrosis and associated mortality. Our findings suggest that appropriate doses of thrombin inhibitors or PAR4 antagonists may provide benefit against progressive lung fibrosis with evidence of deregulated thrombin activity.

Biomarker profiles of coagulopathy and alveolar epithelial injury in acute respiratory distress syndrome with idiopathic/immune-related disease or common direct risk factors

BACKGROUND

Altered coagulation and alveolar injury are the hallmarks of acute respiratory distress syndrome (ARDS). However, whether the biomarkers that reflect pathophysiology differ depending on the etiology of ARDS has not been examined. This study aimed to investigate the biomarker profiles of coagulopathy and alveolar epithelial injury in two subtypes of ARDS: patients with direct common risk factors (dARDS) and those with idiopathic or immune-related diseases (iARDS), which are classified as "ARDS without common risk factors" based on the Berlin definition.

METHODS

This retrospective, observational study included adult patients who were admitted to the intensive care unit (ICU) at a university hospital with a diagnosis of ARDS with no indirect risk factors. Plasma biomarkers (thrombin-antithrombin complex [TAT], plasminogen activator inhibitor [PAI]-1, protein C [PC] activity, procalcitonin [PCT], surfactant protein [SP]-D, and KL-6) were routinely measured during the first 5 days of the patient's ICU stay.

RESULTS

Among 138 eligible patients with ARDS, 51 were excluded based on the exclusion criteria (n = 41) or other causes of ARDS (n = 10). Of the remaining 87 patients, 56 were identified as having dARDS and 31 as having iARDS. Among the iARDS patients, TAT (marker of thrombin generation) and PAI-1 (marker of inhibited fibrinolysis) were increased, and PC activity was above normal. In contrast, PC activity was significantly decreased, and TAT or PAI-1 was present at much higher levels in dARDS compared with iARDS patients. Significant differences were also observed in PCT, SP-D, and KL-6 between patients with dARDS and iARDS. The receiver operating characteristic (ROC) analysis showed that areas under the ROC curve for PC activity, PAI-1, PCT, SP-D, and KL-6 were similarly high for distinguishing between dARDS and iARDS (PC 0.86, P = 0.33; PAI-1 0.89, P = 0.95; PCT 0.89, P = 0.66; and SP-D 0.88, P = 0.16 vs. KL-6 0.90, respectively).

CONCLUSIONS

Coagulopathy and alveolar epithelial injury were observed in both patients with dARDS and with iARDS. However, their biomarker profiles were significantly different between the two groups. The different patterns of PAI-1, PC activity, SP-D, and KL-6 may help in differentiating between these ARDS subtypes.

Registration of the extracellular matrix components constituting the fibroblastic focus in idiopathic pulmonary fibrosis

The extracellular matrix (ECM) in idiopathic pulmonary fibrosis (IPF) drives fibrosis progression; however, the ECM composition of the fibroblastic focus (the hallmark lesion in IPF) and adjacent regions remains incompletely defined. Herein, we serially sectioned IPF lung specimens constructed into tissue microarrays and immunostained for ECM components reported to be deregulated in IPF. Immunostained sections were imaged, anatomically aligned, and 3D reconstructed. The myofibroblast core of the fibroblastic focus (defined by collagen I, α-smooth muscle actin, and procollagen I immunoreactivity) was associated with collagens III, IV, V, and VI; fibronectin; hyaluronan; and versican immunoreactivity. Hyaluronan immunoreactivity was also present at the fibroblastic focus perimeter and at sites where early lesions appear to be forming. Fibrinogen immunoreactivity was often observed at regions of damaged epithelium lining the airspace and the perimeter of the myofibroblast core but was absent from the myofibroblast core itself. The ECM components of the fibroblastic focus were distributed in a characteristic and reproducible manner in multiple patients. This information can inform the development of high-fidelity model systems to dissect mechanisms by which the IPF ECM drives fibrosis progression.

Type VI collagen promotes lung epithelial cell spreading and wound-closure

Basement membrane (BM) is an essential part of the extracellular matrix (ECM) that plays a crucial role in mechanical support and signaling to epithelial cells during lung development, homeostasis and repair. Abnormal composition and remodeling of the lung ECM have been associated with developmental abnormalities observed in multiple pediatric and adult respiratory diseases. Collagen VI (COL6) is a well-studied muscle BM component, but its role in the lung and its effect on pulmonary epithelium is largely undetermined. We report the presence of COLVI immediately subjacent to human airway and alveolar epithelium in the pediatric lung, in a location where it is likely to interact with epithelial cells. In vitro, both primary human lung epithelial cells and human lung epithelial cell lines displayed an increased rate of “wound healing” in response to a scratch injury when plated on COL6 as compared to other matrices. For the 16HBE cell line, wounds remained >5-fold larger for cells on COL1 (p<0.001) and >6-fold larger on matrigel (p<0.001), a prototypical basement membrane, when compared to COL6 (>96% closure at 10 hr). The effect of COL6 upon lung epithelial cell phenotype was associated with an increase in cell spreading. Three hours after initial plating, 16HBE cells showed >7-fold less spreading on matrigel (p<0.01), and >4-fold less spreading on COL1 (p<0.01) when compared to COL6. Importantly, the addition of COL6 to other matrices also enhanced cell spreading. Similar responses were observed for primary cells. Inhibitor studies indicated both integrin β1 activity and activation of multiple signaling pathways was required for enhanced spreading on all matrices, with the PI3K/AKT pathway (PI3K, CDC42, RAC1) showing both significant and specific effects for spreading on COL6. Genetic gain-of-function experiments demonstrated enhanced PI3K/AKT pathway activity was sufficient to confer equivalent cell spreading on other matrices as compared to COL6. We conclude that COL6 has significant and specific effects upon human lung epithelial cell-autonomous functions.

Comorbidities, Complications and Non-Pharmacologic Treatment in Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive and fatal disease. The treatment is challenging and nowadays a comprehensive approach based not only in pharmacological strategies is necessary. Identification and control of comorbidities, non-pharmacological treatment, prevention and management of exacerbations as well as other areas of care (social, psychological) are fundamental for a holistic management of IPF. Gastroesophageal reflux, pulmonary hypertension, obstructive sleep apnea, combined with emphysema, lung cancer and cardiovascular involvement are the main comorbidities associated with IPF. Non-pharmacological treatment includes the use of oxygen in patients with rest or nocturnal hypoxemia and other support therapies such as non-invasive ventilation or even a high-flow nasal cannula to improve dyspnea. In some patients, lung transplant should be considered as this enhances survival. Pulmonary rehabilitation can add benefits in outcomes such control of dyspnea, exercise capacity distance and, overall, improve the quality of life; therefore it should be considered in patients with IPF. Also, multidisciplinary palliative care programs could help with symptom control and psychological support, with the aim of maintaining quality of life during the whole process of the disease. This review intends to provide clear information to help those involved in IPF follow up to improve patients’ daily care.

Epithelial cell-derived cytokines CST3 and GDF15 as potential therapeutics for pulmonary fibrosis

While wound healing is completed, the epithelium functions to normalize the interstitial context by eliminating fibroblasts excited during matrix reconstruction. If not, tissues undergo pathologic fibrosis. Pulmonary fibrosis is a fatal and hardly curable disorder. We here tried to identify epithelium-derived cytokines capable of ameliorating pulmonary fibrosis. Human lung fibroblasts were inactivated in epithelial cell-conditioned media. Cystatin C (CST3) and growth differentiation factor 15 (GDF15) were found to be enriched in the conditioned media and to inhibit the growth and activation of lung fibroblasts by inactivating the TGF–Smad pathway. In mouse and human lungs with interstitial fibrosis, CST3 and GDF15 expressions were markedly reduced, and the restoration of these cytokines alleviated the fibrotic changes in mouse lungs. These results suggest that CST3 and GDF15 are bona fide regulators to prevent excessive proliferation and activation of fibroblasts in injured lungs. These cytokines could be potential therapeutics for ameliorating interstitial lung fibrosis.

The impaired proteases and anti-proteases balance in Idiopathic Pulmonary Fibrosis

Idiopathic Pulmonary Fibrosis (IPF) is a devastating chronic, progressive and irreversible disease that remains refractory to current therapies. Matrix metalloproteinases (MMPs) and their inhibitors, tissue inhibitors of MMPs (TIMPs), have been implicated in the development of pulmonary fibrosis since decades. Coagulation signalling deregulation, which influences several key inflammatory and fibro-proliferative responses, is also essential in IPF pathogenesis, and a growing body of evidence indicates that Protease-Activated Receptors (PARs) inhibition in IPF may be promising for future evaluation. Therefore, proteases and anti-proteases aroused great biomedical interest over the past years, owing to the identification of their potential roles in lung fibrosis. During these last decades, numerous other proteases and anti-proteases have been studied in lung fibrosis, such as matriptase, Human airway trypsin-like protease (HAT), Hepatocyte growth factor activator (HGFA)/HGFA activator inhibitor (HAI) system, Plasminogen activator inhibitor (PAI)-1, Protease nexine (PN)-1, cathepsins, calpains, and cystatin C. Herein, we provide a general overview of the proteases and anti-proteases unbalance during lung fibrogenesis and explore potential therapeutics for IPF.

Idiopathic pulmonary fibrosis: lessons from clinical trials over the past 25 years

Idiopathic pulmonary fibrosis (IPF) is a progressive and ultimately fatal disease. A major breakthrough in treatment came when, after decades of clinical trials which failed to identify an efficacious treatment regimen, two therapies were successful in Phase-III trials. The advent of these therapies, nintedanib and pirfenidone, meant that for the first time IPF patients had two treatment options that could reduce disease progression. This review summarises the key lessons to be obtained from the clinical trials that led to the current international clinical practice guidelines for the treatment of IPF and provides insights for the design of future clinical trials that are needed if we are to improve outcomes that are clinically meaningful to IPF patients.

Human airway trypsin-like protease, a serine protease involved in respiratory diseases

More than 2% of all human genes are coding for a complex system of more than 700 proteases and protease inhibitors. Among them, serine proteases play extraordinary, diverse functions in different physiological and pathological processes. The human airway trypsin-like protease (HAT), also referred to as TMPRSS11D and serine 11D, belongs to the emerging family of cell surface proteolytic enzymes, the type II transmembrane serine proteases (TTSPs). Through the cleavage of its four major identified substrates, HAT triggers specific responses, notably in epithelial cells, within the pericellular and extracellular environment, including notably inflammatory cytokine production, inflammatory cell recruitment, or anticoagulant processes. This review summarizes the potential role of this recently described protease in mediating cell surface proteolytic events, to highlight the structural features, proteolytic activity, and regulation, including the expression profile of HAT, and discuss its possible roles in respiratory physiology and disease.

Targeting coagulation factor receptors - protease-activated receptors in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a lethal lung disease with a 5-year mortality rate of > 50% and unknown etiology. Treatment options remain limited and, currently, only two drugs are available, i.e. nintedanib and pirfenidone. However, both of these antifibrotic agents only slow down the progression of the disease, and do not remarkably prolong the survival of IPF patients. Hence, the discovery of new therapeutic targets for IPF is crucial. Studies exploring the mechanisms that are involved in IPF have identified several possible targets for therapeutic interventions. Among these, blood coagulation factor receptors, i.e. protease-activated receptors (PARs), are key candidates, as these receptors mediate the cellular effects of coagulation factors and play central roles in influencing inflammatory and fibrotic responses. In this review, we will focus on the controversial role of the coagulation cascade in the pathogenesis of IPF. In the light of novel data, we will attempt to reconciliate the apparently conflicting data and discuss the possibility of pharmacologic targeting of PARs for the treatment of fibroproliferative diseases.

The fibrogenic actions of lung fibroblast-derived urokinase: a potential drug target in IPF

The role of urokinase plasminogen activator (uPA) in idiopathic pulmonary fibrosis (IPF) remains unclear. uPA-generated plasmin has potent fibrogenic actions involving protease activated receptor-1 (PAR-1) and interleukin-6 (IL-6). Here we characterize uPA distribution or levels in lung tissue and sera from IPF patients to establish the mechanism of its fibrogenic actions on lung fibroblasts (LFs). uPA immunoreactivity was detected in regions of fibrosis including fibroblasts of lung tissue from IPF patients (n = 7). Serum uPA levels and activity were also higher in IPF patients (n = 18) than controls (n = 18) (P < 0.05), being negatively correlated with lung function as measured by forced vital capacity (FVC) %predicted (P < 0.05). The culture supernatants of LFs from IPF patients, as compared to controls, showed an increase in plasmin activity after plasminogen incubation (5–15 μg/mL), corresponding with increased levels of uPA and IL-6 (n = 5–6, P < 0.05). Plasminogen-induced increases in plasmin activity and IL-6 levels were attenuated by reducing uPA and/or PAR-1 expression by RNAi. Plasmin(ogen)-induced mitogenesis was also attenuated by targeting uPA, PAR-1 or IL-6. Our data shows uPA is formed in active regions of fibrosis in IPF lung and contributes to LF plasmin generation, IL-6 production and proliferation. Urokinase is a potential target for the treatment of lung fibrosis.

Efficacy of recombinant human soluble thrombomodulin for the treatment of acute exacerbation of idiopathic pulmonary fibrosis: a single arm, non-randomized prospective clinical trial

BACKGROUND

Coagulation abnormalities are involved in the pathogenesis of acute exacerbations of idiopathic pulmonary fibrosis (AE-IPF). The administration of recombinant human soluble thrombomodulin (rhTM), which has both anti-inflammatory and anticoagulant activities, improves outcomes and respiratory function in patients with acute respiratory distress syndrome. Therefore, we conducted a prospective clinical study to examine the effects of rhTM on respiratory function, coagulation markers, and outcomes for patients with AE-IPF.

METHODS

After registration of the protocol, the patients with AE-IPF who satisfied the study inclusion criteria were treated daily with 380 U/kg of rhTM for 7 days and steroid pulse therapy. The concomitant administration of immunosuppressants and polymyxin B-immobilized fiber column treatment was prohibited. The sample size was 10 subjects. The primary study outcome was the improvement of PaO₂/FiO₂ ratio a week after treatment initiation. Secondary outcomes were change in D-dimer level over time and 28-day survival rate in patients without intubation. Study data were compared with historical untreated comparison group, including 13 patients with AE-IPF who were treated without rhTM before the registration.

RESULTS

The mean PaO₂/FiO₂ ratio for the rhTM treatment group (n = 10) on day 8 significantly improved compared with that on day one (two-way analysis of variance, p = 0.01). The mean D-dimer level tended to decrease in the rhTM group on day 8, but the change was not significant. The 28-day survival rate was 50 % higher in the rhTM group than in the historical untreated comparison group, but the difference was not significant. A post hoc analysis showed that overall survival time was significantly longer in the treated group compared with that of the historical untreated comparison group (p = 0.04, log-rank test).

CONCLUSION

rhTM plus steroid pulse therapy improves respiratory functions in patients with AE-IPF and is expected to improve overall patient survival without using other combination therapies.

TRIAL REGISTRATION

The study was registered with University Hospital Medical Information Network Clinical Trial Registry (UMIN-CTR) in October 2012 (UMIN000009082).

Advances in the treatment of idiopathic pulmonary fibrosis

INTRODUCTION

Idiopathic pulmonary fibrosis (IPF) is a lung limited, progressive fibrotic disease with a poor prognosis. The cause is unknown, and currently there is no treatment that reverses the disease or stops progression. This combination of a poor prognosis and the absence of curative therapy has prompted a sustained investigative effort to identify beneficial treatments. Recently released trial results suggest progress.

AREAS COVERED

Although the mechanism of disease is poorly understood, a number of compounds that influence pathways thought to play a mechanistic role have been studied for use in IPF. This article discusses a number of these landmark trials.

EXPERT OPINION

From these studies we conclude that the future treatment of IPF will include expanding pharmacological options. Recent studies have identified two agents that appear to slow disease progression and may offer a window into pathogenesis and future drug targets.

Fibrinolytic system related to pulmonary arterial pressure and lung function of patients with idiopathic pulmonary fibrosis

OBJECTIVES AND AIMS

To investigate urokinase-(uPA) and tissue-type (tPA) plasminogen activator and plasminogen activator inhibitor type-1 (PAI-1) levels in patients with idiopathic pulmonary fibrosis (IPF) and to determine the relationship between fibrinolytic system and pulmonary arterial pressure and pulmonary function.

METHODS

Seventy-nine patients with IPF were included. Bronchoalveolar lavage fluid (BALF) and blood samples were collected. The concentrations of tPA, uPA and PAI-1 were measured using enzyme-linked immunosorbent assay. Doppler echocardiography was used to detect tricuspid regurgitation pressure gradient (TRPG) to estimate pulmonary arterial pressure.

RESULTS

BALF tPA elevated (P < 0.005), circulatory PAI-1 decreased (P = 0.05) and the ratio of uPA and PAI-1 decreased (P = 0.01) in BALF in IPF patients with pulmonary hypertension (PH) compared to those without PH. Positive linear correlations were found: BALF tPA and TRPG (r = 0.558, P = 0.013); the predicted percentage of diffusion capacity of lung for carbon monoxide adjustments for alveolar volume and BALF uPA (r = 0.319, P = 0.035). Negative linear correlations were as follows: BALF PAI-1 and the predicted percentage of VC_max (r = -0.325, P = 0.020), or total lung capacity (r = -0.312, P = 0.033); circulatory PAI-1 and TRPG (r = -0.697, P = 0.003).

CONCLUSIONS

The change of alveolar fibrolytic system in IPF, especially the uPA reduction and the PAI-1elevation, contributes to the deterioration of lung function. During the lung injury initiating fibrosis, tPA and PAI-1 might be leaked out of the pulmonary capillaries into alveoli, resulting in their elevation in alveoli and reduction in circulation, and finally contributing to the development of PH in IPF.

The Rho kinases: critical mediators of multiple profibrotic processes and rational targets for new therapies for pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is characterized by progressive lung scarring, short median survival, and limited therapeutic options, creating great need for new pharmacologic therapies. IPF is thought to result from repetitive environmental injury to the lung epithelium, in the context of aberrant host wound healing responses. Tissue responses to injury fundamentally involve reorganization of the actin cytoskeleton of participating cells, including epithelial cells, fibroblasts, endothelial cells, and macrophages. Actin filament assembly and actomyosin contraction are directed by the Rho-associated coiled-coil forming protein kinase (ROCK) family of serine/threonine kinases (ROCK1 and ROCK2). As would therefore be expected, lung ROCK activation has been demonstrated in humans with IPF and in animal models of this disease. ROCK inhibitors can prevent fibrosis in these models, and more importantly, induce the regression of already established fibrosis. Here we review ROCK structure and function, upstream activators and downstream targets of ROCKs in pulmonary fibrosis, contributions of ROCKs to profibrotic cellular responses to lung injury, ROCK inhibitors and their efficacy in animal models of pulmonary fibrosis, and potential toxicities of ROCK inhibitors in humans, as well as involvement of ROCKs in fibrosis in other organs. As we discuss, ROCK activation is required for multiple profibrotic responses, in the lung and multiple other organs, suggesting ROCK participation in fundamental pathways that contribute to the pathogenesis of a broad array of fibrotic diseases. Multiple lines of evidence therefore indicate that ROCK inhibition has great potential to be a powerful therapeutic tool in the treatment of fibrosis, both in the lung and beyond.

Role of serine proteases in the regulation of interleukin-877 during the development of bronchopulmonary dysplasia in preterm ventilated infants

RATIONALE

The chemokine interleukin-8 is implicated in the development of bronchopulmonary dysplasia in preterm infants. The 77-amino acid isoform of interleukin-8 (interleukin-877) is a less potent chemoattractant than other shorter isoforms. Although interleukin-877 is abundant in the preterm circulation, its regulation in the preterm lung is unknown.

OBJECTIVES

To study expression and processing of pulmonary interleukin-877 in preterm infants who did and did not develop bronchopulmonary dysplasia.

METHODS

Total interleukin-8 and interleukin-877 were measured in bronchoalveolar lavage fluid from preterm infants by immunoassay. Neutrophil serine proteases were used to assess processing. Neutrophil chemotaxis assays and degranulation of neutrophil matrix metalloproteinase-9 were used to assess interleukin-8 function.

MAIN RESULTS

Peak total interleukin-8 and interleukin-877 concentrations were increased in infants who developed bronchopulmonary dysplasia compared to those who did not. Shorter forms of interleukin-8 predominated in the preterm lung (96.3% No-bronchopulmonary dysplasia vs 97.1% bronchopulmonary dysplasia, p>0.05). Preterm bronchoalveolar lavage fluid significantly converted exogenously added interleukin-877 to shorter isoforms (p<0.001). Conversion was greater in bronchopulmonary dysplasia infants (p<0.05). This conversion was inhibited by α-1 antitrypsin and antithrombin III (p<0.01). Purified neutrophil serine proteases efficiently converted interleukin-877 to shorter isoforms in a time- and dose-dependent fashion; shorter interleukin-8 isoforms were primarily responsible for neutrophil chemotaxis (p<0.001). Conversion by proteinase-3 resulted in significantly increased interleukin-8 activity in vitro (p<0.01).

CONCLUSIONS

Shorter, potent, isoforms interleukin-8 predominate in the preterm lung, and are increased in infants developing bronchopulmonary dysplasia, due to conversion of interleukin-877 by neutrophil serine proteases and thrombin. Processing of interleukin-8 provides an attractive therapeutic target to prevent development of bronchopulmonary dysplasia.

New treatment and markers of prognosis for idiopathic pulmonary fibrosis: lessons learned from translational research

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive interstitial lung disease with increasing prevalence, high mortality rates and poor treatment options. The diagnostic process is complex and often requires an interdisciplinary approach between different specialists. Information gained over the past 10 years of intense research resulted in improved diagnostic algorithms, a better understanding of the underlying pathogenesis and the development of new therapeutic options. Specifically, the change from the traditional concept that viewed IPF as a chronic inflammatory disorder to the current belief that is primarily resulting from aberrant wound healing enabled the identification of novel treatment targets. This increased the clinical trial activity dramatically and resulted in the approval of the first IPF-specific therapy in many countries. Still, the natural history and intrinsic behavior of IPF are very difficult to predict. There is an urgent need for new therapies and also for development and validation of prognostic markers that predict disease progression, survival and also response to antifibrotic drugs. This review provides an up to date summary of the most relevant clinical trials, novel therapeutic drug targets and outlines a spectrum of potential prognostic biomarkers for IPF.

Recent Evidence for Pharmacological Treatment of Idiopathic Pulmonary Fibrosis

Objective: To describe emerging evidence for the pharmacological treatment of idiopathic pulmonary fibrosis (IPF). Data Sources: A search of PubMed (1966 to July 2014) was performed using the terms idiopathic pulmonary fibrosis and treatment. Study Selection and Data Extraction: Review of articles was restricted to articles in English and relating to placebo-controlled or comparative clinical trial data of recent significance. Evidence statements from the most recent international guidelines and some historical trial data were also included for context. Data Synthesis: Numerous treatment options have been evaluated for IPF. Therapies evaluated in large trials have either resulted in increased mortality (anticoagulation, triple-therapy with N-acetylcysteine [NAC], azathioprine, and prednisone) or demonstrated a lack of efficacy (endothelin receptor antagonists, single-agent NAC). Pirfenidone, a novel antifibrotic and anti-inflammatory agent, has demonstrated efficacy in several recent analyses and is the only approved medication for the treatment of IPF in more than 30 countries outside of the United States, with resubmission to the Food and Drug Administration (FDA) recently made. Nintedanib, a tyrosine kinase inhibitor, has demonstrated encouraging results in phase III studies and has also recently been submitted for FDA approval. Conclusions: Limited options have existed for the treatment of IPF. New evidence suggests that safe and efficacious treatment options for IPF are on the horizon in the form of pirfenidone and nintedanib, although both agents await FDA decisions.

Procoagulant, tissue factor-bearing microparticles in bronchoalveolar lavage of interstitial lung disease patients: an observational study

Coagulation factor Xa appears involved in the pathogenesis of pulmonary fibrosis. Through its interaction with protease activated receptor-1, this protease signals myofibroblast differentiation in lung fibroblasts. Although fibrogenic stimuli induce factor X synthesis by alveolar cells, the mechanisms of local posttranslational factor X activation are not fully understood. Cell-derived microparticles are submicron vesicles involved in different physiological processes, including blood coagulation; they potentially activate factor X due to the exposure on their outer membrane of both phosphatidylserine and tissue factor. We postulated a role for procoagulant microparticles in the pathogenesis of interstitial lung diseases. Nineteen patients with interstitial lung diseases and 11 controls were studied. All subjects underwent bronchoalveolar lavage; interstitial lung disease patients also underwent pulmonary function tests and high resolution CT scan. Microparticles were enumerated in the bronchoalveolar lavage fluid with a solid-phase assay based on thrombin generation. Microparticles were also tested for tissue factor activity. In vitro shedding of microparticles upon incubation with H₂O₂ was assessed in the human alveolar cell line, A549 and in normal bronchial epithelial cells. Tissue factor synthesis was quantitated by real-time PCR. Total microparticle number and microparticle-associated tissue factor activity were increased in interstitial lung disease patients compared to controls (84±8 vs. 39±3 nM phosphatidylserine; 293±37 vs. 105±21 arbitrary units of tissue factor activity; mean±SEM; p<.05 for both comparisons). Microparticle-bound tissue factor activity was inversely correlated with lung function as assessed by both diffusion capacity and forced vital capacity (r² = .27 and .31, respectively; p<.05 for both correlations). Exposure of lung epithelial cells to H₂O₂ caused an increase in microparticle-bound tissue factor without affecting tissue factor mRNA.

Procoagulant microparticles are increased in interstitial lung diseases and correlate with functional impairment. These structures might contribute to the activation of factor X and to the factor Xa-mediated fibrotic response in lung injury.

The wound healing, chronic fibrosis, and cancer progression triad

For decades tumors have been recognized as "wounds that do not heal." Besides the commonalities that tumors and wounded tissues share, the process of wound healing also portrays similar characteristics with chronic fibrosis. In this review, we suggest a tight interrelationship, which is governed as a concurrence of cellular and microenvironmental reactivity among wound healing, chronic fibrosis, and cancer development/progression (i.e., the WHFC triad). It is clear that the same cell types, as well as soluble and matrix elements that drive wound healing (including regeneration) via distinct signaling pathways, also fuel chronic fibrosis and tumor progression. Hence, here we review the relationship between fibrosis and cancer through the lens of wound healing.

Thrombin induces epithelial-mesenchymal transition via PAR-1, PKC, and ERK1/2 pathways in A549 cells

Thrombin activates protease-activated receptor (PAR)-1 and induces a myofibroblast phenotype in normal lung fibroblasts. The origins of myofibroblasts are resident fibroblasts, fibrocytes, and epithelial-mesenchymal transition (EMT). We investigated the effects of thrombin, an important mediator of interstitial lung fibrosis, on EMT in A549 human alveolar epithelial cells. We show that thrombin induced EMT and collagen I secretion through the activation of PAR-1, and PKC and ERK1/2 phosphorylation in A549 cells. These effects were largely prevented by a specific PAR-1 antagonist, short interfering RNA (siRNA) directed against PAR-1, or specific PKCα/β, δ, and ε inhibitors. These data indicated that interaction with thrombin and alveolar epithelial cells might directly contribute to the pathogenesis of pulmonary fibrosis through EMT. Targeting PAR-1 on the pulmonary epithelium or specific inhibitors to PKCα/β, δ, and ε might stop the fibrotic processes in human idiopathic pulmonary fibrosis by preventing thrombin-induced EMT.

The clinical assessment of protease-activated receptor-2 expression in inflammatory cells from peripheral blood and bronchoalveolar lavage fluid in idiopathic pulmonary fibrosis

Background

Idiopathic pulmonary fibrosis (IPF) is a lethal pulmonary fibrotic disease. In general, the exaggerated activation of the coagulation cascade has been observed during initiation or maintenance of the fibrotic disease. In our recent study, immunohistochemical expression of protease-activated receptor-2 (PAR-2), which plays a key role in coagulation cascade, was observed in surgical specimen of IPF patients, and associated with poor clinical outcome. The aim of this study was to evaluate the overexpression of PAR-2 in inflammatory cells from peripheral blood and bronchoalveolar lavage fluid in IPF patients.

Methods

From May 2011 to March 2012, IPF patients and controls were enrolled in Seoul National University Hospital. Peripheral blood and bronchoalveolar lavage fluid were collected for analysis of PAR-2 expression. Flow cytometry and reverse transcription polymerase chain reaction were used for PAR-2 receptor and mRNA assessment.

Results

Twelve IPF patients and 14 controls were included in this study. Among them, flow cytometry analysis was conducted from 26 peripheral blood (patient group, 11; control group, 13) and 7 bronchoalveolar lavage fluid (patient group, 5; control group, 2). The expression of PAR-2 receptor was not different between patient and control groups (p=0.074). Among all 24 population, PAR-2 mRNA assessment was performed in 19 persons (patient group, 10; control group, 9). The mRNA expression of PAR-2 was not significant different (p=0.633).

Conclusion

In IPF patients, PAR-2 receptor and mRNA expression were not different from control group.

A review of current and novel therapies for idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressively fibrotic interstitial lung disease that is associated with a median survival of 2-3 years from initial diagnosis. To date, there is no treatment approved for IPF in the United States, and only one pharmacological agent has been approved outside of the United States. Nevertheless, research over the past 10 years has provided us with a wealth of information on its histopathology, diagnostic work-up, and a greater understanding of its pathophysiology. Specifically, IPF is no longer thought to be a predominantly pro-inflammatory disorder. Rather, the fibrosis in IPF is increasingly understood to be the result of a fibroproliferative and aberrant wound healing cascade. The development of therapeutic targets has shifted in accord with this paradigm change. This review highlights the current understanding of IPF, and the recent as well as novel therapeutics being explored in clinical trials for the treatment of this devastating disease.

Coagulation and coagulation signalling in fibrosis

Following tissue injury, a complex and coordinated wound healing response comprising coagulation, inflammation, fibroproliferation and tissue remodelling has evolved to nullify the impact of the original insult and reinstate the normal physiological function of the affected organ. Tissue fibrosis is thought to result from a dysregulated wound healing response as a result of continual local injury or impaired control mechanisms. Although the initial insult is highly variable for different organs, in most cases, uncontrolled or sustained activation of mesenchymal cells into highly synthetic myofibroblasts leads to the excessive deposition of extracellular matrix proteins and eventually loss of tissue function. Coagulation was originally thought to be an acute and transient response to tissue injury, responsible primarily for promoting haemostasis by initiating the formation of fibrin plugs to enmesh activated platelets within the walls of damaged blood vessels. However, the last 20years has seen a major re-evaluation of the role of the coagulation cascade following tissue injury and there is now mounting evidence that coagulation plays a critical role in orchestrating subsequent inflammatory and fibroproliferative responses during normal wound healing, as well as in a range of pathological contexts across all major organ systems. This review summarises our current understanding of the role of coagulation and coagulation initiated signalling in the response to tissue injury, as well as the contribution of uncontrolled coagulation to fibrosis of the lung, liver, kidney and heart. This article is part of a Special Issue entitled: Fibrosis: Translation of basic research to human disease.

Coagulation cascade proteinases in lung injury and fibrosis

The primary function of the coagulation cascade is to promote hemostasis and limit blood loss in response to tissue injury. In addition, there is now considerable evidence that coagulation plays pivotal roles in orchestrating inflammatory and tissue repair responses via both the generation of fibrin and activation of the family of proteinase-activated receptors (PARs). Consequently, uncontrolled coagulation and PAR signaling responses have been shown to contribute to excessive inflammatory and fibroproliferative responses in the context of a broad range of conditions, including acute lung injury and fibrotic lung disease. In terms of the cellular origin of excessive coagulation activity in the context of lung injury, coagulation zymogens are principally thought to be derived from the circulation and locally activated via the extrinsic tissue factor-dependent coagulation pathway within the intraalveolar compartment. More recently, we have provided compelling evidence that several key coagulation zymogens are locally synthesized by the hyperplastic alveolar epithelium in pulmonary fibrosis. In terms of signaling receptors activated in response to the coagulation cascade, current evidence suggests a major role for PAR1 in influencing endothelial-epithelial barrier disruption, inflammatory cell recruitment, and collagen deposition in response to lung injury, whereas PAR2 signaling has been implicated mainly in mediating lung inflammatory responses. This article reviews current understanding of coagulation pathways in acute and fibrotic lung injury and expands on the scientific rationale for strategies that specifically target intraalveolar coagulation or PAR signaling responses.

Clinical implication of protease-activated receptor-2 in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a lethal pulmonary disease which is characterized by progressive fibrosis. In general, the exaggerated activation of the coagulation cascade has been observed during initiation or maintenance of the fibrotic disease. In a recent study, protease-activated receptor (PAR)-2, which plays a key role in coagulation cascade, was up-regulated in IPF patients, however, its clinical implications have not been understood. The objective of the present study was to evaluate the clinical significance of PAR-2 expression in the alveolar epithelial cells of IPF patients. PAR-2 expression was evaluated by immunohistochemical method in formalin-fixed and paraffin-embedded tissues of surgical lung biopsies from patients with IPF. Fibrosis scores from hematoxylin and eosin-stained lung sections and honeycombing scores in chest CT were calculated. Medical records were retrospectively reviewed and the correlation between the expression of PAR-2 and clinical profiles were assessed. Among thirty-three IPF patients, PAR-2 expression was observed in 25 (75.8%). The lymphocyte counts in peripheral blood (2317 vs. 1753, p = 0.044) and honeycombing scores in chest CT (4.0 vs. 3.0 p = 0.046) were higher in PAR-2 positive group compared with PAR-2 negative group. During a follow-up duration of median 40.3 months, 7 (21.2%) patients died and they were all included in the PAR-2 positive group (p = 0.113). We conclude that PAR-2 is expressed in the alveolar epithelial cells of a substantial number of IPF patients, and the expression of PAR-2 significantly correlates with the extent of honeycombing shown in chest CT.