Mitochondria-mediated apoptosis of lung epithelial cells in idiopathic interstitial pneumonias

TOM5 regulates the mitochondrial membrane potential of alveolar epithelial cells in organizing pneumonia

Deficiency of TOM5, a mitochondrial protein, causes organizing pneumonia (OP) in mice. The clinical significance and mechanisms of TOM5 in the pathogenesis of OP remain elusive. We demonstrated that TOM5 was significantly increased in the lung tissues of OP patients, which was positively correlated with the collagen deposition. In a bleomycin-induced murine model of chronic OP, increased TOM5 was in line with lung fibrosis. In vitro, TOM5 regulated the mitochondrial membrane potential in alveolar epithelial cells. TOM5 reduced the proportion of early apoptotic cells and promoted cell proliferation. Our study shed light on the roles of TOM5 in OP.

Vistusertib improves pulmonary inflammation and fibrosis by modulating inflammatory/oxidative stress mediators via suppressing the mTOR signalling

INTRODUCTION

Inflammation and oxidative stress are key factors in the development of pulmonary fibrosis (PF) by promoting the differentiation of fibroblasts through modulating various pathways including Wnt/β-catenin, TGF-β and mTOR signalling.

OBJECTIVE AND METHODS

This study aimed to evaluate the effects and elucidate the mechanisms of vistusertib (VSB) in treating pulmonary inflammation/fibrosis, specifically by targeting the mTOR pathway using various in vitro and in vivo models.

RESULTS

Lipopolysaccharide (LPS)-induced inflammation model in macrophages (RAW 264.7), epithelial (BEAS-2B) and endothelial (HMVEC-L) cells revealed that treatment with VSB significantly reduced the IL-6, TNF-α, CCL2, and CCL7 expression. TGF-β induced differentiation was also significantly reduced upon VSB treatment in fibrotic cells (LL29 and DHLF). Further, bleomycin-induced inflammation and fibrosis models demonstrated that treatment with VSB significantly ameliorated the severe inflammation, and lung architectural distortion, by reducing the inflammatory markers expression/levels, inflammatory cells and oxidative stress indicators. Further, fibrosis model results exhibited that, VSB treatment significantly reduced the α-SMA, collagen and TGF-β expressions, improved the lung architecture and restored lung functions.

CONCLUSION

Overall, this study uncovers the anti-inflammatory/anti-fibrotic effects of VSB by modulating the mTOR activation. Although VSB was tested for lung fibrosis, it can be tested for other fibrotic disorders to improve the patient's survival and quality of life.

SLC15A3 plays a crucial role in pulmonary fibrosis by regulating macrophage oxidative stress

Idiopathic pulmonary fibrosis (IPF) is a fatal and irreversible disease with few effective treatments. Alveolar macrophages (AMs) are involved in the development of IPF from the initial stages due to direct exposure to air and respond to external oxidative damage (a major inducement of pulmonary fibrosis). Oxidative stress in AMs plays an indispensable role in promoting fibrosis development. The oligopeptide histidine transporter SLC15A3, mainly expressed on the lysosomal membrane of macrophages and highly expressed in the lung, has proved to be involved in innate immune and antiviral signaling pathways. In this study, we demonstrated that during bleomycin (BLM)- or radiation-induced pulmonary fibrosis, the recruitment of macrophages induced an increase of SLC15A3 in the lung, and the deficiency of SLC15A3 protected mice from pulmonary fibrosis and maintained the homeostasis of the pulmonary microenvironment. Mechanistically, deficiency of SLC15A3 resisted oxidative stress in macrophages, and SLC15A3 interacted with the scaffold protein p62 to regulate its expression and phosphorylation activation, thereby regulating p62-nuclear factor erythroid 2-related factor 2 (NRF2) antioxidant stress pathway protein, which is related to the production of reactive oxygen species (ROS). Overall, our data provided a novel mechanism for targeting SLC15A3 to regulate oxidative stress in macrophages, supporting the therapeutic potential of inhibiting or silencing SLC15A3 for the precautions and treatment of pulmonary fibrosis.

Lung Expression of Macrophage Markers CD68 and CD163, Angiotensin Converting Enzyme 2 (ACE2), and Caspase-3 in COVID-19

Background and Objectives: The coronavirus (SARS-CoV-2) damages all systems and organs. Yet, to a greater extent, the lungs are particularly involved, due to the formation of diffuse exudative inflammation in the form of acute respiratory distress syndrome (ARDS) with next progression to pulmonary fibrosis. SARS-associated lung damage is accompanied by the pronounced activation of mononuclear cells, damage of the alveoli and microvessels, and the development of organized pneumonia. To study the expression of macrophage markers (CD68 and CD163), angiotensin-converting enzyme-2 (ACE2), and caspase-3 on the results of two fatal clinical observations of COVID-19. Materials and Methods: In both clinical cases, the female patients died from complications of confirmed COVID-19. Conventional morphological and immunohistochemical methods were used. Results: There was an acute exudative hemorrhagic pneumonia with the formation of hyaline membranes, focal organization of fibrin, stromal sclerosis, stasis, and thrombus formation in the lung vessels. Signs such as the formation of hyaline membranes, organization, and fibrosis were more pronounced in severe disease activity. The activation of CD68+/CD163+ macrophages could cause cell damage at an early stage of pneumonia development, and subsequently cause fibrotic changes in lung tissue. ACE2 expression in lung tissue was not detected in severe pneumonia, while in moderate pneumonia, weak expression was noted in individual cells of the alveolar epithelium and vascular endothelium. Conclusions: This finding could show the dependence of ACE2 expression on the severity of the inflammatory process in the lungs. The expression of caspase-3 was more pronounced in severe pneumonia.

Pulmonary toxicity in driver gene positive non-small cell lung cancer therapy

Molecular targeted therapy significantly improved the therapeutic efficacy in non-small cell lung cancer (NSCLC) patients with driver gene mutations but also with new toxicity profiles. Although most patients treated with these drugs developed relatively controllable toxicity, significant pulmonary toxicity events, including interstitial lung disease, occurred in a small proportion of patients and can lead to discontinuation or even be life-threatening. Pulmonary toxicity associated with these anti-tumor drugs is a problem that cannot be ignored in clinical practice. The prompt diagnosis of drug-related lung injury and the consequent differential diagnosis with other forms of pulmonary disease are critical in the management of pulmonary toxicity. Current knowledge of the pathophysiology and management of pulmonary toxicity associated with these targeted drugs is limited, and participants should be able to identify and respond to the development of drug-induced pulmonary toxicity. This review offers information about the potential pathogenesis, risk factors and management for the development of these events based on the available literature. This review focused on pulmonary toxicities in driver gene-positive NSCLC therapy by describing the related adverse events to promote the awareness and management of this important toxicity related to antitumor-targeted therapy.

Aqueous Extract of Sea Squirt (Halocynthia roretzi) with Potent Activity against Human Cancer Cells Acts Synergistically with Doxorubicin

Marine ascidian is becoming one of the main sources of an antitumor drug that has shown high bioactivity and extensive application in cancer treatment. Halocynthia roretzi, an edible marine sea squirt, has been demonstrated to have various kinds of biological activities, such as anti-diabetic, anti-hypertension, and enhancing immunity. In this study, we reported that aqueous extracts from the edible parts of H. roretzi presented significantly inhibiting the efficiency on HepG-2 cell viability. The separate mixed compound exhibited strong effects of inhibitory proliferation and induced apoptosis via the generation of ROS along with the concurrent loss of mitochondrial membrane potential on tumor cells. Furthermore, we found that there existed a significantly synergistic effect of the ascidian-extracted compound mixture with the anti-cancer drug doxorubicin. In the presence of the extracts from H. roretzi, the dose of doxorubicin at the cellular level could be reduced by a half dose. The extracts were further divided by semipreparative-HPLC and the active ingredients were identified as a mixture of fatty amide, which was composed of hexadecanamide, stearamide, and erucamide by UHPLC-MS/MS. Our results suggest that the potential toxicity of ascidian H. roretzi in tumor cells, and the compounds extracted from H. roretzi could be potentially utilized on functional nutraceuticals or as an adjunct in combination with chemotherapy.

Anti-Myxovirus Resistance Protein-1 Immunoglobulin A Autoantibody in Idiopathic Pulmonary Fibrosis

Background

We have previously analysed serum autoantibody levels in patients with idiopathic pulmonary fibrosis (IPF), idiopathic nonspecific interstitial pneumonia (iNSIP), and healthy controls and identified the autoantibody against anti-myxovirus resistance protein-1 (MX1) to be a specific autoantibody in iNSIP. We found that a higher anti-MX1 autoantibody level was a significant predictor of a good prognosis in patients with non-IPF idiopathic interstitial pneumonias. In this retrospective study, we sought to clarify the prognostic significance of the anti-MX1 autoantibody in IPF.

Methods

We measured anti-MX1 immunoglobulin (Ig) G, IgA, and IgM autoantibody levels by enzyme-linked immunosorbent assay in serum collected at the time of diagnosis from 71 patients with IPF diagnosed according to the 2018 IPF guideline. The gender-age-physiology (GAP) index was calculated in each case.

Results

The study population (59 men and 12 women) had a median age of 67 years. Serum anti-MX1 IgG and IgA autoantibody levels correlated positively with GAP stage (p < 0.05). Univariate Cox proportional hazards regression analysis did not identify an elevated anti-MX1 IgG, IgA, or IgM autoantibody level as a significant prognostic factor; however, a higher anti-MX1 IgA autoantibody level heralded significantly poorer survival after adjustment for GAP stage (p=0.030) and for percent forced vital capacity and modified Medical Research Council score (p=0.018). Neither the anti-MX1 IgG autoantibody nor the IgM autoantibody could predict survival after these adjustments.

Conclusions

The serum anti-MX1 IgA autoantibody level is a significant prognostic factor in IPF. Further studies are needed to clarify the pathophysiological role of this autoantibody in IPF.

Inhibition of lung microbiota-derived proapoptotic peptides ameliorates acute exacerbation of pulmonary fibrosis

Idiopathic pulmonary fibrosis is an incurable disease of unknown etiology. Acute exacerbation of idiopathic pulmonary fibrosis is associated with high mortality. Excessive apoptosis of lung epithelial cells occurs in pulmonary fibrosis acute exacerbation. We recently identified corisin, a proapoptotic peptide that triggers acute exacerbation of pulmonary fibrosis. Here, we provide insights into the mechanism underlying the processing and release of corisin. Furthermore, we demonstrate that an anticorisin monoclonal antibody ameliorates lung fibrosis by significantly inhibiting acute exacerbation in the human transforming growth factorβ1 model and acute lung injury in the bleomycin model. By investigating the impact of the anticorisin monoclonal antibody in a general model of acute lung injury, we further unravel the potential of corisin to impact such diseases. These results underscore the role of corisin in the pathogenesis of acute exacerbation of pulmonary fibrosis and acute lung injury and provide a novel approach to treating this incurable disease.

GSPE Protects against Bleomycin-Induced Pulmonary Fibrosis in Mice via Ameliorating Epithelial Apoptosis through Inhibition of Oxidative Stress

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive interstitial lung disease of unknown cause which leads to alveolar epithelial cell apoptosis followed by basement membrane disruption and accumulation of extracellular matrix, destroying the lung architecture. Oxidative stress is involved in the development of alveolar injury, inflammation, and fibrosis. Oxidative stress-mediated alveolar epithelial cell (AEC) apoptosis is suggested to be a key process in the pathogenesis of IPF. Therefore, the present study investigated whether grape seed proanthocyanidin extract (GSPE) could inhibit the development of pulmonary fibrosis via ameliorating epithelial apoptosis through the inhibition of oxidative stress. We found that GSPE significantly ameliorated the histological changes and the level of collagen deposition in bleomycin (BLM)-induced lungs. Moreover, GSPE attenuated lung inflammation by reducing the total number of cells in bronchoalveolar lavage (BAL) fluid and decreasing the expression of IL-6. We observed that the levels of H2O2 leading to oxidative stress were increased following BLM instillation, which significantly decreased with GSPE treatment both in vivo and in vitro. These findings showed that GSPE attenuated BLM-induced epithelial apoptosis in the mouse lung and A549 alveolar epithelial cell through the inhibition of oxidative stress. Furthermore, GSPE could attenuate mitochondrial-associated cell apoptosis via decreasing the Bax/Bcl-2 ratio. The present study demonstrates that GSPE could ameliorate bleomycin-induced pulmonary fibrosis in mice via inhibition of epithelial apoptosis through the inhibition of oxidative stress.

Long Noncoding RNA HOXA Cluster Anti-Sense RNA 2 Inhibits Mycoplasma pneumoniae-Induced Inflammation by Regulating the Nuclear Factor-KappaB Signaling Pathway

Mycoplasma pneumoniae (MP) is the primary cause of community-acquired lung inflammation. The MP-induced manifestations of pneumonia are associated with the release of pro-inflammatory cytokines; however, the mechanisms of MP-induced inflammation have not been fully clarified. The purpose of the present study was to determine whether long noncoding RNA HOXA cluster anti-sense RNA 2 (lncRNA HOXA-AS2) is involved in MP-induced inflammation. A model of MP-induced cellular inflammation was established using the human BEAS-2B lung epithelial cell line and lncRNA HOXA-AS2 levels were detected using reverse transcription-quantitative (RT-q) PCR. MTT and flow cytometric analysis were used to assess cell viability and apoptosis, respectively. The secretion of pro-inflammatory factors including tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6 were measured by ELISA, and protein levels of phosho- (p-)p65 and p-NF-κB inhibitor α (p-IκBα) were detected by western blotting. The results suggest that MP infection significantly decreases the level of lncRNA HOXA-AS2 in BEAS-2B cells. lncRNA HOXA-AS2 overexpression significantly enhanced cell viability, inhibited apoptosis, decreased pro-inflammatory factor expression (TNF-α, IL-β and IL-6) and inhibited NF-κB pathway activation in MP-stimulated BEAS-2B cells. Conversely, lncRNA HOXA-AS2-knockdown resulted in the opposite effects. In conclusion, lncRNA HOXA-AS2 is involved in MP infection-induced inflammation and regulates the NF-κB signaling pathway.

TGFβ1 induces resistance of human lung myofibroblasts to cell death via down-regulation of TRPA1 channels

BACKGROUND AND PURPOSE

TGFβ1-mediated myofibroblast activation contributes to pathological fibrosis in many diseases including idiopathic pulmonary fibrosis (IPF), where myofibroblast resistance to oxidant-mediated apoptosis is also evident. We therefore investigated the involvement of redox-sensitive TRPA1 ion channels on human lung myofibroblasts (HLMFs) cell death and TGFβ1-mediated pro-fibrotic responses.

EXPERIMENTAL APPROACH

The effects of TGFβ1 stimulation on TRPA1 expression and cell viability was studied in HLMFs derived from IPF patients and non-fibrotic patients. We also examined a model of TGFβ1-dependent fibrogenesis in human lung. We used qRT-PCR, immunofluorescent assays, overexpression with lentiviral vectors and electrophysiological methods.

KEY RESULTS

TRPA1 mRNA, protein and ion currents were expressed in HLMFs derived from both non-fibrotic patient controls and IPF patients, and expression was reduced by TGFβ1. TRPA1 mRNA was also down-regulated by TGFβ1 in a model of lung fibrogenesis in human lung. TRPA1 over-expression or activation induced HLMF apoptosis, and activation of TRPA1 channel activation by H₂ O₂ induced necrosis. TRPA1 inhibition following TGFβ1 down-regulation or pharmacological inhibition, protected HLMFs from both apoptosis and necrosis. Lentiviral vector mediated TRPA1 expression was also found to induce sensitivity to H₂ O₂ induced cell death in a TRPA1-negative HEK293T cell line.

CONCLUSION AND IMPLICATIONS

TGFβ1 induces resistance of HLMFs to TRPA1 agonist- and H₂ O₂ -mediated cell death via down-regulation of TRPA1 channels. Our data suggest that therapeutic strategies which prevent TGFβ1-dependent down-regulation of TRPA1 may reduce myofibroblast survival in IPF and therefore improve clinical outcomes.

Increased Levels of ER Stress and Apoptosis in a Sheep Model for Pulmonary Fibrosis Are Alleviated by In Vivo Blockade of the KCa3.1 Ion Channel

Idiopathic pulmonary fibrosis (IPF) is a fatal interstitial lung disease, characterized by progressive damage to the lung tissues. Apoptosis and endoplasmic reticulum stress (ER stress) in type II alveolar epithelial cells (AECs) and lung macrophages have been linked with the development of IPF. Therefore, apoptosis- and ER stress-targeted therapies have drawn attention as potential avenues for treatment of IPF. The calcium-activated potassium ion channel KCa3.1 has been proposed as a potential therapeutic target for fibrotic diseases including IPF. While KCa3.1 is expressed in AECs and macrophages, its influence on ER stress and apoptosis during the disease process is unclear. We utilized a novel sheep model of pulmonary fibrosis to demonstrate that apoptosis and ER stress occur in type II AECs and macrophages in sheep with bleomycin-induced lung fibrosis. Apoptosis in type II AEC and macrophages was identified using the TUNEL method of tagging fragmented nuclear DNA, while ER stress was characterized by increased expression of GRP-78 ER chaperone proteins. We demonstrated that apoptosis and ER stress in type II AECs and macrophages increased significantly 2 weeks after the final bleomycin infusion and remained high for up to 7 weeks post-bleomycin injury. Senicapoc treatment significantly reduced the rates of ER stress in type II AECs and macrophages that were resident in bleomycin-infused lung segments. There were also significant reductions in the rates of apoptosis of type II AECs and macrophages in the lung segments of senicapoc-treated sheep. In vivo blockade of the KCa3.1 ion channel alleviates the ER stress and apoptosis in type II AECs and macrophages, and this effect potentially contributes to the anti-fibrotic effects of senicapoc.

sFasL-The Key to a Riddle: Immune Responses in Aging Lung and Disease

By dint of the aging population and further deepened with the Covid-19 pandemic, lung disease has turned out to be a major cause of worldwide morbidity and mortality. The condition is exacerbated when the immune system further attacks the healthy, rather than the diseased, tissue within the lung. Governed by unremittingly proliferating mesenchymal cells and increased collagen deposition, if inflammation persists, as frequently occurs in aging lungs, the tissue develops tumors and/or turns into scars (fibrosis), with limited regenerative capacity and organ failure. Fas ligand (FasL, a ligand of the Fas cell death receptor) is a key factor in the regulation of these processes. FasL is primarily found in two forms: full length (membrane, or mFasL) and cleaved (soluble, or sFasL). We and others found that T-cells expressing the mFasL retain autoimmune surveillance that controls mesenchymal, as well as tumor cell accumulation following an inflammatory response. However, mesenchymal cells from fibrotic lungs, tumor cells, or cells from immune-privileged sites, resist FasL⁺ T-cell-induced cell death. The mechanisms involved are a counterattack of immune cells by FasL, by releasing a soluble form of FasL that competes with the membrane version, and inhibits their cell death, promoting cell survival. This review focuses on understanding the previously unrecognized role of FasL, and in particular its soluble form, sFasL, in the serum of aged subjects, and its association with the evolution of lung disease, paving the way to new methods of diagnosis and treatment.

Intractable diffuse pulmonary diseases: Manual for diagnosis and treatment

This manual has been compiled by a joint production committee with the Diffuse Lung Disease Assembly of the Japanese Respiratory Society (JRS) to provide a practical manual for the epidemiology, diagnosis, and treatment of intractable diffuse pulmonary diseases. The contents are based upon the results of research into these diseases by the Diffuse Pulmonary Diseases Study Group (principal researcher: Sakae Homma) supported by the FY2014-FY2016 Health and Labor Sciences Research Grant on Intractable Diseases. This manual focuses on: 1) pulmonary alveolar microlithiasis, 2) bronchiolitis obliterans, and 3) Hermansky-Pudlak Syndrome with interstitial pneumonia. As these are rare/intractable diffuse lung diseases (2 and 3 were first recognized as specified intractable diseases in 2015), there have not been sufficient epidemiological studies made, and there has been little progress in formulating diagnostic criteria and severity scales; however, the results of Japan's first surveys and research into such details are presented herein. In addition, the manual provides treatment guidance and actual cases for each disease, aiming to assist in the establishment of future modalities. The manual was produced with the goal of enabling clinicians specialized in respiratory apparatus to handle these diseases in clinical settings and of further advancing future research and treatment.

Current advances in idiopathic pulmonary fibrosis: the pathogenesis, therapeutic strategies and candidate molecules

Idiopathic pulmonary fibrosis (IPF) is a type of chronic, progressive lung disease with unknown cause, which is characterized by increasing dyspnea and destruction of lung function with a high mortality rate. Evolving evidence demonstrated that the pathogenesis of IPF involved multiple signaling pathways such as inflammation, oxidative stress and fibrosis. However, drug discovery to prevent or revert IPF has been insufficient to cope with the development. Drug discovery targeting multiple links should be considered. In this review, we will brief the pathogenesis of IPF and discuss several small chemical entities toward the pathogenesis for IPF studied in animal models and clinical trials. The field of novel anti-IPF agents and the future directions for the prevention and treatment of IPF are detailed thoroughly discussed.

Deterioration of alveolar development in mice with both HIF-3α knockout and HIF-2α knockdown

Objective

Earlier studies from our group using hypoxia-inducible factor 3α knockout mice showed impairments in lung remodeling and lung endothelial cells. Another research from our group demonstrated that impaired expression of hypoxia-inducible factor 2α induced compensatory expression of hypoxia-inducible factor 1α in hypoxia-inducible factor 2α knockdown mice. The present study uncovers more insights by extending the investigation, utilizing mice with both hypoxia-inducible factor 3α knockout and hypoxia-inducible factor 2α knockdown.

Results

No mice with both hypoxia-inducible factor 3α knockout and hypoxia-inducible factor 2α knockdown died immediately after birth. The mice with both hypoxia-inducible factor 3α knockout and hypoxia-inducible factor 2α knockdown exhibited impaired alveolar sacs and lung alveolar structure and decreased endothelial cell numbers. Analysis of relative mRNA expression revealed depressed expressions of hypoxia-inducible factor 1α, vascular cell adhesion molecule 1, vascular endothelial cadherin, angiopoietin 2, Tie-2, and vascular endothelial growth factor in the lungs of mice with both hypoxia-inducible factor 3α knockout and hypoxia-inducible factor 2α knockdown compared to that in wild-type mice. Further analysis is needed to elucidate the impaired development occurred in the lung endothelial cells.

Potential contribution of alveolar epithelial type I cells to pulmonary fibrosis

Pulmonary fibrosis (PF) is characterized by inflammation and fibrosis of the interstitium and destruction of alveolar histoarchitecture ultimately leading to a fatal impairment of lung function. Different concepts describe either a dominant role of inflammatory pathways or a disturbed remodeling of resident cells of the lung parenchyma during fibrogenesis. Further, a combination of both the mechanisms has been postulated. The present review emphasizes the particular involvement of alveolar epithelial type I cells in all these processes, their contribution to innate immune/inflammatory functions and maintenance of proper alveolar barrier functions. Amongst the different inflammatory and repair events the purinergic receptor P2X7, an ATP-gated cationic channel that regulates not only apoptosis, necrosis, autophagy, and NLPR3 inflammosome activation, but also the turnover of diverse tight junction (TJ) and water channel proteins, seems to be essential for the stability of alveolar barrier integrity and for the interaction with protective factors during lung injury.

Oxidative Modifications of Protein Tyrosyl Residues Are Increased in Plasma of Human Subjects with Interstitial Lung Disease

RATIONALE

Interstitial lung diseases (ILDs) are associated with oxidative stress. Plasma biomarkers that are directly linked to oxidative stress responses in this disease have not been identified. Stable oxidation products of tyrosine residues in proteins may reflect the oxidative microenvironment in the lung or a systemic inflammatory state.

OBJECTIVES

To determine if levels of protein tyrosine oxidation are elevated in plasma of patients with ILD compared with an age- and sex-matched healthy control cohort.

METHODS

Three tyrosine oxidation products (3-chlorotyrosine, 3-nitrotyrosine, and o,o'-dityrosine) were quantified by tandem mass spectrometry in cellular models, a mouse model of injury-induced fibrosis, and in plasma of healthy control subjects and patients with ILD (n = 42 in each group).

MEASUREMENTS AND MAIN RESULTS

Plasma levels of 3-chlorotyrosine, 3-nitrotyrosine, and o,o'-dityrosine were markedly elevated in patients with ILD compared with control subjects with receiver operating characteristic curves separating these groups of 0.872, 0.893, and 0.997, respectively. In a murine model of lung fibrosis, levels of all three oxidative tyrosine modifications were increased in plasma and lung tissue. Cellular models support a critical role for a heme peroxidase and enzymatic sources of reactive oxygen species in the generation of these oxidized products.

CONCLUSIONS

We demonstrate an increase in oxidized tyrosine moieties within proteins in the circulating plasma of patients with ILD. These data support the potential for development of oxidative stress-related biomarkers in early diagnosis, prognostication, and/or in evaluating responsiveness to emerging therapies for ILD.

Breakdown of Epithelial Barrier Integrity and Overdrive Activation of Alveolar Epithelial Cells in the Pathogenesis of Acute Respiratory Distress Syndrome and Lung Fibrosis

Individual alveolar epithelial cells (AECs) collaboratively form a tight barrier between atmosphere and fluid-filled tissue to enable normal gas exchange. The tight junctions of AECs provide intercellular sealing and are integral to the maintenance of the AEC barrier integrity. Disruption and failure of reconstitution of AEC barrier result in catastrophic consequences, leading to alveolar flooding and subsequent devastating fibrotic scarring. Recent evidences reveal that many of the fibrotic lung diseases involve AECs both as a frequent target of injury and as a driver of ongoing pathological processes. Aberrantly activated AECs express most of the growth factors and chemokines responsible for the proliferation, migration, and activation of fibroblasts. Current evidences suggest that AECs may acquire overdrive activation in the initial step of fibrosis by several mechanisms, including abnormal recapitulation of the developmental pathway, defects of the molecules essential for epithelial integrity, and acceleration of aging-related properties. Among these initial triggering events, epithelial Pten, a multiple phosphatase that negatively regulates the PI3K/Akt pathway and is crucial for lung development, is essential for the prevention of alveolar flooding and lung fibrosis through the regulation of AEC barrier integrity after injury. Reestablishment of AEC barrier integrity also involves the deployment of specialized stem/progenitor cells.

Increased ectodomain shedding of cell adhesion molecule 1 as a cause of type II alveolar epithelial cell apoptosis in patients with idiopathic interstitial pneumonia

BACKGROUND

Lung alveolar epithelial cell (AEC) apoptosis has attracted attention as an early pathogenic event in the development of idiopathic interstitial pneumonia (IIP); however, the causative mechanism remains unclear. Cell adhesion molecule 1 (CADM1) is an AEC adhesion molecule in the immunoglobulin superfamily. It generates a membrane-associated C-terminal fragment, αCTF, through protease-mediated ectodomain shedding, termed α-shedding. Increased CADM1 α-shedding contributes to AEC apoptosis in emphysematous lungs.

METHODS

Formalin-fixed, paraffin-embedded lung lobes (n = 39) from 36 autopsied patients with IIP were classified as acute IIP (n = 10), fibrosing-type nonspecific IIP (f-NSIP, n = 10), cryptogenic organizing IIP (n = 9), and usual IIP (n = 10). CADM1 expression in the lung sections was examined by western blotting and compared with control lungs (n = 10). The rate of CADM1 α-shedding was calculated as the relative amount of αCTF to full-length CADM1, and the full-length CADM1 level was estimated per epithelial cell by normalization to cytokeratin 7, a lung epithelial marker. Apoptotic AECs were detected by immunohistochemistry for single-stranded DNA (ssDNA). NCI-H441 and A549 human lung epithelial cells were transfected with small interfering RNA (siRNA) to silence CADM1 expression and analyzed by terminal nucleotide nick end labeling assays.

RESULTS

The rate of CADM1 α-shedding was higher in all IIP subtypes than in the control (P ≤ 0.019), and the full-length CADM1 level was lower in f-NSIP (P = 0.007). The α-shedding rate and full-length CADM1 level were correlated with each other (P = 0.015) and with the proportion of ssDNA-positive AECs (P ≤ 0.024). NCI-H441 cells transfected with siRNA exhibited a 61 % lower rate of expression of full-length CADM1 and a 17-fold increased proportion of apoptotic cells. Similar results were obtained with A549 cells.

CONCLUSIONS

CADM1 α-shedding appeared to be increased in all four IIP subtypes and consequently contributed to AEC apoptosis by decreasing the full-length CADM1 level. This mechanism particularly impacted f-NSIP. The molecular mechanism causing AEC apoptosis may be similar between IIP and emphysema.

Beyond TGFβ--novel ways to target airway and parenchymal fibrosis

Within the lungs, fibrosis can affect both the parenchyma and the airways. Fibrosis is a hallmark pathological change in the parenchyma in patients with idiopathic pulmonary fibrosis (IPF), whilst in asthma or chronic obstructive pulmonary disease (COPD) fibrosis is a component of the remodelling of the airways. In the past decade, significant advances have been made in understanding the disease behaviour and pathogenesis of parenchymal and airway fibrosis and as a result a variety of novel therapeutic targets for slowing or preventing progression of these fibrotic changes have been identified. This review highlights a number of these targets and discusses the potential for treating parenchymal or airway fibrosis through these mediators/pathways in the future.

Revealing the pathogenic and aging-related mechanisms of the enigmatic idiopathic pulmonary fibrosis. an integral model

A growing body of evidence indicates that aberrant activation of alveolar epithelial cells and fibroblasts in an aging lung plays a critical role in the pathogenesis of idiopathic pulmonary fibrosis (IPF). However, the biopathological processes linking aging with IPF and the mechanisms responsible for the abnormal activation of epithelial cells and fibroblasts have not been elucidated. Many of the hallmarks of aging (e.g., genomic instability, telomere attrition, epigenetic alterations, mitochondrial dysfunction, and cellular senescence) have been proposed as essential mechanisms for the development of IPF; however, these disturbances are not restricted to IPF and also occur in other aging-related lung disorders, primarily chronic obstructive pulmonary disease (COPD). Therefore, an unanswered question is why a current/former smoker of about 60 years of age with shorter telomeres, alveolar epithelial senescence, excessive oxidative stress, and mitochondrial dysfunction develops IPF and not COPD; in other words, what makes old lungs specifically susceptible to develop IPF? In this Perspective, we propose an integral model in which the combination of some gene variants and/or gene expression in the aging lung results in the loss of epithelial integrity and consequently in the failure of the alveoli to correctly respond to injury and to face the stress associated with mechanical stretch. Afterward, a distinctive epigenetic "reprogramming" that affects both epithelial cells and fibroblasts provokes, among others, the recapitulation of developmental pathways and the aberrant activation and miscommunication between both cell types, resulting in the exaggerated production and accumulation of extracellular matrix and the subsequent destruction of the lung architecture.

The role of Bcl-2 family proteins in pulmonary fibrosis

Pulmonary fibrosis is characterized by epithelial injury, abnormal tissue repair, fibroproliferation and loss of pulmonary function as a result of a complex interaction of multiple cellular and molecular processes. There is accumulating evidence in support of a role for apoptosis in the pathogenesis of interstitial lung diseases. The Bcl-2 (B-cell lymphoma-2) family of proteins, which consists of antiapoptotic and pro-apoptotic members, is a critical regulator for apoptosis and development of pulmonary fibrosis. The association between Bcl-2 family members and various pathways and mediators has been also described in the pulmonary fibrosis. This article reviews the recent advances regarding the roles of Bcl-2 family as the apoptosis-regulatory factors in pulmonary fibrosis from human tissue studies, animal models, ex vivo and in vitro studies. Further understanding of apoptosis signaling regulation through Bcl-2 family proteins in the lung tissue may lead to better design of new therapeutic interventions for pulmonary fibrosis.

Influence of age on wound healing and fibrosis

The incidence and severity of fibrotic lung diseases increase with age, but very little is known about how age-related changes affect the mechanisms that underlie disease emergence and progression. Normal ageing includes accumulation of DNA mutations, oxidative and cell stresses, mitochondria dysfunction, increased susceptibility to apoptosis, telomere length dysfunction and differential gene expression as a consequence of epigenetic changes and miR regulation. These inevitable ageing-related phenomena may cause dysfunction and impaired repair capacity of lung epithelial cells, fibroblasts and MSCs. As a consequence, the composition of the extracellular matrix changes and the dynamic interaction between cells and their environment is damaged, resulting ultimately in predisposition for several diseases. This review summarizes what is known about age-related molecular changes that are implicated in the pathobiology of lung fibrosis in lung tissue.

Homeodomain-interacting protein kinase2 in human idiopathic pulmonary fibrosis

Homeodomain-interacting protein kinase 2 (Hipk2) is an emerging player in cell response to genotoxic agents that contributes to the cell's decision between cell cycle arrest or apoptosis. HIPK2 acts as co-regulator of an increasing number of transcription factors and modulates many different basic cellular processes such as apoptosis, proliferation, DNA damage response, differentiation. Idiopathic pulmonary fibrosis (IPF) is characterized by an anatomical disarrangement of the lung due to fibroblast proliferation, extracellular matrix deposition and lung function impairment. Although the role of inflammation is still debated, attention has been focused on lung cell functions as fibroblast phenotype and activity. Aim of the present study was to analyze the loss of heterozygosity (LOH) at HIPK2 locus 7q32.34 in human lung fibroblasts and the HIPK2 expression in 15 IPF samples and in four primary fibroblast cell cultures isolated from IPF biopsies using semi-quantitative RT-PCR, Western blots and immunohistochemistry. We demonstrated a frequency of LOH in IPF fibroblasts of 46% for the internal D7S6440 microsatellite and 26.6% for the external D7S2468 microsatellite. Furthermore, we demonstrated low HIPK2 protein expression in those fibroblasts from IPF patients that present the HIPK2 LOH. The restoration of HIPK2 expression in IPF derived cells induced a significant reduction of chemoresistance after treatment with cisplatin. The results obtained allow us to hypothesize that HIPK2 dysfunction may play a role in fibroblasts behavior and in IPF pathogenesis. HIPK2 may be considered as a novel potential target for anti-fibrosis therapy.

Hypermethylation-mediated silencing of p14(ARF) in fibroblasts from idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a devastating lung disease of unknown etiology. A conspicuous feature is the formation and persistence of fibroblastic/myofibroblastic foci throughout the lung parenchyma. Mechanisms remain unknown, but data indicate that fibroblasts acquire an antiapoptotic phenotype. We hypothesized that transcriptional silencing of proapoptotic genes may be implicated, and accordingly we evaluated the epigenetic regulation of p14(ARF). The expression of p14(ARF) was analyzed by RT-PCR in IPF (n = 8) and normal derived fibroblasts (n = 4) before and after treatment with 5-aza-2'-deoxycytidine (5-aza) and trichostatin A (TSA). p14(ARF) gene promoter methylation was determined by methylation-specific PCR (MS-PCR) and by DNA digestion with endonuclease McrBc, which cleaves 50% of methylated CpG. Apoptosis was evaluated by Annexin-V and nuclear staining. p14(ARF) expression was significantly decreased in four of the eight IPF fibroblasts lines, which was restored after 5-aza treatment. No changes were found with TSA. MS-PCR of bisulfite-treated genomic DNA showed a correlation between the reduced expression of p14(ARF) and the presence of hypermethylated promoter. No amplification was observed in the DNA treated with the McrBc enzyme, corroborating promoter hypermethylation. p14(ARF)-hypermethylated IPF fibroblasts were significantly more resistant to staurosporine-and S-nitrosoglutathione-induced apoptosis compared with normal and nonmethylated IPF fibroblasts (P < 0.01) and showed reduced levels of p53. Resistance to apoptosis was provoked in fibroblasts when p14(ARF) expression was inhibited by siRNA (P < 0.05). These findings demonstrate that many IPF fibroblasts have reduced expression of the proapoptotic p14(ARF) attributable to promoter hypermethylation and indicate that epigenetic mechanisms may underlie their resistance to apoptosis.

Targeting NOX enzymes in pulmonary fibrosis

Oxidative stress has been associated with a number of human fibrotic diseases, including idiopathic pulmonary fibrosis (IPF). Oxidative stress is most often defined as an imbalance between the generation of reactive oxygen species (ROS) in excess of the capacity of cells/tissues to detoxify or scavenge them. Additionally, the regulated production of ROS participates in cellular signaling. Therapeutic strategies to treat IPF have, thus far, focused on augmenting anti-oxidant capacity. Recent studies have demonstrated a critical role for ROS-generating enzymatic systems, specifically, NADPH oxidase (NOX) family oxidoreductases in fibrotic processes. In this review, we examine the evidence for NOX isoforms in the generation and perpetuation of fibrosis, and the potential to target this gene family for the treatment of IPF and related fibrotic disorders.

Drug-induced interstitial lung disease in tyrosine kinase inhibitor therapy for non-small cell lung cancer: a review on current insight

PURPOSE

With recent advances in targeted therapy such as tyrosine kinase inhibitor (TKI) therapy for non-small cell lung cancer (NSCLC), pulmonary toxicity has emerged as a problem. The recognition of common CT findings and patterns of TKI-induced interstitial lung disease (ILD) is mandatory for achieving a timely diagnosis and for the appropriate management of this condition. Therefore, familiarity with this complicating ILD is crucial.

METHODS

We reviewed all published literature in the English language regarding the ILD among NSCLC patients receiving TKIs.

RESULTS

The previous reports focused on the incidence, mortality rate, and risk factors of TKI-induced ILDs. This review elaborates on the diverse CT findings and predominant patterns of ILDs associated with TKI therapy. Emphases will be given on the role of CT, in particular, for the diagnosis of the subacute or chronic appearance of ILDs. This review also offers information about the pathogenesis and risk factor for the development of TKI-induced ILD. Representative cases will be presented as a pictorial review.

CONCLUSIONS

It is important to recognize the various patterns of TKI-induced ILDs, which increase in incidence with the introduction of diverse types of molecularly targeted agents. Poor prognoses are expected when there is a short interval from the initiation of target therapy to the onset of ILD, acute interstitial pneumonia pattern of ILD, and preexisting pulmonary fibrosis.

Modern concepts on the role of inflammation in pulmonary fibrosis

CONTEXT

Idiopathic pulmonary fibrosis is a uniformly lethal disease with limited biomarkers and no proven therapeutic intervention short of lung transplantation. Pulmonary fibrosis at one time was thought to be a result of inflammation in the lung. Although some forms of pulmonary fibrosis may result from inflammation, idiopathic pulmonary fibrosis is currently thought to result from cell death primarily and inflammation secondarily.

OBJECTIVE

To determine the role of inflammation in pulmonary fibrosis in light of our laboratory's published and unpublished research and published literature.

DATA SOURCES

Review based on our laboratory's published and unpublished experimental data with relevant background and clinical context provided.

CONCLUSIONS

Although cell death is central to pulmonary fibrosis, the proper cytokine environment leading to macrophage polarization is also critical. Evaluation of this environment is promising both for the development of disease biomarkers and for targets for therapeutic intervention.

Severe lung fibrosis requires an invasive fibroblast phenotype regulated by hyaluronan and CD44

Hyaluronan synthase 2 and CD44 are required for severe lung fibrosis in response to bleomycin.

Tissue fibrosis is a major cause of morbidity, and idiopathic pulmonary fibrosis (IPF) is a terminal illness characterized by unremitting matrix deposition in the lung. The mechanisms that control progressive fibrosis are unknown. Myofibroblasts accumulate at sites of tissue remodeling and produce extracellular matrix components such as collagen and hyaluronan (HA) that ultimately compromise organ function. We found that targeted overexpression of HAS2 (HA synthase 2) by myofibroblasts produced an aggressive phenotype leading to severe lung fibrosis and death after bleomycin-induced injury. Fibroblasts isolated from transgenic mice overexpressing HAS2 showed a greater capacity to invade matrix. Conditional deletion of HAS2 in mesenchymal cells abrogated the invasive fibroblast phenotype, impeded myofibroblast accumulation, and inhibited the development of lung fibrosis. Both the invasive phenotype and the progressive fibrosis were inhibited in the absence of CD44. Treatment with a blocking antibody to CD44 reduced lung fibrosis in mice in vivo. Finally, fibroblasts isolated from patients with IPF exhibited an invasive phenotype that was also dependent on HAS2 and CD44. Understanding the mechanisms leading to an invasive fibroblast phenotype could lead to novel approaches to the treatment of disorders characterized by severe tissue fibrosis.

A lysosomal-mitochondrial death pathway is induced by solamargine in human K562 leukemia cells

Solamargine (SM), a steroidal alkaloid glycoside from Solanum nigrum L., displayed a superior cytotoxicity to many human tumor cells. Further investigation with human K562 leukemia cells found that SM could induce an early lysosomal rupture within 2h as assessed by acridine-orange relocation and alkalinization of lysosomes. Intracellular lysosomal rupture is also confirmed with the release of cathepsin B to cytosol detected by western blot. Subsequent mitochondrial damage including mitochondrial membrane permeabilization detected by decrease membrane potential as well as the release of cytochrome c from mitochondria was also observed. The cellular Ca(2+) overload is more pronounced in SM-treated cells. Cells exposed to 10 microM SM for 30 min showed a maximum 7-fold increase in intracellular calcium concentration compared with vehicle-treated controls. The down-expression of Bcl-2, up-regulation of Bax, caspase-3 and caspase-9 activities followed by above changes revealed that the cytotoxicity of SM was involved in a lysosomal-mitochondrial death pathway induced by SM.

Epithelial apoptosis as a clinical marker in idiopathic interstitial pneumonia

BACKGROUNDS

Epithelial cell apoptosis plays an important role in the pathogenesis of idiopathic interstitial pneumonia (IIP).

METHODS

Serum levels of caspase-cleaved cytokeratin-18 (M30) were measured in 55 patients with IIP and 34 healthy controls using enzyme-linked immunosorbent assays. The IIP cases included usual interstitial pneumonia (UIP; n = 30), nonspecific interstitial pneumonia (NSIP; n = 15), and cryptogenic organizing pneumonia (COP; n = 10). The radiological scoring was performed based on high-resolution computed tomography (HRCT) findings.

RESULTS

Patients with IIP had higher serum M30 levels than did the control group (178.6 ± 91.5 vs. 113.7 ± 46.8 U/L, p < 0.05). Among IIP patients, COP patients had higher serum M30 levels than did UIP or NSIP patients (264.9 ± 132.7, 139.2 ± 49.7, and 201.2 ± 81.1 U/L, respectively; COP vs. UIP, p < 0.01). Serum M30 levels were negatively correlated with forced vital capacity (FVC; r(s) = -0.31), percent-predicted FVC (FVC%; r(s) = -0.38), and percent-predicted forced expiratory volume in 1 s (FEV(1)%; r(s) = -0.36). Serum M30 levels were correlated with radiological ground-glass opacity scores (r(s) = 0.61).

CONCLUSION

The epithelial apoptosis marker serum level was correlated with IIP clinical status and is a potential marker to assess IIP.

Titanium dioxide nanoparticles cause apoptosis in BEAS-2B cells through the caspase 8/t-Bid-independent mitochondrial pathway

To understand the underlying mechanism for apoptosis induced by titanium dioxide nanoparticles (TNP), human airway epithelial cell line was cultured to investigate the relevant apoptosis pathways. Our results showed that the levels of reactive oxygen species and morphological apoptosis increased in a dose-dependent manner whereas cell viability decreased in a similar manner in response to TNP exposure in the BEAS-2B cells. The activities of caspase 3 and PARP were also increased in parallel to the morphological apoptosis. Levels of caspase 9 increased significantly whereas there were no detectable changes in caspase 8 and t-Bid in the TNP treated cells. Caspase 9 inhibition blocked the TNP-induced activation of caspase 3 significantly. The levels of bax, cytochrome C, p53 and bcl-2 also changed reflecting the activation of intrinsic apoptosis pathway. Our results provide solid evidence that apoptosis in BEAS-2B cells exposed to TNP occurred via a mitochondrial apoptosis pathway independent of caspase 8/t-Bid pathway.

Therapeutic effect of lecithinized superoxide dismutase on bleomycin-induced pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is thought to involve inflammatory infiltration of leukocytes, lung injury induced by reactive oxygen species (ROS), in particular superoxide anion, and fibrosis (collagen deposition). No treatment has been shown to improve definitively the prognosis for IPF patients. Superoxide dismutase (SOD) catalyzes the dismutation of superoxide anion to hydrogen peroxide, which is subsequently detoxified by catalase. Lecithinized SOD (PC-SOD) has overcome clinical limitations of SOD, including low tissue affinity and low stability in plasma. In this study, we examined the effect of PC-SOD on bleomycin-induced pulmonary fibrosis. Severity of the bleomycin-induced fibrosis in mice was assessed by various methods, including determination of hydroxyproline levels in lung tissue. Intravenous administration of PC-SOD suppressed the bleomycin-induced increase in the number of leukocytes in bronchoalveolar lavage fluid. Bleomycin-induced collagen deposition and increased hydroxyproline levels in the lung were also suppressed in animals treated with PC-SOD, suggesting that PC-SOD suppresses bleomycin-induced pulmonary fibrosis. The dose-response profile of PC-SOD was bell-shaped, but concurrent administration of catalase restored the ameliorative effect at high doses of PC-SOD. Intratracheal administration or inhalation of PC-SOD also attenuated the bleomycin-induced inflammatory response and fibrosis. The bell-shaped dose-response profile of PC-SOD was not observed for these routes of administration. We consider that, compared with intravenous administration, inhalation of PC-SOD may be a more therapeutically beneficial route of administration due to the higher safety and quality of life of the patient treated with this drug.

Protective effect of geranylgeranylacetone, an inducer of heat shock protein 70, against drug-induced lung injury/fibrosis in an animal model

BACKGROUND

To determine whether oral administration of geranylgeranylacetone (GGA), a nontoxic anti-ulcer drug that is an inducer of heat shock protein (HSP) 70, protects against drug-induced lung injury/fibrosis in vivo.

METHODS

We used a bleomycin (BLM)-induced lung fibrosis model in which mice were treated with oral 600 mg/kg of GGA before and after BLM administration. Inflammation and fibrosis were evaluated by histological scoring, hydroxyproline content in the lung and inflammatory cell count, and quantification by ELISA of macrophage inflammatory protein-2 (MIP-2) in bronchoalveolar lavage fluid. Apoptosis was evaluated by the TUNEL method. The induction of HSP70 in the lung was examined with western blot analysis and its localization was determined by immunohistochemistry.

RESULTS

We confirmed the presence of inflammation and fibrosis in the BLM-induced lung injury model and induction of HSP70 by oral administration of GGA. GGA prevented apoptosis of cellular constituents of lung tissue, such as epithelial cells, most likely related to the de novo induction of HSP70 in the lungs. GGA-treated mice also showed less fibrosis of the lungs, associated with the findings of suppression of both production of MIP-2 and inflammatory cell accumulation in the injured lung, compared with vehicle-treated mice.

CONCLUSION

GGA had a protective effect on drug-induced lung injury/fibrosis. Disease-modifying antirheumatic drugs such as methotrexate, which are indispensable for the treatment of rheumatoid arthritis, often cause interstitial lung diseases, an adverse event that currently cannot be prevented. Clinical use of GGA for drug-induced pulmonary fibrosis might be considered in the future.

Oxidative stress in the pathogenesis of diffuse lung diseases: a review

Oxidative stress is an imbalance between oxidants (reactive oxygen and nitrogen species) and antioxidants that may affect lipids, DNA, carbohydrates and proteins. The lung is continuously exposed to endogenous and exogenous oxidants (cigarette smoke, mineral dust, ozone, radiation). Reactive oxygen and nitrogen species are mainly produced by phagocytes as well as by polymorphonuclear, alveolar, bronchial and endothelial cells. A potential role of oxidative stress in the pathogenesis of diffuse lung diseases (particularly idiopathic pulmonary fibrosis) has been demonstrated. Increased oxidant levels and decreased antioxidant defences can contribute to the progression of idiopathic pulmonary fibrosis and other diffuse lung diseases. The growing number of papers on the different aspects of oxidant/antioxidant imbalance in diffuse lung diseases in the last decade reflects increasing interest in this topic and suggests that specific DLDs may be characterized by specific patterns of oxidation and antioxidant responses. The study of oxidative stress can provide insights into etiopathogenesis and favour the discovery of new treatments. In this review of the literature on oxidants and antioxidants in diffuse lung diseases, the focus is on idiopathic pulmonary fibrosis, sarcoidosis, pneumoconiosis and pulmonary fibrosis associated with systemic sclerosis.

WNT1-inducible signaling protein-1 mediates pulmonary fibrosis in mice and is upregulated in humans with idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is characterized by distorted lung architecture and loss of respiratory function. Enhanced (myo)fibroblast activation, ECM deposition, and alveolar epithelial type II (ATII) cell dysfunction contribute to IPF pathogenesis. However, the molecular pathways linking ATII cell dysfunction with the development of fibrosis are poorly understood. Here, we demonstrate, in a mouse model of pulmonary fibrosis, increased proliferation and altered expression of components of the WNT/beta-catenin signaling pathway in ATII cells. Further analysis revealed that expression of WNT1-inducible signaling protein-1 (WISP1), which is encoded by a WNT target gene, was increased in ATII cells in both a mouse model of pulmonary fibrosis and patients with IPF. Treatment of mouse primary ATII cells with recombinant WISP1 led to increased proliferation and epithelial-mesenchymal transition (EMT), while treatment of mouse and human lung fibroblasts with recombinant WISP1 enhanced deposition of ECM components. In the mouse model of pulmonary fibrosis, neutralizing mAbs specific for WISP1 reduced the expression of genes characteristic of fibrosis and reversed the expression of genes associated with EMT. More importantly, these changes in gene expression were associated with marked attenuation of lung fibrosis, including decreased collagen deposition and improved lung function and survival. Our study thus identifies WISP1 as a key regulator of ATII cell hyperplasia and plasticity as well as a potential therapeutic target for attenuation of pulmonary fibrosis.

Identification of annexin 1 as a novel autoantigen in acute exacerbation of idiopathic pulmonary fibrosis

Consistent with the hypothesis that pulmonary epithelial apoptosis is the key to the acute exacerbation of idiopathic pulmonary fibrosis (IPF), we conducted serological identification of Ags by recombinant expression cloning (SEREX) analysis using type II alveolar cell carcinoma (A549) cell lines to identify disease-related Abs. In a survey of Abs to the recombinant autoantigens identified by SEREX analysis, five Abs were identified as novel candidates for the acute exacerbation of IPF. Abs to annexin 1 were detected in 47 and 53% of the sera and bronchoalveolar lavage materials from patients with acute exacerbation of IPF. Some identical TCR Vbeta genes were identified in sequential materials obtained at 1-3 mo in all 10 acute exacerbation IPF cases, suggesting that some infiltrating CD4-positive T cells sharing limited epitopes expand by Ag-driven stimulation during disease extension. The CDR3 region of these identical TCR Vbeta genes showed high homology with the N-terminal portion of annexin 1, including in the HLA-DR ligand epitopes predicted by TEPITOPE analysis. By Western blotting analysis and observation of the CD4-positive T cell responses in bronchoalveolar lavage samples, the N-terminal portion of annexin 1 was cleaved and found to induce marked proliferative responses of CD4-positive T cells in three patients. Our study demonstrates that annexin 1 is an autoantigen that raises both Ab production and T cell response in patients with acute exacerbation of IPF, and that the N-terminal portion of annexin 1 plays some role in the pathogenesis of acute exacerbation in IPF patients.

The role of high mobility group box1 in pulmonary fibrosis

High mobility group box1 protein (HMGB1) was originally discovered as a nuclear binding protein, and is known to play an important role in acute lung injury. However, the role of HMGB1 in pulmonary fibrosis has not been addressed. Therefore, we measured the HMGB1 levels in serum and bronchoalveolar lavage fluids (BALF) from patients with idiopathic pulmonary fibrosis (IPF), nonspecific interstitial pneumonia, interstitial pneumonia associated with collagen vascular diseases, and hypersensitivity pneumonitis (HP) by enzyme-linked immunosorbent assay. We also assessed the HMGB1 expression in bleomycin-induced pulmonary fibrosis in mice, and examined the effect of anti-HMGB1 antibody and ethyl pyluvate, which inhibits the HMGB1 secretion from alveolar macrophages. In addition, we examined the effect of HMGB1 on fibroblast proliferation, apoptosis, and collagen synthesis in vitro. Serum HMGB1 levels were not significantly increased in interstitial lung diseases compared with control subjects. BALF HMGB1 levels were significantly increased in IPF and HP compared with control subjects. HMGB1 protein was predominantly detected in inflammatory cells and hyperplasic epithelial cells in IPF. In bleomycin-induced pulmonary fibrosis in mice, HMGB1 protein was predominantly up-regulated in bronchiolar epithelial cells at early phase and in alveolar epithelial and inflammatory cells in fibrotic lesions at later phase. Intraperitoneal injection of anti-HMGB1 antibody or ethyl pyluvate significantly attenuated lung inflammation and fibrosis in this model. HMGB1 significantly induced proliferation, but not apoptosis or collagen synthesis on cultured fibroblasts. HMGB1 may be a promising target against pulmonary fibrosis as well as acute lung injury.

Involvement of epithelial cell apoptosis in interstitial lung diseases

Lung epithelium is the primary site of lung damage in interstitial lung diseases. Although there are various initiating factors, the terminal stages are characterized by pulmonary fibrosis. Conventional therapy consisting of glucocorticoids or immunosuppressive drugs is usually ineffective. Epithelial cell apoptosis have been considered to be initial events in interstitial lung diseases. The death receptor-mediated signaling pathway directly induces caspase activation and apoptosis. Other stresses induce the release of cytochrome from mitochondria and caspase activation. Endoplasmic reticulum stress also induces apoptosis. Epithelial cell death is followed by remodeling processes, which consist of epithelial and fibroblast activation, cytokine production, activation of the coagulation pathway, neoangiogenesis, re-epithelialization and fibrosis. Epithelial and mesenchymal interaction plays important roles in these processes. Further understanding of apoptosis signaling may lead to effective strategies against devastating lung diseases. We review the role of epithelial cell apoptosis in the molecular mechanisms of pulmonary fibrosis.

(5R)-5-hydroxytriptolide (LLDT-8) protects against bleomycin-induced lung fibrosis in mice

AIM

To study the protective effects of a triptolide-derived, novel compound, (5R)-5-hydroxytriptolide (LLDT-8), on bleomycin-induced lung fibrosis.

METHODS

C57BL/6 mice received an intratracheal injection of bleomycin and were then treated with LLDT-8 (0.5, 1, 2 mg/kg, ip) once daily for 7 or 14 consecutive days. The body weight loss and lung index augmentation was observed; the inflammatory response including differential cells counts of neutrophils, macrophages, and lymphocytes in the bronchoalveolar lavage fluid (BALF), superoxide dismutase (SOD), and malondialdehyde (MDA) level in the lung homogenates was detected, and the fibrosis extent was evaluated by hydroxyproline content and histopathological changes in the lungs. In addition, the pro-inflammatory and pro-fibrotic cytokines, tumor necrosis factor-alpha (TNF-alpha), interleukin-4 (IL-4), and transforming growth factor-alpha (TGF-alpha) production in the lungs were measured.

RESULTS

LLDT-8 alleviated the body weight loss and lung index increase caused by bleomycin, reduced neutrophils and lymphocytes in the BALF, promoted SOD activity, decreased MDA production, and inhibited the hydroxyproline level and the amelioration of lung tissue histological damage. Moreover, LLDT-8 suppressed TNF-alpha, IL-4, and TGF-beta production in the lung homogenates.

CONCLUSION

LLDT-8 showed protective effects against bleomycin-induced lung fibrosis, and the results suggested the potential role of LLDT-8 in the treatment of this disease.

Evolving concepts of apoptosis in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, relentlessly progressive fibrosing disease of the lung of unknown etiology. Significant progress has been made in recent years in elucidating key aspects of the pathobiology of IPF. Insights into disease pathogenesis have come from studies of cell biology, growth factor/cytokine signaling, animal models of pulmonary fibrosis, and human IPF cells and tissue. A consistent finding in the ultrastructural pathology of IPF is alveolar epithelial cell injury and apoptosis. Another consistent finding in the histopathology of human IPF, described as usual interstitial pneumonia, is the accumulation of aggregates of myofibroblasts in fibroblastic foci. The extent or profusion of fibroblastic foci in lung biopsies is strongly correlated with increased mortality in patients with IPF. There is emerging evidence that myofibroblasts in IPF/usual interstitial pneumonia, both in the in vivo microenvironment and during the process of differentiation in vitro, acquire resistance to apoptosis. Here, we review the current evidence and mechanisms for this apparent "apoptosis paradox" in the pathogenesis of IPF.

Interstitial lung disease in patients with non-small-cell lung cancer treated with epidermal growth factor receptor inhibitors

Interstitial lung disease (ILD) refers to a diverse range of pulmonary fibrotic disorders and may be hard to accurately diagnose, as distinguishing it from other pulmonary diseases can be difficult. Estimations of the incidence in populations are confounded by the complexity of the different forms of the disorder. In addition, ILD is a comorbid disease of lung cancer and is seen after most forms of chemotherapy and radiotherapy for advanced lung cancer. Incidences of >or=10% have been reported; however, whatever the true incidence, both chemotherapy and radiotherapy enhance the risk of developing ILD. ILD has also been reported with the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors, including erlotinib (Tarceva, OSI-774) and gefitinib (IRESSA). In a large number of gefitinib-treated patients (n > 185,000) an incidence of approx 1% has been observed (approx 2% in Japan; 0.3% in the rest of the world). Nevertheless, as with other treatments for advanced non-small-cell lung cancer, the clinical benefit outweighs the risk of ILD. In this article, we review the data on ILD with EGFR inhibitors and other common lung cancer treatments.

Critical roles of capillary endothelial cells for alveolar remodeling in nonspecific and usual interstitial pneumonias

To characterize the relationship between angiogenesis factors and alveolar remodeling in interstitial lung diseases, we examined alveolar capillary endothelial cells in the normal lung (n=5) and in lungs with nonspecific interstitial pneumonia (NSIP) (n=4) or usual interstitial pneumonia (UIP) (n=6) using immunofluorescence staining for thrombmodulin and von Willebrand factor (vWF). With three-dimensional images of alveolar capillaries, the diameter of capillary tubes and their branching frequency per unit length were determined to define rearrangement of the capillary meshwork. Alveolar capillary endothelial cells in normal lungs expressed surface thrombomodulin, and those in lungs with cellular NSIP often showed coexpression of surface thrombmodulin and cytoplasmic vWF. In the alveolar septa of fibrotic NSIP and UIP, capillary endothelial cells demonstrated vWF in only the cytoplasm. Capillary branching frequencies in NSIP and UIP were decreased to 45% and 22%, respectively, of the normal level (p<0.002). Compared with normal lungs, in NSIP and UIP lungs alveolar capillaries containing TUNEL-positive endothelial cells (p<0.05) showed increases of 3.6-fold and 4.3-fold, respectively, indicating a close correlation between endothelial cell apoptosis and remodeling of alveolar capillary frameworks. The analysis of mRNA expression of vascular endothelial growth factors (VEGF) and their receptors (VEGFR1 and VEGFR2) showed a significant decrease in each VEGF isoform and in VEGFR2 mRNA in representative alveolar wall tissues microdissected from the normal, NSIP, and UIP lungs. These results suggest that decreased expression of VEGF mRNA is associated with a reduction in the number of capillary tubes via endothelial cell apoptosis that possibly results in alveolar remodeling in NSIP and UIP. However, whether VEGF is related to fibroblastic activation in the interstitial matrix remains unclear.