Apoptosis in pulmonary fibrosis: too much or not enough?

Amifostine attenuates bleomycin-induced pulmonary fibrosis in mice through inhibition of the PI3K/Akt/mTOR signaling pathway

Amifostine is a normal cell protection agent, not only used in the adjuvant therapy of lung cancer, ovarian cancer, breast cancer, nasopharyngeal cancer, bone tumor, digestive tract tumor, blood system tumor and other cancers in order to reduce the toxicity of chemotherapy drugs, and recent studies have reported that the drug can also reduce lung tissue damage in patients with pulmonary fibrosis, but its mechanism of action is not yet fully understood. In this study, we explored the potential therapeutic effects and molecular mechanisms of AMI on bleomycin (BLM)-induced pulmonary fibrosis in mice. A mouse model of pulmonary fibrosis was established using BLM. We then assessed histopathological changes, inflammatory factors, oxidative indicators, apoptosis, epithelial-mesenchymal transition, extracellular matrix changes, and levels of phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling pathway-related proteins in the BLM-treated mice to determine the effect of AMI treatment on these factors. BLM-treated mice had substantial lung inflammation and abnormal extracellular matrix deposition. Overall, treatment with AMI significantly improved BLM-induced lung injury and pulmonary fibrosis. More specifically, AMI alleviated BLM-induced oxidative stress, inflammation, alveolar cell apoptosis, epithelial-mesenchymal transition, and extracellular matrix deposition by regulating the PI3K/Akt/mTOR signaling pathway. This finding that AMI can alleviate pulmonary fibrosis in a mouse model by inhibiting activation of the PI3K/Akt/mTOR signaling pathway lays a foundation for potential future clinical application of this agent in patients with pulmonary fibrosis.

Oxymatrine inhibits TGF‑β1‑mediated mitochondrial apoptotic signaling in alveolar epithelial cells via activation of PI3K/AKT signaling

Although pulmonary fibrosis (PF) causes respiratory failure and death, effective therapies for PF have not been developed. Oxymatrine (OMT), an active ingredient in the Chinese herb Sophora flavescens, exerts antifibrotic effects; however, its effect on PF remains unclear. The present study aimed to determine whether OMT decreases transforming growth factor-β1 (TGF-β1)-induced PF in human lung cancer A549 cells by inhibiting apoptosis and targeting the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway. To construct a PF cell model, A549 cells were stimulated with TGF-β1. The experimental groups were as follows: control (untreated cells grown in complete medium), TGF-β1 (cells treated with 5 ng/ml TGF-β1), OMT (cells treated with 5 ng/ml TGF-β1 and 0.25, 0.50, or 1.00 mg/ml OMT), and OMT + LY294002 (cells treated with 5 ng/ml TGF-β1, 1.0 mg/ml OMT. and 25 µmol/l LY294002). The effects of OMT on cell morphology (via electron microscopy), apoptosis (via Annexin V-PI staining), mitochondrial apoptosis signaling [using JC-1 method to analyze mitochondrial membrane potential (MMP)], and Bcl-2, as well as Bax expression (via western blotting and reverse transcription-quantitative polymerase chain reaction), were analyzed. OMT significantly protected cells against TGF-β1-induced PF by inhibiting apoptosis. The specific manifestations were cell injury, as evidenced by morphological changes and decreased MMP. Following OMT treatment, the expression of the pro-apoptotic protein Bax increased, whereas that of the anti-apoptotic protein Bcl-2 decreased. The PI3K/AKT-specific inhibitor LY294002 significantly inhibited the ameliorative effects of OMT on TGF-β1-induced apoptosis. Collectively, OMT attenuated TGF-β1-mediated mitochondrial apoptosis of alveolar epithelial cells by activating the PI3K/AKT signaling pathway. Therefore, OMT may be a promising drug for PF treatment.

Elevated expression of macrophage MERTK exhibits profibrotic effects and results in defective regulation of efferocytosis function in pulmonary fibrosis

Increased apoptosis of alveolar epithelial cells is a prominent feature of pulmonary fibrosis. Macrophage efferocytosis, phagocytosis of apoptotic cells by macrophages, is crucial for maintaining tissue homeostasis. Expression of Mer tyrosine kinase (MERTK, an important recognition receptor in efferocytosis) in macrophages is thought to be associated with fibrosis. However, how macrophage MERTK affects pulmonary fibrosis and whether it depends on efferocytosis are not yet clear. Here, we found elevated MERTK expression in lung macrophages from IPF patients and mice with bleomycin-induced pulmonary fibrosis. In vitro experiments showed that macrophages overexpressing MERTK exhibit profibrotic effects and that macrophage efferocytosis abrogates the profibrotic effect of MERTK by downregulating MERTK, forming a negative regulatory loop. In pulmonary fibrosis, this negative regulation is defective, and MERTK mainly exhibits profibrotic effects. Our study reveals a previously unsuspected profibrotic effect of elevated macrophage MERTK in pulmonary fibrosis and defective regulation of efferocytosis function as a result of that elevation, suggesting that targeting MERTK in macrophages may help to attenuate pulmonary fibrosis.

p53 and Myofibroblast Apoptosis in Organ Fibrosis

Organ fibrosis represents a dysregulated, maladaptive wound repair response that results in progressive disruption of normal tissue architecture leading to detrimental deterioration in physiological function, and significant morbidity/mortality. Fibrosis is thought to contribute to nearly 50% of all deaths in the Western world with current treatment modalities effective in slowing disease progression but not effective in restoring organ function or reversing fibrotic changes. When physiological wound repair is complete, myofibroblasts are programmed to undergo cell death and self-clearance, however, in fibrosis there is a characteristic absence of myofibroblast apoptosis. It has been shown that in fibrosis, myofibroblasts adopt an apoptotic-resistant, highly proliferative phenotype leading to persistent myofibroblast activation and perpetuation of the fibrotic disease process. Recently, this pathological adaptation has been linked to dysregulated expression of tumour suppressor gene p53. In this review, we discuss p53 dysregulation and apoptotic failure in myofibroblasts and demonstrate its consistent link to fibrotic disease development in all types of organ fibrosis. An enhanced understanding of the role of p53 dysregulation and myofibroblast apoptosis may aid in future novel therapeutic and/or diagnostic strategies in organ fibrosis.

Immune Mechanisms of Pulmonary Fibrosis with Bleomycin

Fibrosis and structural remodeling of the lung tissue can significantly impair lung function, often with fatal consequences. The etiology of pulmonary fibrosis (PF) is diverse and includes different triggers such as allergens, chemicals, radiation, and environmental particles. However, the cause of idiopathic PF (IPF), one of the most common forms of PF, remains unknown. Experimental models have been developed to study the mechanisms of PF, and the murine bleomycin (BLM) model has received the most attention. Epithelial injury, inflammation, epithelial-mesenchymal transition (EMT), myofibroblast activation, and repeated tissue injury are important initiators of fibrosis. In this review, we examined the common mechanisms of lung wound-healing responses after BLM-induced lung injury as well as the pathogenesis of the most common PF. A three-stage model of wound repair involving injury, inflammation, and repair is outlined. Dysregulation of one or more of these three phases has been reported in many cases of PF. We reviewed the literature investigating PF pathogenesis, and the role of cytokines, chemokines, growth factors, and matrix feeding in an animal model of BLM-induced PF.

The Role of Myofibroblasts in Physiological and Pathological Tissue Repair

Myofibroblasts are the construction workers of wound healing and repair damaged tissues by producing and organizing collagen/extracellular matrix (ECM) into scar tissue. Scar tissue effectively and quickly restores the mechanical integrity of lost tissue architecture but comes at the price of lost tissue functionality. Fibrotic diseases caused by excessive or persistent myofibroblast activity can lead to organ failure. This review defines myofibroblast terminology, phenotypic characteristics, and functions. We will focus on the central role of the cell, ECM, and tissue mechanics in regulating tissue repair by controlling myofibroblast action. Additionally, we will discuss how therapies based on mechanical intervention potentially ameliorate wound healing outcomes. Although myofibroblast physiology and pathology affect all organs, we will emphasize cutaneous wound healing and hypertrophic scarring as paradigms for normal tissue repair versus fibrosis. A central message of this review is that myofibroblasts can be activated from multiple cell sources, varying with local environment and type of injury, to either restore tissue integrity and organ function or create an inappropriate mechanical environment.

Effects of bone morphogenetic protein 4 on TGF-β1-induced cell proliferation, apoptosis, activation and differentiation in mouse lung fibroblasts via ERK/p38 MAPK signaling pathway

Fibroblasts, in particular myofibroblasts, are the critical effector cells in idiopathic pulmonary fibrosis (IPF), a deadly lung disease characterized by abnormal lung remodeling and the formation of "fibroblastic foci". Aberrant activation of TGF-β1 is frequently encountered and promotes fibroblast proliferation, activation, and differentiation in pulmonary fibrosis. Hence, the inhibition of TGF-β1-induced lung fibroblast activation holds promise as a therapeutic strategy for IPF. The present study aimed to investigate the potential effect and underlying mechanisms of bone morphogenetic protein 4 (BMP4) on TGF-β1-induced proliferation, apoptosis, activation and myofibroblast differentiation of adult lung fibroblasts. Here, we demonstrated that BMP4 expression was significantly decreased in TGF-β1-stimulated mouse primary lung fibroblasts (PLFs). BMP4 inhibited proliferation and apoptosis resistance of TGF-β1-stimulated mouse PLFs. BMP4 suppressed TGF-β1-induced fibroblast activation and differentiation in mouse PLFs. We also found that BMP4 inhibited TGF-β1-induced ERK and p38 MAPK phosphorylation. Our findings indicate that BMP4 exerts its anti-fibrotic effects by regulating fibroblast proliferation, apoptosis, activation and differentiation via the inhibition of the ERK/p38 MAPK signaling pathway, and thus has a potential for the treatment of pulmonary fibrosis.

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.

Interstitial lung disease in children with Rubinstein-Taybi syndrome

INTRODUCTION

Rubinstein-Taybi syndrome (RSTS) is a rare genetic syndrome caused primarily by a mutation in the CREBBP gene found on chromosome 16. Patients with RSTS are at greater risk for a variety of medical problems, including upper airway obstruction and aspiration. Childhood interstitial lung disease (ILD) thus far has not been definitively linked to RSTS. Here we present three patients with RSTS who developed ILD and discuss possible mechanisms by which a mutation in CREBBP may be involved in the development of ILD.

METHODS

Routine hematoxylin and eosin staining was performed on lung biopsy tissue for histological analysis. Immunofluorescent staining was performed on lung biopsy tissue for markers of fibrosis, surfactant deficiency and histone acetylation. Cases 1 and 2 had standard clinical microarray analysis. Case 3 had whole exome sequencing. Bioinformatics analyses were performed to identify possible causative genes using ToppGene.

RESULTS

Computed tomography images in all cases showed consolidated densities overlying ground glass opacities. Lung histopathology revealed accumulation of proteinaceous material within alveolar spaces, evidence of fibrosis, and increased alveolar macrophages. Immunofluorescent staining showed increase in surfactant protein C staining, patchy areas of increased anti-smooth muscle antibody staining, and increased staining for acetylated histone 2 and histone 3 lysine 9.

DISCUSSION

Clinical characteristics, radiographic imaging, lung histopathology, and immunofluorescent staining results shared by all cases demonstrated findings consistent with ILD. Immunofluorescent staining suggests two possible mechanisms for the development of ILD: abnormal surfactant metabolism and/or persistent activation of myofibroblasts. These two pathways could be related to dysfunctional CREBBP protein.

Mechanism of Fei-Xian Formula in the Treatment of Pulmonary Fibrosis on the Basis of Network Pharmacology Analysis Combined with Molecular Docking Validation

Objective

This study aimed to clarify the mechanism of Fei-Xian formula (FXF) in the treatment of pulmonary fibrosis based on network pharmacology analysis combined with molecular docking validation.

Methods

Firstly, ingredients in FXF with pharmacological activities, together with specific targets, were identified based on the BATMA-TCM and TCMSP databases. Then, targets associated with pulmonary fibrosis, which included pathogenic targets as well as those known therapeutic targets, were screened against the CTD, TTD, GeneCards, and DisGeNet databases. Later, Cytoscape was employed to construct a candidate component-target network of FXF for treating pulmonary fibrosis. In addition, for nodes within the as-constructed network, topological parameters were calculated using CytoHubba plug-in, and the degree value (twice as high as the median degree value for all the nodes) was adopted to select core components as well as core targets of FXF for treating pulmonary fibrosis, which were subsequently utilized for constructing the core network. Furthermore, molecular docking study was carried out on those core active ingredients together with the core targets using AutoDock Vina for verifying results of network pharmacology analysis. At last, OmicShare was employed for enrichment analysis of the core targets.

Results

Altogether 12 active ingredients along with 13 core targets were identified from our constructed core component-target network of FXF for the treatment of pulmonary fibrosis. As revealed by enrichment analysis, the 13 core targets mostly concentrated in regulating biological functions, like response to external stimulus (from oxidative stress, radiation, UV, chemical substances, and virus infection), apoptosis, cell cycle, aging, immune process, and protein metabolism. In addition, several pathways, like IL-17, AGE-RAGE, TNF, HIF-1, PI3K-AKT, NOD-like receptor, T/B cell receptor, and virus infection-related pathways, exerted vital parts in FXF in the treatment of pulmonary fibrosis.

Conclusions

FXF can treat pulmonary fibrosis through a “multicomponent, multitarget, and multipathway” mean. Findings in this work lay foundation for further exploration of the FXF mechanism in the treatment of pulmonary fibrosis.

An updated review of mechanistic potentials of melatonin against cancer: pivotal roles in angiogenesis, apoptosis, autophagy, endoplasmic reticulum stress and oxidative stress

Cancers are serious life-threatening diseases which annually are responsible for millions of deaths across the world. Despite many developments in therapeutic approaches for affected individuals, the rate of morbidity and mortality is high. The survival rate and life quality of cancer patients is still low. In addition, the poor prognosis of patients and side effects of the present treatments underscores that finding novel and effective complementary and alternative therapies is a critical issue. Melatonin is a powerful anticancer agent and its efficiency has been widely documented up to now. Melatonin applies its anticancer abilities through affecting various mechanisms including angiogenesis, apoptosis, autophagy, endoplasmic reticulum stress and oxidative stress. Regarding the implication of mentioned cellular processes in cancer pathogenesis, we aimed to further evaluate the anticancer effects of melatonin via these mechanisms.

Role of various imbalances centered on alveolar epithelial cell/fibroblast apoptosis imbalance in the pathogenesis of idiopathic pulmonary fibrosis

There have been recent extensive studies and rapid advancement on the pathogenesis underlying idiopathic pulmonary fibrosis (IPF), and intricate pathogenesis of IPF has been suggested. The purpose of this study was to clarify the logical relationship between these mechanisms. An extensive search was undertaken of the PubMed using the following keywords: “etiology,” “pathogenesis,” “alveolar epithelial cell (AEC),” “fibroblast,” “lymphocyte,” “macrophage,” “epigenomics,” “histone,” acetylation,” “methylation,” “endoplasmic reticulum stress,” “mitochondrial dysfunction,” “telomerase,” “proteases,” “plasminogen,” “epithelial-mesenchymal transition,” “oxidative stress,” “inflammation,” “apoptosis,” and “idiopathic pulmonary fibrosis.” This search covered relevant research articles published up to April 30, 2020. Original articles, reviews, and other articles were searched and reviewed for content; 240 highly relevant studies were obtained after screening. IPF is likely the result of complex interactions between environmental, genetic, and epigenetic factors: environmental exposures affect epigenetic marks; epigenetic processes translate environmental exposures into the regulation of chromatin; epigenetic processes shape gene expression profiles; in turn, an individual's genetic background determines epigenetic marks; finally, these genetic and epigenetic factors act in concert to dysregulate gene expression in IPF lung tissue. The pathogenesis of IPF involves various imbalances including endoplasmic reticulum, telomere length homeostasis, mitochondrial dysfunction, oxidant/antioxidant imbalance, Th1/Th2 imbalance, M1–M2 polarization of macrophages, protease/antiprotease imbalance, and plasminogen activation/inhibition imbalance. These affect each other, promote each other, and ultimately promote AEC/fibroblast apoptosis imbalance directly or indirectly. Excessive AEC apoptosis and impaired apoptosis of fibroblasts contribute to fibrosis. IPF is likely the result of complex interactions between environmental, genetic, and epigenetic factors. The pathogenesis of IPF involves various imbalances centered on AEC/fibroblast apoptosis imbalance.

Evasion of apoptosis by myofibroblasts: a hallmark of fibrotic diseases

Organ fibrosis is a lethal outcome of autoimmune rheumatic diseases such as systemic sclerosis. Myofibroblasts are scar-forming cells that are ultimately responsible for the excessive synthesis, deposition and remodelling of extracellular matrix proteins in fibrosis. Advances have been made in our understanding of the mechanisms that keep myofibroblasts in an activated state and control myofibroblast functions. However, the mechanisms that help myofibroblasts to persist in fibrotic tissues remain poorly understood. Myofibroblasts evade apoptosis by activating molecular mechanisms in response to pro-survival biomechanical and growth factor signals from the fibrotic microenvironment, which can ultimately lead to the acquisition of a senescent phenotype. Growing evidence suggests that myofibroblasts and senescent myofibroblasts, rather than being resistant to apoptosis, are actually primed for apoptosis owing to concomitant activation of cell death signalling pathways; these cells are poised to apoptose when survival pathways are inhibited. This knowledge of apoptotic priming has paved the way for new therapies that trigger apoptosis in myofibroblasts by blocking pro-survival mechanisms, target senescent myofibroblast for apoptosis or promote the reprogramming of myofibroblasts into scar-resolving cells. These novel strategies are not only poised to prevent progressive tissue scarring, but also have the potential to reverse established fibrosis and to regenerate chronically injured tissues.

Oxidative/nitrosative stress, autophagy and apoptosis as therapeutic targets of melatonin in idiopathic pulmonary fibrosis

INTRODUCTION

Idiopathic pulmonary fibrosis (IPF) is a fatal interstitial lung disease associated with disruption of alveolar epithelial cell layer and expansion of fibroblasts/myofibroblasts. Excessive levels of oxidative/nitrosative stress, induction of apoptosis, and insufficient autophagy may be involved in IPF pathogenesis; hence, the targeting of these pathways may ameliorate IPF. Areas covered: We describe the ameliorative effect of melatonin on IPF. We summarize the research on IPF pathogenesis with a focus on oxidative/nitrosative stress, autophagy and apoptosis pathways and discuss the potential effects of melatonin on these pathways. Expert opinion: Oxidative/nitrosative stress, apoptosis and autophagy could be interesting targets for therapeutic intervention in IPF. Melatonin, as a potent antioxidant, induces the expression of antioxidant enzymes, scavenges free radicals and modulates apoptosis and autophagy pathways. The effect of melatonin in the induction of autophagy could be an important mechanism against fibrotic process in IPF lungs. Further clinical studies are necessary to determine if melatonin could be a candidate for treating IPF.

CGRP attenuates hyperoxia-induced oxidative stress-related injury to alveolar epithelial type II cells via the activation of the Sonic hedgehog pathway

The aim of this study was to examine the effect of calcitonin gene-related peptide (CGRP) on primary alveolar epithelial type II (AECII) cells and expression of Sonic hedgehog (SHH) signaling pathway components following exposure to hyperoxia. The AECII cells were isolated and purified from premature rats and exposed to air (21% oxygen), air + CGRP, hyperoxia (95% oxygen) or hyperoxia + CGRP. The production of intracellular reactive oxygen species (ROS) was determined using the 2',7'-dichlorofluorescin diacetate molecular probe. The levels of malondialdehyde (MDA) and superoxide dismutase (SOD) in the culture supernatant were detected by spectrophotometry. The apoptosis of AECII cells was assayed by flow cytometry, and the mRNA and protein expression levels of Shh and Ptc1 in the AECII cells were detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR), western blot analysis and immunofluorescence, respectively. The cellular pathological changes partly improved and apoptosis was markedly decreased upon treatment with CGRP under hyperoxic conditions. The levels of ROS in the hyperoxia + CGRP group were significantly lower than thoe in the hyperoxia group. In addition, the hyperoxia-induced increase in MDA levels and the decrease in SOD activity in the culture supernatant of the AECII cells were attenuated by CGRP. Compared with the cells exposed to air, hyperoxia markedly inhibited the mRNA and protein expression levels of Shh and Ptc1 in the AECII cells; however, this inhibition was partly attenuated by treatment with CGRP. On the whole, our data suggest that CGRP can partly protect AECII cells from hyperoxia-induced injury, and the upregulation of CGRP may be a potential therapeutic approach with which to combat hyperoxia-induced lung injury, which may be associated with the activation of the SHH signaling pathway.

Mouse Lung Fibroblast Resistance to Fas-Mediated Apoptosis Is Dependent on the Baculoviral Inhibitor of Apoptosis Protein 4 and the Cellular FLICE-Inhibitory Protein

A characteristic feature of idiopathic pulmonary fibrosis (IPF) is accumulation of apoptotic resistant fibroblasts/myofibroblasts in the fibroblastic foci. As caveolin (Cav)-null mice develop pulmonary fibrosis (PF), we hypothesized that the participating fibroblasts display an apoptosis-resistant phenotype. To test this hypothesis and identify the molecular mechanisms involved we isolated lung fibroblasts from Cav-null mice and examined the expression of several inhibitors of apoptosis (IAPs), of c-FLIP, of Bcl-2 proteins and of the death receptor CD95/Fas. We found significant increase in XIAP and c-FLIP constitutive protein expression with no alteration of Bcl-2 and lower levels of CD95/Fas. The isolated fibroblasts were then treated with the CD95/Fas ligand (FasL) to induce apoptosis. While the morphological and biochemical alterations induced by FasL were similar in wild-type (wt) and Cav-null mouse lung fibroblasts, the time course and the extent of the alterations were greater in the Cav-null fibroblasts. Several salient features of Cav-null fibroblasts response such as loss of membrane potential, fragmentation of the mitochondrial continuum concurrent with caspase-8 activation, and subsequent Bid cleavage, prior to caspase-3 activation were detected. Furthermore, M30 antigen formation, phosphatidylserine expression and DNA fragmentation were caspase-3 dependent. SiRNA-mediated silencing of XIAP and c-FLIP, individually or combined, enhanced the sensitivity of lung fibroblasts to FasL-induced apoptosis. Pharmacological inhibition of Bcl-2 had no effect. Together our findings support a mechanism in which CD95/Fas engagement activates caspase-8, inducing mitochondrial apoptosis through Bid cleavage. XIAP and c-FLIP fine tune this process in a cell-type specific manner.

Thy-1 interaction with Fas in lipid rafts regulates fibroblast apoptosis and lung injury resolution

Thy-1-negative lung fibroblasts are resistant to apoptosis. The mechanisms governing this process and its relevance to fibrotic remodeling remain poorly understood. By using either sorted or transfected lung fibroblasts, we found that Thy-1 expression is associated with downregulation of anti-apoptotic molecules Bcl-2 and Bcl-xL, as well as increased levels of cleaved caspase-9. Addition of rhFasL and staurosporine, well-known apoptosis inducers, caused significantly increased cleaved caspase-3, -8, and PARP in Thy-1-transfected cells. Furthermore, rhFasL induced Fas translocation into lipid rafts and its colocalization with Thy-1. These in vitro results indicate that Thy-1, in a manner dependent upon its glycophosphatidylinositol anchor and lipid raft localization, regulates apoptosis in lung fibroblasts via Fas-, Bcl-, and caspase-dependent pathways. In vivo, Thy-1 deficient (Thy1^-/-) mice displayed persistence of myofibroblasts in the resolution phase of bleomycin-induced fibrosis, associated with accumulation of collagen and failure of lung fibrosis resolution. Apoptosis of myofibroblasts is decreased in Thy1^-/- mice in the resolution phase. Collectively, these findings provide new evidence regarding the role and mechanisms of Thy-1 in initiating myofibroblast apoptosis that heralds the termination of the reparative response to bleomycin-induced lung injury. Understanding the mechanisms regulating fibroblast survival/apoptosis should lead to novel therapeutic interventions for lung fibrosis.

Emodin ameliorates bleomycin-induced pulmonary fibrosis in rats by suppressing epithelial-mesenchymal transition and fibroblast activation

Aberrant activation of TGF-β1 is frequently encountered and promotes epithelial-mesenchymal transition (EMT) and fibroblast activation in pulmonary fibrosis. The present study investigated whether emodin mediates its effect via suppressing TGF-β1-induced EMT and fibroblast activation in bleomycin (BLM)-induced pulmonary fibrosis in rats. Here, we found that emodin induced apoptosis and inhibited cellular proliferation, migration and differentiation in TGF-β1-stimulated human embryonic lung fibroblasts (HELFs). Emodin suppressed TGF-β1-induced EMT in a dose- and time-dependent manner in alveolar epithelial A549 cells. Emodin also inhibited TGF-β1-induced Smad2, Smad3 and Erk1/2 activation, suggesting that Smad2/3 and Erk1/2 inactivation mediated the emodin-induced effects on TGF-β1-induced EMT. Additionally, we provided in vivo evidence suggesting that emodin apparently alleviated BLM-induced pulmonary fibrosis and improved pulmonary function by inhibiting TGF-β1 signaling and subsequently repressing EMT, fibroblast activation and extracellular matrix (ECM) deposition. Taken together, our data suggest that emodin mediates its effects mainly via inhibition of EMT and fibroblast activation and thus has a potential for the treatment of pulmonary fibrosis.

Exposure to Iron Oxide Nanoparticles Coated with Phospholipid-Based Polymeric Micelles Induces Biochemical and Histopathological Pulmonary Changes in Mice

The biochemical and histopathological changes induced by the exposure to iron oxide nanoparticles coated with phospholipid-based polymeric micelles (IONPs-PM) in CD-1 mice lungs were analyzed. After 2, 3, 7 and 14 days following the intravenous injection of IONPs-PM (5 and 15 mg Fe/kg bw), lactate dehydrogenase (LDH) activity, oxidative stress parameters and the expression of Bax, Bcl-2, caspase-3 and TNF-α were evaluated in lung tissue. An increase of catalase (CAT) and glutathione reductase (GR) activities on the second day followed by a decrease on the seventh day, as well as a decline of lactate dehydrogenase (LDH), superoxide dismutase (SOD) and glutathione peroxidase (GPx) activity on the third and seventh day were observed in treated groups vs. controls. However, all these enzymatic activities almost fully recovered on the 14th day. The reduced glutathione (GSH) and protein thiols levels decreased significantly in nanoparticles-treated groups and remained diminished during the entire experimental period; by contrast malondialdehyde (MDA) and protein carbonyls increased between the 3rd and 14th day of treatment vs. control. Relevant histopathological modifications were highlighted using Hematoxylin and Eosin (H&E) staining. In addition, major changes in the expression of apoptosis markers were observed in the first week, more pronounced for the higher dose. The injected IONPs-PM generated a dose-dependent decrease of the mouse lung capacity, which counteracted oxidative stress, thus creating circumstances for morphopathological lesions and oxidation processes.

MUC5B and Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF), a fatal disease that is a result of complex interactions between genetics and the environment, has limited treatment options. We have identified the MUC5B promoter polymorphism and other common genetic variants that in aggregate explain roughly one-third of disease risk. The MUC5B promoter polymorphism is the strongest and the most replicated genetic risk factor for IPF, appears to be protective and predictive in this disease, and is likely involved in disease pathogenesis through an increase in MUC5B expression in terminal bronchi and honeycombed cysts. Expression of MUC5B is also highly correlated with expression of cilium genes in IPF lung. Our work suggests that mucociliary dysfunction in the distal airway may play a role in the development of progressive fibroproliferative lung disease. In addition, our work has important implications for secondary prevention, early detection, and future early and personalized treatment based on genetic profiles.

Epigenetics in lung fibrosis: from pathobiology to treatment perspective

PURPOSE OF REVIEW

Idiopathic pulmonary fibrosis (IPF) is a fatal disease with limited treatment options and extensive gene expression changes identified in the lung parenchyma. Multiple lines of evidence suggest that epigenetic factors contribute to dysregulation of gene expression in IPF lung. Most importantly, risk factors that predispose to IPF - age, sex, cigarette smoke, and genetic variants - all influence epigenetic marks. This review summarizes recent findings of association of DNA methylation and histone modifications with the presence of disease and fibroproliferation.

RECENT FINDINGS

In addition to targeted studies focused on specific gene loci, genome-wide profiles of DNA methylation demonstrate widespread DNA methylation changes in IPF lung tissue and a substantial effect of these methylation changes on gene expression. Genetic loci that have been recently associated with IPF also contain differentially methylated regions, suggesting that genetic and epigenetic factors act in concert to dysregulate gene expression in IPF lung.

SUMMARY

Although we are in very early stages of understanding the role of epigenetics in IPF, the potential for the use of epigenetic marks as biomarkers and therapeutic targets is high and discoveries made in this field will likely bring us closer to better prognosticating and treating this fatal disease.

miR-9-5p suppresses pro-fibrogenic transformation of fibroblasts and prevents organ fibrosis by targeting NOX4 and TGFBR2

Uncontrolled extracellular matrix (ECM) production by fibroblasts in response to injury contributes to fibrotic diseases, including idiopathic pulmonary fibrosis (IPF). Reactive oxygen species (ROS) generation is involved in the pathogenesis of IPF. Transforming growth factor-β1 (TGF-β1) stimulates the production of NADPH oxidase 4 (NOX4)-dependent ROS, promoting lung fibrosis (LF). Dysregulation of microRNAs (miRNAs) has been shown to contribute to LF. To identify miRNAs involved in redox regulation relevant for IPF, we performed arrays in human lung fibroblasts exposed to ROS. miR-9-5p was selected as the best candidate and we demonstrate its inhibitory effect on TGF-β receptor type II (TGFBR2) and NOX4 expression. Increased expression of miR-9-5p abrogates TGF-β1-dependent myofibroblast phenotypic transformation. In the mouse model of bleomycin-induced LF, miR-9-5p dramatically reduces fibrogenesis and inhibition of miR-9-5p and prevents its anti-fibrotic effect both in vitro and in vivo. In lung specimens from patients with IPF, high levels of miR-9-5p are found. In omentum-derived mesothelial cells (MCs) from patients subjected to peritoneal dialysis (PD), miR-9-5p also inhibits mesothelial to myofibroblast transformation. We propose that TGF-β1 induces miR-9-5p expression as a self-limiting homeostatic response.

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.

MicroRNA regulatory networks in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and fatal scarring lung disease of unknown etiology, characterized by changes in microRNA expression. Activation of transforming growth factor (TGF-β) is a key event in the development of IPF. Recent reports have also identified epigenetic modification as an important player in the pathogenesis of IPF. In this review, we summarize the main results of studies that address the role of microRNAs in IPF and highlight the synergistic actions of these microRNAs in regulating TGF-β, the primary fibrogenic mediator. We outline epigenetic regulation of microRNAs by methylation. Functional studies identify microRNAs that alter proliferative and migratory properties of fibroblasts, and induce phenotypic changes in epithelial cells consistent with epithelial-mesenchymal transition. Though these studies were performed in isolation, we identify multiple co-operative actions after assembling the results into a network. Construction of such networks will help identify disease-propelling hubs that can be targeted for therapeutic purposes.

Epigenetics of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a complex lung disease of unknown etiology. Development of IPF is influenced by both genetic and environmental factors. Recent work by our and other groups has identified strong genetic predisposition factors for the development of pulmonary fibrosis, and cigarette smoke remains the most strongly associated environmental exposure risk factor. Gene expression profiling studies of IPF lung have taught us quite a bit about the biology of this fatal disease, and those of peripheral blood have provided important biomarkers. However, epigenetic marks may be the missing link that connects the environmental exposure in genetically predisposed individuals to transcriptional changes associated with disease development. Moreover, epigenetic marks represent a promising therapeutic target for IPF. In this review, the disease is introduced, genetic and gene expression studies in IPF are summarized, exposures relevant to IPF and known epigenetic changes associated with cigarette smoke exposure are discussed, and epigenetic studies conducted so far in IPF are summarized. Limitations, challenges, and future opportunities in this field are also discussed.

Gallic Acid Induces a Reactive Oxygen Species-Provoked c-Jun NH2-Terminal Kinase-Dependent Apoptosis in Lung Fibroblasts

Idiopathic pulmonary fibrosis is a chronic lung disorder characterized by fibroblasts proliferation and extracellular matrix accumulation. Induction of fibroblast apoptosis therefore plays a crucial role in the resolution of this disease. Gallic acid (3,4,5-trihydroxybenzoic acid), a common botanic phenolic compound, has been reported to induce apoptosis in tumor cell lines and renal fibroblasts. The present study was undertaken to examine the role of mitogen-activated protein kinases (MAPKs) in lung fibroblasts apoptosis induced by gallic acid. We found that treatment with gallic acid resulted in activation of c-Jun NH₂-terminal kinase (JNK), extracellular signal-regulated kinase (ERK), and protein kinase B (PKB, Akt), but not p38MAPK, in mouse lung fibroblasts. Inhibition of JNK using pharmacologic inhibitor (SP600125) and genetic knockdown (JNK specific siRNA) significantly inhibited p53 accumulation, reduced PUMA and Fas expression, and abolished apoptosis induced by gallic acid. Moreover, treatment with antioxidants (vitamin C, N-acetyl cysteine, and catalase) effectively diminished gallic acid-induced hydrogen peroxide production, JNK and p53 activation, and cell death. These observations imply that gallic acid-mediated hydrogen peroxide formation acts as an initiator of JNK signaling pathways, leading to p53 activation and apoptosis in mouse lung fibroblasts.

Treatment of dermal fibroblasts with GPI-anchored human TIMP-1 protein moderates processes linked to scar formation

Tissue inhibitors of metalloproteinases exhibit diverse physiological/biological functions including moderation of the proteolytic processing of growth factors and turnover of extracellular matrix. These various biological activities are linked in part to the stoichiometry of tissue inhibitor of metalloprotein/matrix metalloprotein (TIMP/MMP)/surface protein interactions. TIMP-1, a secreted protein, can be detected on the cell surface only through its interaction with surface-bound proteins. Proteins anchored by glycosylphosphatidylinositol (GPI), when purified and added to cells or tissues, are efficiently incorporated into their surface membranes. A GPI anchor was fused to TIMP-1 to focus defined concentrations of the inhibitory protein independently on the surface of primary dermal fibroblast cells. Exogenously added recombinant TIMP-1-GPI effectively inserted into the cell membrane of fibroblasts blocked the secretion of MMPs and markedly altered the stoichiometry of MMP association with the cell surface. TIMP-1-GPI treatment resulted in inhibition of fibroblast-reduced proliferation, and transiently reduced expression of fibrosis-associated genes. These effects were dose dependent. Treated cells also showed a more proapoptotic phenotype based on apoptotic assays and western blot analysis for apoptosis-associated protein expression. GPI-anchored TIMP-1 may represent a more effective version of the protein for use in therapeutic approaches to help control fibrosis and scar formation.

Epigenomics of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a complex lung disease of unknown etiology. Development of IPF is influenced by both genetic and environmental factors. Gene-expression profiling studies have taught us quite a bit about the biology of this fatal disease, but epigenetic marks may be the missing link that connects the environmental exposure in genetically predisposed individuals to transcriptome changes associated with the development of IPF. This review will begin with an introduction to the disease, followed by brief summaries of studies of gene expression in IPF and epigenetic marks associated with exposures relevant to IPF. The majority of the discussion will focus on epigenetic studies conducted so far in IPF, the limitations, challenges nd future directions in this field.

New insights into the role of oxidative stress in scleroderma fibrosis

Systemic sclerosis (Scleroderma – SSc) is a connective tissue disorder of unknown aetiology characterized by extensive fibrosis of the skin and visceral organs, by vascular abnormalities and immunological manifestations.

Recent evidence suggest that the cellular redox state may play a significant role in the progression of scleroderma fibrosis. Mechanisms involved include an autoamplification circuit linking ROS, Ras and ERK 1-2 which in turn amplifies and maintains the autocrine loop made up by cytokines, growth factors and their cognate receptors.

This review summarizes the recent progress on the role of oxidative stress in the pathophysiology of scleroderma and disorders characterised by organ fibrosis

Invasive breast cancer induces laminin-332 upregulation and integrin β4 neoexpression in myofibroblasts to confer an anoikis-resistant phenotype during tissue remodeling

INTRODUCTION

Although development of anoikis-resistant myofibroblasts during tissue remodeling is known to be associated with tumor invasion, the mechanism by which myofibroblasts become resistant to anoikis is unknown. We previously demonstrated laminin-332 upregulation in the fibrosis around invasive ductal carcinoma (IDC). Because laminin-332 promotes cell survival through binding to integrins, we hypothesized that invasive breast cancer cells confer an anoikis-resistant phenotype on myofibroblasts by upregulating laminin-332 expression during tissue remodeling. Here, we demonstrate that invasive breast cancer cells induce laminin-332 upregulation and integrin β4 neoexpression in myofibroblasts to confer an anoikis-resistant phenotype.

METHODS

Three types of fibroblasts were isolated from the tumor burden, the fibrosis, and normal tissue of patients with early stage IDC (less than 10 mm diameter), designated cancer-associated fibroblasts (CAFs), interface fibroblasts (InFs), and normal breast fibroblasts (NBFs), respectively. To investigate direct and indirect crosstalk with tumor cells, fibroblasts were co-cultured with invasive MDA-MB-231 or noninvasive MCF7 cells or in conditioned medium. Anoikis resistance of fibroblasts was measured by cell viability and caspase-3 activity after incubation on poly-HEMA coated plates for 72 hours. Involvement of laminin-332/integrin α3β1 or α6β4 signaling in anoikis resistance was confirmed by treatment with purified laminin-332 or blocking antibodies against laminin-332, integrin β1, or integrin β4.

RESULTS

MDA-MB-231 cells induced laminin-332 upregulation and integrin β4 neoexpression in fibroblasts, leading to anoikis resistance. InFs showed a higher endogenous level of laminin-332 than did CAFs and NBFs. After stimulation with MDA-MB-231-conditioned medium, laminin-332 expression of InFs was dramatically increased and maintained under anoikis conditions. Laminin-332 upregulation was also observed in CAFs and NBFs, but at a lower level than in InFs. Laminin-332 induced Akt (Ser473) phosphorylation by binding to integrin α3β1. Integrin β4 neoexpression induced laminin-332-independent Rac1 activation and promoted anoikis resistance in fibroblasts approximately twofold more effectively than did laminin-332, regardless of the type of fibroblast. In addition, integrin β4 expression suppressed fibroblast aggregation in conditions of anoikis.

CONCLUSION

Invasive breast cancer cells confer an anoikis-resistant phenotype on myofibroblasts during tissue remodeling by inducing laminin-332 upregulation and integrin β4 neoexpression. Interface fibroblasts appear to be the primary myofibroblasts that interact with invasive tumor cells during tissue remodeling.

Global methylation patterns in idiopathic pulmonary fibrosis

BACKGROUND

Idiopathic Pulmonary Fibrosis (IPF) is characterized by profound changes in the lung phenotype including excessive extracellular matrix deposition, myofibroblast foci, alveolar epithelial cell hyperplasia and extensive remodeling. The role of epigenetic changes in determining the lung phenotype in IPF is unknown. In this study we determine whether IPF lungs exhibit an altered global methylation profile.

METHODOLOGY/PRINCIPAL FINDINGS

Immunoprecipitated methylated DNA from 12 IPF lungs, 10 lung adenocarcinomas and 10 normal histology lungs was hybridized to Agilent human CpG Islands Microarrays and data analysis was performed using BRB-Array Tools and DAVID Bioinformatics Resources software packages. Array results were validated using the EpiTYPER MassARRAY platform for 3 CpG islands. 625 CpG islands were differentially methylated between IPF and control lungs with an estimated False Discovery Rate less than 5%. The genes associated with the differentially methylated CpG islands are involved in regulation of apoptosis, morphogenesis and cellular biosynthetic processes. The expression of three genes (STK17B, STK3 and HIST1H2AH) with hypomethylated promoters was increased in IPF lungs. Comparison of IPF methylation patterns to lung cancer or control samples, revealed that IPF lungs display an intermediate methylation profile, partly similar to lung cancer and partly similar to control with 402 differentially methylated CpG islands overlapping between IPF and cancer. Despite their similarity to cancer, IPF lungs did not exhibit hypomethylation of long interspersed nuclear element 1 (LINE-1) retrotransposon while lung cancer samples did, suggesting that the global hypomethylation observed in cancer was not typical of IPF.

CONCLUSIONS/SIGNIFICANCE

Our results provide evidence that epigenetic changes in IPF are widespread and potentially important. The partial similarity to cancer may signify similar pathogenetic mechanisms while the differences constitute IPF or cancer specific changes. Elucidating the role of these specific changes will potentially allow better understanding of the pathogenesis of IPF.

Interstitial lung disease: physiopathology in the context of lung growth

Interstitial lung diseases (ILDs) in children represent a heterogeneous group of respiratory disorders characterized by derangements of the alveolar walls. The key pathologic feature of ILDs is the altered repair of the alveolar surface after injury with a marked disruption in the integrity of the epithelium and, consequently, a dysregulated communication between epithelial and mesenchymal pulmonary components. Concomitant to the loss of cell-cell contact, epithelial cells undergo a process called epithelial to mesenchymal transition and acquire a mesenchymal identity. Among the factors involved in disease progression, transforming growth factor-β has been identified as a master switch in the induction of fibrosis. This article reviews recent advances in the understanding of the mechanisms involved in the pathogenesis of ILDs, and provides information on their adaptation in the context of lung growth.

Antifibrotic effects of curcumin are associated with overexpression of cathepsins K and L in bleomycin treated mice and human fibroblasts

Background

Lung fibrosis is characterized by fibroblast proliferation and the deposition of collagens. Curcumin, a polyphenol antioxidant from the spice tumeric, has been shown to effectively counteract fibroblast proliferation and reducing inflammation and fibrotic progression in animal models of bleomycin-induced lung injury. However, there is little mechanistic insight in the biological activity of curcumin. Here, we study the effects of curcumin on the expression and activity of cathepsins which have been implicated in the development of fibrotic lung diseases.

Methods

We investigated the effects of curcumin administration to bleomycin stimulated C57BL/6 mice and human fetal lung fibroblasts (HFL-1) on the expression of cathepsins K and L which have been implicated in matrix degradation, TGF-β1 modulation, and apoptosis. Lung tissues were evaluated for their contents of cathepsins K and L, collagen, and TGF-β1. HFL-1 cells were used to investigate the effects of curcumin and cathepsin inhibition on cell proliferation, migration, apoptosis, and the expression of cathepsins K and L and TGF-β1.

Results

Collagen deposition in lungs was decreased by 17-28% after curcumin treatment which was accompanied by increased expression levels of cathepsins L (25%-39%) and K (41%-76%) and a 30% decrease in TGF-β1 expression. Moreover, Tunel staining of lung tissue revealed a 33-41% increase in apoptotic cells after curcumin treatment. These in vivo data correlated well with data obtained from the human fibroblast line, HFL-1. Here, cathepsin K and L expression increased 190% and 240%, respectively, in the presence of curcumin and the expression of TGF-β1 decreased by 34%. Furthermore, curcumin significantly decreased cell proliferation and migration and increased the expression of surrogate markers of apoptosis. In contrast, these curcumin effects were partly reversed by a potent cathepsin inhibitor.

Conclusion

This study demonstrates that curcumin increases the expression of cathepsins K and L in lung which an effect on lung fibroblast cell behavior such as proliferation, migration and apoptosis rates and on the expression of TGF-β1 in mouse lung and HFL-1 cells. These results suggest that cathepsin-inducing drugs such as curcumin may be beneficial in the treatment of lung fibrosis.

Myofibroblast differentiation and survival in fibrotic disease

During wound healing, contractile fibroblasts called myofibroblasts regulate the formation and contraction of granulation tissue; however, pathological and persistent myofibroblast activation, which occurs in hypertrophic scars or tissue fibrosis, results in a loss of function. Many reviews outline the cellular and molecular features of myofibroblasts and their roles in a variety of diseases. This review focuses on the origins of myofibroblasts and the factors that control their differentiation and prolonged survival in fibrotic tissues. Pulmonary fibrosis is used to illustrate many key points, but examples from other tissues and models are also included. Myofibroblasts originate mostly from tissue-resident fibroblasts, and also from epithelial and endothelial cells or other mesenchymal precursors. Their differentiation is influenced by cytokines, growth factors, extracellular matrix composition and stiffness, and cell surface molecules such as proteoglycans and THY1, among other factors. Many of these effects are modulated by cell contraction. Myofibroblasts resist programmed cell death, which promotes their accumulation in fibrotic tissues. The cause of resistance to apoptosis in myofibroblasts is under ongoing investigation, but many of the same stimuli that regulate their differentiation are involved. The contributions of oxidative stress, the WNT-β-catenin pathway and PPARγ to myofibroblast differentiation and survival are increasingly appreciated.

TLR9-induced interferon β is associated with protection from gammaherpesvirus-induced exacerbation of lung fibrosis

Background

We have shown previously that murine gammaherpesvirus 68 (γHV68) infection exacerbates established pulmonary fibrosis. Because Toll-like receptor (TLR)-9 may be important in controlling the immune response to γHV68 infection, we examined how TLR-9 signaling effects exacerbation of fibrosis in response to viral infection, using models of bleomycin- and fluorescein isothiocyanate-induced pulmonary fibrosis in wild-type (Balb/c) and TLR-9^-/- mice.

Results

We found that in the absence of TLR-9 signaling, there was a significant increase in collagen deposition following viral exacerbation of fibrosis. This was not associated with increased viral load in TLR-9^-/- mice or with major alterations in T helper (Th)1 and Th2 cytokines. We examined alveolar epithelial-cell apoptosis in both strains, but this could not explain the altered fibrotic outcomes. As expected, TLR-9^-/- mice had a defect in the production of interferon (IFN)-β after viral infection. Balb/c fibroblasts infected with γHV68 in vitro produced more IFN-β than did infected TLR-9^-/- fibroblasts. Accordingly, in vitro infection of Balb/c fibroblasts resulted in reduced proliferation rates whereas infection of TLR-9^-/- fibroblasts did not. Finally, therapeutic administration of CpG oligodeoxynucleotides ameliorated bleomycin-induced fibrosis in wild-type mice.

Conclusions

These results show a protective role for TLR-9 signaling in murine models of lung fibrosis, and highlight differences in the biology of TLR-9 between mice and humans.

Role of vasoactive intestinal peptide in hyperoxia-induced injury of primary type II alveolar epithelial cells

OBJECTIVE

We investigated the effect of VIP on primary type II alveolar epithelial cells (AECIIs) upon the exposure of hyperoxia.

METHODS

AECIIs were isolated and purified from premature rats and exposed to air (21% oxygen), hyperoxia(95% oxygen), VIP+air and VIP+hyperoxia, respectively. The proliferation and apoptosis of AECIIs were detected by MTT cell proliferation assay, flow cytometry and western blot. The production of intracellular reactive oxygen species (ROS) was determined by 2 ', 7'-dichloro-dihydrotestosterone fluorescein diacetate (DCFH-DA) molecular probe and the total antioxidant capacity (TAOC) by ultraviolate spectro-photometer.

RESULTS

Cell proliferation significantly increased and apoptosis decreased upon the treatment with VIP. In addition, the level of ROS in the hyperoxia+VIP group was significantly lower than in the hyperoxia group, in contrast, TAOC was higher in the hyperoxia+VIP group than that in the hyperoxia group.

CONCLUSIONS

VIP exerts a protective role in the hyperoxia-induced oxidative stress damage in AECIIs, which probably attributed to its anti-oxidant and anti-apoptosis property.

MicroRNAs in idiopathic pulmonary fibrosis

In this review, we describe the recent advances in the understanding of the role of microRNAs in idiopathic pulmonary fibrosis (IPF), a chronic progressive and lethal fibrotic lung disease. Approximately 10% of the microRNAs are significantly changed in IPF lungs. Among the significantly downregulated microRNAs are members of let-7, mir-29, and mir-30 families as well as miR-17∼92 cluster among the upregulated mir-155 and mir-21. Downregulation of let-7 family members leads to changes consistent with epithelial mesenchymal transition in lung epithelial cells both in vitro and in vivo, whereas inhibition of mir-21 modulates fibrosis in the bleomycin model of lung fibrosis. Perturbations of mir-155 and mir-29 have profibrotic effects in vitro but have not yet been assessed in vivo in the context of lung fibrosis. A recurrent global theme is that many microRNAs studied in IPF are both regulated by transforming growth factor β1 (TGFβ1) and regulate TGFβ1 signaling pathway by their target genes. As a result, their aberrant expression leads to a release of inhibitions on the TGFβ1 pathway and to the creation of feed-forward loops. Coanalysis of published microRNA and gene expression microarray data in IPF reveals enrichment of the TGFβ1, Wnt, sonic hedgehog, p53, and vascular endothelial growth factor pathways and complex regulatory networks. The changes in microRNA expression in the IPF lung and the evidence for their role in the fibrosis suggest that microRNAs should be evaluated as therapeutic targets in IPF.

TGF-beta driven lung fibrosis is macrophage dependent and blocked by Serum amyloid P

The pleiotropic growth factor TGFβ(1) promotes many of the pathogenic mechanisms observed in lung fibrosis and airway remodeling, such as aberrant extracellular matrix deposition due to both fibroblast activation and fibroblast to myofibroblast differentiation. Serum amyloid P (SAP), a member of the pentraxin family of proteins inhibits bleomycin-induced lung fibrosis through an inhibition of pulmonary fibrocyte and pro-fibrotic alternative (M2) macrophage accumulation. It is unknown if SAP has effects downstream of TGFβ(1), a major mediator of pulmonary fibrosis. Using the lung specific TGFβ(1) transgenic mouse model, we determined that SAP inhibits all of the pathologies driven by TGFβ(1) including apoptosis, airway inflammation, pulmonary fibrocyte accumulation and collagen deposition, without affecting levels of TGFβ(1). To explore the role of monocyte derived cells in this model we used liposomal clodronate to deplete pulmonary macrophages. This led to pronounced anti-fibrotic effects that were independent of fibrocyte accumulation. Administration of SAP mirrored these effects and reduced both pulmonary M2 macrophages and increased chemokine IP10/CXCL10 expression in a SMAD 3-independent manner. Interestingly, SAP concentrations were reduced in the circulation of IPF patients and correlated with disease severity. Last, SAP directly inhibited M2 macrophage differentiation of monocytes obtained from these patients. These data suggest that the beneficial anti-fibrotic effects of SAP in TGFβ(1)-induced lung disease are via modulating monocyte responses.

Gender influences the response to experimental silica-induced lung fibrosis in mice

Accumulating evidence suggests that gender can have a profound effect on incidence and severity of a variety of pulmonary diseases. To address the influence of gender on the development of silica-induced pulmonary fibrosis, we instilled 0.2 g/kg silica into male and female C57BL/6 mice and examined the fibrotic and inflammatory response at 14 days postexposure. Both silica-exposed male and female mice had significant increases in total lung hydroxyproline compared with saline controls. However, silica-exposed female mice had significantly less total lung hydroxyproline than silica-exposed male mice. This observation was confirmed by color thresholding image analysis. Interestingly, silica-exposed female mice had significantly more inflammatory cells, the majority of which were macrophages, as well as higher levels of the macrophage-specific chemokines MCP-1 and CCL9 in whole lung lavage compared with silica-exposed male mice. We also show that at baseline, estrogen receptor α (ERα) mRNA expression is lower in female mice than in males and that ERα mRNA expression is decreased by silica exposure. Finally, we show that the response of ovariectomized female mice to silica instillation is similar to that of male mice. These observations together show that gender influences the lung response to silica.

Interstitial lung diseases in children

Interstitial lung disease (ILD) in infants and children comprises a large spectrum of rare respiratory disorders that are mostly chronic and associated with high morbidity and mortality. These disorders are characterized by inflammatory and fibrotic changes that affect alveolar walls. Typical features of ILD include dyspnea, diffuse infiltrates on chest radiographs, and abnormal pulmonary function tests with restrictive ventilatory defect and/or impaired gas exchange. Many pathological situations can impair gas exchange and, therefore, may contribute to progressive lung damage and ILD. Consequently, diagnosis approach needs to be structured with a clinical evaluation requiring a careful history paying attention to exposures and systemic diseases. Several classifications for ILD have been proposed but none is entirely satisfactory especially in children. The present article reviews current concepts of pathophysiological mechanisms, etiology and diagnostic approaches, as well as therapeutic strategies. The following diagnostic grouping is used to discuss the various causes of pediatric ILD: 1) exposure-related ILD; 2) systemic disease-associated ILD; 3) alveolar structure disorder-associated ILD; and 4) ILD specific to infancy. Therapeutic options include mainly anti-inflammatory, immunosuppressive, and/or anti-fibrotic drugs. The outcome is highly variable with a mortality rate around 15%. An overall favorable response to corticosteroid therapy is observed in around 50% of cases, often associated with sequelae such as limited exercise tolerance or the need for long-term oxygen therapy.

Genomic phenotype of non-cultured pulmonary fibroblasts in idiopathic pulmonary fibrosis

Activated fibroblasts are the central effector cells of the progressive fibrotic process in idiopathic pulmonary fibrosis (IPF). Characterizing the genomic phenotype of isolated fibroblasts is essential to understanding IPF pathogenesis. Comparing the genomic phenotype of non-cultured pulmonary fibroblasts from advanced IPF patients' and normal lungs revealed novel genes, biological processes and concomitant pathways previously unreported in IPF fibroblasts. We demonstrate altered expression in proteasomal constituents, ubiquitination-mediators, Wnt, apoptosis and vitamin metabolic pathways and cell cycle regulators, suggestive of loss of cellular homeostasis. Specifically, FBXO32, CXCL14, BDKRB1 and NMNAT1 were up-regulated, while RARA and CDKN2D were down-regulated. Paradoxically, pro-apoptotic inducers TNFSF10, BAX and CASP6 were also found to be increased. This comprehensive description of altered gene expression in isolated IPF fibroblasts underscores the complex biological processes characteristic of IPF and may provide a foundation for future research into this devastating disease.

Neuropeptide substance P attenuates hyperoxia-induced oxidative stress injury in type II alveolar epithelial cells via suppressing the activation of JNK pathway

Hyperoxia-induced oxidative stress plays a key role in many pulmonary diseases. In an earlier study we found the protective effect of the neuropeptide substance P (SP) on type II alveolar epithelial cells (AECIIs) after hyperoxia exposure. Then, we investigated c-Jun N-terminal kinase (C-JNK) signal transduction pathways in AECIIs before and after hyperoxia exposure. Primary AECIIs were isolated and purified from premature rats. Subsequently, the cells were treated with air (21% oxygen), hyperoxia (95% oxygen), SP+ air, and SP+ hyperoxia. SP was added in advance to reach a final concentration 1 x 10(-6) mol/l. The cells were then exposed to air and hyperoxia for 12, 24, and 48 h. XTT cell proliferation assay and fluorescence-activated cell sorting (FACS) were employed to detect cell growth and apoptosis. Phosphorylated JNK (p-JNK) levels were measured using Western blot assay. The morphological alteration of AECIIs was observed using a transmission electron microscope (TEM). Compared with the simple hyperoxia treatment, the cell growth and apoptosis percentage was significantly increased and decreased after adding additional SP. Meanwhile, the reduced levels of p-JNKs could be found after adding SP. Furthermore, the morphological damage of AECIIs was greatly improved. These data suggest that SP can promote AECII proliferation and inhibit apoptosis by suppressing JNK signal pathways after hyperoxia exposure, which attenuates hyperoxia-induced oxidative stress damage in AECIIs. It might be a potential therapy for acute pulmonary injury under hyperoxia-induced oxidative stress.

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.

Pulmonary fibrosis: pathogenesis, etiology and regulation

Pulmonary fibrosis and architectural remodeling of tissues can severely disrupt lung function, often with fatal consequences. The etiology of pulmonary fibrotic diseases is varied, with an array of triggers including allergens, chemicals, radiation and environmental particles. However, the cause of one of the most common pulmonary fibrotic conditions, idiopathic pulmonary fibrosis (IPF), is still unclear. This review examines common mechanisms of pulmonary wound-healing responses following lung injury, and highlights the pathogenesis of some of the most widespread pulmonary fibrotic diseases. A three phase model of wound repair is reviewed that includes; (1) injury; (2) inflammation; and (3) repair. In most pulmonary fibrotic conditions dysregulation at one or more of these phases has been reported. Chronic inflammation can lead to an imbalance in the production of chemokines, cytokines, growth factors, and disrupt cellular recruitment. These changes coupled with excessive pro-fibrotic IL-13 and/or TGFbeta1 production can turn a well-controlled healing response into a pathogenic fibrotic response. Endogenous regulatory mechanisms are discussed including novel areas of therapeutic intervention. Restoring homeostasis to these dysregulated healing responses, or simply neutralizing the key pro-fibrotic mediators may prevent or slow the progression of pulmonary fibrosis.

Lung alveolar epithelium and interstitial lung disease

Interstitial lung diseases (ILDs) comprise a group of lung disorders characterized by various levels of inflammation and fibrosis. The current understanding of the mechanisms underlying the development and progression of ILD strongly suggests a central role of the alveolar epithelium. Following injury, alveolar epithelial cells (AECs) may actively participate in the restoration of a normal alveolar architecture through a coordinated process of re-epithelialization, or in the development of fibrosis through a process known as epithelial-mesenchymal transition (EMT). Complex networks orchestrate EMT leading to changes in cell architecture and behaviour, loss of epithelial characteristics and gain of mesenchymal properties. In the lung, AECs themselves may serve as a source of fibroblasts and myofibroblasts by acquiring a mesenchymal phenotype. This review covers recent knowledge on the role of alveolar epithelium in the pathogenesis of ILD. The mechanisms underlying disease progression are discussed, with a main focus on the apoptotic pathway, the endoplasmic reticulum stress response and the developmental pathway.