Augmented pulmonary IL-4 and IL-13 receptor subunit expression in idiopathic interstitial pneumonia

The Intersection between Immune System and Idiopathic Pulmonary Fibrosis-A Concise Review

Idiopathic pulmonary fibrosis (IPF) is marked by progressive alveolar destruction, impaired tissue regeneration, and relentless fibrogenesis, culminating in respiratory failure and death. A diverse array of resident and non-resident cells within the lung contribute to disease pathogenesis. Notably, immune cells, both resident and recruited, respond to cues from sites of lung injury by undergoing phenotypic transitions and producing a wide range of mediators that influence, initiate, or dictate the function, or dysfunction, of key effector cells in IPF pathology, such as alveolar epithelial cells, lung fibroblasts, and capillary endothelial cells. The role of the immune system in IPF has undergone an interesting evolution, oscillating from initial enthusiasm to skepticism, and now to a renewed focus. This shift reflects both the past failures of immune-targeting therapies for IPF and the unprecedented insights into immune cell heterogeneity provided by emerging technologies. In this article, we review the historical evolution of perspectives on the immune system's role in IPF pathogenesis and examine the lessons learned from previous therapeutic failures targeting immune responses. We discuss the major immune cell types implicated in IPF progression, highlighting their phenotypic transitions and mechanisms of action. Finally, we identify key knowledge gaps and propose future directions for research on the immune system in IPF.

Altered expression pattern of immune response-related genes and isoforms in hypersensitivity pneumonitis lung fibroblasts

Hypersensitivity pneumonitis (HP) is an immune-mediated inflammatory interstitial lung disease that may evolve to pulmonary fibrosis, a progressive disorder with a poor prognosis characterized by fibroblast activation and extracellular matrix accumulation. In HP lung fibroblasts, the gene expression of proteins involved in the interaction with the immune response, their isoforms, and how they influence their phenotype have yet to be elucidated. We analyzed the expression and splicing variants of 16 target genes involved in the interaction between HP fibroblasts and immune signaling and evaluated possible correlations with clinical data. The comparison of HP and control fibroblasts revealed distinct gene expression patterns. HP lung fibroblasts displayed an increased expression of IFI27 and PDFGRA and a downregulation of IL17RC and TGFBR3. IFI27 immunoreactive protein was markedly increased in HP lung tissues and normal fibroblasts treated with TGF-β. Furthermore, IFI27 overexpression in normal fibroblasts increased α-SMA and decreased cell number over time. The isoform analysis showed similar expression patterns for most genes, except for the AGER receptor with increased soluble variants relative to full-length AGER in HP fibroblasts. These findings indicate important differences in the expression of genes related to the immune response by HP fibroblasts, highlighting their unique characteristics and providing further insight into a possible profibrotic role of IFI27 in the disease.

The liver metabolic features of Mogroside V compared to Siraitia grosvenorii fruit extract in allergic pneumonia mice

BACKGROUND

For a long time, Siraitia grosvenorii fruit extract (SGFE) and its dominant compounds, mogroside V(MV) were both reported to have therapeutic effects on allergic pneumonia, while previous studies only stay on phenotype and mechanism of the two active ingredients, hardly have any studies compared the two ingredients on the effect of liver metabolic, and revealed the relationship between mechanism and liver metabolism.

OBJECTIVE

Here we elucidated and compared the curative mechanisms of SGFE and MV on allergic pneumonia through liver metabolomics.

METHODS

We established allergic pneumonia mice using ovalbumin, then treated the mice with SGFE, MV and positive drug of Suhuang Zhike Jiaonang. The effects of the drugs were evaluated by detecting inflammatory cytokines, pathological examination and liver oxidative stress biomarkers. We explored the metabolic features between SGFE and MV through liver metabolomics consequently.

RESULTS

At phenotype, we confirmed that MV and SGFE both inhibited the expression of inflammatory cytokines including interleukins-5 (IL-5), IL-13, IL-17 and OVA-induced immunoglobulin E, which can also relieve inflammatory cells infiltration and mesenchymal thickening in lung tissue compared with positive drug. In addition, both of them can alleviate oxidative stress damage in liver, while MV showed a superior effect than SGFE. In metabolomic analysis, the two ingredients were found to ameliorate inflammatory and oxidative reaction mainly in controlling pathways of Riboflavin metabolism and Glutathione metabolism. While SGFE were found to control other metabolic pathways such as Phenylalanine metabolism, Sphingolipid metabolism, Glycerollipid metabolism, Glycine, serine and threonine metabolism and Arginine and proline metabolism.

CONCLUSION

From the results we can infer that the minor ingredients except MV in SGFE contribute poor function to the treatment of allergic pneumonia and MV may be the main functional constituent that relieve allergic pneumonia in SGFE. This study will be beneficial to figuring out a systematic theory of Siraitia grosvenorii active ingredients and proposing a guidance for pharmacology development.

The perplexing role of RAGE in pulmonary fibrosis: causality or casualty?

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal lung disease in which most patients die within 3 years of diagnosis. With an unknown etiology, IPF results in progressive fibrosis of the lung parenchyma, diminishing normal lung function, which results in respiratory failure, and eventually, death. While few therapies are available to reduce disease progression, patients continue to advance toward respiratory failure, leaving lung transplantation the only viable option for survival. As incidence and mortality rates steadily increase, the need for novel therapeutics is imperative. The receptor for advanced glycation endproducts (RAGE) is most highly expressed in the lungs and plays a significant role in a number of chronic lung diseases. RAGE has long been linked to IPF; however, confounding data from both human and experimental studies have left an incomplete and perplexing story. This review examines the present understanding of the role of RAGE in human and experimental models of IPF, drawing parallels to recent advances in RAGE biology. Moreover, this review discusses the role of RAGE in lung injury response, type 2 immunity, and cellular senescence, and how such mechanisms may relate to RAGE as both a biomarker of disease progression and potential therapeutic target in IPF.The reviews of this paper are available via the supplemental material section.

Interstitial Score and Concentrations of IL-4Rα, PAR-2, and MMP-7 in Bronchoalveolar Lavage Fluid Could Be Useful Markers for Distinguishing Idiopathic Interstitial Pneumonias

Idiopathic interstitial pneumonia (IIP) entails a variable group of lung diseases of unknown etiology. Idiopathic pulmonary fibrosis, nonspecific interstitial pneumonia, interstitial lung diseases related to connective tissue disease (CTD-ILD), and hypersensitivity pneumonitis (HP) can manifest with similar clinical, radiological, and histopathological features. In a differential diagnosis, biomarkers can play a significant role. We assume that levels of specific cyto- or chemokines or their receptors can signal pathogenetic processes in the lungs. Eighty patients with different types of idiopathic interstitial pneumonia were enrolled in this study. Cell counts and concentrations of tumor necrosis factor (TNF)-α, interleukin-4 receptor α, proteinase-activated receptor (PAR)-2, matrix metalloproteinase (MMP)-7, and B cell-activating factor were measured in bronchoalveolar lavage fluid using commercial ELISA kits. High resolution computer tomography results were evaluated using alveolar and interstitial (IS) score scales. Levels of TNF-α were significantly higher in HP compared to fibrosing IIP (p < 0.0001) and CTD-ILD (p = 0.0381). Concentrations of IL-4Rα, PAR-2, and MMP-7 were positively correlated with IS (p = 0.0009; p = 0.0256; p = 0.0015, respectively). Since TNF-α plays a major role in inflammation, our results suggest that HP is predominantly an inflammatory disease. From the positive correlation with IS we believe that IL-4Rα, PAR-2, and MMP-7 could serve as fibroproliferative biomarkers in differential diagnosis of IIP.

Protective role of overexpressed MUC5AC against fibrosis in MHV-68-induced combined pulmonary fibrosis and emphysema mouse model

Mucins have long been regarded to play a role as a barrier to prevent mucosal infections; however, some studies report that overexpression of mucins induces obstruction and inflammation of airways. We investigated whether the secretion of overexpressed mucin, mucin5ac (MUC5AC), could improve protection against pathogens. To examine the possible roles of mucin hypersecretion in augmenting host defense against disease-promoting muco-obstructive lung disease, a mouse model that overexpressed MUC5AC was generated. We had previously proved that murine gammaherpesvirus-68 (MHV-68) infection could induce emphysema in mice, which later developed into combined pulmonary fibrosis and emphysema (CPFE). We further explored whether increased MUC5AC secretion could provide benefits against MHV-68 induced fibrosis. We initially developed a pcDNA3.1-MUC5AC mouse model. Next, the experimental mice were randomly divided into five groups: normal control, pcDNA3.1 control, pcDNA3.1-MUC5AC, CPFE, and pcDNA3.1- MUC5AC + CPFE. Morphometric analysis of each group was performed by hematoxylin and eosin staining and Masson trichrome staining. MUC5AC levels in lung tissues were analyzed by immunohistochemical staining, real-time polymerase chain reaction, and Western blot analysis. The airway inflammation was determined by differential cell counts of bronchoalveolar lavage fluid (BALF) and measurement of cytokines and chemokines in BALF by enzyme-linked immunosorbent assay. MUC5AC hypersecretion alone was not sufficient to drive goblet cell metaplasia to induce obvious mucus plugging and airway inflammation. However, MUC5AC overexpression served as a protective barrier against MHV-68 virus infection in vivo. Infectivity of MHV-68 was decreased in the pcDNA3.1-MUC5AC + CPFE group compared with that in CPFE group. Meanwhile, a reduction of MHV-68 virus attenuated the expressions of chemokine (C-C motif) ligand 2 (CCL2), chemokine (C-X-C motif) ligand 5 (CXCL5), interleukin-13 (IL-13), and transforming growth factor-β1 (TGF-β1), and weakened airway inflammation and fibrosis in the pcDNA3.1-MUC5AC + CPFE group. Overexpression of MUC5AC appears to exhibit a protective role against MHV-68 infection in mice with emphysema that subsequently developed into CPFE and to further decrease airway inflammation and fibrosis induced by MHV-68 by decreasing the expressions of CCL2, CXCL5, IL-13, and TGF-β1.

Interleukin-13 disrupts type 2 pneumocyte stem cell activity

The T helper 2 (Th2) inflammatory cytokine interleukin-13 (IL-13) has been associated with both obstructive and fibrotic lung diseases; however, its specific effect on the epithelial stem cells in the gas exchange compartment of the lung (alveolar space) has not been explored. Here, we used in vivo lung models of homeostasis and repair, ex vivo organoid platforms, and potentially novel quantitative proteomic techniques to show that IL-13 disrupts the self-renewal and differentiation of both murine and human type 2 alveolar epithelial cells (AEC2s). Significantly, we find that IL-13 promotes ectopic expression of markers typically associated with bronchiolar airway cells and commonly seen in the alveolar region of lung tissue from patients with idiopathic pulmonary fibrosis. Furthermore, we identify a number of proteins that are differentially secreted by AEC2s in response to IL-13 and may provide biomarkers to identify subsets of patients with pulmonary disease driven by "Th2-high" biology.

Ability of Periostin as a New Biomarker of Idiopathic Pulmonary Fibrosis

The primarily pathogenesis of IPF, an incurable respiratory disease is believed to over-repair to lung injury. The development of new drugs for IPF has increased the necessity of identifying biomarkers for predicting clinical behavior and the selection of the appropriate treatment strategy for individual patient.We and another group found that periostin, a matricellular protein expressed specifically in areas of ongoing fibrotic lesions, such as fibroblastic foci in lung tissues from human IPF or murine bleomycin-induced lung injury models. Murine bleomycin-induced lung injury was improved by the constant suppression of periostin expression and treatment with neutralizing anti-periostin antibodies at the fibroproliferative phase. Moreover, total periostin can predict both short-term declines of pulmonary function and overall survival in IPF patients. Our group also established a new enzyme-linked immunosorbent assay (ELISA) kit that is more specific for IPF compared with the conventional kit. This new periostin ELISA kit specifically detects monomeric form, whereas the conventional kit detects both monomeric and oligomeric forms. The monomeric periostin levels can be used to predict pulmonary function decline and to distinguish IPF patients from healthy controls.In conclusion, periostin may play an important role in fibrogenesis and could be a potential biomarker for predicting disease progression and therapeutic effect in IPF patients.

TRAIL-Dependent Resolution of Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is the most common form of interstitial lung disease characterized by the persistence of activated myofibroblasts resulting in excessive deposition of extracellular matrix proteins and profound tissue remodeling. In the present study, the expression of tumor necrosis factor- (TNF-) related apoptosis-inducing ligand (TRAIL) was key to the resolution of bleomycin-induced pulmonary fibrosis. Both in vivo and in vitro studies demonstrated that Gr-1⁺TRAIL⁺ bone marrow-derived myeloid cells blocked the activation of lung myofibroblasts. Although soluble TRAIL was increased in plasma from IPF patients, the presence of TRAIL⁺ myeloid cells was markedly reduced in IPF lung biopsies, and primary lung fibroblasts from this patient group expressed little of the TRAIL receptor-2 (DR5) when compared with appropriate normal samples. IL-13 was a potent inhibitor of DR5 expression in normal fibroblasts. Together, these results identified TRAIL⁺ myeloid cells as a critical mechanism in the resolution of pulmonary fibrosis, and strategies directed at promoting its function might have therapeutic potential in IPF.

HIF1A up-regulates the ADORA2B receptor on alternatively activated macrophages and contributes to pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a deadly chronic lung disease. Extracellular accumulation of adenosine and subsequent activation of the ADORA2B receptor play important roles in regulating inflammation and fibrosis in IPF. Additionally, alternatively activated macrophages (AAMs) expressing ADORA2B have been implicated in mediating adenosine's effects in IPF. Although hypoxic conditions are present in IPF, hypoxia's role as a direct modulator of macrophage phenotype and identification of factors that regulate ADORA2B expression on AAMs in IPF is not well understood. In this study, an experimental mouse model of pulmonary fibrosis and lung samples from patients with IPF were used to examine the effects and interactions of macrophage differentiation and hypoxia on fibrosis. We demonstrate that hypoxia-inducible factor 1-α (HIF1A) inhibition in late stages of bleomycin-induced injury attenuates pulmonary fibrosis in association, with reductions in ADORA2B expression in AAMs. Additionally, ADORA2B deletion or pharmacological antagonism along with HIF1A inhibition disrupts AAM differentiation and subsequent IL-6 production in cultured macrophages. These findings suggest that hypoxia, through HIF1A, contributes to the development and progression of pulmonary fibrosis through its regulation of ADORA2B expression on AAMs, cell differentiation, and production of profibrotic mediators. These studies support a potential role for HIF1A or ADORA2B antagonists in the treatment of IPF.-Philip, K., Mills, T. W., Davies, J., Chen, N.-Y., Karmouty-Quintana, H., Luo, F., Molina, J. G., Amione-Guerra, J., Sinha, N., Guha, A., Eltzschig, H. K., Blackburn, M. R. HIF1A up-regulates the ADORA2B receptor on alternatively activated macrophages and contributes to pulmonary fibrosis.

Aerobic Exercise Attenuated Bleomycin-Induced Lung Fibrosis in Th2-Dominant Mice

INTRODUCTION

The aim of this study was to investigate the effect of aerobic exercise (AE) in reducing bleomycin-induced fibrosis in mice of a Th2-dominant immune background (BALB/c).

METHODS

BALB/c mice were distributed into: sedentary, control (CON), Exercise-only (EX), sedentary, bleomycin-treated (BLEO) and bleomycin-treated+exercised (BLEO+EX); (n = 8/group). Following treadmill adaptation, 15 days following a single, oro-tracheal administration of bleomycin (1.5U/kg), AE was performed 5 days/week, 60min/day for 4 weeks at moderate intensity (60% of maximum velocity reached during a physical test) and assessed for pulmonary inflammation and remodeling, and cytokine levels in bronchoalveolar lavage (BAL).

RESULTS

At 45 days post injury, compared to BLEO, BLEO+EX demonstrated reduced collagen deposition in the airways (p<0.001) and also in the lung parenchyma (p<0.001). In BAL, a decreased number of total leukocytes (p<0.01), eosinophils (p<0.001), lymphocytes (p<0.01), macrophages (p<0.01), and neutrophils (p<0.01), as well as reduced pro-inflammatory cytokines (CXCL-1; p<0.01), (IL-1β; p<0.001), (IL-5; p<0.01), (IL-6; p<0.001), (IL-13; p<0.01) and pro-fibrotic growth factor IGF-1 (p<0.001) were observed. Anti-inflammatory cytokine IL-10 was increased (p<0.001).

CONCLUSION

AE attenuated bleomycin-induced collagen deposition, inflammation and cytokines accumulation in the lungs of mice with a predominately Th2-background suggesting that therapeutic AE (15-44 days post injury) attenuates the pro-inflammatory, Th2 immune response and fibrosis in the bleomycin model.

Identification of Potential Key Long Non-Coding RNAs and Target Genes Associated with Pneumonia Using Long Non-Coding RNA Sequencing (lncRNA-Seq): A Preliminary Study

Background

This study aimed to identify the potential key long non-coding RNAs (lncRNAs) and target genes associated with pneumonia using lncRNA sequencing (lncRNA-seq).

Material/Methods

A total of 9 peripheral blood samples from patients with mild pneumonia (n=3) and severe pneumonia (n=3), as well as volunteers without pneumonia (n=3), were received for lncRNA-seq. Based on the sequencing data, differentially expressed lncRNAs (DE-lncRNAs) were identified by the limma package. After the functional enrichment analysis, target genes of DE-lncRNAs were predicted, and the regulatory network was constructed.

Results

In total, 99 DE-lncRNAs (14 upregulated and 85 downregulated ones) were identified in the mild pneumonia group and 85 (72 upregulated and 13 downregulated ones) in the severe pneumonia group, compared with the control group. Among these DE-lncRNAs, 9 lncRNAs were upregulated in both the mild and severe pneumonia groups. A set of 868 genes were predicted to be targeted by these 9 DE-lncRNAs. In the network, RP11-248E9.5 and RP11-456D7.1 targeted the majority of genes. RP11-248E9.5 regulated several genes together with CTD-2300H10.2, such as QRFP and EPS8. Both upregulated RP11-456D7.1 and RP11-96C23.9 regulated several genes, such as PDK2. RP11-456D7.1 also positively regulated CCL21.

Conclusions

These novel lncRNAs and their target genes may be closely associated with the progression of pneumonia.

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.

Epithelium-dependent profibrotic milieu in the pathogenesis of idiopathic pulmonary fibrosis: current status and future directions

BACKGROUND AND AIM

Idiopathic pulmonary fibrosis (IPF) is characterized by hyperplasia of type II alveolar epithelial cells, aggregation of activated (myo)fibroblasts and excessive deposition of extracellular matrix, which will ultimately lead to lung architecture destruction with no proven effective therapies. Despite a significant increase in our understanding on the etiology and pathogenesis of IPF, the real triggers that initiate epithelial cell injury and promote fibrosis evolution are still elusive. We wanted to discuss the evolution of hypothesis on IPF pathogenesis and to suggest some new directions which need to be further elucidated.

METHODS

We have done a literature search in PubMed database by using the term 'idiopathic pulmonary fibrosis' AND (pathogenesis OR inflammation OR wound healing OR apoptosis OR extracellular matrix OR animal model).

RESULTS

Inflammatory hypothesis had been the dominant idea for several decades which suggests that chronic inflammation drives the onset and advance of the fibrotic process. However, it is seriously challenged nowadays because lung tissues from IPF patients exhibit little inflammatory lesions. Also, anti-inflammation therapy failed to exert a beneficial effect to IPF patients. Furthermore, experimental lung fibrosis can be realized independent of inflammation. Today, modern paradigm suggests that IPF is mainly driven by the profibtic milieu formed by epithelial injury/ disability and dysregulated epithelial mesenchymal interaction.

CONCLUSIONS

Epithelium-dependent profibrotic milieu formation and mesenchymal activation is the current view on the pathogenesis of IPF. New evidence from more analogous animal models may emerge and shift our thinking to a new and more faithful concept in the future.

Targeting interleukin-13 with tralokinumab attenuates lung fibrosis and epithelial damage in a humanized SCID idiopathic pulmonary fibrosis model

The aberrant fibrotic and repair responses in the lung are major hallmarks of idiopathic pulmonary fibrosis (IPF). Numerous antifibrotic strategies have been used in the clinic with limited success, raising the possibility that an effective therapeutic strategy in this disease must inhibit fibrosis and promote appropriate lung repair mechanisms. IL-13 represents an attractive target in IPF, but its disease association and mechanism of action remains unknown. In the present study, an overexpression of IL-13 and IL-13 pathway markers was associated with IPF, particularly a rapidly progressive form of this disease. Targeting IL-13 in a humanized experimental model of pulmonary fibrosis using tralokinumab (CAT354) was found to therapeutically block aberrant lung remodeling in this model. However, targeting IL-13 was also found to promote lung repair and to restore epithelial integrity. Thus, targeting IL-13 inhibits fibrotic processes and enhances repair processes in the lung.

Association of the SNP rs1800925(C/T) in the interleukin-13 gene promoter with pulmonary function in Chinese Han patients with idiopathic pulmonary fibrosis

The present report studied potential association of the rs1800925(C/T) single nucleotide polymorphism (SNP) of the Interleukin (IL)-13 gene promoter with idiopathic pulmonary fibrosis (IPF) in patients of Chinese Han ethnicity. Seventy patients with IPF were enrolled and divided into three subgroups: group A (61-79 % pred. DLCO; n = 22), group B (51-60% pred. DLCO; n = 20), and group C (≤50% pred. DLCO; n = 28). Control group consisted of 80 healthy individuals of Chinese Han ethnicity. The SNP rs1800925(C/T) was genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. The IL-13 CC genotype was present in 28/70 (40.0%), homozygous TT in 6/70 (8.6%) and heterozygous CT in 36/70 (51.4%) patients with IPF. In control group, these genotypes were present in 30/80 (37.5%), 11/80 (13.75%), 39/80 (48.75%), respectively, indicating that the distribution of the above three genotypes was not significantly different between patients with IPF and healthy controls. When the patients were stratified according to their DLCO and DLCO/VA, the frequencies of genotypes CT and TT in the groups A, B, and C were, respectively, 40.9% (9/22), 50% (10/20), and 82.1% (23/28). Thus, significant differences in the distribution of alleles at -1112 region of IL-13 gene were observed among the study groups A, B, and C, with the highest frequency in group C (p < 0.05). In conclusion, the rs1800925 T allele of the IL-13 gene is associated with worse pulmonary function in patients with IPF of Chinese Han ethnicity.

Matrix regulation of idiopathic pulmonary fibrosis: the role of enzymes

Repairing damaged tissues is an essential homeostatic mechanism that enables clearance of dead or damaged cells after injury, and the maintenance of tissue integrity. However, exaggeration of this process in the lung can lead to the development of fibrotic scar tissue. This is characterized by excessive accumulation of extracellular matrix (ECM) components such as fibronectin, proteoglycans, hyaluronic acid, and interstitial collagens. After tissue injury, or a breakdown of tissue integrity, a cascade of events unfolds to maintain normal tissue homeostasis. Inflammatory mediators are released from injured epithelium, leading to both platelet activation and inflammatory cell migration. Inflammatory cells are capable of releasing multiple pro-inflammatory and fibrogenic mediators such as transforming growth factor (TGF)β and interleukin (IL)-13, which can trigger myofibroblast proliferation and recruitment. The myofibroblast population is also expanded as a result of epithelial cells undergoing epithelial-to-mesenchymal transition and of the activation of resident fibroblasts, leading to ECM deposition and tissue remodeling. In the healthy lung, wound healing then proceeds to restore the normal architecture of the lung; however, fibrosis can develop when the wound is severe, the tissue injury persists, or the repair process becomes dysregulated. Understanding the processes regulating aberrant wound healing and the matrix in the chronic fibrotic lung disease idiopathic pulmonary fibrosis (IPF), is key to identifying new treatments for this chronic debilitating disease. This review focuses primarily on the emerging role of enzymes in the lungs of patients with IPF. Elevated expression of a number of enzymes that can directly modulate the ECM has been reported, and recent data indicates that modulating the activity of these enzymes can have a downstream effect on fibrotic tissue remodeling.

STAT6 and lung inflammation

Lung inflammation has many etiologies, including diseases of Th2-type immunity, such as asthma and anti-parasitic responses. Inflammatory diseases of the lung involve complex interactions among structural cells (airway epithelium, smooth muscle, and fibroblasts) and immune cells (B and T cells, macrophages, dendritic cells, and innate lymphoid cells). Signal transducer and activator of transcription 6 (STAT6) has been demonstrated to regulate many pathologic features of lung inflammatory responses in animal models including airway eosinophilia, epithelial mucus production, smooth muscle changes, Th2 cell differentiation, and IgE production from B cells. Cytokines IL-4 and IL-13 that are upstream of STAT6 are found elevated in human asthma and clinical trials are underway to therapeutically target the IL-4/IL-13/STAT6 pathway. Additionally, recent work suggests that STAT6 may also regulate lung anti-viral responses and contribute to pulmonary fibrosis. This review will focus on the role of STAT6 in lung diseases and mechanisms by which STAT6 controls immune and structural lung cell function.

Biomarkers of fibroproliferative healing in fibrosing idiopathic interstitial pneumonias

Aims:

The main feature of fibrosing idiopathic interstitial pneumonias (fIIPs) is the fibroproliferative potential of underlying pathogenetic process. We hypothesize that the concentration of potential markers of fibroproliferative healing, PAR-2, TGF-β1, TNF-α and IL-4Rα in bronchoalveolar lavage fluid (BALF) differ in patients with fIIPs compared to controls (C).

Patients and Methods:

10 patients with fIIPs and 9 controls (C) were included to the study.

Concentrations of CD124 (IL4Rα), PAR-2, TGF-β1 and TNF-α in BALF were determined using the ELISA method.

Results:

We observed higher concentrations of IL4Rα (fIIPS 1499.4 pg/ml vs C 255.5 pg/ml; p < 0.05), PAR-2 (fIIPS 1807.9 pg/ml vs C 421.0 pg/ml; p < 0.05) and TGF-β1(fIIPS 283.0 pg/ml vs C 197.1 pg/ml; p < 0.01) in BALF in fIIPs versus C. The values of TNF-a in BALF did not differ significantly in fIIPs compared to controls. The ratios also showed differences in fIIPS and C: IL4Rα/TGF-β1 (fIIPS 6.19 vs C 0.68; p = 0.0143); TNF-α/IL4Rα (fIIPS 0.84 vs C 7.93; p = 0.043); TGF-β1/TNF-α (fIIPS 0.21 vs C 0.16; p = 0.0179) and protein/PAR-2 (fIIPS 0.06 vs C 0.28; p = 0.0033).

Conclusions:

We found that PAR-2, TGF-β1 and IL-4Rα are significantly up-regulated in the BALF of fIIPs compared to controls, therefore we suppose they could become biomarkers of fibroproliferative healing.

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.

γδ T cells attenuate bleomycin-induced fibrosis through the production of CXCL10

γδ T cells are a subset of T cells associated with epithelial mucosal tissues and play a prominent role in both promoting and dampening inflammatory responses to pathogens; in addition, they strongly mediate epithelial repair. By using a bleomycin model of pulmonary fibrosis, we found that γδ T-cell populations dramatically increased after bleomycin administration. To determine the importance of these cells, we exposed mice lacking the δ chain of the γδ T-cell receptor (γδ knockout [KO]) to bleomycin. Pulmonary fibrosis was more severe in γδ KO mice, as measured by collagen deposition (hydroxyproline) and histopathological features. Furthermore, there was no evidence of resolution of the fibrotic response up to 45 days after bleomycin therapy. In contrast to control mice, γδ KO mice had decreased concentrations of IL-6, granulocyte colony stimulating factor, chemokine CXC ligand (CXCL) 1, and interferon inducible protein 10/CXCL10. In vitro culture of γδ T cells purified from lungs 17 days after bleomycin exposure (a time of peak influx of these cells) demonstrated that γδ T cells produced substantial quantities of all four of these cytokines, suggesting that γδ T cells are a predominant source of these proteins. To demonstrate that γδ T cells are effector cells in the fibrotic response, we performed adoptive transfer experiments with γδ T cells sorted from bleomycin-treated lungs; these cells were sufficient to resolve fibrosis in γδ KO mice and restore CXCL10 levels comparable to wild-type mice. Furthermore, overexpression of CXCL10 in the lung decreased the severity of fibrosis seen in the γδ KO mice. Finally, adoptive transfer of γδ T cells from CXCL10(-/-) mice failed to reverse the severe fibrosis in γδ KO mice. These results indicate that γδ T cells promote the resolution of fibrosis through the production of CXCL10.

The effect of interleukin-13 (IL-13) and interferon-γ (IFN-γ) on expression of surfactant proteins in adult human alveolar type II cells in vitro

Background

Surfactant proteins are produced predominantly by alveolar type II (ATII) cells, and the expression of these proteins can be altered by cytokines and growth factors. Th1/Th2 cytokine imbalance is suggested to be important in the pathogenesis of several adult lung diseases. Recently, we developed a culture system for maintaining differentiated adult human ATII cells. Therefore, we sought to determine the effects of IL-13 and IFN-γ on the expression of surfactant proteins in adult human ATII cells in vitro. Additional studies were done with rat ATII cells.

Methods

Adult human ATII cells were isolated from deidentified organ donors whose lungs were not suitable for transplantation and donated for medical research. The cells were cultured on a mixture of Matrigel and rat-tail collagen for 8 d with differentiation factors and human recombinant IL-13 or IFN-γ.

Results

IL-13 reduced the mRNA and protein levels of surfactant protein (SP)-C, whereas IFN-γ increased the mRNA level of SP-C and proSP-C protein but not mature SP-C. Neither cytokine changed the mRNA level of SP-B but IFN-γ slightly decreased mature SP-B. IFN-γ reduced the level of the active form of cathepsin H. IL-13 also reduced the mRNA and protein levels of SP-D, whereas IFN-γ increased both mRNA and protein levels of SP-D. IL-13 did not alter SP-A, but IFN-γ slightly increased the mRNA levels of SP-A.

Conclusions

We demonstrated that IL-13 and IFN-γ altered the expression of surfactant proteins in human adult ATII cells in vitro. IL-13 decreased SP-C and SP-D in human ATII cells, whereas IFN-γ had the opposite effect. The protein levels of mature SP-B were decreased by IFN-γ treatment, likely due to the reduction in active form cathpesin H. Similarly, the active form of cathepsin H was relatively insufficient to fully process proSP-C as IFN-γ increased the mRNA levels for SP-C and proSP-C protein, but there was no increase in mature SP-C. These observations suggest that in disease states with an overexpression of IL-13, there would be some deficiency in mature SP-C and SP-D. In disease states with an excess of IFN-γ or therapy with IFN-γ, these data suggest that there might be incomplete processing of SP-B and SP-C.

Cytoplasmic tail of IL-13Ralpha2 regulates IL-4 signal transduction

IL (interleukin)-4 and IL-13 are key cytokines in the pathogenesis of allergic inflammatory disease. IL-4 and IL-13 share many functional properties as a result of their utilization of a common receptor complex comprising IL-13Ralpha1 (IL-13 receptor alpha-chain 1) and IL-4Ralpha. The second IL-13R (IL-13 receptor) has been identified, namely IL-13Ralpha2. This has been thought to be a decoy receptor due to its short cytoplasmic tail and its high binding affinity for IL-13 but not IL-4. IL-13Ralpha2 exists on the cell membrane, intracellularly and in a soluble form. Recent reports revealed that membrane IL-13Ralpha2 may have some signalling capabilities, and a soluble form of IL-13Ralpha2 can be generated in the presence of environmental allergens such as DerP. Interestingly, IL-13Ralpha2 has also been shown to regulate both IL-13 and IL-4 response in primary airway cells, despite the fact that IL-13Ralpha2 does not bind IL-4. The regulator mechanism is still unclear but the physical association of IL-13Ralpha2 with IL-4Ralpha appears to be a key regulatory step. These results suggest that the cytoplasmic tail of IL-13Ralpha2 may interfere with the association or activation of signalling molecules, such as JAK1 (Janus kinase 1), on IL-4Ralpha and thus prevents downstream signal cascade. The receptor has more complicated functions than a simple decoy receptor. In this review, we discuss newly revealed functions of IL-13Ralpha2.

Interleukin-13 and its receptors in idiopathic interstitial pneumonia: clinical implications for lung function

Idiopathic interstitial pneumonia (IIP) is characterized by varying degrees of interstitial fibrosis. IL-13 and IL-4 are strong inducers of tissue fibrosis, whereas IFN-gamma has antifibrotic potential. However, the roles of these substances in IIP remain unknown. IL-13, IL-4, and IFN-gamma were measured in the BAL fluid of 16 idiopathic pulmonary fibrosis (IPF) patients, 10 nonspecific interstitial pneumonia (NSIP) patients, and 8 normal controls. The expression of IL-13 and IL-13Ralpha1/alpha2 in lung tissues was analyzed using ELISA and immunohistochemistry. IL-13 levels were significantly higher in IPF patients than the others (P<0.05). IL-4 levels were higher in both IPF and NSIP patients than in normal controls (P<0.05), and IFN-gamma levels were lower in NSIP patients than in normal controls (P=0.047). IL-13 levels correlated inversely with FVC% (r=-0.47, P=0.043) and DLCO% (r=-0.58, P=0.014) in IPF and NSIP patients. IL-13 was strongly expressed in the smooth muscle, bronchial epithelium, alveolar macrophages and endothelium of IPF patients. IL-13Ralpha1, rather than IL-13Ralpha2, was strongly expressed in the smooth muscle, bronchial epithelium, and endothelium of IPF patients. IL-13 and its receptors may contribute to the pathogenesis of fibrosis in IIP and appear to be related to the severity of the disease.

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.

TLR9 is expressed in idiopathic interstitial pneumonia and its activation promotes in vitro myofibroblast differentiation

Infectious diseases can be cofactors in idiopathic interstitial pneumonias (IIP) pathogenesis; recent data suggests that toll-like receptors 9 (TLR9) ligands contribute to experimental chronic tissue remodeling. Real-time TAQMAN and immunohistochemical analysis of IIP normal surgical lung biopsies (SLBs), primary fibroblast lines grown from both IIP and normal SLBs indicate that TLR9 is prominently and differentially expressed in a disease-specific manner. TLR9 expression was increased in biopsies from patients with IIP compared with normal lung biopsies and its expression is localized to areas of marked interstitial fibrosis. TLR9 in fibroblasts appeared to be increased by profibrotic Th2 cytokines (IL-4 and IL-13) and this was true in fibroblasts cultured from the most severe form of IIP, idiopathic pulmonary fibrosis (IPF) SLBs, in non-specific interstitial pneumonia fibroblast lines, and in normal fibroblasts. Finally, confocal microscopy studies have shown that TLR9 activation by its synthetic agonist CpG-ODN significantly increased the expression of alpha smooth muscle actin, the main marker of myofibroblast differentiation. These data indicate that TLR9 expression may drive the abnormal tissue healing response in severe forms of IIP and its activation can have a key role in myofibroblast differentiation promoting the progression of disease during the terminal phase of IPF.

Hyper-responsiveness of IPF/UIP fibroblasts: interplay between TGFbeta1, IL-13 and CCL2

One of the hallmarks of idiopathic pulmonary fibrosis with a usual interstitial pneumonia histological pathology (IPF/UIP) is excess collagen deposition, due to enhanced fibroblast extracellular matrix synthetic activity. Studies using murine models of lung fibrosis have elucidated a pro-fibrotic pathway involving IL-13 driving CCL2, which in turn drives TGFbeta1 in lung fibroblasts. Therefore, we sought to determine whether this pathway exists in the human fibrotic setting by evaluating human IPF/UIP fibroblasts. IPF/UIP fibroblasts have an increased baseline fibrotic phenotype compared to non-fibrotic fibroblasts. Interestingly, non-fibrotic fibroblasts responded in a pro-fibrotic manner to TGFbeta1 but were relatively non-responsive to IL-13 or CCL2, whereas, IPF/UIP cells were hyper-responsive to TGFbeta1, IL-13 and CCL2. Interestingly, TGFbeta1, CCL2 and IL-13 all upregulated TGFbeta receptor and IL-13 receptor expression, suggesting an ability of the mediators to modulate the function of each other. Furthermore, in vivo, neutralization of both JE and MCP5, the two functional orthologs of CCL2, during bleomycin-induced pulmonary fibrosis significantly reduced collagen deposition as well as JE and CCR2 expression. Also in the bleomycin model, CTGF, which is highly induced following TGFbeta stimulation, was attenuated with anti-JE/anti-MCP5 treatment. Overall this study demonstrates an interplay between TGFbeta1, IL-13 and CCL2 in IPF/UIP, where these three mediators feedback on each other, promoting the fibrotic response.

The role of inflammation in the pathogenesis of idiopathic pulmonary fibrosis

The role of inflammation in idiopathic pulmonary fibrosis (IPF) is controversial. If inflammation were critical to the disease process, lung pathology would demonstrate an influx of inflammatory cells, and that the disease would respond to immunosuppression. Neither is true. The classic pathology does not display substantial inflammation, and no modulation of the immune system is effective as treatment. Recent data suggest that the pathophysiology of the disease is more a product of fibroblast dysfunction than of dysregulated inflammation. The role of inflammation in disease pathogenesis comes from pathology from atypical patients, biologic samples procured during exacerbations of the disease, and careful examination of biologic specimens from patients with stable disease. We suggest that inflammation is indeed a critical factor in IPF and propose five potential nontraditional mechanisms for the role of inflammation in the pathogenesis of IPF: the direct inflammatory hypothesis, the matrix hypothesis, the growth factor-receptor hypothesis, the plasticity hypothesis, and the vascular hypothesis. To address these, we review the literature exploring the differences in pathology, prognosis, and clinical course, as well as the role of cytokines, growth factors, and other mediators of inflammation, and last, the role of matrix and vascular supply in patients with IPF.

Inhibition of NF-kappaB activation reduces the tissue effects of transgenic IL-13

IL-13 is a major Th2 cytokine that is capable of inducing inflammation, excessive mucus production, airway hyperresponsiveness, alveolar remodeling, and fibrosis in the murine lung. Although IL-13 through its binding to IL-4Ralpha/IL-13Ralpha1 uses the canonical STAT6-signaling pathway to mediate these tissue responses, recent studies have demonstrated that other signaling pathways may also be involved. Previous studies from our laboratory demonstrated that IL-13 mediates its tissue effects by inducing a wide variety of downstream genes many of which are known to be regulated by NF-kappaB. As a result, we hypothesized that NF-kappaB activation plays a critical role in the pathogenesis of IL-13-induced tissue alterations. To test this hypothesis, we compared the effects of transgenic IL-13 in mice with normal and diminished levels of NF-kappaB activity. Three pharmacologic approaches were used to inhibit NF-kappaB including 1) PS1145, a small molecule inhibitor of IkappaBalpha kinase (IKK2), 2) antennapedia-linked NF-kappaB essential modulator-binding domain (NBD) peptide (wild-type NBD), and 3) an adenoviral construct expressing a dominant-negative version of IKK2. We also crossed IL-13-transgenic mice with mice with null mutations of p50 to generate mice that overproduced IL-13 in the presence and absence of this NF-kappaB component. These studies demonstrate that all these interventions reduced IL-13-induced tissue inflammation, fibrosis and alveolar remodeling. In addition, we show that both PS1145 and wild-type NBD inhibit lung inflammatory and structural cell apoptosis. PS1145 inhibits caspase activation and up-regulates inhibitor of apoptosis protein cellular-inhibitor of apoptosis protein 1 (c-IAP-1). Therefore, NF-kappaB is an attractive target for immunotherapy of IL-13-mediated diseases.

Allergy-driven alternative splicing of IL-13 receptor alpha2 yields distinct membrane and soluble forms

IL-13 is a key mediator of allergic inflammation. Its diverse functions are mediated by a complex receptor system including IL-4Ralpha, IL-13Ralpha1, and IL-13Ralpha2. IL-4Ralpha and IL-13Ralpha1 form a high-affinity signaling heterodimer. IL-13Ralpha2 binds IL-13 with high affinity and has been found to exist in membrane and soluble forms. Soluble IL-13Ralpha2 has been postulated as a critical endogenous modulator of IL-13 responses. However, the mechanism of generation for the soluble form remains unclear. We present the initial study that a mechanism for generation of the soluble form is alternative splicing and that alternative splicing yields a distinct form of soluble IL-13Ralpha2. We found that several mouse organs expressed two IL-13Ralpha2 transcripts, the 1152-bp transcript encoding the full-length protein and the 1020-bp transcript lacking exon10, which encodes the transmembrane region. Deletion of exon 10 (DeltaEx10) caused a frameshift resulting in a different amino acid sequence from position 327 to position 339 and early termination. Constructs encoding both splice variants were transfected into WEHI-274.1 cells. Transfectants expressing the full-length transcript had IL-13Ralpha2 on the cell surface but produced minimal soluble IL-13Ralpha2 in the supernatants. In contrast, transfectants expressing the DeltaEx10 transcript displayed no membrane IL-13Ralpha2 but secreted high levels of soluble IL-13Ralpha2 capable of inhibiting IL-13 signaling. Both variants bound IL-13, but the DeltaEx10 variant displayed approximately 2-fold increase in IL-13 binding activity. Expression of the two IL-13Ralpha2 transcripts was differentially regulated in vivo in an experimental allergic asthma model. Thus, alternatively spliced variants of IL-13Ralpha2 may have a distinct biologic function in vivo.

Role of interleukin-13 in cancer, pulmonary fibrosis, and other T(H)2-type diseases

Interleukin (IL)-13 plays a major role in various inflammatory diseases including cancer, asthma, and allergy. It mediates a variety of different effects on various cell types including B cells, monocytes, natural killer cells, endothelial cells, and fibroblasts. IL-13 binds to two primary receptor chains IL-13Ralpha1 and IL-13Ralpha2. The IL-13Ralpha2 but not IL-13Ralpha1 chain binds IL-13 with high affinity and is overexpressed in a variety of human cancer cells derived from glioma, squamous cell carcinoma of head and neck, and AIDS-associated Kaposi's sarcoma. We have also demonstrated that IL-13Ralpha2 expression is greatly increased in lung cells when mice were challenged intranasally with bleomycin or Aspergillus fumigatus. In addition, IL-13Ralpha2 increased in surgical lung biopsies from patients with usual interstitial pneumonia, nonspecific interstitial pneumonia, and respiratory bronchiolitic interstitial pneumonia of unknown origin. Based on various studies, it is concluded that IL-13Ralpha2-expressing cells are involved in various pulmonary pathological conditions. In contrast, normal tissues such as brain, lung, endothelial cells, and head and neck tissues express IL-13Ralpha1 chain, but show only marginal expression of IL-13Ralpha2 chain. Thus, IL-13Ralpha2 chain may serve as a novel biomarker for diseased cells such as cancer or fibrosis and a target for receptor-directed therapeutic agents. To target IL-13R, a recombinant fusion protein composed of IL-13 and a derivative of Pseudomonas exotoxin (PE) has been produced. This cytotoxin termed as IL-13PE38QQR or IL-13PE38, or IL-13PE is highly and specifically cytotoxic to a variety of human tumor cell lines. In preclinical models of human glioblastoma, head and neck and AIDS-associated Kaposi's cancer, IL-13PE has been found to have significant antitumor activity at a tolerated dose. Several phase I clinical trials have been completed in patients with recurrent malignant glioma. Recently a phase III clinical trial (PRECISE) in patients with recurrent malignant glioma has been completed recruiting a total of 294 patients. IL-13PE cytotoxin has also shown a significant therapeutic effect in preclinical bleomycin or A. fumigatus or Schistosoma mansoni-induced pulmonary pathology including granulomatous fibrosis in mouse models. A clinical study in these diseases has yet to be initiated.

N-linked glycosylation of IL-13R alpha2 is essential for optimal IL-13 inhibitory activity

A high-affinity receptor for interleukin (IL)-13 (interleukin-13R alpha 2) is over-expressed in disease-related fibroblasts and neoplastic cells and is involved in cancer, allergic, and inflammatory diseases. The extracellular domain of IL-13R alpha2 (ECD alpha2) could be cleaved, which serves as a decoy receptor. We have expressed and purified ECD alpha2 in both Escherichia coli (E. coli) and mammalian systems as a soluble fragment and studied its biological activities. Although both products of ECD alpha2 showed IL-13 inhibitory activities, mammalian cell-derived ECD alpha2 appeared to be superior compared with purified protein from E. coli. When expressed in E. coli, ECD alpha2 appeared to be a monomer of 42 but a 60 kDa protein when purified from mammalian cells due to heavy glycosylation. The purified glycosylated ECD alpha2 efficiently inhibited IL-13-induced STAT6 phosphorylation in immune and Hodgkin's lymphoma cell lines, IL-13 binding, and cytotoxicity of IL-13 cytotoxin in various cancer cell lines. The improved potency of mammalian cell-derived ECD alpha2 was shown over ECD alpha2/Fc fusion protein. The N-linked glycosylation of ECD alpha2 was found to be essential for optimal IL-13 inhibitory activity as deglycosylation by PNGase F showed lower activity. ECD alpha2 did not inhibit IL-4-induced STAT6 phosphorylation, indicating that inhibitory effects of ECD alpha2 are receptor specific. These results indicate that glycosylated ECD alpha2 can serve as a potent inhibitor of IL-13 in a variety of conditions in which IL-13 is a key mediator, e.g., pulmonary, allergic, fibrotic, and neoplastic diseases.

Obligatory role for interleukin-13 in obstructive lesion development in airway allografts

The pathogenesis of bronchiolitis obliterans (BO), a common and devastating obliterative disorder of small airways following lung transplantation, remains poorly understood. Lesions are characterized in their early stages by lymphocyte influx that evolves into dense fibrotic infiltrates. Airway specimens taken from patients with histological BO revealed infiltrating myofibroblasts, which strongly expressed the signaling chain of the high affinity interleukin-13 (IL-13) receptor IL-13Ralpha1. Because IL-13 has proinflammatory and profibrotic actions, a contributory role for IL-13 in BO development was examined using murine models of orthotopic and heterotopic tracheal transplantation. Compared with airway isografts, allografts exhibited a significant increase in relative IL-13 mRNA and protein levels. Allogeneic tracheas transplanted into IL-13-deficient mice were protected from BO in both transplant models. Flow cytometric analysis of orthotopic transplant tissue digests revealed markedly fewer infiltrating mononuclear phagocytes and CD3(+) T lymphocytes in IL-13-deficient recipients. Furthermore, protection from luminal obliteration, collagen deposition, and myofibroblast infiltration was observed in heterotopic airways transplanted into the IL-13(-/-) recipients. Transforming growth factor-beta1 expression was significantly decreased in tracheal allografts into IL-13(-/-) recipients, compared to wild-type counterparts. These human and murine data implicate IL-13 as a critical effector cytokine driving cellular recruitment and subsequent fibrosis in clinical and ex-perimental BO.

Focal interstitial CC chemokine receptor 7 (CCR7) expression in idiopathic interstitial pneumonia

BACKGROUND/AIMS

Idiopathic interstitial pneumonias (IIPs) are a diverse grouping of chronic pulmonary diseases characterised by varying degrees of pulmonary fibrosis. The triggers of the fibroproliferative process in IIP remain enigmatic but recent attention has been directed towards chemokine involvement in this process.

METHODS

The expression of two chemokine receptors, CCR7 and CXCR4, and their respective ligands, CCL19, CCL21, and CXCL12, were examined in surgical lung biopsies (SLBs) from patients with IIP. Transcript and protein expression of these receptors and their ligands was compared with that detected in histologically normal margin SLBs.

RESULTS

CCR7 and CXCR4 were detected by gene array and real time polymerase chain reaction analysis and CCR7, but not CXCR4, expression was significantly raised in usual interstitial pneumonia (UIP) relative to biopsies from patients diagnosed with non-specific interstitial pneumonia (NSIP) or respiratory bronchiolitis/interstitial lung disease (RBILD). CCR7 protein was expressed in interstitial areas of all upper and lower lobe UIP SLBs analysed. CCR7 expression was present in 50% of NSIP SLBs, and CCR7 was restricted to blood vessels and mononuclear cells in 75% of RBILD SLBs. Immune cell specific CXCR4 expression was seen in IIP and normal margin biopsies. CCR7 positive areas in UIP biopsies were concomitantly positive for CD45 (the leucocyte common antigen) but CCR7 positive areas in all IIP SLBs lacked the haemopoietic stem cell antigen CD34, collagen 1, and alpha smooth muscle actin.

CONCLUSION

This molecular and immunohistochemical analysis showed that IIPs are associated with abnormal CCR7 transcript and protein expression.

Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and usually fatal pulmonary disease for which there are no proven drug therapies. Anti-inflammatory and immunosuppressive agents have been largely ineffective. The precise relationship of IPF to other idiopathic interstitial pneumonias (IIPs) is not known, despite the observation that different histopathologic patterns of IIP may coexist in the same patient. We propose that these different histopathologic 'reaction' patterns may be determined by complex interactions between host and environmental factors that alter the local alveolar milieu. Recent paradigms in IPF pathogenesis have focused on dysregulated epithelial-mesenchymal interactions, an imbalance in T(H)1/T(H)2 cytokine profile and potential roles for aberrant angiogenesis. In this review, we discuss these evolving concepts in disease pathogenesis and emerging therapies designed to target pro-fibrogenic pathways in IPF.

A role for MCP-1/CCR2 in interstitial lung disease in children

BACKGROUND

Interstitial lung diseases (ILD) are chronic inflammatory disorders leading to pulmonary fibrosis. Monocyte chemotactic protein 1 (MCP-1) promotes collagen synthesis and deletion of the MCP-1 receptor CCR2 protects from pulmonary fibrosis in ILD mouse models. We hypothesized that pulmonary MCP-1 and CCR2+ T cells accumulate in pediatric ILD and are related to disease severity.

METHODS

Bronchoalveolar lavage fluid was obtained from 25 children with ILD and 10 healthy children. Levels of pulmonary MCP-1 and Th1/Th2-associated cytokines were quantified at the protein and the mRNA levels. Pulmonary CCR2+, CCR4+, CCR3+, CCR5+ and CXCR3+ T cells were quantified by flow-cytometry.

RESULTS

CCR2+ T cells and MCP-1 levels were significantly elevated in children with ILD and correlated with forced vital capacity, total lung capacity and ILD disease severity scores. Children with lung fibrosis had significantly higher MCP-1 levels and CCR2+ T cells in bronchoalveolar lavage fluid compared to non-fibrotic children.

CONCLUSION

The results indicate that pulmonary CCR2+ T cells and MCP-1 contribute to the pathogenesis of pediatric ILD and might provide a novel target for therapeutic strategies.