Pirfenidone is an antifibrotic agent that has been evaluated in three multinational phase 3 trials in patients with idiopathic pulmonary fibrosis (IPF). We analysed pooled data from the multinational trials to obtain the most precise estimates of the magnitude of treatment effect on measures of disease progression.
All patients randomised to pirfenidone 2403 mg·day−1 or placebo in the CAPACITY or ASCEND studies were included in the analysis. Pooled analyses of outcomes at 1 year were based on the pre-specified end-points and analytic methods described in the ASCEND study protocol.
A total of 1247 patients were included in the analysis. At 1 year, pirfenidone reduced the proportion of patients with a ≥10% decline in per cent predicted forced vital capacity or death by 43.8% (95% CI 29.3–55.4%) and increased the proportion of patients with no decline by 59.3% (95% CI 29.0–96.8%). A treatment benefit was also observed for progression-free survival, 6-min walk distance and dyspnoea. Gastrointestinal and skin-related adverse events were more common in the pirfenidone group, but rarely led to discontinuation.
Analysis of data from three phase 3 trials demonstrated that treatment with pirfenidone for 1 year resulted in clinically meaningful reductions in disease progression in patients with IPF.
Treatment with pirfenidone for 1 year results in clinically meaningful reductions in IPF disease progression
Follistatin-like 1 (Fstl1) is induced in response to lung injury and promotes the accumulation of myofibroblasts and subsequent fibrosis via regulation of TGF-β and BMP. Reducing Fstl1 in mice reduces bleomycin-induced fibrosis in vivo, offering a potential therapeutic target for progressive lung fibrosis.
Progressive tissue fibrosis is a cause of major morbidity and mortality. Pulmonary fibrosis is an epithelial-mesenchymal disorder in which TGF-β1 plays a central role in pathogenesis. Here we show that follistatin-like 1 (FSTL1) differentially regulates TGF-β and bone morphogenetic protein signaling, leading to epithelial injury and fibroblast activation. Haplodeletion of Fstl1 in mice or blockage of FSTL1 with a neutralizing antibody in mice reduced bleomycin-induced fibrosis in vivo. Fstl1 is induced in response to lung injury and promotes the accumulation of myofibroblasts and subsequent fibrosis. These data suggest that Fstl1 may serve as a novel therapeutic target for treatment of progressive lung fibrosis.
β-arrestins regulate G protein (heterotrimeric guanine nucleotide-binding protein)-coupled receptors (GPCRs) through receptor desensitization while also acting as signaling scaffolds to facilitate numerous effector pathways. Recent studies have provided evidence that β-arrestins play a key role in inflammatory responses. We here summarize these advances on the roles of β-arrestins in immune regulation and inflammatory responses under physiological and pathological conditions, with an emphasis on translational implications of β-arrestins on human diseases.
Pulmonary fibrosis occurs in a variety of clinical settings, constitutes a major cause of morbidity and mortality, and represents an enormous unmet medical need. However, the disease is heterogeneous, and the failure to accurately discern between forms of fibrosing lung diseases leads to inaccurate treatments. Pulmonary fibrosis occurring in the context of connective tissue diseases is often characterized by a distinct pattern of tissue pathology and may be amenable to immunosuppressive therapies. In contrast, idiopathic pulmonary fibrosis (IPF) is a progressive and lethal form of fibrosing lung disease that is recalcitrant to therapies that target the immune system. Although animal models of fibrosis imperfectly recapitulate IPF, they have yielded numerous targets for therapeutic intervention. Understanding the heterogeneity of these diseases and elucidating the final common pathways of fibrogenesis are critical for the development of efficacious therapies for severe fibrosing lung diseases.
The lung is a complex organ with multiple functions; in addition to facilitating gas exchange, it also serves as the first line of defense against inhaled environmental pathogens and toxins. Given these critical roles, disruption of normal cell function or cell-cell interactions can have devastating health consequences. The articles of this Review Series highlight recent progress in understanding the pathophysiology of several pulmonary diseases and suggest how these insights are leading to the development of new therapeutic strategies.
The chemokine, CXCL10, and its cognate receptor, CXCR3, are important mediators of the pathobiology of lung fibrosis. Macrophages are a known source of CXCL10, but their specific source in the lung is poorly defined due to incomplete characterization of macrophage subpopulations. We recently developed a novel flow cytometric approach that discriminates resident alveolar macrophages from recruited exudative macrophages (ExMacs) after infectious lung injury. We hypothesized that ExMacs are present after noninfectious lung injury with bleomycin, and are a source of CXCL10. We found that ExMacs are recruited to the lung after injury, peaking at Day 7, then maintained through Day 28. ExMac recruitment was significantly reduced, but not abolished, in CCR2 null mice. ExMacs, but not alveolar macrophages, produce CXCL10, both constitutively and after stimulation with hyaluronan (HA) fragments. Interestingly, ExMac stimulation with LPS resulted in complete suppression of CXCL10. In contrast, ExMacs produced TNF-α and CXCL2/MIP-2 (Macrophage Inflammatory Protein-2) after stimulation with both HA and LPS. ExMacs were present in CXCR3 null mice after bleomycin, but produced minimal CXCL10. This impairment was overcome by administration of exogenous IFN-γ or IFN-γ with HA. Collectively, these data suggest that ExMacs are recruited and maintained in the lung after noninfectious lung injury, are a source of a variety of cytokines, but importantly, are essential for the production of antifibrotic CXCL10. Understanding the contribution of ExMacs to the pathobiology of lung injury and repair could lead to new treatment options for fibrosing lung diseases.
macrophage; bleomycin; pulmonary fibrosis; CXCR3; CXCL10
The characteristics of human asthma are chronic inflammation and airway remodeling. Hyaluronan (HA), a major extracellular matrix component, accumulates during inflammatory lung diseases including asthma. Hyaluronan fragments stimulate macrophages to produce inflammatory cytokines. We hypothesized that HA and its receptors would play a role in human asthma.
To investigate the role of HA and HA binding proteins in human asthma.
Twenty-one subjects with asthma and 25 normal control subjects underwent bronchoscopy with endobronchial biopsy and bronchoalveolar lavage (BAL). Fibroblasts were cultured, HA and HA synthase expression was determined at baseline and after exposure to several mediators relevant to asthma pathobiology. The expression of HA binding proteins, CD44, TLR2 and TLR4 on BAL macrophages was determined by flow cytometry. IL-8 production by macrophages in response to HA fragment stimulation was compared.
Airway fibroblasts from asthma patients produced significantly increased concentrations of lower molecular weight HA compared to those of normal fibroblasts. Hyaluronan synthase 2 mRNA was markedly increased in asthmatic fibroblasts. Asthmatic macrophages showed a decrease in cell surface CD44 expression and an increase in TLR2 and TLR4 expression. Macrophages from asthmatic subjects showed an increase in responsiveness to low molecular weight HA stimulation, as demonstrated by increased IL-8 production.
HA homeostasis is deranged in asthma with increased production by fibroblasts and decreased CD44 expression on alveolar macrophages. Upregulation of TLR2 and TLR4 on macrophages with increased sensitivity to HA fragments suggests a novel pro-inflammatory mechanism by which persistence of HA fragments could contribute to chronic inflammation and airway remodeling in asthma.
Asthma; Hyaluronan; Cytokines; Fibroblasts; Macrophages
Hyaluronan synthase 2 and CD44 are required for severe lung fibrosis in response to bleomycin.
Tissue fibrosis is a major cause of morbidity, and idiopathic pulmonary fibrosis (IPF) is a terminal illness characterized by unremitting matrix deposition in the lung. The mechanisms that control progressive fibrosis are unknown. Myofibroblasts accumulate at sites of tissue remodeling and produce extracellular matrix components such as collagen and hyaluronan (HA) that ultimately compromise organ function. We found that targeted overexpression of HAS2 (HA synthase 2) by myofibroblasts produced an aggressive phenotype leading to severe lung fibrosis and death after bleomycin-induced injury. Fibroblasts isolated from transgenic mice overexpressing HAS2 showed a greater capacity to invade matrix. Conditional deletion of HAS2 in mesenchymal cells abrogated the invasive fibroblast phenotype, impeded myofibroblast accumulation, and inhibited the development of lung fibrosis. Both the invasive phenotype and the progressive fibrosis were inhibited in the absence of CD44. Treatment with a blocking antibody to CD44 reduced lung fibrosis in mice in vivo. Finally, fibroblasts isolated from patients with IPF exhibited an invasive phenotype that was also dependent on HAS2 and CD44. Understanding the mechanisms leading to an invasive fibroblast phenotype could lead to novel approaches to the treatment of disorders characterized by severe tissue fibrosis.
Accumulation and turnover of extracellular matrix components are the hallmarks of tissue injury. Fragmented hyaluronan stimulates the expression of inflammatory genes by a variety of immune cells at the injury site. Hyaluronan binds to a number of cell surface proteins on a variety of cell types. Hyaluronan fragments signal through both Toll-like receptor (TLR) 4 and TLR2 as well as CD44 to stimulate inflammatory genes in inflammatory cells. Hyaluronan is also present on the cell surface of epithelial cells and provides protection against tissue damage by interacting with TLR2 and TLR4 on these parenchymal cells. Hyaluronan and hyaluronan-binding proteins regulate inflammation, tissue injury and repair through regulating inflammatory cell recruitment, release of inflammatory cytokines, and stem cell migration. This review focuses on the role of hyaluronan as an immune regulator in human diseases.
The median survival of patients with idiopathic pulmonary fibrosis (IPF) continues to be approximately 3 years from the time of diagnosis, underscoring the lack of effective medical therapies for this disease. In the United States alone, approximately 40,000 patients die of this disease annually. In November 2012, the NHLBI held a workshop aimed at coordinating research efforts and accelerating the development of IPF therapies. Basic, translational, and clinical researchers gathered with representatives from the NHLBI, patient advocacy groups, pharmaceutical companies, and the U.S. Food and Drug Administration to review the current state of IPF research and identify priority areas, opportunities for collaborations, and directions for future research. The workshop was organized into groups that were tasked with assessing and making recommendations to promote progress in one of the following six critical areas of research: (1) biology of alveolar epithelial injury and aberrant repair; (2) role of extracellular matrix; (3) preclinical modeling; (4) role of inflammation and immunity; (5) genetic, epigenetic, and environmental determinants; (6) translation of discoveries into diagnostics and therapeutics. The workshop recommendations provide a basis for directing future research and strategic planning by scientific, professional, and patient communities and the NHLBI.
idiopathic pulmonary fibrosis; alveolar epithelial cells; extracellular matrix; interstitial lung disease; inflammation
An important hallmark of tissue remodeling is the dynamic turnover of extracellular matrix (ECM). ECM performs a variety of functions in tissue repair including scaffold formation, modulation of fluid dynamics, and regulating cell behavior. During non-infectious tissue injury ECM degradation products are generated that acquire signaling functions not attributable to the native precursor molecules. Hyaluronan (HA) is a non-sulfated glycosaminoglycan which is produced in great abundance following tissue injury. It exists both in a soluble form and as side chains on proteoglycans. HA has critical roles in development as well as a variety of biological processes including wound healing, tumor growth and metastasis, and inflammation. HA fragments share structural similarities with pathogens and following tissue injury can be recognized by innate immune receptors. Elucidating the protean roles of HA in tissue injury, inflammation, and repair will generate new insights into mechanisms of disease characterized by chronic inflammation and tissue remodeling.
extracellular matrix; glycosaminoglycan; lung injury
Background and objective
Pirfenidone is an oral antifibrotic agent that is approved in several countries for the treatment of idiopathic pulmonary fibrosis (IPF). We performed a comprehensive analysis of safety across four clinical trials evaluating pirfenidone in patients with IPF.
All patients receiving pirfenidone 2403 mg/day in the Phase 3 CAPACITY studies (Studies 004 and 006) and all patients receiving at least one dose of pirfenidone in one of two ongoing open-label studies in patients with IPF (Studies 002 and 012) were selected for inclusion. Safety outcomes were evaluated from baseline until 28 days after the last dose of study drug.
A total of 789 patients were included in the analysis. The median duration of exposure to pirfenidone was 2.6 years (range, 1 week–7.7 years), and the cumulative total exposure was 2059 person exposure years (PEY). Gastrointestinal and skin-related events were the most commonly reported adverse events; these were almost always mild to moderate in severity, and rarely led to treatment discontinuation. Elevations (>3× upper limit of normal) in alanine aminotransferase (ALT) or aspartate aminotransferase (AST) occurred in 21/789 (2.7%) patients; the adjusted incidence of AST/ALT elevations was 1.7 per 100 PEY.
This comprehensive analysis of safety in a large cohort of IPF patients receiving pirfenidone for a total of 2059 PEY demonstrates that long-term treatment with pirfenidone is safe and generally well tolerated.
adverse event; idiopathic pulmonary fibrosis; pirfenidone; safety; treatment
Pulmonary fibrosis is a progressive, dysregulated response to injury culminating in compromised lung function due to excess extracellular matrix production. The heparan sulfate proteoglycan syndecan-4 is important in mediating fibroblast-matrix interactions, but its role in pulmonary fibrosis has not been explored. To investigate this issue, we used intratracheal instillation of bleomycin as a model of acute lung injury and fibrosis. We found that bleomycin treatment increased syndecan-4 expression. Moreover, we observed a marked decrease in neutrophil recruitment and an increase in both myofibroblast recruitment and interstitial fibrosis in bleomycin-treated syndecan-4–null (Sdc4–/–) mice. Subsequently, we identified a direct interaction between CXCL10, an antifibrotic chemokine, and syndecan-4 that inhibited primary lung fibroblast migration during fibrosis; mutation of the heparin-binding domain, but not the CXCR3 domain, of CXCL10 diminished this effect. Similarly, migration of fibroblasts from patients with pulmonary fibrosis was inhibited in the presence of CXCL10 protein defective in CXCR3 binding. Furthermore, administration of recombinant CXCL10 protein inhibited fibrosis in WT mice, but not in Sdc4–/– mice. Collectively, these data suggest that the direct interaction of syndecan-4 and CXCL10 in the lung interstitial compartment serves to inhibit fibroblast recruitment and subsequent fibrosis. Thus, administration of CXCL10 protein defective in CXCR3 binding may represent a novel therapy for pulmonary fibrosis.
Peripheral blood biomarkers might improve diagnostic accuracy for idiopathic pulmonary fibrosis (IPF).
Gene expression profiles were obtained from 89 patients with IPF and 26 normal controls. Samples were stratified according to severity of disease based on pulmonary function. The stratified dataset was split into subsets; two-thirds of the samples were selected to comprise the training set, while one-third was reserved for the validation set. Bayesian probit regression was used on the training set to develop a gene expression model for IPF versus normal. The gene expression model was tested by using it on the validation set to perform class prediction. Unsupervised clustering failed to discriminate between samples of different severity. Therefore, samples of all severities were included in the training and validation sets, in equal proportions. A gene signature model was developed from the training set. The model was built in an iterative fashion with the number of gene features selected to minimize the misclassification error in cross validation. The final model was based on the top 108 discriminating genes in the training set. The signature was successfully applied to the validation set, ROC area under the curve = 0.893, p < 0.0001. Using the optimal threshold (0.74) accurate class predictions were made for 77% of the test cases with sensitivity = 0.70, specificity = 1.00.
By using Bayesian probit regression to develop a model, we show that it is entirely possible to make a diagnosis of IPF from the peripheral blood with gene signatures.
Electronic supplementary material
The online version of this article (doi:10.1186/1471-2164-15-902) contains supplementary material, which is available to authorized users.
IPF; FIP; gene signature; Bayesian probit regression
Mechanisms that regulate regional epithelial cell diversity and pathologic remodeling in airways are poorly understood. We hypothesized that regional differences in cell composition and injury-related tissue remodeling result from the type and composition of local progenitors. We used surface markers and the spatial expression pattern of an SFTPC-GFP transgene to subset epithelial progenitors by airway region. Green fluorescent protein (GFP) expression ranged from undetectable to high in a proximal-to-distal gradient. GFPhi cells were subdivided by CD24 staining into alveolar (CD24neg) and conducting airway (CD24low) populations. This allowed for the segregation of three types of progenitors displaying distinct clonal behavior in vitro. GFPneg and GFPlow progenitors both yielded lumen containing colonies but displayed transcriptomes reflective of pseudostratified and distal conducting airways, respectively. CD24lowGFPhi progenitors were present in an overlapping distribution with GFPlow progenitors in distal airways, yet expressed lower levels of Sox2 and expanded in culture to yield undifferentiated self-renewing progeny. Colony-forming ability was reduced for each progenitor cell type after in vivo bleomycin exposure, but only CD24lowGFPhi progenitors showed robust expansion during tissue remodeling. These data reveal intrinsic differences in the properties of regional progenitors and suggest that their unique responses to tissue damage drive local tissue remodeling. Disclosure of potential conflicts of interest is found at the end of this article.
Regional; Progenitor; Epithelium; Lung; Bleomycin
CXC chemokine receptor 3 (CXCR3) is the receptor for the IFN-γ–inducible C-X-C chemokines MIG/CXCL9, IP-10/CXCL10, and I-TAC/CXCL11. CXCR3 is expressed on activated immune cells and proliferating endothelial cells. The role of CXCR3 in fibroproliferation has not been investigated. We examined the role of CXCR3 in pulmonary injury and repair in vivo. CXCR3-deficient mice demonstrated increased mortality with progressive interstitial fibrosis relative to WT mice. Increased fibrosis occurred without increased inflammatory cell recruitment. CXCR3 deficiency resulted in both a reduced early burst of IFN-γ production and decreased expression of CXCL10 after lung injury. We identified a relative deficiency in lung NK cells in the unchallenged CXCR3-deficient lung and demonstrated production of IFN-γ by WT lung NK cells in vivo following lung injury. The fibrotic phenotype in the CXCR3-deficient mice was significantly reversed following administration of exogenous IFN-γ or restoration of endogenous IFN-γ production by adoptive transfer of WT lymph node and spleen cells. Finally, pretreatment of WT mice with IFN-γ–neutralizing Ab’s enhanced fibrosis following lung injury. These data demonstrate a nonredundant role for CXCR3 in limiting tissue fibroproliferation and suggest that this effect may be mediated, in part, by the innate production of IFN-γ following lung injury.
These discussions are selected from the weekly staff conferences in the Department of Medicine, University of California, San Francisco. Taken from transcriptions, they are prepared by Homer A. Boushey, MD, Professor of Medicine, and John G. Fitz, MD, Assistant Professor of Medicine, under the direction of Lloyd H. Smith, Jr, MD, Professor of Medicine and Associate Dean in the School of Medicine. Requests for reprints should be sent to the Department of Medicine, University of California, San Francisco, School of Medicine, San Francisco, CA 94143.
Gas exchange in the lung occurs within alveoli, air-filled sacs composed of type 2 and type 1 epithelial cells (AEC2s and AEC1s), capillaries, and various resident mesenchymal cells. Here, we use a combination of in vivo clonal lineage analysis, different injury/repair systems, and in vitro culture of purified cell populations to obtain new information about the contribution of AEC2s to alveolar maintenance and repair. Genetic lineage-tracing experiments showed that surfactant protein C–positive (SFTPC-positive) AEC2s self renew and differentiate over about a year, consistent with the population containing long-term alveolar stem cells. Moreover, if many AEC2s were specifically ablated, high-resolution imaging of intact lungs showed that individual survivors undergo rapid clonal expansion and daughter cell dispersal. Individual lineage-labeled AEC2s placed into 3D culture gave rise to self-renewing “alveolospheres,” which contained both AEC2s and cells expressing multiple AEC1 markers, including HOPX, a new marker for AEC1s. Growth and differentiation of the alveolospheres occurred most readily when cocultured with primary PDGFRα+ lung stromal cells. This population included lipofibroblasts that normally reside close to AEC2s and may therefore contribute to a stem cell niche in the murine lung. Results suggest that a similar dynamic exists between AEC2s and mesenchymal cells in the human lung.
Chemokines and chemokine receptors have been implicated in the pathogenesis of bronchiolitis. CXCR3 ligands (CXCL10, CXCL9, and CXCL11) were elevated in patients with bronchiolitis obliterans syndrome (BOS) and chronic allorejection. Studies also suggested that blockage of CXCR3 or its ligands changed the outcome of T-cell recruitment and airway obliteration. We wanted to determine the role of the chemokine CXCL10 in the pathogenesis of bronchiolitis and BOS. In this study, we found that CXCL10 mRNA levels were significantly increased in patients with BOS. We generated transgenic mice expressing a mouse CXCL10 cDNA under control of the rat CC10 promoter. Six-month-old CC10-CXCL10 transgenic mice developed bronchiolitis characterized by airway epithelial hyperplasia and developed peribronchiolar and perivascular lymphocyte infiltration. The airway hyperplasia and T-cell inflammation were dependent on the presence of CXCR3. Therefore, long-term exposure of the chemokine CXCL10 in the lung causes bronchiolitis-like inflammation in mice.
bronchiolitis; chemokine CXCL10; inflammation; airway inflammation
Asthma remains an important cause of morbidity and mortality with an incidence that continues to rise. Despite the importance of this disease, the mechanisms by which the host develops allergic airways disease remain poorly understood. The development of allergic airways disease appears to be contingent on activation of both the innate and adaptive immune system, but little is known about the cross-talk between these two systems. The extracellular matrix protein mindin (Spondin 2) has been previously demonstrated to have functional roles in both the innate and adaptive immunological responses. Previous work supports that pulmonary challenge with fungal-associated allergenic proteinase (FAP) induces an innate allergic response. We hypothesized that mindin would modify the biological response to FAP. Saline or FAP was administered by oropharyngeal aspiration to C57BL/6 wild type or mindin-null mice every 4 days for a total of five exposures. FAP exposed C57BL/6 mice developed enhanced airway hyperresponsiveness (AHR) to methacholine challenge and increased neutrophils and eosinophils in the bronchoalveolar lavage as compared to saline exposed controls. These responses were significantly reduced in mindin-null mice exposed to FAP. FAP challenge was associated with a broad induction of cytokines (IL-1β, TNFα, Th1, Th2, and IL-17), chemokines, and growth factors, which were reduced in mindin-null mice exposed to FAP. RNA expression in lung monocytes for representative M1 and M2 activation markers were increased by FAP, but were independent of mindin. Our observations support that challenge with FAP results in activation of both innate and adaptive immune signaling pathways in a manner partially dependent on mindin. These findings suggest a potential role for the extracellular matrix protein mindin in cross-talk between the innate and adaptive immune systems.
Environment; Asthma; Reactive airways disease; Extracellular matrix; Allergy; Aspergillus
BACKGROUND AND PURPOSE
Inhalation of a β-adrenoceptor agonist (β-agonist) is first-line asthma therapy, used for both prophylaxis against, and acute relief of, bronchoconstriction. However, repeated clinical use of β-agonists leads to impaired bronchoprotection and, in some cases, adverse patient outcomes. Mechanisms underlying this β2-adrenoceptor dysfunction are not well understood, due largely to the lack of a comprehensive animal model and the uncertainty as to whether or not bronchorelaxation in mice is mediated by β2-adrenoceptors. Thus, we aimed to develop a mouse model that demonstrated functional β-agonist-induced β2-adrenoceptor desensitization in the context of allergic inflammatory airway disease.
We combined chronic allergen exposure with repeated β-agonist inhalation in allergen-treated BALB/C mice and examined the contribution of β2-adrenoceptors to albuterol-induced bronchoprotection using FVB/NJ mice with genetic deletion of β2-adrenoceptors (KO). Associated inflammatory changes – cytokines (ELISA), cells in bronchoalevolar lavage and airway remodelling (histology) and β2-adrenoceptor density (radioligand binding) – were also measured.
β2-Adrenoceptors mediated albuterol-induced bronchoprotection in mice. Chronic treatment with albuterol induced loss of bronchoprotection, associated with exacerbation of the inflammatory components of the asthma phenotype.
CONCLUSIONS AND IMPLICATIONS
This animal model reproduced salient features of human asthma and linked loss of bronchoprotection with airway pathobiology. Accordingly, the model offers an advanced tool for understanding the mechanisms of the effects of chronic β- agonist treatment on β-adrenoceptor function in asthma. Such information may guide the clinical use of β-agonists and provide insight into development of novel β-adrenoceptor ligands for the treatment of asthma.
β-adrenoceptor; β-agonist; receptor desensitization; airway remodelling; airway inflammation; asthma; loss of bronchoprotection; mouse
The molecular mechanisms of acute lung injury are incompletely understood. MicroRNAs (miRNAs) are crucial biological regulators that act by suppressing their target genes and are involved in a variety of pathophysiologic processes. miR-127 appears to be down-regulated during lung injury. We set out to investigate the role of miR-127 in lung injury and inflammation. Expression of miR-127 significantly reduced cytokine release by macrophages. Looking into the mechanisms of regulation of inflammation by miR-127, we found that IgG Fcγ Receptor I (FcγRI/CD64) was a target of miR-127, as evidenced by reduced CD64 protein expression in macrophages over-expressing miR-127. Furthermore, miR-127 significantly reduced the luciferase activity with a reporter construct containing the native 3′-UTR of CD64. Importantly, we demonstrated that miR-127 attenuated lung inflammation in an IgG immune complex (IgG IC) model in vivo. Collectively, these data show that miR-127 targets macrophage CD64 expression and promotes the reduction of lung inflammation. Understanding how miRNAs regulate lung inflammation may represent an attractive way to control inflammation induced by infectious or non-infectious lung injury.
Rationale: Surfactant protein (SP)-D and SP-A have been implicated in immunomodulation in the lung. It has been reported that patients with idiopathic pulmonary fibrosis (IPF) often have elevated serum levels of SP-A and SP-D, although their role in the disease is not known.
Objectives: The goal of this study was to test the hypothesis that SP-D plays an important role in lung fibrosis using a mouse model of fibrosis induced by bleomycin (BLM).
Methods: Triple transgenic inducible SP-D mice (iSP-D mice), in which rat SP-D is expressed in response to doxycycline (Dox) treatment, were administered BLM (100 U/kg) or saline subcutaneously using miniosmotic pumps.
Measurements and Main Results: BLM-treated iSP-D mice off Dox (SP-D off) had increased lung fibrosis compared with mice on Dox (SP-D on). SP-D deficiency also increased macrophage-dominant cell infiltration and the expression of profibrotic cytokines (transforming growth factor [TGF]-β1, platelet-derived growth factor-AA). Alveolar macrophages isolated from BLM-treated iSP-D mice off Dox (SP-D off) secreted more TGF-β1. Fibrocytes, which are bone marrow–derived mesenchymal progenitor cells, were increased to a greater extent in the lungs of the BLM-treated iSP-D mice off Dox (SP-D off). Fibrocytes isolated from BLM-treated iSP-D mice off Dox (SP-D off) expressed more of the profibrotic cytokine TGF-β1 and more CXCR4, a chemokine receptor that is important in fibrocyte migration into the lungs. Exogenous SP-D administered intratracheally attenuated BLM-induced lung fibrosis in SP-D−/− mice.
Conclusions: These data suggest that alveolar SP-D regulates numbers of macrophages and fibrocytes in the lungs, profibrotic cytokine expression, and fibrotic lung remodeling in response to BLM injury.
surfactant; lung fibrosis; macrophage; fibrocyte; growth factor
Inhalation of ambient ozone alters populations of lung macrophages. However, the impact of altered lung macrophage populations on the pathobiology of ozone is poorly understood. We hypothesized that sub-populations of macrophages modulate the response to ozone. We exposed C57BL/6 mice to ozone (2 ppm × 3h) or filtered air. 24 h after the exposure, the lungs were harvested and digested and the cells underwent flow cytometry. Analysis revealed a novel macrophage subset present in ozone exposed mice, which were distinct from resident alveolar macrophages (AM) and identified by enhanced Gr-1+ expression (Gr-1 Macs). Further analysis identified that Gr-1+ Macs exhibited high expression of MARCO, CX3CR1, and NQO1. Gr-1+ Macs were present in the absence of CCR2, suggesting that they were not derived from a CCR2-dependent circulating intermediate. Using PKH26-PCL to label resident phagocytic cells, we demonstrated that Gr-1 Macs were derived from resident lung cells. This new subset was diminished in the absence of CX3CR1. Interestingly, CX3CR1-null mice exhibited enhanced responses to ozone, including increased airway hyperresponsiveness (AHR), exacerbated neutrophil influx, accumulation of 8-isoprostanes and protein carbonyls, and increased expression of cytokines (CXCL2, IL-1β, IL-6, CCL2, and TNF-α). Our results identify a novel subset of lung macrophages, which are derived from a resident intermediate, dependent upon CX3CR1, and appear to protect the host from the biological response to ozone.
Rationale: Invasive cell phenotypes have been demonstrated in malignant transformation, but not in other diseases, such as asthma. Cellular invasiveness is thought to be mediated by transforming growth factor (TGF)-β1 and matrix metalloproteinases (MMPs). IL-13 is a key TH2 cytokine that directs many features of airway remodeling through TGF-β1 and MMPs.
Objectives: We hypothesized that, in human asthma, IL-13 stimulates increased airway fibroblast invasiveness via TGF-β1 and MMPs in asthma compared with normal controls.
Methods: Fibroblasts were cultured from endobronchial biopsies in 20 subjects with mild asthma (FEV1: 90 ± 3.6% pred) and 17 normal control subjects (FEV1: 102 ± 2.9% pred) who underwent bronchoscopy. Airway fibroblast invasiveness was investigated using Matrigel chambers. IL-13 or IL-13 with TGF-β1 neutralizing antibody or pan-MMP inhibitor (GM6001) was added to the lower chamber as a chemoattractant. Flow cytometry and immunohistochemistry were performed in a subset of subjects to evaluate IL-13 receptor levels.
Measurements and Main Results: IL-13 significantly stimulated invasion in asthmatic airway fibroblasts, compared with normal control subjects. Inhibitors of both TGF-β1 and MMPs blocked IL-13–induced invasion in asthma, but had no effect in normal control subjects. At baseline, in airway tissue, IL-13 receptors were expressed in significantly higher levels in asthma, compared with normal control subjects. In airway fibroblasts, baseline IL-13Rα2 was reduced in asthma compared with normal control subjects.
Conclusions: IL-13 potentiates airway fibroblast invasion through a mechanism involving TGF-β1 and MMPs. IL-13 receptor subunits are differentially expressed in asthma. These effects may result in IL-13–directed airway remodeling in asthma.
airway remodeling; interleukin-13; transforming growth factor-β; matrix metalloproteinase