Pulmonary type II cell hypertrophy and pulmonary lipoproteinosis are features of chronic IL-13 exposure

Airway allergy causes alveolar macrophage death, profound alveolar disorganization and surfactant dysfunction

Respiratory disorders caused by allergy have been associated to bronchiolar inflammation leading to life-threatening airway narrowing. However, whether airway allergy causes alveolar dysfunction contributing to the pathology of allergic asthma remains unaddressed. To explore whether airway allergy causes alveolar dysfunction that might contribute to the pathology of allergic asthma, alveolar structural and functional alterations were analyzed during house dust mite (HDM)-induced airway allergy in mice, by flow cytometry, light and electron microscopy, monocyte transfer experiments, assessment of intra-alveolarly-located cells, analysis of alveolar macrophage regeneration in Cx3cr1 ^cre:R26-yfp chimeras, analysis of surfactant-associated proteins, and study of lung surfactant biophysical properties by captive bubble surfactometry. Our results demonstrate that HDM-induced airway allergic reactions caused severe alveolar dysfunction, leading to alveolar macrophage death, pneumocyte hypertrophy and surfactant dysfunction. SP-B/C proteins were reduced in allergic lung surfactant, that displayed a reduced efficiency to form surface-active films, increasing the risk of atelectasis. Original alveolar macrophages were replaced by monocyte-derived alveolar macrophages, that persisted at least two months after the resolution of allergy. Monocyte to alveolar macrophage transition occurred through an intermediate stage of pre-alveolar macrophage and was paralleled with translocation into the alveolar space, Siglec-F upregulation, and downregulation of CX3CR1. These data support that the severe respiratory disorders caused by asthmatic reactions not only result from bronchiolar inflammation, but additionally from alveolar dysfunction compromising an efficient gas exchange.

Early Immunomodulatory Effects of Different Natural Surfactant Preparations in Preterms With Respiratory Distress

BACKGROUND

Respiratory distress syndrome (RDS) is the most common respiratory disease in premature infants. Exogenous natural surfactant preparations are used in the treatment of RDS. In recent years, it has become increasingly evident that surfactant plays an immunoregulatory role.

OBJECTIVES

The aim of this study was to evaluate cytokine and chemokine response following three different regimens of natural surfactant treatment in preterm newborns with RDS.

METHODS

Premature newborns below 32 weeks of gestation who were intubated for RDS and given early surfactant rescue therapy were included in the study. Newborns were randomly divided into three groups and Beractant 100 mg/kg (B-100), Poractant alfa 100 mg/kg (Pα-100) and Poractant alfa 200 mg/kg (Pα-200) were administered intratracheally. Blood samples and transtracheal aspirates (TA) were collected just before and 4-6 h after the surfactant treatment. Total eosinophil count, inducible T Cell alpha chemoattractant (ITaC), macrophage inflammatory protein 3 beta (MIP3b), interleukins (IL) 5, 8, 9, 10, 13, immunoglobulin E (IgE), interferon gamma (IFN-γ), eotaxin and tumor necrosis factor beta-1 (TGF-β1) were measured from blood and tracheal aspirate samples.

RESULTS

A total of 45 infants, 15 in each group, were included in the study. Mean gestational age, birth weight, antenatal, demographic and clinical characteristics of the study groups were similar. IFNγ concentration and eosinophil counts in TA decreased after surfactant replacement in all groups, especially in the infants treated with Pα-100 and Pα-200. Eotaxin, TGF beta and IL-8 concentrations in TA increased significantly in the infants treated with Pα-100 and Pα-200. IL-9 levels in TA decreased in the B-100 group but increased in the Pα-100 and Pα-200 groups. Blood levels of cytokines and chemokines showed significantly decreased levels of ITaC and MIP3b only in the B-100 group, but no significant change was observed in the Pα-100 and Pα-200 groups.

CONCLUSION

In our study, the different immunomodulatory effects of natural surfactant preparations on newborn lung is proven. We found that Poractant α, one of the natural surfactant preparations, shifted the lung immune system toward TH2.

Pulmonary alveolar proteinosis

Pulmonary alveolar proteinosis (PAP) is a syndrome characterized by the accumulation of alveolar surfactant and dysfunction of alveolar macrophages. PAP results in progressive dyspnoea of insidious onset, hypoxaemic respiratory failure, secondary infections and pulmonary fibrosis. PAP can be classified into different types on the basis of the pathogenetic mechanism: primary PAP is characterized by the disruption of granulocyte-macrophage colony-stimulating factor (GM-CSF) signalling and can be autoimmune (caused by elevated levels of GM-CSF autoantibodies) or hereditary (due to mutations in CSF2RA or CSF2RB, encoding GM-CSF receptor subunits); secondary PAP results from various underlying conditions; and congenital PAP is caused by mutations in genes involved in surfactant production. In most patients, pathogenesis is driven by reduced GM-CSF-dependent cholesterol clearance in alveolar macrophages, which impairs alveolar surfactant clearance. PAP has a prevalence of at least 7 cases per million individuals in large population studies and affects men, women and children of all ages, ethnicities and geographical locations irrespective of socioeconomic status, although it is more-prevalent in smokers. Autoimmune PAP accounts for >90% of all cases. Management aims at improving symptoms and quality of life; whole-lung lavage effectively removes excessive surfactant. Novel pathogenesis-based therapies are in development, targeting GM-CSF signalling, immune modulation and cholesterol homeostasis.

Surfactant Protein D in Respiratory and Non-Respiratory Diseases

Surfactant protein D (SP-D) is a multimeric collectin that is involved in innate immune defense and expressed in pulmonary, as well as non-pulmonary, epithelia. SP-D exerts antimicrobial effects and dampens inflammation through direct microbial interactions and modulation of host cell responses via a series of cellular receptors. However, low protein concentrations, genetic variation, biochemical modification, and proteolytic breakdown can induce decomposition of multimeric SP-D into low-molecular weight forms, which may induce pro-inflammatory SP-D signaling. Multimeric SP-D can decompose into trimeric SP-D, and this process, and total SP-D levels, are partly determined by variation within the SP-D gene, SFTPD. SP-D has been implicated in the development of respiratory diseases including respiratory distress syndrome, bronchopulmonary dysplasia, allergic asthma, and chronic obstructive pulmonary disease. Disease-induced breakdown or modifications of SP-D facilitate its systemic leakage from the lung, and circulatory SP-D is a promising biomarker for lung injury. Moreover, studies in preclinical animal models have demonstrated that local pulmonary treatment with recombinant SP-D is beneficial in these diseases. In recent years, SP-D has been shown to exert antimicrobial and anti-inflammatory effects in various non-pulmonary organs and to have effects on lipid metabolism and pro-inflammatory effects in vessel walls, which enhance the risk of atherosclerosis. A common SFTPD polymorphism is associated with atherosclerosis and diabetes, and SP-D has been associated with metabolic disorders because of its effects in the endothelium and adipocytes and its obesity-dampening properties. This review summarizes and discusses the reported genetic associations of SP-D with disease and the clinical utility of circulating SP-D for respiratory disease prognosis. Moreover, basic research on the mechanistic links between SP-D and respiratory, cardiovascular, and metabolic diseases is summarized. Perspectives on the development of SP-D therapy are addressed.

Aberrant expression of cytokine interleukin 9 along with interleukin 4 and interferon γ in connective tissue disease-associated interstitial lung disease: association with severity of pulmonary fibrosis

INTRODUCTION

Connective tissues diseases (CTDs) are a heterogeneous group of disorders that share certain clinical characteristics and disturbed immunoregulation. Interstitial lung diseases (ILDs), also known as diffuse parenchymal lung diseases, are among the most serious pulmonary complications associated with CTDs. Interleukin 9 (IL-9), IL-4 and interferon γ (IFN-γ) - cytokines with important roles in autoimmune disease - were studied in CTD patients and CTD-ILD patients.

MATERIAL AND METHODS

Sixty-one hospitalized untreated CTD patients were recruited, and 20 healthy volunteers were enrolled as controls. The 61 CTD patients were divided into a simple CTD group and a CTD-ILD group, and the plasma protein IL-9, IL-4 and IFN-γ levels were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The results indicate that the serum IL-9 levels were significantly higher in CTD-ILD and simple CTD patients than they were in healthy controls (each p < 0.05) and that the levels were elevated in CTD-ILD patients compared with simple CTD patients (p < 0.05). The IL-4 levels were higher in CTD-ILD patients than they were in the simple CTD patients (p < 0.05) and healthy controls (p < 0.01). In addition, the serum IL-9 levels were negatively correlated with the level of IFN-γ (r (2) = 0.34, p = 0.01), the estimated percentage of predicted forced vital capacity (FVC%) (r (2) = 0.36, p = 0.00) and the estimated percentage of predicted diffusing capacity (DLCO%) (r (2) = 0.27, p = 0.04) and were positively correlated with the IL-4 level (r (2) = 0.31, p = 0.01).

CONCLUSIONS

Interleukin-9 may play an important role in the pathogenesis of CTD and may contribute to the progression of interstitial lung injury in CTD patients.

Linking GATA-3 and interleukin-13: implications in asthma

INTRODUCTION

Asthma is one of the serious global health problems and cause of huge mortality and morbidity. It is characterized by persistent airway inflammation, airway hyperresponsiveness, increased IgE levels and mucus hypersecretion. Asthma is mediated by dominant Th2 immune response, causing enhanced expression of Th2 cytokines. These cytokines are responsible for the various pathological changes associated with allergic asthma.

MATERIALS AND METHODS

The role of Th2 cells in the pathogenesis of the asthma is primarily mediated through the cytokine IL-13, also produced by type 2 innate lymphoid cells, that comes under the transcriptional regulation of GATA3. In this review we will try to explore the link between IL-13 and GATA3 in the progression and regulation of asthma and its possible role as a therapeutic target.

CONCLUSION

Inhibition of GATA3 activity or blockade of GATA3 expression may attenuate the interleukin-13 mediated asthma phenotypes. So, GATA3 might be a potential therapeutic target for the treatment of allergic asthma.

Transcription repressor Bach2 is required for pulmonary surfactant homeostasis and alveolar macrophage function

Pulmonary alveolar proteinosis (PAP) results from a dysfunction of alveolar macrophages (AMs), chiefly due to disruptions in the signaling of granulocyte macrophage colony-stimulating factor (GM-CSF). We found that mice deficient for the B lymphoid transcription repressor BTB and CNC homology 2 (Bach2) developed PAP-like accumulation of surfactant proteins in the lungs. Bach2 was expressed in AMs, and Bach2-deficient AMs showed alterations in lipid handling in comparison with wild-type (WT) cells. Although Bach2-deficient AMs showed a normal expression of the genes involved in the GM-CSF signaling, they showed an altered expression of the genes involved in chemotaxis, lipid metabolism, and alternative M2 macrophage activation with increased expression of Ym1 and arginase-1, and the M2 regulator Irf4. Peritoneal Bach2-deficient macrophages showed increased Ym1 expression when stimulated with interleukin-4. More eosinophils were present in the lung and peritoneal cavity of Bach2-deficient mice compared with WT mice. The PAP-like lesions in Bach2-deficient mice were relieved by WT bone marrow transplantation even after their development, confirming the hematopoietic origin of the lesions. These results indicate that Bach2 is required for the functional maturation of AMs and pulmonary homeostasis, independently of the GM-CSF signaling.

Lung surfactant protein D (SP-D) response and regulation during acute and chronic lung injury

BACKGROUND

Surfactant protein D (SP-D) is a collection that plays important roles in modulating host defense functions and maintaining phospholipid homeostasis in the lung. The aim of current study was to characterize comparatively the SP-D response in bronchoalveolar lavage (BAL) and serum in three murine models of lung injury, using a validated ELISA technology for estimation of SP-D levels.

METHODS

Mice were exposed to lipopolysaccharide, bleomycin, or Pneumocystis carinii (Pc) and sacrificed at different time points.

RESULTS

In lipopolysaccharide-challenged mice, the level of SP-D in BAL increased within 6 h, peaked at 51 h (4,518 ng/ml), and returned to base level at 99 h (612 ng/ml). Serum levels of SP-D increased immediately (8.6 ng/ml), peaked at 51 h (16 ng/ml), and returned to base levels at 99 h (3.8 ng/ml). In a subacute bleomycin inflammation model, SP-D levels were 4,625 and 367 ng/ml in BAL and serum, respectively, 8 days after exposure. In a chronic Pc inflammation model, the highest level of SP-D was observed 6 weeks after inoculation, with BAL and serum levels of 1,868 and 335 ng/ml, respectively.

CONCLUSIONS

We conclude that serum levels of SP-D increase during lung injury, with a sustained increment during chronic inflammation compared with acute inflammation. A quick upregulation of SP-D in serum in response to acute airway inflammation supports the notion that SP-D translocates from the airways into the vascular system, in favor of being synthesized systemically. The study also confirms the concept of using increased SP-D serum levels as a biomarker of especially chronic airway inflammation.

Linking surfactant protein SP-D and IL-13: implications in asthma and allergy

Surfactant protein D (SP-D) is an innate immune molecule that plays a protective role against lung infection, allergy, asthma and inflammation. In vivo experiments with murine models have shown that SP-D can protect against allergic challenge via a range of mechanisms including inhibition of allergen-IgE interaction, histamine release by sensitised mast cells, downregulation of specific IgE production, suppression of pulmonary and peripheral eosinophilia, inhibition of mechanisms that cause airway remodelling, and induction of apoptosis in sensitised eosinophils. SP-D can also shift helper T cell polarisation following in vivo allergenic challenge, from pathogenic Th2 to a protective Th1 cytokine response. Interestingly, SP-D gene deficient (-/-) mice show an IL-13 over-expressing phenotype. IL-13 has been shown to be involved in the development of asthma. Transgenic mice over-expressing IL-13 in the lung develop several characteristics of asthma such as pulmonary eosinophilia, airway epithelial hyperplasia, mucus cell metaplasia, sub-epithelial fibrosis, charcot-Leyden-Like crystals, airways obstruction, and non-specific airways hyper-responsiveness to cholinergic stimulation. Although both IL-4 and IL-13 are capable of inducing asthma like phenotype, the effector activity of IL-13 appears to be greater than that of IL-4. SP-D -/- mice seem to express considerably higher levels of IL-13, which is consistent with increased sensitivity and exaggerated immune response of the mice to allergenic challenge. Allergenic exposure also induces elevation in SP-D protein levels in an IL-4/IL-13-dependent manner, which prevents further activation of sensitised T cells. This negative feedback loop seems essential in protecting the airways from inflammatory damage after allergen inhalation. Here, we examine this link between IL-13 and SP-D, and its implications in the progression/regulation of asthma and allergy.

IL-13 in asthma and allergic disease: asthma phenotypes and targeted therapies

Decades of research in animal models have provided abundant evidence to show that IL-13 is a key T(H)2 cytokine that directs many of the important features of airway inflammation and remodeling in patients with allergic asthma. Several promising focused therapies for asthma that target the IL-13/IL-4/signal transducer and activator of transcription 6 pathway are in development, including anti-IL-13 mAbs and IL-4 receptor antagonists. The efficacy of these new potential asthma therapies depends on the responsiveness of patients. However, an understanding of how IL-13-directed therapies might benefit asthmatic patients is confounded by the complex heterogeneity of the disease. Recent efforts to classify subphenotypes of asthma have focused on sputum cellular inflammation profiles, as well as cluster analyses of clinical variables and molecular and genetic signatures. Researchers and clinicians can now evaluate biomarkers of T(H)2-driven airway inflammation in asthmatic patients, such as serum IgE levels, sputum eosinophil counts, fraction of exhaled nitric oxide levels, and serum periostin levels, to aid decision making in clinical trials and drug development and to identify subsets of patients who might benefit from therapies. Although it is unlikely that these therapies will benefit all asthmatic patients with this heterogeneous disease, advances in understanding asthma subphenotypes in relation to clinical variables and T(H)2 cytokine responses offer the opportunity to improve the efficacy and safety of proposed therapies for asthma.

Cadherin-11 contributes to pulmonary fibrosis: potential role in TGF-β production and epithelial to mesenchymal transition

Pulmonary fibrosis, characterized by excess deposition of extracellular matrix by myofibroblasts, is a serious component of chronic lung diseases. Cadherin-11 (CDH11) is increased in wound healing and fibrotic skin. We hypothesized that CDH11 is increased in pulmonary fibrosis and contributes its development. CDH11 expression was assessed in lung tissue from idiopathic pulmonary fibrosis patients. The role of CDH11 in lung fibrosis was determined using the bleomycin model of pulmonary fibrosis, and in vitro analyses were performed on A549 cells during the process of epithelial to mesenchymal transition (EMT). Immunohistochemical studies demonstrated CDH11 expression on fibroblasts, epithelial cells, and alveolar macrophages of patients with pulmonary fibrosis and mice given bleomycin. Interestingly, CDH11-deficient mice had decreased fibrotic endpoints in the bleomycin model of pulmonary fibrosis compared to wild-type mice. Furthermore, anti-CDH11-neutralizing monoclonal antibodies successfully treated established pulmonary fibrosis induced by bleomycin. TGF-β levels were reduced in bronchoalveolar lavage (BAL) fluid, BAL cells, and primary alveolar macrophages from CDH11-deficient mice. Mechanistic studies demonstrated that TGF-β up-regulated CDH11 expression on A549 cells, and inhibition of CDH11 expression using siRNA reduced TGF-β-induced EMT. Together, these results identify CDH11 as a novel therapeutic target for pulmonary fibrosis.

Modern concepts on the role of inflammation in pulmonary fibrosis

CONTEXT

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

OBJECTIVE

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

DATA SOURCES

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

CONCLUSIONS

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

Effects of furosemide on allergic asthmatic responses in mice

BACKGROUND

The syndrome of allergic asthma features reversible bronchoconstriction, airway inflammation and hyperresponsiveness as well as airway remodelling, including goblet cell hyperplasia. Managing severe asthma is still a clinical challenge. Numerous studies report that furosemide, an inhibitor of Na(+)-K(+)-Cl(-) cotransporter (NKCC) reduces airway hyperresponsiveness (AHR) in asthmatic patients. However, the mechanism by which furosemide exerts anti-asthmatic action remains unclear.

OBJECTIVE

This study sought to investigate the cellular profile of NKCC1 expression in the lung and examine the effects of furosemide on several outcome measurements in a mouse model of allergic asthma.

METHODS

Mice were sensitized and challenged with ovalbumin (OVA). Before challenge, the OVA-sensitized mice were treated with furosemide (4.0 mg/kg/day, via daily intraperitoneal injection for 5 days). Outcome measurements in naïve, OVA-exposure, furosemide-treated naïve and furosemide-treated OVA-exposed mice included the slope of the relationship between inhaled methacholine (MCh) concentration and respiratory system resistance (Slope·R(RS)), bronchoalveolar lavage (BAL) cell counts and immunohistochemical and immunoblotting assays of lung tissues.

RESULTS

NKCC1 immunoreactivity was observed in airway epithelial cells (AECs) and alveolar type II (ATII) cells of the control mice. OVA exposure enhanced the expression of NKCC1 in AECs and ATII cells, and increased the infiltration of NKCC1-expressing T lymphocytes in the lung. NKCC1 immunoreactivity was not detected in the airway smooth muscle (ASM) cells. Furosemide treatment reduced the Slope·R(RS) in both naïve and OVA-exposed mice by about 50%. Furosemide treatment also increased T lymphocyte infiltration to the lung in OVA-exposed mice by approximately 53%, but had no effect on pulmonary goblet cell hyperplasia.

CONCLUSIONS AND CLINICAL RELEVANCE

Furosemide decreases basal airway responsiveness, thereby reducing the extent of allergen-induced AHR. However, the same treatment also increases T lymphocytes infiltration in the course of allergic asthma. Further studies are necessary to address the usefulness of furosemide in the clinical treatment of asthma.

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.

Lung surfactant proteins A and D as pattern recognition proteins

Lung surfactant proteins A and D belong to a group of soluble humoral pattern recognition receptors, called collectins, which modulate the immune response to microorganisms. They bind essential carbohydrate and lipid antigens found on the surface of microorganisms via low affinity C-type lectin domains and regulate the host's response by binding to immune cell surface receptors. They form multimeric structures that bind, agglutinate, opsonise and neutralize many different pathogenic microorganisms including bacteria, yeast, fungi and viruses. They modulate the uptake of these microorganisms by phagocytic cells as well as both the inflammatory and the adaptive immune responses. Recent data have also highlighted their involvement in clearance of apoptotic cells, hypersensitivity and a number of lung diseases.

Protective role of the lung collectins surfactant protein A and surfactant protein D in airway inflammation

The acute inflammatory airway response is characterized by a time-dependent onset followed by active resolution. Emerging evidence suggests that epithelial cells of the proximal and distal air spaces release host defense mediators that can facilitate both the initiation and the resolution part of inflammatory airway changes. These molecules, also known as the hydrophilic surfactant proteins (surfactant protein [SP]-A and SP-D) belong to the class of collagenous lectins (collectins). The collectins are a small family of soluble pattern recognition receptors containing collagenous regions and C-type lectin domains. SP-A and SP-D are most abundant in the lung. Because of their structural uniqueness, specific localization, and functional versatility, lung collectins are important players of the pulmonary immune responses. Recent studies in our laboratory and others indicated significant associations of lung collectin levels with acute and chronic airway inflammation in both animal models and patients, suggesting the usefulness of these molecules as disease biomarkers. Research on wild-type and mutant recombinant molecules in vivo and in vitro showed that SP-A and SP-D bind carbohydrates, lipids, and nucleic acids with a broad-spectrum specificity and initiate phagocytosis of inhaled pathogens as well as apoptotic cells. Investigations on gene-deficient and conditional overexpresser mice indicated that lung collectins also directly modulate innate immune cell function and T-cell-dependent inflammatory events. Thus, these molecules have a unique, dual-function capacity to induce pathogen elimination and control proinflammatory mechanisms, suggesting a potential suitability for therapeutic prevention and treatment of chronic airway inflammation. This article reviews evidence supporting that the lung collectins play an immune-protective role and are essential for maintenance of the immunologic homeostasis in the lung.

Children with absent surfactant protein D in bronchoalveolar lavage have more frequently pneumonia

Surfactant protein D (SP-D) is an important component of the pulmonary host defense system. We hypothesized that bronchoalveolar lavage (BAL) SP-D levels are lower in children presenting with recurrent bronchitis, providing evidence for a role of SP-D in human respiratory diseases. SP-D levels in BAL were measured in 45 children, who suffered from recurrent bronchitis for an average of 2-3 yr. Clinical outcome was assessed 2 yr after BAL. For comparison, BAL fluids from 15 control children without respiratory symptoms were evaluated. Among the 45 children with recurrent bronchitis, 12 had no SP-D in their BAL at the time of investigation. These SP-D-deficient patients had more frequently pneumonias and their long-term outcome was worse than that of the children with detectable SP-D. No genetic cause could be identified for the SP-D deficiency. Among the children with recurrent bronchitis and SP-D clearly detectable in BAL, those with the diagnosis of allergic asthma had threefold elevated levels compared with controls. In accordance with animal and in vitro data, elevated SP-D concentrations in BAL may represent an up-regulation due to allergic airway inflammation. In contrast, SP-D deficiency due to consumption or failure to up-regulate SP-D may be linked to pulmonary morbidity in children.

Therapeutic use of surfactant components in allergic asthma

Pulmonary surfactant is a complex mixture of lipids and proteins that reduces the surface tension at the air-liquid interface. In addition to its biophysical function, some surfactant components play an important role for the innate and adaptive immunity of the lung. A negative modulation of the surfactant function was observed in allergic asthma leading to the assumption that the therapeutic application of surfactant components might be beneficial in this disease. So far, there are a number of preclinical and already some clinical studies demonstrating various effects of different surfactant components that were administered with preventive or therapeutic aim in allergic asthma. This review summarizes the current knowledge on the possibilities to treat allergic asthma with surfactant components.

Methods for studying stem cells: adult stem cells for lung repair

Recent progress in lung biology includes the description of a series of pulmonary stem and progenitor cells involved in homeostasis and regeneration of the respiratory system. Moreover, the contribution of extrapulmonary stem cells to healthy and pathological lung tissue has been observed and the developmental biology of such processes should provide important hints for understanding maintenance and repair of adult lung structure and function. Despite such remarkable advances, the phenotypic and especially the functional characterization of these stem and progenitor cells, and their derivatives, along with an understanding of the molecular cues and pathways underlying differentiation into specific respiratory lineages is still in its infancy. Accordingly, the role of endogenous and extrapulmonary stem cells in normal tissue repair and pathogenesis is still largely mysterious and added basic knowledge is required in order to explore their potential for novel regenerative therapies. This review provides an overview of the current state of the art in adult lung stem cell biology including technical aspects of isolation, characterization and differentiation, and a discussion of perspectives for future regenerative therapies.

Developmental regulation of NO-mediated VEGF-induced effects in the lung

Vascular endothelial growth factor (VEGF) is known to have a pivotal role in lung development and in a variety of pathologic conditions in the adult lung. Our earlier studies have shown that NO is a critical mediator of VEGF-induced vascular and extravascular effects in the adult murine lung. As significant differences have been reported in the cytokine responses in the adult versus the neonatal lung, we hypothesized that there may be significant differences in VEGF-induced alterations in the developing as opposed to the mature lung. Furthermore, nitric oxide (NO) mediation of these VEGF-induced effects may be developmentally regulated. Using a novel externally regulatable lung-targeted transgenic murine model, we found that VEGF-induced pulmonary hemorrhage was mediated by NO-dependent mechanisms in adults and newborns. VEGF enhanced surfactant production in adults as well as increased surfactant and lung development in newborns, via an NO-independent mechanism. While the enhanced survival in hyperoxia in the adult was partly NO-dependent, there was enhanced hyperoxia-induced lung injury in the newborn. In addition, human amniotic fluid VEGF levels correlated positively with surfactant phospholipids. Tracheal aspirate VEGF levels had an initial spike, followed by a decline, and then a subsequent rise, in human neonates with an outcome of bronchopulmonary dysplasia or death. Our data show that VEGF can have injurious as well as potentially beneficial developmental effects, of which some are NO dependent, others NO independent. This opens up the possibility of selective manipulation of any VEGF-based intervention using NO inhibitors for maximal potential clinical benefit.

Cysteinyl leukotriene receptor antagonist MK-571 alters bronchoalveolar lavage fluid proteome in a mouse asthma model

Cysteinyl leukotriene receptor type 1 (leukotriene CysLT(1) receptor) antagonist is one of the most effective anti-inflammatory agents for asthma. The spectrum of protein targets that can be regulated by leukotriene CysLT(1) receptor antagonist in asthma is not fully understood. The present study tried to identify novel protein targets of a selective leukotriene CysLT(1) receptor antagonist MK-571 in allergic airway inflammation by analyzing the proteome of mouse bronchoalveolar lavage fluid. BALB/c mice sensitized and challenged with ovalbumin showed increased pulmonary inflammatory cell infiltration, airway mucus production and serum ovalbumin-specific IgE level. MK-571 inhibited all these allergic airway inflammation endpoints. Lavage fluid proteins were resolved by two-dimensional gel electrophoresis and identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The level of fourteen bronchoalveolar lavage fluid protein spots was markedly altered by MK-571. A family of chitinases (Ym1, Ym2 and acidic mammalian chitinase), lungkine, surfactant protein-D and gamma-actin have been found for the first time to be down-regulated by leukotriene CysLT(1) receptor antagonist in mouse allergic airways. Some of the down-regulatory effects were confirmed with reverse transcription-polymerase chain reaction analyses. Taken together, we have identified novel protein targets that can be regulated by leukotriene CysLT(1) receptor antagonist in mouse allergic airway inflammation, and our findings reveal additional pharmacological actions of leukotriene CysLT(1) receptor antagonist in the treatment of asthma.

Regulation of surfactant secretion in alveolar type II cells

Molecular mechanisms of surfactant delivery to the air/liquid interface in the lung, which is crucial to lower the surface tension, have been studied for more than two decades. Lung surfactant is synthesized in the alveolar type II cells. Its delivery to the cell surface is preceded by surfactant component synthesis, packaging into specialized organelles termed lamellar bodies, delivery to the apical plasma membrane and fusion. Secreted surfactant undergoes reuptake, intracellular processing, and finally resecretion of recycled material. This review focuses on the mechanisms of delivery of surfactant components to and their secretion from lamellar bodies. Lamellar bodies-independent secretion is also considered. Signal transduction pathways involved in regulation of these processes are discussed as well as disorders associated with their malfunction.

Surfactant protein A and surfactant protein D variation in pulmonary disease

Surfactant proteins A (SP-A) and D (SP-D) have been implicated in pulmonary innate immunity. The proteins are host defense lectins, belonging to the collectin family which also includes mannan-binding lectin (MBL). SP-A and SP-D are pattern-recognition molecules with the lectin domains binding preferentially to sugars on a broad spectrum of pathogen surfaces and thereby facilitating immune functions including viral neutralization, clearance of bacteria, fungi and apoptotic and necrotic cells, modulation of allergic reactions, and resolution of inflammation. SP-A and SP-D can interact with receptor molecules present on immune cells leading to enhanced microbial clearance and modulation of inflammation. SP-A and SP-D also modulate the functions of cells of the adaptive immune system including dendritic cells and T cells. Studies on SP-A and SP-D polymorphisms and protein levels in bronchoalveolar lavage and blood have indicated associations with a multitude of pulmonary inflammatory diseases. In addition, accumulating evidence in mouse models of infection and inflammation indicates that recombinant forms of the surfactant proteins are biologically active in vivo and may have therapeutic potential in controlling pulmonary inflammatory disease. The presence of the surfactant collectins, especially SP-D, in non-pulmonary tissues, such as the gastrointestinal tract and genital organs, suggest additional actions located to other mucosal surfaces. The aim of this review is to summarize studies on genetic polymorphisms, structural variants, and serum levels of human SP-A and SP-D and their associations with human pulmonary disease.

The immunoregulatory roles of lung surfactant collectins SP-A, and SP-D, in allergen-induced airway inflammation

It has become increasingly evident that pulmonary surfactant proteins, SP-A and SP-D, present in the alveolar and bronchial epithelial fluid linings, not only play significant functions in the innate defense mechanism against pathogens, but also are involved in immunomodulatory roles, which result in the protection against, and resolution of, allergen-induced airway inflammation. Studies on allergen-sensitized murine models, and asthmatic patients, show that SP-A and SP-D can: specifically bind to aero-allergens; inhibit mast cell degranulation and histamine release; and modulate the activation of alveolar macrophages and dendritic cells during the acute hypersensitive phase of allergic response. They also can alleviate chronic allergic inflammation by inhibiting T-lymphocyte proliferation as well as increasing phagocytosis of DNA fragments and clearance of apoptotic cell debris. Furthermore, it has emerged, from the studies on SP-D-deficient mice, that, when these mice are challenged with allergen, they develop increased eosinophil infiltration, and abnormal activation of lymphocytes, leading to the production of Th2 cytokines. Intranasal administration of SP-D significantly attenuated the asthmatic-like symptoms seen in allergen-sensitized wild-type, and SP-D-deficient, mice. These important findings provide a new insight of the role that surfactant proteins play in handling environmental stimuli and in their immunoregulation of airway inflammatory disease.

Dexamethasone alters bronchoalveolar lavage fluid proteome in a mouse asthma model

BACKGROUND

Glucocorticoid is the most effective anti-inflammatory agent for asthma. The spectrum of protein targets that can be regulated by glucocorticoid in asthma is not fully understood. The present study tried to identify novel protein targets of dexamethasone in allergic airway inflammation by analyzing the proteome of mouse bronchoalveolar lavage (BAL) fluid.

METHODS

BALB/c mice sensitized and challenged with ovalbumin (OVA) showed increased pulmonary inflammatory cell infiltration, airway mucus production and serum OVA-specific IgE level. Dexamethasone inhibited all these allergic airway inflammation endpoints. BAL fluid proteins were resolved by two-dimensional gel electrophoresis and identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

RESULTS

The levels of 26 BAL fluid proteins were found to be markedly altered by dexamethasone. A family of chitinases (Ym1, Ym2 and acidic mammalian chitinase, AMCase), lungkine, gob-5, surfactant protein D and polymeric immunoglobulin receptor have been found for the first time to be downregulated by dexamethasone in allergic airways. The downregulatory effects were confirmed by immunoblotting and RT-PCR analyses. Dexamethasone was also shown to significantly inhibit lavage fluid chitinase bioactivity. In addition, dexamethasone promoted airway expression of vitamin D-binding protein, heptoglobin and alpha(1)-antitrypsin.

CONCLUSIONS

Among all these newly identified protein targets of dexamethasone, AMCase and gob-5 have been shown to be pro-inflammatory in asthma. Downregulation of AMCase and gob-5 may be considered as two novel anti-inflammatory actions of glucocorticoid in asthma.

IL-13 is associated with reduced illness and replication in primary respiratory syncytial virus infection in the mouse

The role of IL-13 in respiratory syncytial virus (RSV) immunopathogenesis is incompletely described. To assess the effect of IL-13 on primary RSV infection, transgenic mice which either overexpress IL-13 in the lung (IL-13 OE) or non-transgenic littermates (IL-13 NT) were challenged intranasally with RSV. IL-13 OE mice had significantly decreased peak viral titers four days after infection compared to non-transgenic littermates. In addition, IL-13 OE mice had significantly lower RSV-induced weight loss and reduced lung IFN-γ protein expression compared with IL-13 NT mice. In contrast, primary RSV challenge of IL-13 deficient mice resulted in a small, but statistically significant increase in viral titers on day four after infection, no difference in RSV-induced weight loss compared to wild type mice, and augmented IFN-γ production on day 6 after infection. In STAT1-deficient (STAT1 KO) mice, where primary RSV challenge produced high levels of IL-13 production in the lungs, treatment with an IL-13 neutralizing protein resulted in greater peak viral titers both four and six days after RSV and greater RSV-induced weight loss compared to mice treated with a control protein. These results suggest that IL-13 modulates illness from RSV-infection.

Surfactant protein levels in bronchoalveolar lavage after segmental allergen challenge in patients with asthma

BACKGROUND

Allergic asthma is associated with airway inflammation and dysfunction of pulmonary surfactant. Because surfactant proteins (SP) account for immunomodulatory functions as well as biophysical functions, we hypothesized that the allergic response in asthma might be accompanied by a dysregulation of SPs.

METHODS

We measured levels of SP-A, SP-B, SP-C and SP-D by enzyme-linked immunosorbent assay in bronchoalveolar lavage (BAL) fluid of 23 asthma patients and 10 healthy control subjects under well-controlled conditions before and 24 h after segmental allergen provocation. These data were related to surfactant function, Th(2) cytokine levels in BAL fluid and to the degree of eosinophilic inflammation.

RESULTS

In patients with asthma, allergen challenge increased BAL levels of SP-B, SP-C and SP-D while SP-A was decreased. For SP-B and SP-D, a moderate increase was also observed after saline challenge. In contrast, no alterations were observed in healthy control subjects. Levels of SP-B and SP-C in asthmatics correlated with the ratio of small to large surfactant aggregates (SA/LA ratio) and correlated negatively with BAL surface activity. Furthermore, increased SP-C but not SP-B levels after allergen challenge correlated with eosinophil numbers, interleukin (IL)-5, and IL-13 in BAL while increased SP-D levels only correlated with eosinophil numbers.

CONCLUSIONS

This study demonstrates significant alterations of all SPs in BAL fluid after allergen challenge of which SP-C was most closely related to surfactant dysfunction and the degree of the allergic inflammation.

Differential expression of chitinases identify subsets of murine airway epithelial cells in allergic inflammation

The mammalian chitinase family includes members both with and without enzymatic activity against chitin, a product of fungal cell walls, exoskeletons of crustaceans and insects, and the microfilarial sheaths of parasitic nematodes. Two members of that family, Ym1 and acidic mammalian chitinase (AMCase), are strongly upregulated in pulmonary T helper (Th) 2 inflammation but not in Th1 inflammation. The sites of expression of these products are incompletely known. We show here that, in two different models of Th2 inflammation, Ym1 and AMCase are mutually exclusively expressed in proximal vs. distal airway epithelium, respectively, whereas both are expressed in alveolar macrophages. This regional difference along the airway corresponds to the previously noted distinction between mucus positive proximal cells and mucus negative distal cells under the same conditions. Among distal cells, AMCase colocalizes with epithelial cells expressing the Clara cell marker Clara cell secretory protein. These AMCase-expressing cells retain expression of FOXA2, a transcription factor whose downregulation in association with IL-13 signaling has previously been associated with production of mucus in proximal airway epithelial cells. These results provide evidence that secretory cells of proximal and distal airways undergo fundamentally different gene expression programs in response to allergic inflammation. Furthermore, AMCase provides the first positive molecular marker of distal Clara cell secretory protein-expressing cells under these conditions.

Genetic and environmental influences of surfactant protein D serum levels

The collectin surfactant protein D (SP-D) is an important component of the pulmonary innate immune system, but SP-D is also present on extrapulmonary epithelial surfaces and in serum, where it has been used as a biomarker for pulmonary disease states. In this study, we investigate the mechanisms defining the constitutional serum level of SP-D and determine the magnitude of the genetic contribution to serum SP-D in the adult population. Recent studies have demonstrated that serum SP-D concentrations in children are genetically determined and that a single nucleotide polymorphism (SNP) located in the NH(2)-terminal region (Met11Thr) of the mature protein is significantly associated with the serum SP-D levels. A classic twin study was performed on a twin population including 1,476 self-reported healthy adults. The serum SP-D levels increased with male sex, age, and smoking status. The intraclass correlation was significantly higher for monozygotic (MZ) twin pairs than for dizygotic (DZ) twin pairs. Serum SP-D variance was influenced by nonshared environmental effects and additive genetic effects. Multivariate analysis of MZ and DZ covariance matrixes showed significant genetic correlation among serum SP-D and metabolic variables. The Met11Thr variant explained a significant part of the heritability indicating that serum SP-D variance could be decomposed into non-shared environmental effects (e(2) = 0.19), additive genetic effects (h(2) = 0.42), and the effect of the Met11Thr variations (q(2) = 0.39).

Lung infection with gamma-herpesvirus induces progressive pulmonary fibrosis in Th2-biased mice

Idiopathic pulmonary fibrosis (IPF) is a progressive, fibrotic lung disease of unknown etiology. A viral pathogenesis in IPF has been suggested since >95% of IPF patients have evidence of chronic pulmonary infection with one or more herpesviruses. To determine whether pulmonary infection with herpesvirus can cause lung fibrosis, we infected mice with the murine gamma-herpesvirus 68 (MHV68). Because IPF patients have a T helper type 2 (Th2) pulmonary phenotype, we used IFN-gammaR-/-, a strain of mice biased to develop Th2 responses. Chronic MHV68 infection of IFN-gammaR-/- mice resulted in progressive deposition of interstitial collagen as shown by light and electron microscopy. A significant decrease in tidal volume paralleled the collagen deposition. Five features typically seen in IPF, increased transforming growth factor-beta expression, myofibroblast transformation, production of Th2 cytokines, hyperplasia of type II cells, and increased expression of matrix metalloproteinase-7, were also present in chronically infected IFN-gammaR-/- mice. There also was altered synthesis of surfactant proteins, which is seen in some patients with familial IPF. MHV68 viral protein was found in type II alveolar epithelial cells, especially in lung areas with extensive alveolar remodeling. In summary, chronic herpesvirus pulmonary infection in IFN-gammaR-/- mice causes progressive pulmonary fibrosis and many of the pathological features seen in IPF.

Role and regulation of lung collectins in allergic airway sensitization

Inhalation of allergens in atopic patients results in a characteristic inflammatory response while in normal, healthy individuals it elicits no symptoms. The mechanisms by which the pulmonary immune system accomplishes elimination of inhaled particles and suppression of the ensuing inflammatory response are poorly understood. Based on their structural uniqueness, specific localization and functional versatility the hydrophilic surfactant proteins [surfactant protein (SP)-A and SP-D] are important candidate regulators of these processes. Recent studies in our laboratory and others indicated significant changes in levels of these molecules during the asthmatic response in animal models as well as in asthmatic patients. Because of their capability to directly inhibit T-cell activation and T-cell-dependent allergic inflammatory events, SP-A and SP-D may be significant contributors to the local control of T-helper (Th)2-type inflammation in the airways. This review will discuss their relevant structural-functional features and recent evidence supporting the hypothesis that SP-A and SP-D have a role in regulation of allergic airway sensitization.

Role of collectins in innate immunity against aspergillosis

The protective role of lung surfactant proteins SP-A, SP-D and MBL in the host defense against both allergic and invasive aspergillosis was identified and established by a series of in vitro and in vivo studies. Therapeutic administration of SP-D and MBL proteins in a murine model of pulmonary invasive aspergillosis rescued mice from death. In mice mimicking human allergic bronchopulmonary aspergillosis, SP-A and SP-D suppressed IgE levels, eosinophilia, pulmonary cellular infiltration and cause a marked shift from a pathogenic Th2 to a protective Th1 cytokine profile. SP-A and SP-D knock-out mice studies made significant contributions in understanding the mechanisms by which SP-A and SP-D modulate the host defense response in patients suffering from pulmonary allergies and infections. The results suggested that individuals with any structural or functional defects in these innate immune molecules due to genetic variations might be susceptible to aspergillosis. SNPs in SP-A2 and MBL genes showed significant associations with patients of allergic bronchopulmonary aspergillosis in an Indian population. The patients carrying either one or both of GCT and AGG alleles of SP-A2 and patients with A allele at position 1011 of MBL had markedly higher eosinophilia, total IgE antibodies and lower FEV1 (the clinical markers of ABPA). Our results show that collectins play an important role in Aspergillus mediated allergies and infections.

Surfactant proteins SP-A and SP-D: structure, function and receptors

Surfactant proteins, SP-A and SP-D, are collagen-containing C-type (calcium dependent) lectins called collectins, which contribute significantly to surfactant homeostasis and pulmonary immunity. These highly versatile innate immune molecules are involved in a range of immune functions including viral neutralization, clearance of bacteria, fungi and apoptotic and necrotic cells, down regulation of allergic reaction and resolution of inflammation. Their basic structures include a triple-helical collagen region and a C-terminal homotrimeric lectin or carbohydrate recognition domain (CRD). The trimeric CRDs can recognize carbohydrate or charge patterns on microbes, allergens and dying cells, while the collagen region can interact with receptor molecules present on a variety of immune cells in order to initiate clearance mechanisms. Studies involving gene knock-out mice, murine models of lung hypersensitivity and infection, and functional characterization of cell surface receptors have revealed the diverse roles of SP-A and SP-D in the control of lung inflammation. A recently proposed model based on studies with the calreticulin-CD91 complex as a receptor for SP-A and SP-D has suggested an anti-inflammatory role for SP-A and SP-D in naïve lungs which would help minimise the potential damage that continual low level exposure to pathogens, allergens and apoptosis can cause. However, when the lungs are overwhelmed with exogenous insults, SP-A and SP-D can assume pro-inflammatory roles in order to complement pulmonary innate and adaptive immunity. This review is an update on the structural and functional aspects of SP-A and SP-D, with emphasis on their roles in controlling pulmonary infection, allergy and inflammation. We also try to put in perspective the controversial subject of the candidate receptor molecules for SP-A and SP-D.

Therapeutic targeting of IL-4- and IL-13-responsive cells in pulmonary fibrosis

Severe forms of idiopathic interstitial pneumonia (IIP), such as usual interstitial pneumonia (UIP), can be impervious to modern steroid and immunosuppressive treatment regimens, thereby emphasizing the need for novel effective therapies. Understanding the cytokine networks that may affect immune and structural cell activation and, hence, the progression of these fatal fibrotic diseases, has been a focus in our research. In this regard, we have examined the role of interleukin (IL)-4 and IL-13 and their respective receptor subunits in this process. Examination of clinical surgical lung biopsies (SLBs) showed that IIP is characterized by the abnormal, heightened expression of the receptor subunits that bind IL-4 and IL-13. Specifically, IL-4Ralpha and IL-13Ralpha2 (the high-affinity IL-13 receptor subunit) was present in greater abundance in SLBs and fibroblasts from IIP patients compared with normal patients, who exhibited no evidence of pulmonary fibrosis. These clinical findings prompted us to investigate whether the targeting of pulmonary cell types that were highly responsive to IL-4 and IL-13 was a viable therapeutic option in IIP. Using a chimeric protein comprised of human IL-13 and a truncated version of an exotoxin from Pseudomonas (abbreviated IL13-PE), we observed that IL13-PE selectively targeted human pulmonary fibroblasts grown from IIP SLBs, whereas it had a minimal effect on fibroblasts grown from biopsies from normal patients. In murine models characterized by abnormal airway or interstitial fibrotic responses, the intranasal administration of IL13-PE significantly attenuated the fibrotic response through the targeting of IL-4Ralpha- and IL-13Ralpha2-expressing pulmonary cells, including monocytes, macrophages, and pulmonary fibroblasts. Together, these data demonstrate that IL-4 and IL-13 are required for the initiation and maintenance of pulmonary fibrosis, and highlight the importance of further investigation of anti-fibrotic therapeutics that prevent the action of both cytokines during clinical pulmonary fibrosis.

Serum surfactant protein D is elevated in allergic patients

BACKGROUND

There is evidence that surfactant protein (SP)-D is important in the innate, as well as in the adaptive pulmonary immune response. Serum concentrations of SP-D have been proposed as parameter of the integrity of the blood-airspace barrier in interstitial lung diseases. We hypothesized that serum SP-D concentrations are affected in allergic patients and correlate with changes in allergic airway inflammation.

OBJECTIVE

To determine levels of serum SP-D in allergic patients compared with non-allergic controls. Furthermore, to investigate associations between serum SP-D concentrations on the one hand and changes in commonly used markers of bronchial inflammation in allergic airways disease on the other hand.

MATERIALS AND METHODS

Fifty allergic patients were studied and bronchial allergen challenge was used as a model to increase bronchial allergic inflammation in these patients. Serum SP-D concentrations, inflammatory parameters in induced sputum and bronchial hyper-responsiveness (BHR) were determined before and after allergen challenge. Twenty-five non-allergic volunteers served as controls.

RESULTS

Baseline serum SP-D was significantly higher in allergic patients as compared with controls (mean serum SP-D concentration (95% confidence interval): 62.7 (55.5, 70.0) in allergic patients vs. 49.5 (36.7, 62.3) ng/mL in non-allergic controls, P=0.006). In addition, baseline serum SP-D appeared to be an independent predictor for the magnitude of the late asthmatic response after allergen challenge. Furthermore, serum SP-D was predictive for the sputum eosinophil cationic protein concentration after allergen challenge.

CONCLUSION

We propose that serum SP-D concentrations are associated with allergic bronchial inflammation and may give additional information, beside BHR and sputum eosinophils, about the degree of bronchial inflammation in allergic patients.

Embryonic Stem Cells Generate Airway Epithelial Tissue

Embryonic stem (ES) cells are self-renewable and pluripotent cells derived from the inner cell mass of a blastocyst-stage embryo. ES cell pluripotency is being investigated increasingly to obtain specific cell lineages for therapeutic treatments and tissue engineering. Type II alveolar epithelial cells have been derived from murine ES cells, but the capacity of the latter to generate differentiated airway epithelial tissue has never been reported. Herein, we show by RT-PCR and immunocytochemistry that murine ES cells are able to differentiate into nonciliated secretory Clara cells, and that type I collagen induces this commitment. Moreover, when cultured at the air-liquid interface, ES cells give rise to a fully differentiated airway epithelium. By quantitative histologic examination, immunohistochemistry, and scanning electron microscopy, we show that the bioengineered epithelium is composed of basal, ciliated, intermediate, and Clara cells, similar to those of native tracheobronchial airway epithelium. Transmission electron microscopy and Western blotting reveal that the generated epithelium also exhibits the ultrastructural features and secretory functions characteristic of airway epithelial tissue. These results open new perspectives for cell therapy of injured epithelium in airway diseases, such as bronchopulmonary dysplasia, cystic fibrosis, or bronchiolitis obliterans.

Design-based stereological analysis of the lung parenchymal architecture and alveolar type II cells in surfactant protein A and D double deficient mice

Alveolar epithelial type II cells synthesize and secrete surfactant. The surfactant-associated proteins A and D (SP-A and SP-D), members of the collectin protein family, participate in pulmonary immune defense, modulation of inflammation, and surfactant metabolism. Both proteins are known to have overlapping as well as distinct functions. The present study provides a design-based stereological analysis of adult mice deficient in both SP-A and SP-D (A(-)D(-)) with special emphasis on parameters characterizing alveolar architecture and surfactant-producing type II cells. Compared to wild-type, A(-)D(-) mice have fewer and larger alveoli, an increase in the number and size of type II cells, as well as more numerous and larger alveolar macrophages. More surfactant-storing lamellar bodies are seen in type II cells, leading to a threefold increase in the total volume of lamellar bodies per lung, but the mean volume of a single lamellar body remains constant. These results demonstrate that chronic deficiency of SP-A and SP-D in mice leads to parenchymal remodeling, type II cell hyperplasia and hypertrophy, and disturbed intracellular surfactant metabolism. The design-based stereological approach presented here provides a framework for the quantitative lung structure analysis in gene-manipulated mice as well as in human lung disease.

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

BACKGROUND

Some idiopathic interstitial pneumonias (IIPs) are characterised by fibroproliferation and deposition of extracellular matrix. Because efficacious treatment options are limited, research has been directed towards understanding the cytokine networks that may affect fibroblast activation and, hence, the progression of certain IIPs.

AIMS

To examine the expression of interleukin 4 (IL-4), IL-13, and their corresponding receptor subunits in the various forms of IIP and normal patient groups.

METHODS

Molecular and immunohistochemical analysis of IL-4, interferon gamma (IFNgamma), IL-13, IL-4 receptor (IL-R), and IL-13 receptor subunits in surgical lung biopsies (SLBs) from 39 patients (21 usual interstitial pneumonia (UIP), six non-specific interstitial pneumonia (NSIP), eight respiratory bronchiolitic interstitial lung disease (RBILD), and five normal controls).

RESULTS

Molecular analysis demonstrated that IL-13Ralpha2, IL-13Ralpha1, and IL-4Ralpha were present in a greater proportion of upper and lower lobe biopsies from patients with UIP than patients with NSIP and RBILD. Immunohistochemical analysis of patients with UIP, NSIP, and RBILD revealed interstitial staining for all three receptor subunits, whereas such staining was only seen in mononuclear cells present in normal SLBs. Fibroblastic foci in patients with UIP strongly stained for IL-4Ralpha and IL-13Ralpha2. Localised expression of IL-4Ralpha was also seen in SLBs from patients with NSIP but not in other groups.

CONCLUSION

Some histological subtypes of IIP are associated with increased pulmonary expression of receptor subunits responsive to IL-4 and IL-13. These findings may be of particular importance in understanding the pathogenesis of IIP and, more importantly, may provide important novel therapeutic targets.

IL-4 induces production of the lung collectin surfactant protein-D

BACKGROUND

Surfactant protein (SP)-D is an epithelial cell product of the distal air spaces that aids uptake and clearance of inhaled pathogens and allergens. Allergic airway inflammation significantly increases SP-D levels in the bronchoalveolar lavage fluid in asthmatic patients and mouse models, but the mechanisms involved remain unknown.

OBJECTIVE

To investigate the effects of the TH2-type cytokine IL-4 on SP-D production by isolated pulmonary epithelial cells.

METHODS

Rat type II alveolar epithelial cells were purified and cultured with dexamethasone, cAMP, and isobutyl-1-methylxanthine (DCI). The effects of IL-4 on SP-D expression were investigated at the protein and mRNA levels by means of Western and Northern blot analyses.

RESULTS

In contrast to a lamellar body protein ABCA3 and surfactant protein-A, expression of SP-D significantly declined when cells were cultured in medium alone for 24 hours. The presence of DCI in the culture medium restored SP-D levels, which were enhanced by 2-fold after addition of recombinant IL-4. The enhancing effects of IL-4 were concentration-dependent, with maximum effects observed at 20 ng/mL (1.43 nmol/L). IL-4 did not rescue cycloheximide-induced decrease of intracellular SP-D levels and did not inhibit extracellular release of SP-D. However, IL-4 significantly augmented DCI-induced SP-D mRNA expression by approximately 2.5-fold over control levels.

CONCLUSIONS

IL-4 selectively upregulates SP-D expression, and it may act at the level of mRNA in isolated pulmonary epithelial cells. Since SP-D has a potent anti-inflammatory function, this mechanism may be part of a negative feedback loop providing a regulatory link between adaptive and innate immunity during allergic inflammation.

Increased Surfactant Protein-A Levels in Patients With Newly Diagnosed Idiopathic Pulmonary Fibrosis

STUDY OBJECTIVES

To measure surfactant protein-A (SP-A) in the BAL of patients with idiopathic pulmonary fibrosis (IPF).

DESIGN

We examined SP-A in BAL and lung tissue of patients with IPF who met the stricter recommended criteria for IPF at the time of diagnosis and prior to the beginning of treatment.

PATIENTS

Twenty-six patients with IPF confirmed at biopsy and 22 patients with hypersensitivity pneumonitis (HP) were compared with 9 normal volunteers.

INTERVENTIONS

All patients were subjected to pulmonary function testing, BAL, and lung biopsy prior to the beginning of treatment.

MEASUREMENTS AND RESULTS

We measured SP-A in BAL fluids and performed SP-A immunohistochemistry on lung specimens. Lung tissues of patients with IPF showed extensive type II cell hyperplasia, usually containing greatly increased levels of immunoreactive SP-A. By enzyme-linked immunosorbent assay, we found a twofold increase over normal values in BAL SP-A without changes in total phospholipids. These data were in agreement with semiquantitative assessments of SP-A by protein immunoblotting and by Western blotting of sodium dodecyl sulfate gels. Patients with HP exhibited a threefold increase of BAL SP-A.

CONCLUSIONS

The reasons for the difference between our results and previously published reports describing decreased SP-A levels in IPF is not clear. It may relate to the stricter criteria for diagnosis, the absence of treatment prior to BAL, differences in the patient population, or to other methodologic differences.

Attenuated allergic airway hyperresponsiveness in C57BL/6 mice is associated with enhanced surfactant protein (SP)-D production following allergic sensitization

Background

C57BL/6 mice have attenuated allergic airway hyperresponsiveness (AHR) when compared with Balb/c mice but the underlying mechanisms remain unclear. SP-D, an innate immune molecule with potent immunosuppressive activities may have an important modulatory role in the allergic airway response and the consequent physiological changes. We hypothesized that an elevated SP-D production is associated with the impaired ability of C57BL/6 mice to develop allergic AHR.

Methods

SP-D mRNA and protein expression was investigated during development of allergic airway changes in a model of Aspergillus fumigatus (Af)-induced allergic inflammation. To study whether strain dependency of allergic AHR is associated with different levels of SP-D in the lung, Balb/c and C57BL/6 mice were compared.

Results

Sensitization and exposure to Af induced significant airway inflammation in both mouse strains in comparison with naïve controls. AHR to acetylcholine however was significantly attenuated in C57BL/6 mice in spite of increased eosinophilia and serum IgE when compared with Balb/c mice (p < 0.05). Af challenge of sensitized C57BL/6 mice induced a markedly increased SP-D protein expression in the SA surfactant fraction (1,894 ± 170% of naïve controls) that was 1.5 fold greater than the increase in Balb/c mice (1,234 ± 121% p < 0.01). These changes were selective since levels of the hydrophobic SP-B and SP-C and the hydrophilic SP-A were significantly decreased following sensitization and challenge with Af in both strains. Further, sensitized and exposed C57BL/6 mice had significantly lower IL-4 and IL-5 in the BAL fluid than that of Balb/c mice (p < 0.05).

Conclusions

These results suggest that enhanced SP-D production in the lung of C57BL/6 mice may contribute to an attenuated AHR in response to allergic airway sensitization. SP-D may act by inhibiting synthesis of Th2 cytokines.