GM-CSF regulates alveolar macrophage differentiation and innate immunity in the lung through PU.1

Optimization of inhaled therapies for tuberculosis: the role of macrophages and dendritic cells

Inhaled therapies in the form of drugs or vaccines for tuberculosis treatment were reported about a decade ago. Experts around the world met to discuss the scientific progress in inhaled therapies at the international symposium "Optimization of inhaled Tuberculosis therapies and implications for host-pathogen interactions" held in New Delhi, India on November 3-5, 2009. The meeting was organized by the Central Drug Research Institute (CDRI) Lucknow, India. The lung is the main route for infection with Mycobacterium tuberculosis bacilli and the primary site of reactivation of latent disease. The only available vaccine BCG is relatively ineffective at preventing tuberculosis disease and current therapy requires prolonged treatment with drugs which results in low patient compliance. Consequently, there is a need to design new vaccines and therapies for this disease. Recently there has been increased interest in the development of inhaled formulations to deliver anti-mycobacterial drugs and vaccines directly to the lung and many of these therapies are designed to target lung macrophages and dendritic cells. However, the development of effective inhaled therapies requires an understanding of the unique function and immunosuppressive environment of the lung which is driven, in part, by alveolar macrophages and dendritic cells. In this review, we will discuss the role of alveolar macrophages and dendritic cells in the host immune response to M. tuberculosis infection and the ways in which inhaled therapies might enhance the anti-microbial response of phagocytes and boost pulmonary immunity.

Effectiveness of granulocyte-macrophage colony-stimulating factor therapy in autoimmune pulmonary alveolar proteinosis: a meta-analysis of observational studies

BACKGROUND

Autoimmune pulmonary alveolar proteinosis (aPAP) is a rare pulmonary disease caused by functional deficiency of granulocyte-macrophage colony-stimulating factor (GM-CSF). Administration of GM-CSF represents a potential therapeutic strategy in management of aPAP. Herein, we systematically review the efficacy of GM-CSF therapy in aPAP.

METHODS

We searched the PubMed and EmBase databases for studies reporting the use of GM-CSF in aPAP. We calculated the proportion with 95% CI to assess the response and relapse rates of GM-CSF therapy in individual studies and pooled them using a random-effects model. Statistical heterogeneity was assessed using the I(2) and Cochran Q tests. Publication bias was analyzed using funnel plot and Egger and Begg-Mazumdar tests.

RESULTS

Our initial searches yielded 1,585 studies. Of these, five observational studies (involving 94 patients) were included for analysis. Three studies used the subcutaneous route, and two studies used the inhalational route for GM-CSF administration. The response rate of GM-CSF varied from 43% to 92%, with the pooled response rate being 58.6% (95% CI, 42.7-72.9). The relapse rate in GM-CSF responders was 29.7% (95% CI, 10.5-60.4). There was no evidence of statistical heterogeneity or publication bias for the outcome of response. GM-CSF therapy was associated with minor complications, such as fever and local complications at the site of administration.

CONCLUSIONS

GM-CSF represents a useful approach in the treatment of aPAP. The optimal indication, dose and duration of therapy, and the factors predicting response and relapse need to be defined by future studies.

Local delivery of GM-CSF protects mice from lethal pneumococcal pneumonia

The growth factor GM-CSF has an important role in pulmonary surfactant metabolism and the regulation of antibacterial activities of lung sentinel cells. However, the potential of intra-alveolar GM-CSF to augment lung protective immunity against inhaled bacterial pathogens has not been defined in preclinical infection models. We hypothesized that transient overexpression of GM-CSF in the lungs of mice by adenoviral gene transfer (Ad-GM-CSF) would protect mice from subsequent lethal pneumococcal pneumonia. Our data show that intra-alveolar delivery of Ad-GM-CSF led to sustained increased pSTAT5 expression and PU.1 protein expression in alveolar macrophages during a 28-d observation period. Pulmonary Ad-GM-CSF delivery 2-4 wk prior to infection of mice with Streptococcus pneumoniae significantly reduced mortality rates relative to control vector-treated mice. This increased survival was accompanied by increased inducible NO synthase expression, antibacterial activity, and a significant reduction in caspase-3-dependent apoptosis and secondary necrosis of lung sentinel cells. Importantly, therapeutic treatment of mice with rGM-CSF improved lung protective immunity and accelerated bacterial clearance after pneumococcal challenge. We conclude that prophylactic delivery of GM-CSF triggers long-lasting immunostimulatory effects in the lung in vivo and rescues mice from lethal pneumococcal pneumonia by improving antibacterial immunity. These data support use of novel antibiotic-independent immunostimulatory therapies to protect patients against bacterial pneumonias.

Oxidized phospholipid, 1-palmitoyl-2-(9'-oxo-nonanoyl)-glycerophosphocholine (PON-GPC), produced in the lung due to cigarette smoking, impairs immune function in macrophages

INTRODUCTION

Pulmonary innate immunity is impaired in cigarette smokers, because the abundant oxidants present in cigarette smoke (CS) cause injury to lung cells. Pulmonary surfactant is a unique material that is important roles in reducing surface tension in the lung and defending against invading pathogens. Oxidants reportedly cleave surfactant phospholipids, resulting in the production of oxidized phospholipids, such as 1-palmitoyl-2-(9'-oxo-nonanoyl)-glycerophosphocholine (PON-GPC). Although oxidation of surfactant lipids is thought to be involved in the pathogenesis of smoking-related lung disease, there are no reports on the effect of oxidized surfactant lipid on the immune function of macrophages. We hypothesized that cigarette smoking elevates PON-GPC levels in the lung, and that PON-GPC impairs the innate immune function of macrophages.

METHODS

The levels of PON-GPC in bronchoalveolar lavage fluid (BALF) recovered from mice exposed to CS for 2 weeks (n = 7) were measured by liquid chromatography with electrospray-ionization tandem mass spectrometry. The effects of PON-GPC on inducibility of tumor necrosis factor (TNF)-α, nitric oxide (NO), and nicotinamide adenine dinucleotide phosphate (NADP(+)) production, as well as bactericidal activity, were investigated in RAW264.7 cells or primary alveolar macrophages.

RESULTS

The levels of PON-GPC in BALF of mice exposed to CS were significantly elevated, compared with those of control mice. PON-GPC attenuated TNF-α, NO, and NADP(+) production in macrophages on stimulation with LPS plus IFN-γ. PON-GPC treatment attenuated the phosphorylation of p38 mitogen-activated protein kinase (MAPK). In addition, PON-GPC reduced the bactericidal activity of RAW264.7 cells.

CONCLUSIONS

CS may attenuate innate immunity in the lungs through oxidization of surfactant phospholipids.

Functional PU.1 in macrophages has a pivotal role in NF-κB activation and neutrophilic lung inflammation during endotoxemia

Although the role of ETS family transcriptional factor PU.1 is well established in macrophage maturation, its role in mature macrophages with reference to sepsis- related animal model has not been elucidated. Here, we report the in vivo function of PU.1 in mediating mature macrophage inflammatory phenotype by using bone marrow chimera mice with conditional PU.1 knockout. We observed that the expression of monocyte/macrophage-specific markers CD 11b, F4/80 in fetal liver cells, and bone marrow-derived macrophages were dependent on functional PU.1. Systemic inflammation as measured in terms of NF-κB reporter activity in lung, liver, and spleen tissues was significantly decreased in PU.1-deficient chimera mice compared with wild-type chimeras on lipopolysaccharide (LPS) challenge. Unlike wild-type chimera mice, LPS challenge in PU.1-deficient chimera mice resulted in decreased lung neu-trophilic inflammation and myeloperoxidase activity. Similarly, we found attenuated inflammatory gene expression (cyclooxygenase-2, inducible nitric-oxide synthase, and TLR4) and inflammatory cytokine secretion (IL-6, MCP-1, IL-1β, TNF-α, and neutrophilic chemokine keratinocyte-derived chemokine) in PU.1-deficient mice. Most importantly, this attenuated lung and systemic inflammatory phenotype was associated with survival benefit in LPS-challenged heterozygotic PU.1-deficient mice, establishing a novel protective mechanistic role for the lineage-specific transcription factor PU.1.

GM-CSF modulates pulmonary resistance to influenza A infection

Alveolar type II epithelial or other pulmonary cells secrete GM-CSF that regulates surfactant catabolism and mucosal host defense through its capacity to modulate the maturation and activation of alveolar macrophages. GM-CSF enhances expression of scavenger receptors MARCO and SR-A. The alveolar macrophage SP-R210 receptor binds the surfactant collectin SP-A mediating clearance of respiratory pathogens. The current study determined the effects of epithelial-derived GM-CSF in host resistance to influenza A pneumonia. The results demonstrate that GM-CSF enhanced resistance to infection with 1.9×10(4) ffc of the mouse-adapted influenza A/Puerto Rico/8/34 (PR8) H1N1 strain, as indicated by significant differences in mortality and mean survival of GM-CSF-deficient (GM(-/-)) mice compared to GM(-/-) mice in which GM-CSF is expressed at increased levels. Protective effects of GM-CSF were observed both in mice with constitutive and inducible GM-CSF expression under the control of the pulmonary-specific SFTPC or SCGB1A1 promoters, respectively. Mice that continuously secrete high levels of GM-CSF developed desquamative interstitial pneumonia that impaired long-term recovery from influenza. Conditional expression of optimal GM-CSF levels at the time of infection, however, resulted in alveolar macrophage proliferation and focal lymphocytic inflammation of distal airways. GM-CSF enhanced alveolar macrophage activity as indicated by increased expression of SP-R210 and CD11c. Infection of mice lacking the GM-CSF-regulated SR-A and MARCO receptors revealed that MARCO decreases resistance to influenza in association with increased levels of SP-R210 in MARCO(-/-) alveolar macrophages. In conclusion, GM-CSF enhances early host resistance to influenza. Targeting of MARCO may reinforce GM-CSF-mediated host defense against pathogenic influenza.

Zinc supplementation restores PU.1 and Nrf2 nuclear binding in alveolar macrophages and improves redox balance and bacterial clearance in the lungs of alcohol-fed rats

BACKGROUND

Chronic alcohol abuse causes oxidative stress, impairs alveolar macrophage immune function, and increases the risk of pneumonia and acute lung injury. Recently we determined that chronic alcohol ingestion in rats decreases zinc levels and macrophage function in the alveolar space; provocative findings in that zinc is essential for normal immune and antioxidant defenses. Alveolar macrophage immune function depends on stimulation by granulocyte/monocyte colony-stimulating factor, which signals via the transcription factor PU.1. In parallel, the antioxidant response element signals via the transcription factor Nrf2. However, the role of zinc bioavailability on these signaling pathways within the alveolar space is unknown.

METHODS

To determine the efficacy of dietary zinc supplementation on lung bacterial clearance and oxidative stress, we tested 3 different groups of rats: control-fed, alcohol-fed, and alcohol-fed with zinc supplementation. Rats were then inoculated with intratracheal Klebsiella pneumoniae, and lung bacterial clearance was determined 24 hours later. Isolated alveolar macrophages were isolated from uninfected animals and evaluated for oxidative stress and signaling through PU.1 and Nrf2.

RESULTS

Alcohol-fed rats had a 5-fold decrease in lung bacterial clearance compared to control-fed rats. Dietary zinc supplementation of alcohol-fed rats normalized bacterial clearance and mitigated oxidative stress in the alveolar space, as reflected by the relative balance of the thiol redox pair cysteine and cystine, and increased nuclear binding of both PU.1 and Nrf2 in alveolar macrophages from alcohol-fed rats.

CONCLUSIONS

Dietary zinc supplementation prevents alcohol-induced alveolar macrophage immune dysfunction and oxidative stress in a relevant experimental model, suggesting that such a strategy could decrease the risk of pneumonia and lung injury in individuals with alcohol use disorders.

Chronic fetal exposure to Ureaplasma parvum suppresses innate immune responses in sheep

The chorioamnionitis associated with preterm delivery is often polymicrobial with ureaplasma being the most common isolate. To evaluate interactions between the different proinflammatory mediators, we hypothesized that ureaplasma exposure would increase fetal responsiveness to LPS. Fetal sheep were given intra-amniotic (IA) injections of media (control) or Ureaplasma parvum serovar 3 either 7 or 70 d before preterm delivery. Another group received an IA injection of Escherichia coli LPS 2 d prior to delivery. To test for interactions, IA U. parvum-exposed animals were challenged with IA LPS and delivered 2 d later. All animals were delivered at 124 ± 1-d gestation (term = 150 d). Compared with the 2-d LPS exposure group, the U. parvum 70 d + LPS group had 1) decreased lung pro- and anti-inflammatory cytokine expression and 2) fewer CD3(+) T lymphocytes, CCL2(+), myeloperoxidase(+), and PU.1(+) cells in the lung. Interestingly, exposure to U. parvum for 7 d did not change responses to a subsequent IA LPS challenge, and exposure to IA U. parvum alone induced mild lung inflammation. Exposure to U. parvum increased pulmonary TGF-β1 expression but did not change mRNA expression of either the receptor TLR4 or some of the downstream mediators in the lung. Monocytes from fetal blood and lung isolated from U. parvum 70 d + LPS but not U. parvum 7 d + LPS animals had decreased in vitro responsiveness to LPS. These results are consistent with the novel finding of downregulation of LPS responses by chronic but not acute fetal exposures to U. parvum. The findings increase our understanding of how chorioamnionitis-exposed preterm infants may respond to lung injury and postnatal nosocomial infections.

Mavrilimumab, a human monoclonal antibody targeting GM-CSF receptor-α, in subjects with rheumatoid arthritis: a randomised, double-blind, placebo-controlled, phase I, first-in-human study

Objective

To evaluate the safety, tolerability, pharmacokinetic and pharmacodynamic profiles of mavrilimumab, a human monoclonal antibody targeting the granulocyte-macrophage colony-stimulating factor receptor-α, in subjects with rheumatoid arthritis (RA).

Methods

A randomised, double-blind, placebo-controlled, dose-escalating phase I study in subjects with RA who received stable methotrexate treatment for ≥3 months before enrolment. Subjects received single intravenous escalating doses of mavrilimumab (0.01–10.0 mg/kg) or placebo.

Results

32 subjects were enrolled in this study (1 unblinded subject at 0.01 mg/kg and another at 0.03 mg/kg were followed by five sequential double-blinded cohorts, n=6 each, treated with 0.1, 0.3, 1.0, 3.0 and 10.0 mg/kg, respectively). Adverse events were mild or moderate and were reported with similar frequency across all treatment cohorts. One subject (10.0 mg/kg) experienced moderate face and neck urticaria during infusion that resolved with symptomatic treatment. Systemic clearance of mavrilimumab approached that of endogenous IgG at doses >1.0 mg/kg; pharmacodynamic activity was confirmed in the 1.0 and 3.0 mg/kg cohorts by suppression of suppressor of cytokine signalling 3 mRNA transcripts. In exploratory analyses, reductions of acute phase reactants were observed in subjects with elevated C-reactive protein (>5 mg/l) and erythrocyte sedimentation rate (≥20.0 mm/h) at baseline. No significant change in Disease Activity Score 28-joint assessment (DAS28) was seen in any of the cohorts. In mavrilimumab-treated subjects (n=15) with baseline DAS28 >3.2, mean disease activity (DAS28) was significantly reduced at 4 weeks.

Conclusion

In this first-in-human study, mavrilimumab showed preliminary evidence of pharmacodynamic activity. Importantly, the safety and pharmacokinetic profiles of mavrilimumab support further clinical studies in RA.

Trial registration number: NCT00771420.

Granulocyte macrophage-colony-stimulating factor autoantibodies and increased intestinal permeability in Crohn disease

BACKGROUND

Alterations in intestinal permeability have been implicated in the pathogenesis of Crohn disease (CD). We have reported that granulocyte macrophage-colony-stimulating factor (GM-CSF) is required for mucosal barrier function in mice, and elevated neutralizing GM-CSF autoantibodies (Ab) are associated with stricturing ileal disease and surgery in patients with CD. We hypothesized that children with CD with elevated GM-CSF Ab would exhibit increased intestinal permeability.

PATIENTS AND METHODS

Subjects were divided into 3 groups: 15 with CD and high GM-CSF Ab (≥ 1.6 μg/mL, GM-CSF Ab Hi), 12 with CD and low GM-CSF Ab (<1.6 μg/mL, GM-CSF Ab Lo), and 15 healthy controls. Subjects ingested a lactulose:mannitol (L:M) solution, and urinary excretion of LM was measured by high-performance liquid chromatography. Serum GM-CSF Ab, endotoxin core Ab (EndoCAb), and lipopolysaccharide-binding protein (LBP), and fecal S100A12 were determined by enzyme-linked immunosorbent assay.

RESULTS

The CD groups did not vary by age, sex, disease location, or activity. Neither systemic (serum LBP) nor mucosal (fecal S100A12) inflammation differed between the CD groups. Intestinal permeability as measured by the urine L:M ratio and endotoxin exposure as measured by serum EndoCAb were increased in the GM-CSF Ab Hi group compared to the GM-CSF Ab Lo group and controls.

CONCLUSIONS

Patients with CD with elevated GM-CSF Ab exhibit an increase in bowel permeability relative to patients with CD with lower levels of GM-CSF Ab in the absence of differences in systemic or intestinal inflammation. Therapies that target the mucosal barrier may be of particular benefit in this subgroup of patients with CD.

GM-CSF in the lung protects against lethal influenza infection

RATIONALE

Alveolar macrophages contribute to host defenses against influenza in animal models. Enhancing alveolar macrophage function may contribute to protection against influenza.

OBJECTIVES

To determine if increased expression of granulocyte/macrophage colony-stimulating factor (GM-CSF) in the lung increases resistance to influenza.

METHODS

Wild-type mice and transgenic mice that expressed GM-CSF in the lung were infected with influenza virus, and lung pathology, weight loss, and mortality were measured. We also administered GM-CSF to the lungs of wild-type mice that were infected with influenza virus.

MEASUREMENTS AND MAIN RESULTS

Wild-type mice all died after infection with different strains of influenza virus, but all transgenic mice expressing GM-CSF in the lungs survived. The latter also had greatly reduced weight loss and lung injury, and showed histologic evidence of a rapid host inflammatory response that controlled infection. The resistance of transgenic mice to influenza was abrogated by elimination of alveolar phagocytes, but not by depletion of T cells, B cells, or neutrophils. Transgenic mice had far more alveolar macrophages than did wild-type mice, and they were more resistant to influenza-induced apoptosis. Delivery of intranasal GM-CSF to wild-type mice also conferred resistance to influenza.

CONCLUSIONS

GM-CSF confers resistance to influenza by enhancing innate immune mechanisms that depend on alveolar macrophages. Pulmonary delivery of this cytokine has the potential to reduce the morbidity and mortality due to influenza virus.

Human IL-3/GM-CSF knock-in mice support human alveolar macrophage development and human immune responses in the lung

Mice with a functional human immune system have the potential to allow in vivo studies of human infectious diseases and to enable vaccine testing. To this end, mice need to fully support the development of human immune cells, allow infection with human pathogens, and be capable of mounting effective human immune responses. A major limitation of humanized mice is the poor development and function of human myeloid cells and the absence of human immune responses at mucosal surfaces, such as the lung. To overcome this, we generated human IL-3/GM-CSF knock-in (hIL-3/GM-CSF KI) mice. These mice faithfully expressed human GM-CSF and IL-3 and developed pulmonary alveolar proteinosis because of elimination of mouse GM-CSF. We demonstrate that hIL-3/GM-CSF KI mice engrafted with human CD34(+) hematopoietic cells had improved human myeloid cell reconstitution in the lung. In particular, hIL-3/GM-CSF KI mice supported the development of human alveolar macrophages that partially rescued the pulmonary alveolar proteinosis syndrome. Moreover, human alveolar macrophages mounted correlates of a human innate immune response against influenza virus. The hIL-3/GM-CSF KI mice represent a unique mouse model that permits the study of human mucosal immune responses to lung pathogens.

Anticytokine autoantibodies in infectious diseases: pathogenesis and mechanisms

Autoantibodies to cytokines occur in many different conditions and situations and can cause a wide range of disease, including pulmonary alveolar proteinosis, disseminated non-tuberculous mycobacterial disease, pure red-cell aplasia, and chronic mucocutaneous candidiasis. Anticytokine autoantibodies may also develop against exogenously administered cytokines, sometimes diminishing their effects or inhibiting the activity of the endogenous cytokine. Unlike primary congenital immunodeficiencies, autoantibodies may develop over time, wax and wane, and may change in titre or avidity. Naturally occurring autoantibodies to interferons α, β, and γ, interleukins 1α, 2, 6, and 10, tumour necrosis factor, and granulocyte-macrophage colony-stimulating factor have been reported in healthy individuals and have been identified in rheumatological diseases, graft-versus-host disease, and cancer. Therapeutic antibodies, growth factors, other biological agents, and cytokines used to treat acute, chronic, malignant, and immune diseases may elicit or overcome autoantibodies, hence influencing the primary intended therapy. The increasing number of biologically active anticytokine autoantibodies being reported suggests that currently "idiopathic" diseases may someday be explained by neutralising or agonising autoantibodies. Their protean roles in causing, treating, preventing, and responding to disease, as well as simply maintaining normal homoeostasis, offer fascinating insights into the biology of immunity, inflammation, and infection.

Restoration of PPARγ reverses lipid accumulation in alveolar macrophages of GM-CSF knockout mice

Pulmonary alveolar proteinosis (PAP) is a lung disease characterized by a deficiency of functional granulocyte macrophage colony-stimulating factor (GM-CSF) resulting in surfactant accumulation and lipid-engorged alveolar macrophages. GM-CSF is a positive regulator of PPARγ that is constitutively expressed in healthy alveolar macrophages. We previously reported decreased PPARγ and ATP-binding cassette transporter G1 (ABCG1) levels in alveolar macrophages from PAP patients and GM-CSF knockout (KO) mice, suggesting PPARγ and ABCG1 involvement in surfactant catabolism. Because ABCG1 represents a PPARγ target, we hypothesized that PPARγ restoration would increase ABCG1 and reduce macrophage lipid accumulation. Upregulation of PPARγ was achieved using a lentivirus expression system in vivo. GM-CSF KO mice received intratracheal instillation of lentivirus (lenti)-PPARγ or control lenti-eGFP. Ten days postinstillation, 79% of harvested alveolar macrophages expressed eGFP, demonstrating transduction. Alveolar macrophages showed increased PPARγ and ABCG1 expression after lenti-PPARγ instillation, whereas PPARγ and ABCG1 levels remained unchanged in lenti-eGFP controls. Alveolar macrophages from lenti-PPARγ-treated mice also exhibited reduced intracellular phospholipids and increased cholesterol efflux to HDL, an ABCG1-mediated pathway. In vivo instillation of lenti-PPARγ results in: 1) upregulating ABCG1 and PPARγ expression of GM-CSF KO alveolar macrophages, 2) reducing intracellular lipid accumulation, and 3) increasing cholesterol efflux activity.

Phenotypic and functional characterization of pulmonary macrophages subpopulations after intratracheal injection of Paracoccidioides brasiliensis cell wall components

A shift in the activation of pulmonary macrophages characterized by an increase of IL-1, TNF-α and IL-6 production has been induced in mice infected with Paracoccidioides brasiliensis. It is still unclear whether a functional shift in the resident alveolar macrophage population would be responsible for these observations due to the expression of cell surface molecules. We investigated pulmonary macrophages by flow cytometry from mice treated with P. brasiliensis derivatives by intratracheal route. In vivo labeling with the dye PKH26GL was applied to characterize newly recruited pulmonary macrophages from the bloodstream. Pulmonary macrophages from mice inflamed with P. brasiliensis derivatives showed a high expression of the surface antigens CD11b/CD18 and CD23 among several cellular markers. The expression of these markers indicated a pattern of activation of a subpopulation characterized as CD11b+ or CD23+, which was modulated in vitro by IFN-γ and IL-4. Analysis of monocytes labelled with PKH26GL demonstrated that CD11b+ cells did infiltrate the lung exhibiting a proinflammatory pattern of activation, whereas CD23+ cells were considered to be resident in the lung. These findings may contribute to better understand the pathology of lung inflammation caused by P. brasiliensis infection.

Immune dysregulation in the pathogenesis of pulmonary alveolar proteinosis

Pulmonary alveolar proteinosis (PAP) is a rare disease of the lung characterized by the accumulation of surfactant-derived lipoproteins within pulmonary alveolar macrophages and alveoli, resulting in respiratory insufficiency and increased infections. The disease is caused by a disruption in surfactant catabolism by alveolar macrophages due to loss of functional granulocyte-macrophage colony-stimulating factor (GM-CSF) signaling. The underlying molecular mechanisms causing deficiencies in GM-CSF signaling are as follows: 1) high levels of neutralizing GM-CSF autoantibodies observed in autoimmune PAP; 2) mutations in CSF2RA, the gene encoding the alpha chain of the GM-CSF receptor, observed in hereditary PAP; and 3) reduced numbers and function of alveolar macrophages as a result of other clinical diseases seen in secondary PAP. Recent studies investigating the biology of GM-CSF have revealed that not only does this cytokine have an indispensable role in lung physiology, but it is also a critical regulator of innate immunity and lung host defense.

Immunodeficiency secondary to anticytokine autoantibodies

PURPOSE OF REVIEW

Anticytokine autoantibodies are an important and emerging mechanism of disease pathogenesis. We will review the clinical and laboratory features of syndromes in which immunodeficiency is caused by or associated with neutralizing anticytokine autoantibodies.

RECENT FINDINGS

A growing number of patients have been described who demonstrate unique infectious phenotypes associated with neutralizing autoantibodies that target a particular cytokine known to participate in host defense against the offending organism. Examples include antigranulocyte macrophage-colony stimulating factor (GM-CSF) autoantibodies and pulmonary alveolar proteinosis; anti-interferon (IFN)-γ autoantibodies and disseminated nontuberculous mycobacteria (NTM); anti-interleukin-(IL)-6 autoantibodies and severe staphylococcal skin infection; anti-IL-17A, anti-IL-17F, or anti-IL-22 autoantibodies in patients with mucocutaneous candidiasis in the setting of both the autoimmune polyendocrinopathy, candidiasis, ectodermal dystrophy (APECED) syndrome and in cases of thymoma.

SUMMARY

Anticytokine autoantibodies have manifestations that are diverse, ranging from asymptomatic to life-threatening. These emerging and fascinating causes of acquired immunodeficiency may explain some previously idiopathic syndromes.

GM-CSF pathway correction in pulmonary alveolar proteinosis

IMPORTANCE OF THE FIELD

Pulmonary alveolar proteinosis (PAP) is a rare disease in which the abnormalities in surfactant metabolism are caused most often by impairments of GM-CSF pathway at different levels in different disease subsets (congenital, secondary, acquired/idiopathic) and for which there are only few, costly invasive therapeutic methods.

AREAS COVERED IN THIS REVIEW

This review discusses these impairments, and their pathogenic and clinical consequences along with potential corrective therapies such as exogenous inhaled GM-CSF.

WHAT THE READER WILL GAIN

Among the PAP disease subsets, in autoimmune PAP the GM-CSF autoantibodies play a major role in disease pathogenesis and their deleterious pulmonary effects can be blocked efficaciously with inhaled GM-CSF.

TAKE HOME MESSAGE

In PAP correction of the abnormalities of the GM-CSF pathway represent a plausible approach demonstrated to be efficacious also in the case of inhaled GM-CSF used for autoimmune PAP.

Physical properties, lung deposition modeling, and bioactivity of recombinant GM-CSF aerosolised with a highly efficient nebulizer

Pulmonary alveolar proteinosis (PAP) is a rare condition characterized by the accumulation of lipoproteinaceous material within air spaces. Although whole lung lavage is the current standard of care, recent advances in our understanding of PAP pathophysiology suggest that the disorder may benefit from inhalation of recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF). The aim of this study was to determine the physical properties and bioactivity of rGM-CSF aerosolised by the highly efficient AKITA² APIXNEB® nebulizer system. The physical properties of aerosolised rGM-CSF were investigated in terms of droplet size, output and output rate by laser diffraction and gravimetrical analysis. Lung deposition was assessed using deposition modeling (ICRP). Molecular mass before and after aerosolisation was determined by SDS-PAGE, while the bioactivity of rGM-CSF was evaluated by measuring the GM-CSF-stimulated increase in pSTAT5 using mAM-hGM-R cells. Ninety-six % of the rGM-CSF filling dose was aerosolised with the Akita² Apixneb® nebulizer system. Particle size was highly reproducible, and the amount deposited within the lung was 80.35% of the delivered dose. The aerosolisation did not alter the molecular structure of rGM-CSF, nor its ability to stimulate the pSTAT5, which increased by 99.5%, similar to values for rGM-CSF prior to aerosolisation. We conclude that the highly efficient AKITA² APIXNEB® nebulizer system is likely to efficaciously deliver rGM-CSF to the airways of patients with autoimmune PAP.

Anti-cytokine autoantibodies are associated with opportunistic infection in patients with thymic neoplasia

Patients with thymic malignancy have high rates of autoimmunity leading to a variety of autoimmune diseases, most commonly myasthenia gravis caused by anti-acetylcholine receptor autoantibodies. High rates of autoantibodies to cytokines have also been described, although prevalence, spectrum, and functionality of these anti-cytokine autoantibodies are poorly defined. To better understand the presence and function of anti-cytokine autoantibodies, we created a luciferase immunoprecipitation system panel to search for autoantibodies against 39 different cytokines and examined plasma from controls (n = 30) and patients with thymic neoplasia (n = 17). In this screen, our patients showed statistically elevated, but highly heterogeneous immunoreactivity against 16 of the 39 cytokines. Some patients showed autoantibodies to multiple cytokines. Functional testing proved that autoantibodies directed against interferon-α, interferon-β, interleukin-1α (IL-1α), IL-12p35, IL-12p40, and IL-17A had biologic blocking activity in vitro. All patients with opportunistic infection showed multiple anti-cytokine autoantibodies (range 3-11), suggesting that anti-cytokine autoantibodies may be important in the pathogenesis of opportunistic infections in patients with thymic malignancy. This study was registered at http://clinicaltrials.gov as NCT00001355.

Hereditary pulmonary alveolar proteinosis: pathogenesis, presentation, diagnosis, and therapy

RATIONALE

We identified a 6-year-old girl with pulmonary alveolar proteinosis (PAP), impaired granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor function, and increased GM-CSF.

OBJECTIVES

Increased serum GM-CSF may be useful to identify individuals with PAP caused by GM-CSF receptor dysfunction.

METHODS

We screened 187 patients referred to us for measurement of GM-CSF autoantibodies to diagnose autoimmune PAP. Five were children with PAP and increased serum GM-CSF but without GM-CSF autoantibodies or any disease causing secondary PAP; all were studied with family members, subsequently identified patients, and controls.

MEASUREMENT AND MAIN RESULTS

Eight children (seven female, one male) were identified with PAP caused by recessive CSF2RA mutations. Six presented with progressive dyspnea of insidious onset at 4.8 ± 1.6 years and two were asymptomatic at ages 5 and 8 years. Radiologic and histopathologic manifestations were similar to those of autoimmune PAP. Molecular analysis demonstrated that GM-CSF signaling was absent in six and severely reduced in two patients. The GM-CSF receptor β chain was detected in all patients, whereas the α chain was absent in six and abnormal in two, paralleling the GM-CSF signaling defects. Genetic analysis revealed multiple distinct CSF2RA abnormalities, including missense, duplication, frameshift, and nonsense mutations; exon and gene deletion; and cryptic alternative splicing. All symptomatic patients responded well to whole-lung lavage therapy.

CONCLUSIONS

CSF2RA mutations cause a genetic form of PAP presenting as insidious, progressive dyspnea in children that can be diagnosed by a combination of characteristic radiologic findings and blood tests and treated successfully by whole-lung lavage.

A novel TNF receptor-associated factor 6 binding domain mediates NF-kappa B signaling by the common cytokine receptor beta subunit

GM-CSF, IL-3, and IL-5 are proinflammatory cytokines that control the production and function of myeloid and lymphoid cells. Their receptors are composed of a ligand-specific alpha subunit and a shared common signal-transducing beta subunit (beta common receptor or GM-CSFR beta [beta(c)]). The pleiotropic nature of biologic outcomes mediated by beta(c) and the presence of large, uncharacterized regions of its cytoplasmic domain suggest that much remains to be learned about its downstream signaling pathways. Although some previous work has attempted to link beta(c) with NF-kappaB activation, a definitive mechanism that mediates this pathway has not been described and, to date, it has not been clear whether the receptor can directly activate NF-kappaB. We demonstrate that NF-kappaB activation by beta(c) is dependent on TNFR-associated factor 6 (TRAF6) and that association of TRAF6 with beta(c) requires a consensus-binding motif found in other molecules known to interact with TRAF6. Furthermore, point mutation of this motif abrogated the ability of beta(c) to mediate NF-kappaB activation and reduced the viability of an IL-3-dependent hematopoietic cell line. Because this receptor plays a key role in hematopoiesis and the beta(c) cytoplasmic domain identified in this work mediates hematopoietic cell viability, this new pathway is likely to contribute to immune cell biology. This work is significant because it is the first description of a TRAF6-dependent signaling pathway associated with a type I cytokine receptor. It also suggests that TRAF6, a mediator of TNFR and TLR signaling, may be a common signaling intermediate in diverse cytokine receptor systems.

Patient-derived granulocyte/macrophage colony-stimulating factor autoantibodies reproduce pulmonary alveolar proteinosis in nonhuman primates

RATIONALE

Granulocyte/macrophage colony-stimulating factor (GM-CSF) autoantibodies (GMAb) are strongly associated with idiopathic pulmonary alveolar proteinosis (PAP) and are believed to be important in its pathogenesis. However, levels of GMAb do not correlate with disease severity and GMAb are also present at low levels in healthy individuals.

OBJECTIVES

Our primary objective was to determine whether human GMAb would reproduce PAP in healthy primates. A secondary objective was to determine the concentration of GMAb resulting in loss of GM-CSF signaling in vivo (i.e., critical threshold).

METHODS

Nonhuman primates (Macaca fascicularis) were injected with highly purified, PAP patient-derived GMAb in dose-ranging (2.2-50 mg) single and multiple administration studies, and after blocking antihuman immunoglobulin immune responses, in chronic administration studies maintaining serum levels greater than 40 microg/ml for up to 11 months.

MEASUREMENTS AND MAIN RESULTS

GMAb blocked GM-CSF signaling causing (1) a milky-appearing bronchoalveolar lavage fluid containing increased surfactant lipids and proteins; (2) enlarged, foamy, surfactant-filled alveolar macrophages with reduced PU.1 and PPARgamma mRNA, and reduced tumor necrosis factor-alpha secretion; (3) pulmonary leukocytosis; (4) increased serum surfactant protein-D; and (5) impaired neutrophil functions. GM-CSF signaling varied inversely with GMAb concentration below a critical threshold of 5 microg/ml, which was similar in lungs and blood and to the value observed in patients with PAP.

CONCLUSIONS

GMAb reproduced the molecular, cellular, and histopathologic features of PAP in healthy primates, demonstrating that GMAb directly cause PAP. These results have implications for therapy of PAP and help define the therapeutic window for potential use of GMAb to treat other disorders.

Alveolar surfactant homeostasis and the pathogenesis of pulmonary disease

The alveolar region of the lung creates an extensive epithelial surface that mediates the transfer of oxygen and carbon dioxide required for respiration after birth. Maintenance of pulmonary function depends on the function of type II epithelial cells that synthesize and secrete pulmonary surfactant lipids and proteins, reducing the collapsing forces created at the air-liquid interface in the alveoli. Genetic and acquired disorders associated with the surfactant system cause both acute and chronic lung disease. Mutations in the ABCA3, SFTPA, SFTPB, SFTPC, SCL34A2, and TERT genes disrupt type II cell function and/or surfactant homeostasis, causing neonatal respiratory failure and chronic interstitial lung disease. Defects in GM-CSF receptor function disrupt surfactant clearance, causing pulmonary alveolar proteinosis. Abnormalities in the surfactant system and disruption of type II cell homeostasis underlie the pathogenesis of pulmonary disorders previously considered idiopathic, providing the basis for improved diagnosis and therapies of these rare lung diseases.

Cellular responses of A549 alveolar epithelial cells to serially collected Pseudomonas aeruginosa from cystic fibrosis patients at different stages of pulmonary infection

Pseudomonas aeruginosa is the major cause of chronic pulmonary disease in cystic fibrosis (CF) patients. During chronic infection, P. aeruginosa lose certain virulence factors, transform into a mucoid phenotype, and develop antibiotic resistance. We hypothesized that these genetic and phenotypic alterations of P. aeruginosa affect the airway epithelial responses. A549 cells were infected with 27 well-characterized isolates of P. aeruginosa from CF patients obtained during longitudinal observation, or with P. aeruginosa mutant strains lacking flagella, pili, lipopolysaccharide, or pyocyanin. Pseudomonas aeruginosa isolates from the early stages of the infection exhibited high adherence to A549 cells, were readily internalized, and able to induce reactive oxygen species (ROS) production, apoptosis of infected cells, and the release of granulocyte macrophage colony-stimulating factor. Late P. aeruginosa isolates collected from patients with chronic lung infection were shown to have reduced adherence to and internalization into A549 cells compared with bacteria from patients with intermittent P. aeruginosa colonization, and induced lower production of ROS and apoptosis, but caused high proinflammatory cytokine and adhesion molecule expression. Our findings suggest that despite the loss of virulence factors during the adaptation process in the CF lung by late P. aeruginosa strains, they retain high proinflammatory abilities that likely contribute to the disease pathogenesis.

GM-CSF-facilitated dendritic cell recruitment and survival govern the intestinal mucosal response to a mouse enteric bacterial pathogen

Granulocyte-macrophage colony-stimulating factor (GM-CSF) promotes dendritic cell (DC) differentiation and survival in vitro. However, its role in host defense at the intestinal mucosa is unknown. We report that infection with the mouse enteric pathogen, Citrobacter rodentium, increased colonic GM-CSF production and CD11c(+) DC recruitment. After infection, GM-CSF(-/-) mice had fewer mucosal CD11c(+) DCs, greater bacterial burden, increased mucosal inflammation and systemic spread of infection, decreased antibody responses, and delayed pathogen clearance. This defective mucosal response was rescued by GM-CSF administration to GM-CSF(-/-) mice and mimicked by CD11c(+) DC depletion in wild-type animals. Diminished mucosal DC numbers in infected GM-CSF(-/-) mice reflected decreased DC recruitment and survival, with the recruitment defect being related to a failure to upregulate epithelial cell production of the DC chemoattractant, CCL22. Thus, GM-CSF produced in the intestinal mucosa acts to enhance host protection against an enteric bacterial pathogen through regulating recruitment and survival of DCs.

The molecular basis of pulmonary alveolar proteinosis

Pulmonary alveolar proteinosis (PAP) comprises a heterogenous group of diseases characterized by abnormal surfactant accumulation resulting in respiratory insufficiency, and defects in alveolar macrophage- and neutrophil-mediated host defense. Basic, clinical and translational research over the past two decades have raised PAP from obscurity, identifying the molecular pathogenesis in over 90% of cases as a spectrum of diseases involving the disruption of GM-CSF signaling. Autoimmune PAP represents the vast majority of cases and is caused by neutralizing GM-CSF autoantibodies. Genetic mutations that disrupt GM-CSF receptor signaling comprise a rare form of hereditary PAP. In both autoimmune and hereditary PAP, loss of GM-CSF signaling blocks the terminal differentiation of alveolar macrophages in the lungs impairing the ability of alveolar macrophages to catabolize surfactant and to perform many host defense functions. Secondary PAP occurs in a variety of clinical diseases that presumedly cause the syndrome by reducing the numbers or functions of alveolar macrophages, thereby impairing alveolar macrophage-mediated pulmonary surfactant clearance. A similar phenotype occurs in mice deficient in the production of GM-CSF or GM-CSF receptors. PAP and related research has uncovered a critical and emerging role for GM-CSF in the regulation of pulmonary surfactant homeostasis, lung host defense, and systemic immunity.

Genetic Basis of Children's Interstitial Lung Disease

Specific genetic causes for children's interstitial lung disease (chILD) have been identified within the past decade. These include deletions of or mutations in genes encoding proteins important in surfactant production and function (SP-B, SP-C, and ABCA3), surfactant catabolism (GM-CSF receptor), as well as transcription factors important for surfactant production (TTF1) or lung development (Fox F1), with heterozygous deletions or loss-of-function mutations of the latter resulting in alveolar capillary dysplasia (ACD) with misalignment of the pulmonary veins. Familial pulmonary fibrosis in adults may result from mutations in genes encoding components of telomerase and SP-A2. While not yet reported in children, the expression of these genes in alveolar type II epithelial cells supports a key role for the disruption of normal homeostasis in this cell type in the pathogenesis of interstitial lung disease. The identification of specific genetic causes for chILD now allows for the possibility of non-invasive diagnosis, and provides insight into basic cellular mechanisms that may allow the development of novel therapies.

Neutralizing granulocyte/macrophage colony-stimulating factor inhibits cigarette smoke-induced lung inflammation

RATIONALE

Cigarette smoke is the major cause of chronic obstructive pulmonary disease (COPD), and there is currently no satisfactory therapy to treat people with COPD. We have previously shown that granulocyte/macrophage colony-stimulating factor (GM-CSF) regulates lung innate immunity to LPS through Akt/Erk activation of nuclear factor-kappaB and activator protein (AP)-1.

OBJECTIVES

The aim of this study was to determine whether neutralization of GM-CSF can inhibit cigarette smoke-induced lung inflammation in vivo.

METHODS

Male BALB/c mice were exposed to cigarette smoke generated from 9 cigarettes per day for 4 days. Mice were treated intranasally with 100 microg 22E9 (anti-GM-CSF mAb) and isotype control antibody on Days 2 and 4, 1 hour before cigarette smoke or sham exposure. On the fifth day mice were killed, and the lungs were lavaged with PBS and then harvested for genomic and proteomic analysis.

MEASUREMENTS AND MAIN RESULTS

Cigarette smoke-exposed mice treated with anti-GM-CSF mAb had significantly less BALF macrophages and neutrophils, whole lung TNF-alpha, macrophage inflammatory protein (MIP)-2, and matrix metalloproteinase (MMP)-12 mRNA expression and lost less weight compared with smoke-exposed mice treated with isotype control. In contrast, smoke-induced increases in MMP-9 and net gelatinase activity were unaffected by treatment with anti-GM-CSF. In addition, neutralization of GM-CSF did not affect the phagocytic function of alveolar macrophages.

CONCLUSIONS

GM-CSF is a key mediator in smoke-induced airways inflammation, and its neutralization may have therapeutic implications in diseases such as COPD.

Inhaled granulocyte/macrophage-colony stimulating factor as therapy for pulmonary alveolar proteinosis

RATIONALE

Inhaled granulocyte/macrophage-colony stimulating factor (GM-CSF) is a promising therapy for pulmonary alveolar proteinosis (PAP) but has not been adequately studied.

OBJECTIVES

To evaluate safety and efficacy of inhaled GM-CSF in patients with unremitting or progressive PAP.

METHODS

We conducted a national, multicenter, self-controlled, phase II trial at nine pulmonary centers throughout Japan. Patients who had lung biopsy or cytology findings diagnostic of PAP, an elevated serum GM-CSF antibody level, and a Pa(O(2)) of less than 75 mm Hg entered a 12-week observation period. Those who improved (i.e., alveolar-arterial oxygen difference [A-aDO(2)] decreased by 10 mm Hg) during observation were excluded. The rest entered sequential periods of high-dose therapy (250 microg Days 1-8, none Days 9-14; x six cycles; 12 wk); low-dose therapy (125 microg Days 1-4, none Days 5-14; x six cycles; 12 wk), and follow-up (52 wk).

MEASUREMENTS AND MAIN RESULTS

Fifty patients with PAP were enrolled in the study. During observation, nine improved and two withdrew; all of these were excluded. Of 35 patients completing the high- and low-dose therapy, 24 improved, resulting in an overall response rate of 62% (24/39; intention-to-treat analysis) and reduction in A-aDO(2) of 12.3 mm Hg (95% confidence interval, 8.4-16.2; n = 35, P < 0.001). No serious adverse events occurred, and serum GM-CSF autoantibody levels were unchanged. A treatment-emergent correlation occurred between A-aDO(2) and diffusing capacity of the lung, and high-resolution CT revealed improvement of ground-glass opacity. Twenty-nine of 35 patients remained stable without further therapy for 1 year.

CONCLUSIONS

Inhaled GM-CSF therapy is safe, effective, and provides a sustained therapeutic effect in autoimmune PAP. Clinical trial registered with www.controlled-trials.com/isrctn (ISRCTN18931678), www.jmacct.med.or.jp/english (JMA-IIA00013).

Downregulation of PU.1 leads to decreased expression of Dectin-1 in alveolar macrophages during Pneumocystis pneumonia

Dectin-1 is an important macrophage phagocytic receptor recognizing fungal beta-glucans. In this study, the mRNA levels of the Dectin-1 gene were found to be decreased by 61% in alveolar macrophages (AMs) from Pneumocystis-infected mice. The expression of Dectin-1 protein on the surface of these cells was also significantly decreased. By fluorescence in situ hybridization, mRNA expression levels of the transcription factor PU.1 were also found to be significantly reduced in AMs from Pneumocystis-infected mice. Electrophoretic mobility shift assay showed that PU.1 protein bound Dectin-1 gene promoter. With a luciferase reporter gene driven by the Dectin-1 gene promoter, the expression of the PU.1 gene in NIH 3T3 cells was found to enhance the luciferase activity in a dose-dependent manner. PU.1 expression knockdown by small interfering RNA (siRNA) caused a 63% decrease in Dectin-1 mRNA level and 40% decrease in protein level in AMs. Results of this study indicate that downregulation of PU.1 during Pneumocystis pneumonia leads to decreased expression of Dectin-1 in AMs.

Targeted PPAR{gamma} deficiency in alveolar macrophages disrupts surfactant catabolism

Surfactant accumulates in alveolar macrophages of granulocyte-macrophage colony-stimulating factor (GM-CSF) knockout (KO) mice and pulmonary alveolar proteinosis (PAP) patients with a functional loss of GM-CSF resulting from neutralizing anti-GM-CSF antibody. Alveolar macrophages from PAP patients and GM-CSF KO mice are de-ficient in peroxisome proliferator-activated receptor-gamma (PPARgamma) and ATP-binding cassette (ABC) lipid transporter ABCG1. Previous studies have demonstrated that GM-CSF induces PPARgamma. We therefore hypothesized that PPARgamma promotes surfactant catabolism through regulation of ABCG1. To address this hypothesis, macrophage-specific PPARgamma (MacPPARgamma) knockout mice were utilized. MacPPARgamma KO mice develop foamy, lipid-engorged Oil Red O positive alveolar macrophages. Lipid analyses revealed significant increases in the cholesterol and phospholipid contents of MacPPARgamma KO alveolar macrophages and extracellular bronchoalveolar lavage (BAL)-derived fluids. MacPPARgamma KO alveolar macrophages showed decreased expression of ABCG1 and a deficiency in ABCG1-mediated cholesterol efflux to HDL. Lipid metabolism may also be regulated by liver X receptor (LXR)-ABCA1 pathways. Interestingly, ABCA1 and LXRbeta expression were elevated, indicating that this pathway is not sufficient to prevent surfactant accumulation in alveolar macrophages. These results suggest that PPARgamma mediates a critical role in surfactant homeostasis through the regulation of ABCG1.

Mechanisms of suppression of alveolar epithelial cell GM-CSF expression in the setting of hyperoxic stress

Pulmonary expression of granulocyte/macrophage colony-stimulating factor (GM-CSF) is critically important for normal functional maturation of alveolar macrophages. We found previously that lung GM-CSF is dramatically suppressed in mice exposed to hyperoxia. Alveolar epithelial cells (AEC) are a major source of GM-CSF in the peripheral lung, and in vivo hyperoxia resulted in greatly reduced expression of GM-CSF protein by AEC ex vivo. We now explore the mechanisms responsible for this effect, using primary cultures of murine AEC exposed to hyperoxia in vitro. Exposure of AEC to 80% oxygen/5% CO(2) for 48 h did not induce overt toxicity, but resulted in significantly decreased GM-CSF protein and mRNA expression compared with cells in normoxia. Similar effects were seen when AEC were stressed with serum deprivation, an alternative inducer of oxidative stress. The effects in AEC were opposite those in a murine lung epithelial cell line (MLE-12 cells), in which hyperoxia induced GM-CSF expression. Both hyperoxia and serum deprivation resulted in increased intracellular reactive oxygen species (ROS) in AEC. Hyperoxia and serum deprivation induced significantly accelerated turnover of GM-CSF mRNA. Treatment of AEC with catalase during oxidative stress preserved GM-CSF protein and mRNA and was associated with stabilization of GM-CSF mRNA. We conclude that hyperoxia-induced suppression of AEC GM-CSF expression is a function of ROS-induced destabilization of GM-CSF mRNA. We speculate that AEC oxidative stress results in significantly impaired pulmonary innate immune defense due to effects on local GM-CSF expression in the lung.

SP-D counteracts GM-CSF-mediated increase of granuloma formation by alveolar macrophages in lysinuric protein intolerance

BACKGROUND

Pulmonary alveolar proteinosis (PAP) is a syndrome with multiple etiologies and is often deadly in lysinuric protein intolerance (LPI). At present, PAP is treated by whole lung lavage or with granulocyte/monocyte colony stimulating factor (GM-CSF); however, the effectiveness of GM-CSF in treating LPI associated PAP is uncertain. We hypothesized that GM-CSF and surfactant protein D (SP-D) would enhance the clearance of proteins and dying cells that are typically present in the airways of PAP lungs.

METHODS

Cells and cell-free supernatant of therapeutic bronchoalveolar lavage fluid (BALF) of a two-year-old patient with LPI were isolated on multiple occasions. Diagnostic BALF samples from an age-matched patient with bronchitis or adult PAP patients were used as controls. SP-D and total protein content of the supernatants were determined by BCA assays and Western blots, respectively. Cholesterol content was determined by a calorimetic assay or Oil Red O staining of cytospin preparations. The cells and surfactant lipids were also analyzed by transmission electron microscopy. Uptake of Alexa-647 conjugated BSA and DiI-labelled apoptotic Jurkat T-cells by BAL cells were studied separately in the presence or absence of SP-D (1 microg/ml) and/or GM-CSF (10 ng/ml), ex vivo. Specimens were analyzed by light and fluorescence microscopy.

RESULTS

Here we show that large amounts of cholesterol, and large numbers of cholesterol crystals, dying cells, and lipid-laden foamy alveolar macrophages were present in the airways of the LPI patient. Although SP-D is present, its bioavailability is low in the airways. SP-D was partially degraded and entrapped in the unusual surfactant lipid tubules with circular lattice, in vivo. We also show that supplementing SP-D and GM-CSF increases the uptake of protein and dying cells by healthy LPI alveolar macrophages, ex vivo. Serendipitously, we found that these cells spontaneously generated granulomas, ex vivo, and GM-CSF treatment drastically increased the number of granulomas whereas SP-D treatment counteracted the adverse effect of GM-CSF.

CONCLUSIONS

We propose that increased GM-CSF and decreased bioavailability of SP-D may promote granuloma formation in LPI, and GM-CSF may not be suitable for treating PAP in LPI. To improve the lung condition of LPI patients with PAP, it would be useful to explore alternative therapies for increasing dead cell clearance while decreasing cholesterol content in the airways.

Pulmonary surfactant: an immunological perspective

Pulmonary surfactant has two crucial roles in respiratory function; first, as a biophysical entity it reduces surface tension at the air water interface, facilitating gas exchange and alveolar stability during breathing, and, second, as an innate component of the lung's immune system it helps maintain sterility and balance immune reactions in the distal airways. Pulmonary surfactant consists of 90% lipids and 10% protein. There are four surfactant proteins named SP-A, SP-B, SP-C, and SP-D; their distinct interactions with surfactant phospholipids are necessary for the ultra-structural organization, stability, metabolism, and lowering of surface tension. In addition, SP-A and SP-D bind pathogens, inflict damage to microbial membranes, and regulate microbial phagocytosis and activation or deactivation of inflammatory responses by alveolar macrophages. SP-A and SP-D, also known as pulmonary collectins, mediate microbial phagocytosis via SP-A and SP-D receptors and the coordinated induction of other innate receptors. Several receptors (SP-R210, CD91/calreticulin, SIRPalpha, and toll-like receptors) mediate the immunological functions of SP-A and SP-D. However, accumulating evidence indicate that SP-B and SP-C and one or more lipid constituents of surfactant share similar immuno-regulatory properties as SP-A and SP-D. The present review discusses current knowledge on the interaction of surfactant with lung innate host defense.

Surfactant protein B propeptide contains a saposin-like protein domain with antimicrobial activity at low pH

Surfactant protein B (SP-B) proprotein contains three saposin-like protein (SAPLIP) domains: a SAPLIP domain corresponding to the mature SP-B peptide is essential for lung function and postnatal survival; the function of SAPLIP domains in the N-terminal (SP-BN) and C-terminal regions of the proprotein is not known. In the current study, SP-BN was detected in the supernatant of mouse bronchoalveolar lavage fluid (BALF) and in nonciliated bronchiolar cells, alveolar type II epithelial cells, and alveolar macrophages. rSP-BN indirectly promoted the uptake of bacteria by macrophage cell lines and directly killed bacteria at acidic pH, consistent with a lysosomal, antimicrobial function. Native SP-BN isolated from BALF also killed bacteria but only at acidic pH; the bactericidal activity of BALF at acidic pH was completely blocked by SP-BN Ab. Transgenic mice overexpressing SP-BN and mature SP-B peptide had significantly decreased bacterial burden and increased survival following intranasal inoculation with bacteria. These findings support the hypothesis that SP-BN contributes to innate host defense of the lung by supplementing the nonoxidant antimicrobial defenses of alveolar macrophages.

Azithromycin suppresses interleukin-12p40 expression in lipopolysaccharide and interferon-gamma stimulated macrophages

Azithromycin (AZM), a 15-member macrolide antibiotic, possesses anti-inflammatory activity. Macrophages are important in innate and acquired immunity, and produce pro-inflammatory cytokines such as interleukin (IL)-12, which are composed of subunit p40 and p35. The key function of IL-12 is the induction and maintenance of T-helper-1 responses, which is associated with the pathogenesis of chronic inflammatory diseases. We investigated the effect of azithromycin on IL-12p40 production in macrophages after lipopolysaccharide (LPS)/interferon (IFN)-γ stimulation. RAW264.7 macrophage cell line was pre-treated with vehicle or AZM, followed by the stimulation with LPS/IFN-γ. We measured IL-12 production by RT-PCR and ELISA. IL-12 transcriptional regulation was assessed by electrophoretic mobility shift assay and reporter assay. Phosphorylation of activator protein (AP)-1 and interferon consensus sequence binding protein (ICSBP) was assessed by immunoprecipitation using phosphotyrosine antibody, and immunoblotting using specific antibodies against JunB and ICSBP. AZM reduced the induction of IL-12p40 by LPS/IFN-γ in a dose dependent manner. AZM inhibited the binding of AP-1, nuclear factor of activated T cells (NFAT), and ICSBP, to the DNA binding site in the IL-12p40 promoter. AZM also reduced LPS/IFN-γ-induced IL-12p40 promoter activity. Phosphorylation of JunB and ICSBP was inhibited by azithromycin-treatment in stimulated cells. In conclusion, AZM reduced IL-12p40 transcriptional activity by inhibiting the binding of AP-1, NFAT, and ICSBP to the promoter site. This may represent an important mechanism for regulating the anti-inflammatory effects of AZM in macrophages.

Pulmonary alveolar proteinosis, a primary immunodeficiency of impaired GM-CSF stimulation of macrophages

Pulmonary alveolar proteinosis (PAP) is a rare syndrome characterized by accumulation of pulmonary surfactant, respiratory insufficiency, and increased infections. It occurs in various clinical settings that disrupt surfactant catabolism in alveolar macrophages, including a relatively more common autoimmune disease caused by GM-CSF autoantibodies and a rare congenital disease caused by CSF2RA mutations. Recent results demonstrate that GM-CSF is crucial for alveolar macrophage terminal differentiation and immune functions, pulmonary surfactant homeostasis, and lung host defense. GM-CSF is also required to determine the basal functional capacity of circulating neutrophils, including adhesion, phagocytosis, and microbial killing. PAP research has illuminated the crucial role of GM-CSF in innate immunity and led to novel therapy for PAP and the potential use of anti-GM-CSF therapy in other common disorders.

Pulmonary alveolar proteinosis: a bench-to-bedside story of granulocyte-macrophage colony-stimulating factor dysfunction

Pulmonary alveolar proteinosis (PAP) is a rare disorder characterized by ineffective clearance of surfactant by alveolar macrophages. Through recent studies with genetically altered mice, the etiology of this idiopathic disease is becoming clearer. Functional deficiency of granulocyte-macrophage colony-stimulating factor (GM-CSF) appears to contribute to disease pathogenesis because mutant mice deficient in GM-CSF or its receptor spontaneously develop PAP. Recent human studies further suggest a connection between PAP and defective GM-CSF activity because inactivating anti-GM-CSF autoantibodies are observed in all patients with idiopathic PAP, and additional rare cases of PAP in children have been accompanied by genetic defects in the alpha chain of the GM-CSF receptor. In patients and mouse models of PAP, deficient GM-CSF activity appears to result in defective alveolar macrophages that are unable to maintain pulmonary surfactant homeostasis and display defective phagocytic and antigen-presenting capabilities. The most recent studies also suggest that neutrophil dysfunction additionally contributes to the increased susceptibility to lung infections seen in PAP. Because the phenotypic and immunologic abnormalities of PAP in mouse models can be corrected by GM-CSF reconstituting therapies, early clinical trials are underway utilizing administration of GM-CSF to potentially treat human PAP. The development of novel treatment approaches for PAP represents a dramatic illustration in pulmonary medicine of the "bench-to-bedside" process, in which basic scientists, translational researchers, and clinicians have joined together to rapidly take advantage of the unexpected observations frequently made in the modern molecular biology research laboratory.

Update in nonneoplastic lung diseases

CONTEXT

Nonneoplastic lung diseases include a wide range of pathologic disorders from asthma to interstitial lung disease to pulmonary hypertension. Recent advances in our understanding of the pathophysiology of many of these disorders may ultimately impact diagnosis, therapy, and prognosis. It is important for the practicing pathologist to be aware of this new information and to understand how it impacts the diagnosis, treatment, and outcome of these diseases.

OBJECTIVE

To update current progress toward elucidating the pathophysiology of pulmonary alveolar proteinosis, idiopathic pulmonary hemosiderosis, and pulmonary arterial hypertension, as well as to present classification systems for pulmonary hypertension, asthma, and interstitial lung disease and describe how these advances relate to the current practice of pulmonary pathology.

DATA SOURCES

Published literature from PubMed (National Library of Medicine) and primary material from the authors' institution.

CONCLUSIONS

Improved understanding of the pathophysiology of pulmonary alveolar proteinosis, pulmonary hypertension, and idiopathic hemosiderosis may impact the role of the surgical pathologist. New markers of disease may need to be assessed by immunohistochemistry or molecular techniques. The classification systems for interstitial lung disease, asthma, and pulmonary hypertension are evolving, and surgical pathologists should consider the clinicopathologic context of their diagnoses of these entities.

Cooperation between PU.1 and CAAT/enhancer-binding protein beta is necessary to induce the expression of the MD-2 gene

Myeloid differentiation factor 2 (MD-2) binds Gram-negative bacterial lipopolysaccharide with high affinity and is essential for Toll-like receptor 4-dependent signal transduction. MD-2 has recently been recognized as a type II acute phase protein. Plasma concentrations of the soluble form of MD-2 increase markedly during the course of severe infections. Its production is regulated in hepatocytes and myeloid cells by interleukin-6 (IL-6) but not IL-1beta. In the present work we show that two transcription factors (TF), PU.1 and CAAT/enhancer-binding protein beta (C/EBPbeta), participate in the activation of the human MD-2 gene in hepatocytic cells after stimulation with IL-6. PU.1 TF and proximal PU.1 binding sites in the MD-2 promoter were shown to be critical for the basal activity of the promoter as well as for IL-6-induced soluble MD-2 production. Deletions of proximal portions of the MD-2 promoter containing PU.1 and/or NF-IL-6 consensus binding sites as well as site-directed mutagenesis of these binding sites abrogated IL-6-dependent MD-2 gene activation. We show that the cooperation between C/EBPbeta and PU.1 is critical for the transcriptional activation of the MD-2 gene by IL-6. PU.1 was essentially known as a TF involved in the differentiation of myeloid precursor cells and the expression of surface receptors of the innate immunity. Herein, we show that it also participates in the regulation of an acute phase protein, MD-2, in nonmyeloid cells cooperatively with C/EBPbeta, a classical IL-6-inducible TF.

Impaired terminal differentiation of pulmonary macrophages in a Guinea pig model of chronic ethanol ingestion

BACKGROUND

Alcoholic patients have an increased risk of respiratory infections, which is partially due to an impaired immune response of alveolar macrophages. The mechanisms by which alcohol impairs alveolar macrophage function are poorly understood. In this study, we demonstrated in a guinea pig model that chronic ethanol ingestion significantly impaired alveolar macrophage differentiation and function.

METHODS

Isolated alveolar macrophages were separated into 4 different subpopulations with varying densities and levels of maturation.

RESULTS

Compared to control values, chronic ethanol ingestion decreased the percentage of alveolar macrophages in the mature fractions by approximately 60%. Alveolar macrophage function in each subpopulation was determined by measuring phagocytosis of fluorescein isothiocyanate-labeled Staphylococcus aureus. Alveolar macrophages from ethanol-fed animals had approximately 80% decrease in the phagocytic index. Western blot and immunohistochemical analysis of the differential markers granulocyte/macrophage colony-stimulating factor (GM-CSF) receptor alpha (GM-CSFR-alpha), PU.1, CD11c, and CD11b verified that alcoholic macrophages displayed impaired terminal differentiation. While oral supplementation with the glutathione precursor S-adenosyl-methionine (SAM) did not alter the maturational status of control animals, SAM supplementation shifted the distribution of macrophages to more mature fractions, normalized the phagocytic index; as well as normalized expression of CD11c, CD11b, PU.1, and GM-CSFR-alpha. Chronic ethanol ingestion also impaired the differentiation status of interstitial macrophages which was normalized by SAM supplementation.

CONCLUSION

This improvement in the maturational status suggested that ethanol-induced oxidant stress is a central feature in impaired terminal differentiation of macrophages in the interstitial and alveolar space. Therefore, strategies targeting pulmonary oxidant stress may restore macrophage differentiation and function even after chronic ethanol ingestion.

Transcriptional regulation of the novel Toll-like receptor Tlr13

Little has been known about Tlr13 (Toll-like receptor 13), a novel member of the Toll-like receptor family. To elucidate the molecular basis of murine Tlr13 gene expression, the activity of the Tlr13 gene promoter was characterized. Reporter gene analysis and electrophoretic mobility shift assays demonstrated that Tlr13 gene transcription was regulated through three cis-acting elements that interacted with the Ets2, Sp1, and PU.1 transcription factors. Furthermore, our work suggests that these transcription factors may cooperate, culminating in maximal transcription of the Tlr13 gene. In contrast, NF-kappaB appeared to act as an inhibitor of Tlr13 transcription. Overexpression of Ets2 caused a strong increase in the transcriptional activity of the Tlr13 promoter; however, overexpression of NF-kappaB p65 dramatically inhibited it. Additionally, interferon-beta is capable of acting Tlr13 transcription, but the activated signaling of lipopolysaccharide/TLR4 and peptidoglycan/TLR2 strongly inhibited the Tlr13 gene promoter. Thus, these findings reveal the mechanism of Tlr13 gene regulation, thereby providing insight into the function of Tlr13 in the immune response to pathogen.