Effect of Benralizumab on Mucus Plugs in Severe Eosinophilic Asthma.

INTRODUCTION: Mucus plugs are associated with airway obstruction in severe asthma and are involved in the formation of activated eosinophils. Benralizumab, an anti-interleukin-5 receptor antibody, markedly reduces not only peripheral blood eosinophils but also airway eosinophils; however, its effects on mucus plugs have not been clarified. In this study, we examined the efficacy of benralizumab on mucus plugs using computed tomography (CT) imaging. METHODS: Twelve patients who were administered benralizumab and underwent CT before and approximately 4 months after the introduction of benralizumab were included in this study, and the number of mucus plugs before and after benralizumab administration was compared. The correlation between the clinical background and treatment effect was also examined. RESULTS: The number of mucus plugs significantly decreased after the introduction of benralizumab. The number of mucus plugs was correlated with sputum eosinophil percentage and eosinophil cationic protein in the sputum supernatants and inversely correlated with forced expiratory volume in 1 s (FEV1). Benralizumab induction resulted in a marked decrease in blood and sputum eosinophil levels and a significant improvement in asthma symptoms, quality of life scores, FEV1, and exacerbation frequency. Furthermore, there was a significant correlation between the reduction in mucus plugs and changes in the symptom score or FEV1. DISCUSSION/CONCLUSION: These data suggest that benralizumab may have the potential to improve symptoms and respiratory function in patients with severe eosinophilic asthma by reducing mucus plugs.

Effects of Benralizumab on Three-Dimensional Computed Tomography Analysis in Severe Eosinophilic Asthma.

INTRODUCTION: Benralizumab, an anti-interleukin-5 receptor chain monoclonal antibody, is used to treat severe asthma and control asthma symptoms or exacerbations. The aim of this study was to examine the changes in airway morphology using computed tomography (CT) images in accordance with clinical efficacy following the administration of benralizumab. METHODS: The clinical efficacy of benralizumab was evaluated in 11 patients with severe asthma by analyzing the changes in parameters, such as the asthma control test, asthma quality of life questionnaire, pulmonary function, and exacerbation count. We also investigated the airway wall thickness of the right bronchus (B1) and the total airway count (TAC) using CT images. RESULTS: Most patients treated with benralizumab showed improvements in asthma symptoms and exacerbations. CT imaging analyses showed a decrease in the right B1 airway wall thickness and an increase in the TAC. Correlations between blood eosinophil count and changes in CT imaging were observed. DISCUSSION/CONCLUSION: The data suggested that benralizumab has the potential to improve airway wall thickening and ventilation by alleviating the obstruction and clearing an obstructed airway.

A murine model of hereditary pulmonary alveolar proteinosis caused by homozygous Csf2ra gene disruption.

Hereditary pulmonary alveolar proteinosis (hPAP) is a rare disorder caused by recessive mutations in GM-CSF receptor subunit α/ß genes (CSF2RA/CSF2RB, respectively) characterized by impaired GM-CSF-dependent surfactant clearance by alveolar macrophages (AMs) resulting in alveolar surfactant accumulation and hypoxemic respiratory failure. Because hPAP is caused by CSF2RA mutations in most patients, we created an animal model of hPAP caused by Csf2ra gene disruption (Csf2ra-/- mice) and evaluated the effects on AMs and lungs. Macrophages from Csf2ra-/- mice were unable to bind and clear GM-CSF, did not exhibit GM-CSF signaling, and had functional defects in phagocytosis, cholesterol clearance, and surfactant clearance. Csf2ra-/- mice developed a time-dependent, progressive lung disease similar to hPAP in children caused by CSF2RA mutations with respect to the clinical, physiological, histopathological, biochemical abnormalities, biomarkers of PAP lung disease, and clinical course. In contrast, Csf2ra+/- mice had functionally normal AMs and no lung disease. Pulmonary macrophage transplantation (PMT) without myeloablation resulted in long-term engraftment, restoration of GM-CSF responsiveness to AMs, and a safe and durable treatment effect that lasted for the duration of the experiment (6 mo). Results demonstrate that homozygous (but not heterozygous) Csf2ra gene ablation caused hPAP identical to hPAP in children with CSF2RA mutations, identified AMs as the cellular site of hPAP pathogenesis in Csf2ra-/- mice, and have implications for preclinical studies supporting the translation of PMT as therapy of hPAP in humans.

Serum Anti-interferon-γ Autoantibody Titer as a Potential Biomarker of Disseminated Non-tuberculous Mycobacterial Infection.

PURPOSE: In the past decade, the relationship between naturally occurring interferon-γ-neutralizing autoantibodies (IFNγ-Ab) and disseminated non-tuberculous mycobacteria (NTM) infection has been established. Furthermore, immune suppressive therapy aimed at the suppression of antibody production has shown efficacy as a supportive treatment. However, the nature of antibody behavior and antibody titer during the course of this disease, as well as the pathophysiological significance of IFNγ-Ab, has not yet been fully elucidated. METHODS: Thirteen Japanese subjects suffering from disseminated NTM (dNTM) infection with IFNγ-Ab were evaluated. The fluctuation of IFNγ-Ab titer and the neutralizing capacity against IFN-γ during the course of the disease were retrospectively analyzed. IFNγ-Ab titers in the sera were quantified using an enzyme-linked immunosorbent assay; neutralizing capacity was evaluated via flow cytometry. RESULTS: Serum antibody titers were not constant during the treatment period and varied over the course of the disease. The antibody titer decreased when the disease was improved by anti-mycobacterial treatment (p < 0.01) and increased as the disease progressed (p < 0.05). Even after the antibody titer decreased, the neutralizing capacity against IFN-γ was maintained by individual sera. CONCLUSIONS: Despite the improvement in the pathological condition via treatment, the patients' sera maintained neutralizing capacity against IFN-γ. Antibody titer fluctuated over the course of the disease and exhibited potential as a biomarker for judgment of the disease state.

Effective hematopoietic stem cell-based gene therapy in a murine model of hereditary pulmonary alveolar proteinosis.

Hereditary pulmonary alveolar proteinosis due to GM-CSF receptor deficiency (herPAP) constitutes a life-threatening lung disease characterized by alveolar deposition of surfactant protein secondary to defective alveolar macrophage function. As current therapeutic options are primarily symptomatic, we have explored the potential of hematopoietic stem cell-based gene therapy. Using Csf2rb-/- mice, a model closely reflecting the human herPAP disease phenotype, we here demonstrate robust pulmonary engraftment of an alveolar macrophage population following intravenous transplantation of lentivirally corrected hematopoietic stem and progenitor cells. Engraftment was associated with marked improvement of critical herPAP disease parameters, including bronchoalveolar fluid protein, cholesterol and cytokine levels, pulmonary density on computed tomography scans, pulmonary deposition of Periodic Acid-Schiff+ material as well as respiratory mechanics. These effects were stable for at least nine months. With respect to engraftment and alveolar macrophage differentiation kinetics, we demonstrate the rapid development of CD11c+/SiglecF+ cells in the lungs from a CD11c-/SiglecF+ progenitor population within four weeks after transplantation. Based on these data, we suggest hematopoietic stem cell-based gene therapy as an effective and cause-directed treatment approach for herPAP.

Long-Term Safety and Efficacy of Gene-Pulmonary Macrophage Transplantation Therapy of PAP in Csf2ra-/- Mice.

Hereditary pulmonary alveolar proteinosis (PAP) is a genetic lung disease characterized by surfactant accumulation and respiratory failure arising from disruption of GM-CSF signaling. While mutations in either CSF2RA or CSF2RB (encoding GM-CSF receptor α or ß chains, respectively) can cause PAP, α chain mutations are responsible in most patients. Pulmonary macrophage transplantation (PMT) is a promising new cell therapy in development; however, no studies have evaluated this approach for hereditary PAP (hPAP) caused by Csf2ra mutations. Here, we report on the preclinical safety, tolerability, and efficacy of lentiviral-vector (LV)-mediated Csf2ra expression in macrophages and PMT of gene-corrected macrophages (gene-PMT therapy) in Csf2ra gene-ablated (Csf2ra-/-) mice. Gene-PMT therapy resulted in a stable transgene integration and correction of GM-CSF signaling and functions in Csf2ra-/- macrophages in vitro and in vivo and resulted in engraftment and long-term persistence of gene-corrected macrophages in alveoli; restoration of pulmonary surfactant homeostasis; correction of PAP-specific cytologic, histologic, and biomarker abnormalities; and reduced inflammation associated with disease progression in untreated mice. No adverse consequences of gene-PMT therapy in Csf2ra-/- mice were observed. Results demonstrate that gene-PMT therapy of hPAP in Csf2ra-/- mice was highly efficacious, durable, safe, and well tolerated.

Inhibition of IRAK1 Ubiquitination Determines Glucocorticoid Sensitivity for TLR9-Induced Inflammation in Macrophages.

Inflammatory responses are controlled by signaling mediators that are regulated by various posttranslational modifications. Recently, transcription-independent functions for glucocorticoids (GC) in restraining inflammation have emerged, but the underlying mechanisms are unknown. In this study, we report that GC receptor (GR)-mediated actions of GC acutely suppress TLR9-induced inflammation via inhibition of IL-1R-associated kinase 1 (IRAK1) ubiquitination. ß-TrCP-IRAK1 interaction is required for K48-linked ubiquitination of IRAK1 at Lys134 and subsequent membrane-to-cytoplasm trafficking of IRAK1 interacting partners TNFR-associated factor 6 and TAK1 that facilitates NF-κB and MAPK activation. Upon costimulation of macrophages with GC and TLR9-engaging ligand, GR physically interacts with IRAK1 and interferes with protein-protein interactions between ß-TrCP and IRAK1. Ablation of GR in macrophages prevents GC-dependent suppression of ß-TrCP-IRAK1 interactions. This GC-mediated suppression of IRAK1 activation is unique to TLR9, as GC treatment impairs TLR9 but not TLR4 ligand-induced K48-linked IRAK1 ubiquitination and trafficking of IRAK1 interacting partners. Furthermore, mutations in IRAK1 at Lys134 prevent TLR9 ligand-induced activation of inflammatory signaling mediators and synthesis of proinflammatory cytokines to an extent comparable to GC-mediated inhibition. Collectively, these findings identify a transcription-independent, rapid, and nongenomic GC suppression of TLR9 ligand-mediated IRAK1 ubiquitination as a novel mechanism for restraining acute inflammatory reactions.

Clinical Significance of Interferon-γ Neutralizing Autoantibodies Against Disseminated Nontuberculous Mycobacterial Disease.

Background: Interferon-γ neutralizing autoantibodies (nIFNγ-autoAbs) are reported in patients with disseminated nontuberculous mycobacteria (NTM) infection and may function by increasing the infection risk. Notwithstanding, the prevalence of nIFNγ-autoAbs as well as the clinical presentation, diagnosis, and natural history of disseminated NTM infection in these patients is poorly understood. Methods: In this retrospective observational study, data and sera for 331 Japanese subjects with mycobacterial infection were collected and analyzed. IFNγ-autoAb titers in sera were quantified using an enzyme-linked immunosorbent assay; neutralizing capacity was evaluated via flow cytometry. Results: Disseminated NTM was identified in 50 human immunodeficiency virus-uninfected patients. Of these, 30 of 37 (81%) immunocompetent patients had an increased nIFNγ-autoAb titer whereas only 1 of 13 (7.7%) immunodeficient patients had an increased nIFNγ-autoAb titer (P < .0001, χ2 test). Presenting symptoms were nonspecific and NTM infection was not included in the differential diagnosis in most cases. All patients with disseminated NTM and an increased serum nIFNγ-autoAb level received prolonged antimicrobial therapy. In 6 cases when antibiotic treatment was discontinued, NTM infection recurred and required resumption of antibiotic therapy for infection control. The mortality rate was 3.2% in disseminated NTM patients with nIFNγ-autoAbs and 21% in those without. Conclusions: nIFNγ-autoAbs were present in most patients with disseminated NTM infection without a diagnosis of clinical immunodeficiency. Diagnosis of disseminated NTM requires a high degree of suspicion and can be improved by measuring serum nIFNγ-autoAb titer. Long-term antibiotic therapy helps prevent recrudescent NTM infection.

Effects of sublingual immunotherapy in a murine asthma model sensitized by intranasal administration of house dust mite extracts.

BACKGROUND: Sublingual immunotherapy (SLIT) has received attention as a method for allergen immunotherapy. However, the mechanism of SLIT has not yet been fully investigated. Therefore, we evaluated the effects of SLIT in a murine asthma model, sensitized by intranasal administration of house dust mite (HDM) extracts. METHODS: Female BALB/c mice were intranasally exposed to HDM for either 3 or 5 weeks (5 consecutive days per week). Mice were administered either low-dose (0.5 mg/day) or high-dose (5 mg/day) sublingual HDM extracts for 2 weeks, followed by an additional week of intranasal exposure. Airway hyperresponsiveness (AHR), bronchoalveolar lavage fluid (BALF) cell count, cytokine levels in the BALF and lymph node cell culture supernatants, and allergen-specific antibodies were measured. Lung histology was also investigated. RESULTS: In mice sensitized for 5 weeks, high-dose SLIT ameliorated AHR, airway eosinophilia and goblet cell metaplasia. In mice sensitized for 3 weeks, even low dose SLIT ameliorated AHR and airway eosinophilia. Th2 cytokine levels in culture supernatants of submandibular lymph node cells in high-dose SLIT mice decreased, whereas IL-10 levels increased. Total IgA in BALF increased in mice sensitized for 3 or 5 weeks, and high-dose SLIT also increased allergen-specific IgG2a in mice sensitized for 5 weeks. CONCLUSIONS: These data suggest that earlier induction of SLIT in HDM-sensitized mice provides superior suppression of AHR and goblet cell metaplasia. The modulation of allergen specific IgG2a and local IgA might play a role in the amelioration of AHR and airway inflammation.

The Effects of All-Trans Retinoic Acid on the Induction of Oral Tolerance in a Murine Model of Bronchial Asthma.

BACKGROUND: Active suppression induced by regulatory T (Treg) cells is reported to be one of the mechanisms involved in oral tolerance. All-trans retinoic acid (ATRA) has been reported to affect Treg cell differentiation. The present study examined the effects of ATRA on the induction of oral tolerance in a murine model of bronchial asthma. METHODS: BALB/c mice were sensitized to and challenged with ovalbumin (OVA) through feeding followed by OVA challenges. In some study groups ATRA was orally administered concomitantly with OVA feeding either in the presence or absence of the retinoic acid receptor antagonist LE135. Lung CD4+ T cells were isolated from mice exposed to ATRA and/or OVA, and transferred to control mice. Airway hyperresponsiveness (AHR), cell counts and cytokine levels in bronchoalveolar lavage (BAL) fluid, and lung histology were assessed. RESULTS: Concomitant administration of ATRA with OVA ameliorated AHR, airway eosinophilia, elevation of cytokines in BAL fluid and goblet cell metaplasia. The proportion of Treg cells in the lungs was increased in mice treated with OVA and ATRA, as compared to those treated with OVA only. Transfer of lung CD4+ T cells from mice treated with OVA and ATRA induced suppression of AHR and airway inflammation. LE135 completely reversed the effects of ATRA on AHR, airway allergic inflammation and the number of Treg cells in the lungs. CONCLUSION: These data suggested that oral administration of ATRA with OVA had the potential to enhance oral tolerance in this murine model of bronchial asthma. These effects were mediated, at least in part, by Treg cell expansion.

Characteristics of eosinophilic and non-eosinophilic asthma during treatment with inhaled corticosteroids.

OBJECTIVE: Eosinophilic inflammation in the respiratory tract is a hallmark of bronchial asthma. In naïve cases, the inflammatory profile is associated with disease severity and reactivity to inhaled corticosteroids (ICS). Sustained airway eosinophilia has been reported during ICS treatment. However, the immunological characteristics of these cases are not known and it is unclear if this situation contributes to asthma control. This study was performed to determine the answer of these questions. METHODS: To compare phenotypes of eosinophilic and non-eosinophilic asthma (EA and NEA, respectively) under ICS treatment, clinical data were obtained from asthmatic subjects (n = 22) and healthy controls (n = 10), and the leukocyte compositions of induced sputum and peripheral blood were determined. T lymphocyte profiles in systemic blood were assessed by flow cytometry. RESULTS: A higher frequency of emergency room visits was observed in the NEA group, which had a higher neutrophil count relative to the total inflammatory cell population in induced sputum than the EA group (59.5 versus 36.6%; p < 0.01). The fraction of helper T (Th)17 lymphocytes as well as the ratio of Th17 to regulatory T cells (Treg) in the peripheral blood was higher in the NEA than in the EA group (0.24 versus 0.13; p < 0.05). CONCLUSIONS: Th17 were more prevalent than Treg cells in the peripheral blood of NEA patients under ICS treatment, corresponding to neutrophil-dominant airway inflammation and a severe asthmatic phenotype. Thus, an imbalance in Th17/Treg may be associated with the pathogenesis of NEA in patients undergoing ICS treatment.

Cluster analysis identifies characteristic phenotypes of asthma with accelerated lung function decline.

OBJECTIVE: While the majority of individuals with asthma retain normal lung function over time, some exhibit accelerated lung function decline. Preservation of lung function is an important aspect of asthma management. Whether the asthma guidelines can prevent lung function decline remains controversial. This study was performed to determine the distribution of asthmatic subjects with greater lung function decline and to identify characteristic clinical features of such subjects treated in accordance with clinical guidelines by using hierarchical cluster analysis. METHODS: Eighty-six asthmatic subjects without a history of smoking were assessed with respect to eight variables selected from clinical phenotypes by using step-wise multiple regression analysis. Hierarchical cluster analysis using Ward's method generated a dendrogram for estimation of the number of clusters within the population and the differences between them. RESULTS: Three distinct clusters were identified. Cluster 1 (n = 40) comprised women with late-onset asthma. Cluster 2 (n = 17) comprised subjects with early-onset asthma, atopy and long disease duration. Cluster 3 (n = 29) predominantly comprised older men who had late-onset asthma, a lower prevalence of exacerbation and a lower predicted % forced expiratory volume in 1 s (FEV1) at baseline. Subjects in cluster 3 showed a mean decline in FEV1 of 69 mL/year, which was the greatest lung function decline among the three clusters. CONCLUSION: We identified a subgroup of patients with accelerated lung function decline despite appropriate asthma treatment based on guidelines constructed by using subjective symptoms.

Novel assay to detect increased level of neutralizing anti-interferon gamma autoantibodies in non-tuberculous mycobacterial patients.

Subjects exposed to non-tuberculous mycobacterium (NTM) species do not always develop an active disease, which likely reflects underlying host susceptibility factors. Recent reports have shown that anti interferon gamma (IFN-γ) neutralizing autoantibodies (IFN-γ Ab) are associated with the development of disseminated NTM in patients without known evidence of immunodeficiency. The purpose of this study is to establish the screening method if subjects have IFN-γ Ab. Whole blood was obtained from patients with disseminated NTM, those with pulmonary NTM, and healthy controls. The neutralizing capacity to IFN-γ activity was assessed as an inhibition of Signal Transducer and Activation of Transcription 1 (STAT-1) phosphorylation in leukocyte after stimulation with exogenous IFN-γ by flow cytometer. The strength of phosphorylation was described as STAT1 phosphorylation index. Antigen capture assay was performed to measure the relative titer of Immunoglobulin-G fraction of IFN-γ Ab. STAT1 phosphorylation by IFN-γ was significantly inhibited in the leukocytes from patients with disseminated NTM compared to that in healthy subjects, while this inhibition was not observed in patients with pulmonary NTM. All subjects with inhibited STAT1 phosphorylation had high titer of Immunoglobulin-G that reacted with IFN-γ in the antigen capture assay. The measurement of STAT1 phosphorylation index in whole blood leukocytes and antigen capture assay are simple and useful method for detection of anti-IFN-γ neutralizing autoantibodies, and is valuable in the pathophysiological diagnosis of disseminated NTM patients without obvious immunodeficiency.

Successful Treatment with Mycophenolate Mofetil in a Patieint with Anti-MDA 5 Antibody-positive Interstitial Lung Disease and Posterior Reversible Encephalopathy syndrome: A Case Report.

A 59-year-old woman presented with a rash on the top part of her hands and pain in the wrist joint and was diagnosed with dermatomyositis complicated by interstitial pneumonia positive for anti-melanoma differentiation-associated gene 5 (MDA-5) antibody. However, the patient reported a severe headache following treatment with oral prednisolone and tacrolimus. Posterior reversible encephalopathy syndrome (PRES) was diagnosed based on the brain magnetic resonance imaging findings. Tacrolimus was discontinued, and mycophenolate mofetil was instead administered with a favorable outcome. Mycophenolate mofetil should therefore be considered as an alternative treatment for anti-MDA-5-positive interstitial lung disease in cases where calcineurin inhibitors cannot be used.

Cytokine profiles associated with disease severity and prognosis of autoimmune pulmonary alveolar proteinosis.

BACKGROUND: Pulmonary alveolar proteinosis (PAP) is characterized by an abnormal accumulation of surfactants in the alveoli. Most cases are classified as autoimmune PAP (APAP) because they are associated with autoantibodies against granulocyte-macrophage colony-stimulating factor (GM-CSF). However, GM-CSF autoantibody levels are unlikely to correlate with the disease severity or prognosis of APAP. METHODS: We collected clinical records and measured 38 serum cytokine concentrations for consecutive patients with APAP. After exclusion of 21 cytokines because of undetectable levels, 17 cytokine levels were compared between low and high disease severity scores (DSSs). We also compared whole lung lavage (WLL)-free survival with cut-off values defined by receiver operating characteristic (ROC) curves of cytokine levels and WLL administration at 11 months. RESULTS: Nineteen patients with APAP were enrolled in the study. Five were classified as DSS 1 or 2, while the others were classified as DSS 4 or 5. Comparison between DSS 1-2 and 4-5 revealed that the concentrations of IP-10 and GRO increased in the latter groups (p < 0.05). Fifteen patients underwent WLL. Comparison between those who underwent WLL within 11 months and the others showed that IP-10 and TNF-α were tended to be elevated in the former group (p = 0.082 and 0.057, respectively). The cut-off values of IP-10, 308.8 pg/mL and TNF-α, 19.1 pg/mL, defined by the ROC curves, significantly separated WLL-free survivals with log-rank analyses (p = 0.005). CONCLUSIONS: The concentrations of IP-10 and GRO may reflect the DSSs of APAP. A combination of IP-10 and TNF-α levels could be a biomarker to predict WLL-free survival.

A toxicology study of Csf2ra complementation and pulmonary macrophage transplantation therapy of hereditary PAP in mice.

Pulmonary macrophage transplantation (PMT) is a gene and cell transplantation approach in development as therapy for hereditary pulmonary alveolar proteinosis (hPAP), a surfactant accumulation disorder caused by mutations in CSF2RA/B (and murine homologs). We conducted a toxicology study of PMT of Csf2ra gene-corrected macrophages (mGM-Rα+Mϕs) or saline-control intervention in Csf2raKO or wild-type (WT) mice including single ascending dose and repeat ascending dose studies evaluating safety, tolerability, pharmacokinetics, and pharmacodynamics. Lentiviral-mediated Csf2ra cDNA transfer restored GM-CSF signaling in mGM-Rα+Mϕs. Following PMT, mGM-Rα+Mϕs engrafted, remained within the lungs, and did not undergo uncontrolled proliferation or result in bronchospasm, pulmonary function abnormalities, pulmonary or systemic inflammation, anti-transgene product antibodies, or pulmonary fibrosis. Aggressive male fighting caused a similarly low rate of serious adverse events in saline- and PMT-treated mice. Transient, minor pulmonary neutrophilia and exacerbation of pre-existing hPAP-related lymphocytosis were observed 14 days after PMT of the safety margin dose but not the target dose (5,000,000 or 500,000 mGM-Rα+Mϕs, respectively) and only in Csf2raKO mice but not in WT mice. PMT reduced lung disease severity in Csf2raKO mice. Results indicate PMT of mGM-Rα+Mϕs was safe, well tolerated, and therapeutically efficacious in Csf2raKO mice, and established a no adverse effect level and 10-fold safety margin.

Occupational Lung Disease Caused by Exposure to Polytetrafluoroethylene.

We herein report a 45-year-old-man with multiple foreign body granulomas in the lungs caused by polytetrafluoroethylene (PTFE). A mass in the right lower lobe of the lung and bilateral centrilobular lung nodules were found unexpectedly during the patient's visit to a hospital for a respiratory infection. The patient's occupation for 26 years involved spraying PTFE. A lung biopsy using bronchoscopy revealed granulomatous lesions and giant cells. The presence of fluorine in the granulomatous lesions was confirmed using an electron probe microanalyzer with wavelength dispersive spectrometer. Fluorine is a component of PTFE and is not found in normal lung tissue.

Role of GM-CSF in regulating metabolism and mitochondrial functions critical to macrophage proliferation.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) exerts pleiotropic effects on macrophages and is required for self-renewal but the mechanisms responsible are unknown. Using mouse models with disrupted GM-CSF signaling, we show GM-CSF is critical for mitochondrial turnover, functions, and integrity. GM-CSF signaling is essential for fatty acid ß-oxidation and markedly increased tricarboxylic acid cycle activity, oxidative phosphorylation, and ATP production. GM-CSF also regulated cytosolic pathways including glycolysis, pentose phosphate pathway, and amino acid synthesis. We conclude that GM-CSF regulates macrophages in part through a critical role in maintaining mitochondria, which are necessary for cellular metabolism as well as proliferation and self-renewal.

Statin as a novel pharmacotherapy of pulmonary alveolar proteinosis.

Pulmonary alveolar proteinosis (PAP) is a syndrome of reduced GM-CSF-dependent, macrophage-mediated surfactant clearance, dysfunctional foamy alveolar macrophages, alveolar surfactant accumulation, and hypoxemic respiratory failure for which the pathogenetic mechanism is unknown. Here, we examine the lipids accumulating in alveolar macrophages and surfactant to define the pathogenesis of PAP and evaluate a novel pharmacotherapeutic approach. In PAP patients, alveolar macrophages have a marked increase in cholesterol but only a minor increase in phospholipids, and pulmonary surfactant has an increase in the ratio of cholesterol to phospholipids. Oral statin therapy is associated with clinical, physiological, and radiological improvement in autoimmune PAP patients, and ex vivo statin treatment reduces cholesterol levels in explanted alveolar macrophages. In Csf2rb-/- mice, statin therapy reduces cholesterol accumulation in alveolar macrophages and ameliorates PAP, and ex vivo statin treatment increases cholesterol efflux from macrophages. These results support the feasibility of statin as a novel pathogenesis-based pharmacotherapy of PAP.