The molecular basis of pulmonary alveolar proteinosis

The Pathogenic Role of Anti-Granulocyte-Macrophage Colony-Stimulating Factor Autoantibodies in the Nocardiosis with the Central Nervous System Involvement

PURPOSE

Anti-granulocyte-macrophage colony-stimulating factor autoantibodies (anti-GM-CSF Abs) are implicated in the pathogenesis of Cryptococcus gattii (C. gattii) infection and pulmonary alveolar proteinosis (PAP). Their presence has also been noted in nocardiosis cases, particularly those with disseminated disease. This study delineates a case series characterizing clinical features and specificity of anti-GM-CSF Abs in nocardiosis patients.

METHODS

In this study, eight patients were recruited to determine the presence or absence of anti-GM-CSF Abs. In addition to the detailed description of the clinical course, we thoroughly investigated the autoantibodies regarding the characteristics, isotypes, subclasses, titers, and neutralizing capacities by utilizing the plasma samples from patients.

RESULTS

Of eight patients, five tested positive for anti-GM-CSF Abs, all with central nervous system (CNS) involvement; patients negative for these antibodies did not develop CNS nocardiosis. Distinct from previously documented cases, none of our patients with anti-GM-CSF Abs exhibited PAP symptoms. The titer and neutralizing activity of anti-GM-CSF Abs in our cohort did not significantly deviate from those found in C. gattii cryptococcosis and PAP patients. Uniquely, one individual (Patient 3) showed a minimal titer and neutralizing action of anti-GM-CSF Abs, with no relation to disease severity. Moreover, IgM autoantibodies were notably present in all CNS nocardiosis cases investigated.

CONCLUSION

The presence of anti-GM-CSF Abs suggests an intrinsic immunodeficiency predisposing individuals toward CNS nocardiosis. The presence of anti-GM-CSF Abs helps to elucidate vulnerability to CNS nocardiosis, even with low titer of autoantibodies. Consequently, systematic screening for anti-GM-CSF Abs should be considered a crucial diagnostic step for nocardiosis patients.

The Nonlinear Relationship Between High-Density Lipoprotein and Changes in Pulmonary Structure Function and Pulmonary Function in COPD Patients in China

Background

The previous findings on the correlation between spirometry and high-density lipoprotein (HDL) cholesterol are intriguing yet conflicting. The aim of this research is to evaluate the relationship between HDL levels and spirometry as well as imaging parameters in patients with chronic obstructive pulmonary disease (COPD) in China.

Methods

This study encompasses a total of 907 COPD patients. Participants with complete data from questionnaire interviews, lipid profile examinations, spirometry testing, and computed tomography (CT) scans were included in the analysis. A generalized additive model was employed to identify the non-linear relationship between HDL levels and both spirometry and imaging parameters. In the presence of non-linear correlations, segmented linear regression model was applied to ascertain threshold effects.

Results

After adjusting for various factors, we found a non-linear correlation between HDL levels and spirometry/imaging parameters, with an inflection point at 4.2 (66 mg/dL). When Ln (HDL) was below 4.2, each unit increase correlated significantly with reduced post-bronchodilator FEV1 (0.32L, 95% CI: 0.09-0.55), decreased predicted FEV1% (11.0%, 95% CI: 2.7-19.3), and lowered FEV1/FVC (8.0%, 95% CI: 4.0-12.0), along with notable increases in Ln (LAA-950) by 1.20 (95% CI: 0.60-1.79) and Ln (LAA-856) by 0.77 (95% CI: 0.37-1.17). However, no significant associations were observed when Ln (HDL) was greater than or equal to 4.2.

Conclusion

A non-linear correlation existed between HDL levels with lung function and CT imaging in COPD patients. Prior to reaching 66 mg/dL, an elevation in HDL was significantly associated with impaired lung function, more severe gas trapping and emphysema.

A Comprehensive Outlook on Pulmonary Alveolar Proteinosis-A Review

Pulmonary alveolar proteinosis (PAP) is an ultra-rare disease caused by impaired pulmonary surfactant clearance due to the dysfunction of alveolar macrophages or their signaling pathways. PAP is categorized into autoimmune, congenital, and secondary PAP, with autoimmune PAP being the most prevalent. This article aims to present a comprehensive review of PAP classification, pathogenesis, clinical presentation, diagnostics, and treatment. The literature search was conducted using the PubMed database and a total of 67 articles were selected. The PAP diagnosis is usually based on clinical symptoms, radiological imaging, and bronchoalveolar lavage, with additional GM-CSF antibody tests. The gold standard for PAP treatment is whole-lung lavage. This review presents a summary of the most recent findings concerning pulmonary alveolar proteinosis, pointing out specific features that require further investigation.

Redox regulation of macrophages

Redox signaling, a mode of signal transduction that involves the transfer of electrons from a nucleophilic to electrophilic molecule, has emerged as an essential regulator of inflammatory macrophages. Redox reactions are driven by reactive oxygen/nitrogen species (ROS and RNS) and redox-sensitive metabolites such as fumarate and itaconate, which can post-translationally modify specific cysteine residues in target proteins. In the past decade our understanding of how ROS, RNS, and redox-sensitive metabolites control macrophage function has expanded dramatically. In this review, we discuss the latest evidence of how ROS, RNS, and metabolites regulate macrophage function and how this is dysregulated with disease. We highlight the key tools to assess redox signaling and important questions that remain.

Lipid-Laden Macrophages in Pulmonary Diseases

Pulmonary surfactants play a crucial role in managing lung lipid metabolism, and dysregulation of this process is evident in various lung diseases. Alternations in lipid metabolism lead to pulmonary surfactant damage, resulting in hyperlipidemia in response to lung injury. Lung macrophages are responsible for recycling damaged lipid droplets to maintain lipid homeostasis. The inflammatory response triggered by external stimuli such as cigarette smoke, bleomycin, and bacteria can interfere with this process, resulting in the formation of lipid-laden macrophages (LLMs), also known as foamy macrophages. Recent studies have highlighted the potential significance of LLM formation in a range of pulmonary diseases. Furthermore, growing evidence suggests that LLMs are present in patients suffering from various pulmonary conditions. In this review, we summarize the essential metabolic and signaling pathways driving the LLM formation in chronic obstructive pulmonary disease, pulmonary fibrosis, tuberculosis, and acute lung injury.

Human inherited CCR2 deficiency underlies progressive polycystic lung disease

We describe a human lung disease caused by autosomal recessive, complete deficiency of the monocyte chemokine receptor C-C motif chemokine receptor 2 (CCR2). Nine children from five independent kindreds have pulmonary alveolar proteinosis (PAP), progressive polycystic lung disease, and recurrent infections, including bacillus Calmette Guérin (BCG) disease. The CCR2 variants are homozygous in six patients and compound heterozygous in three, and all are loss-of-expression and loss-of-function. They abolish CCR2-agonist chemokine C-C motif ligand 2 (CCL-2)-stimulated Ca2+ signaling in and migration of monocytic cells. All patients have high blood CCL-2 levels, providing a diagnostic test for screening children with unexplained lung or mycobacterial disease. Blood myeloid and lymphoid subsets and interferon (IFN)-γ- and granulocyte-macrophage colony-stimulating factor (GM-CSF)-mediated immunity are unaffected. CCR2-deficient monocytes and alveolar macrophage-like cells have normal gene expression profiles and functions. By contrast, alveolar macrophage counts are about half. Human complete CCR2 deficiency is a genetic etiology of PAP, polycystic lung disease, and recurrent infections caused by impaired CCL2-dependent monocyte migration to the lungs and infected tissues.

CRISPR-Cas12a for Highly Efficient and Marker-Free Targeted Integration in Human Pluripotent Stem Cells

The CRISPR-Cas12a platform has attracted interest in the genome editing community because the prototypical Acidaminococcus Cas12a generates a staggered DNA double-strand break upon binding to an AT-rich protospacer-adjacent motif (PAM, 5'-TTTV). The broad application of the platform in primary human cells was enabled by the development of an engineered version of the natural Cas12a protein, called Cas12a Ultra. In this study, we confirmed that CRISPR-Cas12a Ultra ribonucleoprotein complexes enabled allelic gene disruption frequencies of over 90% at multiple target sites in human T cells, hematopoietic stem and progenitor cells (HSPCs), and induced pluripotent stem cells (iPSCs). In addition, we demonstrated, for the first time, the efficient knock-in potential of the platform in human iPSCs and achieved targeted integration of a GFP marker gene into the AAVS1 safe harbor site and a CSF2RA super-exon into CSF2RA in up to 90% of alleles without selection. Clonal analysis revealed bi-allelic integration in >50% of the screened iPSC clones without compromising their pluripotency and genomic integrity. Thus, in combination with the adeno-associated virus vector system, CRISPR-Cas12a Ultra provides a highly efficient genome editing platform for performing targeted knock-ins in human iPSCs.

Infections in autoimmune pulmonary alveolar proteinosis: a large retrospective cohort

BACKGROUND

Autoimmune pulmonary alveolar proteinosis (aPAP) is a rare disease, predisposing to an increased risk of infection. A complete picture of these infections is lacking.

RESEARCH QUESTION

Describe the characteristics and clinical outcomes of patients diagnosed with aPAP, and to identify risk factors associated with opportunistic infections.

METHODS

We conducted a retrospective cohort including all patients diagnosed with aPAP between 2008 and 2018 in France and Belgium. Data were collected using a standardised questionnaire including demographics, comorbidities, imaging features, outcomes and microbiological data.

RESULTS

We included 104 patients, 2/3 were men and median age at diagnosis was 45 years. With a median follow-up of 3.4 years (IQR 1.7-6.6 years), 60 patients (58%), developed at least one infection, including 23 (22%) with opportunistic infections. Nocardia spp was the main pathogen identified (n=10). Thirty-five (34%) patients were hospitalised due to infection. In univariate analysis, male gender was associated with opportunistic infections (p=0.04, OR=3.88; 95% CI (1.02 to 22.06)). Anti-granulocyte macrophage colony-stimulating factor antibody titre at diagnosis was significantly higher among patients who developed nocardiosis (1058 (316-1591) vs 580 (200-1190), p=0.01). Nine patients had died (9%), but only one death was related to infection.

INTERPRETATION

Patients with aPAP often presented with opportunistic infections, especially nocardiosis, which highlights the importance of systematic search for slow-growing bacteria in bronchoalveolar lavage or whole lung lavage.

Discovery of the Potent and Selective Inhaled Janus Kinase 1 Inhibitor AZD4604 and Its Preclinical Characterization

JAK-STAT cytokines are critical in regulating immunity. Persistent activation of JAK-STAT signaling pathways by cytokines drives chronic inflammatory diseases such as asthma. Herein, we report on the discovery of a highly JAK1-selective, ATP-competitive series of inhibitors having a 1000-fold selectivity over other JAK family members and the approach used to identify compounds suitable for inhaled administration. Ultimately, compound 16 was selected as the clinical candidate, and upon dry powder inhalation, we could demonstrate a high local concentration in the lung as well as low plasma concentrations, suggesting no systemic JAK1 target engagement. Compound 16 has progressed into clinical trials. Using 16, we found JAK1 inhibition to be more efficacious than JAK3 inhibition in IL-4-driven Th2 asthma.

Role of the pioneer transcription factor GATA2 in health and disease

The transcription factor GATA2 is involved in human diseases ranging from hematopoietic disorders, to cancer, to infectious diseases. GATA2 is one of six GATA-family transcription factors that act as pioneering transcription factors which facilitate the opening of heterochromatin and the subsequent binding of other transcription factors to induce gene expression from previously inaccessible regions of the genome. Although GATA2 is essential for hematopoiesis and lymphangiogenesis, it is also expressed in other tissues such as the lung, prostate gland, gastrointestinal tract, central nervous system, placenta, fetal liver, and fetal heart. Gene or transcriptional abnormalities of GATA2 causes or predisposes patients to several diseases including the hematological cancers acute myeloid leukemia and acute lymphoblastic leukemia, the primary immunodeficiency MonoMAC syndrome, and to cancers of the lung, prostate, uterus, kidney, breast, gastric tract, and ovaries. Recent data has also linked GATA2 expression and mutations to responses to infectious diseases including SARS-CoV-2 and Pneumocystis carinii pneumonia, and to inflammatory disorders such as atherosclerosis. In this article we review the role of GATA2 in the etiology and progression of these various diseases.

Anti-GM-CSF Neutralizing Autoantibodies in Colombian Patients with Disseminated Cryptococcosis

BACKGROUND

Cryptococcosis is a potentially life-threatening fungal disease caused by encapsulated yeasts of the genus Cryptococcus, mostly C. neoformans or C. gattii. Cryptococcal meningitis is the most frequent clinical manifestation in humans. Neutralizing autoantibodies (auto-Abs) against granulocyte-macrophage colony-stimulating factor (GM-CSF) have recently been discovered in otherwise healthy adult patients with cryptococcal meningitis, mostly caused by C. gattii. We hypothesized that three Colombian patients with cryptococcal meningitis caused by C. neoformans in two of them would carry high plasma levels of neutralizing auto-Abs against GM-CSF.

METHODS

We reviewed medical and laboratory records, performed immunological evaluations, and tested for anti-cytokine auto-Abs three previously healthy HIV-negative adults with disseminated cryptococcosis.

RESULTS

Peripheral blood leukocyte subset levels and serum immunoglobulin concentrations were within the normal ranges. We detected high levels of neutralizing auto-Abs against GM-CSF in the plasma of all three patients.

CONCLUSIONS

We report three Colombian patients with disseminated cryptococcosis associated with neutralizing auto-Abs against GM-CSF. Further studies should evaluate the genetic contribution to anti-GM-CSF autoantibody production and the role of the GM-CSF signaling pathway in the immune response to Cryptococcus spp.

Pathological Comparison of Rat Pulmonary Models Induced by Silica Nanoparticles and Indium-Tin Oxide Nanoparticles

Purpose

The objective of this study was to evaluate and compare the histopathological implications of silica nanoparticles (Nano-SiO₂) and indium-tin oxide nanoparticles (Nano-ITO), in vivo.

Methods

Male Sprague-Dawley rats were exposed to Nano-SiO₂ (50 mg/kg) and Nano-ITO (6 mg/kg) by a single intratracheal instillation, respectively. Broncho-alveolar lavage fluid (BALF) and lung tissue were obtained at 7, 14, 28, and 56 days post exposure for analysis of BALF inflammatory factors, total protein, and for lung tissue pathology. Histopathological and ultrastructural change in lungs were investigated by hematoxylin and eosin, Masson’s trichrome, sirius red staining, periodic acid Schiff stain, and transmission electron microscopy. The expression of SP-A, collagen type I and III in lung tissue was determined by immunohistochemistry and ELISA.

Results

The rats in both models exhibited obvious collagen fibrosis and the severity of the lung injury increased with time after exposure to respective dosage increased. Several parameters of pulmonary inflammation and fibrosis significantly increased in both groups, which was reflected by increased LDH activity, total proteins, TNF-α, and IL-6 levels in BALF, and confirmed by histopathological examination. The results also showed that the two models exhibited different features. Exposure to Nano-ITO caused persistent chronic lung inflammation, illustrated by the infiltration of a large amount of enlarged and foamy macrophages and neutrophils into the lung parenchyma. In Nano-SiO₂ exposed rat lung tissue, granulomatous inflammation was most prominent followed by progressive and massive fibrotic nodules. Compared with the Nano-SiO₂ rats, Nano-ITO exposed rats exhibited significantly severe pulmonary alveolar proteinosis (PAP) pathological changes, lower fibrosis, and higher levels of inflammatory biomarkers. However, Nano-SiO₂ exposed rats had greater fibrosis pathological changes and more severe granulomas than Nano-ITO exposed rats.

Conclusion

This study suggests that the Nano-SiO₂-induced model has greater value in research into granulomas and fibrosis, while the Nano-ITO-induced model has greater repeatability in area of PAP.

A 44-year-old stone worker with progressive dyspnea: lessons from a new twist on an old foe

Silicosis is typically an indolent lung disease caused by long-standing occupational exposure to respirable crystalline silica, classically in professions such as sandblasting and mining.  An increasingly popular industry that has earned particular interest because of its association with silicosis is customization and installation of artificial stone countertops for domestic applications. In addition to causing a spike in cases of chronic and accelerated silicosis, both quite familiar to respiratory clinicians, outbreaks of artificial stone silicosis have brought to the fore a historically rare entity known as acute silicosis, or silicoproteinosis, a more rapid presentation of the disease. Failure to suspect this uncommon condition can lead to diagnostic confusion and therefore ineffective treatment as was true initially of the patient we describe herein.  The case description is followed by a clinical, radiological, and pathological overview of acute artificial stone silicosis (or silicoproteinosis), which is an emerging pneumoconiosis with sparse coverage in the literature to date.  This case also adds to the few existing reports on the use of therapeutic whole lung lavage for silicoproteinosis.      

Cryptococcus gattii Infection as the Major Clinical Manifestation in Patients with Autoantibodies Against Granulocyte-Macrophage Colony-Stimulating Factor

PURPOSE

Anti-granulocyte-macrophage colony-stimulating factor autoantibodies (anti-GM-CSF Abs) are a predisposing factor for pulmonary alveolar proteinosis (PAP) and Cryptococcus gattii cryptococcosis. This study aimed to investigate clinical manifestations in anti-GM-CSF Ab-positive patients with C. gattii cryptococcosis and analyze the properties of anti-GM-CSF Abs derived from these patients and patients with PAP.

METHODS

Thirty-nine patients diagnosed with cryptococcosis (caused by C. neoformans or C. gattii) and 6 with PAP were enrolled in the present study. Clinical information was obtained from medical records. Blood samples were collected for analysis of autoantibody properties. We also explored the National Health Insurance Research Database (NHIRD) of Taiwan to investigate the epidemiology of cryptococcosis and PAP.

RESULTS

High titers of neutralizing anti-GM-CSF Abs were identified in 15 patients with cryptococcosis (15/39, 38.5%). Most anti-GM-CSF Ab-positive cryptococcosis cases had central nervous system (CNS) involvement (14/15, 93.3%). Eleven out of 14 (78.6%) anti-GM-CSF Ab-positive CNS cryptococcosis patients were confirmed to be infected with C. gattii, and PAP did not occur synchronously or metachronously in a single patient from our cohort. Exploration of an association between HLA and anti-GM-CSF Ab positivity or differential properties of autoantibodies from cryptococcosis patients and PAP yielded no significant results.

CONCLUSION

Anti-GM-CSF Abs can cause two diseases, C. gattii cryptococcosis and PAP, which seldom occur in the same subject. Current biological evidence regarding the properties of anti-GM-CSF Abs cannot provide clues regarding decisive mechanisms. Further analysis, including more extensive cohort studies and investigations into detailed properties, is mandatory to better understand the pathogenesis of anti-GM-CSF Abs.

High-Density Lipoproteins: A Role in Inflammation in COPD

Chronic obstructive pulmonary disease (COPD) is a widespread disease associated with high rates of disability and mortality. COPD is characterized by chronic inflammation in the bronchi as well as systemic inflammation, which contributes significantly to the clinically heterogeneous course of the disease. Lipid metabolism disorders are common in COPD, being a part of its pathogenesis. High-density lipoproteins (HDLs) are not only involved in lipid metabolism, but are also part of the organism's immune and antioxidant defense. In addition, HDL is a versatile transport system for endogenous regulatory agents and is also involved in the removal of exogenous substances such as lipopolysaccharide. These functions, as well as information about lipoprotein metabolism disorders in COPD, allow a broader assessment of their role in the pathogenesis of heterogeneous and comorbid course of the disease.

Minute Cellular Nodules as Early Lesions in Rats with Silica Exposure via Inhalation

Mechanisms of silicosis have yet to be clarified, and pathological conditions are inaccurately described in some experimental studies on silicosis. This study was aimed at describing initial lesions in silicosis, as observed in rats with silica exposure via inhalation, and major histopathologic alterations. Male Wistar rats were exposed to silica for 24 weeks. Hematoxylin and eosin staining indicated the presence of “cellular nodule+ macrophage alveolitis” in rats exposed to silica from the 2–16 weeks time points and “fibrotic cellular + cellular nodule” in rats exposed to silica via inhalation for 24 weeks. By immunohistochemistry, the following were noted: a continual increase in the positive expression of CD68 in macrophages in the lungs of rats exposed to silica; hyperplasia in alveolar type II cells (AT2); loss of original phenotypes in fibrotic cellular nodules, macrophages, and AT2 cells; loss of endothelial cells in silicotic nodules; and positive expression of α-smooth muscle actin in macrophages. Typical pathological changes in silicosis were also summarized. Among these changes were macrophage alveolitis, cellular nodules, and fibrotic cellular nodules, including an increase in minute cellular nodules in the early stages and the formation of fibrotic cellular nodules in the late stages.

Macrophages, Metabolism and Heterophagy in the Heart

The heart is a never-stopping engine that relies on a formidable pool of mitochondria to generate energy and propel pumping. Because dying cardiomyocytes cannot be replaced, this high metabolic rate creates the challenge of preserving organelle fitness and cell function for life. Here, we provide an immunologist's perspective on how the heart solves this challenge, which is in part by incorporating macrophages as an integral component of the myocardium. Cardiac macrophages surround cardiomyocytes and capture dysfunctional mitochondria that these cells eject to the milieu, effectively establishing a client cell-support cell interaction. We refer to this heterologous partnership as heterophagy. Notably, this process shares analogies with other biological systems, is essential for proteostasis and metabolic fitness of cardiomyocytes, and unveils a remarkable degree of dependence of the healthy heart on immune cells for everyday function.

Whole lung lavage: Treating pulmonary alveolar proteinosis at the time of COVID pandemic

Pulmonary alveolar proteinosis (PAP) is a rare syndrome due to increased production or decreased clearance of surfactant in alveoli and terminal bronchi that cause hypoxemic respiratory insufficiency. Here we present a patient with PAP whose disease was exacerbated by superimposed COVID-19 pneumonia. He underwent whole lung lavage (WLL). Evaluation of the viral count of the first and the last lavage of the left lung showed viral load in the alveolar space dropped by approximately 10-folds, however the magnitude of the viral load was substantial in both lavage samples. Whole pulmonary lavage may be used as a treatment option on patients with PAP even when the disease is exacerbated by COVID-19 pneumonia.

The Role of GM-CSF Autoantibodies in Infection and Autoimmune Pulmonary Alveolar Proteinosis: A Concise Review

Autoantibodies to multiple cytokines have been identified and some, including antibodies against granulocyte-macrophage colony-stimulating factor (GM-CSF), have been associated with increased susceptibility to infection. High levels of GM-CSF autoantibodies that neutralize signaling cause autoimmune pulmonary alveolar proteinosis (aPAP), an ultrarare autoimmune disease characterized by accumulation of excess surfactant in the alveoli, leading to pulmonary insufficiency. Defective GM-CSF signaling leads to functional deficits in multiple cell types, including macrophages and neutrophils, with impaired phagocytosis and host immune responses against pulmonary and systemic infections. In this article, we review the role of GM-CSF in aPAP pathogenesis and pulmonary homeostasis along with the increased incidence of infections (particularly opportunistic infections). Therefore, recombinant human GM-CSF products may have potential for treatment of aPAP and possibly other infectious and pulmonary diseases due to its pleotropic immunomodulatory actions.

CISH attenuates homeostatic cytokine signaling to promote lung-specific macrophage programming and function

[Figure: see text].

IFN-γ is essential for alveolar macrophage driven pulmonary inflammation in macrophage activation syndrome

Macrophage activation syndrome (MAS) is a life-threatening cytokine storm complicating systemic juvenile idiopathic arthritis (SJIA) driven by IFNγ. SJIA and MAS are associated with an unexplained emerging lung disease (SJIA-LD), with our recent work supporting pulmonary activation of IFNγ pathways pathologically linking SJIA-LD and MAS. Our objective was to mechanistically define the novel observation of pulmonary inflammation in the TLR9 mouse model of MAS. In acute MAS, lungs exhibit mild but diffuse CD4-predominant, perivascular interstitial inflammation with elevated IFNγ, IFN-induced chemokines, and AMΦ expression of IFNγ-induced genes. Single-cell RNA-sequencing confirmed IFN-driven transcriptional changes across lung cell types with myeloid expansion and detection of MAS-specific macrophage populations. Systemic MAS resolution was associated with increased AMΦ and interstitial lymphocytic infiltration. AMΦ transcriptomic analysis confirmed IFNγ-induced proinflammatory polarization during acute MAS, which switches towards an anti-inflammatory phenotype after systemic MAS resolution. Interestingly, recurrent MAS led to increased alveolar inflammation and lung injury, and reset AMΦ polarization towards a proinflammatory state. Furthermore, in mice bearing macrophages insensitive to IFNγ, both systemic feature of MAS and pulmonary inflammation were attenuated. These findings demonstrate that experimental MAS induces IFNγ-driven pulmonary inflammation replicating key features of SJIA-LD, and provides a model system for testing novel treatments directed towards SJIA-LD.

Autoimmune pulmonary alveolar proteinosis successfully treated with lung lavage in an adolescent patient: a case report

Background

Pulmonary alveolar proteinosis is a rare interstitial lung disease characterized by accumulating surfactant materials in the alveoli. The autoimmune form is by far the most common in adults, while in the pediatric age group, the vast majority of cases are congenital. We report a case of an adolescent patient diagnosed with autoimmune pulmonary alveolar proteinosis, which is unusual in this age group.

Case presentation

A-15 year-old Saudi male presented to the emergency department with a history of shortness of breath and low oxygen saturation. High-resolution computed tomography of his chest showed a global crazy-paving pattern. Autoantibodies against granulocyte-macrophage colony-stimulating factor were detected in his serum. A diagnosis of the autoimmune form of pulmonary alveolar proteinosis was confirmed after excluding other possible causes. The patient improved after he underwent whole lung lavage under general anesthesia, and he was independent of oxygen therapy after 6 months of follow-up.

Conclusion

The autoimmune form of pulmonary alveolar proteinosis is rare in the pediatric age group and should be considered when no apparent cause of this disease was found. Whole lung lavage should be the first treatment modality offered in this setting with close follow-up and monitoring.

Pulmonary alveolar proteinosis complicated with tuberculosis: A case report

BACKGROUND

Pulmonary alveolar proteinosis (PAP) is a rare lung disease characterized by the accumulation of phospholipoproteinaceous material in the alveoli. Cases of PAP complicated with tuberculosis are much more complex and have rarely been well recorded.

CASE SUMMARY

We describe a 21-year-old Han Chinese patient with suspicious lung infection associated with mild restrictive ventilatory dysfunction and diffusion reduction. High resolution computed tomography revealed a “crazy-paving” appearance and multiple pulmonary miliary nodules around the bronchi. Bronchoalveolar lavage demonstrated a small amount of periodic acid-Schiff positive proteinaceous materials. A serological test for the presence of a Mycobacterium tuberculosis antibody and an interferon-gamma release assay were both positive. The patient received a standard course of first-line anti-tuberculosis treatment after diagnostic bronchoalveolar lavage. To date, clinical remission has been achieved and maintained for five years.

CONCLUSION

In summary, the diagnosis of PAP complicated with tuberculosis was supported by a combination of clinical manifestations, imaging, pulmonary function, laboratory examinations, bronchoalveolar lavage, etc. This case highlighted that diagnostic bronchoalveolar lavage in combination with anti-tuberculosis treatment is a safe and effective option for mild PAP patients with tuberculosis.

Immunoregulatory therapy strategies that target cytokine storms in patients with COVID-19 (Review)

A cytokine storm is an uncontrolled, excessive immune response that contributes to the pathogenesis of coronavirus disease 2019 (COVID-19). Viral infections lead to the loss of negative feedback in immune regulation and an abnormal elevation of the levels of multiple cytokines. In COVID-19, this causes diffuse damage to alveolar functions and may culminate in multiple organ dysfunction. Immunoregulatory therapies target the cytokine storms induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes COVID-19, and include monoclonal antibodies, recombinant granulocyte-macrophage colony stimulating factor, interferon, mesenchymal stem cell-based therapy, thymosin, immunoglobulins and blood purification therapies. These approaches may be effective in the alleviation of COVID-19 symptoms. In this review, cytokine storms caused by SARS-CoV-2 infections are evaluated and discussed, and advances in immunoregulatory therapy strategies for patients with COVID-19 are reviewed.

Calming the inflammatory storm in severe COVID-19 infections: Role of biologics- A narrative review

The risk of Coronavirus infection continues, and the fear of resurgence indicates the lack of a successful therapeutic strategy. In severe COVID-19 infection, many immune cells and their products are involved, making management difficult. The abundant release of cytokines and chemokines in severe COVID-19 patients leads to profound hyper inflammation and the mobilization of immune cells, triggering the cytokine storm. The complications associated with the cytokine storm include severe respiratory distress, intravascular coagulation, multi-organ failure, and death. The enormous formation of interleukin (IL)-6 and hemopoietic factors such as granulocyte-macrophage colony-stimulating factor (GM-CSF) are implicated in the severity of the infection. Moreover, these inflammatory cytokines and factors signal through the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway causing the activation of cytokine-related genes. The neutralization of these proteins could be of therapeutic help in COVID-19 patients and could mitigate the risk of mortality. IL-6 antagonist, IL-6 receptor antagonists, GM-CSF receptor inhibitors, and JAK-STAT inhibitors are being investigated to prevent intense lung injury in COVID-19 patients and increase the chances of survival. The review focuses the role of IL-6, GM-CSF, and JAK-STAT inhibitors in regulating the immune response in severely affected COVID-19 patients.

Mass spectrometry imaging of phosphatidylcholine metabolism in lungs administered with therapeutic surfactants and isotopic tracers

Mass spectrometry imaging (MSI) visualizes molecular distributions throughout tissues but is blind to dynamic metabolic processes. Here, MSI with high mass resolution together with multiple stable isotope labeling provided spatial analyses of phosphatidylcholine (PC) metabolism in mouse lungs. Dysregulated surfactant metabolism is central to many respiratory diseases. Metabolism and turnover of therapeutic pulmonary surfactants were imaged from distributions of intact and metabolic products of an added tracer, universally 13C-labeled dipalmitoyl PC (U13C-DPPC). The parenchymal distributions of newly synthesized PC species were also imaged from incorporations of methyl-D9-choline. This dual labeling strategy demonstrated both lack of inhibition of endogenous PC synthesis by exogenous surfactant and location of acyl chain remodeling processes acting on the U13C-DPPC-labeled surfactant, leading to formation of polyunsaturated PC lipids. This ability to visualize discrete metabolic events will greatly enhance our understanding of lipid metabolism in diverse tissues and has potential application to both clinical and experimental studies.

Cross-Talk Between Alveolar Macrophages and Lung Epithelial Cells is Essential to Maintain Lung Homeostasis

The main function of the lung is to perform gas exchange while maintaining lung homeostasis despite environmental pathogenic and non-pathogenic elements contained in inhaled air. Resident cells must keep lung homeostasis and eliminate pathogens by inducing protective immune response and silently remove innocuous particles. Which lung cell type is crucial for this function is still subject to debate, with reports favoring either alveolar macrophages (AMs) or lung epithelial cells (ECs) including airway and alveolar ECs. AMs are the main immune cells in the lung in steady-state and their function is mainly to dampen inflammatory responses. In addition, they phagocytose inhaled particles and apoptotic cells and can initiate and resolve inflammatory responses to pathogens. Although AMs release a plethora of mediators that modulate immune responses, ECs also play an essential role as they are more than just a physical barrier. They produce anti-microbial peptides and can secrete a variety of mediators that can modulate immune responses and AM functions. Furthermore, ECs can maintain AMs in a quiescent state by expressing anti-inflammatory membrane proteins such as CD200. Thus, AMs and ECs are both very important to maintain lung homeostasis and have to coordinate their action to protect the organism against infection. Thus, AMs and lung ECs communicate with each other using different mechanisms including mediators, membrane glycoproteins and their receptors, gap junction channels, and extracellular vesicles. This review will revisit characteristics and functions of AMs and lung ECs as well as different communication mechanisms these cells utilize to maintain lung immune balance and response to pathogens. A better understanding of the cross-talk between AMs and lung ECs may help develop new therapeutic strategies for lung pathogenesis.

Pharmacotherapy options in pulmonary alveolar proteinosis

INTRODUCTION

Pulmonary alveolar proteinosis (PAP) is a heterogeneous group of rare diseases characterized by the abnormal production and impaired degradation of pulmonary surfactant as a result of malfunctioning of alveolar macrophages. This is due to the downstream dysregulation of the GM-CSF pathway, which can be caused by specific autoantibodies (autoimmune, aPAP formerly known as idiopathic iPAP), direct injury to alveolar macrophages (e.g. by toxic inhaled agents.), or by genetic defects (hereditary or congenital PAP). Few pharmacotherapy options are currently available to treat this disease.

AREA COVERED

The authors discuss the exogenous administration of GM-CSF, rituximab, and the potential role of cholesterol lowering medications in this review. The authors, furthermore, provide their opinion on the available pharmacotherapeutic options and give their future perspectives.

EXPERT OPINION

Inhaled GM-CSF remains the most commonly used therapy in patients with iPAP but other inhaled therapies such as PPARγ activators should be considered, especially in patients who are partially responsive or unresponsive to traditional treatments.

Alveolar lipids in pulmonary disease. A review

Lung lipid metabolism participates both in infant and adult pulmonary disease. The lung is composed by multiple cell types with specialized functions and coordinately acting to meet specific physiologic requirements. The alveoli are the niche of the most active lipid metabolic cell in the lung, the type 2 cell (T2C). T2C synthesize surfactant lipids that are an absolute requirement for respiration, including dipalmitoylphosphatidylcholine. After its synthesis and secretion into the alveoli, surfactant is recycled by the T2C or degraded by the alveolar macrophages (AM). Surfactant biosynthesis and recycling is tightly regulated, and dysregulation of this pathway occurs in many pulmonary disease processes. Alveolar lipids can participate in the development of pulmonary disease from their extracellular location in the lumen of the alveoli, and from their intracellular location in T2C or AM. External insults like smoke and pollution can disturb surfactant homeostasis and result in either surfactant insufficiency or accumulation. But disruption of surfactant homeostasis is also observed in many chronic adult diseases, including chronic obstructive pulmonary disease (COPD), and others. Sustained damage to the T2C is one of the postulated causes of idiopathic pulmonary fibrosis (IPF), and surfactant homeostasis is disrupted during fibrotic conditions. Similarly, surfactant homeostasis is impacted during acute respiratory distress syndrome (ARDS) and infections. Bioactive lipids like eicosanoids and sphingolipids also participate in chronic lung disease and in respiratory infections. We review the most recent knowledge on alveolar lipids and their essential metabolic and signaling functions during homeostasis and during some of the most commonly observed pulmonary diseases.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection: let the virus be its own demise

There has been a collaborative global effort to construct novel therapeutic and prophylactic approaches to SARS-CoV-2 management. Although vaccine development is crucial, acute management of newly infected patients, especially those with severe acute respiratory distress syndrome, is a priority. Herein we describe the rationale and potential of repurposing a dual plasmid, Vigil (pbi-shRNA^furin-GM-CSF), now in Phase III cancer trials, for the treatment of and, in certain circumstances, enhancement of the immune response to SARS-CoV-2.

Secondary pulmonary alveolar proteinosis treated by lung transplant: A case report

BACKGROUND

Pulmonary alveolar proteinosis (PAP) is a pulmonary disease characterized by disruption of surfactant homeostasis resulting in its accumulation in the alveoli. PAP is classically classified into three categories (Table 1): 1/primary (or autoimmune) with antibodies targeting the GM-CSF pathway, 2/secondary to another disease, typically a hematologic malignancy, and 3/genetic.

CASE-REPORT

A 30 year-old woman received an allogenic hematopoietic stem cell transplantation (HSCT) after treatment for acute myeloid leukemia (AML). Within the first 6 months post HSCT, she developed an ocular, oral, digestive and hepatic graft-versus-host disease associated with a mixed ventilatory defect with a very severe obstructive syndrome and a severe CO diffusion impairment. High resolution computed tomography showed a classical "crazy paving" pattern. Aspect and differential cell count of BAL were normal. All microbiological samples remained culture negative. Histo-pathological analysis of transbronchial biopsies was unremarkable. Because of the severity of the respiratory insufficiency, open-lung biopsy (OBL) could not be performed. Despite multiple immunosuppressive therapies, lung function deteriorated rapidly; the patient also developed an excavated fungal lesion unresponsive to treatment. She underwent a bilateral lung transplant 48 months after HSCT. Histo-pathological analysis of explanted lungs showed obliterative bronchiolitis (OB), diffuse PAP and invasive cavitary pulmonary aspergillosis.

CONCLUSIONS

This case illustrates the simultaneous occurrence of OB, PAP and a fungal infection in a 30-year old female patient who underwent HSCT for acute myeloid leukemia (AML). To our knowledge this is the only documented case of PAP associated with OB treated by lung transplantation.

Lipid-Protein and Protein-Protein Interactions in the Pulmonary Surfactant System and Their Role in Lung Homeostasis

Pulmonary surfactant is a lipid/protein complex synthesized by the alveolar epithelium and secreted into the airspaces, where it coats and protects the large respiratory air–liquid interface. Surfactant, assembled as a complex network of membranous structures, integrates elements in charge of reducing surface tension to a minimum along the breathing cycle, thus maintaining a large surface open to gas exchange and also protecting the lung and the body from the entrance of a myriad of potentially pathogenic entities. Different molecules in the surfactant establish a multivalent crosstalk with the epithelium, the immune system and the lung microbiota, constituting a crucial platform to sustain homeostasis, under health and disease. This review summarizes some of the most important molecules and interactions within lung surfactant and how multiple lipid–protein and protein–protein interactions contribute to the proper maintenance of an operative respiratory surface.

Granulocyte-Macrophage Colony-Stimulating Factor Inhalation Therapy for Severe Pulmonary Alveolar Proteinosis

BACKGROUND

Some patients with pulmonary alveolar proteinosis (PAP) still present with high recurrence rate after large-volume whole lung lavage (WLL). Granulocyte-macrophage colony-stimulating factor (GM-CSF) has been proved to be effective for PAP, but clinical research on GM-CSF inhalation therapy combined with WLL for severe PAP is rare in Asia.

STUDY QUESTION

This study aimed to investigate the clinical efficacy of GM-CSF inhalation combined with WLL in Chinese patients with PAP.

STUDY DESIGN

We performed regression analysis on 33 patients with severe PAP who underwent WLL alone or WLL combined with GM-CSF inhalation. The patients were put into 2 groups, WLL group and GM-CSF/WLL group.

MEASURES AND OUTCOMES

Physiologic, serologic, and radiologic features of the 2 groups at different time points after treatment and the recurrence rates at 1-year follow-up were compared.

RESULTS

There were no significant differences in lung function, blood gas analysis indices, and lung CT between the 2 groups after 1-week treatment (P > 0.05). After 3-month treatment, the GM-CSF/WLL group showed significantly faster improvement in FEV1%Pred (P = 0.028), FVC%Pred (P = 0.014), PaO2 (P = 0.022), PA-aO2 (P = 0.009), PaO2/FiO2 (P = 0.025), 6-minute walking test (P = 0.002), and lung CT parameters (P < 0.05) compared with the WLL group. The recurrence rate at the 1-year follow-up in the GM-CSF/WLL group (5.5%) was significantly higher than that in the WLL group (46.67%; P < 0.05).

CONCLUSIONS

GM-CSF inhalation therapy combined with WLL is an effective treatment for patients with severe PAP, with further improvement in lung function at the base of WILL as well as reduction on re-WLL incidence.

The Role of Granulocyte-Macrophage Colony-Stimulating Factor in Murine Models of Multiple Sclerosis

Multiple sclerosis (MS) is an immune-mediated disease that predominantly impacts the central nervous system (CNS). Animal models have been used to elucidate the underpinnings of MS pathology. One of the most well-studied models of MS is experimental autoimmune encephalomyelitis (EAE). This model was utilized to demonstrate that the cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) plays a critical and non-redundant role in mediating EAE pathology, making it an ideal therapeutic target. In this review, we will first explore the role that GM-CSF plays in maintaining homeostasis. This is important to consider, because any therapeutics that target GM-CSF could potentially alter these regulatory processes. We will then focus on current findings related to the function of GM-CSF signaling in EAE pathology, including the cell types that produce and respond to GM-CSF and the role of GM-CSF in both acute and chronic EAE. We will then assess the role of GM-CSF in alternative models of MS and comment on how this informs the understanding of GM-CSF signaling in the various aspects of MS immunopathology. Finally, we will examine what is currently known about GM-CSF signaling in MS, and how this has promoted clinical trials that directly target GM-CSF.

Natural Autoantibodies in Chronic Pulmonary Diseases

In autoantibody-mediated autoimmune diseases, pathogenic autoantibodies generated by a failure of central or peripheral tolerance, have different effects mediated by a variety of mechanisms. Interestingly, even non-autoimmune chronic diseases have a set of disease-specific natural autoantibodies that are maintained for a long time. Because most of these natural autoantibodies target intracellular proteins or long non-coding RNAs, they are speculated to be non-pathological and have some important as yet unrecognized physiological functions such as debris clearance. Recently, we revealed a set of disease-specific natural autoantibodies of chronic pulmonary diseases with unknown etiology by protein arrays that enable detection of specific autoantibodies against >8000 targets. Surprisingly, some of the targeted antigens of disease-specific autoantibodies were subsequently reported by other laboratories as strongly associated with the disease, suggesting that these antigens reflect the pathology of each disease. Furthermore, some of these autoantibodies that target extracellular antigens might modify the original course of each disease. Here, we review the disease-specific natural autoantibodies of chronic pulmonary diseases, including chronic fibrosing idiopathic interstitial pneumonias, sarcoidosis, and autoimmune pulmonary alveolar proteinosis, and discuss their utility and effects.

Lung-restricted inhibition of Janus kinase 1 is effective in rodent models of asthma

Preclinical and clinical evidence indicates that a subset of asthma is driven by type 2 cytokines such as interleukin-4 (IL-4), IL-5, IL-9, and IL-13. Additional evidence predicts pathogenic roles for IL-6 and type I and type II interferons. Because each of these cytokines depends on Janus kinase 1 (JAK1) for signal transduction, and because many of the asthma-related effects of these cytokines manifest in the lung, we hypothesized that lung-restricted JAK1 inhibition may confer therapeutic benefit. To test this idea, we synthesized iJak-381, an inhalable small molecule specifically designed for local JAK1 inhibition in the lung. In pharmacodynamic models, iJak-381 suppressed signal transducer and activator of transcription 6 activation by IL-13. Furthermore, iJak-381 suppressed ovalbumin-induced lung inflammation in both murine and guinea pig asthma models and improved allergen-induced airway hyperresponsiveness in mice. In a model driven by human allergens, iJak-381 had a more potent suppressive effect on neutrophil-driven inflammation compared to systemic corticosteroid administration. The inhibitor iJak-381 reduced lung pathology, without affecting systemic Jak1 activity in rodents. Our data show that local inhibition of Jak1 in the lung can suppress lung inflammation without systemic Jak inhibition in rodents, suggesting that this strategy might be effective for treating asthma.

An updated review on phenocopies of primary immunodeficiency diseases

Primary immunodeficiency diseases (PIDs) refer to a heterogenous group of disorders characterized clinically by increased susceptibility to infections, autoimmunity and increased risk of malignancies.

These group of disorders present with clinical manifestations similar to PIDs with known genetic defects but have either no genetic defect or have a somatic mutation and thus have been labelled as “Phenocopies of PIDs”. These diseases have been further subdivided into those associated with somatic mutations and those associated with presence of auto-antibodies against various cytokines.

In this review, we provide an update on clinical manifestations, diagnosis and management of these diseases.

Greater Efficacy of Black Ginseng (CJ EnerG) over Red Ginseng against Lethal Influenza A Virus Infection

Black ginseng (BG, CJ EnerG), prepared via nine repeated cycles of steaming and drying of fresh ginseng, contains more accessible acid polysaccharides and smaller and less polar ginsenosides than red ginseng (RG) processed only once. Because RG exhibits the ability to increase host protection against viral respiratory infections, we investigated the antiviral effects of BG. Mice were orally administered either BG or RG extract at 10 mg/kg bw daily for two weeks. Mice were then infected with a A(H1N1) pdm09 (A/California/04/2009) virus and fed extracts for an additional week. Untreated, infected mice were assigned to either the negative control, without treatments, or the positive control, treated with Tamiflu. Infected mice were monitored for 14 days to determine the survival rate. Lung tissues were evaluated for virus titer and by histological analyses. Cytokine levels were measured in bronchoalveolar lavage fluid. Mice treated with BG displayed a 100% survival rate against infection, while mice treated with RG had a 50% survival rate. Further, mice treated with BG had fewer accumulated inflammatory cells in bronchioles following viral infection than did mice treated with RG. BG also enhanced the levels of GM-CSF and IL-10 during the early and late stages of infection, respectively, compared to RG. Thus, BG may be useful as an alternative antiviral adjuvant to modulate immune responses to influenza A virus.

Pulmonary alveolar proteinosis with upper-lobe predominance in a non-smoking female

In this report, we describe an unusual manifestation of pulmonary alveolar proteinosis (PAP). The patient is a 43-year-old non-smoking female without underlying hematologic or auto-immune disorder. Her initial presentation included non-specific respiratory symptoms (exertional dyspnoea and cough), an unremarkable physical examination, a mild elevation in her serum level of lactate dehydrogenase, a mild impairment in the diffusion capacity for carbon monoxide but a normal spirometry, and multiple ground-glass opacities with a "crazy-paving" pattern predominantly in upper lung zones on her chest radiographic images. PAP was diagnosed histologically. PAP commonly occurs in males with smoking history, and tends to affect the lung parenchyma diffusely or, as in auto-immune PAP, lower lobes predominantly. Upper-lobe predominant PAP, particularly in a non-smoking female, is rare. This report would add PAP to the list of differential diagnosis for upper-lung ground-glass opacities. A review on the relevant literature is also included in the discussion.

Avian pulmonary proteinosis: six cases and a review of the literature

Pulmonary alveolar proteinosis (PAP) is a disease of surfactant clearance in which functional abnormalities in alveolar macrophages lead to accumulation of surfactant within alveoli in mammals. Histologic examination of 6 avian autopsies, including 4 chickens, a turkey, and a cockatiel, revealed accumulation of hypereosinophilic densely arrayed lamellar material in the lungs that was magenta by periodic acid-Schiff stain and diastase resistant. Transmission electron microscopy of the proteinaceous material in 2 cases demonstrated alternating electron-dense and electron-lucent lamellae that formed whorls and had a regular periodicity of 6-14 nm, consistent with pulmonary surfactant. Given the anatomic differences between avian and mammalian lungs, we designated the presented condition "pulmonary proteinosis," which can be observed as both an incidental finding or, when severe, may be a contributing factor to death through respiratory failure.

Pulmonary alveolar proteinosis

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

Myeloid malignancies with somatic GATA2 mutations can be associated with an immunodeficiency phenotype

Germline mutations in GATA2 are associated with a complex immunodeficiency and cancer predisposition syndrome. Somatic GATA2^mut in myeloid malignancies may impart a similar phenotype. We reviewed adult patients with a diagnosis of GATA2^mut hematological malignancy who were referred to our HHMC for genetic testing, and identified to have somatic GATA2^mut. Nine patients with a median age of 63 years were included. Six patients (66.7%) were males. Atypical CML and acute myeloid leukemia were the most common initial presentation. The median overall VAF was 47.14%. Monocytopenia was pronounced when the GATA2^mut involved the C-terminal ZFD. GATA2 N-terminal ZFD mutations tend to be co-mutated with biCEBPA^mut. Unlike germline GATA2 mutations, monocytopenia associated with somatic GATA2 mutations often resolved at remission. We concluded that similar to germline GATA2 mutations, a subset of somatic GATA2 mutations can impart a germline phenotype.

Granulocyte-Macrophage Colony-Stimulating Factor as a Therapeutic Target in Multiple Sclerosis

Multiple sclerosis is an inflammatory neurodegenerative disease of the central nervous system (CNS) and the most frequent cause of non-traumatic disability in adults in the Western world. Currently, several drugs have been approved for the treatment of multiple sclerosis. While the newer drugs are more effective, they have less favourable safety profiles. Thus, there is a need to identify new targets for effective and safe therapies, particularly in patients with progressive disease for whom no treatments are available. One such target is granulocyte-macrophage colony-stimulating factor (GM-CSF) or its receptor. In this article we review data on the potential role of GM-CSF and GM-CSF inhibition in MS. We discuss the expression and function of GM-CSF and its receptor in the CNS, as well as data from animal studies and clinical trials in MS.

An immune cell spray (ICS) formulation allows for the delivery of functional monocyte/macrophages

Macrophages are key cells of the innate immune system and act as tissue resident macrophages (TRMs) in the homeostasis of various tissues. Given their unique functions and therapeutic use as well as the feasibility to derive macrophages in vitro from hematopoietic stem cell (HSC) sources, we propose an “easy-to-use” immune cell spray (ICS) formulation to effectively deliver HSC-derived macrophages. To achieve this aim, we used classical pump spray devices to spray either the human myeloid cell line U937 or primary murine HSC-derived macrophages. For both cell types used, one puff could deliver cells with maintained morphology and functionality. Of note, cells tolerated the spraying process very well with a recovery of more than 90%. In addition, we used osmotic preconditioning to reduce the overall cell size of macrophages. While a 800 mosm hyperosmolar sucrose solution was able to reduce the cell size by 27%, we identified 600 mosm to be effective to reduce the cell size by 15% while maintaining macrophage morphology and functionality. Using an isolated perfused rat lung preparation, the combinatorial use of the ICS with preconditioned and genetically labeled U937 cells allowed the intra-pulmonary delivery of cells, thus paving the way for a new cell delivery platform.

NAMPT: A pleiotropic modulator of monocytes and macrophages

Nicotinamide phosphoribosyltransferase (NAMPT) is the bottleneck enzyme of the NAD salvage pathway and thereby is a controller of intracellular NAD concentrations. It has been long known that the same enzyme can be secreted by a number of cell types and acts as a cytokine, although its receptor is at present unknown. Investigational compounds have been developed that target the enzymatic activity as well as the extracellular action (i.e. neutralizing antibodies). The present contribution reviews the evidence that links intracellular and extracellular NAMPT to myeloid biology, for example governing monocyte/macrophage differentiation, polarization and migration. Furthermore, it reviews the evidence that links this protein to some disorders in which myeloid cells have a prominent role (acute infarct, inflammatory bowel disease, acute lung injury and rheumatoid arthritis) and the data showing that inhibition of the enzymatic activity or the neutralization of the cytokine is beneficial in preclinical animal models.

New interplay between interstitial and alveolar macrophages explains pulmonary alveolar proteinosis (PAP) induced by indium tin oxide particles

Occupational exposure to indium tin oxide (ITO) particles has been associated with the development of severe lung diseases, including pulmonary alveolar proteinosis (PAP). The mechanisms of this lung toxicity remain unknown. Here, we reveal the respective roles of resident alveolar (Siglec-F^high AM) and recruited interstitial (Siglec-F^low IM) macrophages contributing in concert to the development of PAP. In mice treated with ITO particles, PAP is specifically associated with IL-1α (not GM-CSF) deficiency and Siglec-F^high AM (not Siglec-F^low IM) depletion. Mechanistically, ITO particles are preferentially phagocytosed and dissolved to soluble In³⁺ by Siglec-F^low IM. In contrast, Siglec-F^high AM weakly phagocytose or dissolve ITO particles, but are sensitive to released In³⁺ through the expression of the transferrin receptor-1 (TfR1). Blocking pulmonary Siglec-F^low IM recruitment in CCR2-deficient mice reduces ITO particle dissolution, In³⁺ release, Siglec-F^high AM depletion, and PAP formation. Restoration of IL-1-related Siglec-F^high AM also prevented ITO-induced PAP. We identified a new mechanism of secondary PAP development according to which metal ions released from inhaled particles by phagocytic IM disturb IL-1α-dependent AM self-maintenance and, in turn, alveolar clearance.

Macrophages and lipid metabolism

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The transcriptional signature of Kupffer cells & Alveolar macrophages are enriched for lipid metabolism genes.

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Lipid metabolism may control macrophage phenotype.

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Dysregulated lipid metabolism in macrophages contributes to disease pathology.

Distinct macrophage populations throughout the body display highly heterogeneous transcriptional and epigenetic programs. Recent research has highlighted that these profiles enable the different macrophage populations to perform distinct functions as required in their tissue of residence, in addition to the prototypical macrophage functions such as in innate immunity. These ‘extra’ tissue-specific functions have been termed accessory functions. One such putative accessory function is lipid metabolism, with macrophages in the lung and liver in particular being associated with this function. As it is now appreciated that cell metabolism not only provides energy but also greatly influences the phenotype and function of the cell, here we review how lipid metabolism affects macrophage phenotype and function and the specific roles played by macrophages in the pathogenesis of lipid-related diseases. In addition, we highlight the current questions limiting our understanding of the role of macrophages in lipid metabolism.