Progranulin is a substrate for neutrophil-elastase and proteinase-3 in the airway and its concentration correlates with mediators of airway inflammation in COPD

Progranulin in Musculoskeletal Inflammatory and Degenerative Disorders, Focus on Rheumatoid Arthritis, Lupus and Intervertebral Disc Disease: A Systematic Review

Progranulin (PGRN) is a glycoprotein formed by 593 amino acids encoded by the GRN gene. It has an important role in immunity and inflammatory response, as well as in tissue recovery. Its role in musculoskeletal inflammatory diseases such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and intervertebral disc degeneration disease (IVDD), is, nowadays, an important target to investigate. The objective of this review is to systematically sum up all the recent findings concerning PGRN as a target in the development and resolution of the inflammatory diseases. PubMed was examined with the terms combinations (Progranulin) AND (Lupus Erythematosus, Systemic), (Progranulin) AND (Arthritis, Rheumatoid), and (Progranulin) AND (Intervertebral Disc Degeneration). PubMed was examined with the terms combinations (Atsttrin) AND (Lupus Erythematosus, Systemic), (Atsttrin) AND (Arthritis, Rheumatoid), and (Atsttrin) AND (Intervertebral Disc Degeneration). Moreover, research through Web of Science was performed searching the same items. The inclusion criteria were: studies whose main topic were progranulin, or atsttrin, with emphasis on the three selected diseases. On the other hand, the exclusion criteria were studies that only focused on diseases not related to RA, lupus or IVDD, in addition to the previous published literature reviews. Since few results were obtained, we did not filter by year. The records assessed for eligibility were 23, including all the studies with the information in state of art of progranulin and its capability to be a potential target or treatment for each one of the selected diseases. As these results are descriptive and not clinical trials, we did not perform risk of bias methods. Within these results, many studies have shown an anti-inflammatory activity of PGRN in RA. PGRN levels in serum and synovial fluids in RA patients were reported higher than controls. On the other hand, serum levels were directly correlated with SLE disease activity index, suggesting an important role of PGRN as a player in the progression of inflammatory diseases and a therapeutical approach for the recovery. This review has some limitations due to the small number of studies in this regard; therefore, we highlight the importance and the necessity of further investigation. No external funding was implicated in this systematical review.

Association between chronic obstructive pulmonary disease and periodontitis: The common role of innate immune cells?

Innate immune cells are of broad interest in a variety of diseases. These cells include neutrophils, macrophages, dendritic cells and mast cells, etc. Innate immune cells are often mentioned in inflammatory diseases as the first line of defense against pathogens' invasion. As chronic obstructive pulmonary disease and periodontitis are inflammatory diseases, innate immune cells play an important role in the development of both diseases. COPD and periodontitis are common epidemic diseases with a very high prevalence, thus affecting a large number of people and also reducing the quality of life of patients. In addition, epidemiological studies suggested a link between the two, creating a co-morbid burden, but the mechanism of the link is yet to be explained. This article discusses the possible mechanism of the link between the two diseases in terms of innate immune cells and discusses possible future targeted therapies that could alleviate the burden on patients.

Charge and Redox States Modulate Granulin-TDP-43 Coacervation Toward Phase Separation or Aggregation

Cytoplasmic inclusions containing aberrant proteolytic fragments of TDP-43 are associated with frontotemporal lobar degeneration (FTLD) and other related pathologies. In FTLD, TDP-43 is translocated into the cytoplasm and proteolytically cleaved to generate a prion-like domain (PrLD) containing C-terminal fragments (C25 and C35) that form toxic inclusions. Under stress, TDP-43 partitions into membraneless organelles called stress granules (SGs) by coacervating with RNA and other proteins. To glean into the factors that influence the dynamics between these cytoplasmic foci, we investigated the effects of cysteine-rich granulins (GRNs 1-7), which are the proteolytic products of progranulin, a protein implicated in FTLD, on TDP-43. We show that extracellular GRNs, typically generated during inflammation, internalize and colocalize with PrLD as puncta in the cytoplasm of neuroblastoma cells but show less likelihood of their presence in SGs. In addition, we show GRNs and PrLD coacervate to undergo liquid-liquid phase separation (LLPS) or form gel- or solid-like aggregates. Using charge patterning and conserved cysteines among the wild-type GRNs as guides, along with specifically engineered mutants, we discover that the negative charges on GRNs drive LLPS while the positive charges and the redox state of cysteines modulate these phase transitions. Furthermore, RNA and GRNs compete and expel one another from PrLD condensates, providing a basis for GRN's absence in SGs. Together, the results help uncover potential modulatory mechanisms by which extracellular GRNs, formed during chronic inflammatory conditions, could internalize, and modulate cytoplasmic TDP-43 inclusions in proteinopathies.

Progranulin as a Potential Therapeutic Target in Immune-Mediated Diseases

Progranulin (PGRN), a secretory glycoprotein consisting of 593 amino acid residues, is a key actor and regulator of multiple system functions such as innate immune response and inflammation, as well as tissue regeneration. Recently, there is emerging evidence that PGRN is protective in the development of a variety of immune-mediated diseases, including rheumatoid arthritis (RA), inflammatory bowel disease (IBD), type 1 diabetes mellitus (T1DM) and multiple sclerosis (MS) by regulating signaling pathways known to be critical for immunology, particularly the tumor necrosis factor alpha/TNF receptor (TNF-α/TNFR) signaling pathway. Whereas, the role of PGRN in psoriasis, systemic lupus erythematosus (SLE) and systemic sclerosis (SSc) is controversial. This review summarizes the immunological functions of PGRN and its role in the pathogenesis of several immune-mediated diseases, in order to provide new ideas for developing therapeutic strategies for these diseases.

Progranulin/GP88, A Complex and Multifaceted Player of Tumor Growth by Direct Action and via the Tumor Microenvironment

Investigation of the role of progranulin/GP88 on the proliferation and survival of a wide variety of cells has been steadily increasing. Several human diseases stem from progranulin dysregulation either through its overexpression in cancer or its absence as in the case of null mutations in some form of frontotemporal dementia. The present review focuses on the role of progranulin/GP88 in cancer development, progression, and drug resistance. Various aspects of progranulin identification, biology, and signaling pathways will be described. Information will be provided about its direct role as an autocrine growth and survival factor and its paracrine effect as a systemic factor as well as via interaction with extracellular matrix proteins and with components of the tumor microenvironment to influence drug resistance, migration, angiogenesis, inflammation, and immune modulation. This chapter will also describe studies examining progranulin/GP88 tumor tissue expression as well as circulating level as a prognostic factor for several cancers. Due to the wealth of publications in progranulin, this review does not attempt to be exhaustive but rather provide a thread to lead the readers toward more in-depth exploration of this fascinating and unique protein.

Macrophage-derived progranulin promotes allergen-induced airway inflammation

BACKGROUND

Progranulin (PGRN), mainly produced by immune and epithelial cells, has been known to be involved in the development of various inflammatory diseases. However, the function of PGRN in allergic airway inflammation has not been clearly elucidated, and we investigated the role of PGRN in allergic airway inflammation.

METHODS

Production of PGRN and various type 2 cytokines was evaluated in mouse airways exposed to house dust mite allergen, and main cellular sources of these molecules were investigated using macrophage, airway epithelial cell, and NKT cell lines. We elucidated the role of PGRN in allergic airway inflammation in mouse models of asthma using macrophage-derived PGRN-deficient mice and NKT cell knockout mice by evaluating cytokine levels in bronchoalveolar lavage fluids and histopathology. We also supplemented recombinant PGRN in the mouse models to confirm the role of PGRN in allergic airway inflammation.

RESULTS

PGRN production preceded other cytokines, mainly from macrophages, in the airway exposed to allergen. PGRN induced IL-4 and IL-13 production in NKT cells and IL-33 and TSLP in airway epithelial cells. PGRN-induced Th2 cytokine production was abolished in NKT-deficient mice. Finally, allergic inflammation was significantly attenuated in allergen-exposed PGRN-deficient mice, but inflammation was restored when recombinant PGRN was supplemented during the allergen sensitization period.

CONCLUSION

The presence of macrophage-derived PGRN in airways in the early sensitization period may be critical for mounting a Th2 immune response and for following an allergic airway inflammation pathway via induction of type 2 cytokine production in NKT and airway epithelial cells.

Recent advances in the study of progranulin and its role in sepsis

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. The mortality rate of in-hospital patients whose conditions are complicated by sepsis remains high in spite of intensive-care treatment, therefore placing a significant financial burden on the health care system. In recent years, progranulin (PGRN), a cysteine-rich secretory protein (CRISP), has been found to play a crucial role in sepsis. PGRN participates in the pathogenesis of sepsis via diverse pathways, including bacterial clearance, cell growth and survival, tissue repair, and the regulation of inflammation. PGRN knockout mice suffer from serious infectious processes, whereas therapeutic administration of recombinant PGRN to such mice enhances bacterial clearance and reduces organ injury and mortality rate. Even though PGRN plays an important role in regulating sepsis, its potential mechanisms have not been completely clarified. In this review, we summarize the most recent research advances in the study of PGRN and its role in sepsis.

The role of progranulin (PGRN) in the modulation of anti-inflammatory response in asthma

Asthma is one of the most common chronic diseases. Epidemiological studies show that asthma will develop among around 40% of children under six years old with symptoms of bronchial obstruction. Diagnosis of asthma is complicated, especially in the paediatric population. As a result, a lot of research is being carried out to establish the pathophysiology and to find new biomarkers of this disease. Progranulin (PGRN) is a recently discovered growth factor with many biological functions. PGRN has anti-inflammatory properties because it inhibits neutrophil degranulation and blocks tumor necrosis factor α (TNF-α) transmission. The underlying mechanisms are still being researched, but TNF-α is considered to be a cytokine responsible for neutrophilic inflammation in the airways and bronchial hyperresponsiveness. Therefore, PGRN, by lowering TNF-α concentration and stimulating regulatory T-cell (Treg) proliferation, relieves symptoms of bronchial inflammatory diseases. This article attempts to verify the current knowledge about basic pathophysiological mechanisms in asthma. We also summarise the most recent research advances in the role of PGRN in the respiratory system.

Microglial Progranulin: Involvement in Alzheimer's Disease and Neurodegenerative Diseases

Neurodegenerative diseases such as Alzheimer’s disease have proven resistant to new treatments. The complexity of neurodegenerative disease mechanisms can be highlighted by accumulating evidence for a role for a growth factor, progranulin (PGRN). PGRN is a glycoprotein encoded by the GRN/Grn gene with multiple cellular functions, including neurotrophic, anti-inflammatory and lysosome regulatory properties. Mutations in the GRN gene can lead to frontotemporal lobar degeneration (FTLD), a cause of dementia, and neuronal ceroid lipofuscinosis (NCL), a lysosomal storage disease. Both diseases are associated with loss of PGRN function resulting, amongst other features, in enhanced microglial neuroinflammation and lysosomal dysfunction. PGRN has also been implicated in Alzheimer’s disease (AD). Unlike FTLD, increased expression of PGRN occurs in brains of human AD cases and AD model mice, particularly in activated microglia. How microglial PGRN might be involved in AD and other neurodegenerative diseases will be discussed. A unifying feature of PGRN in diseases might be its modulation of lysosomal function in neurons and microglia. Many experimental models have focused on consequences of PGRN gene deletion: however, possible outcomes of increasing PGRN on microglial inflammation and neurodegeneration will be discussed. We will also suggest directions for future studies on PGRN and microglia in relation to neurodegenerative diseases.

Innate Anti-microbial and Anti-chemotaxis Properties of Progranulin in an Acute Otitis Media Mouse Model

Acute otitis media (AOM) is one of the most common infectious diseases primarily caused by Streptococcus pneumoniae (S.pn) among children. Progranulin (PGRN) is a multifunctional growth factor widely expressed in various tissues and cells. Studies have confirmed that PGRN is involved in the development of a variety of inflammatory diseases. We found that the expression of PGRN increased significantly in the middle ear of wild mice with AOM. However, its physiological functions in AOM still remain unknown. To examine the role of PGRN during AOM, we established an acute otitis media model in both C57BL/6 wild mice and PGRN-deficient (PGRN^−/−) mice via transbullar injection with S.pn clinical strain serotype 19F. Interestingly, we observed dual results: on one hand, macrophage recruitment notably increased in PGRN^−/− mice compared with WT mice; on the other hand, the overall bacterial clearance was surprisingly dampened in PGRN^−/− mice. The enhanced recruitment of macrophages was associated with increased production of chemokine (C-C motif) ligand 2 (CCL2), while the decreased bacterial clearance was associated with impaired endocytosis capacity of macrophages. The scavenging ability of bacteria in PGRN^−/− mice was recovered with administration of recombinant PGRN. These results suggested a novel dual role of PGRN in affecting the activities of macrophages.

Progranulin is a novel biomarker for predicting an acute exacerbation of chronic obstructive pulmonary disease

BACKGROUND

Progranulin is a pleiotropic glycosylated protein precursor that plays an important role in inflammation. Limited data exist regarding the role of progranulin in the acute exacerbation of chronic obstructive pulmonary disease (AECOPD).

OBJECTIVES

The study is to assess the efficiency of progranulin as a circulating biomarker of AECOPD.

METHODS

The plasma progranulin levels were measured and compared in patients with AECOPD (n = 52), patients with stable COPD (n = 56), and healthy controls (n = 36). In patients with AECOPD, plasma progranulin levels were measured repeatedly on the last day of hospitalization. Demographical data, pulmonary function, and laboratory parameters were recorded.

RESULTS

Patients with AECOPD had higher plasma progranulin levels than both stable COPD patients and healthy controls (158.77 ± 48.17, 109.00 ± 25.05, 93.67 ± 14.71 ng/mL, respectively; P < .001). In patients with AECOPD, the plasma progranulin levels significantly decreased on the last day of hospitalization compared with those on the first day of hospitalization (138.51 ± 44.68 vs. 158.77 ± 48.17 ng/mL, P = .042). The progranulin levels were negatively correlated to FEV1%pred but positively correlated to neutrophil-to-lymphocyte ratio and C-reactive protein in all patients with COPD. Multivariate logistic regression and ROC analysis revealed progranulin (odds ratio 1.05, 95% confidence interval 1.03-1.08, P < .001) as an independent predictor of AECOPD, with an area under the curve of 0.82.

CONCLUSIONS

Progranulin may be a valuable blood biomarker of AECOPD and progranulin may be involved in the pathogenesis of AECOPD by disturbing inflammatory responses.

Proteinase 3; a potential target in chronic obstructive pulmonary disease and other chronic inflammatory diseases

Chronic Obstructive Pulmonary Disease (COPD) is a common, multifactorial lung disease which results in significant impairment of patients' health and a large impact on society and health care burden. It is believed to be the result of prolonged, destructive neutrophilic inflammation which results in progressive damage to lung structures. During this process, large quantities of neutrophil serine proteinases (NSPs) are released which initiate the damage and contribute towards driving a persistent inflammatory state.Neutrophil elastase has long been considered the key NSP involved in the pathophysiology of COPD. However, in recent years, a significant role for Proteinase 3 (PR3) in disease development has emerged, both in COPD and other chronic inflammatory conditions. Therefore, there is a need to investigate the importance of PR3 in disease development and hence its potential as a therapeutic target. Research into PR3 has largely been confined to its role as an autoantigen, but PR3 is involved in triggering inflammatory pathways, disrupting cellular signalling, degrading key structural proteins, and pathogen response.This review summarises what is presently known about PR3, explores its involvement particularly in the development of COPD, and indicates areas requiring further investigation.

Role of clusterin/progranulin in toluene diisocyanate-induced occupational asthma

Toluene diisocyanate (TDI) exposure induces oxidative stress and epithelial cell-derived inflammation, which affect the pathogenesis of TDI-induced occupational asthma (TDI-OA). Recent studies suggested a role for clusterin (CLU) and progranulin (PGRN) in oxidative stress-mediated airway inflammation. To evaluate CLU and PGRN involvement in airway inflammation in TDI-OA, we measured their serum levels in patients with TDI-OA, asymptomatic exposed controls (AECs), and unexposed healthy normal controls (NCs). Serum CLU and PGRN levels were significantly lower in the TDI-OA group than in the AEC and NC groups (P < 0.05). The sensitivity and specificity for predicting the TDI-OA phenotype were 72.4% and 53.4% when either CLU or PGRN levels were below the cutoff values (≤125 μg/mL and ≤68.4 ng/mL, respectively). If both parameters were below the cutoff levels, the sensitivity and specificity were 58.6% and 89.8%, respectively. To investigate CLU and PGRN function, we evaluated their production by human airway epithelial cells (HAECs) in response to TDI exposure and co-culturing with neutrophils. TDI-human serum albumin stimulation induced significant CLU/PGRN release from HAECs in a dose-dependent manner, which positively correlated with IL-8 and folliculin levels. Co-culturing with neutrophils significantly decreased CLU/PGRN production by HAECs. Intracellular ROS production in epithelial cells co-cultured with neutrophils tended to increase initially, but the ROS production decreased gradually at a higher ratio of neutrophils. Our results suggest that CLU and PGRN may be involved in TDI-OA pathogenesis by protecting against TDI-induced oxidative stress-mediated inflammation. The combined CLU/PGRN serum level may be used as a potential serological marker for identifying patients with TDI-OA among TDI-exposed workers.

Cigarette Smoke Extract Enhances IL-17A-Induced IL-8 Production via Up-Regulation of IL-17R in Human Bronchial Epithelial Cells

Interleukin-17A (IL-17A) is a pro-inflammatory cytokine mainly derived from T helper 17 cells and is known to be involved in the pathogenesis of chronic obstructive pulmonary disease (COPD). Cigarette smoke (CS) has been considered as a primary risk factor of COPD. However, the interaction between CS and IL-17A and the underlying molecular mechanisms have not been clarified. In the current study, we investigated the effects of cigarette smoke extract (CSE) on IL-17A-induced IL-8 production in human bronchial epithelial cells, and sought to identify the underlying molecular mechanisms. IL-8 production was significantly enhanced following treatment with both IL-17A and CSE, while treatment with either IL-17A or CSE alone caused only a slight increase in IL-8 production. CSE increased the transcription of IL-17RA/RC and surface membrane expression of IL-17R, which was suppressed by an inhibitor of the phosphoinositide 3-kinase (PI3K)/Akt pathway (LY294002). CSE caused inactivation of glycogen synthase kinase-3β (GSK-3β) via the PI3K/Akt pathway. Blockade of GSK-3β inactivation by overexpression of constitutively active GSK-3β (S9A) completely suppressed the CSE-induced up-regulation of IL-17R expression and the CSE-induced enhancement of IL-8 secretion. In conclusion, inactivation of GSK-3β via the PI3K/Akt pathway mediates CSE-induced up-regulation of IL-17R, which contributes to the enhancement of IL-17A-induced IL-8 production.

A BODIPY-Tagged Phosphono Peptide as Activity-Based Probe for Human Leukocyte Elastase

Human leukocyte elastase plays a crucial role in a variety of inflammatory disorders and represents an important subject of biomedical studies. The chemotype of peptidic phosphonates was employed for the design of a new activity-based probe for human leukocyte elastase. Its structure combines the phosphonate warhead with an adequate peptide portion and a BODIPY fluorophore with a clickable ethinylphenyl moiety at meso position. The probe 6 was assembled by copper-catalyzed alkyne-azide 1,3-dipolar cycloaddition. It was characterized as an active site-directed elastase inhibitor exhibiting a second-order rate constant of inactivation of 88400 M^-1s^-1. The suitability of 6 as a fluorescent probe for human leukocyte elastase was demonstrated by in-gel fluorescence analysis. Labeling experiments and inhibition data toward a panel of related proteases underlined the selectivity of the probe for the targeted leukocyte elastase.

Effect of Pingchuan Guben decoction on patients with chronic obstructive pulmonary disease: Results from a randomized comparative effectiveness research trial

Chronic obstructive pulmonary disease (COPD) is known to be a systemic low-grade ongoing inflammation exerting major health and economic burden worldwide. Complementary and alternative medicines, such as Traditional Chinese Medicine, are widely used for the treatment of patients with COPD. The present study was designed to investigate the efficacy of Pingchuan Guben decoction on patients with COPD through a double-blinded, open-labeled, randomized controlled trial. A total of 86 patients were randomly assigned to two groups, with 43 patients in the intervention group and 43 cases in the control group. The patients in the control group were treated with conventional western medicine, and the intervention group received a combination of conventional western medicine and Pingchuan Guben decoction. After 12 weeks of treatment, the mean 6-minute walking distance, forced expiratory volume in 1 sec (FEV1), forced vital capacity (FVC) and FEV1/FVC in the intervention group were significantly higher than those of the control group (P<0.05). The levels of inflammation factors and protease molecules were significantly ameliorated in the intervention group compared with the control group (P<0.05). The levels of Kelch-like ECH-associated protein 1 (Keap1), nuclear factor-E2-related factor-2 (Nrf2), superoxide anions, malondialdehyde, glutathione S-transferase and glutathione peroxidase were significantly more improved in the intervention group compared with those in the control group over the 12-week study period (P<0.05). Therefore, combinations of western medicine with Pingchuan Guben decoction may exert therapeutic effects on patients with COPD via modulations of inflammation factors and protease molecules, as well as the activation of the Keap1/Nrf2 signaling pathway.

Contribution of Progranulin to Protective Lung Immunity During Bacterial Pneumonia

Background

Progranulin (PGRN) is an important immunomodulatory factor in a variety of inflammatory diseases. However, its role in pulmonary immunity against bacterial infection remains unknown.

Methods

Pneumonia was induced in PGRN-deficient and normal wild-type mice using Pseudomonas aeruginosa or Staphylococcus aureus, and we assessed the effects of PGRN on survival, bacterial burden, cytokine and chemokine production, and pulmonary leukocyte recruitment after bacterial pneumonia.

Results

Patients with community-acquired pneumonia displayed elevated PGRN levels. Likewise, mice with Gram-negative and Gram-positive pneumonia had increased PGRN production in the lung and circulation. Progranulin deficiency led to increased bacterial growth and dissemination accompanied by enhanced lung injury and mortality in bacterial pneumonia, which was associated with impaired recruitment of macrophages and neutrophils in the lung. The reduced number of pulmonary macrophages and neutrophils observed in PGRN-deficient mice was related to a reduction of CCL2 and CXCL1 in the lungs after bacterial pneumonia. Importantly, therapeutic administration of PGRN improved mortality in severe bacterial pneumonia.

Conclusions

This study supports a novel role for PGRN in pulmonary immunity and suggests that treatment with PGRN may be a viable therapy for bacterial pneumonia.

Progranulin Plays a Central Role in Host Defense during Sepsis by Promoting Macrophage Recruitment

RATIONALE

Progranulin, a widely expressed protein, has multiple physiological functions. The functional role of progranulin in the host response to sepsis remains unknown.

OBJECTIVES

To assess the role of progranulin in the host response to sepsis.

METHODS

Effects of progranulin on host response to sepsis were determined.

MEASUREMENTS AND MAIN RESULTS

Progranulin concentrations were significantly elevated in adult (n = 74) and pediatric (n = 26) patients with sepsis relative to corresponding healthy adult (n = 36) and pediatric (n = 17) control subjects, respectively. By using a low-lethality model of nonsevere sepsis, we observed that progranulin deficiency not only increased mortality but also decreased bacterial clearance during sepsis. The decreased host defense to sepsis in progranulin-deficient mice was associated with reduced macrophage recruitment, with correspondingly impaired chemokine CC receptor ligand 2 (CCL2) production in peritoneal lavages during the early phase of sepsis. Progranulin derived from hematopoietic cells contributed to host defense in sepsis. Therapeutic administration of recombinant progranulin not only rescued impaired host defense in progranulin-deficient mice after nonsevere sepsis but also protected wild-type mice against a high-lethality model of severe sepsis. Progranulin-mediated protection against sepsis was closely linked to improved peritoneal macrophage recruitment. In addition, CCL2 treatment of progranulin-deficient mice improved survival and decreased peritoneal bacterial loads during sepsis, at least in part through promotion of peritoneal macrophage recruitment.

CONCLUSIONS

This proof-of-concept study supports a central role of progranulin-dependent macrophage recruitment in host defense to sepsis, opening new opportunities to host-directed therapeutic strategy that manipulate host immune response in the treatment of sepsis.

Role of Neutrophil Extracellular Traps in Asthma and Chronic Obstructive Pulmonary Disease

Objective:

Asthma and chronic obstructive pulmonary disease (COPD) are representative chronic inflammatory airway diseases responsible for a considerable burden of disease. In this article, we reviewed the relationship between neutrophil extracellular traps (NETs) and chronic inflammatory airway diseases.

Data Sources:

Articles published up to January 1, 2017, were selected from the PubMed, Ovid Medline, Embase databases, with the keywords of “asthma” or “pulmonary disease, chronic obstructive”, “neutrophils” and “extracellular traps.”

Study Selection:

Articles were obtained and reviewed to analyze the role of NETs in asthma and COPD.

Results:

NETs are composed of extracellular DNA, histones, and granular proteins, which are released from activated neutrophils. Multiple studies have indicated that there are a large amount of NETs in the airways of asthmatics and COPD patients. NETs can engulf and kill invading pathogens in the host. However, disordered regulation of NET formation has shown to be involved in the development of asthma and COPD. An overabundance of NETs in the airways or lung tissue could cause varying degrees of damage to lung tissues by inducing the death of human epithelial and endothelial cells, and thus resulting in impairing pulmonary function and accelerating the progress of the disease.

Conclusions:

Excessive NETs accumulate in the airways of asthmatics and COPD patients. Although NETs play an essential role in the innate immune system against infection, excessive components of NETs can cause lung tissue damage and accelerate disease progression in asthmatics and COPD patients. These findings suggest that administration of NETs could be a novel approach to treat asthma and COPD. Mechanism studies, clinical practice, and strategies to regulate neutrophil activation or directly interrupt NET function in asthmatics and COPD patients are desperately needed.

Anti-inflammatory ent-kaurenoic acids and their glycosides from Gochnatia decora

Nineteen ent-kaurane diterpenes were isolated and identified from the barks of Gochnatia decora (Kurz) A. L. Cabrera (Compositae), which has been used as an ethnic medicine for treating cough, asthma and wounds in southwestern China. Among them, six compounds are previously undescribed ent-kaurenoic acids, and a known compound, 7β,15β-dihydroxy-ent-kaur-16-en-19-oic acid, was obtained for the first time from nature. Based on its traditional effects in Chinese folk, the potential anti-inflammatory activities of its methanol extracts (ME) and isolated diterpenes were evaluated by the tests of the xylene-induced ear swelling in mice, lipopolysaccharide (LPS)-induced nitric oxide (NO) production in mouse macrophage cellular RAW 264.7 and inhibition assay of neutrophil elastase, respectively, resulting that ME performed obvious effect against mouse ear swelling with a dose-dependent inhibition in vivo, and nine compounds showed significant inhibition of NO production in vitro, with IC₅₀ values ranging from 0.042 to 8.22 μM, while they also exhibited inhibition of neutrophil elastase at 100 μM in vitro, speculating that those diterpenes may be the active substances correlated with their traditional efficacy.

Multiparameter Single Cell Profiling of Airway Inflammatory Cells

Airway diseases affect over 7% of the U.S. population and millions of patients worldwide. Asthmatic patients have wide variation in clinical severity with different clinical and physiologic manifestations of disease that may be driven by distinct biologic mechanisms. Further, the immunologic underpinnings of this complex trait disease are heterogeneous and treatment success depends on defining subgroups of asthmatics. Because of the limited availability and number of cells from the lung, the active site, in-depth investigation has been challenging. Recent advances in technology support transcriptional analysis of cells from induced sputum. Flow cytometry studies have described cells present in the sputum but a detailed analysis of these subsets is lacking. Mass cytometry or CyTOF (Cytometry by Time-Of-Flight) offers tremendous opportunities for multiparameter single cell analysis. Experiments can now allow detection of up to ∼40 markers to facilitate unprecedented multidimensional cellular analyses. Here we demonstrate the use of CyTOF on primary airway samples obtained from well-characterized patients with asthma and cystic fibrosis. Using this technology, we quantify cellular frequency and functional status of defined cell subsets. Our studies provide a blueprint to define the heterogeneity among subjects and underscore the power of this single cell method to characterize airway immune status. © 2016 International Clinical Cytometry Society.

Neutrophil plasticity enables the development of pathological microenvironments: implications for cystic fibrosis airway disease

INTRODUCTION

The pathological course of several chronic inflammatory diseases, including cystic fibrosis, chronic obstructive pulmonary disease, and rheumatoid arthritis, features an aberrant innate immune response dominated by neutrophils. In cystic fibrosis, neutrophil burden and activity of neutrophil elastase in the extracellular fluid have been identified as strong predictors of lung disease severity.

REVIEW

Although neutrophils are generally considered to be rigid, pre-programmed effector leukocytes, recent studies suggest extensive plasticity in how neutrophil functions unfold upon recruitment to peripheral tissues, and how they choose their ultimate fate. Indeed, upon migration to cystic fibrosis airways, neutrophils display dysregulated lifespan, metabolic activation, and altered effector and regulatory functions, consistent with profound adaptation and phenotypic reprogramming. Licensed by signals present in cystic fibrosis airway microenvironment to survive and develop these novel functions, neutrophils orchestrate, in partnership with the epithelium and with the resident microbiota, the evolution of a pathological microenvironment. This microenvironment is defined by altered proteolytic, redox, and metabolic balance and the presence of stable luminal structures in which neutrophils and microbes coexist.

CONCLUSIONS

The elucidation of molecular mechanisms driving neutrophil plasticity in vivo will open new treatment opportunities designed to modulate, rather than block, the crucial adaptive functions fulfilled by neutrophils. This review aims to outline emerging mechanisms of neutrophil plasticity and their participation in the building of pathological microenvironments in the context of cystic fibrosis and other diseases with similar features.

Serum progranulin as an indicator of neutrophilic airway inflammation and asthma severity

BACKGROUND

Progranulin, a protein secreted from the airway epithelium, is known to attenuate the downstream cascade of neutrophilic inflammation in particular. We hypothesized that progranulin may have a role in inflammatory regulation in asthma.

OBJECTIVE

To investigate the association between serum progranulin levels and various clinical features in patients with asthma.

METHODS

Serum samples and clinical data of 475 patients with asthma and 35 healthy controls at a tertiary referral hospital and its affiliated health promotion center were collected. Serum progranulin levels were compared between patients with asthma and healthy controls and then were compared within the patients with asthma in terms of pulmonary function and measures of inflammatory status. Univariate and multivariate analyses were performed to identify factors associated with severity of asthma.

RESULTS

Serum progranulin levels were significantly lower in the asthma group than in healthy group and were positively correlated with prebronchodilator forced expiratory volume in 1 second predicted within patients with asthma. We found a negative correlation between serum progranulin levels and blood neutrophil counts. Multivariate analysis revealed that higher serum progranulin levels were associated with a lower risk of severe asthma (odds ratio, 0.888; 95% confidence interval, 0.846-0.932; P < .001) after adjustment for other variables, such as age, sex, smoking status, blood neutrophil count, and current use of systemic corticosteroids.

CONCLUSION

Although the exact mechanism of the anti-inflammatory action of progranulin remains unknown, we suggest that serum progranulin may be an indicator of severe asthma with airflow limitation. Future studies with comprehensive airway sampling strategies are warranted to clarify its role, particularly in neutrophilic asthma.

Neutrophil Extracellular Traps in Pulmonary Diseases: Too Much of a Good Thing?

Neutrophil extracellular traps (NETs) arise from the release of granular and nuclear contents of neutrophils in the extracellular space in response to different classes of microorganisms, soluble factors, and host molecules. NETs are composed by decondensed chromatin fibers coated with antimicrobial granular and cytoplasmic proteins, such as myeloperoxidase, neutrophil elastase (NE), and α-defensins. Besides being expressed on NET fibers, NE and MPO also regulate NET formation. Furthermore, histone deimination by peptidylarginine deiminase 4 (PAD4) is a central step to NET formation. NET formation has been widely demonstrated to be an effective mechanism to fight against invading microorganisms, as deficiency in NET release or dismantling NET backbone by bacterial DNases renders the host susceptible to infections. Therefore, the primary role of NETs is to prevent microbial dissemination, avoiding overwhelming infections. However, an excess of NET formation has a dark side. The pathogenic role of NETs has been described for many human diseases, infectious and non-infectious. The detrimental effect of excessive NET release is particularly important to lung diseases, because NETs can expand more easily in the pulmonary alveoli, causing lung injury. Moreover, NETs and its associated molecules are able to directly induce epithelial and endothelial cell death. In this regard, massive NET formation has been reported in several pulmonary diseases, including asthma, chronic obstructive pulmonary disease, cystic fibrosis, respiratory syncytial virus bronchiolitis, influenza, bacterial pneumonia, and tuberculosis, among others. Thus, NET formation must be tightly regulated in order to avoid NET-mediated tissue damage. Recent development of therapies targeting NETs in pulmonary diseases includes DNA disintegration with recombinant human DNase, neutralization of NET proteins, with anti-histone antibodies and protease inhibitors. In this review, we summarize the recent knowledge on the pathophysiological role of NETs in pulmonary diseases as well as some experimental and clinical approaches to modulate their detrimental effects.

Progranulin as a candidate biomarker for therapeutic trial in patients with ALS and FTLD

The loss-of-function mechanism in progranulin (PGRN) mutation carriers makes PGRN an interesting target for upregulation as a therapeutic approach in neurodegenerative diseases like frontotemporal lobar degeneration. This gives rise to several questions: (1) how stable are PGRN levels in blood and cerebrospinal fluid (CSF) in follow-up? (2) Is it necessary to measure PGRN levels in CSF to monitor a therapeutic effect? Therefore, concentrations of PGRN were measured in paired CSF and serum samples of 22 patients with behavioural variant frontotemporal dementia, including one GRN mutation carrier (c.349+1G>C), 16 patients with amyotrophic lateral sclerosis and 17 non-neurodegenerative patients, which included 22 follow-up levels. PGRN levels of 14 patients with isolated dysfunction of the blood-CSF barrier were measured and PGRN was correlated with albumin quotients as a marker for blood-CSF barrier function. The intrathecal fraction of PGRN was calculated on the basis of CSF-to-serum ratios and hydrodynamic properties. Follow-up measurements of CSF and serum PGRN levels did not show any significant change in diagnostic groups. Mean PGRN levels are 35 times higher in blood than in CSF. However, the CSF-to-serum PGRN ratio does not correlate with the albumin quotient even in patients with severe impairment of the blood-CSF barrier. The calculated intrathecal fraction of CSF PGRN levels ranged between 80 and 90 %. Assuming that CSF PGRN is either brain-derived or transported from the vascular compartment via receptor mediated mechanisms, we propose that monitoring CNS specific effects of PGRN modulating drugs should be done in CSF.

New aspects on the structure of neutrophil extracellular traps from chronic obstructive pulmonary disease and in vitro generation

Polymorphonuclear neutrophils have in recent years attracted new attention due to their ability to release neutrophil extracellular traps (NETs). These web-like extracellular structures deriving from nuclear chromatin have been depicted in ambiguous roles between antimicrobial defence and host tissue damage. NETs consist of DNA strands of varying thickness and are decorated with microbicidal and cytotoxic proteins. Their principal structure has in recent years been characterised at molecular and ultrastructural levels but many features that are of direct relevance to cytotoxicity are still incompletely understood. These include the extent of chromatin decondensation during NET formation and the relative amounts and spatial distribution of the microbicidal components within the NET. In the present work, we analyse the structure of NETs found in induced sputum of patients with acutely exacerbated chronic obstructive pulmonary disease (COPD) using confocal laser microscopy and electron microscopy. In vitro induced NETs from human neutrophils serve for purposes of comparison and extended analysis of NET structure. Results demonstrate that COPD sputa are characterised by the pronounced presence of NETs and NETotic neutrophils. We provide new evidence that chromatin decondensation during NETosis is most extensive and generates substantial amounts of double-helix DNA in ‘beads-on-a-string’ conformation. New information is also presented on the abundance and location of neutrophil elastase (NE) and citrullinated histone H3 (citH3). NE occurs in high densities in nearly all non-fibrous constituents of the NETs while citH3 is much less abundant. We conclude from the results that (i) NETosis is an integral part of COPD pathology; this is relevant to all future research on the etiology and therapy of the disease; and that (ii) release of ‘beads-on-a-string’ DNA studded with non-citrullinated histones is a common feature of in vivo NETosis; this is of relevance to both the antimicrobial and the cytotoxic effects of NETs.