Elevated levels of lung surfactant protein A in sera from patients with idiopathic pulmonary fibrosis and pulmonary alveolar proteinosis

Risk factors for severe immune-related pneumonitis after nivolumab plus ipilimumab therapy for non-small cell lung cancer

BACKGROUND

The efficacy of anti-CTLA-4 antibody (ipilimumab) plus anti-programmed cell death 1 antibody (nivolumab) in treating advanced non-small cell lung cancer (NSCLC) is impeded by an elevated risk of severe immune-related adverse events. However, our understanding of associations among pre-existing fibrosis, emphysematous changes, and objective indicators as predictive factors is limited for severe pneumonitis in NSCLC patients receiving this combination therapy. Thus, we retrospectively investigated these associations, including overall tumor burden, before treatment initiation in the Japanese population.

METHODS

We focused on patients (n = 76) with pre-existing interstitial lung disease (ILD) to identify predictors of severe pneumonitis. Variables included age, sex, smoking status, programmed cell death ligand 1 expression, overall tumor burden, chest computed tomography-confirmed fibrosis, serum markers, and respiratory function test results.

RESULTS

Severe pneumonitis was more frequent in patients with squamous cell carcinoma, fibrosis, low diffusing capacity for carbon monoxide (%DLCO), and high surfactant protein D (SP-D) level. Notably, squamous cell carcinoma, baseline %DLCO, and SP-D level were significant risk factors. Our findings revealed the nonsignificance of tumor burden (≥85 mm) in predicting severe pneumonitis, emphasizing the importance of pre-existing ILD. Conversely, in cases without pre-existing fibrosis, severe pneumonitis was not associated with %DLCO or SP-D level (93.2% vs. 91.9%, and 63.3 vs. 40.9 ng/mL, respectively) and was more common in patients with a large overall tumor burden (97.5 vs. 70.0 mm).

CONCLUSION

Vigilant monitoring and early intervention are crucial for patients with squamous cell carcinoma, high SP-D level, or low %DLCO undergoing ipilimumab plus nivolumab therapy.

Could SP-A and SP-D Serum Levels Predict COVID-19 Severity?

Given the various clinical manifestations that characterize Coronavirus Disease 2019 (COVID-19), the scientific community is constantly searching for biomarkers with prognostic value. Surfactant proteins A (SP-A) and D (SP-D) are collectins that play a crucial role in ensuring proper alveolar function and an alteration of their serum levels was reported in several pulmonary diseases characterized by Acute Respiratory Distress Syndrome (ARDS) and pulmonary fibrosis. Considering that such clinical manifestations can also occur during Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection, we wondered if these collectins could act as prognostic markers. In this regard, serum levels of SP-A and SP-D were measured by enzyme immunoassay in patients with SARS-CoV-2 infection (n = 51) at admission (T0) and after seven days (T1) and compared with healthy donors (n = 11). SP-D increased in COVID-19 patients compared to healthy controls during the early phases of infection, while a significant reduction was observed at T1. Stratifying SARS-CoV-2 patients according to disease severity, increased serum SP-D levels were observed in severe compared to mild patients. In light of these results, SP-D, but not SP-A, seems to be an eligible marker of COVID-19 pneumonia, and the early detection of SP-D serum levels could be crucial for preventive clinical management.

Serum Biomarkers in a Radiological Pattern of Non-Fibrotic Hypersensitivity Pneumonitis: Implications for Mechanistic Difference and Differential Diagnosis

Hypersensitivity pneumonitis (HP) is a consequence of immune-mediated reactions caused by recurrent exposure to environmental agents. Recently, clinical practice guidelines for the diagnosis of HP were published and increased interest in HP. On the other hand, novel therapies have recently emerged for various diseases, and the management of drug-related pneumonitis (DRP) has become increasingly important. Among DRP, the HP pattern (DRP-HP) shows small, poorly defined centrilobular nodules with or without widespread areas of ground-glass opacity or lobular areas of decreased attenuation and vascularity. A similar radiological pattern of non-fibrotic HP can be induced, irrespective of inhalation (non-fibrotic HP) or intravenous administration (DRP-HP). However, their difference has not been well described, although the distribution of lesions in the lungs was slightly different between these two conditions. In this review, we focus on serum biomarkers of lung epithelial cells in order to investigate the difference between DRP-HP and non-fibrotic HP (common-HP). Serum levels of Krebs von den Lungen 6 (KL-6) might be relatively lower (occasionally normal) in DRP-HP than in common-HP, implying a mechanistic difference. KL-6 could be useful in discriminating between DRP and non-fibrotic HP (common type).

Autoimmune Pulmonary Alveolar Proteinosis

Autoimmune pulmonary alveolar proteinosis (PAP) is a rare disease characterized by myeloid cell dysfunction, abnormal pulmonary surfactant accumulation, and innate immune deficiency. It has a prevalence of 7-10 per million; occurs in individuals of all races, geographic regions, sex, and socioeconomic status; and accounts for 90% of all patients with PAP syndrome. The most common presentation is dyspnea of insidious onset with or without cough, production of scant white and frothy sputum, and diffuse radiographic infiltrates in a previously healthy adult, but it can also occur in children as young as 3 years. Digital clubbing, fever, and hemoptysis are not typical, and the latter two indicate that intercurrent infection may be present. Low prevalence and nonspecific clinical, radiological, and laboratory findings commonly lead to misdiagnosis as pneumonia and substantially delay an accurate diagnosis. The clinical course, although variable, usually includes progressive hypoxemic respiratory insufficiency and, in some patients, secondary infections, pulmonary fibrosis, respiratory failure, and death. Two decades of research have raised autoimmune PAP from obscurity to a paradigm of molecular pathogenesis-based diagnostic and therapeutic development. Pathogenesis is driven by GM-CSF (granulocyte/macrophage colony-stimulating factor) autoantibodies, which are present at high concentrations in blood and tissues and form the basis of an accurate, commercially available diagnostic blood test with sensitivity and specificity of 100%. Although whole-lung lavage remains the first-line therapy, inhaled GM-CSF is a promising pharmacotherapeutic approach demonstrated in well-controlled trials to be safe, well tolerated, and efficacious. Research has established GM-CSF as a pulmonary regulatory molecule critical to surfactant homeostasis, alveolar stability, lung function, and host defense.

Biomarkers for the adverse effects on respiratory system health associated with atmospheric particulate matter exposure

Large amounts of epidemiological evidence have confirmed the atmospheric particulate matter (PM_2.5) exposure was positively correlated with the morbidity and mortality of respiratory diseases. Nevertheless, its pathogenesis remains incompletely understood, probably resulting from the activation of oxidative stress, inflammation, altered genetic and epigenetic modifications in the lung upon PM_2.5 exposure. Currently, biomarker investigations have been widely used in epidemiological and toxicological studies, which may help in understanding the biologic mechanisms underlying PM_2.5-elicited adverse health outcomes. Here, the emerging biomarkers to indicate PM_2.5-respiratory system interactions were summarized, primarily related to oxidative stress (ROS, MDA, GSH, etc.), inflammation (Interleukins, FE_NO, CC16, etc.), DNA damage (8-OHdG, γH2AX, OGG1) and also epigenetic modulation (DNA methylation, histone modification, microRNAs). The identified biomarkers shed light on PM_2.5-elicited inflammation, fibrogenesis and carcinogenesis, thus may favor more precise interventions in public health. It is worth noting that some inconsistent findings may possibly relate to the inter-study differentials in the airborne PM_2.5 sample, exposure mode and targeted subjects, as well as methodological issues. Further research, particularly by -omics technique to identify novel, specific biomarkers, is warranted to illuminate the causal relationship between PM_2.5 pollution and deleterious lung outcomes.

Safety of inhaled ivermectin as a repurposed direct drug for treatment of COVID-19: A preclinical tolerance study

Introduction

SARS-CoV-2 replication in cell cultures has been shown to be inhibited by ivermectin. However, ivermectin's low aqueous solubility and bioavailability hinders its application in COVID-19 treatment. Also, it has been suggested that best outcomes for this medication can be achieved via direct administration to the lung.

Objectives

This study aimed at evaluating the safety of a novel ivermectin inhalable formulation in rats as a pre-clinical step.

Methods

Hydroxy propyl-β-cyclodextrin (HP-β-CD) was used to formulate readily soluble ivermectin lyophilized powder. Adult male rats were used to test lung toxicity for ivermectin-HP-β-CD formulations in doses of 0.05, 0.1, 0.2, 0.4 and 0.8 mg/kg for 3 successive days.

Results

The X-ray diffraction for lyophilized ivermectin-HP-β-CD revealed its amorphous structure that increased drug aqueous solubility 127-fold and was rapidly dissolved within 5 s in saline. Pulmonary administration of ivermectin-HP-β-CD in doses of 0.2, 0.4 and 0.8 mg/kg showed dose-dependent increase in levels of TNF-α, IL-6, IL-13 and ICAM-1 as well as gene expression of MCP-1, protein expression of PIII-NP and serum levels of SP-D paralleled by reduction in IL-10. Moreover, lungs treated with ivermectin (0.2 mg/kg) revealed mild histopathological alterations, while severe pulmonary damage was seen in rats treated with ivermectin at doses of 0.4 and 0.8 mg/kg. However, ivermectin-HP-β-CD formulation administered in doses of 0.05 and 0.1 mg/kg revealed safety profiles.

Conclusion

The safety of inhaled ivermectin-HP-β-CD formulation is dose-dependent. Nevertheless, use of low doses (0.05 and 0.1 mg/kg) could be considered as a possible therapeutic regimen in COVID-19 cases.

Surfactant protein D: a useful marker for differentiation of drug-induced pneumonia and bacterial pneumonia

Background

Drug-induced pneumonia (d-pneumonia) and bacterial pneumonia (b-pneumonia) are often difficult to differentiate; therefore, this study examined the possibility of differentiating them using serum biomarkers.

Methods

The study included 22 and 16 patients diagnosed with b- and d-pneumonia, respectively, at our institution or affiliated institutions. For d-pneumonia, the causative drug was minocycline hydrochloride in four patients, gefitinib in two patients, nivolumab in two patients, pembrolizumab in two patients, sulfasalazine in two patients, loxoprofen in one patient, Bouiougitou in one patient, edoxaban tosilate hydrate in one patient, and abemaciclib in one patient. White blood cell (WBC), C-reactive protein (CRP), Krebs von den Lungen-6 (KL-6), surfactant protein (SP)-D, and SP-A levels were measured in each patient and compared between the groups.

Results

Significant differences were noted in the WBC and SP-D levels between the two groups (P < 0.05, P < 0.001), but not in the CRP, KL-6, or SP-A levels.

Conclusion

The study results suggest that SP-D is a useful marker for differentiating b-pneumonia and d-pneumonia.

Biomarkers in Progressive Fibrosing Interstitial Lung Disease: Optimizing Diagnosis, Prognosis, and Treatment Response

Interstitial lung disease (ILD) comprises a heterogenous group of diffuse lung disorders that commonly result in irreversible pulmonary fibrosis. While idiopathic pulmonary fibrosis (IPF) is the prototypical progressive fibrosing ILD (PF-ILD), a high proportion of patients with other ILD subtypes develop a PF-ILD phenotype. Evidence exists for shared pathobiology leading to progressive fibrosis, suggesting that biomarkers of disease activity may prove informative across the wide spectrum of ILDs. Biomarker investigation to date has identified a number of molecular markers that predict relevant ILD endpoints, including disease presence, prognosis, and/or treatment response. In this review, we provide an overview of potentially informative biomarkers in patients with ILD, including those suggestive of a PF-ILD phenotype. We highlight the recent genomic, transcriptomic, and proteomic investigations that identified these biomarkers and discuss the body compartments in which they are found, including the peripheral blood, airway, and lung parenchyma. Finally, we identify critical gaps in knowledge within the field of ILD biomarker research and propose steps to advance the field toward biomarker implementation.

Changes of Damage Associated Molecular Patterns in COVID-19 Patients

Background

The development of severe coronavirus disease 2019 (COVID-19) is associated with systemic hyperinflammation, which drives multi-organ failure and death. Disease deterioration tends to occur when the virus is receding; however, whether other factors besides viral products are involved in the inflammatory cascade remains unclear.

Methods

Twenty-eight COVID-19 patients with laboratory-confirmed SARS-CoV-2 infection hospitalized at the Fifth Medical Center of Chinese PLA General Hospital from January 23 to February 20, 2020 and nine healthy donors during the same period were recruited in the study. COVID-19 patients were grouped as mild, moderate, severe based on disease severity. Plasma damage-associated molecular patterns (DAMPs), including high mobility group box 1 (HMGB1), calprotectin (S100A8/A9), surfactant protein A (SP-A), cold-inducible RNA-binding protein (CIRBP), and Histone H4 were detected by ELISA assay, and analyzed in combination with clinical data. Plasma cytokines, chemokines and lymphocytes were determined by flow cytometry.

Results

Plasma levels of HMGB1 (38292.3 ± 4564.4 vs. 32686.3 ± 3678.1, P = 0.002), S100A8/A9 (1490.8 ± 819.3 vs. 742.2 ± 300.8, P = 0.015), and SP-A (6713.6 ± 1708.7 vs. 5296.3 ± 1240.4, P = 0.048) were increased in COVID-19 patients compared to healthy donors, while CIRBP (57.4 ± 30.7 vs. 111.9 ± 55.2, P = 0.004) levels decreased. Five DAMPs did not vary among mild, moderate, and severe patients. Moreover, SP-A levels correlated positively with inflammatory cytokines and negatively with time elapsed after symptom onset, whereas CIRBP showed an opposite pattern.

Conclusions

These findings suggest SP-A may involve in the inflammation of COVID-19, while CIRBP likely plays a protective role. Therefore, DAMPs represent a potential target in the prevention or treatment of COVID-19.

Soluble pattern recognition molecules: Guardians and regulators of homeostasis at airway mucosal surfaces

Maintenance of homeostasis at body barriers that are constantly challenged by microbes, toxins and potentially bioactive (macro)molecules requires complex, highly orchestrated mechanisms of protection. Recent discoveries in respiratory research have shed light on the unprecedented role of airway epithelial cells (AEC), which, besides immune cells homing to the lung, also significantly contribute to host defence by expressing membrane‐bound and soluble pattern recognition receptors (sPRR). Recent evidence suggests that distinct, evolutionary ancient, sPRR secreted by AEC might become activated by usually innocuous proteins, commonly referred to as allergens. We here provide a systematic overview on sPRR detectable in the mucus lining of AEC. Some of them become actively produced and secreted by AECs (like the pentraxins C‐reactive protein and pentraxin 3; the collectins mannose binding protein and surfactant proteins A and D; H‐ficolin; serum amyloid A; and the complement components C3 and C5). Others are elaborated by innate and adaptive immune cells such as monocytes/macrophages and T cells (like the pentraxins C‐reactive protein and pentraxin 3; L‐ficolin; serum amyloid A; and the complement components C3 and C5). Herein we discuss how sPRRs may contribute to homeostasis but sometimes also to overt disease (e.g. airway hyperreactivity and asthma) at the alveolar–air interface.

Inhalation of titanium dioxide (P25) nanoparticles to rats and changes in surfactant protein (SP-D) levels in bronchoalveolar lavage fluid and serum

Titanium dioxide (TiO₂) nanoparticles are typical and widely used nanomaterials, and there are many studies on the inflammatory responses induced by their inhalation. In this study, we conducted a 4-week inhalation exposure study of aerosolized TiO_2> nanoparticles (P25) to male Wistar rats. The mean aerosol concentration measured at each day was 4.1 mg/m³ by dry powder dispersion of TiO₂ nanoparticles. Control and exposure groups of rats were killed at 3 and 30 days after the termination of exposure, and bronchoalveolar lavage fluid (BALF) and serum were collected for analysis of total cell count, neutrophil count, and surfactant protein (SP-D) in BALF and SP-D in serum, as well as other serum biomarkers. SP-D is a component of lung surfactants produced in type II alveolar epithelial cells and Clara cells and secreted into the alveolar space and blood. The neutrophil count in the BALF was significantly elevated at 3 and 30 days. The levels of SP-D in the BALF were also elevated at 3 and 30 days, while the serum SP-D levels were elevated at 3 days only. We determined the amounts of TiO₂ in the rat lungs in the exposure group at 3, 30, and 73 days to analyze the lung deposition fraction (10.2%) and the biological half-life time (72.4 days) of inhaled TiO₂ nanoparticles. Histopathological analysis revealed mild pulmonary inflammation in lung tissue at 3 days. Serum SP-D was found to be a potential biomarker for exposure to TiO₂ nanoparticles in this study.

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.

Reduced serum club cell protein as a pulmonary damage marker for chronic fine particulate matter exposure in Chinese population

BACKGROUND

Exposure to fine particulate matter (PM_2.5) pollution is associated with increased morbidity and mortality from respiratory diseases. However, few population-based studies have been conducted to assess the alterations in circulating pulmonary proteins due to long-term PM_2.5 exposure.

METHODS

We designed a two-stage study. In the first stage (training set), we assessed the associations between PM_2.5 exposure and levels of pulmonary damage markers (CC16, SP-A and SP-D) and lung function in a coke oven emission (COE) cohort with 558 coke plant workers and 210 controls. In the second stage (validation set), significant initial findings were validated by an independent diesel engine exhaust (DEE) cohort with 50 DEE exposed workers and 50 controls.

RESULTS

Serum CC16 levels decreased in a dose response manner in association with both external and internal PM_2.5 exposures in the two cohorts. In the training set, serum CC16 levels decreased with increasing duration of occupational PM_2.5 exposure history. An interquartile range (IQR) (122.0μg/m³) increase in PM_2.5 was associated with a 5.76% decrease in serum CC16 levels, whereas an IQR (1.06μmol/mol creatinine) increase in urinary 1-hydroxypyrene (1-OHP) concentration was associated with a 5.36% decrease in serum CC16 levels in the COE cohort. In the validation set, the concentration of serum CC16 in the PM_2.5 exposed group was 22.42% lower than that of the controls and an IQR (1.24μmol/mol creatinine) increase in urinary 1-OHP concentration was associated with a 12.24% decrease in serum CC16 levels in the DEE cohort.

CONCLUSIONS

Serum CC16 levels may be a sensitive marker for pulmonary damage in populations with high PM_2.5 exposure.

Biomarkers in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, debilitating, fibrotic lung disease leading to respiratory failure and ultimately to death. Being the prototype of interstitial lung diseases, IPF is characterized by marked heterogeneity regarding its clinical course. Despite significant progress in the understanding of its pathogenesis, we still cannot reliably predict the course of the disease and the response to treatment of an individual patient. Non-invasive biomarkers, in particular serum biomarkers, for the (early) diagnosis, differential diagnosis, prognosis and prediction of therapeutic response are urgently needed. Numerous molecules involved in alveolar epithelial cell injury, fibroproliferation and matrix remodeling as well as immune regulation have been proposed as potential biomarkers. Furthermore, genetic variants of TOLLIP, MUC5B, and other genes are associated with a differential response to treatment and with the development and/or the prognosis of IPF. Additionally, the bacterial signature in IPF lungs, as shown from microbiome analyses, as well as mitochondrial DNA seem to have promising roles as biomarkers. Moreover, combination of multiple biomarkers may identify comprehensive biomarker signatures in IPF patients. However, there is still a long way until these potential biomarkers complete or substitute for the clinical and functional parameters currently available for IPF.

Impact of serum SP-A and SP-D levels on comparison and prognosis of idiopathic pulmonary fibrosis: A systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

Idiopathic pulmonary fibrosis (IPF) has a poor prognosis in general; however, it is heterogeneous to detect relative biomarkers for predicting the disease progression. Serum biomarkers can be conveniently collected to detect and help to differentially diagnose IPF and predict IPF prognosis. This meta-analysis aimed to evaluate the use of serum surfactant proteins A and D (SP-A and SP-D) for differential diagnosis and prognosis of IPF.

METHODS

Relevant articles were searched in PubMed, Embase, and Chinese National Knowledge Infrastructure databases and reviewed by 2 independent readers. Standard mean difference (SMD) and 95% confidence interval (CI) were calculated to assess the difference in serum levels of SP-A/D among patients with IPF, when compared to patients with non-IPF interstitial lung disease (ILD), pulmonary infection, and healthy control. Hazard ratio (HR) and 95% CI were used to compare the relative risk of mortality.

RESULTS

Twenty-one articles (totalling 1289 IPF patients) were included in final meta-analysis. Serum SP-A levels were significantly higher in patients with IPF than in patients with non-IPF ILD (SMD: 1.108 [0.584, 1.632], P < .001), or pulmonary infection (SMD: 1.320 [0.999, 1.640], P < .001) and healthy controls (SMD: 2.802 [1.901, 3.702], P < .001). There was no significant difference in serum SP-D levels between patients with IPF and those with non-IPF ILD patients (SMD: 0.459 [-0.000, 0.919], P = .050). Serum SP-D levels were significantly higher in patients with IPF than in patients with pulmonary infection (SMD: 1.308 [0.813, 1.803], P < .001) and healthy controls (SMD: 2.235 [1.739, 2.731], P < .001). Risk of death in patients with IPF and elevated serum SP-A was increased 39% compared to patients with low SP-A groups. Elevated SP-D increased risk by 111% when compared to low SP-D. In acute exacerbation of IPF, serum SP-A/D were higher than those in stable stage. The comparisons and prognosis might be different in Asian and Caucasian patients.

CONCLUSIONS

Serum SP-A/D detection might be useful for differential diagnosis and prediction of survival in patients with IPF.

Structure, genetics and function of the pulmonary associated surfactant proteins A and D: The extra-pulmonary role of these C type lectins

The collectins family encompasses several collagenous Ca²⁺-dependent defense lectins that are described as pathogen recognition molecules. They play an important role in both adaptive and innate immunity. Surfactant proteins A and D are two of these proteins which were initially discovered in association with surfactant in the pulmonary system. The structure, immune and inflammatory functions, and genetic variations have been well described in relation to their roles, function and pathophysiology in the pulmonary system. Subsequently, these proteins have been discovered in a wide range of other organs and organ systems. The role of these proteins outside the pulmonary system is currently an active area of research. This review intends to provide a current overview of the genetics, structure and extra-pulmonary functions of the surfactant collectin proteins.

Toll-like receptor 4 activation attenuates profibrotic response in control lung fibroblasts but not in fibroblasts from patients with IPF

Idiopathic pulmonary fibrosis (IPF) is a devastating lung disease with a median survival of 3 yr. IPF deteriorates upon viral or bacterial lung infection although pulmonary infection (pneumonia) in healthy lungs rarely induces fibrosis. Bacterial lipopolysaccharide (LPS) activates Toll-like receptor 4 (TLR4), initiating proinflammatory pathways. As TLR4 has already been linked to hepatic fibrosis and scleroderma, we now investigated the role of TLR4 in IPF fibroblasts. Lung tissue sections from patients with IPF were analyzed for TLR4 expression. Isolated normal human lung fibroblasts (NL-FB) and IPF fibroblasts (IPF-FB) were exposed to LPS and transforming growth factor-β (TGF-β) before expression analysis of receptors, profibrotic mediators, and cytokines. TLR4 is expressed in fibroblast foci of IPF lungs as well as in primary NL-FB and IPF-FB. As a model for a gram-negative pneumonia in the nonfibrotic lung, NL-FB and IPF-FB were coexposed to LPS and TGF-β. Whereas NL-FB produced significantly less connective tissue growth factor upon costimulation compared with TGF-β stimulation alone, IPF-FB showed significantly increased profibrotic markers compared with control fibroblasts after costimulation. Although levels of antifibrotic prostaglandin E2 were elevated after costimulation, they were not responsible for this effect. However, significant downregulation of TGF-β receptor type 1 in control fibroblasts seems to contribute to the reduced profibrotic response in our in vitro model. Normal and IPF fibroblasts thus differ in their profibrotic response upon LPS-induced TLR4 stimulation.

Identification of CD245 as myosin 18A, a receptor for surfactant A: A novel pathway for activating human NK lymphocytes

CD245 is a human surface antigen expressed on peripheral blood lymphocytes, initially delineated by two monoclonal antibodies DY12 and DY35. Until now, CD245 molecular and functional characteristics remained largely unknown. We combined immunological and proteomic approaches and identified CD245 as the unconventional myosin 18A, a highly conserved motor enzyme reported as a receptor for the surfactant protein A (SP-A), that plays a critical role in cytoskeleton organization and Golgi budding. We report that the recruitment of CD245 strongly enhanced NK cell cytotoxicity. Further, we show that the enhancement of the NK lymphocytes killing ability toward CD137-ligand expressing target cells could result from the induction of CD137 expression following CD245 engagement. The SP-A receptor could therefore represent a novel and promising target in cancer immunotherapy.

Specific Serum Markers of IPF

Idiopathic pulmonary fibrosis (IPF) is defined as a specific form of chronic, progressive, fibrosing interstitial pneumonia of unknown cause. It is characterized by the progressive worsening of lung function and has a poor prognosis (median survival is approximately 3 years). However, the clinical course of disease shows considerable individual variability. Therefore, it is important to monitor the clinical course and to predict prognosis for optimal therapy. Serum biomarkers are both less invasive and reproducible diagnostic tools. Useful biomarkers for patients with IPF are strongly coveted; however, to date, there are no biomarkers that are globally known. In Japan, surfactant protein (SP)-A, SP-D, and KL-6 are commonly used as serum markers of interstitial pneumonia, including IPF, in the clinical setting, and empirical data has been accumulated over 10 years. SP-A and SP-D are hydrophilic proteins and members of the collectin family. These collectins have been shown to function as host defense lectins in the lung. KL-6 is a high molecular weight glycoprotein and now classified as a human MUC1 mucin protein. These three proteins are mainly synthesized by alveolar type II cells. The mechanisms of increase for these protein levels in sera of patients with IPF are probably a combination of a loss of epithelial integrity due to injury and an increased mass of type II cells due to hyperplasia. It has been revealed that those proteins are useful for monitoring the clinical course and predicting prognosis as well as for the diagnosis of IPF. In this review article, the molecular structures and biological functions of these biomarkers are outlined, and we discuss the clinical application of these biomarkers for patients with IPF.

Thyroid Disease Is Prevalent and Predicts Survival in Patients With Idiopathic Pulmonary Fibrosis

BACKGROUND

A significant minority of patients with idiopathic pulmonary fibrosis (IPF) display features of autoimmunity without meeting the criteria for overt connective tissue disease. A link between IPF and other immune-mediated processes, such as hypothyroidism (HT), has not been reported. In this investigation, we aimed to determine whether HT is associated with IPF and if outcomes differ between patients with IPF with and without HT.

METHODS

A retrospective case-control analysis was conducted. Of 311 patients referred to the University of Chicago Interstitial Lung Disease Center with an initial diagnosis of IPF, 196 met the inclusion criteria and were included in the final analysis. Each case was matched 1:1 by age, sex, and race to a control subject with COPD.

RESULTS

HT was identified in 16.8% of cases and 7.1% of control subjects (OR, 2.7; 95% CI, 1.31-5.54; P = .01). Among patients with IPF, HT was associated with reduced survival time (P < .001) and was found to be an independent predictor of mortality in multivariable Cox regression analysis (hazard ratio, 2.12; 95% CI, 1.31-3.43; P = .002). A secondary analysis of two IPF clinical trial datasets supports these findings.

CONCLUSIONS

HT is common among patients with IPF, with a higher prevalence than in those with COPD and the general population. The presence of HT also predicts mortality in IPF, a finding that may improve future prognostication models. More research is needed to determine the biologic link between IPF and HT and how the presence of thyroid disease may influence disease progression.

Analysis of pulmonary surfactant in rat lungs after inhalation of nanomaterials: Fullerenes, nickel oxide and multi-walled carbon nanotubes

The health risks of inhalation exposure to engineered nanomaterials in the workplace are a major concern in recent years, and hazard assessments of these materials are being conducted. The pulmonary surfactant of lung alveoli is the first biological entity to have contact with airborne nanomaterials in inhaled air. In this study, we retrospectively evaluated the pulmonary surfactant components of rat lungs after a 4-week inhalation exposure to three different nanomaterials: fullerenes, nickel oxide (NiO) nanoparticles and multi-walled carbon nanotubes (MWCNT), with similar levels of average aerosol concentration (0.13-0.37 mg/m(3)). Bronchoalveolar lavage fluid (BALF) of the rat lungs stored after previous inhalation studies was analyzed, focusing on total protein and the surfactant components, such as phospholipids and surfactant-specific SP-D (surfactant protein D) and the BALF surface tension, which is affected by SP-B and SP-C. Compared with a control group, significant changes in the BALF surface tension and the concentrations of phospholipids, total protein and SP-D were observed in rats exposed to NiO nanoparticles, but not in those exposed to fullerenes. Surface tension and the levels of surfactant phospholipids and proteins were also significantly different in rats exposed to MWCNTs. The concentrations of phospholipids, total protein and SP-D and BALF surface tension were correlated significantly with the polymorphonuclear neutrophil counts in the BALF. These results suggest that pulmonary surfactant components can be used as measures of lung inflammation.

Distinct compartmentalization of SP-A and SP-D in the vasculature and lungs of patients with idiopathic pulmonary fibrosis

Background

Surfactant proteins SP-A and SP-D are useful biomarkers in diagnosis, monitoring, and prognosis of idiopathic pulmonary fibrosis (IPF). Despite their high structural homology, their serum concentrations often vary in IPF patients. This retrospective study aimed to investigate distinct compartmentalization of SP-A and SP-D in the vasculature and lungs by bronchoalveolar lavage fluid (BALF)/serum analysis, hydrophilicity and immunohistochemistry.

Methods

We included 36 IPF patients, 18 sarcoidosis (SAR) patients and 20 healthy subjects. Low-speed centrifugal supernatants of BALF (Sup-1) were obtained from each subject. Sera were also collected from each patient. Furthermore, we separated Sup-1 of IPF patients into hydrophilic supernatant (Sup-2) and hydrophobic precipitate (Ppt) by high-speed centrifugation. We measured SP-A and SP-D levels of each sample with the sandwich ELISA technique. We analyzed the change of the BALF/serum level ratios of the two proteins in IPF patients and their hydrophilicity in BALF. The distribution in the IPF lungs was also examined by immunohistochemical staining.

Results

In BALF, SP-A levels were comparable between the groups; however, SP-D levels were significantly lower in IPF patients than in others. Although IPF reduced the BALF/serum level ratios of the two proteins, the change in concentration of SP-D was more evident than SP-A. This suggests a higher disease impact for SP-D. Regarding hydrophilicity, although more than half of the SP-D remained in hydrophilic fractions (Sup-2), almost all of the SP-A sedimented in the Ppt with phospholipids. Hydrophilicity suggests that SP-D migrates into the blood more easily than SP-A in IPF lungs. Immunohistochemistry revealed that SP-A was confined to thick mucus-filling alveolar space, whereas SP-D was often intravascular. This data also suggests that SP-D easily leaks into the bloodstream, whereas SP-A remains bound to surfactant lipids in the alveolar space.

Conclusions

The current study investigated distinct compartmentalization of SP-A and SP-D in the vasculature and lungs. Our results suggest that serum levels of SP-D could reflect pathological changes of the IPF lungs more incisively than those of SP-A.

New treatment and markers of prognosis for idiopathic pulmonary fibrosis: lessons learned from translational research

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive interstitial lung disease with increasing prevalence, high mortality rates and poor treatment options. The diagnostic process is complex and often requires an interdisciplinary approach between different specialists. Information gained over the past 10 years of intense research resulted in improved diagnostic algorithms, a better understanding of the underlying pathogenesis and the development of new therapeutic options. Specifically, the change from the traditional concept that viewed IPF as a chronic inflammatory disorder to the current belief that is primarily resulting from aberrant wound healing enabled the identification of novel treatment targets. This increased the clinical trial activity dramatically and resulted in the approval of the first IPF-specific therapy in many countries. Still, the natural history and intrinsic behavior of IPF are very difficult to predict. There is an urgent need for new therapies and also for development and validation of prognostic markers that predict disease progression, survival and also response to antifibrotic drugs. This review provides an up to date summary of the most relevant clinical trials, novel therapeutic drug targets and outlines a spectrum of potential prognostic biomarkers for IPF.

Diagnostic value of surfactant protein-a in severe acute pancreatitis-induced acute respiratory distress syndrome

Background

The complexity of multiple-item criteria in acute respiratory distress syndrome (ARDS) often causes inconvenience for physicians in the management of patients with severe acute pancreatitis (SAP). We evaluated whether serum SP-A levels in the presence of diffuse alveolar damage (DAD) can be qualitatively assessed for diagnosis of SAP-induced ARDS.

Material/Methods

Eighty rats were randomly divided into 2 groups (n=40 each) – the sham-operated (SO) group and the SAP group – and then randomly subdivided into 4 subgroups in a time-course manner. Furthermore, rats in the SAP group were subdivided into the SAP induced-ARDS group (ARDS group) and the SAP without ARDS group (non-ARDS group) according to the diagnostic standard of ARDS. The diagnostic cut-off values of SP-A for SAP-induced ARDS were determined by the receiver operating characteristic curve (ROC).

Results

Serum SP-A levels in Baseline, SO group, SAP group, ARDS group, and non-ARDS group were 43.15±14.29, 51.91±16.99, 193.4±35.37, 198.0+29.73, and 185.7±43.21 ug/ml, respectively. The best cut-off value for the serum SP-A level for the diagnosis of SAP-induced ARDS was 150 ug/ml and the area under the ROC curve of SP-A was 0.88. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of SP-A in the diagnosis of SAP-induced ARDS were 100.0%, 81.8%, 71.4%, 100.0%, and 87.5%, respectively.

Conclusions

Serum SP-A levels may allow the detection of SAP-induced ARDS and may help to support the clinical diagnosis of ARDS. The optimal serum SP-A cut-off value to discriminate SAP-induced ARDS and other groups (SO group and non-ARDS group) is around 150 ug/ml.

Double-blind controlled trial of lecithinized superoxide dismutase in patients with idiopathic interstitial pneumonia - short term evaluation of safety and tolerability

BACKGROUND

Idiopathic interstitial pneumonias such as idiopathic pulmonary fibrosis or fibrotic nonspecific interstitial pneumonia are irreversible progressive pulmonary diseases that often have fatal outcomes. Although the etiology of idiopathic interstitial pneumonias is not yet fully understood, anti-fibrotic and anti-inflammatory agents have shown limited therapeutic effectiveness. Reactive oxygen species and their cytotoxic effects on the lung epithelial cells have been reported to participate in the pathophysiology of the disease. Because superoxide dismutase catalyzes the detoxification of reactive oxygen species, we developed lecithinized superoxide dismutase for the treatment of patients with idiopathic interstitial pneumonias.

METHODS

A multicenter, randomized, placebo-controlled trial was conducted as a pilot study to investigate the safety and effectiveness of 40 or 80 mg lecithinized superoxide dismutase in patients with progressive idiopathic interstitial pneumonias who presented with either idiopathic pulmonary fibrosis or corticosteroid-resistant fibrotic nonspecific interstitial pneumonia and showed arterial oxygen tension compatible with stage III or IV on the Japanese severity grading scale for idiopathic interstitial pneumonias. Before and following infusion of lecithinized superoxide dismutase for 28 days, the primary endpoint of forced vital capacity and the secondary endpoints of lactate dehydrogenase, surfactant protein-A, surfactant protein-D and Krebs von den Lungen-6 levels were measured in the serum.

RESULTS

The primary endpoint of forced vital capacity did not improve significantly in the lecithinized superoxide dismutase groups in comparison with the placebo group. The secondary endpoints of lactate dehydrogenase and surfactant protein-A levels were significantly attenuated by 28 days in the higher-dose (80 mg) group. However, these changes returned to the baseline levels by 56 days after the cessation of lecithinized superoxide dismutase. Adverse events and mortality in the drug-treated groups did not differ from those in the placebo group.

CONCLUSIONS

Treatment with lecithinized superoxide dismutase is safe and improves the levels of serum markers such as lactate dehydrogenase and surfactant protein-A in patients with advanced idiopathic interstitial pneumonias with severe respiratory dysfunction. Considering the results of the current study, further investigations into the effects and treatment potential of long-term administration of lecithinized superoxide dismutase may be warranted.

TRIAL REGISTRATION

University hospital Medical Information Network (UMIN) clinical trials registry no. 000000752.

Differences in serum SP-D levels between German and Japanese subjects are associated with SFTPD gene polymorphisms

BACKGROUND

Surfactant protein A (SP-A) and SP-D are clinically established in Japan as serum biomarkers for diagnosing interstitial lung diseases (ILDs). Serum SP-D levels are affected by genetic variants. We conducted the present study to examine whether serum SP-A and/or SP-D levels in healthy subjects (HS) and patients with ILDs differ between populations with different genetic backgrounds.

METHODS

German subjects (n = 303; 138 patients with idiopathic interstitial pneumonias [IIPs] and 165 HS) and Japanese subjects (n = 369; 94 patients with IIPs and 275 HS) were enrolled. Serum SP-A and SP-D levels were measured using an enzyme-linked immunosorbent assay, and four single-nucleotide polymorphisms (SNPs) in the SFTPD gene were genotyped using genomic DNA extracted from blood samples.

RESULTS

In both the German and Japanese cohorts, serum SP-A and SP-D levels were significantly higher in patients with IIPs than in HS. There were no significant differences in SP-A levels between the German and Japanese cohorts; however, we found that serum SP-D levels were significantly higher in the German cohort, both in patients with IIPs and in HS (p < 0.001 and p = 0.005, respectively). Furthermore, the genotype distributions of the four SNPs in the SFTPD gene (rs721917, rs1998374, rs2243639, and rs3088308) were significantly different between German and Japanese cohorts (p < 0.001, p < 0.001, p = 0.022, and p < 0.001, respectively), and univariate linear regression analyses revealed that the genotypes of rs721917, rs1998374, and rs2243639 significantly correlated with serum SP-D levels (p < 0.001, p < 0.001, and p = 0.011, respectively). Furthermore, multivariate analyses revealed that the genotypes of these three SNPs correlated independently with serum SP-D levels (p < 0.001, p = 0.001, and p = 0.038, respectively), whereas ethnicity did not significantly correlate with serum SP-D levels.

CONCLUSIONS

In patients with IIPs and HS, serum SP-D, but not SP-A, levels were significantly higher in the German than in the Japanese cohort, in part, because of the different frequencies of SFTPD gene polymorphisms.

Bronchoalveolar lavage fluid and serum canine surfactant protein A concentrations in dogs with chronic cough by bronchial and interstitial lung diseases

We measured bronchoalveolar lavage fluid (BALF) and serum canine surfactant protein (cSP)-A concentrations in dogs with chronic cough. There were no significant differences between bronchial and interstitial lung diseases in BALF cSP-A concentrations. However, serum cSP-A concentrations in dogs with the interstitial lung disease as diffuse panbronchiolitis and idiopathic pulmonary fibrosis were significantly higher than those in dogs with the bronchial disease as chronic bronchitis. These results suggest that serum cSP-A concentrations may be a useful and noninvasive biomarker to understand the existence of interstitial lung damage in dogs with chronic cough.

CYFRA 21-1 as a disease severity marker for autoimmune pulmonary alveolar proteinosis

BACKGROUND AND OBJECTIVE

Serum markers, including Krebs von den Lungen (KL-6), surfactant protein (SP)-D, SP-A and carcinoembryonic antigen (CEA), are reported to reflect autoimmune pulmonary alveolar proteinosis (APAP) disease severity. We evaluated serum CYFRA21-1 levels as a marker of APAP.

METHODS

In addition to KL-6, SP-D and CEA, we prospectively measured serum CYFRA 21-1 levels in 48 patients with APAP, consecutively diagnosed between 2002 and 2010. Diagnostic usefulness of CYFRA 21-1 was determined from 68 patients with interstitial lung diseases by receiver operator characteristic curve analysis. We evaluated the association between these serum markers and other disease severity markers, including pulmonary function parameters, alveolar-arterial oxygen gradient, British Medical Research Council score reflecting shortness of breath, and disease severity score. CYFRA 21-1 localization in the lung was examined by immunohistochemistry.

RESULTS

Receiver operator characteristic curve demonstrated that CYFRA 21-1 effectively identified APAP. Serum CYFRA 21-1 levels at diagnosis were significantly associated with the measured disease severity parameters. Following whole lung lavage (n = 10) and granulocyte-macrophage colony-stimulating factor (GM-CSF) inhalation (n = 20), serum CYFRA 21-1 levels were significantly decreased. Responders (n = 11) to GM-CSF inhalation revealed significantly higher serum CYFRA 21-1 levels than non-responders (n = 9). Serum CYFRA 21-1 appeared to be a significant predictor of effectiveness of GM-CSF based on regression analysis. Immunohistochemistry showed that CYFRA 21-1 was localized on hyperplastic alveolar type II cells and lipoproteinaceous substances in alveoli.

CONCLUSIONS

Serum CYFRA 21-1 is a sensitive and useful serum marker for diagnosis and evaluation of disease severity of APAP, and may predict the response to GM-CSF inhalation.

Subclinical interstitial lung damage in workers exposed to indium compounds

Objectives

The present study was designed to determine whether there is a relationship between indium compound exposure and interstitial lung damage in workers employed at indium tin oxide manufacturing and reclaiming factories in Korea.

Methods

In 2012, we conducted a study for the prevention of indium induced lung damage in Korea and identified 78 workers who had serum indium or Krebs von den Lungen-6 (KL-6) levels that were higher than the reference values set in Japan (3 μg/L and 500 U/mL, respectively). Thirty-four of the 78 workers underwent chest high-resolution computed tomography (HRCT), and their data were used for statistical analysis.

Results

Geometric means (geometric standard deviations) for serum indium, KL-6, and surfactant protein D (SP-D) were 10.9 (6.65) μg/L, 859.0 (1.85) U/mL, and 179.27 (1.81) ng/mL, respectively. HRCT showed intralobular interstitial thickening in 9 workers. A dose–response trend was statistically significant for blood KL-6 levels. All workers who had indium levels ≥50 μg/L had KL-6 levels that exceeded the reference values. However, dose–response trends for blood SP-D levels, KL-6 levels, SP-D levels, and interstitial changes on the HRCT scans were not significantly different.

Conclusions

Our findings suggest that interstitial lung changes could be present in workers with indium exposure. Further studies are required and health risk information regarding indium exposure should be communicated to workers and employers in industries where indium compounds are used to prevent indium induced lung damage in Korea.

Fetal and neonatal samples of a precursor surfactant protein B inversely related to gestational age

Background

Alveolar–capillary membrane leaks can increase the amount of surfactant protein B (SP-B) in the bloodstream. The purpose of this study was to measure the concentration of C-proSP-B, a SP-B precursor that includes C-terminal domains, in various body fluids of newborn infants and determine its dependence on gestational age.

Methods

C-pro-SPB was measured in amniotic fluid and umbilical cord blood at birth, and in peripheral blood and urine on postnatal day 3 in 137 newborn infants with a median birth weight of 2015 g (range, 550–4475 g) and gestational age of 34 weeks (range, 23–42 weeks).

Results

C-proSP-B levels differed more than 100-fold among samples. The levels (median; interquartile range) were highest in peripheral blood (655.6 ng/mL; 419.0-1467.0 ng/mL) and lowest in urine (3.08 ng/mL; 2.96-3.35 ng/mL). C-proSP-B levels in amniotic fluid (314.9 ng/mL; 192.7–603.6 ng/mL) were approximately half of those in peripheral blood. In cord blood C-proSP-B was slightly lower (589.1 ng/mL; 181.2-1129.0 ng/mL) compared with peripheral blood. C-proSP-B levels significantly increased in all the fluids sampled except urine with decreasing gestational age (p < 0.001).

Conclusions

This novel assay allows for the quantitative measurement of C-proSP-B in blood and amniotic fluid. The dependence of C-proSP-B on gestational age may hamper its use for the detection of alveolar leaks in preterm newborns.

Surfactant protein-A concentration in sera from dogs with pulmonary parenchymal diseases

Pulmonary surfactant protein A (SP-A) is used as a biomarker to understand the clinical features of pulmonary diseases and associated prognostic indices in human medicine. This study was conducted to investigate whether or not serum SP-A concentration can be used as a biomarker for identifying pulmonary parenchymal diseases in dogs. Thirty-two dogs with pulmonary parenchymal diseases, 34 with nonrespiratory diseases and 57 healthy dogs were included. Serum SP-A concentration was measured in all dogs using sandwich enzyme linked immunosorbent assay with an anti-dog SP-A polyclonal antibody. Median serum SP-A concentration in healthy dogs was <2.0 ng/ml, whereas that in dogs with aspiration pneumonia (n=11), primary lung tumors (n=9) and blunt traumatic lung injury (BTLI; n=12) was 3.1, 7.2 and 2.6 ng/ml, respectively; these values were significantly higher than those in healthy dogs. The serum SP-A concentration in dogs with nonrespiratory diseases was comparable with that in healthy dogs. No correlation was observed between the serum SP-A and plasma C-reactive protein concentrations in dogs with aspiration pneumonia and BTLI. There was a significant correlation between the serum SP-A concentration and thoracic radiographic changes in dogs with BTLI. These findings suggest that the serum SP-A concentration may be a useful clinical biomarker of alveolar damage that can be used for differential diagnosis of pulmonary parenchymal diseases and nonrespiratory diseases in dogs.

The elevation of serum napsin A in idiopathic pulmonary fibrosis, compared with KL-6, surfactant protein-A and surfactant protein-D

Background

Napsin A, an aspartic protease, is mainly expressed in alveolar type-II cells and renal proximal tubules and is a putative immunohistochemical marker for pulmonary adenocarcinomas. This study sought to determine whether napsin A could be measured in the serum to evaluate its relationship to idiopathic pulmonary fibrosis (IPF) and determine whether renal dysfunction might affect serum napsin A levels.

Methods

Serum levels of napsin A were measured in 20 patients with IPF, 34 patients with lung primary adenocarcinoma, 12 patients with kidney diseases, and 20 healthy volunteers. Surfactant protein (SP)-A, SP-D, and Krebs von den Lungen-6 (KL-6) levels in serum and pulmonary function tests were also evaluated in IPF patients.

Results

Circulating levels of napsin A were increased in patients with IPF, as compared with healthy controls, and they correlated with the severity of disease. Moreover, the serum napsin A levels were not elevated in patients with pulmonary adenocarcinoma or renal dysfunction. The distinguishing point between IPF and the controls was that the area under the receiver operating characteristic curve (ROC) of napsin A was larger than that of KL-6, SP-A, or SP-D.

Conclusion

These findings suggest that serum napsin A may be a candidate biomarker for IPF.

An Insight into the Diverse Roles of Surfactant Proteins, SP-A and SP-D in Innate and Adaptive Immunity

Surfactant proteins SP-A and SP-D are hydrophilic, collagen-containing calcium-dependent lectins, which appear to have a range of innate immune functions at pulmonary as well as extrapulmonary sites. These proteins bind to target ligands on pathogens, allergens, and apoptotic cells, via C-terminal homotrimeric carbohydrate recognition domains, while the collagen region brings about the effector functions via its interaction with cell surface receptors. SP-A and SP-D deal with various pathogens, using a range of innate immune mechanisms such as agglutination/aggregation, enhancement of phagocytosis, and killing mechanisms by phagocytic cells and direct growth inhibition. SP-A and SP-D have also been shown to be involved in the control of pulmonary inflammation including allergy and asthma. Emerging evidence suggest that SP-A and SP-D are capable of linking innate immunity with adaptive immunity that includes modulation of dendritic cell function and helper T cell polarization. This review enumerates immunological properties of SP-A and SP-D inside and outside lungs and discusses their importance in human health and disease.

Bioinformatic identification of proteins with tissue-specific expression for biomarker discovery

BACKGROUND

There is an important need for the identification of novel serological biomarkers for the early detection of cancer. Current biomarkers suffer from a lack of tissue specificity, rendering them vulnerable to non-disease-specific increases. The present study details a strategy to rapidly identify tissue-specific proteins using bioinformatics.

METHODS

Previous studies have focused on either gene or protein expression databases for the identification of candidates. We developed a strategy that mines six publicly available gene and protein databases for tissue-specific proteins, selects proteins likely to enter the circulation, and integrates proteomic datasets enriched for the cancer secretome to prioritize candidates for further verification and validation studies.

RESULTS

Using colon, lung, pancreatic and prostate cancer as case examples, we identified 48 candidate tissue-specific biomarkers, of which 14 have been previously studied as biomarkers of cancer or benign disease. Twenty-six candidate biomarkers for these four cancer types are proposed.

CONCLUSIONS

We present a novel strategy using bioinformatics to identify tissue-specific proteins that are potential cancer serum biomarkers. Investigation of the 26 candidates in disease states of the organs is warranted.

Pulmonary Collectins in Diagnosis and Prevention of Lung Diseases

Pulmonary surfactant is a complex mixture of lipids and proteins, and is synthesized and secreted by alveolar type II epithelial cells and bronchiolar Clara cells. It acts to keep alveoli from collapsing during the expiratory phase of the respiratory cycle. After its secretion, lung surfactant forms a lattice structure on the alveolar surface, known as tubular myelin. Surfactant proteins (SP)-A, B, C and D make up to 10% of the total surfactant. SP-B and SPC are relatively small hydrophobic proteins, and are involved in the reduction of surface-tension at the air-liquid interface. SP-A and SP-D, on the other hand, are large oligomeric, hydrophilic proteins that belong to the collagenous Ca²⁺-dependent C-type lectin family (known as “Collectins”), and play an important role in host defense and in the recycling and transport of lung surfactant (Awasthi 2010) (Fig. 43.1). In particular, there is increasing evidence that surfactant-associated proteins A and -D (SP-A and SP-D, respectively) contribute to the host defense against inhaled microorganisms (see 10.1007/978-3-7091-1065_24 and 10.1007/978-3-7091-1065_25). Based on their ability to recognize pathogens and to regulate the host defense, SP-A and SP-D have been recently categorized as “Secretory Pathogen Recognition Receptors”. While SP-A and SP-D were first identified in the lung; the expression of these proteins has also been observed at other mucosal surfaces, such as lacrimal glands, gastrointestinal mucosa, genitourinary epithelium and periodontal surfaces. SP-A is the most prominent among four proteins in the pulmonary surfactant-system. The expression of SP-A is complexly regulated on the transcriptional and the chromosomal level. SP-A is a major player in the pulmonary cytokine-network and moreover has been described to act in the pulmonary host defense. This chapter gives an overview on the understanding of role of SP-A and SP-D in for human pulmonary disorders and points out the importance for pathology-orientated research to further elucidate the role of these molecules in adult lung diseases. As an outlook, it will become an issue of pulmonary pathology which might provide promising perspectives for applications in research, diagnosis and therapy (Awasthi 2010).

Genetic variant associations of human SP-A and SP-D with acute and chronic lung injury

Pulmonary surfactant, a lipoprotein complex, maintains alveolar integrity and plays an important role in lung host defense, and control of inflammation. Altered inflammatory processes and surfactant dysfunction are well described events that occur in patients with acute or chronic lung disease that can develop secondary to a variety of insults. Genetic variants of surfactant proteins, including single nucleotide polymorphisms, haplotypes, and other genetic variations have been associated with acute and chronic lung disease throughout life in several populations and study groups. The hydrophilic surfactant proteins SP-A and SP-D, also known as collectins, in addition to their surfactant-related functions, are important innate immunity molecules as these, among others, exhibit the ability to bind and enhance clearance of a wide range of pathogens and allergens. This review focuses on published association studies of human surfactant proteins A and D genetic polymorphisms with respiratory, and non-respiratory diseases in adults, children, and newborns. The potential role of genetic variations in pulmonary disease or pathogenesis is discussed following an evaluation, and comparison of the available literature.

Idiopathic pulmonary fibrosis may be a disease of recurrent, tractional injury to the periphery of the aging lung: a unifying hypothesis regarding etiology and pathogenesis

CONTEXT

Idiopathic pulmonary fibrosis is a progressive, fatal lung disease occurring in older individuals. Despite 50 years of accrued data about the disease, little progress has been made in slowing functional loss or in decreasing patient mortality.

OBJECTIVE

To present a novel hypothesis on the etiology and pathogenesis of idiopathic pulmonary fibrosis.

DESIGN

Published data are reviewed regarding the epidemiology, clinical presentation, natural history, radiologic findings, and pathologic findings in patients with idiopathic pulmonary fibrosis.

RESULTS

Patients with idiopathic pulmonary fibrosis may be predisposed genetically to tractional injury to the peripheral lung. The result is recurrent damage to the epithelial-mesenchymal interface, preferentially at the outer edges of the basilar lung lobules where tractional stress is high during inspiration, compliance is relatively low, and there is a greater tendency for alveolar collapse at end-expiration. A distinctive "reticular network of injury" (the fibroblast focus) forms, attended by a prolonged phase of wound repair (tear and slow repair). Discrete areas of alveolar collapse are observed in scar at the periphery of the lung lobules. The cycle repeats over many years resulting in progressive fibrous remodeling and replacement of the alveoli in a lobule by bronchiolar cysts surrounded by scar (honeycomb lung). Abnormalities in surfactant function are proposed as a potential mechanism of initial lung damage. Age of onset may be a function of a required threshold of environmental exposures (eg, cigarette smoking) or other comorbid injury to the aging lung.

CONCLUSIONS

Evidence supporting this hypothesis is presented and potential mechanisms are discussed. A potential role for contributing cofactors is presented.

Development and validation of a sandwich ELISA for use in measuring concentrations of canine surfactant protein A in serum of dogs

OBJECTIVE

To develop and evaluate a sandwich ELISA incorporating rabbit antiserum specific for canine surfactant protein A (SP-A) for use in measuring concentrations of SP-A in serum of dogs.

SAMPLE

Serum samples obtained from 6 healthy dogs and 3 dogs with pulmonary disease.

PROCEDURES

Rabbit antiserum was prepared against purified canine SP-A. The IgG fraction was isolated via protein G affinity chromatography and was then biotinylated. The sandwich ELISA was performed by use of anti-SP-A antibody (IgG) preabsorbed with sera from healthy dogs. Validity of the ELISA was confirmed by determination of the detection limit, precision, reproducibility, and accuracy. Serum SP-A concentrations were measured in 6 healthy dogs and 3 dogs with pulmonary disease.

RESULTS

Detection limit of the ELISA was 2.0 ng/mL. Within- and between-assay coefficients of variation ranged from 3.8% to 14.1% and from 15.5% to 35.6%, respectively. The observed-to-expected recovery ratio ranged from 77.1% to 89.9%. Serum SP-A concentrations measured by use of the ELISA were ≤ 2.3 ng/mL in the 6 healthy dogs, 25.6 ng/mL in a dog with severe cardiac pulmonary edema, 8.3 ng/mL in a dog with pneumonia, and 10.1 ng/mL in a dog with lung lobe torsion.

CONCLUSIONS AND CLINICAL RELEVANCE

The sandwich ELISA was found to be useful for measuring purified canine SP-A concentrations and canine SP-A concentrations in serum samples. The ELISA was precise, reproducible, and accurate. The ELISA may be beneficial in assessing serum concentrations of canine SP-A as a potential biomarker of pulmonary diseases in dogs.

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

RATIONALE

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

OBJECTIVES

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

METHODS

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

MEASUREMENTS AND MAIN RESULTS

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

CONCLUSIONS

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

The radiological patterns of interstitial change at an early phase: over a 4-year follow-up

OBJECTIVES

The identification of early phase interstitial changes may influence the understanding of idiopathic interstitial pneumonitis. This study aimed to clarify its radiological patterns and the association with smoking.

METHODS

The subjects underwent low-dose computed tomography to screen lung cancer. The selected subjects with interstitial changes were monitored for the precise morphology of interstitial changes using a high-resolution computed tomography (HRCT) scan. The subjects were classified into normal and abnormal HRCT subjects. The radiological findings on the HRCT scan, serum Klebs von der Lungen-6 (KL-6), surfactant protein (SP)-A, SP-D, pulmonary function, and computed tomography (CT) scores were analyzed. Abnormal HRCT subjects were classified based on the radiological patterns, and were followed-up over a 4-year period.

RESULTS

HRCT abnormalities suggesting interstitial changes were identified in 80 of 3079 subjects. Seven subjects with honeycombing and 14 with combined pulmonary fibrosis and emphysema (CPFE) were identified. The frequencies of sex (male) and smoking in the subjects with honeycombing was higher than that of other patterns. The smoking history and the levels of serum KL-6, SP-A, and SP-D in abnormal HRCT subjects were significantly higher than those in normal HRCT subjects. Thirty-two of 73 abnormal HRCT subjects showed a progression of the CT scores in a chest HRCT over a 4-year period. Eighteen abnormal HRCT current smokers were included in the progression of CT scores.

CONCLUSIONS

HRCT patterns, excluding interlobular septal thickening, show the progression of CT scores. Smokers with CT abnormalities may have a tendency to demonstrate worsening interstitial changes.

Elevated levels of thioredoxin 1 in the lungs and sera of idiopathic pulmonary fibrosis, non-specific interstitial pneumonia and cryptogenic organizing pneumonia

OBJECTIVE

Oxidant stress is thought to be involved in the establishment of idiopathic interstitial pneumonia (IIP). Thioredoxin 1 (TRX1) plays a role as a strong antioxidant in vivo, suggesting that TRX1 may be involved in the pathogenesis of IIPs. However, there is no report on TRX1 levels in the sera of IIPs. In addition, TRX1 expression in the lungs of non-specific interstitial pneumonia (NSIP) and cryptogenic organizing pneumonia (COP) patients also has not been reported. Here, we investigated whether or not TRX1 levels are altered in the lungs and sera of patients with idiopathic pulmonary fibrosis (IPF), NSIP, and COP.

METHODS

Immunohistochemical analysis was performed to examine the expression of TRX1. TRX1 levels in sera were measured using an ELISA kit.

RESULTS

TRX1 was expressed in the bronchiole-alveolar epithelium, especially with regenerative or metaplastic feature, and in alveolar macrophages in usual interstitial pneumonia (UIP) and fibrotic NSIP. TRX1 was weakly expressed in the lungs of cellular NSIP and COP. TRX1 producing cells in UIP (n=16), fibrotic NSIP (n=15), cellular NSIP (n=4), and COP (n=5) were significantly increased when compared to nonsmokers (n=7). TRX1 producing cells in UIP and fibrotic NSIP were significantly increased when compared to cellular NSIP and COP. TRX1 levels in the sera of the patients with IPF (n=32; 74.2 ± 7.5 ng/mL), fibrotic NSIP (n=7; 82.5 ± 18.4 ng/mL), cellular NSIP (n=3; 62.2 ± 3.2 ng/mL) and COP (n=17; 88.8 ± 19.7 ng/mL) were significantly higher than those of control subjects (n=74; 35.3 ± 2.7 ng/mL). Furthermore, TRX1 levels in the sera of IPF patients who later showed acute exacerbation (n=7; 106.6 ± 16.3 ng/mL) were significantly higher than those of IPF patients without acute exacerbation (n=25; 65.1 ± 7.6 ng/mL).

CONCLUSION

Overproduction of TRX1 in the lungs and sera may play an important role in the pathogenesis of IIPs.

Generation of lung epithelial-like tissue from human embryonic stem cells

Background

Human embryonic stem cells (hESC) have the capacity to differentiate in vivo and in vitro into cells from all three germ lineages. The aim of the present study was to investigate the effect of specific culture conditions on the differentiation of hESC into lung epithelial cells.

Methods

Undifferentiated hESC, grown on a porous membrane in hESC medium for four days, were switched to a differentiation medium for four days; this was followed by culture in air-liquid interface conditions during another 20 days. Expression of several lung markers was measured by immunohistochemistry and by quantitative real-time RT-PCR at four different time points throughout the differentiation and compared to appropriate controls.

Results

Expression of CC16 and NKX2.1 showed a 1,000- and 10,000- fold increase at day 10 of differentiation. Other lung markers such as SP-C and Aquaporin 5 had the highest expression after twenty days of culture, as well as two markers for ciliated cells, FOXJ1 and β-tubulin IV. The results from qRT-PCR were confirmed by immunohistochemistry on paraffin-embedded samples. Antibodies against CC16, SP-A and SP-C were chosen as specific markers for Clara Cells and alveolar type II cells. The functionality was tested by measuring the secretion of CC16 in the medium using an enzyme immunoassay.

Conclusion

These results suggest that by using our novel culture protocol hESC can be differentiated into the major cell types of lung epithelial tissue.

Proteomics of human lung tissue identifies surfactant protein A as a marker of chronic obstructive pulmonary disease

Chronic Obstructive Pulmonary Disease (COPD), a lung disease related to smoking, is one of the leading causes of chronic morbidity and mortality around the world. One goal in COPD research is the identification of biomarkers for early diagnosis of the disease. Here, we sought COPD-specific changes in the proteome from human lung tissue. This revealed increased levels of surfactant protein A (SP-A) in COPD but not in the normal or fibrotic lung. The results were confirmed by immunohistochemistry, morphometry and Western blotting. Furthermore, elevated SP-A protein levels were detected from the induced sputum supernatants of COPD patients. The levels of other surfactant proteins (SP-B, SP-C, SP-D) were not altered. Our results suggest that SP-A is linked to the pathogenesis of COPD and could be considered as a potential COPD biomarker.