Expression and localization of lung surfactant protein A in human tissues

A clinical proteomics study of exhaled breath condensate and biomarkers for pulmonary embolism

Pulmonary embolism (PE) can be a diagnostic challenge. Current diagnostic markers for PE are unspecific and new diagnostic tools are needed. The air we exhale is a possible new source for biomarkers which can be tapped into by analysing the exhaled breath condensate (EBC). We analysed the EBC from patients with PE and controls to investigate if the EBC is a useful source for new diagnostic biomarkers of PE. We collected and analysed EBC samples from patients with suspected PE and controls matched on age and sex. Patients in whom PE was ruled out after diagnostic work-up were included in the control group to increase the sensitivity and generalizability of the identified markers. EBC samples were collected using an RTube™. The protein composition of the EBCs were analysed using data dependent label-free quantitative nano liquid chromatography-tandem mass spectrometry. EBC samples from 28 patients with confirmed PE, and 49 controls were analysed. A total of 928 EBC proteins were identified in the 77 EBC samples. As expected, a low protein concentration was determined which resulted in many proteins with unmeasurable levels in several samples. The levels of HSPA5, PEBP1 and SFTPA2 were higher and levels of POF1B, EPPK1, PSMA4, ALDOA, and CFL1 were lower in PE compared with controls. In conclusion, the human EBC contained a variety of endogenous proteins and may be a source for new diagnostic markers of PE and other diseases.

Improved targeting delivery of WED-load immunoliposomes modified with SP-A mAb for the treatment of pulmonary fibrosis

The epithelial-mesenchymal transition (EMT) of type Ⅱ alveolar epithelial cells (AECS Ⅱ) induced by transforming growth factor (TGF-β1) is a primary pathogenesis of pulmonary fibrosis (PF). To augment the therapeutic potency of wedelolactone (WED) for PF, herein, pulmonary surfactant protein A (SP-A) specifically expressed on AECS Ⅱ was selected as the targeted receptor. Immunoliposomes modified with SP-A monoclonal antibody (SP-A mAb), novel anti-PF drug delivery systems, were developed and investigated in vivo and in vitro. In vivo fluorescence imaging technique was performed to evaluate the pulmonary-targeting effects of immunoliposomes. The result showed that immunoliposomes accumulated more in the lung, compared with non-modified nanoliposomes. Fluorescence detection methods and flow cytometry were used to investigate the function of SP-A mAb and the cellular uptake efficiency of WED-ILP in vitro. SP-A mAb enabled the immunoliposomes to specifically target the A549 cells and increased uptake more effectively. The mean fluorescence intensity (MFI) of cells treated with the targeted immunoliposomes was about 1.4-fold higher than that of cells treated with regular nanoliposomes. The cytotoxicity of nanoliposomes was assessed by the MTT assay, which demonstrated that blank nanoliposomes have no significant effect on A549 cell proliferation even at the SPC concentration of 1000 µg/mL. Additionally, in vitro pulmonary fibrosis model was established to further investigate the anti-pulmonary fibrosis effect of WED-ILP. WED-ILP significantly (**P < 0.01) inhibited the proliferation of A549 cells stimulated by TGF-β1 indicating that WED-ILP has great potential for the clinical treatment of PF.

Dysregulated serum and seminal plasma levels of surfactant protein D and MCP-1 in men with genital tract infection/inflammation

PROBLEM

Surfactant protein D (SP-D), a multimeric collectin expressed by testicular mucosal epithelia and is positively regulated by testosterone. It exerts antimicrobial effects, modulates inflammation and rescued spermatogenesis in a murine model. Various cytokines and chemokines, including MCP-1, play a key role in regulating the inflammation in rat and human testis. The study aimed to investigate the role of SP-D and involvement of chemokines and cytokines in the male infertility associated with urogenital infections or inflammation.

METHOD OF STUDY

The cross-sectional study evaluated levels of SP-D, testosterone, estradiol and the cytokines/chemokines including MCP-1 in the serum and semen samples of fertile and infertile Indian men with and without urogenital infections/inflammation (n = 76).

RESULTS

Both fertile and infertile males with urogenital infection/inflammation had significantly lower levels of SP-D and higher levels of the chemokine, Monocyte chemoattractant protein 1 (MCP-1) in the serum and seminal plasma. Seminal plasma of these males exhibited significantly higher proportion of proteolytically degraded forms of SP-D. The serum SP-D levels positively correlated with testosterone/estradiol (TE) ratio. There was no significant correlation between the SP-D levels in seminal plasma and sperm count/motility. With a significant area under the Receiver Operating Characteristic curves, the serum and seminal plasma SP-D levels exhibited significant potential to predict infertility with high sensitivity and specificity in men with genital infections/inflammation.

CONCLUSIONS

The circulating and seminal plasma SP-D levels were decreased in men with urogenital infection and inflammation. This could be due to their engagement at the site of infection, dysregulated expression owing to the altered hormonal profile and increased proteolytic degradation.

Idiopathic pulmonary fibrosis and the role of genetics in the era of precision medicine

Idiopathic pulmonary fibrosis (IPF) is a chronic, rare progressive lung disease, characterized by lung scarring and the irreversible loss of lung function. Two anti-fibrotic drugs, nintedanib and pirfenidone, have been demonstrated to slow down disease progression, although IPF mortality remains a challenge and the patients die after a few years from diagnosis. Rare pathogenic variants in genes that are involved in the surfactant metabolism and telomere maintenance, among others, have a high penetrance and tend to co-segregate with the disease in families. Common recurrent variants in the population with modest effect sizes have been also associated with the disease risk and progression. Genome-wide association studies (GWAS) support at least 23 genetic risk loci, linking the disease pathogenesis with unexpected molecular pathways including cellular adhesion and signaling, wound healing, barrier function, airway clearance, and innate immunity and host defense, besides the surfactant metabolism and telomere biology. As the cost of high-throughput genomic technologies continuously decreases and new technologies and approaches arise, their widespread use by clinicians and researchers is efficiently contributing to a better understanding of the pathogenesis of progressive pulmonary fibrosis. Here we provide an overview of the genetic factors known to be involved in IPF pathogenesis and discuss how they will continue to further advance in this field. We also discuss how genomic technologies could help to further improve IPF diagnosis and prognosis as well as for assessing genetic risk in unaffected relatives. The development and validation of evidence-based guidelines for genetic-based screening of IPF will allow redefining and classifying this disease relying on molecular characteristics and contribute to the implementation of precision medicine approaches.

Markers of Bronchiolitis Obliterans Syndrome after Lung Transplant: Between Old Knowledge and Future Perspective

Bronchiolitis obliterans syndrome (BOS) is the most common form of CLAD and is characterized by airflow limitation and an obstructive spirometric pattern without high-resolution computed tomography (HRCT) evidence of parenchymal opacities. Computed tomography and microCT analysis show abundant small airway obstruction, starting from the fifth generation of airway branching and affecting up to 40-70% of airways. The pathogenesis of BOS remains unclear. It is a multifactorial syndrome that leads to pathological tissue changes and clinical manifestations. Because BOS is associated with the worst long-term survival in LTx patients, many studies are focused on the early identification of BOS. Markers may be useful for diagnosis and for understanding the molecular and immunological mechanisms involved in the onset of BOS. Diagnostic and predictive markers of BOS have also been investigated in various biological materials, such as blood, BAL, lung tissue and extracellular vesicles. The aim of this review was to evaluate the scientific literature on markers of BOS after lung transplant. We performed a systematic review to find all available data on potential prognostic and diagnostic markers of BOS.

Surfactant proteins analysis in perinatal deceased preterm twins among the Romanian population

The molecular basis of the evaluation of children suspected of having disorders of surfactant proteins is still under discussion. In this study, we aimed to describe the morphological characteristics and to evaluate the immunohistochemical expression of surfactant proteins (surfactant protein A [SPA], surfactant protein B, and pro-surfactant protein C) in the preterm twins that deceased due to unexplained respiratory distress syndrome (n = 12). Results showed statistically significant positive correlations between surfactant protein B expressions and pulmonary hemorrhage (ρ = 0.678; P < .05), SPA levels, and Apgar score (ρ = 0.605; P < .05) and also expressions of SPA and bronchopneumonia (ρ = 0.695; P < .05). The fetuses and neonates of the same gestational age showed differences among surfactant proteins regarding the immunostaining expression. Our data evidence a marked interindividual variability in the expression of all 3 surfactant proteins among the cases analyzed (n = 12), suggesting the intervention of some individual and epigenetic factors during gestation that might influence surfactant protein production and consequently survival rate.

Betamethasone phosphate reduces the efficacy of antenatal steroid therapy and is associated with lower birthweights when administered to pregnant sheep in combination with betamethasone acetate

BACKGROUND

Antenatal corticosteroid therapy is a standard of care for women at imminent risk of preterm labor. However, the optimal (maximum benefit and minimal risk of side effects) antenatal corticosteroid dosing strategy remains unclear. Although conveying overall benefit when given to the right patient at the right time, antenatal corticosteroid treatment efficacy is highly variable and is not risk-free. Building on earlier findings, we hypothesized that when administered in combination with slow-release betamethasone acetate, betamethasone phosphate and the high maternal-fetal betamethasone concentrations it generates are redundant for fetal lung maturation.

OBJECTIVE

Using an established sheep model of prematurity and postnatal ventilation of the preterm lamb, we aimed to compare the pharmacodynamic effects of low-dosage treatment with betamethasone acetate only against a standard dosage of betamethasone phosphate and betamethasone acetate as recommended by the American College of Obstetricians and Gynecologists for women at risk of imminent preterm delivery between 24 0/7 and 35 6/7 weeks' gestation.

STUDY DESIGN

Ewes carrying a single fetus at 122±1 days' gestation (term=150 days) were randomized to receive either (1) maternal intramuscular injections of sterile saline (the saline negative control group, n=12), (2) 2 maternal intramuscular injections of 0.25 mg/kg betamethasone phosphate+betamethasone acetate administered at 24-hour dosing intervals (the betamethasone phosphate+betamethasone acetate group, n=12); or (3) 2 maternal intramuscular injections of 0.125 mg/kg betamethasone acetate administered at 24-hour dosing intervals (the betamethasone acetate group, n=11). The fetuses were surgically delivered 48 hours after treatment initiation and ventilated for 30 minutes to determine functional lung maturation. The fetuses were euthanized after ventilation, and the lungs were collected for analysis using quantitative polymerase chain reaction and Western blot assays. Fetal plasma adrenocorticotropic hormone levels were measured in the cord blood samples taken at delivery.

RESULTS

Preterm lambs were defined as either antenatal corticosteroid treatment responders or nonresponders using an arbitrary cutoff, being a PaCO₂ level at 30 minutes of ventilation being more extreme than 2 standard deviations from the mean value of the normally distributed saline control group values. Compared with the animals in the saline control group, the animals in the antenatal corticosteroid treatment groups showed significantly improved lung physiological responses (blood gas and ventilation data) and had a biochemical signature (messenger RNA and surfactant protein assays) consistent with functional maturation. However, the betamethasone acetate group had a significantly higher treatment response rate than the betamethasone phosphate+betamethasone acetate group. These physiological results were strongly correlated to the amount of surfactant protein A. Birthweight was lower in the betamethasone phosphate+betamethasone acetate group and the fetal hypothalamic-pituitary-adrenal axis was suppressed to a greater extent in the betamethasone phosphate+betamethasone acetate group.

CONCLUSION

Low-dosage antenatal corticosteroid therapy solely employing betamethasone acetate was sufficient for fetal lung maturation. The elevated maternal-fetal betamethasone concentrations associated with the coadministration of betamethasone phosphate did not in addition improve lung maturation but were associated with greater fetal hypothalamic-pituitary-adrenal axis suppression, a lower antenatal corticosteroid treatment response rate, and lower birthweight-outcomes not desirable in a clinical setting. These data warranted a clinical investigation of sustained low-dosage antenatal corticosteroid treatments that avoid high maternal-fetal betamethasone exposures.

Histone H4 potentiates neutrophil inflammatory responses to influenza A virus: Down-modulation by H4 binding to C-reactive protein and Surfactant protein D

Neutrophils participate in the early phase of the innate response to uncomplicated influenza A virus (IAV) infection but also are a major component in later stages of severe IAV or COVID 19 infection where neutrophil extracellular traps (NETs) and associated cell free histones are highly pro-inflammatory. It is likely that IAV interacts with histones during infection. We show that histone H4 binds to IAV and aggregates viral particles. In addition, histone H4 markedly potentiates IAV induced neutrophil respiratory burst responses. Prior studies have shown reactive oxidants to be detrimental during severe IAV infection. C reactive protein (CRP) and surfactant protein D (SP-D) rise during IAV infection. We now show that both of these innate immune proteins bind to histone H4 and significantly down regulate respiratory burst and other responses to histone H4. Isolated constructs composed only of the neck and carbohydrate recognition domain of SP-D also bind to histone H4 and partially limit neutrophil responses to it. These studies indicate that complexes formed of histones and IAV are a potent neutrophil activating stimulus. This finding could account for excess inflammation during IAV or other severe viral infections. The ability of CRP and SP-D to bind to histone H4 may be part of a protective response against excessive inflammation in vivo.

SP-A and SP-D: Dual Functioning Immune Molecules With Antiviral and Immunomodulatory Properties

Surfactant proteins A (SP-A) and D (SP-D) are soluble innate immune molecules which maintain lung homeostasis through their dual roles as anti-infectious and immunomodulatory agents. SP-A and SP-D bind numerous viruses including influenza A virus, respiratory syncytial virus (RSV) and human immunodeficiency virus (HIV), enhancing their clearance from mucosal points of entry and modulating the inflammatory response. They also have diverse roles in mediating innate and adaptive cell functions and in clearing apoptotic cells, allergens and other noxious particles. Here, we review how the properties of these first line defense molecules modulate inflammatory responses, as well as host-mediated immunopathology in response to viral infections. Since SP-A and SP-D are known to offer protection from viral and other infections, if their levels are decreased in some disease states as they are in severe asthma and chronic obstructive pulmonary disease (COPD), this may confer an increased risk of viral infection and exacerbations of disease. Recombinant molecules of SP-A and SP-D could be useful in both blocking respiratory viral infection while also modulating the immune system to prevent excessive inflammatory responses seen in, for example, RSV or coronavirus disease 2019 (COVID-19). Recombinant SP-A and SP-D could have therapeutic potential in neutralizing both current and future strains of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus as well as modulating the inflammation-mediated pathology associated with COVID-19. A recombinant fragment of human (rfh)SP-D has recently been shown to neutralize SARS-CoV-2. Further work investigating the potential therapeutic role of SP-A and SP-D in COVID-19 and other infectious and inflammatory diseases is indicated.

Collectins: Innate Immune Pattern Recognition Molecules

Collectins are collagen-containing C-type (calcium-dependent) lectins which are important pathogen pattern recognising innate immune molecules. Their primary structure is characterised by an N-terminal, triple-helical collagenous region made up of Gly-X-Y repeats, an a-helical coiled-coil trimerising neck region, and a C-terminal C-type lectin or carbohydrate recognition domain (CRD). Further oligomerisation of this primary structure can give rise to more complex and multimeric structures that can be seen under electron microscope. Collectins can be found in serum as well as in a range of tissues at the mucosal surfaces. Mannanbinding lectin can activate the complement system while other members of the collectin family are extremely versatile in recognising a diverse range of pathogens via their CRDs and bring about effector functions designed at the clearance of invading pathogens. These mechanisms include opsonisation, enhancement of phagocytosis, triggering superoxidative burst and nitric oxide production. Collectins can also potentiate the adaptive immune response via antigen presenting cells such as macrophages and dendritic cells through modulation of cytokines and chemokines, thus they can act as a link between innate and adaptive immunity. This chapter describes the structure-function relationships of collectins, their diverse functions, and their interaction with viruses, bacteria, fungi and parasites.

Intra-individual variation of particles in exhaled air and of the contents of Surfactant protein A and albumin

INTRODUCTION

Particles in exhaled air (PEx) provide samples of respiratory tract lining fluid from small airways containing, for example, Surfactant protein A (SP-A) and albumin, potential biomarkers of small airway disease. We hypothesized that there are differences between morning, noon, and afternoon measurements and that the variability of repeated measurements is larger between days than within days.

METHODS

PEx was obtained in sixteen healthy non-smoking adults on 11 occasions, within one day and between days. SP-A and albumin were quantified by ELISA. The coefficient of repeatability (CR), intraclass correlation coefficient (ICC), and coefficient of variation (CV) were used to assess the variation of repeated measurements.

RESULTS

SP-A and albumin increased significantly from morning towards the noon and afternoon by 13% and 25% on average, respectively, whereas PEx number concentration and particle mean mass did not differ significantly between the morning, noon and afternoon. Between-day CRs were not larger than within-day CRs.

CONCLUSIONS

Time of the day influences the contents of SP-A and albumin in exhaled particles. The variation of repeated measurements was rather high but was not influenced by the time intervals between measurements.

Human SP-D Acts as an Innate Immune Surveillance Molecule Against Androgen-Responsive and Androgen-Resistant Prostate Cancer Cells

Surfactant Protein D (SP-D), a pattern recognition innate immune molecule, has been implicated in the immune surveillance against cancer. A recent report showed an association of decreased SP-D expression in human prostate adenocarcinoma with an increased Gleason score and severity. In the present study, the SP-D expression was evaluated in primary prostate epithelial cells (PrEC) and prostate cancer cell lines. LNCaP, an androgen dependent prostate cancer cell line, exhibited significantly lower mRNA and protein levels of SP-D than PrEC and the androgen independent cell lines (PC3 and DU145). A recombinant fragment of human SP-D, rfhSP-D, showed a dose and time dependent binding to prostate cancer cells via its carbohydrate recognition domain. This study, for the first time, provides evidence of significant and specific cell death of tumor cells in rfhSP-D treated explants as well as primary tumor cells isolated from tissue biopsies of metatstatic prostate cancer patients. Viability of PrEC was not altered by rfhSP-D. Treated LNCaP (p53+/+) and PC3 (p53 -/-) cells exhibited reduced cell viability in a dose and time dependent manner and were arrested in G2/M and G1/G0 phase of the cell cycle, respectively. rfhSP-D treated LNCaP cells showed a significant upregulation of p53 whereas a significant downregulation of pAkt was observed in both PC3 and LNCaP cell lines. The rfhSP-D-induced apoptosis signaling cascade involved upregulation of Bax:Bcl2 ratio, cytochrome c and cleaved products of caspase 7. The study concludes that rfhSP-D induces apoptosis in prostate tumor explants as well as in androgen dependent and independent prostate cancer cells via p53 and pAkt pathways.

Idiopathic Pulmonary Fibrosis and Lung Cancer: Mechanisms and Molecular Targets

Idiopathic pulmonary fibrosis (IPF) is the most common idiopathic interstitial pulmonary disease with a median survival of 2–4 years after diagnosis. A significant number of IPF patients have risk factors, such as a history of smoking or concomitant emphysema, both of which can predispose the patient to lung cancer (LC) (mostly non-small cell lung cancer (NSCLC)). In fact, IPF itself increases the risk of LC development by 7% to 20%. In this regard, there are multiple common genetic, molecular, and cellular processes that connect lung fibrosis with LC, such as myofibroblast/mesenchymal transition, myofibroblast activation and uncontrolled proliferation, endoplasmic reticulum stress, alterations of growth factors expression, oxidative stress, and large genetic and epigenetic variations that can predispose the patient to develop IPF and LC. The current approved IPF therapies, pirfenidone and nintedanib, are also active in LC. In fact, nintedanib is approved as a second line treatment in NSCLC, and pirfenidone has shown anti-neoplastic effects in preclinical studies. In this review, we focus on the current knowledge on the mechanisms implicated in the development of LC in patients with IPF as well as in current IPF and LC-IPF candidate therapies based on novel molecular advances.

FIBCD1 Binds Aspergillus fumigatus and Regulates Lung Epithelial Response to Cell Wall Components

Aspergillus fumigatus (A. fumigatus) is a ubiquitous fungus of clinical importance associated with development of various pulmonary diseases and allergic hypersensitivity reactions. It is protected against environmental stress by a cell wall that contains polysaccharides such as chitin. We previously demonstrated that fibrinogen C domain-containing protein 1 (FIBCD1) is a membrane-bound protein that binds chitin through a conserved S1 binding site and is expressed in intestinal epithelium and salivary glands. Here, we further localized FIBCD1 protein expression at the surface of bronchial and alveolar human lung epithelium, observed recognition of A. fumigatus cell wall with S1 site-independent recognition. We observed FIBCD1-mediated suppression of IL-8 secretion, mucin production, and transcription of genes associated with airway inflammation and homeostasis in FIBCD1-transfected lung epithelial cells. These modulations were generally enforced by stimulation with A. fumigatus cell wall polysaccharides. In parallel, we demonstrated a FIBCD1-mediated modulation of IL-8 secretion induced by TLR2,−4, and −5. Collectively, our findings support FIBCD1 as a human lung epithelial pattern recognition receptor that recognizes the complex A. fumigatus cell wall polysaccharides and modulates the lung epithelial inflammatory response by suppressing inflammatory mediators and mucins.

Surfactant protein A suppresses preterm delivery induced by live Escherichia coli in mice

Preterm birth accounts for the majority of neonatal morbidity and mortality in the developed world. A significant proportion of cases of spontaneous preterm labor are attributable to infections within gestational tissues. Surfactant protein A (SP-A), a collectin produced in the fetal lung and other tissues, has been shown previously in mice to suppress preterm delivery due to intrauterine (IU) instillation of sterile proinflammatory substances. Here we report a powerful antilabor effect for SP-A after IU infection with live Escherichia coli. SP-A abolished preterm birth (rate reduced from 100% to 0%) when it was administered into the uterus simultaneously with bacterial infection, reducing it by 75% when administered intravenously at the same time as IU bacterial inoculation, and by 48% when administered intravenously 4 h after IU bacterial infection. This effect on preterm delivery was accompanied by a parallel benefit on fetal survival in utero. SP-A had no effect on bacterial growth but reversed several major consequences of infection, including increased production of inflammatory mediators and a shift in macrophage polarization to the M1 phenotype. These findings suggest that exogenous SP-A has potential use to counteract infection-induced labor by reversing its proinflammatory consequences.

Biomarkers of respiratory allergy in laboratory animal care workers: an observational study

OBJECTIVES

Laboratory animal allergy is a highly prevalent occupational disease among exposed workers. The aim of the study was to validate the biomarkers of airway inflammation in laboratory animal (LA) care workers.

METHODS

All of the participants in this observational study (63 LA care workers and 64 controls) were administered a clinical questionnaire, underwent spirometry and a skin prick or radioallergosorbent test for common and occupational aeroallergens, and the fraction of exhaled nitric oxide (FeNO₅₀), exhaled breath condensate hydrogen peroxide (EBC H₂O₂) and serum pneumoprotein levels were measured. Multivariate analysis (ANCOVA) was used to assess the interactions of the variables.

RESULTS

FeNO₅₀ levels correlated with exposure (p = 0.002), sensitisation (p = 0.000) and age (p = 0.001), but there was no interaction between exposure and sensitisation when age was considered in the model (p = 0.146). EBC-H₂O₂ levels were higher in the sensitised workers than in the sensitised controls [0.14 (0.08-0.29) µM vs 0.07 (0.05-0.12) µM; p < 0.05]. Serum surfactant protein A (SP-A) levels were unaffected by exposure, sensitisation or age, although higher levels were observed in symptomatic workers; however, SP-D levels were influenced by exposure (p = 0.024) and age (p = 0.022), and club cell 16 levels were influenced by sensitisation (p = 0.027) and age (p = 0.019).

CONCLUSIONS

The presence of the clinical symptoms associated with LA exposure and high FeNO levels should prompt further medical assessments in LA workers. Although EBC-H₂O₂ levels do not seem to reflect eosinophilic inflammation, serum SP-A levels could be used to monitor progression from rhinitis to asthma.

Surfactant Proteins SP-A and SP-D Ameliorate Pneumonia Severity and Intestinal Injury in a Murine Model of Staphylococcus Aureus Pneumonia

Staphylococcus aureus pneumonia is an important cause of sepsis which causes gut injury, inflammation, and apoptosis. The surfactant proteins surfactant protein A (SP-A) and surfactant protein D (SP-D) bind bacterial pathogens and facilitate clearance of pathogens, apoptotic bodies, and modulate immune responses. SP-A and SP-D are expressed in both lung and gut epithelia. We hypothesize SP-A and SP-D regulate pneumonia severity and gut injury during pneumonia.

METHODS

Wild-type (WT) and SP-A and SP-D double knockout (SP-A/D KO) mice were subjected to S. aureus or sham pneumonia. Bronchoalveolar lavage and tissue harvest were performed 24 h later. Pneumonia severity, gut mucosal injury, inflammation, and apoptosis were measured using a combination of histology, immunohistochemistry, cytokine assay, TUNEL assay, quantitative real-time polymerase chain reaction, and Western blot analyses.

RESULTS

Pneumonia increased gut inflammation, apoptosis, and mucosal injury in both groups. Pneumonia histology and bacterial growth in bronchoalveolar lavage fluid demonstrate more severe infection in SP-A/D KO mice compared with WT controls. SP-A/D KO mice with pneumonia also demonstrate more severe histologic gut mucosal injury, increased gut apoptosis, elevated caspase-3 levels, and Bax/Bcl-2 mRNA expression compared with WT pneumonia mice. Nuclear factor κB (NF-κB) p65 expression and its nuclear translocation, gut levels of tumor necrosis factor α and interleukin-1β were all increased in SP-A/D KO mice with pneumonia compared with WT controls.

CONCLUSIONS

These data provide evidence SP-A and SP-D attenuate S. aureus pneumonia severity resulting in decreased intestinal mucosal injury, apoptosis, and inflammation. Improved pulmonary clearance of S. aureus decreased caspase-3 and Bax/Bcl-2 expressions and decreased activation of the NF-κB signaling pathway in intestine represent potential mechanisms for the effects of SP-A and SP-D on gut injury during pneumonia.

Role of Soluble Innate Effector Molecules in Pulmonary Defense against Fungal Pathogens

Fungal infections of the lung are life-threatening but rarely occur in healthy, immunocompetent individuals, indicating efficient clearance by pulmonary defense mechanisms. Upon inhalation, fungi will first encounter the airway surface liquid which contains several soluble effector molecules that form the first barrier of defense against fungal infections. These include host defense peptides, like LL-37 and defensins that can neutralize fungi by direct killing of the pathogen, and collectins, such as surfactant protein A and D, that can aggregate fungi and stimulate phagocytosis. In addition, these molecules have immunomodulatory activities which can aid in fungal clearance from the lung. However, existing observations are based on in vitro studies which do not reflect the complexity of the lung and its airway surface liquid. Ionic strength, pH, and the presence of mucus can have strong detrimental effects on antifungal activity, while the potential synergistic interplay between soluble effector molecules is largely unknown. In this review, we describe the current knowledge on soluble effector molecules that contribute to antifungal activity, the importance of environmental factors and discuss the future directions required to understand the innate antifungal defense in the lung.

Surfactant protein A deficiency exacerbates renal interstitial fibrosis following obstructive injury in mice

Renal interstitial fibrosis is an inevitable consequence of virtually every type of chronic kidney disease. The underlying mechanisms, however, are not completely understood. In the present study, we identified surfactant protein A (SP-A) as a novel protein factor involved in the renal fibrosis induced by unilateral ureter obstruction (UUO). UUO induced SP-A expression in mouse kidney epithelium, likely due to the increased acidic stress and inflammation. Interestingly, SP-A deficiency aggravated UUO-prompted kidney structural damage, macrophage accumulation, and tubulointerstitial fibrosis. SP-A deficiency appeared to worsen the fibrosis by enhancing interstitial myofibroblast accumulation. Moreover, SP-A deficiency increased the expression of TGF-β1, the major regulator of kidney fibrosis, particularly in the interstitial cells. Mechanistically, SP-A deficiency increased the expression and release of high mobility group box 1 (HMGB1), a factor regulating TGF-β expression/signaling and implicated in renal fibrosis. SP-A also blocked HMGB1 activities in inducing TGF-β1 expression and myofibroblast transdifferentiation from kidney fibroblasts, demonstrating that SP-A protected kidney by impeding both the expression and fibrogenic function of HMGB1. Since SP-A physically interacted with HMGB1 both in vitro and in kidney tissue in vivo, SP-A may exert its protective role by binding to HMGB1 and thus titrating its activity during UUO-induced renal fibrosis.

Surfactant protein A: A key player in lung homeostasis

The respiratory tract is continually exposed to various insults that are a permanent threat to the maintenance of lung homeostasis. Repair of the parenchyma structure, particularly of the alveolar epithelium, requires complex cellular strategies. Among the molecular components that play an important role in these processes are the surfactant proteins (SPs), particularly SP-A. The present review examines current evidence regarding the role of SP-A in lung host defence mechanisms through its implication in innate/adaptive immunity of the lung and epithelium integrity and repair. New information on SP-A deficiency in various forms of pulmonary diseases could help define therapeutic strategies aimed at restoring functional SP-A within the alveolar structure.

Low Levels of Exhaled Surfactant Protein A Associated With BOS After Lung Transplantation

BACKGROUND

There is no clinically available marker for early detection or monitoring of chronic rejection in the form of bronchiolitis obliterans syndrome (BOS), the main long-term complication after lung transplantation. Sampling and analysis of particles in exhaled air is a valid, noninvasive method for monitoring surfactant protein A (SP-A) and albumin in the distal airways.

METHODS

We asked whether differences in composition of exhaled particles can be detected when comparing stable lung transplant recipients (LTRs) (n = 26) with LTRs who develop BOS (n = 7). A comparison between LTRs and a matching group of healthy controls (n = 33) was also conducted. Using a system developed in-house, particles were collected from exhaled air by the principal of inertial impaction before chemical analysis by immunoassays.

RESULTS

Surfactant protein A in exhaled particles and the SP-A/albumin ratio were lower (P = 0.002 and P = 0.0001 respectively) in the BOS group compared to the BOS-free group. LTRs exhaled higher amount of particles (P < 0.0001) and had lower albumin content (P < 0.0001) than healthy controls.

CONCLUSIONS

We conclude that low levels of SP-A in exhaled particles are associated with increased risk of BOS in LTRs. The possibility that this noninvasive method can be used to predict BOS onset deserves further study with prospective and longitudinal approaches.

Developmental regulation of chicken surfactant protein A and its localization in lung

Surfactant Protein A (SP-A) is a collagenous C-type lectin (collectin) that plays an important role in the early stage of the host immune response. In chicken, SP-A (cSP-A) is expressed as a 26 kDa glycosylated protein in the lung. Using immunohistochemistry, cSP-A protein was detected mainly in the lung lining fluid covering the parabronchial epithelia. Specific cSP-A producing epithelial cells, resembling mammalian type II cells, were identified in the parabronchi. Gene expression of cSP-A markedly increased from embryonic day 14 onwards until the time of hatch, comparable to the SP-A homologue chicken lung lectin, while mannan binding lectin and collectins CL-L1 and CL-K1 only showed slightly changed expression during development. cSP-A protein could be detected as early as ED 18 in lung tissue using Western blotting, and expression increased steadily until day 28 post-hatch. Our observations are a first step towards understanding the role of this protein in vivo.

Role of collectins and complement protein C1q in pregnancy and parturition

Collectins such as surfactant proteins SP-A, SP-D, and mannan-binding lectin (MBL), as well as complement protein C1q are evolutionarily conserved innate immune molecules. They are known to opsonize a range of microbial pathogens (bacteria, fungi, virus, and parasites) and trigger effector clearance mechanisms involving phagocytosis and/or complement activation. Collectins and C1q have also attracted attention in studies involving pregnancy as they are expressed in the female reproductive tissues during pregnancy; a unique state of immune suppression with increased susceptibility to infectious diseases. Recent studies are beginning to unravel their functional significance in implantation, placentation, pregnancy maintenance and parturition in normal and adverse pregnancies. Collectins and C1q, expressed in gestational tissues during pregnancy, might alter the status of mother's immune response to the allogenic fetus and the microenvironment, thereby serving as important regulators of fetus-mother interaction. Here, we discuss the functional roles that have been assigned to SP-A, SP-D, MBL and C1q in pregnancy and parturition.

Surfactant Protein A in Exhaled Endogenous Particles Is Decreased in Chronic Obstructive Pulmonary Disease (COPD) Patients: A Pilot Study

Background

Exhaled, endogenous particles are formed from the epithelial lining fluid in small airways, where surfactant protein A (SP-A) plays an important role in pulmonary host defense. Based on the knowledge that chronic obstructive pulmonary disease (COPD) starts in the small airway epithelium, we hypothesized that chronic inflammation modulates peripheral exhaled particle SP-A and albumin levels. The main objective of this explorative study was to compare the SP-A and albumin contents in exhaled particles from patients with COPD and healthy subjects and to determine exhaled particle number concentrations.

Methods

Patients with stable COPD ranging from moderate to very severe (n = 13), and healthy non-smoking subjects (n = 12) were studied. Subjects performed repeated breath maneuvers allowing for airway closure and re-opening, and exhaled particles were optically counted and collected on a membrane using the novel PExA^® instrument setup. Immunoassays were used to quantify SP-A and albumin.

Results

COPD patients exhibited significantly lower SP-A mass content of the exhaled particles (2.7 vs. 3.9 weight percent, p = 0.036) and lower particle number concentration (p<0.0001) than healthy subjects. Albumin mass contents were similar for both groups.

Conclusions

Decreased levels of SP-A may lead to impaired host defense functions of surfactant in the airways, contributing to increased susceptibility to COPD exacerbations. SP-A in exhaled particles from small airways may represent a promising non-invasive biomarker of disease in COPD patients.

Expression and Localization of Lung Surfactant Proteins in Human Testis

Background

Surfactant proteins (SPs) have been described in various tissues and fluids including tissues of the nasolacrimal apparatus, airways and digestive tract. Human testis have a glandular function as a part of the reproductive and the endocrine system, but no data are available on SPs in human testis and prostate under healthy and pathologic conditions.

Objective

The aim of the study was the detection and characterization of the surfactant proteins A, B, C and D (SP-A, SP-B, SP-C, SP-D) in human testis. Additionally tissue samples affected by testicular cancer were investigated.

Results

Surfactant proteins A, B, C and D were detected using RT-PCR in healthy testis. By means of Western blot analysis, these SPs were detected at the protein level in normal testis, seminoma and seminal fluid, but not in spermatozoa. Expression of SPs was weaker in seminoma compared to normal testicular tissue. SPs were localized in combination with vimentin immunohistochemically in cells of Sertoli and Leydig.

Conclusion

Surfactant proteins seem to be inherent part of the human testis. By means of physicochemical properties the proteins appear to play a role during immunological and rheological process of the testicular tissue. The presence of SP-B and SP-C in cells of Sertoli correlates with their function of fluid secretion and may support transportation of spermatozoa. In seminoma the expression of all SP's was generally weaker compared to normal germ cells. This could lead to a reduction of immunomodulatory and rheology processes in the germ cell tumor.

Understanding Idiopathic Interstitial Pneumonia: A Gene-Based Review of Stressed Lungs

Pulmonary fibrosis is the main cause of severe morbidity and mortality in idiopathic interstitial pneumonias (IIP). In the past years, there has been major progress in the discovery of genetic factors that contribute to disease. Genes with highly penetrant mutations or strongly predisposing common risk alleles have been identified in familial and sporadic IIP. This review summarizes genes harbouring causative rare mutations and replicated common predisposing alleles. To date, rare mutations in nine different genes and five risk alleles fulfil this criterion. Mutated genes represent three genes involved in surfactant homeostasis and six genes involved in telomere maintenance. We summarize gene function, gene expressing cells, and pathological consequences of genetic alterations associated with disease. Consequences of the genetic alteration include dysfunctional surfactant processing, ER stress, immune dysregulation, and maintenance of telomere length. Biological evidence shows that these processes point towards a central role for alveolar epithelial type II cell dysfunction. However, tabulation also shows that function and consequence of most common risk alleles are not known. Most importantly, the predisposition of the MUC5B risk allele to disease is not understood. We propose a mechanism whereby MUC5B decreases surface tension lowering capacity of alveolar surfactant at areas with maximal mechanical stress.

Immunolocalization of surfactant protein D in the liver from infants with cholestatic liver disease

PURPOSE

Surfactant protein D (SP-D) is one of specific surfactant proteins constituting pulmonary surfactant. Recent studies have revealed that SP-D is detected in various non-pulmonary tissues and is involved in the host defense and immunomodulation. However, the relationship between SP-D and liver diseases has not yet been investigated. The aim of this study was to detect the immunolocalization of SP-D in the livers of infants with cholestatic liver disease.

METHODS

The expression of immunoreactive SP-D was assessed in infants with cholestasis, including biliary atresia (BA, n=7), neonatal hepatitis (NH, n=2), and paucity of the intrahepatic bile duct (PIBD, n=4). Immunoreactive SP-D was also assessed in six infants who died of non-liver disease as controls. Tissue samples were obtained at liver biopsy, or by post-mortem sampling. The tissue sections were incubated with anti-SP-D polyclonal antibodies and were counterstained with hematoxylin.

RESULTS

In the normal livers, SP-D was detected in the intrahepatic bile ducts, but was not detected in hepatocytes. In contrast, intense SP-D staining was noted in the hepatocytes from infants with BA, NH, and PIBD. Although SP-D was detected in the intrahepatic bile ducts in the infants with NH, negative or weak staining was seen in the intrahepatic bile ducts in infants with BA.

CONCLUSION

Our data showed that SP-D is present in the bile ducts of the normal infant liver, and it was found to accumulate in the hepatocytes of cholestatic livers. These results suggest that SP-D is produced in hepatocytes and is secreted into the bile ducts.

Pulmonary surfactant in the airway physiology: a direct relaxing effect on the smooth muscle

Beside alveoli, surface active material plays an important role in the airway physiology. In the upper airways it primarily serves in local defense. Lower airway surfactant stabilizes peripheral airways, provides the transport and defense, has barrier and anti-edematous functions, and possesses direct relaxant effect on the smooth muscle. We tested in vitro the effect of two surfactant preparations Curosurf® and Alveofact® on the precontracted smooth muscle of intra- and extra-pulmonary airways. Relaxation was more pronounced for lung tissue strip containing bronchial smooth muscle as the primary site of surfactant effect. The study does not confirm the participation of ATP-dependent potassium channels and cAMP-regulated epithelial chloride channels known as CFTR chloride channels, or nitric oxide involvement in contractile response of smooth muscle to surfactant.By controlling wall thickness and airway diameter, pulmonary surfactant is an important component of airway physiology. Thus, surfactant dysfunction may be included in pathophysiology of asthma, COPD, or other diseases with bronchial obstruction.

Eosinophil-associated lung diseases. A cry for surfactant proteins A and D help?

Surfactant proteins (SP)-A and SP-D (SP-A/-D) play important roles in numerous eosinophil-dominated diseases, including asthma, allergic bronchopulmonary aspergillosis, and allergic rhinitis. In these settings, SP-A/-D have been shown to modulate eosinophil chemotaxis, inhibit eosinophil mediator release, and mediate macrophage clearance of apoptotic eosinophils. Dysregulation of SP-A/-D function in eosinophil-dominated diseases is also not uncommon. Alterations in serum SP-A/-D levels are associated with disease severity in allergic rhinitis and chronic obstructive pulmonary disease. Furthermore, oligimerization of SP-A/-D, necessary for their proper function, can be perturbed by reactive nitrogen species, which are increased in eosinophilic disease. In this review, we highlight the associations of eosinophilic lung diseases with SP-A and SP-D levels and functions.

Surfactant proteins A, B, C and D in the human nasal airway: associated with mucosal glands and ciliated epithelium but absent in fluid-phase secretions and mucus

AIMS

To investigate the presence of surfactant protein (SP) A, B, C and D in nasal airways and to determine whether the proteins exert their main functions in nasal secretions or in the deeper layers of the nasal mucosa.

METHODS

Volunteers were recruited from the Department of ENT Head and Neck Surgery, Odense University Hospital, Denmark. The study included 39 subjects. Nasal mucosal biopsies were analyzed by immunohistochemistry, and bronchoalveolar and nasal lavages, nasal brush biopsies and nasal mucus were analyzed for SP-A, -B, -C and -D by SDS-PAGE and Western blotting. The presence of SP-A and SP-D in the first three samplings were also analyzed by enzyme-linked immunosorbent assay.

RESULTS

In nasal mucosal biopsies, SP-A, -B, -C and -D were all demonstrated in the serous acini of the submucosal glands and in the surface epithelium. SP-D was detected in nasal brush biopsies, whereas the other SPs were absent. Moreover, SP-A, -B, -C and -D were absent in nasal lavage and mucus.

CONCLUSION

SP-A, -B, -C and -D exert their protective effect in the ductal epithelium of the submucosal glands rather than in nasal secretions and mucus. Further studies are required to clarify the functions of these proteins in nasal secretory pathways for understanding upper airway diseases.

Severe respiratory insufficiency during pandemic H1N1 infection: prognostic value and therapeutic potential of pulmonary surfactant protein A

For almost two decades, studies have shown collectins to be critical for effective antimicrobial defense of the airways. Members of this protein family, which includes surfactant proteins (SP)-A and D, provide broad-spectrum protection through promoting the aggregation and clearance of pathogens. Interestingly, these proteins may also modulate the immune response, and growing evidence has shown collectins to be protective against several markers of inflammation and injury. In a recent study by Herrera-Ramos and colleagues, genetic variants of collectins were examined in Spanish patients with the pandemic 2009 H1N1 influenza A virus. Comparing genotypes for measures of poor lung function, inflammation, and admission to intensive care, these authors identified three variants of the SP-A gene SFTPA2 that positively correlated with flu severity. Remarkably, they also found the haplotype 1A¹ of SFTPA2 to be protective against these indicators, suggesting that targeted therapy with a recombinant form of SP-A2 may improve patient outcome. Although further work is required to confirm the specificity and efficacy of SP-A in therapeutic H1N1 protection, this study is one of the first to suggest a clinical role for SP-A in pandemic influenza.

Correlation analysis between single nucleotide polymorphisms of pulmonary surfactant protein A gene and pulmonary tuberculosis in the Han population in China

OBJECTIVE

To investigate the correlation of single nucleotide polymorphisms (SNPs) in SFTPA1 and SFTPA2 genes encoding pulmonary surfactant protein A (SP-A) with the susceptibility to pulmonary tuberculosis (PTB) in the Han population in China.

METHODS

This study included 248 patients with active PTB (case group) and 124 normal individuals (control group). SNPs at loci aa19, aa50, aa62, aa133, and aa219 of SFTPA1, and at loci aa9, aa91, aa140, and aa223 of SFTPA2 were analyzed with PCR. Multivariate logistic regression analysis was used to identify the correlation of age, sex, and SNPs with PTB.

RESULTS

The frequencies of the G allele at aa91 and T allele at aa140 in SFTPA2 were significantly higher in the case group than in the control group (p=0.0002 and p=0.045). The distribution of haplotype CGAAC in SFTPA1 was significantly lower in the case group than in the control group (p=0.025). In SFTPA2, the distributions of haplotypes 1A(6), 1A(10), 1A(9), and 1A(2) were higher (all p<0.05), but the distributions of haplotypes 1A(13), 1A(5), and 1A(12) were lower in the case group than in the control group (all p<0.05). When SFTPA1 and SFTPA2 were combined and analyzed, haplotype 6A(11)-1A(8) was only found in the case group (4.1%, p=0.001 compared with the control group), but the distribution of haplotype CGAAC-1A(0) or 6A(4)-1A(12) was significantly lower in the case group than in the control group (all p<0.05).

CONCLUSIONS

SNP in SP-A is associated with PTB in the Han population in China. The G allele at aa91, T allele at aa140, and haplotype 6A11-1A8 are risk factors for PTB, but haplotype CGAAC-1A(0) and 6A(4)-1A(12) are protective factors for PTB.

Branching morphogenesis of immortalized human bronchial epithelial cells in three-dimensional culture

While mouse models have contributed in our understanding of lung development, repair and regeneration, inherent differences between the murine and human airways requires the development of new models using human airway epithelial cells. In this study, we describe a three-dimensional model system using human bronchial epithelial cells (HBECs) cultured on reconstituted basement membrane. HBECs form complex budding and branching structures on reconstituted basement membrane when co-cultured with human lung fetal fibroblasts. These structures are reminiscent of the branching epithelia during lung development. The HBECs also retain markers indicative of epithelial cell types from both the central and distal airways suggesting their multipotent potential. In addition, we illustrate how the model can be utilized to understand respiratory diseases such as lung cancer. The 3D novel cell culture system recapitulates stromal-epithelial interactions in vitro that can be utilized to understand important aspects of lung development and diseases.

Purification of surfactant protein D (SP-D) from pooled amniotic fluid and bronchoalveolar lavage

Surfactant protein SP-D is a multimeric collagenous lectin, called collectin. SP-D is a multifunctional, pattern recognition innate immune molecule, which binds in a calcium dependent manner to an array of carbohydrates and lipids, thus offering resistance to invading pathogens, allergen challenge, and pulmonary inflammation. SP-D is predominantly found in the endoplasmic reticulum of type 2 pneumocytes and in the secretory granules of Clara or non-ciliated bronchiolar cells. The highest expression of SP-D is observed in the distal airways and alveoli. There is also an extra pulmonary existence of SP-D. The common sources of native full-length human SP-D are bronchoalveolar lavage (BAL) washings from normal or preferably patients suffering from alveolar proteinosis who overproduce SP-D in the lungs. Amniotic fluid collected at the term during parturition is another reasonable source. Here, we describe a simple and rapid method of purifying native SP-D away from SP-A which is also present in the same source. We also describe procedures of expressing and purifying a recombinant fragment of human SP-D (rhSP-D) comprising trimeric neck and carbohydrate recognition domains that has been shown to have therapeutic effects in murine models of allergy and infection.

Lipase member H is a novel secreted protein selectively upregulated in human lung adenocarcinomas and bronchioloalveolar carcinomas

Lung cancer is one of the most frequent causes of cancer-related death worldwide. However, molecular markers for lung cancer have not been well established. To identify novel genes related to lung cancer development, we surveyed publicly available DNA microarray data on lung cancer tissues. We identified lipase member H (LIPH, also known as mPA-PLA1) as one of the significantly upregulated genes in lung adenocarcinoma. LIPH was expressed in several adenocarcinoma cell lines when they were analyzed by quantitative real-time polymerase chain reaction (qPCR), western blotting, and sandwich enzyme-linked immunosorbent assay (ELISA). Immunohistochemical analysis detected LIPH expression in most of the adenocarcinomas and bronchioloalveolar carcinomas tissue sections obtained from lung cancer patients. LIPH expression was also observed less frequently in the squamous lung cancer tissue samples. Furthermore, LIPH protein was upregulated in the serum of early- and late-phase lung cancer patients when they were analyzed by ELISA. Interestingly, high serum level of LIPH was correlated with better survival in early phase lung cancer patients after surgery. Thus, LIPH may be a novel molecular biomarker for lung cancer, especially for adenocarcinoma and bronchioloalveolar carcinoma.

Evidence of surfactant protein A and D expression decrement and their localizations in human prostate adenocarcinomas

AIM

Surfactant proteins (SP-A and SP-D) were originally described in the lung; however, they are also present in the prostate. Purpose of this study, therefore, was to determine how surfactant proteins are altered in prostate adenocarcinomas (PCa) and find out any connection exists between their expressions and their staining patterns, prostate-specific antigen (PSA) values, Gleason score, age, tumor volume and tumor, node, metastases (TNM) clinical stage.

METHODS

Thirty-five tissue samples were obtained during radical prostatectomy. All specimens were classified to three groups based on the Gleason score <7, 7 and Gleason score >7. Surfactant proteins' expressions were tested by immunohistochemical and Western blotting methods.

RESULTS

Immunoreactivity was detected in the cytoplasm from both basal cells and secretory epithelial cells in malignant and non-malignant areas. About 80% of the malignant basal cells were characterized as either weak or strong while non-malignant epithelial cells demonstrated strong immunoreactivity for SP-A. Also malignant (81.8%) and non-malignant cells (90.6%) were characterized as either weak or strong for SP-D. Decrement of SP-A and SP-D immunostaining tended to associate with an increasing Gleason score (p > 0.05, p < 0.05), tumor volume (p < 0.05, p > 0.05) and age (p > 0.05, p > 0.05). There was a strong positive correlation between Gleason score and tumor volume (p < 0.01). Also, either none or weak SP-A and SP-D immunoreactivity was observed specimens with Gleason score 7 or higher. SP-A and SP-D reacted with 34 kDa (SP-A) and 43 kDa (SP-D) immunoreactive single bands were decreased in tumor tissues.

CONCLUSIONS

The development of prostate cancer may be related to decreased level of surfactant protein A and D.

Surfactant protein (SP)-A suppresses preterm delivery and inflammation via TLR2

Toll like receptors (TLRs) are pattern-recognition molecules that initiate the innate immune response to pathogens. Pulmonary surfactant protein (SP)-A is an endogenously produced ligand for TLR2 and TLR4. SP-A has been proposed as a fetally produced signal for the onset of parturition in the mouse. We examined the effect of interactions between SP-A and the pathogenic TLR agonists lipopolysaccharide (LPS), peptidoglycan (PGN) and polyinosinic:cytidylic acid (poly(I:C)) (ligands for TLR4, TLR2 and TLR3, respectively) on the expression of inflammatory mediators and preterm delivery. Three types of mouse macrophages (the cell line RAW 264.7, and fresh amniotic fluid and peritoneal macrophages, including macrophages from TLR4 and TLR2 knockout mice) were treated for up to 7 hours with pathogenic TLR agonists with or without SP-A. SP-A alone had no effect upon inflammatory mediators in mouse macrophages and did not independently induce preterm labor. SP-A significantly suppressed TLR ligand-induced expression of inflammatory mediators (interleukin (IL)-1β, tumor necrosis factor (TNF)-α and the chemokine CCL5) via a TLR2 dependent mechanism. In a mouse inflammation-induced preterm delivery model, intrauterine administration of SP-A significantly inhibited preterm delivery, suppressed the expression of proinflammatory mediators and enhanced the expression of the CXCL1 and anti-inflammatory mediator IL-10. We conclude that SP-A acts via TLR2 to suppress TLR ligand-induced preterm delivery and inflammatory responses.

Creation of lung-targeted dexamethasone immunoliposome and its therapeutic effect on bleomycin-induced lung injury in rats

OBJECTIVE

Acute lung injury (ALI), is a major cause of morbidity and mortality, which is routinely treated with the administration of systemic glucocorticoids. The current study investigated the distribution and therapeutic effect of a dexamethasone(DXM)-loaded immunoliposome (NLP) functionalized with pulmonary surfactant protein A (SP-A) antibody (SPA-DXM-NLP) in an animal model.

METHODS

DXM-NLP was prepared using film dispersion combined with extrusion techniques. SP-A antibody was used as the lung targeting agent. Tissue distribution of SPA-DXM-NLP was investigated in liver, spleen, kidney and lung tissue. The efficacy of SPA-DXM-NLP against lung injury was assessed in a rat model of bleomycin-induced acute lung injury.

RESULTS

The SPA-DXM-NLP complex was successfully synthesized and the particles were stable at 4°C. Pulmonary dexamethasone levels were 40 times higher with SPA-DXM-NLP than conventional dexamethasone injection. Administration of SPA-DXM-NLP significantly attenuated lung injury and inflammation, decreased incidence of infection, and increased survival in animal models.

CONCLUSIONS

The administration of SPA-DXM-NLP to animal models resulted in increased levels of DXM in the lungs, indicating active targeting. The efficacy against ALI of the immunoliposomes was shown to be superior to conventional dexamethasone administration. These results demonstrate the potential of actively targeted glucocorticoid therapy in the treatment of lung disease in clinical practice.

Lipopolysaccharide-induced expression of surfactant proteins A1 and A2 in human renal tubular epithelial cells

Background

Surfactant protein A (SP-A), encoded by two functional genes, SP-A1 and SP-A2, is essential for the inflammatory process and host defence in the lungs. Recent studies have demonstrated the extrapulmonary expression of SP-A. Similar to the lungs, the kidneys are organs exposed to external pathogens. The present study evaluated the expression and location of SP-A in the kidneys. The effect of lipopolysaccharide (LPS) on the expression of SP-A subtypes was also studied in renal tubular epithelial (HK-2) cells.

Methods

Immunohistochemical staining was performed using polyclonal antibody against SP-A. RT-PCR was also performed using mRNA from normal human renal tissues and HK-2 cells. The expressions of the SP-A1 and SP-A2 genes were determined by PCR-based RFLP analysis, gene-specific amplification, and direct sequencing of RT-PCR products. Western blot was conducted to analyse the SP-A protein. HK-2 cells were treated with LPS at various concentrations (0, 0.1, 1, 2, 5, and 10 μg/mL) for 8 h and at 5 μg/mL at various time points (0, 2, 4, 8, 16, and 24 h). The LPS-induced expressions of SP-A1 and SP-A2 mRNA and protein were analysed by RT-PCR and Western blot.

Results

SP-A was localised in the renal tubular epithelial cells in the proximal and distal convoluted tubules. SP-A1 and SP-A2 mRNA and protein were expressed in HK-2 cells and human renal tissues, which were significantly increased in time- and dose-dependent manners after LPS treatment (P < 0.05).

Conclusions

Human renal tubular epithelial cells can express both SP-A1 and SP-A2 genes, which may play important roles in the inflammatory modulation of the kidney.

Immunohistochemical staining of surfactant proteins A and B in skin of psoriatic patients before and after narrow-band UVB phototherapy

BACKGROUND

Psoriasis is a chronic inflammatory disorder that is mediated by elements of the innate and adaptive immune systems. Surfactant proteins (SPs) play an important role in host defense mechanisms. They are thought to have a potential role in some inflammatory skin diseases including psoriasis.

OBJECTIVE

The aim of the study was to evaluate SP-A and SP-B immunohistochemical staining in skin of psoriatic patients before and after narrow-band UV radiation type B (NB-UVB) phototherapy.

STUDY DESIGN

Immunohistochemical staining for SP-A and SP-B was performed on tissues from 20 psoriatic patients before and after NB-UVB. Results were compared with the degree of improvement assessed by the Psoriasis Area and Severity Index (PASI) and duration of treatment.

RESULTS

In unaffected skin, SP-A and SP-B were restricted to the basal layer; however, in psoriatic skin, they appeared in suprabasal layers in 80% and 85% of cases, respectively. Dermal inflammatory cells showed SP-A in 11 cases (55%) and SP-B in only one case (5%). After treatment by NB-UVB, SP-A and SP-B staining showed predilection to the basal layer. Absence of SP-A staining in suprabasal layers after NB-UVB therapy was correlated to better response to therapy (p=0.003) and shorter duration of treatment (p<0.0001).

CONCLUSIONS

SP-A and SP-B positivity is increased in psoriatic skin and reduced after NB-UVB therapy. Absence of SP-A in suprabasal layers after NB-UVB therapy is associated with better response and shorter duration of treatment.

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.

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.