The role of surfactant protein A in bleomycin-induced acute lung injury

Softness enhanced macrophage-mediated therapy of inhaled apoptotic-cell-inspired nanosystems for acute lung injury

Engineered nanosystems offer a promising strategy for macrophage-targeted therapies for various diseases, and their physicochemical parameters including surface-active ligands, size and shape are widely investigated for improving their therapeutic efficacy. However, little is known about the synergistic effect of elasticity and surface-active ligands. Here, two kinds of anti-inflammatory N-acetylcysteine (NAC)-loaded macrophage-targeting apoptotic-cell-inspired phosphatidylserine (PS)-containing nano-liposomes (PSLipos) were constructed, which had similar size and morphology but different Young's modulus (E) (H, ~ 100 kPa > E_macrophage vs. L, ~ 2 kPa < E_macrophage). Interestingly, these PSLipos-NAC showed similar drug loading and encapsulation efficiency, and in vitro slow-release behavior of NAC, but modulus-dependent interactions with macrophages. Softer PSLipos-L-NAC could resist macrophage capture, but remarkably prolong their targeting effect period on macrophages via durable binding to macrophage surface, and subsequently more effectively suppress inflammatory response in macrophages and then hasten inflammatory lung epithelial cell wound healing. Especially, pulmonary administration of PSLipos-L-NAC could significantly reduce the inflammatory response of M1-like macrophages in lung tissue and promote lung injury repair in a bleomycin-induced acute lung injury (ALI) mouse model, providing a potential therapeutic approach for ALI. The results strongly suggest that softness may enhance ligand-directed macrophage-mediated therapeutic efficacy of nanosystems, which will shed new light on the design of engineered nanotherapeutics.

Signaling Pathways That Mediate Alveolar Macrophage Activation by Surfactant Protein A and IL-4

Activation of tissue repair program in macrophages requires the integration of IL-4/IL-13 cytokines and tissue-specific signals. In the lung, surfactant protein A (SP-A) is a tissue factor that amplifies IL-4Rα-dependent alternative activation and proliferation of alveolar macrophages (AMs) through the myosin18A receptor. However, the mechanism by which SP-A and IL-4 synergistically increase activation and proliferation of AMs is unknown. Here we show that SP-A amplifies IL-4-mediated phosphorylation of STAT6 and Akt by binding to myosin18A. Blocking PI3K activity or the myosin18A receptor abrogates SP-A´s amplifying effects on IL-4 signaling. SP-A alone activates Akt, mTORC1, and PKCζ and inactivates GSK3α/β by phosphorylation, but it cannot activate arginase-1 activity or AM proliferation on its own. The combined effects of IL-4 and SP-A on the mTORC1 and GSK3 branches of PI3K-Akt signaling contribute to increased AM proliferation and alternative activation, as revealed by pharmacological inhibition of Akt (inhibitor VIII) and mTORC1 (rapamycin and torin). On the other hand, the IL-4+SP-A-driven PKCζ signaling axis appears to intersect PI3K activation with STAT6 phosphorylation to achieve more efficient alternative activation of AMs. Consistent with IL-4+SP-A-driven activation of mTORC1 and mTORC2, both agonists synergistically increased mitochondrial respiration and glycolysis in AMs, which are necessary for production of energy and metabolic intermediates for proliferation and alternative activation. We conclude that SP-A signaling in AMs activates PI3K-dependent branched pathways that amplify IL-4 actions on cell proliferation and the acquisition of AM effector functions.

Genetics and animal models of familial pulmonary fibrosis

Pulmonary fibrosis is caused by the interplay between genetic and environmental factors. Recent studies have revealed various genes associated with idiopathic pulmonary fibrosis, as well as the causative genes for familial pulmonary fibrosis. Although increased death or dysfunction of type 2 alveolar epithelial (AT2) cells has been detected in lung specimens from pulmonary fibrosis patients, it remains unclear whether and how AT2 cell death or dysfunction is responsible for the progression of pulmonary fibrosis. A recent study showed that increased AT2 cell necroptosis is the initial event in pulmonary fibrosis by analyzing patients with familial pulmonary fibrosis and an animal model that harbors the same mutation as patients. The contribution of AT2 cell necroptosis to the pathogenesis of pulmonary fibrosis has not been identified in animal model studies, which validates the effectiveness of genetic analysis of familial diseases to uncover unknown pathogeneses. Thus, further extensive genetic studies of pulmonary fibrosis along with functional studies based on genetic analysis will be crucial not only in elucidating the precise disease process but also, ultimately, in identifying novel treatment strategies for both familial and non-familial pulmonary fibrosis.

Gas6 Ameliorates Inflammatory Response and Apoptosis in Bleomycin-Induced Acute Lung Injury

Acute lung injury (ALI) is characterized by alveolar damage, lung edema, and exacerbated inflammatory response. Growth arrest-specific protein 6 (Gas6) mediates many different functions, including cell survival, proliferation, inflammatory signaling, and apoptotic cell clearance (efferocytosis). The role of Gas6 in bleomycin (BLM)-induced ALI is unknown. We investigated whether exogenous administration of mouse recombinant Gas6 (rGas6) has anti-inflammatory and anti-apoptotic effects on BLM-induced ALI. Compared to mice treated with only BLM, the administration of rGas6 reduced the secretion of proinflammatory cytokines, including tumor necrosis factor-α, interleukin-1β, and macrophage inflammatory protein-2, and increased the secretion of hepatocyte growth factor in bronchoalveolar lavage (BAL) fluid. rGas6 administration also reduced BLM-induced inflammation and apoptosis as evidenced by reduced neutrophil recruitment into the lungs, total protein levels in BAL fluid, caspase-3 activity, and TUNEL-positive lung cells in lung tissue. Apoptotic cell clearance by alveolar macrophages was also enhanced in mice treated with both BLM and rGas6 compared with mice treated with only BLM. rGas6 also had pro-resolving and anti-apoptotic effects in mouse bone marrow-derived macrophages and alveolar epithelial cell lines stimulated with BLM in vitro. These findings indicate that rGas6 may play a protective role in BLM-induced ALI.

Protective effect of extracorporeal membrane pulmonary oxygenation combined with cardiopulmonary resuscitation on post-resuscitation lung injury

BACKGROUND

Cardiac arrest (CA) is a critical condition that is a concern to healthcare workers. Comparative studies on extracorporeal cardiopulmonary resuscitation (ECPR) and conventional cardiopulmonary resuscitation (CCPR) technologies have shown that ECPR is superior to CCPR. However, there is a lack of studies that compare the protective effects of these two resuscitative methods on organs. Therefore, we aim to perform experiments in swine models of ventricular fibrillation-induced CA to study whether the early application of ECPR has advantages over CCPR in the lung injury and to explore the protective mechanism of ECPR on the post-resuscitation pulmonary injury.

METHODS

Sixteen male swine were randomized to CCPR (CCPR; n=8; CCPR alone) and ECPR (ECPR; n=8; extracorporeal membrane oxygenation with CCPR) groups, with the restoration of spontaneous circulation at 6 hours as an endpoint.

RESULTS

For the two groups, the survival rates between the two groups were not statistically significant (P>0.05), the blood and lung biomarkers were statistically significant (P<0.05), and the extravascular lung water and pulmonary vascular permeability index were statistically significant (P<0.01). Compared with the ECPR group, electron microscopy revealed mostly vacuolated intracellular alveolar type II lamellar bodies and a fuzzy lamellar structure with widening and blurring of the blood-gas barrier in the CCPR group.

CONCLUSIONS

ECPR may have pulmonary protective effects, possibly related to the regulation of alveolar surface-active proteins and mitigated oxidative stress response post-resuscitation.

Pulmonary surfactants affinity Pluronic-hybridized liposomes enhance the treatment of drug-resistant lung cancer

For a long time, the incidence and mortality of lung cancer have ranked first among all kinds of cancers, of which the major type is non-small cell lung cancer (NSCLC). Until now, chemotherapy and radiotherapy are still the first choice for patients with advanced or metastatic NSCLC. However, the emergence of multi-drug resistance (MDR) always leads to the failure of chemotherapy and increases cancer-related mortality. In this study, we prepared a Pluronic-hybridized paclitaxel-loaded liposome (PPL), which was used in combination with ambroxol (Ax) to not only resensitize drug-resistant tumor cells, but also increase the preparation retention in the lung. On the one hand, Ax induced the production of pulmonary surfactants (PS) and responsively improved the accumulation of pulmonary surfactants affinity liposomes whose skeleton was exogenous pulmonary surfactant phospholipids DPPC, because of the specific affinity of phospholipids related to pulmonary surfactant proteins. On the other hand, drug-resistant tumor cells were resensitized due to the inhibition of autophagy by Ax and the reduced expression of the drug-resistant protein P-glycoprotein (P-gp) by Pluronic P105. Therefore, we concluded that the combination of PPL and Ax achieved excellent killing tumor effects through multi-path and multi-strategy, having great application prospects in the future.

Methane Inhalation Protects Against Lung Ischemia-Reperfusion Injury in Rats by Regulating Pulmonary Surfactant via the Nrf2 Pathway

Methane (CH₄) exerted protective effects against lung ischemia-reperfusion (I/R) injury, but the mechanism remains unclear, especially the role of pulmonary surfactant. Therefore, this study aimed to explore the effects of CH₄ inhalation on pulmonary surfactant in rat lung I/R injury and to elucidate the mechanism. Rats were randomly divided into three groups (n = 6): the sham, I/R control, and I/R CH₄ groups. In the sham group, only thoracotomy was performed on the rats. In the I/R control and I/R CH₄ groups, the rats underwent left hilum occlusion for 90 min, followed by reperfusion for 180 min and ventilation with O₂ or 2.5% CH₄, respectively. Compared with those of the sham group, the levels of large surfactant aggregates (LAs) in pulmonary surfactant, lung compliance, oxygenation decreased, the small surfactant aggregates (SAs), inflammatory response, oxidative stress injury, and cell apoptosis increased in the control group (P < 0.05). Compared to the control treatment, CH₄ increased LA (0.42 ± 0.06 vs. 0.31 ± 0.09 mg/kg), oxygenation (201 ± 11 vs. 151 ± 14 mmHg), and lung compliance (16.8 ± 1.0 vs. 11.5 ± 1.3 ml/kg), as well as total antioxidant capacity and Nrf2 protein expression and decreased the inflammatory response and number of apoptotic cells (P < 0.05). In conclusion, CH₄ inhalation decreased oxidative stress injury, inflammatory response, and cell apoptosis, and improved lung function through Nrf2-mediated pulmonary surfactant regulation in rat lung I/R injury.

Genetic variation in surfactant protein-A2 alters responses to ozone

BACKGROUND

Increased exposure to Ozone (O3) is associated with adverse health effects in individuals afflicted with respiratory diseases. Surfactant protein-A (SP-A), encoded by SP-A1 and SP-A2, is the largest protein component in pulmonary surfactant and is functionally impaired by O3-oxidation.

OBJECTIVE

We used humanized SP-A2 transgenic mice with allelic variation corresponding to a glutamine (Q) to lysine (K) amino acid substitution at position 223 in the lectin domain to determine the impact of this genetic variation in regards to O3 exposure.

METHODS

Mice were exposed to 2ppm O3 or Filtered Air (FA) for 3 hours and 24 hrs post-challenge pulmonary function tests and other parameters associated with inflammation were assessed in the bronchoalveolar lavage (BAL) fluid and lung tissue. Additionally, mouse tracheal epithelial cells were cultured and TEER measurements recorded for each genotype to determine baseline epithelial integrity.

RESULTS

Compared to FA, O3 exposure led to significantly increased sensitivity to methacholine challenge in all groups of mice. SP-A2 223Q variant mice were significantly protected from O3-induced AHR compared to SP-A-/- and SP-A2 223K mice. Neutrophilia was observed in all genotypes of mice post O3-exposure, however, SP-A2 223Q mice had a significantly lower percentage of neutrophils compared to SP-A-/- mice. Albumin levels in BAL were unchanged in O3-exposed SP-A2 223Q mice compared to their FA controls, while levels were significantly increased in all other genotypes of O3-exposed mice. SP-A 223Q MTECS has significant higher TEER values than all other genotypes, and WT MTECS has significantly higher TEER than the SP-A KO and SP-A 223K MTECS.

SIGNIFICANCE

Taken together, our study suggests that expression of a glutamine (Q) as position 223 in SP-A2, as opposed to expression of lysine (K), is more protective in acute exposures to ozone and results in attenuated O3-induced AHR, neutrophilia, and vascular permeability.

Trauma-induced lung injury is associated with infiltration of activated TLR expressing myeloid cells

INTRODUCTION

Traumatic injury with hemorrhage (TH) induces an inflammatory response in the lung resulting in lung injury involving activation of immune cells including myeloid cells (i.e., monocytes, granulocytes and macrophages), in part through TLRs. TLRs, via the recognition of damage associated molecular patterns (DAMPs), are a key link between tissue injury and inflammation. Nonetheless, the role of TLRs in myeloid cell activation and TH-induced lung injury remains ill defined.

METHODS

C57BL/6 male mice were subjected to TH or sham treatment (n = 4-6 /group). Lung tissues were collected two hrs. after injury. Single cells were isolated from the lungs by enzymatic digestion and myeloid cell TLR expression and activation (i.e., cytokine production) were assessed using flow cytometry techniques.

RESULTS

The injury was associated with a profound change in the lung myeloid cell population. TH markedly increased lung CD11b⁺ monocyte numbers and Gr1⁺ granulocyte numbers as compared to sham mice. The number of cells expressing TLR2, TLR4, and TLR9 were increased 4-7 fold in the TH mice. Activation for elevated cytokine (TNFα, IL-10) production was observed in the lung monocyte population of the TH mice.

CONCLUSIONS

Trauma-induced lung injury is associated with infiltration of the lungs with TLR expressing myeloid cells that are activated for elevated cytokine responses. This elevation in TLR expression may contribute to DAMP-mediated pulmonary complications of an inflammatory nature and warrants further investigation.

Impact of ENaC downregulation in transgenic mice on the outcomes of acute lung injury induced by bleomycin

NEW FINDINGS

What is the central question of this study? How does the downregulation of ENaC, the major driving force for alveolar fluid clearance, impact acute lung injury outcomes induced by bleomycin, featuring alveolar damage, as observed during ARDS exudative phase? What is the main finding and its importance? ENaC downregulation in αENaC(-/-)Tg+ mice did not elicit a substantial worsening impact on the main bleomycin outcomes. In ARDS patients, both ENaC alteration and alveolar damage are observed. Thus, novel therapeutic avenues, favouring alveolar integrity restauration, in addition to lung oedema resolution capacity, mainly driven by ENaC, would be essential.

ABSTRACT

The exudative phase of acute respiratory distress syndrome (ARDS) is characterized by extended alveolar damage, resulting in accumulation of protein-rich inflammatory oedematous fluid in the alveolar space. Na⁺ reabsorption through ENaC channels is a major driving force for alveolar fluid clearance (AFC) in physiological and pathological conditions. It has previously been shown that partial αENaC impairment in transgenic (αENaC(-/-)Tg+) mice results in reduced AFC in basal conditions and increased wet/dry ratio after thiourea-induced lung oedema, a model in which the integrity of the alveolar epithelium is preserved. The goal of this study was to further investigate the impact of αENaC downregulation in αENaC(-/-)Tg+ mice using an experimental model of acute lung injury induced by bleomycin. A non-significant trend in enhanced weight loss and mortality rates was observed after the bleomycin challenge in αENaC(-/-)Tg+ compared to wild-type (WT) mice. Bronchoalveolar lavage analyses revealed increased TNFα levels and protein concentrations, as indexes of lung inflammation and alveolar damage, in αENaC(-/-)Tg+ mice, compared to WT, at day 3 post-bleomycin, although a statistical difference was no longer measured at day 7. Differential immune cell counts were similar in WT and αENaC(-/-)Tg+ mice challenged with bleomycin. Moreover, lung weight measurements indicated similar oedema levels in WT mice and in transgenic mice with impaired ENaC channels. Altogether, our data indicated that change in ENaC expression does not elicit a significant impact on lung oedema level/resolution in the bleomycin model, featuring alveolar damage.

Genetic Risk Factors for Idiopathic Pulmonary Fibrosis: Insights into Immunopathogenesis

Idiopathic pulmonary fibrosis is an etiologically complex interstitial lung disease characterized by progressive scarring of the lungs with a subsequent decline in lung function. While much of the pathogenesis of IPF still remains unclear, it is now understood that genetic variation accounts for at least one-third of the risk of developing the disease. The single-most validated and most significant risk factor, genetic or otherwise, is a gain-of-function promoter variant in the MUC5B gene. While the functional impact of these IPF risk variants at the cellular and tissue levels are areas of active investigation, there is a growing body of evidence that these genetic variants may influence disease pathogenesis through modulation of innate immune processes.

Surfactant Protein-A Function: Knowledge Gained From SP-A Knockout Mice

Pulmonary surfactant proteins have many roles in surfactant- related functions and innate immunity. One of these proteins is the surfactant protein A (SP-A) that plays a role in both surfactant-related processes and host defense and is the focus in this review. SP-A interacts with the sentinel host defense cell in the alveolus, the alveolar macrophage (AM), to modulate its function and expression profile under various conditions, as well as other alveolar epithelial cells such as the Type II cell. Via these interactions, SP-A has an impact on the alveolar microenvironment. SP-A is also important for surfactant structure and function. Much of what is understood of the function of SP-A and its various roles in lung health has been learned from SP-A knockout (KO) mouse experiments, as reviewed here. A vast majority of this work has been done with infection models that are bacterial, viral, and fungal in nature. Other models have also been used, including those of bleomycin-induced lung injury and ozone-induced oxidative stress either alone or in combination with an infectious agent, bone marrow transplantation, and other. In addition, models investigating the effects of SP-A on surfactant components or surfactant structure have contributed important information. SP-A also appears to play a role in pathways involved in sex differences in response to infection and/or oxidative stress, as well as at baseline conditions. To date, this is the first review to provide a comprehensive report of the functions of SP-A as learned through KO mice.

Dexamethasone fails to improve bleomycin-induced acute lung injury in mice

Acute respiratory distress syndrome (ARDS) features an exudative phase characterized by alveolar damage, lung edema and exacerbated inflammatory response. Given their anti‐inflammatory properties, the potential therapeutic effect of corticosteroids has been evaluated in ARDS clinical trials and experimental models of ALI. These studies produced contradictory results. Therefore, our aim was to investigate the effects of dexamethasone in an animal model of bleomycin‐induced acute lung injury and then to determine if the lack of response could be related to an impairment in repair ability of alveolar epithelial cells after injury. NMRI mice were challenged with bleomycin and then treated daily with dexamethasone or saline. Bronchoalveolar lavages (BAL) and lungs were collected for assessment of the inflammatory response and wet/dry ratio (lung edema) and for histological analyses. The effect of bleomycin and dexamethasone on wound repair was also evaluated in vitro on primary alveolar epithelial cell (ATII) cultures. Our data first showed that dexamethasone treatment did not reduce the weight loss or mortality rates induced by bleomycin. Although the TNF‐α level in BAL of bleomycin‐treated mice was reduced by dexamethasone, the neutrophil infiltration remained unchanged. Dexamethasone also failed to reduce lung edema and damage scores. Finally, bleomycin elicited a time‐ and dose‐dependent reduction in repair rates of ATII cell cultures. This inhibitory effect was further enhanced by dexamethasone, which also affected the expression of β3‐ and β6‐integrins, key proteins of alveolar repair. Altogether, our data indicate that the inability of dexamethasone to improve the resolution of ALI might be due to his deleterious effect on the alveolar epithelium repair.

Flow-Controlled Ventilation Attenuates Lung Injury in a Porcine Model of Acute Respiratory Distress Syndrome: A Preclinical Randomized Controlled Study

OBJECTIVES

Lung-protective ventilation for acute respiratory distress syndrome aims for providing sufficient oxygenation and carbon dioxide clearance, while limiting the harmful effects of mechanical ventilation. "Flow-controlled ventilation", providing a constant expiratory flow, has been suggested as a new lung-protective ventilation strategy. The aim of this study was to test whether flow-controlled ventilation attenuates lung injury in an animal model of acute respiratory distress syndrome.

DESIGN

Preclinical, randomized controlled animal study.

SETTING

Animal research facility.

SUBJECTS

Nineteen German landrace hybrid pigs.

INTERVENTION

Flow-controlled ventilation (intervention group) or volume-controlled ventilation (control group) with identical tidal volume (7 mL/kg) and positive end-expiratory pressure (9 cm H2O) after inducing acute respiratory distress syndrome with oleic acid.

MEASUREMENTS AND MAIN RESULTS

PaO2 and PaCO2, minute volume, tracheal pressure, lung aeration measured via CT, alveolar wall thickness, cell infiltration, and surfactant protein A concentration in bronchoalveolar lavage fluid. Five pigs were excluded leaving n equals to 7 for each group. Compared with control, flow-controlled ventilation elevated PaO2 (154 ± 21 vs 105 ± 9 torr; 20.5 ± 2.8 vs 14.0 ± 1.2 kPa; p = 0.035) and achieved comparable PaCO2 (57 ± 3 vs 54 ± 1 torr; 7.6 ± 0.4 vs 7.1 ± 0.1 kPa; p = 0.37) with a lower minute volume (6.4 ± 0.5 vs 8.7 ± 0.4 L/min; p < 0.001). Inspiratory plateau pressure was comparable in both groups (31 ± 2 vs 34 ± 2 cm H2O; p = 0.16). Flow-controlled ventilation increased normally aerated (24% ± 4% vs 10% ± 2%; p = 0.004) and decreased nonaerated lung volume (23% ± 6% vs 38% ± 5%; p = 0.033) in the dependent lung region. Alveolar walls were thinner (5.5 ± 0.1 vs 7.8 ± 0.2 µm; p < 0.0001), cell infiltration was lower (20 ± 2 vs 32 ± 2 n/field; p < 0.0001), and normalized surfactant protein A concentration was higher with flow-controlled ventilation (1.1 ± 0.04 vs 1.0 ± 0.03; p = 0.039).

CONCLUSIONS

Flow-controlled ventilation enhances lung aeration in the dependent lung region and consequently improves gas exchange and attenuates lung injury. Control of the expiratory flow may provide a novel option for lung-protective ventilation.

Using toponomics to characterize phenotypic diversity in alveolar macrophages from male mice treated with exogenous SP-A1

Background

We used the Toponome Imaging System (TIS) to identify “patterns of marker expression”, referred to here as combinatorial molecular phenotypes (CMPs) in alveolar macrophages (AM) in response to the innate immune molecule, SP-A1.

Methods

We compared 114 AM from male SP-A deficient mice. One group (n = 3) was treated with exogenous human surfactant protein A1 (hSP-A1) and the other with vehicle (n = 3). AM obtained by bronchoalveolar lavage were plated onto slides and analyzed using TIS to study the AM toponome, the spatial network of proteins within intact cells. With TIS, each slide is sequentially immunostained with multiple FITC-conjugated antibodies. Images are analyzed pixel-by-pixel identifying all of the proteins within each pixel, which are then designated as CMPs. CMPs represent organized protein clusters postulated to contribute to specific functions.

Results

1) We compared identical CMPs in KO and SP-A1 cells and found them to differ significantly (p = 0.0007). Similarities between pairs of markers in the two populations also differed significantly (p < 0.0001). 2) Focusing on the 20 most abundant CMPs for each cell, we developed a method to generate CMP “signatures” that characterized various groups of cells. Phenotypes were defined as cells exhibiting similar signatures of CMPs. i) AM were extremely diverse and each group contained cells with multiple phenotypes. ii) Among the 114 AM analyzed, no two cells were identical. iii) However, CMP signatures could distinguish among cell subpopulations within and between groups. iv) Some cell populations were enriched with SP-A1 treatment, some were more common without SP-A1, and some seemed not to be influenced by the presence of SP-A1. v) We also found that AM were more diverse in mice treated with SP-A1 compared to those treated with vehicle.

Conclusions

AM diversity is far more extensive than originally thought. The increased diversity of SP-A1-treated mice points to the possibility that SP-A1 enhances or activates several pathways in the AM to better prepare it for its innate immune functions and other functions shown previously to be affected by SP-A treatment. Future studies may identify key protein(s) responsible for CMP integrity and consequently for a given function, and target it for therapeutic purposes.

Mechanism of IL-8-induced acute lung injury through pulmonary surfactant proteins A and B

This study explored how interleukin-8 (IL-8) causes acute lung injury (ALI) through pulmonary surfactant protein A (SP-A) and surfactant protein B (SP-B). Serum was collected from 53 ALI patients and further 56 healthy subjects who underwent physical examination. The IL-8, SP-A, and SP-B levels were determined using enzyme-linked immunosorbent assay (ELISA). An ALI model was constructed using lipopolysaccharide (LSP)-induced normal A549 cells. siRNA was employed to interfere with the expression of IL-8, SP-A and SP-B. Western blot analysis was carried out to determine the protein levels, and MTT assay to determine the cell activity. In addition, co-immunoprecipitation (Co-IP) assay was used to verify the interaction between IL-8, SP-A and SP-B. ALI patients showed high expression of serum IL-8, and low expression of SP-A and SP-B, and IL-8 was negatively correlated with SP-A and SP-B, respectively. LSP-induced normal A549 cells showed increased expression of IL-8 and decreased expression of SP-A and SP-B. Silencing IL-8 led to increased expression levels of SP-A, SP-B and Bcl2, decreased expression levels of caspase-9, caspase-3, Bax, TNF-α, IL-17 and IL-1β, reduced cell apoptosis rate, and enhanced cell viability. Silencing SP-A and SP-B resulted in increased expression of IL-8, caspase-9, caspase-3, Bax, TNF-α, IL-17 and IL-1β, and decreased expression of Bcl2. Co-IP assay revealed that IL-8 could interact with SP-A and SP-B, respectively. IL-8 induces apoptosis by inhibiting SP-A and SP-B, and intensifies cellular inflammatory reaction, leading eventually to ALI.

The role of surfactant protein-A in sinusitis

PURPOSE OF REVIEW

Surfactant protein-A (SP-A) is a collectin protein expressed in airway epithelia that is critical in the modulation of both innate and adaptive immunity against inhaled pathogens. In this review, we highlight associations of altered SP-A function in asthma and chronic rhinosinusitis, and its potential role as a targeted therapy for sinusitis.

RECENT FINDINGS

SP-A has been shown to bind and opsonize inhaled pathogens, thereby clearing bacteria through phagocytosis. We have recently identified that SP-A levels are increased in response to Pseudomonas aeruginosa, a common bacterial pathogen in chronic rhinosinusitis. Moreover, SP-A has also been shown to modulate epithelial inflammatory mediators and play a role in eosinophil-mediated airway disease. The development of a transgenic murine model expressing human genetic variants of SP-A2 have suggested that the human surfactant protein-A2 223K variant significantly increases eosinophil degranulation, suggesting a genotype-phenotype correlation in human airway disease.

SUMMARY

SP-A is important in both the innate and adaptive host defense mechanisms in the upper and lower airways. Although research in this field in sinusitis is nascent, initial work suggests that aberrant SP-A regulation may be one etiologic factor in the development of bacterial and eosinophilic-associated sinusitis.

Genetic Variation in Surfactant Protein-A2 Delays Resolution of Eosinophilia in Asthma

Surfactant protein-A (SP-A) is an important mediator of pulmonary immunity. A specific genetic variation in SP-A2, corresponding to a glutamine (Q) to lysine (K) amino acid substitution at position 223 of the lectin domain, was shown to alter the ability of SP-A to inhibit eosinophil degranulation. Because a large subgroup of asthmatics have associated eosinophilia, often accompanied by inflammation associated with delayed clearance, our goal was to define how SP-A mediates eosinophil resolution in allergic airways and whether genetic variation affects this activity. Wild-type, SP-A knockout (SP-A KO) and humanized (SP-A2 223Q/Q, SP-A2 223K/K) C57BL/6 mice were challenged in an allergic OVA model, and parameters of inflammation were examined. Peripheral blood eosinophils were isolated to assess the effect of SP-A genetic variation on apoptosis and chemotaxis. Five days postchallenge, SP-A KO and humanized SP-A2 223K/K mice had persistent eosinophilia in bronchoalveolar lavage fluid compared with wild-type and SP-A2 223Q/Q mice, suggesting an impairment in eosinophil resolution. In vitro, human SP-A containing either the 223Q or the 223K allele was chemoattractant for eosinophils whereas only 223Q resulted in decreased eosinophil viability. Our results suggest that SP-A aids in the resolution of allergic airway inflammation by promoting eosinophil clearance from lung tissue through chemotaxis, independent of SP-A2 Q223K, and by inducing apoptosis of eosinophils, which is altered by the polymorphism.

A Macrophage-Pericyte Axis Directs Tissue Restoration via Amphiregulin-Induced Transforming Growth Factor Beta Activation

The epidermal growth factor receptor ligand Amphiregulin has a well-documented role in the restoration of tissue homeostasis after injury; however, the mechanism by which Amphiregulin contributes to wound repair remains unknown. Here we show that Amphiregulin functioned by releasing bioactive transforming growth factor beta (TGF-β) from latent complexes via integrin-α_V activation. Using acute injury models in two different tissues, we found that by inducing TGF-β activation on mesenchymal stromal cells (pericytes), Amphiregulin induced their differentiation into myofibroblasts, thereby selectively contributing to the restoration of vascular barrier function within injured tissue. Furthermore, we identified macrophages as a critical source of Amphiregulin, revealing a direct effector mechanism by which these cells contribute to tissue restoration after acute injury. Combined, these observations expose a so far under-appreciated mechanism of how cells of the immune system selectively control the differentiation of tissue progenitor cells during tissue repair and inflammation.

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Macrophages express Amphiregulin upon tissue damage

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Amphiregulin activates integrin-α_V complexes on pericytes

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Integrin-α_V-activated TGF-β induces pericyte into myofibroblast differentiation

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Myofibroblast-derived collagen contributes to wound healing

Deleterious Pulmonary Surfactant System Gene Mutations in Lung Adenocarcinomas Associated With Usual Interstitial Pneumonia

Purpose

Usual interstitial pneumonia (UIP) is a risk factor for lung carcinogenesis. This study was performed to characterize mutagenesis and mutational target genes underlying lung carcinogenesis in patients with UIP.

Patients and Methods

A cohort of 691 Japanese patients with lung adenocarcinoma (LADC), of whom 54 had UIP and 637 did not, was studied for driver oncogene aberrations. Whole-exome analysis was performed for 296 cases, including 51 with UIP, to deduce mutagenic processes and identify commonly affected genes. Logistic regression analysis was used to detect associations of gene aberrations with clinicopathological factors.

Results

The EGFR mutation was markedly less prevalent in patients with LADC with UIP than in those without (1.9% [one of 54] v. 49.9% [318 of 637]; P < .001), even in heavy smokers (25.3% [38 of 150] of patients with > 40 pack-years; P < .001). Mutational signature analysis indicated that UIP-positive LADCs develop through accumulation of single-nucleotide and indel mutations caused by smoking. Pulmonary surfactant system genes (PSSGs) NKX2-1/TTF1, SFTPA1, SFTPA2, SFTPB, and SFTPC were identified as targets for mutations (preferentially indels), and mutations were specifically associated with shorter overall survival of patients with UIP-positive LADC, independent of pathologic stage (hazard ratio, 4.9; 95% CI, 1.7 to 14.4; P = .0037).

Conclusion

LADCs with UIP develop through mutational events caused by smoking, independently of EGFR mutation. PSSGs were identified as a mutational target and as a novel prognostic factor in UIP-positive LADC. PSSG deficiency might increase the malignancy of tumor cells by increasing the tumor-promoting effects of UIP.

Evaluation of 99mTc-rhAnnexin V-128 SPECT/CT as a diagnostic tool for early stages of interstitial lung disease associated with systemic sclerosis

Background

Given the need for early detection of organ involvement in systemic sclerosis, we evaluated ^99mTc-rhAnnexin V-128 for the detection of early stages of interstitial lung disease (ILD) in respective animal models using single photon emission computed tomography (SPECT/CT).

Methods

In bleomycin (BLM)-challenged mice, fos-related antigen 2 (Fra-2) transgenic (tg) mice and respective controls, lung injury was evaluated by analysis of hematoxylin and eosin (HE) and Sirius red staining, with semi-quantification of fibrosis by the Ashcroft score. Apoptotic cells were identified by TUNEL assay, cleaved caspase 3 staining and double staining with specific cell markers. To detect early stages of lung remodeling by visualization of apoptosis, mice were injected intravenously with ^99mTc-rhAnnexin V-128 and imaged by small animal SPECT/CT. For confirmation, biodistribution and ex vivo autoradiography studies were performed.

Results

In BLM-induced lung fibrosis, inflammatory infiltrates occurred as early as day 3 with peak at day 7, whereas pulmonary fibrosis developed from day 7 and was most pronounced at day 21. In accordance, the number of apoptotic cells was highest at day 3 compared with saline controls and then decreased over time. Epithelial cells (E-cadherin+) and inflammatory cells (CD45+) were the primary cells undergoing apoptosis in the earliest remodeling stages of experimental ILD. This was also true in the pathophysiologically different Fra-2 tg mice, where apoptosis of CD45+ cells occurred in the inflammatory stage. In accordance with the findings on tissue level, at day 3 in the BLM and at week 16 in the Fra-2 tg model, biodistribution and/or ex vivo autoradiography showed increased pulmonary uptake of ^99mTc-rhAnnexin V-128 compared with controls. However, accumulation of the radiotracer and thus the signal intensity in lungs was too low to allow the differentiation of healthy and injured lungs in vivo.

Conclusion

At the tissue level, ^99mTc-rhAnnexin V-128 successfully demonstrated early stages of ILD in two animal models by detection of apoptotic epithelial and/or inflammatory cells. In vivo, however, we did not detect early lung injury. It remains to be investigated whether the same applies to human ILD.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1681-1) contains supplementary material, which is available to authorized users.

Lysosomal Protein Lamtor1 Controls Innate Immune Responses via Nuclear Translocation of Transcription Factor EB

Amino acid metabolism plays important roles in innate immune cells, including macrophages. Recently, we reported that a lysosomal adaptor protein, Lamtor1, which serves as the scaffold for amino acid-activated mechanistic target of rapamycin complex 1 (mTORC1), is critical for the polarization of M2 macrophages. However, little is known about how Lamtor1 affects the inflammatory responses that are triggered by the stimuli for TLRs. In this article, we show that Lamtor1 controls innate immune responses by regulating the phosphorylation and nuclear translocation of transcription factor EB (TFEB), which has been known as the master regulator for lysosome and autophagosome biogenesis. Furthermore, we show that nuclear translocation of TFEB occurs in alveolar macrophages of myeloid-specific Lamtor1 conditional knockout mice and that these mice are hypersensitive to intratracheal administration of LPS and bleomycin. Our observation clarified that the amino acid-sensing pathway consisting of Lamtor1, mTORC1, and TFEB is involved in the regulation of innate immune responses.

Synthesis of phosphatidylcholine in rats with oleic acid-induced pulmonary edema and effect of exogenous pulmonary surfactant on its De Novo synthesis

In mammals, oleic acid (OA) induces pulmonary edema (PE), which can initiate acute lung injury (ALI) and lead to acute respiratory distress syndrome (ARDS). Pulmonary surfactant (PS) plays a key role in a broad range of treatments for ARDS. The aim of the present investigation was to assess changes in the synthesis of phosphatidylcholine (PC) from choline and determine the effect of exogenous PS on its de novo synthesis in rats with OA-induced PE. Experimental rats were randomized into three groups, including a control group, OA-induced PE group, and OA-induced group treated with exogenous PS (OA-PS). Twenty-four rats were sacrificed 4 h after induction of the OA model, and tissue was examined by light and electron microscopy to assess the severity of ALI using an established scoring system at the end of the experiment. After 15 μCi ³H-choline chloride was injected intravenously, eight rats in each group were sacrificed at 4, 8, and 16 h. The radioactivity of ³H incorporated into total phospholipid (TPL) and desaturated phosphatidylcholine (DSPC) was measured in bronchoalveolar lavage fluid (BALF) and lung tissue (LT) using a liquid scintillation counter and was expressed as counts per minute (CPM). Results showed that TPL, DSPC, and the ratio of DSPC/total protein (TP) in lung tissue decreased 4 h after challenge with OA, but the levels recovered after 8 and 16 h. At 8 h after injection, ³H-TPL and ³H-DSPC radioactivity in the lungs reached its peak. Importantly, ³H-DSPC CPM were significantly lower in the PS treatment group (LT: Control: 62327 ± 9108; OA-PE: 97315 ± 10083; OA-PS: 45127 ± 10034, P < 0.05; BALF: Control: 7771 ± 1768; OA-PE: 8097 ± 1799; OA-PE: 3651 ± 1027, P < 0.05). Furthermore, DSPC secretory rate (SR) in the lungs was significantly lower in the PS treatment group at 4 h after injection (Control: 0.014 ± 0.003; OA-PE: 0.011 ± 0.004; OA-PS: 0.023 ± 0.006, P < 0.05). Therefore, we hypothesize that exogenous PS treatments may adversely affect endogenous de novo synthetic and secretory phospholipid pathways via feedback inhibition. This novel finding reveals the specific involvement of exogenous PS in endogenous synthetic and secretory phospholipid pathways during the treatment of ARDS. This information improves our understanding of how PS treatment is beneficial against ARDS and opens new opportunities for expanding its use.

Intratracheal instillation of alveolar type II cells enhances recovery from acute lung injury in rats

BACKGROUND

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are characterized by excess production of inflammatory factors. Alveolar type II (ATII) cells help repair damaged lung tissue, rapidly proliferating and differentiating into alveolar type I cells after epithelial cell injury. In ALI, the lack of viable ATII favors progression to more severe lung injury. ATII cells regulate the immune response by synthesizing surfactant and other anti-inflammatory proteins and lipids. Cross-talk between ATII and other cells such as macrophages may also be part of the ATII function. The aim of this study was to test the anti-inflammatory and reparative effects of ATII cells in an experimental model of ALI.

METHODS

In this study ATII cells (2.5 × 10⁶ cells/animal) were intratracheally instilled in rats with HCl and lipopolysaccharide (LPS)-induced ALI and in healthy animals to check for side effects. The specific effect of ATII cells was compared with fibroblast transplantation.

RESULTS

ATII cell transplantation promoted recovery of lung function, decrease mortality and lung inflammation of the animals with ALI. The primary mechanisms for benefit were paracrine effects of prostaglandin E₂ (PGE₂) and surfactant protein A (SPA) released from ATII cells that modulate alveolar macrophages to an anti-inflammatory phenotype. To our knowledge, these data are the first to provide evidence that ATII cells secrete PGE₂ and SPA, reducing pro-inflammatory macrophage activation and ALI.

CONCLUSION

ATII cells and their secreted molecules have shown an ability to resolve ALI, thereby highlighting a potential novel therapeutic target.

Hyperoxia treatment of TREK-1/TREK-2/TRAAK-deficient mice is associated with a reduction in surfactant proteins

We previously proposed a role for the two-pore domain potassium (K2P) channel TREK-1 in hyperoxia (HO)-induced lung injury. To determine whether redundancy among the three TREK isoforms (TREK-1, TREK-2, and TRAAK) could protect from HO-induced injury, we now examined the effect of deletion of all three TREK isoforms in a clinically relevant scenario of prolonged HO exposure and mechanical ventilation (MV). We exposed WT and TREK-1/TREK-2/TRAAK-deficient [triple knockout (KO)] mice to either room air, 72-h HO, MV [high and low tidal volume (TV)], or a combination of HO + MV and measured quasistatic lung compliance, bronchoalveolar lavage (BAL) protein concentration, histologic lung injury scores (LIS), cellular apoptosis, and cytokine levels. We determined surfactant gene and protein expression and attempted to prevent HO-induced lung injury by prophylactically administering an exogenous surfactant (Curosurf). HO treatment increased lung injury in triple KO but not WT mice, including an elevated LIS, BAL protein concentration, and markers of apoptosis, decreased lung compliance, and a more proinflammatory cytokine phenotype. MV alone had no effect on lung injury markers. Exposure to HO + MV (low TV) further decreased lung compliance in triple KO but not WT mice, and HO + MV (high TV) was lethal for triple KO mice. In triple KO mice, the HO-induced lung injury was associated with decreased surfactant protein (SP) A and SPC but not SPB and SPD expression. However, these changes could not be explained by alterations in the transcription factors nuclear factor-1 (NF-1), NKX2.1/thyroid transcription factor-1 (TTF-1) or c-jun, or lamellar body levels. Prophylactic Curosurf administration did not improve lung injury scores or compliance in triple KO mice.

Local amplifiers of IL-4Rα-mediated macrophage activation promote repair in lung and liver

The type 2 immune response controls helminth infection and maintains tissue homeostasis but can lead to allergy and fibrosis if not adequately regulated. We have discovered local tissue-specific amplifiers of type 2-mediated macrophage activation. In the lung, surfactant protein A (SP-A) enhanced interleukin-4 (IL-4)-dependent macrophage proliferation and activation, accelerating parasite clearance and reducing pulmonary injury after infection with a lung-migrating helminth. In the peritoneal cavity and liver, C1q enhancement of type 2 macrophage activation was required for liver repair after bacterial infection, but resulted in fibrosis after peritoneal dialysis. IL-4 drives production of these structurally related defense collagens, SP-A and C1q, and the expression of their receptor, myosin 18A. These findings reveal the existence within different tissues of an amplification system needed for local type 2 responses.

Epithelial disruption of Gab1 perturbs surfactant homeostasis and predisposes mice to lung injuries

GRB2-associated-binding protein 1 (Gab1) belongs to Gab adaptor family, which integrates multiple signals in response to the epithelial growth factors. Recent genetic studies identified genetic variants of human Gab1 gene as potential risk factors of asthmatic inflammation. However, the functions of Gab1 in lungs remain largely unknown. Alveolar type-II cells (AT-IIs) are responsible for surfactant homeostasis and essentially regulate lung inflammation following various injuries (3). In this study, in vitro knockdown of Gab1 was shown to decrease the surfactant proteins (SPs) levels in AT-IIs. We further examined in vivo Gab1 functions through alveolar epithelium-specific Gab1 knockout mice (Gab1^Δ/Δ). In vivo Gab1 deficiency leads to a decrease in SP synthesis and the appearance of disorganized lamellar bodies. Histological analysis of the lung sections in Gab1^Δ/Δ mice shows no apparent pathological alterations or inflammation. However, Gab1^Δ/Δ mice demonstrate inflammatory responses during the LPS-induced acute lung injury. Similarly, in mice challenged with bleomycin, fibrotic lesions were found to be aggravated in Gab1^Δ/Δ These observations suggest that the abolishment of Gab1 in AT-IIs impairs SP homeostasis, predisposing mice to lung injuries. In addition, we observed that the production of surfactants in AT-IIs overexpressing Gab1 mutants, in which Shp2 phosphatase and PI3K kinase binding sites have been mutated (Gab1^ΔShp2, Gab1^ΔPI3K), has been considerably attenuated. Together, these findings provide the direct evidence about the roles of docking protein Gab1 in lungs, adding to our understanding of acute and interstitial lung diseases caused by the disruption of alveolar SP homeostasis.

Dynamics of Structural Parameters and Accumulation of Collagen Fibrils in Rat Lung after Inhalations of Surfactant-BL at Various Terms of Bleomycin-Induced Alveolitis

Rats were subjected to surfactant-BL inhalations at the early and late phases of bleomycininduced alveolitis. In both regimens, the drug reduced the severity of inflammation. In the acute phase of alveolitis, the therapeutic effect of inhalation was accompanied by activation of the synthesis of fine lose collagen fibrils. In the late phase of alveolitis, inhalation of surfactant-BL thickened the fibrils and diminished their population in alveolar walls.

Deleted in malignant brain tumors 1 protein is a potential biomarker of acute respiratory distress syndrome induced by pneumonia

Acute respiratory distress syndrome (ARDS) is associated with high mortality and morbidity. Early diagnosis and risk stratification in patients with ARDS should improve prognosis. Unfortunately, no clinical biomarkers are available for use in early diagnosis. Quantitative proteomics is a powerful tool for biomarker discovery in cancer, autoimmune diseases, and ARDS. Here, we employed isobaric tags for relative and absolute quantitation (iTRAQ) technology to identify potential biomarkers for early ARDS diagnosis and predict the risk for increased disease severity induced by pneumonia. We collected the bronchoalveolar lavage fluid (BALF) and plasma from ARDS patients with differing degrees of ARDS severity. We identified 338 proteins dysregulated in ARDS through iTRAQ, 18 of which showed significant differences with at least 1.5-fold differential expression in patients with mild or severe ARDS. Differential plasma expression of pulmonary surfactant associated protein A, apolipoprotein A1, and deleted in malignant brain tumors 1 protein (DMBT1) was verified in plasma samples. Our results indicate that DMBT1 can potentially serve as a biomarker for early ARDS diagnosis and disease severity assessment.

Osthole Alleviates Bleomycin-Induced Pulmonary Fibrosis via Modulating Angiotensin-Converting Enzyme 2/Angiotensin-(1-7) Axis and Decreasing Inflammation Responses in Rats

Studies have shown that angiotensin-converting enzyme 2 (ACE2) plays modulating roles in lung pathophysiology, including pulmonary fibrosis (PF) and acute lung injury. Pulmonary fibrosis is a common complication in these interstitial lung diseases, and PF always has a poor prognosis and short survival. To date, there are few promising methods for treating PF, and they are invariably accompanied by severe side effects. Recent studies have showed that the traditional Chinese herbal extract, osthole, had beneficial effects on lipopolysaccharide (LPS) induced acute lung injury (ALI) via an ACE2 pathway. Here we further investigated the protective effects of osthole on bleomycin induced pulmonary fibrosis and attempted to determine the underlying mechanism. PF mode rats were induced by bleomycin (BLM) and then subsequently administered osthole. Histopathological analyses were employed to identify PF changes. The results showed that BLM resulted in severe PF and diffuse lung inflammation, together with significant elevation of inflammatory factors and a marked increase in expression of angiotensin II (ANG II) and transforming growth factor-beta 1 (TGF-β1). ACE2 and angiotensin-(1-7) [ANG-(1-7)] were both greatly reduced after BLM administration. Meanwhile, osthole treatment attenuated BLM induced PF and inflammation, decreased the expression of these inflammatory mediators, ANG II, and TGF-β1, and reversed ACE2 and ANG-(1-7) production in rat lungs. We conclude that osthole may exert beneficial effects on BLM induced PF in rats, perhaps via modulating the ACE2/ANG-(1-7) axis and inhibiting lung inflammation pathways.

Effects of basic drugs on prognosis of acute lung injury in mice

The aim of this study was to investigate the effects of basic drugs that alkalizes blood, on prognosis of acute lung injury in mice. Mice were randomized into three groups: Group normal saline, Group THAM, injected with 3.64% tri-(hydroxymethyl) methylamine (THAM), and Group NaHCO3, injected with 5% NaHCO3 (n=26, each group). The acute lung injury model was established by intraperitoneal injection of lipopolysaccharide (LPS; 50 mg/kg), followed by infusion of varying concentrations of the above solution into tail vein at the rate of 0.5 ml/h (controlled by micro pump) for over 2 h. Thirty minutes later, 6 mice from each group were randomly selected for blood gas analysis; then, the mice were killed and their lung tissues were sampled for detection of relative indicators, and the remaining mice were observed for signs of mortality for 72 h. Arterial pH, bicarbonate (HCO3 (-)), and BE and mortality of group THAM and NaHCO3 increased significantly compared to the corresponding parameters of the group normal saline (P<0.05); compared to the group normal saline, group NaHCO3 had increased blood [Na(+)] and decreased [K(+)] and [Ca(2+)] (P<0.05). Blood [Na(+)] of group THAM decreased while the lactic acid concentration increased (P<0.05) compared to the corresponding values of the group normal saline. Malondialdehyde (MDA) and myeloperoxidase (MPO) activity and wet-to-dry lung weight ratio (W/D) of group THAM and NaHCO3 increased significantly relative to group normal saline (P<0.05). Compared with the biopsy results of (A), pathological biopsy of (B) and (C) clearly revealed alveolar wall thickening, edema of alveolar epithelial cells, and infiltration of large neutrophils. Alkalizing blood could neither inhibit inflammatory reactions in LPS mouse model nor reduce the mortality rate of mice with acute lung injury, while excessive alkalization of blood could increase mice mortality.

Role of surfactant proteins A and D in sepsis-induced acute kidney injury

Sepsis is a major cause of acute kidney injury (AKI) with high rates of morbidity and mortality. Surfactant proteins A and D (SP-A, SP-D) play a critical role in host defense and regulate inflammation during infection. Recent studies indicate SP-A and SP-D are expressed in the kidney. The current study examines the role of SP-A and SP-D in the pathogenesis of sepsis-induced AKI. Wild-type (WT) and SP-A/SP-D double-knockout (KO) C57BL/6 mice were treated by cecal ligation and puncture (CLP) or sham surgery. Histological, cellular, and molecular indices of kidney injury were investigated in septic mice 6 and 24 h after CLP. Twenty-four hours after CLP, kidney injury was more severe, renal function was decreased, and blood creatinine and blood urea nitrogen were higher in septic SP-A/SP-D KO mice (P < 0.05, versus septic WT mice). Kidney edema and vascular permeability were increased in septic SP-A/SP-D KO mice (P < 0.01, versus septic WT mice). Apoptotic cells increased significantly (P < 0.01) in the kidney of septic SP-A/SP-D KO mice compared with septic WT mice. Molecular analysis revealed levels of Bcl-2 (an inhibitor of apoptosis) were lower and levels of caspase 3 (a biomarker of apoptosis) were higher in the kidney of septic SP-A/SP-D KO mice (P < 0.01, versus septic WT mice). Furthermore, levels of nuclear factor κB and phosphorylated IκB-α increased significantly in the kidney of septic SP-A/SP-D KO mice compared with septic WT mice, suggesting SP-A/SP-D KO mice have a more pronounced inflammatory response to sepsis. We conclude SP-A and SP-D attenuate kidney injury by modulating inflammation and apoptosis in sepsis-induced AKI.

Role of surfactant protein A in non-infectious lung diseases

Surfactant protein A (SP-A) is a large multimeric protein found in the airways and alveoli of the lungs. SP-A is a member of the collectin family of proteins, characterized by NH2-terminal collagen-like regions and COOH-terminal lectin domains. Although other surfactant proteins such as SP-B function to reduce surface tension in the lungs, SP-A as well as SP-D regulates the pulmonary immune response. To date, a number of studies have shown the immunoregulatory function of SP-A, mainly in the field of infectious diseases. By binding to a wide variety of pathogens, SP-A opsonizes and enhances pathogen uptake by phagocytes. In addition to the effect on pathogens, recent studies have shown that SP-A also modulates lung immune system in the area of non-infectious lung diseases. In this review, the potential role of SP-A in the multiple aspects of pulmonary host defense will be discussed, focusing mainly on non-infectious lung diseases such as acute and chronic pulmonary fibrosis and lung cancer. J. Med. Invest. 61: 1-6, February, 2014.

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 protein D attenuates sub-epithelial fibrosis in allergic airways disease through TGF-β

Background

Surfactant protein D (SP-D) can regulate both innate and adaptive immunity. Recently, SP-D has been shown to contribute to the pathogenesis of airway allergic inflammation and bleomycin-induced pulmonary fibrosis. However, in allergic airways disease, the role of SP-D in airway remodeling remains unknown. The objective of this study was to determine the contribution of functional SP-D in regulating sub-epithelial fibrosis in a mouse chronic house dust mite model of allergic airways disease.

Methods

C57BL/6 wild-type (WT) and SP-D−/− mice (C57BL/6 background) were chronically challenged with house dust mite antigen (Dermatophagoides pteronyssinus, Dp). Studies with SP-D rescue and neutralization of TGF-β were conducted. Lung histopathology and the concentrations of collagen, growth factors, and cytokines present in the airspace and lung tissue were determined. Cultured eosinophils were stimulated by Dp in presence or absence of SP-D.

Results

Dp-challenged SP-D−/− mice demonstrate increased sub-epithelial fibrosis, collagen production, eosinophil infiltration, TGF-β1, and IL-13 production, when compared to Dp-challenged WT mice. By immunohistology, we detected an increase in TGF-β1 and IL-13 positive eosinophils in SP-D−/− mice. Purified eosinophils stimulated with Dp produced TGF-β1 and IL-13, which was prevented by co-incubation with SP-D. Additionally, treatment of Dp challenged SP-D−/− mice with exogenous SP-D was able to rescue the phenotypes observed in SP-D−/− mice and neutralization of TGF-β1 reduced sub-epithelial fibrosis in Dp-challenged SP-D−/− mice.

Conclusion

These data support a protective role for SP-D in the pathogenesis of sub-epithelial fibrosis in a mouse model of allergic inflammation through regulation of eosinophil-derived TGF-β.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-014-0143-9) contains supplementary material, which is available to authorized users.

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.

Claudin 4 knockout mice: normal physiological phenotype with increased susceptibility to lung injury

Claudins are tight junction proteins that regulate paracellular ion permeability of epithelium and endothelium. Claudin 4 has been reported to function as a paracellular sodium barrier and is one of three major claudins expressed in lung alveolar epithelial cells (AEC). To directly assess the role of claudin 4 in regulation of alveolar epithelial barrier function and fluid homeostasis in vivo, we generated claudin 4 knockout (Cldn4 KO) mice. Unexpectedly, Cldn4 KO mice exhibited normal physiological phenotype although increased permeability to 5-carboxyfluorescein and decreased alveolar fluid clearance were noted. Cldn4 KO AEC monolayers exhibited unchanged ion permeability, higher solute permeability, and lower short-circuit current compared with monolayers from wild-type mice. Claudin 3 and 18 expression was similar between wild-type and Cldn4 KO alveolar epithelial type II cells. In response to either ventilator-induced lung injury or hyperoxia, claudin 4 expression was markedly upregulated in wild-type mice, whereas Cldn4 KO mice showed greater degrees of lung injury. RNA sequencing, in conjunction with differential expression and upstream analysis after ventilator-induced lung injury, suggested Egr1, Tnf, and Il1b as potential mediators of increased lung injury in Cldn4 KO mice. These results demonstrate that claudin 4 has little effect on normal lung physiology but may function to protect against acute lung injury.

Sex differences in the acute in vivo effects of different human SP-A variants on the mouse alveolar macrophage proteome

Surfactant protein A (SP-A) is involved in lung innate immunity. Humans have two SP-A genes, SFTPA1 and SFTPA2, each with several variants. We examined the in vivo effects of treatment with specific SP-A variants on the alveolar macrophage (AM) proteome from SP-A knockout (KO) mice. KO mice received either SP-A1, SP-A2, or both. AM were collected and their proteomes examined with 2D-DIGE. We identified 90 proteins and categorized them as related to actin/cytoskeleton, oxidative stress, protease balance/chaperones, regulation of inflammation, and regulatory/developmental processes. SP-A1 and SP-A2 had different effects on the AM proteome and these effects differed between sexes. In males more changes occurred in the oxidative stress, protease/chaperones, and inflammation groups with SP-A2 treatment than with SP-A1. In females most SP-A1-induced changes were in the actin/cytoskeletal and oxidative stress groups. We conclude that after acute SP-A1 and SP-A2 treatment, sex-specific differences were observed in the AM proteomes from KO mice, and that these sex differences differ in response to SP-A1 and SP-A2. Females are more responsive to SP-A1, whereas the gene-specific differences in males were minimal. These observations not only demonstrate the therapeutic potential of exogenous SP-A, but also illustrate sex- and gene-specific differences in the response to it.

BIOLOGICAL SIGNIFICANCE

This study shows that changes occur in the alveolar macrophage proteome in response to a single in vivo treatment with exogenous SP-A1 and/or SP-A2. We demonstrate that SP-A1 and SP-A2 have different effects on the AM proteome and that sex differences exist in the response to each SP-A1 and SP-A2 gene product. This study illustrates the potential of exogenous SP-A1 and SP-A2 treatment for the manipulation of macrophage function and indicates that the specific SP-A variant used for treatment may vary with sex and with the cellular functions being modified. The observed changes may contribute to sex differences in the incidence of some lung diseases.

Hydrogel scaffolds as in vitro models to study fibroblast activation in wound healing and disease

Wound healing results from complex signaling between cells and their environment in response to injury. Fibroblasts residing within the extracellular matrix (ECM) of various connective tissues are critical for matrix synthesis and repair. Upon injury or chronic insult, these cells activate into wound-healing cells, called myofibroblasts, and repair the damaged tissue through enzyme and protein secretion. However, misregulation and persistence of myofibroblasts can lead to uncontrolled accumulation of matrix proteins, tissue stiffening, and ultimately disease. Extracellular cues are important regulators of fibroblast activation and have been implicated in their persistence. Hydrogel-based culture models have emerged as useful tools to examine fibroblast response to ECM cues presented during these complex processes. In this Mini-Review, we will provide an overview of these model systems, which are built upon naturally-derived or synthetic materials, and mimic relevant biophysical and biochemical properties of the native ECM with different levels of control. Additionally, we will discuss the application of these hydrogel-based systems for the examination of fibroblast function and fate, including adhesion, migration, and activation, as well as approaches for mimicking both static and temporal aspects of extracellular environments. Specifically, we will highlight hydrogels that have been used to investigate the effects of matrix rigidity, protein binding, and cytokine signaling on fibroblast activation. Last, we will describe future directions for the design of hydrogels to develop improved synthetic models that mimic the complex extracellular environment.

Potential effects of medicinal plants and secondary metabolites on acute lung injury

Acute lung injury (ALI) is a life-threatening syndrome that causes high morbidity and mortality worldwide. ALI is characterized by increased permeability of the alveolar-capillary membrane, edema, uncontrolled neutrophils migration to the lung, and diffuse alveolar damage, leading to acute hypoxemic respiratory failure. Although corticosteroids remain the mainstay of ALI treatment, they cause significant side effects. Agents of natural origin, such as medicinal plants and their secondary metabolites, mainly those with very few side effects, could be excellent alternatives for ALI treatment. Several studies, including our own, have demonstrated that plant extracts and/or secondary metabolites isolated from them reduce most ALI phenotypes in experimental animal models, including neutrophil recruitment to the lung, the production of pro-inflammatory cytokines and chemokines, edema, and vascular permeability. In this review, we summarized these studies and described the anti-inflammatory activity of various plant extracts, such as Ginkgo biloba and Punica granatum, and such secondary metabolites as epigallocatechin-3-gallate and ellagic acid. In addition, we highlight the medical potential of these extracts and plant-derived compounds for treating of ALI.

Animal models of fibrotic lung disease

Interstitial lung fibrosis can develop as a consequence of occupational or medical exposure, as a result of genetic defects, and after trauma or acute lung injury leading to fibroproliferative acute respiratory distress syndrome, or it can develop in an idiopathic manner. The pathogenesis of each form of lung fibrosis remains poorly understood. They each result in a progressive loss of lung function with increasing dyspnea, and most forms ultimately result in mortality. To better understand the pathogenesis of lung fibrotic disorders, multiple animal models have been developed. This review summarizes the common and emerging models of lung fibrosis to highlight their usefulness in understanding the cell-cell and soluble mediator interactions that drive fibrotic responses. Recent advances have allowed for the development of models to study targeted injuries of Type II alveolar epithelial cells, fibroblastic autonomous effects, and targeted genetic defects. Repetitive dosing in some models has more closely mimicked the pathology of human fibrotic lung disease. We also have a much better understanding of the fact that the aged lung has increased susceptibility to fibrosis. Each of the models reviewed in this report offers a powerful tool for studying some aspect of fibrotic lung disease.

N-acetylcysteine-pretreated human embryonic mesenchymal stem cell administration protects against bleomycin-induced lung injury

INTRODUCTION

The transplantation of mesenchymal stem cells (MSCs) has been reported to be a promising approach in the treatment of acute lung injury. However, the poor efficacy of transplanted MSCs is one of the serious handicaps in the progress of MSC-based therapy. Therefore, the purpose of this study was to investigate whether the pretreatment of human embryonic MSCs (hMSCs) with an antioxidant, namely N-acetylcysteine (NAC), can improve the efficacy of hMSC transplantation in lung injury.

METHODS

In vitro, the antioxidant capacity of NAC-pretreated hMSCs was assessed using intracellular reactive oxygen species (ROS) and glutathione assays and cell adhesion and spreading assays. In vivo, the therapeutic potential of NAC-pretreated hMSCs was assessed in a bleomycin-induced model of lung injury in nude mice.

RESULTS

The pretreatment of hMSCs with NAC improved antioxidant capacity to defend against redox imbalances through the elimination of cellular ROS, increasing cellular glutathione levels, and the enhancement of cell adhesion and spreading when exposed to oxidative stresses in vitro. In addition, the administration of NAC-pretreated hMSCs to nude mice with bleomycin-induced lung injury decreased the pathological grade of lung inflammation and fibrosis, hydroxyproline content and numbers of neutrophils and inflammatory cytokines in bronchoalveolar lavage fluid and apoptotic cells, while enhancing the retention and proliferation of hMSCs in injured lung tissue and improving the survival rate of mice compared with results from untreated hMSCs.

CONCLUSIONS

The pretreatment of hMSCs with NAC could be a promising therapeutic approach to improving cell transplantation and, therefore, the treatment of lung injury.

Dipeptidyl peptidase IV is a human and murine neutrophil chemorepellent

In Dictyostelium discoideum, AprA is a secreted protein that inhibits proliferation and causes chemorepulsion of Dictyostelium cells, yet AprA has little sequence similarity to any human proteins. We found that a predicted structure of AprA has similarity to human dipeptidyl peptidase IV (DPPIV). DPPIV is a serine protease present in extracellular fluids that cleaves peptides with a proline or alanine in the second position. In Insall chambers, DPPIV gradients below, similar to, and above the human serum DPPIV concentration cause movement of human neutrophils away from the higher concentration of DPPIV. A 1% DPPIV concentration difference between the front and back of the cell is sufficient to cause chemorepulsion. Neutrophil speed and viability are unaffected by DPPIV. DPPIV inhibitors block DPPIV-mediated chemorepulsion. In a murine model of acute respiratory distress syndrome, aspirated bleomycin induces a significant increase in the number of neutrophils in the lungs after 3 d. Oropharyngeal aspiration of DPPIV inhibits the bleomycin-induced accumulation of mouse neutrophils. These results indicate that DPPIV functions as a chemorepellent of human and mouse neutrophils, and they suggest new mechanisms to inhibit neutrophil accumulation in acute respiratory distress syndrome.

Effectiveness of omalizumab in severe allergic asthma: a retrospective UK real-world study

Objective.

The aim of this study was to evaluate the “real world” effects of the monoclonal antibody omalizumab (OMB) when used to treat severe persistent allergic asthma in UK clinical practice.

Methods.

A 10-center retrospective observational study was carried out to compare oral corticosteroid (OCS) use and exacerbation frequency in 12 months pre- versus post-OMB initiation in 136 patients aged ≥12 years with severe persistent allergic asthma. All patients received ≥1 dose of OMB. Patients who had received OMB in a clinical trial were excluded. Data were obtained from hospital and if necessary general practitioners’ (GPs’) records on OCS use, lung function, hospital resource use, and routinely used quality of life (QoL) measures at baseline (pre-OMB), 16 weeks, and up to 12 months post-OMB initiation.

Results.

Mean total quantity of OCS prescribed per year decreased by 34% between the 12 months pre- and post-OMB initiation. During the 12 months post-OMB initiation, 87 patients (64%) stopped/reduced OCS use by 20% or more and 66 (49%) stopped OCS completely. Mean percent predicted forced expiratory volume in one second (FEV₁) increased from 66.0% at baseline to 75.2% at week 16 of OMB therapy. The number of asthma exacerbations decreased by 53% during the 12 months post-initiation. Accident and emergency visits reduced by 70% and hospitalizations by 61% in the 12 months post-OMB initiation.

Conclusion.

This retrospective analysis showed a reduction in exacerbations and improved QoL as per previous studies with OMB. However, the total reduction in annual steroid burden and improved lung function in this severely ill group of patients taking regular or frequent OCS is greater than that seen in previous trials.

Surfactant protein A suppresses lung cancer progression by regulating the polarization of tumor-associated macrophages

Surfactant protein A (SP-A) is a large multimeric protein found in the lungs. In addition to its immunoregulatory function in infectious respiratory diseases, SP-A is also used as a marker of lung adenocarcinoma. Despite the finding that SP-A expression levels in cancer cells has a relationship with patient prognosis, the function of SP-A in lung cancer progression is unknown. We investigated the role of SP-A in lung cancer progression by introducing the SP-A gene into human lung adenocarcinoma cell lines. SP-A gene transduction suppressed the progression of tumor in subcutaneous xenograft or lung metastasis mouse models. Immunohistochemical analysis showed that the number of M1 antitumor tumor-associated macrophages (TAMs) was increased and the number of M2 tumor-promoting TAMs was not changed in the tumor tissue produced by SP-A-expressing cells. In addition, natural killer (NK) cells were also increased and activated in the SP-A-expressing tumor. Moreover, SP-A did not inhibit tumor progression in mice depleted of NK cells. Taking into account that SP-A did not directly activate NK cells, these results suggest that SP-A inhibited lung cancer progression by recruiting and activating NK cells via controlling the polarization of TAMs.