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Background: One of the most common entry gates for systemic infection is the lung. In humans, pulmonary infections can lead to significant neurological impairment, ranging from acute sickness behavior to long-term disorders. Surfactant proteins (SP), essential parts of the pulmonary innate immune defense, have been detected in the brain of rats and humans. Recent evidence suggests that SP-A, the major protein component of surfactant, also plays a functional role in modulating neuroinflammation. This study aimed to determine whether SP-A deficiency affects the inflammatory response in the brain of adult mice during pulmonary infection., Experimental Procedure: Adult male wild-type (WT, n = 72) and SP-A-deficient (SP-A -/- , n = 72) mice were oropharyngeally challenged with lipopolysaccharide (LPS), Pseudomonas aeruginosa (P. aeruginosa), or PBS (control). Both, behavioral assessment and subsequent brain tissue analysis, were performed 24, 48, and 72 h after challenge. The brain concentrations of the pro-inflammatory cytokines TNF-α, IL-6, and IL-1β were determined by ELISA. Quantitative rtPCR was used to detect SP-A mRNA expression in brain homogenates and immunohistochemistry was applied for the detection of SP-A protein expression in brain coronal slices., Results: SP-A mRNA and histological evidence of protein expression were detected in both the lungs and brains of WT mice, with significantly higher amounts in lung samples. SP-A -/- mice exhibited significantly higher baseline concentrations of brain TNF-α, IL-6, and IL-1β compared to WT mice. Oropharyngeal application of either LPS or P. aeruginosa elicited significantly higher brain levels of TNF-α and IL-1β in SP-A -/- mice compared to WT mice at all time points. In comparison, behavioral impairment as a measure of sickness behavior, was significantly stronger in WT than in SP-A -/- mice, particularly after LPS application., Conclusion: SP-A is known for its anti-inflammatory role in the pulmonary immune response to bacterial infection. Recent evidence suggests that in an abdominal sepsis model SP-A deficiency can lead to increased cytokine levels in the brain. Our results extend this perception and provide evidence for an anti-inflammatory role of SP-A in the brain of adult WT mice after pulmonary infection., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: The serum markers Krebs von den Lungen-6 (KL-6), surfactant protein A (SP-A), and surfactant protein D (SP-D) have been used for the diagnosis, differential diagnosis, and prognosis prediction of interstitial pneumonia. However, the significance of measuring the serum and bronchoalveolar lavage fluid (BALF) KL-6, SP-D, and SP-A levels in predicting the prognosis of chronic fibrosing interstitial pneumonia (CFIP), idiopathic pulmonary fibrosis, and idiopathic nonspecific interstitial pneumonia remains unclear. We aimed to clarify the significance of measuring the serum and BALF KL-6, SP-A, and SP-D levels in predicting the prognosis of patients with CFIP., Methods: Among 173 patients who were diagnosed with CFIP between September 2008 and February 2021, 39 who underwent bronchoalveolar lavage were included in this study. Among these, patients experiencing an annual decrease in forced vital capacity (FVC) of ≥10% or those facing challenges in undergoing follow-up pulmonary function tests owing to significant deterioration in pulmonary function were categorized as the rapidly progress group. Conversely, individuals with an annual decrease in the FVC of <10% were classified into the slowly progress group. The serum and BALF KL-6, SP-D, and SP-A levels, as well as BALF/serum SP-D and SP-A ratios were compared between the two groups., Results: Among the patients with CFIP, the BALF SP-D level (p=0.0111), BALF SP-A level (p<0.0010), BALF/serum SP-D ratio (p=0.0051), and BALF/serum SP-A ratio (p<0.0010) were significantly lower in the rapidly than in the slowly progress group (p<0.0010). The receiver operating characteristics analysis results demonstrated excellent performance for diagnosing patients with CFIP, with the BALF SP-D level (area under the curve [AUC], 0.7424), BALF SP-A level (AUC, 0.8842), BALF/serum SP-D ratio (AUC, 0.7673), and BALF/serum SP-A ratio (AUC, 0.8556). Moreover, the BALF SP-A level showed a notably superior CFIP diagnostic capability. Survival analysis using the Kaplan-Meier method revealed that patients with a BALF SP-A level of <1500 ng/mL and BALF/serum SP-A ratio of <15.0 had poor prognoses., Conclusions: Our results suggest that BALF SP-A measurement may be useful for predicting the prognosis in patients with CFIP., (© 2024. The Author(s).)

Surfactant protein A (SP-A) and Surfactant protein D (SP-D) glycoproteins play a crucial role in maintaining lung homeostasis and lung host defense. Interestingly, these proteins are also expressed in extra-pulmonary tissues, including the female genital tract. The ovarian tissue, where SP-A and SP-D expression increases with follicular development, may serve as the primary site of defense for this tissue. However, their functions in these tissues are not well understood and are currently an active area of research. Therefore, the objective of this study is to investigate the expression of SP-A and SP-D in the ovine ovary throughout the ovarian cycle using immunohistochemistry by semiquantitative intensity classification and Western blotting techniques. These findings revealed the presence of SP-A and SP-D in various compartments of the ovary, such as the follicular epithelium, granulosa cells, cumulus cells, theca cells, oocyte I, follicular fluid, and luteal cells of Graafian follicles, excluding the corpus albicans. SP-A and SP-D likely act as a first line of defense against potential pathogens that infiltrate the ovaries. Further investigation of the differential expression of SP-A and SP-D proteins in ovarian follicles will provide a basis for understanding their interactions with key proteins involved in oogenesis., (© 2024. The Author(s).)

Human papillomavirus (HPV) infection poses a significant health challenge, particularly in low- and middle-income countries (LMIC), where limited healthcare access and awareness hinder vaccine accessibility. To identify alternative HPV targeting interventions, we previously reported on surfactant protein A (SP-A) as a novel molecule capable of recognising HPV16 pseudovirions (HPV16-PsVs) and reducing infection in a murine cervicovaginal HPV challenge model. Building on these findings, our current study aimed to assess SP-A's suitability as a broad-spectrum HPV-targeting molecule and its impact on innate immune responses. We demonstrate SP-A's ability to agglutinate and opsonise multiple oncogenic HPV-PsVs types, enhancing their uptake and clearance by RAW264.7 murine macrophages and THP-1 human-derived immune cells. The SP-A opsonisation of HPV not only led to increased lysosomal accumulation in macrophages and HaCaT keratinocytes but also resulted in a decreased infection of HaCaT cells, which was further decreased when co-cultured with innate immune cells. An analysis of human innate immune cell cytokine profiles revealed a significant inflammatory response upon SP-A exposure, potentially contributing to the overall inhibition of HPV infection. These results highlight the multi-layered impact of SP-A on HPV, innate immune cells and keratinocytes and lay the basis for the development of alternative prophylactic interventions against diverse HPV types.

Background: Influenza A virus (IAV) infection is a significant risk factor for respiratory diseases, but the host defense mechanisms against IAV remain to be defined. Immune regulators such as surfactant protein A (SP-A) and Toll-interacting protein (Tollip) have been shown to be involved in IAV infection, but whether SP-A and Tollip cooperate in more effective host defense against IAV infection has not been investigated., Methods: Wild-type (WT), Tollip knockout (KO), SP-A KO, and Tollip/SP-A double KO (dKO) mice were infected with IAV for four days. Lung macrophages were isolated for bulk RNA sequencing. Precision-cut lung slices (PCLS) from WT and dKO mice were pre-treated with SP-A and then infected with IAV for 48 h., Results: Viral load was significantly increased in bronchoalveolar lavage (BAL) fluid of dKO mice compared to all other strains of mice. dKO mice had significantly less recruitment of neutrophils into the lung compared to Tollip KO mice. SP-A treatment of PCLS enhanced expression of TNF and reduced viral load in dKO mouse lung tissue. Pathway analysis of bulk RNA sequencing data suggests that macrophages from IAV-infected dKO mice reduced expression of genes involved in neutrophil recruitment, IL-17 signaling, and Toll-like receptor signaling., Conclusions: Our data suggests that both Tollip and SP-A are essential for the lung to exert more effective innate defense against IAV infection., (© 2024. The Author(s).)

Lung surfactant collectins, surfactant protein A (SP-A) and D (SP-D), are oligomeric C-type lectins involved in lung immunity. Through their carbohydrate recognition domain, they recognize carbohydrates at pathogen surfaces and initiate lung innate immune response. Here, we propose that they may also be able to bind to other carbohydrates present in typical cell surfaces, such as the alveolar epithelial glycocalyx. To test this hypothesis, we analyzed and quantified the binding affinity of SP-A and SP-D to different sugars and glycosaminoglycans (GAGs) by microscale thermophoresis (MST). In addition, by changing the calcium concentration, we aimed to characterize any consequences on the binding behavior. Our results show that both oligomeric proteins bind with high affinity (in nanomolar range) to GAGs, such as hyaluronan (HA), heparan sulfate (HS) and chondroitin sulfate (CS). Binding to HS and CS was calcium-independent, as it was not affected by changing calcium concentration in the buffer. Quantification of GAGs in bronchoalveolar lavage (BAL) fluid from animals deficient in either SP-A or SP-D showed changes in GAG composition, and electron micrographs showed differences in alveolar glycocalyx ultrastructure in vivo. Taken together, SP-A and SP-D bind to model sulfated glycosaminoglycans of the alveolar epithelial glycocalyx in a multivalent and calcium-independent way. These findings provide a potential mechanism for SP-A and SP-D as an integral part of the alveolar epithelial glycocalyx binding and interconnecting free GAGs, proteoglycans, and other glycans in glycoproteins, which may influence glycocalyx composition and structure. NEW & NOTEWORTHY SP-A and SP-D function has been related to innate immunity of the lung based on their binding to sugar residues at pathogen surfaces. However, their function in the healthy alveolus was considered as limited to interaction with surfactant lipids. Here, we demonstrated that these proteins bind to glycosaminoglycans present at typical cell surfaces like the alveolar epithelial glycocalyx. We propose a model where these proteins play an important role in interconnecting alveolar epithelial glycocalyx components.

This study addressed the efficacy of a liposome-encapsulated nine amino acid peptide [peroxiredoxin 6 PLA 2 inhibitory peptide-2 (PIP-2)] for the prevention or treatment of acute lung injury (ALI) +/- sepsis. PIP-2 inhibits the PLA 2 activity of peroxiredoxin 6 (Prdx6), thereby preventing rac release and activation of NADPH oxidases (NOXes), types 1 and 2. Female Yorkshire pigs were infused intravenously with lipopolysaccharide (LPS) + liposomes (untreated) or LPS + PIP-2 encapsulated in liposomes (treated). Pigs were mechanically ventilated and continuously monitored; they were euthanized after 8 h or earlier if preestablished humane endpoints were reached. Control pigs (mechanical ventilation, no LPS) were essentially unchanged over the 8 h study. LPS administration resulted in systemic inflammation with manifestations of clinical sepsis-like syndrome, decreased lung compliance, and a marked decrease in the arterial Po 2 with vascular instability leading to early euthanasia of 50% of untreated animals. PIP-2 treatment significantly reduced the requirement for supportive vasopressors and the manifestations of lung injury so that only 25% of animals required early euthanasia. Bronchoalveolar lavage fluid from PIP-2-treated versus untreated pigs showed markedly lower levels of total protein, cytokines (TNF-α, IL-6, IL-1β), and myeloperoxidase. Thus, the porcine LPS-induced sepsis-like model was associated with moderate to severe lung pathophysiology compatible with ALI, whereas treatment with PIP-2 markedly decreased lung injury, cardiovascular instability, and early euthanasia. These results indicate that inhibition of reactive oxygen species (ROS) production via NOX1/2 has a beneficial effect in treating pigs with LPS-induced ALI plus or minus a sepsis-like syndrome, suggesting a potential role for PIP-2 in the treatment of ALI and/or sepsis in humans. NEW & NOTEWORTHY Currently available treatments that can alter lung inflammation have failed to significantly alter mortality of acute lung injury (ALI). Peroxiredoxin 6 PLA 2 inhibitory peptide-2 (PIP-2) targets the liberation of reactive O 2 species (ROS) that is associated with adverse cell signaling events, thereby decreasing the tissue oxidative injury that occurs early in the ALI syndrome. We propose that treatment with PIP-2 may be effective in preventing progression of early disease into its later stages with irreversible lung damage and relatively high mortality.

Prolonged labor can lead to infection, fetal distress, asphyxia, and life-threatening harm to both the mother and the baby. Surfactant protein A (SP-A) was shown to contribute to the maintenance of pregnancy and timing of term labor. SP-A modulates the stoichiometric expression of the SP-R210 L and SP-R210 S isoforms of the SP-R210 receptor on alveolar macrophages (AMs). Lack of SP-R210 L dysregulates macrophage inflammatory responses. We asked whether SP-A alters normal and inflammation-induced parturition through SP-R210 using SP-A- and SP-R210 L -deficient mice. Labor and delivery of time-pregnant mice were monitored in real time using a time-lapse infrared camera. Intrauterine injection with either vehicle or Escherichia coli lipopolysaccharide (LPS) on embryonic (E) day 18.5 post coitus was used to assess the effect of gene disruption in chorioamnionitis-induced labor. We report that either lack of SP-A or disruption of SP-R210 L delays parturition by 0.40 and 0.55 days compared with controls, respectively. LPS induced labor at 0.60, 1.01, 0.40, 1.00, and 1.31 days earlier than PBS controls in wild type (WT), SP-A-deficient, littermate controls, heterozygous, and homozygous SP-R210 L -deficient mice, respectively. Lack of SP-A reduced litter size in PBS-treated mice, whereas the total number of pups delivered was similar in all LPS-treated mice. The number of live pups, however, was significantly reduced by 50%-70% in SP-A and SP-R210 L -deficient mice compared with controls. Differences in gestational length were not associated with intrauterine growth restriction. The present findings support the novel concept that the SP-A/SP-R210 pathway modulates timely labor and delivery and supports fetal lung barrier integrity during fetal-to-neonatal transition in term pregnancy. NEW & NOTEWORTHY To our knowledge, this study is the first to report that SP-A prevents delay of labor and inflammation-induced stillbirth through the receptor SP-R210 L .

Surfactant protein A (SP-A), a natural immune molecule, plays an important role in lung health. SP-A recognizes and binds microbial surface glycogroups through the C-type carbohydrate recognition domain, and then binds corresponding cell surface receptors (such as C1qRp, CRT-CD91 complex, CD14, SP-R210, Toll-like receptor, SIRP-α, CR3, etc.) through collagen-like region, and subsequently mediates biological effects. SP-A regulates lung innate immunity by promoting surfactant absorption by alveolar type II epithelial cells and phagocytosis of pathogenic microorganisms by alveolar macrophages. SP-A also regulates lung adaptive immunity by inhibiting DC maturation, and T cell proliferation and differentiation. This article reviews latest relationships between SP-A and adaptive and intrinsic immunity., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Surfactant Protein A (SP-A) is an innate immune modulator produced by the lung with known protective effects against bacteria and viruses. Its role in asthma, an inflammatory lung disease that affects 10% of the world's population, is not entirely known. In this review, we demonstrate that SP-A confers protection against exposure to interleukin-13, a type 2 cytokine integral to eosinophilic asthma, in a mouse model of SP-A deficiency, a house dust mite model of asthma, and in human bronchial epithelial cells from participants with asthma. We also show that small peptides derived from SP-A, such as the major allele of single nucleotide polymorphism (SNP) rs1965708, which includes the carbohydrate recognition domain of SP-A2 at position 223, reduce airway hyperresponsiveness, airway eosinophils, and mucus in a mouse model of asthma. These data suggest that SP-A has beneficial effects relevant to asthma and that an SP-A peptide may have a new therapeutic use in asthma., (© 2024 The American Clinical and Climatological Association.)

Objective: To assess the role and possible mechanism of surfactant protein A (SPA) in the pathogenesis of otitis media with effusion (OME)., Methods: This was a multi-part study with both an in vivo mouse model study as well as an in vitro study. The control and study groups (OME group) received phosphate-buffered saline and inactivated Streptococcus pneumoniae, respectively, via external auditory meatus injections. Changes in the surface tension of secretions from the eustachian tube (ET) and SPA expression were measured in both groups. A transwell assay was performed to observe the effect of different concentrations of SPA on the migration ability of macrophages. We examined the differentially expressed genes related to SPA-treated macrophages using RNA-seq analysis., Results: On Day 3, the surface tension of the OME group was higher than that of the control group (p = 0.014). The variation intensity of SPA in the ET of the OME group was significantly lower than that of the control group (p < 0.001). Surface tension was correlated with SPA (r = -0.525, p = 0.037). The expression of SPA and macrophages in the ET was different between the two groups. In vitro experiments revealed that macrophages showed different migration abilities with SPA concentration changes (p < 0.05). RNA-seq and western blotting were performed after macrophages were treated with SPA. The results showed that RhoA and Rac1/2/3 were differentially expressed., Conclusions: SPA can change the surface tension of secretions from the ET and affect macrophage migration to alter the function of the ET. Although research in this field of OME is nascent, initial work suggests that SPA likely plays an important role in OME progression., Level of Evidence: NA Laryngoscope, 133:1726-1733, 2023., (© 2022 The American Laryngological, Rhinological and Otological Society, Inc.)

Introduction: Pneumonia-induced sepsis can cause multiple organ dysfunction including acute lung and kidney injury (ALI and AKI). Surfactant protein A (SP-A), a critical innate immune molecule, is expressed in the lung and kidney. Extracellular vesicles like exosomes are involved in the processes of pathophysiology. Here we tested one hypothesis that SP-A regulates pneumonia-induced AKI through the modulation of exosomes and cell death., Methods: Wild-type (WT), SP-A knockout (KO), and humanized SP-A transgenic (hTG, lung-specific SP-A expression) mice were used in this study., Results: After intratracheal infection with Pseudomonas aeruginosa , KO mice showed increased mortality, higher injury scores, more severe inflammation in the lung and kidney, and increased serum TNF-α, IL-1β, and IL-6 levels compared to WT and hTG mice. Infected hTG mice exhibited similar lung injury but more severe kidney injury than infected WT mice. Increased renal tubular apoptosis and pyroptosis in the kidney of KO mice were found when compared with WT and hTG mice. We found that serum exosomes from septic mice cause ALI and AKI through mediating apoptosis and proptosis when mice were injected intravenously. Furthermore, primary proximal tubular epithelial cells isolated from KO mice showed more sensitivity than those from WT mice after exposure to septic serum exosomes., Discussion: Collectively, SP-A attenuates pneumonia-induced ALI and AKI by regulating inflammation, apoptosis and pyroptosis; serum exosomes are important mediators in the pathogenesis of AKI., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Chen, Guo, Mahmoud, Vanga, Liu, Xu, Xiong, Xiong, Abdel-Razek and Wang.)

Pulmonary collectins have been reported to bind carbohydrates on pathogens and inhibit infection by agglutination, neutralization, and opsonization. In this study, surfactant protein A (SP-A) was identified from goose lung and characterized at expression- and agglutination-functional levels. The deduced amino acid sequence of goose surfactant protein A (gSP-A) has two characteristic structures: a shorter, collagen-like region and a carbohydrate recognition domain. The latter contains two conserved motifs in its Ca 2+ -binding site: EPN (Glu-Pro-Asn) and WND (Trp-Asn-Asp). Expression analysis using qRT-PCR and fluorescence IHC revealed that gSP-A was highly expressed in the air sac and present in several other tissues, including the lung and trachea. We went on to produce recombinant gSP-A (RgSP-A) using a baculovirus/insect cell system and purified using a Ni 2+ affinity column. A biological activity assay showed that all bacterial strains tested in this study were aggregated by RgSP-A, but only Escherichia coli AE17 (E. coli AE17, O2) and E. coli AE158 (O78) were susceptible to RgSP-A-mediated growth inhibition at 2-6 h. Moreover, the swarming motility of the two bacterial strains were weakened with increasing RgSP-A concentration, and their membrane permeability was compromised at 3 h, as determined by flow cytometry and laser confocal microscopy. Therefore, RgSP-A is capable of reducing bacterial viability of E. coli O2 and O78 via an aggregation-dependent mechanism which involves decreasing motility and increasing the bacterial membrane permeability. These data will facilitate detailed studies into the role of gSP-A in innate immune defense as well as for development of antibacterial agents., Competing Interests: Declaration of competing interest The authors disclose no conflicts of interest., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Background: Injury to the lung is a common, clinically serious inflammatory disease. However, its pathogenesis remains unclear, and the existing treatments, including cytokine therapy, stem cell therapy, and hormone therapy, are not completely effective in treating this disease. Dimethyl itaconate (DMI) is a surfactant with important anti-inflammatory effects., Objective: The present study used alveolar type II (AT II) and bronchial epithelial cells as models to determine the role of DMI in lung injury., Material and Methods: First, the effects of DMI were established on the survival, inflammatory release, and apoptosis in lipopolysaccharide (LPS)-induced AT II and bronchial epithelial cells. The association between DMI and Sirtuin1 (SIRT1) was assessed using molecular docking. Next, by constructing interference plasmids to inhibit surfactant protein (SP)-A and SP-D expressions, the effect of DMI was observed on inflammatory release and apoptosis., Results: The results revealed that DMI increased the survival rate and expression levels of SP-A, SP-D, and SIRT1, and inhibited inflammatory factors as well as apoptosis in LPS-induced cells. Furthermore, DMI could bind to SIRT1 to regulate SP-A and SP-D expressions. After SP-A and SP-D expressions were inhibited, the inhibitory effect of DMI was reversed on inflammatory release and apoptosis., Conclusion: The findings of the present study revealed that DMI inhibited LPS-induced inflammatory release and apoptosis in cells by targeting SIRT1 and then activating SP-A and SP-D. This novel insight into the pharmacological mechanism of DMI lays the foundation for its later use for alleviating lung injury., Competing Interests: The authors declared that they had no competing interests.

Exposure to silica nanoparticles (SiNPs) is related to the dysregulation of pulmonary surfactant that maintains lung stability and function. Nevertheless, there are limited studies concerning the interaction and influence between SiNPs and pulmonary surfactant, and the damage and mechanism are still unclear. Herein, we used A549 cells to develop an in vitro model, with which we investigated the effect of SiNPs exposure on the expression of pulmonary surfactant and the potential regulatory mechanism. The results showed that SiNPs were of cytotoxicity in regarding of reduced cell viability and promoted the production of excessive reactive oxygen species (ROS). Additionally, the JNK/c-Jun signaling pathway was activated, and the expression of surfactant protein A (SP-A) and surfactant protein B (SP-B) was decreased. After the cells being treated with N-acetyl-L-cysteine (NAC), we found that the ROS content was effectively downregulated, and the expression of proteins related to JNK and c-Jun signaling pathways was suppressed. In contrast, the expression of SP-A and SP-B was enhanced. Furthermore, we treated the cells with JNK inhibitor and c-Jun-siRNA and found that the expression of protein related to JNK and c-Jun signaling pathways, as well as SP-A and SP-B, changed in line with that of NAC treatment. These findings suggest that SiNPs exposure can upregulate ROS and activate the JNK/c-Jun signaling pathway in A549 cells, thereby inhibiting the expression of SP-A and SP-B proteins., (© 2022 Wiley Periodicals LLC.)

Human surfactant protein (SP)-A1 and SP-A2 exhibit differential qualitative and quantitative effects on the alveolar macrophage (AM), including a differential impact on the AM miRNome. Moreover, SP-A rescue (treatment) of SP-A-knockout (KO) infected mice impoves survival. Here, we studied for the first time the role of exogenous SP-A protein treatment on the regulation of lung alveolar cell (LAC) miRNome, the miRNA-RNA targets, and gene expression of SP-A-KO infected mice of both sexes. Toward this, SP-A-KO mice of both sexes were infected with Klebsiella pneumoniae , and half of them were also treated with SP-A2 (1A 0 ). After 6 h of infection/SP-A treatment, the expression levels and pathways of LAC miRNAs, genes, and target miRNA-mRNAs were studied in both groups. We found 1) significant differences in the LAC miRNome, genes, and miRNA-mRNA targets in terms of sex, infection, and infection plus SP-A2 (1A 0 ) protein rescue; 2) an increase in the majority of miRNA-mRNA targets in both study groups in KO male vs. female mice and involvement of the miRNA-mRNA targets in pathways of inflammation, antiapoptosis, and cell cycle; 3) genes with significant changes to be involved in TP-53, tumor necrosis factor (TNF), and cell cycle signaling nodes; 4) when significant changes in the expression of molecules from all analyses (miRNAs, miRNA-mRNA targets, and genes) were considered, two signaling pathways, the TNF and cell cycle, referred to as "integrated pathways" were shown to be significant; 5) the cell cycle pathway to be present in all comparisons made. Because SP-A could be used therapeutically in pulmonary diseases, it is important to understand the molecules and pathways involved in response to an SP-A acute treatment. The information obtained contributes to this end and may help to gain insight especially in the case of infection., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Thorenoor and Floros.)

Respiratory tract lining fluid (RTLF) is an important component of the lung epithelial barrier. Pathological changes in RTLF may cause increased permeability of the epithelial barrier, but changes within RTLF are difficult to assess non-invasively. The aim of this study was to explore if the use of the non-invasive measurement technique, Particles in Exhaled Air (PEx) and blood test were useful in assessing epithelial barrier, and if cigarette smoking affects the relationship. In a general population subcohort from the European Community Respiratory Health Survey III in Iceland (n = 112), we collected RTLF droplets using the PEx technique, in conjunction with blood samples and questionnaire data. We measured surfactant protein A (SP-A) in the collected plasma and PEx samples. Participants were defined as healthy if they did not currently have asthma, were non-smokers and had forced expiratory volume in one second ≥ 80% of predicted value. Of the 112 participants, 97 were healthy and 15 were current smokers. There was no correlation between plasma and PEx SP-A levels. However, the ratio of plasma to PEx SP-A was significantly higher in smokers compared to healthy subjects. The lack of correlation between PEx and plasma SP-A in healthy participants, indicates that SP-A in plasma does not diffuse freely over the lung epithelial barrier. However, the lung epithelial barrier may be injured by smoking, leading to diffusion of SP-A across the barrier into the bloodstream, causing an increased ratio of plasma to PEx SP-A., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Idiopathic pulmonary fibrosis (IPF) is a devastating and common chronic lung disease that is pathologically characterized by the destruction of lung architecture and the accumulation of extracellular matrix in the lung. Previous studies have shown an association between lung surfactant protein (SP) and the pathogenesis of IPF, as demonstrated by mutations and the altered expression of SP in patients with IPF. However, the role of SP in the development of lung fibrosis is poorly understood. In this study, the role of surfactant protein A (SP-A) was explored in experimental lung fibrosis induced with a low or high dose of bleomycin (BLM) and CRISPR/Cas9-mediated genetic deletion of SP-A. Our results showed that lung SP-A deficiency in mice promoted the development of fibrotic damage and exacerbated inflammatory responses to the BLM challenge. In vitro experiments with murine lung epithelial LA-4 cells demonstrated that in response to transforming growth factor-β1 (TGF-β1), LA-4 cells had a decreased protein expression of SP-A. Furthermore, exogenous SP administration to LA-4 cells inhibited the TGF-β1-induced upregulation of fibrotic markers. Overall, these findings suggest a novel antifibrotic mechanism of SP-A in the development of lung fibrosis, which indicates the therapeutic potential of the lung SP-A in preventing the development of IPF.

Background: Surfactant protein-A (SP-A) plays a critical role in lung innate immunity by regulating alveolar macrophages (AM), expression of inflammatory mediators, and other host defense proteins. The toponome imaging system (TIS), a serial immunostainer, was used to study the AM toponome because it characterizes the localization of multiple markers and identifies marker combinations in each pixel as combinatorial molecular phenotypes (CMPs). We used TIS to study the AM toponome from wild type (WT) and SP-A knockout (KO) mice and changes following Klebsiella pneumoniae exposure., Methods: WT or KO mice received intratracheal K. pneumoniae or vehicle and AM were obtained by bronchoalveolar lavage after one hour. AM were attached to slides and underwent TIS analysis. Images were analyzed to characterize all pixels. AM CMPs from WT vehicle (n=3) and infected (n=3) mice were compared to each other and to AM from KO (n=3 vehicle; n=3 infected). Histograms provided us with a tool to summarize the representation of each marker in a set of CMPs., Results: Using the histograms and other tools we identified markers of interest and observed that: 1) Both comparisons had conserved (present in all group members) CMPs, only in vehicle AM and only in infected AM, or common to both vehicle and infected AM, (i.e., unaffected by the condition). 2) the CMP number decreased with infection in WT and KO versus vehicle controls. 3) More infection-specific CMPs in WT vs KO AM. 4) When AM from WT and KO vehicle or infected were compared, there were more unique CMPs exclusive to the KO AM. 5) All comparisons showed CMPs shared by both groups., Conclusions: The decrease of CMPs exclusive to infected AM in KO mice may underlie the observed susceptibility of KO mice to infection. However, both KO groups had more exclusive CMPs than the corresponding WT groups, perhaps indicating a vigorous effort by KO to overcome deficits in certain proteins and CMPs that are dysregulated by the absence of SP-A. Moreover, the presence of shared CMPs in the compared groups indicates that regulation of these CMPs is not dependent on either infection or the presence or absence of SP-A., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Phelps, Chinchilli, Zhang, Shearer, Weisz and Floros.)

Objective: To study the mechanism of chronic obstructive pulmonary disease (COPD) in diagnosing alveolar factors and analyze the effect of miR-149-3p on alveolar inflammatory factors and the expression of surfactant protein D (SP-D) and SP-A on the lung surface mediated by Wnt pathway., Methods: Patients with stable COPD were taken as the research subjects, and healthy volunteers as the control group. Cardiac color Doppler ultrasound was adopted to measure the ventricular structure of patients. The ultrasound simulation method was introduced in the ultrasound imaging. The ultrasound image was processed based on the intelligent ultrasound simulation algorithm. The changes in the structure of the left and right ventricles were analyzed and compared in the two groups. The expression changes of miR-149-3p, Wnt1, β -catenin, RhoA, and Wnt5a in lung tissues of mice in three groups were detected, as well as the content of tumor necrosis factor- (TNF-) α , IL-1 β , interleukin (IL-6), nuclear factor kB (NF-kB), and other inflammatory factors in bronchoalveolar tissues of mice in three groups., Results: The position where the attenuation ratio was less than 0.92 in the experiment under the ultrasonic simulation algorithm had a gray value of 50. Compared with the control group, the right ventricular mass index of patients with stable COPD was statistically considerable ( P < 0.05). In patients with stable COPD, the overall right ventricular longitudinal strain, right ventricular diastolic longitudinal strain rate (RV DLSR), right ventricular diastolic circumferential strain rate, and right ventricular longitudinal displacement were significantly impaired ( P < 0.05). The content of miR-149-3p in the lung tissue of the model group was dramatically inferior to that of the control group and the interference group ( P < 0.05). The contents of Wnt1, β -catenin, RhoA, and Wnt5a in the lung tissue of the model group were dramatically superior to those of the control group ( P < 0.05). In addition, the expressions of TNF- α , IL-1 β , IL-6, and NF-kB in the alveolar lavage fluid of the model group were statistically different from those of control group ( P < 0.05). The expression levels of SP-D and surfactant protein A (SP-A) in the COPD group were also statistically different from those of control group ( P < 0.05)., Conclusion: miR-149-3p regulated the expression of Wnt1, β -catenin, RhoA, and Wnt5a, which also affected the signal transmission of the Wnt pathway, causing changes in the expression of alveolar inflammatory factors. Eventually, it affected the development of COPD., Competing Interests: The authors declare that they have no potential conflicts of interest., (Copyright © 2022 Xiuli Zhang et al.)

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., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 García-Fojeda, Minutti, Montero-Fernández, Stamme and Casals.)

Using the Toponome Imaging System (TIS), a serial immunostainer, we studied the patterns of expression of multiple markers in alveolar macrophages (AM) from female mice lacking surfactant protein A (SP-A knockouts; KO) after "rescue" with exogenous SP-A1. We also used a 7-marker subset to compare with AM from males. AM were harvested 18 h after intrapharyngeal SP-A1 or vehicle, attached to slides, and subjected to serial immunostaining for 12 markers. Expression of the markers in each pixel of the image was analyzed both in the whole image and in individual selected cells. The marker combination in each pixel is referred to as a combinatorial molecular phenotype (CMP). A subset of antibodies was used to compare AM from male mice to the females. We found: (a) extensive AM heterogeneity in females by CMP analysis and by clustering analysis of CMPs in single cells; (b) AM from female KO mice respond to exogenous SP-A1 by increasing CMP phenotypic diversity and perhaps enhancing their potential innate immune capabilities; and (c) comparison of male and female AM responses to SP-A1 revealed that males respond more vigorously than females and clustering analysis was more effective in distinguishing males from females rather than treated from control., (© 2022. The Author(s).)

Although it is thought that there is a close relationship between Notch signal and preterm birth, the functioning of this mechanism in the cervix is unknown. The efficacy of surfactants and prostaglandin inhibitors in preterm labor is also still unclear. In this study, 48 female CD-1 mice were distributed to pregnant control (PC), Sham, PBS, indomethacin (2 mg/kg; intraperitoneally), lipopolysaccharides (LPS) (25 μg/100 μl; intrauterine), LPS + IND, and Surfactant Protein A Block (SP-A Block: SP-A B; the anti-SP-A antibody was applied 20 µg/100μl; intrauterine) groups. Tissues were examined by immunohistochemistry, immunofluorescence, and Western blot analysis. LPS administration increased the expression of N1 Dll-1 and Jagged-2 (Jag-2). Although Toll-like receptor (Tlr)-2 significantly increased in the LPS-treated and SP-A-blocked groups, Tlr-4 significantly increased only in the LPS-exposed groups. It was observed that Jag-2 is specifically expressed by mast cells. Overall, this experimental model shows that some protein responses increase throughout the uterus, starting at a specific point on the cervix epithelium. Surfactant Protein A, which we observed to be significantly reduced by LPS, may be associated with the regulation of the epithelial response, especially during preterm delivery due to infection. On the contrary, prostaglandin inhibitors can be considered an option to delay infection-related preterm labor with their dose-dependent effects. Finally, the link between mast cells and Jag-2 could potentially be a control switch for preterm birth.

Pulmonary surfactant protein A1 (SFTPA1) is a member of the C-type lectin subfamily that plays a critical role in maintaining lung tissue homeostasis and the innate immune response. SFTPA1 disruption can cause several acute or chronic lung diseases, including lung cancer. However, little research has been performed to associate SFTPA1 with immune cell infiltration and the response to immunotherapy in lung cancer. The findings of our study describe the SFTPA1 expression profile in multiple databases and was validated in BALB/c mice, human tumor tissues, and paired normal tissues using an immunohistochemistry assay. High SFTPA1 mRNA expression was associated with a favorable prognosis through a survival analysis in lung adenocarcinoma (LUAD) samples from TCGA. Further GeneOntology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses showed that SFTPA1 was involved in the toll-like receptor signaling pathway. An immune infiltration analysis clarified that high SFTPA1 expression was associated with an increased number of M1 macrophages, CD8 + T cells, memory activated CD4 + T cells, regulatory T cells, as well as a reduced number of M2 macrophages. Our clinical data suggest that SFTPA1 may serve as a biomarker for predicting a favorable response to immunotherapy for patients with LUAD. Collectively, our study extends the expression profile and potential regulatory pathways of SFTPA1 and may provide a potential biomarker for establishing novel preventive and therapeutic strategies for lung adenocarcinoma., (© 2021. The Author(s).)

The classic surfactant proteins (SPs) A, B, C, and D were discovered in the lungs, where they contribute to host defense and regulate the alveolar surface tension during breathing. Their additional importance for brain physiology was discovered decades later. SP-G, a novel amphiphilic SP, was then identified in the lungs and is mostly linked to inflammation. In the brain, it is also present and significantly elevated after hemorrhage in premature infants and in distinct conditions affecting the cerebrospinal fluid circulation of adults. However, current knowledge on SP-G-expression is limited to ependymal cells and some neurons in the subventricular and superficial cortex. Therefore, we primarily focused on the distribution of SP-G-immunoreactivity (ir) and its spatial relationships with components of the neurovascular unit in murine forebrains. Triple fluorescence labeling elucidated SP-G-co-expressing neurons in the habenula, infundibulum, and hypothalamus. Exploring whether SP-G might play a role in Alzheimer's disease (AD), 3xTg-AD mice were investigated and displayed age-dependent hippocampal deposits of β-amyloid and hyperphosphorylated tau separately from clustered, SP-G-containing dots with additional Reelin-ir-which was used as established marker for disease progression in this specific context. Semi-quantification of those dots, together with immunoassay-based quantification of intra- and extracellular SP-G, revealed a significant elevation in old 3xTg mice when compared to age-matched wildtype animals. This suggests a role of SP-G for the pathophysiology of AD, but a confirmation with human samples is required.

Surfactant protein A (SP-A) is well-known for its protective role in pulmonary immunity. Previous studies from our group have shown that SP-A mediates eosinophil activities, including degranulation and apoptosis. In order to identify potential binding partners on eosinophils for SP-A, eosinophil lysates were subjected to SP-A pull-down and tandem mass spectrometry (MS/MS) analysis. We identified one membrane-bound protein, myeloid-associated differentiation marker (MYADM), as a candidate SP-A binding partner. Blocking MYADM on mouse and human eosinophils ex vivo prevented SP-A from inducing apoptosis; blocking MYADM in vivo led to increased persistence of eosinophilia and airway hyper-responsiveness in an ovalbumin (OVA) allergy model and increased airways resistance and mucus production in a house dust mite (HDM) asthma model. Examination of a subset of participants in the Severe Asthma Research Program (SARP) cohort revealed a significant association between epithelial expression of MYADM in asthma patients and parameters of airway inflammation, including: peripheral blood eosinophilia, exhaled nitric oxide (FeNO) and the number of exacerbations in the past 12 months. Taken together, our studies provide the first evidence of MYADM as a novel SP-A-associated protein that is necessary for SP-A to induce eosinophil apoptosis and we bring to light the potential importance of this previously unrecognized transmembrane protein in patients with asthma., (© 2021. The Author(s).)

The human SFTPA1 and SFTPA2 genes encode the surfactant protein A1 (SP-A1) and SP-A2, respectively, and they have been identified with significant genetic and epigenetic variability including sequence, deletion/insertions, and splice variants. The surfactant proteins, SP-A1 and SP-A2, and their corresponding variants play important roles in several processes of innate immunity as well in surfactant-related functions as reviewed elsewhere [1]. The levels of SP-A have been shown to differ among individuals both under baseline conditions and in response to various agents or disease states. Moreover, a number of agents have been shown to differentially regulate SFTPA1 and SFTPA2 transcripts. The focus in this review is on the differential regulation of SFTPA1 and SFTPA2 with primary focus on the role of 5' and 3' untranslated regions (UTRs) and flanking sequences on this differential regulation as well molecules that may mediate the differential regulation., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Floros and Tsotakos.)

As key components of innate immunity, lung antimicrobial proteins play a critical role in warding off invading respiratory pathogens. Lung surfactant protein A (SP-A) exerts synergistic antimicrobial activity with the N -terminal segment of the SP-B proprotein (SP-B N ) against Klebsiella pneumoniae K2 in vivo. However, the factors that govern SP-A/SP-B N antimicrobial activity are still unclear. The aim of this study was to identify the mechanisms by which SP-A and SP-B N act synergistically against K. pneumoniae , which is resistant to either protein alone. The effect of these proteins on K. pneumoniae was studied by membrane permeabilization and depolarization assays and transmission electron microscopy. Their effects on model membranes of the outer and inner bacterial membranes were analyzed by differential scanning calorimetry and membrane leakage assays. Our results indicate that the SP-A/SP-B N complex alters the ultrastructure of K. pneumoniae by binding to lipopolysaccharide molecules present in the outer membrane, forming packing defects in the membrane that may favor the translocation of both proteins to the periplasmic space. The SP-A/SP-B N complex depolarized and permeabilized the inner membrane, perhaps through the induction of toroidal pores. We conclude that the synergistic antimicrobial activity of SP-A/SP-B N is based on the capability of this complex, but not either protein alone, to alter the integrity of bacterial membranes.

Lung surfactant protein A (SP-A) is critical for immunomodulation. Thymic stromal lymphopoietin (TSLP)-activated dendritic cells (DCs) drive T follicular helper (Tfh) cells differentiation in allergic asthma. We employed wild-type (WT) and SP-A -/- mice injected with TSLP and ovalbumin (OVA)-activated DCs and challenged with OVA. Compared with WT mice, we showed that allergic inflammation was dramatically increased in SP-A -/- mice. In parallel, both IL-4-producing CD45RA - CXCR5 + PD-1 + CD4 + cells (Tfh2) and IgE were markedly increased in SP-A -/- mice. Further study showed that SP-A prohibited TSLP activated-DCs from expressing OX40L. When we blocked OX40L-OX40 and IL-4R signaling, the differentiation of Tfh2 and IgE responses in SP-A -/- mice was significantly inhibited. In severe asthma patients, SP-A is dysfunctional in modulating the TSLP-DCs-mediated differentiation of Tfh cells. This study suggests that SP-A acts as a modulator of Tfh differentiation and IgE generation in asthma., (Copyright © 2021 Elsevier Inc. All rights reserved.)

The TLR4-interacting SPA4 peptide suppresses inflammation. We assessed the structural and physicochemical properties and binding of SPA4 peptide to TLR4-MD2. We also studied the changes at the whole transcriptome level, cell morphology, viability, secreted cytokines and chemokines, and cell influx in cell systems and mouse models challenged with LPS and treated with SPA4 peptide. Our results demonstrated that the SPA4 peptide did not alter the cell viability and size and only moderately affected the transcriptome of the cells. Computational docking and rendering suggested that the SPA4 peptide intercalates with LPS-induced TLR4-MD2 complex. Results with alanine mutations of D-2 amino acid and NYTXXXRG-12-19 motif of SPA4 peptide suggested their role in binding to TLR4 and in reducing the cytokine response against LPS stimulus. Furthermore, therapeutically administered SPA4 peptide significantly suppressed the secreted levels of cytokines and chemokines in cells and bronchoalveolar lavage fluids of LPS-challenged mice. The results suggest that the SPA4 peptide intercalates with LPS-induced TLR4 complex and signaling for the suppression of inflammation., (Copyright © 2021 The Authors.)

The human innate host defense molecules, SP-A1 and SP-A2 variants, differentially affect survival after infection in mice and in lung transplant patients. SP-A interacts with the sentinel innate immune cell in the alveolus, the alveolar macrophage (AM), and modulates its function and regulation. SP-A also plays a role in pulmonary surfactant-related aspects, including surfactant structure and reorganization. For most (if not all) pulmonary diseases there is a dysregulation of host defense and inflammatory processes and/or surfactant dysfunction or deficiency. Because SP-A plays a role in both of these general processes where one or both may become aberrant in pulmonary disease, SP-A stands to be an important molecule in health and disease. In humans (unlike in rodents) SP-A is encoded by two genes ( SFTPA1 and SFTPA2 ) and each has been identified with extensive genetic and epigenetic complexity. In this review, we focus on functional, structural, and regulatory differences between the two SP-A gene-specific products, SP-A1 and SP-A2, and among their corresponding variants. We discuss the differential impact of these variants on the surfactant structure, the alveolar microenvironment, the regulation of epithelial type II miRNome, the regulation and function of the AM, the overall survival of the organism after infection, and others. Although there have been a number of reviews on SP-A, this is the first review that provides such a comprehensive account of the differences between human SP-A1 and SP-A2., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Floros, Thorenoor, Tsotakos and Phelps.)

The increasing use of metal oxide nanoparticles (MONPs) as TiO 2 NPs or ZnO NPs has led to environmental release and human exposure. The respiratory system, effects on lamellar bodies and surfactant protein A (SP-A) of pneumocytes, can be importantly affected. Exposure of human alveolar epithelial cells (A549) induced differential responses; a higher persistence of TiO 2 in cell surface and uptake (measured by Atomic Force Microscopy) and sustained inflammatory response (by means of TNF-α, IL-10, and IL-6 release) and ROS generation were observed, whereas ZnO showed a modest response and low numbers in cell surface. A reduction in SP-A levels at 24 h of exposure to TiO 2 NPs (concentration-dependent) or ZnO NPs (the higher concentration) was also observed, reversed by blocking the inflammatory response (by the inhibition of IL-6). Loss of SP-A represents a relevant target of MONPs-induced inflammatory response that could contribute to cellular damage and loss of lung function., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Background: Respiratory diseases are a major cause of morbidity and mortality in the horses of all ages including foals. There is limited understanding of the expression of immune molecules such as tetraspanins and surfactant proteins (SP) and the regulation of the immune responses in the lungs of the foals. Therefore, the expression of CD9, SP-A and SP-D in foal lungs was examined., Results: Lungs from one day old (n = 6) and 30 days old (n = 5) foals were examined for the expression of CD9, SP-A, and SP-D with immunohistology and Western blots. Western blot data showed significant increase in the amount of CD9 protein (p = 0.0397) but not of SP-A and SP-D at 30 days of age compared to one day. Immunohistology detected CD9 in the alveolar septa and vascular endothelium but not the bronchiolar epithelium in the lungs of the foals in both age groups. SP-A and SP-D expression was localized throughout the alveolar septa including type II alveolar epithelial cells and the vascular endothelium of the lungs in all the foals. Compared to one day old foals, the expression of SP-A and SP-D appeared to be increased in the bronchiolar epithelium of 30 day old foals. Pulmonary intravascular macrophages were also positive for SP-A and SP-D in 30 days old foals and these cells are not developed in the day old foals., Conclusions: This is the first data on the expression of CD9, SP-A and SP-D in the lungs of foals.

The lung is a complex organ, and its physiology and immunology are regulated by various immune molecules and cells. Lung surfactant, a mixture of phospholipids and proteins produced by the bronchiolar and type II alveolar epithelial cells, is one such important player in lung physiology. Compared to knowledge about the biology of the surfactant in rodents and humans, only limited data are available on the surfactant in the horse. Although there are data linking levels of surfactant proteins with respiratory disease in the horse, there are no data on the cellular localization of surfactant protein A (SP-A) and surfactant protein D (SP-D). A member of the tetraspanin family of proteins, CD9 is a cell-signaling and adhesion protein and its expression has been detected in both normal and cancer cells, including those in the lung. Because there are no immunolocalization data on SP-A, SP-D, and CD9 in the normal lungs of the horse, our objective was to conduct a light and electron microscopic immunocytochemical study on normal lungs of the horse. The data showed SP-A and SP-D in bronchiolar epithelial and type II alveolar epithelial cells. These proteins were also localized in type I alveolar epithelial cells, pulmonary intravascular macrophages, and neutrophils, which is likely an outcome of endocytosis of the proteins by these cells. CD9 was present in the airway and vascular smooth muscle cells, endothelium, and blood cells, but not in the airway epithelium. These new data provide a baseline to further examine the expression and functions of SP-A, SP-D, and CD9 proteins in inflammation associated with respiratory diseases in the horse., (Copyright and/or publishing rights held by the Canadian Veterinary Medical Association.)

Objective: Acute respiratory distress syndrome (ARDS) is characterized by quantitative and qualitative changes in surfactant composition, leading to surfactant dysregulation with alveolar collapse and acute respiratory hypoxic failure. Recently, surfactant has been hypothesized to play a relevant role in COVID-19, representing a strong defender against SARS-CoV-2 infection. The aim of our work was the study of immunohistochemical surfactant expression in the lungs of patients died following SARS-CoV-2 ARDS, in order to shed light on a possible therapeutic surfactant administration., Patients and Methods: We investigated four patients who died due to ARDS following SARS-COV-2 infection and four patients submitted to lung biopsy, in the absence of SARS-CoV-2 infection. In all 8 cases, lung specimens were immunostained with anti-surfactant protein A (SP-A) and B (SP-B)., Results: In control subjects, reactivity for SP-B was restricted to type II alveolar cells. Immunostaining for SP-A was observed on the surface of alveolar spaces. In the COVID-19 positive lungs, immunoreactivity for SP-B was similar to that observed in control lungs; SP-A was strongly expressed along the alveolar wall. Moreover, dense aggregates of SP-A positive material were observed in the alveolar spaces., Conclusions: Our immunohistochemical data show the dysregulation of surfactant production in COVID-19 patients, particularly regarding SP-A expression. The increased presence of SP-A in condensed masses inside alveolar spaces could invalidate the therapeutic efficacy of the treatment with exogenous surfactant.

Small airways are difficult to access. Exhaled droplets, also referred to as particles, provide a sample of small airway lining fluid and may reflect inflammatory responses. We aimed to explore the effect of smoking on the composition and number of exhaled particles in a smoker-enriched study population. We collected and chemically analyzed exhaled particles from 102 subjects (29 never smokers, 36 former smokers and 37 current smokers) aged 39 to 83 years (median 63). A breathing maneuver maximized the number exhaled particles, which were quantified with a particle counter. The contents of surfactant protein A and albumin in exhaled particles was quantified with immunoassays and the contents of the phospholipids dipalmitoyl- and palmitoyl-oleoyl- phosphatidylcholine with mass spectrometry. Subjects also performed spirometry and nitrogen single breath washout. Associations between smoking status and the distribution of contents in exhaled particles and particle number concentration were tested with quantile regression, after adjusting for potential confounders. Current smokers, compared to never smokers, had higher number exhaled particles and more surfactant protein A in the particles. The magnitude of the effects of current smoking varied along the distribution of each PEx-variable. Among subjects with normal lung function, phospholipid levels were elevated in current smokers, in comparison to no effect of smoking on these lipids at abnormal lung function. Smoking increased exhaled number of particles and the contents of lipids and surfactant protein A in the particles. These findings might reflect early inflammatory responses to smoking in small airway lining fluid, also when lung function is within normal limits., Competing Interests: I have read the journal’s policy and the authors of this manuscript have the following competing interests: The authors Emilia Viklund, Björn Bake, Per Larsson and Anna-Carin Olin are shareholders in PExA AB (www.PEXA.se). Anna-Carin Olin is one of the inventors of the PExA method and is a board member of PExA AB. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Cigarette smoke exposure induces inflammation marked by rapid and sustained neutrophil infiltration, IL-1α, release and altered surfactant homeostasis. However, the extent to which neutrophils and IL-1α contribute to the maintenance of pulmonary surfactant homeostasis is not well understood. We sought to investigate whether neutrophils play a role in surfactant clearance as well as the effect of neutrophil depletion and IL-1α blockade on the response to cigarette smoke exposure. In vitro and in vivo administration of fluorescently labeled surfactant phosphatidylcholine was used to assess internalization of surfactant by lung neutrophils and macrophages during or following cigarette smoke exposure in mice. We also depleted neutrophils using anti-Ly-6G or anti-Gr-1 Abs, or we neutralized IL-1α using a blocking Ab to determine their respective roles in regulating surfactant homeostasis during cigarette smoke exposure. We observed that neutrophils actively internalize labeled surfactant both in vitro and in vivo and that IL-1α is required for smoke-induced elevation of surfactant protein (SP)-A and SP-D levels. Neutrophil depletion during cigarette smoke exposure led to a further increase in SP-A levels in the bronchoalveolar lavage and increased IL-1α, CCL2, GM-CSF, and G-CSF release. Finally, macrophage expression of Mmp12 , a protease linked to emphysema, was increased in neutrophil-depleted groups and decreased following IL-1α blockade. Taken together, our results indicate that neutrophils and IL-1α signaling are actively involved in surfactant homeostasis and that the absence of neutrophils in the lungs during cigarette smoke exposure leads to an IL-1α-dependent exacerbation of the inflammatory response., (Copyright © 2021 by The American Association of Immunologists, Inc.)

Objective: The objective of this study is to determine the role of SPA (surfactant protein A) in vascular smooth muscle cell (SMC) phenotypic modulation and vascular remodeling. Approach and Results: PDGF-BB (Platelet-derived growth factor-BB) and serum induced SPA expression while downregulating SMC marker gene expression in SMCs. SPA deficiency increased the contractile protein expression. Mechanistically, SPA deficiency enhanced the expression of myocardin and TGF (transforming growth factor)-β, the key regulators for contractile SMC phenotype. In vivo, SPA was induced in medial and neointimal SMCs following mechanical injury in both rat and mouse carotid arteries. SPA knockout in mice dramatically attenuated the wire injury-induced intimal hyperplasia while restoring SMC contractile protein expression in medial SMCs. These data indicate that SPA plays an important role in SMC phenotype modulation and vascular remodeling in vivo., Conclusions: SPA is a novel protein factor modulating SMC phenotype. Blocking the abnormal elevation of SPA may be a potential strategy to inhibit the development of proliferative vascular diseases.

Plate bodies are facultative organelles occasionally described in the adult lungs of various species, including sheep and goat. They consist of multiple layers of plate-like cisterns with an electron dense middle bar. The present study was performed to elucidate the three-dimensional (3D) characteristics of this organelle and its presumed function in surfactant protein A (SP-A) biology. Archived material of four adult goat lungs and PFA-fixed lung samples of two adult sheep lungs were used for the morphological and immunocytochemical parts of this study, respectively. 3D imaging was performed by electron tomography and focused ion beam scanning electron microscopy (FIB-SEM). Immuno gold labeling was used to analyze whether plate bodies are positive for SP-A. Transmission electron microscopy revealed the presence of plate bodies in three of four goat lungs and in both sheep lungs. Electron tomography and FIB-SEM characterized the plate bodies as layers of two up to over ten layers of membranous cisterns with the characteristic electron dense middle bar. The membranes of the plates were in connection with the rough endoplasmic reticulum and showed vesicular inclusions in the middle of the plates and a vesicular network at the sides of the organelle. Immuno gold labeling revealed the presence of SP-A in the vesicular network of plate bodies but not in the characteristic plates themselves. In conclusion, the present study clearly proves the connection of plate bodies with the rough endoplasmic reticulum and the presence of a vesicular network as part of the organelle involved in SP-A trafficking.

Alveolar macrophages (AMs) are differentially regulated by human surfactant protein-A1 (SP-A1) or SP-A2. However, AMs are very heterogeneous and differences are difficult to characterize in intact cells. Using the Toponome Imaging System (TIS), an imaging technique that uses sequential immunostaining to identify patterns of biomarker expression or combinatorial molecular phenotypes (CMPs), we studied individual single cells and identified subgroups of AMs (n = 168) from SP-A-KO mice and mice expressing either SP-A1 or SP-A2. The effects, as shown by CMPs, of SP-A1 and SP-A2 on AMs were significant and differed. SP-A1 AMs were the most diverse and shared the fewest CMPs with KO and SP-A2. Clustering analysis of each group showed 3 clusters where the CMP-based phenotype was distinct in each cluster. Moreover, a clustering analysis of all 168 AMs revealed 10 clusters, many dominated by 1 group. Some CMP overlap among groups was observed with SP-A2 AMs sharing the most CMPs and SP-A1 AMs the fewest. The CMP-based patterns identified here provide a basis for understanding not only AMs' diversity, but also most importantly, the molecular basis for the diversity of functional differences in mouse models where the impact of genetics of innate immune molecules on AMs has been studied.

Objective: Our aim was to investigate the effect of emodin on intestinal and lung injury induced by acute intestinal injury in rats and explore potential molecular mechanisms., Methods: Healthy male Sprague-Dawley (SD) rats were randomly divided into five groups (n=10, each group): normal group; saline group; acute intestinal injury model group; model + emodin group; model+NF-κB inhibitor pynolidine dithiocarbamate (PDTC) group. Histopathological changes in intestine/lung tissues were observed by Hematoxylin and Eosin (H&E) and terminal deoxynucleotidyl transferase biotin-dUTP nick-end labeling (TUNEL) staining. Serum IKBα, p-IKBα, surfactant protein-A (SP-A) and toll-like receptor 4 (TLR4) levels were examined using enzyme-linked immunosorbent assay (ELISA). RT-qPCR was performed to detect the mRNA expression levels of IKBα, SP-A and TLR4 in intestine/lung tissues. Furthermore, the protein expression levels of IKBα, p-IKBα, SP-A and TLR4 were detected by Western blot., Results: The pathological injury of intestinal/lung tissues was remarkedly ameliorated in models treated with emodin and PDTC. Furthermore, the intestinal/lung injury scores were significantly decreased after emodin or PDTC treatment. TUNEL results showed that both emodin and PDTC treatment distinctly attenuated the apoptosis of intestine/lung tissues induced by acute intestinal injury. At the mRNA level, emodin significantly increased the expression levels of SP-A and decreased the expression levels of IKBα and TLR4 in intestine/lung tissues. According to ELISA and Western blot, emodin remarkedly inhibited the expression of p-IKBα protein and elevated the expression of SP-A and TLR4 in serum and intestine/lung tissues induced by acute intestinal injury., Conclusion: Our findings suggested that emodin could protect against intestinal and lung injury induced by acute intestinal injury by modulating SP-A and TLR4/NF-κB pathway., (© 2020 The Author(s).)

Background: Idiopathic pulmonary fibrosis (IPF) is a serious disorder with a high mortality rate worldwide. It is characterized by irreversible scarring of the lung parenchyma resulting from excessive collagen production by proliferating fibroblasts/myofibroblasts. Previous studies have revealed that mutations in surfactant protein-related genes and telomerase complex genes are crucial underlying genetic factors., Methods: In this study, we enrolled a family with IPF from the central southern region of China. Whole-exome sequencing was employed to explore candidate genes in this family. Real-time PCR and western blotting were used to study the functions of the identified mutations in vitro., Results: A novel mutation (NM&#95;001098668.4: c.619A>T; NP&#95;001092138.1: p.N207Y) in surfactant protein A2 (SFTPA2,), having not been previously reported to be a mutation, was identified and co-separated with all affected individuals in the IPF family. Functional research further revealed that the novel mutation affects the secretion of SFTPA2 protein and induces endoplasmic reticulum stress as well as apoptosis in A549 cells., Conclusion: We are confident that this novel mutation (NM&#95;001098668.4: c.619A>T; NP&#95;001092138.1: p.N207Y) in SFTPA2 is the genetic mutation of the IPF family. Our study not only confirms the importance of SFTPA2 in IPF but also expands the spectrum of SFTPA2 mutations and contributes to the genetic diagnosis and counseling of IPF patients., (© 2020 The Authors. Molecular Genetics & Genomic Medicine published by Wiley Periodicals LLC.)

The mechanisms underlying interstitial lung disease (ILD) are characterized by variable inflammation or fibrosis of the pulmonary interstitium. A negative heart sign (NHS) on 67 Ga scintigrams of patients with ILD is due to considerably increased inflammatory activity in the lungs. We retrospectively analyzed relationships between NHS and established biomarkers of disease severity in patients with ILD. Among 81 consecutive non-smoking patients with ILD (mean age, 63 years) who had been hospitalized between April 2009 and October 2011, we selected 52 who had been assessed by 67 Ga scintigraphy. We then evaluated relationships between NHS and blood biomarkers, pulmonary function and high-resolution computed tomography (HRCT). Among these 52 patients, 10 showed idiopathic pulmonary fibrosis and 42 had other ILD. Multivariate analysis with stepwise variable selection, serum surfactant protein (SP)-A (OR (odds ratio), 1.026; 95%CI (confidence interval), 1.003-1.050; P = 0.024) and inflammation index calculated from HRCT findings (OR, 1.358; 95%CI, 1.079-1.709; P = 0.009) were significant predictors of an NHS. Serum SP-A offered 85% sensitivity and 75% specificity for predicting NHS at an optimal cut-off of 45.8 ng/mL. Serum SP-A concentrations correlated positively with inflammation index (r = 0.344, P = 0.015). In conclusion, serum SP-A might serve as a surrogate biomarker for predicting an NHS in patients with ILD., Competing Interests: None of the authors have any real or perceived conflicts of interest to declare regarding the subject of this manuscript.

The lung surfactant proteins are recognized as critical not only for their role in lowering lung surface tension but also in innate host defense. Reports have shown that some asthmatic patients have decreased levels of one member of this protein family in particular, surfactant protein-A (SP-A). Our studies set out to determine the contribution of SP-A to the response of a key effector cytokine in asthma, IL-13. Our studies employ both animal models sufficient and deficient in SP-A challenged with IL-13 and primary epithelial cells from participants with asthma that are exogenously treated with SP-A in the context of IL-13 challenge. The inflammatory response and mucin production were assessed in both model systems. As compared with WT mice, we show that the activity of IL-13 is dramatically augmented in SP-A -/- mice, which have significantly increased neutrophil and eosinophil recruitment, mucin production and asthma-associated cytokines in the bronchoalveolar lavage fluid. In parallel, we show asthma-associated factors are attenuated in human cells from asthma subjects when exogenous SP-A is added during IL-13 challenge. Although many of these phenotypes have previously been associated with STAT6 signaling, SP-A inhibited IL-13-induced STAT3 phosphorylation in mice and in human epithelial cells while having little effect on STAT6 phosphorylation. In addition, when either STAT3 or IL-6 were inhibited in mice, the phenotypes observed in SP-A -/- mice were significantly attenuated. These studies suggest a novel mechanism for SP-A in asthma as a modulator of IL-13-induced inflammation via mediating downstream IL-6/STAT3 signaling., (Copyright © 2020 by The American Association of Immunologists, Inc.)

Purpose: To provide a better understanding of the interplay between the immune system and brain metastases to advance therapeutic options for this life-threatening disease., Experimental Design: Tumor-infiltrating lymphocytes (TIL) were quantified by semiautomated whole-slide analysis in brain metastases from 81 lung adenocarcinomas. Multi-color staining enabled phenotyping of TILs (CD3, CD8, and FOXP3) on a single-cell resolution. Molecular determinants of the extent of TILs in brain metastases were analyzed by transcriptomics in a subset of 63 patients. Findings in lung adenocarcinoma brain metastases were related to published multi-omic primary lung adenocarcinoma The Cancer Genome Atlas data ( n = 230) and single-cell RNA-sequencing (scRNA-seq) data ( n = 52,698)., Results: TIL numbers within tumor islands was an independent prognostic marker in patients with lung adenocarcinoma brain metastases. Comparative transcriptomics revealed that expression of three surfactant metabolism-related genes ( SFTPA1, SFTPB , and NAPSA ) was closely associated with TIL numbers. Their expression was not only prognostic in brain metastasis but also in primary lung adenocarcinoma. Correlation with scRNA-seq data revealed that brain metastases with high expression of surfactant genes might originate from tumor cells resembling alveolar type 2 cells. Methylome-based estimation of immune cell fractions in primary lung adenocarcinoma confirmed a positive association between lymphocyte infiltration and surfactant expression. Tumors with a high surfactant expression displayed a transcriptomic profile of an inflammatory microenvironment., Conclusions: The expression of surfactant metabolism-related genes ( SFTPA1, SFTPB , and NAPSA ) defines an inflamed subtype of lung adenocarcinoma brain metastases characterized by high abundance of TILs in close vicinity to tumor cells, a prolonged survival, and a tumor microenvironment which might be more accessible to immunotherapeutic approaches., (©2020 American Association for Cancer Research.)

Introduction: Long-term pulmonary complications are one of the major long-term consequences of sulfur mustard (SM) exposure. Toll-like receptor 4 (TLR4) involves in the pathogenesis of several pulmonary disorders. Surfactant protein-A (SP-A) regulates LPS-induced TLR4 localization and activation responses. However, the intensity and significance of TLR4 and SP-A expression by lung cells in SM-exposed patients is not clear., Methods: The gene expression of TLR4 (through real-time PCR) and TLR4 and SP-A positive cells and alveolar type II cells, as SP-A producers, (using IHC) were assessed in formalin fixed paraffin embedded (FFPE) specimens from SM-exposed (n = 17), and non-SM exposed individuals (n = 12)., Results: TLR4 gene expression did not change between study groups. However, its cell surface presentation was significantly reduced in SM-exposed patients and particularly in which with constrictive bronchiolitis compared with the control group (P < 0.001 and P = 0.002, respectively). Frequency of alveolar type II cells was lower in the case group rather than the control group while the number of SP-A positive cells did not alter., Conclusions: These findings suggest that reduced TLR4 cell surface presentation may have anti-inflammatory function and SP-A may have a critical role in regulation of inflammatory responses in SM-exposed patients. Further investigation on other possible mechanisms involved in TLR4 internalization maybe help to illustrate the modulatory or inflammatory activity of TLR4 in these patients., Competing Interests: Declaration of Competing Interest All of the authors declare no conflict of interest., (Copyright © 2019. Published by Elsevier B.V.)

This study investigated the effect of dexamethasone (DEX) on intracellular calcium levels and the expressions of transient receptor potential cation channel subcomponent V member 6 ( TRPV6 ), sodium-calcium exchanger 1 ( NCX1 ), and plasma membrane calcium ATPase 1 ( PMCA1 ) in A549 cells. The intracellular calcium level, by using the calcium indicator pGP-CMV-GCaMP6f, increased following DEX treatment for 6, 12, and 24 h in A549 cells. In addition, Rhod-4 assay after DEX treatment for 24 h showed that DEX increased the level of intracellular calcium. The expression of the calcium influx TRPV6 gene significantly increased, whereas the expressions of the calcium outflow NCX1 and PMCA1 genes significantly decreased with DEX treatment. The mRNA levels of surfactant protein genes SFTPA1 , SFTPB , SFTPC , and SFTPD and the secreted airway mucin genes MUC1 and MUC5AC were investigated by treating cells with DEX. The DEX treatment decreased the mRNA levels of SFTPA1 and SFTPB but increased the mRNA levels of SFTPC and SFTPD . The MUC1 mRNA level was increased by DEX treatment, whereas MUC5AC mRNA was significantly decreased. These results indicate that DEX influences the intracellular calcium level through TRPV6 , and affects pulmonary surfactant genes and secreted airway mucin genes in A549 cells.

Cigarette smoking is considered the main risk factor for chronic obstructive pulmonary disease (COPD), although the mechanism remains unknown. surfactant protein A (SP-A) is thought to protect the lung from smoking-induced damage, but related studies performed in China are scarce. The aim of the study is to assess alterations of SP-A expression and distribution in lung samples from Chinese smokers with or without COPD.This cross-sectional study assessed 45 men in Wuhan Tongji Hospital after lobectomy for lung cancer in June 2010 to September 2010. Peripheral lung specimens were collected from control nonsmokers without airflow obstruction (nonsmoking group, n = 15), smokers without airflow obstruction (smoking group, n = 15), and patients with COPD (COPD group, n = 15). SP-A expression levels in lung tissue samples and its distribution in lung cells, type II pneumocytes (PNII), and alveolar macrophages (MACR) were determined by immunoblotting and immunohistochemistry.SP-A levels were significantly decreased in the COPD group (1.00 ± 0.25) compared with the smoking (2.31 ± 0.64) and nonsmoking (8.03 ± 2.80) groups; the smoking group also showed significantly reduced levels compared with the nonsmoking group (P < .05). PNII expressing SP-A were less abundant in the COPD group (39.3% ± 7.1%) compared with the smoking group (76.2% ± 29.8%), whereas SP-A MACR were more abundant (92.4% ± 7.1% vs 68.5% ± 20.2%) (all P < .05). Among the 30 smokers, forced expiratory volume in one second (% predicted) was positively correlated with SP-A levels (r = 0.739) and the rate of SP-A+ PNII (r = 0.811), and negatively correlated with the rate of SP-A+ MACR (r = -0.758) (all P < .05).Changes in SP-A expression and distribution in lung tissues may be involved in COPD pathogenesis in smokers.

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., Competing Interests: I have read the journal's policy and the authors of this manuscript have the following competing interests: Björn Bake, Marianne Andersson and Gunilla Runström Eden are shareholders of PEXA® AB (www.PEXA.se) and Anna-Carin Olin is a board member (patent WO2009045163). This does not alter our adherence to PLOS ONE policies on sharing data and materials.