Surfactant-associated Protein Research Articles

Biophysical impact of lubricating base oil aerosols on natural pulmonary surfactant film

Lubricating base oils have been extensively employed for producing various industrial and consumer products. Therefore, their environmental and health impacts should be carefully evaluated. Although there have been many reports on pulmonary cytotoxicity and inflammatory responses of inhaled lubricating base oils, their potential influences on pulmonary surfactant (PS) films that play an essential role in maintaining respiratory mechanics and pulmonary immunity remains largely unknown. Here a systematic study on the interactions between an animal-derived natural PS and aerosols of water and representative mineral and vegetable base oils is performed using a novel biophysical assessing technique called constrained drop surfactometry capable of providing in vitro simulations of normal tidal breathing and physiologically relevant temperature and humidity in the lung. It was found that the mineral oil aerosols can impose strong inhibitions to the biophysical property of PS film, while the airborne vegetable oils and water show negligible adverse effects within the studied concentration range. The inhibitory effect is originated from the strong hydrophobicity of mineral oil, which makes it able to disrupt the interfacial molecular ordering of both phospholipid and protein compositions and consequently suppress the formation of condensed phase and multilayer scaffolds in a PS film. Environmental ImplicationUnderstanding the biophysical influence of airborne lubricating base oils on pulmonary surfactant (PS) films can provide new insights into the environmental impacts and health concerns of various industrial lubricant products. Here a comparative study on interactions between an animal-derived natural PS film and the aerosols of water and representative mineral and vegetable base oils under the true physiological conditions was conducted in situ using constrained drop surfactometry. We show that the most frequently used mineral base oil can cause strong inhibitions to the PS film by disrupting the molecular ordering of saturated phospholipids and surfactant-associated proteins at the interface.

Multi-omics analysis of diabetic pig lungs reveals molecular derangements underlying pulmonary complications of diabetes mellitus.

Growing evidence shows that the lung is an organ prone to injury by diabetes mellitus. However, the molecular mechanisms of these pulmonary complications have not yet been characterized comprehensively. To systematically study the effects of insulin deficiency and hyperglycaemia on the lung, we combined proteomics and lipidomics with quantitative histomorphological analyses to compare lung tissue samples from a clinically relevant pig model for mutant INS gene-induced diabetes of youth (MIDY) with samples from wild-type littermate controls. Among others, the level of pulmonary surfactant-associated protein A (SFTPA1), a biomarker of lung injury, was moderately elevated. Furthermore, key proteins related to humoral immune response and extracellular matrix organization were significantly altered in abundance. Importantly, a lipoxygenase pathway was dysregulated as indicated by 2.5-fold reduction of polyunsaturated fatty acid lipoxygenase ALOX15 levels, associated with corresponding changes in the levels of lipids influenced by this enzyme. Our multi-omics study points to an involvement of reduced ALOX15 levels and an associated lack of eicosanoid switching as mechanisms contributing to a proinflammatory milieu in the lungs of subjects with diabetes mellitus.

SFTPB in serum extracellular vesicles as a biomarker of progressive pulmonary fibrosis.

Progressive pulmonary fibrosis (PPF), defined as the worsening of various interstitial lung diseases (ILDs), currently lacks useful biomarkers. To identify novel biomarkers for early detection of patients at risk of PPF, we performed a proteomic analysis of serum extracellular vesicles (EVs). Notably, the identified candidate biomarkers were enriched for lung-derived proteins participating in fibrosis-related pathways. Among them, pulmonary surfactant-associated protein B (SFTPB) in serum EVs could predict ILD progression better than the known biomarkers, serum KL-6 and SP-D, and it was identified as an independent prognostic factor from ILD-gender-age-physiology index. Subsequently, the utility of SFTPB for predicting ILD progression was evaluated further in 2 cohorts using serum EVs and serum, respectively, suggesting that SFTPB in serum EVs but not in serum was helpful. Among SFTPB forms, pro-SFTPB levels were increased in both serum EVs and lungs of patients with PPF compared with those of the control. Consistently, in a mouse model, the levels of pro-SFTPB, primarily originating from alveolar epithelial type 2 cells, were increased similarly in serum EVs and lungs, reflecting pro-fibrotic changes in the lungs, as supported by single-cell RNA sequencing. SFTPB, especially its pro-form, in serum EVs could serve as a biomarker for predicting ILD progression.

Untargeted lipidomics of bronchopulmonary dysplasia induced by hyperoxia exposure in rats.

Bronchopulmonary dysplasia (BPD), characterized by impaired lung development, remains a leading cause of morbidity and mortality in premature infants. The synthesis and metabolism of lipids play a critical role in normal lung development, such as dipalmitoylphosphatidylcholine, a key component of pulmonary surfactant (PS). Therefore, we conducted a lipidomics study of rat lung tissue to explore the changes of pulmonary lipid composition in the progression of BPD disease. In this study, we exposed neonatal Sprague-Dawley (SD) rats to hyperoxia for 14 days. After hyperoxia exposure, the lung tissues of rats were analyzed pathologically, and untargeted lipidomics was analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Hematoxylin-eosin (H&E) staining showed that the alveoli enlarged, the number of alveoli decreased and the pulmonary surfactant-associated protein D (SFTPD) decreased in hyperoxia-exposed rats. A total of 620 pulmonary lipids were detected by LC-MS/MS, covering 27 lipid categories. The most common lipids were triacylglycerol (TAG), followed by phosphatidylcholine (PC) and phosphatidylethanolamine (PE). Compared with those rats exposed to normoxic conditions, the lipid levels in the lungs of rats exposed to hyperoxia for 14 days generally decreased, with the levels of TAG and PC decreasing most significantly. In short, our results provide a clue for finding therapeutic targets and biomarkers of a BPD rat model lung liposome.

Abstract 3040: Quantitative Proteomic Analysis Of HDL Shows Apolipoprotein M (ApoM) As A Possible Marker For COVID-19 Mortality

Introduction: High-density lipoprotein (HDL) comprises a heterogeneous group of particles that differ in many aspects, such as density, size, composition and function. The use of mass spectrometry-based proteomics to investigate HDL protein composition has brought some new insights into the field. The qualitative and quantitative HDL proteome is remodeled in different disease states, such as diabetes mellitus, hypercholesterolemia and kidney dysfunction. Beyond its established role in inflammatory and cardiovascular diseases, HDL's involvement in infectious diseases, such as COVID-19, has recently come to light. Here, we investigate the remodeling of HDL proteome in hospitalized and non-hospitalized COVID-19 patients. Hypothesis: We hypothesize HDL proteome is remodeled in infectious diseases and may be a marker and perhaps a predictor of a poor prognosis. Methods: We implemented a robust, global label-free quantification proteomic approach to unravel relative changes in HDL protein composition. We analyzed the proteome of COVID-19 subjects from Brazil categorized in two groups, hospitalized (n=30) and non-hospitalized (n=11). Results: Comparative analysis between hospitalized and non-hospitalized patients revealed a more than 50% increase in relative levels of certain proteins in hospitalized patients, including the inflammatory proteins serum amyloid A1 and A2, as well as pulmonary surfactant-associated protein B. We also observed reductions in the lipid-metabolism related apolipoprotein A2 and phospholipid transfer protein. These findings, independent of sex, triglyceride and HDL-cholesterol, suggest an inflammatory remodeling of the HDL particles. Further analysis of surviving (n=35) and deceased patients (n=6) indicated a negative association between ApoM levels and odds of death due to COVID-19 complications (odds ratio per 1-SD increase in ApoM was 0.27 [0.07 to 0.72], P=0.007). Conclusions: Our results point out HDL remodeling is a marker of COVID-19 severity and ApoM-carried sphingosine-1-phosphate signaling pathway may play a pivotal role in the disease outcome.

Forensic application of three interstitial pneumonia markers: search for new pneumonia markers in dead bodies.

In forensic cases, detailed identification of pneumonia is important. Our objective was to statistically determine the applicability of three interstitial lung disease (ILD) markers for forensic diagnosis using serum collected from dead bodies with various postmortem intervals (PMIs). We retrospectively analyzed the levels of postmortem serum Krebs von den Lungen-6 (KL-6) and pulmonary surfactant-associated proteins A and D (SP-A and SP-D) using 221 samples obtained during forensic autopsy at our facility from 2019 to 2023. We evaluated the diagnostic efficacy of ILD markers for various pneumonias against the pathological diagnosis, and examined the assessment of the severity of ILD. When comparing the ILD group with bacterial pneumonia (BP) versus the control group, there was a significant increase in KL-6 in the ILD group. When comparing the severe ILD (SILD) group with the mild ILD (MILD) group, there was a significant increase in KL-6 and SP-D in the SILD group. The optimal cutoff values for differentiating SILD were 607.0 U/mL for KL-6, 55.5ng/mL for SP-A, and 160.0ng/mL for SP-D, and the sensitivity/specificity (%) of KL-6, SP-A, and SP-D for SILD were 84.1/95.2, 55.6/85.7, and 66.7/74.6, respectively. This is the first study to examine KL-6 in postmortem serum in forensic medicine. By analyzing dead bodies with various PMIs, our results confirmed statistically that postmortem serum KL-6 specifically detects ILD, postmortem serum SP-A has high sensitivity to lung injury, and postmortem serum SP-D is potentially useful in assessing the severity of ILD.

Transcriptomic analysis of skin immunity genes in the Chinese spiny frog (Quasipaa spinosa) after Proteus mirabilis infection

Recently, populations of Chinese spiny frogs (Quasipaa spinosa), an important amphibian species in China, have decreased, mainly due to a disease caused by the gram-negative bacteria Proteus mirabilis. To elucidate the immune response of the frogs, this study aimed to identify novel candidate genes functionally associated with P. mirabilis infection-induced “rotting skin” disease. Chinese spiny frogs were infected with P. mirabilis, and the skin transcriptome was sequenced using the MGISEQ-2000 platform. A total of 233,965 unigenes were obtained by sequencing, of which 27.23 % were known genes. Screening of differentially expressed genes (DEGs) indicated 210 unigenes differentially expressed after P. mirabilis infection, of which 132 unigenes were up-regulated, and 78 unigenes were down-regulated. Using Kyoto Encyclopedia of Genes and Genomes enrichment analysis, DEGs were identified as enriched in signal pathways, such as oxidative phosphorylation, apoptosis, and the Janus kinase-signal transducer and activator of transcription pathway. Of the DEGs, there was a significant upregulation of the colony stimulating factor 2 receptor beta common subunit, interleukin 2 receptor subunit gamma, cathelicidin antimicrobial peptide, interleukin-17 receptor E, receptor-interacting serine/threonine-protein kinase 3, and pulmonary surfactant-associated protein D immune genes following P. mirabilis infection. Conversely, scavenger receptor cysteine-rich domain-containing group B protein, tumor protein p53 inducible nuclear protein 2, suppressor of cytokine signaling 2, and metalloreductase STEAP3 were significantly downregulated. In conclusion, the first skin transcriptome database of Chinese spiny frogs was established, and several immune genes were identified to elucidate the pathogenic mechanism of “skin rot” in Chinese spiny frogs and other cultured frogs.

Sodium butyrate ameliorates sepsis-associated lung injury by enhancing gut and lung barrier function in combination with modulation of CD4+Foxp3+ regulatory T cells

Sepsis-associated lung injury often coexists with intestinal dysfunction. Butyrate, an essential gut microbiota metabolite, participates in gut-lung crosstalk and has immunoregulatory effects. This study aims to investigate the effect and mechanism of sodium butyrate (NaB) on lung injury. Sepsis-associated lung injury was established in mice by cecal ligation and puncture (CLP). Mice in treatment groups received NaB gavage after surgery. The survival rate, the oxygenation index and the lung wet-to-dry weight (W/D) ratio were calculated respectively. Pulmonary and intestinal histologic changes were observed. The total protein concentration in bronchoalveolar lavage fluid (BALF) was measured, and inflammatory factors in serum and BALF were examined. Diamine oxidase (DAO), lipopolysaccharide (LPS), and surfactant-associated protein D (SP-D) levels in serum and amphiregulin in lung tissue were assessed. Intercellular junction protein expression in the lung and intestinal tissues were examined. Changes in immune cells were analyzed. NaB treatment improved the survival rate, the oxygenation index and the histologic changes. NaB decreased the W/D ratio, total protein concentration, and the levels of proinflammatory cytokines, as well as SP-D, DAO and LPS, while increased the levels of anti-inflammatory cytokines and amphiregulin. The intercellular junction protein expression were improved by NaB. Furthermore, the CD4+/CD8+ T-cell ratio and the proportion of CD4+Foxp3+ regulatory T cells (Tregs) were increased by NaB. Our data suggested that NaB gavage effectively improved the survival rate and mitigated lung injury in CLP mice. The possible mechanism was that NaB augmented CD4+Foxp3+ Tregs and enhanced the barrier function of the gut and the lung.

Fusu mixture alleviates inflammatory reactions in lipopolysaccharide-induced acute respiratory distress syndrome mice via regulation of surfactant-associated protein C, aquaporin 5, and Notch1.

Acute respiratory distress syndrome (ARDS) is a common life-threatening critical illness with high mortality. Fusu mixture (FSM) can improve the mechanical ventilation in ARDS patients. However, the detailed pharmacological mechanisms and active substances of FSM are still unclear. This study aimed to explore the potential pharmacological mechanisms of FSM for treating ARDS and its chemical compositions. A lipopolysaccharide (LPS)-induced ARDS mouse model was established, and the mice subsequently received FSM (50 mg/kg) orally for 5 days. Then, the blood samples and lung tissues were collected. Enzyme-linked immunosorbent assay (ELISA) was used to determine the levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in serum, and histopathology examinations were applied to analyze the inflammatory response of lung tissues in ARDS mice. In addition, protein expressions of aquaporin 5 (AQP-5), surfactant-associated protein C (SP-C), and Notch1 were detected by western blot assays and immunohistochemical (IHC) examination. In addition, the chemical compositions of FSM were analyzed by high performance liquid chromatography (HPLC), using standard reference agents. After LPS induction, the serum levels of IL-6 and TNF-α in ARDS mice were significantly increased (P<0.01, vs. Control), and FSM significantly reduced these 2 pro-inflammatory cytokines (IL-6 and TNF-α) compared to the model mice (P<0.01). Histopathology examinations showed FSM significantly attenuated the inflammatory responses in lung tissues. Furthermore, after FSM treatment, the SP-C and AQP-5 were significantly increased, compared to the Model mice (P<0.01), and FSM also up-regulated the Notch1 expressions in lung tissues of ARDS mice (P<0.001, vs. Model). Collectively, it is suggested that FSM alleviates inflammatory reactions and promotes the proliferation of alveolar epithelial cells in LPS-induced ARDS mice via regulation of SP-C, AQP-5, and Notch1 in lung tissues.

Airway allergy causes alveolar macrophage death, profound alveolar disorganization and surfactant dysfunction.

Respiratory disorders caused by allergy have been associated to bronchiolar inflammation leading to life-threatening airway narrowing. However, whether airway allergy causes alveolar dysfunction contributing to the pathology of allergic asthma remains unaddressed. To explore whether airway allergy causes alveolar dysfunction that might contribute to the pathology of allergic asthma, alveolar structural and functional alterations were analyzed during house dust mite (HDM)-induced airway allergy in mice, by flow cytometry, light and electron microscopy, monocyte transfer experiments, assessment of intra-alveolarly-located cells, analysis of alveolar macrophage regeneration in Cx3cr1 cre:R26-yfp chimeras, analysis of surfactant-associated proteins, and study of lung surfactant biophysical properties by captive bubble surfactometry. Our results demonstrate that HDM-induced airway allergic reactions caused severe alveolar dysfunction, leading to alveolar macrophage death, pneumocyte hypertrophy and surfactant dysfunction. SP-B/C proteins were reduced in allergic lung surfactant, that displayed a reduced efficiency to form surface-active films, increasing the risk of atelectasis. Original alveolar macrophages were replaced by monocyte-derived alveolar macrophages, that persisted at least two months after the resolution of allergy. Monocyte to alveolar macrophage transition occurred through an intermediate stage of pre-alveolar macrophage and was paralleled with translocation into the alveolar space, Siglec-F upregulation, and downregulation of CX3CR1. These data support that the severe respiratory disorders caused by asthmatic reactions not only result from bronchiolar inflammation, but additionally from alveolar dysfunction compromising an efficient gas exchange.

Neutrophil extracellular traps promote bronchopulmonary dysplasia-like injury in neonatal mice via the WNT/β-catenin pathway.

Bronchopulmonary dysplasia (BPD) is one of the most common and severe chronic diseases in preterm infants. Premature infants are susceptible to BPD due to immature lungs and adverse perinatal episodes of infection, hyperoxia, and mechanical ventilation. Neutrophils are the first line of host defence, and the release of neutrophil extracellular traps (NETs) is an important strategy to immobilize and kill invading microorganisms. This study examined whether NETs were associated with BPD in preterm infants and contributed to hyperoxia-induced lung injury in neonatal mice via the WNT/β-catenin pathway. In this study, we found that preterm infants with BPD had higher levels of NETs in their tracheal aspirates than those without BPD. Neonatal mice treated with NETs after birth exhibited BPD-like changes in their lungs. Furthermore, the levels of Aquaporin 5 (AQP5) and surfactant-associated protein C (SPC), which represent alveolar differentiation and development, were significantly lower than those in the controls. The WNT/β-catenin pathway is one of the most well-known signalling pathways involved in lung growth. We found that the expression of the target genes c-MYC, cyclin D, and vascular endothelial growth factor (VEGF) and the important proteins WNT3a and β-catenin significantly decreased. Moreover, heparin, which is a NET inhibitor, attenuated changes in gene and protein expression, thereby attenuating BPD-like changes. This finding indicates that NETs are associated with BPD and can induce BPD-like changes in neonatal mice via the WNT/β-catenin pathway.

Alveolar-Capillary Barrier Protection In Vitro: Lung Cell Type-Specific Effects and Molecular Mechanisms Induced by 1α, 25-Dihydroxyvitamin D3.

Low serum levels of 1α, 25-dihydroxyvitamin D3 (VD3) are associated with a higher mortality in trauma patients with sepsis or ARDS. However, the molecular mechanisms behind this observation are not yet understood. VD3 is known to stimulate lung maturity, alveolar type II cell differentiation, or pulmonary surfactant synthesis and guides epithelial defense during infection. In this study, we investigated the impact of VD3 on the alveolar-capillary barrier in a co-culture model of alveolar epithelial cells and microvascular endothelial cells respectively in the individual cell types. After stimulation with bacterial LPS (lipopolysaccharide), gene expression of inflammatory cytokines, surfactant proteins, transport proteins, antimicrobial peptide, and doublecortin-like kinase 1 (DCLK1) were analyzed by real-time PCR, while corresponding proteins were evaluated by ELISA, immune-fluorescence, or Western blot. The effect of VD3 on the intracellular protein composition in H441 cells was analyzed by quantitative liquid chromatography-mass spectrometry-based proteomics. VD3 effectively protected the alveolar-capillary barrier against LPS treatment, as indicated by TEER measurement and morphological assessment. VD3 did not inhibit the IL-6 secretion by H441 and OEC but restricted the diffusion of IL-6 to the epithelial compartment. Further, VD3 could significantly suppress the surfactant protein A expression induced in the co-culture system by LPS treatment. VD3 induced high levels of the antimicrobial peptide LL-37, which counteracted effects by LPS and strengthened the barrier. Quantitative proteomics identified VD3-dependent protein abundance changes ranging from constitutional extracellular matrix components and surfactant-associated proteins to immune-regulatory molecules. DCLK1, as a newly described target molecule for VD3, was prominently stimulated by VD3 (10 nM) and seems to influence the alveolar-epithelial cell barrier and regeneration.

Diagnosis of asphyxiation in advanced decomposed corpses by using Oil-Red-O Stain and immunohistochemical technology

BackgroundThe unambiguous diagnosis of asphyxiation is still a major challenge for the forensic pathologist, especially in terms of highly advanced decomposed corps. MethodologyIn order to demonstrate asphyxiation particularly in profoundly putrid bodies we hypothesized that hypoxic stress is basically responsible for generalized fatty degeneration of visceral organs which can be detected by histological examination using a special staining technique referred to as Oil-Red-O Stain (Sudan III-red-B-stain). To test this hypothesis we examined different tissues (myocardium, liver, lung and kidney) of 107 people divided into 5 groups. These are: (i) 71 case-victims who were found in a truck and died most likely due to asphyxiation, whereby any other violent or natural cause of death was ruled out by postmortem examination; (ii) 10 barely decomposed positive-control-victims; (iii) 6 non-decomposed positive-control-victims; iv) 10 drowning non-decomposed positive-control victims, and v) 10 negative-control-victims. Apart from general histological special staining methods, an immunohistochemically approach as a case-control-study on lung tissues of same individuals was carried out by means of using two polyclonal rabbit-antibodies against (i) HIF-1-α (Hypoxia Inducing Factor-1 alpha) and (ii) SP-A (pulmonary surfactant-associated protein A) to detect both the transcription factor and pulmonary surfactants. The positive proof of already either of them gives evidence of death caused by hypoxia. ResultsHistological examination of myocardium, liver and kidney of the 71 case-victims and the 10 positive-control-victims using Oil-Red-O Stain showed a fatty degeneration of small droplet type; there was no evidence for fatty degeneration in tissues of the 10 negative-control-victims. These findings strongly indicate a causal association between oxygen deficiency and generalized fatty degeneration of viscera due to insufficient oxygen supply. In terms of methodology, this special staining technique seems to be very informative, even applicable on decomposed corps. Results of immunohistochemistry indicate that on the one hand the detection of HIF-1α is not possible to perform on (advanced) putrid bodies, whereas the verification of SP-A is still feasible on the other. ConclusionPositive Oil-Red-O staining and the immunohistochemical detection of SP-A can serve as a serious hint for the diagnosis of asphyxia on putrid corpses, considering other circumstances of death that have been determined.

Expression and role of deleted in malignant brain tumor protein 1 in acute respiratory distress syndrome rats induced by sepsis

To observe the expression of deleted in malignant brain tumor protein 1 (DMBT1) in rat acute respiratory distress syndrome (ARDS) model induced by sepsis and its relationship with ARDS related biomarkers. Forty-eight healthy male rats were randomly divided into sham operation group (Sham group) and ARDS model group, and the rats in each group were further divided into three subgroups at 6, 12 and 24 hours after operation, with 8 rats in each subgroup. The rats in the Sham group were exposed to the cecum only, and sepsis induced ARDS model was reproduced by cecal ligation and puncture (CLP) in the ARDS model group. The general performance was observed at 6, 12, 24 hours after operation. Abdominal aortic blood of rats was collected, and the levels of DMBT1, surfactant-associated protein D (SP-D), vascular endothelial growth factor (VEGF), interleukins (IL-6, IL-10) in serum were determined by enzyme-linked immunosorbent assay (ELISA). The lung tissues were collected, and the lung wet/dry weight (W/D) ratio was determined. The lung tissue pathological changes were observed under light microscope after hematoxylin-eosin (HE) staining, and the lung tissue injury score was evaluated. The expression of DMBT1 protein in lung tissue was determined by Western blotting. The relationship between the serum DMBT1 and SP-D, VEGF, IL-6, IL-10, lung tissue injury score were analyzed by Pearson correlation analysis. Rats in the ARDS model group showed obvious pathological manifestations after operation. The alveolar structure destruction, inflammatory cell infiltration, and alveolar hemorrhage were observed under microscope. Compared with the Sham group, the lung tissue injury score and the lung W/D ratio at 12 hours after operation in the ARDS model group were significantly increased (lung tissue injury score: 3.35±0.13 vs. 1.16±0.07, lung W/D ratio: 5.36±0.44 vs. 4.38±0.35, both P < 0.05), and pulmonary edema was present, which suggested that the ARDS model caused by CLP was successfully reproduced. The results of ELISA and Western blotting showed that the levels of serum DMBT1, SP-D, VEGF and IL-6 in the ARDS model group increased gradually with time, while the level of IL-10 increased first and then decreased. Compared with the Sham group, the levels of DMBT1 in serum and the expressions of DMBT1 protein in lung tissue in the ARDS model group were significantly increased from 6 hours after operation [serum (ng/L) : 231.96±19.17 vs. 187.44±10.19, lung tissue (DMBT1/β-actin): 2.05±0.19 vs. 0.93±0.25, both P < 0.05], and the levels of SP-D, VEGF, IL-6 and IL-10 in serum were significantly increased from 12 hours after operation [SP-D (ng/L): 73.35±8.05 vs. 43.28±5.77, VEGF (ng/L): 89.85±8.47 vs. 43.19±5.11, IL-6 (ng/L): 36.01±2.48 vs. 17.49±1.77, IL-10 (ng/L): 84.55±8.41 vs. 39.83±5.02, all P < 0.05]. Pearson correlation analysis showed that serum DMBT1 was positively correlated with serum SP-D, VEGF, IL-6, IL-10 and lung injury score at 12 hours and 24 hours in the ARDS model group (12 hours: r values were 0.946, 0.942, 0.931, 0.936, 0.748, respectively; 24 hours: r values were 0.892, 0.945, 0.951, 0.918, 0.973, respectively; all P < 0.05). DMBT1 is a novel early biomarker of ARDS by affecting alveolar epithelial cell, alveolar capillary permeability and inflammatory response.

Fusu mixture alleviates inflammatory reactions in lipopolysaccharide-induced acute respiratory distress syndrome mice via regulation of surfactant-associated protein C, aquaporin 5, and Notch1

Song Zhang, Yan Yue, Jing Liu, Lijia Zhi, Li Zhang, Kaichen Zhang, Peng Ding, Peiyang Gao, Kunlan Long

Disulfide bonds in the SAPA domain of the pulmonary surfactant protein B precursor

The disulfide bonds formed in the SAPA domain of a recombinant version of the NH2-terminal propeptide (SP-BN) from the precursor of human pulmonary surfactant protein B (SP-B) were identified through sequential digestion of SP-BN with GluC/trypsin or thermolysin/GluC, followed by mass spectrometry (MS) analysis. MS spectra allowed identification of disulfide bonds between Cys32-Cys49 and Cys40-Cys55, and we propose a disulfide connectivity pattern of 1–3 and 2–4 within the SAPA domain, with the Cys residues numbered according to their position from the N-terminus of the propeptide sequence. The peaks with m/z ∼ 2136 and ∼ 1780 in the MS spectrum of the GluC/trypsin digest were assigned to peptides 24AWTTSSLACAQGPE37 and 45QALQCR50 linked by Cys32-Cys49 and 38FWCQSLE44 and 51ALGHCLQE58 linked by Cys40-Cys55 respectively. Tandem mass spectrometry (MS/MS) analysis verified the position of the bonds. The results of the series ions, immonium ions and internal fragment ions were all compatible with the proposed 1–3/2–4 position of the disulfide bonds in the SAPA domain. This X-pattern differs from the kringle-type found in the SAPB domain of the SAPLIP proteins, where the first Cys in the sequence links to the last, the second to the penultimate and the third to the fourth one. Regarding the SAPB domain of the SP-BN propeptide, the MS analysis of both digests identified the bond Cys100-Cys112, numbered 7–8, which is coincident with the bond position in the kringle motif. SignificanceThe SAPLIP (saposin-like proteins) family encompasses several proteins with homology to saposins (sphingolipids activator proteins). These are proteins with mainly alpha-helical folds, compact packing including well conserved disulfide bonds and ability to interact with phospholipids and membranes. There are two types of saposin-like domains termed as Saposin A (SAPA) and Saposin B (SAPB) domains. While disulfide connectivity has been well established in several SAPB domains, the position of disulfide bonds in SAPA domains is still unknown. The present study approaches a detailed proteomic study to determine disulfide connectivity in the SAPA domain of the precursor of human pulmonary surfactant-associated protein SP-B. This task has been a challenge requiring the combination of different sequential proteolytic treatments followed by MS analysis including MALDI-TOF and tandem mass MS/MS spectrometry. The determination for first time of the position of disulfide bonds in SAPA domains is an important step to understand the structural determinants defining its biological functions.

Inflammation and remodeling pathways and risk of cardiovascular events in patients with ischemic heart failure and reduced ejection fraction

Patients with heart failure (HF) and coronary artery disease (CAD) have a high risk for cardiovascular (CV) events including HF hospitalization, stroke, myocardial infarction (MI) and sudden cardiac death (SCD). The present study evaluated associations of proteomic biomarkers with CV outcome in patients with CAD and HF with reduced ejection fraction (HFrEF), shortly after a worsening HF episode. We performed a case–control study within the COMMANDER HF international, double-blind, randomized placebo-controlled trial investigating the effects of the factor-Xa inhibitor rivaroxaban. Patients with the following first clinical events: HF hospitalization, SCD and the composite of MI or stroke were matched with corresponding controls for age, sex and study drug. Plasma concentrations of 276 proteins with known associations with CV and cardiometabolic mechanisms were analyzed. Results were corrected for multiple testing using false discovery rate (FDR). In 485 cases and 455 controls, 49 proteins were significantly associated with clinical events of which seven had an adjusted FDR < 0.001 (NT-proBNP, BNP, T-cell immunoglobulin and mucin domain containing 4 (TIMD4), fibroblast growth factor 23 (FGF-23), growth differentiation factor-15 (GDF-15), pulmonary surfactant-associated protein D (PSP-D) and Spondin-1 (SPON1)). No significant interactions were identified between the type of clinical event (MI/stroke, SCD or HFH) and specific biomarkers (all interaction FDR > 0.20). When adding the biomarkers significantly associated with the above outcome to a clinical model (including NT-proBNP), the C-index increase was 0.057 (0.033–0.082), p < 0.0001 and the net reclassification index was 54.9 (42.5 to 67.3), p < 0.0001. In patients with HFrEF and CAD following HF hospitalization, we found that NT-proBNP, BNP, TIMD4, FGF-23, GDF-15, PSP-D and SPON1, biomarkers broadly associated with inflammation and remodeling mechanistic pathways, were strong but indiscriminate predictors of a variety of individual CV events.

HDL, heart disease, and the lung

HDL, heart disease, and the lung

Antimicrobial and immunoregulatory activities of the derived peptide of a natural killer lysin from black rockfish (Sebastes schlegelii)

Natural killer lysin (NK-lysin) is a small molecule antimicrobial peptide secreted by natural killer cells and T lymphocytes. In this study, we characterized a cDNA sequence encoding an NK-lysin homologue (SsNKL1) from black rockfish, Sebastes schlegelii. The open reading frame (ORF) of SsNKL1 encodes a putative protein of 149 amino acids and shares 44%–87% overall sequence identities with other teleost NK-lysins. SsNKL1 possesses conserved NK-lysin family features, including a signal sequence and a surfactant-associated protein B (SapB) domain, sequence analysis revealed that SsNKL1 is most closely related to false kelpfish (Sebastiscus marmoratus) NK-lysin (with 87% sequence identity). SsNKL1 transcripts were detected in all the tested tissues, with the highest level in the kidney, followed by the spleen and gills. Upon Listonella anguillarum infection, the mRNA expression of SsNKL1 in the black rockfish was significantly up-regulated in the liver and kidney. The derived peptide SsNKLP27 from SsNKL1 was synthesized, and its biological function was studied. SsNKLP27 showed direct antibacterial activity against Gram-negative and Gram-positive bacteria, including Staphylococcus aureus, Bacillus subtilis, L. anguillarum, Vibrio parahaemolyticus, Vibrio alginolyticus and Vibrio vulnificus. SsNKLP27 treatment facilitated the bactericidal process of erythromycin by enhancing the permeability of the outer membrane. In the process of interaction with the target bacterial cells, SsNKLP27 changed the permeability and retained the morphological integrity of the cell membrane, then penetrated into the cytoplasm, and induced the degradation of genomic DNA and total RNA. In vivo studies showed that administration of SsNKLP27 before bacterial and viral infection significantly reduced the transmission and replication of pathogens in tissues. In vitro analysis showed that SsNKLP27 could enhance the respiratory burst ability and regulate the expression of some immune-related genes of macrophages. In summary, these results provided new insights into the function of NK-lysins in teleost fish and support that SsNKLP27 is a new broad-spectrum antimicrobial peptide that has a potential application prospect in aquaculture against pathogenic infection.

Fox Serum Proteomics Analysis Suggests Host-Specific Responses to Angiostrongylusvasorum Infection in Canids.

Dogs infected with the cardiopulmonary nematode Angiostrongylus vasorum may suffer from respiratory distress and/or bleeding disorders. Descriptions of clinical signs in foxes are rare, despite high prevalence. To evaluate the impact of infection on coagulation and immune response, serum proteins from eight experimentally infected foxes before and after inoculation (day 0, 35, 84, 154) were subjected to differential proteomic analyses based on quantitative data and compared to available data from dogs. The number of proteins with differential abundance compared to the uninfected baseline increased with chronicity of infection. Bone marrow proteoglycan, chitinase 3-like protein 1 and pulmonary surfactant-associated protein B were among the most prominently increased proteins. The abundance of several proteins involved in coagulation was decreased. Enriched pathways obtained from both increased and decreased proteins included, among others, “platelet degranulation” and “haemostasis”, and indicated both activation and suppression of coagulation. Qualitative comparison to dog data suggests some parallel serum proteomic alterations. The comparison, however, also indicates that foxes have a more adequate immunopathological response to A. vasorum infection compared to dogs, facilitating persistent infections in foxes. Our findings imply that foxes may be more tolerant to A. vasorum infection, as compared to dogs, reflecting a longer evolutionary host–parasite adaptation in foxes, which constitute a key wildlife reservoir.