Sphingolipids in the lungs

The Pseudomonas aeruginosa sphBC genes are important for growth in the presence of sphingosine by promoting sphingosine metabolism

Sphingoid bases, including sphingosine, are important components of the antimicrobial barrier at epithelial surfaces where they can cause growth inhibition and killing of susceptible bacteria. Pseudomonas aeruginosa is a common opportunistic pathogen that is less susceptible to sphingosine than many Gram-negative bacteria. Here, we determined that the deletion of the sphBCD operon reduced growth in the presence of sphingosine. Using deletion mutants, complementation and growth assays in P. aeruginosa PAO1, we determined that the sphC and sphB genes, encoding a periplasmic oxidase and periplasmic cytochrome c, respectively, were important for growth on sphingosine, while sphD was dispensable under these conditions. Deletion of sphBCD in P. aeruginosa PA14, Pseudomonas protegens Pf-5 and Pseudomonas fluorescens Pf01 also showed reduced growth in the presence of sphingosine. The P. aeruginosa sphBC genes were also important for growth in the presence of two other sphingoid bases, phytosphingosine and sphinganine. In WT P. aeruginosa, sphingosine is metabolized to an unknown non-inhibitory product, as sphingosine concentrations drop in the culture. However, in the absence of sphBC, sphingosine accumulates, pointing to SphC and SphB as having a role in sphingosine metabolism. Finally, the metabolism of sphingosine by WT P. aeruginosa protected susceptible cells from full growth inhibition by sphingosine, pointing to a role for sphingosine metabolism as a public good. This work shows that the metabolism of sphingosine by P. aeruginosa presents a novel pathway by which bacteria can alter host-derived sphingolipids, but it remains an open question whether SphB and SphC act directly on sphingosine.

Deep multiomic profiling reveals molecular signatures that underpin preschool wheeze and asthma

BACKGROUND

Wheezing in childhood is prevalent, with over one-half of all children experiencing at least 1 episode by age 6. The pathophysiology of wheeze, especially why some children develop asthma while others do not, remains unclear.

OBJECTIVES

This study addresses the knowledge gap by investigating the transition from preschool wheeze to asthma using multiomic profiling.

METHODS

Unsupervised, group-agnostic integrative multiomic factor analysis was performed using host/bacterial (meta)transcriptomic and bacterial shotgun metagenomic datasets from bronchial brush samples paired with metabolomic/lipidomic data from bronchoalveolar lavage samples acquired from children 1-17 years old.

RESULTS

Two multiomic factors were identified: one characterizing preschool-aged recurrent wheeze and another capturing an inferred trajectory from health to wheeze and school-aged asthma. Recurrent wheeze was driven by type 1-immune signatures, coupled with upregulation of immune-related and neutrophil-associated lipids and metabolites. Comparatively, progression toward asthma from ages 1 to 18 was dominated by changes related to airway epithelial cell gene expression, type 2-immune responses, and constituents of the airway microbiome, such as increased Haemophilus influenzae.

CONCLUSIONS

These factors highlighted distinctions between an inflammation-related phenotype in preschool wheeze, and the predominance of airway epithelial-related changes linked with the inferred trajectory toward asthma. These findings provide insights into the differential mechanisms driving the progression from wheeze to asthma and may inform targeted therapeutic strategies.

Quercetin: A Flavonoid with Potential for Treating Acute Lung Injury

In intensive care units, acute lung injury (ALI) is a syndrome that is frequently encountered. It is associated with a high rate of morbidity and mortality. Despite the extensive research conducted by the medical community on its treatment, no specific effective drugs have been identified. Quercetin is a natural flavonoid with many biological activities and pharmacological effects. Research indicates that Quercetin can modulate various targets and signaling pathways, inhibiting oxidative stress, inflammatory responses, ferroptosis, apoptosis, fibrosis, and bacterial and viral infections in ALI. This regulation suggests its potential therapeutic application for the condition. Currently, there is no comprehensive review addressing the application of Quercetin in the treatment of ALI. This paper begins with a classification of ALI, followed by a detailed summary of the mechanisms through which Quercetin may treat ALI to evaluate its potential as a novel therapeutic option.

The Pseudomonas aeruginosa sphBC genes are important for growth in the presence of sphingosine by promoting sphingosine metabolism

Sphingoid bases, including sphingosine, are important components of the antimicrobial barrier at epithelial surfaces where they can cause growth inhibition and killing of susceptible bacteria. Pseudomonas aeruginosa is a common opportunistic pathogen that is less susceptible to sphingosine than many Gram-negative bacteria. Here, we determined that deletion of the sphBCD operon reduced growth in the presence of sphingosine. Using deletion mutants, complementation, and growth assays in P. aeruginosa PAO1, we determined that the sphC and sphB genes, encoding a periplasmic oxidase and periplasmic cytochrome c, respectively, were important for growth on sphingosine, while sphD was dispensable under these conditions. Deletion of sphBCD in P. aeruginosa PA14, P. protegens Pf-5, and P. fluorescens Pf01 also showed reduced growth in the presence of sphingosine. The P. aeruginosa sphBC genes were also important for growth in the presence of two other sphingoid bases, phytosphingosine and sphinganine. In wild-type P. aeruginosa, sphingosine is metabolized to an unknown non-inhibitory product, as sphingosine concentrations drop in the culture. However, in the absence of sphBC, sphingosine accumulates, pointing to SphC and SphB as having a role in sphingosine metabolism. Finally, metabolism of sphingosine by wild-type P. aeruginosa protected susceptible cells from full growth inhibition by sphingosine, pointing to a role for sphingosine metabolism as a public good. This work shows that metabolism of sphingosine by P. aeruginosa presents a novel pathway by which bacteria can alter host-derived sphingolipids, but it remains an open question whether SphB and SphC act directly on sphingosine.

Acid sphingomyelinase deficiency and Gaucher disease in adults: Similarities and differences in two macrophage storage disorders

The lysosomal storage diseases chronic visceral acid sphingomyelinase deficiency (ASMD) and Gaucher disease type 1 (GD1) are both macrophage storage disorders with overlapping clinical manifestations. We compared cross-sectional data on visceral, hematological, and biochemical manifestations of untreated adult patients with chronic visceral ASMD (n = 19) and GD1 (n = 85). Spleen volume, liver volume, and bone marrow fat fraction did not significantly differ between the two disease groups (p >0.05 for all). Chitotriosidase activity was higher in GD1 (GD1: median 30 940 nmol/(mL.h), range 513-201 352, ASMD: median 1693 nmol/(mL.h), range 326-6620, p <0.001), whereas platelet levels were lower (GD1: median 102 109/L, range 16-726, ASMD: median 154 109/L, range 86-484, p <0.010), as were hemoglobin levels (GD1: median 7.8 mmol/L, range 5.0-10.4, ASMD: median 9.0 mmol/L, range 7.0-10.4, p <0.001). No bone complications were reported for ASMD, compared to 33% in GD1 (p <0.005). In ASMD pulmonary disease was more severe as evidenced by a median diffusion capacity of the lungs for carbon monoxide of 73% of predicted (range 26-104), compared to 85% (range 53-126) in GD1 (p = 0.029). In conclusion, bone complications, hematological abnormalities, chitotriosidase activity, and CCL18 levels were more prominent in GD1, while pulmonary manifestations were more common in AMSD. Different secondary pathophysiological processes surrounding sphingomyelin and glucosylceramide accumulation might explain these differences.

Lipids in Equine Airway Inflammation: An Overview of Current Knowledge

Mild-moderate and severe equine asthma (MEA and SEA) are prevalent inflammatory airway conditions affecting horses of numerous breeds and disciplines. Despite extensive research, detailed disease pathophysiology and the differences between MEA and SEA are still not completely understood. Bronchoalveolar lavage fluid cytology, broadly used in clinical practice and in equine asthma research, has limited means to represent the inflammatory status in the lower airways. Lipidomics is a field of science that can be utilized in investigating cellular mechanisms and cell-to-cell interactions. Studies in lipidomics have a broad variety of foci, of which fatty acid and lipid mediator profile analyses and global lipidomics have been implemented in veterinary medicine. As many crucial proinflammatory and proresolving mediators are lipids, lipidomic studies offer an interesting yet largely unexplored means to investigate inflammatory reactions in equine airways. The aim of this review article is to collect and summarize the findings of recent lipidomic studies on equine airway inflammation.

Boosting the immunogenicity of the CoronaVac SARS-CoV-2 inactivated vaccine with Huoxiang Suling Shuanghua Decoction: a randomized, double-blind, placebo-controlled study

Introduction

In light of the public health burden of the COVID-19 pandemic, boosting the safety and immunogenicity of COVID-19 vaccines is of great concern. Numerous Traditional Chinese medicine (TCM) preparations have shown to beneficially modulate immunity. Based on pilot experiments in mice that showed that supplementation with Huoxiang Suling Shuanghua Decoction (HSSD) significantly enhances serum anti-RBD IgG titers after inoculation with recombinant SARS-CoV-2 S-RBD protein, we conducted this randomized, double-blind, placebo-controlled clinical trial aimed to evaluate the potential immunogenicity boosting effect of oral HSSD after a third homologous immunization with Sinovac's CoronaVac SARS-CoV-2 (CVS) inactivated vaccine.

Methods

A total of 70 participants were randomly assigned (1:1 ratio) to receive a third dose of CVS vaccination and either oral placebo or oral HSSD for 7 days. Safety aspects were assessed by recording local and systemic adverse events, and by blood and urine biochemistry and liver and kidney function tests. Main outcomes evaluated included serum anti-RBD IgG titer, T lymphocyte subsets, serum IgG and IgM levels, complement components (C3 and C4), and serum cytokines (IL-6 and IFN-γ). In addition, metabolomics technology was used to analyze differential metabolite expression after supplementation with HSSD.

Results

Following a third CVS vaccination, significantly increased serum anti-RBD IgG titer, reduced serum IL-6 levels, increased serum IgG, IgM, and C3 and C4 levels, and improved cellular immunity, evidenced by reduce balance deviations in the distribution of lymphocyte subsets, was observed in the HSSD group compared with the placebo group. No serious adverse events were recorded in either group. Serum metabolomics results suggested that the mechanisms by which HSSD boosted the immunogenicity of the CVS vaccine are related to differential regulation of purine metabolism, vitamin B6 metabolism, folate biosynthesis, arginine and proline metabolism, and steroid hormone biosynthesis.

Conclusion

Oral HSSD boosts the immunogenicity of the CVS vaccine in young and adult individuals. This trial provides clinical reference for evaluation of TCM immunomodulators to improve the immune response to COVID-19 vaccines.

The role of cellular senescence-related genes in Asthma: Insights from bioinformatics and animal experiments

BACKGROUND

Asthma is a heterogeneous chronic respiratory disease, affecting about 10% of the global population. Cellular senescence is a multifaceted phenomenon defined as the irreversible halt of the cell cycle, commonly referred to as the senescence-associated secretory phenotype. Recent studies suggest that cellular senescence may play a role in asthma. This study aims to dissect the role and biological mechanisms of CSRGs in asthma, enhancing our understanding of the progression of asthma.

METHODS

The study utilized the GSE147878 dataset, employing methods like WGCNA, Differential analysis, Cibersort, GO, KEGG, unsupervised clustering, and GSVA to explore CSRGs functions and immune cell patterns in asthma. Machine learning identified key diagnostic genes, validated externally with the GSE165934 dataset and through qRT-PCR and WB experiments in animal models.

RESULT

From the GSE147878 dataset, 24 CSRGs were identified, highlighting their role in immune and inflammatory processes in asthma. Differences in CD4 naive T cells and activated dendritic cells between asthma and control groups underscored CSRGs' role in immune regulation. Cluster analysis revealed two distinct asthma patient groups with unique immune microenvironments. Machine learning identified five genes, leading to a TF-miRNA-mRNA network and singling out RHOA and RBM39 as key diagnostic genes, which were experimentally validated. Finally, a nomogram was created based on these genes.

CONCLUSION

This study, utilizing bioinformatics and animal experiments, identified RHOA and RBM39 as key diagnostic genes for asthma, providing new insights into the potential role and biological mechanisms of CSRGs in asthma.

JTE-013 Alleviates Pulmonary Fibrosis by Affecting the RhoA/YAP Pathway and Mitochondrial Fusion/Fission

Pulmonary fibrosis may be due to the proliferation of fibroblasts and the aggregation of extracellular matrix, resulting in the stimulation of inflammation damage, destroying lung tissue structure, seriously affecting the patient's respiratory function, and even leading to death. We investigated the role and mechanism of JTE-013 in attenuating bleomycin (BLM)-induced pulmonary fibrosis. BLM-induced pulmonary fibrosis was established in mice. Type 2 alveolar epithelial cells (MLE-12) were stimulated with sphingosine monophosphate (S1P) in vitro. JTE-013, an S1PR2 (sphingosine 1-phosphate receptor 2) antagonist, and Verteporfin were administered in vivo and in vitro. IL-4, IL-5, TNF-α, and IFN-γ were measured by ELISA. IL-4 and IFN-γ positive cells were detected by flow cytometry. Inhibition of S1PR2 with JTE-013 significantly ameliorated BLM-induced pathological changes and inflammatory cytokine levels. JTE-013 also significantly reduced the expression of RHOA/YAP pathway proteins and mitochondrial fission protein Drp1, apoptosis, and the colocalization of α-SMA with YAP, Drp1, and Tom20, as detected by immunohistochemistry, immunofluorescence staining, TUNEL, and Western blot. In vitro, S1PR2 and YAP knockdown downregulated RHOA/YAP pathway protein expression, Drp1 phosphorylation, and Drp1 translocation, promoted YAP phosphorylation and phenotypic transformation of MFN2, and inhibited the up-regulation of mitochondrial membrane potential, reactive oxygen species production, and cell apoptosis (7.13% vs. 18.14%), protecting the integrity of the mitochondrial dynamics. JTE-013 also inhibited the expression of fibrosis markers α-SMA, MMP-9, and COL1A1, and alleviated the symptoms of pulmonary fibrosis. Conclusively, JTE-013 has great anti-pulmonary fibrosis potential by regulating RHOA/YAP and mitochondrial fusion/fission.

Multi-omic assessment shows dysregulation of pulmonary and systemic immunity to e-cigarette exposure

Electronic cigarette (Ecig) use has become more common, gaining increasing acceptance as a safer alternative to tobacco smoking. However, the 2019 outbreak of Ecig and Vaping-Associated Lung Injury (EVALI) alerted the community to the potential for incorporation of deleterious ingredients such as vitamin E acetate into products without adequate safety testing. Understanding Ecig induced molecular changes in the lung and systemically can provide a path to safety assessment and protect consumers from unsafe formulations. While vitamin E acetate has been largely removed from commercial and illicit products, many Ecig products contain additives that remain largely uncharacterized. In this study, we determined the lung-specific effects as well as systemic immune effects in response to exposure to a common Ecig base, propylene glycol and vegetable glycerin (PGVG), with and without a 1% addition of phytol, a diterpene alcohol that has been found in commercial products. We exposed animals to PGVG with and without phytol and assessed metabolite, lipid, and transcriptional markers in the lung. We found both lung-specific as well as systemic effects in immune parameters, metabolites, and lipids. Phytol drove modest changes in lung function and increased splenic CD4 T cell populations. We also conducted multi-omic data integration to better understand early complex pulmonary responses, highlighting a central enhancement of acetylcholine responses and downregulation of palmitic acid connected with conventional flow cytometric assessments of lung, systemic inflammation, and pulmonary function. Our results demonstrate that Ecig exposure not only leads to changes in pulmonary function but also affects systemic immune and metabolic parameters.

Nuclear SPHK2/S1P induces oxidative stress and NLRP3 inflammasome activation via promoting p53 acetylation in lipopolysaccharide-induced acute lung injury

A bulk of evidence identified that macrophages, including resident alveolar macrophages and recruited macrophages from the blood, played an important role in the pathogenesis of acute respiratory distress syndrome (ARDS). However, the molecular mechanisms of macrophages-induced acute lung injury (ALI) by facilitating oxidative stress and inflammatory responses remain unclear. Herein, we noticed that the levels of mitochondrial reactive oxygen species (mtROS), SPHK2 and activated NLRP3 inflammasome were higher in peripheral blood mononuclear cells (PBMCs) of ARDS patients than that in healthy volunteers. Similar observations were recapitulated in LPS-treated RAW264.7 and THP-1 cells. After exposure to LPS, the SPHK2 enzymatic activity, NLRP3 inflammasome activation and mtROS were significantly upregulated in macrophages. Moreover, knockdown SPHK2 via shRNA or inhibition SPHK2 could prominently decrease LPS-induced M1 macrophage polarization, oxidative stress and NLRP3 inflammasome activation. Further study indicated that upregulated SPHK2 could increase nuclear sphingosine-1-phosphate (S1P) levels and then restrict the enzyme activity of HDACs to facilitate p53 acetylation. Acetylation of p53 reinforced its binding to the specific region of the NLRP3 promoter and drove expression of NLRP3. In the in vivo experiments, it was also observed that treating with Opaganib (ABC294640), a specific SPHK2 inhibitor, could observably alleviate LPS-induced ALI, evidencing by lowered infiltration of inflammatory cells, increased M2 macrophages polarization and reduced oxidative damage in lung tissues. Besides, SPHK2 inhibition can also decrease the accumulation of acetylated p53 protein and the activation of NLRP3 inflammasome. Taken together, our results demonstrated for the first time that nuclear S1P can regulate the acetylation levels of non-histone protein through affecting HDACs enzyme activities, linking them to oxidative stress and inflammation in response to environmental signals. These data provide a theoretical basis that SPHK2 may be an effective therapeutic target of ARDS.

Combined intervention with N-acetylcysteine and desipramine alleviated silicosis development by regulating the Nrf2/HO-1 and ASMase/ceramide signaling pathways

Silicosis is a systemic disease characterized by diffuse fibrosis of the lung tissue caused by long-term inhalation of large amounts of free silica (SiO₂) dust. The pathogenesis of silicosis has not been fully elucidated, and there is a lack of effective treatment methods. N-acetylcysteine (NAC) can potentially treat pulmonary fibrosis by exerting antioxidant effects. Desipramine (DMI) can influence pulmonary fibrosis development by inhibiting acid sphingomyelinase (ASMase) activity and regulating ceramide concentrations. Both can interfere with pulmonary fibrosis through different mechanisms, but the intervention effects of NAC combined with DMI on silicosis fibrosis have not been reported. Therefore, this study established a rat silicosis model using a single tracheal drip of SiO₂ dust suspension in Wistar rats to investigate the effect of NAC combined with DMI on SiO₂ dust-induced silicosis and its related molecular mechanisms. The histopathological examination of the SiO₂ dust-induced silicosis rats suggested that NAC and DMI alone or in combination could decrease the severity of pulmonary fibrosis in rats. The combined intervention had a better effect on reducing fibrosis than the individual interventions. NAC and DMI, alone or in combination, decreased the levels of markers related to pulmonary fibrosis in rats (smooth muscle α-actin (α-SMA), collagen (Col) I, Col III, hydroxyproline (HYP), inflammatory factors (transforming growth factor-β1 (TGF-β1) and tumor necrosis factor-α (TNF-α)), and lipid peroxidase malondialdehyde (MDA)). The nuclear factor-erythroid 2-related factor 2 (Nrf2)/heme-oxygenase-1 (HO-1) and ASMase/ceramide pathways were inhibited to some extent by increasing the superoxide dismutase (SOD) levels of antioxidant enzymes and 8-iso-prostaglandin F2α (8-iso-PGF2α) levels of lipid peroxides. The combined intervention and NAC alone inhibited the SiO₂ dust-induced elevation of matrix metalloproteinase 1 (MMP-1) and tissue inhibitor matrix metalloproteinase 1 (TIMP-1), but the effect was not significant in the DMI-treated group. Combining DMI and NAC inhibited Col I deposition and reduced HO-1, TIMP-1, and ASMase levels in lung tissues compared to individual treatments. In summary, the SiO₂ dust could induce oxidative stress and inflammation in rats, resulting in an imbalance in extracellular matrix (ECM) synthesis/catabolism and ASMase/ceramide signaling pathway activation, leading to silicosis development.The combined intervention of DMI and NAC may synergistically regulate the Nrf2/HO-1 pathway, maintain the anabolic balance of the ECM, inhibit ASMase/ceramide signaling pathway activation by suppressing the inflammatory response and effectively delay silicosis fibrosis progression.

Novel 5-fluorouracil sensitizers for colorectal cancer therapy: Design and synthesis of S1P receptor 2 (S1PR2) antagonists

Sphingosine-1-phosphate receptor 2 (S1PR2) has been identified as a brand-new GPCR target for designing antagonists to reverse 5-FU resistance. We herein report the structural optimization and structure-activity relationship of JTE-013 derivatives as S1PR2 antagonists. Compound 9d was the most potent S1PR2 antagonist (K_D = 34.8 nM) among developed compounds. Here, compound 9d could significantly inhibit the expression of dihydropyrimidine dehydrogenase (DPD) to reverse 5-FU-resistance in HCT116^DPD and SW620/5-FU cells. Further mechanism studies demonstrated that compound 9d not only inhibited S1PR2 but also affected the transcription of S1PR2. In addition, compound 9d also showed acceptable selectivity to normal cells (NCM460). Importantly, compound 9d with suitable pharmacokinetic properties could significantly reverse 5-FU-resistance in the HCT116^DPD and SW620/5-FU xenograft models without obvious toxicity, in which the inhibition rates of 5-FU were increased from 23.97% to 65.29% and 27.23% to 60.81%, respectively. Further immunohistochemistry and western blotting analysis also demonstrated that compound 9d significantly decreases the expression of DPD in tumor and liver tissues. These results indicated that compound 9d is a promising lead compound to reverse 5-FU-resistance for colorectal cancer therapy.

Chorioamnionitis alters lung surfactant lipidome in newborns with respiratory distress syndrome

BACKGROUND

Chorioamnionitis is associated with preterm delivery and morbidities; its role in lung disease is controversial. The aim of this study is to assess the effect of chorioamnionitis on metabolite and lipid profiles of epithelial lining fluid in preterm newborns with respiratory distress syndrome (RDS).

METHODS

The study involved 30 newborns with RDS, born from mothers with or without histological chorioamnionitis (HCA): HCA+, N = 10; HCA-, N = 20. Patients had a gestational age ≤30 weeks; the groups were matched for age and birth weights. Tracheal aspirates were collected within 24 h after birth and analyzed using liquid chromatography/mass spectrometry-based untargeted lipidomics.

RESULTS

According to Mann-Whitney U tests, 570 metabolite features had statistically significantly higher or lower concentrations (p < 0.05) in tracheal aspirates of HCA+ compared to HCA-, and 241 metabolite features were putatively annotated and classified. The most relevant changes involved higher levels of glycerophospholipids (fold change 2.42-17.69) and sphingolipids, with lower concentration of all annotated sphingomyelins in HCA+ (fold change 0.01-0.50).

CONCLUSIONS

Untargeted lipidomics of tracheal aspirates suggested the production of lipid mediators in the context of an ongoing inflammatory status in HCA+ babies. However, the effect of chorioamnionitis on epithelial lining fluid composition deserves further investigations on a larger group of infants.

IMPACT

Our lipidomics investigation on tracheal aspirates of preterm newborns at birth suggested that exposure to maternal histological chorioamnionitis may cause changes in epithelial lining fluid composition. This is the first description of epithelial lining fluid lipidomic profiles in preterm infants with and without exposition to chorioamnionitis. These results could provide novel link between placental membrane inflammation and newborns' respiratory outcome.

Inferring a causal relationship between ceramide levels and COVID-19 respiratory distress

A causal relationship between plasma ceramide concentration and respiratory distress symptoms in COVID-19 patients is inferred. In this study, plasma samples of 52 individuals infected with COVID-19 were utilized in a lipidomic analysis. Lipids belonging to the ceramide class exhibited a 400-fold increase in total plasma concentration in infected patients. Further analysis led to the demonstration of concentration dependency for severe COVID-19 respiratory symptoms in a subclass of ceramides. The subclasses Cer(d18:0/24:1), Cer(d18:1/24:1), and Cer(d18:1/22:0) were shown to be increased by 48-, 40-, and 33-fold, respectively, in infected plasma samples and to 116-, 91- and 50-fold, respectively, in plasma samples with respiratory distress. Hence, monitoring plasma ceramide concentration, can be a valuable tool for measuring effects of therapies on COVID-19 respiratory distress patients.

Orosomucoid-like protein 3, rhinovirus and asthma

The genetic variants of orosomucoid-like protein 3 (ORMDL3) gene are associated with highly significant increases in the number of human rhinovirus (HRV)-induced wheezing episodes in children. Recent investigations have been focused on the mechanisms of ORMDL3 in rhinovirus infection for asthma and asthma exacerbations. ORMDL3 not only regulates major human rhinovirus receptor intercellular adhesion molecule 1 expression, but also plays pivotal roles in viral infection through metabolisms of ceramide and sphingosine-1-phosphate, endoplasmic reticulum (ER) stress, ER-Golgi interface and glycolysis. Research on the roles of ORMDL3 in HRV infection will lead us to identify new biomarkers and novel therapeutic targets in childhood asthma and viral induced asthma exacerbations.

Sphingolipid profiles and their relationship with inflammatory factors in asthmatic patients of different sexes

BACKGROUND

Asthma is a heterogeneous disease with distinct prevalence and manifestation between sexes. This study was to identify sex-specific features of asthma via metabolomic analysis of sphingolipids.

METHODS

Forty-two asthma patients (27 women and 15 men) admitted to the Peking University Third Hospital from January 2015 to December 2015 were enrolled. Peripheral venous blood was collected for metabolomic analysis by targeted liquid chromatography-mass spectrometry. Sex hormones(estradiol, progesterone, testosterone, and androstenedione) and multiple inflammatory factors (periostin, leptin, IgE, IL-4, IL-5, IL-10, IL-13, IL-17A, and IFN-γ) were also assessed. The eosinophil percentage in induced sputum was also detected. All these data were applied to comparative analysis between sexes.

RESULTS

Testosterone was negatively related to periostin (ρ = -0.420, P = 0.009) and IL-5 (ρ = -0.540, P = 0.012), while estradiol was positively related to the blood eosinophil percentage (ρ = 0.384, P = 0.025). Among the eighteen species of sphingolipids detected in the 42 patients, five ceramide (Cer) species (Cer16:0, Cer:20:0, Cer22:0, Cer24:0, and Cer26:0) and one sphingomyelin (SM) species (SM38:0) were significantly higher in male than in female patients. Further investigation found that the correlation between Cer20:0 and IL-5 was positive in males (ρ = 0.943, P = 0.005) but negative in females (ρ = -0.561, P = 0.030).

CONCLUSIONS

Testosterone was negatively correlated with eosinophil inflammatory factors, but estradiol was positively correlated. Male asthma patients had higher ceramide and sphingomyelin levels than female patients. Different sexes had opposite correlations with ceramide and IL-5, respectively, suggesting that therapeutic strategies targeting ceramide should be different between sexes.

Spns2 Transporter Contributes to the Accumulation of S1P in Cystic Fibrosis Human Bronchial Epithelial Cells

The role of S1P in Cystic Fibrosis (CF) has been investigated since 2001, when it was first described that the CFTR channel regulates the inward transport of S1P. From then on, various studies have associated F508del CFTR, the most frequent mutation in CF patients, with altered S1P expression in tissue and plasma. We found that human bronchial epithelial immortalized and primary cells from CF patients express more S1P than the control cells, as evidenced by mass spectrometry analysis. S1P accumulation relies on two- to four-fold transcriptional up-regulation of SphK1 and simultaneous halving of SGPL1 in CF vs. control cells. The reduction of SGPL1 transcription protects S1P from irreversible degradation, but the excessive accumulation is partially prevented by the action of the two phosphatases that are up-regulated compared to control cells. For the first time in CF, we describe that Spns2, a non-ATP dependent transporter that normally extrudes S1P out of the cells, shows deficient transcriptional and protein expression, thus impairing S1P accrual dissipation. The in vitro data on CF human bronchial epithelia correlates with the impaired expression of Spns2 observed in CF human lung biopsies compared to healthy control.

Platelet extracellular vesicles mediate transfusion-related acute lung injury by imbalancing the sphingolipid rheostat

Transfusion-related acute lung injury (TRALI) is a hazardous transfusion complication with an associated mortality of 5% to 15%. We previously showed that stored (5 days) but not fresh platelets (1 day) cause TRALI via ceramide-mediated endothelial barrier dysfunction. As biological ceramides are hydrophobic, extracellular vesicles (EVs) may be required to shuttle these sphingolipids from platelets to endothelial cells. Adding to complexity, EV formation in turn requires ceramide. We hypothesized that ceramide-dependent EV formation from stored platelets and EV-dependent sphingolipid shuttling induces TRALI. EVs formed during storage of murine platelets were enumerated, characterized for sphingolipids, and applied in a murine TRALI model in vivo and for endothelial barrier assessment in vitro. Five-day EVs were more abundant, had higher long-chain ceramide (C16:0, C18:0, C20:0), and lower sphingosine-1-phosphate (S1P) content than 1-day EVs. Transfusion of 5-day, but not 1-day, EVs induced characteristic signs of lung injury in vivo and endothelial barrier disruption in vitro. Inhibition or supplementation of ceramide-forming sphingomyelinase reduced or enhanced the formation of EVs, respectively, but did not alter the injuriousness per individual EV. Barrier failure was attenuated when EVs were abundant in or supplemented with S1P. Stored human platelet 4-day EVs were more numerous compared with 2-day EVs, contained more long-chain ceramide and less S1P, and caused more endothelial cell barrier leak. Hence, platelet-derived EVs become more numerous and more injurious (more long-chain ceramide, less S1P) during storage. Blockade of sphingomyelinase, EV elimination, or supplementation of S1P during platelet storage may present promising strategies for TRALI prevention.

The Mystery of Red Blood Cells Extracellular Vesicles in Sleep Apnea with Metabolic Dysfunction

Sleep is very important for overall health and quality of life, while sleep disorder has been associated with several human diseases, namely cardiovascular, metabolic, cognitive, and cancer-related alterations. Obstructive sleep apnea (OSA) is the most common respiratory sleep-disordered breathing, which is caused by the recurrent collapse of the upper airway during sleep. OSA has emerged as a major public health problem and increasing evidence suggests that untreated OSA can lead to the development of various diseases including neurodegenerative diseases. In addition, OSA may lead to decreased blood oxygenation and fragmentation of the sleep cycle. The formation of free radicals or reactive oxygen species (ROS) can emerge and react with nitric oxide (NO) to produce peroxynitrite, thereby diminishing the bioavailability of NO. Hypoxia, the hallmark of OSA, refers to a decline of tissue oxygen saturation and affects several types of cells, playing cell-to-cell communication a vital role in the outcome of this interplay. Red blood cells (RBCs) are considered transporters of oxygen and nutrients to the tissues, and these RBCs are important interorgan communication systems with additional functions, including participation in the control of systemic NO metabolism, redox regulation, blood rheology, and viscosity. RBCs have been shown to induce endothelial dysfunction and increase cardiac injury. The mechanistic links between changes of RBC functional properties and cardiovascular are largely unknown. Extracellular vesicles (EVs) are secreted by most cell types and released in biological fluids both under physiological and pathological conditions. EVs are involved in intercellular communication by transferring complex cargoes including proteins, lipids, and nucleic acids from donor cells to recipient cells. Advancing our knowledge about mechanisms of RBC-EVs formation and their pathophysiological relevance may help to shed light on circulating EVs and to translate their application to clinical practice. We will focus on the potential use of RBC-EVs as valuable diagnostic and prognostic biomarkers and state-specific cargoes, and possibilities as therapeutic vehicles for drug and gene delivery. The use of RBC-EVs as a precision medicine for the diagnosis and treatment of the patient with sleep disorder will improve the prognosis and the quality of life in patients with cardiovascular disease (CVD).

Serum sphingolipid profile in asthma

Sphingolipids metabolism is an important cell process and plays critical roles in asthma. However, the involvement of sphingolipids in the pathogenesis of asthma and its subtypes is unknown. The present study aimed to determine the role of sphingolipids in asthma and its subtypes. Clinical data from 51 asthma patients and 9 healthy individuals were collected and serum samples were performed to analyze the levels of serum sphingolipids by liquid chromatography-mass spectrometry-based targeted metabolomics. Results showed that the levels of sphingomyelin (SM) including SM34:2, SM38:1, and SM40:1 were significantly decreased in asthmatic patients compared to healthy controls. Moreover, serum SM levels were obviously decreased in the blood noneosinophilic asthma (bNEA) group compared with blood eosinophilic asthma group. Similar tendencies of serum SM level changes were observed in the early-onset group compared with late-onset group. Correlation analysis revealed that SM 40:1 was negatively related to sputum IL-17A (r = -0.621, P = 0.042). The present study presented that the SM may be a protective factor of asthma and contributes to the mechanism of asthma, especially bNEA. SM may be a potential biomarker and therapeutic target in asthma.

Convergence: Lactosylceramide-Centric Signaling Pathways Induce Inflammation, Oxidative Stress, and Other Phenotypic Outcomes

Lactosylceramide (LacCer), also known as CD17/CDw17, is a member of a large family of small molecular weight compounds known as glycosphingolipids. It plays a pivotal role in the biosynthesis of glycosphingolipids, primarily by way of serving as a precursor to the majority of its higher homolog sub-families such as gangliosides, sulfatides, fucosylated-glycosphingolipids and complex neutral glycosphingolipids—some of which confer “second-messenger” and receptor functions. LacCer is an integral component of the “lipid rafts,” serving as a conduit to transduce external stimuli into multiple phenotypes, which may contribute to mortality and morbidity in man and in mouse models of human disease. LacCer is synthesized by the action of LacCer synthase (β-1,4 galactosyltransferase), which transfers galactose from uridine diphosphate galactose (UDP-galactose) to glucosylceramide (GlcCer). The convergence of multiple physiologically relevant external stimuli/agonists—platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), stress, cigarette smoke/nicotine, tumor necrosis factor-α (TNF-α), and in particular, oxidized low-density lipoprotein (ox-LDL)—on β-1,4 galactosyltransferase results in its phosphorylation or activation, via a “turn-key” reaction, generating LacCer. This newly synthesized LacCer activates NADPH (nicotinamide adenine dihydrogen phosphate) oxidase to generate reactive oxygen species (ROS) and a highly “oxidative stress” environment, which trigger a cascade of signaling molecules and pathways and initiate diverse phenotypes like inflammation and atherosclerosis. For instance, LacCer activates an enzyme, cytosolic phospholipase A2 (cPLA2), which cleaves arachidonic acid from phosphatidylcholine. In turn, arachidonic acid serves as a precursor to eicosanoids and prostaglandin, which transduce a cascade of reactions leading to inflammation—a major phenotype underscoring the initiation and progression of several debilitating diseases such as atherosclerosis and cancer. Our aim here is to present an updated account of studies made in the field of LacCer metabolism and signaling using multiple animal models of human disease, human tissue, and cell-based studies. These advancements have led us to propose that previously unrelated phenotypes converge in a LacCer-centric manner. This LacCer synthase/LacCer-induced “oxidative stress” environment contributes to inflammation, atherosclerosis, skin conditions, hair greying, cardiovascular disease, and diabetes due to mitochondrial dysfunction. Thus, targeting LacCer synthase may well be the answer to remedy these pathologies.

Prognostic Impact of Sphingosine Kinase 1 in Nonsmall Cell Lung Cancer

Bioactive sphingolipid is clearly relevant to lung physiology. The relationship of the bioactive sphingolipid pathway to pulmonary disease has been studied in cellular, tissue, and animal model, including lung cancer models. The samples of 53 patients diagnosed with nonsmall cell lung carcinoma (NSCLC) between June 2009 and May 2014 at our hospital were analyzed. Immunohistochemical (IHC) analysis was performed. The degree of immunostaining was reviewed and scored. Using this method of assessment, we evaluated the IHC score of sphingosine kinase 1 (SPHK1), vimentin, E-cadherin, and Ki-67. Both invasive adenocarcinoma cell and squamous cell carcinoma cell were well stained by SPHK1, and fibroblasts were also well stained by SPHK1. Although the IHC score of SPHK1 was not significantly differed between invasive adenocarcinoma and squamous cell carcinoma, the IHC scores of fibroblast, vimentin, and Ki-67 were higher in squamous cell carcinoma than invasive adenocarcinoma. Correlation among IHC scores in each of invasive adenocarcinoma and squamous cell carcinoma was performed. SPHK1 had positive correlation with both fibroblast and Ki-67, and fibroblast and Ki-67 had also positive correlation in invasive adenocarcinoma. On the contrary, SPHK1 had no significant correlation with fibroblast, and had negative correlation with Ki-67 in squamous cell carcinoma. Although there was not significant prognostic difference in SPHK1 score (P = .09), IHC score high group tended to be worse on relapse-free survival. SPHK1 might be prognostic factor in lung-invasive adenocarcinoma and novel target for drug against lung-invasive adenocarcinoma.

Ceramide induces MMP-9 expression through JAK2/STAT3 pathway in airway epithelium

BACKGROUND

Ceramide, a bioactive lipid, plays an essential role in the development of several pulmonary inflammatory diseases. Matrix metallopeptidase 9 (MMP-9) regulates the synthesis and degradation of extracellular matrix, and is associated with airway remodeling and tissue injury. This study was conducted to investigate the effects and underlying mechanisms of ceramide on MMP-9 expression in airway epithelium.

METHODS

BEAS-2B cells, normal human bronchial epithelium cell lines, were pretreated with AG490, a selective janus tyrosine kinase 2 (JAK2) inhibitor, or Stattic, a selective signal transducer and activator of transcription 3 (STAT3) inhibitor. The cells were then stimulated with C6-ceramide. The levels of MMP-9 were determined by ELISA and real-time quantitative PCR (RT-qPCR). JAK2, phosphorylated JAK2 (p-JAK2), STAT3, and phosphorylated STAT3 (p-STAT3) expression was examined by Western blotting. BALB/c mice were pretreated with AG490 or Stattic before intratracheally instillated with C6-ceramide. Pathological changes in lung tissues were examined by Hematoxylin and Eosin staining, Periodic-acid Schiff staining, and Masson's trichrome staining. MMP-9, JAK2, p-JAK2, STAT3, and p-STAT3 expression in the lung tissues was examined by Western blotting.

RESULTS

The expression of MMP-9, p-JAK2 and p-STAT3 in BEAS-2B cells was significantly increased after the treatment of C6-ceramide. Furthermore, the increased expression of MMP-9 induced by C6-ceramide was inhibited by AG490 and Stattic. Similar results were obtained in the lung tissues of C6-ceramide-exposed mice which were treated with AG490 or Stattic.

CONCLUSIONS

Ceramide could up-regulate MMP-9 expression through the activation of the JAK2/STAT3 pathway in airway epithelium. Targeted modulation of the ceramide signaling pathway may offer a potential therapeutic approach for inhibiting MMP-9 expression. This study points to a potentially novel approach to alleviating airway remodeling in inflammatory airway diseases.

Advancements in understanding the role of lysophospholipids and their receptors in lung disorders including bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a devastating chronic neonatal lung disease leading to serious adverse consequences. Nearly 15 million babies are born preterm accounting for >1 in 10 births globally. The aetiology of BPD is multifactorial and the survivors suffer lifelong respiratory morbidity. Lysophospholipids (LPL), which include sphingosine-1-phosphate (S1P), and lysophosphatidic acid (LPA) are both naturally occurring bioactive lipids involved in a variety of physiological and pathological processes such as cell survival, death, proliferation, migration, immune responses and vascular development. Altered LPL levels have been observed in a number of lung diseases including BPD, which underscores the importance of these signalling lipids under normal and pathophysiological situations. Due to the paucity of information related to LPLs in BPD, most of the ideas related to BPD and LPL are speculative. This article is intended to promote discussion and generate hypotheses, in addition to the limited review of information related to BPD already established in the literature.

Alveolar lipids in pulmonary disease. A review

Lung lipid metabolism participates both in infant and adult pulmonary disease. The lung is composed by multiple cell types with specialized functions and coordinately acting to meet specific physiologic requirements. The alveoli are the niche of the most active lipid metabolic cell in the lung, the type 2 cell (T2C). T2C synthesize surfactant lipids that are an absolute requirement for respiration, including dipalmitoylphosphatidylcholine. After its synthesis and secretion into the alveoli, surfactant is recycled by the T2C or degraded by the alveolar macrophages (AM). Surfactant biosynthesis and recycling is tightly regulated, and dysregulation of this pathway occurs in many pulmonary disease processes. Alveolar lipids can participate in the development of pulmonary disease from their extracellular location in the lumen of the alveoli, and from their intracellular location in T2C or AM. External insults like smoke and pollution can disturb surfactant homeostasis and result in either surfactant insufficiency or accumulation. But disruption of surfactant homeostasis is also observed in many chronic adult diseases, including chronic obstructive pulmonary disease (COPD), and others. Sustained damage to the T2C is one of the postulated causes of idiopathic pulmonary fibrosis (IPF), and surfactant homeostasis is disrupted during fibrotic conditions. Similarly, surfactant homeostasis is impacted during acute respiratory distress syndrome (ARDS) and infections. Bioactive lipids like eicosanoids and sphingolipids also participate in chronic lung disease and in respiratory infections. We review the most recent knowledge on alveolar lipids and their essential metabolic and signaling functions during homeostasis and during some of the most commonly observed pulmonary diseases.

Functional contribution of sphingosine-1-phosphate to airway pathology in cigarette smoke-exposed mice

BACKGROUND AND PURPOSE

A critical role for sphingosine kinase/sphingosine-1-phosphate (S1P) pathway in the control of airway function has been demonstrated in respiratory diseases. Here, we address S1P contribution in a mouse model of mild chronic obstructive pulmonary disease (COPD).

EXPERIMENTAL APPROACH

C57BL/6J mice have been exposed to room air or cigarette smoke up to 11 months and killed at different time points. Functional and molecular studies have been performed.

KEY RESULTS

Cigarette smoke caused emphysematous changes throughout the lung parenchyma coupled to a progressive collagen deposition in both peribronchiolar and peribronchial areas. The high and low airways showed an increased reactivity to cholinergic stimulation and α-smooth muscle actin overexpression. Similarly, an increase in airway reactivity and lung resistances following S1P challenge occurred in smoking mice. A high expression of S1P, Sph-K₂ , and S1P receptors (S1P₂ and S1P₃ ) has been detected in the lung of smoking mice. Sphingosine kinases inhibition reversed the increased cholinergic response in airways of smoking mice.

CONCLUSIONS AND IMPLICATIONS

S1P signalling up-regulation follows the disease progression in smoking mice and is involved in the development of airway hyperresponsiveness. Our study defines a therapeutic potential for S1P inhibitors in management of airways hyperresponsiveness associated to emphysema in smokers with both asthma and COPD.

ToF-SIMS mediated analysis of human lung tissue reveals increased iron deposition in COPD (GOLD IV) patients

Chronic obstructive pulmonary disease (COPD) is a debilitating lung disease that is currently the third leading cause of death worldwide. Recent reports have indicated that dysfunctional iron handling in the lungs of COPD patients may be one contributing factor. However, a number of these studies have been limited to the qualitative assessment of iron levels through histochemical staining or to the expression levels of iron-carrier proteins in cells or bronchoalveolar lavage fluid. In this study, we have used time of flight secondary ion mass spectrometry (ToF-SIMS) to visualize and relatively quantify iron accumulation in lung tissue sections of healthy donors versus severe COPD patients. An IONTOF 5 instrument was used to perform the analysis, and further multivariate analysis was used to analyze the data. An orthogonal partial least squares discriminant analysis (OPLS-DA) score plot revealed good separation between the two groups. This separation was primarily attributed to differences in iron content, as well as differences in other chemical signals possibly associated with lipid species. Further, relative quantitative analysis revealed twelve times higher iron levels in lung tissue sections of COPD patients when compared to healthy donors. In addition, iron accumulation observed within the cells was heterogeneously distributed, indicating cellular compartmentalization.

Exploring the effect of chirality on the therapeutic potential of N-alkyl-deoxyiminosugars: anti-inflammatory response to Pseudomonas aeruginosa infections for application in CF lung disease

In the frame of a research program aimed to explore the relationship between chirality of iminosugars and their therapeutic potential, herein we report the synthesis of N-akyl l-deoxyiminosugars and the evaluation of the anti-inflammatory properties of selected candidates for the treatment of Pseudomonas aeruginosa infections in Cystic Fibrosis (CF) lung disease. Target glycomimetics were prepared by the shortest and most convenient approach reported to date, relying on the use of the well-known PS-TPP/I₂ reagent system to prepare reactive alkoxyalkyl iodides, acting as key intermediates. Iminosugars ent-1-3 demonstrated to efficiently reduce the inflammatory response induced by P. aeruginosa in CuFi cells, either alone or in synergistic combination with their d-enantiomers, by selectively inhibiting NLGase. Surprisingly, the evaluation in murine models of lung disease showed that the amount of ent-1 required to reduce the recruitment of neutrophils was 40-fold lower than that of the corresponding d-enantiomer. The remarkably low dosage of the l-iminosugar, combined with its inability to act as inhibitor for most glycosidases, is expected to limit the onset of undesired effects, which are typically associated with the administration of its d-counterpart. Biological results herein obtained place ent-1 and congeners among the earliest examples of l-iminosugars acting as anti-inflammatory agents for therapeutic applications in Cystic Fibrosis.

Choline Supplementation in Cystic Fibrosis-The Metabolic and Clinical Impact

Background: Choline is essential for the synthesis of liver phosphatidylcholine (PC), parenchymal maintenance, bile formation, and lipoprotein assembly to secrete triglycerides. In choline deficiency, the liver accretes choline/PC at the expense of lung tissue, thereby impairing pulmonary PC homoeostasis. In cystic fibrosis (CF), exocrine pancreas insufficiency results in impaired cleavage of bile PC and subsequent fecal choline loss. In these patients, the plasma choline concentration is low and correlates with lung function. We therefore investigated the effect of choline supplementation on plasma choline/PC concentration and metabolism, lung function, and liver fat. Methods: 10 adult male CF patients were recruited (11/2014–1/2016), and orally supplemented with 3 × 1 g choline chloride for 84 (84–91) days. Pre-/post-supplementation, patients were spiked with 3.6 mg/kg [methyl-D₉]choline chloride to assess choline/PC metabolism. Mass spectrometry, spirometry, and hepatic nuclear resonance spectrometry served for analysis. Results: Supplementation increased plasma choline from 4.8 (4.1–6.2) µmol/L to 10.5 (8.5–15.5) µmol/L at d84 (p < 0.01). Whereas plasma PC concentration remained unchanged, D₉-labeled PC was decreased (12.2 [10.5–18.3] µmol/L vs. 17.7 [15.5–22.4] µmol/L, p < 0.01), indicating D₉-tracer dilution due to higher choline pools. Supplementation increased Forced Expiratory Volume in 1 second percent of predicted (ppFEV1) from 70.0 (50.9–74.8)% to 78.3 (60.1–83.9)% (p < 0.05), and decreased liver fat from 1.58 (0.37–8.82)% to 0.84 (0.56–1.17)% (p < 0.01). Plasma choline returned to baseline concentration within 60 h. Conclusions: Choline supplementation normalized plasma choline concentration and increased choline-containing PC precursor pools in adult CF patients. Improved lung function and decreased liver fat suggest that in CF correcting choline deficiency is clinically important. Choline supplementation of CF patients should be further investigated in randomized, placebo-controlled trials.

High-resolution atmospheric-pressure MALDI mass spectrometry imaging workflow for lipidomic analysis of late fetal mouse lungs

Mass spectrometry imaging (MSI) provides label-free, non-targeted molecular and spatial information of the biomolecules within tissue. Lipids play important roles in lung biology, e.g. as surfactant, preventing alveolar collapse during normal and forced respiration. Lipidomic characterization of late fetal mouse lungs at day 19 of gestation (E19) has not been performed yet. In this study we employed high-resolution atmospheric pressure scanning microprobe matrix-assisted laser desorption/ionization MSI for the lipidomic analysis of E19 mouse lungs. Molecular species of different lipid classes were imaged in E19 lung sections at high spatial and mass resolution in positive- and negative-ion mode. Lipid species were characterized based on accurate mass and on-tissue tandem mass spectrometry. In addition, a dedicated sample preparation protocol, homogenous deposition of matrices on tissue surfaces and data processing parameters were optimized for the comparison of signal intensities of lipids between different tissue sections of E19 lungs of wild type and Pex11β-knockout mice. Our study provides lipid information of E19 mouse lungs, optimized experimental and data processing strategies for the direct comparison of signal intensities of metabolites (lipids) among the tissue sections from MSI experiments. To best of our knowledge, this is the first MSI and lipidomic study of E19 mouse lungs.

Anaerobes in cystic fibrosis patients' airways

Anaerobes are known to constitute an important part of the airway microbiota in both healthy subjects and cystic fibrosis (CF) patients. Studies on the potential role of anaerobic bacteria in CF and thus their involvement in CF pathophysiology have reported contradictory results, and the question is still not elucidated. The aim of this study was to summarize anaerobe diversity in the airway microbiota and its potential role in CF, to provide an overview of the state of knowledge on anaerobe antibiotic resistances (resistome), and to investigate the detectable metabolites produced by anaerobes in CF airways (metabolome). This review emphasizes key metabolites produced by strict anaerobic bacteria (sphingolipids, fermentation-induced metabolites and metabolites involved in quorum-sensing), which may be essential for the better understanding of lung disease pathophysiology in CF.

Ceramide and Regulation of Vascular Tone

In addition to playing a role as a structural component of cellular membranes, ceramide is now clearly recognized as a bioactive lipid implicated in a variety of physiological functions. This review aims to provide updated information on the role of ceramide in the regulation of vascular tone. Ceramide may induce vasodilator or vasoconstrictor effects by interacting with several signaling pathways in endothelial and smooth muscle cells. There is a clear, albeit complex, interaction between ceramide and redox signaling. In fact, reactive oxygen species (ROS) activate different ceramide generating pathways and, conversely, ceramide is known to increase ROS production. In recent years, ceramide has emerged as a novel key player in oxygen sensing in vascular cells and mediating vascular responses of crucial physiological relevance such as hypoxic pulmonary vasoconstriction (HPV) or normoxic ductus arteriosus constriction. Likewise, a growing body of evidence over the last years suggests that exaggerated production of vascular ceramide may have detrimental effects in a number of pathological processes including cardiovascular and lung diseases.

Surfactant Protein D Deficiency Aggravates Cigarette Smoke-Induced Lung Inflammation by Upregulation of Ceramide Synthesis

Cigarette smoke (CS) is the main cause of chronic obstructive pulmonary disease. Surfactant protein D (SP-D) is an important anti-inflammatory protein that regulates host immune defense in the lungs. Here, we investigated the role of SP-D in a murine model of CS-induced inflammation. Pulmonary SP-D localization and abundance was compared between smoker and non-smoker individuals. For in vivo studies, wildtype, and SP-D-deficient mice were exposed to CS for either 12 weeks or 3 days. Moreover, the effect of therapeutic administration of recombinant fragment of human SP-D on the acute CS-induced changes was evaluated. Pulmonary SP-D appeared with heterogenous expression in human smokers, while mouse lung SP-D was uniformly upregulated after CS exposure. We found that SP-D-deficient mice were more susceptible to CS-induced macrophage-rich airway inflammation. SP-D deficiency influenced local pro-inflammatory cytokine levels, with increased CCL3 and interleukin-6 but decreased CXCL1. Furthermore, CS exposure caused significant upregulation of pro-inflammatory ceramides and related ceramide synthase gene transcripts in SP-D-deficient mice compared to wildtype littermates. Administration of recombinant fragment of human SP-D (rfhSP-D) alleviated CS-induced macrophage infiltration and prevented induction of ceramide synthase gene expression. Finally, rfhSP-D treatment attenuated CS-induced human epithelial cell apoptosis in vitro. Our results indicate that SP-D deficiency aggravates CS-induced lung inflammation partly through regulation of ceramide synthesis and that local SP-D enrichment rescues CS-induced inflammation.

An update on sphingosine-1-phosphate receptor 1 modulators

Sphingolipids represent an essential class of lipids found in all eukaryotes, and strongly influence cellular signal transduction. Autoimmune diseases like asthma and multiple sclerosis (MS) are mediated by the sphingosine-1-phosphate receptor 1 (S1P₁) to express a variety of symptoms and disease patterns. Inspired by its natural substrate, an array of artificial sphingolipid derivatives has been developed to target this specific G protein-coupled receptor (GPCR) in an attempt to suppress autoimmune disorders. FTY720, also known as fingolimod, is the first oral disease-modifying therapy for MS on the market. In pursuit of improved stability, bioavailability, and efficiency, structural analogues of this initial prodrug have emerged over time. This review covers a brief introduction to the sphingolipid metabolism, the mechanism of action on S1P₁, and an updated overview of synthetic sphingosine S1P₁ agonists.

Quantitative lipidomic analysis of mouse lung during postnatal development by electrospray ionization tandem mass spectrometry

Lipids play very important roles in lung biology, mainly reducing the alveolar surface tension at the air-liquid interface thereby preventing end-expiratory collapse of the alveoli. In the present study we performed an extensive quantitative lipidomic analysis of mouse lung to provide the i) total lipid quantity, ii) distribution pattern of the major lipid classes, iii) composition of individual lipid species and iv) glycerophospholipid distribution pattern according to carbon chain length (total number of carbon atoms) and degree of unsaturation (total number of double bonds). We analysed and quantified 160 glycerophospholipid species, 24 sphingolipid species, 18 cholesteryl esters and cholesterol from lungs of a) newborn (P1), b) 15-day-old (P15) and c) 12-week-old adult mice (P84) to understand the changes occurring during postnatal pulmonary development. Our results revealed an increase in total lipid quantity, correlation of lipid class distribution in lung tissue and significant changes in the individual lipid species composition during postnatal lung development. Interestingly, we observed significant stage-specific alterations during this process. Especially, P1 lungs showed high content of monounsaturated lipid species; P15 lungs exhibited myristic and palmitic acid containing lipid species, whereas adult lungs were enriched with polyunsaturated lipid species. Taken together, our study provides an extensive quantitative lipidome of the postnatal mouse lung development, which may serve as a reference for a better understanding of lipid alterations and their functions in lung development and respiratory diseases associated with lipids.

Supplementation with Qter® and Creatine improves functional performance in COPD patients on long term oxygen therapy

BACKGROUND

Skeletal muscle dysfunction and poor functional capacity are important extra-pulmonary manifestations of chronic obstructive pulmonary disease (COPD), especially in COPD patients on long-term O₂ therapy (LTOT). Beside the role of pulmonary rehabilitation, the effect of nutritional interventions is still controversial, and there are knowledge gaps on the effective role of nutraceutical supplementation on hard endpoints. The aim of this study was to investigate the effects of nutritional supplementation with Coenzyme Q10 (QTer^®) - a powerful antioxidant with the potential to reduce oxidative stress and improve mitochondrial function - and Creatine on functional, nutritional, and metabolomic profile in COPD patients on long-term O₂ therapy.

METHODS

One-hundred and eight patients with COPD from 9 Italian hospitals were enrolled in this double-blinded randomized placebo-controlled clinical study. At baseline and after 2 months of therapy, the patients underwent spirometry, 6-minute walk test (6MWT), bioelectrical impedance analysis, and activities of daily living questionnaire (ADL). Also, dyspnea scores and BODE index were calculated. At both time points, plasma concentration of CoQ10 and metabolomic profiling were measured.

FINDINGS

Ninety patients, who randomly received supplementation with QTer^® and Creatine or placebo, completed the study. Compared with placebo, supplemented patients showed improvements in 6MWT (51 ± 69 versus 15 ± 91 m, p < 0.05), body cell mass and phase angle, sodium/potassium ratio, dyspnea indices and ADL score. The CoQ10 plasma concentration increased in the supplementation group whereas it did not change in the placebo group. The metabolomics profile also differed between groups. Adverse events were similar in both groups.

INTERPRETATION

These results show that in patients with COPD, dietary supplementation with CoQ10 and Creatine improves functional performance, body composition and perception of dyspnea. A systemic increase in some anti-inflammatory metabolites supports a pathobiological mechanism as a reason for these benefits. Further trials should help clarifying the role of QTer^® and Creatine supplementation in patients with COPD.

Unique Lipid Signatures of Extracellular Vesicles from the Airways of Asthmatics

Asthma is a chronic inflammatory disease process involving the conductive airways of the human lung. The dysregulated inflammatory response in this disease process may involve multiple cell-cell interactions mediated by signaling molecules, including lipid mediators. Extracellular vesicles (EVs) are lipid membrane particles that are now recognized as critical mediators of cell-cell communication. Here, we compared the lipid composition and presence of specific lipid mediators in airway EVs purified from the bronchoalveolar lavage (BAL) fluid of healthy controls and asthmatic subjects with and without second-hand smoke (SHS) exposure. Airway exosome concentrations were increased in asthmatics, and correlated with blood eosinophilia and serum IgE levels. Frequencies of HLA-DR⁺ and CD54⁺ exosomes were also significantly higher in asthmatics. Lipidomics analysis revealed that phosphatidylglycerol, ceramide-phosphates, and ceramides were significantly reduced in exosomes from asthmatics compared to the non-exposed control groups. Sphingomyelin 34:1 was more abundant in exosomes of SHS-exposed asthmatics compared to healthy controls. Our results suggest that chronic airway inflammation may be driven by alterations in the composition of lipid mediators within airway EVs of human subjects with asthma.

Chronic lung injury and impaired pulmonary function in a mouse model of acid ceramidase deficiency

Farber disease (FD) is a debilitating lysosomal storage disorder (LSD) caused by a deficiency of acid ceramidase (ACDase) activity due to mutations in the gene ASAH1. Patients with ACDase deficiency may develop a spectrum of clinical phenotypes. Severe cases of FD are frequently associated with neurological involvement, failure to thrive, and respiratory complications. Mice homozygous ( Asah1P361R/P361R) for an orthologous patient mutation in Asah1 recapitulate human FD. In this study, we show significant impairment in lung function, including low compliance and increased airway resistance in a mouse model of ACDase deficiency. Impaired lung mechanics in Farber mice resulted in decreased blood oxygenation and increased red blood cell production. Inflammatory cells were recruited to both perivascular and peribronchial areas of the lung. We observed large vacuolated foamy histiocytes that were full of storage material. An increase in vascular permeability led to protein leakage, edema, and impacted surfactant homeostasis in the lungs of Asah1P361R/P361R mice. Bronchial alveolar lavage fluid (BALF) extraction and analysis revealed accumulation of a highly turbid lipoprotein-like substance that was composed in part of surfactants, phospholipids, and ceramides. The phospholipid composition of BALF from Asah1P361R/P361R mice was severely altered, with an increase in both phosphatidylethanolamine (PE) and sphingomyelin (SM). Ceramides were also found at significantly higher levels in both BALF and lung tissue from Asah1P361R/P361R mice when compared with levels from wild-type animals. We demonstrate that a deficiency in ACDase leads to sphingolipid and phospholipid imbalance, chronic lung injury caused by significant inflammation, and increased vascular permeability, leading to impaired lung function.

Obesogenic diets alter metabolism in mice

Obesity and accompanying metabolic disease is negatively correlated with lung health yet the exact mechanisms by which obesity affects the lung are not well characterized. Since obesity is associated with lung diseases as chronic bronchitis and asthma, we designed a series of experiments to measure changes in lung metabolism in mice fed obesogenic diets. Mice were fed either control or high fat/sugar diet (45%kcal fat/17%kcal sucrose), or very high fat diet (60%kcal fat/7% sucrose) for 150 days. We performed untargeted metabolomics by GC-TOFMS and HILIC-QTOFMS and lipidomics by RPLC-QTOFMS to reveal global changes in lung metabolism resulting from obesity and diet composition. From a total of 447 detected metabolites, we found 91 metabolite and lipid species significantly altered in mouse lung tissues upon dietary treatments. Significantly altered metabolites included complex lipids, free fatty acids, energy metabolites, amino acids and adenosine and NAD pathway members. While some metabolites were altered in both obese groups compared to control, others were different between obesogenic diet groups. Furthermore, a comparison of changes between lung, kidney and liver tissues indicated few metabolic changes were shared across organs, suggesting the lung is an independent metabolic organ. These results indicate obesity and diet composition have direct mechanistic effects on composition of the lung metabolome, which may contribute to disease progression by lung-specific pathways.

S1PR3 Signaling Drives Bacterial Killing and Is Required for Survival in Bacterial Sepsis

RATIONALE

Efficient elimination of pathogenic bacteria is a critical determinant in the outcome of sepsis. Sphingosine-1-phosphate receptor 3 (S1PR3) mediates multiple aspects of the inflammatory response during sepsis, but whether S1PR3 signaling is necessary for eliminating the invading pathogens remains unknown.

OBJECTIVES

To investigate the role of S1PR3 in antibacterial immunity during sepsis.

METHODS

Loss- and gain-of-function experiments were performed using cell and murine models. S1PR3 levels were determined in patients with sepsis and healthy volunteers.

MEASUREMENTS AND MAIN RESULTS

S1PR3 protein levels were up-regulated in macrophages upon bacterial stimulation. S1pr3^-/- mice showed increased mortality and increased bacterial burden in multiple models of sepsis. The transfer of wild-type bone marrow-derived macrophages rescued S1pr3^-/- mice from lethal sepsis. S1PR3-overexpressing macrophages further ameliorated the mortality rate of sepsis. Loss of S1PR3 led to markedly decreased bacterial killing in macrophages. Enhancing endogenous S1PR3 activity using a peptide agonist potentiated the macrophage bactericidal function and improved survival rates in multiple models of sepsis. Mechanically, the reactive oxygen species levels were decreased and phagosome maturation was delayed in S1pr3^-/- macrophages due to impaired recruitment of vacuolar protein-sorting 34 to the phagosomes. In addition, S1RP3 expression levels were elevated in monocytes from patients with sepsis. Higher levels of monocytic S1PR3 were associated with efficient intracellular bactericidal activity, better immune status, and preferable outcomes.

CONCLUSIONS

S1PR3 signaling drives bacterial killing and is essential for survival in bacterial sepsis. Interventions targeting S1PR3 signaling could have translational implications for manipulating the innate immune response to combat pathogens.

Evidence for the Involvement of Lipid Rafts and Plasma Membrane Sphingolipid Hydrolases in Pseudomonas aeruginosa Infection of Cystic Fibrosis Bronchial Epithelial Cells

Cystic fibrosis (CF) is the most common autosomal genetic recessive disease caused by mutations of gene encoding for the cystic fibrosis transmembrane conductance regulator. Patients with CF display a wide spectrum of symptoms, the most severe being chronic lung infection and inflammation, which lead to onset of cystic fibrosis lung disease. Several studies indicate that sphingolipids play a regulatory role in airway inflammation. The inhibition and downregulation of GBA2, the enzyme catabolizing glucosylceramide to ceramide, are associated with a significant reduction of IL-8 production in CF bronchial epithelial cells. Herein, we demonstrate that GBA2 plays a role in the proinflammatory state characterizing CF cells. We also report for the first time that Pseudomonas aeruginosa infection causes a recruitment of plasma membrane-associated glycosphingolipid hydrolases into lipid rafts of CuFi-1-infected cells. This reorganization of cell membrane may be responsible for activation of a signaling cascade, culminating in aberrant inflammatory response in CF bronchial epithelial cells upon bacterial infection. Taken together, the presented data further support the role of sphingolipids and their metabolic enzymes in controlling the inflammatory response in CF.

Novel therapeutic roles for surfactant-inositols and -phosphatidylglycerols in a neonatal piglet ARDS model: a translational study

The biological and immune-protective properties of surfactant-derived phospholipids and phospholipid subfractions in the context of neonatal inflammatory lung disease are widely unknown. Using a porcine neonatal triple-hit acute respiratory distress syndrome (ARDS) model (repeated airway lavage, overventilation, and LPS instillation into airways), we assessed whether the supplementation of surfactant (S; poractant alfa) with inositol derivatives [inositol 1,2,6-trisphosphate (IP3) or phosphatidylinositol 3,5-bisphosphate (PIP2)] or phosphatidylglycerol subfractions [16:0/18:1-palmitoyloleoyl-phosphatidylglycerol (POPG) or 18:1/18:1-dioleoyl-phosphatidylglycerol (DOPG)] would result in improved clinical parameters and sought to characterize changes in key inflammatory pathways behind these improvements. Within 72 h of mechanical ventilation, the oxygenation index (S+IP3, S+PIP2, and S+POPG), the ventilation efficiency index (S+IP3 and S+POPG), the compliance (S+IP3 and S+POPG) and resistance (S+POPG) of the respiratory system, and the extravascular lung water index (S+IP3 and S+POPG) significantly improved compared with S treatment alone. The inositol derivatives (mainly S+IP3) exerted their actions by suppressing acid sphingomyelinase activity and dependent ceramide production, linked with the suppression of the inflammasome nucleotide-binding domain, leucine-rich repeat-containing protein-3 (NLRP3)-apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC)-caspase-1 complex, and the profibrotic response represented by the cytokines transforming growth factor-β1 and IFN-γ, matrix metalloproteinase (MMP)-1/8, and elastin. In addition, IκB kinase activity was significantly reduced. S+POPG and S+DOPG treatment inhibited polymorphonuclear leukocyte activity (MMP-8 and myeloperoxidase) and the production of interleukin-6, maintained alveolar-capillary barrier functions, and reduced alveolar epithelial cell apoptosis, all of which resulted in reduced pulmonary edema. S+DOPG also limited the profibrotic response. We conclude that highly concentrated inositol derivatives and phosphatidylglycerol subfractions in surfactant preparations mitigate key inflammatory pathways in inflammatory lung disease and that their clinical application may be of interest for future treatment of the acute exudative phase of neonatal ARDS.

The T Allele of rs8075977 in the 5'-Flanking Region of the PEDF Gene Is Associated with Reduced Risk of Coronary Artery Disease in Elderly Chinese Men

Coronary artery disease (CAD) is a multifactorial disease with a genetic component. Pigment epithelium-derived factor (PEDF) exerts anti-inflammatory, anti-oxidant, anti-thrombotic, and anti-angiogenic effects and thus has received increasing attention as a sensitive biomarker of atherosclerosis and CAD. To explore the potential association between PEDF single nucleotide polymorphisms (SNPs) and CAD, we performed this case-control study of consecutive elderly Chinese Han male patients (n = 416) and age-matched male controls (n = 528) without a history of CAD or electrocardiographic signs of CAD. The enrolled CAD patients (age ≥ 60 years) are not biologically related. A tag approach was used to examine 100% of common variations in the PEDF gene (r² ≥ 0.8, minor allele frequency > 0.1). PEDF tag SNPs (tSNPs) were selected using the HapMap Data-CHB which describes the common patterns of human DNA sequence variation and Tagger program. SNPs were genotyped using ligase detection reaction (LDR). Seven tSNPs (rs8075977, rs11658342, rs1136287, rs12603825, rs12453107, rs6828 and rs11078634) were selected. Among them, only one SNP, rs8075977 (C/T) located in the 5'-flanking region, showed the significant effect on the susceptibility to CAD. The frequency of its T allele was significantly higher in the controls (52.7%) than that in the CAD group (46.2%) (adjusted OR = 0.88, 95% CI: 0.80-0.96; P = 0.005). In conclusion, the T allele of rs8075977 in the 5'-flanking region of the PEDF gene may be protective for CAD. Conversely, the C allele at this variation site is associated with CAD in elderly Chinese Han men.

A metabolomic approach shows sphingosine 1-phosphate and lysophospholipids as mediators of the therapeutic effect of liver growth factor in emphysema

Tobacco smoke exposure is the principal cause of lung tissue destruction, which in turn results in emphysema that leads into shortness of breath. Liver growth factor (LGF, a cell and tissue regenerating factor with therapeutic activity in several organs) has antifibrotic and antioxidant properties that could be useful to promote lung tissue regenerating capacity in damaged lungs. The current study has examined differences in metabolite profiles (fingerprints) of plasma from mice (strain C57BL/6J, susceptible to develop emphysema) exposed to tobacco smoke during six months. One group of mice received a treatment with Liver Growth Factor (LGF) after emphysema was established, whereas the other group did not receive the treatment. Age and sex-matched mice not exposed to smoke were also maintained with or without treatment as controls. Metabolic fingerprints (untargeted analysis) of plasma after protein precipitation were obtained by LC-QTOF-MS. The signals were processed and a large number of possible metabolites were found (23944). Multivariate data analysis provided models that highlighted the differences between control and smoke exposed mice in both conditions. Accurate masses of features (possible compounds) representing significant differences were searched using online public databases. Lipid mediators, related to intracellular signaling in inflammation, were found among the metabolites putatively identified as markers of the different conditions and among them, sphingosine, sphingosine 1-phosphate and lysophospholipids point at the relevance of such metabolites in the regulation of the processes related to tissue regeneration mediated by LGF. These results also suggest that metabolomic fingerprinting could potentially guide the characterization of relevant metabolites leading the regeneration of lungs in emphysema disease.