Pulmonary surfactant phosphatidylglycerol inhibits Mycoplasma pneumoniae-stimulated eicosanoid production from human and mouse macrophages

Investigating the effects of dexamethasone on pulmonary surfactant lipids based on lipidomics studies

Dexamethasone, a glucocorticoid commonly used in pediatric patients, has potent anti-inflammatory and immunosuppressive properties. However, it is associated with side effects such as reduced lung function and decreased immunity. Pulmonary surfactant lipids are closely linked to lung disease and play a role in reducing surface tension, immune response and antiviral activity. The dysregulation of lipid metabolism is closely associated with lung disease. Hence, untargeted lipidomics may be instrumental in elucidating the effects of dexamethasone on pulmonary surfactant lipids. We obtained surfactant lipid samples from the bronchoalveolar lavage fluid of young mice injected subcutaneously with dexamethasone and conducted a comprehensive lipidomic analysis, comparing them with a control group. We observed a decrease in lipids, such as phosphatidylcholine, phosphatidylglycerol and phosphatidylethanolamine, and an increase in ceramide, fatty acid, diacylglycerol and monoglyceride, which may impact lung health. This study revealed the influence of dexamethasone on pulmonary surfactant lipids, offering new insights into adverse reactions in clinical settings.

AnGong NiuHuang (AGNH) pill attenuated traumatic brain injury through regulating NF-κB/Nlrp3 axis and glycerophospholipid metabolism

BACKGROUND

Traumatic brain injury (TBI), especially neuroinflammation after TBI persists for a long time and causes significant neurodegenerative pathologies and neuropsychiatric problems.

PURPOSE

In this study, the neuroprotective effect of AnGong NiuHuang (AGNH) on TBI was investigated and the mechanism was revealed by integrating multiple omics.

METHODS

The rats with TBI were administrated with AGNH for 5 consecutive days and the effect was evaluated by using modified neurologic severity score (mNSS), brain edema, H&E staining, Nissl staining and TUNEL staining. The mechanism was revealed by using RNA sequencing (RNA-seq) and metabolomic analysis. The inflammatory factors, apoptosis-related proteins and identified vital targets were validated by enzyme-linked immunosorbent assay, western blotting and immunofluorescence staining.

RESULTS

Administration of AGNH decreased mNSS, brain edema, brain structure damage, but increased Nissl body density in the rats with TBI. Additionally, AGNH reduced IL-1β, IL-17A, TNF-α, MMP9, MCP-1, IL-6, Bax and TUNEL staining,but elevated Bcl2 level. Integrating transcriptomic analysis and metabolomic analysis identified vital targets and critical metabolic pathways. Importantly, AGNH treatment reduced the expression of TLR4, MYD88, NLRP3, BTK, IL-18 and Caspase 1 as well as glycerophospholipid metabolism-related protein AGPAT2 and PLA2G2D, and decreased the nuclear translocation of NF-κB p65 in the brain of TBI rats. Additionally, AGNH increased phosphatidylcholine (PC), phosphatidylglycerol (PG), phosphatidylserine (PS), phosphatidylethanolamine (PE), but decreased 1-acyl-sn-glycero-3-phosphocholine (LysoPC) in the metabolic pathway of glycerophospholipid metabolism.

CONCLUSION

Taken together, AGNH inhibited NF-κB/NLRP3 axis to suppress neuroinflammation, cell apoptosis and pyroptosis, and improved metabolic pathways of glycerophospholipid metabolism after TBI.

The consumption of lard oil during pregnancy and postpartum periods has negative effects on cognitive function by altering the fatty acid profile and activating neuroinflammation via calcium signaling pathway in the maternal mice brain

It has been suggested that dietary intake of lipids and fatty acids may influence cognitive function, however, the effect of lard intake during pregnancy and postpartum periods on cognitive function of mother remains to be elucidated. We investigated the effect and mechanism of consuming soybean oil (SO), the mixed oil of lard and soybean oil at the ratio of 1:1 (LS) and lard oil (LO) during the pregnancy and postpartum periods on cognitive function of the maternal mice. All pregnant C57BL/6JNifdc mice were fed with soybean oil diet during day 0-10 (the day when vaginal plugs appeared in female mice was recorded as day 0), and then randomly assigned to SO, LS and LO groups (n = 10) from day 11 to day 44. The time in center zone and the number of times to enter in center zone were significantly higher in the SO group than in the LO group detected by the open-field test. The levels of neuroglial cells, NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome complex and pyroptosis related proteins in brain of the LO group were significantly higher than those in the SO group. RNA-sequencing results showed that the calcium signaling pathway related genes in brain, including Adcy8, Ntsr1, Trhr, Oxtr, Htr5b and Camk2d levels significantly higher in the LO group than in the SO group. Lipidomic analysis indicated that PG 18:2_18:2, PG 20:5_22:6, and CL 12:0_16:0_22:3_22:5 of glycerophospholipid metabolism in brain significantly connected with Htr5b of calcium signaling pathway. In conclusion, the intake of lard during the pregnancy and postpartum periods is detrimental to the cognitive function of maternal mice, which probably due to changes in the composition of fatty acid in the brain, thereby activating neuroinflammation via calcium signaling pathway in brain.

Enrichment of Bioactive Lipids in Urinary Extracellular Vesicles and Evidence of Apoptosis in Kidneys of Hypertensive Diabetic Cathepsin B Knockout Mice after Streptozotocin Treatment

Cathepsin B (CtsB) is a ubiquitously expressed cysteine protease that plays important roles in health and disease. Urinary extracellular vesicles (uEVs) are released from cells associated with urinary organs. The antibiotic streptozotocin (STZ) is known to induce pancreatic islet beta cell destruction, diabetic nephropathy, and hypertension. We hypothesized that streptozotocin-induced diabetic kidney disease and hypertension result in the release of bioactive lipids from kidney cells that induce oxidative stress and renal cell death. Lipidomics was performed on uEVs isolated from CtsB knockout mice treated with or without STZ, and their kidneys were used to investigate changes in proteins associated with cell death. Lysophosphatidylethanolamine (LPE) (18:1), lysophosphatidylserine (LPS) (22:6), and lysophosphatidylglycerol (LPG) (22:5) were among the bioactive lipids enriched in uEVs from CtsB knockout mice treated with STZ compared to untreated CtsB mice (n = 3 uEV preparations per group). Anti-oxidant programming was activated in the kidneys of the CtsB knockout mice treated with STZ, as indicated by increased expression of glutathione peroxidase 4 (GPX4) and the cystine/glutamate antiporter SLC7A11 (XCT) (n = 4 mice per group), which was supported by a higher reactivity to 4-hydroxy-2-nonenal (4-HNE), a marker for oxidative stress (n = 3 mice per group). Apoptosis but not ferroptosis was the ongoing form of cell death in these kidneys as cleaved caspase-3 levels were significantly elevated in the STZ-treated CtsB knockout mice (n = 4 mice per group). There were no appreciable differences in the pro-ferroptosis enzyme acyl-CoA synthetase long-chain family member 4 (ACSL4) or the inflammatory marker CD93 in the kidneys (n = 3 mice per group), which further supports apoptosis as the prevalent mechanism of pathology. These data suggest that STZ treatment leads to oxidative stress, inducing apoptotic injury in the kidneys during the development of diabetic kidney disease and hypertension.

Repair and regeneration of the alveolar epithelium in lung injury

Considerable progress has been made in understanding the function of alveolar epithelial cells in a quiescent state and regeneration mechanism after lung injury. Lung injury occurs commonly from severe viral and bacterial infections, inhalation lung injury, and indirect injury sepsis. A series of pathological mechanisms caused by excessive injury, such as apoptosis, autophagy, senescence, and ferroptosis, have been studied. Recovery from lung injury requires the integrity of the alveolar epithelial cell barrier and the realization of gas exchange function. Regeneration mechanisms include the participation of epithelial progenitor cells and various niche cells involving several signaling pathways and proteins. While alveoli are damaged, alveolar type II (AT2) cells proliferate and differentiate into alveolar type I (AT1) cells to repair the damaged alveolar epithelial layer. Alveolar epithelial cells are surrounded by various cells, such as fibroblasts, endothelial cells, and various immune cells, which affect the proliferation and differentiation of AT2 cells through paracrine during alveolar regeneration. Besides, airway epithelial cells also contribute to the repair and regeneration process of alveolar epithelium. In this review, we mainly discuss the participation of epithelial progenitor cells and various niche cells involving several signaling pathways and transcription factors.

Multi-omics integration reveals a nonlinear signature that precedes progression of lung fibrosis

Objectives

Idiopathic pulmonary fibrosis (IPF) is a devastating progressive interstitial lung disease with poor outcomes. While decades of research have shed light on pathophysiological mechanisms associated with the disease, our understanding of the early molecular events driving IPF and its progression is limited. With this study, we aimed to model the leading edge of fibrosis using a data-driven approach.

Methods

Multiple omics modalities (transcriptomics, metabolomics and lipidomics) of healthy and IPF lung explants representing different stages of fibrosis were combined using an unbiased approach. Multi-Omics Factor Analysis of datasets revealed latent factors specifically linked with established fibrotic disease (Factor1) and disease progression (Factor2).

Results

Features characterising Factor1 comprised well-established hallmarks of fibrotic disease such as defects in surfactant, epithelial-mesenchymal transition, extracellular matrix deposition, mitochondrial dysfunction and purine metabolism. Comparatively, Factor2 identified a signature revealing a nonlinear trajectory towards disease progression. Molecular features characterising Factor2 included genes related to transcriptional regulation of cell differentiation, ciliogenesis and a subset of lipids from the endocannabinoid class. Machine learning models, trained upon the top transcriptomics features of each factor, accurately predicted disease status and progression when tested on two independent datasets.

Conclusion

This multi-omics integrative approach has revealed a unique signature which may represent the inflection point in disease progression, representing a promising avenue for the identification of therapeutic targets aimed at addressing the progressive nature of the disease.

Lactobacillus johnsonii N6.2 phospholipids induce immature-like dendritic cells with a migratory-regulatory-like transcriptional signature

Shifts in the gut microbiota composition, called dysbiosis, have been directly associated with acute and chronic diseases. However, the underlying biological systems connecting gut dysbiosis to systemic inflammatory pathologies are not well understood. Phospholipids (PLs) act as precursors of both, bioactive inflammatory and resolving mediators. Their dysregulation is associated with chronic diseases including cancer. Gut microbial-derived lipids are structurally unique and capable of modulating host's immunity. Lactobacillus johnsonii N6.2 is a Gram-positive gut symbiont with probiotic characteristics. L. johnsonii N6.2 reduces the incidence of autoimmunity in animal models of Type 1 Diabetes and improves general wellness in healthy volunteers by promoting, in part, local and systemic anti-inflammatory responses. By utilizing bioassay-guided fractionation methods with bone marrow-derived dendritic cells (BMDCs), we report here that L. johnsonii N6.2 purified lipids induce a transcriptional signature that resembles that of migratory (mig) DCs. RNAseq-based analysis showed that BMDCs stimulated with L. johnsonii N6.2 total lipids upregulate maturation-mig related genes Cd86, Cd40, Ccr7, Icam1 along with immunoregulatory genes including Itgb8, Nfkbiz, Jag1, Adora2a, IL2ra, Arg1, and Cd274. Quantitative reverse transcription (qRT)-PCR analysis indicated that PLs are the bioactive lipids triggering the BMDCs response. Antibody-blocking of surface Toll-like receptor (TLR)2 resulted in boosted PL-mediated upregulation of pro-inflammatory Il6. Chemical inhibition of the IKKα kinase from the non-canonical NF-κB pathway specifically restricted upregulation of Il6 and Tnf. Phenotypically, PL-stimulated BMDCs displayed an immature like-phenotype with significantly increased surface ICAM-1. This study provides insight into the immunoregulatory capacity of Gram-positive, gut microbial-derived phospholipids on innate immune responses.

Review of Eukaryote Cellular Membrane Lipid Composition, with Special Attention to the Fatty Acids

Biological membranes, primarily composed of lipids, envelop each living cell. The intricate composition and organization of membrane lipids, including the variety of fatty acids they encompass, serve a dynamic role in sustaining cellular structural integrity and functionality. Typically, modifications in lipid composition coincide with consequential alterations in universally significant signaling pathways. Exploring the various fatty acids, which serve as the foundational building blocks of membrane lipids, provides crucial insights into the underlying mechanisms governing a myriad of cellular processes, such as membrane fluidity, protein trafficking, signal transduction, intercellular communication, and the etiology of certain metabolic disorders. Furthermore, comprehending how alterations in the lipid composition, especially concerning the fatty acid profile, either contribute to or prevent the onset of pathological conditions stands as a compelling area of research. Hence, this review aims to meticulously introduce the intricacies of membrane lipids and their constituent fatty acids in a healthy organism, thereby illuminating their remarkable diversity and profound influence on cellular function. Furthermore, this review aspires to highlight some potential therapeutic targets for various pathological conditions that may be ameliorated through dietary fatty acid supplements. The initial section of this review expounds on the eukaryotic biomembranes and their complex lipids. Subsequent sections provide insights into the synthesis, membrane incorporation, and distribution of fatty acids across various fractions of membrane lipids. The last section highlights the functional significance of membrane-associated fatty acids and their innate capacity to shape the various cellular physiological responses.

The anti-inflammatory and antiviral properties of anionic pulmonary surfactant phospholipids

The pulmonary surfactant system of the lung is a lipid and protein complex, which regulates the biophysical properties of the alveoli to prevent lung collapse and the innate immune system in the lung. Pulmonary surfactant is a lipoprotein complex consisting of 90% phospholipids and 10% protein, by weight. Two minor components of pulmonary surfactant phospholipids, phosphatidylglycerol (PG) and phosphatidylinositol (PI), exist at very high concentrations in the extracellular alveolar compartments. We have reported that one of the most dominant molecular species of PG, palmitoyl-oleoyl-phosphatidylglycerol (POPG) and PI inhibit inflammatory responses induced by multiple toll-like receptors (TLR2/1, TLR3, TLR4, and TLR2/6) by interacting with subsets of multiprotein receptor components. These lipids also exert potent antiviral effects against RSV and influenza A, in vitro, by inhibiting virus binding to host cells. POPG and PI inhibit these viral infections in vivo, in multiple animal models. Especially noteworthy, these lipids markedly attenuate SARS-CoV-2 infection including its variants. These lipids are natural compounds that already exist in the lung and, thus, are less likely to cause adverse immune responses by hosts. Collectively, these data demonstrate that POPG and PI have strong potential as novel therapeutics for applications as anti-inflammatory compounds and preventatives, as treatments for broad ranges of RNA respiratory viruses.

Molecular Impact of Conventional and Electronic Cigarettes on Pulmonary Surfactant

The alveolar epithelium is covered by a non-cellular layer consisting of an aqueous hypophase topped by pulmonary surfactant, a lipo-protein mixture with surface-active properties. Exposure to cigarette smoke (CS) affects lung physiology and is linked to the development of several diseases. The macroscopic effects of CS are determined by several types of cell and molecular dysfunction, which, among other consequences, lead to surfactant alterations. The purpose of this review is to summarize the published studies aimed at uncovering the effects of CS on both the lipid and protein constituents of surfactant, discussing the molecular mechanisms involved in surfactant homeostasis that are altered by CS. Although surfactant homeostasis has been the topic of several studies and some molecular pathways can be deduced from an analysis of the literature, it remains evident that many aspects of the mechanisms of action of CS on surfactant homeostasis deserve further investigation.

Phosphatidylglycerol to Treat Chronic Skin Wounds in Diabetes

This review proposes the use of dioleoylphosphatidylglycerol (DOPG) to enhance diabetic wound healing. Initially, the characteristics of diabetic wounds are examined, focusing on the epidermis. Hyperglycemia accompanying diabetes results in enhanced inflammation and oxidative stress in part through the generation of advanced glycation end-products (AGEs), in which glucose is conjugated to macromolecules. These AGEs activate inflammatory pathways; oxidative stress results from increased reactive oxygen species generation by mitochondria rendered dysfunctional by hyperglycemia. These factors work together to reduce the ability of keratinocytes to restore epidermal integrity, contributing to chronic diabetic wounds. DOPG has a pro-proliferative action on keratinocytes (through an unclear mechanism) and exerts an anti-inflammatory effect on keratinocytes and the innate immune system by inhibiting the activation of Toll-like receptors. DOPG has also been found to enhance macrophage mitochondrial function. Since these DOPG effects would be expected to counteract the increased oxidative stress (attributable in part to mitochondrial dysfunction), decreased keratinocyte proliferation, and enhanced inflammation that characterize chronic diabetic wounds, DOPG may be useful in stimulating wound healing. To date, efficacious therapies to promote the healing of chronic diabetic wounds are largely lacking; thus, DOPG may be added to the armamentarium of drugs to enhance diabetic wound healing.

Maturation of the malarial phosphatidylserine decarboxylase is mediated by high affinity binding to anionic phospholipids

Decarboxylation of phosphatidylserine (PS) to form phosphatidylethanolamine by PS decarboxylases (PSDs) is an essential process in most eukaryotes. Processing of a malarial PSD proenzyme into its active alpha and beta subunits is by an autoendoproteolytic mechanism regulated by anionic phospholipids, with PS serving as an activator and phosphatidylglycerol (PG), phosphatidylinositol, and phosphatidic acid acting as inhibitors. The biophysical mechanism underlying this regulation remains unknown. We used solid phase lipid binding, liposome-binding assays, and surface plasmon resonance to examine the binding specificity of a processing-deficient Plasmodium PSD (PkPSDS308A) mutant enzyme and demonstrated that the PSD proenzyme binds strongly to PS and PG but not to phosphatidylethanolamine and phosphatidylcholine. The equilibrium dissociation constants (Kd) of PkPSD with PS and PG were 80.4 nM and 66.4 nM, respectively. The interaction of PSD with PS is inhibited by calcium, suggesting that the binding mechanism involves ionic interactions. In vitro processing of WT PkPSD proenzyme was also inhibited by calcium, consistent with the conclusion that PS binding to PkPSD through ionic interactions is required for the proenzyme processing. Peptide mapping identified polybasic amino acid motifs in the proenzyme responsible for binding to PS. Altogether, the data demonstrate that malarial PSD maturation is regulated through a strong physical association between PkPSD proenzyme and anionic lipids. Inhibition of the specific interaction between the proenzyme and the lipids can provide a novel mechanism to disrupt PSD enzyme activity, which has been suggested as a target for antimicrobials, and anticancer therapies.

The Role of Pulmonary Surfactant Phospholipids in Fibrotic Lung Diseases

Diffuse parenchymal lung diseases (DPLD) or Interstitial lung diseases (ILD) are a heterogeneous group of lung conditions with common characteristics that can progress to fibrosis. Within this group of pneumonias, idiopathic pulmonary fibrosis (IPF) is considered the most common. This disease has no known cause, is devastating and has no cure. Chronic lesion of alveolar type II (ATII) cells represents a key mechanism for the development of IPF. ATII cells are specialized in the biosynthesis and secretion of pulmonary surfactant (PS), a lipid-protein complex that reduces surface tension and minimizes breathing effort. Some differences in PS composition have been reported between patients with idiopathic pulmonary disease and healthy individuals, especially regarding some specific proteins in the PS; however, few reports have been conducted on the lipid components. This review focuses on the mechanisms by which phospholipids (PLs) could be involved in the development of the fibroproliferative response.

Mycoplasma pneumoniae downregulates RECK to promote matrix metalloproteinase-9 secretion by bronchial epithelial cells

Airway epithelial cells function as both a physical barrier against harmful substances and pathogenic microorganisms and as an important participant in the innate immune system. Matrix metalloproteinase-9 (MMP-9) plays a crucial role in modulating inflammatory responses during respiratory infections. However, the signalling cascade that induces MMP-9 secretion from epithelial cells infected with Mycoplasma pneumoniae remains poorly understood. In this study, we investigated the mechanism of MMP-9 secretion in airway epithelial cells infected with M. pneumoniae. Our data clearly showed that M. pneumoniae induced the secretion of MMP-9 from bronchial epithelial cells and upregulated its enzymatic activity in a time- and dose-dependent manner. Using specific inhibitors and chromatin co-precipitation experiments, we confirmed that the expression of MMP-9 is reliant on the activation of the Toll-like receptor 2 (TLR2) and TLR6-dependent mitogen-activated protein kinase/nuclear factor- κB/activator protein-1 (MAPK/NF-κB/AP-1) pathways. Additionally, epigenetic modifications such as histone acetylation and the nuclear transcription factor Sp1 also regulate MMP-9 expression. M. pneumoniae infection also decreased the expression of the tumour suppressor reversion-inducing cysteine-rich protein with Kazal motifs (RECK) by inducing Sp1 phosphorylation. Overexpression of RECK significantly impaired the M. pneumoniae-triggered increase in MMP-9 enzymatic activity, although the level of MMP-9 protein remained constant. The study demonstrated that M. pneumoniae-triggered MMP-9 expression is modulated by TLR2 and 6, the MAPK/NF-κB/AP-1 signalling cascade, and histone acetylation, and M. pneumoniae downregulated the expression of RECK, thereby increasing MMP-9 activity to modulate the inflammatory response, which could play a role in airway remodelling.

Sonodynamic therapy by phase-transition nanodroplets for reducing epidermal hyperplasia in psoriasis

The cross-talk between hyperproliferative keratinocytes and activated immune cells is responsible for the progression of psoriasis. The strategy to alleviate psoriasis through inhibiting the abnormal proliferation of keratinocytes remains challenging due to limited therapeutic effects and low skin penetration of drugs. Herein we designed an ultrasound-triggered phase-transition nanodroplet that could produce cavitation to enhance skin penetration and effectively generate reactive oxygen species (ROS) to induce keratinocyte apoptosis for psoriasis treatment. After ultrasound stimulation, the perfluoro-n-pentane (PFP) liquid core of the nanodroplets vaporized, and the Haematoporphyrin monomethyl ether (HMME) encapsulated in the nanodroplets generated plenty of intracellular ROS which caused the apoptosis of HaCat cells through inducing mitochondrial dysfunction. In addition, the blank nanodroplets successfully inhibited the secretion of IL-6 and TNF-α from macrophages and dendritic cells in vitro due to the anti-inflammatory effect of POPG. For the skin penetration test, the phase-transition nanodroplets could effectively accumulate in the epidermis of the skin and generate intracellular ROS. The in-vivo anti-psoriasis experiment demonstrated that the phase-transition nanodroplets relieved the symptoms of psoriasis lesion and inhibited epidermal hyperplasia through induction of cell apoptosis under ultrasound irritation. Meanwhile, the inflammatory cytokines in the skin lesion almost decreased to the normal baseline level after SDT. Collectively, this study demonstrated a new strategy to inhibit keratinocyte hyperproliferation for psoriasis management based on sonodynamic responded nanodroplets.

Mass spectrometry imaging identifies altered hepatic lipid signatures during experimental Leishmania donovani infection

Introduction

Spatial analysis of lipids in inflammatory microenvironments is key to understand the pathogenesis of infectious disease. Granulomatous inflammation is a hallmark of leishmaniasis and changes in host and parasite lipid metabolism have been observed at the bulk tissue level in various infection models. Here, mass spectrometry imaging (MSI) is applied to spatially map hepatic lipid composition following infection with Leishmania donovani, an experimental mouse model of visceral leishmaniasis.

Methods

Livers from naïve and L. donovani-infected C57BL/6 mice were harvested at 14- and 20-days post-infection (n=5 per time point). 12 µm transverse sections were cut and covered with norhamane, prior to lipid analysis using MALDI-MSI. MALDI-MSI was performed in negative mode on a Rapiflex (Bruker Daltonics) at 5 and 50 µm spatial resolution and data-dependent analysis (DDA) on an Orbitrap-Elite (Thermo-Scientific) at 50 µm spatial resolution for structural identification analysis of lipids.

Results

Aberrant lipid abundances were observed in a heterogeneous distribution across infected mouse livers compared to naïve mouse liver. Distinctive localized correlated lipid masses were found in granulomas and surrounding parenchymal tissue. Structural identification revealed 40 different lipids common to naïve and d14/d20 infected mouse livers, whereas 15 identified lipids were only detected in infected mouse livers. For pathology-guided MSI imaging, we deduced lipids from manually annotated granulomatous and parenchyma regions of interests (ROIs), identifying 34 lipids that showed significantly different intensities between parenchyma and granulomas across all infected livers.

Discussion

Our results identify specific lipids that spatially correlate to the major histopathological feature of Leishmania donovani infection in the liver, viz. hepatic granulomas. In addition, we identified a three-fold increase in the number of unique phosphatidylglycerols (PGs) in infected liver tissue and provide direct evidence that arachidonic acid-containing phospholipids are localized with hepatic granulomas. These phospholipids may serve as important precursors for downstream oxylipin generation with consequences for the regulation of the inflammatory cascade. This study provides the first description of the use of MSI to define spatial-temporal lipid changes at local sites of infection induced by Leishmania donovani in mice.

Anti-inflammatory and anti-viral actions of anionic pulmonary surfactant phospholipids

Pulmonary surfactant is a mixture of lipids and proteins, consisting of 90% phospholipid, and 10% protein by weight, found predominantly in pulmonary alveoli of vertebrate lungs. Two minor components of pulmonary surfactant phospholipids, phosphatidylglycerol (PG) and phosphatidylinositol (PI), are present within the alveoli at very high concentrations, and exert anti-inflammatory effects by regulating multiple Toll like receptors (TLR2/1, TLR4, and TLR2/6) by antagonizing cognate ligand-dependent activation. POPG also attenuates LPS-induced lung injury in vivo. In addition, these lipids bind directly to RSV and influenza A viruses (IAVs) and block interaction between host cells and virions, and thereby prevent viral replication in vitro. POPG and PI also inhibit RSV and IAV infection in vivo, in mice and ferrets. The lipids markedly inhibit SARS-CoV-2 infection in vitro. These findings suggest that both POPG and PI have strong potential to be applied as both prophylaxis and post-infection treatments for problematic respiratory viral infections.

Characterization of phospholipid-modified lung surfactant in vitro and in a neonatal ARDS model reveals anti-inflammatory potential and surfactant lipidome signatures

A strong inflammatory immune response drives the lung pathology in neonatal acute respiratory distress syndrome (nARDS). Anti-inflammatory therapy is therefore a promising strategy for improved treatment of nARDS. We demonstrate a new function of the anionic phospholipids POPG, DOPG, and PIP2 as inhibitors of IL-1β release by LPS and ATP-induced inflammasome activation in human monocyte-derived and lung macrophages. Curosurf® surfactant was enriched with POPG, DOPG, PIP2 and the head-group derivative IP3, biophysically characterized and applicability was evaluated in a piglet model of nARDS. The composition of pulmonary surfactant from piglets was determined by shotgun lipidomics screens. After 72 h of nARDS, levels of POPG, DOPG, and PIP2 were enhanced in the respective treatment groups. Otherwise, we did not observe changes of individual lipid species in any of the groups. Surfactant proteins were not affected, with the exception of the IP3 treated group. Our data show that POPG, DOPG, and PIP2 are potent inhibitors of inflammasome activation; their enrichment in a surfactant preparation did not induce any negative effects on lipid profile and reduced biophysical function in vitro was mainly observed for PIP2. These results encourage to rethink the current strategies of improving surfactant preparations by inclusion of anionic lipids as potent anti-inflammatory immune regulators.

Updated Perspectives on Keratinocytes and Psoriasis: Keratinocytes are More Than Innocent Bystanders

Psoriasis is a complex disease triggered by genetic, immunologic, and environmental stimuli. Many genes have been linked to psoriasis, like the psoriasis susceptibility genes, some of which are critical in keratinocyte biology and epidermal barrier function. Still, the exact pathogenesis of psoriasis is unknown. In the disease, the balance between the proliferative and differentiative processes of keratinocytes becomes altered. Multiple studies have highlighted the role of dysregulated immune cells in provoking the inflammatory responses seen in psoriasis. In addition to immune cells, accumulating evidence shows that keratinocytes are involved in psoriasis pathogenesis, as discussed in this review. Although certain immune cell-derived factors stimulate keratinocyte hyperproliferation, activated keratinocytes can also produce anti-microbial peptides, cytokines, and chemokines that can promote their proliferation, as well as recruit immune cells to help initiate and reinforce inflammatory feedback loops. Psoriatic keratinocytes also show intrinsic differences from normal keratinocytes even after removal from the in vivo inflammatory environment; thus, psoriatic keratinocytes have been found to exhibit abnormal calcium metabolism and possible epigenetic changes that contribute to psoriasis. The Koebner phenomenon, in which injury promotes the development of psoriatic lesions, also provides evidence for keratinocytes' contributions to disease pathogenesis. Furthermore, transgenic mouse studies have confirmed the importance of keratinocytes in the etiology of psoriasis. Finally, in addition to immune cells and keratinocytes, data in the literature support roles for other cell types, tissues, and systems in psoriasis development. These other contributors are all potential targets for therapies, suggesting the importance of a holistic approach when treating psoriasis.

Towards the Development of Long Circulating Phosphatidylserine (PS)- and Phosphatidylglycerol (PG)-Enriched Anti-Inflammatory Liposomes: Is PEGylation Effective?

The anionic phospholipids (PLs) phosphatidylserine (PS) and phosphatidylglycerol (PG) are endogenous phospholipids with anti-inflammatory and immunomodulatory activity. A potential clinical use requires well-defined systems and for several applications, a long circulation time is desirable. Therefore, we aimed the development of long circulating liposomes with intrinsic anti-inflammatory activity. Hence, PS- and PG-enriched liposomes were produced, whilst phosphatidylcholine (PC) liposomes served as control. Liposomes were either formulated as conventional or PEGylated formulations. They had diameters below 150 nm, narrow size distributions and composition-dependent surface charges. Pharmacokinetics were assessed non-invasively via in vivo fluorescence imaging (FI) and ex vivo in excised organs over 2 days. PC liposomes, conventionally formulated, were rapidly cleared from the circulation, while PEGylation resulted in prolongation of liposome circulation robustly distributing among most organs. In contrast, PS and PG liposomes, both as conventional or PEGylated formulations, were rapidly cleared. Non-PEGylated PS and PG liposomes did accumulate almost exclusively in the liver. In contrast, PEGylated PS and PG liposomes were observed mainly in liver and spleen. In summary, PEGylation of PS and PG liposomes was not effective to prolong the circulation time but caused a higher uptake in the spleen.

The Potential for Phospholipids in the Treatment of Airway Inflammation: An Unexplored Solution

Asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis (CF) are major inflammatory respiratory diseases. Current mainstay therapy for asthma, and chronic obstructive pulmonary disease are corticosteroids, which have well-established side effect profiles. Phospholipids (PLs) are ubiquitous, diverse compounds with varying functions such as their structural role incell membrane, energy storage, and cell signaling.Recent advances in understanding PLs role as inflammatory mediators in the body as well as their widespread long-standing use as carrier molecules in drug delivery demonstrate the potential application of phospholipids in modulating inflammatory conditions. This review briefly explains the main mechanisms of inflammation in chronic respiratory diseases, currentanti-inflammatory treatments and areas of unmet need. The structural features, roles of endogenous and exogenous phospholipids, including their use as pharmaceutical excipients are reviewed. Current research on the immunomodulatory properties of PLs and their potentialapplication in inflammatory diseasesis the major section of this review. Considering the roles of PLs as inflammatory mediators and their safety profile established in pharmaceutical formulations, these small molecules demonstrate great potential as candidates in respiratory inflammation. Future studies need to focus on the immunomodulatory properties and the underlying mechanisms of phospholipids in respiratory inflammatory diseases.

Interactions of particulate matter and pulmonary surfactant: Implications for human health

Particulate matter (PM), which is the primary contributor to air pollution, has become a pervasive global health threat. When PM enters into a respiratory tract, the first body tissues to be directly exposed are the cells of respiratory tissues and pulmonary surfactant. Pulmonary surfactant is a pivotal component to modulate surface tension of alveoli during respiration. Many studies have proved that PM would interact with pulmonary surfactant to affect the alveolar activity, and meanwhile, pulmonary surfactant would be adsorbed to the surface of PM to change the toxic effect of PM. This review focuses on recent studies of the interactions between micro/nanoparticles (synthesized and environmental particles) and pulmonary surfactant (natural surfactant and its models), as well as the health effects caused by PM through a few significant aspects, such as surface properties of PM, including size, surface charge, hydrophobicity, shape, chemical nature, etc. Moreover, in vitro and in vivo studies have shown that PM leads to oxidative stress, inflammatory response, fibrosis, and cancerization in living bodies. By providing a comprehensive picture of PM-surfactant interaction, this review will benefit both researchers for further studies and policy-makers for setting up more appropriate regulations to reduce the adverse effects of PM on public health.

Phosphatidylglycerol and surfactant: A potential treatment for COVID-19?

A hypothesis concerning the potential utility of surfactant supplementation for the treatment of critically ill patients with COVID-19 is proposed, along with a brief summary of the data in the literature supporting this idea. It is thought that surfactant, which is already approved by the Food and Drug Administration for intratracheal administration to treat neonatal respiratory distress syndrome in pre-term infants, could benefit COVID-19-infected individuals by: (1) restoring surfactant damaged by lung infection and/or decreased due to the virus-induced death of the type II pneumocytes that produce it and (2) reducing surface tension to decrease the work of breathing and limit pulmonary edema. In addition, a constituent of surfactant, phosphatidylglycerol, could mitigate COVID-19-induced lung pathology by: (3) decreasing excessive innate immune system stimulation via its inhibition of toll-like receptor-2 and -4 activation by microbial components and cellular proteins released by damaged cells, thereby limiting inflammation and the resultant pulmonary edema, and (4) possibly blocking spread of the viral infection to non-infected cells in the lung. Therefore, it is suggested that surfactant preparations containing phosphatidylglycerol be tested for their ability to improve lung function in critically ill patients with COVID-19.

Drosophila PTPMT1 Has a Function in Tracheal Air Filling

The fly trachea is the equivalent of the mammalian lung and is a useful model for human respiratory diseases. However, little is known about the molecular mechanisms underlying tracheal air filling during larval development. In this study, we discover that PTPMT1 has a function in tracheal air filling. PTPMT1 is a widely conserved, ubiquitously expressed mitochondrial phosphatase. To reveal PTPMT1's functions in genetically tractable invertebrates and whether those functions are tissue specific, we generate a Drosophila model of PTPMT1 depletion. We find that fly PTPMT1 mutants show impairments in tracheal air filling and subsequent activation of innate immune responses. On a cellular level, these defects are preceded by aggregation of mitochondria within the tracheal epithelial cells. Our work demonstrates a cell-type-specific role for PTPMT1 in fly tracheal epithelial cells to support air filling and to prevent immune activation. The establishment of this model will facilitate exploration of PTPMT1's physiological functions in vivo.

Kupffer cell activation by different microbial lysates: Toll-like receptor-2 plays pivotal role on thromboxane A2 production in mice and humans

Thromboxane (TX) A₂ has been identified as an important intrahepatic vasoconstrictor upon Kupffer cell (KC) activation during infections such as spontaneous bacterial peritonitis (SBP). The study aimed to investigate the role of TLRs in the TXA₂ increase in liver nonparenchymal cells and their related mechanisms. Here, we identified TLR-2 as a common pathway for different microbials: microbial lysates including Gram-positive bacteria, Gram-negative bacteria, and fungi all increased TXA₂ secretion via activation of TLR-2 in human KCs, accompanied by increased expression and phosphorylation of Myd88-related pathway. Of all TLR agonists, only TLR-1, -2, and -4 agonists increased TXA₂ in human KCs. These results were further confirmed by mouse liver nonparenchymal cells. Comparing the effects of TLR-1, -2, and -4 antagonists, only TLR-2 antagonist showed inhibitory effects with all tested microbial lysates. Pretreatment with TLR-2 antagonist in human KCs blocked the secretion of IL-10, CXCL-10, TNF-α, and IL-6 induced by Gram-positive and Gram-negative bacterial stimulation. IL-23 and IL-1β were only induced by Gram-negative bacteria. Thus, TLR-2 might be a potential marker and an attractive target for future treatment of patients with SBP. In addition, IL-23 and IL-1β might distinguish early between Gram-positive and Gram-negative SBP.

Dioleoylphosphatidylglycerol Accelerates Corneal Epithelial Wound Healing

Purpose

In contact with the external environment, the cornea can easily be injured. Although corneal wounds generally heal rapidly, the pain and increased risk of infection associated with a damaged cornea, as well as the impaired healing observed in some individuals, emphasize the need for novel treatments to accelerate corneal healing. We previously demonstrated in epidermal keratinocytes that the glycerol channel aquaporin-3 (AQP3) interacts with phospholipase D2 (PLD2) to produce the signaling phospholipid phosphatidylglycerol (PG), which has been shown to accelerate skin wound healing in vivo. We hypothesized that the same signaling pathway might be operational in corneal epithelial cells.

Methods

We used co-immunoprecipitation, immunohistochemistry, scratch wound healing assays in vitro, and corneal epithelial wound healing assays in vivo to determine the role of the AQP3/PLD2/PG signaling pathway in corneal epithelium.

Results

AQP3 was present in human corneas in situ, and AQP3 and PLD2 were co-immunoprecipitated from corneal epithelial cell lysates. The two proteins could also be co-immunoprecipitated from insect cells simultaneously infected with AQP3- and PLD2-expressing baculoviruses, suggesting a likely direct interaction. A particular PG, dioleoylphosphatidylglycerol (DOPG), enhanced scratch wound healing of a corneal epithelial monolayer in vitro. DOPG also accelerated corneal epithelial wound healing in vivo, both in wild-type mice and in a mouse model exhibiting impaired corneal wound healing (AQP3 knockout mice).

Conclusions

These results indicate the importance of the AQP3/PLD2/PG signaling pathway in corneal epithelial cells and suggest the possibility of developing DOPG as a pharmacologic therapy to enhance corneal wound healing in patients.

Phosphatidylserine (PS) and phosphatidylglycerol (PG) enriched mixed micelles (MM): A new nano-drug delivery system with anti-inflammatory potential?

Phosphatidylserine (PS) and phosphatidylglycerol (PG) are naturally occurring phospholipids (PL) with intrinsic anti-inflammatory properties. The therapeutic potential of PS and PG has not been extensively explored and the main focus had been directed towards PS- and PG-liposomes. In order to increase the formulation options, we explored whether mixed micelles (MM) could be an alternative to liposomes. Potential advantages of MM are their thermodynamic stability, small size and ease of manufacture. DOPS- and DOPG-enriched MM were obtained via a co-precipitation technique and physicochemical characterization was performed. The MM, approximately 10 nm in diameter, showed no toxicity on fibroblast cell lines in vitro and virtually no hemolytic activity. The MM suppressed the TNFα-production of mIFNγ/LPS-stimulated mouse peritoneal macrophages (MPM) in vitro similar to DOPS- and DOPG-liposomes. Therefore, DOPS- and DOPG-loaded MM are promising new options for the treatment of inflammatory diseases.

The lipid droplet protein Pgc1 controls the subcellular distribution of phosphatidylglycerol

The biosynthesis of yeast phosphatidylglycerol (PG) takes place in the inner mitochondrial membrane. Outside mitochondria, the abundance of PG is low. Here, we present evidence that the subcellular distribution of PG is maintained by the locally controlled enzymatic activity of the PG-specific phospholipase, Pgc1. A fluorescently labeled Pgc1 protein accumulates on the surface of lipid droplets (LD). We show, however, that LD are not only dispensable for Pgc1-mediated PG degradation, but do not even host any phospholipase activity of Pgc1. Our in vitro assays document the capability of LD-accumulated Pgc1 to degrade PG upon entry to the membranes of the endoplasmic reticulum, mitochondria and even of artificial phospholipid vesicles. Fluorescence recovery after photobleaching analysis confirms the continuous exchange of GFP-Pgc1 within the individual LD in situ, suggesting that a steady-state equilibrium exists between LD and membranes to regulate the immediate phospholipase activity of Pgc1. In this model, LD serve as a storage place and shelter Pgc1, preventing its untimely degradation, while both phospholipase activity and degradation of the enzyme occur in the membranes.

Pathogen-Associated Molecular Pattern-Induced TLR2 and TLR4 Activation Increases Keratinocyte Production of Inflammatory Mediators and is Inhibited by Phosphatidylglycerol

Skin serves not only as a protective barrier to microbial entry into the body but also as an immune organ. The outer layer, the epidermis, is composed predominantly of keratinocytes, which can be stimulated to produce proinflammatory mediators. Although some inflammation is useful to defend against infection, excessive or persistent inflammation can lead to the development of inflammatory skin diseases, such as psoriasis, a common skin disorder affecting approximately 2% of the US population. We have previously found that phosphatidylglycerol (PG) derived from soy can inhibit inflammation in a contact irritant ear edema mouse model. Here, we investigated the ability of soy PG to inhibit inflammatory mediator expression in response to activators of the pattern recognition receptors, toll-like receptor-2 (TLR2) and -4 (TLR4). We found that in epidermal keratinocytes, soy PG inhibited TLR2 and TLR4 activation and inflammatory mediator expression in response to a synthetic triacylated lipopeptide and lipopolysaccharide, respectively, as well as an endogenous danger-associated molecular pattern. However, at higher concentrations, soy PG alone enhanced the expression of some proinflammatory cytokines, suggesting a narrow therapeutic window for this lipid. Dioleoylphosphatidylglycerol (DOPG), but not dioleoylphosphatidylcholine, exerted a similar inhibitory effect, completely blocking keratinocyte inflammatory mediator expression induced by TLR2 and TLR4 activators as well as NFκB activation in a macrophage cell line (RAW264.7); however, DOPG was not itself proinflammatory even at high concentrations. Furthermore, DOPG had no effect on NFκB activation in response to a TLR7/8 agonist. Our results suggest that DOPG could be used to inhibit excessive skin inflammation. SIGNIFICANCE STATEMENT: Although inflammation is beneficial for clearing an infection, in some cases, the infection can be excessive and/or become chronic, thereby resulting in considerable tissue damage and pathological conditions. We show here that the phospholipid phosphatidylglycerol can inhibit the activation of toll-like receptors 2 and 4 of the innate immune system as well as the downstream inflammatory mediator expression in response to microbial component-mimicking agents in epidermal keratinocytes that form the physical barrier of the skin.

Upregulation of PD-L1 Expression by Prostaglandin E2 and the Enhancement of IFN-γ by Anti-PD-L1 Antibody Combined With a COX-2 Inhibitor in Mycoplasma bovis Infection

Bovine mycoplasmosis caused by Mycoplasma bovis results in pneumonia and mastitis in cattle. We previously demonstrated that the programmed death 1 (PD-1)/PD-ligand 1 (PD-L1) pathway is involved in immune dysfunction during M. bovis infection and that prostaglandin E₂ (PGE₂) suppressed immune responses and upregulated PD-L1 expression in Johne's disease, a bacterial infection in cattle. In this study, we investigated the role of PGE₂ in immune dysfunction and the relationship between PGE₂ and the PD-1/PD-L1 pathway in M. bovis infection. In vitro stimulation with M. bovis upregulated the expressions of PGE₂ and PD-L1 presumably via Toll-like receptor 2 in bovine peripheral blood mononuclear cells (PBMCs). PGE₂ levels of peripheral blood in infected cattle were significantly increased compared with those in uninfected cattle. Remarkably, plasma PGE₂ levels were positively correlated with the proportions of PD-L1⁺ monocytes in M. bovis-infected cattle. Additionally, plasma PGE₂ production in infected cattle was negatively correlated with M. bovis-specific interferon (IFN)-γ production from PBMCs. These results suggest that PGE₂ could be one of the inducers of PD-L1 expression and could be involved in immunosuppression during M. bovis infection. In vitro blockade assays using anti-bovine PD-L1 antibody and a cyclooxygenase 2 inhibitor significantly upregulated the M. bovis-specific IFN-γ response. Our study findings might contribute to the development of novel therapeutic strategies for bovine mycoplasmosis that target PGE₂ and the PD-1/PD-L1 pathway.

Pulmonary surfactant lipids inhibit infections with the pandemic H1N1 influenza virus in several animal models

The influenza A (H1N1)pdm09 outbreak in 2009 exemplified the problems accompanying the emergence of novel influenza A virus (IAV) strains and their unanticipated virulence in populations with no pre-existing immunity. Neuraminidase inhibitors (NAIs) are currently the drugs of choice for intervention against IAV outbreaks, but there are concerns that NAI-resistant viruses can transmit to high-risk populations. These issues highlight the need for new approaches that address the annual influenza burden. In this study, we examined whether palmitoyl-oleoyl-phosphatidylglycerol (POPG) and phosphatidylinositol (PI) effectively antagonize (H1N1)pdm09 infection. POPG and PI markedly suppressed cytopathic effects and attenuated viral gene expression in (H1N1)pdm09-infected Madin-Darby canine kidney cells. POPG and PI bound to (H1N1)pdm09 with high affinity and disrupted viral spread from infected to noninfected cells in tissue culture and also reduced (H1N1)pdm09 propagation by a factor of 102 after viral infection was established in vitro In a mouse infection model of (H1N1)pdm09, POPG and PI significantly reduced lung inflammation and viral burden. Of note, when mice were challenged with a typically lethal dose of 1000 plaque-forming units of (H1N1)pdm09, survival after 10 days was 100% (14 of 14 mice) with the POPG treatment compared with 0% (0 of 14 mice) without this treatment. POPG also significantly reduced inflammatory infiltrates and the viral burden induced by (H1N1)pdm09 infection in a ferret model. These findings indicate that anionic phospholipids potently and efficiently disrupt influenza infections in animal models.

Porcine versus bovine surfactant therapy for RDS in preterm neonates: pragmatic meta-analysis and review of physiopathological plausibility of the effects on extra-pulmonary outcomes

BACKGROUND

While porcine seems to be superior to bovine surfactants in terms of respiratory outcomes, it is unclear if a surfactant can improve extra-pulmonary outcomes in preterm neonates with respiratory distress syndrome and if there is any physiopathological/biological mechanism linking surfactant therapy to these outcomes. We aim to fill these knowledge gaps.

METHODS

Systematic and pragmatic review coupled with meta-analysis of randomized controlled trials of bovine or porcine surfactants administered to treat RDS in preterm neonates; common extra-pulmonary neonatal intensive care outcomes were considered. As additional analysis, animal or human translational studies about mechanisms linking surfactant replacement to extra-pulmonary neonatal outcomes were also systematically reviewed.

RESULTS

Porcine surfactant is associated with lower incidence of patent ductus arteriosus (OR:0.655; 95%CI:0.460-0.931); p = 0.018; 12 trials; 1472 patients); prenatal steroids (coeff.:-0.009, 95%CI:-0.03-0.009, p = 0.323) and gestational age (coeff.:0.079, 95%CI:-0.18-0.34, p = 0.554) did not influence this effect size. No significant differences were found between porcine and bovine surfactants on neonatal intensive care unit length of stay (mean difference (days):-2.977; 95%CI:-6.659-0.705; p = 0.113; 8 trials; 855 patients), intra-ventricular hemorrhage of any grade (OR:0.860; 95%CI:0.648-1.139); p = 0.293; 15 trials; 1703 patients), severe intra-ventricular hemorrhage (OR:0.852; 95%CI:0.624-1.163); p = 0.313; 15 trials; 1672 patients), necrotizing entero-colitis (OR:1.190; 95%CI:0.785-1.803); p = 0.412; 9 trials; 1097 patients) and retinopathy of prematurity (OR:0.801; 95%CI:0.480-1.337); p = 0.396; 10 trials; 962 patients).

CONCLUSIONS

Physiopathological mechanisms explaining the effect of surfactant have been found for patent ductus arteriosus only, while they are lacking for all other endpoints. Porcine surfactant is associated with lower incidence of PDA than bovine surfactants. As there are no differences in terms of other extra-pulmonary outcomes and no physiopathological plausibility, these endpoints should not be used in future trials.

REGISTRATION

PROSPERO n.CRD42018100906.

The Effect of n-3 PUFA Binding Phosphatidylglycerol on Metabolic Syndrome-Related Parameters and n-3 PUFA Accretion in Diabetic/Obese KK-Ay Mice

n-3 Polyunsaturated fatty acid binding phospholipids (n-3 PUFA-PLs) are known to be potent carriers of n-3 PUFAs and provide health benefits. We previously prepared n-3 PUFA binding phosphatidylglycerol (n-3 PUFA-PG) by phospholipase D-mediated transphosphatidylation. Because PG has excellent emulsifiability, n-3 PUFA-PG is expected to work as a functional molecule with properties of both PG and n-3 PUFAs. In the present study, the health benefits and tissue accretion of dietary n-3 PUFA-PG were examined in diabetic/obese KK-A^y mice. After a feeding duration over 30 days, n-3 PUFA-PG significantly reduced the total and non-HDL cholesterols in the serum of diabetic/obese KK-A^y mice. In the mice fed n-3 PUFA-PG, but not n-3 PUFA-TAG, hepatic lipid content was markedly alleviated depending on the neutral lipid reduction compared with the SoyPC-fed mice. Further, the n-3 PUFA-PG diet increased eicosapentaenoic acid and docosahexaenoic acid (DHA) and reduced arachidonic acid in the small intestine, liver, perirenal white adipose tissue, and brain, and the ratio of the n-6 PUFAs to n-3 PUFAs in those tissues became lower compared to the SoyPC-fed mice. Especially, the DHA level was more significantly elevated in the brains of n-3 PUFA-PG-fed mice compared to the SoyPC-fed mice, whereas n-3 PUFA-TAG did not significantly alter DHA in the brain. The present results indicate that n-3 PUFA-PG is a functional lipid for reducing serum and liver lipids and is able to supply n-3 PUFAs to KK-A^y mice.

Mycoplasma contamination affects cell characteristics and decreases the sensitivity of BV2 microglia to LPS stimulation

Mycoplasma is the most common contaminant and greatly affects host cells. The influence of mycoplasma on microglia cells remains unknown. Here, we investigated the influence of mycoplasma contamination on BV2 cells (a microglia cell line). We found that mycoplasma contamination increased the phosphorylation of NF-kB and MAPK signal pathway and induced the activation of BV2 cells. These mycoplasma-contaminated BV2 cells exhibited a transition of cell morphology and slower proliferation, as well as increased gene expression and protein secretion of inflammatory factors. Furthermore, mycoplasma-contaminated BV2 cells had decreased sensitivity to lipopolysaccharide stimulation. These findings suggested that mycoplasma contamination greatly influenced the characteristics and function of microglia cells. It is important to prevent and exclude mycoplasma contamination in our research.

Characterizing the Natural History of Acute Radiation Syndrome of the Gastrointestinal Tract: Combining High Mass and Spatial Resolution Using MALDI-FTICR-MSI

The acute radiation syndrome of the gastrointestinal tract has been histologically characterized, but the molecular and functional mechanisms that lead to these cellular alterations remain enigmatic. Mass spectrometry imaging is the only technique that enables the simultaneous detection and cellular or regional localization of hundreds of biomolecules in a single experiment. This current study utilized matrix-assisted laser desorption/ionization mass spectrometry imaging for the molecular characterization of the first natural history study of gastrointestinal acute radiation syndrome in the nonhuman primate. Jejunum samples were collected at days 4, 8, 11, 15, and 21 following 12-Gy partial-body irradiation with 2.5% bone marrow sparing. Mass spectrometry imaging investigations identified alterations in lipid species that further understanding of the functional alterations that occur over time in the different cellular regions of the jejunum following exposure to high doses of irradiation. Alterations in phosphatidylinositol species informed on dysfunctional epithelial cell differentiation and maturation. Differences in glycosphingolipids of the villi epithelium that would influence the absorptive capacity and functional structure of the brush border membrane were detected. Dichotomous alterations in cardiolipins indicated altered structural and functional integrity of mitochondria. Phosphatidylglycerol species, known regulators of toll-like receptors, were detected and localized to regions in the lamina propria that contained distinct immune cell populations. These results provide molecular insight that can inform on injury mechanism in a nonhuman primate model of the acute radiation syndrome of the gastrointestinal tract. Findings may contribute to the identification of therapeutic targets and the development of new medical countermeasures.

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.

Phospholipid regulation of innate immunity and respiratory viral infection

Toll-like receptors (TLRs) coupled to intracellular signaling cascades function as central elements of innate immunity that control transcription of numerous pro-inflammatory genes. Two minor anionic phospholipids present in the pulmonary surfactant complex, palmitoyl-oleoyl-phosphatidylglycerol (POPG) and phosphatidylinositol (PI), antagonize the cognate ligand activation of TLRs 2 and 4. The lipids block recognition of activating ligands by the TLRs, either directly or via the TLR4 coreceptors CD14 and MD2. Antagonism of TLR activation results in inhibition of the initiating step of the pro-inflammatory signaling pathways. Evidence for this mechanism of action comes from direct binding studies between CD14 and MD2 with POPG and PI. Additional evidence for this mechanism of antagonism also comes from monitoring the reduction of protein phosphorylation events that characterize the intracellular signaling by activated TLRs. The pathogenesis of respiratory syncytial virus (RSV) and influenza A virus (IAV) have been linked to TLR4 activation, and we examined the action of POPG and PI as potential antagonists of the pathology of these viruses. Surprisingly, POPG and PI dramatically curtail infection, in addition to inhibiting inflammatory sequelae associated with RSV and IAV infections. The mechanism of action by the lipids is disruption of virus particle binding to host cell plasma membrane receptors, required for viral uptake. The antagonism of activation of TLRs and virus binding to the alveolar epithelium by resident constituents of the pulmonary surfactant system suggests that POPG and PI function in homeostasis, to prevent inflammatory processes that result in reductions in gas exchange within the alveolar compartment.

Phosphatidylglycerol Inhibits Toll-Like Receptor-Mediated Inflammation by Danger-Associated Molecular Patterns

Psoriasis is a common skin disorder characterized by hyperproliferation and aberrant differentiation of epidermal keratinocytes and inflammation. We previously showed that phosphatidylglycerol (PG) can regulate keratinocyte function and suppress skin inflammation. Based on data suggesting that PG can inhibit toll-like receptor (TLR) activation induced by microorganisms and their components, we determined whether PG can inhibit TLR activation in response to antimicrobial peptides. These peptides, which are up-regulated in psoriasis, are known to function as danger-associated molecular patterns (i.e., DAMPs) to activate TLRs and the innate immune system. Because S100A9 is elevated in psoriatic skin and in animal models of psoriasis, we selected S100A9 as a representative antimicrobial peptide DAMP. We showed that in primary keratinocytes and a macrophage cell line, PG suppressed inflammatory mediator production induced by recombinant S100A9 functioning through both TLR2 and TLR4. In addition, PG, but not phosphatidylcholine, inhibited downstream S100A9-elicited TLR2 and NF-κB activation. These results, to our knowledge previously unreported, show PG's ability to inhibit DAMP-induced TLR activation, thereby reducing inflammatory signals. In addition, topical PG ameliorated skin lesions and inflammation in a mouse model of psoriasis. Together, these results suggest the possibility of developing PG as a therapy for psoriasis.

Mycoplasma pneumoniae and toll-like receptors: A mutual avenue

Mycoplasma pneumoniae is an intracellular bacterium leading to several complications in humans. M. pneumoniae is cleared in some cases and induces complications in others. The main responsible mechanisms regarding the controversy are yet to be cleared. Toll-like receptors (TLRs) are the important cell membrane and intracellular receptors which recognize a wide range of microbial macromolecules. The roles of TLRs in the eradication of several pathogens and also induction of their related complications have been demonstrated. This review article presents recent data about the roles of TLRs in the induction of immune responses which lead to M. pneumoniae eradication and related complications.

Soy Phosphatidylglycerol Reduces Inflammation in a Contact Irritant Ear Edema Mouse Model In Vivo

We have previously shown that phosphatidylglycerol (PG) regulates the function of keratinocytes, the predominant cells that compose the epidermis, inhibiting the proliferation of rapidly dividing keratinocytes. In particular, soy PG, a PG mixture with a high proportion of polyunsaturated fatty acids, is efficacious at inhibiting these proliferating keratinocytes. Psoriasis is a skin disorder characterized by hyperproliferation of keratinocytes and inflammation. Data in the lung suggest that PG in pulmonary surfactant inhibits inflammation. To investigate the possibility of using PG containing polyunsaturated fatty acids for the treatment of psoriasis, we examined the effect of soy PG on inflammation induced by the application of 12-O-tetradecanoylphorbol 13-acetate (TPA), a contact irritant, to mouse ears in vivo. We monitored ear thickness and weight as a measure of ear edema, as well as CD45-positive immune cell infiltration. Our results indicate that soy PG when applied together with 1,25-dihydroxyvitamin D3 (vitamin D), an agent known to acutely disrupt the skin barrier, suppressed ear edema and inhibited the infiltration of CD45-positive immune cells. On the other hand, neither PG nor vitamin D alone was effective. The combination also decreased tumor necrosis factor-α (TNFα) levels. This result suggested the possibility that PG was not permeating the skin barrier efficiently. Therefore, in a further study we applied PG in a penetration-enhancing vehicle and found that it inhibited inflammation induced by the phorbol ester and decreased CD45-positive immune cell infiltration. Our results suggest the possibility of using soy PG as a topical treatment option for psoriasis.

Phosphatidylglycerol Incorporates into Cardiolipin to Improve Mitochondrial Activity and Inhibits Inflammation

Chronic inflammation and concomitant oxidative stress can induce mitochondrial dysfunction due to cardiolipin (CL) abnormalities in the mitochondrial inner membrane. To examine the responses of mitochondria to inflammation, macrophage-like RAW264.7 cells were activated by Kdo2-Lipid A (KLA) in our inflammation model, and then the mitochondrial CL profile, mitochondrial activity, and the mRNA expression of CL metabolism-related genes were examined. The results demonstrated that KLA activation caused CL desaturation and the partial loss of mitochondrial activity. KLA activation also induced the gene upregulation of cyclooxygenase (COX)-2 and phospholipid scramblase 3, and the gene downregulation of COX-1, lipoxygenase 5, and Δ-6 desaturase. We further examined the phophatidylglycerol (PG) inhibition effects on inflammation. PG supplementation resulted in a 358-fold inhibition of COX-2 mRNA expression. PG(18:1)₂ and PG(18:2)₂ were incorporated into CLs to considerably alter the CL profile. The decreased CL and increased monolysocardiolipin (MLCL) quantity resulted in a reduced CL/MLCL ratio. KLA-activated macrophages responded differentially to PG(18:1)₂ and PG(18:2)₂ supplementation. Specifically, PG(18:1)₂ induced less changes in the CL/MLCL ratio than did PG(18:2)₂, which resulted in a 50% reduction in the CL/MLCL ratio. However, both PG types rescued 20–30% of the mitochondrial activity that had been affected by KLA activation.

Surfactant Lipids at the Host-Environment Interface. Metabolic Sensors, Suppressors, and Effectors of Inflammatory Lung Disease

The lipid composition of pulmonary surfactant is unlike that of any other body fluid. This extracellular lipid reservoir is also uniquely susceptible by virtue of its direct and continuous exposure to environmental oxidants, inflammatory agents, and pathogens. Historically, the greatest attention has been focused on those biophysical features of surfactant that serve to reduce surface tension at the air-liquid interface. More recently, surfactant lipids have also been recognized as bioactive molecules that maintain immune quiescence in the lung but can also be remodeled by the inhaled environment into neolipids that mediate key roles in inflammation, immunity, and fibrosis. This review focuses on the roles in inflammatory and infectious lung disease of two classes of native surfactant lipids, glycerophospholipids and sterols, and their corresponding oxidized species, oxidized glycerophospholipids and oxysterols. We highlight evidence that surfactant composition is sensitive to circulating lipoproteins and that the lipid milieu of the alveolus should thus be recognized as susceptible to diet and common systemic metabolic disorders. We also discuss intriguing evidence suggesting that oxidized surfactant lipids may represent an evolutionary link between immunity and tissue homeostasis that arose in the primordial lung. Taken together, the emerging picture is one in which the unique environmental susceptibility of the lung, together with its unique extracellular lipid requirements, may have made this organ both an evolutionary hub and an engine for lipid-immune cross-talk.

Tandem mass spectrometry of novel ether-linked phospholipid analogs of anionic pulmonary surfactant phospholipids

RATIONALE

Structural analogs of the bioactive lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol were synthesized with a xylitol polar head group and both diacyl and diether radyl groups. Mass spectral characterization of xylitol phospholipids (PX) was carried out using collisional activation and high-resolution mass measurements of positive molecular ion species and compared with the phosphatidylglycerol (PG) analogs.

METHODS

PX were synthesized using a transphosphatidylation reaction catalyzed by phospholipase D and purified by high-performance liquid chromatography (HPLC). Compounds were subjected to electrospray ionization and collision-induced dissociation (CID) was performed using a tandem quadrupole mass spectrometer to generate positive and negative molecular ions. Diether phospholipids were additionally analyzed by high-resolution mass spectrometry as protonated and sodiated molecular species in positive ion mode.

RESULTS

Ester-linked PX analogs behaved similarly to PG after collisional activation of [M - H]^- . The product ions formed by CID of the diether PG and PX negative ions only revealed information about the head group with no information about the aliphatic chains. In contrast, CID of protonated and sodiated diether phospholipid positive ions revealed reactions corresponding to cleavage of the ether chain, likely occurring by charge-driven reaction mechanisms.

CONCLUSIONS

Novel PX analogs with diacyl and diether radyl substituents of the glycerol backbone were characterized by tandem mass spectrometry. These unique diether phospholipid analogs enabled exploration of ether cleavage reactions of the positive molecular ion species resulting from collision-induced decomposition. Copyright © 2016 John Wiley & Sons, Ltd.

Structural analogs of pulmonary surfactant phosphatidylglycerol inhibit toll-like receptor 2 and 4 signaling

The pulmonary surfactant phospholipid, 1-palmitoyl-2-oleoylphosphatidylglycerol (POPG), potently inhibits toll-like receptor (TLR)2 and TLR4 signaling from the cell surface of macrophages. Analogs of POPG that vary in polar head group length, hydroxylation, and alkyl branching were synthesized using a phospholipase D-catalyzed transphosphatidylation reaction and a 1-palmitoyl-2-oleoyl phosphatidylcholine substrate. Lipid analogs with C3 and C4 alkyl head group length (POP-propanol and POP-butanol) are less effective than POPG as TLR2 and TLR4 antagonists. However, adding a hydroxyl group at the alkyl chain 3- or 4-position (POP-propanediols or POP-butanediols) greatly increased their inhibitory effects against TLR2 and TLR4. POP-2',2'-dimethylpropanediol is a weak inhibitor of TLR2 and TLR4 activation that results in arachidonic acid release, but an effective inhibitor of TLR4 activation that results in TNF-α production. Addition of an amino group at the alkyl-2 position (POP-2'-aminopropanediol) completely abolished the antagonism of TLRs 2 and 4. Multiple analogs strongly bind to the TLR4 coreceptors, cluster of differentiation 14 (CD14) and myeloid differentiation 2, but competition for di[3-deoxy-D-manno-octulosonyl]-lipid A binding to CD14 is the best predictor of biological activity at the cellular level. Collectively, these findings identify new compounds for antagonizing TLR2 and TLR4 activation and define structural properties of POPG analogs for discriminating between two TLR systems.

Effects of the New Generation Synthetic Reconstituted Surfactant CHF5633 on Pro- and Anti-Inflammatory Cytokine Expression in Native and LPS-Stimulated Adult CD14+ Monocytes

Background

Surfactant replacement therapy is the standard of care for the prevention and treatment of neonatal respiratory distress syndrome. New generation synthetic surfactants represent a promising alternative to animal-derived surfactants. CHF5633, a new generation reconstituted synthetic surfactant containing SP-B and SP-C analogs and two synthetic phospholipids has demonstrated biophysical effectiveness in vitro and in vivo. While several surfactant preparations have previously been ascribed immunomodulatory capacities, in vitro data on immunomodulation by CHF5633 are limited, so far. Our study aimed to investigate pro- and anti-inflammatory effects of CHF5633 on native and LPS-stimulated human adult monocytes.

Methods

Highly purified adult CD14⁺ cells, either native or simultaneously stimulated with LPS, were exposed to CHF5633, its components, or poractant alfa (Curosurf^®). Subsequent expression of TNF-α, IL-1β, IL-8 and IL-10 mRNA was quantified by real-time quantitative PCR, corresponding intracellular cytokine synthesis was analyzed by flow cytometry. Potential effects on TLR2 and TLR4 mRNA and protein expression were monitored by qPCR and flow cytometry.

Results

Neither CHF5633 nor any of its components induced inflammation or apoptosis in native adult CD14⁺ monocytes. Moreover, LPS-induced pro-inflammatory responses were not aggravated by simultaneous exposure of monocytes to CHF5633 or its components. In LPS-stimulated monocytes, exposure to CHF5633 led to a significant decrease in TNF-α mRNA (0.57 ± 0.23-fold, p = 0.043 at 4h; 0.56 ± 0.27-fold, p = 0.042 at 14h). Reduction of LPS-induced IL-1β mRNA expression was not significant (0.73 ± 0.16, p = 0.17 at 4h). LPS-induced IL-8 and IL-10 mRNA and protein expression were unaffected by CHF5633. For all cytokines, the observed CHF5633 effects paralleled a Curosurf®-induced modulation of cytokine response. TLR2 and TLR4 mRNA and protein expression were not affected by CHF5633 and Curosurf®, neither in native nor in LPS-stimulated adult monocytes.

Conclusion

The new generation reconstituted synthetic surfactant CHF5633 was tested for potential immunomodulation on native and LPS-activated adult human monocytes. Our data confirm that CHF5633 does not exert unintended pro-inflammatory effects in both settings. On the contrary, CHF5633 significantly suppressed TNF-α mRNA expression in LPS-stimulated adult monocytes, indicating potential anti-inflammatory effects.

Therapeutic applications of reconstituted HDL: When structure meets function

Reconstituted forms of HDL (rHDL) are under development for infusion as a therapeutic approach to attenuate atherosclerotic vascular disease and to reduce cardiovascular risk following acute coronary syndrome and ischemic stroke. Currently available rHDL formulations developed for clinical use contain apolipoprotein A-I (apoA-I) and one of the major lipid components of HDL, either phosphatidylcholine or sphingomyelin. Recent data have established that quantitatively minor molecular constituents of HDL particles can strongly influence their anti-atherogenic functionality. Novel rHDL formulations displaying enhanced biological activities, including cellular cholesterol efflux, may therefore offer promising prospects for the development of HDL-based, anti-atherosclerotic therapies. Indeed, recent structural and functional data identify phosphatidylserine as a bioactive component of HDL; the content of phosphatidylserine in HDL particles displays positive correlations with all metrics of their functionality. This review summarizes current knowledge of structure-function relationships in rHDL formulations, with a focus on phosphatidylserine and other negatively-charged phospholipids. Mechanisms potentially underlying the atheroprotective role of these lipids are discussed and their potential for the development of HDL-based therapies highlighted.

Pitfalls in flow cytometric analyses of surfactant-exposed human leukocytes

BACKGROUND

Surfactant replacement treatment is the standard of care for the prevention and treatment of neonatal respiratory distress syndrome in preterm infants and may also improve oxygenation in acute respiratory distress syndrome in children, adolescents and adults. Beside surface tension- and mechanical shear-reducing functions, natural surfactants have been ascribed immunomodulatory capacities. Current in vitro studies on immunomodulatory effects of pulmonary surfactant preparations on human leukocytes rely on ELISA, Western blot and polymerase chain reaction. Data obtained by flow cytometry are missing, so far, most likely due to confounding phospholipid residues. Intracellular cytokine flow cytometry in surfactant-exposed immune cells would provide information on pro- and anti-inflammatory immunomodulation at the single-cell level and would allow for integrating detailed immunophenotyping, functional assays and assessment of viability.

AIM

We implemented a flow cytometry protocol for reliable quantitative assessment of in vitro intracellular cytokine production in surfactant-exposed human lymphocytes (CD4(+)) and monocytes (CD14(+)).

METHODS

Two different permeabilization techniques were tested for their ability to provide intracellular cytokine staining in surfactant-exposed CD14(+) monocytes and CD4(+) lymphocytes. Both a commercially available solution containing saponin and ice-cold methanol were used as permeabilization reagents.

RESULTS

For both cell types, flow cytometry following saponin-based permeabilization revealed pronounced unspecific fluorescence signals in surfactant-exposed samples overlapping with the fluorescence spectra of the majority of conjugates. Autofluorescence of surfactant phospholipid particles interfered significantly with reliable quantification of fluorochrome-specific signals and conclusive analysis. Implementation of a methanol-based permeabilization protocol resulted in the elimination of confounding non-cell particle signals allowing for an accurate quantification of intracellular cytokine production.

CONCLUSION

Reliable detection of intracellular cytokines by flow cytometry may be challenging in surfactant-exposed cell samples due to significant autofluorescence of aggregated phospholipid particles. This issue has been addressed for the first time and may be of high relevance for all types of surfactant research. We demonstrate that a methanol-based permeabilization approach completely removes interfering fluorescent surfactant micelles and allows for correct evaluation of data. The successful removal of confounding surfactant phospholipids opens up a wide variety of multiparameter flow cytometry; a method that has not been applied in the field of surfactant research, yet.