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

Surfactant protein A modulates neuroinflammation in adult mice upon pulmonary infection

BACKGROUND

One of the most common entry gates for systemic infection is the lung. In humans, pulmonary infections can lead to significant neurological impairment, ranging from acute sickness behavior to long-term disorders. Surfactant proteins (SP), essential parts of the pulmonary innate immune defense, have been detected in the brain of rats and humans. Recent evidence suggests that SP-A, the major protein component of surfactant, also plays a functional role in modulating neuroinflammation. This study aimed to determine whether SP-A deficiency affects the inflammatory response in the brain of adult mice during pulmonary infection.

EXPERIMENTAL PROCEDURE

Adult male wild-type (WT, n = 72) and SP-A-deficient (SP-A-/-, n = 72) mice were oropharyngeally challenged with lipopolysaccharide (LPS), Pseudomonas aeruginosa (P. aeruginosa), or PBS (control). Both, behavioral assessment and subsequent brain tissue analysis, were performed 24, 48, and 72 h after challenge. The brain concentrations of the pro-inflammatory cytokines TNF-α, IL-6, and IL-1β were determined by ELISA. Quantitative rtPCR was used to detect SP-A mRNA expression in brain homogenates and immunohistochemistry was applied for the detection of SP-A protein expression in brain coronal slices.

RESULTS

SP-A mRNA and histological evidence of protein expression were detected in both the lungs and brains of WT mice, with significantly higher amounts in lung samples. SP-A-/- mice exhibited significantly higher baseline concentrations of brain TNF-α, IL-6, and IL-1β compared to WT mice. Oropharyngeal application of either LPS or P. aeruginosa elicited significantly higher brain levels of TNF-α and IL-1β in SP-A-/- mice compared to WT mice at all time points. In comparison, behavioral impairment as a measure of sickness behavior, was significantly stronger in WT than in SP-A-/- mice, particularly after LPS application.

CONCLUSION

SP-A is known for its anti-inflammatory role in the pulmonary immune response to bacterial infection. Recent evidence suggests that in an abdominal sepsis model SP-A deficiency can lead to increased cytokine levels in the brain. Our results extend this perception and provide evidence for an anti-inflammatory role of SP-A in the brain of adult WT mice after pulmonary infection.

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.

Lipoprotein(a) and Lung Function Are Associated in Older Adults: Longitudinal and Cross-Sectional Analyses

While numerous studies have confirmed a causal association between lipoprotein(a) [Lp(a)] and cardiovascular diseases, only a few studies have assessed the relationship between Lp(a) and pulmonary health, with inconsistent findings regarding this topic. This study's aim was to examine whether levels of serum Lp(a) are associated with lung function in a dataset of relatively healthy older adults. We used longitudinal data collected at two time points 7.4 ± 1.5 years apart from 679 participants (52% women, 68 [65-71] years old) from the Berlin Aging Study II (BASE-II). Multiple linear regression models adjusting for covariates were applied to examine the association between Lp(a) and lung function. The forced expiratory volume in one second (FEV1) and the forced vital capacity (FVC) were higher in both men and women with higher Lp(a) levels. However, since this association between lung function parameters and Lp(a) was not supported by Mendelian randomization analyses using recent genome-wide association study data, these relationships should be investigated in future work, as the observed differences are, in part, considerable and potentially clinically relevant.

Association of blood lipid profiles and asthma: A bidirectional two-sample Mendelian randomization study

BACKGROUND

Observational studies and meta-analyses have indicated associations between blood lipid profiles and asthma. However, the causal association is unknown. Therefore, this study investigated the causal relationship between blood lipid profiles and asthma using bidirectional Mendelian randomization analysis.

METHODS AND MATERIALS

Our analyses were performed using individual data from the Taiwan Biobank and summary statistics from the Asian Genetic Epidemiology Network (AGEN). The causal estimates between all genetic variants, exposures of interest and asthma were calculated using an inverse-variance weighted method based on Taiwan Biobank data from 24,853 participants (mean age, 48.8 years; 49.8% women). Sensitivity analyses, including the weighted median, MR Egger regression, MR-PRESSO, mode-based estimate, contamination mixture methods, and leave-one-out analysis, were applied to validate the results and detect pleiotropy.

RESULTS

In the inverse-variance weighted (IVW) analyses, we found evidence of a significant causal effect of an increased level of low-density lipoprotein cholesterol on asthma risk (βIVW = 1.338, p = 0.001). A genetically decreased level of high-density lipoprotein cholesterol was also associated with asthma risk (βIVW = -0.338, p = 0.01). We also found that an increased level of total cholesterol was associated with an increased risk of asthma (βIVW = 1.343, p = 0.001). Several sensitivity analyses generated consistent findings. We did not find evidence to support the causality between asthma and blood lipid profiles in either direction.

CONCLUSION

Our results supported the causal relationship between higher levels of LDL cholesterol and total cholesterol and lower levels of HDL cholesterol with an increased risk of asthma.

SCARLET (Supplemental Citicoline Administration to Reduce Lung injury Efficacy Trial): study protocol for a single-site, double-blinded, placebo-controlled, and randomized Phase 1/2 trial of i.v. citicoline (CDP-choline) in hospitalized SARS CoV-2-infected patients with hypoxemic acute respiratory failure

BACKGROUND

The SARS CoV-2 pandemic has resulted in more than 1.1 million deaths in the USA alone. Therapeutic options for critically ill patients with COVID-19 are limited. Prior studies showed that post-infection treatment of influenza A virus-infected mice with the liponucleotide CDP-choline, which is an essential precursor for de novo phosphatidylcholine synthesis, improved gas exchange and reduced pulmonary inflammation without altering viral replication. In unpublished studies, we found that treatment of SARS CoV-2-infected K18-hACE2-transgenic mice with CDP-choline prevented development of hypoxemia. We hypothesize that administration of citicoline (the pharmaceutical form of CDP-choline) will be safe in hospitalized SARS CoV-2-infected patients with hypoxemic acute respiratory failure (HARF) and that we will obtain preliminary evidence of clinical benefit to support a larger Phase 3 trial using one or more citicoline doses.

METHODS

We will conduct a single-site, double-blinded, placebo-controlled, and randomized Phase 1/2 dose-ranging and safety study of Somazina® citicoline solution for injection in consented adults of any sex, gender, age, or ethnicity hospitalized for SARS CoV-2-associated HARF. The trial is named "SCARLET" (Supplemental Citicoline Administration to Reduce Lung injury Efficacy Trial). We hypothesize that SCARLET will show that i.v. citicoline is safe at one or more of three doses (0.5, 2.5, or 5 mg/kg, every 12 h for 5 days) in hospitalized SARS CoV-2-infected patients with HARF (20 per dose) and provide preliminary evidence that i.v. citicoline improves pulmonary outcomes in this population. The primary efficacy outcome will be the SpO2:FiO2 ratio on study day 3. Exploratory outcomes include Sequential Organ Failure Assessment (SOFA) scores, dead space ventilation index, and lung compliance. Citicoline effects on a panel of COVID-relevant lung and blood biomarkers will also be determined.

DISCUSSION

Citicoline has many characteristics that would be advantageous to any candidate COVID-19 therapeutic, including safety, low-cost, favorable chemical characteristics, and potentially pathogen-agnostic efficacy. Successful demonstration that citicoline is beneficial in severely ill patients with SARS CoV-2-induced HARF could transform management of severely ill COVID patients.

TRIAL REGISTRATION

The trial was registered at www.

CLINICALTRIALS

gov on 5/31/2023 (NCT05881135).

TRIAL STATUS

Currently enrolling.

Particles in Exhaled Air (PExA): Clinical Uses and Future Implications

Access to distal airway samples to assess respiratory diseases is not straightforward and requires invasive procedures such as bronchoscopy and bronchoalveolar lavage. The particles in exhaled air (PExA) device provides a non-invasive means of assessing small airways; it captures distal airway particles (PEx) sized around 0.5-7 μm and contains particles of respiratory tract lining fluid (RTLF) that originate during airway closure and opening. The PExA device can count particles and measure particle mass according to their size. The PEx particles can be analysed for metabolites on various analytical platforms to quantitatively measure targeted and untargeted lung specific markers of inflammation. As such, the measurement of distal airway components may help to evaluate acute and chronic inflammatory conditions such as asthma, chronic obstructive pulmonary disease, acute respiratory distress syndrome, and more recently, acute viral infections such as COVID-19. PExA may provide an alternative to traditional methods of airway sampling, such as induced sputum, tracheal aspirate, or bronchoalveolar lavage. The measurement of specific biomarkers of airway inflammation obtained directly from the RTLF by PExA enables a more accurate and comprehensive understanding of pathophysiological changes at the molecular level in patients with acute and chronic lung diseases.

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.

Structure and Function of Canine SP-C Mimic Proteins in Synthetic Surfactant Lipid Dispersions

Lung surfactant is a mixture of lipids and proteins and is essential for air breathing in mammals. The hydrophobic surfactant proteins B and C (SP-B and SP-C) assist in reducing surface tension in the lung alveoli by organizing the surfactant lipids. SP-B deficiency is life-threatening, and a lack of SP-C can lead to progressive interstitial lung disease. B-YL (41 amino acids) is a highly surface-active, sulfur-free peptide mimic of SP-B (79 amino acids) in which the four cysteine residues are replaced by tyrosine. Mammalian SP-C (35 amino acids) contains two cysteine-linked palmitoyl groups at positions 5 and 6 in the N-terminal region that override the β-sheet propensities of the native sequence. Canine SP-C (34 amino acids) is exceptional because it has only one palmitoylated cysteine residue at position 4 and a phenylalanine at position 5. We developed canine SP-C constructs in which the palmitoylated cysteine residue at position 4 is replaced by phenylalanine (SP-Cff) or serine (SP-Csf) and a glutamic acid-lysine ion-lock was placed at sequence positions 20-24 of the hydrophobic helical domain to enhance its alpha helical propensity. AI modeling, molecular dynamics, circular dichroism spectroscopy, Fourier Transform InfraRed spectroscopy, and electron spin resonance studies showed that the secondary structure of canine SP-Cff ion-lock peptide was like that of native SP-C, suggesting that substitution of phenylalanine for cysteine has no apparent effect on the secondary structure of the peptide. Captive bubble surfactometry demonstrated higher surface activity for canine SP-Cff ion-lock peptide in combination with B-YL in surfactant lipids than with canine SP-Csf ion-lock peptide. These studies demonstrate the potential of canine SP-Cff ion-lock peptide to enhance the functionality of the SP-B peptide mimic B-YL in synthetic surfactant lipids.

MXSGD alleviates CsA-induced hypoimmunity lung injury by regulating microflora metabolism

Context

Ma Xing Shi Gan Decoction (MXSGD) is a traditional remedy for treating lung injuries that was developed by the Typhoid and Fever School of Pharmaceutical Biology. It has antitussive and expectorant effects, anti-inflammatory, antiviral, regulates the body's immunity, etc.

Aim

The aim of this study is to investigate whether MXSGD can ameliorate cyclosporine A (CsA)-induced hypoimmunity lung injury by regulating microflora metabolism. Methods: Establishment of a model for CsA-induced hypoimmunity lung injury. Using 16S rRNA high-throughput sequencing and LC-MS, the effects of MXSGD on gut flora and lung tissue microecology of mice with CsA-induced hypoimmunity were investigated.

Results

MXSGD was able to preserve lung tissue morphology and structure, reduce serum inflammatory marker expression and protect against CsA-induced lung tissue damage. Compared to the model, MXSGD increased beneficial gut bacteria: Eubacterium ventriosum group and Eubacterium nodatum group; decreased intestinal pathogens: Rikenellaceae RC9 intestinal group; reduced the abundance of Chryseobacterium and Acinetobacter, promoted the production of Lactobacillus and Streptococcus, and then promoted the lung flora to produce short-chain fatty acids. MXSGD was able to enhance the expression of serum metabolites such as Americine, 2-hydroxyhexadecanoylcarnitine, Emetine, All-trans-decaprenyl diphosphate, Biliverdin-IX-alpha, Hordatin A and N-demethyl mifepristone in the CsA-induced hypoimmunity lung injury model.

Conclusion

MXSGD can restore gut and lung microbiota diversity and serum metabolite changes to inhibit inflammation, ameliorate CsA-induced hypoimmunity lung injury.

Optimization of bronchoalveolar lavage fluid volume for untargeted lipidomic method and application in influenza A virus infection

Bronchoalveolar lavage (BAL) has been widely applied for the diagnosis of pulmonary diseases in clinical as it was recognized as a minimally invasive, well-tolerated and easily performed procedure. Lipid analysis of BAL fluid is a comprehensive strategy to observe lipid phenotypes, explore potential biomarkers, and elucidate the biological mechanisms of respiratory diseases. However, the highly diverse concentration of lipids in BAL fluid due to the deviation between the retrieved and injected aliquot volumes during lavage raised a challenge in obtaining high-quality lipidomic data. Here, this study aims to investigate what volume of BAL fluid is suitable for lipidomic analysis. Specifically, the BAL fluid harvested from H1N1 infected mice and controls was concentrated to varying degrees by freeze-drying technique before preparation for lipidomic analysis. The optimal concentration multiple of BAL fluid was approved by comparing the coverage and quality of identified lipids, as well as the number of differentially expressed lipids in the H1N1 infection model. Sixty-two differential lipids were identified respectively in the positive and negative modes when the BAL fluid was condensed five times, and they were classified into glycerolipids, phospholipids and fatty acids. This study focuses on the alterations of phospholipids, since they are the main constituents of pulmonary surfactants. Several phospholipids significantly accumulated in the BAL fluid of H1N1-infected mice, while most of them contained omega-3 polyunsaturated fatty acids, indicating disrupted inflammatory homeostasis in lungs. This study recommends freeze-drying/reconstitution prior to lipid extraction from BAL fluid for lipidomic analysis, as this procedure increased the richness and abundance of lipids.

Association between serum high-density lipoprotein cholesterol and lung function in adults: three cross-sectional studies from US and Korea National Health and Nutrition Examination Survey

INTRODUCTION

Cholesterol is an irreplaceable nutrient in pulmonary metabolism; however, studies on high-density lipoprotein cholesterol (HDL-C) levels have shown conflicting results regarding lung function. Therefore, we investigated the association between lung function and HDL-C levels in three cross-sectional studies conducted in the USA and South Korea.

METHODS

US National Health and Nutrition Examination Survey (NHANES) III, US NHANES 2007-2012, and Korea National Health and Nutrition Examination Survey (KNHANES) IV-VII performed spirometry and met the American Thoracic Society recommendations. Multiple linear regression models were used to determine the relationship between serum lipid levels and lung function. The models were adjusted for age, sex, household income, body mass index, smoking pack year, use of lipid-lowering medication and race. Serum HDL-C levels were classified into three groups to assess the dose-response relationship according to the guideline from the National Cholesterol Education Program-Adult Treatment Panel III.

RESULTS

The adult participants of the KNHANES (n=31 288), NHANES III (n=12 182) and NHANES 2007-2012 (n=9122) were analysed. Multivariate linear regression analysis of the serum cholesterol profiles revealed that only serum HDL-C was associated with forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) in all three studies. A 1 SD increase in the HDL-C level increased the percent predicted FVC by 0.5%-1.5% p, and the per cent predicted FEV1 by 0.5%-1.7% p. In terms of HDL-C levels, correlations between the HDL-C groups and the per cent predicted FVC and FEV1 showed dose-response relationships. Compared with the normal group, high HDL-C levels increased FVC by 0.75%-1.79% p and FEV1 by 0.55%-1.90% p, while low levels led to 0.74%-2.19% p and 0.86%-2.68% p reductions in FVC and FEV1, respectively. Subgroup analyses revealed weaker associations in females from KNHANES and NHANES III.

CONCLUSION

In the three nationwide cross-sectional studies, high HDL-C levels were associated with improved FVC and FEV1. However, future studies are needed to confirm this correlation and elucidate the underlying mechanisms.

Analysis of tissue lipidomics and computed tomography pulmonary fat attenuation volume (CTPFAV ) in idiopathic pulmonary fibrosis

BACKGROUND AND OBJECTIVE

There is increasing interest in the role of lipids in processes that modulate lung fibrosis with evidence of lipid deposition in idiopathic pulmonary fibrosis (IPF) histological specimens. The aim of this study was to identify measurable markers of pulmonary lipid that may have utility as IPF biomarkers.

STUDY DESIGN AND METHODS

IPF and control lung biopsy specimens were analysed using a unbiased lipidomic approach. Pulmonary fat attenuation volume (PFAV) was assessed on chest CT images (CTPFAV ) with 3D semi-automated lung density software. Aerated lung was semi-automatically segmented and CTPFAV calculated using a Hounsfield-unit (-40 to -200HU) threshold range expressed as a percentage of total lung volume. CTPFAV was compared to pulmonary function, serum lipids and qualitative CT fibrosis scores.

RESULTS

There was a significant increase in total lipid content on histological analysis of IPF lung tissue (23.16 nmol/mg) compared to controls (18.66 mol/mg, p = 0.0317). The median CTPFAV in IPF was higher than controls (1.34% vs. 0.72%, p < 0.001) and CTPFAV correlated significantly with DLCO% predicted (R2  = 0.356, p < 0.0001) and FVC% predicted (R2  = 0.407, p < 0.0001) in patients with IPF. CTPFAV correlated with CT features of fibrosis; higher CTPFAV was associated with >10% reticulation (1.6% vs. 0.94%, p = 0.0017) and >10% honeycombing (1.87% vs. 1.12%, p = 0.0003). CTPFAV showed no correlation with serum lipids.

CONCLUSION

CTPFAV is an easily quantifiable non-invasive measure of pulmonary lipids. In this pilot study, CTPFAV correlates with pulmonary function and radiological features of IPF and could function as a potential biomarker for IPF disease severity assessment.

Metabolic heterogeneity of tissue-resident macrophages in homeostasis and during helminth infection

Tissue-resident macrophage populations constitute a mosaic of phenotypes, yet how their metabolic states link to the range of phenotypes and functions in vivo is still poorly defined. Here, using high-dimensional spectral flow cytometry, we observe distinct metabolic profiles between different organs and functionally link acetyl CoA carboxylase activity to efferocytotic capacity. Additionally, differences in metabolism are evident within populations from a specific site, corresponding to relative stages of macrophage maturity. Immune perturbation with intestinal helminth infection increases alternative activation and metabolic rewiring of monocyte-derived macrophage populations, while resident TIM4+ intestinal macrophages remain immunologically and metabolically hyporesponsive. Similar metabolic signatures in alternatively-activated macrophages are seen from different tissues using additional helminth models, but to different magnitudes, indicating further tissue-specific contributions to metabolic states. Thus, our high-dimensional, flow-based metabolic analyses indicates complex metabolic heterogeneity and dynamics of tissue-resident macrophage populations at homeostasis and during helminth infection.

Analysis of serum metabolome of laborers exposure to welding fume

OBJECTIVE

Welding fume exposure is inevitable of welding workers and poses a severe hazard to their health since welding is a necessary industrial process. Thus, preclinical diagnostic symptoms of worker exposure are of great importance. The aim of this study was to screen serum differential metabolites of welding fume exposure based on UPLC-QTOF-MS/MS.

METHODS

In 2019, 49 participants were recruited at a machinery manufacturing factory. The non-target metabolomics technique was used to clarify serum metabolic signatures in people exposed to welding fume. Differential metabolites were screened by OPLS-DA analysis and Student's t-test. The receiver operating characteristic curve evaluated the discriminatory power of differential metabolites. And the correlations between differential metabolites and metal concentrations in urine and whole blood were analyzed utilizing Pearson correlation analysis.

RESULTS

Thirty metabolites were increased significantly, and 5 metabolites were decreased. The differential metabolites are mainly enriched in the metabolism of arachidonic acid, glycero phospholipid, linoleic acid, and thiamine. These results observed that lysophosphatidylcholine (20:1/0:0) and phosphatidylglycerol(PGF1α/16:0) had a tremendous anticipating power with relatively increased AUC values (AUC > 0.9), and they also presented a significant correlation of Mo concentrations in whole blood and Cu concentrations in urine, respectively.

CONCLUSION

The serum metabolism was changed significantly after exposure to welding fume. Lysophosphatidylcholine (20:1/0:0) and phosphatidylglycerol (PGF1α/16:0) may be a potential biological mediator and biomarker for laborers exposure to welding fume.

Alveolar type II epithelial cell FASN maintains lipid homeostasis in experimental COPD

Alveolar epithelial type II (AEC2) cells strictly regulate lipid metabolism to maintain surfactant synthesis. Loss of AEC2 cell function and surfactant production are implicated in the pathogenesis of the smoking-related lung disease chronic obstructive pulmonary disease (COPD). Whether smoking alters lipid synthesis in AEC2 cells and whether altering lipid metabolism in AEC2 cells contributes to COPD development are unclear. In this study, high-throughput lipidomic analysis revealed increased lipid biosynthesis in AEC2 cells isolated from mice chronically exposed to cigarette smoke (CS). Mice with a targeted deletion of the de novo lipogenesis enzyme, fatty acid synthase (FASN), in AEC2 cells (FasniΔAEC2) exposed to CS exhibited higher bronchoalveolar lavage fluid (BALF) neutrophils, higher BALF protein, and more severe airspace enlargement. FasniΔAEC2 mice exposed to CS had lower levels of key surfactant phospholipids but higher levels of BALF ether phospholipids, sphingomyelins, and polyunsaturated fatty acid-containing phospholipids, as well as increased BALF surface tension. FasniΔAEC2 mice exposed to CS also had higher levels of protective ferroptosis markers in the lung. These data suggest that AEC2 cell FASN modulates the response of the lung to smoke by regulating the composition of the surfactant phospholipidome.

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.

CES1 Releases Oxylipins from Oxidized Triacylglycerol (oxTAG) and Regulates Macrophage oxTAG/TAG Accumulation and PGE2/IL-1β Production

Triacylglycerols (TAGs) are storage forms of fat, primarily found in cytoplasmic lipid droplets in cells. TAGs are broken down to their component free fatty acids by lipolytic enzymes when fuel reserves are required. However, polyunsaturated fatty acid (PUFA)-containing TAGs are susceptible to nonenzymatic oxidation reactions, leading to the formation of oxylipins that are esterified to the glycerol backbone (termed oxTAGs). Human carboxylesterase 1 (CES1) is a member of the serine hydrolase superfamily and defined by its ability to catalyze the hydrolysis of carboxyl ester bonds in both toxicants and lipids. CES1 is a bona fide TAG hydrolase, but it is unclear which specific fatty acids are preferentially released during lipolysis. To better understand the biochemical function of CES1 in immune cells, such as macrophages, its substrate selectivity when it encounters oxidized PUFAs in TAG lipid droplets requires study. We sought to identify those esterified oxidized fatty acids liberated from oxTAGs by CES1 because their release can activate signaling pathways that enforce the development of lipid-driven inflammation. Gaining this knowledge will help fill data gaps that exist between CES1 and the lipid-sensing nuclear receptors, PPARγ and LXRα, which are important drivers of lipid metabolism and inflammation in macrophages. Oxidized forms of triarachidonoylglycerol (oxTAG20:4) or trilinoleoylglycerol (oxTAG18:2), which contain physiologically relevant levels of oxidized PUFAs (<5 mol %), were incubated with recombinant CES1 to release oxylipins and nonoxidized arachidonic acid (AA) or linoleic acid (LA). CES1 hydrolyzed each oxTAG, yielding regioisomers of hydroxyeicosatetraenoic acids (5-, 11-, 12-, and 15-HETE) and hydroxyoctadecadienoic acids (9- and 13-HODE). Furthermore, human THP-1 macrophages with deficient CES1 levels exhibited a differential response to extracellular stimuli (oxTAGs, lipopolysaccharide, and 15-HETE) as compared to those with normal CES1 levels, including enhanced oxTAG/TAG lipid accumulation and altered cytokine and prostaglandin E2 profiles. This study suggests that CES1 can metabolize oxTAG lipids to release oxylipins and PUFAs, and it further specifies the substrate selectivity of CES1 in the metabolism of bioactive lipid mediators. We suggest that the accumulation of oxTAGs/TAGs within lipid droplets that arise due to CES1 deficiency enforces an inflammatory phenotype in macrophages.

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.

Stratification of asthma by lipidomic profiling of induced sputum supernatant

BACKGROUND

Asthma is a chronic respiratory disease with significant heterogeneity in its clinical presentation and pathobiology. There is need for improved understanding of respiratory lipid metabolism in asthma patients and its relation to observable clinical features.

OBJECTIVE

We performed a comprehensive, prospective, cross-sectional analysis of the lipid composition of induced sputum supernatant obtained from asthma patients with a range of disease severities, as well as from healthy controls.

METHODS

Induced sputum supernatant was collected from 211 adults with asthma and 41 healthy individuals enrolled onto the U-BIOPRED (Unbiased Biomarkers for the Prediction of Respiratory Disease Outcomes) study. Sputum lipidomes were characterized by semiquantitative shotgun mass spectrometry and clustered using topologic data analysis to identify lipid phenotypes.

RESULTS

Shotgun lipidomics of induced sputum supernatant revealed a spectrum of 9 molecular phenotypes, highlighting not just significant differences between the sputum lipidomes of asthma patients and healthy controls, but also within the asthma patient population. Matching clinical, pathobiologic, proteomic, and transcriptomic data helped inform the underlying disease processes. Sputum lipid phenotypes with higher levels of nonendogenous, cell-derived lipids were associated with significantly worse asthma severity, worse lung function, and elevated granulocyte counts.

CONCLUSION

We propose a novel mechanism of increased lipid loading in the epithelial lining fluid of asthma patients resulting from the secretion of extracellular vesicles by granulocytic inflammatory cells, which could reduce the ability of pulmonary surfactant to lower surface tension in asthmatic small airways, as well as compromise its role as an immune regulator.

Association of Metabolites, Nutrients, and Toxins in Maternal and Cord Serum with Asthma, IgE, SPT, FeNO, and Lung Function in Offspring

The role of metabolites, nutrients, and toxins (MNTs) in sera at the end of pregnancy and of their association with offspring respiratory and allergic disorders is underexplored. Untargeted approaches detecting a variety of compounds, known and unknown, are limited. In this cohort study, we first aimed at discovering associations of MNTs in grandmaternal (F0) serum with asthma, immunoglobulin E, skin prick tests, exhaled nitric oxide, and lung function parameters in their parental (F1) offspring. Second, for replication, we tested the identified associations of MNTs with disorders in their grandchildren (F2-offspring) based on F2 cord serum. The statistical analyses were sex-stratified. Using liquid chromatography/high-resolution mass spectrometry in F0, we detected signals for 2286 negative-ion lipids, 59 positive-ion lipids, and 6331 polar MNTs. Nine MNTs (one unknown MNT) discovered in F0-F1 and replicated in F2 showed higher risks of respiratory/allergic outcomes. Twelve MNTs (four unknowns) constituted a potential protection in F1 and F2. We recognized MNTs not yet considered candidates for respiratory/allergic outcomes: a phthalate plasticizer, an antihistamine, a bile acid metabolite, tryptophan metabolites, a hemiterpenoid glycoside, triacylglycerols, hypoxanthine, and polyphenol syringic acid. The findings suggest that MNTs are aspirants for clinical trials to prevent adverse respiratory/allergic outcomes.

The effect of natural surfactants on the development of postoperative intraabdominal adhesion

Background/aim

The development of postoperative adhesion after abdominal surgery is sometimes a severe problem. Our study investigates the effectiveness of exogenous surfactant application in preventing adhesion development in the experimental adhesion model.

Materials and methods

This randomized-controlled interventional study was carried out in the animal laboratory of Kahramanmaraş Sütçü İmam University between March 1 and March 31, 2020. An experimental intra-abdominal adhesion model was established in 24 adult female rats by cecal abrasion. Rats were randomly divided into four groups. Groups I, II, and III were taken intraperitoneally as beractant, poractant, and calfactant applied groups, respectively. Group IV was the control group. Relaparotomy was performed in all groups on the 15th postoperative day, and intra-abdominal adhesions were scored macroscopically according to the Canbaz scoring system. In addition, the cecal regions were evaluated microscopically and scored according to the Zühlke microscopic classification system. The scores of the groups were compared statistically.

Results

The Zühlke adhesion development score was significantly lower in the exogenous surfactant applied groups. In addition, when the surfactant-applied groups were compared among themselves, it was seen that the adhesion score in the beractant group was significantly better than the other surfactant types (p < 0.01).

Conclusion

Our study results showed that prophylactic intraperitoneal surfactant application significantly reduced postoperative adhesion development, particularly beractant.

Aqueous extract of Platycodon grandiflorus attenuates lipopolysaccharide-induced apoptosis and inflammatory cell infiltration in mouse lungs by inhibiting PI3K/Akt signaling

BACKGROUND

Acute lung injury (ALI), an acute inflammatory lung disease, can cause a rapid inflammatory response in clinic, which endangers the patient's life. The components of platycodon grandiflorum, such as platycodins have a wide range of pharmacological activities such as expectorant, anti-apoptotic, anti-inflammatory, anti-tumor and anti-oxidant properties, and can be used for improving human immunity. Previous studies have shown that aqueous extract of platycodon grandiflorum (PAE) has a certain protective effect on ALI, but the main pharmacodynamic components and the mechanism of action are not clear.

METHODS

The anti-inflammatory properties of PAE were studied using the lipopolysaccharide (LPS)-induced ALI animal model. Hematoxylin and eosin stains were used to assess the degree of acute lung damage. Changes in RNA levels of pro-inflammatory cytokines in the lungs were measured using quantitative RT-qPCR. The potential molecular mechanism of PAE preventing ALI was predicted by lipidomics and network pharmacology. To examine the anti-apoptotic effects of PAE, TdT-mediated dUTP nick-end labelling (TUNEL) was employed to determine apoptosis-related variables. The amounts of critical pathway proteins and apoptosis-related proteins were measured using Western blotting.

RESULTS

Twenty-six chemical components from the PAE were identified, and their related pathways were obtained by the network pharmacology. Combined with the analysis of network pharmacology and literature, it was found that the phosphatidylinositol 3 kinase (PI3K)/protein kinase B (AKT) signaling pathway is related to ALI. The results of lipidomics show that PAE alleviates ALI via regulating lung lipids especially phosphatidylinositol (PI). Finally, the methods of molecular biology were used to verify the mechanism of PAE. It can be found that PAE attenuates the inflammatory response to ALI by inhibiting apoptosis through PI3K/Akt signaling pathway.

CONCLUSION

The study revealed that the PAE attenuates lipopolysaccharide-induced apoptosis and inflammatory cell infiltration in mouse lungs by inhibiting PI3K/Akt signaling. Furthermore, our findings provide a novel strategy for the application of PAE as a potential agent for preventing patients with ALI.

Oxidative phosphorylation selectively orchestrates tissue macrophage homeostasis

In vitro studies have associated oxidative phosphorylation (OXPHOS) with anti-inflammatory macrophages, whereas pro-inflammatory macrophages rely on glycolysis. However, the metabolic needs of macrophages in tissues (TMFs) to fulfill their homeostatic activities are incompletely understood. Here, we identified OXPHOS as the highest discriminating process among TMFs from different organs in homeostasis by analysis of RNA-seq data in both humans and mice. Impairing OXPHOS in TMFs via Tfam deletion differentially affected TMF populations. Tfam deletion resulted in reduction of alveolar macrophages (AMs) due to impaired lipid-handling capacity, leading to increased cholesterol content and cellular stress, causing cell-cycle arrest in vivo. In obesity, Tfam depletion selectively ablated pro-inflammatory lipid-handling white adipose tissue macrophages (WAT-MFs), thus preventing insulin resistance and hepatosteatosis. Hence, OXPHOS, rather than glycolysis, distinguishes TMF populations and is critical for the maintenance of TMFs with a high lipid-handling activity, including pro-inflammatory WAT-MFs. This could provide a selective therapeutic targeting tool.

Phenotypic changes in low-density lipoprotein particles as markers of adverse clinical outcomes in COVID-19

BACKGROUND AND AIMS

Low-density lipoprotein (LDL) plasma concentration decline is a biomarker for acute inflammatory diseases, including coronavirus disease-2019 (COVID-19). Phenotypic changes in LDL during COVID-19 may be equally related to adverse clinical outcomes.

METHODS

Individuals hospitalized due to COVID-19 (n = 40) were enrolled. Blood samples were collected on days 0, 2, 4, 6, and 30 (D0, D2, D4, D6, and D30). Oxidized LDL (ox-LDL), and lipoprotein-associated phospholipase A2 (Lp-PLA2) activity were measured. In a consecutive series of cases (n = 13), LDL was isolated by gradient ultracentrifugation from D0 and D6 and was quantified by lipidomic analysis. Association between clinical outcomes and LDL phenotypic changes was investigated.

RESULTS

In the first 30 days, 42.5% of participants died due to Covid-19. The serum ox-LDL increased from D0 to D6 (p < 0.005) and decreased at D30. Moreover, individuals who had an ox-LDL increase from D0 to D6 to over the 90th percentile died. The plasma Lp-PLA2 activity also increased progressively from D0 to D30 (p < 0.005), and the change from D0 to D6 in Lp-PLA2 and ox-LDL were positively correlated (r = 0.65, p < 0.0001). An exploratory untargeted lipidomic analysis uncovered 308 individual lipids in isolated LDL particles. Paired-test analysis from D0 and D6 revealed higher concentrations of 32 lipid species during disease progression, mainly represented by lysophosphatidyl choline and phosphatidylinositol. In addition, 69 lipid species were exclusively modulated in the LDL particles from non-survivors as compared to survivors.

CONCLUSIONS

Phenotypic changes in LDL particles are associated with disease progression and adverse clinical outcomes in COVID-19 patients and could serve as a potential prognostic biomarker.

Biomarkers for Lipid and Albumin Metabolism in Hospitalized Patients with Underlying Diseases and Community-Acquired Pneumonia Caused by Bacterial or SARS-CoV-2 Infection

Background

To look at the differences and similarities in albumin and lipid metabolism in non-severe COVID-19 infection, non-severe community-acquired pneumonia, and severe community pneumonia with underlying diseases, as well as the relationship between albumin and lipid metabolism and inflammatory mediators.

Methods

This retrospective analysis comprised 253 individuals with bacterial pneumonia and COVID-19 infection (1 May 2021-1 May 2022). Routine blood examination, blood lipid levels, albumin level, C-reactive protein (CRP) levels, coagulation function, cardiac enzymes, liver function, renal function, immunological function, and bacterial culture were also collected. Correlation analysis was performed using Spearman's test for lipid parameter and Inflammatory factors in the blood. Furthermore, the multiple linear regression (MLR) analysis was employed to analyze the multicollinearity in lipidomics data. The statistical analysis was performed using SPSS statistic version 19.0.

Results

There were 63 (24.90%) non-severe community-acquired pneumonia patients (NSCAP), 48 (18.97%) severe community-acquired pneumonia patients (SCAP), 112 (44.27%) non-severe COVID-19 infection patients (NSCOV), and 30 (11.86%) healthy volunteers (HV). In all, 45.59% (116/253) of the patients had underlying diseases. Patients with community-acquired pneumonia had lower albumin and cholesterol levels than those with non-severe COVID-19 infection and healthy controls (t = -3.81, -2.09, P = 0.00, 0.04). Albumin, triglyceride, cholesterol, and LDL-C levels in peripheral blood were considerably lower in the SCAP group than in the NSCAP group. Albumin, cholesterol, HDL-C, LDL-C, and aop-A were all inversely connected with CRP in the SCAP with underlying illness group, but cholesterol level was favorably correlated with lymphocyte count (R = 0.36, P = 0.01). Hypoproteinemia, hypotriglyceridemia, and an elevated neutrophil-to-lymphocyte count ratio are all risk factors for severe community-acquired pneumonia.

Conclusion

Hypoalbuminemia and abnormal lipid metabolism are important indicators of bacterial infection, especially severe bacterial pneumonia.

Physiology and pathophysiology of human airway mucus

The mucus clearance system is the dominant mechanical host defense system of the human lung. Mucus is cleared from the lung by cilia and airflow, including both two-phase gas-liquid pumping and cough-dependent mechanisms, and mucus transport rates are heavily dependent on mucus concentration. Importantly, mucus transport rates are accurately predicted by the gel-on-brush model of the mucociliary apparatus from the relative osmotic moduli of the mucus and periciliary-glycocalyceal (PCL-G) layers. The fluid available to hydrate mucus is generated by transepithelial fluid transport. Feedback interactions between mucus concentrations and cilia beating, via purinergic signaling, coordinate Na+ absorptive vs Cl- secretory rates to maintain mucus hydration in health. In disease, mucus becomes hyperconcentrated (dehydrated). Multiple mechanisms derange the ion transport pathways that normally hydrate mucus in muco-obstructive lung diseases, e.g., cystic fibrosis (CF), chronic obstructive pulmonary disease (COPD), non-CF bronchiectasis (NCFB), and primary ciliary dyskinesia (PCD). A key step in muco-obstructive disease pathogenesis is the osmotic compression of the mucus layer onto the airway surface with the formation of adherent mucus plaques and plugs, particularly in distal airways. Mucus plaques create locally hypoxic conditions and produce airflow obstruction, inflammation, infection, and, ultimately, airway wall damage. Therapies to clear adherent mucus with hydrating and mucolytic agents are rational, and strategies to develop these agents are reviewed.

Dietary Cholesterol Metabolite Regulation of Tissue Immune Cell Development and Function

Obesity is considered the primary environmental factor associated with morbidity and severity of wide-ranging inflammatory disorders. The molecular mechanism linking high-fat or cholesterol diet to imbalances in immune responses, beyond the increased production of generic inflammatory factors, is just beginning to emerge. Diet cholesterol by-products are now known to regulate function and migration of diverse immune cell subsets in tissues. The hydroxylated metabolites of cholesterol oxysterols as central regulators of immune cell positioning in lymphoid and mucocutaneous tissues is the focus of this review. Dedicated immunocyte cell surface receptors sense spatially distributed oxysterol tissue depots to tune cell metabolism and function, to achieve the "right place at the right time" axiom of efficient tissue immunity.

Targeting autophagy regulation in NLRP3 inflammasome-mediated lung inflammation in COVID-19

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Emerging evidence indicates that the NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome is activated, which results in a cytokine storm at the late stage of COVID-19. Autophagy regulation is involved in the infection and replication of SARS-CoV-2 at the early stage and the inhibition of NLRP3 inflammasome-mediated lung inflammation at the late stage of COVID-19. Here, we discuss the autophagy regulation at different stages of COVID-19. Specifically, we highlight the therapeutic potential of autophagy activators in COVID-19 by inhibiting the NLRP3 inflammasome, thereby avoiding the cytokine storm. We hope this review provides enlightenment for the use of autophagy activators targeting the inhibition of the NLRP3 inflammasome, specifically the combinational therapy of autophagy modulators with the inhibitors of the NLRP3 inflammasome, antiviral drugs, or anti-inflammatory drugs in the fight against COVID-19.

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.

Insights Gained Into the Treatment of COVID19 by Pulmonary Surfactant and Its Components

Pulmonary surfactant constitutes an important barrier that pathogens must cross to gain access to the rest of the organism via the respiratory surface. The presence of pulmonary surfactant prevents the dissemination of pathogens, modulates immune responses, and optimizes lung biophysical activity. Thus, the application of pulmonary surfactant for the treatment of respiratory diseases provides an effective strategy. Currently, several clinical trials are investigating the use of surfactant preparations to treat patients with coronavirus disease 2019 (COVID-19). Some factors have been considered in the application of pulmonary surfactant for the treatment COVID-19, such as mechanical ventilation strategy, timing of treatment, dose delivered, method of delivery, and preparation utilized. This review supplements this list with two additional factors: accurate measurement of surfactants in patients and proper selection of pulmonary surfactant components. This review provides a reference for ongoing exogenous surfactant trials involving patients with COVID-19 and provides insight for the development of surfactant preparations for the treatment of viral respiratory infections.

Tissue Imprinting on 2D Nanoflakes-Capped Silicon Nanowires for Lipidomic Mass Spectrometry Imaging and Cancer Diagnosis

Spatially resolved tissue lipidomics is essential for accurate intraoperative and postoperative cancer diagnosis by revealing molecular information in the tumor microenvironment. Matrix-free laser desorption ionization mass spectrometry imaging (LDI-MSI) is an emerging attractive technology for label-free visualization of metabolites distributions in biological specimens. However, the development of LDI-MSI technology that could conveniently and authentically reveal molecular distribution on tissue samples is still a challenge. Herein, we present a tissue imprinting technology by retaining tissue lipids on 2D nanoflakes-capped silicon nanowires (SiNWs) for further mass spectrometry imaging and cancer diagnosis. The 2D nanoflakes were prepared by liquid exfoliation of molybdenum disulfide (MoS₂) with nitrogen-doped graphene quantum dots (NGQDs), which serve as both intercalation agent and dispersant. The obtained NGQD@MoS₂ nanoflakes were then decorated on the tip of vertical SiNWs, forming a hybrid NGQD@MoS₂/SiNWs nanostructure, which display excellent lipid extraction ability, enhanced LDI efficiency and molecule imaging capability. The peak number and total ion intensity of different lipids species on animal lung tissues obtained by tissue imprinting LDI-MSI on NGQD@MoS₂/SiNWs were ∼4-5 times greater than those on SiNWs substrate. As a proof-of-concept demonstration, the NGQD@MoS₂/SiNWs nanostructure was further applied to visualize phospholipids on sliced non small cell lung cancer (NSCLC) tissue along with the adjacent normal tissue. On the basis of selected feature lipids and machine learning algorithm, a prediction model was constructed to discriminate NSCLC tissues from the adjacent normal tissues with an accuracy of 100% for the discovery cohort and 91.7% for the independent validation cohort.

Deuterated Arachidonic Acid Ameliorates Lipopolysaccharide-Induced Lung Damage in Mice

Arachidonic acid (ARA) is a major component of lipid bilayers as well as the key substrate for the eicosanoid cascades. ARA is readily oxidized, and its non-enzymatic and enzymatic oxidation products induce inflammatory responses in nearly all tissues, including lung tissues. Deuteration at bis-allylic positions substantially decreases the overall rate of ARA oxidation when hydrogen abstraction is an initiating event. To compare the effects of dosing of arachidonic acid (H-ARA) and its bis-allylic hexadeuterated form (D-ARA) on lungs in conventionally healthy mice and in an acute lung injury model, mice were dosed with H-ARA or D-ARA for six weeks through dietary supplementation and then challenged with intranasal lipopolysaccharide (LPS) for subsequent analysis of bronchoalveolar lavage fluid and lung tissue. Dosing on D-ARA resulted in successful incorporation of D-ARA into various tissues. D-ARA significantly reduced LPS-induced adverse effects on alveolar septal thickness and the bronchoalveolar area. Oral deuterated ARA is taken up efficiently and protects against adverse LPS-induced pathology. This suggests novel therapeutic avenues for reducing lung damage during severe infections and other pathological conditions with inflammation in the pulmonary system and other inflammatory diseases.

Lung targeted liposomes for treating ARDS

Acute Respiratory Distress Syndrome (ARDS), associated with Covid-19 infections, is characterized by diffuse lung damage, inflammation and alveolar collapse that impairs gas exchange, leading to hypoxemia and patient’ mortality rates above 40%. Here, we describe the development and assessment of 100-nm liposomes that are tailored for pulmonary delivery for treating ARDS, as a model for lung diseases. The liposomal lipid composition (primarily DPPC) was optimized to mimic the lung surfactant composition, and the drug loading process of both methylprednisolone (MPS), a steroid, and N-acetyl cysteine (NAC), a mucolytic agent, reached an encapsulation efficiency of 98% and 92%, respectively. In vitro, treating lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages with the liposomes decreased TNFα and nitric oxide (NO) secretion, while NAC increased the penetration of nanoparticles through the mucus. In vivo, we used LPS-induced lung inflammation model to assess the accumulation and therapeutic efficacy of the liposomes in C57BL/6 mice, either by intravenous (IV), endotracheal (ET) or IV plus ET nanoparticles administrations.

Using both administration methods, liposomes exhibited an increased accumulation profile in the inflamed lungs over 48 h. Interestingly, while IV-administrated liposomes distributed widely throughout the lung, ET liposomes were present in lungs parenchyma but were not detected at some distal regions of the lungs, possibly due to imperfect airflow regimes. Twenty hours after the different treatments, lungs were assessed for markers of inflammation. We found that the nanoparticle treatment had a superior therapeutic effect compared to free drugs in treating ARDS, reducing inflammation and TNFα, IL-6 and IL-1β cytokine secretion in bronchoalveolar lavage (BAL), and that the combined treatment, delivering nanoparticles IV and ET simultaneously, had the best outcome of all treatments. Interestingly, also the DPPC lipid component alone played a therapeutic role in reducing inflammatory markers in the lungs. Collectively, we show that therapeutic nanoparticles accumulate in inflamed lungs holding potential for treating lung disorders.

Significance

In this study we compare intravenous versus intratracheal delivery of nanoparticles for treating lung disorders, specifically, acute respiratory distress syndrome (ARDS). By co-loading two medications into lipid nanoparticles, we were able to reduce both inflammation and mucus secretion in the inflamed lungs. Both modes of delivery resulted in high nanoparticle accumulation in the lungs, intravenously administered nanoparticles reached lung endothelial while endotracheal delivery reached lung epithelial. Combining both delivery approaches simultaneously provided the best ARDS treatment outcome.

Association of Lipid Levels With COVID-19 Infection, Disease Severity and Mortality: A Systematic Review and Meta-Analysis

Background

Coronavirus disease 2019 (COVID-19) ranges from asymptomatic infection to severe illness. Cholesterol in the host cell plasma membrane plays an important role in the SARS-CoV-2 virus entry into cells. Serum lipids, especially low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C), are in constant interaction with the lipid rafts in the host cell membranes and can modify the interaction of virus with host cells and the resultant disease severity. Recent studies on serum lipid levels and COVID-19 disease severity lack consistency.

Objectives

Our systematic review and meta-analysis compared the serum levels of total cholesterol (TC), LDL-C, HDL-C, and triglycerides (TG) between (1) COVID-19 patients vs. healthy controls; (2) severe vs. non-severe COVID-19 disease; (3) deceased vs. surviving COVID-19 patients.

Methods

PRISMA guidelines were followed. We included peer-reviewed articles on observational (case-control and cohort) studies from PubMed and Embase published from the database inception until September 1, 2021. We used random-effects meta-analysis for pooled mean-differences (pMD) in lipid levels (mg/dL) for the above groups.

Results

Among 441 articles identified, 29 articles (26 retrospective and 3 prospective cohorts), with an aggregate of 256,721 participants, were included. COVID-19 patients had lower TC (pMD-14.9, 95%CI-21.6 to -8.3) and HDL-C (pMD-6.9, 95%CI -10.2 to -3.7) levels (mg/dL). Severe COVID-19 patients had lower TC (pMD-10.4, 95%CI -18.7 to -2.2), LDL-C (pMD-4.4, 95%CI -8.4 to -0.42), and HDL-C (pMD-4.4, 95%CI -6.9 to -1.8) at admission compared to patients with non-severe disease. Deceased patients had lower TC (pMD-14.9, 95%CI -21.6 to -8.3), LDL-C (pMD-10.6, 95%CI -16.5 to -4.6) and HDL-C (pMD-2.5, 95%CI -3.9 to -1.0) at admission. TG levels did not differ based on COVID-19 severity or mortality. No publication bias was noted.

Conclusion

We demonstrated lower lipid levels in patients with COVID-19 infection and an association with disease severity and mortality. Their potential role in COVID-19 pathogenesis and their utility as prognostic factors require further investigation.

Metabolism of tissue macrophages in homeostasis and pathology

Cellular metabolism orchestrates the intricate use of tissue fuels for catabolism and anabolism to generate cellular energy and structural components. The emerging field of immunometabolism highlights the importance of cellular metabolism for the maintenance and activities of immune cells. Macrophages are embryo- or adult bone marrow-derived leukocytes that are key for healthy tissue homeostasis but can also contribute to pathologies such as metabolic syndrome, atherosclerosis, fibrosis or cancer. Macrophage metabolism has largely been studied in vitro. However, different organs contain diverse macrophage populations that specialize in distinct and often tissue-specific functions. This context specificity creates diverging metabolic challenges for tissue macrophage populations to fulfill their homeostatic roles in their particular microenvironment and conditions their response in pathological conditions. Here, we outline current knowledge on the metabolic requirements and adaptations of macrophages located in tissues during homeostasis and selected diseases.

Alterations of Lipid Profile in COVID-19: A Narrative Review

The COVID-19 pandemic has led to over 100 million infections and over 3 million deaths worldwide. Understanding its pathogenesis is crucial to guide prognostic and therapeutic implications. Viral infections are known to alter the lipid profile and metabolism of their host cells, similar to the case with MERS and SARS-CoV-2002. Since lipids play various metabolic roles, studying lipid profile alterations in COVID-19 is an inevitable step as an attempt to achieve better therapeutic strategies, as well as a potential prognostic factor in the course of this disease. Several studies have reported changes in lipid profile associated with COVID-19. The most frequently reported changes are a decline in serum cholesterol and ApoA1 levels and elevated triglycerides. The hyper-inflammatory state mediated by the Cytokine storm disturbs several fundamental lipid biosynthesis pathways. Virus replication is a process that drastically changes the host cell's lipid metabolism program and overuses cell lipid resources. Lower HDL-C and ApoA1 levels are associated with higher severity and mortality rates and with higher levels of inflammatory markers. Studies suggest that arachidonic acid omega-3 derivatives might help modulate hyper-inflammation and cytokine storm resulting from pulmonary involvement. Also, statins have been shown to be beneficial when administered after COVID-19 diagnosis via unclear mechanisms probably associated with anti-inflammatory effects and HDL-C rising effects.

Association between cardiometabolic risk factors and COVID-19 susceptibility, severity and mortality: a review

The novel coronavirus, which began spreading from China Wuhan and gradually spreaded to most countries, led to the announcement by the World Health Organization on March 11, 2020, as a new pandemic. The most important point presented by the World Health Organization about this disease is to better understand the risk factors that exacerbate the course of the disease and worsen its prognosis. Due to the high majority of cardio metabolic risk factors like obesity, hypertension, diabetes, and dyslipidemia among the population over 60 years old and higher, these cardio metabolic risk factors along with the age of these people could worsen the prognosis of the coronavirus disease of 2019 (COVID-19) and its mortality. In this study, we aimed to review the articles from the beginning of the pandemic on the impression of cardio metabolic risk factors on COVID-19 and the effectiveness of COVID-19 on how to manage these diseases. All the factors studied in this article, including hypertension, diabetes mellitus, dyslipidemia, and obesity exacerbate the course of Covid-19 disease by different mechanisms, and the inflammatory process caused by coronavirus can also create a vicious cycle in controlling these diseases for patients.

Anti-prothrombin autoantibodies enriched after infection with SARS-CoV-2 and influenced by strength of antibody response against SARS-CoV-2 proteins

Antiphospholipid antibodies (aPL), assumed to cause antiphospholipid syndrome (APS), are notorious for their heterogeneity in targeting phospholipids and phospholipid-binding proteins. The persistent presence of Lupus anticoagulant and/or aPL against cardiolipin and/or β2-glycoprotein I have been shown to be independent risk factors for vascular thrombosis and pregnancy morbidity in APS. aPL production is thought to be triggered by-among other factors-viral infections, though infection-associated aPL have mostly been considered non-pathogenic. Recently, the potential pathogenicity of infection-associated aPL has gained momentum since an increasing number of patients infected with Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has been described with coagulation abnormalities and hyperinflammation, together with the presence of aPL. Here, we present data from a multicentric, mixed-severity study including three cohorts of individuals who contracted SARS-CoV-2 as well as non-infected blood donors. We simultaneously measured 10 different criteria and non-criteria aPL (IgM and IgG) by using a line immunoassay. Further, IgG antibody response against three SARS-CoV-2 proteins was investigated using tripartite automated blood immunoassay technology. Our analyses revealed that selected non-criteria aPL were enriched concomitant to or after an infection with SARS-CoV-2. Linear mixed-effects models suggest an association of aPL with prothrombin (PT). The strength of the antibody response against SARS-CoV-2 was further influenced by SARS-CoV-2 disease severity and sex of the individuals. In conclusion, our study is the first to report an association between disease severity, anti-SARS-CoV-2 immunoreactivity, and aPL against PT in patients with SARS-CoV-2.

COVID-19: A Redox Disease-What a Stress Pandemic Can Teach Us About Resilience and What We May Learn from the Reactive Species Interactome About Its Treatment

Significance: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus causing coronavirus disease 2019 (COVID-19), affects every aspect of human life by challenging bodily, socioeconomic, and political systems at unprecedented levels. As vaccines become available, their distribution, safety, and efficacy against emerging variants remain uncertain, and specific treatments are lacking. Recent Advances: Initially affecting the lungs, COVID-19 is a complex multisystems disease that disturbs the whole-body redox balance and can be long-lasting (Long-COVID). Numerous risk factors have been identified, but the reasons for variations in susceptibility to infection, disease severity, and outcome are poorly understood. The reactive species interactome (RSI) was recently introduced as a framework to conceptualize how cells and whole organisms sense, integrate, and accommodate stress. Critical Issues: We here consider COVID-19 as a redox disease, offering a holistic perspective of its effects on the human body, considering the vulnerability of complex interconnected systems with multiorgan/multilevel interdependencies. Host/viral glycan interactions underpin SARS-CoV-2's extraordinary efficiency in gaining cellular access, crossing the epithelial/endothelial barrier to spread along the vascular/lymphatic endothelium, and evading antiviral/antioxidant defences. An inflammation-driven "oxidative storm" alters the redox landscape, eliciting epithelial, endothelial, mitochondrial, metabolic, and immune dysfunction, and coagulopathy. Concomitantly reduced nitric oxide availability renders the sulfur-based redox circuitry vulnerable to oxidation, with eventual catastrophic failure in redox communication/regulation. Host nutrient limitations are crucial determinants of resilience at the individual and population level. Future Directions: While inflicting considerable damage to health and well-being, COVID-19 may provide the ultimate testing ground to improve the diagnosis and treatment of redox-related stress diseases. "Redox phenotyping" of patients to characterize whole-body RSI status as the disease progresses may inform new therapeutic approaches to regain redox balance, reduce mortality in COVID-19 and other redox diseases, and provide opportunities to tackle Long-COVID. Antioxid. Redox Signal. 35, 1226-1268.

Inflammasome activation at the crux of severe COVID-19

The COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), results in life-threatening disease in a minority of patients, especially elderly people and those with co-morbidities such as obesity and diabetes. Severe disease is characterized by dysregulated cytokine release, pneumonia and acute lung injury, which can rapidly progress to acute respiratory distress syndrome, disseminated intravascular coagulation, multisystem failure and death. However, a mechanistic understanding of COVID-19 progression remains unclear. Here we review evidence that SARS-CoV-2 directly or indirectly activates inflammasomes, which are large multiprotein assemblies that are broadly responsive to pathogen-associated and stress-associated cellular insults, leading to secretion of the pleiotropic IL-1 family cytokines (IL-1β and IL-18), and pyroptosis, an inflammatory form of cell death. We further discuss potential mechanisms of inflammasome activation and clinical efforts currently under way to suppress inflammation to prevent or ameliorate severe COVID-19.

Potential Therapeutic Applications of Pulmonary Surfactant Lipids in the Host Defence Against Respiratory Viral Infections

Pulmonary surfactant is a complex and highly surface-active material. It covers the alveolar epithelium and consists of 90% lipids and 10% proteins. Pulmonary surfactant lipids together with pulmonary surfactant proteins facilitate breathing by reducing surface tension of the air-water interface within the lungs, thereby preventing alveolar collapse and the mechanical work required to breathe. Moreover, pulmonary surfactant lipids, such as phosphatidylglycerol and phosphatidylinositol, and pulmonary surfactant proteins, such as surfactant protein A and D, participate in the pulmonary host defense and modify immune responses. Emerging data have shown that pulmonary surfactant lipids modulate the inflammatory response and antiviral effects in some respiratory viral infections, and pulmonary surfactant lipids have shown promise for therapeutic applications in some respiratory viral infections. Here, we briefly review the composition, antiviral properties, and potential therapeutic applications of pulmonary surfactant lipids in respiratory viral infections.

Antiphospholipid antibodies in critically ill COVID-19 patients with thromboembolism: cause of disease or epiphenomenon?

Coronavirus 2019 disease (COVID-19) is associated with coagulation dysfunction that predisposes patients to an increased risk for both arterial (ATE) and venous thromboembolism (VTE) and consequent poor prognosis; in particular, the incidence of ATE and VTE in critically ill COVID-19 patients can reach 5% and 31%, respectively. The mechanism of thrombosis in COVID-19 patients is complex and still not completely clear. Recent literature suggests a link between the presence of antiphospholipid antibodies (aPLs) and thromboembolism in COVID-19 patients. However, it remains uncertain whether aPLs are an epiphenomenon or are involved in the pathogenesis of the disease.

Serum levels of small HDL particles are negatively correlated with death or lung transplantation in an observational study of idiopathic pulmonary fibrosis

BACKGROUND

Serum lipoproteins, such as high density lipoproteins (HDL), may influence disease severity in idiopathic pulmonary fibrosis (IPF). Here, we investigated associations between serum lipids and lipoproteins and clinical endpoints in IPF.

METHODS

Clinical data and serum lipids were analyzed from a discovery cohort (59 IPF subjects, 56 healthy volunteers) and validated using an independent, multicenter cohort (207 IPF subjects) from the Pulmonary Fibrosis Foundation registry. Associations between lipids and clinical endpoints (FVC, forced vital capacity; 6MWD, 6 min walk distance; GAP (Gender Age Physiology) index; death or lung transplantation) were examined using Pearson's correlation and multivariable analyses.

RESULTS

Serum concentrations of small HDL particles (S-HDLP_NMR), measured by nuclear magnetic resonance (NMR) spectroscopy, correlated negatively with the GAP index in the discovery cohort of IPF subjects. The negative correlation of S-HDLP_NMR with GAP index was confirmed in the validation cohort of IPF subjects. Higher levels of S-HDLP_NMR were associated with lower odds of death or its competing outcome, lung transplantation (OR of 0.9 for each 1 μmol·L^-1 increase in S-HDLP_NMR, p<0.05), at 1, 2, and 3 years from study entry in a combined cohort of all IPF subjects.

CONCLUSIONS

Higher serum levels of S-HDLP_NMR are negatively correlated with the GAP index, as well as with lower observed mortality or lung transplantation in IPF subjects. These findings support the hypothesis that S-HDLP_NMR may modify mortality risk in patients with IPF.

Surfactant phospholipids act as molecular switches for premature induction of quorum sensing-dependent virulence in Pseudomonas aeruginosa

The virulence behaviors of many Gram-negative bacterial pathogens are governed by quorum-sensing (QS), a hierarchical system of gene regulation that relies on population density by producing and detecting extracellular signaling molecules. Although extensively studied under in vitro conditions, adaptation of QS system to physiologically relevant host environment is not fully understood. In this study, we investigated the influence of lung environment on the regulation of Pseudomonas aeruginosa virulence factors by QS in a mouse model of acute pneumonia. When cultured under laboratory conditions in lysogeny broth, wild-type P. aeruginosa strain PAO1 began to express QS-regulated virulence factors elastase B (LasB) and rhamnolipids (RhlA) during transition from late-exponential into stationary growth phase. In contrast, during acute pneumonia as well as when cultured in mouse bronchial alveolar lavage fluids (BALF), exponential phase PAO1 bacteria at low population density prematurely expressed QS regulatory genes lasI-lasR and rhlI-rhlR and their downstream virulence genes lasB and rhlA. Further analysis indicated that surfactant phospholipids were the primary components within BALF that induced the synthesis of N-(3-oxododecanoyl)-L-homoserine lactone (C12-HSL), which triggered premature expression of LasB and RhlA. Both phenol extraction and phospholipase A2 digestion abolished the ability of mouse BALF to promote LasB and RhlA expression. In contrast, provision of the major surfactant phospholipid dipalmitoylphosphatidylcholine (DPPC) restored the expression of both virulence factors. Collectively, our study demonstrates P. aeruginosa modulates its QS to coordinate the expression of virulence factors during acute pneumonia by recognizing pulmonary surfactant phospholipids.

NAD(H)-mediated tetramerization controls the activity of Legionella pneumophila phospholipase PlaB

The virulence factor PlaB promotes lung colonization, tissue destruction, and intracellular replication of Legionella pneumophila, the causative agent of Legionnaires' disease. It is a highly active phospholipase exposed at the bacterial surface and shows an extraordinary activation mechanism by tetramer deoligomerization. To unravel the molecular basis for enzyme activation and localization, we determined the crystal structure of PlaB in its tetrameric form. We found that the tetramer is a dimer of identical dimers, and a monomer consists of an N-terminal α/β-hydrolase domain expanded by two noncanonical two-stranded β-sheets, β-6/β-7 and β-9/β-10. The C-terminal domain reveals a fold displaying a bilobed β-sandwich with a hook structure required for dimer formation and structural complementation of the enzymatic domain in the neighboring monomer. This highlights the dimer as the active form. Δβ-9/β-10 mutants showed a decrease in the tetrameric fraction and altered activity profiles. The variant also revealed restricted binding to membranes resulting in mislocalization and bacterial lysis. Unexpectedly, we observed eight NAD(H) molecules at the dimer/dimer interface, suggesting that these molecules stabilize the tetramer and hence lead to enzyme inactivation. Indeed, addition of NAD(H) increased the fraction of the tetramer and concomitantly reduced activity. Together, these data reveal structural elements and an unprecedented NAD(H)-mediated tetramerization mechanism required for spatial and enzymatic control of a phospholipase virulence factor. The allosteric regulatory process identified here is suited to fine tune PlaB in a way that protects Legionella pneumophila from self-inflicted lysis while ensuring its activity at the pathogen-host interface.

Metabolomic profiling of extraesophageal reflux disease in children

Although respiratory symptoms in children are often attributed to gastroesophageal reflux disease, establishing a clear diagnosis of extraesophageal reflux disease (EERD) can be challenging, as there are no sensitive or specific EERD biomarkers. The aim of this study was to evaluate the metabolite profile in bronchoalveolar (BAL) fluid from children with suspected EERD and assess the impact of reflux treatment on these metabolites. In this prospective pilot study, we performed nontargeted global metabolomic profiling on BAL fluid from 43 children undergoing testing with bronchoscopy, upper endoscopy, and multichannel intraluminal impedance with pH (pH-MII) for evaluation of chronic respiratory symptoms. Twenty-three (54%) patients had an abnormal pH-MII study. Seventeen (40%) patients were on proton pump inhibitors (PPIs) for testing. Levels of histamine, malate, adenosine 5'-monophosphate, and ascorbate were significantly lower in subjects with abnormal pH-MII studies compared to those normal studies. Furthermore, in children off PPI therapy, those with abnormal pH-MII studies had robust increases in a number of glycerophospholipids within phospholipid metabolic pathways, including derivatives of glycerophosphorylcholine, glycerophosphoglycerol, and glycerophosphoinositol, compared to those with normal pH-MII studies. These findings offer insight into the impact of reflux and PPIs on the lungs and provide a foundation for future studies using targeted metabolomic analysis to identify potential biomarkers of EERD.

Dietary Carbohydrates and Fat Induce Distinct Surfactant Alterations in Mice

Obesity and type 2 diabetes are nutrition-related conditions associated with lung function impairment and pulmonary diseases; however, the underlying pathomechanisms are incompletely understood. Pulmonary surfactant is essential for lung function, and surfactant synthesis by AT2 (alveolar epithelial type 2) cells relies on nutrient uptake. We hypothesized that dietary amounts of carbohydrates or fat affect surfactant homeostasis and composition. Feeding mice a starch-rich diet (StD), sucrose-rich diet (SuD), or fat-rich diet (FaD) for 30 weeks resulted in hypercholesterolemia and hyperinsulinemia compared with a fiber-rich control diet. In SuD and FaD groups, lung mechanic measurements revealed viscoelastic changes during inspiration, indicating surfactant alterations, and interfacial adsorption of isolated surfactant at the air-liquid interface was decreased under FaD. The composition of characteristic phospholipid species was modified, including a shift from dipalmitoyl-phosphatidylcholine (PC16:0/16:0) to palmitoyl-palmitoleoyl-phosphatidylcholine (PC16:0/16:1) in response to carbohydrates and decreased myristic acid-containing phosphatidylcholine species (PC14:0/14:0; PC16:0/14:0) on excess fat intake, as well as higher palmitoyl-oleoyl-phosphatidylglycerol (PG16:0/18:1) and palmitoyl-linoleoyl-phosphatidylglycerol (PG16:0/18:2) fractions in StD, SuD, and FaD groups than in the control diet. Moreover, mRNA expression levels of surfactant synthesis-related proteins within AT2 cells were altered. Under the StD regimen, AT2 cells showed prominent lipid accumulations and smaller lamellar bodies. Thus, in an established mouse model, distinct diet-related surfactant alterations were subtle, yet detectable, and may become challenging under conditions of reduced respiratory capacity. Dietary fat was the only macronutrient significantly affecting surfactant function. This warrants future studies examining alimentary effects on lung surfactant, with special regard to pulmonary complications in obesity and type 2 diabetes.

Interactions between ABCC4/MRP4 and ABCC7/CFTR in human airway epithelial cells in lung health and disease

ATP binding cassette (ABC) transporters are present in all three domains of life - Archaea, Bacteria, and Eukarya. The conserved nature is a testament to the importance of these transporters in regulating endogenous and exogenous substrates required for life to exist. In humans, 49 ABC transporters have been identified to date with broad expression in different lung cell types with multiple transporter family members contributing to lung health and disease. The ABC transporter most commonly known to be linked to lung pathology is ABCC7, also known as cystic fibrosis transmembrane conductance regulator - CFTR. Closely related to the CFTR genomic sequence is ABCC4/multi-drug resistance protein-4. Genomic proximity is shared with physical proximity, with ABCC4 and CFTR physically coupled in cell membrane microenvironments of epithelial cells to orchestrate functional consequences of cyclic-adenosine monophosphate (cAMP)-dependent second messenger signaling and extracellular transport of endogenous and exogenous substrates. The present concise review summarizes the emerging data defining a role of the (ABCC7/CFTR)-ABCC4 macromolecular complex in human airway epithelial cells as a physiologically important pathway capable of impacting endogenous and exogenous mediator transport and ion transport in both lung health and disease.