Emerging lysophospholipid mediators, lysophosphatidylserine, lysophosphatidylthreonine, lysophosphatidylethanolamine and lysophosphatidylglycerol. Prostaglandins Other Lipid Mediat. 2009;89:135-139. [PMID: 19427394 DOI: 10.1016/j.prostaglandins.2009.04.009]

Lipidomic profiling of serum and liver tissue reveals hepatoprotective mechanism of taxifolin in rats with CCl4-induced subacute hepatic injury based on LC-MS/MS

Currently, the hepatoprotective activity of taxifolin, a flavonoid isolated from Pseudotsuga taxifolia, has been reported in many animal models. However, whether the protective effect of taxifolin on the liver is related to its effect on lipidomics is unclear. Based on the significant therapeutic effect of taxifolin on CCl4 induced subacute hepatic injury, we observed the intervention of taxifolin by lipidomics. The results demonstrate that taxifolin can effectively reverse the damage caused by CCl4, which including hepatocyte vacuolization and necrosis. Lipomic profiling based on liquid chromatography-mass spectrometry showed that taxifolin was able to restore lipidomic changes caused by CCl4, including the levels of lysophosphatidylserine (LPS), phosphatidylcholine (PC), coenzyme (Co), phosphatidylglyceride (PG), phosphatidylserine (PS), dimethylphosphatidylethanolamine (dMePE), ceramide (Cer), sphingosine (So), triglycerides (TG), and monogalactosyl diacylglycerol (MGDG) in the rat liver, and phosphatidylcarbinol (PMe) and phosphatidylethanolamine (PE), plant sphingosine (phSM), glucose ceramide (CerG1), TG, and diglycerides (DG) in serum. Spearman's correlation analysis showed that CerG1, phSM, PE, and PMe in serum, and Cer, dMePE, PG, PS, So, TG, and MGDG in liver were positively correlated with serum levels of aspartate transaminase, alanine transaminase, and liver index; while TG, DG in serum, and Co, LPS, PC in liver were negatively correlated with the parameters. In total, 43 and 34 lipid molecules were altered by taxifolin treatment in the liver and serum, respectively, mainly including glycerophosphoglycerols, glycerophosphocholines, glycerophosphoethanolamines, and linoleic acids and derivatives. Our findings help to provide novel insights into the mechanism of the hepatoprotective effect of taxifolin from a lipidomics approach.

Differential effects of structurally different lysophosphatidylethanolamine species on proliferation and differentiation in pre-osteoblast MC3T3-E1 cells

Lysophosphatidylethanolamine (LPE) is a bioactive lipid mediator involved in diverse cellular functions. In this study, we investigated the effects of three LPE species, 1-palmitoyl LPE (16:0 LPE), 1-stearoyl LPE (18:0 LPE), and 1-oleoyl LPE (18:1 LPE) on pre-osteoblast MC3T3-E1 cells. All LPE species stimulated cell proliferation and activated the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) 1/2. MAPK/ERK1/2 activation by 16:0 LPE and 18:1 LPE was inhibited by the Gq/11 inhibitor YM-254890, while activation by 18:0 LPE was blocked by the Gi/o inhibitor pertussis toxin. Intracellular Ca2+ transients were triggered by 16:0 LPE and 18:1 LPE but not by 18:0 LPE, with YM-254890 suppressing these responses. These results suggest that 16:0 and 18:1 LPE act via Gq/11-coupled G protein coupled receptors (GPCRs), and 18:0 LPE acts via Gi/o-coupled GPCRs. Furthermore, receptor desensitization experiments suggested that each LPE acts through distinct GPCRs. Interestingly, 18:0 LPE suppressed osteogenic differentiation, reducing mineralization, alkaline phosphatase activity, and osteogenic gene expression, whereas 16:0 LPE and 18:1 LPE had no such effects. These results suggest the physiological significance of LPEs in bone formation and indicate that different LPE species and their receptors play distinctive roles in this process.

Advanced Method for the In Vivo Measurements of Lysophospholipid Translocation Across the Inner (Cytoplasmic) Membrane of Escherichia coli

Phospholipid translocation occurs ubiquitously in biological membranes and primarily is protein catalyzed. Lipid flippases mediate the net translocation of specific phospholipids from one leaflet of a membrane to the other. In the inner (cytoplasmic) membrane (IM) of Gram-negative bacteria, lysophospholipid translocase (LplT) and cytosolic bifunctional acyl-acyl carrier protein (ACP) synthetase/2-acylglycerolphosphoethanolamine acyltransferase (Aas) form a glycerophospholipid regeneration system, which is capable of facilitating rapid retrograde translocation of lyso forms of phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and cardiolipin (CL) but not exogenous (host-derived) phosphatidylcholine (PC) across the IM of Gram-negative diderm (two-membraned) bacteria in consequential order lyso-PE = lyso-PG > > lysophosphatidic acid (lyso-PA) >> lyso-PC. Although several flippases that bind and move non-glycerophosphatidyl lipids across the IM are characterized in Gram-negative bacteria, LplT appears to be the first example of a bacterial protein capable of facilitating the rapid translocation of monoacylated glycerophospholipids. On the cytoplasmic surface, Aas restores the lysophospholipids to their diacyl forms with comparable efficiency but excludes any exogenous monoacylated lipid species. This coupled remodeling enzyme tandem provides an effective means to examine substrate specificity of lipid regeneration and lysophospholipid transport per se across the membrane. The current chapter describes two distinct but complementary methods for the measurement of lysophospholipid transport across membranes using Escherichia coli spheroplasts.

Determination of plasma lysophosphatidylethanolamines (lyso-PE) by LC-MS/MS revealed a possible relation between obesity and lyso-PE in Japanese preadolescent children: The Hokkaido study

BACKGROUND

Lysophosphatidylethanolamines (lyso-PEs) are the partial hydrolysis products of phosphatidylethanolamine. Although lyso-PEs are important biomarkers in various diseases, their determination is limited by the lack of simple and efficient quantification methods. This study aims to develop an improved quantitative method for the determination of lyso-PEs and its application to an epidemiological study.

METHODS

Single reaction monitoring channels by collision-induced dissociation for seven lyso-PEs were established using liquid chromatography-tandem mass spectrometry. Plasma lyso-PEs were extracted with a single-phase method using an isotopically labelled internal standard for quantification. The proposed method was adopted to define lyso-PEs in plasma samples of children aged 9-12 years living in Sapporo, Japan.

RESULTS

The limit of detection and limit of quantification for each lyso-PE ranged between 0.001-0.015 and 0.002-0.031 pmol/μL, respectively. Recoveries were found to be > 91% for all the species. The analysis results of children's plasma showed that the total lyso-PE concentrations in boys (n = 181) and girls (n = 161) were 11.53 and 11.00 pmol/μL (median), respectively. Participants were further classified by the percentage of overweight and subgrouped as underweight (n = 12), normal range (n = 292), or overweight (n = 38). Interestingly, the reduction of lyso-PE 16:0 and increased lyso-PE 22:6 were observed in overweight children compared with normal range (Fold change: 0.909 and 1.174, respectively).

CONCLUSIONS

This study successfully established a simple quantitative method to determine lyso-PE concentrations. Furthermore, our method revealed the possible relation between plasma lyso-PEs and overweight status.

St. John's Wort Extract Ze 117 and Escitalopram Alter Plasma and Hippocampal Lipidome in a Rat Model of Chronic-Stress-Induced Depression

Chronic stress is a key factor in the development of depression. It leads to hyperactivation of the hypothalamic-pituitary-adrenal (HPA) axis, which in turn increases the formation of glucocorticoids (GCs). Chronically elevated GC levels disrupt neuroplasticity and affect brain lipid metabolism, which may, ultimately, contribute to the development of depression. This study aimed to investigate the effects of the antidepressants St. John's Wort extract and escitalopram on lipid metabolism in vivo. Therefore, repeated corticosterone injections were used to induce depression-like behavior in rats. Male Sprague-Dawley rats were stressed with corticosterone injections (40 mg/kg, s.c.) over 22 consecutive days and were concomitantly treated with varying doses of the St. John's wort extract Ze 117 (30, 90 or 180 mg/kg, p.o.) or escitalopram (10 mg/kg, p.o.) and behavioral changes were evaluated using a modified forced swim test. The results indicate that repeated corticosterone injections significantly decreased the latency to first immobility. Furthermore, co-treatment of corticosterone with Ze 117 increased latency to first immobility significantly compared to rats treated with corticosterone alone. To further investigate the biochemical effects of corticosterone-induced stress, as well as the possible counter-regulation by antidepressants, the lipidomes of the plasma and hippocampus samples were analyzed by shotgun mass spectrometry. Corticosterone-induced stress significantly altered key lipid metabolites in the plasma but not in the hippocampal samples. In the hippocampus, however, specific glycerophospholipids such as lysophosphatidylethanolamines (LPEs) increased with escitalopram treatment and with Ze 117, both showing significant correlations with behavioral parameters. In summary, our study shows significant behavioral- and lipidome-altering processes with Ze 117 and escitalopram in rat plasma and hippocampal samples, thereby providing new targets and biomarker ideas for clinical diagnosis and antidepressant intervention.

PHARC syndrome: an overview

PHARC, polyneuropathy, hearing loss, cerebellar ataxia, retinitis pigmentosa and cataracts, or PHARC is a very rare progressive neurodegenerative autosomal recessive disease caused by biallelic mutations in the ABHD12 (a/b-hydrolase domain containing 12) gene, which encodes a lyso-phosphatidylserine (lyso-PS) lipase. The Orpha number for PHARC is ORPHA171848. The clinical picture of PHARC syndrome is very heterogeneous with a wide range of age at onset for each symptom, making a clinical diagnosis very challenging. Differential diagnoses of the disease include Refsum disease, Charcot-Marie-Tooth disease, and Usher syndrome. Many aspects of the disease, such as the biochemistry and pathophysiology, are still not fully understood. We generated a clinical overview of all PHARC patients, including their mutations, described in literature so far. Furthermore, we give an outline of the most recent developments in research on the pathophysiology of PHARC syndrome in an attempt to gain more insight into and increase awareness of the heterogeneity of the disease. We included 58 patients with PHARC from 37 different families with 27 known ABHD12 mutations. The age at onset (from early childhood to late thirties) and the severity of each feature of PHARC varied widely among patients. Demyelinating polyneuropathy was reported in 91% of the patients. In 86% of patients, hearing loss was present and 74% had cerebellar ataxia, the most variable symptom of PHARC. Retinitis pigmentosa and cataracts occurred in 82% and 86% of patients, respectively. Due to the rareness of the disease and the variable clinical phenotype, a diagnosis of PHARC is often delayed and mostly only made after an extensive genetic work-up. Therefore, we recommend adding the ABHD12 gene to diagnostic gene panels for polyneuropathy, cerebellar ataxia, hearing loss, retinal dystrophy, and cataracts. In addition, a full clinical work-up, neurological (with EMG and neuroimaging of the brain) and ophthalmological (with ERG) examination and audiological tests are indispensable to obtain a comprehensive overview of the clinical phenotype as some symptoms in PHARC may be very subtle and easily overlooked if not tested for. In conclusion, we strongly recommend that patients with (suspected) PHARC should be evaluated in a multidisciplinary setting involving ophthalmologists, audiologists, neurologists, and geneticists to ensure the best possible care. Furthermore, we discuss whether PHARC is a spectrum with various incomplete phenotypes even later in life, or whether it is a syndrome in which the clinical symptoms are variable in severity and age of onset.

Cognitive improvements linked to lysophosphatidylethanolamine after olanzapine treatment in drug-naïve first-episode schizophrenia

BACKGROUND

Cognitive impairments are a hallmark symptom of schizophrenia (SCZ). Phosphatidylethanolamine (PE) is the second most abundant phospholipid in mammalian cells, yet its role in cognitive deficits remains unexplored. The aim of this study was to investigate the association between plasma LysoPE and cognitive improvements following olanzapine monotherapy in drug-naïve first-episode (DNFE) SCZ patients.

METHODS

Twenty-five female DNFE SCZ patients were treated with olanzapine for four weeks, and cognitive function was assessed using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) at baseline and after the 4-week follow-up. Utilizing an untargeted ultra-performance liquid chromatography-mass spectrometry (UPLC-MS)-based metabolomics approach, we measured LysoPE concentrations.

RESULTS

Significant improvements in immediate and delayed memory domains were observed post-treatment. We identified nine differential LysoPE species after olanzapine monotherapy, with increased concentrations for all LysoPE except LysoPE (22:6). Elevated LysoPE (22:1) concentration positively correlated with cognitive improvement in patients. Baseline LysoPE (16:1) emerged as a predictive factor for cognitive improvement following olanzapine monotherapy.

CONCLUSIONS

This study offers preliminary evidence for the involvement of LysoPE in cognitive improvements observed in drug-naïve first-episode SCZ patients after olanzapine treatment.

Phosphatidylserine: A comprehensive overview of synthesis, metabolism, and nutrition

Phosphatidylserine (PtdS) is classified as a glycerophospholipid and a primary anionic phospholipid and is particularly abundant in the inner leaflet of the plasma membrane in neural tissues. It is synthesized from phosphatidylcholine or phosphatidylethanolamine by exchanging the base head group with serine, and this reaction is catalyzed by PtdS synthase-1 and PtdS synthase-2 located in the endoplasmic reticulum. PtdS exposure on the outside surface of the cell is essential for eliminating apoptotic cells and initiating the blood clotting cascade. It is also a precursor of phosphatidylethanolamine, produced by PtdS decarboxylase in bacteria, yeast, and mammalian cells. Furthermore, PtdS acts as a cofactor for several necessary enzymes that participate in signaling pathways. Beyond these functions, several studies indicate that PtdS plays a role in various cerebral functions, including activating membrane signaling pathways, neuroinflammation, neurotransmission, and synaptic refinement associated with the central nervous system (CNS). This review discusses the occurrence of PtdS in nature and biosynthesis via enzymes and genes in plants, yeast, prokaryotes, mammalian cells, and the brain, and enzymatic synthesis through phospholipase D (PLD). Furthermore, we discuss metabolism, its role in the CNS, the fortification of foods, and supplementation for improving some memory functions, the results of which remain unclear. PtdS can be a potentially beneficial addition to foods for kids, seniors, athletes, and others, especially with the rising consumer trend favoring functional foods over conventional pills and capsules. Clinical studies have shown that PtdS is safe and well tolerated by patients.

Cell-Death Metabolites from Cocconeis scutellum var. parva Identified by Integrating Bioactivity-Based Fractionation and Non-Targeted Metabolomic Approaches

Epiphytic diatoms growing in Mediterranean seagrass meadows, particularly those of the genus Cocconeis, are abundant and ecologically significant, even in naturally acidified environments. One intriguing aspect of some benthic diatoms is their production of an unidentified cell-death-promoting compound, which induces destruction of the androgenic gland in Hippolyte inermis Leach, 1816, a shrimp exhibiting protandric hermaphroditism, principally under normal environmental pH levels. The consumption of Cocconeis spp. by this shrimp is vital for maintaining the stability of its natural populations. Although many attempts have been made to reveal the identity of the apoptotic compound, it is still unknown. In this study, we strategically integrated a bioactivity-based fractionation, a metabolomic approach, and two different experimental avenues to identify potential apoptotic metabolites from Cocconeis scutellum var. parva responsible for the sex reversal in H. inermis. Our integrated analysis uncovered two potential candidate metabolites, one putatively identified as a lysophosphatidylglycerol (LPG) (16:1) and the other classified as a fatty acid ester. This is the first time LPG (16:1) has been reported in C. scutellum var. parva and associated with cell-death processes. These candidate metabolites mark substantial progress in elucidating the factors responsible for triggering the removal of the androgenic gland in the early post-larval phases of H. inermis.

Hyphenation of Liquid Chromatography and Trapped Ion Mobility - Mass Spectrometry for Characterization of Isomeric Phosphatidylethanolamines with Focus on N-Acylated Species

In prior research, hydrophilic interaction liquid chromatography coupled to tandem mass spectrometry (HILIC-MS/MS) has demonstrated applicability for characterizing regioisomers in lipidomics studies, including phosphatidylglycerols (PG) and bis(monoacyl)glycerophosphates (BMP). However, there are other lipid regioisomers, such as phosphatidylethanolamines (PE) and lyso-N-acyl-PE (LNAPE), that have not been studied as extensively. Therefore, hyphenated mass spectrometric methods are needed to investigate PE and LNAPE regioisomers individually. The asymmetric structure of LNAPE favors isomeric species, which can result in coelution and chimeric MS/MS spectra. One way to address the challenge of chimeric MS/MS spectra is through mobility-resolved fragmentation using trapped ion mobility spectrometry (TIMS). Therefore, we developed a multidimensional HILIC-TIMS-MS/MS approach for the structural characterization of isomeric phosphatidylethanolamines in both negative and positive ionization modes. The study revealed the complementary fragmentation pattern and ion mobility behavior of LNAPE in both ionization modes, which was confirmed by a self-synthesized LNAPE standard. With this knowledge, a distinction of regioisomeric PE and LNAPE was achieved in human plasma samples. Furthermore, regioisomeric LNAPE species containing at least one unsaturated fatty acid were noted to exhibit a change in collision cross-section in positive ionization mode, leading to a lipid characterization with respect to fatty acyl positional level. Similar mobility behavior was also observed for the biological LNAPE precursor N-acyl-PE (NAPE). Application of this approach to plasma and cereal samples demonstrated its effectiveness in regioisomeric LNAPE and NAPE species' elucidation.

The Role of Lipid Metabolism Disorders in the Development of Thyroid Cancer

Thyroid cancer (TC) is a neoplasm with an increasing incidence worldwide. Its etiology is complex and based on a multi-layered interplay of factors. Among these, disorders of lipid metabolism have emerged as an important area of investigation. Cancer cells are metabolically reprogrammed to promote their rapid growth, proliferation, and survival. This reprogramming is associated with significant changes at the level of lipids, mainly fatty acids (FA), as they play a critical role in maintaining cell structure, facilitating signaling pathways, and providing energy. These lipid-related changes help cancer cells meet the increased demands of continued growth and division while adapting to the tumor microenvironment. In this review, we examine lipid metabolism at different stages, including synthesis, transport, and oxidation, in the context of TC and the effects of obesity and hormones on TC development. Recent scientific efforts have revealed disturbances in lipid homeostasis that are specific to thyroid cancer, opening up potential avenues for early detection and targeted therapeutic interventions. Understanding the intricate metabolic pathways involved in FA metabolism may provide insights into potential interventions to prevent cancer progression and mitigate its effects on surrounding tissues.

Lipidomics analysis reveals new insights into crisp grass carp associated with meat texture

Feeding faba beans to grass carp could crisp its muscle texture to avoid softening, the relationship between texture formation throughout the crisping process and the critical lipids regulating the fish quality has not yet been clarified. Herein, an 60-day nutritional trial and untargeted lipidomic analysis was used to study the changes of lipids in crisp grass carp dorsal muscle. A total of 1036 lipids were remarkably different between ordinary and crisp grass carp. The concentrations of the LPC, LPE, PG, Cer, Hex2Cer, SM, MG and MGMG were positively correlated with hardness and springiness, and the CL, TG, PMe, WE, dMePE and AcCa were negative correlation. High content of lipids involved in storage in ordinary grass carp, such as glycerophospholipids, polyunsaturated and saturated fatty acid content. In contrast, high content of membrane components in crisp grass carp, such as monounsaturated fatty acid, sphingolipid and glycerolipids content, and the distribution of PUFA in lipid molecules was related to lipid biosynthesis. This study might provide some insights into improved knowledge of the association between meat texture and lipid molecules in fish fed with faba bean.

Comparing massa medicata fermentata before and after charred in terms of digestive promoting effect via metabolomics and microbiome analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Massa Medicata Fermentata, a fermented Chinese medicine, is produced by the fermentation of six traditional Chinese medicines. Liu Shenqu (LSQ) and charred Liu Shenqu (CLSQ) have been used for strengthening the spleen and enhancing digestion for over a thousand years, and CLSQ is commonly used in clinical practice. However, it is unclear whether there is a difference in the spleen strengthening and digestion effects between LSQ and CLSQ, as well as their mechanisms of action.

AIM OF STUDY

This study aims to compare the effects of LSQ and CLSQ on the digestive function of functional dyspepsia (FD) rats and reveal their mechanisms of action.

MATERIALS AND METHODS

SPF grade SD rats were randomly divided into 6 groups: control group, model group, Liu Shenqu decoction low-dosage (LSQ LD) group, Liu Shenqu decoction high-dosage (LSQ HD) group, charred Liu Shenqu decoction low-dosage (CLSQ LD) group, and charred Liu Shenqu decoction high-dosage (CLSQ HD) group. Rats were injected intraperitoneally with reserpine to create an FD model and then treated by intragastric administration. During this period, record the weight and food intake of the animals. After 18 days of treatment, specimens of the gastric antrum, spleen, and duodenum of rats were taken for pathological staining and immunohistochemical detection of Ghrelin protein expression. Enzyme linked immunosorbent assay (ELISA) was used to determine the concentration of relevant gastrointestinal hormones in serum. The 16 S rDNA sequencing method was used to evaluate the effect of cecal contents on the structure of the gut microbiota in experimental rats. Plasma metabolomics analysis was performed using ultra high performance liquid chromatography coupled with quadrupole time of flight mass spectrometry (UPLC-QTOF-MS) to further reveal their mechanism of action.

RESULTS

LSQ and CLSQ improved the pathological tissue histological structure of FD rats and increased the levels of MTL and GAS hormones in serum and the levels of ghrelin in the gastric antrum, spleen, and duodenum, while reducing VIP, CCK, and SP hormone levels. The above results showed that the therapeutic efficacy of CLSQ is better than that of LSQ. Futhermore, the mechanism of action of LSQ and CLSQ were revealed. The 16 S rDNA sequencing results showed that both LSQ and CLSQ can improve the composition and diversity of the gut microbiota. And metabolomic analysis demonstrated that 20 metabolites changed after LSQ treatment, and 16 metabolites underwent continuous changes after CLSQ treatment. Further analysis revealed that LSQ mainly intervened in the metabolic pathways of glycerol phospholipid metabolism and arginine and proline metabolism, but CLSQ mainly intervened in the metabolic pathways of ether lipid metabolism, sphingolipid metabolism, and glycerophospholipid metabolism.

CONCLUSIONS

Both LSQ and CLSQ can improve functional dyspepsia in FD rats, but CLSQ has a stronger improvement effect on FD. Although their mechanisms of action are all related to regulating gastrointestinal hormone secretion, significantly improving intestinal microbiota disorders, and improving multiple metabolic pathways, but the specific gut microbiota and metabolic pathways they regulate are different.

Changes of Facial Lipidomics by Intense Pulsed Light Treatment Based on LC-MS

BACKGROUND

Intense pulsed light (IPL) has been widely used to improve cutaneous photoaging in recent years. Several studies began to explore the changes of skin barrier function after treatment, but the changes of skin surface lipids (SSL), especially specific lipid content and types are still unclear.

METHODS

A total of 25 female volunteers were included in our study, and each of them received three full-face treatments with one month apart. Before the first treatment and 1 month after the last treatment, we collected clinical photos and skin stratum corneum samples from individuals. A 5-level scale was used to evaluate the efficacy of IPL treatment, liquid chromatography-mass spectrometry (LC-MS), and Orthogonal Partial Least Squares Discrimination Analysis (OPLS-DA) were used to analyze the changes of SSL.

RESULTS

Two patients got no improvement after treatment, 6 patients had poor improvement and mild improvement was achieved in 9 patients, 5 and 3 patients reported moderate and significant improvement. The overall "effective" rate was 68 % and the "significant effective" rate was 32 %. The results showed 18 lipid subclasses and 487 lipid molecules were identified. The change of total lipid volume was not statistically significant (P = 0.088>0.05), but lipid subclass analysis showed the amount of Triglyceride (TG), Phosphatidic Acid (PA), Phosphatidylglycerol (PG) and Lysophosphatidylglycerol (LPG) were significantly increased (P < 0.05). There were 55 kinds of lipid molecules with significant difference after treatment (P < 0.05), and 51 of them belong to TG. The analysis of chain saturation of TG showed that the quantity of TG with 0, 1 and 2 unsaturated bonds increased significantly (P < 0.05).

CONCLUSIONS

IPL treatment does not have a significant effect on the overall amount of lipids while the amount of TG, PA, PG, LPG were significantly increased. These lipid changes may potentially improve the skin barrier function, but more high-quality and comprehensive studies are still needed.

BULLET POINT

Lipidomics analysis based on LC-MS; Changes of skin surface lipid after IPL treatment; the relationships between skin surface lipid and skin barrier functions.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Plasma metabolomic analysis reveals the metabolic characteristics and potential diagnostic biomarkers of spinal tuberculosis

Objectives

This study aimed to conduct a non-targeted metabolomic analysis of plasma from patients with spinal tuberculosis (STB) to systematically elucidate the metabolomic alterations associated with STB, and explore potential diagnostic biomarkers for STB.

Methods

From January 2020 to January 2022, 30 patients with spinal tuberculosis (STBs) clinically diagnosed at the General Hospital of Ningxia Medical University and 30 age- and sex-matched healthy controls (HCs) were selected for this study. Using ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-QTOF/MS) based metabolomics, we analyzed the metabolic profiles of 60 plasma samples. Statistical analyses, pathway enrichment, and receiver operating characteristic (ROC) analyses were performed to screen and evaluate potential diagnostic biomarkers.

Results

Metabolomic profiling revealed distinct alterations between the STBs and HCs cohorts. A total of 1635 differential metabolites were screened, functionally clustered, and annotated. The results showed that the differential metabolites were enriched in sphingolipid metabolism, tuberculosis, cutin, suberine and wax biosynthesis, beta-alanine metabolism, methane metabolism, and other pathways. Through the random forest algorithm, LysoPE (18:1(11Z)/0:0), 8-Demethyl-8-formylriboflavin 5'-phosphate, Glutaminyl-Gamma-glutamate, (2R)-O-Phospho-3-sulfolactate, and LysoPE (P-16:0/0:0) were determined to have high independent diagnostic value.

Conclusions

STBs exhibited significantly altered metabolite profiles compared with HCs. Here, we provide a global metabolomic profile and identify potential diagnostic biomarkers of STB. Five potential independent diagnostic biomarkers with high diagnostic value were screened. This study provides novel insights into the pathogenesis, diagnosis, and treatment strategies of STB.

Investigating mouse hepatic lipidome dysregulation following exposure to emerging per- and polyfluoroalkyl substances (PFAS)

Per- and polyfluoroalkyl substances (PFAS) are environmental pollutants that have been associated with adverse health effects including liver damage, decreased vaccine responses, cancer, developmental toxicity, thyroid dysfunction, and elevated cholesterol. The specific molecular mechanisms impacted by PFAS exposure to cause these health effects remain poorly understood, however there is some evidence of lipid dysregulation. Thus, lipidomic studies that go beyond clinical triglyceride and cholesterol tests are greatly needed to investigate these perturbations. Here, we have utilized a platform coupling liquid chromatography, ion mobility spectrometry, and mass spectrometry (LC-IMS-MS) separations to simultaneously evaluate PFAS bioaccumulation and lipid metabolism disruptions. For the study, liver samples collected from C57BL/6 mice exposed to either of the emerging PFAS hexafluoropropylene oxide dimer acid (HFPO-DA or "GenX") or Nafion byproduct 2 (NBP2) were assessed. Sex-specific differences in PFAS accumulation and liver size were observed for both PFAS, in addition to disturbed hepatic liver lipidomic profiles. Interestingly, GenX resulted in less hepatic bioaccumulation than NBP2 yet gave a higher number of significantly altered lipids when compared to the control group, implying that the accumulation of substances in the liver may not be a reliable measure of the substance's capacity to disrupt the liver's natural metabolic processes. Specifically, phosphatidylglycerols, phosphatidylinositols, and various specific fatty acyls were greatly impacted, indicating alteration of inflammation, oxidative stress, and cellular signaling processes due to emerging PFAS exposure. Overall, these results provide valuable insight into the liver bioaccumulation and molecular mechanisms of GenX- and NBP2-induced hepatotoxicity.

Gestational testosterone excess early to mid-pregnancy disrupts maternal lipid homeostasis and activates biosynthesis of phosphoinositides and phosphatidylethanolamines in sheep

Gestational hyperandrogenism is a risk factor for adverse maternal and offspring outcomes with effects likely mediated in part via disruptions in maternal lipid homeostasis. Using a translationally relevant sheep model of gestational testosterone (T) excess that manifests maternal hyperinsulinemia, intrauterine growth restriction (IUGR), and adverse offspring cardiometabolic outcomes, we tested if gestational T excess disrupts maternal lipidome. Dimensionality reduction models following shotgun lipidomics of gestational day 127.1 ± 5.3 (term 147 days) plasma revealed clear differences between control and T-treated sheep. Lipid signatures of gestational T-treated sheep included higher phosphoinositides (PI 36:2, 39:4) and lower acylcarnitines (CAR 16:0, 18:0, 18:1), phosphatidylcholines (PC 38:4, 40:5) and fatty acids (linoleic, arachidonic, Oleic). Gestational T excess activated phosphatidylethanolamines (PE) and PI biosynthesis. The reduction in key fatty acids may underlie IUGR and activated PI for the maternal hyperinsulinemia evidenced in this model. Maternal circulatory lipids contributing to adverse cardiometabolic outcomes are modifiable by dietary interventions.

Improvements in in vitro spermatogenesis: oxygen concentration, antioxidants, tissue-form design, and space control

Incorporation of bovine serum-derived albumin formulation (AlbuMAX) into a basic culture medium, MEMα, enables the completion of in vitro spermatogenesis through testicular tissue culture in mice. However, this medium was not effective in other animals. Therefore, we sought an alternative approach for in vitro spermatogenesis using a synthetic medium without AlbuMAX and aimed to identify its essential components. In addition to factors known to be important for spermatogenesis, such as retinoic acid and reproductive hormones, we found that antioxidants (vitamin E, vitamin C, and glutathione) and lysophospholipids are vital for in vitro spermatogenesis. Moreover, based on our experience with microfluidic devices (MFD), we developed an alternative approach, the PDMS-ceiling method (PC method), which involves simply covering the tissue with a flat chip made of PDMS, a silicone resin material used in MFD. The PC method, while straightforward, integrates the advantages of MFD, enabling improved and uniform oxygen and nutrient supply via tissue flattening. Furthermore, our studies underscored the significance of lowering the oxygen concentration to 10-15%. Using an integrated cultivation method based on these findings, we successfully achieved in vitro spermatogenesis in rats, which has been a long-standing challenge. Further improvements in culture conditions would pave the way for spermatogenesis completion in diverse animal species.

Metabolomics Profiling Predicts Ventricular Arrhythmia in Patients with an Implantable Cardioverter Defibrillator

Implantable cardioverter defibrillators (ICDs) reduce sudden cardiac death (SCD) when patients experience life-threatening ventricular arrhythmias (LTVA). However, current strategies determining ICD patient selection and risk stratification are inefficient. We used metabolomics to assess whether dysregulated metabolites are associated with LTVA and identify potential biomarkers. Baseline plasma samples were collected from 72 patients receiving ICDs. Over a median follow-up of 524.0 days (range 239.0-705.5), LTVA occurred in 23 (31.9%) patients (22 effective ICD treatments and 1 SCD). After confounding risk factors adjustment for age, smoking, secondary prevention, and creatine kinase MB, 23 metabolites were significantly associated with LTVA. Pathway analysis revealed LTVA associations with disrupted metabolism of glycine, serine, threonine, and branched chain amino acids. Pathway enrichment analysis identified a panel of 6 metabolites that potentially predicted LTVA, with an area under the receiver operating characteristic curve of 0.8. Future studies are necessary on biological mechanisms and potential clinical use.

Mouse Model of Nitrogen Mustard Ocular Surface Injury Characterization and Sphingolipid Signaling

Vesicating chemicals like sulfur mustard (SM) or nitrogen mustard (NM) can cause devastating damage to the eyes, skin, and lungs. Eyes, being the most sensitive, have complicated pathologies that can manifest immediately after exposure (acute) and last for years (chronic). No FDA-approved drug is available to be used as medical counter measures (MCMs) against such injuries. Understanding the pathological mechanisms in acute and chronic response of the eye is essential for developing effective MCMs. Here, we report the clinical and histopathological characterization of a mouse model of NM-induced ocular surface injury (entire surface) developed by treating the eye with 2% (w/v) NM solution for 5 min. Unlike the existing models of specific injury, our model showed severe ocular inflammation, including the eyelids, structural deformity of the corneal epithelium and stroma, and diminished visual and retinal functions. We also observed alterations of the inflammatory markers and their expression at different phases of the injury, along with an activation of acidic sphingomyelinase (aSMase), causing an increase in bioactive sphingolipid ceramide and a reduction in sphingomyelin levels. This novel ocular surface mouse model recapitulated the injuries reported in human, rabbit, and murine SM or NM injury models. NM exposure of the entire ocular surface in mice, which is similar to accidental or deliberate exposure in humans, showed severe ocular inflammation and caused irreversible alterations to the corneal structure and significant vision loss. It also showed an intricate interplay between inflammatory markers over the injury period and alteration in sphingolipid homeostasis in the early acute phase.

Bioactive signalling lipids as drivers of chronic liver diseases

Lipids are important in multiple cellular functions, with most having structural or energy storage roles. However, a small fraction of lipids exert bioactive roles through binding to G protein-coupled receptors and induce a plethora of processes including cell proliferation, differentiation, growth, migration, apoptosis, senescence and survival. Bioactive signalling lipids are potent modulators of metabolism and energy homeostasis, inflammation, tissue repair and malignant transformation. All these events are involved in the initiation and progression of chronic liver diseases. In this review, we focus specifically on the roles of bioactive lipids derived from phospholipids (lyso-phospholipids) and poly-unsaturated fatty acids (eicosanoids, pro-resolving lipid mediators and endocannabinoids) in prevalent chronic liver diseases (alcohol-associated liver disease, non-alcoholic fatty liver disease, viral hepatitis and hepatocellular carcinoma). We discuss the balance between pathogenic and beneficial bioactive lipids as well as potential therapeutic targets related to the agonism or antagonism of their receptors.

Hypoxia induced deregulation of sphingolipids in colon cancer is a prognostic marker for patient outcome

Sphingolipids are important for the physicochemical properties of cellular membranes and deregulated in tumors. In human colon cancer tissue ceramide synthase (CerS) 4 and CerS5 are reduced which correlates with a reduced survival probability of late-stage colon cancer patients. Both enzymes are reduced after hypoxia in advanced colorectal cancer (CRC) cells (HCT-116, SW620) but not in non-metastatic CRC cells (SW480, Caco-2). Downregulation of CerS4 or CerS5 in advanced CRC cells enhanced tumor formation in nude mice and organoid growth in vitro. This was accompanied by an enhanced proliferation rate and metabolic changes leading to a shift towards the Warburg effect. In contrast, CerS4 or CerS5 depletion in Caco-2 cells reduced tumor growth in vivo. Lipidomic and proteomic analysis of membrane fractions revealed significant changes in tumor-promoting cellular pathways and cellular transporters. This study identifies CerS4 and CerS5 as prognostic markers for advanced colon cancer patients and provides a comprehensive overview about the associated cellular metabolic changes. We propose that the expression level of CerS4 and CerS5 in colon tumors could serve as a basis for decision-making for personalized treatment of advanced colon cancer patients. Trial registration: The study was accredited by the study board of the Deutsche Krebsgesellschaft (Registration No: St-D203, 2017/06/30, retrospectively registered).

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.

Acute joint inflammation induces a sharp increase in the number of synovial fluid EVs and modifies their phospholipid profile

Inflammation is the hallmark of most joint disorders. However, the precise regulation of induction, perpetuation, and resolution of joint inflammation is not entirely understood. Since extracellular vesicles (EVs) are critical for intercellular communication, we aim to unveil their role in these processes. Here, we investigated the EVs' dynamics and phospholipidome profile from synovial fluid (SF) of healthy equine joints and from horses with lipopolysaccharide (LPS)-induced synovitis. LPS injection triggered a sharp increase of SF-EVs at 5-8 h post-injection, which started to decline at 24 h post-injection. Importantly, we identified significant changes in the lipid profile of SF-EVs after synovitis induction. Compared to healthy joint-derived SF-EVs (0 h), SF-EVs collected at 5, 24, and 48 h post-LPS injection were strongly increased in hexosylceramides. At the same time, phosphatidylserine, phosphatidylcholine, and sphingomyelin were decreased in SF-EVs at 5 h and 24 h post-LPS injection. Based on the lipid changes during acute inflammation, we composed specific lipid profiles associated with healthy and inflammatory state-derived SF-EVs. The sharp increase in SF-EVs during acute synovitis and the correlation of specific lipids with either healthy or inflamed states-derived SF-EVs are findings of potential interest for unveiling the role of SF-EVs in joint inflammation, as well as for the identification of EV-biomarkers of joint inflammation.

Cryo-EM structures of human GPR34 enable the identification of selective antagonists

GPR34 is a functional G-protein-coupled receptor of Lysophosphatidylserine (LysoPS), and has pathogenic roles in numerous diseases, yet remains poorly targeted. We herein report a cryo-electron microscopy (cryo-EM) structure of GPR34 bound with LysoPS (18:1) and Gi protein, revealing a unique ligand recognition mode with the negatively charged head group of LysoPS occupying a polar cavity formed by TM3, 6 and 7, and the hydrophobic tail of LysoPS residing in a lateral open hydrophobic groove formed by TM3-5. Virtual screening and subsequent structural optimization led to the identification of a highly potent and selective antagonist (YL-365). Design of fusion proteins allowed successful determination of the challenging cryo-EM structure of the inactive GPR34 complexed with YL-365, which revealed the competitive binding of YL-365 in a portion of the orthosteric binding pocket of GPR34 and the antagonist-binding-induced allostery in the receptor, implicating the inhibition mechanism of YL-365. Moreover, YL-365 displayed excellent activity in a neuropathic pain model without obvious toxicity. Collectively, this study offers mechanistic insights into the endogenous agonist recognition and antagonist inhibition of GPR34, and provides proof of concept that targeting GPR34 represents a promising strategy for disease treatment.

Serum High-Mobility Group Box 1 and Heme Oxygenase-1 as Biomarkers in COVID-19 Patients at Hospital Admission

The careful monitoring of patients with mild/moderate COVID-19 is of particular importance because of the rapid progression of complications associated with COVID-19. For prognostic reasons and for the economic management of health care resources, additional biomarkers need to be identified, and their monitoring can conceivably be performed in the early stages of the disease. In this retrospective cross-sectional study, we found that serum concentrations of high-mobility group box 1 (HMGB1) and heme oxygenase-1 (HO-1), at the time of hospital admission, could be useful biomarkers for COVID-19 management. The study included 160 randomly selected recovered patients with mild to moderate COVID-19 on admission. Compared with healthy controls, serum HMGB1 and HO-1 levels increased by 487.6 pg/mL versus 43.1 pg/mL and 1497.7 pg/mL versus 756.1 pg/mL, respectively. Serum HO-1 correlated significantly with serum HMGB1, oxidative stress parameters (malondialdehyde (MDA), the phosphatidylcholine/lysophosphatidylcholine ratio (PC/LPC), the ratio of reduced and oxidative glutathione (GSH/GSSG)), and anti-inflammatory acute phase proteins (ferritin, haptoglobin). Increased heme catabolism/hemolysis were not detected. We hypothesize that the increase in HO-1 in the early phase of COVID-19 disease is likely to have a survival benefit by providing protection against oxidative stress and inflammation, whereas the level of HMGB1 increase reflects the activity of the innate immune system and represents levels within which the disease can be kept under control.

Metabolically Active Zones Involving Fatty Acid Elongation Delineated by DESI-MSI Correlate with Pathological and Prognostic Features of Colorectal Cancer

Colorectal cancer (CRC) is the second leading cause of cancer deaths. Despite recent advances, five-year survival rates remain largely unchanged. Desorption electrospray ionization mass spectrometry imaging (DESI) is an emerging nondestructive metabolomics-based method that retains the spatial orientation of small-molecule profiles on tissue sections, which may be validated by ‘gold standard’ histopathology. In this study, CRC samples were analyzed by DESI from 10 patients undergoing surgery at Kingston Health Sciences Center. The spatial correlation of the mass spectral profiles was compared with histopathological annotations and prognostic biomarkers. Fresh frozen sections of representative colorectal cross sections and simulated endoscopic biopsy samples containing tumour and non-neoplastic mucosa for each patient were generated and analyzed by DESI in a blinded fashion. Sections were then hematoxylin and eosin (H and E) stained, annotated by two independent pathologists, and analyzed. Using PCA/LDA-based models, DESI profiles of the cross sections and biopsies achieved 97% and 75% accuracies in identifying the presence of adenocarcinoma, using leave-one-patient-out cross validation. Among the m/z ratios exhibiting the greatest differential abundance in adenocarcinoma were a series of eight long-chain or very-long-chain fatty acids, consistent with molecular and targeted metabolomics indicators of de novo lipogenesis in CRC tissue. Sample stratification based on the presence of lympovascular invasion (LVI), a poor CRC prognostic indicator, revealed the abundance of oxidized phospholipids, suggestive of pro-apoptotic mechanisms, was increased in LVI-negative compared to LVI-positive patients. This study provides evidence of the potential clinical utility of spatially-resolved DESI profiles to enhance the information available to clinicians for CRC diagnosis and prognosis.

Exploration of LPS2 agonist binding modes using the combination of a new hydrophobic scaffold and homology modeling

Lysophosphatidylserine (LysoPS) is an endogenous pan-agonist of three G-protein coupled receptors (GPCRs): LPS₁/GPR34, LPS₂/P2Y₁₀, and LPS₃/GPR174, and we previously reported a series of LysoPS-based agonists of these receptors. Interestingly, we found that LPS₁ agonist activity was very sensitive to structural change at the hydrophobic fatty acid moiety, whereas LPS₂ agonist activity was not. Here, to probe the molecular basis of LPS₂ agonist binding, we developed a new class of hydrophobic fatty acid surrogates having a biphenyl-ether scaffold. The LPS₂ agonist activity of these compounds proved sensitive to molecular modification of the hydrophobic skeleton. Thus, we next constructed an LPS₂ model by homology modeling and docking/molecular dynamics (MD) simulation, and validated it by means of SAR studies together with point mutations of selected receptor amino-acid residues. The putative ligand-binding site of LPS₂ is Γ-shaped, with a hydrophilic site horizontally embedded in the receptor transmembrane helix bundles and a perpendicular hydrophobic groove adjoining transmembrane domains 4 and 5 that is open to the membrane bilayer. The binding poses of LPS₂ agonists to this site are consistent with easy incorporation of various kinds of fatty acid surrogates. Structural development based on this model afforded a series of potent and selective LPS₂ full agonists, which showed enhanced in vitro actin stress fiber formation effect.

Moderate-intensity continuous training has time-specific effects on the lipid metabolism of adolescents

Background and Objectives

Moderate-intensity continuous training (MICT) is used to observe lipidomic effects in adults. However, the efects of MICT on lipid metabolism in adolescents remain unclear. Therefore, we aimed to longitudinally characterize the lipid profile in adolescents during different periods of 6-week MICT.

Methods

Fifteen adolescents undertook bicycle training at 65% of maximal oxygen consumption. Plasma samples were collected at four time points (T0, T1, T2, and T3). Targeted lipidomics was assessed by ultra-performance liquid chromatography–tandem mass spectrometry to characterize the plasma lipid profiles of the participants to identify the lipids present at differing concentrations and changes in lipid species with time.

Results

MICT afected the plasma lipid profiles of the adolescents. The concentrations of diglycerides, phosphatidylinositol, lysophosphatidic acid, lysophosphatidylcholine, and lysophosphatidylethanolamine were increased at T1, decreased at T2, and increased again at T3. Fatty acids (FAs) showed an opposite trend. Ether-linked alkylphosphatidylcholine and triglycerides were significantly increased and remained high. Sphingolipid concentrations initially decreased and then remained low. Therefore, a single bout of exercise had substantial efects on lipid metabolism, but by T3, fewer lipid species were present at significantly diferent concentrations and the magnitudes of the remaining diferences were smaller than those at earlier times. Among all the changed lipids, only DG(14:1/18:1), HexCer(d18:1/22:1) and FA(22:0) showed no significant correlations with any other 51 lipids (P < 0.05). Glycerides and phospholipids showed positive correlations with each other (P < 0.05), but FAs were significantly negatively correlated with glycerides and phospholipids while positively with other FAs (P < 0.05). Pathway enrichment analysis showed that 50% of the metabolic pathways represented were related to lipid metabolism and lipid biosynthesis.

Conclusion

MICT increases ether-linked alkylphosphatidylcholine and triglyceride concentrations. Diglyceride, phosphatidylinositol, and lysophosphatidylcholine concentrations initially rise and then decrease 6 weeks after MICT, but FA concentrations show an opposite trend. These changes might correlate with lipid metabolism or biosynthesis pathways.

PFAS-induced lipidomic dysregulations and their associations with developmental toxicity in zebrafish embryos

Per- and polyfluoroalkyl substances (PFASs) are persistent environmental contaminants, posing developmental toxicity to fish and human. PFAS-induced lipid metabolism disorders were demonstrated using the zebrafish (Danio rerio) embryo model, but the detailed changes of lipid compositions and the influence of these changes on the biological development are still unclear. Herein, lipidomics analysis was performed to reveal the dysregulations of lipid metabolism in zebrafish embryos exposed to perfluorooctanoic acid (PFOA) or perfluorooctane sulfonate (PFOS) through microinjection. Various abnormal phenotypes were observed, including heart bleeding, pericardium edema, spinal curvature and increased heart rate at 72 h after fertilization, especially in the PFOS exposure groups. Lipidomic profiling found downregulated phosphatidylethanolamines in the PFAS-exposed embryos, especially those containing a docosahexaenoyl (DHA) chain, indicating an excessive oxidative damage to the embryos. Glycerolipids were mainly upregulated in the PFOA groups but downregulated in the PFOS groups. These aberrations may reflect oxidative stress, energy metabolism malfunction and proinflammatory signals induced by PFASs. However, supplement of DHA may not be effective in recovering the lipidomic dysregulations and protecting from the developmental toxicity induced by PFASs, showing the complexity of the toxicological mechanisms. This work has revealed the associations between the abnormal phenotypes and dysregulations of lipid metabolism in zebrafish embryos induced by PFASs from the aspect of lipidomics, and discovered the underlying molecular mechanisms of the developmental toxicity of PFASs.

Targeted Lipidomics and Inflammation Response to Six Weeks of Sprint Interval Training in Male Adolescents

Lipids play an important role in coordinating and regulating metabolic and inflammatory processes. Sprint interval training (SIT) is widely used to improve sports performance and health outcomes, but the current understanding of SIT-induced lipid metabolism and the corresponding systemic inflammatory status modification remains controversial and limited, especially in male adolescents. To answer these questions, twelve untrained male adolescents were recruited and underwent 6 weeks of SIT. The pre- and post-training testing included analyses of peak oxygen consumption (VO2peak), biometric data (weight and body composition), serum biochemical parameters (fasting blood glucose, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triacylglycerol, testosterone, and cortisol), inflammatory markers, and targeted lipidomics. After the 6-week SIT, the serum C-reactive protein (CRP), interleukin (IL)-1β, IL-2, IL-4, IL-10, tumor necrosis factor (TNF)-α, and transforming growth factor (TGF)-β significantly decreased (p < 0.05), whereas IL-6 and IL-10/TNF-α significantly increased (p < 0.05). In addition, the targeted lipidomics revealed changes in 296 lipids, of which 33 changed significantly (p < 0.05, fold change > 1.2 or <1/1.2). The correlation analysis revealed that the changes in the inflammatory markers were closely correlated with the changes in some of the lipids, such as LPC, HexCer, and FFA. In conclusion, the 6-week SIT induced significant changes in the inflammatory markers and circulating lipid composition, offering health benefits to the population.

Phospholipid remodeling and its derivatives are associated with COVID-19 severity

BACKGROUND

Timely medical intervention in severe cases of coronavirus disease 2019 (COVID-19) and better understanding of the disease's pathogenesis are essential for reducing mortality, but early classification of severe cases and its progression is challenging.

OBJECTIVE

We investigated the levels of circulating phospholipid metabolites and their relationship with COVID-19 severity, as well as the potential role of phospholipids in disease progression.

METHODS

We performed nontargeted lipidomic analysis of plasma samples (n = 150) collected from COVID-19 patients (n = 46) with 3 levels of disease severity, healthy individuals, and subjects with metabolic disease.

RESULTS

Phospholipid metabolism was significantly altered in COVID-19 patients. Results of a panel of phosphatidylcholine (PC) and lysophosphatidylcholine (LPC) and of phosphatidylethanolamine and lysophosphatidylethanolamine (LPE) ratios were significantly correlated with COVID-19 severity, in which 16 phospholipid ratios were shown to distinguish between patients with severe disease, mild disease, and healthy controls, 9 of which were at variance with those in subjects with metabolic disease. In particular, relatively lower ratios of circulating (PC16:1/22:6)/LPC 16:1 and (PE18:1/22:6)/LPE 18:1 were the most indicative of severe COVID-19. The elevation of levels of LPC 16:1 and LPE 18:1 contributed to the changes of related lipid ratios. An exploratory functional study of LPC 16:1 and LPE 18:1 demonstrated their ability in causing membrane perturbation, increased intracellular calcium, cytokines, and apoptosis in cellular models.

CONCLUSION

Significant Lands cycle remodeling is present in patients with severe COVID-19, suggesting a potential utility of selective phospholipids with functional consequences in evaluating COVID-19's severity and pathogenesis.

Effects of various thermal treatments on interfacial composition and physical properties of bovine milk fat globules

This study aimed to investigate changes of milk fat globules (MFG) and their membranes after thermal treatments, and further analyzed the relationship between the stability of MFG and interfacial compositions of milk fat globule membrane (MFGM). We characterized the influence of three kinds of thermal treatments on fat globule interfacial components (including interfacial phospholipids and interfacial protein) and physical properties using phospholipidomics and several microscopy techniques. The results showed that size of MFG increased from 2.96 μm to 3.59 μm and ζ-potential decreased from -9.71 mV to -13.23 mV after thermal treatment, suggesting that MFGM was damaged and MFG occurred coalescence. Thermal treatment increased the Young's modulus of MFGM and made membranes more fragile. The abundance of MFGM proteins decreased while casein and β-lactoglobulin increased after thermal treatment. Results of phospholipidomics showed that 27 phospholipid species could be used to distinguish the samples. Pasteurization reduced mainly SM and PC located in the outer bilayer of MFGM, while ultra-pasteurization reduced not only SM and PC but also PI and PE located in the inner leaflet. Based on correlation analysis, the increase in Young's modulus of MFGM during thermal treatment might be related to changes in chemical components on the membrane, suggesting a potential link between the change of MFGM components and fat globule coalescence behavior.

Isosteric Replacement of Ester Linkage of Lysophospholipids with Heteroaromatic Rings Retains Potency and Subtype Selectivity

Our group has reported various derivatives of lysophosphatidylserine (LysoPS) as potent and subtype-selective agonists for G-protein-coupled receptors (GPCRs). However, the ester linkage between the glycerol moiety and fatty acid or fatty acid surrogate is present in all of them. In order to develop these LysoPS analogs as drug candidates, appropriate pharmacokinetic consideration is essential. Here, we found that the ester bond of LysoPS is highly susceptible to metabolic degradation in mouse blood. Accordingly, we examined isosteric replacement of the ester linkage with heteroaromatic rings. The resulting compounds showed excellent retention of potency and receptor subtype selectivity, as well as increased metabolic stability in vitro.

Biological functions of bacterial lysophospholipids

Lysophospholipids (LPLs) are lipid-derived metabolic intermediates in the cell membrane. The biological functions of LPLs are distinct from their corresponding phospholipids. In eukaryotic cells LPLs are important bioactive signaling molecules that regulate many important biological processes, but in bacteria the function of LPLs is still not fully defined. Bacterial LPLs are usually present in cells in very small amounts, but can strongly increase under certain environmental conditions. In addition to their basic function as precursors in membrane lipid metabolism, the formation of distinct LPLs contributes to the proliferation of bacteria under harsh circumstances or may act as signaling molecules in bacterial pathogenesis. This review provides an overview of the current knowledge of the biological functions of bacterial LPLs including lysoPE, lysoPA, lysoPC, lysoPG, lysoPS and lysoPI in bacterial adaptation, survival, and host-microbe interactions.

PNPLA3 148M/M Is More Susceptible to Palmitic Acid-Induced Endoplasmic Reticulum Stress-Associated Apoptosis in HepG2 Cells

BACKGROUND

Patatin-like phospholipase domain-containing 3 (PNPLA3) is a major susceptibility gene for nonalcoholic fatty liver disease (NAFLD), and its rs738409 (I148M) polymorphism is associated with the occurrence and progression of NAFLD. Endoplasmic reticulum (ER) stress-related hepatocyte lipoapoptosis contributes to the progress of NAFLD. PNPLA3 is also known as a member of the calcium-independent phospholipase A2ε family, which can hydrolyze fatty acids to generate lysophosphatidylcholine (LPC) that induces ER stress-related hepatocyte lipoapoptosis. Whether the PNPLA3 risk genotype 148M/M is involved in more severe ER stress-associated lipoapoptosis is unclear.

METHODS

A PNPLA3148I knock-in HepG2 cell model was constructed based on HepG2 expressing PNPLA3 148M/M using the Cas9/sgRNA system. PNPLA3 148M/M, I/M, and I/I cells were treated with 0.3 mM palmitic acid (PA) for 24 h to induce lipid deposition. Cellular lipid deposition was detected by oil red staining. Apoptosis was observed by TUNEL. LPC was determined by ELISA, and the expression of PNPLA3, the ER stress marker Bip, molecules involved in the ER stress PERK/elF-2a pathway, and its downstream C/EBP homologous protein (CHOP)-mediated apoptotic pathway were detected by western blot.

RESULTS

The results showed no difference in PNPLA3 basal expression and basal hepatocyte lipid content between the three genotypes of cells. Lipid deposition and apoptosis were more severe in PNPLA3 148M/M and 148I/M cells than in I/I cells after PA treatment. PA-induced upregulation of protein expression of Bip, ER stress-responsive PERK pathway molecules p-PERK, p-eIF2α, CHOP, and CHOP-associated apoptotic molecules PUMA and Bax were more pronounced in PNPLA3 148M/M cells than in PNPLA3 148I/I cells. The basal LPC levels and the PA-treated increase of LPC levels in the cell culture supernatants did not differ between the three genotypic cells.

CONCLUSION

PNPLA3 148M/M cells were more susceptible to PA-induced lipid deposition and ER stress-related apoptosis than 148I/I cells, and the proapoptotic susceptibility of PNPLA3 148M/M is independent of LPC.

Acinar ATP8b1/LPC pathway promotes macrophage efferocytosis and clearance of inflammation during chronic pancreatitis development

Noninflammatory clearance of dying cells by professional phagocytes, termed efferocytosis, is fundamental in both homeostasis and inflammatory fibrosis disease but has not been confirmed to occur in chronic pancreatitis (CP). Here, we investigated whether efferocytosis constitutes a novel regulatory target in CP and its mechanisms. PRSS1 transgenic (PRSS1^Tg) mice were treated with caerulein to mimic CP development. Phospholipid metabolite profiling and epigenetic assays were performed with PRSS1^Tg CP models. The potential functions of Atp8b1 in CP model were clarified using Atp8b1-overexpressing adeno-associated virus, immunofluorescence, enzyme-linked immunosorbent assay(ELISA), and lipid metabolomic approaches. ATAC-seq combined with RNA-seq was then used to identify transcription factors binding to the Atp8b1 promoter, and ChIP-qPCR and luciferase assays were used to confirm that the identified transcription factor bound to the Atp8b1 promoter, and to identify the specific binding site. Flow cytometry was performed to analyze the proportion of pancreatic macrophages. Decreased efferocytosis with aggravated inflammation was identified in CP. The lysophosphatidylcholine (LPC) pathway was the most obviously dysregulated phospholipid pathway, and LPC and Atp8b1 expression gradually decreased during CP development. H3K27me3 ChIP-seq showed that increased Atp8b1 promoter methylation led to transcriptional inhibition. Atp8b1 complementation substantially increased the LPC concentration and improved CP outcomes. Bhlha15 was identified as a transcription factor that binds to the Atp8b1 promoter and regulates phospholipid metabolism. Our study indicates that the acinar Atp8b1/LPC pathway acts as an important "find-me" signal for macrophages and plays a protective role in CP, with Atp8b1 transcription promoted by the acinar cell-specific transcription factor Bhlha15. Bhlha15, Atp8b1, and LPC could be clinically translated into valuable therapeutic targets to overcome the limitations of current CP therapies.

The role of sphingolipids in meibomian gland dysfunction and ocular surface inflammation

Inflammation occurs in response to tissue injury and invasion of microorganisms and is carried out by the innate and adaptive immune systems, which are regulated by numerous chemokines, cytokines, and lipid mediators. There are four major families of bioactive lipid mediators that play an integral role in inflammation - eicosanoids, sphingolipids (SPL), specialized pro-resolving mediators (SPM), and endocannabinoids. SPL have been historically recognized as important structural components of cellular membranes; their roles as bioactive lipids and inflammatory mediators are recent additions. Major SPL metabolites, including sphingomyelin, ceramide, ceramide 1-phosphate (C1P), sphingosine, sphingosine 1-phosphate (S1P), and their respective enzymes have been studied extensively, primarily in cell-culture and animal models, for their roles in cellular signaling and regulating inflammation and apoptosis. Less focus has been given to the involvement of SPL in eye diseases. As such, the aim of this review was to examine relationships between the SPL family and ocular surface diseases, focusing on their role in disease pathophysiology and discussing the potential of therapeutics that disrupt SPL pathways.

Effects of Two Kinds of Extracts of Cistanche deserticola on Intestinal Microbiota and Its Metabolism

Cistanche deserticola belongs to the Liedang family. Known as "desert ginseng", it has high medicinal value and plays important roles in endocrine regulation, neuroprotection, immune regulation, and other processes. Some studies have shown that single substances such as polysaccharides and phenylethanolside can affect intestinal microbiota, but few studies have studied the synergistic effect of various components in Cistanche deserticola extracts on intestinal microbiota. Therefore, in this study, through an in vitro digestion model (Changdao Moni, CDMN) combined with 16S rRNA gene amplification sequencing technology and untargeted metabolomics technology, it was found that the two extracts all had significant effects on the enteric cavity and mucosal flora. Both extracts inhibited Bacteroides in the intestinal cavity and Parabacteroides and Ruminococcus 2 in the intestinal mucosa and promoted Bifidobacterium and Prevotella in the intestinal cavity and Megasphaera in the intestinal mucosa. The aqueous extract also inhibited Phascolarctobacterium. Both extracts also significantly increased the production of short-chain fatty acids, especially butyrate. The intake of extract had significant effects on the metabolic pathways related to amino acids and lipids. Indoles were upregulated by the aqueous extract but downregulated by the alcohol extract. In addition, the extract also had a significant effect on the hemolytic phosphorus esters. In conclusion, the two kinds of extracts have different effects on intestinal microbiota and its metabolism. This study provides guiding significance for the edibility and food development of Cistanche deserticola.

Lipidomic changes in the liver of beagle dogs associated with Toxocara canis infection

A global lipidomic analysis using liquid chromatography–tandem mass spectrometry was performed on the liver of beagle dogs infected with Toxocara canis to profile hepatic lipid species at 12 h post-infection (hpi), 24 hpi, and 36 days post-infection (dpi). This analysis identified six categories and 42 subclasses of lipids, including 173, 64, and 116 differentially abundant lipid species at 12 hpi, 24 hpi, and 36 dpi, respectively. Many of the identified lysophospholipids, such as lysophosphatidylglycerol, lysophosphatidylserine, and lysophosphatidylcholine, may contribute to the migration and development of T. canis during the early infection stage. Pathway analysis revealed significant alterations of several immune-inflammatory pathways, such as the B-cell receptor signaling pathway, the NF-kappa B signaling pathway, and the C-type lectin receptor signaling pathway at 12 and 24 hpi. These findings demonstrate the value of lipidomic profiling in revealing the extent of changes in the composition and abundance of hepatic lipidome caused by T. canis infection and their relevance to the pathophysiology of toxocariasis in beagle dogs.

Sphingosine 1-phosphate lyase facilitates cancer progression through converting sphingolipids to glycerophospholipids

BACKGROUND

In addition to potent agonist properties for sphingosine 1-phosphate (S1P) receptors, intracellularly, S1P is an intermediate in metabolic conversion pathway from sphingolipids to glycerolysophospholipids (glyceroLPLs). We hypothesized that this S1P metabolism and its products might possess some novel roles in the pathogenesis of cancer, where S1P lyase (SPL) is a key enzyme.

METHODS

The mRNA levels of sphingolipid-related and other cancer-related factors were measured in human hepatocellular carcinoma (HCC), colorectal cancer, and esophageal cancer patients' tumours and in their adjacent non-tumour tissues. Phospholipids (PL) and glyceroLPLs were measured by using liquid chromatography-tandem mass spectrometry (LC-MS/MS). In-vitro experiments were performed in Colon 26 cell line with modulation of the SPL and GPR55 expressions. Xenograft model was used for determination of the cancer progression and for pharmacological influence.

RESULTS

Besides high SPL levels in human HCC and colon cancer, SPL levels were specifically and positively linked with levels of glyceroLPLs, including lysophosphatidylinositol (LPI). Overexpression of SPL in Colon 26 cells resulted in elevated levels of LPI and lysophosphatidylglycerol (LPG), which are agonists of GPR55. SPL overexpression-enhanced cell proliferation was inhibited by GPR55 silencing. Conversely, inhibition of SPL led to the opposite outcome and reversed by adding LPI, LPG, and metabolites generated during S1P degradation, which is regulated by SPL. The xenograft model results suggested the contribution of SPL and glyceroLPLs to tumour progression depending on levels of SPL and GPR55. Moreover, the pharmacological inhibition of SPL prevented the progression of cancer. The underlying mechanisms for the SPL-mediated cancer progression are the activation of p38 and mitochondrial function through the LPI, LPG-GPR55 axis and the suppression of autophagy in a GPR55-independent manner.

CONCLUSION

A new metabolic pathway has been proposed here in HCC and colon cancer, SPL converts S1P to glyceroLPLs, mainly to LPI and LPG, and facilitates cancer development.

Profiling of lysophosphatidylethanolamine molecular species in human serum and in silico prediction of the binding site on albumin

Lysophosphatidylethanolamine (LPE) is a major lysophospholipid produced by phospholipids and binds to human serum albumin (HSA). LPEs may play various roles in vivo depending on the differences in their acyl chains. However, only few reports have been published on the biological functions of LPEs. Hence, we determined the exact relative abundance of the major LPEs in the serum of healthy participants (n = 8) using liquid chromatography-tandem mass spectrometry. Consequently, LPE 18:2 (24.1 ± 5.2%) was found to be the most abundant in serum. To understand the distribution of LPEs, the serum separated via gel-filtration high-performance liquid chromatography was subjected to quantitative measurement. LPEs were more observed in the albumin fraction than the lipoprotein fraction. We also performed a fluorescence displacement assay and an in silico molecular docking experiment using AutoDock to confirm the affinity and binding sites of the LPEs on HSA. The binding affinities of the LPEs for drug sites 1 and 2 on HSA were relatively low, with Ki values of approximately 11 and 3.8 μM, respectively. AutoDock analysis revealed the conformation of the LPEs bound to drug sites and the possibility of LPEs binding to other HSA sites. These findings could help to elucidate the biological and pathological functions of LPEs.

Integrated microbiome and metabolome analysis reveals the potential therapeutic mechanism of Qing-Fei-Pai-Du decoction in mice with coronavirus-induced pneumonia

Current studies have shown that gut microbiota may be closely related to the severity of coronavirus disease 2019 (COVID-19) by regulating the host immune response. Qing-Fei-Pai-Du decoction (QFPDD) is the recommended drug for clinical treatment of patients with COVID-19 in China, but whether it exerts a therapeutic effect by modulating the immune response through gut microbiota remains unclear. In this study, we evaluated the therapeutic effects of QFPDD in pneumonia model mice and performed 16S rRNA sequencing and serum and lung tissue metabolomic analysis to explore the underlying mechanisms during the treatment. Then, Spearman correlation analysis was performed on gut microbiome, serum metabolome, and immune-inflammation-related indicators. Our results suggest that QFPDD can restore the richness and diversity of gut microbiota, and multiple gut microbiota (including Alistipes, Odoribacter, Staphylococcus, Lachnospiraceae_NK4A136_group Enterorhabdus, and unclassified_f_Lachnospiraceae) are significantly associated with immune-inflammation-related indicators. In addition, various types of lipid metabolism changes were observed in serum and lung tissue metabolome, especially glycerophospholipids and fatty acids. A total of 27 differential metabolites (DMs) were significantly correlated with immune-inflammation-related indicators, including 9 glycerophospholipids, 7 fatty acids, 3 linoleic acid, 2 eicosanoids, 2 amino acids, 2 bile acids, and 2 others. Interestingly, these DMs showed a good correlation with the gut microbiota affected by QFPDD. The above results suggest that QFPDD can improve the immune function and reduce inflammation in pneumonia model mice by remodeling gut microbiota and host metabolism.

Drug-Initiated Activity Metabolomics Identifies Myristoylglycine as a Potent Endogenous Metabolite for Human Brown Fat Differentiation

Worldwide, obesity rates have doubled since the 1980s and in the USA alone, almost 40% of adults are obese, which is closely associated with a myriad of metabolic diseases such as type 2 diabetes and arteriosclerosis. Obesity is derived from an imbalance between energy intake and consumption, therefore balancing energy homeostasis is an attractive target for metabolic diseases. One therapeutic approach consists of increasing the number of brown-like adipocytes in the white adipose tissue (WAT). Whereas WAT stores excess energy, brown adipose tissue (BAT) can dissipate this energy overload in the form of heat, increasing energy expenditure and thus inhibiting metabolic diseases. To facilitate BAT production a high-throughput screening approach was developed on previously known drugs using human Simpson-Golabi-Behmel Syndrome (SGBS) preadipocytes. The screening allowed us to discover that zafirlukast, an FDA-approved small molecule drug commonly used to treat asthma, was able to differentiate adipocyte precursors and white-biased adipocytes into functional brown adipocytes. However, zafirlukast is toxic to human cells at higher dosages. Drug-Initiated Activity Metabolomics (DIAM) was used to investigate zafirlukast as a BAT inducer, and the endogenous metabolite myristoylglycine was then discovered to mimic the browning properties of zafirlukast without impacting cell viability. Myristoylglycine was found to be bio-synthesized upon zafirlukast treatment and was unique in inducing brown adipocyte differentiation, raising the possibility of using endogenous metabolites and bypassing the exogenous drugs to potentially alleviate disease, in this case, obesity and other related metabolic diseases.

Liuwei Dihuang Decoction Alleviates Cognitive Dysfunction in Mice With D-Galactose-Induced Aging by Regulating Lipid Metabolism and Oxidative Stress via the Microbiota-Gut-Brain Axis

Background

Aging is an important cause of cognitive dysfunction. Liuwei Dihuang decoction (LW), a commonly applied Chinese medicine formula, is widely used for the treatment of aging-related diseases in China. Previously, LW was confirmed to be effective in prolonging life span and reducing oxidative stress in aged mice. Unfortunately, the underlying mechanism of LW remains unclear. The aim of this study was to interpret the mechanism by which LW alleviates cognitive dysfunction related to aging from the perspective of the microbiota-gut-brain axis.

Method

All C57BL/6 mice (n = 60) were randomly divided into five groups: the control, model, vitamin E (positive control group), low-dose LW and high-dose LW groups (n = 12 in each group). Except for those in the control group, D-galactose was subcutaneously injected into mice in the other groups to induce the aging model. The antiaging effect of LW was evaluated by the water maze test, electron microscopy, 16S rRNA sequencing, combined LC–MS and GC–MS metabolomics, and ELISA.

Results

Liuwei Dihuang decoction ameliorated cognitive dysfunction and hippocampal synaptic ultrastructure damage in aging mice. Moreover, LW decreased Proteobacteria abundance and increased gut microbiota diversity in aging mice. Metabolomic analysis showed that LW treatment was associated with the significantly differential abundance of 14 metabolites, which were mainly enriched in apelin signaling, sphingolipid metabolism, glycerophospholipid and other metabolic pathways. Additionally, LW affected lipid metabolism and oxidative stress in aging mice. Finally, we also found that LW-regulated microbial species such as Proteobacteria and Fibrobacterota had potential relationships with lipid metabolism, oxidative stress and hippocampal metabolites.

Conclusion

In brief, LW improved cognitive function in aging mice by regulating lipid metabolism and oxidative stress through restoration of the homeostasis of the microbiota-gut-brain axis.

Pretransplant Systemic Lipidomic Profiles in Allogeneic Stem Cell Transplant Recipients

Simple Summary

Stem cell transplantation is used in the treatment of aggressive hematological malignancies and consists of initial high-dose and potentially lethal chemotherapy, followed by rescue with the transplantation of hematopoietic stem cells. Transplantation with stem cells from a healthy donor (i.e., allogeneic stem cells) has the strongest anti-cancer effect, but also the highest risk of severe toxicity. Furthermore, the clinical status at the time of transplantation (inflammation, fluid overload) is associated with posttransplant mortality, and immune-mediated acute graft-versus-host disease (GVHD) is a potential lethal complication. Finally, lipid metabolism regulates the proliferation and survival of both malignant hematological cells and immunocompetent cells that cause GVHD. Our study shows that the pretransplant lipid profiles differ between allotransplant recipients and can be used for the subclassification of patients and possibly to identify patients with an increased risk of death due to disease relapse or treatment toxicity. The therapeutic targeting of lipid metabolism should therefore be further explored in these transplant recipients.

Abstract

Allogeneic stem cell transplantation is used in the treatment of high-risk hematological malignancies. However, this treatment is associated with severe treatment-related morbidity and mortality. The metabolic status of the recipient may be associated with the risk of development of transplant-associated complications such as graft-versus-host disease (GVHD). To better understand the impact of the lipidomic profile of transplant recipients on posttransplant complications, we evaluated the lipid signatures of patients with hematological disease using non-targeted lipidomics. In the present study, we studied pretransplant serum samples derived from 92 consecutive patients with acute myeloid leukemia (AML) or high-risk myelodysplastic syndrome (MDS). A total of 960 lipid biochemicals were identified, and the pretransplant lipidomic profiles differed significantly when comparing patients with and without the risk factors: (i) pretransplant inflammation, (ii) early fluid overload, and (iii) patients with and without later steroid-requiring acute GVHD. All three factors, but especially patients with pretransplant inflammation, were associated with decreased levels of several lipid metabolites. Based on the overall concentrations of various lipid subclasses, we identified a patient subset characterized by low lipid levels, increased frequency of MDS patients, signs of inflammation, decreased body mass index, and an increased risk of early non-relapse mortality. Metabolic targeting has been proposed as a possible therapeutic strategy in allotransplant recipients, and our present results suggest that the clinical consequences of therapeutic intervention (e.g., nutritional support) will also differ between patients and depend on the metabolic context.

GPR174 signals via Gαs to control a CD86-containing gene expression program in B cells

GPR174 is abundantly expressed in B and T lymphocytes and has a role in restraining T cell responses, but the function of GPR174 in B cells is less clear. Here we report that upon in vitro culture B cells undergo a spontaneous GPR174-dependent activation process that is associated with marked changes in gene expression, including up-regulation of Cd86, Nr4a1, Ccr7, and phosphodiesterases. B cells lacking Gαs show a block in induction of the GPR174-dependent program. Spontaneous up-regulation of CD86 in cultured B cells is dependent on protein kinase A. Both GPR174- and Gαs-deficient B cells show enhanced survival in culture. In vivo, GPR174 contributes to NUR77 expression in follicular B cells and is needed for establishing a marginal zone compartment of normal size. Treatment of mice with lysophosphatidylserine (lysoPS), a GPR174 ligand, is sufficient to promote CD86 up-regulation by follicular B cells. These findings demonstrate that GPR174 can signal via Gαs to modulate B cell gene expression and show this can occur in vivo in response to lysoPS. Additionally, the findings illuminate a pathway that might be targeted to improve systems for the in vitro study of B cell responses.

Persistent elevation of lysophosphatidylcholine promotes radiation brain necrosis with microglial recruitment by P2RX4 activation

Brain radiation necrosis (RN) or neurocognitive disorder is a severe adverse effect that may occur after radiation therapy for malignant brain tumors or head and neck cancers. RN accompanies inflammation which causes edema or micro-bleeding, and no fundamental treatment has been developed. In inflammation, lysophospholipids (LPLs) are produced by phospholipase A₂ and function as bioactive lipids involved in sterile inflammation in atherosclerosis or brain disorders. To elucidate its underlying mechanisms, we investigated the possible associations between lysophospholipids (LPLs) and RN development in terms of microglial activation with the purinergic receptor P2X purinoceptor 4 (P2RX4). We previously developed a mouse model of RN and in this study, measured phospholipids and LPLs in the brains of RN model by liquid chromatography tandem mass spectrometry (LC–MS/MS) analyses. We immune-stained microglia and the P2RX4 in the brains of RN model with time-course. We treated RN model mice with ivermectin, an allosteric modulator of P2RX4 and investigate the effect on microglial activation with P2RX4 and LPLs’ production, and resulting effects on overall survival and working memory. We revealed that LPLs (lysophosphatidylcholine (LPC), lysophosphatidyl acid, lysophosphatidylserine, lysophosphatidylethanolamine, lysophosphatidylinositol, and lysophosphatidylglycerol) remained at high levels during the progression of RN with microglial accumulation, though phospholipids elevations were limited. Both microglial accumulation and activation of the P2RX4 were attenuated by ivermectin. Moreover, the elevation of all LPLs except LPC was also attenuated by ivermectin. However, there was limited prolongation of survival time and improvement of working memory disorders. Our findings suggest that uncontrollable increased LPC, even with ivermectin treatment, promoted the development of RN and working memory disorders. Therefore, LPC suppression will be essential for controlling RN and neurocognitive disorder after radiation therapy.