Phosphatidylcholine Research Articles

A molecular mechanism for how pressure induces interdigitation of phospholipid bilayer membranes

The phase transition from the ripple gel phase to the interdigitated gel phase of bilayers of phosphatidylcholines (PCs) with two saturated long-chain fatty acids under high pressure was investigated by pressure-scanning microscopy, fluorometry, and dynamic light scattering (DLS) measurements. Microscopic observation for giant vesicles (GVs) of distearoyl-PC (DSPC) under high pressure showed that spherical GVs transforms significantly into warped and distorted spherical ones instantaneously at the pressure-induced interdigitation. The fluorescence intensities of amphiphilic probe Prodan and hydrophobic probe Laurdan in the dipalmitoyl-PC (DPPC) bilayer steeply decreased and increased, respectively, at the interdigitation, suggesting that the conformational change of the polar head group of DPPC molecule in the bilayer transiently occurred at the interdigitation. Further, it was found from the high-pressure DLS measurements that the size of the vesicle particles of the DPPC and DSPC transiently increases near the interdigitation pressure, whereas the chemically induced interdigitation by adding ethanol to the DSPC bilayer membrane under atmospheric pressure produce no such change in the particle size. Taking account of the critical packing parameter of the PC molecule, the above experimental results would lead us to the conclusion that the pressure-induced interdigitation is attributable to the increase in repulsive interaction between the polar head groups of the PC molecules resulting from the orientational change of the head group from a parallel alignment to a perpendicular one with respect to the bilayer surface by applying pressure, namely the transient state: it occurs when the repulsive interaction exceeds a threshold value for the balance between the repulsive interaction and the attractive interaction among the hydrophobic acyl chains.

Efficient preparation of diglycerides from rapeseed oil sediment using phospholipase C in a solvent-free phospholipid hydrolysis system

Diacylglycerols (DAGs), which are involved in rapid energy supply and fat reduction, are typically produced from triglycerides, glycerol and fatty acids through lipase-catalysis. This study introduces a novel method for preparing DAGs in a solvent-free system by using phospholipase C (PLC) hydrolysis of rapeseed oil sediment, which is a byproduct of the rapeseed oil water degumming. The optimisation of DAGs production by PLC hydrolysis using Response Surface Methodology (RMS) and Box-Behnken design. Under optimal conditions of 0.6% enzyme concentration, 51 °C reaction temperature, 56% water content and 2.2 h reaction time, phosphatidylcholine (PC) and phosphatidylethanolamine in the oil sediment were almost entirely converted into DAGs. This reaction yielded an oil product containing 27.1% DAGs, with 1,2-DAGs at 24.88% ± 0.01% and 1,3-DAGs at 2.22% ± 0.01%, which is favoured in drug delivery systems, and the fatty acid composition of DAGs oil was almost consistent with rapeseed oil. Moreover, the residual phospholipids were primarily phosphatidylinositol (PI), with an amount of 69.73%, suggesting the potential for high-purity PI production. In this study, rapeseed oil sediment achieved comprehensive utilization through hydrolysis by PLC, which not only enhanced the value of the oil sediment but also provided a new approach for the synthesis of DAGs.

Phosphatidylcholine's influence on Dysmenorrhea: conclusive insights from Mendelian randomization analysis.

This study aimed to investigate the causal relationship between phosphatidylcholine (PC) levels and dysmenorrhea using Mendelian randomization (MR) analysis. We conducted a two-sample MR analysis using GWAS data on PC levels and dysmenorrhea. Single nucleotide polymorphisms (SNPs) associated with PC levels were used as instrumental variables. MR-Egger regression and inverse variance weighting (IVW) were used to estimate the causal effect of PC levels on dysmenorrhea. Sensitivity analyses were performed to assess the robustness of the results. The IVW analysis revealed a significant positive association between higher PC levels and dysmenorrhea (OR: 1.533, 95% CI: 1.039-2.262, P = 0.031). The MR-Egger regression did not detect pleiotropy. Sensitivity analyses confirmed the robustness of the results. This study provides evidence suggesting a causal link between increased PC levels and dysmenorrhea. Further research is needed to understand the biological mechanisms underlying this relationship and to explore potential therapeutic implications.

The emerging role of ethanolamine phosphate phospholyase in regulating hepatic phosphatidylethanolamine and plasma lipoprotein metabolism in mice.

Ethanolamine phosphate phospholyase (ETNPPL) is an enzyme that irreversibly degrades phospho-ethanolamine (p-ETN), an intermediate in the Kennedy pathway of phosphatidylethanolamine (PE) biosynthesis. PE is the second most abundant phospholipid in mammalian membranes. Disturbance of hepatic phospholipid homeostasis has been linked to the development of metabolic dysfunction-associated steatotic liver disease (MASLD). We generated whole-body Etnppl knockout mice to investigate the impact of genetic deletion of Etnppl on hepatic lipid metabolism. Primary hepatocytes isolated from Etnppl-/- mice showed increased conversion of [3H]ethanolamine to [3H]p-ETN and [3H]PE compared to Etnppl+/+ mice. Male and female Etnppl+/+ and Etnppl-/- mice were fed either a chow or a western-type diet (WTD). Irrespective of diet, Etnppl-/- mice had elevated fasting levels of total plasma cholesterol, triglyceride (TG) and apolipoprotein B100 (VLDL particles). Interestingly, hepatic TG secretion was unchanged between groups. Although hepatic lipids (phosphatidylcholine (PC), PE, TG, and cholesterol) were not different between mice, RNA sequencing analysis showed downregulation in genes related to cholesterol biosynthesis in Etnppl-/- mice. Furthermore, hepatic low-density lipoprotein receptor-related protein1 (LRP1) protein level was lower in female Etnppl-/- mice, which may indicate reduced uptake of remnant VLDL particles from circulation. Hepatic PE levels were only increased in WTD-fed female Etnppl-/- mice, not chow diet-fed mice. However, hepatic lipid accumulation and metabolic dysfunction-associated steatohepatitis (MASH) development were unchanged between Etnppl+/+ and Etnppl-/- mice. To conclude, ETNPPL has a role in regulating plasma lipoprotein metabolism independent of hepatic TG levels.

Exploring the causal effects of serum lipids and lipidomes on lewy body dementia: a Mendelian randomization study.

Lewy body dementia (LBD) is a neurodegenerative disorder characterized by the accumulation of Lewy bodies, which primarily composed of misfolded alpha-synuclein (αS). The development of LBD and APOE4 subtypes is thought to be associated with disorders of lipid metabolism. In this study, we investigated the causal relationship between serum lipids, liposomes and LBD using a two-sample Mendelian randomization (TSMR) method. A TSMR analysis of genome-wide association study (GWAS) data for 8 serum lipids, 179 lipidomes components, LBD and its subtypes was performed, using inverse variance weighted as the primary outcome. To ensure robustness, the sensitivity analyses including MR Pleiotropy RESidual Sum and Outlier, Cochran's test, leave-one-out method and funnel plots were performed. In this study, we found that low-density lipoprotein cholesterol (LDL-C) (OR=1.45, 95% CI=1.19-1.77, P<0.001) and remnant cholesterol (RC) (OR=2.64, 95% CI=1.64-4.28, P<0.001) had significant positive causal effects on LBD, and RC also had a positive effect on LBD in carriers of the APOE4 gene. The results of lipidome analysis showed that phosphatidylcholine (PC) (O-16:0_20:4) levels (OR=0.86, 95% CI=0.75-0.98, P=0.02) and PC (O-18:1_20:4) levels (OR=0.76, 95% CI=0.65-0.89, P <0.001) had negative causal effects on LBD, whereas phosphatidylinositol (PI) (18:1_20:4) levels had a positive causal effect on LBD (OR=1.19, 95% CI=1.02-1.39, P=0.03). For LBD with APOE4 carriers, high levels of PC (16:1_18:0) and PC (O-18:2_18:1) had a significant positive effect, while high levels of PC (O-16:1_18:0), phosphatidylethanolamine (PE) (O-18:2_18:1), sphingomyelin (SM) (d38:2), and triacylglycerol (TAG) (56:5) significantly reduced the risk. No heterogeneity and horizontal pleiotropy were observed in sensitivity analysis. Elevated LDL-C and RC levels are significant risk factors for LBD, with RC also impacting APOE4-carrying LBD. Glycerophospholipids play a crucial role in the pathogenesis of LBD, but the specific components that play a role differ from those with the APOE4 carries. These findings highlight the importance of lipid metabolism in LBD and APOE4 subtypes.

Enhanced stability and catalytic performance of immobilized phospholipase D on chitosan-encapsulated magnetic nanoparticles using oxidized dextran and glutaraldehyde as cross-linkers

Phospholipase D (PLD) is essential for the bioconversion of phosphatidylcholine (PC) to phosphatidylserine (PS), a process valuable in functional food and medicine. This study explores the stability and catalytic properties of PLD immobilized on chitosan-encapsulated magnetic nanoparticles (CMNPs), utilizing oxidized dextran (DX) and glutaraldehyde (Glu) as cross-linkers. The cross-linker concentration and immobilization time were optimized to assess their effects on PLD catalytic performance. PLD immobilized on CMNPs with DX (DX-CMNPs-PLD) exhibited optimal activity at pH 8.0 and 30 °C, retaining over 40 % activity after 14 cycles, while Glu-cross-linked PLD (Glu-CMNPs-PLD) retained approximately 65 %. DX-CMNPs-PLD demonstrated superior pH, temperature, and operational stability compared to free PLD. Additionally, the immobilized PLD was characterized using transmission electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. Kinetics parameters (Vmax and Km) of the immobilized PLD were also studied with free PLD serving as a control. Conformational analyses indicated a significant change in PLD's secondary structure, particularly in β-sheet content, which likely contributed to the enhanced stability and activity. These findings suggest a promising approach for PLD immobilization on CMNPs, with notable implications for biotechnological applications.

Abstract B036: Hypoxic cancer cells condition immunosuppressive macrophages via secreted non-protein mediators in pancreatic ductal adenocarcinoma

Abstract INTRODUCTION: Hypoxia is a defining feature of pancreatic ductal adenocarcinoma (PDAC) that contributes to the immunosuppressive microenvironment defined by increased tumor-associated macrophages (TAMs). However, there is an unmet need to define mechanisms by which hypoxia drives the immunosuppressive macrophage phenotype. We hypothesize that hypoxic cancer cells secrete non-protein metabolites to induce immunosuppressive phenotypes in macrophages. METHODS: We generated conditioned media (CM) by culturing the pancreatic adenocarcinoma cell line KPC under normoxia (21% O2) or hypoxia (0.5% O2) conditions for 48 hours. We treated bone marrow-derived macrophages (BMDMs) or the macrophage line RAW264.7 with CM. We assessed immunosuppressive gene expression using RNAseq and qRT-PCR. Proteins in CM were depleted using Sera-Mag Magnetic Carboxylate Modified Beads or denatured by boiling at 100°C for 15 minutes. We identified changes in metabolites between hypoxic and normoxic CM using HPLC. RESULTS: Compared to BMDMs treated with normoxic CM, we observed that BMDMs treated with hypoxic CM induced multiple immunosuppressive proteins (Arg1), cytokines (Ccl22, Cxcl3) and interleukins (Il1b, Il1a, Il6). Similarly, GSEA analysis demonstrated that hypoxic CM induced TNFa signaling via NfkB and IL6-JAK-STAT3 signaling. Consistent with RNA-seq analysis, qRT-PCR measured Arg1 expression 53 times higher in hypoxic CM-treated BMDMs compared to nomoxic CM (p=0.0286). Compared to normoxic CM, hypoxic CM stimulated macrophage migration, a marker for macrophage infiltration, as measured by transwell assays (p&amp;lt;0.0001). An increase in Arg1 expression in RAW264.7 cells was still observed when treated with protein depleted or boiled hypoxic CM, excluding proteins as soluble factor(s) mediating immunosuppression. To identify non-protein mediators of immune suppression, mass spectrometry quantified lipids and metabolites enriched in HCM. Metabolomic analysis identified 40 metabolites increased in hypoxic CM including the monounsaturated or polyunsaturated fatty acids linoelaidic acid, DGLA, and arachidonic acid. Similarly, lipidomic analysis revealed that multiple PC (phosphatidylcholine) and LPC (lysophosphatidylcholine) lipid species were enriched in HCM. CONCLUSION: We observe that hypoxic tumor cells induce immunosuppressive changes in macrophages likely via secreted non-protein metabolites. The hypoxic metabolome of PDAC tumor cells may be a key driver of the accumulation of immunosuppressive tumor associated macrophages. We are currently characterizing the role of individual lipids or metabolites in macrophage polarization. Citation Format: Matthew T Cribb, Sahar Fattani, Ayeisha Colon-Ortiz, Dadi Jiang, Michael Spiotto, Albert Koong. Hypoxic cancer cells condition immunosuppressive macrophages via secreted non-protein mediators in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr B036.

Abstract C038: Cancer-associated fibroblasts maintain critical pancreatic cancer cell lipid homeostasis in the tumor microenvironment

Abstract Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy whose abundant cancer-associated fibroblasts (CAFs) create a hallmark “desmoplasia” that severely limits oxygen and nutrient delivery. Hypoxia inhibits oxygen-dependent metabolic processes. For example, unsaturated lipid biosynthesis relies on oxygen to maintain desaturase enzymatic activities. Here, we investigated the mechanisms by which PDAC cells maintain lipid homeostasis under these conditions. Exogenous unsaturated lipids, rather than de novo synthesis, sustain PDAC cell viability by relieving endoplasmic reticulum (ER) stress under nutrient scarcity. Furthermore, CAFs are less hypoxic than adjacent malignant cells in vivo due to proximal blood vessel accessibility, nominating them as a potential source of these obligatory species. CAF-conditioned medium promoted PDAC cell survival upon nutrient and oxygen deprivation, an effect reversed by delipidation. We determined that lysophosphatidylcholines (LPCs) are particularly enriched in CAF-conditioned medium and preferentially taken up by PDAC cells, where they are converted to phosphatidylcholines (PCs) to sustain membrane integrity. Inhibiting LPC to PC conversion reversed the ability of exogenous unsaturated LPCs to sustain cancer cell survival and restrain ER stress in vitro and in vivo. Collectively, these results reveal a critical lipid cross-feeding mechanism enabling PDAC cell survival and identify an innovative approach to targeting this metabolic dependency. Efforts to target lipid crosstalk between CAFs and PDAC cells will be discussed. Citation Format: Xu Han, Michelle Burrows, Laura C Kim, Jimmy Xu, Will Vostrejs, Tran Ngoc Van Le, Yanqing Jiang, Edna Cukierman, Reiss Binder Kim, Ben Z Stanger, Clementina Mesaros, Brian Keith, Celeste Simon. Cancer-associated fibroblasts maintain critical pancreatic cancer cell lipid homeostasis in the tumor microenvironment [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr C038.

Arabidopsis trigalactosyldiacylglycerol1 mutants reveal a critical role for phosphtidylcholine remodeling in lipid homeostasis.

Lipid remodeling plays a critical role in plant response to abiotic stress and metabolic perturbations. Key steps in this process involve modifications of phosphatidylcholine (PC) acyl chains mediated by lysophosphatidylcholine: acyl-CoA acyltransferases (LPCATs) and phosphatidylcholine: diacylglycerol cholinephosphotransferase (ROD1). To assess their importance in lipid homeostasis, we took advantage of the trigalactosyldiacylglycerol1 (tgd1) mutant that exhibits marked increases in fatty acid synthesis and fatty acid flux through PC due to a block in inter-organelle lipid trafficking. Here, we showed that the increased fatty acid synthesis in tgd1 is due to posttranslational activation of the plastidic acetyl-coenzyme A carboxylase. Genetic analysis showed that knockout of LPCAT1 and 2 resulted in a lethal phenotype in tgd1. In addition, plants homozygous for lpcat2 and heterozygous for lpcat1 in the tgd1 background showed reduced levels of PC and triacylglycerols (TAG) and alterations in their fatty acid profiles. We further showed that disruption of ROD1 in tgd1 resulted in changes in fatty acid composition of PC and TAG, decreased leaf TAG content and reduced seedling growth. Together, our results reveal a critical role of LPCATs and ROD1 in maintaining cellular lipid homeostasis under conditions, in which fatty acid production largely exceeds the cellular demand for membrane lipid synthesis.

In situ gel-forming oil solubilizing α-lipoic acid as a physical shielding alleviated chemotherapy-induced oral mucositis via inhibiting oxidative stress

Oral mucositis (OM) is a common and serious complication of cancer chemoradiotherapy. OM managements mainly focused on topical healthcare or analgesia, which offers limited wound healing. Herein, in situ gel-forming oil (LGF) have been developed as a physical shielding for OM treatment. LGF oil, composed of soybean phosphatidyl choline (40 %, w/w), glycerol dioleate (54 %, w/w), and alcohols (6 %, w/w), is a viscous oil-like liquid. The contact angle of LGF oil on porcine buccal mucosa were 30°, significantly smaller than that of water (60°), indicating its good wetting and spreading properties. Besides, the adhesion force and adhesion energy of LGF oil toward porcine buccal mucosa was as high as 3.9 ± 0.2 N and 60 ± 2 J/m2, respectively, indicating its good adhesive property. Moreover, the hydrophobic α-lipoic acid (LA) as a native antioxidative agent was highly solubilized in LGF oil, its solubility in which was above 100 mg/mL. Upon contacting with saliva, LA-loaded LGF oil (LA-LGF) could rapidly transform from oil into gel that adheres on oral mucosa. Moreover, LA was slowly released from the formed LA-LGF gel, which benefited alleviating oxidative stress caused by chemoradiotherapy. In vivo animal experiments showed that LA-LGF could effectively promote the repairing of oral mucosa wound of 5-fluorouracil induced OM rats. Besides, the mucosa edema was greatly improved and new granulation around wound was produced after LA-LGF treatment. Meanwhile, the production of proinflammatory cytokines such as IL-1β, TNF-α, 1L-6 was substantially inhibited by LA-LGF. Collectively, LGF oil as carrier of hydrophobic drug might be a promising strategy for oral mucositis.

Influence of phospholipid structures on volatile organic compounds generation in model systems

To investigate the regularities and differences in oxidation products of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) by gas chromatography-mass spectrometry (GC–MS), and examine the influence of variations in fatty acid compositions and head groups on the kinds and contents of volatile organic compounds (VOCs) generated. A total of 42 VOCs were identified from PE (16:0–18:2), PC (16:0–18:2), and PC (16:0–18:1), with aldehydes and ketones being the main VOCs in three phospholipids (PLs). The content of most VOCs produced by PE (16:0–18:2), PC (16:0–18:2), and PC (16:0–18:1) increases with the increase of oxidation temperature and time. Reached peak at 175 °C for 60 min. The total VOCs contents generated by PE (16:0–18:2) and PC (16:0–18:2) were higher than those produced by PC (16:0–18:1), with PC (16:0–18:2) showing the highest total VOCs contents. PLs exhibited three mass loss processes with increasing temperature, namely stability, reduction, and stabilization. PC (16:0–18:2) experienced the highest mass loss, followed by PE (16:0–18:2), while PC (16:0–18:1) showed the least mass loss. These findings showed that polyunsaturated fatty acids were more susceptible to oxidation and degradation during oxidation, and the presence of choline groups in the form of PE may enhance the oxidative stability of fatty acyl groups compared to PC.

Transamniotic Delivery of Surfactant Protein B mRNA in a Healthy Model

Introduction: We sought to determine whether exogenous surfactant protein B (SPB) mRNA could be incorporated and translated by the fetal lung after simple transamniotic administration. Methods: Fetuses (n = 149) of twelve time-dated dams underwent intra-amniotic injections of either human SPB (hSPB) mRNA encapsulated into lipopolyplex (mRNA, n = 99) or lipopolyplex without mRNA (control; n = 50) on gestational day 17 (E17, term = E21–22). Lungs were screened for hSPB by enzyme-linked immunosorbent assay daily until term. Phosphatidylcholine (PC) (a surrogate for surfactant production) was measured in the amniotic fluid by fluorometric assay. Statistical analysis included nonparametric Wilcoxon rank sum test. Results: Significantly improved survival in the mRNA group compared to controls was observed at E18 (100% vs. 85.7%) and E20 (100% vs. 83.3%) (both p < 0.001). When controlled by mRNA-free injections, hSPB protein was detected in the mRNA group’s lungs at E18, 19, and term (p = 0.002 to <0.001). Amniotic fluid PC levels were increased compared to control at term [285.9 (251.1, 363.9) μM versus 263.1 (222.8, 309.1) μM]; however, this did not reach significance (p = 0.33). Conclusions: Encapsulated exogenous SPB mRNA can be incorporated and translated by fetal lung cells following intra-amniotic injection in a healthy rat model. Transamniotic mRNA delivery could become a novel strategy for perinatal surfactant protein replacement.

Exploring the causal relationship between plasma lipids and varicose veins of lower extremity: A comprehensive two-sample Mendelian randomization study.

Varicose veins of the lower extremities (VVs) is a common chronic vascular disease, with high prevalence rates in some countries; however, their pathogenesis remains unclear. Some studies have identified associations between changes in specific plasma lipid molecules, such as phosphatidylethanolamine (PE), phosphatidylcholine (PC), and sphingomyelin (SM), and the onset of VVs, but due to confounders and reverse causality, the causal relationship remains unclear. Meanwhile, studies on the potential link between other plasma lipids beyond PE, PC, and SM and the risk of VVs in the lower extremities are lacking. This study aimed to explore the potential causal relationship between VVs and plasma lipid levels to provide theoretical insights into the interrelation of plasma lipids and VVs in their occurrence and progression. We conducted a two-sample Mendelian randomization (MR) analysis to assess the potential connection between genetically predicted levels of individual plasma lipids and the risk of developing VVs. We utilized data from a large-scale genome-wide association study involving 7174 Finnish individuals for 179 plasma lipidomes along with VVs genome-wide association study data from 408,455 UK individuals. MR analysis employed methods, such as inverse-variance weighting, weighted median, Bayesian Weighted Mendelian Randomization, and MR-Egger regression. The inverse-variance weighting method was primarily used to assess causality. The validity of the results was demonstrated through sensitivity analysis. In total, 12 lipids were found to have their plasma levels associated with an increased risk of VVs. This includes 3 types of PE, 7 types of PC, and 2 types of phosphatidylinositol. However, no significant causal relationship was found between the plasma levels of 11 types of SM and VVs. These results support the existence of a potential causal relationship between specific types of lipid levels and the risk of VVs, which can provide clues for further studies on biological mechanisms and the exploration of potential therapeutic targets.

Role of myeloid cells in mediating the effects of lipids on ulcerative colitis.

To evaluate the causal relationship between lipids and ulcerative colitis (UC) through Mendelian Randomization (MR), and to further investigate the involvement of immune cells in mediating this process. Utilizing summary statistics from genome-wide association studies (GWAS) of individuals with European ancestry, we analyzed the causal link between 179 lipid types and UC (2,569 UC cases and 453,779 controls) through Two-sample Mendelian randomization (2SMR) and Bayesian-weighted MR (BWMR). Based on this, a mediation screening of 731 immune cell phenotypes was conducted to identify exposure and mediator factors. Lastly, the role and proportion of immune cells in mediating the causal effects of lipids on UC were assessed via reverse MR (RMR) and two-step MR. The results of MR showed that there was a causal relationship between the six genetically predicted lipid types and UC (P <0.05), and the four immune cell phenotypes were identified as mediators of the association between lipids and UC. Notably, Phosphatidylcholine (PC) (16:0_0:0) served as the exposure factor, and myeloid cells CD11b on CD33+ HLA DR+ CD14dim acted as the mediator. Mediation analysis showed that CD11b on CD33+ HLA DR+ CD14dim had a mediation effect of -0.0205 between PC (16:0_0:0) and UC, with the mediation effect ratio at 15.38%. Our findings elucidate the causal effect of lipids on UC and identify the significant mediating role of myeloid cells CD11b on CD33+ HLA DR+ CD14dim in regulating UC through PC (16:0_0:0), offering new pathways and strategies for UC clinical treatment.

Effect of phosphatidylcholine regioisomerism on lateral segregation of milk sphingomyelin in bilayer membranes

Milk fat globule membrane (MFGM) promotes the lateral phase separation of milk lipids and stabilizes the fat globules in milk. The composition and structures of lipids have a significant impact on physicochemical properties of MFGM, which in turn influences the digestion and absorption of milk lipids. Phospholipids (PL), sphingolipids, and cholesterol are the major lipid constituents of MFGM. While the effects of the head-group and structure of the fatty acids (FAs) on membrane properties are commonly studied, little is known on the impact of PL regioisomerism. The present study investigated the impact of phosphatidylcholine (PC) regioisomerism on lateral segregation of milk-sphingomyelin (milk-SM) as well as the influence on the interaction of milk-SM with ceramide and cholesterol in simulated membrane systems. The regioisomer pairs of four molecular species PC 16:0/18:1n-9, PC 16:0/18:2n-6, PC 16:0/18:3n-3, and PC 16:0/20:4n-6 were included in this study. The lateral segregation was determined using lifetime analysis of trans-parinaric acid (tPA) fluorescence. Thermostability of the domains was detected using steady-state anisotropy of tPA. Our results demonstrated a clear impact of PC regioisomerism on membrane properties. PC regioisomers having the unsaturated FAs at the sn-2 position enhanced the lateral segregation of milk-SM with and without the presence of ceramide and cholesterol compared to the regioiosmers having 16:0 at the sn-2 position. Furthermore, the characteristics i. e. the acyl chain length and degree of unsaturatin of sn-2 FA of the PCs had a major impact on the milk-SM gel phase and the intermolecular forces between milk-SM and ceramide/cholesterol. This work is the first investigation showing the effect of PL regioisomerism on milk-SM domains, which might have significant influence on functional properties of MFGM.

Postmortem Fatty Acid Abnormalities in the Cerebellum of Patients with Essential Tremor.

Fatty acids play many critical roles in brain function but have not been investigated in essential tremor (ET), a frequent movement disorder suspected to involve cerebellar dysfunction. Here, we report a postmortem comparative analysis of fatty acid profiles by gas chromatography in the cerebellar cortex from ET patients (n = 15), Parkinson's disease (PD) patients (n = 15) and Controls (n = 17). Phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI)/ phosphatidylserine (PS) were separated by thin-layer chromatography and analyzed separately. First, the total amounts of fatty acids retrieved from the cerebellar cortex were lower in ET patients compared with PD patients, including monounsaturated (MUFA) and polyunsaturated fatty acids (PUFA). The diagnosis of ET was associated with lower cerebellar levels of saturated fatty acids (SFA) and PUFA (DHA and ARA) in the PE fraction specifically, but with a higher relative content of dihomo-γ-linolenic acid (DGLA; 20:3 ω-6) in the PC fraction. In contrast, a diagnosis of PD was associated with higher absolute concentrations of SFA, MUFA and ω-6 PUFA in the PI + PS fractions. However, relative PI + PS contents of ω-6 PUFA were lower in both PD and ET patients. Finally, linear regression analyses showed that the ω-3:ω-6 PUFA ratio was positively associated with age of death, but inversely associated with insoluble α-synuclein. Although it remains unclear how these FA changes in the cerebellum are implicated in ET or PD pathophysiology, they may be related to an ongoing neurodegenerative process or to dietary intake differences. The present findings provide a window of opportunity for lipid-based therapeutic nutritional intervention.

Biotransformation of nanoplastics in human plasma and their permeation through a model in vitro blood-brain barrier: An in-depth quantitative analysis

Challenges in characterizing and quantifying nanoplastics within the human body hinder understanding of their transport, biotransformation, and potential for cellular penetration and barrier crossing. By implementing an innovative analytical workflow, including incorporation of gadolinium (Gd) as a tracer into the polymer matrix of nanoplastics, the fate of nanoplastics relative to an in vitro blood-brain barrier (BBB) model is elucidated in the absence or presence of a biomomolecule corona. The nanoplastics were incubated in human plasma for 5 min, 1 h, 6 h, and 24 h, after which the absorbed proteins and lipids (biocorona) were determined. A total of 268 proteins were identified in the biological coronas on polystyrene (PS) and polyvinyl chloride (PVC) nanoplastics, with the initial compositions being broadly similar on both PS and PVC. Both nanoplastics exhibited a strong affinity for phosphatidylcholines (PC) and lysophosphocholines (LPC) from human plasma. The inherent chemical composition of the nanoplastics plays a pivotal role in the corona’s evolution over time. Human induced pluripotent stem cell (iPSC)-derived endothelial cells (iECs) and astrocytes were exposed for 2 h to 5 µg L−1 of pristine nanoplastics or nanoplastics covered with a biological corona (following incubation in plasma for 6 h). A relatively low concentration of PS and PVC nanoplastics was determined to be present within the cellular layer of the BBB. The number of PVC nanoplastics crossing the BBB was higher than the number of PS nanoplastics. The presence of a biological corona on these particles decreases their uptake and transcytosis. This understanding might further the development of preventive measures or therapeutic strategies to counteract potential nanoplastic-induced neurotoxicity, and provide a foundation for development of in silico models to predict the neurotoxic implications of nanoplastics.

Mechanisms insights into bisphenol S-induced oxidative stress, lipid metabolism disruption, and autophagy dysfunction in freshwater crayfish

Bisphenol S (BPS) is widely used in plastic products, food packaging, electronic products, and other applications. In recent years, BPS emissions have increasingly impacted aquatic ecosystems. The effects of BPS exposure on aquatic animal health have been documented; however, our understanding of its toxicology remains limited. This study aimed to explore the mechanisms of lipid metabolism disorders, oxidative stress, and autophagy dysfunction induced in freshwater crayfish (Procambarus clarkii) by exposure to different concentrations of BPS (0 µg/L, 1 µg/L, 10 µg/L, and 100 µg/L) over 14 d. The results indicated that BPS exposure led to oxidative stress by inducing elevated levels of reactive oxygen species (ROS) and inhibiting the activity of antioxidant-related enzymes. Additionally, BPS exposure led to increased lipid content in the serum and hepatopancreas, which was associated with elevated lipid-related enzyme activity and increased expression of related genes. Furthermore, BPS exposure decreased levels of phosphatidylcholine (PC) and phosphatidylinositol (PI), disrupted glycerophospholipid (GPI) metabolism, and caused lipid deposition in the hepatopancreatic. These phenomena may have occurred because BPS exposure reduced the transport of fatty acids and led to hepatopancreatic lipid deposition by inhibiting the transport and synthesis of PC and PI in the hepatopancreas, thereby inhibiting the PI3K-AMPK pathway. In conclusion, BPS exposure induced oxidative stress, promoted lipid accumulation, and led to autophagy dysfunction in the hepatopancreas of freshwater crayfish. Collectively, our findings provide the first evidence that environmentally relevant levels of BPS exposure can induce hepatopancreatic lipid deposition through multiple pathways, raising concerns about the potential population-level harm of BPS and other bisphenol analogues.

Unraveling gender-specific lipids and flavor volatiles in giant salamander (Andrias davidianus) livers via lipidomics and GC-IMS

To uncover the relationships between lipid components and flavor volatiles, distinctness in lipid components and odor substances in giant salamander livers of different genders were comparatively characterized through UPLC-Q Exactive-MS lipidomics and gas chromatography-ion migration spectrometry (GC-IMS). A total of 2171 and 974 lipid metabolites were detected in positive and negative ion modes, respectively. Triglycerides (TG) and phosphatidylcholines (PC) are the most abundant types of lipids. TG level in male livers was higher than that in female livers (P < 0.05), whereas PC level showed no marked variation (P > 0.05). Additionally, a total of 51 volatile components were detected through GC-IMS. Ketones (42.18 % ∼ 45.44 %) and alcohols (24.19 % ∼ 26.50 %) were the predominant categories, and their relative contents were higher in female livers. Finally, 30 differential lipid metabolites and 12 differential odor substances were screened and could be used as distinguishing labels in giant salamander livers of different genders. Correlation analysis indicated that PS(36:2e), TG(48:13), ZyE(37:6), and ZyE(33:6) correlated positively with 3-methyl butanal, 3-hydroxy-2-butanone, and 2-methyl-1-propanol (P < 0.05), but adversely linked with 1-penten-3-one, and 1-octen-3-one (P < 0.01). By three-fold cross-validation, prediction accuracies of these differential lipids and volatile compounds for gender recognition based on random forest model were 100 % and 92 %, respectively. These findings might not only add knowledge on lipid and volatile profiles in giant salamander livers as affected by genders, but also provide clues for their gender recognition.

PD-1 signaling limits expression of phospholipid phosphatase 1 and promotes intratumoral CD8+ T cell ferroptosis

The tumor microenvironment (TME) promotes metabolic reprogramming and dysfunction in immune cells. Here, we examined the impact of the TME on phospholipid metabolism in CD8+ Tcells. In lung cancer, phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were lower in intratumoral CD8+ Tcells than in circulating CD8+ Tcells. Intratumoral CD8+ Tcells exhibited decreased expression of phospholipid phosphatase 1 (PLPP1), which catalyzes PE and PC synthesis. Tcell-specific deletion of Plpp1 impaired antitumor immunity and promoted Tcell death by ferroptosis. Unsaturated fatty acids in the TME stimulated ferroptosis of Plpp1-/- CD8+ Tcells. Mechanistically, programmed death-1 (PD-1) signaling in CD8+ Tcells induced GATA1 binding to the promoter region Plpp1 and thereby suppressed Plpp1 expression. PD-1 blockade increased Plpp1 expression and restored CD8+ Tcell antitumor function but did not rescue dysfunction of Plpp1-/- CD8+ Tcells. Thus, PD-1 signaling regulates phospholipid metabolism in CD8+ Tcells, with therapeutic implications for immunotherapy.