Glycerophosphocholine molecular species profiling in the biological tissue using UPLC/MS/MS

Lipid responses to perfluorooctane sulfonate exposure for multiple rat organs

Perfluorooctane sulfonate (PFOS) is a persistent chemical that has long been a threat to human health. However, the molecular effects of PFOS on various organs are not well studied. In this study, male Sprague-Dawley rats were treated with various doses of PFOS through gavage for 21 days. Subsequently, the liver, lung, heart, kidney, pancreas, testis, and serum of the rats were harvested for lipid analysis. We applied a focusing lipidomic analytical strategy to identify key lipid responses of phosphorylcholine-containing lipids, including phosphatidylcholines and sphingomyelins. Partial least squares discriminant analysis revealed that the organs most influenced by PFOS exposure were the liver, kidney, and testis. Changes in the lipid profiles of the rats indicated that after exposure, levels of diacyl-phosphatidylcholines and 22:6-containing phosphatidylcholines in the liver, kidney, and testis of the rats decreased, whereas the level of 20:3-containing phosphatidylcholines increased. Furthermore, levels of polyunsaturated fatty acids-containing plasmenylcholines decreased. Changes in sphingomyelin levels indicated organ-dependent responses. Decreased levels of sphingomyelins in the liver, nonmonotonic dose responses in the kidney, and irregular responses in the testis after PFOS exposure are observed. These lipid responses may be associated with alterations pertaining to phosphatidylcholine synthesis, fatty acid metabolism, membrane properties, and oxidative stress in the liver, kidney, and testis. Lipid responses in the liver could have contributed to the observed increase in liver to body weight ratios. The findings suggest potential toxicity and possible mechanisms associated with PFOS in multiple organs.

Toxicological response of Pacific white shrimp Litopenaeus vannamei to a hazardous cyanotoxin nodularin exposure

Nodularin (NOD) is a harmful cyanotoxin that affects shrimp farming. The hepatopancreas and intestine of shrimp are the main target organs of cyanotoxins. In this study, we exposed Litopenaeus vannamei to NOD at 0.1 and 1 μg/L for 72 h, respectively, and changes in histology, oxidative stress, gene transcription, metabolism, and intestinal microbiota were investigated. After NOD exposure, the hepatopancreas and intestine showed obvious histopathological damage and elevated oxidative stress response. Transcription patterns of immune genes related to detoxification, prophenoloxidase and coagulation system were altered in the hepatopancreas. Furthermore, metabolic patterns, especially amino acid metabolism and arachidonic acid related metabolites, were also disturbed. The integration of differential genes and metabolites revealed that the functions of "alanine, aspartic acid and glutamate metabolism" and "aminoacyl-tRNA biosynthesis" were highly affected. Alternatively, NOD exposure induced the variation of the diversity and composition of intestinal microbiota, especially the abundance of potentially beneficial bacteria (Demequina, Phyllobacterium and Pseudoalteromonas) and pathogenic bacteria (Photobacterium and Vibrio). Several intestinal bacteria were correlated with the changes of host the metabolic function and immune factors. These results revealed the toxic effects of NOD on shrimp, and identified some biomarkers.

Hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry method for quantification of five phospholipid classes in various matrices

Hydrophilic interaction liquid chromatography (HILIC), coupled to tandem mass spectrometry, can be used to separate and determine various polar lipid classes. The development of an HILIC chromatographic separation of several molecular species among five phospholipid classes (PC, PE, PG, PI and PS) is reported here. In this method, a gradient with acetonitrile and 40 mM ammonium acetate buffer was employed. The initial composition was 95% of acetonitrile, then this proportion was decreased to 70% in order to elute all the compounds of interest for a total running time of 11 mins. Furthermore, mobile phase pH can affect the ionizable character of the compounds, according to their pKa values, and also the stationary phase charge state. The influence of such a parameter on both retention times and resolution was evaluated. Besides, the response of different kinds of internal standards (post-extraction standard addition) was evaluated in four different biological matrices, two microalgae extracts and two marine fish extracts. This study found that the recovery rates were between 70 and 140% of the expected value, with relative standard deviations between 10 and 35%, and then limited matrix effects.•HILIC approach can be used to separate phospholipid according to their polar head-group, and electrospray ionization in negative mode as well as MS/MS allows further identification of the molecular species within each phospholipid class.•Matrix effects are low and compensated with appropriate internal standards.•The limits of quantifications were ranging from 0.05 to 0.14 µg.mL^-1, depending on the analyte.

Comprehensive analysis of phospholipids and glycerol glycolipids in green pepper by ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry

RATIONALE

As important components of plant cells, lipids are involved in various biological functions. However, the composition and content of lipids in cell membranes changes at low temperature resulting in chilling injury and affecting the commercial value of green peppers. Detecting the changes in lipids helps to understand the mechanism of low-temperature stress in green peppers; however, a comprehensive study of lipid profiles in green pepper has not been well documented.

METHODS

Herein, we report an ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC/QTOF MS) method to determine phospholipids and glycolipids in green peppers and compare five extraction methods among which the isopropanol/chloroform/water (ICW) method demonstrated the best extraction efficiency. The established method was used to determine the membrane lipids of fresh samples, chilled samples(4°C-20d), and control samples (10°C-20d).

RESULTS

A total of 98 lipids, including 77 phospholipids and 21 glycolipids, were extracted from green peppers using ICW extraction. The content and profile of phosphatidylcholine (PC) among phospholipids were found to be the highest, accounting for 58.58% of all the phospholipids. The monogalactosyldiacylglycerol (MGDG) content among the glycolipids was the highest, accounting for 1.43%. The samples stored at low temperature (4°C, 20d) had a significantly higher PC content and a higher content of lipids containing unsaturated fatty acid residues as compared with the control samples (10°C, 20d). The recovery ranged from 75.55% to 96.64% while the limit of quantification ranged from 10 to 1000 ng mL^-1 .

CONCLUSIONS

The results indicated that the established method provided a reliable platform to study the changes in membrane lipids of a green pepper under low-temperature conditions.

Lipid changes in extrapulmonary organs and serum of rats after chronic exposure to ambient fine particulate matter

Fine particulate matter (PM_2.5) is able to pass through the respiratory barrier to enter the circulatory system and can consequently spread to the whole body to cause toxicity. Although our previous studies have revealed significantly altered levels of phosphorylcholine-containing lipids in the lungs of rats after chronic inhalation exposure to PM_2.5, the effects of PM_2.5 on phosphorylcholine-containing lipids in the extrapulmonary organs have not yet been elucidated. In this study, we examined the lipid effects of chronic PM_2.5 exposure on various organs and serum by using a rat inhalation model followed by a mass spectrometry-based lipidomic approach. Male Sprague-Dawley rats were continuously exposed at the whole body level to nonfiltered and nonconcentrated ambient air from the outside environment of Taipei city for 8 months, while the control rats inhaled filtered air simultaneously. After exposure, serum samples and various organs, including the testis, pancreas, heart, liver, kidney, spleen, and epididymis, were collected for lipid extraction and analysis to examine the changes in phosphorylcholine-containing lipids after exposure. The results from the partial least squares discriminant analysis models demonstrated that the lipid profiles in the PM_2.5 exposure group were different from those in the control group in the rat testis, pancreas, heart, liver, kidney and serum. The greatest PM_2.5-induced lipid effects were observed in the testes. Decreased lyso-phosphatidylcholines (PCs) as well as increased unsaturated diacyl-PCs and sphingomyelins in the testes may be related to maintaining the membrane integrity of spermatozoa, antioxidation, and cell signaling. Additionally, our results showed that decreased PC(16:0/18:1) was observed in both the serum and testes. In conclusion, exposure to chronic environmental concentrations of PM_2.5 caused lipid perturbation, especially in the testes of rats. This study highlighted the susceptibility of the testes and suggested possible molecular events for future study.

Lipid responses to environmental perfluoroalkyl substance exposure in a Taiwanese Child cohort

Although recent epidemiologic studies have focused on some of the health effects of perfluoroalkyl substance (PFASs) exposure in humans, the associations between PFASs exposure and the lipidome in children are still unclear. The purpose of this study was to assess lipid changes in children to understand possible molecular events of environmental PFASs exposure and suggest potential health effects. A total of 290 Taiwanese children (8-10 years old) were included in this study. Thirteen PFASs were analyzed in their serum by high-performance liquid chromatography-tandem mass spectrometry (LC-MS). MS-based lipidomic approaches were applied to examine lipid patterns in the serum of children exposed to different levels of PFASs. LC coupling with triple quadrupole MS technology was conducted to analyze phosphorylcholine-containing lipids. Multivariate analyses, such as partial least squares analysis along with univariate analyses, including multiple linear regression, were used to analyze associations between s exposure and unique lipid patterns. Our results showed that different lipid patterns were discovered in children exposed to different levels of specific PFASs, such as PFTrDA, PFOS, and PFDA. These changes in lipid levels may be involved in hepatic lipid metabolism, metabolic disorders, and PFASs-membrane interactions. This study showed that lipidomics is a powerful approach to identify critical PFASs that cause metabolite perturbation in the serum of children and suggest possible adverse health effects of these chemicals in children.

Metabonomics Study on the Infertility Treated With Zishen Yutai Pills Combined With In Vitro Fertilization-embryo Transfer

Zishen Yutai Pills (ZYP) is a safe and well quality-controlled TCM preparation with promising effects in many fields of reproduction, including prevention of miscarriage, increase of pregnancy rate during in vitro fertilization-embryo transfer (IVF-ET). The plasma of patients was collected from a clinical trial, namely, “Effect of Traditional Chinese Medicine vs placebo on live births among women undergoing in vitro fertilization, a multi-center randomized controlled trial.” Plasma samples were analyzed with metabonomics method. UPLC-MS technology was used to establish the plasma metabolic fingerprint. Multivariate statistical analysis was applied for comparing the differences of plasma metabolites between ZYP group and placebo group, 44 potential metabolites were screen out and identified. Pathway analysis was conducted with database mining. Compared with placebo, chemicals were found to be significantly down-regulated on HCG trigger day and 14 days after embryo transplantation, including trihexosylceramide (d18:1/26:1), glucosylceramide(d18:1/26:0), TG(22:6/15:0/22:6), TG(22:4/20:4/18:4). Compared with placebo, some chemicals were found to be significantly up-regulated on HCG trigger day and 14 days after embryo transplantation, i.e., PIP3(16:0/16:1), PIP2(18:1/18:1), tauroursodeoxycholic acid, L-asparagine, L-glutamic acid, kynurenic acid, 11-deoxycorticosterone, melatonin glucuronide, hydroxytyrosol. These metabolites were highly enriched in pathways including sphingolipid metabolism, alanine, aspartic acid and glutamic acid metabolism, aminoacyl tRNA biosynthesis, taurine and hypotaurine metabolism. This study revealed metabolic differences between subjects administered with ZYP and placebo. Relating metabolites were identified and pathways were enriched, providing basis on the exploration on the underlying mechanisms of ZYP combined with IVF-ET in the treatment of infertility.

Brain lipid profiles in the spontaneously hypertensive rat after subchronic real-world exposure to ambient fine particulate matter

Recent studies have illustrated an association between ambient fine particulate matter (PM_2.5) exposure and neuronal toxicity in epidemiological studies and animal models. However, the possible molecular effects on brains under real-world exposure to PM_2.5 remain unclear. In this pilot study, male spontaneously hypertensive rats were whole-bodily exposed to ambient air from the outdoor environment of Taipei City for 3 months, while the control rats inhaled HEPA-filtered air. The PM_2.5-induced phosphatidylcholine and sphingomyelin profiles in the hippocampus, cortex, medulla, cerebellum, and olfactory bulb were assessed by mass spectrometry (MS)-based lipidomics. Partial least squares discriminant analysis (PLS-DA) and the Wilcoxon rank sum test were used to examine the lipid changes between the exposed and control groups. The PLS-DA models showed that phosphatidylcholine and sphingomyelin profiles of the PM_2.5 exposure group were different from those of the control group in each brain region except the cortex. More lipid changes were found in the hippocampus, while fewer lipid changes were observed in the olfactory bulb. The lipid alteration in the hippocampus may strengthen membrane integrity, modulate signaling pathways, and avoid accumulation of lipofuscin to counter the PM_2.5-induced stress. The lipid changes in the cortex and medulla may respond to PM_2.5-induced injury and inflammation; while the lipid changes in the cerebellum were associated with neuron protection. This study suggests that the MS-based lipidomics is a powerful approach to discriminate the brain lipid profiles even at the environmental level of ambient PM_2.5 and has the potential to suggest possible adverse health effects in long-term PM_2.5 exposure studies.

Mass spectrometry-based lipidomics to explore the biochemical effects of naphthalene toxicity or tolerance in a mouse model

Naphthalene causes mouse airway epithelial injury. However, repeated exposures of naphthalene result in mouse airway tolerance. Previous results showed that toxicity or tolerance was correlated with changes of phosphorylcholine-containing lipids. In this study, a mass spectrometry-based lipidomic approach was applied to examine the effects of naphthalene-induced injury or tolerance in the male ICR mice. The injury model was vehicle x 7 plus 300 mg/kg naphthalene while the tolerant one was 200 mg/kg daily x 7 followed by 300 mg/kg naphthalene on day 8. The lung, liver, kidney, and serum samples were collected for profiles of phosphorylcholine-containing lipids including phosphatidylcholines (PCs) and sphingomyelins (SMs). A partial least-square-discriminate analysis model showed different lung phosphorylcholine-containing lipid profiles from the injured, tolerant, and control groups. Perturbation of diacyl-PCs and plasmenylcholines may be associated with enhanced membrane flexibility and anti-oxidative mechanisms in the lungs of tolerant mice. Additionally, alterations of lyso-PCs and SMs may be responsible for pulmonary dysfunction and inflammation in the lungs of injured mice. Moreover, serum PC(16:0/18:1) has potential to reflect naphthalene-induced airway injuries. Few phosphorylcholine-containing lipid alterations were found in the mouse livers and kidneys across different treatments. This study revealed the changes in lipid profiles associated with the perturbations caused by naphthalene tolerance and toxicity; examination of lipids in serum may assist biomarker development with the potential for application in the human population.

Lipidomics study of the protective effects of isosteviol sodium on stroke rats using ultra high-performance supercritical fluid chromatography coupling with ion-trap and time-of-flight tandem mass spectrometry

Isosteviol sodium (STV-Na) was reported to possess significant protective effects on ischemic stroke in recent years. However, the protective mechanism of STV-Na against stroke was still unclear. In this work, an untargeted lipidomics approach based on the ultra high-performance supercritical fluid chromatography coupling with ion-trap and time-of-flight tandem mass spectrometry (UHSFC-IT-TOF/MS) was employed to investigate the lipid profiles of stroke rats with STV-Na treatment for the first time. The possible mechanism of STV-Na was further elucidated. The UHSFC-IT-TOF/MS-based method achieved a fast separation of various lipids within 9 min with a qualified repeatability. Multivariate statistical analysis was used to show differences in lipid profiles induced by stroke and STV-Na treatment. The results showed a clear separation of the model group and the sham group, with the STV-Na group as well as EDA group located much closer to the sham group than the model group, which was consistent with the results of physiological and pathological assays, indicating the protective effects of STV-Na. Fifteen differential lipids that presented significant differences between the sham group and the model group were screened and identified. With the treatment of STV-Na, 15 differential lipids in stroke rats showed a tendency to the normal levels. Among them, 6 lipids were significantly reversed to the normal levels by STV-Na. The results of pathway analysis suggested the protective effects of STV-Na might be related to the regulation of several metabolic pathways including glycerophospholipid metabolism, arachidonic acid metabolism and sphingolipid metabolism. This work demonstrated that the UHSFC-IT-TOF/MS-based lipidomics profiling method was a useful tool to investigate the protective effects of STV-Na against stroke.

Alterations in rat pulmonary phosphatidylcholines after chronic exposure to ambient fine particulate matter

This study elucidated the underlying pathophysiological changes that occur after chronic ambient fine particulate matter (PM2.5) exposure via a lipidomic approach. Five male Sprague-Dawley rats were continually whole-body exposed to ambient air containing PM2.5 at 16.7 ± 10.1 μg m(-3) from the outside of the building for 8 months, whereas a control group (n = 5) inhaled filtered air. Phosphorylcholine-containing lipids were extracted from lung tissue and profiled using ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The phosphatidylcholine (PC) signal features of the two groups were compared using partial least squares discriminant analysis (PLS-DA) and Wilcoxon rank sum tests. The PC profile of the exposure group differed from that of the control group; the R(2)Y and Q(2) were 0.953 and 0.677, respectively, in the PLS-DA model. In the exposure group, a significant 0.66- to 0.80-fold reduction in lyso-PC levels, which may have resulted from repeated inflammation, was observed. Decreased surfactant PCs by 16% at most may indicate injuries to alveolar type II cells. Cell function and cell signalling are likely to be altered because the decrease in unsaturated PCs may reduce membrane fluidity. Accompanied by the decline in plasmenylcholines, decreased unsaturated PCs may indicate the attack of reactive oxygen species generated by PM2.5 exposure. The physiological findings conformed to the histopathological changes in the exposed animals. PC profiling using UPLC-MS/MS-based lipidomics is sensitive for reflecting pathophysiological perturbations in the lung after long-term and low concentration PM2.5 exposure.

Platelet-activating factors are associated with cognitive deficits in depressed coronary artery disease patients: a hypothesis-generating study

Background

Patients with coronary artery disease (CAD) are at risk of accelerated cognitive decline, particularly those with major depression. Mechanisms for cognitive deficits associated with CAD, and the effects of depression, remain poorly understood. However, CAD is associated with inflammatory processes that have been linked to neurodegeneration, may contribute to cognitive decline, and are elevated in depression. Platelet-activating factors (PAFs) are emerging as key lipid mediators that may be central to those processes and highly relevant to cognitive decline in CAD.

Methods

This cross-sectional study investigated relationships between various PAFs and cognitive performance in 24 patients with CAD (age, 60.3 ± 9.4; 70.8% male). Analyses were repeated in a subgroup of 15 patients with CAD with major depression (DSM-IV). Cognitive performance was assessed using a standardized battery and summary z scores were calculated based on age, sex, and education norms. Global cognitive performance was the average of domain-specific z scores. Plasma PAF analyses were performed using electrospray ionization mass spectrometry (precursor ion scan).

Results

A greater abundance of PAF PC(O-18:0/2:0) was associated with poorer global cognitive performance in patients with CAD (r = -0.45, P = 0.03). In the major depressed subgroup, PAF PC(O-18:0/2:0) (r = -0.59, P = 0.02) as well as PC(O-16:0/2:0) (r = -0.52, P = 0.04), and lyso-PAF PC(O-16:0/0:0) (r = -0.53, P = 0.04) were associated with poorer global cognitive performance. A greater abundance of PAF PC(O-19:5/2:0) was associated with better global cognitive performance (r = 0.55, P = 0.03), suggesting a possible compensatory species.

Conclusions

This study suggests that certain PAFs might be associated with global cognitive performance in patients with CAD, with stronger relationships observed in those with major depression. Confirmation of these preliminary findings is warranted.

Predicting glycerophosphoinositol identities in lipidomic datasets using VaLID (Visualization and Phospholipid Identification)--an online bioinformatic search engine

The capacity to predict and visualize all theoretically possible glycerophospholipid molecular identities present in lipidomic datasets is currently limited. To address this issue, we expanded the search-engine and compositional databases of the online Visualization and Phospholipid Identification (VaLID) bioinformatic tool to include the glycerophosphoinositol superfamily. VaLID v1.0.0 originally allowed exact and average mass libraries of 736,584 individual species from eight phospholipid classes: glycerophosphates, glyceropyrophosphates, glycerophosphocholines, glycerophosphoethanolamines, glycerophosphoglycerols, glycerophosphoglycerophosphates, glycerophosphoserines, and cytidine 5'-diphosphate 1,2-diacyl-sn-glycerols to be searched for any mass to charge value (with adjustable tolerance levels) under a variety of mass spectrometry conditions. Here, we describe an update that now includes all possible glycerophosphoinositols, glycerophosphoinositol monophosphates, glycerophosphoinositol bisphosphates, and glycerophosphoinositol trisphosphates. This update expands the total number of lipid species represented in the VaLID v2.0.0 database to 1,473,168 phospholipids. Each phospholipid can be generated in skeletal representation. A subset of species curated by the Canadian Institutes of Health Research Training Program in Neurodegenerative Lipidomics (CTPNL) team is provided as an array of high-resolution structures. VaLID is freely available and responds to all users through the CTPNL resources web site.