Profiling of lipids in Leishmania donovani using hydrophilic interaction chromatography in combination with Fourier transform mass spectrometry

Plasmodium falciparum adapts its investment into replication versus transmission according to the host environment

The malaria parasite life cycle includes asexual replication in human blood, with a proportion of parasites differentiating to gametocytes required for transmission to mosquitoes. Commitment to differentiate into gametocytes, which is marked by activation of the parasite transcription factor ap2-g, is known to be influenced by host factors but a comprehensive model remains uncertain. Here, we analyze data from 828 children in Kilifi, Kenya with severe, uncomplicated, and asymptomatic malaria infection over 18 years of falling malaria transmission. We examine markers of host immunity and metabolism, and markers of parasite growth and transmission investment. We find that inflammatory responses associated with reduced plasma lysophosphatidylcholine levels are associated with markers of increased investment in parasite sexual reproduction (i.e. transmission investment) and reduced growth (i.e. asexual replication). This association becomes stronger with falling transmission and suggests that parasites can rapidly respond to the within-host environment, which in turn is subject to changing transmission.

Fatty Acid Composition and Metabolism in Leishmania Parasite Species: Potential Biomarkers or Drug Targets for Leishmaniasis?

Fatty acids have received growing interest in Leishmania biology with the characterization of the enzymes allowing the complete fatty acid synthesis of this trypanosomatid parasite. This review presents a comparative analysis of the fatty acid profiles of the major classes of lipids and phospholipids in different species of Leishmania with cutaneous or visceral tropism. Specificities relating to the parasite forms, resistance to antileishmanial drugs, and host/parasite interactions are described as well as comparisons with other trypanosomatids. Emphasis is placed on polyunsaturated fatty acids and their metabolic and functional specificities, in particular, their conversion into oxygenated metabolites that are inflammatory mediators able to modulate metacyclogenesis and parasite infectivity. The impact of lipid status on the development of leishmaniasis and the potential of fatty acids as therapeutic targets or candidates for nutritional interventions are discussed.

Plasma-Droplet Reaction Systems: A Direct Mass Spectrometry Approach for Enhanced Characterization of Lipids at Multiple Isomer Levels

Neutral triacylglyceride (TG) lipids are critical in cellular function, signaling, and energy storage. Multiple molecular pathways control TG structure via nonselective routes making them structurally complex and analytically challenging to characterize. The presence of C=C bond positional isomers exacerbates this challenge as complete structural elucidation is not possible by conventional tandem mass spectrometric methods such as collision-induced dissociation (CID), alone. Herein, we report a custom-made coaxial contained-electrospray ionization (ESI) emitter that allows the fusion of plasma discharge with charged microdroplets during electrospray (ES). Etched capillaries were incorporated into this contained-ES emitter, facilitating the generation of reactive oxygen species (ROS) at low (3 kV) ESI voltages and allowing stable ESI ion signal to be achieved at an unprecedented high (7 kV) spray voltage. The analytical utility of inducing plasma discharge during electrospray was investigated using online ionization of neutral TGs, in situ epoxidation of unsaturation sites, and C=C bond localization via conventional CID mass spectrometry. Collisional activation of the lipid epoxide generated during the online plasma-droplet fusion experiment resulted in a novel fragmentation pattern that showed a quadruplet of diagnostic ions for confident assignment of C=C bond positions and subsequent isomer differentiation. This phenomenon enabled the identification of a novel TG lipid, composed of conjugated linoleic acid, that is isomeric with two other TG lipids naturally found in extra virgin olive oil. To validate our findings, we analyzed various standards of TG lipids, including triolein, trilinolein, and trilinolenin, and isomeric mixtures in the positive-ion mode, each of which produced the expected quadruplet diagnostic fragment ions. Further validation was obtained by analyzing standards of free fatty acids expected from the hydrolysis of the TG lipids in the negative-ion mode, together with isomeric mixtures. The chemistry governing the gas-phase fragmentation of the lipid epoxides was carefully elucidated for each TG lipid analyzed. This comprehensive shotgun lipidomic approach has the potential to impact biomedical research since it can be accomplished on readily available mass spectrometers without the need for instrument modification.

Spatially Resolved Immunometabolism to Understand Infectious Disease Progression

Infectious diseases, including those of viral, bacterial, fungal, and parasitic origin are often characterized by focal inflammation occurring in one or more distinct tissues. Tissue-specific outcomes of infection are also evident in many infectious diseases, suggesting that the local microenvironment may instruct complex and diverse innate and adaptive cellular responses resulting in locally distinct molecular signatures. In turn, these molecular signatures may both drive and be responsive to local metabolic changes in immune as well as non-immune cells, ultimately shaping the outcome of infection. Given the spatial complexity of immune and inflammatory responses during infection, it is evident that understanding the spatial organization of transcripts, proteins, lipids, and metabolites is pivotal to delineating the underlying regulation of local immunity. Molecular imaging techniques like mass spectrometry imaging and spatially resolved, highly multiplexed immunohistochemistry and transcriptomics can define detailed metabolic signatures at the microenvironmental level. Moreover, a successful complementation of these two imaging techniques would allow multi-omics analyses of inflammatory microenvironments to facilitate understanding of disease pathogenesis and identify novel targets for therapeutic intervention. Here, we describe strategies for downstream data analysis of spatially resolved multi-omics data and, using leishmaniasis as an exemplar, describe how such analysis can be applied in a disease-specific context.

LIPIC: An Automated Workflow to Account for Isotopologue-Related Interferences in Electrospray Ionization High-Resolution Mass Spectra of Phospholipids

In the past decade, hydrophilic interaction liquid chromatography (HILIC) has emerged as an efficient alternative to reversed-phase chromatography (RPC) for the analysis of phospholipid (PL) mixtures based on mass spectrometric detection. Since the separation of PL by HILIC is chiefly based on their headgroup, the mass spectrum of each class can be obtained by spectral averaging under the corresponding HILIC band. Using experimental m/z values resulting from high mass resolution/accuracy instruments, the sum compositions of PL in a specific class can be thus inferred but partial overlapping may occur between signals related to the M + 0 isotopologue of one species and the M + 2/M + 4 isotopologues of species having one/two more C═C bonds in their chemical structures. Here, an automated workflow, named LIPIC (lipid isotopic pattern interference correction), is proposed to account for such interferences. Starting from the experimentally verified assumption that peaks in isotope patterns are Gaussian, LIPIC predicts, as a function of m/z ratio, signal intensities due to M + 2 and M + 4 isotopologues of species with one or two more C = C bonds than the target one and calculates the corrected intensity for the M + 0 isotopologue of the latter. Thanks to an iterative procedure, the suggested algorithm compensates also for slight shifts occurring between experimental and theoretical m/z ratios related to isotopologue peaks. Examples of applications to simulated and experimental mass spectra of two PL classes, i.e., phosphatidylcholines (PC) and cardiolipins (CL), emphasize the increased extent of correction at the increase of molecular masses of involved species.

De Novo Synthesis of Phosphatidylcholine Is Essential for the Promastigote But Not Amastigote Stage in Leishmania major

Phosphatidylcholine (PC) is the most abundant type of phospholipids in eukaryotes constituting ~30% of total lipids in Leishmania. PC synthesis mainly occurs via the choline branch of the Kennedy pathway (choline ⇒ choline-phosphate ⇒ CDP-choline ⇒ PC) and the N-methylation of phosphatidylethanolamine (PE). In addition, Leishmania parasites can acquire PC and other lipids from the host or culture medium. In this study, we assessed the function and essentiality of choline ethanolamine phosphotransferase (CEPT) in Leishmania major which is responsible for the final step of the de novo synthesis of PC and PE. Our data indicate that CEPT is localized in the endoplasmic reticulum and possesses the activity to generate PC from CDP-choline and diacylglycerol. Targeted deletion of CEPT is only possible in the presence of an episomal CEPT gene in the promastigote stage of L. major. These chromosomal null parasites require the episomal expression of CEPT to survive in culture, confirming its essentiality during the promastigote stage. In contrast, during in vivo infection of BALB/c mice, these chromosomal null parasites appeared to lose the episomal copy of CEPT while maintaining normal levels of virulence, replication and cellular PC. Therefore, while the de novo synthesis of PC/PE is indispensable for the proliferation of promastigotes, intracellular amastigotes appear to acquire most of their lipids through salvage and remodeling.

Shotgun Lipidomic Analysis of Leishmania Cells

To understand the interplay of lipids between Leishmania promastigotes, amastigotes, and vertebrate host cells, a robust method for cultivating Leishmania parasites, lipid extraction, and shotgun lipidomic analysis with loop injection is described. This book chapter provides the step-by-step workflow to guide readers from sample preparation to the global lipid analysis by multiple stage mass spectrometry with high resolution and tandem quadrupole mass spectrometric approaches toward studying the metabolomic roles that lipids may play in Leishmania parasite infections.

Total Phenolic Fraction (TPF) from Extra Virgin Olive Oil: Induction of apoptotic-like cell death in Leishmania spp. promastigotes and in vivo potential of therapeutic immunomodulation

BACKGROUND

Leishmaniasis is a serious multifactorial parasitic disease with limited treatment options. Current chemotherapy is mainly consisted of drugs with serious drawbacks such as toxicity, variable efficacy and resistance. Alternative bioactive phytocompounds may provide a promising source for discovering new anti-leishmanial drugs. Extra Virgin Olive Oil (EVOO), a key-product in the Mediterranean diet, is rich in phenols which are associated with anti-inflammatory, anti-cancer and anti-microbial effects. In this study, we investigate the anti-leishmanial effect of Total Phenolic Fraction (TPF) derived from EVOO in both in vitro and in vivo systems by investigating the contributing mechanism of action.

METHODOLOGY/PRINCIPAL FINDINGS

We tested the ability of TPF to cause apoptotic-like programmed cell death in L. infantum and L. major exponential-phase promastigotes by evaluating several apoptotic indices, such as reduction of proliferation rate, sub-G0/G1 phase cell cycle arrest, phosphatidylserine externalization, mitochondrial transmembrane potential disruption and increased ROS production, by using flow cytometry and microscopy techniques. Moreover, we assessed the therapeutic effect of TPF in L. major-infected BALB/c mice by determining skin lesions, parasite burden in popliteal lymph nodes, Leishmania-specific antibodies and biomarkers of tissue site cellular immune response, five weeks post-treatment termination. Our results show that TPF triggers cell-cycle arrest and apoptotic-like changes in Leishmania spp. promastigotes. Moreover, TPF treatment induces significant reduction of parasite burden in draining lymph nodes together with an antibody profile indicative of the polarization of Th1/Th2 immune balance towards the protective Th1-type response, characterized by the presence of IFN-γ-producing CD4+ T-cells and increased Tbx21/GATA-3 gene expression ratio in splenocytes.

CONCLUSIONS/SIGNIFICANCE

TPF exhibits chemotherapeutic anti-leishmanial activity by inducing programmed cell death on cell-free promastigotes and immunomodulatory properties that induce in vivo T cell-mediated responses towards the protective Th1 response in experimental cutaneous leishmaniasis. These findings enable deeper understanding of TPF's dual mode of action that encourages further studies.

Lipid profile of Trichinella papuae muscle-stage larvae

Outbreaks of trichinellosis caused by Trichinella papuae have been reported in South-East Asia. Mebendazole and thiabendazole are the treatments of choice for trichinellosis; however, both drugs result in significant side effects and are less effective for muscle-stage larvae (L1). An alternative therapeutic agent is needed to improve treatment. Information on lipid composition and metabolic pathways may bridge gaps in our knowledge and lead to new antiparasitics. The T. papuae L1 lipidome was analysed using a mass spectrometry-based approach, and 403 lipid components were identified. Eight lipid classes were found and glycerophospholipids were dominant, corresponding to 63% of total lipids, of which the glycerolipid DG (20:1[11Z]/22:4[7Z,10Z,13Z,16Z]/0:0) (iso2) was the most abundant. Overall, 57% of T. papuae lipids were absent in humans; therefore, lipid metabolism may be dissimilar in the two species. Proteins involved T. papuae lipid metabolism were explored using bioinformatics. We found that 4-hydroxybutyrate coenzyme A transferase, uncharacterized protein (A0A0V1MCB5) and ML-domain-containing protein are not present in humans. T. papuae glycerophospholipid metabolic and phosphatidylinositol dephosphorylation processes contain several proteins that are dissimilar to those in humans. These findings provide insights into T. papuae lipid composition and metabolism, which may facilitate the development of novel trichinellosis treatments.

The occurrence of inositolphosphoceramides in spirulina microalgae

Spirulina microalga (Arthrospira platensis) is an interesting phototrophic organism because of its high content of nutrients including proteins, lipids, essential amino acids, antioxidants, vitamins, polysaccharides, and minerals. Hydrophilic interaction liquid chromatography (HILIC) coupled to linear ion trap (LIT) and Orbitrap Fourier transform mass spectrometry (FTMS) via ESI was employed for the separation and characterization of lipid species in A. platensis. Inositolphosphoceramides (IPC) are minor but important constituents of spirulina; their investigation was accomplished by HILIC-ESI-MS including collision-induced dissociation (MS² , MS³ ) of deprotonated molecules in the LIT analyzer and a schematic fragmentation pattern is described. All four commercial spirulina samples revealed the occurrence of the same IPC species at m/z 796.6 (d18:0/16:0;1), 810.6 (d18:0/17:0;1), 824.6 (d18:0/18:0;1), and 826.6 (d18:0/17:0;2) but in diverse relative abundance. This study sets the stage for future investigations on IPC in other algae and microalgae.

Potential use of 13-mer peptides based on phospholipase and oligoarginine as leishmanicidal agents

Phospholipase A₂ toxins present in snake venoms interact with biological membranes and serve as structural models for the design of small peptides with anticancer, antibacterial and antiparasitic properties. Oligoarginine peptides are capable of increasing cell membrane permeability (cell penetrating peptides), and for this reason are interesting delivery systems for compounds of pharmacological interest. Inspired by these two families of bioactive molecules, we have synthesized two 13-mer peptides as potential antileishmanial leads gaining insights into structural features useful for the future design of more potent peptides. The peptides included p-Acl, reproducing a natural segment of a Lys49 PLA₂ from Agkistrodon contortrix laticinctus snake venom, and its p-AclR7 analogue where all seven lysine residues were replaced by arginines. Both peptides were active against promastigote and amastigote forms of Leishmania (L.) amazonensis and L. (L.) infantum, while displaying low cytotoxicity for primary murine macrophages. Spectrofluorimetric studies suggest that permeabilization of the parasite's cell membrane is the probable mechanism of action of these biomolecules. Relevantly, the engineered peptide p-AclR7 was more active in both life stages of Leishmania and induced higher rates of ethidium bromide incorporation than its native template p-Acl. Taken together, the results suggest that short peptides based on phospholipase toxins are potential scaffolds for development of antileishmanial candidates. Moreover, specific amino acid substitutions, such those herein employed, may enhance the antiparasitic action of these cationic peptides, encouraging their future biomedical applications.

Phosphatidylcholine synthesis through cholinephosphate cytidylyltransferase is dispensable in Leishmania major

Phosphatidylcholine (PC) is a major cell membrane constituent and precursor of important second messengers. In Leishmania parasites, PC synthesis can occur via the choline branch of the Kennedy pathway, the N-methylation of phosphatidylethanolamine (PE), or the remodeling of exogenous phospholipids. To investigate the role of de novo PC synthesis in Leishmania major, we focused on the cholinephosphate cytidylyltransferase (CPCT) which catalyzes the formation of CDP-choline, a key intermediate in the choline branch of the Kennedy pathway. Without CPCT, L. major parasites cannot incorporate choline into PC, yet the CPCT-null mutants contain similar levels of PC and PE as wild type parasites. Loss of CPCT does not affect the growth of parasites in complete medium or their virulence in mice. These results suggest that other mechanisms of PC synthesis can compensate the loss of CPCT. Importantly, CPCT-null parasites exhibited severe growth defects when ethanolamine and exogenous lipids became limited or when they were co-cultured with certain bacteria that are known to be members of sandfly midgut microbiota. These findings suggest that Leishmania employ multiple PC synthesis pathways to utilize a diverse pool of nutrients, which may be crucial for their survival and development in the sandfly.

Treatment of Active Crohn's Disease With an Ordinary Food-based Diet That Replicates Exclusive Enteral Nutrition

BACKGROUND & AIMS

Exclusive enteral nutrition (EEN) is the only established dietary treatment for Crohn's disease (CD), but its acceptability is limited. There is a need for novel dietary treatments for CD.

METHODS

We evaluated the effects of an individualized food-based diet (CD-TREAT), with similar composition to EEN, on the gut microbiome, inflammation, and clinical response in a rat model, healthy adults, and children with relapsing CD. Twenty-five healthy adults randomly received EEN or CD-TREAT for 7 days, followed by a 14-day washout period, followed by the alternate diet. Fecal microbiome and metabolome were assessed before and after each diet. HLA-B7 and HLA-B27 transgenic rats with gut inflammation received EEN, CD-TREAT, or standard chow for 4 weeks. Fecal, luminal, and tissue microbiome, fecal metabolites, and gut inflammation were assessed. Five children with active CD activity received CD-TREAT and their clinical activity and calprotectin were evaluated after 8 weeks of treatment.

RESULTS

For healthy adults, CD-TREAT was easier to comply with and more acceptable than EEN. CD-TREAT induced similar effects to EEN (EEN vs CD-TREAT) on fecal microbiome composition, metabolome, mean total sulfide (increase 133.0 ± 80.5 vs 54.3 ± 47.0 nmol/g), pH (increase 1.3 ± 0.5 vs 0.9 ± 0.6), and the short-chain fatty acids (μmol/g) acetate (decrease 27.4 ± 22.6 vs 21.6 ± 20.4), propionate (decrease 5.7 ± 7.8 vs 5.2 ± 7.9), and butyrate (decrease 7.0 ± 7.4 vs 10.2 ± 8.5). In the rat model, CD-TREAT and EEN produced similar changes in bacterial load (decrease 0.3 ± 0.3 log₁₀ 16S rRNA gene copies per gram), short-chain fatty acids, microbiome, and ileitis severity (mean histopathology score decreases of 1.25 for EEN [P = .015] and 1.0 for CD-TREAT [P = .044] vs chow). In children receiving CD-TREAT, 4 (80%) had a clinical response and 3 (60%) entered remission, with significant concurrent decreases in fecal calprotectin (mean decrease 918 ± 555 mg/kg; P = .002).

CONCLUSION

CD-TREAT replicates EEN changes in the microbiome, decreases gut inflammation, is well tolerated, and is potentially effective in patients with active CD. ClinicalTrials.gov, numbers NCT02426567 and NCT03171246.

Analysis of Triacylglycerols in Castor Oil Through Liquid Chromatography-Mass Spectrometry Based on Fourier Transform-Ion Cyclotron Resonance-Mass Spectrometry and Gas Chromatography-Mass Spectrometry

Castor oil is a traditional Chinese medicine containing a chemically complex mixture of triacylglycerols (TAGs). Herein, the TAGs in castor oil were analyzed in detail. First, the fatty acid composition of castor oil was examined via methylated derivatisation followed by gas chromatography-mass spectrometry (GC-MS). Then, using the fatty acid composition data, liquid chromatography-mass spectrometry (LC-MS) was applied to analyze the composition and relative content of TAGs. Nine TAGs were identified, wherein triricinolein (RRR) constituted ~81% of the total TAG content based on the peak areas. However, the TAGs in castor oil contain hydroxyl groups, which are incompatible with the equivalent carbon number (ECN) rule. Thus, an extended-ECN rule was expressed as E-ECN = CN (carbon number)-2·DB (double-bond number)-6·OH (hydroxyl group number) to characterize the retention of hydroxyl-containing TAGs in HPLC using a C18 column. Moreover, hydroxyl-containing TAGs may become dehydrated when analyzed using atmospheric pressure chemical ionization (APCI), which was confirmed via APCI Fourier transform-ion cyclotron resonance-mass spectrometry (FT-ICR-MS). Thus, the TAGs in castor oil were accurately identified through LC-MS together with FT-ICR-MS and GC-MS.

High-performance liquid chromatography/electrospray ionisation mass spectrometric characterisation of metabolites produced by Pseudovibrio sp. W64, a marine sponge derived bacterium isolated from Irish waters

RATIONALE

In recent years, metabolites produced by Pseudovibrio species have gained scientific attention due to their potent antimicrobial activity. Recently, we also have assessed the antibacterial activities of Pseudovibrio sp. W64 isolates against Staphylococcus aureus, where only the dominant tropodithietic acid (TDA) was identified. However, characterisation of other metabolites is necessary as these metabolites may also serve as potent antimicrobial agents.

METHODS

Liquid chromatography/tandem mass spectrometry (LC/MS/MS), aided by accurate mass measurements, was employed to screen and characterise a range of metabolites produced by Pseudovibrio sp. W64 via assessment of ethyl acetate fractions generated from bacterial cultures.

RESULTS

Thirteen metabolites unique to the bacterial culture were detected and their chemical structures were assigned by MS/MS and accurate mass measurements. Among the thirteen metabolites, a methyl ester of TDA, a number of cholic acid derivatives, and amino diols and triols were characterised.

CONCLUSIONS

Pseudovibrio sp. W64 produces methylated TDA in addition to TDA, and metabolises lipids and amino acids in the cell-culture medium. To the best of our knowledge, this is the first report of methylated TDA, cholic acid and its various analogs, and sphinganine being detected in this Pseudovibrio strain. The data generated may help to better understand the biochemical processes and metabolism of bacterial strains towards discovery of antimicrobial agents from marine sources.

Complex Interplay between Sphingolipid and Sterol Metabolism Revealed by Perturbations to the Leishmania Metabolome Caused by Miltefosine

With the World Health Organization reporting over 30,000 deaths and 200,000 to 400,000 new cases annually, visceral leishmaniasis is a serious disease affecting some of the world's poorest people. As drug resistance continues to rise, there is a huge unmet need to improve treatment. Miltefosine remains one of the main treatments for leishmaniasis, yet its mode of action (MoA) is still unknown. Understanding the MoA of this drug and parasite response to treatment could help pave the way for new and more successful treatments for leishmaniasis. A novel method has been devised to study the metabolome and lipidome of Leishmania donovani axenic amastigotes treated with miltefosine. Miltefosine caused a dramatic decrease in many membrane phospholipids (PLs), in addition to amino acid pools, while sphingolipids (SLs) and sterols increased. Leishmania major promastigotes devoid of SL biosynthesis through loss of the serine palmitoyl transferase gene (ΔLCB2) were 3-fold less sensitive to miltefosine than wild-type (WT) parasites. Changes in the metabolome and lipidome of miltefosine-treated L. major mirrored those of L. donovani A lack of SLs in the ΔLCB2 mutant was matched by substantial alterations in sterol content. Together, these data indicate that SLs and ergosterol are important for miltefosine sensitivity and, perhaps, MoA.

Secretory lipase from the human pathogen Leishmania major: Heterologous expression in the yeast Pichia pastoris and biochemical characterization

Leishmaniasis is a parasitic reticuloendotheliosis whose pathogen is a zooflagellate belonging to the genus Leishmania transmitted by the bite of an infected phlebotome. Recently, a unique secretory lipase from the human pathogen Leishmania donovani Ldlip3 has been identified and characterized. This lipase has a high identity with a putative triacylglycerol lipase of Leishmania major (Lmlip2). In the present study, Lmlip2 was expressed in the eukaryotic heterologous expression system Pichia pastoris as tagged enzyme of 308 amino acids. Maximal protein production was reached after 2 days of fermentation. Optimal Lmlip2 lipase activity was measured using the pH stat technique at pH 8 at 26 °C using vinyl esters and triacylglycerols (true lipids) as substrates. Moreover, biochemical characterization of Lmlip2 contained in culture supernatant, illustrates that L. major secreted lipase is active and stable at low temperatures especially 26°and prefer neutral pH; concerning substrate specificityLmlip2 presents a preference for short chains lipid substrates vinyl esters such as VC2, VC3 and VC4 likewise, it is capable to hydrolyze long chain triacylglycerols like olive oil. Metal ions and surfactants tested in this study decrease Lmlip2 activity. Further studies are needed to clarify the relation between the lipase activity and the virulence. Thus, it could lead to the identification of novel targets to block cutaneous Leishmaniasis in human hosts.

Comparative sphingolipidomics of disease-causing trypanosomatids reveal unique lifecycle- and taxonomy-specific lipid chemistries

Trypanosomatids are parasitic protozoa which cause a spectrum of diseases, including trypanosomiasis and leishmaniasis, affecting millions of humans and animals worldwide. The surface of most protozoan parasites is heavily decorated with lipids and lipid-anchored molecules, forming protective barriers and acting as virulence factors during infection. Sphingolipids (SP) are major components of eukaryotic biomembranes, which play important roles in structural integrity, energy homeostasis and signaling. However, the precise chemical composition of SP in pathogens as well as their biochemical pathways and functions remain poorly characterized. Here, we present the first system-scale analyses of SP found in a panel of 7 trypanosomatids, including Leishmania donovani, Trypanosoma brucei and Trypanosoma cruzi. We characterized the structure of aminoethylphosphonate-containing ceramides, which are found exclusively in stercorarian Trypanosoma. Employing the sensitive and semi-quantitative sphingolipidomics approach that we developed, we report the detection of over 300 molecular species of SP, and identified unique metabolic signatures which serve as discriminants of the pathogens based on their taxonomy and lifecycle stages. The deep sphingolipidome presented here is an important biochemical and technological resource for future works to dissect SP metabolism and functions in these medically and agriculturally relevant systems.

Leishmania (Viannia) braziliensis Inositol Phosphorylceramide: Distinctive Sphingoid Base Composition

Inositol phosphorylceramide (IPC), the major sphingolipid in the genus Leishmania but not found in mammals, is considered a potentially useful target for chemotherapy against leishmaniasis. Leishmania (Viannia) braziliensis is endemic in Latin America and causes American tegumentary leishmaniasis. We demonstrated that IPCs are localized internally in parasites, using a specific monoclonal antibody. Treatment with 5 μM myriocin (a serine palmitoyltransferase inhibitor) rendered promastigotes 8-fold less infective than controls in experimental hamster infection, as determined by number of parasites per inguinal lymph node after 8 weeks infection, suggesting the importance of parasite IPC or sphingolipid derivatives in parasite infectivity or survival in the host. IPC was isolated from promastigotes of three L. (V.) braziliensis strains and analyzed by positive- and negative-ion ESI-MS. The major IPC ions were characterized as eicosasphinganine and eicosasphingosine. Negative-ion ESI-MS revealed IPC ion species at m/z 778.6 (d20:1/14:0), 780.6 (d20:0/14:0), 796.6 (t20:0/14:0), 806.6 (d20:1/16:0), and 808.6 (d20:0/16:0). IPCs isolated from L. (V.) braziliensis and L. (L.) major showed significant differences in IPC ceramide composition. The major IPC ion from L. (L.) major, detected in negative-ion ESI-MS at m/z 780.6, was composed of ceramide d16:1/18:0. Our results suggest that sphingosine synthase (also known as serine palmitoyltransferase; SPT) in L. (V.) braziliensis is responsible for synthesis of a long-chain base of 20 carbons (d20), whereas SPT in L. (L.) major synthesizes a 16-carbon long-chain base (d16). A phylogenetic tree based on SPT proteins was constructed by analysis of sequence homologies in species of the Leishmania and Viannia subgenera. Results indicate that SPT gene position in L. (V.) braziliensis is completely separated from that of members of subgenus Leishmania, including L. (L.) major, L. (L.) infantum, and L. (L.) mexicana. Our findings clearly demonstrate sphingoid base differences between L. (V.) braziliensis and members of subgenus Leishmania, and are relevant to future development of more effective targeted anti-leishmaniasis drugs.

Ocellatin-PT antimicrobial peptides: High-resolution microscopy studies in antileishmania models and interactions with mimetic membrane systems

Although the mechanism of action of antimicrobial peptides (AMPs) is not clear, they can interact electrostatically with the cell membranes of microorganisms. New ocellatin-PT peptides were recently isolated from the skin secretion of Leptodactylus pustulatus. The secondary structure of these AMPs and their effect on Leishmania infantum cells, and on different lipid surface models was characterized in this work. The results showed that all ocellatin-PT peptides have an α-helix structure and five of them (PT3, PT4, PT6 to PT8) have leishmanicidal activity; PT1 and PT2 affected the cellular morphology of the parasites and showed greater affinity for leishmania and bacteria-mimicking lipid membranes than for those of mammals. The results show selectivity of ocellatin-PTs to the membranes of microorganisms and the applicability of biophysical methods to clarify the interaction of AMPs with cell membranes.

Assessment of altered lipid homeostasis by HILIC-ion mobility-mass spectrometry-based lipidomics

Ion mobility-mass spectrometry (IM-MS) has proven to be a highly informative technique for the characterization of lipids from cells and tissues. We report the combination of hydrophilic-interaction liquid chromatography (HILIC) with traveling-wave IM-MS (TWIM-MS) for comprehensive lipidomics analysis. Main lipid categories such as glycerolipids, sphingolipids, and glycerophospholipids are separated on the basis of their lipid backbones in the IM dimension, whereas subclasses of each category are mostly separated on the basis of their headgroups in the HILIC dimension, demonstrating the orthogonality of HILIC and IM separations. Using our previously established lipid calibrants for collision cross-section (CCS) measurements in TWIM, we measured over 250 CCS values covering 12 lipid classes in positive and negative modes. The coverage of the HILIC-IM-MS method is demonstrated in the analysis of Neuro2a neuroblastoma cells exposed to benzalkonium chlorides (BACs) with C10 or C16 alkyl chains, which we have previously shown to affect gene expression related to cholesterol and lipid homeostasis. We found that BAC exposure resulted in significant changes to several lipid classes, including glycerides, sphingomyelins, phosphatidylcholines, and phosphatidylethanolamines. Our results indicate that BAC exposure modifies lipid homeostasis in a manner that is dependent upon the length of the BAC alkyl chain.

Changes in Lipid and Fatty Acid Composition During Intramacrophagic Transformation of Leishmania donovani Complex Promastigotes into Amastigotes

Leishmania sp., are trypanosomatid parasites that are phagocytized by human and animal macrophages. Transformation from the vector promastigote stage to the intracellular amastigote host cell stage is mandatory, since development in the host depends on the internalization of the parasite. We identified and analyzed the lipids involved in the promastigote to amastigote transformation process in the Leishmania donovani complex. Four lipid classes, phospholipids, free fatty acids, triglycerides and sterols were studied. The derivatization method of Bligh and Dyer was used to establish the fatty acid composition in each stage of the parasite. To stay within the context of Leishmania infection, we used amastigotes extracted from macrophages after experimental in vitro infection. The purification process was checked by electronic microscopy, the absence of major contamination by host-cell debris and a correct purification yield validated our experimental model. Our results show that free fatty acids and cholesterol increased, whereas triglycerides and ergosterol decreased during the transition between promastigotes to amastigotes. With respect to phospholipid classes, we found increased proportion of sphingomyelin and phosphatidylserine and lowered proportion of phosphatidylinositol and lysophosphatidylethanolamine. Regarding fatty acid composition, a significant increase of n-7 fatty acids was observed in amastigotes. Overall, the total n-6 fatty acids were decreased in PL. Several of the changes were also observed in TG and free fatty acids. Particularly, n-7 fatty acids and 20:4n-6 were highly increased, whereas n-9 fatty acid and n-6 precursors decreased.

Metabolomic Profiling of the Effects of Melittin on Cisplatin Resistant and Cisplatin Sensitive Ovarian Cancer Cells Using Mass Spectrometry and Biolog Microarray Technology

In the present study, liquid chromatography-mass spectrometry (LC-MS) was employed to characterise the metabolic profiles of two human ovarian cancer cell lines A2780 (cisplatin-sensitive) and A2780CR (cisplatin-resistant) in response to their exposure to melittin, a cytotoxic peptide from bee venom. In addition, the metabolomics data were supported by application of Biolog microarray technology to examine the utilisation of carbon sources by the two cell lines. Data extraction with MZmine 2.14 and database searching were applied to provide metabolite lists. Principal component analysis (PCA) gave clear separation between the cisplatin-sensitive and resistant strains and their respective controls. The cisplatin-resistant cells were slightly more sensitive to melittin than the sensitive cells with IC₅₀ values of 4.5 and 6.8 μg/mL respectively, although the latter cell line exhibited the greatest metabolic perturbation upon treatment. The changes induced by melittin in the cisplatin-sensitive cells led mostly to reduced levels of amino acids in the proline/glutamine/arginine pathway, as well as to decreased levels of carnitines, polyamines, adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide (NAD+). The effects on energy metabolism were supported by the data from the Biolog assays. The lipid compositions of the two cell lines were quite different with the A2780 cells having higher levels of several ether lipids than the A2780CR cells. Melittin also had some effect on the lipid composition of the cells. Overall, this study suggests that melittin might have some potential as an adjuvant therapy in cancer treatment.

HILIC-MS for metabolomics: An attractive and complementary approach to RPLC-MS

Hydrophilic interaction chromatography (HILIC) is an emerging separation mode of liquid chromatography (LC). Using highly hydrophilic stationary phases capable of retaining polar/ionic metabolites, and accompany with high organic content mobile phase that offer readily compatibility with mass spectrometry (MS) has made HILIC an attractive complementary tool to the widely used reverse-phase (RP) chromatographic separations in metabolomic studies. The combination of HILIC and RPLC coupled with an MS detector expands the number of detected analytes and provides more comprehensive metabolite coverage than use of only RP chromatography. This review describes the recent applications of HILIC-MS/MS in metabolomic studies, ranging from amino acids, lipids, nucleotides, organic acids, pharmaceuticals, and metabolites of specific nature. The biological systems investigated include microbials, cultured cell line, plants, herbal medicine, urine, and serum as well as tissues from animals and humans. Owing to its unique capability to measure more-polar biomolecules, the HILIC separation technique would no doubt enhance the comprehensiveness of metabolite detection, and add significant value for metabolomic investigations. © 2014 Wiley Periodicals, Inc. Mass Spec Rev 35:574-600, 2016.

Zwitterionic hydrophilic interaction solid-phase extraction and multi-dimensional mass spectrometry for shotgun lipidomic study of Hypophthalmichthys nobilis

Zwitterionic hydrophilic interaction liquid chromatography (ZIC-HILIC) material was used as solid-phase extraction sorbent for purification of phospholipids from Hypophthalmichthys nobilis. The conditions were optimized to be pH 6, flow rate 2.0mL·min(-1), loading breakthrough volume ⩽5mL, and eluting solvent 5mL. Afterwards, the extracts were analyzed by multi-dimensional mass spectrometry (MDMS) based shotgun lipidomics; 20 species of phosphatidylcholine (PC), 22 species of phosphatidylethanoamine (PE), 15 species of phosphatidylserine (PS), and 5 species of phosphatidylinositol (PI) were identified, with content 224.1, 124.1, 27.4, and 34.7μg·g(-1), respectively. The MDMS method was validated in terms of linearity (0.9963-0.9988), LOD (3.7ng·mL(-1)), LOQ (9.8ng·mL(-1)), intra-day precision (<3.64%), inter-day precision (<5.31%), and recovery (78.8-85.6%). ZIC-HILIC and MDMS shotgun lipidomics are efficient for studying phospholipids in H. nobilis.

Metabolomic Profiling of Post-Mortem Brain Reveals Changes in Amino Acid and Glucose Metabolism in Mental Illness Compared with Controls

Metabolomic profiling was carried out on 53 post-mortem brain samples from subjects diagnosed with schizophrenia, depression, bipolar disorder (SDB), diabetes, and controls. Chromatography on a ZICpHILIC column was used with detection by Orbitrap mass spectrometry. Data extraction was carried out with m/z Mine 2.14 with metabolite searching against an in-house database. There was no clear discrimination between the controls and the SDB samples on the basis of a principal components analysis (PCA) model of 755 identified or putatively identified metabolites. Orthogonal partial least square discriminant analysis (OPLSDA) produced clear separation between 17 of the controls and 19 of the SDB samples (R2CUM 0.976, Q2 0.671, p-value of the cross-validated ANOVA score 0.0024). The most important metabolites producing discrimination were the lipophilic amino acids leucine/isoleucine, proline, methionine, phenylalanine, and tyrosine; the neurotransmitters GABA and NAAG and sugar metabolites sorbitol, gluconic acid, xylitol, ribitol, arabinotol, and erythritol. Eight samples from diabetic brains were analysed, six of which grouped with the SDB samples without compromising the model (R2 CUM 0.850, Q2 CUM 0.534, p-value for cross-validated ANOVA score 0.00087). There appears on the basis of this small sample set to be some commonality between metabolic perturbations resulting from diabetes and from SDB.

Here, There, and Everywhere: The Ubiquitous Distribution of the Immunosignaling Molecule Lysophosphatidylcholine and Its Role on Chagas Disease

Chagas disease is a severe illness, which can lead to death if the patients are not promptly treated. The disease is caused by the protozoan parasite Trypanosoma cruzi, which is mostly transmitted by a triatomine insect vector. There are 8-10 million people infected with T. cruzi in the world, but the transmission of such disease by bugs occurs only in the Americas, especially Latin America. Chronically infected patients will develop cardiac diseases (30%) and up digestive, neurological, or mixed disorders (10%). Lysophosphatidylcholine (LPC) is the major phospholipid component of oxidized low-density lipoproteins associated with atherosclerosis-related tissue damage. Insect-derived LPC powerfully attracts inflammatory cells to the site of the insect bite, enhances parasite invasion, and inhibits the production of nitric oxide by T. cruzi-stimulated macrophages. The recognition of the ubiquitous presence of LPC on the vector saliva, its production by the parasite itself and its presence both on patient plasma and its role on diverse host × parasite interaction systems lead us to compare its distribution in nature with the title of the famous Beatles song "Here, There and Everywhere" recorded exactly 50 years ago in 1966. Here, we review the major findings pointing out the role of such molecule as an immunosignaling modulator of Chagas disease transmission. Also, we believe that future investigation of the connection of this ubiquity and the immune role of such molecule may lead in the future to novel methods to control parasite transmission, infection, and pathogenesis.

Hydrophilic interaction liquid chromatography-electrospray ionization-tandem mass spectrometry of a complex mixture of native and oxidized phospholipids

A mixture of native and oxidized phospholipids (PLs), generated by the soybean lipoxygenase type V-catalyzed partial oxidation of a lipid extract obtained from human platelets, was analyzed by Hydrophilic Interaction Liquid Chromatography-ElectroSpray Ionization-Tandem Mass Spectrometry (HILIC-ESI-MS/MS). The complexity of the resulting mixture was remarkable, considering that the starting lipid extract, containing (as demonstrated in a previous study) about 130 native PLs, was enriched with enzymatically generated hydroperoxylated derivatives and chemically generated hydroxylated forms of PLs bearing polyunsaturated side chains. Nonetheless, the described analytical approach proved to be very powerful; indeed, focusing on phosphatidylcolines (PCs), the most abundant PL class in human platelets, about fifty different native/oxidized species could be identified in a single HILIC-ESI-MS/MS run. Low-energy collision induced dissociation tandem MS (CID-MS/MS) experiments on chromatographically separated species showed single neutral losses of H2O2 and H2O to be typical fragmentation pathways of hydroperoxylated PCs, whereas a single H2O loss was observed for hydroxylated ones. Moreover, diagnostic losses of n-hexanal or n-pentanol were exploited to recognize PCs hydroperoxylated on the last but five carbon atom of a ɷ-6 polyunsaturated side chain. Despite the low resolution of the 3D ion trap mass analyzer used, the described HILIC-ESI-MS/MS approach appears very promising for the identification of oxidized lipids in oxidatively stressed complex biological systems.

Leishmania amazonensis exhibits phosphatidylserine-dependent procoagulant activity, a process that is counteracted by sandfly saliva

Leishmania parasites expose phosphatidylserine (PS) on their surface, a process that has been associated with regulation of host's immune responses. In this study we demonstrate that PS exposure by metacyclic promastigotes of Leishmania amazonensis favours blood coagulation. L. amazonensis accelerates in vitro coagulation of human plasma. In addition, L. amazonensis supports the assembly of the prothrombinase complex, thus promoting thrombin formation. This process was reversed by annexin V which blocks PS binding sites. During blood meal, Lutzomyia longipalpis sandfly inject saliva in the bite site, which has a series of pharmacologically active compounds that inhibit blood coagulation. Since saliva and parasites are co-injected in the host during natural transmission, we evaluated the anticoagulant properties of sandfly saliva in counteracting the procoagulant activity of L. amazonensis . Lu. longipalpis saliva reverses plasma clotting promoted by promastigotes. It also inhibits thrombin formation by the prothrombinase complex assembled either in phosphatidylcholine (PC)/PS vesicles or in L. amazonensis . Sandfly saliva inhibits factor X activation by the intrinsic tenase complex assembled on PC/PS vesicles and blocks factor Xa catalytic activity. Altogether our results show that metacyclic promastigotes of L. amazonensis are procoagulant due to PS exposure. Notably, this effect is efficiently counteracted by sandfly saliva.

Structural and functional analysis of a platelet-activating lysophosphatidylcholine of Trypanosoma cruzi

Background

Trypanosoma cruzi is the causative agent of the life-threatening Chagas disease, in which increased platelet aggregation related to myocarditis is observed. Platelet-activating factor (PAF) is a potent intercellular lipid mediator and second messenger that exerts its activity through a PAF-specific receptor (PAFR). Previous data from our group suggested that T. cruzi synthesizes a phospholipid with PAF-like activity. The structure of T. cruzi PAF-like molecule, however, remains elusive.

Methodology/Principal findings

Here, we have purified and structurally characterized the putative T. cruzi PAF-like molecule by electrospray ionization-tandem mass spectrometry (ESI-MS/MS). Our ESI-MS/MS data demonstrated that the T. cruzi PAF-like molecule is actually a lysophosphatidylcholine (LPC), namely sn-1 C18:1(delta 9)-LPC. Similar to PAF, the platelet-aggregating activity of C18:1-LPC was abrogated by the PAFR antagonist, WEB 2086. Other major LPC species, i.e., C16:0-, C18:0-, and C18:2-LPC, were also characterized in all T. cruzi stages. These LPC species, however, failed to induce platelet aggregation. Quantification of T. cruzi LPC species by ESI-MS revealed that intracellular amastigote and trypomastigote forms have much higher levels of C18:1-LPC than epimastigote and metacyclic trypomastigote forms. C18:1-LPC was also found to be secreted by the parasite in extracellular vesicles (EV) and an EV-free fraction. A three-dimensional model of PAFR was constructed and a molecular docking study was performed to predict the interactions between the PAFR model and PAF, and each LPC species. Molecular docking data suggested that, contrary to other LPC species analyzed, C18:1-LPC is predicted to interact with the PAFR model in a fashion similar to PAF.

Conclusions/Significance

Taken together, our data indicate that T. cruzi synthesizes a bioactive C18:1-LPC, which aggregates platelets via PAFR. We propose that C18:1-LPC might be an important lipid mediator in the progression of Chagas disease and its biosynthesis could eventually be exploited as a potential target for new therapeutic interventions.

Chagas disease, caused by the parasite Trypanosoma cruzi, was exclusively confined to Latin America but it has recently spread to other regions of the world. Chagas disease affects 8–10 million people and kills thousands of them every year. Lysophosphatidylcholine (LPC) is a major bioactive phospholipid of human plasma low-density lipoproteins (LDL). Platelet-activating factor (PAF) is a phospholipid similar to LPC and a potent intercellular mediator. Both PAF and LPC have been reported to act on mammalian cells through PAF receptor (PAFR). Previous data from our group suggested that T. cruzi produces a phospholipid with PAF activity. Here, we describe the structural and functional analysis of different species of LPC from T. cruzi, including a LPC with a fatty acid chain of 18 carbon atoms and one double bond (C18:1-LPC). We also show that C18:1-LPC is able to induce rabbit platelet aggregation, which is abrogated by a PAFR antagonist. In addition, a three-dimensional model of human PAFR was constructed. Contrary to other T. cruzi LPC molecules, C18:1-LPC is predicted to interact with the PAFR model in a fashion similar to PAF. Further studies are needed to validate the biosynthesis of T. cruzi C18:1-LPC as a potential drug target in Chagas disease.

Comprehensive and simultaneous coverage of lipid and polar metabolites for endogenous cellular metabolomics using HILIC-TOF-MS

The comprehensive metabolomic analyses using eukaryotic and prokaryotic cells are an effective way to identify biomarkers or biochemical pathways which can then be used to characterize disease states, differences between cell lines or inducers of cellular stress responses. One of the most commonly used extraction methods for comprehensive metabolomics is the Bligh and Dyer method (BD) which separates the metabolome into polar and nonpolar fractions. These fractions are then typically analysed separately using hydrophilic interaction liquid chromatography (HILIC) and reversed-phase (RP) liquid chromatography (LC), respectively. However, this method has low sample throughput and can also be biased to either polar or nonpolar metabolites. Here, we introduce a MeOH/EtOH/H2O extraction paired with HILIC-time-of-flight (TOF)-mass spectrometry (MS) for comprehensive and simultaneous detection of both polar and nonpolar metabolites that is compatible for a wide array of cellular species cultured in different growth media. This method has been shown to be capable of separating polar metabolites by a HILIC mechanism and classes of lipids by an adsorption-like mechanism. Furthermore, this method is scalable and offers a substantial increase in sample throughput compared to BD with comparable extraction efficiency. This method was able to cover 92.2% of the detectable metabolome of Gram-negative bacterium Sinorhizobium meliloti, as compared to 91.6% of the metabolome by a combination of BD polar (59.4%) and BD nonpolar (53.9%) fractions. This single-extraction HILIC approach was successfully used to characterize the endometabolism of Gram-negative and Gram-positive bacteria as well as mammalian macrophages.

Two birds with one stone: doing metabolomics with your proteomics kit

Proteomic research facilities and laboratories are facing increasing demands for the integration of biological data from multiple ‘-OMICS’ approaches. The aim to fully understand biological processes requires the integrated study of genomes, proteomes and metabolomes. While genomic and proteomic workflows are different, the study of the metabolome overlaps significantly with the latter, both in instrumentation and methodology. However, chemical diversity complicates an easy and direct access to the metabolome by mass spectrometry (MS). The present review provides an introduction into metabolomics workflows from the viewpoint of proteomic researchers. We compare the physicochemical properties of proteins and peptides with metabolites/small molecules to establish principle differences between these analyte classes based on human data. We highlight the implications this may have on sample preparation, separation, ionisation, detection and data analysis. We argue that a typical proteomic workflow (nLC-MS) can be exploited for the detection of a number of aliphatic and aromatic metabolites, including fatty acids, lipids, prostaglandins, di/tripeptides, steroids and vitamins, thereby providing a straightforward entry point for metabolomics-based studies. Limitations and requirements are discussed as well as extensions to the LC-MS workflow to expand the range of detectable molecular classes without investing in dedicated instrumentation such as GC-MS, CE-MS or NMR.

Mapping an atlas of tissue-specific Drosophila melanogaster metabolomes by high resolution mass spectrometry

Metabolomics can provide exciting insights into organismal function, but most work on simple models has focussed on the whole organism metabolome, so missing the contributions of individual tissues. Comprehensive metabolite profiles for ten tissues from adult Drosophila melanogaster were obtained here by two chromatographic methods, a hydrophilic interaction (HILIC) method for polar metabolites and a lipid profiling method also based on HILIC, in combination with an Orbitrap Exactive instrument. Two hundred and forty two polar metabolites were putatively identified in the various tissues, and 251 lipids were observed in positive ion mode and 61 in negative ion mode. Although many metabolites were detected in all tissues, every tissue showed characteristically abundant metabolites which could be rationalised against specific tissue functions. For example, the cuticle contained high levels of glutathione, reflecting a role in oxidative defence; the alimentary canal (like vertebrate gut) had high levels of acylcarnitines for fatty acid metabolism, and the head contained high levels of ether lipids. The male accessory gland uniquely contained decarboxylated S-adenosylmethionine. These data thus both provide valuable insights into tissue function, and a reference baseline, compatible with the FlyAtlas.org transcriptomic resource, for further metabolomic analysis of this important model organism, for example in the modelling of human inborn errors of metabolism, aging or metabolic imbalances such as diabetes.

Lipid synthesis in protozoan parasites: a comparison between kinetoplastids and apicomplexans

Lipid metabolism is of crucial importance for pathogens. Lipids serve as cellular building blocks, signalling molecules, energy stores, posttranslational modifiers, and pathogenesis factors. Parasites rely on a complex system of uptake and synthesis mechanisms to satisfy their lipid needs. The parameters of this system change dramatically as the parasite transits through the various stages of its life cycle. Here we discuss the tremendous recent advances that have been made in the understanding of the synthesis and uptake pathways for fatty acids and phospholipids in apicomplexan and kinetoplastid parasites, including Plasmodium, Toxoplasma, Cryptosporidium, Trypanosoma and Leishmania. Lipid synthesis differs in significant ways between parasites from both phyla and the human host. Parasites have acquired novel pathways through endosymbiosis, as in the case of the apicoplast, have dramatically reshaped substrate and product profiles, and have evolved specialized lipids to interact with or manipulate the host. These differences potentially provide opportunities for drug development. We outline the lipid pathways for key species in detail as they progress through the developmental cycle and highlight those that are of particular importance to the biology of the pathogens and/or are the most promising targets for parasite-specific treatment.

Phospholipidomics of human blood microparticles

The phospholipidome of blood microparticles (MPs) obtained from platelet-rich plasma of healthy individuals was characterized by hydrophilic interaction liquid chromatography (HILIC) coupled to electrospray ionization tandem mass spectrometry (ESI-MS/MS). The HILIC separation, performed on a silica stationary phase using an acetonitrile/methanol gradient, enabled the separation of several phospholipids (PL) classes, viz., phosphatidyl-cholines (PCs), -ethanolamines (PEs), -serines (PSs), -inositoles (PIs), sphyngomielins (SMs), and lyso forms of PCs and PEs. Structural characterization of species belonging to each class was performed by MS/MS measurements, in either positive or negative ion mode. The set of 131 phospholipids (including regioisomers) here identified represents the most comprehensive phospholipidomic characterization reported for human MPs. Although the phospholipidome composition of MPs and platelets, collected from the same donors, was found to be qualitatively the same, quantitative differences were evidenced for lyso-PCs, which appear to be significantly more abundant in MPs.

Rapid quantification of yeast lipid using microwave-assisted total lipid extraction and HPLC-CAD

We here present simple and rapid methods for fast screening of yeast lipids in Saccharomyces cerevisiae. First we introduced a microwave-assisted technique for fast lipid extraction that allows the extraction of lipids within 10 min. The new method enhances extraction rate by 27 times, while maintaining product yields comparable to conventional methods (n = 14, P > 0.05). The recovery (n = 3) from spiking of synthetic standards were 92 ± 6% for cholesterol, 95 ± 4% for triacylglycerol, and 92 ± 4% for free fatty acids. Additionally, the new extraction method combines cell disruption and extraction in one step, and the approach, therefore, not only greatly simplifies sample handling but also reduces analysis time and minimizes sample loss during sample preparation. Second, we developed a chromatographic separation that allowed separation of neutral and polar lipids from the extracted samples within a single run. The separation was performed based on a three gradient solvent system combined with hydrophilic interaction liquid chromatography-HPLC followed by detection using a charged aerosol detector. The method was shown to be highly reproducible in terms of retention time of the analytes (intraday; 0.002-0.034% RSD; n = 10, interday; 0.04-1.35% RSD; n = 5) and peak area (intraday; 0.63-6% RSD; n = 10, interday; 4-12% RSD; n = 5).

A comparison of five lipid extraction solvent systems for lipidomic studies of human LDL

Lipidome profile of fluids and tissues is a growing field as the role of lipids as signaling molecules is increasingly understood, relying on an effective and representative extraction of the lipids present. A number of solvent systems suitable for lipid extraction are commonly in use, though no comprehensive investigation of their effectiveness across multiple lipid classes has been carried out. To address this, human LDL from normolipidemic volunteers was used to evaluate five different solvent extraction protocols [Folch, Bligh and Dyer, acidified Bligh and Dyer, methanol (MeOH)-tert-butyl methyl ether (TBME), and hexane-isopropanol] and the extracted lipids were analyzed by LC-MS in a high-resolution instrument equipped with polarity switching. Overall, more than 350 different lipid species from 19 lipid subclasses were identified. Solvent composition had a small effect on the extraction of predominant lipid classes (triacylglycerides, cholesterol esters, and phosphatidylcholines). In contrast, extraction of less abundant lipids (phosphatidylinositols, lyso-lipids, ceramides, and cholesterol sulfates) was greatly influenced by the solvent system used. Overall, the Folch method was most effective for the extraction of a broad range of lipid classes in LDL, although the hexane-isopropanol method was best for apolar lipids and the MeOH-TBME method was suitable for lactosyl ceramides.