Multiplex quantitative analysis of eicosanoid mediators in human plasma and serum: Possible introduction into clinical testing

Differential expression of eicosanoid pathways after whole blood stimulation in asthma patients

Objectives

Asthma is a heterogeneous disease regarding its pathophysiology, clinical symptoms, and response to treatment. Eicosanoids are important inflammatory mediators, able to either promote or attenuate the underlying chronic airway inflammation. We compared eicosanoid expression patterns in the blood circulation and in stimulated blood leukocytes of asthma patients to identify differences in eicosanoid release which may be related to airway inflammation.

Methods

Blood was collected from 198 adult asthmatic patients and 63 healthy controls, participating in the German Center for Lung Research (DZL) ALLIANCE cohort. Eicosanoid release from leukocytes was analyzed using heparinized whole blood after in vitro stimulation with zymosan. Additionally, circulating eicosanoids were measured directly from ethylenediaminetetraacetic acid (EDTA) plasma. Eicosanoids were extracted via solid phase extraction and quantified by high-performance-liquid-chromatography-tandem-mass-spectrometry (HPLC-MS2).

Results

Eicosanoid levels were low in blood circulation with no significant differences between asthmatics and controls, except for leukotriene E4 (LTE4) which was slightly elevated in asthmatics. After in vitro stimulation we observed an inhibition of prostaglandin and thromboxane biosynthesis only in patients with severe asthma which was related to the regular use of systemic corticosteroids. In contrast, a significant increase was shown for formation of the 5-Lipoxygenase (5-LOX) product LTE4 in steroid-naïve asthmatics with moderate as well as severe disease severity but not in subjects with systemic steroid treatment. Furthermore 15-Hydorxyeicosatetraenoic acid (15-HETE) production was elevated in asthmatic patients with mild-to-moderate disease activity but dropped down in severe asthmatics.

Conclusions

Profiling of eicosanoid production in stimulated whole blood samples showed a specific biosynthesis pattern of asthmatic patients, which is influenced by the use of systemic corticosteroids.

Assessment of Multidimensional Health Care Parameters Among Adults in Japan for Developing a Virtual Human Generative Model: Protocol for a Cross-sectional Study

BACKGROUND

Human health status can be measured on the basis of many different parameters. Statistical relationships among these different health parameters will enable several possible health care applications and an approximation of the current health status of individuals, which will allow for more personalized and preventive health care by informing the potential risks and developing personalized interventions. Furthermore, a better understanding of the modifiable risk factors related to lifestyle, diet, and physical activity will facilitate the design of optimal treatment approaches for individuals.

OBJECTIVE

This study aims to provide a high-dimensional, cross-sectional data set of comprehensive health care information to construct a combined statistical model as a single joint probability distribution and enable further studies on individual relationships among the multidimensional data obtained.

METHODS

In this cross-sectional observational study, data were collected from a population of 1000 adult men and women (aged ≥20 years) matching the age ratio of the typical adult Japanese population. Data include biochemical and metabolic profiles from blood, urine, saliva, and oral glucose tolerance tests; bacterial profiles from feces, facial skin, scalp skin, and saliva; messenger RNA, proteome, and metabolite analyses of facial and scalp skin surface lipids; lifestyle surveys and questionnaires; physical, motor, cognitive, and vascular function analyses; alopecia analysis; and comprehensive analyses of body odor components. Statistical analyses will be performed in 2 modes: one to train a joint probability distribution by combining a commercially available health care data set containing large amounts of relatively low-dimensional data with the cross-sectional data set described in this paper and another to individually investigate the relationships among the variables obtained in this study.

RESULTS

Recruitment for this study started in October 2021 and ended in February 2022, with a total of 997 participants enrolled. The collected data will be used to build a joint probability distribution called a Virtual Human Generative Model. Both the model and the collected data are expected to provide information on the relationships between various health statuses.

CONCLUSIONS

As different degrees of health status correlations are expected to differentially affect individual health status, this study will contribute to the development of empirically justified interventions based on the population.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/47024.

Monitoring inflammation in psychiatry: Caveats and advice

Most researchers working in the field of immunopsychiatry would agree with the statement that "severe psychiatric disorders are associated with inflammation and more broadly with changes in immune variables". However, as many other fields in biology and medicine, immunopsychiatry suffers from a replication crisis characterized by lack of reproducibility. In this paper, we will comment on four types of immune variables which have been studied in psychiatric disorders: Acute Phase Proteins (AAPs), cytokines, lipid mediators of inflammation and immune cell parameters, and discuss the rationale for looking at them in blood. We will briefly describe the analytical methods that are currently used to measure the levels of these biomarkers and comment on overlooked analytical and statistical methodological issues that may explain some of the conflicting data reported in the literature. Lastly, we will briefly summarize what cross-sectional, longitudinal and mendelian randomization studies have brought to our understanding of schizophrenia (SZ).

Defining Blood Plasma and Serum Metabolome by GC-MS

Metabolomics uses advanced analytical chemistry methods to analyze metabolites in biological samples. The most intensively studied samples are blood and its liquid components: plasma and serum. Armed with advanced equipment and progressive software solutions, the scientific community has shown that small molecules’ roles in living systems are not limited to traditional “building blocks” or “just fuel” for cellular energy. As a result, the conclusions based on studying the metabolome are finding practical reflection in molecular medicine and a better understanding of fundamental biochemical processes in living systems. This review is not a detailed protocol of metabolomic analysis. However, it should support the reader with information about the achievements in the whole process of metabolic exploration of human plasma and serum using mass spectrometry combined with gas chromatography.

Development of Tandem Mass Tag Labeling Method for Lipid Molecules Containing Carboxy and Phosphate Groups, and Their Stability in Human Serum

In clinical lipidomics, it is a challenge to measure a large number of samples and to reproduce the quantitative results. We expanded the range of application of the tandem mass tag (TMT) method, which is widely used in proteomics, to lipidomic fields. There are various types of lipid molecule, for example, eicosanoids have a carboxyl group and phosphatidic acid has a phosphate group. We modified these functional groups simultaneously with TMT. This approach allows for a single analysis by mixing six samples and using one of the six samples as a bridging sample; the quantitative data can be easily normalized even if the number of measurements increases. To accommodate a large number of samples, we utilize a pooled serum sample of 300 individuals as a bridging sample. The stability of these lipid molecules in serum was examined as an analytical validation for the simultaneous TMT labeling. It was found that the stability of these lipid molecules in serum differs greatly depending on the lipid species. These findings reaffirmed the importance of proper sample preparation and storage to obtain reliable data. The TMT labeling method is expected to be a useful method for lipidomics with high-throughput and reliable reproducibility.

Limitations of deuterium-labeled internal standards for quantitative electrospray ionization mass spectrometry analysis of fatty acid metabolites

RATIONALE

The electrospray ionization mass spectrometry (ESI-MS) methodology often shows poor ionization reproducibility in the analysis of biological samples. Therefore, normalization of the measured peak intensities is essential. It is believed that quantitative data with high reproducibility can be obtained by adding a constant amount of an internal standard (IS) material labeled with stable isotopes to each sample, thus allowing the correction of the quantitative value of the target compound by that of the IS. We investigated whether the presence or absence of a labeled IS improves the accuracy of these quantitative values.

METHODS

Triple quadrupole MS coupled with liquid chromatography was used to analyze fatty acid metabolites in biological samples as target compounds. Two independent systems were used to provide a measure of reproducibility in two different laboratories.

RESULTS

Data having poor reproducibility in the raw peak areas were efficiently normalized using the IS, but, crucially, the IS method using stable isotopes was not always necessary. In some cases, the reproducibility was relatively good even without using the IS. In a contaminant matrix, the MS response behavior of the target compound and its stable isotope-labeled material was complicated. Since ion suppression by matrix contaminants was dependent on the concentration of the target compound, the added amounts of the ISs were also important, Furthermore, an equivalent normalization effect was obtained by using a pooled quality control sample as an external standard, thus obviating the need for labeled IS samples, which are often expensive and sometimes not commercially available.

CONCLUSIONS

Our results raise the question as to whether the quantitative method using stable-isotope-labeled ISs is always necessary and beneficial. However, the results obtained in this study cannot be generalized because only fatty acid metabolites were examined using ESI-MS and only a highly substituted deuterium-labeled IS was used.

Simultaneous quantitative determination of arachidonic acid and cascade metabolites in rat serum by UPLC-MS/MS: application for longitudinal metabolomics of anlotinib

Arachidonic acid (AA) and cascade metabolites have been shown to be involved in cancer pathologic states. Anlotinib, a novel oral small molecule inhibitor of multiple receptor tyrosine kinases, has brought significant improvement to the survival of patients with advanced lung cancer. Here, a robust and reproducible ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed, optimized and validated for quantitating AA and cascade metabolites for the first time. Through careful optimization of the analytical conditions, a total of 69 analytes can be efficiently separated and quantitated in a single run of 17 min. A simple and labor-saving protein precipitation procedure was utilized for serum sample pretreatment. The validation parameters and quality control chart of all analytes satisfy the acceptance criteria of bioanalytical method guidelines. The limit of detection (LOD) ranged from 0.005 ng mL^-1 to 1 ng mL^-1, and the volume of serum was only 20 μL. This rapid and sensitive UPLC-MS/MS method was successfully applied to a longitudinal metabolomics study in rat serum after a single administration of anlotinib (6 mg kg^-1). Finally, a total of 41 metabolites can be calculated under the present conditions. Serum samples from the same rat were segregated into a tight cluster in both unsupervised principal component analysis (PCA) and supervised orthogonal partial least-squares discriminant analysis (OPLS-DA) at different sampling time points after anlotinib treatment. Moreover, the number of analytes whose variable importance (VIP) values were larger than 1.0 was 17. The present study not only offers a UPLC-MS/MS analytical reference for AA but also brings out insights for future mechanistic studies or biomarkers to predict the efficacy, toxicity and clinical outcomes in patients with cancer.

Biosynthesis of uniformly carbon isotope-labeled docosahexaenoic acid in Crypthecodinium cohnii

Docosahexaenoic acid (DHA) enriched in brain can yield many important degradation products after the attack of hydroxyl radicals, which is known to serve as a nutraceutical and neuroprotective effects. Oxidative stress is a commonly observed feature of Alzheimer's disease (AD). Therefore, uniformly radiolabeled DHA plays an important role in studying the oxidative fate of DHA in vivo and vitro. However, carbon isotope labeled DHA isn't commercially available now. The heterotrophic microalgae Crypthecodinium cohnii (C. cohnii) has been identified as a prolific producer of DHA. In this study, the growth rate and DHA production in C. cohnii were optimized in a new defined media, and the biosynthesis of U-13C-DHA from U-13C-glucose and U-14C-DHA from U-14C-glucose were analyzed by HPLC-MS/MS. Approximately 40 nmoles of U-13C-DHA with higher isotopic purity of 96.8% was produced in a 300 μL batch, and ~ 0.23 μCi of U-14C-DHA with significant specific activity of 5-6 Ci/mol was produced in a 300 μL batch. It was found that C. cohnii had the optimal growth and DHA accumulation at 25 °C in this defined media (C/N = 10). An efficient protocol for the biosynthesis of U-13C-DHA and U-14C-DHA were set up firstly, which provides the basic support for the analysis of oxidative degradation products of DHA in AD.

The role of autonomously secreted PGE2 and its autocrine/paracrine effect on bone matrix mineralization at the different stages of differentiating MC3T3-E1 cells

Bone is consisted of osteoblast-linage cells, bone-forming cells in various differentiation stages. However, it is not fully understood how communicate and interact these cells immigrated from bone marrow. In this study, we showed that prostaglandin E2 (PGE₂) had a role in autonomous modification of matrix mineralization in osteoblastic cell line, MC3T3-E1, and interactions across the cells in different differentiation stages. Analysis using LC-MS/MS and inhibitors showed the autonomous secretion of PGE₂ among the prostanoids in differentiation stages and that depend on COX-2, a key enzyme for production of PGE₂. Treatment with inhibitors of PGE₂ receptors and COX-2 indicated that secreted PGE₂ regulates matrix mineralization in an autocrine/paracrine manner. In addition, we showed that the expression profile of PGE₂ receptors (EP1-EP4) and PGE₂ effects on matrix mineralization derived from it changed during cell differentiation. Treatment with inhibitors of PGE₂ signaling in the early differentiation stage of MC3T3-E1 cells induced significant changes in matrix mineralization several days after. Stimulation with the extracts from culture medium of the matured cells including PGE₂ and co-culture with the matured cells secreting PGE₂ significantly promoted matrix mineralization of the early stage cells, in contrast, treatment with inhibitor of COX-2 and PGE₂ receptors failed to do so. These results support that PGE₂ plays important roles in the interaction system of osteoblast-linage cells in bone tissue to regulate matrix mineralization reflecting condition of bone-forming cells, that is, population and maturation.

Methods of the Analysis of Oxylipins in Biological Samples

Oxylipins are derivatives of polyunsaturated fatty acids and due to their important and diverse functions in the body, they have become a popular subject of studies. The main challenge for researchers is their low stability and often very low concentration in samples. Therefore, in recent years there have been developments in the extraction and analysis methods of oxylipins. New approaches in extraction methods were described in our previous review. In turn, the old analysis methods have been replaced by new approaches based on mass spectrometry (MS) coupled with liquid chromatography (LC) and gas chromatography (GC), and the best of these methods allow hundreds of oxylipins to be quantitatively identified. This review presents comparative and comprehensive information on the progress of various methods used by various authors to achieve the best results in the analysis of oxylipins in biological samples.

The role of anti-complement factor H antibodies in the development of atypical haemolytic uremic syndrome: a possible contribution to abnormality of platelet function

Atypical haemolytic uremic syndrome (aHUS) is associated with complement system abnormality, such as production of complement factor H (CFH) autoantibodies. The growing evidence indicates complement overactivation on platelets is intimately involved in aHUS pathogenesis, besides endothelial injury. We here showed plasma from patients with anti-CFH antibodies induced aggregation of washed platelets, while purified anti-CFH antibodies suppressed aggregation. This suggested anti-CFH antibody itself suppressed thrombosis, while other plasma factor including complement factors could overactivate the platelets, leading to aggregation, which augmented the notion the state of complement activation influenced by anti-CFH antibodies is important in the aggregation of platelets in aHUS.

Modern Methods of Sample Preparation for the Analysis of Oxylipins in Biological Samples

Oxylipins are potent lipid mediators derived from polyunsaturated fatty acids, which play important roles in various biological processes. Being important regulators and/or markers of a wide range of normal and pathological processes, oxylipins are becoming a popular subject of research; however, the low stability and often very low concentration of oxylipins in samples are a significant challenge for authors and continuous improvement is required in both the extraction and analysis techniques. In recent years, the study of oxylipins has been directly related to the development of new technological platforms based on mass spectrometry (LC–MS/MS and gas chromatography–mass spectrometry (GC–MS)/MS), as well as the improvement in methods for the extraction of oxylipins from biological samples. In this review, we systematize and compare information on sample preparation procedures, including solid-phase extraction, liquid–liquid extraction from different biological tissues.

Comprehensive analysis of oxylipins in human plasma using reversed-phase liquid chromatography-triple quadrupole mass spectrometry with heatmap-assisted selection of transitions

Oxylipins, a subclass of lipid mediators, are metabolites of various polyunsaturated fatty acids with crucial functions in regulation of systemic inflammation. Elucidation of their roles in pathological conditions requires accurate quantification of their levels in biological samples. We refined an ultra-performance liquid chromatography-multiple reaction monitoring-mass spectrometry (UPLC-MRM-MS)-based workflow for comprehensive and specific quantification of 131 endogenous oxylipins in human plasma, in which we optimized LC mobile phase additives, column, and gradient conditions. We employed heatmap-assisted strategy to identify unique transitions to improve the assay selectivity and optimized solid phase extraction procedures to achieve better analyte recovery. The method was validated according to FDA guidelines. Overall, 94.4% and 95.7% of analytes at tested concentrations were within acceptable accuracy (80-120%) and precision (CV < 15%), respectively. Good linearity for most analytes was obtained with R² > 0.99. The method was also validated using a standard reference material-SRM 1950 frozen human plasma to demonstrate inter-lab compatibility. Graphical abstract ᅟ.

MS-based lipidomics of human blood plasma: a community-initiated position paper to develop accepted guidelines

Human blood is a self-regenerating lipid-rich biological fluid that is routinely collected in hospital settings. The inventory of lipid molecules found in blood plasma (plasma lipidome) offers insights into individual metabolism and physiology in health and disease. Disturbances in the plasma lipidome also occur in conditions that are not directly linked to lipid metabolism; therefore, plasma lipidomics based on MS is an emerging tool in an array of clinical diagnostics and disease management. However, challenges exist in the translation of such lipidomic data to clinical applications. These relate to the reproducibility, accuracy, and precision of lipid quantitation, study design, sample handling, and data sharing. This position paper emerged from a workshop that initiated a community-led process to elaborate and define a set of generally accepted guidelines for quantitative MS-based lipidomics of blood plasma or serum, with harmonization of data acquired on different instrumentation platforms across independent laboratories as an ultimate goal. We hope that other fields may benefit from and follow such a precedent.

Astrocytes synthesize primary and cyclopentenone prostaglandins that are negative regulators of their proliferation

Recently, the modulation of cellular inflammatory responses via endogenous regulators became a major focus of medically relevant investigations. Prostaglandins (PGs) are attractive regulatory molecules, but their synthesis and mechanisms of action in brain cells are still unclear. Astrocytes are involved in manifestation of neuropathology and their proliferation is an important part of astrogliosis, a cellular neuroinflammatory response. The aims of our study were to measure synthesis of PGs by astrocytes, and evaluate their influence on proliferation in combination with addition of inflammatory pathway inhibitors. With UPLC-MS/MS analysis we detected primary PGs (1410 ± 36 pg/mg PGE₂, 344 ± 24 PGD₂) and cyclopentenone PGs (cyPGs) (87 ± 17 15d-PGJ₂, 308 ± 23 PGA₂) in the extracellular medium after 24-h lipopolysaccharide (LPS) stimulation of astrocytes. PGs reduced astrocytic proliferation with the following order of potencies (measured as inhibition at 20 μM): most potent 15d-PGJ₂ (90%) and PGA₂ (80%), > PGD₂ (40%) > 15d-PGA₂ (20%) > PGE₂ (5%), the least potent. However, PGF_2α and 2-cyclopenten-1-one, and ciglitazone and rosiglitazone (synthetic agonists of PPARγ) had no effect. Combinations of cyPGs with SC-560 or NS-398 (specific anti-inflammatory inhibitors of cyclooxygenase-1 and -2, respectively) were not effective; while GW9662 (PPARγ antagonist) or MK-741 (inhibitor of multidrug resistance protein-1, MRP1, and CysLT1 receptors) amplified the inhibitory effect of PGA₂ and 15d-PGJ₂. Although concentrations of individual PGs and cyPGs are low, all of them, as well as primary PGs suppress proliferation. Thus, the effects are potentially additive, and activated PGs synthesis suppresses proliferation in astrocytes.