Lipid-based patterning of the immunological synapse

Extended-Synaptotagmin-1 and -2 control T cell signaling and function

Upon T-cell activation, the levels of the secondary messenger diacylglycerol (DAG) at the plasma membrane need to be controlled to ensure appropriate T-cell receptor signaling and T-cell functions. Extended-Synaptotagmins (E-Syts) are a family of inter-organelle lipid transport proteins that bridge the endoplasmic reticulum and the plasma membrane. In this study, we identify a novel regulatory mechanism of DAG-mediated signaling for T-cell effector functions based on E-Syt proteins. We demonstrate that E-Syts downmodulate T-cell receptor signaling, T-cell-mediated cytotoxicity, degranulation, and cytokine production by reducing plasma membrane levels of DAG. Mechanistically, E-Syt2 predominantly modulates DAG levels at the plasma membrane in resting-state T cells, while E-Syt1 and E-Syt2 negatively control T-cell receptor signaling upon stimulation. These results reveal a previously underappreciated role of E-Syts in regulating DAG dynamics in T-cell signaling.

Metabolomics Reveals Molecular Signatures for Psoriasis Biomarkers and Drug Targets Discovery

Purpose

Psoriasis is a chronic, multi-system skin disease that can be influenced by immunological, environmental, and genetic factors. Plasma metabolomic analysis can provide a great deal of information on potential diagnostic biomarkers, pathogenesis and personalized treatment. However, the role of metabolites in psoriasis is unknown.

Patients and Methods

We performed an untargeted metabolomic analysis of plasma based on high-resolution liquid chromatography mass spectrometry from 10 plaque psoriasis patients and 10 healthy controls.

Results

A total of 301 differential metabolites were detected, of which 10 metabolites were possible potential biomarkers, including vitamins, amino acids, and lipids. At the same time, KEGG pathway enrichment analysis was performed for all detected differential metabolites, and it was found that protein digestion and absorption, amino acid metabolism and lipid metabolism may be jointly involved in regulating the pathogenesis of psoriasis. In addition, the proteins ESR1, OPRM1 and HSD11B1 were identified as possible potential topical therapeutic targets for psoriasis through analysis of the metabolite-protein interaction network.

Conclusion

In this study, we identified 10 differential metabolites as possible potential combinatorial biomarkers for the diagnosis of psoriasis. 12 metabolic pathways were significantly enriched that may be closely related to the occurrence and development of psoriasis. Three proteins, ESR1, OPRM1, and HSD11B1, were identified as possible potential therapeutic targets for psoriasis.

Untargeted Plasma Lipidomics Reveal Perturbed Metabolites of Glycerophospholipids, and Sphingolipids in Moderate-to-Severe Acne

Background

Acne vulgaris (AV) is a common inflammatory disorder involving the pilosebaceous unit. The study aimed to explore the plasma lipidome signatures and identify specific lipid biomarkers in moderate-to-severe acne patients.

Patients and Methods

Untargeted plasma lipidomic analysis using ultra-high performance liquid chromatography system (UHPLC) coupled to q-extraction plus was employed on 30 moderate-to-severe acne patients aged between 16-25 years and 30 healthy controls. Multivariate data analyses were used to identify the distinguishing lipid metabolites.

Results

All 1449 species of 37 lipid subclasses were identified from the MS data. There were apparent differences in plasma lipid profiles between acne groups and control groups. With variable influence on projection (VIP) > 1.0 and P-value < 0.05, 26 significantly different lipid metabolites were identified. These metabolites consisted mainly of glycerophospholipids (GPs), sphingolipids (SPs), and glycerolipids (GLs). Combining with AUC≥0.800 as the elected criteria, we obtained five differential lipids with good diagnostic performance for acne severity, including 2 sphingomyelins (SM), 1 phosphatidylglycerol (PG), 1 trihexosylceramide (Hex3Cer), and 1 Phosphatidylcholine (PC). Among them, PG (44:0) had the highest AUC values.

Conclusion

Our study revealed the plasma lipidome signature of patients with moderate-to-severe acne. The results will provide a novel light into the perturbed lipid metabolism leading to the development of acne.

Huangjinsan ameliorates adenine-induced chronic kidney disease by regulating metabolic profiling

Chronic kidney disease is an increasingly serious public health problem worldwide. Our recent studies have shown that Huangjinsan has a renal protective effect on chronic kidney disease, but the specific mechanism by which this effect occurs is not clear. To study the therapeutic effect of Huangjinsan on chronic kidney disease and to explore its possible mechanism of action through nontargeted metabolomics methods, a chronic kidney disease rat model was induced by adenine, and the Huangjinsan extract was given by oral gavage. Body weight, the kidney index, pathological sections, and a series of biochemical indicators were measured. High-performance liquid chromatography quadrupole time-of-flight mass spectrometry was used to analyze the changes in the plasma metabolome. Huangjinsan significantly reduced indicators of kidney damage, including total protein, albumin, the total protein to creatinine ratio, and the albumin to creatinine ratio in urine, as well as IL-2, MCP-1α, and blood urea levels in plasma. Based on nontargeted metabolomics, 13 metabolites related to chronic kidney disease were discovered. These metabolites are closely related to glycerophospholipid metabolism, arginine and proline metabolism, and sphingolipid metabolism. We found that Huangjinsan can restore the renal function of adenine-induced chronic kidney disease by regulating the metabolic profile.

UPLC-MS/MS-Based Rat Serum Metabolomics Reveals the Detoxification Mechanism of Psoraleae Fructus during Salt Processing

Psoraleae Fructus (PF) is a botanical medicine widely used in Asian countries, of which salt products have higher safety and efficacy. However, the biological mechanism of the detoxification of salt-processing Psoraleae Fructus (SPF) has not yet been revealed. In this study, UPLC-MS/MS technology was used to explore the metabolic differences between SPF and PF in normal rats and reveal the mechanism of salt processing. The histopathological results of rat liver and kidney showed that the degree of liver and kidney injure in the SPF group was less than that in the PF group. The results of metabolomics showed that the detoxification mechanism of PF by salt processing might be related to glycerophospholipid metabolism, phenylalanine, tyrosine, and tryptophan biosynthesis, arginine and proline metabolism, phenylalanine metabolism, and linoleic acid metabolism. PF-induced inflammation could be reduced by regulating the expression of metabolites to achieve the purpose of salt processing and detoxification. It included reducing the production of metabolites such as 1-acyl-sn-glycero-3-phosphocholine, sn-glycero-3-phosphocholine, tyrosine, arginine, linoleic acid, arachidonic acid, and phenylacetylglycine/hippuric acid ratio and upregulating the expression of metabolites such as creatine.

Revealing the role of glycerophospholipid metabolism in asthma through plasma lipidomics

Lipid mediators play an essential role in the pathogenesis of asthma. Many studies on the differential expression of sphingolipids and fatty acid exist, but relatively few concerned about glycerophospholipid (GP) metabolites in asthma. Here, plasma samples from 20 healthy controls and 24 asthmatic patients were collected and analyzed. High-performance liquid chromatography with quadrupole time-of-flight mass spectrometry (HPLC-QTOF-MS) revealed that 29 GPs were identified and relatively quantified as differential metabolites for discriminating asthma patients and healthy subjects, consisting of six major subclasses of GPs. Moreover, a significant relevance was found between the selected metabolites and diagnostic and prognostic indicators of asthma. Remarkably, in subgroup analyses, plasma phosphatidic acid (PA), phosphatidylglycerol (PG), and phosphatidylethanolamine (PE) levels were higher in patients with eosinophilic asthma than non-eosinophilic asthma. Receiver-operating characteristic curve analysis revealed that the power of plasma PA and PG levels to distinguish between asthmatic patients and healthy subjects was strong (all areas under the curves > 0.9; P < 0.05). Our study characterized circulating GP metabolites in patients with asthma and explored their clinical relevance which may help to develop reliable biomarkers for early and accurate diagnosis based on lipid metabolites and provide novel insight into the role of GPs in asthma.

Differential Metabolic Alterations and Biomarkers Between Gastric Cancer and Colorectal Cancer: A Systematic Review and Meta-Analysis

Purpose

Numerous metabolomics studies have been conducted to detect the metabolic mechanisms and biomarkers related to gastric cancer and colorectal cancer. Because of the common metabolic features between gastric cancer and colorectal cancer, a differential diagnosis is difficult. Here, we performed a systematic review and meta-analysis to identify differential metabolic biomarkers between these two types of cancers.

Materials and Methods

PubMed, Embase, and ScienceDirect were searched to identify all metabolomics studies of gastric cancer and colorectal cancer published up to September 2018. Differential metabolites or altered pathways were extracted. The intersections and differences for these metabolites and pathways between gastric cancer and colorectal cancer were compared. Candidate biomarker sets for diagnosis were proposed from biofluid or feces by comparing them with tumor tissues.

Results

Totally, 24 and 65 studies were included in gastric cancer and colorectal cancer, and 223 and 472 differential metabolites were extracted, respectively. Eight pathways were reproducibly enriched in blood, tissue and urine in gastric cancer, while, 11 pathways were reproducibly enriched in blood, urine, feces and tissue in colorectal cancer. Candidate metabolic biomarker sets in blood, urine, or feces for these two cancers were proposed. We found 27 pathways (categorized into eight classifications) common to both cancers, five pathways involving 35 metabolites enriched only in gastric cancer, and eight pathways involving 54 metabolites enriched only in colorectal cancer.

Conclusion

The altered metabolic pathways showed signatures of abnormal metabolism in gastric cancer and colorectal cancer; the potential metabolic biomarkers proposed in this study have important implications for the prospective validation of gastric cancer and colorectal cancer.

Introducing Membrane Charge and Membrane Potential to T Cell Signaling

While membrane models now include the heterogeneous distribution of lipids, the impact of membrane charges on regulating the association of proteins with the plasma membrane is often overlooked. Charged lipids are asymmetrically distributed between the two leaflets of the plasma membrane, resulting in the inner leaflet being negatively charged and a surface potential that attracts and binds positively charged ions, proteins, and peptide motifs. These interactions not only create a transmembrane potential but they can also facilitate the formation of charged membrane domains. Here, we reference fields outside of immunology in which consequences of membrane charge are better characterized to highlight important mechanisms. We then focus on T cell receptor (TCR) signaling, reviewing the evidence that membrane charges and membrane-associated calcium regulate phosphorylation of the TCR–CD3 complex and discuss how the immunological synapse exhibits distinct patterns of membrane charge distribution. We propose that charged lipids, ions in solution, and transient protein interactions form a dynamic equilibrium during T cell activation.

Lipidomics profiling reveals the role of glycerophospholipid metabolism in psoriasis

Psoriasis is a common and chronic inflammatory skin disease that is complicated by gene-environment interactions. Although genomic, transcriptomic, and proteomic analyses have been performed to investigate the pathogenesis of psoriasis, the role of metabolites in psoriasis, particularly of lipids, remains unclear. Lipids not only comprise the bulk of the cellular membrane bilayers but also regulate a variety of biological processes such as cell proliferation, apoptosis, immunity, angiogenesis, and inflammation. In this study, an untargeted lipidomics approach was used to study the lipid profiles in psoriasis and to identify lipid metabolite signatures for psoriasis through ultra-performance liquid chromatography-tandem quadrupole mass spectrometry. Plasma samples from 90 participants (45 healthy and 45 psoriasis patients) were collected and analyzed. Statistical analysis was applied to find different metabolites between the disease and healthy groups. In addition, enzyme-linked immunosorbent assay was performed to validate differentially expressed lipids in psoriatic patient plasma. Finally, we identified differential expression of several lipids including lysophosphatidic acid (LPA), lysophosphatidylcholine (LysoPC), phosphatidylinositol (PI), phosphatidylcholine (PC), and phosphatidic acid (PA); among these metabolites, LPA, LysoPC, and PA were significantly increased, while PC and PI were down-regulated in psoriasis patients. We found that elements of glycerophospholipid metabolism such as LPA, LysoPC, PA, PI, and PC were significantly altered in the plasma of psoriatic patients; this study characterizes the circulating lipids in psoriatic patients and provides novel insight into the role of lipids in psoriasis.

Organizing polarized delivery of exosomes at synapses

Exosomes are extracellular vesicles that transport different molecules between cells. They are formed and stored inside multivesicular bodies (MVB) until they are released to the extracellular environment. MVB fuse along the plasma membrane, driving non-polarized secretion of exosomes. However, polarized signaling potentially directs MVBs to a specific point in the plasma membrane to mediate a focal delivery of exosomes. MVB polarization occurs across a broad set of cellular situations, e.g. in immune and neuronal synapses, cell migration and in epithelial sheets. In this review, we summarize the current state of the art of polarized MVB docking and the specification of secretory sites at the plasma membrane. The current view is that MVB positioning and subsequent exosome delivery requires a polarizing, cytoskeletal dependent-trafficking mechanism. In this context, we propose scenarios in which biochemical and mechanical signals could drive the polarized delivery of exosomes in highly polarized cells, such as lymphocytes, neurons and epithelia.