Dynamics of arachidonic acid mobilization by inflammatory cells

Bioactive lipid signaling and lipidomics in macrophage polarization: Impact on inflammation and immune regulation

Macrophages, crucial innate immune cells, defend against pathogens and resolve inflammation, maintaining tissue balance. They perform phagocytosis, present antigens to T cells, and bond innate and adaptive immunity through various activation states. Classical activation is associated with Th1 responses and interferon γ production, while alternative activation, induced by interleukin 4, is characterized by increased endocytosis, reduced secretion of pro-inflammatory cytokines, and roles in immunoregulation and tissue remodeling. Although these represent opposite extremes observed in vitro, the remarkable plasticity of macrophages allows for a wide spectrum of activation phenotypes that are complex to characterize experimentally. While the application of omics techniques has resulted in significant advances in the characterization of macrophage polarization, lipidomic studies have received lesser attention. Beyond their role as structural components and energy sources, lipids function as signaling molecules that regulate macrophage activation and polarization, thereby shaping immune responses. This work reviews the interaction between lipid signaling and macrophage polarization, exploring how lipid metabolism influences macrophage phenotype and function. These insights offer potential therapeutic strategies for immune-mediated diseases and inflammation-related disorders, including inflammaging.

The Octadecanoids: Synthesis and Bioactivity of 18-Carbon Oxygenated Fatty Acids in Mammals, Bacteria, and Fungi

The octadecanoids are a broad class of lipids consisting of the oxygenated products of 18-carbon fatty acids. Originally referring to production of the phytohormone jasmonic acid, the octadecanoid pathway has been expanded to include products of all 18-carbon fatty acids. Octadecanoids are formed biosynthetically in mammals via cyclooxygenase (COX), lipoxygenase (LOX), and cytochrome P450 (CYP) activity, as well as nonenzymatically by photo- and autoxidation mechanisms. While octadecanoids are well-known mediators in plants, their role in the regulation of mammalian biological processes has been generally neglected. However, there have been significant advancements in recognizing the importance of these compounds in mammals and their involvement in the mediation of inflammation, nociception, and cell proliferation, as well as in immuno- and tissue modulation, coagulation processes, hormone regulation, and skin barrier formation. More recently, the gut microbiome has been shown to be a significant source of octadecanoid biosynthesis, providing additional biosynthetic routes including hydratase activity (e.g., CLA-HY, FA-HY1, FA-HY2). In this review, we summarize the current field of octadecanoids, propose standardized nomenclature, provide details of octadecanoid preparation and measurement, summarize the phase-I metabolic pathway of octadecanoid formation in mammals, bacteria, and fungi, and describe their biological activity in relation to mammalian pathophysiology as well as their potential use as biomarkers of health and disease.

PTGS2/GRP78 Activation Triggers Endoplasmic Reticulum Stress Leading to Lipid Metabolism Disruption and Cell Apoptosis, Exacerbating Damage in Bovine Mastitis

Lipoteichoic acid (LTA), an organic acid of Gram-positive bacteria, is closely related to mastitis in dairy cows. This study evaluates the effect of LTA-induced endoplasmic reticulum stress (ER stress) in vitro using MAC-T (mammary epithelial cells) and in dairy cows with mastitis. LTA stimulation significantly increases ER stress and apoptosis-related factors in MAC-T. Further analysis suggests that the increase in ER stress may be associated with interactions involving PTGS2 and GRP78. Protein structural studies indicate a strong interaction between PTGS2 and GRP78. Lipidomics results further demonstrate that LTA disrupts lipid balance in MAC-T cells, affecting lipid metabolism in the endoplasmic reticulum, including PC, PE, TAG, and DAG, thereby exacerbating inflammation and ER stress. In dairy cows with mastitis caused by Gram-positive bacterial infection, damaged epithelial cells, inflammatory cell infiltration, and apoptotic vesicles are observed in affected tissues. In contrast, tissues from healthy cows exhibit regular epithelial cells without inflammatory cells or apoptotic vesicles. Furthermore, a significant ER stress and apoptosis increase is observed in mastitis tissues. This study demonstrates the close association between LTA-induced cell damage and ER stress, contributing to understanding the mechanisms underlying LTA-induced damage and supporting strategies for mastitis prevention and control in dairy cows.

Phospholipase A2 (PLA2) injured lymphatic endothelial cells leading to progression of secondary lymphoedema

Secondary lymphoedema is one of the common complications after lymph node dissection for gynecologic malignancies and breast cancer. In this study, the relationship between PLA2 and postoperative lymphoedema in cancer at the molecular level has been explored through transcriptomics and metabolomic assays. Transcriptome sequencing technology, as well as metabolomic assays, were utilized to explore the expression of PLA2 in lymphoedema patients, and search for potential pathways in the pathogenesis and exacerbation mechanism of lymphoedema. The effect of sPLA2 on human lymphatic endothelial cells was investigated by culturing human lymphatic endothelial cells. Secretory phospholipases A2 (sPLA2) showed high expression levels in lymphoedema tissues, however, cytoplasmic phospholipases A2 (cPLA2), showed low expression in lymphoedema, as demonstrated by RT-qPCR. By culturing human lymphatic vascular endothelial cells, the study found that sPLA2 causes HLEC vacuolization and has an inhibitory effect on HLEC proliferation and migration. By detecting sPLA2 in the serum of lymphoedema patients and analyzing clinical data, it was found that sPLA2 was positively correlated with the severity of lymphoedema. Secretory Phospholipase A2 (sPLA2) is highly expressed in lymphoedema tissue, damages lymphatic vessel endothelial cells, is strongly associated with disease severity, and can be used as a potential predictor of disease severity.Abbreviations: PLA2: Phospholipase A2; DEGs: differentially expressed genes; DMP: differential metabolic production.

Western diet components that increase intestinal permeability with implications on health

Intestinal permeability is a physiological property that allows necessary molecules to enter the organism. This property is regulated by tight junction proteins located between intestinal epithelial cells. However, various factors can increase intestinal permeability (IIP), including diet. Specific components in the Western diet (WD), such as monosaccharides, fat, gluten, salt, alcohol, and additives, can affect the tight junctions between enterocytes, leading to increased permeability. This review explains how these components promote IIP and outlines their potential implications for health. In addition, we describe how a reduction in WD consumption may help improve dietary treatment of diseases associated with IIP. Research has shown that some of these components can cause changes in the gut microbiota, leading to dysbiosis, which can promote greater intestinal permeability and displacement of endotoxins into the bloodstream. These endotoxins include lipopolysaccharides derived from gram-negative bacteria, and their presence has been associated with various diseases, such as autoimmune, neurological, and metabolic diseases like diabetes and cardiovascular disease. Therefore, nutrition professionals should promote the reduction of WD consumption and consider the inclusion of healthy diet components as part of the nutritional treatment for diseases associated with increased intestinal permeability.

Deficiency of long-chain acyl-CoA synthetase 4 leads to lipopolysaccharide-induced mortality in a mouse model of septic shock

Long-chain acyl-CoA synthetase 4 (ACSL4) converts free highly unsaturated fatty acids (HUFAs) into their acyl-CoA esters and is important for HUFA utilization. HUFA-containing phospholipids produced via ACSL4-dependent reactions are involved in pathophysiological events such as inflammatory responses and ferroptosis as a source for lipid mediators and/or a target of oxidative stress, respectively. However, the in vivo role of ACSL4 in inflammatory responses is not fully understood. This study sought to define the effects of ACSL4 deficiency on lipopolysaccharide (LPS)-induced systemic inflammatory responses using global Acsl4 knockout (Acsl4 KO) mice. Intraperitoneal injection of LPS-induced more severe symptoms, including diarrhea, hypothermia, and higher mortality, in Acsl4 KO mice within 24 h compared with symptoms in wild-type (WT) mice. Intestinal permeability induced 3 h after LPS challenge was also enhanced in Acsl4 KO mice compared with that in WT mice. In addition, plasma levels of some eicosanoids in Acsl4 KO mice 6 h post-LPS injection were 2- to 9-fold higher than those in WT mice. The increased mortality observed in LPS-treated Acsl4 KO mice was significantly improved by treatment with the general cyclooxygenase inhibitor indomethacin with a partial reduction in the severity of illness index for hypothermia, diarrhea score, and intestinal permeability. These results suggest that ACSL4 deficiency enhances susceptibility to endotoxin at least partly through the overproduction of cyclooxygenase-derived eicosanoids.

Aberrations in ion channels interacting with lipid metabolism and epithelial-mesenchymal transition in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is the most prevalent malignant gastrointestinal tumor. Ion channels contribute to tumor growth and progression through interactions with their neighboring molecules including lipids. The dysregulation of membrane ion channels and lipid metabolism may contribute to the epithelial-mesenchymal transition (EMT), leading to metastatic progression. Herein, transcriptome profiles of patients with ESCC were analyzed by performing differential gene expression and weighted gene co-expression network analysis to identify the altered ion channels, lipid metabolism- and EMT-related genes in ESCC. A total of 1,081 differentially expressed genes, including 113 ion channels, 487 lipid metabolism-related, and 537 EMT-related genes, were identified in patients with ESCC. Thereafter, EMT scores were correlated with altered co-expressed genes. The altered co-expressed genes indicated a correlation with EMT signatures. Interactions among 22 ion channels with 3 hub lipid metabolism- and 13 hub EMT-related proteins were determined using protein-protein interaction networks. A pathway map was generated to depict deregulated signaling pathways including insulin resistance and the estrogen receptor-Ca²⁺ signaling pathway in ESCC. The relationship between potential ion channels and 5-year survival rates in ESCC was determined using Kaplan-Meier plots and Cox proportional hazard regression analysis. Inositol 1,4,5-trisphosphate receptor type 3 (ITPR3) was found to be associated with poor prognosis of patients with ESCC. Additionally, drugs interacting with potential ion channels, including GJA1 and ITPR3, were identified. Understanding alterations in ion channels with lipid metabolism and EMT in ESCC pathophysiology would most likely provide potential targets for the better treatment of patients with ESCC.

Integrative phosphatidylcholine metabolism through phospholipase A2 in rats with chronic kidney disease

Dysregulation in lipid metabolism is the leading cause of chronic kidney disease (CKD) and also the important risk factors for high morbidity and mortality. Although lipid abnormalities were identified in CKD, integral metabolic pathways for specific individual lipid species remain to be clarified. We conducted ultra-high-performance liquid chromatography-high-definition mass spectrometry-based lipidomics and identified plasma lipid species and therapeutic effects of Rheum officinale in CKD rats. Adenine-induced CKD rats were administered Rheum officinale. Urine, blood and kidney tissues were collected for analyses. We showed that exogenous adenine consumption led to declining kidney function in rats. Compared with control rats, a panel of differential plasma lipid species in CKD rats was identified in both positive and negative ion modes. Among the 50 lipid species, phosphatidylcholine (PC), lysophosphatidylcholine (LysoPC) and lysophosphatidic acid (LysoPA) accounted for the largest number of identified metabolites. We revealed that six PCs had integral metabolic pathways, in which PC was hydrolysed into LysoPC, and then converted to LysoPA, which was associated with increased cytosolic phospholipase A2 protein expression in CKD rats. The lower levels of six PCs and their corresponding metabolites could discriminate CKD rats from control rats. Receiver operating characteristic curves showed that each individual lipid species had high values of area under curve, sensitivity and specificity. Administration of Rheum officinale significantly improved impaired kidney function and aberrant PC metabolism in CKD rats. Taken together, this study demonstrates that CKD leads to PC metabolism disorders and that the dysregulation of PC metabolism is involved in CKD pathology.

Compartmentalized regulation of lipid signaling in oxidative stress and inflammation: Plasmalogens, oxidized lipids and ferroptosis as new paradigms of bioactive lipid research

Perturbations in lipid homeostasis combined with conditions favoring oxidative stress constitute a hallmark of the inflammatory response. In this review we focus on the most recent results concerning lipid signaling in various oxidative stress-mediated responses and inflammation. These include phagocytosis and ferroptosis. The best characterized event, common to these responses, is the synthesis of oxygenated metabolites of arachidonic acid and other polyunsaturated fatty acids. Major developments in this area have highlighted the importance of compartmentalization of the enzymes and lipid substrates in shaping the appropriate response. In parallel, other relevant lipid metabolic pathways are also activated and, until recently, there has been a general lack of knowledge on the enzyme regulation and molecular mechanisms operating in these pathways. Specifically, data accumulated in recent years on the regulation and biological significance of plasmalogens and oxidized phospholipids have expanded our knowledge on the involvement of lipid metabolism in the progression of disease and the return to homeostasis. These recent major developments have helped to establish the concept of membrane phospholipids as cellular repositories for the compartmentalized production of bioactive lipids involved in cellular regulation. Importantly, an enzyme classically described as being involved in regulating the homeostatic turnover of phospholipids, namely the group VIA Ca²⁺-independent phospholipase A₂ (iPLA₂β), has taken center stage in oxidative stress and inflammation research owing to its key involvement in regulating metabolic and ferroptotic signals arising from membrane phospholipids. Understanding the role of iPLA₂β in ferroptosis and metabolism not only broadens our knowledge of disease but also opens possible new horizons for this enzyme as a target for therapeutic intervention.

Differential Mobilization of the Phospholipid and Triacylglycerol Pools of Arachidonic Acid in Murine Macrophages

Innate immune cells such as monocytes and macrophages contain high levels of arachidonic acid (AA), part of which can be mobilized during cellular activation for the formation of a vast array of bioactive oxygenated metabolites. Monocytes and macrophages present in inflammatory foci typically incorporate large amounts of AA, not only in membrane phospholipids, but also in neutral lipids such as triacylglycerol. Thus, it was of interest to investigate the metabolic fate of these two AA pools in macrophages. Utilizing a variety of radiolabeling techniques to distinguish the phospholipid and triacylglycerol pools, we show in this paper that during an acute stimulation of the macrophages with yeast-derived zymosan, the membrane phospholipid AA pool acts as the major, if not the only, source of releasable AA. On the contrary, the AA pool in triacylglycerol appears to be used at a later stage, when the zymosan-stimulated response has declined, as a source to replenish the phospholipid pools that were consumed during the activation process. Thus, phospholipids and triacylglycerol play different in roles AA metabolism and dynamics during macrophage activation.

Modifying Orthobiological PRP Therapies Are Imperative for the Advancement of Treatment Outcomes in Musculoskeletal Pathologies

Autologous biological cellular preparations have materialized as a growing area of medical advancement in interventional (orthopedic) practices and surgical interventions to provide an optimal tissue healing environment, particularly in tissues where standard healing is disrupted and repair and ultimately restoration of function is at risk. These cellular therapies are often referred to as orthobiologics and are derived from patient's own tissues to prepare point of care platelet-rich plasma (PRP), bone marrow concentrate (BMC), and adipose tissue concentrate (ATC). Orthobiological preparations are biological materials comprised of a wide variety of cell populations, cytokines, growth factors, molecules, and signaling cells. They can modulate and influence many other resident cells after they have been administered in specific diseased microenvironments. Jointly, the various orthobiological cell preparations are proficient to counteract persistent inflammation, respond to catabolic reactions, and reinstate tissue homeostasis. Ultimately, precisely delivered orthobiologics with a proper dose and bioformulation will contribute to tissue repair. Progress has been made in understanding orthobiological technologies where the safety and relatively easy manipulation of orthobiological treatment tools has been demonstrated in clinical applications. Although more positive than negative patient outcome results have been registered in the literature, definitive and accepted standards to prepare specific cellular orthobiologics are still lacking. To promote significant and consistent clinical outcomes, we will present a review of methods for implementing dosing strategies, using bioformulations tailored to the pathoanatomic process of the tissue, and adopting variable preparation and injection volume policies. By optimizing the dose and specificity of orthobiologics, local cellular synergistic behavior will increase, potentially leading to better pain killing effects, effective immunomodulation, control of inflammation, and (neo) angiogenesis, ultimately contributing to functionally restored body movement patterns.

A Food-Grade Method for Enhancing the Levels of Low Molecular Weight Proanthocyanidins with Potentially High Intestinal Bioavailability

Proanthocyanidins (PACs) are a group of bioactive molecules found in a variety of plants and foods. Their bioavailability depends on their molecular size, with monomers and dimers being more bioavailable than those that have a higher polymerization degree. This study aimed to develop a method to convert high-molecular-weight PACs to low-molecular-weight ones in a grape seed extract (GSE) from Vitis vinifera L. Therefore, GSE was subjected to alkaline treatment (ATGSE), and its difference in chemical composition, compared to GSE, was evaluated using a molecular networking (MN) approach based on results obtained from HPLC-ESI HRMS/MS characterization analysis. The network analysis mainly noted the PAC cluster with about 142 PAC compounds identified. In particular, the obtained results showed a higher content of monomeric and dimeric PACs in ATGSE compared to GSE, with 58% and 49% monomers and 31% and 24% dimers, respectively. Conversely, trimeric (9%), polymeric (4%), and galloylated PACs (14%) were more abundant in GSE than in ATGSE (6%, 1%, and 4%, respectively). Moreover, in vitro antioxidant and anti-inflammatory activities were investigated, showing the high beneficial potential of both extracts. In conclusion, ATGSE could represent an innovative natural matrix rich in bioavailable and bioaccessible PACs for nutraceutical applications with potential beneficial properties.

Exploring the Anti-inflammatory Effects of Protopine Total Alkaloids of Macleaya Cordata (Willd.) R. Br

Macleaya cordata (Willd). R. Br. is a Chinese medicinal plant commonly used externally to treat inflammatory-related diseases such as arthritis, sores, and carbuncles. This study aimed to evaluate the anti-inflammatory activity of protopine total alkaloids (MPTAs) in Macleaya cordata (Willd.) R. Br. in vivo tests in rats with acute inflammation showed that MPTA (2.54 and 5.08 mg/kg) showed significant anti-inflammatory activity 6 h after carrageenan injection. Similarly, MPTA (3.67 and 7.33 mg/kg) showed significant anti-inflammatory activity in the mouse ear swelling test. In addition, the potential mechanisms of the anti-inflammatory effects of MPTA were explored based on network pharmacology and molecular docking. The two main active components of MPTA, protopine and allocryptopine, were identified, and the potential targets and signaling pathways of MPTA's anti-inflammatory effects were initially revealed using tools and databases (such as SwissTargetPrediction, GeneCards, and STRING) combined with molecular docking results. This study provides the basis for the application of MPTA as an anti-inflammatory agent.

Mycobacterium tuberculosis encodes a YhhN family membrane protein with lysoplasmalogenase activity that protects against toxic host lysolipids

The pathogen Mycobacterium tuberculosis (M.tb) resides in human macrophages, wherein it exploits host lipids for survival. However, little is known about the interaction between M.tb and macrophage plasmalogens, a subclass of glycerophospholipids with a vinyl ether bond at the sn-1 position of the glycerol backbone. Lysoplasmalogens, produced from plasmalogens by hydrolysis at the sn-2 carbon by phospholipase A2, are potentially toxic but can be broken down by host lysoplasmalogenase, an integral membrane protein of the YhhN family that hydrolyzes the vinyl ether bond to release a fatty aldehyde and glycerophospho-ethanolamine or glycerophospho-choline. Curiously, M.tb encodes its own YhhN protein (MtbYhhN), despite having no endogenous plasmalogens. To understand the purpose of this protein, the gene for MtbYhhN (Rv1401) was cloned and expressed in Mycobacterium smegmatis (M.smeg). We found the partially purified protein exhibited abundant lysoplasmalogenase activity specific for lysoplasmenylethanolamine or lysoplasmenylcholine (pLPC) (Vmax∼15.5 μmol/min/mg; Km∼83 μM). Based on cell density, we determined that lysoplasmenylethanolamine, pLPC, lysophosphatidylcholine, and lysophosphatidylethanolamine were not toxic to M.smeg cells, but pLPC and LPC were highly toxic to M.smeg spheroplasts, which are cell wall-deficient mycobacterial forms. Importantly, spheroplasts prepared from M.smeg cells overexpressing MtbYhhN were protected from membrane disruption/lysis by pLPC, which was rapidly depleted from the media. Finally, we found that overexpression of full-length MtbYhhN in M.smeg increased its survival within human macrophages by 2.6-fold compared to vector controls. These data support the hypothesis that MtbYhhN protein confers a growth advantage for mycobacteria in macrophages by cleaving toxic host pLPC into potentially energy-producing products.

Lipid Droplets, Phospholipase A2, Arachidonic Acid, and Atherosclerosis

Lipid droplets, classically regarded as static storage organelles, are currently considered as dynamic structures involved in key processes of lipid metabolism, cellular homeostasis and signaling. Studies on the inflammatory state of atherosclerotic plaques suggest that circulating monocytes interact with products released by endothelial cells and may acquire a foamy phenotype before crossing the endothelial barrier and differentiating into macrophages. One such compound released in significant amounts into the bloodstream is arachidonic acid, the common precursor of eicosanoids, and a potent inducer of neutral lipid synthesis and lipid droplet formation in circulating monocytes. Members of the family of phospholipase A₂, which hydrolyze the fatty acid present at the sn-2 position of phospholipids, have recently emerged as key controllers of lipid droplet homeostasis, regulating their formation and the availability of fatty acids for lipid mediator production. In this paper we discuss recent findings related to lipid droplet dynamics in immune cells and the ways these organelles are involved in regulating arachidonic acid availability and metabolism in the context of atherosclerosis.

Structural Analysis of Lipid Hydroperoxides Using Mass Spectrometry with Alkali Metals

Lipid oxidation is involved in various biological phenomena (e.g., oxylipin generation and oxidative stress). Of oxidized lipid structures, the hydroperoxyl group position of lipid hydroperoxides (LOOHs) is a critical factor in determining their biological roles. Despite such interest, current methods to determine hydroperoxyl group positions possess some drawbacks such as selectivity. While we previously reported mass spectrometric methods using Na⁺ for the highly selective determination of hydroperoxyl group positions, nothing was known except for the fact that sodiated LOOHs (mainly linoleate) provide specific fragment ions. Thus, this study was aimed to investigate the effects of different alkali metals on the fragmentation of LOOHs, assuming its further application to analysis of other complex LOOHs. From the analysis of PC 16:0/18:2;OOH (phosphatidylcholine) and FA 18:2;OOH (fatty acid), we found that fragmentation pathways and ion intensities largely depend on the binding position and type of alkali metals (i.e., Li⁺, Hock fragmentation; Na⁺ and K⁺, α-cleavage (Na⁺ > K⁺); Rb⁺ and Cs⁺, no fragmentation). Furthermore, we proved that this method can be applied to determine the hydroperoxyl group position of esterified lipids (e.g., phospholipids and cholesterol esters) as well as polyunsaturated fatty acids (PUFAs) including n-3, n-6, and n-9 FA. We anticipate that the insights described in this study provide additional unique insights to conventional lipid oxidation research.

The Roles of Phospholipase A2 in Phagocytes

Phagocytic cells, such as macrophages, neutrophils, and dendritic cells, ingest particles larger than about 0.5 μM and thereby clear microbial pathogens and malignant cells from the body. These phagocytic cargoes are proteolytically degraded within the lumen of phagosomes, and peptides derived from them are presented on Major Histocompatibility Complexes (MHC) for the activation of T cells. Mammalian PLA₂ isozymes belong to a large family of enzymes that cleave phospholipids at the second position of the glycerol backbone, releasing a free fatty acid and a lysolipid moiety. In human macrophages, at least 15 different PLA₂ forms are expressed, and expression of many of these is dependent on pathogenic stimulation. Intriguing questions are why so many PLA₂ forms are expressed in macrophages, and what are the functional consequences of their altered gene expression after encountering pathogenic stimuli. In this review, we discuss the evidence of the differential roles of different forms of PLA₂ in phagocytic immune cells. These roles include: lipid signaling for immune cell activation, initial phagocytic particle uptake, microbial action for the killing and degradation of ingested microbes, and the repair of membranes induced by oxygen radicals. We also discuss the roles of PLA₂ in the subsequent digestion of ingested phagocytic cargoes for antigen presentation to T cells.

Anthracyclins Increase PUFAs: Potential Implications in ER Stress and Cell Death

Metabolic and personalized interventions in cancer treatment require a better understanding of the relationship between the induction of cell death and metabolism. Consequently, we treated three primary liver cancer cell lines with two anthracyclins (doxorubicin and idarubin) and studied the changes in the lipidome. We found that both anthracyclins in the three cell lines increased the levels of polyunsaturated fatty acids (PUFAs) and alkylacylglycerophosphoethanolamines (etherPEs) with PUFAs. As PUFAs and alkylacylglycerophospholipids with PUFAs are fundamental in lipid peroxidation during ferroptotic cell death, our results suggest supplementation with PUFAs and/or etherPEs with PUFAs as a potential general adjuvant of anthracyclins. In contrast, neither the markers of de novo lipogenesis nor cholesterol lipids presented the same trend in all cell lines and treatments. In agreement with previous research, this suggests that modulation of the metabolism of cholesterol could be considered a specific adjuvant of anthracyclins depending on the type of tumor and the individual. Finally, in agreement with previous research, we found a relationship across the different cell types between: (i) the change in endoplasmic reticulum (ER) stress, and (ii) the imbalance between PUFAs and cholesterol and saturated lipids. In the light of previous research, this imbalance partially explains the sensitivity to anthracyclins of the different cells. In conclusion, our results suggest that the modulation of different lipid metabolic pathways may be considered for generalized and personalized metabochemotherapies.

Reduction of fibrosis and immune suppressive cells in ErbB2-dependent tumorigenesis by an LXR agonist

One of the central challenges for cancer therapy is the identification of factors in the tumor microenvironment that increase tumor progression and prevent immune surveillance. One such element associated with breast cancer is stromal fibrosis, a histopathologic criterion for invasive cancer and poor survival. Fibrosis is caused by inflammatory factors and remodeling of the extracellular matrix that elicit an immune tolerant microenvironment. To address the role of fibrosis in tumorigenesis, we developed NeuT/ATTAC transgenic mice expressing a constitutively active NeuT/erbB2 transgene, and an inducible, fat-directed caspase-8 fusion protein, which upon activation results in selective and partial ablation of mammary fat and its replacement with fibrotic tissue. Induction of fibrosis in NeuT/ATTAC mice led to more rapid tumor development and an inflammatory and fibrotic stromal environment. In an effort to explore therapeutic options that could reduce fibrosis and immune tolerance, mice were treated with the oxysterol liver X receptor (LXR) pan agonist, N,N-dimethyl-3-β-hydroxy-cholenamide (DMHCA), an agent known to reduce fibrosis in non-malignant diseases. DMHCA reduced tumor progression, tumor multiplicity and fibrosis, and improved immune surveillance by reducing infiltrating myeloid-derived suppressor cells and increasing CD4 and CD8 effector T cells. These effects were associated with downregulation of an LXR-dependent gene network related to reduced breast cancer survival that included Spp1, S100a9, Anxa1, Mfge8 and Cd14. These findings suggest that the use of DMHCA may be a potentially effective approach to reduce desmoplasia and immune tolerance and increase the efficacy of cancer therapy.

The role of metabolism in chondrocyte dysfunction and the progression of osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease characterized by low-grade inflammation and high levels of clinical heterogeneity. Aberrant chondrocyte metabolism is a response to changes in the inflammatory microenvironment and may play a key role in cartilage degeneration and OA progression. Under conditions of environmental stress, chondrocytes tend to adapt their metabolism to microenvironmental changes by shifting from one metabolic pathway to another, for example from oxidative phosphorylation to glycolysis. Similar changes occur in other joint cells, including synoviocytes. Switching between these pathways is implicated in metabolic alterations that involve mitochondrial dysfunction, enhanced anaerobic glycolysis, and altered lipid and amino acid metabolism. The shift between oxidative phosphorylation and glycolysis is mainly regulated by the AMP-activated protein kinase (AMPK) and mechanistic target of rapamycin (mTOR) pathways. Chondrocyte metabolic changes are likely to be a feature of different OA phenotypes. Determining the role of chondrocyte metabolism in OA has revealed key features of disease pathogenesis. Future research should place greater emphasis on immunometabolism and altered metabolic pathways as a means to understand the pathophysiology of age-related OA. This knowledge will advance the development of new drugs against therapeutic targets of metabolic significance.

Choline Glycerophospholipid-Derived Prostaglandins Attenuate TNFα Gene Expression in Macrophages via a cPLA2α/COX-1 Pathway

Macrophages are professional antigen presenting cells with intense phagocytic activity, strategically distributed in tissues and cavities. These cells are capable of responding to a wide variety of innate inflammatory stimuli, many of which are signaled by lipid mediators. The distribution of arachidonic acid (AA) among glycerophospholipids and its subsequent release and conversion into eicosanoids in response to inflammatory stimuli such as zymosan, constitutes one of the most studied models. In this work, we used liquid and/or gas chromatography coupled to mass spectrometry to study the changes in the levels of membrane glycerophospholipids of mouse peritoneal macrophages and the implication of group IVA cytosolic phospholipase A₂ (cPLA₂α) in the process. In the experimental model used, we observed that the acute response of macrophages to zymosan stimulation involves solely the cyclooxygenase-1 (COX-1), which mediates the rapid synthesis of prostaglandins E₂ and I₂. Using pharmacological inhibition and antisense inhibition approaches, we established that cPLA₂α is the enzyme responsible for AA mobilization. Zymosan stimulation strongly induced the hydrolysis of AA-containing choline glycerophospholipids (PC) and a unique phosphatidylinositol (PI) species, while the ethanolamine-containing glycerophospholipids remained constant or slightly increased. Double-labeling experiments with ³H- and ¹⁴C-labeled arachidonate unambiguously demonstrated that PC is the major, if not the exclusive source, of AA for prostaglandin E₂ production, while both PC and PI appeared to contribute to prostaglandin I₂ synthesis. Importantly, in this work we also show that the COX-1-derived prostaglandins produced during the early steps of macrophage activation restrict tumor necrosis factor-α production. Collectively, these findings suggest new approaches and targets to the selective inhibition of lipid mediator production in response to fungal infection.

Parenteral lipid emulsions induce unique ileal fatty acid and metabolomic profiles but do not increase the risk of necrotizing enterocolitis in preterm pigs

Necrotizing enterocolitis (NEC) is a manifestation of maladaptive intestinal responses in preterm infants centrally medicated by unattenuated inflammation. Early in the postnatal period, preterm infants develop a deficit in arachidonic and docosahexaenoic acid, both potent regulators of inflammation. We hypothesized that the fatty acid composition of parenteral lipid emulsions uniquely induces blood and intestinal fatty acid profiles which, in turn, modifies the risk of NEC development. Forty-two preterm pigs were randomized to receive one of three lipid emulsions containing 100% soybean oil (SO), 15% fish oil (MO15), or 100% fish oil (FO100) with enteral feedings over an 8-day protocol. Blood and distal ileum tissue were collected for fatty acid analysis. The distal ileum underwent histologic, proteomic, and metabolomic analyses. Eight pigs [3/14 SO (21%), 3/14 MO15 (21%), and 2/14 FO100 (14%)] developed NEC. No differences in NEC risk were evident between groups despite differences in induced fatty acid profiles in blood and ileal tissue. Metabolomic analysis of NEC versus no NEC tissue revealed differences in tryptophan metabolism and arachidonic acid-containing glycerophospholipids. Proteomic analysis demonstrated no differences by lipid group; however, 15 proteins differentiated NEC versus no NEC in the domains of tissue injury, glucose uptake, and chemokine signaling. Exposure to parenteral lipid emulsions induces unique intestinal fatty acid and metabolomic profiles; however, these profiles are not linked to a difference in NEC development. Metabolomic and proteomic analyses of NEC versus no NEC intestinal tissue provide mechanistic insights into the pathogenesis of NEC in preterm infants.NEW & NOTEWORTHY Exposure to parenteral lipid emulsions induces unique intestinal fatty acid and metabolomic profiles; however, these profiles are not linked to a difference in NEC risk in preterm pigs. Metabolomic and proteomic analyses provide mechanistic insights into NEC pathogenesis. Compared with healthy ileal tissue, metabolites in tryptophan metabolism and arachidonic acid-containing glycerophospholipids are increased in NEC tissue. Proteomic analysis differentiates NEC versus no NEC in the domains of tissue injury, glucose uptake, and chemokine signaling.

Hormonal Dysregulation and Unbalanced Specialized Pro-Resolving Mediator Biosynthesis Contribute toward Impaired B Cell Outcomes in Obesity

Diet-induced obesity is associated with impaired B-cell-driven humoral immunity, which coincides with chronic inflammation and has consequences for responses to infections and vaccinations. Key nutritional, cellular, and molecular mechanisms by which obesity may impair aspects of humoral immunity such as B cell development, class switch recombination, and formation of long-lived antibody secreting cells are reviewed. A key theme to emerge is the central role of white adipose tissue on the formation and function of pro-inflammatory B cell subsets that exacerbate insulin resistance. The underlying role of select hormones such as leptin is highlighted, which may be driving the formation of pro-inflammatory B cells in the absence of antigen stimulation. This review also extensively covers the regulatory role of lipid metabolites such as prostaglandins and specialized pro-resolving mediators (SPMs) that are synthesized from polyunsaturated fatty acids. Notably, SPM biosynthesis is impaired in obesity and contributes toward impaired antibody production. Future directions for research, including avenues for therapeutic intervention, are included.

Integrated study of metabolomics and gut metabolic activity from ulcerative colitis to colorectal cancer: The combined action of disordered gut microbiota and linoleic acid metabolic pathway might fuel cancer

Colorectal cancer (CRC) is one of the most serious complications of ulcerative colitis (UC). Altered gut microbiota is implicated in the development of CRC and metabolic perturbations are often associated with changes in the gut microbiome composition. Given the links between gut microbiome and the metabolic profiles in the body, an approach involving ultra-high-performance liquid chromatography combined with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UHPLC-Q-TOF-MS/MS) metabolomics and 16S rDNA sequencing technology was applied to trace the development UC into CRC in rats. The study identified 11 differential metabolites related to both UC and CRC, which mainly referred to the linoleic acid metabolism. Among these, linoleic acid and 12‑hydroxy‑8,10-octadecadienoic acid could serve as key biomarkers for the development of UC into CRC. Besides, a significant change was observed in the microflora structure during the development from UC to CRC; this mainly involved a gradual increase in Escherichia-Shigella and a gradual decrease in Lactobacillus. In addition, Pearson's correlation analysis revealed strong correlations between intestinal microflora-related metabolites and specific intestinal microflora, which indicated both of them can promote the transition of UC to CRC. The results of the present study provided positive support for the involvement of intestinal microflora and host metabolism in the pathophysiological mechanism that is responsible for the development of UC into CRC. This information can help understand the risk for CRC that accompanies a diagnosis of UC and also provide different means of targeting these differential metabolites and intestinal microbiota to avoid UC-induced CRC.

Phospholipid Arachidonic Acid Remodeling During Phagocytosis in Mouse Peritoneal Macrophages

Macrophages contain large amounts of arachidonic acid (AA), which distributes differentially across membrane phospholipids. This is largely due to the action of coenzyme A-independent transacylase (CoA-IT), which transfers the AA primarily from diacyl choline-containing phospholipids to ethanolamine-containing phospholipids. In this work we have comparatively analyzed glycerophospholipid changes leading to AA mobilization in mouse peritoneal macrophages responding to either zymosan or serum-opsonized zymosan (OpZ). These two phagocytic stimuli promote the cytosolic phospholipase A₂-dependent mobilization of AA by activating distinct surface receptors. Application of mass spectrometry-based lipid profiling to identify changes in AA-containing phospholipids during macrophage exposure to both stimuli revealed significant decreases in the levels of all major choline phospholipid molecular species and a major phosphatidylinositol species. Importantly, while no changes in ethanolamine phospholipid species were detected on stimulation with zymosan, significant decreases in these species were observed when OpZ was used. Analyses of CoA-IT-mediated AA remodeling revealed that the process occurred faster in the zymosan-stimulated cells compared with OpZ-stimulated cells. Pharmacological inhibition of CoA-IT strongly blunted AA release in response to zymosan but had only a moderate effect on the OpZ-mediated response. These results suggest a hitherto undescribed receptor-dependent role for CoA-independent AA remodeling reactions in modulating the eicosanoid biosynthetic response of macrophages. Our data help define novel targets within the AA remodeling pathway with potential use to control lipid mediator formation.

A Lipidomic Perspective of the Action of Group IIA Secreted Phospholipase A2 on Human Monocytes: Lipid Droplet Biogenesis and Activation of Cytosolic Phospholipase A2α

Phospholipase A₂s constitute a wide group of lipid-modifying enzymes which display a variety of functions in innate immune responses. In this work, we utilized mass spectrometry-based lipidomic approaches to investigate the action of Asp-49 Ca²⁺-dependent secreted phospholipase A₂ (sPLA₂) (MT-III) and Lys-49 sPLA2 (MT-II), two group IIA phospholipase A₂s isolated from the venom of the snake Bothrops asper, on human peripheral blood monocytes. MT-III is catalytically active, whereas MT-II lacks enzyme activity. A large decrease in the fatty acid content of membrane phospholipids was detected in MT III-treated monocytes. The significant diminution of the cellular content of phospholipid-bound arachidonic acid seemed to be mediated, in part, by the activation of the endogenous group IVA cytosolic phospholipase A₂α. MT-III triggered the formation of triacylglycerol and cholesterol enriched in palmitic, stearic, and oleic acids, but not arachidonic acid, along with an increase in lipid droplet synthesis. Additionally, it was shown that the increased availability of arachidonic acid arising from phospholipid hydrolysis promoted abundant eicosanoid synthesis. The inactive form, MT-II, failed to produce any of the effects described above. These studies provide a complete lipidomic characterization of the monocyte response to snake venom group IIA phospholipase A₂, and reveal significant connections among lipid droplet biogenesis, cell signaling and biochemical pathways that contribute to initiating the inflammatory response.

Anti-Inflammatory and Physicochemical Characterization of the Croton Rhamnifolioides Essential Oil Inclusion Complex in β-Cyclodextrin

Croton rhamnifolioides is used in popular medicine for the treatment of inflammatory diseases. The objective of this study was to characterize and evaluate the anti-inflammatory effect of C. rhamnifolioides essential oil complexed in β-cyclodextrin (COEFC). The physicochemical characterization of the complexes was performed using different physical methods. The anti-inflammatory activity was evaluated in vivo by ear edema, paw edema, cotton pellet-induced granuloma, and vascular permeability by Evans blue extravasation. The mechanism of action was validated by molecular docking of the major constituent into the cyclooxygenase-2 (COX-2 enzyme). All doses of the COEFC reduced acute paw edema induced by carrageenan and dextran, as well as vascular permeability. Our results suggest the lowest effective dose of all samples inhibited the response induced by histamine or arachidonic acid as well as the granuloma formation. The complexation process showed that the pharmacological effects were maintained, however, showing similar results using much lower doses. The results demonstrated an involvement of the inhibition of pathways dependent on eicosanoids and histamine. Complexation of β-cyclodextrin/Essential oil (β-CD/EO) may present an important tool in the study of new compounds for the development of anti-inflammatory drugs.

Characterizing membrane phospholipid hydrolysis of pork loins throughout three aging periods

Three chops from 20 pork carcasses were aged for 1, 8, and 21 days. Electrospray ionization-tandem mass spectrometry was used to comprehensively analyze profiles of phospholipids from each sample (n = 60). Total phospholipid quantity decreased 4-folds (P < .01) from 1 to 21 days of aging in pork loins. Phosphatidylinositol (PI) and phosphatidylserine (PS) increased by 30% and 73%, respectively, from 1 to 21 days of aging in pork loins (P < .01). This increase was mainly due to relative percentage increase from PI 38:4 (18:0-20:4) and PS 36:2 (18:0-18:2; P < .01). The results also showed that the relative percentage of lysophosphatidylcholine increased by 35% after short term aging (8d), and phosphatidic acid increased by 10-folds after extended aging (21d; P < .01). These results documented that phospholipids undergo enzymatic hydrolysis during aging, but also indicated that lipid species containing 18:2 or 20:4 within PI and PS were slightly more resistant to enzymatic hydrolysis compared with the other phospholipids.

The Contribution of Cytosolic Group IVA and Calcium-Independent Group VIA Phospholipase A2s to Adrenic Acid Mobilization in Murine Macrophages

Adrenic acid (AA), the 2-carbon elongation product of arachidonic acid, is present at significant levels in membrane phospholipids of mouse peritoneal macrophages. Despite its abundance and structural similarity to arachidonic acid, very little is known about the molecular mechanisms governing adrenic acid mobilization in cells of the innate immune system. This contrasts with the wide availability of data on arachidonic acid mobilization. In this work, we used mass-spectrometry-based lipidomic procedures to define the profiles of macrophage phospholipids that contain adrenic acid and their behavior during receptor activation. We identified the phospholipid sources from which adrenic acid is mobilized, and compared the data with arachidonic acid mobilization. Taking advantage of the use of selective inhibitors, we also showed that cytosolic group IVA phospholipase A₂ is involved in the release of both adrenic and arachidonic acids. Importantly, calcium independent group VIA phospholipase A₂ spared arachidonate-containing phospholipids and hydrolyzed only those that contain adrenic acid. These results identify separate mechanisms for regulating the utilization of adrenic and arachidonic acids, and suggest that the two fatty acids may serve non-redundant functions in cells.

Metabolomic profile overlap in prototypical autoimmune humoral disease: a comparison of myasthenia gravis and rheumatoid arthritis

INTRODUCTION

Myasthenia gravis (MG) and rheumatoid arthritis (RA) are examples of antibody-mediated chronic, progressive autoimmune diseases. Phenotypically dissimilar, MG and RA share common immunological features. However, the immunometabolomic features common to humoral autoimmune diseases remain largely unexplored.

OBJECTIVES

The aim of this study was to reveal and illustrate the metabolomic profile overlap found between these two diseases and describe the immunometabolomic significance.

METHODS

Metabolic analyses using acid- and dansyl-labelled was performed on serum from adult patients with seropositive MG (n = 46), RA (n = 23) and healthy controls (n = 49) presenting to the University of Alberta Hospital specialty clinics. Chemical isotope labelling liquid chromatography mass spectrometry (CIL LC-MS) methods were utilized to assess the serum metabolome in patients; 12C/13C-dansyl chloride (DnsCl) was used to label amine/phenol metabolites and 12C/13C-p-dimethylaminophenacyl bromide (DmPA) was used for carboxylic acids. Metabolites matching our criteria for significance were selected if they were present in both groups. Multivariate statistical analysis [including principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA)] and biochemical pathway analysis was then conducted to gain understanding of the principal pathways involved in antibody-mediated pathogenesis.

RESULTS

We found 20 metabolites dysregulated in both MG and RA when compared to healthy controls. Most prominently, observed changes were related to pathways associated with phenylalanine metabolism, tyrosine metabolism, ubiquinone and other terpenoid-quinone biosynthesis, and pyruvate metabolism.

CONCLUSION

From these results it is evident that many metabolites are common to humoral disease and exhibit significant immunometabolomic properties. This observation may lead to an enhanced understanding of the metabolic underpinnings common to antibody-mediated autoimmune disease. Further, contextualizing these findings within a larger clinical and systems biology context could provide new insights into the pathogenesis and management of these diseases.

Serum lysophosphatidylcholines to phosphatidylcholines ratio is associated with symptomatic responders to symptomatic drugs in knee osteoarthritis patients

BACKGROUND

Identification of the optimal treatment for a given patient is of paramount importance. This is of particular relevance in osteoarthritis (OA) because of the high prevalence of the disease, extensive heterogeneity of the disease, and need for long-term treatment. The aim of the study was to examine whether serum lysophosphatidylcholines (lysoPCs) to phosphatidylcholines (PCs) ratio can predict clinical response to licofelone and naproxen treatments in symptomatic knee OA patients.

METHODS

One hundred fifty-eight OA patients who completed the study according to protocol (ATP) of a previous 24-month clinical trial cohort comparing the effect of licofelone vs. naproxen in symptomatic knee OA patients were included. Symptomatic responses to either treatments were classified according to the OARSI-OMERACT criteria based on the WOMAC scores at 24 months. Total concentrations of PCs and lysoPCs were measured in the serum samples collected before the initiation of the treatments, and the lysoPCs to PCs ratio was calculated. Student's t test was utilized to compare the difference in the ratio of lysoPCs to PCs between the symptomatic responders and non-responders. Logistic regression was utilized to adjust for the potential confounders. Receiver operating characteristic (ROC) analysis was performed to identify the optimal cutoff of the ratio for prediction.

RESULTS

Data showed that 61.4% of the patients symptomatically responded to licofelone and naproxen and 38.6% were deemed as therapeutic failures (non-responders). There was no difference in responders between licofelone and naproxen (p = 0.87). Responders had a significantly higher lysoPCs to PCs ratio than non-responders (0.097 ± 0.003 vs. 0.085 ± 0.003; p = 0.006). Patients with a ratio greater than the optimal cutoff of 0.088 had 2.93 times more likely to respond to licofelone and naproxen (p = 0.002).

CONCLUSIONS

Serum lysoPCs to PCs ratio is a marker for response to licofelone and naproxen and may aid in the personalized treatment to knee OA.

Contrasting effects of membrane enrichment with polyunsaturated fatty acids on phospholipid composition and cholesterol efflux from cholesterol-loaded J774 mouse or primary human macrophages

A high consumption of polyunsaturated fatty acids (PUFAs), particularly n-3 PUFAs, is atheroprotective. PUFAs incorporation into membrane phospholipids alters the functionality of membrane proteins. We studied the consequences of the in vitro supplementation of several PUFAs on the FA profiles and on ABCA1-dependent cholesterol efflux capacities from cholesterol-loaded macrophages. Arachidonic acid (AA, C20:4 n-6) and, to a lesser extent, eicosapentaenoic acid (EPA, C20:5 n-3), dose-dependently impaired cholesterol efflux from cholesterol-loaded J774 mouse macrophages without alterations in ABCA1 expression, whereas docosahexaenoic acid (DHA, C22:6 n-3) had no impact. AA cells exhibited higher proportions of arachidonic acid and adrenic acid (C22:4 n-6), its elongation product. EPA cells exhibited slightly higher proportions of EPA associated with much higher proportions of docosapentaenoic acid (C22:5 n-3), its elongation product and with lower proportions of AA. Conversely, both EPA and DHA and, to a lesser extent, AA decreased cholesterol efflux from cholesterol-loaded primary human macrophages (HMDM). The differences observed in FA profiles after PUFA supplementations were different from those observed for the J774 cells. In conclusion, we are the first to report that AA and EPA, but not DHA, have deleterious effects on the cardioprotective ABCA1 cholesterol efflux pathway from J774 foam cells. Moreover, the membrane incorporation of PUFAs does not have the same impact on cholesterol efflux from murine (J774) or human (HMDM) cholesterol-loaded macrophages. This finding emphasizes the key role of the cellular model in cholesterol efflux studies and may partly explain the heterogeneous literature data on the impact of PUFAs on cholesterol efflux.

Neutral Lipids Are Not a Source of Arachidonic Acid for Lipid Mediator Signaling in Human Foamy Monocytes

Human monocytes exposed to free arachidonic acid (AA), a secretory product of endothelial cells, acquire a foamy phenotype which is due to the accumulation of cytoplasmic lipid droplets with high AA content. Recruitment of foamy monocytes to the inflamed endothelium contributes to the development of atherosclerotic lesions. In this work, we investigated the potential role of AA stored in the neutral lipids of foamy monocytes to be cleaved by lipases and contribute to lipid mediator signaling. To this end, we used mass spectrometry-based lipidomic approaches combined with strategies to generate monocytes with different concentrations of AA. Results from our experiments indicate that the phospholipid AA pool in monocytes is stable and does not change upon exposure of the cells to the external AA. On the contrary, the AA pool in triacylglycerol is expandable and can accommodate relatively large amounts of fatty acid. Stimulation of the cells with opsonized zymosan results in the expected decreases of cellular AA. Under all conditions examined, all of the AA decreases observed in stimulated cells were accounted for by decreases in the phospholipid pool; we failed to detect any contribution of the triacylglycerol pool to the response. Experiments utilizing selective inhibitors of phospholipid or triacylglyerol hydrolysis confirmed that the phospholipid pool is the sole contributor of the AA liberated by stimulated cells. Thus, the AA in the triacylglycerol is not a source of free AA for the lipid mediator signaling during stimulation of human foamy monocytes and may be used for other cellular functions.

Beyond the antibodies: serum metabolomic profiling of myasthenia gravis

INTRODUCTION

Myasthenia gravis (MG) is a chronic, potentially debilitating autoimmune disease characterized by weakness and rapid fatigue of the voluntary muscles that worsens on exertion. Left untreated, MG symptoms may cause significant morbidity or even death. To date, no robust biological marker is available to follow the course of the disease. Therefore, new diagnostic approaches and biological markers are essential not only for improved diagnosis of the disease but for improved outcomes.

OBJECTIVES

The present study applied a two-control, multi-label metabolomics profiling approach as a potential strategy for the identification of biomarkers unique to myasthenia gravis (MG).

METHODS

Metabolic analyses using acid- and dansyl-labelled serum from seropositive MG (n = 46), rheumatoid arthritis (RA) (n = 23) and healthy controls (HC) (n = 49) were performed on samples from adult patients presenting to the University of Alberta Hospital neuromuscular and rheumatology clinics. Comparisons between patients with MG vs. HC, and RA vs. HC were made using univariate and multivariate statistics.

RESULTS

Serum biomarker patterns were statistically significantly different between groups. Principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) models exhibited considerable distinction between all groups. Metabolites were then filtered to remove peak pairs common to both disease cohorts. Combined metabolite panels revealed clear separation between MG and HC for both library-matched (AUROC: 0.92 ± 0.03) and highest AUC patients (AUROC: 0.94 ± 0.05).

CONCLUSION

In patients presenting to the clinic with seropositive MG, metabolomic profiling is capable of distinguishing patients with disease from those without. These results provide an important first step towards a potential biomarker for improving MG identification.

Cellular Plasmalogen Content Does Not Influence Arachidonic Acid Levels or Distribution in Macrophages: A Role for Cytosolic Phospholipase A2γ in Phospholipid Remodeling

Availability of free arachidonic acid (AA) constitutes a rate limiting factor for cellular eicosanoid synthesis. AA distributes differentially across membrane phospholipids, which is largely due to the action of coenzyme A-independent transacylase (CoA-IT), an enzyme that moves the fatty acid primarily from diacyl phospholipid species to ether-containing species, particularly the ethanolamine plasmalogens. In this work, we examined the dependence of AA remodeling on plasmalogen content using the murine macrophage cell line RAW264.7 and its plasmalogen-deficient variants RAW.12 and RAW.108. All three strains remodeled AA between phospholipids with similar magnitude and kinetics, thus demonstrating that cellular plasmalogen content does not influence the process. Cell stimulation with yeast-derived zymosan also had no effect on AA remodeling, but incubating the cells in AA-rich media markedly slowed down the process. Further, knockdown of cytosolic-group IVC phospholipase A₂γ (cPLA₂γ) by RNA silencing significantly reduced AA remodeling, while inhibition of other major phospholipase A₂ forms such as cytosolic phospholipase A₂α, calcium-independent phospholipase A₂β, or secreted phospholipase A₂ had no effect. These results uncover new regulatory features of CoA-IT-mediated transacylation reactions in cellular AA homeostasis and suggest a hitherto unrecognized role for cPLA₂γ in maintaining membrane phospholipid composition via regulation of AA remodeling.

Activation of The Phosphatidylcholine to Lysophosphatidylcholine Pathway Is Associated with Osteoarthritis Knee Cartilage Volume Loss Over Time

To identify serum biomarker(s) for predicting knee cartilage volume loss over time, we studied 139 knee osteoarthritis (OA) patients from a previous 24-month clinical trial cohort. Targeted metabolomic profiling was performed on serum collected at baseline. The pairwise metabolite ratios as proxies for enzymatic reaction were calculated and used in the analysis. Cartilage volume loss between baseline and 24 months was assessed quantitatively by magnetic resonance imaging (MRI). Data revealed an association between the serum ratio of lysophosphatidylcholine 18:2 (lysoPC 18:2) to phosphatidylcholine 44:3 (PC44:3) and the cartilage volume loss in the lateral compartment (β = -0.21 ± 0.04, p = 8.53*10^-7) and with joint degradation markers, COMP (r = 0.32, p = 0.0002) and MMP1 (r = 0.26, p = 0.002). The significance remained after adjustment for age, sex, BMI, diabetes, hypertension, dyslipidemia, and the treatment taken in the original study. As the ratio indicated the over activation of the conversion pathway of PC to lysoPC catalyzed by phospholipase A₂ (PLA₂), we assessed and found that a specific PLA₂, PLA₂G5, was significantly increased in human OA cartilage and synovial membrane (85% and 19% respectively, both p < 0.04) compared to controls, and its overexpression correlated with IL-6 (r = 0.63, p = 0.0008). Our data suggest that the serum lysoPC 18:2 to PC44:3 ratio is highly associated with a greater risk of cartilage volume loss of the knee and warrants further investigation in an independent cohort.

Non-canonical NLRP3 inflammasome activation and IL-1β signaling are necessary to L. amazonensis control mediated by P2X7 receptor and leukotriene B4

Leishmaniasis is a neglected tropical disease affecting millions of individuals worldwide. P2X7 receptor has been linked to the elimination of Leishmania amazonensis. Biological responses evoked by P2X7 receptor activation have been well-documented, including apoptosis, phagocytosis, cytokine release, such as IL-1β. It was demonstrated that NLRP3 inflammasome activation and IL-1β signaling participated in resistance against L. amazonensis. Furthermore, our group has shown that L. amazonensis elimination through P2X7 receptor activation depended on leukotriene B₄ (LTB₄) production and release. Therefore, we investigated whether L. amazonensis elimination by P2X7 receptor and LTB₄ involved NLRP3 inflammasome activation and IL-1β signaling. We showed that macrophages from NLRP3^-/-, ASC^-/-, Casp-1/11^-/-, gp91^{phox-/- ,} and IL-1R^-/- mice treated with ATP or LTB₄ did not decrease parasitic load as was observed in WT mice. When ASC^-/- macrophages were treated with exogenous IL-1β, parasite killing was noted, however, we did not see parasitic load reduction in IL-1R^-/- macrophages. Similarly, macrophages from P2X7 receptor-deficient mice treated with IL-1β also showed decreased parasitic load. In addition, when we infected Casp-11^-/- macrophages, neither ATP nor LTB₄ were able to reduce parasitic load, and Casp-11^-/- mice were more susceptible to L. amazonensis infection than were WT mice. Furthermore, P2X7^-/-L. amazonensis-infected mice locally treated with exogenous LTB₄ showed resistance to infection, characterized by lower parasite load and smaller lesions compared to untreated P2X7^-/- mice. A similar observation was noted when infected P2X7^-/- mice were treated with IL-1β, i.e., lower parasite load and smaller lesions compared to P2X7^-/- mice. These data suggested that L. amazonensis elimination mediated by P2X7 receptor and LTB₄ was dependent on non-canonical NLRP3 inflammasome activation, ROS production, and IL-1β signaling.

Leishmania spp. is a protozoan parasite that infects human and causes several diseases. Leishmania amazonensis causes cutaneous leishmaniasis (CL) and mucocutaneous leishmaniasis (MCL). Leishmania parasites preferentially infect macrophages. In macrophages, several mechanisms have been described as controlling L. amazonensis infection. Here, we showed that P2X7 receptor and LTB₄ eliminated L. amazonensis in macrophages by a pathway dependent on non-canonical NLRP3 inflammasome activation and IL-1β signaling.

Lipid Isolation Process and Study on Some Molecular Species of Polar Lipid Isolated from Seed of Madhuca ellitica

This study attempted the lipid extraction process from the seeds of Madhuca ellitica, a lipid-rich plant, and conducted a lipidomic analysis on molecular species of the obtained product. Total lipids of the crude seeds were found to contain 11.2% of polar lipids. The major fatty acids (FAs) of the polar lipids were palmitic (16:0), stearic (18:0), oleic (18:1n-9), and linoleic (18:2n-6) acids, which amounted to 28.5, 12.5, 44.8, and 13.2% of total FAs, respectively. The content and chemical structures of individual molecular species of phosphatidylglycerol (PG), phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylinositol (PI), phosphatidic acid (PA), and sulfoquinovosyldiacylglycerol (SQDG) were determined by HPLC with a tandem high-resolution mass spectrometry (HRMS). The major molecular species were 18:1/18:2 PE, 16:0/18:1 PC, 18:1/18:2 PC, 16:0/18:2 PG, 16:0/18:1 PG, 16:1/18:1 PI, 16:0/18:1 PI, 18:0/18:2 PI, 16:0/18:1 PA, 18:1/18:2 PA, 16:0/18:1 SQDG, and 18:0/18:1 SQDG. The application of a tandem HRMS allows us to determine the content of each isomer in pairs of the monoisotopic molecular species, for example, 18:0/18:2 and 18:1/18:1. The evaluation of the seed polar lipid profile will be helpful for developing the potential of this tree for nutritive and industrial uses.

Bioprospection of anti-inflammatory phytochemicals suggests rutaecarpine and quinine as promising 15-lipoxygenase inhibitors

15-Lipoxygenase (15-LOX) belongs to the family of nonheme iron containing enzymes that catalyzes the peroxidation of polyunsaturated fatty acids (PUFAs) to generate eicosanoids that play an important role in signaling pathways. The role of 15-LOX has been demonstrated in atherosclerosis as well as other inflammatory diseases. In the present study, drug-like compounds were first screened from a set of anti-inflammatory phytochemicals based on Lipinski's rule of five (ROF) and in silico toxicity filters. Two lead compounds-quinine (QUIN) and rutaecarpine (RUT) were shortlisted by analyzing molecular interactions and binding energies of the filtered compounds with the target using molecular docking. Molecular dynamics simulation studies indicate stable trajectories of apo_15-LOX and docked complexes (15-LOX_QUIN and 15-LOX_RUT). In vitro 15-LOX inhibition studies shows that both QUIN and RUT have lower inhibitory concentration (IC₅₀ ) value than the control (quercetin). Both QUIN and RUT exhibit moderate antioxidant activities. The cell viability study of these compounds suggests no significant toxicity in HEK-293 cell lines. Further, QUIN and RUT both did not show any inhibition against selected Gram-positive and Gram-negative bacterial species. Thus, based on our present findings, rutaecarpine and quinine may be suggested as promising 15-LOX inhibitor for the prevention of the atherosclerosis development.

The phosphatidic acid phosphatase lipin-1 facilitates inflammation-driven colon carcinogenesis

Colon cancer is a devastating illness that is associated with gut inflammation. Here, we explored the possible role of lipin-1, a phosphatidic acid phosphatase, in the development of colitis-associated tumorigenesis. Azoxymethane and dextran sodium sulfate-treated (DSS-treated) animals deficient in lipin-1 harbored fewer tumors and carcinomas than WT animals due to decreased cellular proliferation, lower expression of antiapoptotic and protumorigenic factors, and a reduced infiltration of macrophages in colon tumors. They also displayed increased resistance to DSS-induced colitis by producing less proinflammatory cytokines and experiencing less immune infiltration. Lipin-1-deficient macrophages from the colon were less activated and displayed lower phosphatidic acid phosphatase activity than WT macrophages isolated from DSS-treated animals. Transference of WT macrophages into lipin-1-deficient animals was sufficient to increase colitis burden. Furthermore, treatment of lipin-1-deficient mice with IL-23 exacerbated colon inflammation. Analysis of human databases from colon cancer and ulcerative colitis patients showed that lipin-1 expression is increased in those disorders and correlates with the expression of the proinflammatory markers CXCL1 and CXCL2. And finally, clinically, LPIN1 expression had prognostic value in inflammatory and stem-cell subtypes of colon cancers. Collectively, these data demonstrate that lipin-1 is a critical regulator of intestinal inflammation and inflammation-driven colon cancer development.

Label-free quantitative proteomics of rat hypothalamus under fever induced by LPS and PGE2

Fever is a brain-mediated increase in body temperature mainly during inflammatory or infectious challenges. Although there is considerable data regarding the inflammation pathways involved in fever, metabolic alterations necessary to orchestrate the complex inflammatory response are not totally understood. We performed proteomic analysis of rat hypothalamus using label-free LC-MS/MS in a model of fever induced by lipopolysaccharide (LPS) or prostaglandin E₂ (PGE₂). In total, 7021 proteins were identified. As far as we know, this is the largest rat hypothalamus proteome dataset available to date. Pathway analysis showed proteins from both stimuli associated with inflammatory and metabolic pathways. Concerning metabolic pathways, rats exposed to LPS or PGE₂ presented lower relative abundance of proteins involved in glycolysis, pentose phosphate pathway and tricarboxylic acid cycle. Mitochondrial function may also be altered by both stimuli because significant downregulation of several proteins was found, mainly in complexes I and IV. LPS was able to induce downregulation of important proteins in the enzymatic antioxidant system, thereby contributing to oxidative stress. The results offered comprehensive information about fever responses and helped to reveal new insights into proteins potentially involved in inflammatory signaling and metabolic changes in the hypothalamus during systemic LPS and central PGE₂ administration.

SIGNIFICANCE

The evolutionary persistence of fever, despite the elevated cost for maintenance of this response, suggests that elevation in core temperature may represent an interesting strategy for survival. Fever response is achieved through the integrated behavioral, physiological, immunological and biochemical processes that determine the balance between heat generation and elimination. The development of such complex response arouses interest in studying how the cell metabolism responds or even contributes to promote fever. Our results offered comprehensive information about fever responses, including metabolic and inflammatory pathways, providing new insights into candidate proteins potentially involved in inflammatory signaling and metabolic changes in the hypothalamus during fever induced by systemic LPS and central PGE₂ perturbation.

Regulation of Phagocytosis in Macrophages by Membrane Ethanolamine Plasmalogens

Macrophages, as professional phagocytes of the immune system, possess the ability to detect and clear invading pathogens and apoptotic cells through phagocytosis. Phagocytosis involves membrane reorganization and remodeling events on the cell surface, which play an essential role in innate immunity and tissue homeostasis and the control of inflammation. In this work, we report that cells deficient in membrane ethanolamine plasmalogen demonstrate a reduced capacity to phagocytize opsonized zymosan particles. Amelioration of plasmalogen deficiency in these cells by incubation with lysoplasmalogen results in a significant augmentation of the phagocytic capacity of the cells. In parallel with these increases, restoration of plasmalogen levels in the cells also increases the number and size of lipid rafts in the membrane, reduces membrane fluidity down to levels found in cells containing normal plasmalogen levels, and improves receptor-mediated signaling. Collectively, these results suggest that membrane plasmalogen level determines characteristics of the plasma membrane such as fluidity and the formation of microdomains that are necessary for efficient signal transduction leading to optimal phagocytosis by macrophages.

Selectivity of phospholipid hydrolysis by phospholipase A2 enzymes in activated cells leading to polyunsaturated fatty acid mobilization

Phospholipase A₂s are enzymes that hydrolyze the fatty acid at the sn-2 position of the glycerol backbone of membrane glycerophospholipids. Given the asymmetric distribution of fatty acids within phospholipids, where saturated fatty acids tend to be present at the sn-1 position, and polyunsaturated fatty acids such as those of the omega-3 and omega-6 series overwhelmingly localize in the sn-2 position, the phospholipase A₂ reaction is of utmost importance as a regulatory checkpoint for the mobilization of these fatty acids and the subsequent synthesis of proinflammatory omega-6-derived eicosanoids on one hand, and omega-3-derived specialized pro-resolving mediators on the other. The great variety of phospholipase A₂s, their differential substrate selectivity under a variety of pathophysiological conditions, as well as the different compartmentalization of each enzyme and accessibility to substrate, render this class of enzymes also key to membrane phospholipid remodeling reactions, and the generation of specific lipid mediators not related with canonical metabolites of omega-6 or omega-3 fatty acids. This review highlights novel findings regarding the selective hydrolysis of phospholipids by phospholipase A₂s and the influence this may have on the ability of these enzymes to generate distinct lipid mediators with essential functions in biological processes. This brings a new understanding of the cellular roles of these enzymes depending upon activation conditions.

Oxidative stress biomarkers in type 2 diabetes mellitus for assessment of cardiovascular disease risk

AIMS

Type-2 Diabetes Mellitus (T2DM) is one of the most prevalent and progressive metabolic conditions affecting approximately 8.5% of the global population. Individuals with T2DM have a significantly increased risk of developing chronic conditions such as cardiovascular disease (CVD) and its associated complications, therefore, it is of great importance to establish strategies for combatting T2DM and its associated chronic conditions. Current literature has identified several biomarkers that are known to play a key role in the pathogenesis of CVD. Many of these biomarkers affecting CVD are influenced by an increase in oxidative stress as seen in T2DM. The purpose of this review is to analyse and correlate the oxidative stress-related biomarkers that have been identified in the literature to provide an updated summary of their significance in CVD risk factors.

DATA SYNTHESIS

This review has analysed current research on T2DM, CVD, and oxidative stress. Four key cardiovascular risk factors: thrombosis, inflammation, vascular homeostasis and cellular proliferation were searched to identify potential biomarkers for this review. These biomarkers stem from seven major cellular pathways; NF-κB, Keap1-Nrf2, protein kinase-C, macrophage activation, arachidonic acid mobilisation, endothelial dysfunction and advanced glycation end products.

CONCLUSIONS

The pathways and biomarkers were analysed to show their role as contributing factors to CVD development and a summary is made regarding the assessment of cardiovascular risk in T2DM individuals.

Low back pain, obesity, and inflammatory markers: exercise as potential treatment

Low back pain is a health issue with significant impact to patients and society. This narrative review aims to synthesize the relationship between obesity, low-grade inflammation and low back pain. It is known that a sedentary lifestyle is a risk factor for obesity and related disorders. The adipose tissue of obese people secretes a range of cytokines of character pro- and anti-inflammatory, with many molecular effects. In addition, pro-inflammatory cytokines are sensitizers of C-reactive protein (CRP), a marker of acute inflammation that can be linked to the musculoskeletal pain sensation individuals with back pain. Another inflammatory marker deserves mention, prostaglandin E2. Prostaglandin E2 is important in the process of triggering actions such as pyrexia, sensation of pain and inflammation, which are exhibited in low back pain condition. The potential for exercises and physical activity to control these mediators and act as a preventative measure for back pain are important because they work as a nonpharmacological strategy to this target audience. There are two types of exercise discussed in this review, the moderate-intensity continuous training and high-intensity interval training.

Host Lipid Mediators in Leprosy: The Hypothesized Contributions to Pathogenesis

The spectrum of clinical forms observed in leprosy and its pathogenesis are dictated by the host's immune response against Mycobacterium leprae, the etiological agent of leprosy. Previous results, based on metabolomics studies, demonstrated a strong relationship between clinical manifestations of leprosy and alterations in the metabolism of ω3 and ω6 polyunsaturated fatty acids (PUFAs), and the diverse set of lipid mediators derived from PUFAs. PUFA-derived lipid mediators provide multiple functions during acute inflammation, and some lipid mediators are able to induce both pro- and anti-inflammatory responses as determined by the cell surface receptors being expressed, as well as the cell type expressing the receptors. However, little is known about how these compounds influence cellular immune activities during chronic granulomatous infectious diseases, such as leprosy. Current evidence suggests that specialized pro-resolving lipid mediators (SPMs) are involved in the down-modulation of the innate and adaptive immune response against M. leprae and that alteration in the homeostasis of pro-inflammatory lipid mediators versus SPMs is associated with dramatic shifts in the pathogenesis of leprosy. In this review, we discuss the possible consequences and present new hypotheses for the involvement of ω3 and ω6 PUFA metabolism in the pathogenesis of leprosy. A specific emphasis is placed on developing models of lipid mediator interactions with the innate and adaptive immune responses and the influence of these interactions on the outcome of leprosy.