A lipidomic perspective on inflammatory macrophage eicosanoid signaling

Lipidomics of Phospholipase A2 Reveals Exquisite Specificity in Macrophages

Phospholipase A2 (PLA2) constitutes a superfamily of enzymes that hydrolyze phospholipids at their sn-2 fatty acyl position. Our laboratory has demonstrated that PLA2 enzymes regulate membrane remodeling and cell signaling by their specificity toward their phospholipid substrates at the molecular level. Recent in vitro studies show that each type of PLA2, including GIVA cytosolic PLA2 (cPLA2), GV secreted PLA2 (sPLA2), GVIA calcium independent PLA2 (iPLA2) and GVIIA lipoprotein-associated PLA2 (LpPLA2), also known as platelet-activating factor acetyl hydrolase (PAFAH), can discriminate exquisitely between fatty acids at the sn-2 position. Thus, these enzymes regulate the production of diverse polyunsaturated fatty acid (PUFA) precursors of inflammatory metabolites. We now determined PLA2 specificity in macrophage cells grown in cell culture, where the amounts and localization of the phospholipid substrates play a role in which specific phospholipids are hydrolyzed by each enzyme type. We employ PLA2 stereospecific inhibitors in tandem with a novel UPLC-MS/MS based lipidomics platform to quantify more than a thousand unique phospholipid molecular species demonstrating cPLA2, sPLA2, and iPLA2 activity and specificity toward the phospholipids in living cells. The observed specificity follows the in vitro capability of the enzymes and can reflect the enrichment of certain phospholipid species in specific membrane locations where particular PLA2's associate. For assaying, we target 20:4-PI for cPLA2, 22:6-PG for sPLA2 and 18:2-PC for iPLA2. These new results provide great insight into the physiological role of PLA2 enzymes in cell membrane remodeling and could shed light on how PLA2 enzymes underpin inflammation and other lipid-related diseases.

Inhibition of mevalonate pathway by macrophage-specific delivery of atorvastatin prevents their pro-inflammatory polarisation

Adjustment of the cellular metabolism of pro-inflammatory macrophages is essential for their bactericidal function; however, it underlies the development of many human diseases if induced chronically. Therefore, intervention of macrophage metabolic polarisation has been recognised as a potent strategy for their treatment. Although many small-molecule inhibitors affecting macrophage metabolism have been identified, their in vivo administration requires a tool for macrophage-specific delivery to limit their potential side effects. Here, we establish Drosophila melanogaster as a simple experimental model for in vivo testing of macrophage-specific delivery tools. We found that yeast-derived glucan particles (GPs) are suitable for macrophage-specific delivery of small-molecule inhibitors. Systemic administration of GPs loaded with atorvastatin, the inhibitor of hydroxy-methyl-glutaryl-CoA reductase (Hmgcr), leads to intervention of mevalonate pathway specifically in macrophages, without affecting HMGCR activity in other tissues. Using this tool, we demonstrate that mevalonate pathway is essential for macrophage pro-inflammatory polarisation and individual's survival of infection.

Comprehensive analysis of oxylipins using reverse phase liquid chromatography and data dependent acquisition workflow on LTQ-Orbitrap® Velos Pro

Oxylipins - involved in inflammatory processes - are reported in several diseases, in biological, pharmacological, and physiological fields. To face the structural complexity of oxylipins, the study of isomers and isobars species relied on Selected Reaction Monitoring (SRM) and Multiple Reaction Monitoring (MRM) in tandem mass spectrometry such as triple quadrupole, quadrupole-Time of Flight (TOF). Unfortunately, false positive signals in cellular matrix could occur using MRM or SRM mode since the MS/MS spectrum of each molecule is not acquired with the previous mode to help molecule confirmation. Using the versatile ability of LTQ-Orbitrap® Velos Pro mass spectrometer, we developed a novel method based on data dependent acquisition (DDA) workflow for oxylipins analysis. To reach sufficient data points per peak and a better sensitivity to quantify oxylipins traces, an optimization of the acquisition frequency was carried out both on linear trap and Orbitrap analyzers. A segmentation of the chromatographic profile and an optimization of the collision energies by HCD (higher energy collision dissociation) for each eicosanoid increased the acquisition frequency significantly and the detection threshold: around 2 pg for some prostanoids and 0.02-2 pg for some leukotrienes and oxidized species. We validated our method in terms of specificity (RSD <10%), sensitivity, accuracy and precision. The intra and inter-day accuracy were between 86.56% and 114.93%. Besides, a relative standard deviation less than 15% as intra- and inter-day precision were obtained for almost all molecules. A linear range between 2.5 and 12,500 pg was reached. DDA approach on LTQ-Orbitrap® constitutes an alternative to MRM mode on triple quadrupole for eicosanoids quantification in complex matrices. Finally, this method helped us to compare for the first time the amount of prostanoids released by J774 and THP-1 macrophages under lipopolysaccharide (LPS) stimulation.

Impaired hepatic lipid metabolism and biomarkers in fatty liver disease

The liver plays a crucial role in lipid metabolism and metabolic homeostasis. Non-Alcoholic Fatty Liver Disease (NAFLD) is the most common chronic liver disease worldwide and currently has no specific treatments. Lifestyle modifications such as weight loss, exercise, and dietary changes are recommended to reduce the risk factors associated with the disease. Oxidized cholesterol products, some phospholipids and diacylglycerols can activate inflammatory pathways and contribute to the progression to Non-Alcoholic Steatohepatitis. Monitoring the whole plasma and liver lipidome may provide insights into the onset, development, and prevention of inflammatory-related diseases. As Lipid Droplets (LDs) represent augmented lipid reservoirs in NAFLD, new developments are being made on different therapies focused on LD associated proteins modulation (seipin, PLIN-2), as well as LD lipophagy mechanisms. The information covered in this publication provides an overview of the available research on lipid biomarkers linked to NAFLD and can be used to guide the development of future pharmacological therapies.

Fatty acid-mediated signaling as a target for developing type 1 diabetes therapies

INTRODUCTION

Type 1 diabetes (T1D) is an autoimmune disease in which pro-inflammatory and cytotoxic signaling drive the death of the insulin-producing β cells. This complex signaling is regulated in part by fatty acids and their bioproducts, making them excellent therapeutic targets.

AREAS COVERED

We provide an overview of the fatty acid actions on β cells by discussing how they can cause lipotoxicity or regulate inflammatory response during insulitis. We also discuss how diet can affect the availability of fatty acids and disease development. Finally, we discuss development avenues that need further exploration.

EXPERT OPINION

Fatty acids, such as hydroxyl fatty acids, ω-3 fatty acids, and their downstream products, are druggable candidates that promote protective signaling. Inhibitors and antagonists of enzymes and receptors of arachidonic acid and free fatty acids, along with their derived metabolites, which cause pro-inflammatory and cytotoxic responses, have the potential to be developed as therapeutic targets also. Further, because diet is the main source of fatty acid intake in humans, balancing protective and pro-inflammatory/cytotoxic fatty acid levels through dietary therapy may have beneficial effects, delaying T1D progression. Therefore, therapeutic interventions targeting fatty acid signaling hold potential as avenues to treat T1D.

Macrophage COX2 Mediates Efferocytosis, Resolution Reprogramming, and Intestinal Epithelial Repair

BACKGROUND AND AIMS

Phagocytosis (efferocytosis) of apoptotic neutrophils by macrophages anchors the resolution of intestinal inflammation. Efferocytosis prevents secondary necrosis and inhibits further inflammation, and also reprograms macrophages to facilitate tissue repair and promote resolution function. Macrophage efferocytosis and efferocytosis-dependent reprogramming are implicated in the pathogenesis of inflammatory bowel disease. We previously reported that absence of macrophage cyclooxygenase 2 (COX2) exacerbates inflammatory bowel disease-like intestinal inflammation. To elucidate the underlying pathogenic mechanism, we investigated here whether COX2 mediates macrophage efferocytosis and efferocytosis-dependent reprogramming, including intestinal epithelial repair capacity.

METHODS

Using apoptotic neutrophils and synthetic apoptotic targets, we determined the effects of macrophage specific Cox2 knockout and pharmacological COX2 inhibition on the efferocytosis capacity of mouse primary macrophages. COX2-mediated efferocytosis-dependent eicosanoid lipidomics was determined by liquid chromatography tandem mass spectrometry. Small intestinal epithelial organoids were employed to assay the effects of COX2 on efferocytosis-dependent intestinal epithelial repair.

RESULTS

Loss of COX2 impaired efferocytosis in mouse primary macrophages, in part, by affecting the binding capacity of macrophages for apoptotic cells. This effect was comparable to that of high-dose lipopolysaccharide and was accompanied by both dysregulation of macrophage polarization and the inhibited expression of genes involved in apoptotic cell binding. COX2 modulated the production of efferocytosis-dependent lipid inflammatory mediators that include the eicosanoids prostaglandin I2, prostaglandin E2, lipoxin A4, and 15d-PGJ2; and further affected secondary efferocytosis. Finally, macrophage efferocytosis induced, in a macrophage COX2-dependent manner, a tissue restitution and repair phenotype in intestinal epithelial organoids.

CONCLUSIONS

Macrophage COX2 potentiates efferocytosis capacity and efferocytosis-dependent reprogramming, facilitating macrophage intestinal epithelial repair capacity.

Bioactive Sugarcane Lipids in a Circular Economy Context

Most of the global sugar and ethanol supply trade comes from the harvesting of Saccharum officinarum (i.e., sugarcane). Its industrial processing results in numerous by-products and waste streams, such as tops, straw, filter cake, molasses and bagasse. The recovery of lipids (i.e., octacosanol, phytosterols, long-chain aldehydes and triterpenoids) from these residues is an excellent starting point for the development of new products for various application fields, such as health and well-being, representing an important feature of the circular economy. By selecting green scalable extraction procedures, industry can reduce its environmental impact. Refluxed ethanol extraction methods have been demonstrated to meet these characteristics. On the other hand, effective non-solvent methodologies such as molecular distillation and supercritical CO₂ extraction can fractionate lipids based on high temperature and pressure application with similar yields. Sugarcane lipophilic extracts are usually analyzed through gas chromatography (GC) and liquid chromatography (LC) techniques. In many cases, the identification of such compounds involves the development of high-temperature GC–MS/FID techniques. On the other hand, for the identification and quantification of thermolabile lipids, LC–MS techniques are suitable for the separation and identification of major lipid classes. Generically, its composition includes terpenes, phytosterols, tocopherol, free fatty acids, fatty alcohols, wax esters, triglycerides, diglycerides and monoglycerides. These compounds are already known for their interesting application in various fields such as pharma and cosmetics due to their anti-hypercholesterolemic, anti-hyperglycemic, antioxidant and anti-inflammatory properties.

The Impact of the Ca2+-Independent Phospholipase A2β (iPLA2β) on Immune Cells

The Ca²⁺-independent phospholipase A₂β (iPLA₂β) is a member of the PLA₂ family that has been proposed to have roles in multiple biological processes including membrane remodeling, cell proliferation, bone formation, male fertility, cell death, and signaling. Such involvement has led to the identification of iPLA₂β activation in several diseases such as cancer, cardiovascular abnormalities, glaucoma, periodontitis, neurological disorders, diabetes, and other metabolic disorders. More recently, there has been heightened interest in the role that iPLA₂β plays in promoting inflammation. Recognizing the potential contribution of iPLA₂β in the development of autoimmune diseases, we review this issue in the context of an iPLA₂β link with macrophages and T-cells.

Omega-3 Polyunsaturated Fatty Acid Intervention Against Established Autoimmunity in a Murine Model of Toxicant-Triggered Lupus

Workplace exposure to respirable crystalline silica dust (cSiO2) has been etiologically linked to the development of lupus and other human autoimmune diseases. Lupus triggering can be recapitulated in female NZBWF1 mice by four weekly intranasal instillations with 1 mg cSiO2. This elicits inflammatory/autoimmune gene expression and ectopic lymphoid structure (ELS) development in the lung within 1 week, ultimately driving early onset of systemic autoimmunity and glomerulonephritis. Intriguingly, dietary supplementation with docosahexaenoic acid (DHA), an ω-3 polyunsaturated fatty acid (PUFA) found in fish oil, beginning 2 week prior to cSiO2 challenge, prevented inflammation and autoimmune flaring in this novel model. However, it is not yet known how ω-3 PUFA intervention influences established autoimmunity in this murine model of toxicant-triggered lupus. Here we tested the hypothesis that DHA intervention after cSiO2-initiated intrapulmonary autoimmunity will suppress lupus progression in the NZBWF1 mouse. Six-week old NZWBF1 female mice were fed purified isocaloric diet for 2 weeks and then intranasally instilled with 1 mg cSiO2 or saline vehicle weekly for 4 consecutive weeks. One week after the final instillation, which marks onset of ELS formation, mice were fed diets supplemented with 0, 4, or 10 g/kg DHA. One cohort of mice (n = 8/group) was terminated 13 weeks after the last cSiO2 instillation and assessed for autoimmune hallmarks. A second cohort of mice (n = 8/group) remained on experimental diets and was monitored for proteinuria and moribund criteria to ascertain progression of glomerulonephritis and survival, respectively. DHA consumption dose-dependently increased ω-3 PUFA content in the plasma, lung, and kidney at the expense of the ω-6 PUFA arachidonic acid. Dietary intervention with high but not low DHA after cSiO2 treatment suppressed or delayed: (i) recruitment of T cells and B cells to the lung, (ii) development of pulmonary ELS, (iii) elevation of a wide spectrum of plasma autoantibodies associated with lupus and other autoimmune diseases, (iv) initiation and progression of glomerulonephritis, and (v) onset of the moribund state. Taken together, these preclinical findings suggest that DHA supplementation at a human caloric equivalent of 5 g/d was an effective therapeutic regimen for slowing progression of established autoimmunity triggered by the environmental toxicant cSiO2.

Requisite Omega-3 HUFA Biomarker Thresholds for Preventing Murine Lupus Flaring

Lupus is a systemic autoimmune disease typified by uncontrolled inflammation, disruption of immune tolerance, and intermittent flaring - events triggerable by environmental factors. Preclinical and clinical studies reveal that consumption of the marine ω-3 highly unsaturated fatty acids (HUFAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) might be used as a precision nutrition intervention to lessen lupus symptoms. The anti-inflammatory and pro-resolving effects of ω-3 HUFAs are inextricably linked to their presence in membrane phospholipids. The ω-3 HUFA score, calculated as [100 × (ω-3 HUFAs/(ω-3 HUFAs + ω-6 HUFAs))] in red blood cells (RBCs), and the Omega-3 Index (O3I), calculated as [100 × ((DHA+EPA)/total fatty acids)] in RBCs, are two biomarkers potentially amenable to relating tissue HUFA balance to clinical outcomes in individuals with lupus. Using data from three prior preclinical DHA supplementation studies, we tested the hypothesis that the ω-3 HUFA score and the O3I inversely correlate with indicators of autoimmune pathogenesis in the cSiO2-triggered lupus flaring model. The three studies employed both low and high fat rodent diets, as well as more complex diets emulating the U.S. dietary pattern. The ω-3 HUFA scores in RBCs were comparatively more robust than the O3I at predicting HUFA balances in the kidney, liver, spleen, and lung. Importantly, increases in both the ω-3 HUFA score (>40%) and the O3I (>10%) were strongly associated with suppression of cSiO2-triggered (1) expression of interferon-regulated genes, proinflammatory cytokine production, leukocyte infiltration, and ectopic lymphoid structure development in the lung, (2) pulmonary and systemic autoantibody production, and (3) glomerulonephritis. Collectively, these findings identify achievable ω-3 HUFA scores and O3I thresholds that could be targeted in future human intervention studies querying how ω-3 HUFA consumption influences lupus and other autoimmune diseases.

Current and Future molecular mechanism in Inflammation and Arthritis

Inflammation is an immune response of the human body but excessive inflammation is taken as a major factor in the development of many diseases including autoimmune disorders, cancer and nerve disorders etc. In this regards the need is to suppress the inflammatory response. Suppression of extra or imperfect inflammatory response is not a big deal provided there is an exact knowledge of particular target in the body. Recent advancements in Pharmacological aspect made the therapy with improved outcomes in number of patients. Anticytokine therapy might be one of the important and novel approaches for inflammation and Arthritis. This can be achieved only when we go through the pathophysiology of expression and identification of mediators. Let's take an example of cytokine like interleukins (IL), chemokines, interferons (INF), tumor necrosis factors (TNF-α), growth factors, and colony stimulating factors) release pathway which is a major signalling protein in inflammatory response. In the present study we have reviewed the recent pharmacological therapeutic advancement, inflammatory mediators, receptors, and major signalling pathways. Such information will not only provide the idea about the mechanism of action of Pharmaceuticals and molecular targets but also it provides a new aspect for drug designing and new corrective approaches in existing clinical medicines. This study will be a source of good information for the researchers working in the area of drug designing and molecular Pharmacology especially in anti-inflammatory and anti arthritic medicines for target based therapy.

Macrophage polarization is linked to Ca2+-independent phospholipase A2β-derived lipids and cross-cell signaling in mice

Phospholipases A₂ (PLA₂s) catalyze hydrolysis of the sn-2 substituent from glycerophospholipids to yield a free fatty acid (i.e., arachidonic acid), which can be metabolized to pro- or anti-inflammatory eicosanoids. Macrophages modulate inflammatory responses and are affected by Ca²⁺-independent phospholipase A₂ (PLA₂)β (iPLA₂β). Here, we assessed the link between iPLA₂β-derived lipids (iDLs) and macrophage polarization. Macrophages from WT and KO (iPLA₂β-/-) mice were classically M1 pro-inflammatory phenotype activated or alternatively M2 anti-inflammatory phenotype activated, and eicosanoid production was determined by ultra-performance LC ESI-MS/MS. As a genotypic control, we performed similar analyses on macrophages from RIP.iPLA₂β.Tg mice with selective iPLA₂β overexpression in β-cells. Compared with WT, generation of select pro-inflammatory prostaglandins (PGs) was lower in iPLA₂β^-/- , and that of a specialized pro-resolving lipid mediator (SPM), resolvin D2, was higher; both changes are consistent with the M2 phenotype. Conversely, macrophages from RIP.iPLA₂β.Tg mice exhibited an opposite landscape, one associated with the M1 phenotype: namely, increased production of pro-inflammatory eicosanoids (6-keto PGF₁α, PGE₂, leukotriene B₄) and decreased ability to generate resolvin D2. These changes were not linked with secretory PLA₂ or cytosolic PLA₂α or with leakage of the transgene. Thus, we report previously unidentified links between select iPLA₂β-derived eicosanoids, an SPM, and macrophage polarization. Importantly, our findings reveal for the first time that β-cell iPLA₂β-derived signaling can predispose macrophage responses. These findings suggest that iDLs play critical roles in macrophage polarization, and we posit that they could be targeted therapeutically to counter inflammation-based disorders.

An update on lipid oxidation and inflammation in cardiovascular diseases

Cardiovascular diseases (CVD), including ischemic heart diseases and cerebrovascular diseases, are the leading causes of morbidity and mortality worldwide. Atherosclerosis is the major underlying factor for most CVD. It is well-established that oxidative stress and inflammation are two major mechanisms leading to atherosclerosis. Under oxidative stress, polyunsaturated fatty acids (PUFA)-containing phospholipids and cholesterol esters in cellular membrane and lipoproteins can be readily oxidized through a free radical-induced lipid peroxidation (LPO) process to form a complex mixture of oxidation products. Overwhelming evidence demonstrates that these oxidized lipids are actively involved in the inflammatory responses in atherosclerosis by interacting with immune cells (such as macrophages) and endothelial cells. In addition to lipid lowering in the prevention and treatment of atherosclerotic CVD, targeting chronic inflammation has been entering the medical realm. Clinical trials are under way to lower the lipoprotein (a) (Lp(a)) and its associated oxidized phospholipids, which will provide clinical evidence that targeting inflammation caused by oxidized lipids is a viable approach for CVD. In this review, we aim to give an update on our understanding of the free radical oxidation of LPO, analytical technique to analyze the oxidation products, especially the oxidized phospholipids and cholesterol esters in low density lipoproteins (LDL), and focusing on the experimental and clinical evidence on the role of lipid oxidation in the inflammatory responses associated with CVD, including myocardial infarction and calcific aortic valve stenosis. The challenges and future directions in understanding the role of LPO in CVD will also be discussed.

Stereotactic Body Radiation and Interleukin-12 Combination Therapy Eradicates Pancreatic Tumors by Repolarizing the Immune Microenvironment

Over 80% of pancreatic ductal adenocarcinoma (PDA) patients are diagnosed with non-resectable late-stage disease that lacks effective neoadjuvant therapies. Stereotactic body radiation therapy (SBRT) has shown promise as an emerging neoadjuvant approach for treating PDA, and here, we report that its combination with local interleukin-12 (IL-12) microsphere (MS) immunotherapy results in marked tumor reduction and cures in multiple preclinical mouse models of PDA. Our findings demonstrate an increase of intratumoral interferon gamma (IFNγ) production following SBRT/IL-12 MS administration that initiates suppressor cell reprogramming and a subsequent increase in CD8 T cell activation. Furthermore, SBRT/IL-12 MS therapy results in the generation of systemic tumor immunity that is capable of eliminating established liver metastases, providing a rationale for follow-up studies in advanced metastatic disease.

ER-Mitochondria Communication in Cells of the Innate Immune System

In cells the interorganelle communication comprises vesicular and non-vesicular mechanisms. Non-vesicular material transfer predominantly takes place at regions of close organelle apposition termed membrane contact sites and is facilitated by a growing number of specialized proteins. Contacts of the endoplasmic reticulum (ER) and mitochondria are now recognized to be essential for diverse biological processes such as calcium homeostasis, phospholipid biosynthesis, apoptosis, and autophagy. In addition to these universal roles, ER-mitochondria communication serves also cell type-specific functions. In this review, we summarize the current knowledge on ER-mitochondria contacts in cells of the innate immune system, especially in macrophages. We discuss ER- mitochondria communication in the context of macrophage fatty acid metabolism linked to inflammatory and ER stress responses, its roles in apoptotic cell engulfment, activation of the inflammasome, and antiviral defense.

Directed Non-targeted Mass Spectrometry and Chemical Networking for Discovery of Eicosanoids and Related Oxylipins

Eicosanoids and related oxylipins are critical, small bioactive mediators of human physiology and inflammation. While ∼1,100 distinct species have been predicted to exist, to date, less than 150 of these molecules have been measured in humans, limiting our understanding of their role in human biology. Using a directed non-targeted mass spectrometry approach in conjunction with chemical networking of spectral fragmentation patterns, we find over 500 discrete chemical signals highly consistent with known and putative eicosanoids and related oxylipins in human plasma including 46 putative molecules not previously described. In plasma samples from 1,500 individuals, we find members of this expanded oxylipin library hold close association with markers of inflammation, as well as clinical characteristics linked with inflammation, including advancing age and obesity. These experimental and computational approaches enable discovery of new chemical entities and will shed important insight into the role of bioactive molecules in human health and disease.

Fatty acids and selected endocannabinoids content in cerebrospinal fluids from patients with neuroinfections

Neuroinfections are a significant medical problem and can have serious health consequences for patients. Their outcome, if not fatal, can be associated with permanent residual deficits. Cerebrospinal fluid (CSF) examination is commonly used for meningitis confirmation. Fatty acids (FA) are precursors of lipid mediators with pharmacological activity. They actively modulate inflammation as well as contribute to its resolution. Therefore the aim of this study was to determine the FA and selected endocannabinoids (ECB) content in the CSF obtained from patients with bacterial (BM) and viral meningitis (VM) using chromatographic techniques. A significantly lower level of saturated FA was found in patients with BM and VM as compared to controls. There was a significantly higher concentration of long-chain monounsaturated FA and polyunsaturated n-6 FA in the CSF obtained from patients with neuroinfection. Moreover, a significant reduction of n-3 FA in CSF obtained from patients with BM and VM was demonstrated. The highest amount of ECB was detected in the CSF of patients with VM: eicosapentaenoyl ethanolamide (1.65 pg/mL), docosahexaenoyl ethanolamide (655.5 pg/mL) and nervonoyl ethanolamide (3.09 ng/mL). Results indicate the participation of long-chain monounsaturated and polyunsaturated FA and their derivatives in the inflammatory process and likely in the process of resolution of inflammation during neuroinfection. It seems that the determination of the FA and ECB profile in CSF may be a valuable biomarker of health and may allow the development of new pharmacological strategies, therapeutic goals and fatty acids supplementation necessary in the fight against inflammation of the central nervous system.

Oxylipin profiling of human plasma reflects the renal dysfunction in uremic patients

INTRODUCTION

Nearly all the enzymes that mediate the metabolism of polyunsaturated fatty acids (PUFAs) are present in the kidney. However, the correlation of renal dysfunction with PUFAs metabolism in uremic patients remains unknown.

OBJECTIVES

To test whether the alterations in the metabolism of PUFAs reflect the renal dysfunction in uremic patients.

METHODS

LC-MS/MS-based oxylipin profiling was conducted for the plasma samples from the uremic patients and controls. The data were analyzed by principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA). The receiver operating characteristic (ROC) curves and the correlation of the estimated glomerular filtration rate (eGFR) with the key markers were evaluated. Furthermore, qPCR analysis of the whole blood cells was conducted to investigate the possible mechanisms. In addition, a 2nd cohort was used to validate the findings from the 1st cohort.

RESULTS

The plasma oxylipin profile distinguished the uremic patients from the controls successfully by using both PCA and OPLS-DA models. 5,6-Dihydroxyeicosatrienoic acid (5,6-DHET), 5-hydroxyeicosatetraenoic acid (5-HETE), 9(10)-epoxyoctadecamonoenoic acid [9(10)-EpOME] and 12(13)-EpOME were identified as the key markers to discriminate the patients from controls. The excellent predictive performance of these four markers was validated by ROC analysis. The eGFR significantly correlated with plasma levels of 5,6-DHET and 5-HETE positively but with plasma 9(10)-EpOME and 12(13)-EpOME negatively. The changes of these markers may account for the inactivation of cytochrome P450 2C18, 2C19, microsome epoxide hydrolase (EPHX1), and 5-lipoxygenase in the patients.

CONCLUSION

The alterations in plasma metabolic profile reflect the renal dysfunction in the uremic patients.

ApoL1 renal risk variants induce aberrant THP-1 monocyte differentiation and increase eicosanoid production via enhanced expression of cyclooxygenase-2

Apolipoprotein L1 ( ApoL1) genetic variants are strongly associated with kidney diseases. We investigated the role of ApoL1 variants in monocyte differentiation and eicosanoid production in macrophages, as activated tissue macrophages in kidney might contribute to kidney injury. In human monocyte THP-1 cells, transient overexpression of ApoL1 (G0, G1, G2) by transfection resulted in a 5- to 11-fold increase in CD14 and CD68 gene expression, similar to that seen with phorbol-12-myristate acetate treatment. All ApoL1 variants caused monocytes to differentiate into atypical M1 macrophages with marked increase in M1 markers CD80, TNF, IL1B, and IL6 and modest increase in the M2 marker CD163 compared with control cells. ApoL1-G1 transfection induced additional CD206 and TGFB1 expression, and ApoL1-G2 transfection induced additional CD204 and TGFB1 expression. Gene expression of prostaglandin E2 (PGE2) synthase and thromboxane synthase and both gene and protein expression of cyclooxygenase-2 (COX-2) were increased by ApoL1-G1 and -G2 variants compared with -G0 transfection. Higher levels of PGE2 and thromboxane B2, a stable metabolite of thromboxane A2, and transforming growth factor (TGF)-β1 were released into the supernatant of cultured THP-1 cells transfected with ApoL1-G1 and -G2, but not -G0. The increase in PGE2, thromboxane B2, and TGF-β1 was inhibited by COX-2-specific inhibitor CAY10404 but not by COX-1-specific inhibitor SC-560. These results demonstrate a novel role of ApoL1 variants in the regulation of monocyte differentiation and eicosanoid metabolism, which could modify the immune response and promote inflammatory signaling within the local targeted organs and tissues including the kidney.

Role of oxylipins in cardiovascular diseases

Globally, cardiovascular diseases (CVDs) are the number one cause of mortality. Approximately 18 million people died from CVDs in 2015, representing more than 30% of all global deaths. New diagnostic tools and therapies are eagerly required to decrease the prevalence of CVDs related to mortality and/or risk factors leading to CVDs. Oxylipins are a group of metabolites, generated via oxygenation of polyunsaturated fatty acids that are involved in inflammation, immunity, and vascular functions, etc. Thus far, over 100 oxylipins have been identified, and have overlapping and interconnected roles. Important CVD pathologies such as hyperlipidemia, hypertension, thrombosis, hemostasis and diabetes have been linked to abnormal oxylipin signaling. Oxylipins represent a new era of risk markers and/or therapeutic targets in several diseases including CVDs. The role of many oxylipins in the progression or regression in CVD, however, is still not fully understood. An increased knowledge of the role of these oxygenated polyunsaturated fatty acids in cardiovascular dysfunctions or CVDs including hypertension could possibly lead to the development of biomarkers for the detection and their treatment in the future.

Metabolic regulation of macrophage phenotype and function

Studies in the last 20 years have given us a remarkable insight into the functional and phenotypic diversity of macrophages which reflects their integral role in host defence, homeostasis and pathogenesis. Mouse genetics, transcriptomic and epigenetic studies have provided an ontogenic and molecular perspective to the phenotypic diversity of these cells. Recently, metabolic studies have revealed the crucial role of metabolism and metabolites in shaping the phenotype and function of macrophages. Evidence pertaining to this aspect will be reviewed here.

Development and application of a UHPLC-MS/MS metabolomics based comprehensive systemic and tissue-specific screening method for inflammatory, oxidative and nitrosative stress

Oxidative stress and inflammation are underlying pathogenic mechanisms associated with the progression of several pathological conditions and immunological responses. Elucidating the role of signalling lipid classes, which include, among others, the isoprostanes, nitro fatty acids, prostanoids, sphingoid bases and lysophosphatidic acids, will create a snapshot of the cause and effect of inflammation and oxidative stress at the metabolic level. Here we describe a fast, sensitive, and targeted ultra-high-performance liquid chromatography-tandem mass spectrometry metabolomics method that allows the quantitative measurement and biological elucidation of 17 isoprostanes as well as their respective isomeric prostanoid mediators, three nitro fatty acids, four sphingoid mediators, and 24 lysophosphatidic acid species from serum as well as organ tissues, including liver, lung, heart, spleen, kidney and brain. Application of this method to paired mouse serum and tissue samples revealed tissue- and serum-specific stress and inflammatory readouts. Little correlation was found between localized (tissue) metabolite levels compared with the systemic (serum) circulation in a homeostatic model. The application of this method in future studies will enable us to explore the role of signalling lipids in the metabolic pathogenicity of stress and inflammation during health and disease.

Oxidized LDL triggers changes in oxidative stress and inflammatory biomarkers in human macrophages

Oxidized low-density lipoprotein (oxLDL) is a well-recognized proatherogenic particle that functions in atherosclerosis. In this study, we established conditions to generate human oxLDL, characterized according to the grade of lipid and protein oxidation, particle size and oxylipin content. The induction effect of the cellular proatherogenic response was assessed in foam cells by using an oxLDL-macrophage interaction model. Uptake of oxLDL, reactive oxygen species production and expression of oxLDL receptors (CD36, SR-A and LOX-1) were significantly increased in THP-1 macrophages. Analyses of 35 oxylipins revealed that isoprostanes (IsoP) and prostaglandins (PGs) derived from the oxidation of arachidonic, dihomo gamma-linolenic and eicosapentaenoic acids were strongly and significantly induced in macrophages stimulated with oxLDL. Importantly, the main metabolites responsible for the THP1-macrophage response to oxLDL exposure were the oxidative stress markers 5-epi-5-F_2t-IsoP, 15-E_1t-IsoP, 8-F_3t-IsoP and 15-keto-15-F_2t-IsoP as well as inflammatory markers PGDM, 17-trans-PGF_3α, and 11β-PGF_2α, all of which are reported here, for the first time, to function in the interaction of oxLDL with THP-1 macrophages. By contrast, a salvage pathway mediated by anti-inflammatory PGs (PGE₁ and 17-trans-PGF_3α) was also identified, suggesting a response to oxLDL-induced injury. In conclusion, when THP-1 macrophages were treated with oxLDL, a specific induction of biomarkers related to oxidative stress and inflammation was triggered. This work contributes to our understanding of initial atherogenic events mediated by oxLDL-macrophage interactions and helps to generate new approaches for their modulation.

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OxLDL has a potent impact on the oxylipin profiles in THP-1 human macrophages.

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OxLDL induces biomarkers of oxidation and inflammation in THP-1 human macrophages.

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Human Macrophages produce anti-inflammatory prostaglandins after oxLDL exposure.

Global assessment of oxidized free fatty acids in brain reveals an enzymatic predominance to oxidative signaling after trauma

Traumatic brain injury (TBI) is a major health problem associated with significant morbidity and mortality. The pathophysiology of TBI is complex involving signaling through multiple cascades, including lipid peroxidation. Oxidized free fatty acids, a prominent product of lipid peroxidation, are potent cellular mediators involved in induction and resolution of inflammation and modulation of vasomotor tone. While previous studies have assessed lipid peroxidation after TBI, to our knowledge no studies have used a systematic approach to quantify the global oxidative changes in free fatty acids. In this study, we identified and quantified 244 free fatty acid oxidation products using a newly developed global liquid chromatography tandem-mass spectrometry (LC-MS/MS) method. This methodology was used to follow the time course of these lipid species in the contusional cortex of our pediatric rat model of TBI. We show that oxidation peaked at 1h after controlled cortical impact and was progressively attenuated at 4 and 24h time points. While enzymatic and non-enzymatic pathways were activated at 1h post-TBI, enzymatic lipid peroxidation was the predominant mechanism with 15-lipoxygenase (LOX) contributing to the majority of total oxidized fatty acid content. Pro-inflammatory lipid mediators were significantly increased at 1 and 4h after TBI with return to basal levels by 24h. Anti-inflammatory lipid mediators remained significantly increased across all three time points, indicating an elevated and sustained anti-inflammatory response following TBI.

Characterization of the changes in eicosanoid profiles of activated macrophages treated with 20(S)-ginsenoside Rg3

In this study, we used ultra-performance liquid chromatography coupled with tandem mass spectrometry to assess the levels of eicosanoids from RAW264.7 macrophages treated with lipopolysaccharides (LPS) and 20(S)-ginsenoside Rg3 (Rg3). The production of nitric oxide (NO) and the secretion of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were increased in inflammatory macrophages treated with LPS. Rg3 treatment, however, decreased the levels of NO, TNF-α, and IL-6 in activated macrophages. Eicosanoids, known as major metabolites correlated with inflammation, have pro- or anti-inflammatory activities. For a detailed characterization of the eicosanoids altered by treatment with LPS and Rg3, the eicosanoids were profiled by multiple reaction monitoring. A total of 69 macrophage eicosanoids were analyzed and the profiling dataset was statistically analyzed. Principal component and hierarchical cluster analyses differentiated control cells from cells treated with LPS, Rg3, or LPS+Rg3 for 12 or 24h. Furthermore, 18 differentially regulated eicosanoids were found between macrophages treated with LPS for 24h and those treated with LPS+Rg3 for 24h (fold change>2, p value<0.05). These results indicate that Rg3 alters eicosanoid metabolism in activated macrophages treated with LPS. Furthermore, we also identified several eicosanoids correlated with the anti-inflammatory activity of Rg3.

Specific plasma oxylipins increase the odds of cardiovascular and cerebrovascular events in patients with peripheral artery disease

Oxylipins and fatty acids may be novel therapeutic targets for cardiovascular disease. The objective was to determine if plasma oxylipins or fatty acids can influence the odds of cardiovascular/cerebrovascular events. In 98 patients (25 female, 73 male) with peripheral artery disease, the prevalence of transient ischemic attacks, cerebrovascular accidents, stable angina, and acute coronary syndrome was n = 16, 10, 16, and 24, respectively. Risk factors such as being male, diagnosed hypertension, diabetes mellitus, and hyperlipidemia were not associated with events. Plasma fatty acids and oxylipins were analyzed with gas chromatography and HPLC-MS/MS, respectively. None of 24 fatty acids quantified were associated with events. In contrast, 39 plasma oxylipins were quantified, and 8 were significantly associated with events. These 8 oxylipins are known regulators of vascular tone. For example, every 1 unit increase in Thromboxane B₂/Prostaglandin F_1α and every 1 nmol/L increase in plasma 16-hydroxyeicosatetraenoic acid, thromboxane B2, or 11,12-dihydroxyeicosatrienoic acid (DiHETrE) increased the odds of having had ≥2 events versus no event (p < 0.05). The greatest predictor was plasma 8,9-DiHETrE, which increased the odds of acute coronary syndrome by 92-fold. In conclusion, specific oxylipins were highly associated with clinical events and may represent specific biomarkers and (or) therapeutic targets of cardiovascular disease.

Fatty acid-related modulations of membrane fluidity in cells: detection and implications

Metabolic homeostasis of fatty acids is complex and well-regulated in all organisms. The biosynthesis of saturated fatty acids (SFA) in mammals provides substrates for β-oxidation and ATP production. Monounsaturated fatty acids (MUFA) are products of desaturases that introduce a methylene group in cis geometry in SFA. Polyunsaturated fatty acids (n-6 and n-3 PUFA) are products of elongation and desaturation of the essential linoleic acid and α-linolenic acid, respectively. The liver processes dietary fatty acids and exports them in lipoproteins for distribution and storage in peripheral tissues. The three types of fatty acids are integrated in membrane phospholipids and determine their biophysical properties and functions. This study was aimed at investigating effects of fatty acids on membrane biophysical properties under varying nutritional and pathological conditions, by integrating lipidomic analysis of membrane phospholipids with functional two-photon microscopy (fTPM) of cellular membranes. This approach was applied to two case studies: first, pancreatic beta-cells, to investigate hormetic and detrimental effects of lipids. Second, red blood cells extracted from a genetic mouse model defective in lipoproteins, to understand the role of lipids in hepatic diseases and metabolic syndrome and their effect on circulating cells.

Polarization of Macrophages toward M2 Phenotype Is Favored by Reduction in iPLA2β (Group VIA Phospholipase A2)

Macrophages are important in innate and adaptive immunity. Macrophage participation in inflammation or tissue repair is directed by various extracellular signals and mediated by multiple intracellular pathways. Activation of group VIA phospholipase A₂ (iPLA₂β) causes accumulation of arachidonic acid, lysophospholipids, and eicosanoids that can promote inflammation and pathologic states. We examined the role of iPLA₂β in peritoneal macrophage immune function by comparing wild type (WT) and iPLA₂β^-/- mouse macrophages. Compared with WT, iPLA₂β^-/- macrophages exhibited reduced proinflammatory M1 markers when classically activated. In contrast, anti-inflammatory M2 markers were elevated under naïve conditions and induced to higher levels by alternative activation in iPLA₂β^-/- macrophages compared with WT. Induction of eicosanoid (12-lipoxygenase (12-LO) and cyclooxygenase 2 (COX2))- and reactive oxygen species (NADPH oxidase 4 (NOX4))-generating enzymes by classical activation pathways was also blunted in iPLA₂β^-/- macrophages compared with WT. The effects of inhibitors of iPLA₂β, COX2, or 12-LO to reduce M1 polarization were greater than those to enhance M2 polarization. Certain lipids (lysophosphatidylcholine, lysophosphatidic acid, and prostaglandin E₂) recapitulated M1 phenotype in iPLA₂β^-/- macrophages, but none tested promoted M2 phenotype. These findings suggest that (a) lipids generated by iPLA₂β and subsequently oxidized by cyclooxygenase and 12-LO favor macrophage inflammatory M1 polarization, and (b) the absence of iPLA₂β promotes macrophage M2 polarization. Reducing macrophage iPLA₂β activity and thereby attenuating macrophage M1 polarization might cause a shift from an inflammatory to a recovery/repair milieu.

Repair Mechanisms in Oxidant-Driven Chronic Inflammatory Disease

The interplay that governs chronic diseases through pathways specifically associated with chronic inflammation remains undefined. Many metabolic events have been identified during the injury and repair process. Nonetheless, the cellular events that control the pathogenesis of inflammation-induced disease have not been fully characterized. We and others reason that chronic inflammatory diseases associated with a cascade of complex network mediators, such as nitric oxide, arachidonic acid metabolites, cytokines, and reactive oxygen species, play a significant role in the governance of alterations in homeostasis, oxidative stress, and thromboatherosclerosis. In this context, we discuss lipid mediators associated with the maintenance of health, including the specialized proresolving mediators that help drive cellular repair. Emphasis is placed on the pathophysiology of chronic metabolic insults involving both the airways and the cardiovascular system during oxidant-driven inflammatory disease. In this review, we highlight new pathways of inquiry that show promise for the identification of those metabolic targets that can improve therapy for chronic inflammation.

UPLC-MS/MS-Based Profiling of Eicosanoids in RAW264.7 Cells Treated with Lipopolysaccharide

While both the pro- and anti-inflammatory effects of several eicosanoids have been widely studied, the degree of inflammation in cells that results from various eicosanoids has yet to be comprehensively studied. The objective of this study was to assess the effect of lipopolysaccharide (LPS) treatment on eicosanoid content in RAW264.7 cells. An Ultra performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS)-based profiling method was used to analyze the eicosanoid contents of RAW264.7 cells treated with different LPS concentrations. The profiling data were subjected to statistical analyses, such as principal component analysis (PCA) and hierarchical clustering analysis. LPS treatment increased nitric oxide production and secretion of pro-inflammatory cytokines, such as tumor necrosis factor-α and interleukin-6, in a concentration-dependent manner. In total, 79 eicosanoids were identified in the cells. RAW264.7 cells treated with different LPS concentrations were well differentiated in the PCA score plot. A heatmap was used to identify the eicosanoids that were up- or down-regulated according to the degree of inflammation and LPS concentration. Thirty-nine eicosanoids were upregulated and seven were down-regulated by LPS treatment in a concentration-dependent manner. Our novel UPLC-MS/MS technique can profile eicosanoids, and can evaluate the correlations between inflammation and eicosanoid metabolism.

Iron and a mixture of DHA and EPA supplementation, alone and in combination, affect bioactive lipid signalling and morbidity of iron deficient South African school children in a two-by-two randomised controlled trial

We recently reported that iron supplementation increased respiratory morbidity in iron deficient South African children. This increase, however, was attenuated when iron was provided in combination with a mixture of DHA/EPA. To explore potential underlying mechanisms, we examined the effects of iron and DHA/EPA, alone and in combination, on plasma lipid-derived immune modulator concentrations and related gene expression in peripheral blood mononuclear cells (PBMC). DHA/EPA decreased inflammatory 12-hydroxyeicosatetraenoic acid and tended to increase anti-inflammatory and pro-resolving 17-hydroxydocosahexaenoic acid (17-HDHA), while iron decreased 17-HDHA. However, in combination with iron, the anti-inflammatory effect of DHA/EPA was maintained. These biochemical changes may explain the prevention of iron-induced respiratory morbidity that we observed when iron was supplemented in combination with DHA/EPA during the 8.5 month randomised controlled trial and might lead to a safer approach of delivering iron supplementation. The study was registered at clinicaltrials.gov as NCT01092377.

Down-regulation of NF-κB expression by n-3 fatty acid-rich linseed oil is modulated by PPARγ activation, eicosanoid cascade and secretion of cytokines by macrophages in rats fed partially hydrogenated vegetable fat

PURPOSE

The industrially produced partially hydrogenated vegetable fat (PHVF) contains trans fatty acid mostly comprising of elaidic acid (18:1 ∆9t). PHVF is used as a cooking medium in Southeast Asian countries. The purpose of this study is to evaluate the effects of dietary PHVF on inflammatory mediators and possible ameliorative effects of n-3 fatty acid (α-linolenic acid, ALA)-rich linseed oil (LSO) on the inflammatory mediators.

METHODS

Male Wistar weaning rats were fed AIN-93-purified diet supplemented with one of the following lipids for 60 days, groundnut oil (GNO, 10 wt%), PHVF (10 wt%), LSO (10 wt%), PHVF blended with LSO at 2.5, 5.0 and 7.5 wt% levels. The final fat level in the diet was maintained at 10 wt%.

RESULTS

The macrophages from rats fed PHVF showed higher levels of total cholesterol and free cholesterol as compared to those from rats fed GNO and LSO. Macrophages from rats fed PHVF down-regulated the expression of PPARγ and up-regulated the expressions of cytosolic phospholipase A₂, cyclooxygenase-2, 5-lipoxygenase and nuclear factor-kappa B p65. The macrophages from rats fed PHVF secreted higher levels of pro-inflammatory eicosanoids and cytokines. The rats fed PHVF blended with LSO at incremental amounts showed a significant reduction in the expressions of pro-inflammatory markers in dose-dependent manner.

CONCLUSION

Detrimental effects of dietary PHVF in enhancing pro-inflammatory agents in rats could be significantly reduced by providing ALA (n-3 PUFA)-rich LSO.

Phospholipase C δ1 in macrophages negatively regulates TLR4-induced proinflammatory cytokine production and Fcγ receptor-mediated phagocytosis

Macrophages are key players in the innate immune response. Turnover of phosphoinositides (PI), particularly phosphatidylinositol 4,5 bisphosphate (PI(4,5)P2), has been implicated in macrophage functions such as toll-like receptor (TLR)-mediated cytokine production and phagocytosis. However, PI metabolizing enzymes responsible for macrophage functions are not well defined. The phospholipase C (PLC) family of enzymes is critical in PI(4,5)P2 turnover. In this study, we investigated the role of PLCδ1, a prototype PLC, in macrophages on the expression of inflammation-associated genes and phagocytosis. Lipopolysaccharides (LPS) signal through TLR4 to produce proinflammatory cytokines such as interleukin (IL)-1β. LPS stimulation of both RAW264.7 murine macrophages and murine bone marrow-derived macrophages resulted in lower PLCδ1 mRNA and protein expression levels, compared to that in the control. Using chemical inhibitor compounds, we demonstrated that the up-regulation of p38 MAPK activity led to down-regulation of PLCδ1 mRNA expression in macrophages. PLCδ1 reduction by RNAi or gene deletion resulted in greater LPS-induced IL-1β expression than that observed in the control siRNA-treated cells, without increasing TLR4 cell surface expression. PLCδ1 also negatively regulated LPS-induced cell spreading. Analysis of Fcγ receptor-mediated phagocytosis demonstrated an increased phagocytosis index after PLCδ1 knockdown in RAW264.7 cells. Conversely, overexpression of PLCδ1 reduced phagocytosis whereas catalytic inactive PLCδ1 had no effect. Altered levels of PLCδ1 affected the binding of opsonized latex beads with cells, rather than the phagocytic activity. Taken together, the data suggest that PLCδ1 negatively regulates LPS-induced production of IL-1β and Fcγ receptor-mediated phagocytosis in macrophages.

Integrated metabolic modelling reveals cell-type specific epigenetic control points of the macrophage metabolic network

BACKGROUND

The reconstruction of context-specific metabolic models from easily and reliably measurable features such as transcriptomics data will be increasingly important in research and medicine. Current reconstruction methods suffer from high computational effort and arbitrary threshold setting. Moreover, understanding the underlying epigenetic regulation might allow the identification of putative intervention points within metabolic networks. Genes under high regulatory load from multiple enhancers or super-enhancers are known key genes for disease and cell identity. However, their role in regulation of metabolism and their placement within the metabolic networks has not been studied.

METHODS

Here we present FASTCORMICS, a fast and robust workflow for the creation of high-quality metabolic models from transcriptomics data. FASTCORMICS is devoid of arbitrary parameter settings and due to its low computational demand allows cross-validation assays. Applying FASTCORMICS, we have generated models for 63 primary human cell types from microarray data, revealing significant differences in their metabolic networks.

RESULTS

To understand the cell type-specific regulation of the alternative metabolic pathways we built multiple models during differentiation of primary human monocytes to macrophages and performed ChIP-Seq experiments for histone H3 K27 acetylation (H3K27ac) to map the active enhancers in macrophages. Focusing on the metabolic genes under high regulatory load from multiple enhancers or super-enhancers, we found these genes to show the most cell type-restricted and abundant expression profiles within their respective pathways. Importantly, the high regulatory load genes are associated to reactions enriched for transport reactions and other pathway entry points, suggesting that they are critical regulatory control points for cell type-specific metabolism.

CONCLUSIONS

By integrating metabolic modelling and epigenomic analysis we have identified high regulatory load as a common feature of metabolic genes at pathway entry points such as transporters within the macrophage metabolic network. Analysis of these control points through further integration of metabolic and gene regulatory networks in various contexts could be beneficial in multiple fields from identification of disease intervention strategies to cellular reprogramming.

Arachidonic acid-derived signaling lipids and functions in impaired healing

Very little is known about lipid function during wound healing, and much less during impaired healing. Such understanding will help identify what roles lipid signaling plays in the development of impaired/chronic wounds. We took a lipidomics approach to study the alterations in lipid profile in the LIGHT(-/-) mouse model of impaired healing which has characteristics that resemble those of impaired/chronic wounds in humans, including high levels of oxidative stress, excess inflammation, increased extracellular matrix degradation and blood vessels with fibrin cuffs. The latter suggests excess coagulation and potentially increased platelet aggregation. We show here that in these impaired wounds there is an imbalance in the arachidonic acid (AA) derived eicosonoids that mediate or modulate inflammatory reactions and platelet aggregation. In the LIGHT(-/-) impaired wounds there is a significant increase in enzymatically derived breakdown products of AA. We found that early after injury there was a significant increase in the eicosanoids 11-, 12-, and 15-hydroxyeicosa-tetranoic acid, and the proinflammatory leukotrienes (LTD4 and LTE) and prostaglandins (PGE2 and PGF2α ). Some of these eicosanoids also promote platelet aggregation. This led us to examine the levels of other eicosanoids known to be involved in the latter process. We found that thromboxane (TXA2 /B2 ), and prostacyclins 6kPGF1α are elevated shortly after wounding and in some cases during healing. To determine whether they have an impact in platelet aggregation and hemostasis, we tested LIGHT(-/-) mouse wounds for these two parameters and found that, indeed, platelet aggregation and hemostasis are enhanced in these mice when compared with the control C57BL/6 mice. Understanding lipid signaling in impaired wounds can potentially lead to development of new therapeutics or in using existing nonsteroidal anti-inflammatory agents to help correct the course of healing.

Understanding the Mysterious M2 Macrophage through Activation Markers and Effector Mechanisms

The alternatively activated or M2 macrophages are immune cells with high phenotypic heterogeneity and are governing functions at the interface of immunity, tissue homeostasis, metabolism, and endocrine signaling. Today the M2 macrophages are identified based on the expression pattern of a set of M2 markers. These markers are transmembrane glycoproteins, scavenger receptors, enzymes, growth factors, hormones, cytokines, and cytokine receptors with diverse and often yet unexplored functions. This review discusses whether these M2 markers can be reliably used to identify M2 macrophages and define their functional subdivisions. Also, it provides an update on the novel signals of the tissue environment and the neuroendocrine system which shape the M2 activation. The possible evolutionary roots of the M2 macrophage functions are also discussed.

Opposite cross-talk by oleate and palmitate on insulin signaling in hepatocytes through macrophage activation

Chronic low grade inflammation in adipose tissue during obesity is associated with an impairment of the insulin signaling cascade. In this study, we have evaluated the impact of palmitate or oleate overload of macrophage/Kupffer cells in triggering stress-mediated signaling pathways, in lipoapoptosis, and in the cross-talk with insulin signaling in hepatocytes. RAW 264.7 macrophages or Kupffer cells were stimulated with oleate or palmitate, and levels of M1/M2 polarization markers and the lipidomic profile of eicosanoids were analyzed. Whereas proinflammatory cytokines and total eicosanoids were elevated in macrophages/Kupffer cells stimulated with palmitate, enhanced arginase 1 and lower leukotriene B4 (LTB4) levels were detected in macrophages stimulated with oleate. When hepatocytes were pretreated with conditioned medium (CM) from RAW 264.7 or Kupffer cells loaded with palmitate (CM-P), phosphorylation of stress kinases and endoplasmic reticulum stress signaling was increased, insulin signaling was impaired, and lipoapoptosis was detected. Conversely, enhanced insulin receptor-mediated signaling and reduced levels of the phosphatases protein tyrosine phosphatase 1B (PTP1B) and phosphatase and tensin homolog (PTEN) were found in hepatocytes treated with CM from macrophages stimulated with oleate (CM-O). Supplementation of CM-O with LTB4 suppressed insulin sensitization and increased PTP1B and PTEN. Furthermore, LTB4 decreased insulin receptor tyrosine phosphorylation in hepatocytes, activated the NFκB pathway, and up-regulated PTP1B and PTEN, these effects being mediated by LTB4 receptor BTL1. In conclusion, oleate and palmitate elicit an opposite cross-talk between macrophages/Kupffer cells and hepatocytes. Whereas CM-P interferes at the early steps of insulin signaling, CM-O increases insulin sensitization, possibly by reducing LTB4.

n-3 Fatty acids as resolvents of inflammation in the A549 cells

BACKGROUND

Fatty acids and their derivatives are one of the most crucial inflammation mediators. The aim of our study was to evaluate the impact of polyunsaturated fatty acids as eicosanoids precursors on the A549 cell line.

METHODS

Cells were incubated with 40 μM of arachidonic, eicosapentaenoic or docosahexaenoic acid for 24h, then activated with LPS. Fatty acids content in the cell membranes were determined using gas chromatography. COX-2, cPGES and FP-receptor quantities were determined by Western blot. 8-Isoprostane F2α concentrations were determined by EIA. Maresin and protectin D1 contents were analyzed by UHPLC/MS-TOF method.

RESULTS

Significant differences in membrane fatty acids and levels of 8-isoPGF2α in the activated cells were detected. Elevated expression of COX-2 and FP-receptor was observed in cells treated with AA and activated with LPS. Moreover, compared to AA and AA+LPS groups, cells incubated with EPA, DHA, EPA+LPS and DHA+LPS showed decreased expression of COX-2, cPGES and FP-receptor. In cells incubated with EPA or DHA and activated with LPS maresin and protectin D1 were detected.

CONCLUSIONS

The results of the study have revealed the pro-inflammatory properties of AA, while the EPA and DHA had the opposite, resolving effect. Interestingly, FP-receptor inhibition by EPA and DHA demonstrated the unique role of the FP-receptor as a potential target for antagonists, in the diseases of inflammatory character. This study provides new information about n-3 fatty acids and their pro-resolving mediators, which can be used in the process of developing new anti-inflammatory drugs.

Lipid rafts as major platforms for signaling regulation in cancer

Cell signaling does not apparently occur randomly over the cell surface, but it seems to be integrated very often into cholesterol-rich membrane domains, termed lipid rafts. Membrane lipid rafts are highly ordered membrane domains that are enriched in cholesterol, sphingolipids and gangliosides, and behave as major modulators of membrane geometry, lateral movement of molecules, traffic and signal transduction. Because the lipid and protein composition of membrane rafts differs from that of the surrounding membrane, they provide an additional level of compartmentalization, serving as sorting platforms and hubs for signal transduction proteins. A wide number of signal transduction processes related to cell adhesion, migration, as well as to cell survival and proliferation, which play major roles in cancer development and progression, are dependent on lipid rafts. Despite lipid rafts harbor mainly critical survival signaling pathways, including insulin-like growth factor I (IGF-I)/phosphatidylinositol 3-kinase (PI3K)/Akt signaling, recent evidence suggests that these membrane domains can also house death receptor-mediated apoptotic signaling. Recruitment of this death receptor signaling pathway in membrane rafts can be pharmacologically modulated, thus opening up the possibility to regulate cell demise with a therapeutic use. The synthetic ether phospholipid edelfosine shows a high affinity for cholesterol and accumulates in lipid rafts in a number of malignant hematological cells, leading to an efficient in vitro and in vivo antitumor activity by inducing translocation of death receptors and downstream signaling molecules to these membrane domains. Additional antitumor drugs have also been shown to act, at least in part, by recruiting death receptors in lipid rafts. The partition of death receptors together with downstream apoptotic signaling molecules in membrane rafts has led us to postulate the concept of a special liquid-ordered membrane platform coined as "cluster of apoptotic signaling molecule-enriched rafts" (CASMER), referring to raft platforms enriched in apoptotic molecules. CASMERs act as scaffolds for apoptosis signaling compartmentalization, facilitating and stabilizing protein-protein interactions by local assembly of cross-interacting molecules, which leads to apoptosis amplification and a decrease in apoptotic signal threshold. Edelfosine also displaced survival PI3K/Akt signaling from lipid rafts, leading to Akt inhibition, in mantle cell lymphoma cells. Thus, membrane rafts could act as scaffold structures where segregation of pro- from anti-apoptotic molecules could take place. In this review, we summarize our view of how reorganization of the protein composition of lipid raft membrane domains regulates cell death and therefore it might be envisaged as a novel target in the treatment of cancer.

Lipidome of atherosclerotic plaques from hypercholesterolemic rabbits

The cellular, macromolecular and neutral lipid composition of the atherosclerotic plaque has been extensively characterized. However, a comprehensive lipidomic analysis of the major lipid classes within atherosclerotic lesions has not been reported. The objective of this study was to produce a detailed framework of the lipids that comprise the atherosclerotic lesion of a widely used pre-clinical model of plaque progression. Male New Zealand White rabbits were administered regular chow supplemented with 0.5% cholesterol (HC) for 12 weeks to induce hypercholesterolemia and atherosclerosis. Our lipidomic analyses of plaques isolated from rabbits fed the HC diet, using ultra-performance liquid chromatography (UPLC) and high-resolution mass spectrometry, detected most of the major lipid classes including: Cholesteryl esters, triacylglycerols, phosphatidylcholines, sphingomyelins, diacylglycerols, fatty acids, phosphatidylserines, lysophosphatidylcholines, ceramides, phosphatidylglycerols, phosphatidylinositols and phosphatidylethanolamines. Given that cholesteryl esters, triacylglycerols and phosphatidylcholines comprise greater than 75% of total plasma lipids, we directed particular attention towards the qualitative and quantitative assessment of the fatty acid composition of these lipids. We additionally found that sphingomyelins were relatively abundant lipid class within lesions, and compared the abundance of sphingomyelins to their precursor phosphatidylcholines. The studies presented here are the first approach to a comprehensive characterization of the atherosclerotic plaque lipidome.

Fatty acids and cardiac disease: fuel carrying a message

From the viewpoint of the prevention of cardiovascular disease (CVD) burden, there has been a continuous interest in the detrimental effects of the Western-type high-fat diet for more than half a century. More recently, this general view has been subject to change as epidemiological studies showed that replacing fat by carbohydrate may even be worse and that various polyunsaturated fatty acids (FA) have beneficial rather than detrimental effects on CVD outcome. At the same time, advances in lipid biology have provided insight into the mechanisms by which the different lipid components of the Western diet affect the cardiovascular system. In fact, this still is a rapidly growing field of research and in recent years novel FA derivatives and FA receptors have been discovered. This includes fish-oil derived FA-derivatives with anti-inflammatory properties, the so-called resolvins, and various G-protein-coupled receptors that recognize FA as ligands. In the present review, we will extensively discuss the role of FA and their metabolites on cardiac disease, with special emphasis on the role of the different saturated and polyunsaturated FA and their respective metabolites in cellular signal transduction and the possible implications for the development of cardiac hypertrophy and cardiac failure.

Lipid-metabolizing CYPs in the regulation and dysregulation of metabolism

The cytochrome P450s (CYPs) represent a highly divergent class of enzymes involved in the oxidation of organic compounds. A subgroup of CYPs metabolize ω3-arachidonic and linoleic acids and ω6-docosahexaenoic and eicosapentaenoic polyunsaturated fatty acids (PUFAs) into a series of related biologically active mediators. Over the past 20 years, increasing evidence has emerged for a role of these PUFA-derived mediators in physiological and pathophysiological processes in the vasculature, during inflammation, and in the regulation of metabolism. With recent technological advances and increased availability of lipid mass spectroscopy, we are now starting to discern the patterns of these CYP-PUFA products in health and disease. These analyses not only are revealing the diverse spectrum of lipid nutrients regulated by CYPs, but also clearly indicate that the balance of these mediators changes with dietary intake of different PUFA classes. These findings suggest that we are only just beginning to understand all of the relevant lipid species produced by CYP pathways. Moreover, we are still a long way from understanding the nature and presence of their receptors, their tissue expression, and the pathophysiological processes they regulate. This review highlights these future issues in the context of lipid-metabolizing CYP enzymes, focusing particularly on the CYP450 family of epoxygenases and the lipid mediators they produce.