Therapeutic implications of disorders of cell death signalling: membranes, micro-environment, and eicosanoid and docosanoid metabolism

Identification of differentially expressed genes and the role of PDK4 in CD14+ monocytes of coronary artery disease

Background. Coronary artery disease (CAD) is a chronic inflammatory disease caused by development of atherosclerosis (AS), which is the leading cause of mortality and disability. Our study aimed to identify the differentially expressed genes (DEGs) in CD14⁺ monocytes from CAD patients compared with those from non-CAD controls, which might pave the way to diagnosis and treatment for CAD. Methods. The RNA-sequencing (RNA-seq) was performed by BGISEQ-500, followed by analyzing with R package to screening DEGs. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed by R package. In addition, we validated the results of RNA-seq using real-time quantitative polymerase chain reaction (RT-qPCR). Furthermore, we explored the function of selected ten genes in LDL-treated CD14⁺ monocytes by RT-qPCR. Results. a total of 2897 DEGs were identified, including 753 up- and 2144 down-regulated genes in CD14⁺ monocytes from CAD patients. These DEGs were mainly enriched in plasma membrane and cell periphery of cell component, immune system process of biological process, NF-κB signaling pathway, cell adhesion molecules signaling pathway and cytokine–cytokine receptor interaction signaling pathway. In LDL-treated CD14⁺ monocytes, the mRNA expression of pyruvate dehydrogenase kinase 4 (PDK4) was significantly up-regulated. Conclusion. In the present study, we suggested that PDK4 might play a role in progression of CAD. The study will provide some pieces of evidence to investigate the role and mechanism of key genes in the pathogenesis of CAD.

Immunomodulatory Activities of Body Wall Fatty Acids Extracted from Halocynthia aurantium on RAW264.7 Cells

Tunicates are known to contain biologically active materials and one species in particular, the sea peach (Halocynthia aurantium), has not been thoroughly studied. In this study we aimed to analyze the fatty acids profile of the H. aurantium body wall and its immunomodulatory effects on RAW264.7 macrophage-like cells. The fatty acids were classified into three categories: saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), and polyunsaturated fatty acids (PUFAs). Omega-3 fatty acid content, including EPA and DHA, was higher than omega-6 fatty acids. H. aurantium body wall fatty acids exhibited enhanced immune response and anti-inflammatory effects on RAW264.7 macrophage-like cells. Under normal conditions, fatty acids significantly increase nitric oxide (NO) and PGE₂ production in a dose-dependent manner, thereby improving the immune response. On the other hand, in LPS-treated RAW264.7 cells, fatty acids significantly decreased nitric oxide (NO) and PGE2 production in a dose-dependent manner, thereby enhancing anti-inflammatory effects. Fatty acids transcriptionally control the expression of the immune-associated genes, iNOS, IL-1β, IL-6, COX-2, and TNF-α, via the MAPK and NF-κB signaling cascades in RAW264.7 cells. However, in LPSstimulated RAW264.7 cells, H. aurantium body wall fatty acids significantly inhibited expression of inflammatory cytokine; similarly, production of COX-2 and PGE₂ was inhibited. The results of our present study provide insight into the immune-improving and anti-inflammatory effects of H. aurantium body wall fatty acids on macrophages. In addition, our study demonstrates that H. aurantium body wall is a potential source of immune regulatory components.

Insights into the mechanism of inhibition of phospholipase A2 by resveratrol: An extensive molecular dynamics simulation and binding free energy calculation

Phospholipase A2 (PLA2) is one of the enzymes involved in the development of cardiovascular diseases, vascular inflammation, risk of heart attacks, and strokes. This enzyme is responsible for catalyzing the hydrolytic cleavage of ester bonds of phospholipids in the biological pathway of inflammation. To prevent the undesired hydrolysis of phospholipids, the catalytic activity of PLA2 needs to be blocked. Resveratrol is a plant-derived polyphenol inhibitor, proven to have anti-inflammatory properties. However, there is still substantial ambiguity about its inhibitory function. The present study uncovers a detailed molecular mechanism behind the resveratrol action in inhibition of PLA2, by applying and comparing two 200-ns molecular dynamics simulations. The results of structural analyses revealed that the binding of resveratrol to PLA2 reduces the content of β-sheets and increases a 5-helix to PLA2 structure, producing more folding and stability in protein. In the active site, the resveratrol is placed between the N-terminal α-helix and the newly formed 5-helix through the hydrophobic interactions with ILE19 and LEU3 residues, as well as the hydrogen bond interactions. These interactions play the role of a network at the entrance of the enzyme active site and prevent the penetration of water molecules into the PLA2 cavity. A high occupancy hydrogen bonding has been identified between SER23 of the protein and hydroxyl group of resveratrol. Furthermore, the estimation of binding free energy verified the binding affinity of resveratrol is thermodynamically sufficient to be stably bounded to PLA2. It also proved that the van der Waals interactions, particularly hydrophobic interactions, have the most significant role in PLA2-resveratrol binding and stability. Overall, our results provide useful information on the stepwise mechanism of the inhibition of PLA2 enzyme by resveratrol, as a target for improving the pharmacological applications.

Biological Role of Unsaturated Fatty Acid Desaturases in Health and Disease

Polyunsaturated fatty acids (PUFAs) are considered one of the most important components of cells that influence normal development and function of many organisms, both eukaryotes and prokaryotes. Unsaturated fatty acid desaturases play a crucial role in the synthesis of PUFAs, inserting additional unsaturated bonds into the acyl chain. The level of expression and activity of different types of desaturases determines profiles of PUFAs. It is well recognized that qualitative and quantitative changes in the PUFA profile, resulting from alterations in the expression and activity of fatty acid desaturases, are associated with many pathological conditions. Understanding of underlying mechanisms of fatty acid desaturase activity and their functional modification will facilitate the development of novel therapeutic strategies in diseases associated with qualitative and quantitative disorders of PUFA.

Omega-3 Fatty Acids Survey in Men under Active Surveillance for Prostate Cancer: from Intake to Prostate Tissue Level

Dietary omega-3 fatty acids (ω3), particularly long-chain ω3 (LCω3), have protective effects against prostate cancer (PCa) in experimental studies. Observational studies are conflicting, possibly because of the biomarker used. This study aimed at evaluating associations between grade reclassification and ω3 levels assessed in prostatic tissue, red blood cells (RBC), and diet. We conducted a validation cross-sectional study nested within a phase II clinical trial. We identified 157 men diagnosed with low-risk PCa who underwent a first active surveillance repeat prostate biopsy session. Fatty acid (FA) intake was assessed using a food frequency questionnaire and their levels measured in prostate tissue and RBC. Associations were evaluated using logistic regression. At first repeat biopsy session, 39 (25%) men had high-grade PCa (grade group ≥2). We found that high LCω3-eicosapentaenoic acid (EPA) level in prostate tissue (odds ratio (OR) 0.25; 95% (confidence interval (CI) 0.08–0.79; p-trend = 0.03) was associated with lower odds of high-grade PCa. Similar results were observed for LCω3 dietary intake (OR 0.30; 95% CI 0.11-0.83; p-trend = 0.02) but no association for RBC. LCω3-EPA levels in the target prostate tissue are inversely associated with high-grade PCa in men with low-risk PCa, supporting that prostate tissue FA, but not RBC FA, is a reliable biomarker of PCa risk.

Immune-Enhancement and Anti-Inflammatory Activities of Fatty Acids Extracted from Halocynthia aurantium Tunic in RAW264.7 Cells

Halocynthia aurantium, an edible ascidian species, has not been studied scientifically, even though tunicates and ascidians are well-known to contain several unique and biologically active materials. The current study investigated the fatty acid profiles of the H. aurantium tunic and its immune-regulatory effects on RAW264.7 macrophage cells. Results of the fatty acid profile analysis showed a difference in ratios, depending on the fatty acids being analysed, including those of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA). In particular, omega-3 fatty acids, such as eicosatrienoic acid n-3 (ETA n-3), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), were much higher than omega-6 fatty acids. Moreover, the H. aurantium tunic fatty acids, significantly and dose-dependently, increased the NO and prostaglandin E2 (PGE₂) production in RAW264.7 cells, for immune-enhancement without cytotoxicity. In addition, these fatty acids regulated the transcription of immune-associated genes, including iNOS, IL-1β, IL-6, COX-2, and TNF-α. These actions were activated and deactivated via Mitogen-activated protein kinase (MAPK)and NF-κB signaling, to regulate the immune responses. Conversely, the H. aurantium tunic fatty acids effectively suppressed the inflammatory cytokine expressions, including iNOS, IL-1β, IL-6, COX-2, and TNF-α, in LPS-stimulated RAW264.7 cells. Productions of COX-2 and PGE₂, which are key biomarkers for inflammation, were also significantly reduced. These results elucidated the immune-enhancement and anti-inflammatory mechanisms of the H. aurantium tunic fatty acids in macrophage cells. Moreover, the H. aurantium tunic might be a potential fatty acid source for immune-modulation.

The prostaglandin EP4 receptor is a master regulator of the expression of PGE2 receptors following inflammatory activation in human monocytic cells

Prostaglandin E₂ (PGE₂) is responsible for inflammatory symptoms. However, PGE₂ also suppresses pro-inflammatory cytokine production. There are at least 4 subtypes of PGE₂ receptors, EP1-EP4, but it is unclear which of these specifically control cytokine production. The aim of this study was to determine which of the different receptors, EP1R-EP4R modulate production of tumor necrosis factor-α (TNF-α) in human monocytic cells. Human blood, or the human monocytic cell line THP-1 were stimulated with LPS. The actions of PGE₂, alongside selective agonists of EP1-EP4 receptors, were assessed on LPS-induced TNF-α, IL-1β and IL-10 release. The expression profiles of EP2R and EP4R in monocytes and THP-1 cells were characterised by RT-qPCR. In addition, the production of cytokines was evaluated following knockdown of the receptors using siRNA and over-expression of the receptors by transfection with constructs. PGE₂ and also EP2 and EP4 agonists (but not EP1 or EP3 agonists) suppressed TNF-α production in blood and THP-1 cells. LPS also up regulated expression of EP2R and EP4R but not EP1 or EP3. siRNA for either EP2R or EP4R reversed the suppressive actions of PGE₂ on cytokine production and overexpression of EP2R and EP4R enhanced the suppressive actions of PGE₂. This indicates that PGE₂ suppression of TNF-α by human monocytic cells occurs via EP2R and EP4R expression. However EP4Rs also control their own expression and that of EP2 whereas the EP2R does not affect EP4R expression. This implies that EP4 receptors have an important master role in controlling inflammatory responses.

Structural Insight into Binding Mode of 9-Hydroxy Aristolochic Acid, Diclofenac and Indomethacin to PLA2

Phospholipase A₂ (PLA₂) catalyzes the hydrolysis of phospholipids into arachidonic acid and lysophospholipids. Arachidonic acid is modified by cyclooxygenases into active compounds called eicosanoids that act as signaling molecules in a number of physiological processes. Excessive production of eicosanoids leads to several pathological conditions such as inflammation. In order to block the inflammatory effect of these compounds, upstream enzymes such as PLA₂ are valid targets. In the present contribution, molecular dynamic analysis was performed to evaluate the binding of diclofenac, 9-hydroxy aristolochic acid (9-HAA) and indomethacin to PLA₂. Obtained results revealed that 9-HAA could form a more stable complex with PLA₂ when compared to diclofenac and indomethacin. Furthermore, analysis of intermolecular binding energy components indicated that hydrophobic interactions were dominant in binding process. On the basis of obtained data, inhibitors bearing fused rings with hydrogen acceptor/donor substituent(s) interacted with His48 and Asp49 residues of the active site. More affinity toward PLA₂ might be envisaged through negatively charged moieties via interaction with Trp31, Lys34 and Lys69.

Monooxygenase system in Guerin’s carcinoma of rats under conditions of ω-3 polyunsaturated fatty acids administration

The aim of the study was to determine the variations of function in components of monooxygenase system (MOS) of rat Guerin’s carcinoma under ω-3 polyunsaturated fatty acids (PUFAs) administration. The activity of Guerin’s carcinoma microsomal NADH-cytochrome b5 reductase, the content and the rate of cytochrome b5 oxidation-reduction, the content and the rate of cytochrome Р450 oxidation-reduction have been investigated in rats with tumor under conditions of ω-3 PUFAs administration. ω-3 PUFAs supplementation before and after transplantation of Guerin’s carcinoma resulted in the increase of NADH-cytochrome b5 reductase activity and decrease of cytochrome b5 level in the Guerin’s carcinoma microsomal fraction in the logarithmic phases of carcinogenesis as compared to the tumor-bearing rats. Increased activity of NADH-cytochrome b5 reductase facilitates higher electron flow in redox-chain of MOS. Under decreased cytochrome b5 levels the electrons are transferred to oxygen, which leads to heightened generation of superoxide (O2•-) in comparison to control. It was shown, that the decrease of cytochrome P450 level in the Guerin’s carcinoma microsomal fraction in the logarithmic phases of oncogenesis under ω-3 PUFAs administration may be associated with its transition into an inactive form – cytochrome P420. This decrease in cytochrome P450 coincides with increased generation of superoxide by MOS oxygenase chain.

Phytomedicine polypharmacology: Cancer therapy through modulating the tumor microenvironment and oxylipin dynamics

Integrative approaches in cancer therapy have recently been extended beyond the induction of cytotoxicity to controlling the tumor microenvironment and modulating inflammatory cascades and pathways such as lipid mediator biosynthesis and their dynamics. Profiling of important lipid messengers, such as oxylipins, produced as part of the physiological response to pharmacological stimuli, provides a unique opportunity to explore drug pharmacology and the possibilities for molecular management of cancer physiopathology. Whereas single targeted chemotherapeutic drugs commonly lack efficacy and invoke drug resistance and/or adverse effects in cancer patients, traditional herbal medicines are seen as bright prospects for treating complex diseases, such as cancers, in a systematic and holistic manner. Understanding the molecular mechanisms of traditional medicine and its bioactive chemical constituents may aid the modernization of herbal remedies and the discovery of novel phytoagents for cancer management. In this review, systems-based polypharmacology and studies to develop multi-target drugs or leads from phytomedicines and their derived natural products that may overcome the problems of current anti-cancer drugs, are proposed and summarized.

Fatty Acid Desaturases, Polyunsaturated Fatty Acid Regulation, and Biotechnological Advances

Polyunsaturated fatty acids (PUFAs) are considered to be critical nutrients to regulate human health and development, and numerous fatty acid desaturases play key roles in synthesizing PUFAs. Given the lack of delta-12 and -15 desaturases and the low levels of conversion to PUFAs, humans must consume some omega-3 and omega-6 fatty acids in their diet. Many studies on fatty acid desaturases as well as PUFAs have shown that fatty acid desaturase genes are closely related to different human physiological conditions. Since the first front-end desaturases from cyanobacteria were cloned, numerous desaturase genes have been identified and animals and plants have been genetically engineered to produce PUFAs such as eicosapentaenoic acid and docosahexaenoic acid. Recently, a biotechnological approach has been used to develop clinical treatments for human physiological conditions, including cancers and neurogenetic disorders. Thus, understanding the functions and regulation of PUFAs associated with human health and development by using biotechnology may facilitate the engineering of more advanced PUFA production and provide new insights into the complexity of fatty acid metabolism.

n-3 Fatty acids regulate the inflammatory-state related genes in the lung epithelial cells exposed to polycyclic aromatic hydrocarbons

BACKGROUND

Chronic airway inflammation is coordinated by a complex of inflammatory mediators, including eicosanoids. The aim of this study was to evaluate the impact of polycyclic aromatic hydrocarbons (PAHs) on the human lung epithelial carcinoma A549 cells supplemented with docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids.

METHODS

We analyzed the influence of DHA, EPA and/or benzo(a)pyrene (BaP), chrysene (Chr), fluoranthene (Flu) and benzo(a)anthracene (Baa) treatment on the fatty acids (FAs) profile and the formation of isoprostanes. We studied the cyclooxygenase-2, FP-receptor, peroxisome proliferator-activated receptors PPARδ and PPARγ, transcription factor NF-кB p50 and p65 expression by Western blot, phospholipase A2 (cPLA2) activity, as well as aryl hydrocarbon receptor (AHR), cytochrome P450 (CYP1A1), phospholipase A2 (PLA2G4A) and prostaglandin synthase 2 (PTGS2) gene expression by qRT-PCR.

RESULTS

DHA or EPA supplementation and BaP or Baa treatment resulted in a higher level of PGF3α. COX-2 expression was decreased while PPARδ expression and cPLA2 activity was increased after fatty acid supplementation and PAHs treatment. DHA and EPA up-regulated AHR and PLA2G4A genes.

CONCLUSIONS

Supplementation with n-3 FAs resulted in changes of inflammatory-state related genes in the lung epithelial cells exposed to PAHs. The altered profile of lipid mediators from n-3 FA as well as repression of the COX-2 protein by n-3 PUFAs in A549 cells incubated with PAHs suggests anti-inflammatory and pro-resolving properties of DHA and EPA. It remains to be shown whether these pleiotropic and protective actions of n-3 FAs contribute to fish oil's therapeutic effect in asthma.

Docosahexaenoic acid regulates gene expression in HUVEC cells treated with polycyclic aromatic hydrocarbons

The molecular mechanism of inflammation and carcinogenesis induced by exposure of polycyclic aromatic hydrocarbons (PAHs) is not clearly understood. Our study was undertaken due to the strong pro-carcinogenic potential and reactivity of PAH-metabolites, as well as the susceptibility of polyunsaturated fatty acids to oxidation. The aim of this study was to evaluate the pro- or anti-inflammatory impact of n-3 docosahexaenoic acid on human primary umbilical vein endothelial cells (HUVEC) exposed to polycyclic aromatic hydrocarbons. We analysed the influence of docosahexaenoic acid (DHA) and/or PAHs supplementation on the fatty acid profile of cell membranes, on cyclooxygenase-2 (COX-2), aryl hydrocarbon receptor (AHR), and glutathione S transferase Mu1 (GSTM1) protein expression as well as on the prostaglandin synthase 2 (PTGS2), AHR, GSTM1, PLA2G4A, and cytochrome P450 CYP1A1 gene expression. We observed that COX-2 and AHR protein expression was increased while GSTM1 expression was decreased in cells exposed to DHA and PAHs. Docosahexaenoic acid down-regulated CYP1A1 and up-regulated the AHR and PTGS2 genes. Our findings suggested that DHA contributes significantly to alleviate the harmful effects caused by PAHs in endothelial cells. Moreover, these results suggest that a diet rich in n-3 fatty acids is helpful to reduce the harmful effects of PAHs exposure on human living in heavily polluted areas.

Structures and binding studies of the complexes of phospholipase A2 with five inhibitors

Phospholipase A2 (PLA2) catalyzes the hydrolysis of phospholipids into arachidonic acid and lysophospholipids. Arachidonic acid is used as a substrate in the next step of the multistep pathway leading to the production of eicosanoids. The eicosanoids, in extremely low concentrations, are required in a number of physiological processes. However, the increase in their concentrations above the essential physiological requirements leads to various inflammatory conditions. In order to prevent the unwanted rise in the concentrations of eicosanoids, the actions of PLA2 and other enzymes of the pathway need to be blocked. We report here the structures of five complexes of group IIA PLA2 from Daboia russelli pulchella with tightly binding inhibitors, (i) p-coumaric acid, (ii) resveratrol, (iii) spermidine, (iv) corticosterone and (v) gramine derivative. The binding studies using fluorescence spectroscopy and surface plasmon resonance techniques for the interactions of PLA2 with the above five compounds showed high binding affinities with values of dissociation constants (KD) ranging from 3.7×10(-8) M to 2.1×10(-9) M. The structure determinations of the complexes of PLA2 with the above five compounds showed that all the compounds bound to PLA2 in the substrate binding cleft. The protein residues that contributed to the interactions with these compounds included Leu2, Leu3, Phe5, Gly6, Ile9, Ala18, Ile19, Trp22, Ser23, Cys29, Gly30, Cys45, His48, Asp49 and Phe106. The positions of side chains of several residues including Leu2, Leu3, Ile19, Trp31, Lys69, Ser70 and Arg72 got significantly shifted while the positions of active site residues, His48, Asp49, Tyr52 and Asp99 were unperturbed.

Eicosapentaenoic acid suppression of systemic inflammatory responses and inverse up-regulation of 15-deoxyΔ(12,14) prostaglandin J2 production

BACKGROUND AND PURPOSE

Eicosapentaenoic acid (EPA) has been shown to suppress immune cell responses, such as cytokine production and downstream PG production in vitro. Studies in vivo, however, have used EPA as a minor constituent of fish oil with variable results. We investigated the effects of EPA on systemic inflammatory responses as pure EPA has not been evaluated on immune/inflammatory responses in vivo.

EXPERIMENTAL APPROACH

Rabbits were administered polyinosinic: polycytidylic acid (poly I:C) i.v. before and after oral treatment with EPA for 42 days (given daily). The responses to IL-1β and TNF-α were also studied. Immediately following administration of poly I:C, body temperature was continuously monitored and blood samples were taken. Plasma levels of IL-1β, PGE2 (PGE2), and 15-deoxy-Δ(12,14)-PGJ2 (15d-PGJ2) were measured by enzyme immunoassay.

KEY RESULTS

Following EPA treatment, the fever response to poly I:C was markedly suppressed compared with pretreatment responses. This was accompanied by a parallel reduction in the poly I:C-stimulated elevation in plasma levels of IL-1β and PGE2. Paradoxically, the levels of 15d-PGJ2 were higher following EPA treatment. EPA treatment did not significantly alter the fever response or plasma levels of PGE2 in response to either IL-1β or TNF-α.

CONCLUSION AND IMPLICATIONS

Oral treatment with EPA can suppress immune/inflammatory responses in vivo via a suppression of upstream cytokine production resulting in a decreased fever response and indirectly reducing circulating levels of PGE2. EPA also enhances the production of the cytoprotective prostanoid 15d-PGJ2 indicating the therapeutic benefit of EPA.

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.

Erythrocyte membrane fatty acids in multiple myeloma patients

Mounting data show that fatty acids (FA) and fatty acid synthase (FAS) function could be potential targets for multiple myeloma (MM) therapy. Our study aimed at comparing the FA composition of erythrocyte membranes of MM patients and healthy controls. MM patients had higher saturated FA and n-6 polyunsaturated FA (PUFA) and lower monounsaturated, n-3 PUFA and trans-FA indices than controls. The n-3/n-6 PUFA ratio was lower in MM patients and there was distinct clustering of variants of individual FA in MM patients. The FA content of erythrocyte membrane could serve as a diagnostic and/or predictive biomarker in MM.

Characterisation of the prostaglandin E2-ethanolamide suppression of tumour necrosis factor-α production in human monocytic cells

BACKGROUND AND PURPOSE

Prostaglandin ethanolamides or prostamides are naturally occurring neutral lipid derivatives of prostaglandins that have been shown to be synthesised in vivo following COX-facilitated oxygenation of arachidonoyl ethanolamine (anandamide). Although the actions of prostaglandins have been extensively studied, little is known about the physiological or pathophysiological effects of prostamides. Since prostaglandin E2 has potent immunosuppressive/immunomodulating actions, the aim of the present study was to determine whether the derivative, prostaglandin E2 ethanolamide (PGE2-EA), could modulate the production of the pro-inflammatory cytokine tumour necrosis factor-α in human blood and human monocytic cells and indicate whether this action involved the same receptor systems/signals as PGE2.

EXPERIMENTAL APPROACH

Whole human blood, monocytes isolated from the blood or the human monocytic cell line THP-1 was incubated with LPS and the level of TNF-α produced was measured by ELISA assay. The actions of PGE2-EA were assessed on the LPS-induced TNF-α release. In addition, in order to ascertain the receptors involved, the levels of cyclic AMP in cells were measured in monocytes and THP-1 cells in response to PGE2-EA and directly compared to those of PGE2. The effect of PGE2-EA on the binding of radiolabelled PGE2 to cells was also measured. Cells were incubated with radiolabelled arachidonic acid and ethanolamine to estimate the production of PGE2-EA.

KEY RESULTS

PGE2-EA potently suppressed TNF-α production in blood, monocytes and the cell line THP-1 in a concentration-dependent manner. This occurred via cyclic AMP pathways as indicated by agents which interfere with these pathways and also direct ligand binding experiments. It was also shown that the cells were able to endogenously produce PGE2-EA.

CONCLUSIONS AND IMPLICATIONS

This study reports that PGE2-EA can downregulate the production of TNF-α by human mononuclear cells in response to an immune stimulus, i.e. LPS-activated TLR4, and that this appears to occur via a cAMP-dependent mechanism that most likely involves binding to the EP2 receptor.

Emerging targets in lipid-based therapy

The use of prostaglandins and NSAIDS in the clinic has proven that lipid mediators and their associated pathways make attractive therapeutic targets. When contemplating therapies involving lipid pathways, several basic agents come to mind. There are the enzymes and accessory proteins that lead to the metabolism of lipid substrates, provided through diet or through actions of lipases, the subsequent lipid products, and finally the lipid sensors or receptors. There is abundant evidence that molecules along this lipid continuum can serve as prognostic and diagnostic indicators and are in fact viable therapeutic targets. Furthermore, lipids themselves can be used as therapeutics. Despite this, the vernacular dialog pertaining to "biomarkers" does not routinely include mention of lipids, though this is rapidly changing. Collectively these agents are becoming more appreciated for their respective roles in diverse disease processes from cancer to preterm labor and are receiving their due appreciation after decades of ground work in the lipid field. By relating examples of disease processes that result from dysfunction along the lipid continuum, as well as examples of lipid therapies and emerging technologies, this review is meant to inspire further reading and discovery.