Eicosapentaenoic acid membrane incorporation impairs ABCA1-dependent cholesterol efflux via a protein kinase A signaling pathway in primary human macrophages

Activated PARP1/FAK/COL5A1 signaling facilitates the tumorigenesis of cholesterol-resistant ovarian cancer cells through promoting EMT

Cancer cells require plentiful cholesterol for membrane biogenesis and other functional needs due to fast proliferating, leading to the interaction of cholesterol or its metabolites with cancer-related pathways. However, the impact of long-lasting high cholesterol concentrations on tumorigenesis and its underlying mechanisms remains largely unexplored. To the best of our knowledge, this study is the first to establish a cholesterol-resistant ovarian cancer cells, whose intracellular total cholesterol level up to 6-8 mmol/L. We confirmed that high cholesterol facilitated the progression of ovarian cancer in vitro and in vivo. Notably, our findings revealed significant upregulation of collagen type V alpha 1 chain (COL5A1) expression in cholesterol-resistant ovarian cancer cells and human ovarian cancer tissue, which was depended on FAK/Src activation. Mechanistically, PARP1 directly bound to FAK in response to activate FAK/Src/COL5A1 signaling. Intriguingly, COL5A1 depletion significantly impeded the tumorigenesis of these cells, concomitant with a decrease in epithelial-mesenchymal transition (EMT) progression. In conclusion, PARP1/FAK/COL5A1 signaling activation facilitated progression of cholesterol-resistant ovarian cancer cells by promoting EMT, thereby broadening a new therapeutic opportunity.

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.

An iPSC-derived astrocyte model of fragile X syndrome exhibits dysregulated cholesterol homeostasis

Cholesterol is an essential membrane structural component and steroid hormone precursor, and is involved in numerous signaling processes. Astrocytes regulate brain cholesterol homeostasis and they supply cholesterol to the needs of neurons. ATP-binding cassette transporter A1 (ABCA1) is the main cholesterol efflux transporter in astrocytes. Here we show dysregulated cholesterol homeostasis in astrocytes generated from human induced pluripotent stem cells (iPSCs) derived from males with fragile X syndrome (FXS), which is the most common cause of inherited intellectual disability. ABCA1 levels are reduced in FXS human and mouse astrocytes when compared with controls. Accumulation of cholesterol associates with increased desmosterol and polyunsaturated phospholipids in the lipidome of FXS mouse astrocytes. Abnormal astrocytic responses to cytokine exposure together with altered anti-inflammatory and cytokine profiles of human FXS astrocyte secretome suggest contribution of inflammatory factors to altered cholesterol homeostasis. Our results demonstrate changes of astrocytic lipid metabolism, which can critically regulate membrane properties and affect cholesterol transport in FXS astrocytes, providing target for therapy in FXS.

Clinical significance of polyunsaturated fatty acids in the prevention of cardiovascular diseases

Cardiovascular diseases are one of the most important problems of modern medicine. They are associated with a large number of health care visits, hospitalizations and mortality. Prevention of atherosclerosis is one of the most effective strategies and should start as early as possible. Correction of lipid metabolism disorders is associated with definite clinical successes, both in primary prevention and in the prevention of complications of many cardiovascular diseases. A growing body of evidence suggests a multifaceted role for polyunsaturated fatty acids. They demonstrate a variety of functions in inflammation, both participating directly in a number of cellular processes and acting as a precursor for subsequent biosynthesis of lipid mediators. Extensive clinical data also support the importance of polyunsaturated fatty acids, but all questions have not been answered to date, indicating the need for further research.

Eicosapentaenoic acid membrane incorporation stimulates ABCA1-mediated cholesterol efflux from human THP-1 macrophages

A high intake in polyunsaturated fatty acids (PUFAs), especially eicosapentaenoic acid (EPA) (C20:5 n-3), is cardioprotective. Dietary PUFAs incorporate into membrane phospholipids, which may modify the function of membrane proteins. We investigated the consequences of the membrane incorporation of several PUFAs on the key antiatherogenic ABCA1-mediated cholesterol efflux pathway. Human THP-1 macrophages were incubated with EPA, arachidonic acid (AA) (C20:4 n-6) or docosahexaenoic acid (DHA) (C22:6 n-3) for a long time to mimic a chronic exposure. EPA 70 μM, but not AA 50 μM or DHA 15 μM, increased ABCA1-mediated cholesterol efflux to apolipoprotein (apo) AI by 28% without altering aqueous diffusion. No variation in ABCA1 expression or localization was observed after EPA treatment. EPA incorporation did not affect the phenotype of THP-1 macrophages. The membrane phospholipids composition of EPA cells displayed higher levels of both EPA and its elongation product docosapentaenoic acid, which was associated with drastic lower levels of AA. Treatment by EPA increased the ATPase activity of the transporter, likely through a PKA-dependent mechanism. Eicosanoids were not involved in the stimulated ABCA1-mediated cholesterol efflux from EPA-enriched macrophages. In addition, EPA supplementation increased the apo AI binding capacity from macrophages by 38%. Moreover, the increased apo AI binding in EPA-enriched macrophages can be competed. In conclusion, EPA membrane incorporation increased ABCA1 functionality in cholesterol-normal human THP-1 macrophages, likely through a combination of different mechanisms. This beneficial in vitro effect may partly contribute to the cardioprotective effect of a diet enriched with EPA highlighted by several recent clinical trials.

8-HEPE-Concentrated Materials from Pacific Krill Improve Plasma Cholesterol Levels and Hepatic Steatosis in High Cholesterol Diet-Fed Low-Density Lipoprotein (LDL) Receptor-Deficient Mice

Eicosapentaenoic acid (EPA), one of the N-3 polyunsaturated fatty acids (n-3 PUFAs), is a major active ingredient of fish that contributes to improve dyslipidemia. Recently, we demonstrated that 8-hydroxyeicosapentaenoic acid (8-HEPE) had a more positive effect on metabolic syndrome than EPA, and that 8-HEPE induced peroxisome proliferator-activated receptor (PPAR)α activation in the liver. We investigated the effects of 8-HEPE-concentrated materials from Pacific krill on dyslipidemia and hepatic steatosis in low-density lipoprotein (LDL) receptor-deficient (LDLR-KO) mice. Eight-week-old male LDLR-KO mice were fed a Western diet (0.15% cholesterol, WD), WD supplemented with 8-HEPE-concentrated materials from Pacific krill (8-HEPE included; WD +8-HEPE), or a standard diet (SD) for eighteen weeks, respectively. Murine J774.1 macrophages were incubated in the absence or presence of 8-HEPE (50 µM) or EPA (50 µM). 8-HEPE-concentrated materials significantly increased the plasma high-density lipoprotein (HDL)-cholesterol level, and decreased the plasma LDL-cholesterol and hepatic triglyceride levels in WD-fed LDLR-KO mice. Moreover, the rate of Oil Red O-positive staining was higher in the liver of WD-fed LDLR-KO mice than in that of 8-HEPE + WD-fed LDLR-KO mice. 8-HEPE but not EPA significantly increased gene expression levels of ABCA1, CD36, and interleukin 6 (IL-6) in murine J774.1 macrophages compared with those in the control. These results suggest that 8-HEPE-concentrated materials improve dyslipidemia and hepatic steatosis increasing ABCA1, CD36, and IL-6 gene expressions in macrophages.

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

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

Assessment of HDL Cholesterol Removal Capacity: Toward Clinical Application

While there is a controversy regarding the causal relationship between high-density lipoprotein cholesterol (HDL-C) and cardiovascular disease (CVD), recent studies have demonstrated that the cholesterol efflux capacity (CEC) of HDL is associated with the incidence of CVD. However, there are several limitations to current assays of CEC. First, CEC measurements are not instantly applicable in clinical settings, because CEC assay methods require radiolabeled cholesterol and cultured cells, and these procedures are time consuming. Second, techniques to measure CEC are not standardized. Third, the condition of endogenous cholesterol donors would not be accounted for in the CEC assays. Recently, we established a simple, high-throughput, cell-free assay system to evaluate the capacity of HDL to accept additional cholesterol, which is herein referred to as "cholesterol uptake capacity (CUC)". We demonstrated that CUC represents a residual cardiovascular risk in patients with optimal low-density lipoprotein cholesterol control independently of traditional risk factors, including HDL-C. Establishing reproducible approaches for the cholesterol removal capacity of HDL is required to validate the impact of dysfunctional HDL on cardiovascular risk stratification in the "real world".

Re-curation and rational enrichment of knowledge graphs in Biological Expression Language

The rapid accumulation of new biomedical literature not only causes curated knowledge graphs (KGs) to become outdated and incomplete, but also makes manual curation an impractical and unsustainable solution. Automated or semi-automated workflows are necessary to assist in prioritizing and curating the literature to update and enrich KGs. We have developed two workflows: one for re-curating a given KG to assure its syntactic and semantic quality and another for rationally enriching it by manually revising automatically extracted relations for nodes with low information density. We applied these workflows to the KGs encoded in Biological Expression Language from the NeuroMMSig database using content that was pre-extracted from MEDLINE abstracts and PubMed Central full-text articles using text mining output integrated by INDRA. We have made this workflow freely available at https://github.com/bel-enrichment/bel-enrichment.

The effect of intakes of fish and Camelina sativa oil on atherogenic and anti-atherogenic functions of LDL and HDL particles: A randomized controlled trial

BACKGROUND AND AIMS

Omega-3 fatty acids are known to have several cardioprotective effects. Our aim was to investigate the effects of intakes of fish and Camelina sativa oil (CSO), rich in alpha-linolenic acid, on the atherogenic and anti-atherogenic functions of LDL and HDL particles.

METHODS

Altogether, 88 volunteers with impaired glucose metabolism were randomly assigned to CSO (10 g of alpha-linolenic acid/day), fatty fish (4 fish meals/week), lean fish (4 fish meals/week) or control group for 12 weeks. 79 subjects completed the study. The binding of lipoproteins to aortic proteoglycans, LDL aggregation and activation of endothelial cells by LDL and cholesterol efflux capacity of HDL were determined in vitro.

RESULTS

Intake of CSO decreased the binding of lipoproteins to aortic proteoglycans in a non-normalized model (p = 0.006). After normalizing with serum concentrations of non-HDL cholesterol, apolipoprotein B (apoB) or LDL cholesterol, which decreased in the CSO group, the change was no longer statistically significant. In the fish groups, there were no changes in the binding of lipoproteins to proteoglycans. Regarding other lipoprotein functions, there were no changes in any of the groups.

CONCLUSIONS

Intake of CSO decreases the binding of lipoproteins to aortic proteoglycans by decreasing serum LDL cholesterol concentration, which suggests that the level of apoB-containing lipoproteins in the circulation is the main driver of lipoprotein retention within the arterial wall. Intake of fish or CSO has no effects on other lipoprotein functions.

Eicosapentaenoic acid in combination with EPHA2 inhibition shows efficacy in preclinical models of triple-negative breast cancer by disrupting cellular cholesterol efflux

Triple-negative breast cancer (TNBC), the most aggressive breast cancer subtype, currently lacks effective targeted therapy options. Eicosapentaenoic acid (EPA), an omega-3 fatty acid and constituent of fish oil, is a common supplement with anti-inflammatory properties. Although it is not a mainstream treatment, several preclinical studies have demonstrated that EPA exerts anti-tumor activity in breast cancer. However, against solid tumors, EPA as a monotherapy is clinically ineffective; thus, we sought to develop a novel targeted drug combination to bolster its therapeutic action against TNBC. Using a high-throughput functional siRNA screen, we identified Ephrin type-A receptor 2 (EPHA2), an oncogenic cell-surface receptor tyrosine kinase, as a therapeutic target that sensitizes TNBC cells to EPA. EPHA2 expression was uniquely elevated in TNBC cell lines and patient tumors. In independent functional expression studies in TNBC models, EPHA2 gene-silencing combined with EPA significantly reduced cell growth and enhanced apoptosis compared with monotherapies, both in vitro and in vivo. EPHA2 specific inhibitors similarly enhanced the therapeutic action of EPA. Finally, we identified that therapy-mediated apoptosis was attributed to a lethal increase in cancer cell membrane polarity due to ABCA1 inhibition and subsequent dysregulation of cholesterol homeostasis. This study provides new molecular and pre-clinical evidence to support a clinical evaluation of EPA combined with EPHA2 inhibition in patients with TNBC.

The composition of dietary fat alters the transcriptional profile of pathways associated with lipid metabolism in the liver and adipose tissue in the pig

The objective was to investigate the of effect chemical composition of dietary fat on transcription of genes involved in lipid metabolism in adipose tissue and the liver via transcriptional profiling in growing pigs. A total of 48 Genetiporc 6.0 × Genetiporc F25 (PIC, Inc., Hendersonville, TN) barrows (initial BW of 44.1 ± 1.2 kg) were randomly allotted to 1 of 6 dietary treatments. Each experimental diet included 95% of a corn-soybean meal basal diet and 5% cornstarch (control; CNTR), animal-vegetable blend (AV), coconut oil (COCO), corn oil (COIL), fish oil (FO), or tallow (TAL). Pigs were sacrificed on d 10 (final BW of 51.2 ± 1.7 kg) to collect tissues. Expression normalization across samples was performed by calculating a delta cycle threshold (ΔCt) value using . Delta delta cycle threshold (ΔΔCt) values were expressed relative to the CNTR treatment. In adipose tissue, adding dietary fat, regardless of the source, decreased the mRNA abundance of compared with the CNTR ( = 0.014). Pigs fed a COIL-based diet tended to have greater adipose tissue expression of ( = 0.071) than pigs fed the other dietary fat sources tested. Abundance of mRNA was greater in adipose tissue of barrows a fed COIL-based diet than barrows fed CNTR or FO-based diets ( = 0.047). In the liver, adding dietary fat, regardless of source, increased the mRNA abundance of , , , , , and ( ≤ 0.020) and tended to increase the abundance of ( = 0.071) and ( = 0.086) compared with the CNTR. Pigs fed a TAL-based diet had greater hepatic transcription of than pigs fed CNTR-, COCO-, or FO-based diets ( = 0.013). Hepatic transcription of tended to be greater in pigs fed COCO than in pigs fed other dietary fat sources ( = 0.074). Dietary omega-3 fatty acid content tended to negatively correlate with mRNA abundance of ( = 0.065) in adipose tissue and ( = 0.063) in the liver. Dietary fat SFA content was negatively correlated with in the liver ( ≤ 0.039). Dietary fat MUFA content tended to be positively correlated with , , and mRNA abundance in the liver ( ≤ 0.100). To conclude, the intake of omega-3 fatty acids suppressed the mRNA abundance of genes involved in lipolysis in both adipose tissue and the liver. Dietary SFA are greater inhibitors of lipogenesis in adipose tissue than omega-6 fatty acids. Intake of medium-chain fatty acids alters hepatic lipid metabolism differently than intake of long-chain fatty acids.

The Role of Omega-3 Fatty Acids in Reverse Cholesterol Transport: A Review

The beneficial effects of omega-3 polyunsaturated fatty acids (n-3 PUFAs) on cardiovascular disease have been studied extensively. However, it remains unclear to what extent n-3 PUFAs may impact Reverse Cholesterol Transport (RCT). RCT describes a mechanism by which excess cholesterol from peripheral tissues is transported to the liver for hepatobiliary excretion, thereby inhibiting foam cell formation and the development of atherosclerosis. The aim of this review is to summarize the literature and to provide an updated overview of the effects of n-3 PUFAs on key players in RCT, including apoliprotein AI (apoA-I), ATP-binding cassette transporter A1 (ABCA1), ABCG1, apoE, scavenger receptor class B type I (SR-BI), cholesteryl ester transfer protein (CETP), low-density lipoprotein receptor (LDLr), cholesterol 7 alpha-hydroxylase (CYP7A1) and ABCG5/G8. Based on current knowledge, we conclude that n-3 PUFAs may beneficially affect RCT, mainly by influencing high-density lipoprotein (HDL) remodeling and by promoting hepatobiliary sterol excretion.

Eicosapentaenoic acid membrane incorporation impairs cholesterol efflux from cholesterol-loaded human macrophages by reducing the cholesteryl ester mobilization from lipid droplets

A diet containing a high n-3/n-6 polyunsaturated fatty acids (PUFA) ratio has cardioprotective properties. PUFAs incorporation into membranes influences the function of membrane proteins. We investigated the impact of the membrane incorporation of PUFAs, especially eicosapentaenoic acid (EPA) (C20:5 n-3), on the anti-atherogenic cholesterol efflux pathways. We used cholesteryl esters (CE)-loaded human monocyte-derived macrophages (HMDM) to mimic foam cells exposed to the FAs for a long period of time to ensure their incorporation into cellular membranes. Phospholipid fraction of EPA cells exhibited high levels of EPA and its elongation product docosapentaenoic acid (DPA) (C22:5 n-3), which was associated with a decreased level of arachidonic acid (AA) (C20:4 n-6). EPA 70μM reduced ABCA1-mediated cholesterol efflux to apolipoprotein (apo) AI by 30% without any alteration in ABCA1 expression. The other tested PUFAs, DPA, docosahexaenoic acid (DHA) (C22:6 n-3), and AA, were also able to reduce ABCA1 functionality while the monounsaturated oleic FA slightly decreased efflux and the saturated palmitic FA had no impact. Moreover, EPA also reduced cholesterol efflux to HDL mediated by the Cla-1 and ABCG1 pathways. EPA incorporation did not hinder efflux in free cholesterol-loaded HMDM and did not promote esterification of cholesterol. Conversely, EPA reduced the neutral hydrolysis of cytoplasmic CE by 24%. The reduced CE hydrolysis was likely attributed to the increase in cellular TG contents and/or the decrease in apo E secretion after EPA treatment. In conclusion, EPA membrane incorporation reduces cholesterol efflux in human foam cells by reducing the cholesteryl ester mobilization from lipid droplets.

Mycophenolate Mofetil and Rapamycin Induce Apoptosis in the Human Monocytic U937 Cell Line Through Two Different Pathways

Transplant vasculopathy may be considered as an accelerated form of atherosclerosis resulting in chronic rejection of vascularized allografts. After organ transplantation, a diffuse intimal thickening is observed, leading to the development of an atherosclerosis plaque due to a significant monocyte infiltration. This results from a chronic inflammatory process induced by the immune response. In this study, we investigated the impact of two immunosuppressive drugs used in therapy initiated after organ transplantation, mycophenolate mofetil, and rapamycin, on the apoptotic response of monocytes induced or not by oxidized LDL. Here we show the pro-apoptotic effect of these two drugs through two distinct signaling pathways and we highlight a synergistic effect of rapamycin on apoptosis induced by oxidized LDL. In conclusion, since immunosuppressive therapy using mycophenolate mofetil or rapamycin can increase the cell death in a monocyte cell line, this treatment could exert similar effects on human monocytes in transplant patients, and thus, prevent transplant vasculopathy, atherosclerosis development, and chronic allograft rejection. J. Cell. Biochem. 118: 3480-3487, 2017. © 2017 Wiley Periodicals, Inc.

Membrane lipid alterations in the metabolic syndrome and the role of dietary oils

The metabolic syndrome is a cluster of pathological conditions, including hypertension, hyperglycemia, hypertriglyceridemia, obesity and low HDL levels that is of great concern worldwide, as individuals with metabolic syndrome have an increased risk of type-2 diabetes and cardiovascular disease. Insulin resistance, the key feature of the metabolic syndrome, might be at the same time cause and consequence of impaired lipid composition in plasma membranes of insulin-sensitive tissues like liver, muscle and adipose tissue. Diet intervention has been proposed as a powerful tool to prevent the development of the metabolic syndrome, since healthy diets have been shown to have a protective role against the components of the metabolic syndrome. Particularly, dietary fatty acids are capable of modulating the deleterious effects of these conditions, among other mechanisms, by modifications of the lipid composition of the membranes in insulin-sensitive tissues. However, there is still scarce data based of high-level evidence on the effects of dietary oils on the effects of the metabolic syndrome and its components. This review summarizes the current knowledge on the effects of dietary oils on improving alterations of the components of the metabolic syndrome. It also examines their influence in the modulation of plasma membrane lipid composition and in the functionality of membrane proteins involved in insulin activity, like the insulin receptor, GLUT-4, CD36/FAT and ABCA-1, and their effect in the metabolism of glucose, fatty acids and cholesterol, and, in turn, the key features of the metabolic syndrome. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.