Docosahexaenoic acid in phosphatidylcholine mediates cytotoxicity more effectively than other omega-3 and omega-6 fatty acids

Lipid-based nanocarriers co-loaded with artemether and triglycerides of docosahexaenoic acid: Effects on human breast cancer cells

Artemether (ART) was combined with triglyceride of docosahexaenoic acid (DHA) as the lipid-core in nanoemulsions (NE), nanostructured lipid carriers (NLC), and PEG-PLA nanocapsules (NC) formulations, and their effects on human breast cancer cells were evaluated. ART has been extensively used for malaria and has also therapeutic potential against different tumor cells in a repositioning strategy. The concentration-dependent cytotoxicity in vitro was determined in tumor lineages, MDA-MB-231 and MCF-7, and non-tumor MCF-10A cells for free-ART/DHA combination and its formulations. The cells were monitored for viability, effects on cell migration and clonogenicity, cell death mechanism, and qualitative and quantitative cell uptake of nanocarriers. The lipid-nanocarriers showed mean sizes over the range of 110 and 280 nm with monodisperse populations and zeta potential values ranging from -21 to -67 mV. The ART encapsulation efficiencies varied from 57 to 83 %. ART/DHA co-loaded in three different lipid nanocarriers reduced the MDA-MB-231 and MCF-7 viability in a dose-dependent manner with enhanced selectivity toward tumor cell lines. They also reduced clonogenicity and the ability of cells to migrate showing antimetastatic potential in both cell lines and triggered apoptosis in MCF-7 cells. Confocal microscopy and flow cytometry analysis showed that NC, NLC, and NE were rapidly internalized by cells, with higher interaction displayed by NE with MCF-7 cells compared to NC and NLC that was correlated with the strongest NE-fluorescence in cells. Therefore, this study not only demonstrated the value of this new combination of ART/DHA as a new strategy for breast cancer therapy but also showed enhanced cytotoxicity and potential metastatic activity of lipid-based formulations against human breast cancer cells that indicate great potential for pre-clinical and clinical translation.

Diclofenac Enhances Docosahexaenoic Acid-Induced Apoptosis in Vitro in Lung Cancer Cells

Simple Summary

Polyunsaturated fatty acids (PUFAs) and non-steroidal anti-inflammatory drugs (NSAIDs) have limited anticancer capacities when used alone. We examined whether combining NSAIDs with docosahexaenoic (DHA) would increase their anticancer activity on lung cancer cell lines. Our results indicate that combining DHA and NSAIDs increased their anticancer activities by altering the expression of critical proteins in the RAS/MEK/ERK and PI3K/Akt pathways. The data suggest that DHA combined with low dose diclofenac provides more significant anticancer potential, which can be further developed for chemoprevention and adjunct therapy in lung cancer.

Abstract

Polyunsaturated fatty acids (PUFAs) and non-steroidal anti-inflammatory drugs (NSAIDs) show anticancer activities through diverse molecular mechanisms. However, the anticancer capacities of either PUFAs or NSAIDs alone is limited. We examined whether combining NSAIDs with docosahexaenoic (DHA), commonly derived from fish oils, would possibly synergize their anticancer activity. We determined the viability of lung cancer cell lines (NCI-H1573, A549, NCI-H1299, and NCI-H1975) after exposure to DHA and various NSAIDs. We further conducted cell apoptosis assays and analyzed apoptosis-associated proteins and some key proteins in the RAS/MEK/ERK and PI3K/Akt pathways using western blot analysis. We also determined the impact of the treatment on the expression of inducible cancer-related genes using nCounter PanCancer Pathways gene expression analysis. The results showed that the combination of DHA and NSAIDs increased suppression of cell viability in all the lung cancer cell lines tested compared to each of the compounds used alone, with diclofenac being the most potent NSAID tested. This synergistic effect is especially significant in A549 and NCI-H1573 cells. The combination treatment was more effective at inhibiting clonogenic cell growth and anchorage-independent growth in soft agar, inducing caspase-dependent apoptosis, and altering expression of critical proteins in the RAS/MEK/ERK and PI3K/Akt pathways. The data from this study demonstrate that DHA combined with low dose diclofenac provides greater anticancer potential, which can be further developed for chemoprevention and adjunct therapy in lung cancer.

Protection Before Impact: the Potential Neuroprotective Role of Nutritional Supplementation in Sports-Related Head Trauma

Even in the presence of underreporting, sports-related concussions/mild traumatic brain injuries (mTBI) are on the rise. In the absence of proper diagnosis, an athlete may return to play prior to full recovery, increasing the risk of second-impact syndrome or protracted symptoms. Recent evidence has demonstrated that sub-concussive impacts, those sustained routinely in practice and competition, result in a quantifiable pathophysiological response and the accumulation of both concussive and sub-concussive impacts sustained over a lifetime of sports participation may lead to long-term neurological impairments and an increased risk of developing neurodegenerative diseases. The pathophysiological, neurometabolic, and neurochemical cascade that initiates subsequent to the injury is complex and involves multiple mechanisms. While pharmaceutical treatments may target one mechanism, specific nutrients and nutraceuticals have been discovered to impact several pathways, presenting a broader approach. Several studies have demonstrated the neuroprotective effect of nutritional supplementation in the treatment of mTBI. However, given that many concussions go unreported and sub-concussive impacts result in a pathophysiological response that, too, may contribute to long-term brain health, protection prior to impact is warranted. This review discusses the current literature regarding the role of nutritional supplements that, when provided before mTBI and traumatic brain injury, may provide neurological protection.

Docosahexaenoic Acid Induces Apoptosis in Primary Chronic Lymphocytic Leukemia Cells

Chronic lymphocytic leukemia is an indolent disorder with an increased infectious risk remaining one of the main causes of death. Development of therapies with higher safety profile is thus a challenging issue. Docosahexaenoic acid (DHA, 22:6) is an omega-3 fatty acid, a natural compound of normal cells, and has been shown to display antitumor potency in cancer. We evaluated the potential in vitro effect of DHA in primary CLL cells. DHA induces high level of in vitro apoptosis compared to oleic acid in a dose-dependent and time-dependent manner. Estimation of IC50 was only of 4.813 µM, which appears lower than those reported in solid cancers. DHA is highly active on CLL cells in vitro. This observation provides a rationale for further studies aiming to understand its mechanisms of action and its potent in vivo activity.

Anticancer efficacy of a novel propofol-linoleic acid-loaded escheriosomal formulation against murine hepatocellular carcinoma

AIM

The preparation and characterization of a novel escheriosomal nanoparticle formulation of a potent anticancer conjugate, 2,6-diisopropylphenol-linoleic acid (2,6P-LA), and evaluation of its anticancer efficacy against diethyl nitrosamine-induced hepatocellular carcinoma (HCC) in BALB/c mice.

MATERIALS & METHODS

Escheriosomized 2,6P-LA nanoparticles were characterized for size, zeta-potential, entrapment efficiency, release kinetics and in vivo toxicity. Their anticancer potential was evaluated on the basis of survival, DNA fragmentation, caspase-3 activation, western blot analysis of apoptotic factors and histopathological changes in hepatocytes of treated animals.

RESULTS

The escheriosomized 2,6P-LA nanoparticles exhibited low toxicity, biocompatibility and bioavailability. As revealed by apoptosis induction, survival rate, expression profiles of Bax, Bcl-2 and caspase-9, escheriosomized 2,6P-LA nanoparticles were more effective in the treatment of HCC than the free form of 2,6P-LA in experimental animals.

CONCLUSION

2,6P-LA-bearing escheriosome nanoparticles are effective in suppressing HCC in mice. Original submitted 17 January 2012; Revised submitted 27 August 2012; Published online 14 January 2013.

Effect of polyunsaturated fatty acids on drug-sensitive and resistant tumor cells in vitro

Previous studies showed that γ-linolenic acid (GLA, 18: 3 ω-6), arachidonic acid (AA, 20:4 ω -6), eicosapentaenoic acid (EPA, 20: 5 ω -3) and docosahexaenoic acid (DHA, 22:6 ω -3) have selective tumoricidal action. In the present study, it was observed that dihomo-gamma-linolenic acid (DGLA) and AA, EPA and DHA have cytotoxic action on both vincristine-sensitive (KB-3-1) and resistant (KB-Ch^R-8-5) cancer cells in vitro that appeared to be a free-radical dependent process but not due to the formation of prostaglandins, leukotrienes and thromboxanes. Uptake of vincristine and fatty acids was higher while their efflux was lower in KB-3-1 cells compared with KB-Ch^R-8-5 cells, suggesting that drug resistant cells have an effective efflux pump. GLA, DGLA, AA, EPA and DHA enhanced the uptake and decreased efflux in both drug-sensitive and drug-resistant cells and augmented the susceptibility of tumor cells especially, of drug-resistant cells to the cytotoxic action of vincristine. These results suggest that certain polyunsaturated fatty acids have tumoricidal action and are capable of enhancing the cytotoxic action of anti-cancer drugs specifically, on drug-resistant cells by enhancing drug uptake and reducing its efflux. Thus, polyunsaturated fatty acids either by themselves or in combination with chemotherapeutic drugs have the potential as anti-cancer molecules.

Fatty acid and peptide profiles in plasma membrane and membrane rafts of PUFA supplemented RAW264.7 macrophages

The eukaryotic cell membrane possesses numerous complex functions, which are essential for life. At this, the composition and the structure of the lipid bilayer are of particular importance. Polyunsaturated fatty acids may modulate the physical properties of biological membranes via alteration of membrane lipid composition affecting numerous physiological processes, e.g. in the immune system. In this systematic study we present fatty acid and peptide profiles of cell membrane and membrane rafts of murine macrophages that have been supplemented with saturated fatty acids as well as PUFAs from the n-3, the n-6 and the n-9 family. Using fatty acid composition analysis and mass spectrometry-based peptidome profiling we found that PUFAs from both the n-3 and the n-6 family have an impact on lipid and protein composition of plasma membrane and membrane rafts in a similar manner. In addition, we found a relation between the number of bis-allyl-methylene positions of the PUFA added and the unsaturation index of plasma membrane as well as membrane rafts of supplemented cells. With regard to the proposed significance of lipid microdomains for disease development and treatment our study will help to achieve a targeted dietary modulation of immune cell lipid bilayers.

Liposome-incorporated DHA increases neuronal survival by enhancing non-amyloidogenic APP processing

The fluidity of neuronal membranes plays a pivotal role in brain aging and neurodegeneration. In this study, we investigated the role of the omega-3 fatty acid docosahexaenoic acid (DHA) in modulation of membrane fluidity, APP processing, and protection from cytotoxic stress. To this end, we applied unilamellar transfer liposomes, which provided protection from oxidation and effective incorporation of DHA into cell membranes. Liposomes transferring docosanoic acid (DA), the completely saturated form of DHA, to the cell cultures served as controls. In HEK-APP cells, DHA significantly increased membrane fluidity and non-amyloidogenic processing of APP, leading to enhanced secretion of sAPPα. This enhanced secretion of sAPPα was associated with substantial protection against apoptosis induced by ER Ca(2+) store depletion. sAPPα-containing supernatants obtained from HEK-APP cells exerted similar protective effects as DHA in neuronal PC12 cells and HEK293 control cells. Correlating to further increased sAPPα levels, supernatants obtained from DHA-treated HEK-APP cells enhanced protection, whereas supernatants obtained from DHA-treated HEK293 control cells did not inhibit apoptosis, likely due to the low expression of endogenous APP and negligible sAPPα secretion in these cells. Further experiments with the small molecule inhibitors LY294002 and SP600125 indicated that sAPPα-induced cytoprotection relied on activation of the anti-apoptotic PI3K/Akt pathway and inhibition of the stress-triggered JNK signaling pathway in PC12 cells. Our data suggest that liposomal DHA is able to restore or maintain physiological membrane properties, which are required for neuroprotective sAPPα secretion and autocrine modulation of neuronal survival.

Combined reversed phase HPLC, mass spectrometry, and NMR spectroscopy for a fast separation and efficient identification of phosphatidylcholines

In respect of the manifold involvement of lipids in biochemical processes, the analysis of intact and underivatised lipids of body fluids as well as cell and tissue extracts is still a challenging task, if detailed molecular information is required. Therefore, the advantage of combined use of high-pressure liquid chromatography (HPLC), mass spectrometry (MS), and nuclear magnetic resonance (NMR) spectroscopy will be shown analyzing three different types of extracts of the ubiquitous membrane component phosphatidylcholine. At first, different reversed phase modifications were tested on phosphatidylcholines (PC) with the same effective carbon number (ECN) for their applicability in lipid analysis. The results were taken to improve the separation of three natural PC extract types and a new reversed phase (RP)-HPLC method was developed. The individual species were characterized by one- and two-dimensional NMR and positive or negative ion mode quadrupole time of flight (q-TOF)-MS as well as MS/MS techniques. Furthermore, ion suppression effects during electrospray ionisation (ESI), difficulties, limits, and advantages of the individual analytical techniques are addressed.

Docosahexaenoic acid domains: the ultimate non-raft membrane domain

What distinguishes polyunsaturated fatty acids (PUFAs) from less unsaturated fatty acids is the presence of a repeating =CH-CH(2)-CH= unit that produces an extremely flexible structure rapidly isomerizing through conformational states. Docosahexaenoic acid (DHA) with 6 double bonds is the most extreme example. The focus of this review is the profound impact that the high disorder of DHA has on its interaction with cholesterol when the PUFA is incorporated into membrane phospholipids. Results from a battery of biophysical techniques are described. They demonstrate an aversion of DHA for the sterol that drives the lateral segregation of DHA-containing phospholipids into liquid disordered (l(d)) domains that are depleted in cholesterol. These domains are compositionally and organizationally the antithesis of lipid rafts, the much-studied liquid ordered (l(o)) domain that is enriched in predominantly saturated sphingolipids and cholesterol. We hypothesize that the introduction of DHA-rich domains into the plasma membrane where they coexist with lipid rafts is the origin, in part, of the astonishing diversity of health benefits that accrue from dietary consumption of DHA. According to our model, changes in the conformation of signaling proteins when they move between these disparate domains have the potential to modulate cell function.

Plasma, red blood cells phospholipids and clinical evaluation after long chain omega-3 supplementation in children with attention deficit hyperactivity disorder (ADHD)

Omega-3 and omega-6 long-chain polyunsaturated fatty acids (LCPUFAs), are crucial to brain development and function. Increasing evidence indicates that deficiencies or metabolic imbalances of these fatty acids might be associated with childhood developmental and psychiatric disorders including attention-deficit/hyperactivity disorder (ADHD). Omega-3 are often lacking on modern diets. Moreover preliminary evidences suggest that supplementation with omega-3 LCPUFAs, might help in the management of the ADHD linked behavioural and learning difficulties. However, few studies published to date have involved different populations, study designs, treatments and outcome results. Thus, further researches are required to assess the durability of the treatment effects, to determine optimal composition and dosages of the supplement and to develop reliable ways to identify patients that might have some benefits from this kind of treatment, also because the study of LCPUFAs and their metabolism might offer new approaches to the early identification and management of ADHD. In this paper, we provide new insight on the lipid pattern in plasma and red blood cells (RBC) phospholipids, together with evaluation of the arachidonic acid (AA)/eicosapentaenoic acid (EPA) ratio which seems to correlate with the improvement of the patients both from a biochemical and clinical point of view.

In vivo conversion of triacylglycerol to docosahexaenoic acid-containing phospholipids in a thraustochytrid-like microorganism, strain 12B

The thraustochytrid-like microorganism, strain 12B, cultivated in peptone, yeast extract, and 8% (w/v) glucose in 50% (v/v) seawater, accumulated docosahexaenoic acid (DHA)-rich triacylglycerol (TAG) at 67% of total lipid. When these TAG-accumulated cells were cultivated in glucose-deficient medium, dry cell weight (3 mg per ml culture) increased approximately 3-fold relative to baseline but the TAG/total lipid decreased to 5%. At the same time, the amount of phospholipid (5 mg) per whole culture also increased 3-fold. Hence, phospholipid/total lipid increased from 13% to 67%. High levels of DHA (more than 50% of total) were maintained in phosphatidylcholine.

Anticancer properties of propofol-docosahexaenoate and propofol-eicosapentaenoate on breast cancer cells

Introduction

Epidemiological evidence strongly links fish oil, which is rich in docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), with low incidences of several types of cancer. The inhibitory effects of omega-3 polyunsaturated fatty acids on cancer development and progression are supported by studies with cultured cells and animal models. Propofol (2,6-diisopropylphenol) is the most extensively used general anesthetic–sedative agent employed today and is nontoxic to humans at high levels (50 μg/ml). Clinically relevant concentrations of propofol (3 to 8 μg/ml; 20 to 50 μM) have also been reported to have anticancer activities. The present study describes the synthesis, purification, characterization and evaluation of two novel anticancer conjugates, propofol-docosahexaenoate (propofol-DHA) and propofol-eicosapentaenoate (propofol-EPA).

Methods

The conjugates linking an omega-3 fatty acid, either DHA or EPA, with propofol were synthesized and tested for their effects on migration, adhesion and apoptosis on MDA-MB-231 breast cancer cells.

Results

At low concentrations (25 μM), DHA, EPA or propofol alone or in combination had minimal effect on cell adhesion to vitronectin, cell migration against serum and the induction of apoptosis (only 5 to 15% of the cells became apoptotic). In contrast, the propofol-DHA or propofol-EPA conjugates significantly inhibited cell adhesion (15 to 30%) and migration (about 50%) and induced apoptosis (about 40%) in breast cancer cells.

Conclusion

These results suggest that the novel propofol-DHA and propofol-EPA conjugates reported here may be useful for the treatment of breast cancer.

Order from disorder, corralling cholesterol with chaotic lipids. The role of polyunsaturated lipids in membrane raft formation

A myriad of health benefits including the prevention of cancer and heart disease accompanies consumption of polyunsaturated fatty acids (PUFA). Of special importance is the omega-3-PUFA docosahexaenoic acid (DHA), with 22 carbons and six double bonds that constitute the most highly unsaturated fatty acid naturally occurring. Our experiments target the membrane as a likely site of action and focus upon the interaction of cholesterol with PUFA-containing phospholipids. They support the idea that steric incompatibility of the rigid steroid moiety for highly disordered PUFA chains promotes lateral segregation of lipids into PUFA-rich/sterol-poor and PUFA-poor/sterol-rich regions. Solid state 2H NMR and X-ray diffraction demonstrate that the solubility of cholesterol is low in polyunsaturated bilayers. In mixed membranes of phosphatidylethanolamine (PE) with the lipid raft-forming molecules sphingomyelin (SM) and cholesterol, diminished affinity of the sterol for 1-[2H31]palmitoyl-2-docosahexaenoylphosphatidylethanolamine ([2H31]16:0-22:6PE) relative to 1-[2H31]palmitoyl-2-oleoylphosphatidylethanolamine ([2H31]16:0-18:1PE) is identified by 2H NMR order parameters. Here, lies the origin of a potential biological advantage of the relatively modest increase in PUFA content of plasma membranes that would be conferred by dietary supplementation. We hypothesize that the enhanced propensity to form SM-/cholesterol-rich rafts as well as PUFA-rich/cholesterol-poor microdomains would modify the function of proteins for which these respective regions provide a platform.

Conjugated linoleic acid modulation of cell membrane in leukemia cells

This study compared the cellular uptake of pure conjugated linoleic acid isomers (CLA(9c,11t) and CLA(9c,11c)) to linoleic acid (LA) and their effects on polyunsaturated fatty acid (PUFA) synthesis, its metabolism into conjugated long chain fatty acids (FAs) by desaturation and chain-elongation as well as cell proliferation and the associated anticarcinogenic effects on various human leukemia cell lines (K562, REH, CCRF-CEM and U937 cells). Furthermore, selective effects of this individual isomers of CLA on desaturation steps involved in the biosynthesis of PUFAs associated with cell growth were investigated. CLA isomers supplemented in the culture medium was readily incorporated and esterified into phospholipids (PLs) in the four cell lines in a concentration- and time-dependent manner. The incorporation of the specific CLA isomers in PLs was similar to LA. All four incubating leukemia cells (40 microM CLA for 48 h) showed very high cellular CLA content in PLs (range: 32-63 g FA/100 g total phospholipid fatty acid) affected by the nature of CLA and the cell type. Supplementation with CLA or LA altered also cell membrane composition by n-6 PUFA synthesis. Accordingly, CLA metabolism interferes with LA metabolism. We were able to show that CLA isomers are converted by the leukemia cells of the same metabolic pathway into conjugated diene fatty acids (CDFAs) as LA into non-conjugated PUFAs. In this view, the gas chromatography-flame ionization detector detection of major CDFAs (CD-18:3, CD-20:2 and CD-20:3) in cell membrane of CLA-treated cultures resulted from successive Delta6-desaturation, elongation and Delta5-desaturation of CLA isomers. However, in comparison to LA, relatively lower amounts of elongation and/or desaturation metabolites were detected for CLA(9c,11t), and only minor amounts or trace CDFAs were observed for CLA(9c,11c). Furthermore, CLA(9c,11t) revealed only very low levels of CD-20:4 FA and no CLA(9c,11c)-conversion could be detected. The metabolization of CLA indicated that CLA(9c,11c)<CLA(9c,11t) were a poorer substrates in compared to LA for the Delta5,6-desaturation/elongation in REH, CCRF-CEM and U937 cells or for the Delta5-desaturation/elongation in the K562 cells. CLA(9c,11t) suppresses Delta6-desaturation in CCRF-CEM, REH, and U937 cells (43.5, 54.6 and 58.8% Delta6-inhibition, respectively) and as well Delta9-desaturation in all four cell lines (Delta9-inhibition; 47.1, 33.9, 29.8 and 25.9% for CCRF-CEM, REH, K562 and U937 cells, respectively). However, CLA(9c,11c) does not inhibit or only slightly affected these desaturations. CLA(9c,11t) isomer was found as an Delta6-desaturase inhibitor with a dose-dependent relationship between inhibition of Delta6-desaturase activity and decreases in cell growth. The growth inhibitory effects of CLA (with 30-120 microM) on leukemia cells were dependent upon the type and concentration of CLA isomers present. CLA-supplemented cells with low concentrations (<60 microM) were not sufficient to impair cell proliferation. Nevertheless, higher amounts of CLAs (>60 microM) had the CLA type dependent antiproliferative effects. Thus, the 9cis,11trans- and the 9cis,11cis-CLA isomers regulate cell growth and survival in different leukemia cell types through their existence alone and/or by their inhibitory effects of desaturase activity.

Protective effects of dietary enrichment with docosahexaenoic acid plus protein in 5-fluorouracil-induced intestinal injury in the rat

OBJECTIVE

The intestinal side effects of anti-tumoural therapy can be so severe as to preclude its clinical efficacy, although the use of selected nutrients and growth factors may ameliorate the noxious effects. This study examines whether dietary supplementation with the polyunsaturated fatty acid docosahexaenoic acid (DHA) potentiates the protective action of growth hormone in the intestine and whether a synergetic effect occurs with dietary protein and DHA enrichment and growth hormone treatment.

METHODS

Male Wistar rats were divided into nine groups and received a standard diet, or a diet supplemented with protein, or a diet supplemented with DHA, or a diet supplemented with both protein and DHA. Three days later, the rats were given 5-fluorouracil (5-FU) and treated with either growth hormone or placebo. A further group of animals fed a standard diet was not treated and served as a control group. Intestinal morphometry, proliferation and apoptosis were determined.

RESULTS

Supplementing the diet with DHA prevented the negative action of 5-FU on mucosal morphometry, but protein supplementation was necessary to prevent the increased apoptosis. When growth hormone was also given with the dietary supplementation, the hypoproliferative effect of 5-FU was also prevented.

CONCLUSION

Enriching the diet with DHA protects against intestinal lesions produced by the anti-tumoural drug 5-FU but requires the joint administration of supplementary protein and growth hormone to reduce the noxious effects of 5-FU.

Properties of polyunsaturated phosphatidylcholine membranes in the presence and absence of cholesterol

Mixtures of cholesterol with phosphatidylcholine species containing the polyunsaturated acyl chains arachidonoyl or docosahexaenoyl were studied by (13)C magic angle spinning (MAS) NMR using both cross-polarization and direct polarization, by (31)P NMR and by differential scanning calorimetry. Several unique features of these systems were observed. The separation of cholesterol in crystalline form occurred at much lower molar fractions than with other forms of phosphatidylcholine. The crystals that were formed were sensitive to the history of the sample. At cholesterol molar fractions below 0.5, they dissolved into the membrane by sequential heating and cooling scans. With higher molar fractions of cholesterol, larger amounts of anhydrous crystals were formed after the first heating. This was accompanied by the formation of non-lamellar phases. The cholesterol crystals that were formed generally were not observed by direct polarization (13)C MAS NMR, even with delay times of 100 s. This suggests that the cholesterol crystals are in a more rigid state in mixtures with these lipids. This is in contrast with the terminal methyl group of the acyl chains that is too mobile to allow cross-polarization using 1 ms contact times.

Docosahexaenoic acid: membrane properties of a unique fatty acid

Docosahexaenoic acid (DHA) with 22-carbons and 6 double bonds is the extreme example of an omega-3 polyunsaturated fatty acid (PUFA). DHA has strong medical implications since its dietary presence has been positively linked to the prevention of numerous human afflictions including cancer and heart disease. The PUFA, moreover, is essential to neurological function. It is remarkable that one simple molecule has been reported to affect so many seemingly unrelated biological processes. Although details of a molecular mode of action remain elusive, DHA must be acting at a fundamental level common to many tissues that is related to the high degree of conformational flexibility that the multiple double bonds have been identified to confer. One likely target for DHA action is at the cell membrane where the fatty acid is known to readily incorporate into membrane phospholipids. Once esterified into phospholipids DHA has been demonstrated to significantly alter many basic properties of membranes including acyl chain order and "fluidity", phase behavior, elastic compressibility, permeability, fusion, flip-flop and protein activity. It is concluded that DHA's interaction with other membrane lipids, particularly cholesterol, may play a prominent role in modulating the local structure and function of cell membranes.

Phospholipid chlorohydrins cause ATP depletion and toxicity in human myeloid cells

Chlorohydrins of stearoyl-oleoyl phosphatidylcholine (SOPC), stearoyl-linoleoyl phosphatidylcholine, and stearoyl-arachidonyl phosphatidylcholine were incubated with cultured myeloid cells (HL60) for 24 h, and the cellular ATP level was measured using a bioluminescent assay. The chlorohydrins caused significant depletion of cellular ATP in the range 10-100 microM. The ATP depletion by the phospholipid chlorohydrins was slightly less than that of 4-hydroxy-2-nonenal, but greater than that of hexanal, trans-2-nonenal, and autoxidised palmitoyl-arachidonoyl phosphatidylcholine. SOPC chlorohydrin was also found to cause loss of viability in U937 cells, and thus phospholipid chlorohydrins could contribute to the formation of a necrotic core in advanced atherosclerotic lesions.

Synthesis of a novel phosphatidylcholine conjugated to docosahexaenoic acid and methotrexate that inhibits cell proliferation

Here we report the synthesis and characterization of a lipophilic phosphatidylcholine containing the omega-3 fatty acid docosahexaenoic acid (DHA) and the cytotoxic drug methotrexate (MTX). This novel phospholipid combines the fatty acid's and the drug's anticancer activities in a molecule amenable to a liposome bilayer for safe, simultaneous delivery of the two agents. Two phosphatidylcholines were synthesized, from 1-stearoyl or 1-docosahexaenoyl, 2-hydroxy-sn-glycero-3-phosphocholine, to contain MTX in the sn-2 position and either stearic acid or DHA in the sn-1 position. The products contain fatty acid, MTX and phosphorus (1:1:1), and the MTX was released by phospholipase A(2), consistent with the proposed phospholipid structure. The predominant product linked MTX to the glycerol moiety through MTX's gamma-carboxyl group. Liposomes composed of 1-stearoyl, 2-oleoyl phosphatidylcholine plus 1-stearoyl, 2-oleoyl phosphatidylethanolamine and various concentrations of the novel phospholipids caused dose-dependent inhibition of murine leukemia cell proliferation in culture. The DHA- and MTX-containing phosphatidylcholine was more effective than that containing stearic acid, and DHA appeared to synergize with MTX when they were added as free agents or covalently linked in the phospholipid. These data show the feasibility of synthesizing, and the inhibitory activity of phosphatidylcholine with DHA in the sn-1 position and MTX in the sn-2 position, and suggest the compound's potential use in cancer chemotherapy.

Docosahexaenoic acid (DHA) alters the phospholipid molecular species composition of membranous vesicles exfoliated from the surface of a murine leukemia cell line

Previously, we presented evidence that the vesicles routinely exfoliated from the surface of T27A tumor cells arise from vesicle-forming regions of the plasma membrane and possess a set of lateral microdomains distinct from those of the plasma membrane as a whole. We also showed that docosahexaenoic acid (DHA, or 22:6n-3), a fatty acyl chain known to alter microdomain structure in model membranes, also alters the structure and composition of exfoliated vesicles, implying a DHA-induced change in microdomain structure on the cell surface. In this report we show that enrichment of the cells with DHA reverses some of the characteristic differences in composition between the parent plasma membrane and shed microdomain vesicles, but does not alter their phospholipid class composition. In untreated cells, DHA-containing species were found to be a much greater proportion of the total phosphatidylethanolamine (PE) pool than the total phosphatidylcholine (PC) pool in both the plasma membrane and the shed vesicles. After DHA treatment, the proportion of DHA-containing species in the PE and PC pools of the plasma membrane were elevated, and unlike in untreated cells, their proportions were equal in the two pools. In the vesicles shed from DHA-loaded cells, the proportion of DHA-containing species of PE was the same as in the plasma membrane. However, the proportion of DHA-containing species of PC in the vesicles (0.089) was much lower than that found in the plasma membrane (0.194), and was relatively devoid of species with 16-carbon acyl components. These data suggested that DHA-containing species of PC, particularly those having a 16-carbon chain in the sn-1 position, were preferentially retained in the plasma membrane. The data can be interpreted as indicating that DHA induces a restructuring of lateral microdomains on the surface of living cells similar to that predicted by its behavior in model membranes.