Effects of docosapentaenoic acid on neuronal apoptosis

Understanding the effects of omega-3 fatty acid supplementation on the physical properties of brain lipid membranes

A deficiency in omega-3 fatty acids (ω3 FAs) in the brain has been correlated with cognitive impairment, learning deficiencies, and behavioral changes. In this study, we provided ω3 FAs as a supplement to spontaneously hypertensive rats (SHR+ ω3). Our focus was on examining the impact of dietary supplementation on the physicochemical properties of the brain-cell membranes. Significant increases in ω3 levels in the cerebral cortex of SHR+ ω3 were observed, leading to alterations in brain lipid membranes molecular packing, elasticity, and lipid miscibility, resulting in an augmented phase disparity. Results from synthetic lipid mixtures confirmed the disordering effect introduced by ω3 lipids, showing its consequences on the hydration levels of the monolayers and the organization of the membrane domains. These findings suggest that dietary ω3 FAs influence the organization of brain membranes, providing insight into a potential mechanism for the broad effects of dietary fat on brain health and disease.

Docosahexaenoic acid inhibits ischemic stroke to reduce vascular dementia and Alzheimer’s disease

Stroke and dementia are global leading causes of neurological disability and death. The pathology of these diseases is interrelated and they share common, modifiable risk factors. It is suggested that docosahexaenoic acid (DHA) prevents neurological and vascular disorders induced by ischemic stroke and also prevent dementia. The purpose of this study was to review the potential preventative role of DHA against ischemic stroke-induced vascular dementia and Alzheimer's disease. In this review, I analyzed studies on stroke-induced dementia from the PubMed, ScienceDirect, and Web of Science databases as well as studies on the effects of DHA on stroke-induced dementia. As per the results of interventional studies, DHA intake can potentially ameliorate dementia and cognitive function. In particular, DHA derived from foods such as fish oil enters the blood and then migrates to the brain by binding to fatty acid binding protein 5 that is present in cerebral vascular endothelial cells. At this point, the esterified form of DHA produced by lysophosphatidylcholine is preferentially absorbed into the brain instead of free DHA. DHA accumulates in nerve cell membrane and is involved in the prevention of dementia. The antioxidative and anti-inflammatory properties of DHA and DHA metabolites as well as their ability to decrease amyloid beta (Aβ) 42 production were implicated in the improvement of cognitive function. The antioxidant effect of DHA, the inhibition of neuronal cell death by Aβ peptide, improvement in learning ability, and enhancement of synaptic plasticity may contribute to the prevention of dementia induced by ischemic stroke.

Essential omega-3 fatty acids tune microglial phagocytosis of synaptic elements in the mouse developing brain

Omega-3 fatty acids (n-3 PUFAs) are essential for the functional maturation of the brain. Westernization of dietary habits in both developed and developing countries is accompanied by a progressive reduction in dietary intake of n-3 PUFAs. Low maternal intake of n-3 PUFAs has been linked to neurodevelopmental diseases in Humans. However, the n-3 PUFAs deficiency-mediated mechanisms affecting the development of the central nervous system are poorly understood. Active microglial engulfment of synapses regulates brain development. Impaired synaptic pruning is associated with several neurodevelopmental disorders. Here, we identify a molecular mechanism for detrimental effects of low maternal n-3 PUFA intake on hippocampal development in mice. Our results show that maternal dietary n-3 PUFA deficiency increases microglia-mediated phagocytosis of synaptic elements in the rodent developing hippocampus, partly through the activation of 12/15-lipoxygenase (LOX)/12-HETE signaling, altering neuronal morphology and affecting cognitive performance of the offspring. These findings provide a mechanistic insight into neurodevelopmental defects caused by maternal n-3 PUFAs dietary deficiency.

Dietary docosahexaenoic acid inhibits neurodegeneration and prevents stroke

Stroke severely impairs quality of life and has a high mortality rate. On the other hand, dietary docosahexaenoic acid (DHA) prevents neuronal damage. In this review, we describe the effects of dietary DHA on ischemic stroke-associated neuronal damage and its role in stroke prevention. Recent epidemiological studies have been conducted to analyze stroke prevention through DHA intake. The effects of dietary intake and supply of DHA to neuronal cells, DHA-mediated inhibition of neuronal damage, and its mechanism, including the effects of the DHA metabolite, neuroprotectin D1 (NPD1), were investigated. These studies revealed that DHA intake was associated with a reduced risk of stroke. Moreover, studies have shown that DHA intake may reduce stroke mortality rates. DHA, which is abundant in fish oil, passes through the blood-brain barrier to accumulate as a constituent of phospholipids in the cell membranes of neuronal cells and astrocytes. Astrocytes supply DHA to neuronal cells, and neuronal DHA, in turn, activates Akt and Raf-1 to prevent neuronal death or damage. Therefore, DHA indirectly prevents neuronal damage. Furthermore, NDP1 blocks neuronal apoptosis. DHA, together with NPD1, may block neuronal damage and prevent stroke. The inhibitory effect on neuronal damage is achieved through the antioxidant (via inducing the Nrf2/HO-1 system) and anti-inflammatory effects (via promoting JNK/AP-1 signaling) of DHA.

Prefrontal fatty acid composition in schizophrenia and bipolar disorder: Association with reelin expression

OBJECTIVE

The extracellular matrix protein reelin regulates early brain development and synaptic plasticity in adulthood. Reelin is decreased in the postmortem brain in schizophrenia patients. Reelin's two receptors, ApoER2 and VLDLR, are also substrates for ApoE - a key lipoprotein that regulates phospholipid homeostasis in the brain. The goal of the present study was therefore to examine phospholipids and their constituent fatty acids, and determine whether there is an association between reelin, its receptors and phospholipids in the brain.

METHODS

Dorsolateral prefrontal cortex (BA9) grey matter was obtained from the Stanley Foundation Neuropathology Consortium. Samples included tissue from 35 controls, 35 schizophrenia and 34 bipolar disorder patients. Phospholipids were measured using gas liquid chromatography.

RESULTS

We quantified 15 individual fatty acid or plasmalogen species for phosphatidylethanolamine and phosphatidylcholine fractions, each comprising >0.5% of the total fatty acid pool. There were no group differences in phospholipids or individual fatty acid species after correcting for multiple comparisons. However, for the entire cohort, both the polyunsaturated subclass of fatty acids, and ApoE, correlated significantly with reelin expression, with a number of individual ω-6 fatty acid species also demonstrating a significant positive correlation. There was a non-significant trend for similar effects with VLDLR expression as for reelin.

CONCLUSION

Phospholipids and fatty acids in the dorsolateral cortex do not differ in patients with schizophrenia, bipolar disorder and controls. Reelin expression in this brain region is associated with polyunsaturated fatty acids and ApoE, suggesting further study of potential physiological interactions between these substrates is warranted.

Potential neuroprotective and anti-inflammatory effects provided by omega-3 (DHA) against Zika virus infection in human SH-SY5Y cells

Zika virus (ZIKV) has a strong tropism for the nervous system and has been related to post-infection neurological syndromes. Once neuronal cells are infected, the virus is capable of modulating cell metabolism, leading to neurotoxicity and cellular death. The negative effect of ZIKV in neuron cells has been characterized. However, the description of molecules capable of reversing these cytotoxic effects is still under investigation. In this context, it has been largely demonstrated that docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid, is highly neuroprotective. Here, we hypothesized that DHA's neuroprotective proprieties could have an influence on ZIKV-induced neurotoxicity in SH-SY5Y cells. Our data showed that pre-treatment of SH-SY5Y cells with DHA increased the cell viability and proliferation in ZIKV-infected cells. Moreover, DHA triggered an anti-inflammatory response in those infected cells. Besides, DHA was capable of restoring mitochondria function and number in ZIKV-infected SH-SY5Y cells. In addition, cells pre-treated with DHA prior to ZIKV infection presented a lower viral load at different times of infection. Taking together, these results demonstrated that DHA has a potential anti-inflammatory and neuroprotective effect against ZIKV infection in these neuron-like cells and could be a useful tool in the treatment against this virus.

Ameliorative effect of docosahexaenoic acid on hepatocyte apoptosis and inflammation induced by oleic acid in grass carp, Ctenopharyngodon idella

Our previous study has shown that overload of lipid accumulation results in cell apoptosis and inflammation in grass carp (Ctenopharyngodon idella). In this study, we investigated the potential protective effects of docosahexaenoic acid (DHA) on inhibiting oleic acid (OA)-induced apoptosis and inflammation in grass carp hepatocytes. Firstly, the hepatocyte of grass carp were treated with OA (800 μM) and different concentration (0, 50, 100 and 200 μM) of DHA for 24 h, the apoptotic ratio, gene expression levels of apoptosis such as caspase 3, caspase 8, and caspase 9, protein levels of Caspase3, and mRNA levels of inflammation genes such as nf-kb, tnf-α, and il-8 were detected. Furthermore, the mRNA levels of lipogenesis genes srebp1c, fas, acc, and scd and a key enzyme of lipolysis Atgl were also detected. These results showed that the cell apoptosis and the inflammation increased by OA were significantly attenuated by DHA (P < 0.05). Furthermore, DHA could significantly decrease fatty acid synthesis gene expression levels which were induced by OA (P < 0.05). However, the hepatocytes exposed with DHA had no significant influence on the expression of Atgl. Taken together, the study indicated that DHA protects the hepatocytes against apoptosis and inflammation induced by OA might via inhibiting fatty acid synthesis, instead of promoting lipolysis. These results call for further studies to assess the effectiveness of DHA.

MAG-DPA curbs inflammatory biomarkers and pharmacological reactivity in cytokine-triggered hyperresponsive airway models

Bronchial inflammation contributes to a sustained elevation of airway hyperresponsiveness (AHR) in asthma. Conversely, omega-3 fatty acid derivatives have been shown to resolve inflammation in various tissues. Thus, the effects of docosapentaenoic acid monoacylglyceride (MAG-DPA) were assessed on inflammatory markers and reactivity of human distal bronchi as well as in a cultured model of guinea pig tracheal rings. Human bronchi were dissected and cultured for 48 h with 10 ng/mL TNF-α or IL-13. Guinea pig tracheas were maintained in organ culture for 72 h which was previously shown to trigger spontaneous AHR. All tissues were treated with increasing concentrations of MAG-DPA (0.1, 0.3, and 1 μmol/L). Pharmacomechanical reactivity, Ca²⁺ sensitivity, and western blot analysis for specific phosphoproteins and transcription factors were performed to assess the effects of both cytokines, alone or in combination with MAG-DPA, on human and guinea pig airway preparations. Although 0.1 μmol/L MAG-DPA did not significantly reduce inflammatory biomarkers, the higher concentrations of MAG-DPA (0.3 and 1 μmol/L) blunted the activation of the TNF-α/NF κB pathway and abolished COX-2 expression in human and guinea pig tissues. Moreover, 0.3 and 1 μmol/L MAG-DPA consistently decreased the Ca²⁺ sensitivity and pharmacological reactivity of cultured bronchial explants. Furthermore, in human bronchi, IL-13-stimulated phosphorylation of CPI-17 was reversed by 1 μmol/L MAG-DPA. This effect was further amplified in the presence of 100 μmol/L aspirin. MAG-DPA mediates antiphlogistic effects by increasing the resolution of inflammation, while resetting Ca²⁺ sensitivity and contractile reactivity.

Metabolomic analysis of exercise effects in the POLG mitochondrial DNA mutator mouse brain

Mitochondrial DNA (mtDNA) mutator mice express a mutated form of mtDNA polymerase gamma that results an accelerated accumulation of somatic mtDNA mutations in association with a premature aging phenotype. An exploratory metabolomic analysis of cortical metabolites in sedentary and exercised mtDNA mutator mice and wild-type littermate controls at 9-10 months of age was performed. Pathway analysis revealed deficits in the neurotransmitters acetylcholine, glutamate, and aspartate that were ameliorated by exercise. Nicotinamide adenine dinucleotide (NAD) depletion and evidence of increased poly(adenosine diphosphate-ribose) polymerase 1 (PARP1)activity were apparent in sedentary mtDNA mutator mouse cortex, along with deficits in carnitine metabolites and an upregulated antioxidant response that largely normalized with exercise. These data highlight specific pathways that are altered in the brain in association with an accelerated age-related accumulation of somatic mtDNA mutations. These results may have relevance to age-related neurodegenerative diseases associated with mitochondrial dysfunction, such as Alzheimer's disease and Parkinson's disease and provide insights into potential mechanisms of beneficial effects of exercise on brain function.

Phosphatidylserine in the brain: metabolism and function

Phosphatidylserine (PS) is the major anionic phospholipid class particularly enriched in the inner leaflet of the plasma membrane in neural tissues. PS is synthesized from phosphatidylcholine or phosphatidylethanolamine by exchanging the base head group with serine, and this reaction is catalyzed by phosphatidylserine synthase 1 and phosphatidylserine synthase 2 located in the endoplasmic reticulum. Activation of Akt, Raf-1 and protein kinase C signaling, which supports neuronal survival and differentiation, requires interaction of these proteins with PS localized in the cytoplasmic leaflet of the plasma membrane. Furthermore, neurotransmitter release by exocytosis and a number of synaptic receptors and proteins are modulated by PS present in the neuronal membranes. Brain is highly enriched with docosahexaenoic acid (DHA), and brain PS has a high DHA content. By promoting PS synthesis, DHA can uniquely expand the PS pool in neuronal membranes and thereby influence PS-dependent signaling and protein function. Ethanol decreases DHA-promoted PS synthesis and accumulation in neurons, which may contribute to the deleterious effects of ethanol intake. Improvement of some memory functions has been observed in cognitively impaired subjects as a result of PS supplementation, but the mechanism is unclear.

Docosahexaenoic acid signalolipidomics in nutrition: significance in aging, neuroinflammation, macular degeneration, Alzheimer's, and other neurodegenerative diseases

Essential polyunsaturated fatty acids (PUFAs) are critical nutritional lipids that must be obtained from the diet to sustain homeostasis. Omega-3 and -6 PUFAs are key components of biomembranes and play important roles in cell integrity, development, maintenance, and function. The essential omega-3 fatty acid family member docosahexaenoic acid (DHA) is avidly retained and uniquely concentrated in the nervous system, particularly in photoreceptors and synaptic membranes. DHA plays a key role in vision, neuroprotection, successful aging, memory, and other functions. In addition, DHA displays anti-inflammatory and inflammatory resolving properties in contrast to the proinflammatory actions of several members of the omega-6 PUFAs family. This review discusses DHA signalolipidomics, comprising the cellular/tissue organization of DHA uptake, its distribution among cellular compartments, the organization and function of membrane domains rich in DHA-containing phospholipids, and the cellular and molecular events revealed by the uncovering of signaling pathways regulated by DHA and docosanoids, the DHA-derived bioactive lipids, which include neuroprotectin D1 (NPD1), a novel DHA-derived stereoselective mediator. NPD1 synthesis agonists include neurotrophins and oxidative stress; NPD1 elicits potent anti-inflammatory actions and prohomeostatic bioactivity, is anti-angiogenic, promotes corneal nerve regeneration, and induces cell survival. In the context of DHA signalolipidomics, this review highlights aging and the evolving studies on the significance of DHA in Alzheimer's disease, macular degeneration, Parkinson's disease, and other brain disorders. DHA signalolipidomics in the nervous system offers emerging targets for pharmaceutical intervention and clinical translation.

LC/ESR/MS study of pH-dependent radical generation from 15-LOX-catalyzed DPA peroxidation

Docosapentaenoic acid (DPA) is a unique fatty acid that exists in two isomeric forms (n-3 and n-6), which differ in their physiological behaviors. DPA can undergo free radical-mediated peroxidation via lipoxygenase (LOX). 15-LOX, one of the LOX isomers, has received much attention in cancer research because of its very different expression level in normal tissues compared to tumors and some bioactive fatty acid metabolites modulating the tumorigenic pathways in cancer. However, the mechanism linking 15-LOX, DPA metabolites, and their bioactivities is still unclear, and the free radicals generated in DPA peroxidation have never been characterized. In this study, we have studied radicals formed from both soybean and human cellular (PC3-15LOS cells) 15-LOX-catalyzed peroxidation of DPAs at various pH's using a combination of LC/ESR/MS with the spin trapping technique. We observed a total of three carbon-centered radicals formed in 15-LOX-DPA (n-3) stemming from its 7-, 17-, and 20-hydroperoxides, whereas only one formed from 17-hydroperoxide in DPA (n-6). A change in the reaction pH from 8.5 (15-LOX enzyme optimum) to 7.4 (physiological) and to 6.5 (tumor, acidic) not only decreased the total radical formation but also altered the preferred site of oxygenation. This pH-dependent alteration of radical formation and oxygenation pattern may have significant implications and provide a basis for our ongoing investigations of LOXs as well as fatty acids in cancer biology.

The use of omega-3 fatty acids in mental illness

PURPOSE

This article will summarize the current evidence on the effects of omega-3 fatty acids on prevention and treatment of mental illness.

BACKGROUND

Omega-3 fatty acids are involved in many physiologic processes. Since they cannot be made de novo in the body, they are considered essential nutrients. As the Western diet evolved, dietary intake of fatty acids has shifted to increased omega-6 fatty acids and decreased omega-3 fatty acids intake. These changes have been correlated with numerous differences in prevalence and course of mental illnesses.

METHODS

A MEDLINE search from 1966 to December 2010 was completed to identify studies comparing changes in symptoms, functioning, other outcomes, and/or side effects in patients treated with omega-3 fatty acids for mental illness. The studies were reviewed and reported by specific psychiatric disorder studied.

CONCLUSIONS

Omega-3 fatty acids play a role in many biologic functions. Epidemiologic data implicate omega-3 fatty acid deficiencies in many mental illnesses. Data are most robust for omega-3 fatty acids' role in affective disorders. However, data are conflicting, negative, or absent for most mental illnesses.

Retailoring docosahexaenoic acid-containing phospholipid species during impaired neurogenesis following omega-3 alpha-linolenic acid deprivation

Diminished levels of docosahexaenoic acid (22:6n-3), the major fatty acid (FA) synthesized from alpha-linolenic acid (18:3n-3), have been implicated in functional impairment in the developing and adult brain. We have now examined the changes in phospholipid (PL) molecular species in the developing postnatal cortex, a region recently shown to be affected by a robust aberration in neuronal cell migration, after maternal diet alpha-linolenic acid deprivation (Yavin et al. (2009)Neuroscience162(4),1011). The frontal cortex PL composition of 1- to 4-week-old rats was analyzed by gas chromatography and electrospray ionization/tandem mass spectrometry. Changes in the cortical PL molecular species profile by dietary means appear very specific as 22:6n-3 was exclusively substituted by docosapentaenoic acid (22:5n-6). However, molecular species were conserved with respect to the combination of specific polar head groups (i.e. ethanolamine and serine) in sn-3 and defined saturated/mono-unsaturated FA in sn-1 position even when the sn-2 FA moiety underwent diet-induced changes. Our results suggest that substitution of docosahexaenoic acid by docosapentaenoic acid is tightly regulated presumably to maintain a proper biophysical characteristic of membrane PL molecular species. The importance of this conservation may underscore the possible biochemical consequences of this substitution in regulating certain functions in the developing brain.

The polyunsaturated fatty acids, EPA and DPA exert a protective effect in the hippocampus of the aged rat

Age is characterized by deficits in synaptic function identified by decreased performance of aged animals in spatial learning tasks and reduced ability of animals to sustain long term potentiation (LTP). Several cellular and molecular events are correlated with these deficits, many of which are indicative of age-related neuroinflammatory and oxidative cell stress. It is significant that agents which decrease microglial activation are commonly associated with restoration of function. We set out to examine whether the n-3 polyunsaturated fatty acid docosapentaenoic acid (DPA), which is a metabolite of eicosapentaenoic acid (EPA), could modulate the age-related increase in microglial activation and the associated increase in oxidative changes and therefore impact on synaptic function in aged rats. We demonstrate that docosapentaenoic acid possesses neurorestorative effects and is capable of downregulating microglial activation. The data show that it also decreases the coupled activation of sphingomyelinase and caspase 3, probably because of its ability to decrease age-related oxidative changes, and consequently attenuates the age-related decrease in spatial learning and long-term potentiation.

Phosphatidylserine-dependent neuroprotective signaling promoted by docosahexaenoic acid

Enrichment of polyunsaturated fatty acids, particularly docosahexaenoic acid (DHA, 22:6n-3), in the brain is known to be critical for optimal brain development and function. Mechanisms for DHA's beneficial effects in the nervous system are not clearly understood at present. DHA is incorporated into the phospholipids in neuronal membranes, which in turn can influence not only the membrane chemical and physical properties but also the cell signaling involved in neuronal survival, proliferation and differentiation. Our studies have indicated that DHA supplementation promotes phosphatidylserine (PS) accumulation and inhibits neuronal cell death under challenged conditions, supporting a notion that DHA is an important neuroprotective agent. This article summarizes our findings on the DHA-mediated membrane-related signaling mechanisms that might explain some of the beneficial effects of DHA, particularly on neuronal survival.

Significance of long-chain polyunsaturated fatty acids (PUFAs) for the development and behaviour of children

omega-6 and omega-3 polyunsaturated fatty acids (PUFAs) play a central role in the normal development and functioning of the brain and central nervous system. Long-chain PUFAs (LC-PUFAs) such as eicosapentaenoic acid (EPA, C20:5omega-3), docosahexaenoic acid (DHA, C22:6omega-3) and arachidonic acid (AA, C20:4omega-6), in particular, are involved in numerous neuronal processes, ranging from effects on membrane fluidity to gene expression regulation. Deficiencies and imbalances of these nutrients, not only during the developmental phase but throughout the whole life span, have significant effects on brain function. Numerous observational studies have shown a link between childhood developmental disorders and omega-6:omega-3 fatty acid imbalances. For instance, neurocognitive disorders such as attention-deficit hyperactivity disorder (ADHD), dyslexia, dyspraxia and autism spectrum disorders are often associated with a relative lack of omega-3 fatty acids. In addition to a high omega-6 fatty acid intake and, in many cases, an insufficient supply of omega-3 fatty acids among the population, evidence is increasing to suggest that PUFA metabolism can be impaired in individuals with ADHD. In this context, PUFA imbalances are being discussed as potential risk factors for neurodevelopmental disorders. Another focus is whether the nutritive PUFA requirements-especially long-chain omega-3 fatty acid requirements-are higher among some individuals. Meanwhile, several controlled studies investigated the clinical benefits of LC-PUFA supplementation in affected children and adolescents, with occasionally conflicting results.

Starving neurons show sex difference in autophagy

Sex-dependent differences in adaptation to famine have long been appreciated, thought to hinge on female versus male preferences for fat versus protein sources, respectively. However, whether these differences can be reduced to neurons, independent of typical nutrient depots, such as adipose tissue, skeletal muscle, and liver, was heretofore unknown. A vital adaptation to starvation is autophagy, a mechanism for recycling amino acids from organelles and proteins. Here we show that segregated neurons from males in culture are more vulnerable to starvation than neurons from females. Nutrient deprivation decreased mitochondrial respiration, increased autophagosome formation, and produced cell death more profoundly in neurons from males versus females. Starvation-induced neuronal death was attenuated by 3-methyladenine, an inhibitor of autophagy; Atg7 knockdown using small interfering RNA; or L-carnitine, essential for transport of fatty acids into mitochondria, all more effective in neurons from males versus females. Relative tolerance to nutrient deprivation in neurons from females was associated with a marked increase in triglyceride and free fatty acid content and a cytosolic phospholipase A2-dependent increase in formation of lipid droplets. Similar sex differences in sensitivity to nutrient deprivation were seen in fibroblasts. However, although inhibition of autophagy using Atg7 small interfering RNA inhibited cell death during starvation in neurons, it increased cell death in fibroblasts, implying that the role of autophagy during starvation is both sex- and tissue-dependent. Thus, during starvation, neurons from males more readily undergo autophagy and die, whereas neurons from females mobilize fatty acids, accumulate triglycerides, form lipid droplets, and survive longer.

Biochemical and biological functions of docosahexaenoic acid in the nervous system: modulation by ethanol

Docosahexaenoic acid (DHA, 22:6n-3), an n-3 fatty acid highly concentrated in the central nervous system, is essential for proper neuronal and retinal function. While a high level of DHA is generally maintained in neuronal membranes, inadequate supply of n-3 fatty acid or ethanol exposure leads to a significant loss of DHA in neuronal cells. The roles of DHA in neuronal signaling have been emerging. In this review, biological, biochemical and molecular mechanisms supporting the essential function of DHA in neuronal survival and development are described in relation to n-3 fatty acid depleting conditions.

Detection of intracellular phosphatidylserine in living cells

To demonstrate the intracellular phosphatidylserine (PS) distribution in neuronal cells, neuroblastoma cells and hippocampal neurons expressing green fluorescence protein (GFP)-AnnexinV were stimulated with a calcium ionophore and localization of GFP-AnnexinV was monitored by fluorescence microscopy. Initially, GFP-AnnexinV distributed evenly in the cytosol and nucleus. Raising the intracellular calcium level with ionomycin-induced translocation of cytoplasmic GFP-AnnexinV to the plasma membrane but not to the nuclear membrane, indicating that PS distributes in the cytoplasmic side of the plasma membrane. Nuclear GFP-AnnexinV subsequently translocated to the nuclear membrane, indicating PS localization in the nuclear envelope. GFP-AnnexinV also localized in a juxtanuclear organelle that was identified as the recycling endosome. However, minimal fluorescence was detected in any other subcellular organelles including mitochondria, endoplasmic reticulum, Golgi complex, and lysosomes, strongly suggesting that PS distribution in the cytoplasmic face in these organelles is negligible. Similarly, in hippocampal primary neurons PS distributed in the inner leaflet of plasma membranes of cell body and dendrites, and in the nuclear envelope. To our knowledge, this is the first demonstration of intracellular PS localization in living cells, providing an insight for specific sites of PS interaction with soluble proteins involved in signaling processes.

Polyunsaturated fatty acids stimulate phosphatidylcholine synthesis in PC12 cells

The synthesis of phospholipids in mammalian cells is regulated by the availability of three critical precursor pools: those of choline, cytidine triphosphate and diacylglycerol. Diacylglycerols containing polyunsaturated fatty acids (PUFAs) apparently are preferentially utilized for phosphatide synthesis. PUFAs are known to play an important role in the development and function of mammalian brains. We therefore studied the effects of unsaturated, monounsaturated and polyunsaturated fatty acids on the overall rates of phospholipid biosynthesis in PC12 rat pheochromocytoma cells. Docosahexaenoic acid (DHA, 22:6n-3), eicosapentaenoic acid (EPA, 20:5n-3) and arachidonic acid (AA, 20:4n-6) all significantly stimulated the incorporation of (14)C-choline into total cellular phospholipids. In contrast, monounsaturated oleic acid (OA) and the saturated palmitic (PA) and stearic (SA) acids did not have this effect. The action of DHA was concentration-dependent between 5 and 50 microM; it became statistically significant by 3 h after DHA treatment and then increased over the ensuing 3 h. DHA was preferentially incorporated into phosphatidylethanolamine (PE) and phosphatidylserine (PS), while AA predominated in phosphatidylcholine (PC).

The effect of inhibition of Ca2+-independent phospholipase A2 on chemotherapeutic-induced death and phospholipid profiles in renal cells

We demonstrate that cells derived from primary cultures of rabbit proximal tubules (RPTC), human embryonic kidney (HEK293) and human kidney carcinomas (Caki-1) express microsomal Ca(2+)-independent phospholipase A(2) (iPLA(2)gamma) and cytosolic Ca(2+)-independent phospholipase A(2) (iPLA(2)beta). Inhibition of iPLA(2) activity in these cells using the iPLA(2) inhibitor bromoenol lactone (BEL) (0-5.0microM) for 24h did not induce cell death as determined by annexin V and propidium iodide (PI) staining. However, BEL treatment prior to cisplatin (50muM) or vincristine (2microM) exposure reduced apoptosis 30-50% in all cells tested (RPTC, HEK293 and Caki-1 cells). To identify the phospholipids altered during cell death electrospray ionization-mass spectrometry and lipidomic analysis of HEK293 and Caki-1 cells was performed. Cisplatin treatment reduced 14:0-16:0 and 16:0-16:0 phosphatidylcholine (PtdCho) 50% and 35%, respectively, in both cell lines, 16:0-18:2 PtdCho in Caki-1 cells and increased 16:1-22:6 plasmenylcholine (PlsCho). BEL treatment prior to cisplatin exposure further decreased 14:0-16:0 PtdCho, 16:0-16:1 PlsCho and 16:0-18:1 PlsCho in HEK293 cells, and inhibited cisplatin-induced increases in 16:1-22:6 PlsCho in Caki-1 cells. Treatment of cells with BEL prior to cisplatin exposure also increased the levels of several arachidonic containing phospholipids including 16:0-20:4, 18:1-20:4, and 18:0-20:4 PtdCho, compared to cisplatin only treated cells. These data demonstrate that inhibition of iPLA(2) protects against chemotherapeutic-induced cell death in multiple human renal cell models, identifies specific phospholipids whose levels are altered during cell death, and demonstrates that alterations in these phospholipids correlate to the protection against cell death in the presence of iPLA(2) inhibitors.

An extraordinary degree of structural specificity is required in neural phospholipids for optimal brain function: n-6 docosapentaenoic acid substitution for docosahexaenoic acid leads to a loss in spatial task performance

This study was conducted to determine whether provision of preformed dietary docosapentaenoic acid (DPAn-6) can replace docosahexaenoic acid (DHA) for brain function as assessed by spatial task performance. A newly modified artificial rearing method was employed to generate n-3 fatty acid-deficient rats. Newborn pups were separated from their mothers at 2 days of age and given artificial rat milk containing linoleic acid (LA), or LA supplemented with 1% DHA (DHA), 1% DPAn-6 (DPA) or 1% DHA plus 0.4% DPAn-6 (DHA/DPA). The animals were then weaned onto similar pelleted diets. At adulthood, behavioural tasks were administered and then the brains were collected for fatty acid analysis. The LA and DPA groups showed a lower (63-65%) brain DHA than the dam-reared, DHA and DHA/DPA groups and this loss was largely compensated for by an increase in brain DPAn-6. The brain fatty acid composition in the DPA group was the same as that in the LA group at adulthood. In the Morris water maze, the LA and DPA groups exhibited a longer escape latency than the dam-reared and DHA groups and had a defect in spatial retention. In conclusion, DPAn-6 could not replace DHA for brain function, indicating a highly specific structural requirement for DHA.

Omega-3 fatty acids: molecular approaches to optimal biological outcomes

PURPOSE OF REVIEW

This review discusses recent advances in delineating basic mechanisms underlying the beneficial effects of omega-3 fatty acids on health and on disease.

RECENT FINDINGS

While a substantial number of studies have delineated many differences between the biological effects of saturated versus polyunsaturated fatty acids, less is known about the long-chain omega-3 fatty acids commonly present in certain fish oils. In this review, we focus on recent studies relating to basic mechanisms whereby omega-3 fatty acids modulate cellular pathways to exert beneficial effects on promoting health and decreasing risks of certain diseases. We will use, as examples, conditions of the cardiovascular, neurological, and immunological systems as well as diabetes and cancer, and then discuss basic regulatory pathways.

SUMMARY

Omega-3 fatty acids are major regulators of multiple molecular pathways, altering many areas of cellular and organ function, metabolism and gene expression. Generally, these regulatory events lead to "positive" endpoints relating to health and disease.