Docosahexaenoic acid abundance in the brain: a biodevice to combat oxidative stress

Transgenic conversion of omega-6 into omega-3 fatty acids in a mouse model of Parkinson's disease

We have recently identified a neuroprotective role for omega-3 polyunsaturated fatty acids (n-3 PUFAs) in a toxin-induced mouse model of Parkinson's disease (PD). Combined with epidemiological data, these observations suggest that low n-3 PUFA intake is a modifiable environmental risk factor for PD. In order to strengthen these preclinical findings as prerequisite to clinical trials, we further investigated the neuroprotective role of n-3 PUFAs in Fat-1 mice, a transgenic model expressing an n-3 fatty acid desaturase converting n-6 PUFAs into n-3 PUFAs. Here, we report that the expression of the fat-1 transgene increased cortical n-3:n-6 PUFA ratio (+28%), but to a lesser extent than dietary supplementation (92%). Such a limited endogenous production of n-3 PUFAs in the Fat-1 mouse was insufficient to confer neuroprotection against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine neurotoxicity as assessed by dopamine levels, tyrosine hydroxylase (TH)-positive neurons and fibers, as well as nigral Nurr1 and dopamine transporter (DAT) mRNA expression. Nevertheless, higher cortical docosahexaenoic acid (DHA) concentrations were positively correlated with markers of nigral dopaminergic neurons such as the number of TH-positive cells, in addition to Nurr1 and DAT mRNA levels. These associations are consistent with the protective role of DHA in a mouse model of PD. Taken together, these data suggest that dietary intake of a preformed DHA supplement is more effective in reaching the brain and achieving neuroprotection in an animal model of PD.

Docosahexaenoic acid suppresses neuroinflammatory responses and induces heme oxygenase-1 expression in BV-2 microglia: implications of antidepressant effects for ω-3 fatty acids

Accumulating evidence suggests that the pathophysiology of depression might be associated with neuroinflammation, which could be attenuated by pharmacological treatment for depression. Omega-3 polyunsaturated fatty acids (PUFAs) are anti-inflammatory and exert antidepressant effects. The aim of this study was to identify the molecular mechanisms through which docosahexaenoic acid (DHA), the main omega-3 PUFA in the brain, modulates oxidative reactions and inflammatory cytokine production in microglial and neuronal cells. The results of this study showed that DHA reduced expressions of tumor necrosis factor-α, interleukin-6, nitric oxide synthase, and cyclo-oxygenase-2, induced by interferon-γ, and induced upregulation of heme oxygenase-1 (HO-1) in BV-2 microglia. The inhibitory effect of DHA on nitric oxide production was abolished by HO-1 inhibitor zinc protoporphyrin IX. In addition, DHA caused AKT and ERK activation in a time-dependent manner, and the DHA-induced HO-1 upregulation could be attenuated by PI-3 kinase/AKT and MEK/ERK inhibitors. DHA also increased IKKα/β phosphorylation, IκBα phosphorylation, and IκBα degradation, whereas both nuclear factor-κB and IκB protease inhibitors could inhibit DHA-induced HO-1 expressions. The other major n-3 PUFA, eicosapentaenoic acid, showed similar effects of DHA on inflammation and HO-1 in repeated key experiments. In connecting with inflammation hypothesis of depression and clinical studies supporting the antidepressant effects of omega-3 PUFAs, this study provides a novel implication of the antidepressant mechanisms of DHA.

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.

Why pleiotropic interventions are needed for Alzheimer's disease

Alzheimer's disease (AD) involves a complex pathological cascade thought to be initially triggered by the accumulation of beta-amyloid (Abeta) peptide aggregates or aberrant amyloid precursor protein (APP) processing. Much is known of the factors initiating the disease process decades prior to the onset of cognitive deficits, but an unclear understanding of events immediately preceding and precipitating cognitive decline is a major factor limiting the rapid development of adequate prevention and treatment strategies. Multiple pathways are known to contribute to cognitive deficits by disruption of neuronal signal transduction pathways involved in memory. These pathways are altered by aberrant signaling, inflammation, oxidative damage, tau pathology, neuron loss, and synapse loss. We need to develop stage-specific interventions that not only block causal events in pathogenesis (aberrant tau phosphorylation, Abeta production and accumulation, and oxidative damage), but also address damage from these pathways that will not be reversed by targeting prodromal pathways. This approach would not only focus on blocking early events in pathogenesis, but also adequately correct for loss of synapses, substrates for neuroprotective pathways (e.g., docosahexaenoic acid), defects in energy metabolism, and adverse consequences of inappropriate compensatory responses (aberrant sprouting). Monotherapy targeting early single steps in this complicated cascade may explain disappointments in trials with agents inhibiting production, clearance, or aggregation of the initiating Abeta peptide or its aggregates. Both plaque and tangle pathogenesis have already reached AD levels in the more vulnerable brain regions during the "prodromal" period prior to conversion to "mild cognitive impairment (MCI)." Furthermore, many of the pathological events are no longer proceeding in series, but are going on in parallel. By the MCI stage, we stand a greater chance of success by considering pleiotropic drugs or cocktails that can independently limit the parallel steps of the AD cascade at all stages, but that do not completely inhibit the constitutive normal functions of these pathways. Based on this hypothesis, efforts in our laboratories have focused on the pleiotropic activities of omega-3 fatty acids and the anti-inflammatory, antioxidant, and anti-amyloid activity of curcumin in multiple models that cover many steps of the AD pathogenic cascade (Cole and Frautschy, Alzheimers Dement 2:284-286, 2006).

Maternal dietary fat determines metabolic profile and the magnitude of endocannabinoid inhibition of the stress response in neonatal rat offspring

Endocannabinoids (eCBs) are products of phospholipid (PL)-derived arachidonic acid (AA) that regulate hypothalamus-pituitary-adrenal axis activity. We hypothesized that differences in the quality and quantity of maternal dietary fat would modulate the PL AA content in the neonatal brain affecting stress responsiveness via differences in eCB production and activity in stress-activated brain areas. Pregnant rats were fed a 5% [control (C)] or 30% fat [high fat (HF)] diet rich in either n-6 (HF-n-6) or n-3 (HF-n-3) fat during the last week of gestation and lactation. Postnatal d 10 offspring were tested for metabolic hormones, AA (n-6) and eCB brain content, and hormonal effects of eCB receptor antagonism (AM251, 1 or 3 mg/kg ip) on stress responses. Like maternal diet, milk from HF-n-3 mothers had a reduced n-6/n-3 fat ratio compared with that of C and HF-n-6 mothers. Hypothalamic and hippocampal levels of PL AA were diet specific, reflecting the maternal milk and dietary n-6/n-3 ratio, with HF-n-3 offspring displaying reduced AA content relative to C and HF-n-6 offspring. Plasma corticosterone and insulin were elevated in HF-fed pups, whereas leptin was increased only in HF-n-6 pups. Basal eCB concentrations were also diet and brain region specific. In C pups, eCB receptor antagonist pretreatment increased stress-induced ACTH secretion, but not in the HF groups. Stress-induced corticosterone secretion was not sensitive to AM251 treatment in HF-n-3 pups. Thus, the nature of preweaning dietary fat differentially influences neonatal metabolic hormones, brain PL AA levels, and eCB, with functional consequences on hypothalamus-pituitary-adrenal axis modulation in developing rat pups.

Docosahexaenoic acid withstands the Aβ(25-35)-induced neurotoxicity in SH-SY5Y cells

BACKGROUND

Docosahexaenoic acid (DHA, C22:6, n-3) ameliorates the memory-related learning deficits of Alzheimer's disease (AD), which is characterized by fibrillar amyloid deposits in the affected brains. Here, we have investigated whether DHA-induced inhibition of Amyloid β-peptide(25-35) (Aβ(25-35)) fibrillation limits or deteriorates the toxicity of the human neuroblastoma cells (SH-SY5Y).

EXPERIMENTAL METHODS

In vitro fibrillation of Aβ(25-35) was performed in the absence or presence of DHA. Afterwards, SH-SY5Y cells were incubated with Aβ(25-35) in absence or presence 20 μM DHA to evaluate its effect on the Aβ(25-35)-induced neurotoxicity by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide)]-redox and TUNEL (TdT-mediated dUTP-biotin nick end-labeling) assay and immunohistochemistry. The level of Aβ(25-35)-induced lipid peroxide (LPO) was determined in the absence or presence of oligomer-specific antibody. Fatty acid profile was estimated by gas chromatography.

RESULTS

DHA significantly reduced the Aβ(25-35) in vitro fibrillation, as indicated by fluorospectroscopy and transmission electron microscopy. Aβ(25-35) decreased the MTT-redox activity and increased the apoptotic damage and levels of LPO when compared with those of the controls. However, when the SH-SY5Y cells were treated with Aβ(25-35) in the presence of DHA, MTT redox potential significantly increased and the levels LPO decreased, suggesting an inhibition of the Aβ(25-35)-induced neurotoxicity. DHA improved the Aβ(25-35) induced DNA damage and axodendritic loss, with a concomitant increase in the cellular level of DHA, suggesting DHA protects the cell from neurotoxic degeneration.

CONCLUSION

DHA not only inhibits the in vitro fibrillation but also resists the Aβ(25-35)-induced toxicity in the neuronal cells. This might be the basis of the DHA-induced amelioration of Aβ-induced neurodegeneration and related cognitive deficits.

Amyloid-Beta Peptide, Oxidative Stress and Inflammation in Alzheimer's Disease: Potential Neuroprotective Effects of Omega-3 Polyunsaturated Fatty Acids

Alzheimer's disease is the most common form of dementia in the elderly and is a progressive neurodegenerative disorder characterised by a decline in cognitive function and also profound alterations in mood and behaviour. The pathology of the disease is characterised by the presence of extracellular amyloid peptide deposits and intracellular neurofibrillary tangles in the brain. Although many hypotheses have been put forward for the aetiology of the disease, increased inflammation and oxidative stress appear key to be features contributing to the pathology. The omega-3 polyunsaturated fats, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) have well-characterised effects on inflammation and may have neuroprotective effects in a number of neurodegenerative conditions including Alzheimer's disease. The aims of this paper are to review the neuroprotective effects of EPA and DHA in Alzheimer's disease, with special emphasis on their role in modulating oxidative stress and inflammation and also examine their potential as therapeutic agents.

Omega-3 fatty acids and dementia

More than a dozen epidemiological studies have reported that reduced levels or intake of omega-3 fatty acids or fish consumption is associated with increased risk for age-related cognitive decline or dementia such as Alzheimer's disease (AD). Increased dietary consumption or blood levels of docosahexaenoic acid (DHA) appear protective for AD and other dementia in multiple epidemiological studies; however, three studies suggest that the ApoE4 genotype limits protection. DHA is broadly neuroprotective via multiple mechanisms that include neuroprotective DHA metabolites, reduced arachidonic acid metabolites, and increased trophic factors or downstream trophic signal transduction. DHA is also protective against several risk factors for dementia including head trauma, diabetes, and cardiovascular disease. DHA is specifically protective against AD via additional mechanisms: It limits the production and accumulation of the amyloid beta peptide toxin that is widely believed to drive the disease; and it also suppresses several signal transduction pathways induced by Abeta, including two major kinases that phosphorylate the microtubule-associated protein tau and promote neurofibrillary tangle pathology. Based on the epidemiological and basic research data, expert panels have recommended the need for clinical trials with omega-3 fatty acids, notably DHA, for the prevention or treatment of age-related cognitive decline--with a focus on the most prevalent cause, AD. Clinical trials are underway to prevent and treat AD. Results to-date suggest that DHA may be more effective if it is begun early or used in conjunction with antioxidants.

Resolvin D1 controls inflammation initiated by glutathione-lipid conjugates formed during oxidative stress

BACKGROUND AND PURPOSE

Inflammation is associated with oxidative stress and local generation of lipid peroxidation-derived aldehydes, such as 4-hydroxy-trans-2-nonenal (HNE). In most tissues, HNE is readily conjugated with glutathione and presently it is unknown whether glutathionyl-HNE (GS-HNE) plays a functional role in inflammation. Here, we sought to determine whether GS-HNE is a mediator of oxidative stress-initiated inflammation and if its actions can be regulated by the anti-inflammatory and pro-resolving lipid mediator, resolvin D1 (RvD1).

EXPERIMENTAL APPROACH

GS-HNE was administered intraperitoneally to mice and peritoneal lavages were assessed for leukocyte infiltration and lipid mediators were targeted by mediator-lipidomics. RvD1 was administered to mice treated with GS-HNE and leukocyte infiltration was assessed in the peritoneum. Superoxide production and CD11b modulation were measured in isolated human polymorphonuclear leukocytes incubated with GS-HNE.

KEY RESULTS

GS-HNE (1-10 microg) evoked infiltration of Gr-1(+) leukocytes into the peritoneum to form an inflammatory exudate. With isolated human polymorphonuclear leukocytes, GS-HNE stimulated both superoxide generation and CD11b expression. Among the lipid mediators, both cyclooxygenase- and lipoxygenase-derived pro-inflammatory eicosanoids, including prostaglandin E(2), leukotriene B(4) and cysteinyl leukotrienes, were generated in exudates of mice injected intraperitoneally with GS-HNE. RvD1, given i.v. in doses as low as 0.01-10.0 ng, sharply reduced GS-HNE-stimulated leukocyte infiltration ( approximately 30-70%).

CONCLUSIONS AND IMPLICATIONS

Glutathione conjugates of HNE, derived during oxidative stress, are pro-inflammatory in vivo. RvD1 protects against this oxidative stress-initiated inflammation.

AMPA receptor-mediated cell death is reduced by docosahexaenoic acid but not by eicosapentaenoic acid in area CA1 of hippocampal slice cultures

Over the last decade, several studies have shown that high levels of polyunsaturated fatty acids (PUFAs) in the brain might limit neuronal damage in various pathological conditions. For example, in animal models of Alzheimer's disease, omega-3 type PUFAs such as docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids have been proposed to decrease both the cognitive and the cellular manifestations of premature ageing. The mechanisms by which they promote brain integrity remain to be established, and the experiments on cultured hippocampal slices described here examine the possibility that omega-3 fatty acids can modulate brain cell viability by interacting with glutamate receptors. We observed, by lactate dehydrogenase release and propidium iodide (PI) uptake, that excitotoxicity triggered by an alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor agonist was markedly reduced in hippocampal slices treated with DHA. PI uptake experiments also revealed that neuroprotection by DHA was restricted to the hippocampal CA1 region and could not be reproduced by EPA or arachidonic acid, an omega-6 PUFA. Moreover, the beneficial effect of DHA was specific to AMPA receptor stimulation, insofar as the toxicity induced by N-methyl-D-aspartate or kainate receptor agonists was not diminished by DHA preincubation. Biotinylation experiments finally indicated that the neuroprotective actions of DHA could result from down-regulation of AMPA receptors in hippocampal membranes. This investigation thus provides the first indication that a beneficial outcome of DHA on the brain could derive from specific modulation of AMPA-mediated toxicity, reinforcing the notion that dietary DHA uptake might be useful in preventing neurodegenerative diseases.

Docosahexaenoic acid and the aging brain

The dietary essential PUFA docosahexaenoic acid [DHA; 22:6(n-3)] is a critical contributor to cell structure and function in the nervous system, and deficits in DHA abundance are associated with cognitive decline during aging and in neurodegenerative disease. Recent studies underscore the importance of DHA-derived neuroprotectin D1 (NPD1) in the homeostatic regulation of brain cell survival and repair involving neurotrophic, antiapoptotic and antiinflammatory signaling. Emerging evidence suggests that NPD1 synthesis is activated by growth factors and neurotrophins. Evolving research indicates that NPD1 has important determinant and regulatory interactions with the molecular-genetic mechanisms affecting beta-amyloid precursor protein (betaAPP) and amyloid beta (Abeta) peptide neurobiology. Deficits in DHA or its peroxidation appear to contribute to inflammatory signaling, apoptosis, and neuronal dysfunction in Alzheimer disease (AD), a common and progressive age-related neurological disorder unique to structures and processes of the human brain. This article briefly reviews our current understanding of the interactions of DHA and NPD1 on betaAPP processing and Abeta peptide signaling and how this contributes to oxidative and pathogenic processes characteristic of aging and AD pathology.

Binge ethanol-induced neurodegeneration in rat organotypic brain slice cultures: effects of PLA2 inhibitor mepacrine and docosahexaenoic acid (DHA)

Using rat organotypic hippocampal-entorhinal cortical (HEC) slice cultures, we examined whether phospholipase A2 (PLA2) activity is involved in binge alcohol (ethanol)-induced neurodegeneration, and whether docosahexaenoic acid (DHA; 22:6n-3), a fish oil-enriched fatty acid that is anti-inflammatory in brain damage models, is neuroprotective. Assessed with propidium iodide and lactate dehydrogenase (LDH) leakage, neurodamage from ethanol (6 days 100 mM ethanol with four withdrawal periods) was prevented by the PLA2 pan-inhibitor, mepacrine. Also, ethanol-dependent neurodegeneration-particularly in the entorhinal region-was significantly ameliorated by DHA supplementation (25 microM); however, adrenic acid, a 22:4n-6 analog, was ineffective. Consistent with PLA2 activation, [(3)H] liberation was approximately fivefold greater in [(3)H]arachidonic acid-preloaded HEC slice cultures during ethanol withdrawal compared to controls, and DHA supplementation suppressed [(3)H] release to control levels. DHA might antagonize PLA2 activity directly or suppress upstream activators (e.g., oxidative stress); however, other DHA mechanisms could be important in subdueing ethanol-induced PLA2-dependent and independent neuroinflammatory processes.

Effect of dietary docosahexaenoic acid on biosynthesis of docosahexaenoic acid from alpha-linolenic acid in young rats

Docosahexaenoic acid (DHA), a crucial nervous system n-3 PUFA, may be obtained in the diet or synthesized in vivo from dietary alpha-linolenic acid (LNA). We addressed whether DHA synthesis is regulated by the availability of dietary DHA in artificially reared rat pups, during p8 to p28 development. Over 20 days, one group of rat pups was continuously fed deuterium-labeled LNA (d5-LNA) and no other n-3 PUFA (d5-LNA diet), and a second group of rat pups was fed a d5-LNA diet with unlabeled DHA (d5-LNA + DHA diet). The rat pups were then euthanized, and the total amount of deuterium-labeled docosahexaenoic acid (d5-DHA) (synthesized DHA) as well as other n-3 fatty acids present in various body tissues, was quantified. In the d5-LNA + DHA group, the presence of dietary DHA led to a marked decrease (3- to 5-fold) in the total amount of d5-DHA that accumulated in all tissues that we examined, except in adipose. Overall, DHA accretion from d5-DHA was generally diminished by availability of dietary preformed DHA, inasmuch as this was found to be the predominant source of tissue DHA. When preformed DHA was unavailable, d5-DHA and unlabeled DHA were preferentially accreted in some tissues along with a net loss of unlabeled DHA from other organs.

Docosahexaenoic acid-dependent iron accumulation in oligodendroglia cells protects from hydrogen peroxide-induced damage

Iron, a transition metal and essential nutrient, is a typical pro-oxidant forming free radicals, lipid peroxides and causing cell damage when added at high (> or = 50 microM) concentrations to oligodendroglia-like OLN-93 cells that have been enriched for 3 days with 10 microM docosahexaenoic acid (DHA, 22 : 6 n-3). At low (5 microM) iron concentrations lipid peroxides were still formed, but cells turned resistant to 250 microM H2O2, a secondary genotoxic stress. This has been attributed most likely to a time-dependent (16 h preconditioning) increase of cellular antioxidant enzyme activities i.e., glutathione peroxidase (38%) and glutathione reductase (26%). DHA but not arachidonic acid (20 : 4 n-6) supplements induced 3-fold increase in gene expression of divalent metal transporter-1, a transporter protein presumably responsible for the increase in intracellular iron. Elevated iron levels triggered a transient scrambling of membrane lipid asymmetry as evident by an accelerated ethanolamine phosphoglyceride translocation to the outer cell surface. Ethanolamine phosphoglyceride reorientation is proposed to activate certain signaling cascades leading to changes in nuclear transcription, a reaction that could represent a mechanism of preconditioning. These findings may have important implications for understanding the interactive role of iron and DHA in nutritional deficiencies, losses of polyunsaturated fatty acids in the aging brain or excessive iron accumulation in degenerative disorders.

Beneficial effects of dietary omega-3 polyunsaturated fatty acid on toxin-induced neuronal degeneration in an animal model of Parkinson's disease

In this study, we examined whether omega-3 (n-3) polyunsaturated fatty acids (PUFAs) may exert neuroprotective action in Parkinson's disease, as previously shown in Alzheimer's disease. We exposed mice to either a control or a high n-3 PUFA diet from 2 to 12 months of age and then treated them with the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP; 140 mg/kg in 5 days). High n-3 PUFA dietary consumption completely prevented the MPTP-induced decrease of tyrosine hydroxylase (TH)-labeled nigral cells (P<0.01 vs. MPTP mice on control diet), Nurr1 mRNA (P<0.01 vs. MPTP mice on control diet), and dopamine transporter mRNA levels (P<0.05 vs. MPTP mice on control diet) in the substantia nigra. Although n-3 PUFA dietary treatment had no effect on striatal dopaminergic terminals, the high n-3 PUFA diet protected against the MPTP-induced decrease in dopamine (P<0.05 vs. MPTP mice on control diet) and its metabolite dihydroxyphenylacetic acid (P<0.05 vs. MPTP mice on control diet) in the striatum. Taken together, these data suggest that a high n-3 PUFA dietary intake exerts neuroprotective actions in an animal model of Parkinsonism.

Neuroprotective action of omega-3 polyunsaturated fatty acids against neurodegenerative diseases: evidence from animal studies

Studies in animals clearly show that oral intake of docosahexaenoic acid (DHA) can alter brain DHA concentrations and thereby modify brain functions. This provides us with an opportunity to use DHA as a nutraceutical or pharmaceutical tool in brain disorders such as Alzheimer disease (AD) and Parkinson disease (PD). Most of the published epidemiological studies are consistent with a positive association between high reported DHA consumption or high DHA blood levels and a lower risk of developing AD later in life. Such observations have prompted the investigation of DHA in three different transgenic models of AD. These analyses show that animal models of AD are more vulnerable to DHA depletion than controls and that DHA exerts a beneficial effect against pathological signs of AD, including A beta accumulation, cognitive impairment, synaptic marker loss, and hyperphosphorylation of tau. Multiple mechanisms of action can be associated with the neuroprotective effects of DHA and include antioxidant properties and activation of distinct cell signaling pathways. Although the first randomized clinical assays have yet failed to demonstrate convincing beneficial effects of DHA for AD patients, the knowledge gathered in recent years holds out a hope for prevention and suggests that the elderly and people bearing a genetic risk for AD should at least avoid DHA deficiency.

Docosahexaenoic Acid Enhances Iron Uptake by Modulating Iron Transporters and Accelerates Apoptotic Death in PC12 Cells

The effect of docosahexaenoic acid (DHA; 22:6 n-3) on Fe(2+)-mediated and/or H(2)O(2)-mediated oxidative stress (OS) was investigated in a PC12 pheochromocytoma cell line in the presence or absence of 50 ng/ml nerve growth factor (NGF). DHA-supplemented cells showed enhanced Fe(2+)-induced cell damage as evident by increased lipid peroxides formation (10-fold) and reduced neutral red (NR) dye uptake in a NGF-independent fashion. DHA caused a nearly 10-fold increase in free iron uptake in NGF-treated cells and doubled iron uptake in nondifferentiated cells. DHA-enrichment induced an elevation in the transferrin receptor protein in the nondifferentiated cells whereas NGF-treatment led to a substantial increase in the ubiquitous divalent metal ion transporter 1 (DMT-1) as detected by mRNA levels using qRT-PCR. The mechanism of action of DHA to accelerate cell death may be associated with the externalization of amino-phosphoglycerides (PG) species of which, increased ethanolamine plasmalogen levels, may be essential for cell rescue as noted in NGF-treated PC12 cells.

Sustained elevation of intracellular cGMP causes oxidative stress triggering calpain-mediated apoptosis in photoreceptor degeneration

Sustained elevation in cGMP and a concomitant increase in intracellular Ca(2+) levels in the rd1 photoreceptors are followed by a rapid loss of photoreceptors. In a murine-derived photoreceptor cell line, 661W, treated with the phosphodiesterase inhibitor IBMX or the cyclic GMP-gated channel agonist 8-bromo-cGMP, it was previously found that the induced cell death was mediated by calpain and caspase-3. Because oxidative stress is a common product of ionic imbalance or elevated Ca(2+), we tested the role of oxidative stress in cGMP-induced photoreceptor cell death. In the rd1 mouse retina, oxidative stress was found to precede calpain and caspase-3 activation. In 661W cells, the increase in intracellular cGMP and Ca(2+) resulted in the generation of reactive oxygen species (ROS), the activation of oxidative stress enzymes, and the activation of calpain, followed by apoptosis mediated by the effector caspase-3. All these events, including calpain activation, were ameliorated by docosahexanoic acid (DHA). The cell-permeable inhibitor of calpain, SJA6017, while inhibiting cell death, had no effect on the generation of oxidative stress. These results establish a central role for oxidative stress in cGMP-induced cell death and suggest a ROS-mediated sequential activation of signal transduction events, which provide targets for future treatment strategies.

Omega-3 fatty acids and antioxidants in neurological and psychiatric diseases: an overview

RATIONALE

Omega-3 fatty acids are known to play a role in nervous system activity, cognitive development, memory-related learning, neuroplasticity of nerve membranes, synaptogenesis and synaptic transmission. The brain is considered abnormally sensitive to oxidative damage, and aging is considered one of the most significant risk factors for degenerative neurological disorders. Recently, clinical trials of several neurodegenerative diseases have increasingly targeted the evaluation of the effectiveness of various antioxidants.

OBJECTIVES

The effects of omega-3 fatty acids and antioxidants on the anatomic and functional central nervous system development and their possible therapeutical use in some neurological and psychiatric pathologies are evaluated.

RESULTS

A number of critical trials have confirmed the benefits of dietary supplementation with omega-3 fatty acids not only in several psychiatric conditions, but also in inflammatory and autoimmune and neurodegenerative diseases. Many evidences indicate that antioxidants are also essential in maintaining a correct neurophysiology.

CONCLUSIONS

Omega-3 fatty acids could be useful in the prevention of different pathologies, such as cardiovascular, psychiatric, neurological, dermatological and rheumatological disorders. A number of studies suggest that antioxidants can prevent the oxidation of various macromolecules such as DNA, proteins, and lipids. The ideal use of antioxidants should be a prophylactic and continue treatment before aging.

Role of omega-3 fatty acids in brain development and function: potential implications for the pathogenesis and prevention of psychopathology

The principle omega-3 fatty acid in brain, docosahexaenoic acid (DHA), accumulates in the brain during perinatal cortical expansion and maturation. Animal studies have demonstrated that reductions in perinatal brain DHA accrual are associated with deficits in neuronal arborization, multiple indices of synaptic pathology including deficits in serotonin and mesocorticolimbic dopamine neurotransmission, neurocognitive deficits, and elevated behavioral indices of anxiety, aggression, and depression. In primates and humans, preterm delivery is associated with deficits in fetal cortical DHA accrual, and children/adolescents born preterm exhibit deficits in cortical gray matter maturation, neurocognitive deficits particularly in the realm of attention, and increased risk for attention-deficit/hyperactivity disorder (ADHD) and schizophrenia. Individuals diagnosed with ADHD or schizophrenia exhibit deficits in cortical gray matter maturation, and medications found to be efficacious in the treatment of these disorders increase cortical and striatal dopamine neurotransmission. These associations in conjunction with intervention trials showing enhanced cortical visual acuity and cognitive outcomes in preterm and term infants fed DHA, suggest that perinatal deficits in brain DHA accrual may represent a preventable neurodevelopmental risk factor for the subsequent emergence of psychopathology.

Versatile roles of docosahexaenoic acid in the prenatal brain: from pro- and anti-oxidant features to regulation of gene expression

Docosahexaenoic acid (DHA) is the most ubiquitous polyunsaturated fatty acid (FA) in brain tissue. It is selectively esterified to amino phospholipids (PL) and therefore it is highly prevalent at the cytofacial site of the plasma membrane where it may specifically participate in intracellular events. A highly selective DHA accumulation prior to birth is the result of maternal supply via the placenta through a bio-magnification process. Supplements of DHA via the intra-amniotic route to the fetal rat increase brain DHA levels and also confer neuroprotection to fetuses subjected to global ischemic stress. The protective effect has been attributed to an enhanced free radical scavenging capacity of DHA. Dietary deprivation of linolenic acid (LNA) during the perinatal life on the other hand, resulted in losses of DHA from cerebral PLs [M. Schiefermeier, E. Yavin, n-3 deficient and DHA-enriched diets during critical periods of the developing prenatal rat brain, J. Lipid Res. 43 (2002) 124-131]. LNA deprivation also caused changes in a number of gene markers the identification of which was attained by a labor-intensive suppression subtractive hybridization protocol using mRNA from 2-week-old postnatal brains [E. Yakubov, P. Dinerman, F. Kuperstein, S. Saban, E. Yavin, Improved representation of gene markers on microarray by PCR-select subtracted cDNA targets, Mol. Brain Res. 137 (2005) 110-118]. Most notable was a remarkable elevation of dopamine (DA) receptor (D1 and D2) genes as evaluated by quantitative RT-PCR, SDS-PAGE gel electrophoresis and immunochemical staining [F. Kuperstein, E. Yakubov, P. Dinerman, S. Gil, R. Eylam, N. Salem Jr., E. Yavin, Overexpression of dopamine receptor genes and their products in the postnatal rat brain following maternal n-3 FA dietary deficiency, J. Neurochem. 95 (2005) 1550-1562]. Over-expression of DA receptors has been attributed to a compensatory mechanism resulting from impairment in DA neurotransmitter production, storage and processing. In conclusion, DHA is a versatile molecule with a wide range of actions spanning from participation in cellular oxidative processes and intracellular signaling to modulatory roles in gene expression and growth regulation.

How dietary arachidonic- and docosahexaenoic- acid rich oils differentially affect the murine hepatic transcriptome

Introduction

Herein, we expand our previous work on the effects of long chain polyunsaturated fatty acids (LC-PUFA) on the murine hepatic transcriptome using novel statistical and bioinformatic approaches for evaluating microarray data. The analyses focuses on key differences in the transcriptomic response that will influence metabolism following consumption of FUNG (rich in 20:4n6), FISH (rich in 20:5n3, 22:5n3, and 22:6n3) and COMB, the combination of the two.

Results

Using a variance-stabilized F-statistic, 371 probe sets (out of 13 K probe sets in the Affymetrix Mu11K chip set) were changed by dietary treatment (P < 0.001). Relative to other groups, COMB had unique affects on murine hepatic transcripts involved in cytoskeletal and carbohydrate metabolism; whereas FUNG affected amino acid metabolism via CTNB1 signaling. All three diets affected transcripts linked to apoptosis and cell proliferation, with evidence FISH may have increased apoptosis and decreased cell proliferation via various transcription factors, kinases, and phosphatases. The three diets affected lipid transport, lipoprotein metabolism, and bile acid metabolism through diverse pathways. Relative to other groups, FISH activated cyps that form hydroxylated fatty acids known to affect vascular tone and ion channel activity. FA synthesis and delta 9 desaturation were down regulated by COMB relative to other groups, implying that a FA mixture of 20:4n6, 20:5n3, and 22:6n3 is most effective at down regulating synthesis, via INS1, SREBP, PPAR alpha, and TNF signaling. Heme synthesis and the utilization of heme for hemoglobin production were likely affected by FUNG and FISH. Finally, relative to other groups, FISH increased numerous transcripts linked to combating oxidative such as peroxidases, an aldehyde dehydrogenase, and heat shock proteins, consistent with the major LC-PUFA in FISH (20:5n3, 22:5n3, 22:6n3) being more oxidizable than the major fatty acids in FUNG (20:4n6).

Conclusion

Distinct transcriptomic, signaling cascades, and predicted affects on murine liver metabolism have been elucidated for 20:4n6-rich dietary oils, 22:6n3-rich oils, and a surprisingly distinct set of genes were affected by the combination of the two. Our results emphasize that the balance of dietary n6 and n3 LC-PUFA provided for infants and in nutritional and neutraceutical applications could have profoundly different affects on metabolism and cell signaling, beyond that previously recognized.

Translocation of Ethanolamine Phosphoglyceride is Required for Initiation of Apoptotic Death in OLN-93 Oligodendroglial Cells

The possible interplay between extracellular signal-regulated protein kinase (ERK) activation and ethanolamine phosphoglycerides (PG) membrane bilayer translocation following oxidative stress (OS) (0.5 mM H2O2/0.05 mM Fe2+), was examined in oligodendroglia, OLN93, cells with altered plasma membrane PG composition. Cells supplemented with 50 microM docosahexaenoic acid (DHA, 22:6n3) to increase the number of potential double bond targets for OS in ethanolamine-PG (EPG) were compared to cells with diminished content of EPG, attained by the addition of 0.5 mM N,N-dimethylethanolamine (dEa). After 30 min OS, EPG translocation accompanied by sustained ERK activation and nuclear translocation culminating in apoptosis was found in DHA-supplemented cells in contrast to no EPG translocation, a brief ERK activation, but no nuclear translocation, and no cell death in DHA/dEa-supplemented cells. DHA/dEa-supplemented cells pretreated with the protein-tyrosine phosphatases inhibitor Na3VO4 followed by OS, although expressing a sustained ERK activation and nuclear translocation, failed to show apoptosis and lacked EPG translocation. In DHA-supplemented cells U0126, a MEK inhibitor, prevented ERK activation and EPG translocation and protected from cell death. These findings most likely indicate that ERK activation is an indispensable component for the signaling cascades leading to EPG translocation but only activation of the latter is leading to OS-induced apoptotic cell death.

Effects of docosahexaenoic acid on the survival and neurite outgrowth of rat cortical neurons in primary cultures

Effects of docosahexaenoic acid (DHA) on survival and neurite outgrowth were investigated in primary cultures of rat cortical neurons. Cell cultures were prepared from cortex on embryonic day 18 (E-18) for treatment with a series of DHA concentrations (12.5, 25, 50, 75, 100 and 200 microM). Docosahexaenoic acid (25-50 microM) significantly enhanced neuronal viability, but lower concentration of DHA (12.5 microM) did not show an obvious effect. In contrast, higher concentrations of DHA (100-200 microM) exerted the significant opposite effects by decreasing neuronal viability. Furthermore, treatment with 25 microM DHA significantly prevented the neurons from death after different culture days in vitro (DIV). Moreover, measurements from the cultures exposed to 25 microM DHA immediately after plating showed significant increases in the percentage of cells with neurites, the mean number of neurite branches, the total neuritic length per cell and the length of the longest neurite in each cell after 24 and 48 h in vitro (HIV). The DHA-treated neurons had greater growth-associated protein-43 (GAP-43) immunoactivity and higher phosphatidylserine (PS) and phosphatidylethanolamine (PE) contents, but lower phosphatidylcholine (PC) content than control neurons. The significant increased DHA contents were also observed in both PE and PS in the treated neurons. These findings suggest that optimal DHA (25 microM) may have positive effects on the survival and the neurite outgrowth of the cultured fetal rat cortical neurons, and the effects probably are related to DHA-stimulating neuron-specific protein synthesis and its enhancing the discrete phospholipid (PL) content through enrichment of DHA in the PL species.

Dietary n-3 polyunsaturated fatty acid depletion activates caspases and decreases NMDA receptors in the brain of a transgenic mouse model of Alzheimer's disease

Epidemiological data indicate that low n-3 polyunsaturated fatty acids (PFA) intake is a readily manipulated dietary risk factor for Alzheimer's disease (AD). Studies in animals confirm the deleterious effect of n-3 PFA depletion on cognition and on dendritic scaffold proteins. Here, we show that in transgenic mice overexpressing the human AD gene APPswe (Tg2576), safflower oil-induced n-3 PFA deficiency caused a decrease in N-methyl-D-aspartate (NMDA) receptor subunits, NR2A and NR2B, in the cortex and hippocampus with no loss of the presynaptic markers, synaptophysin and synaptosomal-associated protein 25 (SNAP-25). n-3 PFA depletion also decreased the NR1 subunit in the hippocampus and Ca2+/calmodulin-dependent protein kinase (CaMKII) in the cortex of Tg2576 mice. These effects of dietary n-3 PFA deficiency were greatly amplified in Tg2576 mice compared to nontransgenic mice. Loss of the NR2B receptor subunit was not explained by changes in mRNA expression, but correlated with p85alpha phosphatidylinositol 3-kinase levels. Most interestingly, n-3 PFA deficiency dramatically increased levels of protein fragments, corresponding to caspase/calpain-cleaved fodrin and gelsolin in Tg2576 mice. This effect was minimal in nontransgenic mice suggesting that n-3 PFA depletion potentiated caspase activation in the Tg2576 mouse model of AD. Dietary supplementation with docosahexaenoic acid (DHA; 22 : 6n-3) partly protected from NMDA receptor subunit loss and accumulation of fodrin and gelsolin fragments but fully prevented CaMKII decrease. The marked effect of dietary n-3 PFA on NMDA receptors and caspase/calpain activation in the cortex of an animal model of AD provide new insights into how dietary essential fatty acids may influence cognition and AD risk.

Neuroprotectin D1 (NPD1): a DHA-derived mediator that protects brain and retina against cell injury-induced oxidative stress

The biosynthesis of oxygenated arachidonic acid messengers triggered by cerebral ischemia-reperfusion is preceded by an early and rapid phospholipase A2 activation reflected in free arachidonic and docosahexaenoic acid (DHA) accumulation. These fatty acids are released from membrane phospholipids. Both fatty acids are derived from dietary essential fatty acids; however, only DHA, the omega-3 polyunsaturated fatty acyl chain, is concentrated in phospholipids of various cells of brain and retina. Synaptic membranes and photoreceptors share the highest content of DHA of all cell membranes. DHA is involved in memory formation, excitable membrane function, photoreceptor cell biogenesis and function, and neuronal signaling, and has been implicated in neuroprotection. In addition, this fatty acid is required for retinal pigment epithelium cell (RPE) functional integrity. Here we provide an overview of the recent elucidation of a specific mediator generated from DHA that contributes at least in part to its biological significance. In oxidative stress-challenged human RPE cells and rat brain undergoing ischemia-reperfusion, 10,17S-docosatriene (neuroprotectin D1, NPD1) synthesis evolves. In addition, calcium ionophore A23187, IL-1beta, or the supply of DHA enhances NPD1 synthesis. A time-dependent release of endogenous free DHA followed by NPD1 formation occurs, suggesting that a phospholipase A2 releases the mediator's precursor. When NPD1 is infused during ischemia-reperfusion or added to RPE cells during oxidative stress, apoptotic DNA damage is down-regulated. NPD1 also up-regulates the anti-apoptotic Bcl-2 proteins Bcl-2 and BclxL and decreases pro-apoptotic Bax and Bad expression. Moreover, NPD1 inhibits oxidative stress-induced caspase-3 activation. NPD1 also inhibits IL-1beta-stimulated expression of COX-2. Overall, NPD1 protects cells from oxidative stress-induced apoptosis. Because photoreceptors are progressively impaired after RPE cell damage in retinal degenerative diseases, understanding of how these signals contribute to retinal cell survival may lead to the development of new therapeutic strategies. Moreover, NPD1 bioactivity demonstrates that DHA is not only a target of lipid peroxidation, but rather is the precursor to a neuroprotective signaling response to ischemia-reperfusion, thus opening newer avenues of therapeutic exploration in stroke, neurotrauma, spinal cord injury, and neurodegenerative diseases, such as Alzheimer disease, aiming to up-regulate this novel cell-survival signaling.

Prospective study of dietary fat and risk of cataract extraction among US women

The authors examined prospectively the association between dietary fat intake and cataract extraction in adult women from the Nurses' Health Study. A total of 71,083 women were followed prospectively for up to 16 years between 1984 and 2000. Dietary fat was assessed by repeated food frequency questionnaires. Incident cases of cataract extraction were determined by a biennial questionnaire. The multivariate-adjusted relative risk for the highest compared with the lowest quintile of total fat intake was 1.10 (95% confidence interval (CI): 0.99, 1.22; p(trend) = 0.01). Women in the highest quintile of long-chain omega-3 fatty acid had a 12% lower risk of cataract extraction compared with those in the lowest quintile (relative risk = 0.88, 95% CI: 0.79, 0.98; p(trend) = 0.02). Total fish intake was inversely associated with cataract (for intake of > or = 3/week vs. <1/month: relative risk = 0.89, 95% CI: 0.81, 0.98; p(trend) = 0.01). The authors' findings suggest that higher intake of long-chain omega-3 fatty acid (eicosapentaenoic acid and docosahexaenoic acid) and consumption of fish may modestly reduce the risk of cataract.

3-Hydroxy-3-methylglutaryl coenzyme A reductase deregulation and age-related hypercholesterolemia: a new role for ROS

The microsomal enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCoAR) is the rate-limiting enzyme in cholesterol synthesis and is highly regulated by a variety of factors. We have recently reported increased reductase activity during ageing, attributed to a higher activation state and impaired degradation of the hepatic enzyme. One of the widely recognized causes of age-related metabolic modifications is the large increase of reactive oxygen species (ROS). Therefore, the effect of ROS increase on the activity and the regulation of the HMGCoAR has been investigated in two different experimental models of ROS enriched tissue: liver from rats fed on diets deprived of either Vitamin E (Vit. E) or polyunsaturated fatty acids (Pufa). The results show that in these models, compared to that of old rats, full activation the HMGCoAR was detected while a different degradation rate is observed with the respect to old rats. Thus, our data show full correlation between ROS production and increased HMGCoAR activity. The possible therapeutic implications of these results are discussed.

Free radical oxidation of plasmalogen glycerophosphocholine containing esterified docosahexaenoic acid: structure determination by mass spectrometry

Plasmalogen phospholipids have a vinyl ether substituent at the sn-1 position that is susceptible to oxidative reactions that occur at cell membranes. However, the mechanism by which this oxidation occurs and the effect of the polyunsaturated fatty acid at the sn-2 position have not been established. To gain insight into these mechanisms, the oxidized phospholipid products resulting from the exposure of 1-O-hexadec-1'-enyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine (16:0p/22:6-GPCho) to the free radical initiator 2, 2'-azobis (2- amidinopropane) hydrochloride were examined. Electrospray ionization tandem mass spectrometry, UV spectroscopy, and electron ionization-gas chromatography/mass spectrometry were used to structurally characterize the oxidized glycerophosphocholine (GPCho) products. The radical-induced peroxidation of 16:0p/22:6-GPCho revealed two major classes of oxidized phospholipids. The first class of products was formed by oxidation at the sn-1 position and included 1-lyso-2-docosahexaenoyl-GPCho and 1-formyl-2-docosahexaenoyl-GPCho. Additionally, the second class of oxidized products where oxidation occurred at the sn-2 position was classified into three categories that included chain-shortened omega-aldehydes, terminal gamma-hydroxy-alpha,beta-unsaturated aldehydes, and the addition of one or two oxygen atoms onto the sn-2 position of 16:0p/22:6-GPCho. These results clearly indicate that free radical-induced oxidation of plasmalogen phospholipids with esterified docosahexaenoic acid at the sn-2 position underwent oxidation at both the sn-1 and sn-2 positions.

Inhibition of peroxisomal functions due to oxidative imbalance induced by mistargeting of catalase to cytoplasm is restored by vitamin E treatment in skin fibroblasts from Zellweger syndrome-like patients

Many of the peroxisomal diseases exhibit excessive oxidative stress leading to neurological alterations and dysfunction. The role of peroxisomal oxidative stress in cellular function was highlighted by the loss of metabolic functions in peroxisomes of mutant cell lines, where catalase is mistargeted to the cytoplasm, but restored to peroxisomes by genetic manipulation (Sheikh et al. [Proc. Natl. Acad. Sci. USA 95 (1998) 2961)]. We report here that two human skin fibroblast cell lines from Zellweger syndrome-like patients are defective in the import of catalase into peroxisomes, causing impairment of metabolic function of this organelle. However, by lowering the cell culturing temperature (30 degrees C) the targeting of catalase to peroxisomes was restored, and with it the metabolic functions. Furthermore, mislocalization of catalase induces an oxidative imbalance in the cells which on treatment with a natural antioxidant, alpha-tocopherol (vitamin E), resulted in reduction of the oxidative levels and restoration of metabolic function (peroxisomal beta-oxidation and levels of very long chain fatty acids and plasmalogen as well as alpha-oxidation of branched-chain fatty acids). However, restoration of peroxisomal functions was not associated with the targeting of catalase to peroxisomes. Therefore, our finding suggests that correction of mistargeted catalase to peroxisomes is a temperature sensitive event and supports the hypotheses that its location outside peroxisomes induces an oxidative imbalance that results in metabolic dysfunction. The imbalance can be reversed by treatment with vitamin E, leading to normalization of peroxisomal functions. These findings open a novel approach for therapeutic treatment of certain peroxisomal disorders where gene or hypothermic therapies are not an option.

Half-lives of docosahexaenoic acid in rat brain phospholipids are prolonged by 15 weeks of nutritional deprivation of n-3 polyunsaturated fatty acids

Male rat pups (21 days old) were placed on a diet deficient in n-3 polyunsaturated fatty acids (PUFAs) or on an n-3 PUFA adequate diet containing alpha-linolenic acid (alpha-LNA; 18 : 3n-3). After 15 weeks on a diet, [4,5-3H]docosahexaenoic acid (DHA; 22 : 6n-3) was injected into the right lateral cerebral ventricle, and the rats were killed at fixed times over a period of 60 days. Compared with the adequate diet, 15 weeks of n-3 PUFA deprivation reduced plasma DHA by 89% and brain DHA by 37%; these DHA concentrations did not change thereafter. In the n-3 PUFA adequate rats, DHA loss half-lives, calculated by plotting log10 (DHA radioactivity) against time after tracer injection, equaled 33 days in total brain phospholipid, 23 days in phosphatidylcholine, 32 days in phosphatidylethanolamine, 24 days in phosphatidylinositol and 58 days in phosphatidylserine; all had a decay slope significantly greater than 0 (p < 0.05). In the n-3 PUFA deprived rats, these half-lives were prolonged twofold or greater, and calculated rates of DHA loss from brain, Jout, were reduced. Mechanisms must exist in the adult rat brain to minimize DHA metabolic loss, and to do so even more effectively in the face of reduced n-3 PUFA availability for only 15 weeks.

Docosahexaenoic acid protects from dendritic pathology in an Alzheimer's disease mouse model

Learning and memory depend on dendritic spine actin assembly and docosahexaenoic acid (DHA), an essential n-3 (omega-3) polyunsaturated fatty acid (PFA). High DHA consumption is associated with reduced Alzheimer's disease (AD) risk, yet mechanisms and therapeutic potential remain elusive. Here, we report that reduction of dietary n-3 PFA in an AD mouse model resulted in 80%-90% losses of the p85alpha subunit of phosphatidylinositol 3-kinase and the postsynaptic actin-regulating protein drebrin, as in AD brain. The loss of postsynaptic proteins was associated with increased oxidation, without concomitant neuron or presynaptic protein loss. n-3 PFA depletion increased caspase-cleaved actin, which was localized in dendrites ultrastructurally. Treatment of n-3 PFA-restricted mice with DHA protected against these effects and behavioral deficits and increased antiapoptotic BAD phosphorylation. Since n-3 PFAs are essential for p85-mediated CNS insulin signaling and selective protection of postsynaptic proteins, these findings have implications for neurodegenerative diseases where synaptic loss is critical, especially AD.

Fatty acids and homocysteine levels in patients with recurrent depression: an explorative pilot study

Major depressive disorders (MDD) and cardiovascular disease are mutually associated. They share signs and symptoms of the "metabolic syndrome". Two observations that may be causally related with the metabolic syndrome and therefore with both MDD and cardiovascular disease are a decrease in omega-3 polyunsaturated fatty acids (PUFAs) and a rise in plasma homocysteine (tHcy) levels. Both the rise in tHcy and the decrease in omega-3 PUFAs may be associated with enhanced lipid peroxidation. We exploratively studied 44 randomly chosen patients out of a cohort of 134 patients with the recurrent form of MDD (MDD-R). We measured tHcy levels together with saturated FAs, monounsaturated fatty acids (MUFAs) and PUFAs of the omega-3, omega-6 and omega-9 series in plasma and erythrocytes. Levels were compared with laboratory reference values. The main findings were a decrease in the erythrocytes of C22:5omega-3, C22:6omega-3, C24:1omega-9 and C20:3omega-9 and in the plasma a decrease in C24:1omega-9 and C20:3omega-9. The only significant association we found was between the total of omega-6 fatty acids and plasma tHcy. The FA alterations were found in patients although most of them were clinically recovered, suggesting that the alterations may represent a biological" trait" marker for recurrent depression.

Dietary fish oil up-regulates cholesterol 7α-hydroxylase mRNA in mouse liver leading to an increase in bile acid and cholesterol excretion

To investigate the molecular events controlling reverse cholesterol transport, we compared gene expression of normal mouse liver to that of mice fed a long chain (LC) omega-3 fatty acid-enriched diet. Using cDNA microarrays, we assessed expression levels of 1176 genes, and we found that D-site binding protein (DBP) was three-fold increased in mice on a LC omega-3 fatty acid-rich diet compared to controls. DBP is known to increase transcriptional level of cholesterol 7alpha-hydroxylase (C7alpha), the rate-limiting enzyme for bile acid production and cholesterol excretion, and we found that C7alpha mRNA was also up-regulated by LC omega-3 fatty acids. Moreover, liver X receptor-alpha, another transcription factor up-regulating C7alpha, was three- to four-fold increased in liver of treated mice. On the other hand, we demonstrated that bile acid and cholesterol excretion were two-fold increased. These results show that LC omega-3 fatty acids control cholesterol metabolism in mice at a new endpoint.

Dietary fatty acids alter blood pressure, behavior and brain membrane composition of hypertensive rats

The beneficial effect of dietary n-3 polyunsaturated fatty acids (PUFAs) on developing hypertension has been repeatedly demonstrated. However, related changes in brain membrane composition and its cognitive correlates have remained unclear. Our study aimed at a comprehensive analysis of behavior and cerebral fatty acid concentration in hypertension after long-term PUFA-rich dietary treatment. Hypertensive and normotensive rats were provided a placebo, or one of two PUFA-enriched diets with a reduced (n-6)/(n-3) ratio for 75 weeks. Exploratory behavior and spatial learning capacity were tested. Systolic blood pressure (BP) was repeatedly measured. Finally, brain fatty acid composition was analyzed by gas chromatography. Hypertensive rats exhibited more active exploration but impaired spatial learning compared to normotensives. Both diets reduced BP, increased PUFA and monounsaturated fatty acid (MUFA) concentration, and reduced saturated fatty acid content in brain. The level of cerebral PUFAs and MUFAs was lower in hypertensive than in normotensive rats. Furthermore, BP positively, while spatial learning negatively correlated with cerebral (n-6)/(n-3) PUFA ratio. We concluded that regular n-3 PUFA consumption could prevent the development of hypertension, but reached only a very delicate improvement in spatial learning. Furthermore, we consider a potential role of metabolically generated MUFAs in the beneficial effects of PUFA supplementation.

Dietary lipids in the aetiology of Alzheimer's disease: implications for therapy

Amyloid plaques and neurofibrillary tangles are the neuropathological hallmarks of Alzheimer's disease (AD), but no conclusive evidence has emerged showing that these hallmarks are the cause and not a product of the disease. Many studies have implicated oxidation and inflammation in the AD process, and there is growing evidence that abnormalities of lipid metabolism also play a role. Using epidemiology to elucidate risk factors and histological changes to suggest possible mechanisms, the hypothesis is advanced that dietary lipids are the principal risk factor for the development of late-onset sporadic AD. The degree of saturation of fatty acids and the position of the first double bond in essential fatty acids are the most critical factors determining the effect of dietary fats on the risk of AD, with unsaturated fats and n-3 double bonds conferring protection and an overabundance of saturated fats or n-6 double bonds increasing the risk. The interaction of dietary lipids and apolipoprotein E isoforms may determine the risk and rate of sustained autoperoxidation within cellular membranes and the efficacy of membrane repair. Interventions involving dietary lipids and lipid metabolism show great promise in slowing or possibly averting the development of AD, including dietary changes, cholesterol-modifying agents and antioxidants.

Neuroprotective effect of developmental docosahexaenoic acid supplement against excitotoxic brain damage in infant rats

Long-chain polyunsaturated fatty acid (LC-PUFA) composition of neural membranes is a key factor for brain development, in chemical communication of neurons and probably also their survival in response to injury. Viability of cholinergic neurons was tested during brain development following dietary supplementation of fish oil LC-PUFAs (docosahexaenoic acid [DHA], eicosapentaenoic acid, arachidonic acid) in the food of mother rats. Excitotoxic injury was introduced by N-methyl-D,L-aspartate (NMDA) injection into the cholinergic nucleus basalis magnocellularis of 14-day-old rats. The degree of loss of cholinergic cell bodies, and the extend of axonal and dendritic disintegration were measured following immunocytochemical staining of cell bodies and dendrites for choline acetyltransferase and p75 low-affinity neurotrophin receptor and by histochemical staining of acetylcholinesterase-positive fibres in the parietal neocortex. The impact of different feeding regimens on fatty acid composition of neural membrane phospholipids was also assayed at 12 days of age. Supplementation of LC-PUFAs resulted in a resistance against NMDA-induced excitotoxic degeneration of cholinergic neurones in the infant rats. More cholinergic cells survived, the dendritic involution of surviving neurons in the penumbra region decreased, and the degeneration of axons at the superficial layers of parietal neocortex also attenuated after supplementing LC-PUFAs. A marked increment in DHA content in all types of phospholipids was obtained in the forebrain neuronal membrane fraction of supplemented rats. It is concluded that fish oil LC-PUFAs, first of all DHA, is responsible for the neuroprotective action on developing cholinergic neurons against glutamate cytotoxicity.

Abnormal cerebellar histogenesis in PEX2 Zellweger mice reflects multiple neuronal defects induced by peroxisome deficiency

The form and circuitry of the cerebellum develops by a complex process that requires integration of afferent-target interactions between multiple neuronal populations and migratory patterns established by neuron-glial interactions. Analysis of mice lacking the PEX2 peroxisome assembly gene, in which peroxisomal function is disrupted, reveals abnormal cerebellar histogenesis due to the disturbance of multiple cellular processes within neurons. Defects in cerebellar growth and the rostro-caudal foliation pattern reflect a reduced granule neuron population and abnormal Purkinje cell dendrite development. In granule neurons, there is increased apoptotic cell death and delayed movement from the EGL to IGL that reflects cell cycle, maturational and migrational abnormalities. The underlying Purkinje cells have stunted dendrite arbors with abnormal branching patterns, which may reflect altered inductive influences from the delayed granule neuron translocation. A delayed arborization of mutant olivary climbing fibers and their defective translocation from the perisomatic to the dendritic compartment of Purkinje cells results in numerous spines on the soma and proximal dendrites of Purkinje cells. Distal Purkinje cell dendritic spines also display abnormal morphology. These Purkinje cell dendritic abnormalities are seen in association with persistent and enlarged axonal spheroids, further indicating the presence of a degenerative process within the Purkinje cell. This PEX2(-/-) mouse model for the human peroxisomal biogenesis disorder Zellweger syndrome illustrates the complex interplay of abnormal developmental processes in the cerebellum and the importance of peroxisomal function for neuronal migration, proliferation, differentiation, and survival.