Erythrocyte phospholipid molecular species and fatty acids of Down syndrome children compared with non-affected siblings.

The majority of children with Down syndrome (DS) develop Alzheimer's disease (AD) at an early age. Although long-chain n-3 fatty acids (FA) are protective of neurodegeneration, little is known about the FA status in DS. In the present study, we aimed to investigate whether children with DS presented altered plasma and erythrocyte membrane phospholipids (PL) FA composition, when compared with their non-affected siblings. Venous blood samples were analysed for plasma and erythrocyte membrane FA composition by TLC followed by GC techniques. Lipid molecular species were determined by electrospray ionisation/tandem MS (ESI-MS/MS). FA analysis measured by standard GC showed an increased concentration of MUFA and a decreased concentration of plasmalogens in major PL fractions, but there were no differences in the concentrations of arachidonic acid or DHA. However, as identified by ESI-MS/MS, children with DS had increased levels of the following erythrocyte PL molecular species: 16 : 0-16 : 0, 16 : 0-18 : 1 and 16 : 0-18 : 2n-6, with reduced levels of 16 : 0-20 : 4n-6 species. Children with DS presented significantly higher levels of MUFA in both plasma and erythrocyte membrane, as well as higher levels of saturated and monounsaturated molecular species. Of interest was the almost double proportion of 16 : 0-18 : 2n-6 and nearly half the proportion of 16 : 0-20 : 4n-6 of choline phosphoacylglycerol species in children with DS compared with their non-affected siblings. These significant differences were only revealed by ESI-MS/MS and were not observed in the GC analysis. Further investigations are needed to explore molecular mechanisms and to test the association between the pathophysiology of DS and the risk of AD.

Nutritional armor in evolution: docosahexaenoic acid as a determinant of neural, evolution and hominid brain development.

The aim of this article is to draw attention to the special significance of docosahexaenoic acid (DHA) in the brain, the potential relevance of its abundance to the evolution of the brain in past history, and now the relevance of paucity in the food supply to the rise in mental ill-health. Membrane lipids of photoreceptors, synapses, and neurons over the last 600 million years contained consistent and similarly high levels of DHA despite wide genomic change. The consistency is despite the DHA precursor differing only by 2 protons. This striking conservation is an example of Darwin's "Conditions of Existence," which he described as the higher force in evolution. A purpose of this article is to suggest that the present paradigm of food production currently based on protein requirements, should change to serve the specific lipid needs of the brain to address the rise in mental ill-health.(1.)

Metabolic conversion of intra-amniotically-injected deuterium-labeled essential fatty acids by fetal rats following maternal n-3 fatty acid deficiency.

Accumulation of polyunsaturated fatty acids (PUFA) in the fetal brain is accomplished predominantly via a highly selective flow of docosahexaenoic acid (22:6n-3, DHA) and arachidonic acid (20:4n-6, AA) through the placenta. Little is known regarding the endogenous capability of the fetus to generate its own DHA and AA from lower homologues such as linolenic (18:3n-3, ALA) and linoleic (18:2n-6, LA) acids, respectively. Deuterium-labeled d5-ALA and d5-LA at millimolar concentrations were injected directly into the amniotic fluid in order to investigate maternal-independent metabolic conversion of the stable isotopes in brain and liver of the fetus near delivery. After 48h under adequate maternal diet, the levels of d5-ALA metabolites in the fetal brain and fetal liver were 45±2.2 pmol/mg and 86±4 pmol/mg of which 79% and 63.6% were comprised of d5-DHA. At this time point, incorporation of d5-LA metabolites was 103±5 pmol/mg and 772±46 pmol/mg for brain and liver, of which 50% and 30% were comprised of d5-AA. Following sustained maternal dietary ALA deficiency, the levels of total d5-ALA derived metabolites in the fetal brain and fetal liver were increased to 231 pmol/mg and 696 pmol/mg of which 71% and 26% were comprised of d5-DHA. From the time course and relative rates of d5-ALA precursor displacement by d5-DHA in cellular phosphoglycerides, it is concluded that the fetal rat brain can generate its own DHA from its d5-ALA precursors particularly under dietary stress.

NGF blocks polyunsaturated fatty acids biosynthesis in n-3 fatty acid-supplemented PC12 cells.

Regulation of polyunsaturated fatty acid (PUFA) biosynthesis in proliferating and NGF-differentiated PC12 pheochromocytoma cells deficient in n-3 docosahexaenoic acid (DHA 22:6n-3) was studied. A dose- and time-dependent increase in eicosapentaenoic acid (EPA, 20:5n-3), docosapentaenoic acid (DPA, 22:5n-3) and DHA in phosphatidylethanolamine (PtdEtn) and phosphatidylserine (PtdSer) glycerophospholipids (GPL) via the elongation/desaturation pathway following alpha-linolenic acid (ALA, 18:3n-3) supplements was observed. That was accompanied by a marked reduction of eicosatrienoic acid (Mead acid 20:3n-9), an index of PUFA deficiency. EPA supplements were equally effective converted to 22:5n-3 and 22:6n-3. On the other hand, supplements of linoleic acid (LNA, 18:2n-6) were not effectively converted into higher n-6 PUFA intermediates nor did they impair elongation/desaturation of ALA. Co-supplements of DHA along with ALA did not interfere with 20:5n-3 biosynthesis but reduced further elongation to 22-hydrocarbon PUFA intermediates. A marked decrease in the newly synthesized 22:5n-3 and 22:6n-3 following ALA or EPA supplements was observed after nerve growth factor (NGF)-induced differentiation. NGF also inhibited the last step in 22:5n-6 formation from LNA. These results emphasize the importance of overcoming n-3 PUFA deficiency and raise the possibility that growth factor regulation of the last step in PUFA biosynthesis may constitute an important feature of neuronal phenotype acquisition.

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.

Membrane lipid modification by polyunsaturated fatty acids sensitizes oligodendroglial OLN-93 cells against oxidative stress and promotes up-regulation of heme oxygenase-1 (HSP32).

Polyunsaturated fatty acids (PUFA) are highly abundant in brain tissue, and docosahexaenoic acid (DHA) might protect cells from oxidative stress (OS) during inflammation and demyelinating disorders, but also might exert pro-oxidant effects. Here we investigated if PUFA supplements lead to heat shock protein induction, altered cell survival properties and stress responses to OS exerted by hydrogen peroxide in oligodendroglial OLN-93 cells. The data show that supplements of various fatty acids (FA) with 18-22 carbons chain length and 2-6 double bonds led to PUFA enrichment in cellular membranes. Depending on the degree of desaturation, FA-supplements caused the up-regulation of heme oxygenase-1 (HSP32), a stress protein inducible by OS, and an increase in sensitivity to hydrogen peroxide-treatment. DHA, with the highest number of double bonds, was most effective. Co-treatment with DHA and the lipophilic vitamin E analogue alpha-tocopherol, suppressed heme oxygenase-1 up-regulation and cell survival was restored. Analysis of the lipid profile demonstrates that alpha-tocopherol not only has antioxidant capacities, but also directly modified the PUFA profile in cell membranes. Enrichment with higher omega-3, -6 and -9 PUFA and an increase in the biosynthesis rate of very long chain fatty acids, mainly changed the FA profile of ethanolamine and serine phosphoglycerides.

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.

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.

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.

Amyloid Abeta1-40 preconditions non-apoptotic signals in vivo and protects fetal rat brain from intrauterine ischemic stress.

Abstract The dualistic activities of the amyloid beta (Abeta) peptide as a pro-oxidant and ubiquitous constituent of amyloid deposits in Alzheimer's disease plaques and as an antioxidant of purported physiological function has been suggested but the mechanisms are far from being understood. In this report we measure several oxidative stress parameters and signaling cascades in brains of fetal rats subjected to global ischemia in order to evaluate the putative bifunctional properties of the Abeta(1-40) peptide. Intraperitoneal injection of 6 microg Abeta(1-40) into 18-days-old rat fetuses (approximately 3 g body weight) resulted after 24 h in the appearance of the peptide in various fetal organs including brain where it enhanced the levels of glutathione (GSH), glutathione reductase, glutathione peroxidase, and stimulated the levels of pro-survival signaling activities such as Akt serine/threonine kinase, extracellular signal-regulated kinase (ERK) and protein kinase C enzymes. Moreover, pretreatment with Abeta(1-40) reversed the consequences of a transient hypovolemic/hypotensive oxidative stress by restoring GSH levels via its recycling enzymes and by lowering the production of lipid peroxides presumably by activating the aforementioned pro-survival signaling cascades. It also caused a reduction in the number of DAPI-enhanced reactive cells and a decrease in p38 kinase phosphorylation and caspase-9 and -3 activity. These data suggest that pre-exposure to Abeta(1-40) stimulates fetal tolerance to ischemia via regulation of GSH metabolism and as such may be considered as neuroprotective.

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

Docosahexaenoic acid (DHA) (22:6) is a polyunsaturated fatty acid of the n - 3 series which is believed to be a molecular target for lipid peroxides (LPO) formation. Its ubiquitous nature in the nervous tissue renders it particularly vulnerable to oxidative stress, which is high in brain during normal activity because of high oxygen consumption and generation of reactive oxygen species (ROS). Under steady state conditions potentially harmful ROS and LPO are maintained at low levels due to a strong antioxidant defense mechanism, which involves several enzymes and low molecular weight reducing compounds. The present review emphasizes a paradox: a discrepancy between the expected high oxidability of the DHA molecule due to its high degree of unsaturation and certain experimental results which would indicate no change or even decreased lipid peroxidation when brain tissue is supplied or enriched with DHA. The following is a critical review of the experimental data relating DHA levels in the brain to lipid peroxidation and oxidative damage there. A neuroprotective role for DHA, possibly in association with the vinyl ether (VE) linkage of plasmalogens (pPLs) in combating free radicals is proposed.