Omega-3 Polyunsaturated Fatty Acids Antagonize Macrophage Inflammation via Activation of AMPK/SIRT1 Pathway

Macrophages play a key role in obesity-induced inflammation. Omega-3 polyunsaturated fatty acids (ω-3 PUFAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) exert anti-inflammatory functions in both humans and animal models, but the exact cellular signals mediating the beneficial effects are not completely understood. We previously found that two nutrient sensors AMP-activated protein kinase (AMPK) and SIRT1 interact to regulate macrophage inflammation. Here we aim to determine whether ω-3 PUFAs antagonize macrophage inflammation via activation of AMPK/SIRT1 pathway. Treatment of ω-3 PUFAs suppresses lipopolysaccharide (LPS)-induced cytokine expression in macrophages. Luciferase reporter assays, electrophoretic mobility shift assays (EMSA) and Chromatin immunoprecipitation (ChIP) assays show that treatment of macrophages with ω-3 PUFAs significantly inhibits LPS-induced NF-κB signaling. Interestingly, DHA also increases expression, phosphorylation and activity of the major isoform α1AMPK, which further leads to SIRT1 over-expression. More importantly, DHA mimics the effect of SIRT1 on deacetylation of the NF-κB subunit p65, and the ability of DHA to deacetylate p65 and inhibit its signaling and downstream cytokine expression require SIRT1. In conclusion, ω-3 PUFAs negatively regulate macrophage inflammation by deacetylating NF-κB, which acts through activation of AMPK/SIRT1 pathway. Our study defines AMPK/SIRT1 as a novel cellular mediator for the anti-inflammatory effects of ω-3 PUFAs.     

Omega-3 Fatty Acids for Depression in Multiple Sclerosis: A Randomized Pilot Study

Multiple sclerosis is the most common chronic disabling disease in the central nervous system in young to middle aged adults. Depression is common in multiple sclerosis (MS) affecting between 50–60% of patients. Pilot studies in unipolar depression report an improvement in depression when omega-3 fatty acids are given with antidepressants. The objective of this study was to investigate whether omega-3 fatty acid supplementation, as an augmentation therapy, improves treatment-resistant major depressive disorder (MDD) in people with MS. We performed a randomized, double-blind, placebo-controlled pilot study of omega-3 fatty acids at six grams per day over three months. The primary outcome was a 50% or greater improvement on the Montgomery-Asberg Depression Rating Scale (MADRS). Thirty-nine participants were randomized and thirty-one completed the 3-month intervention. Improvement on MADRS between groups was not significantly different at the 3-month end point with 47.4% in the omega-3 fatty acid group and 45.5% in the placebo group showing 50% or greater improvement (p = 0.30). Omega-3 fatty acids as an augmentation therapy for treatment-resistant depression in MS was not significantly different than placebo in this pilot trial. Omega-3 fatty acid supplementation at the dose given was well-tolerated over 3 months.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00122954","term_id":"NCT00122954"}}NCT00122954     

Omega-3 Essential Fatty Acids Modulate Initiation and Progression of Neurodegenerative Disease

The significance of the selective enrichment in omega-3 essential fatty acids in photoreceptors and synaptic membranes of the nervous system has remained, until recently, incompletely understood. While studying mechanisms of cell survival in neural degeneration, we discovered a docosanoid synthesized from unesterified docosahexaenoic acid (DHA) by a 15-lipoxygenase (15-LOX), which we called neuroprotectin D1 (NPD1; 10R,17S-dihydroxy-docosa-4Z,7Z,11E,13E,15E,19Z hexaenoic acid). This lipid mediator is a docosanoid because it is derived from the 22 carbon (22C) precursor DHA, unlike eicosanoids, which are derived from the 20 carbon (20C) arachidonic acid (AA) family member of essential fatty acids. We discovered that NPD1 is promptly made in response to oxidative stress, as a response to brain ischemia–reperfusion, and in the presence of neurotrophins. NPD1 is neuroprotective in experimental brain damage, in oxidative-stressed retinal pigment epithelial (RPE) cells, and in human brain cells exposed to amyloid-β (Aβ) peptides. We thus envision NPD1 as a protective sentinel, one of the very first defenses activated when cell homeostasis is threatened by imbalances in normal neural function. We provide here, in three sections, recent experimental examples that highlight the specificity and potency of NPD1 spanning beneficial bioactivity during initiation and early progression of neurodegeneration: (1) during retinal signal phototransduction, (2) during brain ischemia–reperfusion, and (3) in Alzheimer's disease (AD) and stressed human brain cell models of AD. From this experimental evidence, we conclude that DHA-derived NPD1 regulation targets upstream events of brain cell apoptosis, as well as neuro-inflammatory signaling, promoting and maintaining cellular homeostasis, and restoring neural and retinal cell integrity.     

Neurorestorative Targets of Dietary Long-Chain Omega-3 Fatty Acids in Neurological Injury

Long-chain omega-3 polyunsaturated fatty acids (LC-O3PUFAs) exhibit therapeutic potential for the treatment and prevention of the neurological deficits associated with spinal cord injury (SCI). However, the mechanisms implicated in these protective responses remain unclear. The objective of the present functional metabolomics study was to identify and define the dominant metabolic pathways targeted by dietary LC-O3PUFAs. Sprague-Dawley rats were fed rodent purified chows containing menhaden fish oil-derived LC-O3PUFAs for 8 weeks before being subjected to sham or spinal cord contusion surgeries. We show, through untargeted metabolomics, that dietary LC-O3PUFAs regulate important biochemical signatures associated with amino acid metabolism and free radical scavenging in both the injured and sham-operated spinal cord. Of particular significance, the spinal cord metabolome of animals fed with LC-O3PUFAs exhibited reduced glucose levels (?48 %) and polar uncharged/hydrophobic amino acids (less than ?20 %) while showing significant increases in the levels of antioxidant/anti-inflammatory amino acids and peptides metabolites, including β-alanine (+24 %), carnosine (+33 %), homocarnosine (+27 %), kynurenine (+88 %), when compared to animals receiving control diets (p?N-acetylglutamate (+43 %) and acetyl CoA levels (+27 %), respectively. Interestingly, this dietary intervention resulted in a global correction of the pro-oxidant metabolic profile that characterized the SCI-mediated sensorimotor dysfunction. In summary, the significant benefits of metabolic homeostasis and increased antioxidant defenses unlock important neurorestorative pathways of dietary LC-O3PUFAs against SCI.     

Mapping Quantitative Trait Loci for Omega-3 Fatty Acids in Asian Seabass

Omega-3 fatty acids are essential fatty acids for human health. Therefore, increasing both percentage of omega-3 and a better fatty acid profile in fish fillets is one of the breeding goals in aquaculture. However, it is difficult to increase the omega-3 content in fish fillets, as the phenotypic selection of these traits is not easily feasible. To facilitate the genetic improvement of the Asian seabass for optimal fatty acid profiles, a genome-wide scan for quantitative trait loci (QTL) affecting fatty acid level in the flesh of the Asian seabass was performed on an F₂ family containing 314 offspring. All family members were genotyped using 123 informative microsatellites and 22 SNPs. High percentages of n-3 polyunsaturated fatty acids (PUFA), especially C22:6 (DHA 16.48?±?3.09 %) and C20:5 (EPA 7.19?±?0.86 %) were detected in the flesh. One significant and 54 suggestive QTL for different fatty acids and a water content trait were detected on the whole genome. QTL for C18:0b was located on linkage groups (LG) 5. QTL for total n-3 PUFA content in flesh were mapped onto LG6 and LG23 with the phenotypic variance explained ranging from 3.8 to 6.3 %. Four QTL for C22:6 were detected on LG6, LG23, and LG24, explaining 3.9 to 4.9 % of the phenotypic variance, respectively. Mapping of QTL for contents of different fatty acids is the first step towards improving the omega-3 content in the fillets of fish by using marker-assisted selection and is important for understanding the biology of fatty acid deposition.     

Inflammation in Response to n3 Fatty Acids in a Porcine Obesity Model

Fatty acids have distinct cellular effects related to inflammation and insulin sensitivity. Dietary saturated fat activates toll-like receptor 4, which in turn can lead to chronic inflammation, insulin resistance, and adipose tissue macrophage infiltration. Conversely, n3 fatty acids are generally antiinflammatory and promote insulin sensitivity, in part via peroxisome proliferator-activated receptor γ. Ossabaw swine are a useful biomedical model of obesity. We fed Ossabaw pigs either a low-fat control diet or a diet containing high-fat palm oil with or without additional n3 fatty acids for 30 wk to investigate the effect of saturated fats and n3 fatty acids on obesity-linked inflammatory markers. The diet did not influence the inflammatory markers C-reactive protein, TNFα, IL6, or IL12. In addition, n3 fatty acids attenuated the increase in inflammatory adipose tissue CD16^–CD14⁺ macrophages induced by high palm oil. High-fat diets with and without n3 fatty acids both induced hyperglycemia without hyperinsulinemia. The high-fat only group but not the high-fat group with n3 fatty acids showed reduced insulin sensitivity in response to insulin challenge. This effect was not mediated by decreased phosphorylation of protein kinase B. Therefore, in obese Ossabaw swine, n3 fatty acids partially attenuate insulin resistance but only marginally change inflammatory status and macrophage phenotype in adipose tissue.Abbreviations: AMPKα, AMP-activated protein kinase α, CRP, C-reactive protein, DHA, docosahexanoic acid, EPA, eicosapentanoic acid, HFP, high-fat palm-oil diet, HFPn3, high-fat palm-oil diet supplemented with n3 fatty acids, HOMA-IR, homeostasis model of assessment–, insulin resistance, LFC, low-fat control diet, PKB, protein kinase B, PUFA, polyunsaturated fatty acidsObesity is accompanied by chronic inflammation in adipose tissue; increased circulating concentrations of TNFα, IL6, and C-reactive protein (CRP); and decreased concentrations of adiponectin.² This chronic inflammation links obesity and the development of insulin resistance.³⁹ Dietary saturated fatty acids promote obesity in part through the induction of inflammation via activation of toll-like receptor 4 (the innate immune receptor for LPS).²⁸ The absence of functional tlr4 in mice reduces circulating proinflammatory cytokine concentrations and decreases macrophage infiltration into adipose tissue during high-fat diet-induced obesity.^8,28,32 Furthermore, in 3T3 L1 mouse adipocytes, palmitate activates NFκB, protein kinase C, and mitogen-activated protein kinase, all of which increase the production of inflammatory cytokines.¹For people who consume a diet high in saturated fat, a major determinant of health is the ratio of omega-6 to omega-3 fatty acids (that is, n6:n3) that is consumed.^5,6 Unlike saturated fatty acids, the n3 polyunsaturated fatty acids (PUFA) eicosapentanoic acid (EPA) and docosahexanoic acid (DHA) exert predominantly antiinflammatory effects, as is evident in that DHA antagonizes NFκB activation by palmitate in 3T3 L1 adipocytes.¹ In mice, EPA prevents or reverses hyperinsulinemia, hyperglycemia, and increased circulating monocyte chemotatic protein 1¹⁶ and decreases infiltration of adipose tissue with macrophages.³⁰ Moreover, n3 PUFA alleviate the decline in serum adiponectin that is associated with obesity,^12,15,30 and EPA decreases serum CRP in diabetic patients.²⁶Physiologic differences between rodents and humans underscore the need for comparative models in biomedical research, and the pig is emerging rapidly as a model for studies of energy metabolism and obesity. Like humans, pigs are natural omnivores, rely on apolipoprotein B100 to shuttle cholesterol in the LDL fraction, and have minimal brown fat retention postnatally. Furthermore, adipose depots in pigs are of sufficient size that multiple assays can be done on adipocytes or stromal vascular cells without pooling across depots or animals. Although Ossabaw swine have been used as models for metabolic syndrome, cardiovascular disease, coronary artery disease, and steatohepatisis,^11,20,24 little is known about adipose inflammation in these animals. Consequently, we sought to characterize obesity-linked inflammatory markers in the adipose tissue of this novel model and to test the hypothesis that adding n3 PUFA to a diet high in saturated fat attenuates chronic inflammation, protects against diet-induced insulin resistance, and alters phenotypic changes in adipose tissue macrophages.     

Omega-3 Fatty Acids in Fish from the Laurentian Great Lakes Tribal Fisheries

Dietary fish must be assessed for benefits and risks to formulate risk management strategies. This article demonstrates that Laurentian Great Lakes (GL) freshwater species are good sources of omega-3 fatty acids using new data from a small sample (n = 7) of Lake Superior siscowet lake trout (Salvelinus namaycush siscowet) and five other GL fish species’ data. For Lake Superior (LS) siscowets, the saturates, mono-unsaturates, and poly-unsaturates composed 20.1, 40.7, and 39.1% of total lipid weight, respectively. Omega-3 poly-unsaturates (PUFAs) in these fish were more than twice the omega-6 (omega 3/6 ratio = 2.4). The LS lake trout data were combined with earlier LS data collected during the 1980s for eight other species and from five species of Lake Erie fish. All the GL freshwater species were compared with seven other published marine and freshwater fish studies from other global regions. PUFAs were compared based on latitude and marine versus freshwater origin. Differences between marine and freshwater species in omega-3 fatty acid were less at higher latitudes. GL freshwater fish species can be a good source of beneficial fats like marine fish and must be accounted in effective risk communications involving persistent bioaccumulative toxicants in dietary fish.     

Selective Enrichment of Omega-3 Fatty Acids in Oils by Phospholipase A1

Omega fatty acids are recognized as key nutrients for healthier ageing. Lipases are used to release ω-3 fatty acids from oils for preparing enriched ω-3 fatty acid supplements. However, use of lipases in enrichment of ω-3 fatty acids is limited due to their insufficient specificity for ω-3 fatty acids. In this study use of phospholipase A1 (PLA1), which possesses both sn-1 specific activity on phospholipids and lipase activity, was explored for hydrolysis of ω-3 fatty acids from anchovy oil. Substrate specificity of PLA1 from Thermomyces lenuginosus was initially tested with synthetic p-nitrophenyl esters along with a lipase from Bacillus subtilis (BSL), as a lipase control. Gas chromatographic characterization of the hydrolysate obtained upon treatment of anchovy oil with these enzymes indicated a selective retention of ω-3 fatty acids in the triglyceride fraction by PLA1 and not by BSL. ¹³C NMR spectroscopy based position analysis of fatty acids in enzyme treated and untreated samples indicated that PLA1 preferably retained ω-3 fatty acids in oil, while saturated fatty acids were hydrolysed irrespective of their position. Hydrolysis of structured triglyceride,1,3-dioleoyl-2-palmitoylglycerol, suggested that both the enzymes hydrolyse the fatty acids at both the positions. The observed discrimination against ω-3 fatty acids by PLA1 appears to be due to its fatty acid selectivity rather than positional specificity. These studies suggest that PLA1 could be used as a potential enzyme for selective concentrationof ω-3 fatty acids.     

Omega-3 and Omega-6 Fatty Acids Act as Inhibitors of the Matrix Metalloproteinase-2 and Matrix Metalloproteinase-9 Activity

Polyunsaturated fatty acids have been reported to play a protective role in a wide range of diseases characterized by an increased metalloproteinases (MMPs) activity. The recent finding that omega-3 and omega-6 fatty acids exert an anti-inflammatory effect in periodontal diseases has stimulated the present study, designed to determine whether such properties derive from a direct inhibitory action of these compounds on the activity of MMPs. To this issue, we investigated the effect exerted by omega-3 and omega-6 fatty acids on the activity of MMP-2 and MMP-9, two enzymes that actively participate to the destruction of the organic matrix of dentin following demineralization operated by bacteria acids. Data obtained (both in vitro and on ex-vivo teeth) reveal that omega-3 and omega-6 fatty acids inhibit the proteolytic activity of MMP-2 and MMP-9, two enzymes present in dentin. This observation is of interest since it assigns to these compounds a key role as MMPs inhibitors, and stimulates further study to better define their therapeutic potentialities in carious decay.     

Individual Variation in Lipidomic Profiles of Healthy Subjects in Response to Omega-3 Fatty Acids

Introduction

Conflicting findings in both interventional and observational studies have resulted in a lack of consensus on the benefits of ω3 fatty acids in reducing disease risk. This may be due to individual variability in response. We used a multi-platform lipidomic approach to investigate both the consistent and inconsistent responses of individuals comprehensively to a defined ω3 intervention.

Methods

The lipidomic profile including fatty acids, lipid classes, lipoprotein distribution, and oxylipins was examined multi- and uni-variately in 12 healthy subjects pre vs. post six weeks of ω3 fatty acids (1.9 g/d eicosapentaenoic acid [EPA] and 1.5 g/d docosahexaenoic acid [DHA]).

Results

Total lipidomic and oxylipin profiles were significantly different pre vs. post treatment across all subjects (p=0.00007 and p=0.00002 respectively). There was a strong correlation between oxylipin profiles and EPA and DHA incorporated into different lipid classes (r²=0.93). However, strikingly divergent responses among individuals were also observed. Both ω3 and ω6 fatty acid metabolites displayed a large degree of variation among the subjects. For example, in half of the subjects, two arachidonic acid cyclooxygenase products, prostaglandin E₂ (PGE₂) and thromboxane B2 (TXB₂), and a lipoxygenase product, 12-hydroxyeicosatetraenoic acid (12-HETE) significantly decreased post intervention, whereas in the other half they either did not change or increased. The EPA lipoxygenase metabolite 12-hydroxyeicosapentaenoic acid (12-HEPE) varied among subjects from an 82% decrease to a 5,000% increase.

Conclusions

Our results show that certain defined responses to ω3 fatty acid intervention were consistent across all subjects. However, there was also a high degree of inter-individual variability in certain aspects of lipid metabolism. This lipidomic based phenotyping approach demonstrated that individual responsiveness to ω3 fatty acids is highly variable and measurable, and could be used as a means to assess the effectiveness of ω3 interventions in modifying disease risk and determining metabolic phenotype.     

Dietary n-3 Fatty Acids Inhibit Fever Induced by Inflammation in the Rat

Modification of endogenous eicosanoid synthesis by dietary n-3 fatty acid supplementation reduces febrile responses, but the mechanisms underlying these effects in vivo have not been determined. In the present study, local inflammation was induced by intramuscular injection ofturpentine in rats fed control or n-3 supplemented diets for 8-9 weeks. In animals fed the control diet, turpentine induced fever, hypermetabolism, marked local inflammation (oedema), increased plasma IL-6 concentrations and raised cerebrospinal fluid (CSF) concentrations of PGE2. N-3 fatty acid supplementation significantly inhibited the rise in CSF PGE2, fever and hypermetaboHsm induced by turpentine. Local inflammation and increased plasma IL-6 concentrations were not affected by n-3 supplementation. These findings suggest that modification of dietary fat intake inhibits fever via reduced release of prostaglandins, probably within the brain, but does not affect the local or afferent signals involved in fever generation.     

The Resolution of Inflammation: A Mathematical Model of Neutrophil and Macrophage Interactions

There is growing interest in inflammation due to its involvement in many diverse medical conditions, including Alzheimer’s disease, cancer, arthritis and asthma. The traditional view that resolution of inflammation is a passive process is now being superceded by an alternative hypothesis whereby its resolution is an active, anti-inflammatory process that can be manipulated therapeutically. This shift in mindset has stimulated a resurgence of interest in the biological mechanisms by which inflammation resolves. The anti-inflammatory processes central to the resolution of inflammation revolve around macrophages and are closely related to pro-inflammatory processes mediated by neutrophils and their ability to damage healthy tissue. We develop a spatially averaged model of inflammation centring on its resolution, accounting for populations of neutrophils and macrophages and incorporating both pro- and anti-inflammatory processes. Our ordinary differential equation model exhibits two outcomes that we relate to healthy and unhealthy states. We use bifurcation analysis to investigate how variation in the system parameters affects its outcome. We find that therapeutic manipulation of the rate of macrophage phagocytosis can aid in resolving inflammation but success is critically dependent on the rate of neutrophil apoptosis. Indeed our model predicts that an effective treatment protocol would take a dual approach, targeting macrophage phagocytosis alongside neutrophil apoptosis.     

Perinatal Supplementation with Omega-3 Polyunsaturated Fatty Acids Improves Sevoflurane-Induced Neurodegeneration and Memory Impairment in Neonatal Rats

Objectives

To investigate if perinatal Omega-3 polyunsaturated fatty acids (n-3 PUFAs) supplementation can improve sevoflurane-induced neurotoxicity and cognitive impairment in neonatal rats.

Methods

Female Sprague-Dawley rats (n = 3 each group) were treated with or without an n-3 PUFAs (fish oil) enriched diet from the second day of pregnancy to 14 days after parturition. The offspring rats (P7) were treated with six hours sevoflurane administration (one group without sevoflurane/prenatal n-3 PUFAs supplement as control). The 5-bromodeoxyuridine (Brdu) was injected intraperitoneally during and after sevoflurane anesthesia to assess dentate gyrus (DG) progenitor proliferation. Brain tissues were harvested and subjected to Western blot and immunohistochemistry respectively. Morris water maze spatial reference memory, fear conditioning, and Morris water maze memory consolidation were tested at P35, P63 and P70 (n = 9), respectively.

Results

Six hours 3% sevoflurane administration increased the cleaved caspase-3 in the thalamus, parietal cortex but not hippocampus of neonatal rat brain. Sevoflurane anesthesia also decreased the neuronal precursor proliferation of DG in rat hippocampus. However, perinatal n-3 PUFAs supplement could decrease the cleaved caspase-3 in the cerebral cortex of neonatal rats, and mitigate the decrease in neuronal proliferation in their hippocampus. In neurobehavioral studies, compared with control and n-3 PUFAs supplement groups, we did not find significant spatial cognitive deficit and early long-term memory impairment in sevoflurane anesthetized neonatal rats at their adulthood. However, sevoflurane could impair the immediate fear response and working memory and short-term memory. And n-3 PUFAs could improve neurocognitive function in later life after neonatal sevoflurane exposure.

Conclusion

Our study demonstrated that neonatal exposure to prolonged sevoflurane could impair the immediate fear response, working memory and short-term memory of rats at their adulthood, which may through inducing neuronal apoptosis and decreasing neurogenesis. However, these sevoflurane-induced unfavorable neuronal effects can be mitigated by perinatal n-3 PUFAs supplementation.     

Dietary Omega-3 Fatty Acid Supplementation Reduces Inflammation in Obese Pregnant Women: A Randomized Double-Blind Controlled Clinical Trial

Objective

Long-chain omega 3 fatty acids, eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) exert potent anti-inflammatory properties in humans. This study characterized the effects of omega-3 ω-3 fatty acids supplements (ω-3 FA) on the inflammatory status in the placenta and adipose tissue of overweight/obese pregnant women.

Study Design

A randomized, double-masked controlled trial was conducted in overweight/obese pregnant women that were randomly assigned to receive DHA plus EPA (2g/day) or the equivalent of a placebo twice a day from week 10–16 to term. Inflammatory pathways were characterized in: 1) adipose tissue and placenta of treated vs. untreated women; and 2) adipose and trophoblast cells cultured with long chain FAs.

Results

The sum of plasma DHA and EPA increased by 5.8 fold and ω-3 FA/ ω-6 FA ratio was 1.5 in treated vs. untreated women (p< 0.005). Plasma CRP concentrations were reduced (p<0.001). The adipose tissue and placenta of treated women exhibited a significant decrease in TLR4 adipose and placental expression as well as IL6, IL8, and TNFα In vitro, EPA and DHA suppressed the activation of TLR4, IL6, IL8 induced by palmitate in culture of adipose and trophoblast cells.

Conclusion

Supplementation of overweight/obese pregnant women with dietary ω-3 FAs for >25 weeks reduced inflammation in maternal adipose and the placental tissue. TLR4 appears as a central target of the anti-inflammatory effects at the cellular level.

Trial Registration

ClinicalTrials.gov NCT00957476     

Enriched Endogenous Omega-3 Fatty Acids in Mice Ameliorate Parenchymal Cell Death After Traumatic Brain Injury

Currently no effective therapies are available for the treatment of traumatic brain injury (TBI). Early intervention that specifically provides neuroprotection is of most importance which profoundly influences the outcome of TBI. In the present study, we adopted a closed-skull mild TBI model to investigate potential roles of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) in protecting against TBI. Using two-photon laser scanning microscopy (2PLSM), parenchymal cell death and reactive oxidative species (ROS) expression were directly observed and recorded after TBI through a thinned skull bone window. Fat-1 mice with high endogenous ω-3 PUFAs significantly inhibited ROS expression and attenuated parenchymal cell death after compression injury during the early injury phase. Elevated generation of glutathione (GSH) and neuroprotectin D1 (NPD1) in the parenchyma of fat-1 mice could be the contributor to the beneficial role of ω-3 PUFAs in TBI. The results of the study suggest that ω-3 PUFAs is an effective neuroprotectant as an early pharmacological intervention for TBI and the information derived from this study may help guide dietary advice for those who are susceptible to repetitive mild TBI.     

Modulation of KCa3.1 Channels by Eicosanoids,Omega-3 Fatty Acids,and Molecular Determinants

Background

Cytochrome P450- and ω-hydrolase products (epoxyeicosatrienoic acids (EETs), hydroxyeicosatetraeonic acid (20-HETE)), natural omega-3 fatty acids (ω3), and pentacyclic triterpenes have been proposed to contribute to a wide range of vaso-protective and anti-fibrotic/anti-cancer signaling pathways including the modula-tion of membrane ion channels. Here we studied the modulation of intermediate-conductance Ca²⁺/calmodulin-regulated K⁺ channels (K_Ca3.1) by EETs, 20-HETE, ω3, and pentacyclic triterpenes and the structural requirements of these fatty acids to exert channel blockade.

Methodology/Principal Findings

We studied modulation of cloned human hK_Ca3.1 and the mutant hK_Ca3.1^V275A in HEK-293 cells, of rK_Ca3.1 in aortic endothelial cells, and of mK_Ca3.1 in 3T3-fibroblasts by inside-out and whole-cell patch-clamp experiments, respectively. In inside-out patches, Ca²⁺-activated hK_Ca3.1 were inhibited by the ω3, DHA and α-LA, and the ω6, AA, in the lower µmolar range and with similar potencies. 5,6-EET, 8,9-EET, 5,6-DiHETE, and saturated arachidic acid, had no appreciable effects. In contrast, 14,15-EET, its stable derivative, 14,15-EEZE, and 20-HETE produced channel inhibition. 11,12-EET displayed less inhibitory activity. The K_Ca3.1^V275A mutant channel was insensitive to any of the blocking EETs. Non-blocking 5,6-EET antagonized the inhibition caused by AA and augmented cloned hK_Ca3.1 and rK_Ca3.1 whole-cell currents. Pentacyclic triterpenes did not modulate K_Ca3.1 currents.

Conclusions/Significance

Inhibition of K_Ca3.1 by EETs (14,15-EET), 20-HETE, and ω3 critically depended on the presence of electron double bonds and hydrophobicity within the 10 carbons preceding the carboxyl-head of the molecules. From the physiological perspective, metabolism of AA to non-blocking 5,6,- and 8,9-EET may cause AA-de-blockade and contribute to cellular signal transduction processes influenced by these fatty acids.