Eicosanoids and isoeicosanoids: indices of cellular function and oxidant stress

Secretory phospholipase A2 group IIA modulates insulin sensitivity and metabolism

Secretory phospholipase A₂ group IIA (PLA2G2A) is a member of a family of secretory phospholipases that have been implicated in inflammation, atherogenesis, and antibacterial actions. Here, we evaluated the role of PLA2G2A in the metabolic response to a high fat diet. C57BL/6 (BL/6) mice do not express PLA2g2a due to a frameshift mutation. We fed BL/6 mice expressing the human PLA2G2A gene (IIA+ mice) a fat diet and assessed the physiologic response. After 10 weeks on the high fat diet, the BL/6 mice were obese, but the IIA+ mice did not gain weight or accumulate lipid. The lean mass in chow- and high fat-fed IIA+ mice was constant and similar to the BL/6 mice on a chow diet. Surprisingly, the IIA+ mice had an elevated metabolic rate, which was not due to differences in physical activity. The IIA+ mice were more insulin sensitive and glucose tolerant than the BL/6 mice, even when the IIA+ mice were provided the high fat diet. The IIA+ mice had increased expression of uncoupling protein 1 (UCP1), sirtuin 1 (SIRT1), and PPARγ coactivator 1α (PGC-1α) in brown adipose tissue (BAT), suggesting that PLA2G2A activates mitochondrial uncoupling in BAT. Our data indicate that PLA2G2A has a previously undiscovered impact on insulin sensitivity and metabolism.

Effect of seasonal variation on lipid and fatty acid profile in muscle tissue of male and female Silurus triostegus

Fatty acid (FA) compositions of total lipid, phospholipid (PL) and triacylglycerol (TAG) fractions have been determined in muscle tissues of Silurus triostegus. The distributions of saturated fatty acid (SFA), monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA) proportions were found to be different among total lipid, PL and TAG fractions from lipids in muscle tissues of the male and female S. triostegus in all seasons. Triacylglycerol contained a lower proportion of PUFA and a higher proportion of MUFA and SFA than PL while PL contained higher proportion of PUFA than proportion of MUFA and SFA compared to TAG. Triacylglycerol and PL fatty acid compositions in muscle tissues of the male and female fish species were found different. The most abundant fatty acids in the investigated seasons were palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1 n-9), palmitoleic acid (C16:1 n-7) and docosahexaenoic acid (C22:6 n-3). It was shown that the total lipid content and FA compositions in muscle tissues of the male and female S. triostegus were influenced by reproduction period and season.

Targeted lipidomic strategies for oxygenated metabolites of polyunsaturated fatty acids

Oxidation of polyunsaturated fatty acids (PUFA) through enzymatic or non-enzymatic free radical-mediated reactions can yield an array of lipid metabolites including eicosanoids, octadecanoids, docosanoids and related species. In mammals, these oxygenated PUFA mediators play prominent roles in the physiological and pathological regulation of many key biological processes in the cardiovascular, renal, reproductive and other systems including their pivotal contribution to inflammation. Mass spectrometry-based technology platforms have revolutionized our ability to analyze the complex mixture of lipid mediators found in biological samples, with increased numbers of metabolites that can be simultaneously quantified from a single sample in few analytical steps. The recent development of high-sensitivity and high-throughput analytical tools for lipid mediators affords a broader view of these oxygenated PUFA species, and facilitates research into their role in health and disease. In this review, we illustrate current analytical approaches for a high-throughput lipidomic analysis of eicosanoids and related mediators in biological samples. This article is part of a Special Issue entitled "Oxygenated metabolism of PUFA: analysis and biological relevance."

Oxidative-stress induced increase in circulating fatty acids does not contribute to phospholipase A2-dependent appetitive long-term memory failure in the pond snail Lymnaea stagnalis

Background

Reactive oxygen species (ROS) are essential for normal physiological functioning of the brain. However, uncompensated increase in ROS levels may results in oxidative stress. Phospholipase A₂ (PLA₂) is one of the key players activated by elevated ROS levels resulting in the hydrolysis of various products from the plasmamembrane such as peroxidized fatty acids. Free fatty acids (FFAs) and fatty acid metabolites are often implicated to the genesis of cognitive impairment. Previously we have shown that age-, and experimentally induced oxidative stress causes PLA₂-dependent long-term memory (LTM) failure in an aversive operant conditioning model in Lymnaea stagnalis. In the present study, we investigate the effects of experimentally induced oxidative stress and the role of elevated levels of circulating FFAs on LTM function using a non-aversive appetitive classical conditioning paradigm.

Results

We show that intracoelomic injection of exogenous PLA₂ or pro-oxidant induced PLA₂ activation negatively affects LTM performance in our learning paradigm. In addition, we show that experimental induction of oxidative stress causes significant temporal changes in circulating FFA levels. Importantly, the time of training coincides with the peak of this change in lipid metabolism. However, intracoelomic injection with exogenous arachidonic acid, one of the main FFAs released by PLA₂, does not affect LTM function. Moreover, sequestrating circulating FFAs with the aid of bovine serum albumin does not rescue pro-oxidant induced appetitive LTM failure.

Conclusions

Our data substantiates previous evidence linking lipid peroxidation and PLA₂ activation to age- and oxidative stress-related cognitive impairment, neuronal dysfunction and disease. In addition however, our data indicate that lipid peroxidation induced increased levels of circulating (per)oxidized FFAs are not a factor in oxidative stress induced LTM impairment.

Inflammation after stroke: mechanisms and therapeutic approaches

Reperfusion of ischemic brain can reduce injury and improve outcome, but secondary injury due to inflammatory mechanisms limits the efficacy and time window of such treatments for stroke. This review summarizes the cellular and molecular basis of inflammation in ischemic injury as well as possible therapeutic strategies.

Evidence for inflammation-mediated memory dysfunction in gastropods: putative PLA2 and COX inhibitors abolish long-term memory failure induced by systemic immune challenges

BACKGROUND

Previous studies associate lipid peroxidation with long-term memory (LTM) failure in a gastropod model (Lymnaea stagnalis) of associative learning and memory. This process involves activation of Phospholipase A2 (PLA2), an enzyme mediating the release of fatty acids such as arachidonic acid that form the precursor for a variety of pro-inflammatory lipid metabolites. This study investigated the effect of biologically realistic challenges of L. stagnalis host defense response system on LTM function and potential involvement of PLA2, COX and LOX therein.

RESULTS

Systemic immune challenges by means of β-glucan laminarin injections induced elevated H2O2 release from L. stagnalis circulatory immune cells within 3 hrs of treatment. This effect dissipated within 24 hrs after treatment. Laminarin exposure has no direct effect on neuronal activity. Laminarin injections disrupted LTM formation if training followed within 1 hr after injection but had no behavioural impact if training started 24 hrs after treatment. Intermediate term memory was not affected by laminarin injection. Chemosensory and motor functions underpinning the feeding response involved in this learning model were not affected by laminarin injection. Laminarin's suppression of LTM induction was reversed by treatment with aristolochic acid, a PLA2 inhibitor, or indomethacin, a putative COX inhibitor, but not by treatment with nordihydro-guaiaretic acid, a putative LOX inhibitor.

CONCLUSIONS

A systemic immune challenge administered shortly before behavioural training impairs associative LTM function in our model that can be countered with putative inhibitors of PLA2 and COX, but not LOX. As such, this study establishes a mechanistic link between the state of activity of this gastropod's innate immune system and higher order nervous system function. Our findings underwrite the rapidly expanding view of neuroinflammatory processes as a fundamental, evolutionary conserved cause of cognitive and other nervous system disorders.

Cell signalling by reactive lipid species: new concepts and molecular mechanisms

The process of lipid peroxidation is widespread in biology and is mediated through both enzymatic and non-enzymatic pathways. A significant proportion of the oxidized lipid products are electrophilic in nature, the RLS (reactive lipid species), and react with cellular nucleophiles such as the amino acids cysteine, lysine and histidine. Cell signalling by electrophiles appears to be limited to the modification of cysteine residues in proteins, whereas non-specific toxic effects involve modification of other nucleophiles. RLS have been found to participate in several physiological pathways including resolution of inflammation, cell death and induction of cellular antioxidants through the modification of specific signalling proteins. The covalent modification of proteins endows some unique features to this signalling mechanism which we have termed the ‘covalent advantage’. For example, covalent modification of signalling proteins allows for the accumulation of a signal over time. The activation of cell signalling pathways by electrophiles is hierarchical and depends on a complex interaction of factors such as the intrinsic chemical reactivity of the electrophile, the intracellular domain to which it is exposed and steric factors. This introduces the concept of electrophilic signalling domains in which the production of the lipid electrophile is in close proximity to the thiol-containing signalling protein. In addition, we propose that the role of glutathione and associated enzymes is to insulate the signalling domain from uncontrolled electrophilic stress. The persistence of the signal is in turn regulated by the proteasomal pathway which may itself be subject to redox regulation by RLS. Cell death mediated by RLS is associated with bioenergetic dysfunction, and the damaged proteins are probably removed by the lysosome-autophagy pathway.

Eicosanoid Production following One Bout of Exercise in Middle-Aged African American Pre- and Stage 1 Hypertensives

Endothelial dysfunction and a sedentary lifestyle may be involved in the development of hypertension which is proliferative among middle-aged African Americans (AA). Signaling molecules derived from the oxidation of 20-carbon fatty acid molecules known as eicosanoids influence vascular tone. The relationship between aerobic fitness and eicosanoid formation following exercise in middle-aged African American hypertensives is unknown. Purpose. To determine the relationship between aerobic capacity and eicosanoid formation after a bout of moderate-intensity exercise in middle-aged AA hypertensives. Methods. Ten sedentary hypertensive AA underwent 50 min of aerobic exercise at 65% VO₂max. Urine was collected for 24 hr on two occasions, prior to testing and immediately following the bout of exercise. Urinary metabolites of prostacyclin (6-keto PGF_1α) and thromboxane (11-dTXB₂) were measured during the day and night periods by high-performance liquid chromatography (HPLC). Results. 6-keto PGF_1α levels significantly increased (P = .04) following the bout of exercise compared to the control day. There was a significant relationship (r = .49, P < .05) between 6-keto PGF_1α levels and VO₂max during the exercise day. Conclusion. Based on this preliminary study, there appears to be a relationship between aerobic capacity and exercise-induced 6-keto PGF_1α production in middle-aged hypertensive AAs. AAs with lower VO₂max had lower 6-keto PGF_1α formation.

Molecular cloning and characterization of an ATP-binding cassette (ABC) transmembrane transporter from the white shrimp Litopenaeusvannamei

ATP-binding cassette transmembrane transporters (ABC transporters) have a potential role in drug and xenobiotic resistance. Here, we report for the first time the cloning of an ABC transporter from white shrimp Litopenaeusvannamei (designated LvABCG), along with a study of its phylogenetic relationships, and measurements of its expression in different shrimp tissues exposed to cadmium and pH stress (acidic and alkaline conditions). Sequence analysis showed that LvABCG shares many similarities with the white/ABC transmembrane transporter, including two conserved regions: a highly conserved ATP-binding cassette (ABC) and transmembrane domain (TMD). Spatial analyses of transcript levels for ABCG in shrimp tissues, using reverse transcript PCR, revealed the highest transcript level in the hepatopancreas, less in the intestine and stomach, and none in the other tissues examined. The ABC transporter mRNA transcript in the hepatopancreas of L.vannamei was significantly up-regulated after 1.5 h and 24 h of exposure to alkaline and acidic conditions, respectively. LvABCG was also induced in intestine, but was downregulated in the stomach under the alkaline treatment. Upon exposure to cadmium (4.25 micromol L(-1) and 8.5 micromol L(-1)) for 48 h, the mRNA expression of LvABCG was up-regulated 4.79-fold (at 6 h) and 2.09-fold (at 12 h) in the hepatopancreas. LvABCG was also induced in the stomach after exposure to 4.25 micromol L(-1) cadmium, but downregulated in the stomach and intestine after exposure to 8.5 micromol L(-1) cadmium. These findings indicate that LvABCG might play an important role in the physiological changes related to metabolism and cell detoxification that occur when Pacific white shrimp are exposed to cadmium and pH stress.

Isoprostenes as indicators of oxidative stress in schizophrenia

OBJECTIVE

Free radicals induce oxidative stress and damage to all types of biological molecules and may be involved in pathology of schizophrenia. A cell membrane dysfunction caused by lipid peroxidation can be secondary to a free radical-mediated pathology and may contribute to specific aspects of schizophrenic symptomatology and complications of its treatment.

METHOD

The aim of our study was to estimate oxidative stress in a group of schizophrenic patients by using different biomarkers of free radicals-induced lipid peroxidation (isoprostanes, thiobarbituric acid reactive substances (TBARS)). We also determined the products of enzymatic peroxidation of arachidonic acid, such as thromboxane B2 (TXB2) and its metabolite 11-dehydrothromboxane B2. Isoprostanes (IPs) are a family of novel prostaglandin isomers and are produced in free radical-catalysed reactions from arachidonic acid. They are useful as a specific, sensitive, chemically stable, noninvasive index of free radical generation in vivo. We therefore assessed in schizophrenic patients and control subjects the level of urinary excretion of isoprostane--8-epi-prostaglandin F2 alpha, (8-isoPGF2 alpha)--a marker of lipid peroxidation induced by free radicals using an immunoassay kit. We also studied the level of the other marker of enzymatic arachidonic acid peroxidation--11-dehydrothromboxane B2--in urine from schizophrenic patients and healthy volunteers. Moreover, we estimated the production of TBARS and TXB2 in plasma from schizophrenic patients and the control group. Patients hospitalised in the II Psychiatric Department of Medical University in Lodz, Poland, were interviewed with a special questionnaire (treatment, course of diseases, dyskinesis and other EPS). According to DSM-IV criteria, all patients had diagnosis of paranoid type. All patients were treated with second-generation antipsychotic drugs (risperidone, clozapine, and olanzapine). Mean time of schizophrenia duration was about 2 years.

RESULTS

We observed a statistically increased level of TBARS in plasma (P=0.000162) and isoprostanes (P=3.5 x 10(-12)) in urine of schizophrenic patients in comparison with the control group. The level of markers of enzymatic oxidation of arachidonic acid (TXB2 and its metabolite, 11-dehydrothromboxane B2) did not change. This indicates that free radicals induce peroxidation of unsaturated fatty acid in schizophrenic patients.

CONCLUSION

Considering the data presented in this study, we suggest that non-invasive measurement of 8-isoPGF2 alpha, is a valuable and sensitive (contrary to TBARS) indicator of oxidative stress status in vivo in schizophrenia.

Pharmacokinetics and transcriptional effects of the anti-salmon lice drug emamectin benzoate in Atlantic salmon (Salmo salar L.)

Background

Emamectin benzoate (EB) is a dominating pharmaceutical drug used for the treatment and control of infections by sea lice (Lepeophtheirus salmonis) on Atlantic salmon (Salmo salar L). Fish with an initial mean weight of 132 g were experimentally medicated by a standard seven-day EB treatment, and the concentrations of drug in liver, muscle and skin were examined. To investigate how EB affects Atlantic salmon transcription in liver, tissues were assessed by microarray and qPCR at 7, 14 and 35 days after the initiation of medication.

Results

The pharmacokinetic examination revealed highest EB concentrations in all three tissues at day 14, seven days after the end of the medication period. Only modest effects were seen on the transcriptional levels in liver, with small fold-change alterations in transcription throughout the experimental period. Gene set enrichment analysis (GSEA) indicated that EB treatment induced oxidative stress at day 7 and inflammation at day 14. The qPCR examinations showed that medication by EB significantly increased the transcription of both HSP70 and glutathione-S-transferase (GST) in liver during a period of 35 days, compared to un-treated fish, possibly via activation of enzymes involved in phase II conjugation of metabolism in the liver.

Conclusion

This study has shown that a standard seven-day EB treatment has only a modest effect on the transcription of genes in liver of Atlantic salmon. Based on GSEA, the medication seems to have produced a temporary oxidative stress response that might have affected protein stability and folding, followed by a secondary inflammatory response.

Overexpression of inducible nitric oxide synthase and cyclooxygenase-2 in rat zinc-deficient lung: Involvement of a NF-kappaB dependent pathway

Reactive oxygen and nitrogen species have been implicated in the pathogenesis of pulmonary diseases. The goal of this study was to measure the response of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 enzymes (COX-2) in lung with moderate zinc deficiency. Adult male Wistar rats were divided into two groups receiving (1) a zinc-deficient diet (ZD) or (2) a zinc-adequate control diet. After 2 months of treatment, the zinc-deficient group showed a significant pulmonary edema. This was associated to a reduction of protein thiols and to a significant increase of metallothionein and glutathione disulfide levels. In addition, a higher serum and lung NO production in ZD group was positively related to the higher activity and expression of iNOS and COX-2 found in lungs. Western blot analysis revealed increased IkappaBalpha degradation, an indicator of NF-kappaB activation in ZD lungs. Anatomopathologic analysis of ZD lungs showed an increase of connective tissue fibers with an influx of polymorphonuclear cells. These cells and type II cells from the alveoli showed specific immunohistochemical signals for iNOS. The conclusion is that, during the development of zinc-deficiency, iNOS activity increases in lung and contributes to lung injury. Zinc deficiency implications must be taken into account to design therapies and public health interventions involving targeted zinc supplementation for high-risk subjects or certain diseases, such as asthma.

Oxidative stress, diet, and the etiology of preeclampsia

BACKGROUND

A current theory holds that oxidative stress, ie, an imbalance between maternal prooxidants and antioxidants, is a component of preeclampsia. It is uncertain whether such an imbalance occurs before clinical recognition of the syndrome or whether it is related to diet.

OBJECTIVE

We measured urinary excretion of the isoprostane 8-iso-prostaglandin F(2alpha), which is an indicator of oxidative damage to lipids, and the total antioxidant power, which is a global measure of antioxidant status, at the entry to prenatal care. We also examined the relation of these indexes to diet during pregnancy.

DESIGN

A cohort of 307 gravidae from Camden, NJ, was studied from entry to prenatal care (at 15.0 +/- 0.49 wk gestation). Measures of the maternal diet were obtained by 24-h recall.

RESULTS

Risk of preeclampsia was increased 5-fold with higher urinary isoprostane excretion and decreased 3-fold with higher total antioxidant power. Over the course of pregnancy, there were significant trends for an association of higher isoprostane excretion with increased consumption of energy-adjusted fat, polyunsaturated fat, and polyunsaturated fatty acids (n-3, n-6, and linoleic and linolenic fatty acids), whereas total antioxidant power was not related to diet.

CONCLUSIONS

Increased urinary excretion of isoprostane and decreased antioxidant production is an imbalance that is consistent with oxidative stress, and it precedes clinical recognition of preeclampsia. The maternal diet is an underlying factor that provides an environment for free radical generation.

Effect of dietary fat saturation on lipid metabolism, arachidonic acid turnover and peritoneal macrophage oxidative stress in mice

We investigated the effects of a saturated fat diet on lipid metabolism and arachidonic acid (AA) turnover in mouse resident peritoneal macrophages. The pro-oxidative effect of this diet was also studied. Female C57BL/6 mice were weaned at 21 days of age and assigned to either the experimental diet containing coconut oil (COCO diet), or the control diet containing soybean oil as fat source (10 mice per group). The fat content of each diet was 15% (w/w). Mice were fed for 6 weeks and then sacrificed. The concentration of total lipids, triglycerides, (LDL+VLDL)-cholesterol, thiobarbituric acid-reactive substances (TBARS) and reduced glutathione were increased in the plasma of mice fed the COCO diet, without changes in phospholipid or total cholesterol concentrations compared to control. The concentrations of total cholesterol, free and esterified cholesterol, triglycerides, and TBARS were increased in the macrophages of COCO-fed mice, while the content of total phospholipids did not change. The phospholipid composition showed an increase of phosphatidylcholine and a decrease of phosphatidylethanolamine. The [3H]-AA distribution in the phospholipid classes showed an increase in phosphatidylcholine and phosphatidylethanolamine. Incorporation of [3H]-cholesterol into the macrophages of COCO-fed mice and into the cholesterol ester fraction was increased. The COCO diet did not affect [3H]-AA uptake but induced an increase in [3H]-AA release. The COCO diet also enhanced AA mobilization induced by lipopolysaccharide. These results indicate that the COCO diet, high in saturated fatty acids, alters the lipid metabolism and AA turnover of peritoneal macrophages in female mice and also produces a significant degree of oxidative stress.

Induction of redox changes, inducible nitric oxide synthase and cyclooxygenase-2 by chronic cadmium exposure in mouse peritoneal macrophages

Redox changes and the secretion of inflammatory mediators were investigated in resident peritoneal macrophages of mice chronically exposed to cadmium (Cd, 15 ppm for 2 months) through drinking water. Our results showed that in vivo Cd exposure altered the redox balance in mouse peritoneal macrophages, leading to excessive production of reactive oxygen species (ROS) that overwhelmed the antioxidant defenses. It also led to increased lipid peroxidation and arachidonic acid (AA) release, higher nitric oxide and prostaglandin E(2) (PGE(2)) production, and induction of inducible nitric oxide synthase and cyclooxygenase-2 compared with control macrophages. Oxidative stress and inflammation could be important processes operating in the modulation of mouse macrophage physiology induced by chronic Cd exposure.

Dietary fat saturation produces lipid modifications in peritoneal macrophages of mouse

We investigated the effects of a saturated fat diet on mice lipid metabolism in resident peritoneal macrophages. Male C57BL/6 mice were weaned at 21 days of age and assigned to either the experimental diet, containing coconut oil (COCO diet), or the control diet, containing soybean oil as fat source. Fat content of each diet was 15% (w/w). Mice were fed for 6 weeks until sacrifice. In plasma of mice fed the COCO diet, the concentration of triglyceride, total cholesterol, HLD- and (LDL+VLDL)-cholesterol, and thiobarbituric acid-reactive substances (TBARS) increased, without changes in phospholipid concentration, compared with the controls. In macrophages of COCO-fed mice, the concentration of total (TC), free and esterified cholesterol, triglyceride, phospholipid (P) and TBARS increased, while the TC/P ratio did not change. The phospholipid compositions showed an increase of phosphatidylcholine and phosphatidylserine + phosphadytilinositol, a decrease of phosphatidylethanolamine, and no change in phosphatidylglycerol. (3)H(2)O incorporation into triglyceride and phospholipid fractions of macrophages increased, while its incorporation into free cholesterol decreased. Incorporation of [(3)H]cholesterol into macrophages of COCO-fed mice and the fraction of [(3)H]cholesterol ester increased. COCO diet produced an increase in myrystic, palmitic and palmitoleic acids proportion, a decrease in linoleic and arachidonic acids and no changes in stearic and oleic acids, compared with the control. Also, a higher relative percentage of saturated fatty acid and a decrease in unsaturation index (p <0.001) were observed in macrophages of COCO-fed mice. These results indicate that the COCO-diet, high in saturated fatty acids, alters the lipid metabolism and fatty acid composition of macrophages and produces a significant degree of oxidative stress.

Phospholipase A2 group IIA expression in gastric adenocarcinoma is associated with prolonged survival and less frequent metastasis

We analyzed gene expression patterns in human gastric cancers by using cDNA microarrays representing approximately equal 30,300 genes. Expression of PLA2G2A, a gene previously implicated as a modifier of the Apc(Min/+) (multiple intestinal neoplasia 1) mutant phenotype in the mouse, was significantly correlated with patient survival. We confirmed this observation in an independent set of patient samples by using quantitative RT-PCR. Beyond its potential diagnostic and prognostic significance, this result suggests the intriguing possibility that the activity of PLA2G2A may suppress progression or metastasis of human gastric cancer.

Reactive oxygen species in sustained airway constriction induced by citric acid aerosol inhalation

We tested if there is a direct relationship between reactive oxygen species and citric acid-induced airway constriction. Guinea pigs were divided into two groups: control and dimethylthiourea (a hydroxyl radical scavenger). The animals in each group were further separated into four subgroups: baseline, recovery 2-3 min, recovery 10 min, and recovery 20 min. Each animal was anesthetized, cannulated, paralyzed, and artificially ventilated. Citric acid aerosol inhalation caused the following significant changes in the control group during the recovery period: airway constriction for at least 20 min, increases in luminol-amplified t-butyl hydroperoxide-initiated chemiluminescence counts in the bronchoalveolar lavage samples at 2-3 and 20 min, an increase in bronchoalveolar lavage fluid substance P level at 2-3 min, and elevations in the bronchoalveolar lavage fluid total cell and neutrophil numbers at 20 min. All citric acid-induced alterations were prevented by dimethylthiourea pretreatment. These results suggest that citric acid inhalation induces the initial release of reactive oxygen species and tachykinins, which causes further cellular infiltration and sustained airway constriction.

Dietary and seasonal effects on the dorsal meat lipid composition of Japanese (Silurus asotus) and Thai catfish (Clarias macrocephalus and hybrid Clarias macrocephalus and Clarias galipinus)

The effects of dietary lipids and seasonal variation on the lipids of wild and cultured catfish (Japanese catfish, Silurus asotus; Thai catfish, Clarias macrocephalus and hybrid Clarias macrocephalus x Clarias galipinus) were determined by analysis of the lipid content and fatty acid composition of their dorsal meat. The predominant fatty acids of dorsal meat were 16:0, 18:1n-9, 18:2n-6, 20:4n-6 (arachidonic acid, AA), and 22:6n-3 (docosahexaenoic acid, DHA). The DHA content in the diet of Japanese catfish was higher than that in the diet of Thai catfish, and this was reflected in the dorsal meat of the Japanese catfish, which had a remarkably high percentage of DHA compared with the meat of the Thai catfish. Cultured Japanese catfish had a higher percentage of 18:2n-6 than Thai fish and a lower percentage of AA in winter than in summer season. There were also seasonal variations in the percentage of n-6 fatty acids in Japanese catfish. In summer, the fatty acid composition of the cultured Japanese catfish was similar to that of the wild catfish. These fatty acid changes in the lipid classes, triacylglycerol, phosphatidylcholine and phosphatidylethanolamine were similar to those observed for total lipids. These results indicate that the percentage of DHA in the dorsal meat of catfish is influenced by dietary fatty acid, and it may be that it can be increased in cultivated fish by administering a diet containing a large amount of DHA.

Lipid modification in mouse peritoneal macrophages after chronic cadmium exposure

The effect of cadmium (Cd) exposure through drinking water on lipid status in mouse peritoneal macrophages (pM) was studied. After 2 months, adult male Balb/c mice that had drunk water with 15 ppm of Cd, showed tissue damage mediated by oxidative stress, as assessed by serum measuring of tissue damage and lipoperoxidation indicators. Resident pM obtained from Cd-exposed mice showed diminution in total lipids, total cholesterol, free cholesterol/esterified cholesterol ratio (FC/EC) and phospholipids in relation to control pM. On a percentage basis, the phospholipid composition showed that phosphatidylcholine (PC) and phosphatidylglycerol decreased, phosphatidylethanolamine (PE) increased, while phosphatidylinositol, sphingomyeline and phosphatidylserine did not change. The incorporation in vitro of [14C]-methyl-choline and [14C]-phosphorylcholine, as well as the activity of regulatory enzyme CTP-phosphocholine cytidylyltransferase, decreased in PC after 60 min. The incorporation of [14C]-linoleic acid increased after 1 h and the incorporation of [14C]-ethanolamine increased after 90 min in PC. The incorporation in vitro of [3H]-cholesterol in total lipids decreased after 120 min of incubation. Besides, the stearic acid and arachidonic acid content increased, while the contents of palmitoleic acid and linoleic acid decreased. Chronic Cd exposure alters the lipid composition in resident pM of Balb/c mice.

Review: Alzheimer's amyloid beta-peptide-associated free radical oxidative stress and neurotoxicity

Alzheimer's disease, the major dementing disorder of the elderly that affects over 4 million Americans, is related to amyloid beta-peptide, the principal component of senile plaques in Alzheimer's disease brain. Oxidative stress, manifested by protein oxidation and lipid peroxidation, among other alterations, is a characteristic of Alzheimer's disease brain. Our laboratory united these two observations in a model to account for neurodegeneration in Alzheimer's disease brain, the amyloid beta-peptide-associated oxidative stress model for neurotoxicity in Alzheimer's disease. Under this model, the aggregated peptide, perhaps in concert with bound redox metal ions, initiates free radical processes resulting in protein oxidation, lipid peroxidation, reactive oxygen species formation, cellular dysfunction leading to calcium ion accumulation, and subsequent neuronal death. Free radical antioxidants abrogate these findings. This review outlines the substantial evidence from multiidisciplinary approaches for amyloid beta-peptide-associated free radical oxidative stress and neurotoxicity and protection against these oxidative processes and cell death by free radical scavengers. In addition, we review the strong evidence supporting the notion that the single methionine residue of amyloid beta-peptide is vital to the oxidative stress and neurotoxicological properties of this peptide. Further, we discuss studies that support the hypothesis that aggregated soluble amyloid beta-peptide and not fibrils per se are necessary for oxidative stress and neurotoxicity associated with amyloid beta-peptide.

Nitrogen dioxide induces cis-trans-isomerization of arachidonic acid within cellular phospholipids. Detection of trans-arachidonic acids in vivo

Oxygen free radicals oxidize arachidonic acid to a complex mixture of metabolites termed isoeicosanoids that share structural similarity to enzymatically derived eicosanoids. However, little is known about oxidations of arachidonic acid mediated by reactive radical nitrogen oxides. We have studied the reaction of arachidonic acid with NO2, a free radical generated by nitric oxide and nitrite oxidations. A major group of products appeared to be a mixture of arachidonic acid isomers having one trans-bond and three cis-double bonds. We have termed these new products trans-arachidonic acids. These isomers were chromatographically distinct from arachidonic acid and produced mass spectra that were nearly identical with mass spectra of arachidonic acid. The lack of ultraviolet absorbance above 205 nm and the similarity of mass spectra of dimethyloxazoline derivatives suggested that the trans-bond was not conjugated with any of the cis-bonds, and the C=C bonds were located at carbons 5, 8, 11, and 14. Further identification was based on comparison of chromatographic properties with synthetic standards and revealed that NO2 generated 14-trans-eicosatetraenoic acid and a mixture containing 11-trans-, 8-trans-, and 5-trans-eicosatetraenoic acids. Exposure of human platelets to submicromolar levels of NO2 resulted in a dose-dependent formation of 14-trans-eicosatetraenoic acid and other isomers within platelet glycerophospholipids. Using a sensitive isotopic dilution assay we detected trans-arachidonic acids in human plasma (50.3 +/- 10 ng/ml) and urine (122 +/- 50 pg/ml). We proposed a mechanism of arachidonic acid isomerization that involves a reversible attachment of NO2 to a double bond with formation of a nitroarachidonyl radical. Thus, free radical processes mediated by NO2 lead to generation of trans-arachidonic acid isomers, including biologically active 14-trans-eicosatetraenoic acid, within membrane phospholipids from which they can be released and excreted into urine.

Vitamin C: prospective functional markers for defining optimal nutritional status

Most species of plants and animals synthesize ascorbic acid, but human subjects cannot, making vitamin C an essential component of our diet. Relationships between vitamin C intake and status, and between status and health are not yet clear. There is evidence, however, that higher intake of vitamin C is associated with lower risk of disease, supporting the concept that optimal intake is needed for optimal vitamin C status, and that both factors are required for optimal health. Vitamin C has low toxicity in healthy subjects, but a clear definition of optimal status and the dietary intake required to meet and maintain this status is needed before a change in the current recommended intake can be considered. Available evidence suggests that intake of 200 mg vitamin C/d saturates tissues and maintains fasting plasma levels above the proposed threshold (50 mumol/l) for minimum risk of CHD. However, the issue of whether or not these levels produce 'optimal vitamin C status' awaits the clear and accepted definition of the term. This definition in turn awaits the development of reliable functional markers capable of assessing the effects of varying levels of vitamin C nutriture. In the present paper the relationship between intake and body stores of vitamin C and the role of vitamin C in human health are reviewed briefly. The requirements of a reliable functional marker of human vitamin C status are defined, three classes of functional markers (molecular, biochemical and physiological) are described, and possible candidate markers are examined.