Uptake of dihomo-gamma-linolenic acid by murine macrophages increases series-1 prostaglandin release following lipopolysaccharide treatment

Administration of dihomo-gamma-linolenic acid is useful for atopic dermatitis and atherosclerosis in mice; however, the metabolites of dihomo-gamma-linolenic acid have been little studied. We employed a method which enabled simultaneous analysis of nine prostaglandins using liquid chromatography-tandem mass spectrometry, and determined the concentrations of prostaglandins in the supernatants of cultures of mouse peritoneal macrophages stimulated with lipopolysaccharide after pre-incubation with dihomo-gamma-linolenic acid, arachidonic acid, or eicosapentaenoic acid. Accumulated prostaglandin concentrations from mouse macrophages with dihomo-gamma-linolenic acid uptake increased in a dihomo-gamma-linolenic acid concentration-dependent fashion. These increases were mainly due to prostaglandin D(1) and prostaglandin E(1). The order of accumulated prostaglandin concentrations was dihomo-gamma-linolenic acid>arachidonic acid>eicosapentaenoic acid in supernatants with the same concentration of polyunsaturated fatty acid. Since mouse macrophages can clearly produce series-1 prostaglandins, they must be formed in vivo. These findings suggest that the effects of dihomo-gamma-linolenic acid on diseases may be due to series-1 prostaglandins.

Inhibitory action of polyunsaturated fatty acids on IMP dehydrogenase

We screened the inhibitor of mouse inosine 5'-monophosphate dehydrogenase (IMPDH) type II from natural compounds, and found that a fatty acid, linoleic acid (C18:2), inhibited IMPDH activity. In the C18:2 fatty acid derivatives, all trans-configuration (i.e., linoelaidic acid), ester form, alcohol form, and addition of the hydroxyl group of linoleic acid had no effect on inhibitory activity. Therefore, both parts of a carboxylic acid and an alkyl chain containing cis-type double bonds of fatty acid might be essential for inhibition. Among the various carbon atom lengths and double bonds of fatty acids examined, the strongest inhibitor was C20:2-fatty acid, eicosadienoic acid, and 50% inhibition was observed at a concentration of 16.1 microM. Eicosadienoic acid induced the inhibition of IMPDH activity and was competitive with respect to IMP (K(i)=3.1 microM). For inhibitory effect, the C20-fatty acids ranked as follows: C20:2>C20:3>C20:1>> C20:4>C20:5, and C20:0 showed no inhibition. The energy-minimized three-dimensional structures of linear-chain C20-fatty acids were calculated, and it was found that a length of 20.7-22.5A and width of 4.7-7.2A in the fatty acid molecular structure was suggested to be important for IMPDH inhibition. Docking simulation of C20-fatty acids and mouse IMPDH type II, which was homology modeled from human IMPDH type II (PDB code: 1NF7), was performed, and the fatty acid could bind to Cys331, which is a amino acid residue of the active site, competitively with IMP. Based on these results, the IMPDH-inhibitory mechanism of fatty acids is discussed.

Docosahexaenoic acid stabilizes soluble amyloid-β protofibrils and sustains amyloid-β-induced neurotoxicity in vitro

Enrichment of diet and culture media with the polyunsaturated fatty acid docosahexaenoic acid has been found to reduce the amyloid burden in mice and lower amyloid-beta (Abeta) levels in both mice and cultured cells. However, the direct interaction of polyunsaturated fatty acids, such as docosahexaenoic acid, with Abeta, and their effect on Abeta aggregation has not been explored in detail. Therefore, we have investigated the effect of docosahexaenoic acid, arachidonic acid and the saturated fatty acid arachidic acid on monomer oligomerization into protofibrils and protofibril fibrillization into fibrils in vitro, using size exclusion chromatography. The polyunsaturated fatty acids docosahexaenoic acid and arachidonic acid at micellar concentrations stabilized soluble Abeta42 wild-type protofibrils, thereby hindering their conversion to insoluble fibrils. As a consequence, docosahexaenoic acid sustained amyloid-beta-induced toxicity in PC12 cells over time, whereas Abeta without docosahexaenoic acid stabilization resulted in reduced toxicity, as Abeta formed fibrils. Arachidic acid had no effect on Abeta aggregation, and neither of the fatty acids had any protofibril-stabilizing effect on Abeta42 harboring the Arctic mutation (AbetaE22G). Consequently, AbetaArctic-induced toxicity could not be sustained using docosahexaenoic acid. These results provide new insights into the toxicity of different Abeta aggregates and how endogenous lipids can affect Abeta aggregation.

Cyclooxygenase inhibitors not inhibit resting lung cancer A549 cell proliferation

Cyclooxygenase (COX) inhibitors were regarded as anticarcinogenic agents for lung cancer at least partly via PGE2; but these were based on cytokin stimulation experiment on A549 cell. In order to clarify whether COX inhibitors directly inhibit A549 cell, three COX inhibitors, NS398 (selective COX-2 inhibitor), SC560 (selective COX-1 inhibitor), and acetyl salicylic acid (ASA, non-selective COX inhibitor), were studied. NS398, and ASA, can inhibit PGE2 generation via COX-2 inhibition. The viability of A549 cell was assayed by MTT. However, without cytokin stimulation, all the three inhibitors (NS398 0.2-20 microM; SC560 1.0-100 nM; ASA 0.01-1.0 mM) were not able to inhibit A549 cell proliferation, in the other way round, NS398 promoted cell growth. And arachidonic acid (AA) and lipopolysaccharide (LPS) did not disturb the property of its growth. These data suggested that without cytokin stimulation, COX and PGE2 may not be the kernel molecules involved in A549 cell proliferation, and COX inhibitors could not inhibit A549 cell growth directly.

Suppression of cyclooxygenase-2 overexpression by 15S-hydroxyeicosatrienoic acid in androgen-dependent prostatic adenocarcinoma cells

Emerging reports now implicate alterations of arachidonic acid (AA) metabolism with prostate carcinogenesis. To test this hypothesis, androgen-primed benign hyperplastic (BHC) and malignant tumorigenic (MTC) cells derived from the Lobund-Wistar rat model of autochthonous prostate adenocarcinoma were incubated with (14)C-AA. Our data using MTCs revealed enhanced dual metabolism of (14)C-AA via COX to generate increased PGE(2) and via 5-lipoxygenase (LOX) to generate increased 5S-HETE in tumorigenic cells. Western blot of MTCs revealed upregulation of COX-2 expression. This paralleled the increased biosynthesis of PGE(2). Since some polyunsaturated fatty acids have been reported to modulate AA metabolism and tumorigenesis, we primed the cells with either gamma-linolenic acid (GLA) or its in vivo metabolite, 15S-HETrE, prior to incubation with AA. Our data revealed suppression of COX-2 expression/PGE(2) biosynthesis. In parallel, priming cells with 15S-HETrE resulted in greater suppression of COX-2 expression/PGE(2) biosynthesis. These findings suggest that 15S-HETrE could function in vivo after dietary intake of GLA to suppress DHT-enhanced prostatic COX-2 expression/PGE(2) biosynthesis and, thus, alleviate tumor growth and progression.

Functional conversion between A-type and delayed rectifier K+ channels by membrane lipids

Voltage-gated potassium (Kv) channels control action potential repolarization, interspike membrane potential, and action potential frequency in excitable cells. It is thought that the combinatorial association between distinct alpha and beta subunits determines whether Kv channels function as non-inactivating delayed rectifiers or as rapidly inactivating A-type channels. We show that membrane lipids can convert A-type channels into delayed rectifiers and vice versa. Phosphoinositides remove N-type inactivation from A-type channels by immobilizing the inactivation domains. Conversely, arachidonic acid and its amide anandamide endow delayed rectifiers with rapid voltage-dependent inactivation. The bidirectional control of Kv channel gating by lipids may provide a mechanism for the dynamic regulation of electrical signaling in the nervous system.

Inhibition of formyl-methionyl-leucyl-phenylalanine-stimulated respiratory burst in human neutrophils by adrenaline: inhibition of Phospholipase A2 activity but not p47phox phosphorylation and translocation

The polymorphonuclear neutrophil (PMN)-respiratory burst plays a key role in host defense and inflammatory reactions. Modulation of this key neutrophil function by endogenous agents and the mechanisms involved are poorly understood. This study was designed to analyze the mechanisms involved in the effect of adrenaline on neutrophil superoxide anions production. Using the superoxide dismutase (SOD)-inhibitable cytochrome c reduction assay, we report here that the beta-adrenergic agonist, adrenaline at physiologic concentrations (5-100 nM) inhibited formyl-methionyl-leucyl-phenylalanine (fMLP)-stimulated but not phorbol-myristate-acetate (PMA)-stimulated PMN superoxide anion production. The inhibitory effect of adrenaline runs in parallel with an increase in intracellular levels of cAMP which was reversed by the protein kinase A (PKA) inhibitor H-89, suggesting a role for PKA in mediating the inhibitory effect of adrenaline on fMLP-induced superoxide production. Adrenaline at physiological concentrations did not inhibit the fMLP-stimulated membrane translocation of the NADPH oxidase components p47phox and p67phox, nor the fMLP-stimulated phosphorylation of p47phox. However, adrenaline strongly depressed the activity of the cytosolic isoform of Phospholipase A(2) (cPLA(2)). We suggest that adrenaline inhibits fMLP induced superoxide production upstream of the NADPH oxidase via a mechanism involving PKA and cPLA(2).

Mechanisms of free-radical induction in relation to fenretinide-induced apoptosis of neuroblastoma

The mechanisms of fenretinide-induced cell death of neuroblastoma cells are complex, involving signaling pathways mediated by free radicals or reactive oxygen species (ROS). The aim of this study was to identify mechanisms generating ROS and apoptosis of neuroblastoma cells in response to fenretinide. Fenretinide-induced ROS or apoptosis of SH-SY5Y or HTLA 230 neuroblastoma cells were not blocked by Nitro l-argenine methyl ester (l-NAME), an inhibitor of nitric oxide synthase. Flavoprotein-dependent superoxide-producing enzymes such as NADPH oxidase were also not involved in fenretinide-induced apoptosis or ROS generation. Similarly, ketoconazole, a cytochrome P450 inhibitor, and inhibitors of cyclooxygenase (COX) were also ineffective. In contrast, inhibition of phospholipase A(2) or lipoxygenases (LOX) blocked the induction of ROS and apoptosis in response to fenretinide. Using specific inhibitors of LOX, blocking 12-LOX but not 5- or 15-LOX inhibited both fenretinide-induced ROS and apoptosis. The effects of eicosatriynoic acid, a specific 12-LOX inhibitor, were reversed by the addition of the 12-LOX products, 12 (S)-hydroperoxyeicosatetraenoic acid and 12 (S)-hydroxyeicosatetraenoic acid. The targeting of 12-LOX in neuroblastoma cells may thus be a novel pathway for the development of drugs inducing apoptosis of neuroblastoma with improved tumor specificity.

Differential modulation of NMDA-induced calcium transients by arachidonic acid and nitric oxide in cultured hippocampal neurons

We have examined the effect of arachidonic acid on the transient increases in intracellular Ca2+ evoked by NMDA and AMPA in cultured hippocampal pyramidal cells loaded with Fura-2 AM. Repeated brief pulses of NMDA elicited Ca2+ transients that showed a modest run down. This run down was enhanced if the preparation was shielded from UV light and was reduced by conducting the experiments in the presence of the nitric oxide synthase inhibitor l-nitroarginine (100 micro m). Arachidonic acid (2 micro m) enhanced the Ca2+ transients evoked by NMDA but not those evoked by AMPA. Other C20 unsaturated fatty acids did not alter the time course of the response to NMDA. These experiments suggest that elevated intracellular Ca2+ activates nitric oxide synthase and the resulting synthesis of nitric oxide depresses the Ca2+ response to NMDA while arachidonic acid augments these responses. Therefore two substances implicated in synaptic plasticity (arachidonic acid and nitric oxide) differentially modulate NMDA-mediated Ca2+ entry into hippocampal neurons.

Contribution of 5-hydroxytryptamine1B receptors and 20-hydroxyeiscosatetraenoic acid to fall in cerebral blood flow after subarachnoid hemorrhage

BACKGROUND AND PURPOSE

This study examined the interaction between 5-hydroxytryptamine1B (5-HT1B) receptors and 20-hydroxyeiscosatetraenoic acid (20-HETE) in contributing to the acute fall in regional cerebral blood flow (rCBF) after subarachnoid hemorrhage (SAH) in rats.

METHODS

The effects of intracisternal injection of 0.3 mL of arterial blood, artificial cerebrospinal fluid, and 5-HT on rCBF and the levels of 20-HETE and 5-HT in cerebrospinal fluid were measured in rats pretreated with vehicle, a 5-HT1B receptor antagonist (isamoltane hemifumarate), or an inhibitor of the synthesis of 20-HETE (HET0016). The effects of HET0016 and isamoltane on the vasoconstrictor response and changes in [Ca2+]i to 5-HT were also studied in middle cerebral arteries and vascular smooth muscle cells isolated from these vessels.

RESULTS

20-HETE and 5-HT levels in cerebrospinal fluid rose from 172+/-10 to 629+/-44 ng/mL and from 6+/-4 to 1163+/-200 nmol/mL, respectively, after SAH. rCBF fell by 30% 10 minutes after SAH, and it remained at this level for the next 2 hours. Blockade of 5-HT1B receptors prevented the sustained fall in rCBF seen after SAH. Intracisternal injection of 5-HT mimicked SAH by increasing 20-HETE levels in cerebrospinal fluid to 475+/-94 ng/mL and reducing rCBF by 30%. Blockade of the synthesis of 20-HETE with HET0016 prevented the fall in rCBF produced by 5-HT. Isamoltane and HET0016 reduced the vasoconstrictor response of isolated MCA to 5-HT by >60% and diminished the rise in [Ca2+]i produced by 5-HT in vascular smooth muscle cells isolated from these arteries.

CONCLUSIONS

These results suggest that the release of 5-HT after SAH activates 5-HT1B receptors and the synthesis of 20-HETE and that 20-HETE contributes to the acute fall in rCBF by potentiating the vasoconstrictor response of cerebral vessels to 5-HT.

Inhibitors of glycosphingolipid biosynthesis reduce transepithelial electrical resistance in MDCK I and FRT cells

Madin-Darby canine kidney (MDCK) I and Fisher rat thyroid (FRT) cells exhibit transepithelial electrical resistance (TER) values in excess of 5,000 Omega. cm(2). When these cells were incubated in the presence of various inhibitors of sphingolipid biosynthesis, a >5-fold reduction of TER was observed without changes in the gate function for uncharged solutes or the fence function for apically applied fluorescent lipids. The localization of ZO-1 and occludin was not altered between control and inhibitor-treated cells, indicating that the tight junction was still intact. Furthermore, the complexity of tight junction strands, analyzed by freeze-fracture microscopy, was not reduced. Once the inhibitor was removed and the cells were allowed to synthesize sphingolipids, a gradual recovery of the TER was observed. Interestingly, these inhibitors did not attenuate the TER of MDCK II cells, a cell line that typically exhibits values below 800 omega x cm(2.) These results suggest that glycosphingolipids play a role in regulating the electrical properties of epithelial cells.

Activation of peroxisome proliferator-activated receptor (PPAR)-gamma by 15S-hydroxyeicosatrienoic acid parallels growth suppression of androgen-dependent prostatic adenocarcinoma cells

Although dietary gamma-linolenic acid (GLA) and its 15-lipoxygenase metabolite, 15S-hydroxyeicosatrienoic acid (15S-HETrE), have been reported to exert antiproliferative activities in other systems, their role in prostatic carcinogenesis is unknown. To evolve a possible mechanism for the suppressive effect on growth of prostatic cells, we incubated GLA and 15S-HETrE with androgen-dependent prostatic adenocarcinoma cells. 15S-HETrE but not GLA markedly inhibited [(3)H]thymidine uptake in parallel with the upregulation of peroxisome proliferator-activated receptor-gamma expression (a growth modulating nuclear receptor). The data, taken together, suggest that dietary GLA via its in vivo metabolite 15S-HETrE could serve as an endogenous adjunct to attenuate prostatic tumorigenesis.

Effect of arachidonic and eicosapentaenoic acids on acute lung injury induced by hypochlorous acid

BACKGROUND

Hypochlorous acid (HOCl) is the main oxidant of activated polymorphonuclear neutrophil granulocytes (PMN) and generated by myeloperoxidase during respiratory burst. This study investigates the effects of HOCl on pulmonary artery pressure (PAP) and vascular permeability and characterises the influence of arachidonic acid (AA) and eicosapentaenoic acid (EPA) on the observed effects.

METHODS

HOCl (500, 1,000, 2,000 nmol/min) was continuously infused into the perfusate (Krebs-Henseleit buffer solution, KHB). AA or EPA in subthreshold doses (both 2 nmol/min) or buffer were simultaneously infused using a separate port. PAP, pulmonary venous pressure (PVP), ventilation pressure, and lung weight gain were continuously recorded. The capillary filtration coefficient (Kf,c) was calculated before and 30, 60, and 90 minutes after starting the HOCl infusion.

RESULTS

HOCl application resulted in a dose dependent increase in PAP and Kf,c. The onset of these changes was inversely related to the HOCl dose used. The combined infusion of AA with HOCl resulted in a significant additional rise in pressure and oedema formation which forced premature termination of all experiments. The combination of EPA with HOCl did not result in an enhancement of the HOCl induced rise in pressure and oedema formation.

CONCLUSIONS

Changes in the pulmonary microvasculature caused by HOCl are differently influenced by omega-6 and omega-3 polyunsaturated free fatty acids, suggesting a link between neutrophil derived oxidative stress and pulmonary eicosanoid metabolism.

Saturated triglycerides and fatty acids activate neutrophils depending on carbon chain-length

BACKGROUND

Unsaturated fatty acids are known as neutrophil activators. In the present study we investigated whether saturated triglycerides and fatty acids may also contribute to the previously observed activation of neutrophils by nutritional lipid emulsions. Furthermore we tested the hypothesis that carbon-chain length is of importance in this respect.

MATERIALS AND METHODS

Neutrophils (1 x 10(6) mL(-1)) were isolated from the blood of nine volunteers. Chemiluminescence was used to evaluate neutrophil activation, characterized by the production of oxygen radicals by neutrophils during incubation with 1 mmol L(-1) saturated fatty acid (6-20 carbon) or triglycerides (6-12 carbon fatty acid), dissolved in aqueous medium by preparing micelles with dipalmitoyl phosphatidylcholine (DPPC). Results were expressed as means +/- SEMs of the overall luminescence signal relative to the signal of cells incubated in medium.

RESULTS

Similar to a positive control, the polyunsaturated fatty acid arachidonic acid (C20 : 4), the triglycerides tricaproin (TC6 : 0), tricaprylin (TC8 : 0) and trilaurin (TC12 : 0) as well as the fatty acids lauric acid (C12 : 0), palmitic acid (C16 : 0), stearic acid (C18 : 0) and arachidic acid (C20 : 0) all induced oxygen radical production in neutrophils, while the medium-chain triglyceride tricaprin (TC10 : 0) and fatty acids caproic acid (C6 : 0), caprylic acid (C8 : 0) and capric acid (C10 : 0) exerted no clear effects, similar to negative controls (DPPC and glycerol).

CONCLUSIONS

Besides their (poly)-unsaturated counterparts, saturated triglycerides and fatty acids also activate neutrophils. Carbon chain-length is pivotal in the interaction of fatty acids and triglycerides and cells of the immune system.

Influence of dietary supplementation with long-chain n-3 or n-6 polyunsaturated fatty acids on blood inflammatory cell populations and functions and on plasma soluble adhesion molecules in healthy adults

Greatly increasing the amounts of flaxseed oil [rich in alpha-linolenic acid (ALNA)] or fish oil (FO); [rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)] in the diet can decrease inflammatory cell functions and so might impair host defense. The objective of this study was to determine the effect of dietary supplementation with moderate levels of ALNA, gamma-linolenic acid (GLA), arachidonic acid (ARA), DHA, or FO on inflammatory cell numbers and functions and on circulating levels of soluble adhesion molecules. Healthy subjects aged 55 to 75 yr consumed nine capsules per day for 12 wk. The capsules contained placebo oil (an 80:20 mix of palm and sunflowerseed oils) or blends of placebo oil with oils rich in ALNA, GLA, ARA, or DHA or FO. Subjects in these groups consumed 2 g ALNA; approximately 700 mg GLA, ARA, or DHA; or 1 g EPA plus DHA (720 mg EPA + 280 mg DHA) daily from the capsules. Total fat intake from the capsules was 4 g per day. None of the treatments affected inflammatory cell numbers in the bloodstream; neutrophil and monocyte phagocytosis or respiratory burst in response to E. coli; production of tumor necrosis factor-alpha, interleukin-1beta, and interleukin-6 in response to bacterial lipopolysaccharide; or plasma concentrations of soluble intercellular adhesion molecule-1. In contrast, the ALNA and FO treatments decreased the plasma concentrations of soluble vascular cell adhesion molecule-1 (16 and 28% decrease, respectively) and soluble E-selectin (23 and 17% decrease, respectively). It is concluded that, in contrast to previous reports using higher amounts of these fatty acids, a moderate increase in consumption of long-chain n-6 or n-3 polyunsaturated fatty acids does not significantly affect inflammatory cell numbers or neutrophil and monocyte responses in humans and so would not be expected to cause immune impairment. Furthermore, we conclude that moderate levels of ALNA and FO, which could be incorporated into the diet, can decrease some markers of endothelial activation and that this mechanism of action may contribute to the reported health benefits of n-3 fatty acids.

Effect of oral eicosapentaenoic acid on weight loss in patients with pancreatic cancer

Eicosapentaenoic acid (EPA) has been shown to modulate aspects of the inflammatory response that may contribute to weight loss in cancer. This study aimed to evaluate the acceptability and effects of oral supplementation with high-purity EPA in weight-losing patients with advanced pancreatic cancer. Twenty-six patients were entered into the study. EPA (95% pure) was administered as free acid starting at 1 g/day; the dose was increased to 6 g/day over four weeks, and then a maintenance dose of 6 g/day was administered. Patients were assessed before EPA and at 4, 8, and 12 weeks while receiving EPA, for weight, body composition, hematologic and clinical chemistry variables, acute-phase protein response, and performance status. Overall survival was noted. Supplementation was well tolerated, with only five patients experiencing side effects possibly attributable to the EPA. Before starting EPA, all patients had been losing weight at a median rate of 2 kg/mo. In general, after EPA supplementation, weight was stable. After four weeks of EPA supplementation, patients had a median weight gain of 0.5 kg (p = 0.0009 vs. rate of weight loss at baseline), and this stabilization of weight persisted over the 12-week study period. Total body water as a percentage of body weight remained stable, as did the proportion of patients with an acute-phase protein response, patients' nutritional intake, and performance status. Overall median survival from diagnosis in this study was 203 days. This study suggests that EPA is well tolerated, may stabilize weight in cachectic pancreatic cancer patients, and should be tested as an anticachectic agent in controlled trials.

Facilitation by arachidonic acid of acetylcholine release from the rat hippocampus

We investigated the effect of arachidonic acid (AA) on the release of [3H]acetylcholine ([3H]ACh) from the rat hippocampus. AA (3-30 microM) increased the basal tritium outflow and the field-electrically evoked release of [3H]ACh from hippocampal slices in a concentration-dependent manner. AA (30 microM) produced a 69+/-7% facilitation of the evoked and a 36+/-3% facilitation of basal tritium outflow. The effect of AA (30 microM) on the evoked tritium release was prevented by bovine serum albumin (BSA, 1%), which quenches AA, and was unaffected by the cyclooxygenase inhibitor, indomethacin (100 microM), and the lipooxygenase inhibitor, nordihydroguaiaretic acid (50 microM). Phospholipase A2 (PLA2, 2 U/ml), an enzyme that releases AA from the sn-2 position of phospholipids, mimicked the facilitatory effect of AA on the evoked tritium release (86+/-14% facilitation), an effect prevented by BSA (1%). The PLA2 activator, melittin (1 microM), enhanced the evoked tritium release by 98+/-11%, an effect prevented by the PLA2 inhibitor, arachidonyl trifluromethylketone (AACOCF3, 20 microM), and by BSA (1%). AA (30 microM), but not arachidic acid (30 microM), also facilitated (72+/-9%) the veratridine (10 microM)-evoked [3H]ACh release from superfused hippocampal synaptosomes, whereas PLA2 (2 U/ml) and melittin (1 microM) caused a lower facilitation (46+/-1% and 38+/-5%, respectively). The present results show that both exogenously added and endogenously produced AA increase the evoked release of [3H]ACh from rat hippocampal nerve terminals. Since muscarinic activation triggers AA production and we now observed that AA enhances ACh release, it is proposed that AA may act as a facilitatory retrograde messenger in hippocampal cholinergic muscarinic transmission as it has been proposed to act in glutamatergic transmission.

Calcium entry in Trypanosoma brucei is regulated by phospholipase A2 and arachidonic acid

In contrast with mammalian cells, little is known about the control of Ca2+ entry into primitive protozoans. Here we report that Ca2+ influx in pathogenic Trypanosoma brucei can be regulated by phospholipase A2 (PLA2) and the subsequent release of arachidonic acid (AA). Several PLA2 inhibitors blocked Ca2+ entry; 3-(4-octadecyl)-benzoylacrylic acid (OBAA; IC50 0.4+/-0.1 microM) was the most potent. We identified in live trypanosomes PLA2 activity that was sensitive to OBAA and could be stimulated by Ca2+, suggesting the presence of positive feedback control. The cell-associated PLA2 activity was able to release [14C]AA from labelled phospholipid substrates. Exogenous AA (5-50 microM) also initiated Ca2+ entry in a manner that was inhibited by the Ca2+ antagonist La3+ (100 microM). Ca2+ entry did not depend on AA metabolism or protein kinase activation. The cell response was specific for AA, and fatty acids with greater saturation than tetraeicosanoic acid (AA) or with chain lengths less than C20 exhibited greatly diminished ability to initiate Ca2+ influx. Myristate and palmitate inhibited PLA2 activity and also inhibited Ca2+ influx. Overall, these results demonstrate that Ca2+ entry into T. brucei can result from phospholipid hydrolysis and the release of eicosanoic acids.

Epoxygenase metabolites of arachidonic acid affect electrophysiologic properties of rat tracheal epithelial cells1

Epoxyeicosatrienoic acids (EETs) and dihydroxyeicosatrienoic acids, products of the cytochrome P450 arachidonic acid epoxygenase pathway, have been shown to affect electrolyte transport in the kidney; however, the effects of these compounds on airway epithelial ion transport have not been investigated. Intact rat tracheas and primary cultures of rat tracheal epithelial cells were mounted in Ussing chambers to monitor changes in transepithelial voltage (Vt), short circuit current (Isc) and electrical resistance (Rt), with or without the addition of increasing concentrations (10(-9)-10(-6) M) of arachidonic acid, each of the four regioisomeric EETs and each of the corresponding dihydroxyeicosatrienoic acids. In intact tracheas, 11,12-EET caused dose-dependent decreases in Vt and Isc (DeltaVt = 0. 4 +/- 0.1 mV, DeltaIsc = -16.9 +/- 5.4 microA/cm2 at 10(-6) M, P < . 05 vs. vehicle), whereas changes in Rt were not significantly different than vehicle alone. 11,12-dihydroxyeicosatrienoic acid caused less impressive decreases in Vt and Isc, although arachidonic acid and the other compounds tested were without significant effects. 11,12-EET induced similar changes in cultured tracheal epithelial cell electrical parameters at concentrations as low as 10(-9) M. The effects of 11,12-EET were highly stereoselective, with activity limited to 11(R),12(S)-EET, the least abundant rat lung enantiomer. Pretreatment with amiloride or mucosal exposure to sodium free media did not significantly alter the 11,12-EET-induced changes in Vt. In contrast, pretreatment with bumetanide abolished the 11,12-EET electrophysiologic effects, suggesting that these effects may be mediated through inhibition of a chloride conductive pathway. We conclude that arachidonic acid epoxygenase metabolites cause significant changes in rat airway electrical parameters and may be involved in the control of lung fluid and electrolyte transport.

[Effect of docanol on the status of hemostasis and fibrinolysis systems, as well as lipid spectrum in patients with ischemic heart disease depending on the initial level of fibrinolytic activity]

Forty patients with coronary heart disease (CHD) concurrent with hyperlipidemia were divided into 2 groups according to the baseline fibrinolytic activity. The group with the depressed fibrinolytic system displayed the highest atherogenicity index and levels of cholesterol, low and very low density lipoprotein cholesterol and half levels of high density lipoproteins. After 45-day ingestion of docanol, a new Russian food additive containing docosahexanoic and eicosapentaenoic acids there were positive changes in the lipid spectrum in the both groups. The fibrinolytic changes were heterodirectional: activator and plasma activities increased in the group of fibrinolytic depression while in the group of baseline normal fibrinolysis the activity of plasminogen activator fell.

5-Oxo-eicosanoids are potent eosinophil chemotactic factors. Functional characterization and structural requirements

Human eosinophils produce upon treatment with 5-oxo-eicosatetraenoic acid or (5S,15S)-dihydroxyeicosatetraenoic acid a potent eosinophil-chemotactic eicosanoid, 5-oxo-15-hydroxy-(6E,8Z,11Z,13E)-eicosatetraenoi c acid (5-oxo-15-HETE). 5-Oxo-15-HETE induces human eosinophil (Eo) chemotaxis at nanomolar concentrations with an efficacy in vitro comparable to that seen for platelet activating factor. Comparison of Eo chemotactic activities of several structurally related eicosanoids with different substituents and/or double bound geometry led to the conclusion that maximal potency and efficacy of eosinophil-chemotactic and chemokinetic activity is present in 5-oxo-(6E,8Z,11Z,14Z)-eicosatetraenoic acid (5-oxo-ETE). The presence of a hydroxyl group at position C-15 is not necessary for potent chemotactic activity, whereas a geometric isomer having trans instead of cis double bond at C-atom 8, as well as esterified 5-oxo-ETE usually show a 5-10-fold lower potency. 5-Oxo-eicosanoids elicit a dose-dependent transient rise of intracellular Ca2+ levels in human Eos, however, in contrast to some other Eo chemotaxins do not induce degranulation. Cross-desensitization of Ca2+ mobilization and Eo chemotaxis revealed that the geometric isomers of 5-oxo-eicosanoids, 5(S)-HETE, and (5S,15S)-di-HETE cross-deactivate Eo responses to each other, whereas other, unrelated stimuli did not interfere with these lipids indicating that 5-oxo-eicosanoids activate Eos via a separate receptor.

Effects of fatty acids on proliferation and activation of human synovial compartment lymphocytes

The object of this study was to determine the effects of eicosanoid precursor fatty acids on activation and proliferation of T lymphocytes from synovial fluid and synovial tissue of rheumatoid arthritis patients. Proliferation was determined by direct cell counts; phenotypic characterization of surfaces molecules was by cytofluorometric analysis. Dihomogammalinolenic acid, arachidonic acid, and eicosapentaenoic acid suppressed proliferation of interleukin-2-dependent lymphocytes by as much as 80%; cell viability was not altered by fatty acids. Administration of particular fatty acids may prove to be a useful therapeutic intervention in rheumatoid arthritis patients because of their ability to suppress activation and proliferation of synovial compartment T lymphocytes.

Fungal metabolites. Part 14. Novel potent immunosuppressants, mycestericins, produced by Mycelia sterilia

Mycestericins A, B, C, D and E were isolated from the culture broth of Mycelia sterilia ATCC 20349 along with thermozymocidin (= myriocin). Their structures were elucidated on the basis of spectroscopic studies and chemical evidence. The acetate of mycestericin C was identical with the acetate of 6,7-dihydromyriocin. Mycestericins suppressed the proliferation of lymphocytes in the mouse allogeneic mixed lymphocyte reaction, with a potency similar to that of myriocin.