E-octadecadienoic Acid Research Articles

Strong inhibition of mammalian lipoxygenases by the antiinflammatory seleno-organic compound ebselen in the absence of glutathione

Both human recombinant 5-lipoxygenase (EC 1.13.11.34) and 15-lipoxygenase (EC 1.13.11.33, mammalian enzyme) purified from rabbit reticulocytes were inhibited in the absence of glutathione (GSH) by submicromolar concentrations of the seleno-organic compound ebselen. These concentrations were comparable to those of the enzymes. Soybean lipoxygenase-1 (EC 1.13.11.33, plant enzyme) was not inhibited, whereas prostaglandin endoperoxide synthase-1 (EC 1.14.99.1) was inhibited only at much higher concentrations of ebselen ( ic 50 = 37.7 ± 4.3 μM ). The action of ebselen on reticulocyte 15-lipoxygenase (1050 = 0.17 ± 0.01 μM) was studied in detail. Inhibition occurred instantaneously and appeared to be reversible and was largely abolished by a 20-fold molar excess of GSH over ebselen. In the presence of 1 mM GSH 50% inhibition was observed only at ebselen concentrations as high as 234 ± 27 μM. 13 S-hydroperoxy-9 Z,11 E-octadecadienoic acid, the lipoxygenase product formed from linoleic acid, augmented the inhibitory effect at low concentrations and caused a partial reversal at high concentrations. A variety of derivatives or structural analogues of ebselen were also tested and proved to be either inactive or weaker inhibitors of 15-lipoxygenase. We have concluded that the potent inhibition of 15-lipoxygenase by ebselen is due neither to GSH peroxidase-like activity nor to lowering of the hydroperoxide tone. The pharmacological implications of these unique characteristics of the action of ebselen on lipoxygenases are then discussed.

Inhibitory effects of sulfonated shale oils (ammonium bituminosulphonates, Ichthyols) on enzymes of polyenoic fatty acid metabolism.

The two commercial pharmaceutical preparations of ammonium bituminosulphonates, Leukichthol and Dark Ichthyol, were shown to inhibit the formation of 5S-hydroxy-6E,8Z,11Z,14Z-eicosatetraenoic acid (5-HETE) from external arachidonic acid by human polymorphonuclear leukocytes stimulated by ionophore A-23187 in a dose-dependent manner. Pure arachidonate 15-lipoxygenases from rabbit reticulocytes and soya beans, and the particulate prostaglandin endoperoxide synthase from sheep vesicular glands, were also inhibited. With the reticulocyte lipoxygenase, the Ichthyols suppressed the enzyme activity by two different mechanisms: (1) a prolongation of the lag period typical of lipoxygenase catalysis, and (2) by a lowering of the maximal enzymatic activity after the end of lag period. As expected, the first effect was reversed by the addition of the lipoxygenase product 13S-hydroperoxy-9Z,11E-octadecadienoic acid (13-HpODE). Ammonium bituminosulphonates are thus universal inhibitors of lipoxygenase activities, and the latter are of potential importance in inflammatory dermatoses.

In vitro oxygenation of soybean biomembranes by lipoxygenase-2

The ability of soybean lipoxygenases-1 and -2 to oxygenate biomembranes isolated from soybean seedlings has been investigated. Constituents of the lipid bilayer were analyzed by means of reversed phase and chiral phase high performance liquid chromatography, gas chromatography/mass spectrometry, high performance thin layer chromatography and uv spectroscopy. Evidence is presented that soybean lipoxygenase-2, at variance with the type-1 enzyme, oxygenates the esterified unsaturated fatty acid moieties in biomembranes, whereas membrane-embedded free unsaturated fatty acid moieties were not a suitable substrate for either isoenzyme. The oxygenation products derived from the biomembranes were the 9- and 13-hydroperoxides of linoleic acid residues, in a molar ratio of 1.0 to 1.7, and the 9- and 13-hydroperoxides of α-linolenic acid residues, in a molar ratio of 1.0 to 0.1. The R S ratios of 13-hydroperoxy-9 Z,11 E-octadecadienoic acid and 9-hydroperoxy-10 E,12 Z,15 Z-octadecatrienoic acid were found to be 0.5 and 25.0, respectively. These stereospecificity values were much higher than those of hydroperoxides isolated after incubation of lipoxygenase-2 with non-membraneous fatty acids or their methyl esters. The hydroperoxy fatty acids produced were distributed in neutral lipids and phospholipids isolated from soybean membranes, the former being oxidized to a larger extent. Furthermore, both intracellular and plasma membranes were substrates for the enzymic oxygenation, with a preference for those of chloroplasts followed by those of Golgi apparatus, endoplasmic reticulum, plasma membrane and mitochondria. These data point towards a different action of the two lipoxygenases in soybean cells. We suggest that the type-2 enzyme plays a role in the in vivo remodelling of biomembranes. The physiological relevance of these findings is discussed.

Optimization of Large Scale Preparation of 13-(S)-Hydroperoxy-9Z, 11E-Octadecadienoic Acid Using Soybean Lipoxygenase. Application to the Chemoenzymatic Synthesis of (+)-Coriolic Acid

The optimization of 13-S-hydroperoxy-9Z, 11E-octadecadienoic acid synthesis is described using lipoxygenase-1 from soybeans at high substrate concentration. The optimal values of the tested parameters are as follows: oxygen pressure 2.5 bar, temperature 5°C, pH 11, enzyme concentration 4 mg/ml and substrate concentration 0.1 M. All these values were used in a single reaction, allowing chemoenzymatic synthesis of gram amounts of (+)-coriolic acid (99%, e.e. 97%) with a 54% yield starting from linoleic acid.

Bacterial expression, purification and partial characterization of recombinant rabbit reticulocyte 15-lipoxygenase

The recombinant rabbit reticulocyte 15-lipoxygenase has been expressed in E coli with a yield of about 50–70 βg pure lipoxygenase protein per l of liquid culture. The enzyme has been purified to apparent homogeneity from the bacteria lysis supernatant by ammonium sulfate precipitation, and two consecutive steps of anion exchange chromatography on a Mono Q column. As the native enzyme the recombinant lipoxygenase has a molecular mass of 75 kDa, an isoelectric point of 5.5 and oxygenates both linoleic acid (formation of 13 S-hydroperoxy-9 Z,13 E-octadecadienoic acid) and arachidonic acid. With the latter substrate it exhibits a dual positional specificity (formation of 15 S-hydroperoxy-5 Z,8 Z,11 Z,13 E-eicosatetraenoic acid and 12 S-hydroperoxy-5 Z,8 Z,10 E,14 Z-eicosatetraenoic acid in a ratio of 12:1). Furthermore, the enzyme is capable of oxygenating biomembranes, as indicated by HPLC analysis of esterified oxygenated polyenoic fatty acids.

Oxygenation of lipoproteins by mammalian lipoxygenases.

Oxidative modification converts low-density lipoprotein (LDL) into its atherogenic form and appears to be a necessary precondition for LDL uptake by macrophages during foam cell formation. Cellular lipoxygenases have been implicated in this process. We studied the interaction of purified mammalian lipoxygenases with human LDL in vitro and found that the arachidonate 15-lipoxygenases of rabbit and man are capable of oxygenating lipoproteins as indicated by oxygen uptake and by the formation of thiobarbituric-acid-reactive substances. Furthermore, oxygenated polyenoic fatty acids, such as 13-hydro(pero)xy-9Z,11E-octadecadienoic acid and 15-hydro(pero)xy-5,8,11,13(Z,Z,Z,E)-eicosatetraenoic acid were detected in the lipid compartment of various lipoproteins classes after lipoxygenase treatment. More than 90% of the oxygenated polyenoic fatty acids were found in the ester-lipid fraction, particularly in the cholesterol esters, whereas only small amounts of free hydro(pero)xy polyenoic fatty acids were detected. Lipoxygenase-catalyzed oxygenation of LDL is not restricted to the lipid compartment but also leads to a cooxidative modification of the apoproteins as indicated by changes in the electrophoretic mobility and by the formation of carbonyl derivatives of amino acid side chains. The possible biological significance of lipoxygenase-induced oxidative modification of lipoproteins in the pathogenesis of atherosclerosis is discussed.

A novel chemo-enzymatic enantiospecific synthesis of (S)-coriolic acid mediated via immobilized alcohol dehydrogenase of baker's yeast

(S)-(E)-(+)-1-Bromo-1-octene-3-ol was prepared in 85% yield and high optical purity (e.e. 97.4%) via a stereospecific reduction of corresponding bromo vinyl ketone using alcohol dehydrogenase from baker's yeast (EC 1.1.1.1) and NAD(P)H immobilized on Nucleosil 120-5 C 18, and converted to 13(S)-hydroxy-9Z,11E-octadecadienoic (coriolic) acid.

Bis-Allylic hydroxylation of linoleic acid and arachidonic acid by human hepatic monooxygenases

[ 14C]Linoleic acid was incubated with human liver microsomes and NADPH and biosynthesis of allylic hydroxy fatty acids was investigated. 11-Hydroxy-9Z,12Z-octadecadienoic acid (11-HODE), 9-hydroxy-10 E,12Z-octadecadienoic acid (9-HODE), 13-hydroxy-9Z, 11 E-octadecadienoic acid (13-HODE) and 14-hydroxy-9Z,12Z-octadecadienoic acid were identified. 9-HODE and 13-HODE were formed with stereoselectivity (80% R) provided that 11-HODE was prevented from decomposing to 9( R, S)-ODE and 13( R, S)-HODE by extractive isolation at pH 5–6. Human hepatic microsomes metabolized [ 14C]arachidonic acid to many products, including 13-HETE and small amounts of 15-HETE (⪢ 90% R), 11-HETE (59% R) and 12-HETE (⪢ 90% R). Hepatic microsomes of untreated rats metabolized [ 14C]linoleic acid to 11-HODE as a major product, but significant formation of 11-HODE by purified cytochrome P−450 (P450) (CYP1A1, CYP2B1, CYP2B4, CYP2E1, CYP3A6 and CYP4A1) in a reconstituted system could not be detected, indicating that 11-HODE might be formed by other and constitutive P450 isozymes.

Bis-Allylic Hydroxylation of Polyunsaturated Fatty Acids by Hepatic Monooxygenases and Its Relation to the Enzymatic and Nonenzymatic Formation of Conjugated Hydroxy Fatty Acids

[14C]Linoleic acid was incubated with phenobarbital-induced rat liver microsomes and formation of cis-trans-conjugated hydroxy fatty acids was investigated. 13-Hydroxy-9Z,11E-octadecadienoic acid (13-HODE), 9-hydroxy-10E,12Z-octadecadienoic acid (9-HODE), and three novel metabolites were identified, viz. 1 1-hydroxy-9Z,12Z-octadecadienoic acid (li-HODE), 8-HODE, and14-HODE. 11-HODE (59% R), the main product, was unstable and converted to 9(R, S)-HODE and 13(R, S)HODE in acidic media. All metabolites contained oxygen from O2. Experiments under oxygen-18 gas showed that 13-HODE and 9-HODE contained equal or less amounts of oxygen-18 than the other metabolites. In the former case, 9-HODE and 13-HODE were formed with stereo-selectivity (80-82% R). [11S-2H]Linoleic acid was metabolized to 13R-HODE with loss of deuterium (24% 2H) and to 9R-HODE with deuterium retention (95% 2H), while [11R-2H]linoleic acid was metabolized to 13R-HODE that largely retained the label (71% 2H) and to 9R-HODE that lost most of the label (22% 2H). These data indicated that P450 catalyzed abstraction of the pro-R hydrogen at C11, double bond migration and suprafacial oxygen insertion at C9 to give 9R-HODE, while abstraction of the pro-S hydrogen at C11, followed by double bond migration and oxygen insertion, yielded 13R-HODE. Hepatic microsomes of the cynomolgus monkey metabolized 18:2n-6 as above and 20:4n-6 to 13-hydroxyeicosatetraenoic acid, likely formed in analogy with li-HODE. In summary, one mechanism in the biosynthesis of cis-trans-conjugated hydroxy fatty acids by P450 involves suprafacial hydrogen abstraction and oxygen insertion. In addition, hydrolysis of the unstable bis-allylic hydroxy metabolites may contribute to the formation of conjugated hydroxy fatty acids.

Oxylipin metabolism in the red alga Gracilariopsis lemaneiformis: Mechanism of formation of vicinal dihydroxy fatty acids

Conversion of arachidonic acid into the vicinal diol fatty acid 12 R,13 S-dihydroxy- 5 Z,8 Z,10 E,14 Z-eicosatetraenoic acid using an acetone powder of the marine red alga, Gracilariopsis lemaneiformis, occurred via intermediate formation of 12 S-hydroperoxy-5 Z,8 Z, 10 E,14 Z-eicosatetraenoic acid. Incubations of the linoleic acid-derived 13 S- and 13 R-hydroperoxy-9 Z,11 E-octadecadienoic acids led to the formation of 13 R,14 S-dihydroxy-9 Z, 11 E-octadecadienoic acid and 13 S,14 S-dihydroxy-9 Z,11 E-octadecadienoic acid, respectively, whereas incubation of 9 S-hydroperoxy-10 E,12 Z-octadecadienoic acid resulted in the formation of 8 S,9 R-dihydroxy-10 E, 12 Z-octadecadienoic acid. Experiments with 18O 2-labeled 13 S-hydroperoxyoctadecadienoic acid demonstrated that the oxygens of the two hydroxyl groups of 13 R,14 S-dihydroxy-9 Z,11 E-octadecadienoic acid originated in the hydroperoxy group of the substrate. Furthermore, experiments with mixtures of unlabeled and 18O 2-labeled 13 S-hydroperoxyoctadecadienoic acid showed that conversion into 13 R,14 S-dihydroxyoctadecadienoic acid occurred by a reaction involving an intramolecular hydroxylation at C-14 by the distal hydroperoxide oxygen. The existence of a hydroperoxide isomerase in G. lemaneiformis which catalyzes the conversion of fatty acid hydroperoxides into vicinal diol fatty acids is postulated.

On the identification of a conjugated diene component of duodenal bile as 9Z, 11E-octadecadienoic acid

The lipid free radical marker, termed diene conjugation, in secretin-stimulated human bile obtained from the duodenum was shown by high performance liquid chromatography and capillary gas chromatography-mass spectrometry, to be due mainly to 9Z, 11E-octadecadienoic acid. The lack of evidence for possible conjugated diene isomers argues for an enzymatic origin of this product rather than being due to a random free radical mechanism, as is usuaslly assumed.

Peroxidase-like activity of lipoxygenases: different substrate specificity of potato 5-lipoxygenase and soybean 15-lipoxygenase and particular affinity of vitamin E derivatives for the 5-lipoxygenase

Potato 5-lipoxygenase (5-PLO) catalyzes the reduction of 13(S)-hydroperoxy-9 Z,11 E-octadecadienoic acid (13-HPOD) in the presence of vitamin E. 1 mol of vitamin E is required to consume 2 mol of 13-HPOD. The mechanism of the 5-PLO-catalyzed oxidation of vitamin E by 13-HPOD is similar to that previously established for the soybean 15-lipoxygenase (L-1)-catalyzed oxidation of phenidone by 13-HPOD, and seems to involve a one-electron reduction of the OO bond of 13-HPOD. 5-PLO and L-1 exhibit very different substrate specificities and pH profiles for their peroxidase-like activity. Actually, among the 20 compounds containing various reducible functions and the 10 derivatives of vitamin E which have been studied, only four products containing hydrophobic long chains, ascorbic acid 6-palmitate, the trolox esters of octanol and undecanol, and vitamin E exhibit high peroxidase-like activities for 5-PLO. On the contrary, much more compounds, even not very hydrophobic, are good substrates for the peroxidase-like activity of L-1.

Oxygenation of biological membranes by the pure reticulocyte lipoxygenase.

We find that the reticulocyte lipoxygenase can oxygenate rat liver mitochondrial membranes, beef heart submitochondrial particles, rat liver endoplasmic membranes, and erythrocyte plasma membranes (inside-out and right side-out ghosts) without prior action of a phospholipase. After alkaline hydrolysis of the ester lipids, the main products were identified as 15S-hydro(pero)xy-5Z,8Z,11Z,13E-eicosatetr aenoic acid, 17S-hydro(pero)xy-4Z,7Z,10Z,13Z,15E, 19Z,-docosahexaenoic acid, 13S-hydro(pero)xy-9Z,11E-octadecadienoic acid, 9(S/R)-hydro(pero)xy-10E,12Z-octadecadienoic acid as well as the two all-E hydro(pero)xy octadecadienoic acid isomers. At low membrane concentrations (1 mg of protein/ml), the enzyme maintains a high stereospecificity for the S-configuration, but at higher concentrations (20 mg/ml), the products were virtually racemic. Addition of the antioxidant 2,6-ditert-butyl-p-cresol counteracted this tendency to lose stereospecificity. During these enzyme-catalyzed reactions, substantially more oxygen is consumed than can be accounted for as the hydro(pero)xy products. This discrepancy is due to secondary reactions which lead to the decomposition of the primary oxygenation products, the hydroperoxy lipids, and to oxidative modifications of membrane proteins. These data indicate that the reticulocyte lipoxygenase can oxygenate polyenoic fatty acids in various types of biological membrane and that the oxidative modifications are not restricted to the membrane lipids. The results are discussed in terms of the proposed role of the enzyme in the breakdown of mitochondria and other intracellular organelles during the maturation of red blood cells.

Occurrence of 9- and 13-keto-octadecadienoic acid in biological membranes oxygenated by the reticulocyte lipoxygenase

Membranes of intact rabbit reticulocytes and rat liver mitochondrial membranes oxygenated by the pure reticulocyte lipoxygenase contain 13-keto-9 Z,11 E-octadecadienoic acid and 9-keto-10 E,12 Z-octadecadienoic acid. In mitochondrial membranes not treated with lipoxygenase and in rabbit erythrocyte membranes these products were not detected. The chemical structure of the compounds has been identified by co-chromatography with authentic standards on various types of HPLC columns, by uv and ir spectroscopy and GC/MS. In the membranes of rabbit reticulocytes up to 2% of the linoleate residues are present as its 9- and 13-keto derivatives. Most of the keto compounds (up to 90%) are esterified in the membrane ester lipids, only about 10% were found in the free fatty acid fraction. It is proposed that the keto dienoic fatty acids are formed via decomposition of hydroperoxy polyenoic fatty acids originating from the oxygenation of the membrane lipids by the reticulocyte lipoxygenase.

Occurrence of lipoxygenase products in membranes of rabbit reticulocytes. Evidence for a role of the reticulocyte lipoxygenase in the maturation of red cells.

A lipoxygenase has been found in the reticulocytes of all mammalian species tested so far (rabbit, rat, mouse, monkey, and humans); evidence from in vitro studies suggests that the lipid-peroxidizing effects of this enzyme could render the mitochondrion and other intracellular organelles prone to the proteolytic degradation which is a natural step in development of the reticulocyte to the mature red cell. In this study we sought evidence of an active lipoxygenase in vivo. A bleeding anemia was induced in rabbits, and in the course of the subsequent reticulocytosis the red cell membranes were examined for the presence of the characteristic lipoxygenase products of linoleic and arachidonic acids. Erythrocyte membranes from control collections contained only small amounts of hydroxy fatty acids (0.03-0.08% of the polyenoic fatty acids). In contrast, reticulocyte-enriched red cells contained up to 3.3% of the polyenoic acids as hydroxylated derivatives. The main hydroxy fatty acid in reticulocyte membranes was identified as 13-L(S)-hydroxy-9Z,11E-octadecadienoic acid. Small amounts of other hydroxy derivatives including 15-hydroxy-5,8,11,13-(Z,Z,Z,E)eicosatetraenoic acid were also detected. These products appeared about 3 days after development of reticulocytosis. The precise structures of the hydroxylated polyenoic fatty acids and the time course of their appearance strongly suggest that their formation is due to the intracellular action of the cell-specific reticulocyte lipoxygenase. These findings are the first evidence for an activity of this enzyme in vivo, and the results support the hypothesis that enzymic peroxidation of reticulocyte intracellular membranes is a step in preparation of the intracellular organelles for proteolytic degradation.

Production of unsaturated carbonyl compounds during metabolism of hydroperoxy fatty acids by colonic homogenates

Recent evidence has suggested that unsaturated carbonyl compounds may be the ultimate mitogens produced from the primary auto-oxidation products of unsaturated fatty acids. The present study has investigated the metabolism of 13-hydroperoxyoctadecandienoic acid (13-ROOH) by rat colon homogenates. This hydroperoxide is one of the primary products formed from the oxygenation of linoleic acid, the most abundant dietary polyunsaturated fatty acid. Incubation mixtures contained [1-14C]13-ROOH and colonic homogenates prepared from male Sprague-Dawley rats. After 30 min of incubation the reaction was quenched and the products extracted for analysis by HPLC. The identity of the eluted products were verified by UV, MS and NMR spectroscopy. The major products include a mixture of isomers of 2,4-dienone C18 fatty acids and 13-hydroxyoctadecadienoic acid. Direct comparison of homogenate metabolism to the hematin-catalyzed, alkoxyl radical-mediated decomposition of 13-ROOH shows some significant differences. In particular, no epoxy products are detected in the presence of tissue homogenates whereas these are the major products observed during the decomposition of 13-ROOH by hematin and a number of other agents. These experiments demonstrate the production of relatively large amounts of unsaturated carbonyl-containing fatty acids during the metabolism of hydroperoxy fatty acids by colonic tissue. The major product, 13-oxo-9Z,11E-octadecadienoic acid, when instilled intrarectally stimulates the incorporation of [3H]deoxythymidine into colonic mucosal DNA, and induces colonic mucosal ornithine decarboxylase activity in vivo. These findings have important implications for the mechanism by which dietary fat promotes colon tumorigenesis as the formation of relatively reactive 2,4-dienones may be a key to the in vivo mitogenic activity of oxidized fatty acids.

An efficient synthesis of 13(S)-hydroxy-9Z,11E-octadecadienoic (coriolic) acid.

An efficient and highly selective total synthesis of 13(S)-hydroxy-9Z,11E octadecadienoic (coriolic) acid is described, starting from an optically active lactol easily available through an enantioselective enzymatic hydrolysis.

Oxygenation of mitochondrial membranes by the reticulocyte lipoxygenase. Action on monoamine oxidase activities A and B

Incubation of isolated rat liver mitochondria with the pure rabbit reticulocyte lipoxygenase caused a time-dependent inactivation of the monoamine oxidase activities A and B. Furthermore, a conversion of the monoamine oxidase into a diamine oxidase was observed. The inactivation kinetics for both monoamine oxidase activities A and B showed a biphasic behaviour; a reversible short-term inhibition during the first 5 min of incubation was followed by an irreversible inactivation of the enzyme. The kinetic studies suggest that the slow irreversible inactivation of the monoamine oxidase activities is due to secondary reactions subsequent to the initial attack of the lipoxygenase on the mitochondrial outer membrane. During the interaction of the lipoxygenase with the mitochondria, only about 1.5% of the polyenoic fatty acids present in the mitochondrial membranes were oxygenated. The predominant products formed during the interaction of the lipoxygenase with the mitochondrial membranes are (13 S)-hydro(pero)xy-9 Z,11 E-octadecadienoic acid and (15 S)-hydro(pero)xy-5,8,11,13( Z, Z, Z, E)-eicosatetraenoic acid.

Oxidative metabolism of linoleic acid by human leukocytes

Upon incubation with human leukocytes, [1- 14C] linoleic acid is almost exclusively transformed into 13-hydroxy-9Z, 11E-octadecadienoic acid (13-HODE) if the linoleic acid concentration is lower than 50μM. Identification of 13-HODE was done by GLC-MS at the level of its methyl ester, trimethylsilyl ether and by comparison with authentic 13-HODE in two different HPLC systems. Analysis of the products by chiral phase HPLC shows that 13(S)-hydroxy-9Z, 11E-octadecadienoic acid is by far the major metabolite formed by human leukocytes. Comparison of reactions performed with intact or lyzed cells suggests that the formation of 13(S)-HODE by human leukocytes occurs in two steps, a dioxygenation catalyzed by a 15-lipoxygenase and a reduction of intermediate 13-HPODE by a glutathione-dependent peroxidase.

Iron(II) Complex with 1,3-Bis(2-benzimidazyl)-2-thiapropane as a Model Compound for Lipoxygenase

Abstract Iron(II) complex with 1,3-bis(2-benzimidazyl)-2-thiapropane is stable in air in both the solid and the solution states. This complex is oxidized to Fe(III) state by 13(S)-hydroperoxy-9Z,11E-octadecadienoic acid, and the Fe(III) species is readily reduced to Fe(II) state by phenidone. This suggests the presence of thioether group in the coordination sphere of native lipoxygenase.